Carbon dioxide liquefaction system

Abstract

The present invention provides a method of liquefying a CO2 rich stream (1) to a liquid CO2 product (5), stripped of non-condensable components, in a carbon dioxide liquefaction system, and a carbon dioxide liquefaction system for the method.

Description

[0001] Carbon dioxide liquefaction system

[0002] Field of the invention

[0003] The present invention relates to a carbon dioxide liquefaction system, and a process for liquefaction of carbon dioxide.

[0004] Background

[0005] Liquefaction of carbon dioxide (CO2) on a large scale is well-known in the prior art. Its importance has increased significantly due to the ambitions of capturing and storing CO2 to reduce the amount of CO2 discharged to the atmosphere. However, the prior art CO2 liquefaction systems have various disadvantages regarding energy requirements and the ability to provide the required purity of the liquefied CO2 product and at the same time provide a low loss of CO2 during liquefaction and purification.

[0006] The goal of the present invention is to provide an improved carbon dioxide (CO2) liquefaction system, in which at least some of the disadvantages of the prior art systems are avoided or alleviated. Specifically, the present invention provides an energy efficient method for liquefaction of carbon dioxide, with simultaneous removal of non-condensable trace components (for example nitrogen, oxygen, argon, carbon monoxide, nitrous oxides, light hydrocarbon gas), with minimal loss of CO2.

[0007] The CO2 to be liquefied can be from any source, e.g. from a system removing CO2 from a process gas, or from a system capturing CO2 from a flue gas, or from a system for removing CO2 from ambient air by direct air capture (DAC).

[0008] Summary of the invention

[0009] The present invention is defined by the appended claims and in the following:

[0010] In a first aspect, the present invention provides a method of liquefying a CO2 rich stream to a liquid CO2 product, stripped of non-condensable components, in a carbon dioxide liquefaction system, the method comprising the steps of introducing the CO2 rich stream to a compressor arrangement to obtain a compressor arrangement discharge stream where the CO2 rich stream makes up a portion of the compressor arrangement discharge stream; cooling the compressor arrangement discharge stream in a liquefaction inlet cooler to obtain a liquefaction inlet stream having a liquefaction inlet pressure and a liquefaction inlet temperature; providing the liquefaction inlet stream to a first separator as a first intermediate flash stream at a first separator pressure which is equal to or lower than the liquefaction inlet pressure, the first intermediate flash stream comprising a first intermediate liquid phase and a first intermediate gas phase; routing the first intermediate liquid phase from the first separator as at least a portion of a first separator liquid, and subjecting the first separator liquid to a pressure reduction from the first separator pressure to a stripping column pressure via one or more pressure reduction stages, resulting in a final intermediate flash stream comprising a final intermediate liquid phase and a final intermediate gas phase; introducing the final intermediate flash stream to a stripping column top separation zone of a stripping column operating at the stripping column pressure; flowing the final intermediate liquid phase downwards through a stripping column mass transfer section inside the stripping column to strip non-condensable components from the final intermediate liquid phase, the stripping of non-condensable components being assisted by a stripping gas flowing upwards through the stripping column mass transfer section, to obtain a stripped CO2 liquid having a stripped CO2 liquid temperature, the stripping gas comprising a primary stripping gas; extracting a portion of the stripped CO2 liquid as the liquid CO2 product, the liquid CO2 product has a liquid CO2 product pressure which is essentially equal to the stripping column pressure; extracting at least a portion of the first intermediate gas phase from the first separator as a first reject gas; introducing the first reject gas as a bottom gaseous feed to a rectification column having a rectification mass transferer section, where the first reject gas is in counter current contact with a reflux liquid which is colder than the first reject gas, and where the first reject gas is subjected to a temperature reduction that causes a fraction of the CO2 content of the first reject gas to become condensed to provide a rectification outlet gas having a reduced concentration of CO2 relative to the first reject gas, and a recovered CO2 liquid; and cooling the rectification outlet gas in a partial condenser heat exchanger such that a fraction of the CO2 content of the rectification outlet gas becomes condensed, the CO2 which is condensed is separated from the rectification outlet gas to form the reflux liquid which is recycled to the rectification column, and such that the rectification outlet gas minus the reflux liquid is a partial condenser heat exchanger reject gas having a reduced concentration of CO2 relative to the rectification outlet gas.

[0011] In an embodiment, the method may comprise a step of transferring the liquid CO2 product out of the CO2 liquefaction system, e.g. transferring the liquid CO2 product to a storage tank or to a transport pipeline.

[0012] The method may comprise a step of transferring the partial condenser heat exchanger reject gas out of the CO2 liquefaction system as a final reject gas. The partial condenser heat exchanger reject gas has an increased concentration of noncondensable components relative to any of the rectification outlet gas and the first reject gas.

[0013] The primary stripping gas may also be termed a first stripping gas. The stripping gas may consist of the primary stripping gas or may comprise a further stripping gas, i.e. a secondary stripping gas.

[0014] In an embodiment of the method, one of the one or more pressure reduction stages is a final expansion device. The final expansion device providing the final intermediate flash stream comprising the final intermediate liquid phase and the final intermediate gas phase.

[0015] In an embodiment, the method may comprise a step of routing the recovered CO2 liquid from the rectification column to the stripping column via one or more pressure reduction stages, i.e. such that at least a portion of the recovered CO2 liquid constitutes a part of the final intermediate flash stream.

[0016] In an embodiment of the method, the rectification outlet gas may be cooled in the partial condenser heat exchanger by heat exchange with evaporating CO2, e.g. evaporating CO2 from the stripped CO2 liquid. In other words, at least a portion of the stripped CO2 liquid may be evaporated in the partial condenser heat exchanger (i.e. at a cool side of the partial condenser heat exchanger) to cool the rectification outlet gas on a warm side of the partial condenser heat exchanger.

[0017] In an embodiment of the method, wherein the rectification outlet gas is cooled in the partial condenser heat exchanger by heat exchange with evaporating CO2 from the stripped CO2 liquid, the method may comprise the steps of obtaining a partial condenser heat exchanger cold side feed by extracting at least a portion of the stripped CO2 liquid; evaporating at least a portion of the partial condenser heat exchanger cold side feed in the partial condenser heat exchanger, causing a net cooling duty in the partial condenser heat exchanger; and returning a partial condenser heat exchanger cold side outflow to the stripping column, in the partial condenser heat exchanger cold side outflow at least a portion of the stripped CO2 liquid of the partial condenser heat exchanger cold side feed is evaporated to become a gaseous portion.

[0018] In an embodiment of the method, the gaseous portion of the partial condenser heat exchanger cold side outflow may be the primary stripping gas.

[0019] In an embodiment of the method, the flow of the partial condenser heat exchanger cold side feed to the partial condenser heat exchanger, and the flow of the partial condenser heat exchanger cold side outflow to the stripping column may be driven by a reduction in fluid density occurring for the condenser cold side feed when a portion of the condenser cold side feed is evaporated in the partial condenser heat exchanger.

[0020] In an embodiment of the method, the first separator pressure is lower than the liquefaction inlet pressure, and the liquefaction inlet stream is subjected to a first pressure reduction in a first expansion device from the liquefaction inlet pressure to the first separator pressure, and the first expansion device yields the first intermediate flash stream.

[0021] In an embodiment, the method may comprise the steps of extracting a portion of the first intermediate gas phase from the first separator as a first recycle gas; routing the first recycle gas to the compressor arrangement; and recompressing the first recycle gas to the liquefaction inlet pressure to form a portion of the compressor arrangement discharge stream and the liquefaction inlet stream. In an embodiment of the method, the first separator may operate at essentially the liquefaction inlet pressure, the liquefaction inlet stream may be routed to the first separator and introduced to the first separator as the first intermediate flash stream consisting of the first intermediate liquid phase and the first intermediate gas phase, and the portion of the first intermediate gas phase which is the first reject gas may be 100% of the first intermediate gas phase.

[0022] In an embodiment of the method, the first separator liquid may be subjected to the pressure reduction from the first separator pressure to the stripping column pressure in two pressure reduction stages, and the method may comprise the steps of; routing the first separator liquid to a second pressure reduction in a second expansion device to reduce the pressure from the first separator pressure to a second separator pressure, the second separator pressure being lower than the first separator pressure and higher than the stripping column pressure; obtaining a second intermediate flash stream consisting of a second intermediate liquid phase and a second intermediate gas phase (i.e. the intermediate pressure reduction transforms the first separator liquid to the second intermediate flash stream); separating the second intermediate liquid phase and the second intermediate gas phase in a second separator operating at the second separator pressure to obtain a second separator liquid and a second recycle gas; routing the second separator liquid to the final expansion device, wherein the pressure is reduced from the second separator pressure to the stripping column pressure to provide the final intermediate flash stream; routing the second recycle gas to the compressor arrangement; and recompressing the second recycle gas to the liquefaction inlet pressure to form a portion of the compressor arrangement discharge stream and the liquefaction inlet stream.

[0023] In an embodiment, the method may comprise a step of subjecting the first separator liquid to one or more additional pressure reduction stages arranged between the first separator and the second expansion device. Each of the one or more pressure reduction stages may comprise an additional expansion device and an additional separator configured similar to the first expansion device and the first separator, respectively. An additional separator may provide an additional recycle gas and an additional separator liquid. In an embodiment of the method, the recovered CO2 liquid may be routed to the stripping column by the step of: mixing the recovered CO2 liquid with the first intermediate flash stream upstream of the first separator or with the first intermediate liquid phase in the first separator; or routing the recovered CO2 liquid to the stripping column via a recovered CO2 liquid expansion device.

[0024] In an embodiment of the method, the recovered CO2 liquid may be routed to the stripping column by the step of routing the recovered CO2 liquid to the second separator via a recovered CO2 liquid expansion device.

[0025] In an embodiment, the method according to any of the preceding claims may comprise the steps of mixing the final intermediate gas phase with a stripping column outlet stripping gas to obtain a stripping column recycle gas; routing the stripping column recycle gas to the compressor arrangement; and recompressing the stripping column recycle gas to the liquefaction inlet pressure to form a portion of the compressor arrangement discharge stream and the liquefaction inlet stream.

[0026] The stripping column outlet stripping gas is the gas obtained from the stripping gas after the stripping gas has interacted with the final intermediate liquid phase in the stripping column mass transfer section. In other words, the method may comprise a step of obtaining a stripping column outlet stripping gas by interacting the stripping gas with the final intermediate liquid phase in the stripping column mass transfer section.

[0027] In an embodiment of the method, a secondary stripping gas may be generated by applying a reboiler for evaporation of a portion of the stripped CO2 liquid, and the heat required for evaporating the portion of the stripped CO2 liquid is by heat exchange with a reboiler warm side inlet stream, the method may comprise the steps of obtaining the reboiler warm side inlet stream by extracting a portion of the liquefaction inlet stream, leaving a non-extracted portion of the liquefaction inlet stream which flows to the first expansion device; cooling the reboiler warm side inlet stream to a temperature lower than the liquefaction inlet temperature, but higher than or equal to the stripped CO2 liquid temperature, providing a reboiler warm side outlet stream; regulating the flow of the reboiler warm side inlet stream by a reboiler control valve, the reboiler control valve being located at the reboiler warm side inlet or at the reboiler warm side outlet; and introducing the reboiler warm side outlet stream to a section of the carbon dioxide liquefaction system operating at a pressure lower than the pressure of the liquefaction inlet stream.

[0028] In an embodiment of the method, the reboiler warm side outlet stream may be introduced to the section of the carbon dioxide liquefaction system operating at a pressure lower than the pressure of the liquefaction inlet stream,

[0029] - by introducing the reboiler warm side outlet stream downstream of the first expansion device to form a portion of the first intermediate flash stream; or

[0030] - by introducing the reboiler warm side outlet stream to the first separator.

[0031] In an embodiment of the method, the reboiler warm side outlet stream may be introduced to the section of the carbon dioxide liquefaction system operating at a pressure lower than the pressure of the liquefaction inlet stream,

[0032] - by introducing the reboiler warm side outlet stream downstream of the second expansion device to form a portion of the second intermediate flash stream; or introducing the reboiler warm side outlet stream to the second separator.

[0033] In an embodiment of the method, the reboiler warm side outlet stream may be introduced to the section of the carbon dioxide liquefaction system operating at a pressure lower than the pressure of the liquefaction inlet stream,

[0034] - by introducing the reboiler warm side outlet stream downstream of the final expansion device to form a portion of the final intermediate flash stream; or

[0035] - by introducing the reboiler warm side outlet stream to the stripping column.

[0036] In an embodiment of the method, the cooling in the liquefaction inlet cooler may be provided by any type of refrigeration work cycle. In an embodiment of the method, the liquefaction inlet cooler may be a multi-stream heat exchanger having a warm side and at least one cold side, and the liquefaction inlet cooler is configured to cool the compressor arrangement discharge stream by heat exchange with any of the first recycle gas, the second recycle gas, an intermediate recycle gas stream, the stripping column recycle gas, any available ambient cooling medium stream, and a refrigerant stream provided by a refrigeration work cycle, and wherein the cooled compressor discharge stream exiting the liquefaction inlet cooler is the liquefaction inlet stream.

[0037] In an embodiment of the method, the compressor arrangement may comprise an after cooler for cooling of the compressor arrangement discharge stream.

[0038] In an embodiment of the method, the compressor arrangement discharge stream may be cooled to a pre-liquefaction inlet temperature which enables phase separation at the liquefaction inlet pressure, and the resulting stream is a pre-liquefaction inlet stream, which is introduced to a pre-separator operating at a pressure essentially equal to the liquefaction inlet pressure, and the method may comprise the steps of separating a pre-liquefaction gas phase and a pre-liquefaction liquid phase of the pre-liquefaction inlet stream in the pre-separator;

[0039] - the pre-liquefaction liquid phase from the pre-separator is the liquefaction inlet stream;

[0040] - the pre-liquefaction gas phase from the pre-separator is a pre-liquefaction reject gas comprising CO2 and non-condensable components, which is subject to a pre-liquefaction gas pressure reduction in a pre-liquefaction gas expansion device, reducing pressure of the pre-liquefaction reject gas from the liquefaction inlet pressure to essentially the first separator pressure; and mixing the resulting pressure reduced pre-liquefaction reject gas with the first reject gas, creating a reject gas mix stream which is routed to the rectification column.

[0041] In an embodiment of the method, the first expansion device may comprise a first ejector, where the liquefaction inlet stream having essentially the liquefaction inlet pressure, is connected to a first ejector motive fluid inlet, and a first ejector outlet is the first intermediate flash stream having essentially the first separator pressure, and wherein the flow of fluid through the first ejector from the first ejector motive fluid inlet to the first ejector outlet is creating a pressure at a first ejector low-pressure suction inlet which is lower than or equal to the stripping column pressure, enabling inflow of at least a portion of the stripping column recycle gas to the first ejector, as the first ejector suction gas, such that the first ejector suction gas is being recompressed to the first separator, and wherein any portion of the stripping column recycle gas which is not flowing to the first ejector as the first ejector suction gas, flows to the compressor arrangement as the stripping column compressor recycle gas and is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream and the liquefaction inlet stream.

[0042] In an embodiment of the method, the first expansion device may comprise a first ejector, where the liquefaction inlet stream having essentially the liquefaction inlet pressure, is connected to a first ejector motive fluid inlet, and a first ejector outlet provides the first intermediate flash stream having essentially the first separator pressure, and wherein the flow of fluid through the first ejector from the first ejector motive fluid inlet to the first ejector outlet is creating a pressure at a first ejector low-pressure suction inlet which is enabling inflow of at least a portion of the second recycle gas or at least a portion of an additional recycle gas to the first ejector, as the first ejector suction gas, such that the first ejector suction gas is being recompressed to the first separator, and wherein any portion of the second recycle gas or any portion of the additional recycle gas which is not flowing to the first ejector as the first ejector suction gas, flows to the compressor arrangement to form a portion of the compressor arrangement discharge stream and the liquefaction inlet stream.

[0043] In an embodiment of the method, the second expansion device comprises a second ejector, where at least a portion of the first separator liquid is connected directly or indirectly to a second ejector motive fluid inlet, and a second ejector outlet providing the second intermediate flash stream having essentially the second separator pressure, and wherein the flow of fluid through the second ejector from the second ejector motive fluid inlet to the second ejector outlet is creating a pressure at a second ejector low-pressure suction inlet which is lower than or equal to the stripping column pressure, enabling inflow of at least a portion of the stripping column recycle gas to the second ejector, as the second ejector suction gas, such that the second ejector suction gas is recompressed to the second separator, having the second separator pressure, and wherein any portion of the stripping column recycle gas which is not flowing to the second ejector as the second ejector suction gas, flows to the compressor arrangement as the stripping column compressor recycle gas and is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream and the liquefaction inlet stream.

[0044] In an embodiment of the method, the portion of the first separator liquid is indirectly connected (i.e. in fluid communication) to the second ejector motive fluid inlet via at least one additional separator and at least one corresponding additional expansion device. In an embodiment, the method comprises the steps of:

[0045] - transferring the first separator liquid to the first additional expansion device, resulting in a first additional intermediate flash stream;

[0046] - transferring the first additional intermediate flash stream to the first additional separator to be separated into a first additional recycle gas and a first additional liquid; and

[0047] - transferring the first additional liquid to the second expansion device, optionally via further additional expansion devices and additional separators.

[0048] In an embodiment, the method comprises the steps of

[0049] - transferring the first additional recycle gas, and optionally any further additional recycle gas streams, to the compressor arrangement; and recompressing the first additional recycle gas, and any further additional recycle gas streams, to the liquefaction inlet pressure to form a portion of the compressor arrangement discharge stream.

[0050] In an embodiment of the method, the first ejector may have an integrated device for adjusting the flow of fluid throughput, or a valve device may be applied in conjunction with the first ejector, to control the flow of fluid through the first ejector.

[0051] In an embodiment of the method, the second ejector may have an integrated device for adjusting the flow of fluid throughput, or a valve device may be applied in conjunction with the second ejector, to control the flow of fluid through the second ejector.

[0052] In an embodiment, the method may comprise the steps of introducing a vapour return stream from a liquid CO2 storage to the compressor arrangement; and compressing the vapour return stream in the compressor arrangement to become a portion of the compressor arrangement discharge stream, and consequently also a portion of the liquefaction feed stream.

[0053] In an embodiment, the method may comprise the step of mixing the vapour return stream with the stripping column recycle gas.

[0054] In an embodiment of the method, the CO2 rich stream may be introduced to the compressor arrangement to make up a portion of the compressor arrangement discharge stream,

[0055] - by mixing the CO2 rich stream with the stripping column recycle gas and compressing the resulting mix in the compressor arrangement; or - by mixing the CO2 rich stream with the compressor arrangement discharge stream.

[0056] In an embodiment of the method, the CO2 rich stream may be introduced to the compressor arrangement to make up a portion of the compressor arrangement discharge stream by mixing the CO2 rich stream with the second recycle gas and compressing the resulting mix in the compressor arrangement.

[0057] In an embodiment of the method, the CO2 rich stream may be introduced to the compressor arrangement to make up a portion of the compressor arrangement discharge stream by mixing the CO2 rich stream with the first recycle gas and compressing the resulting mix in the compressor arrangement.

[0058] In an embodiment, the method may comprise a step of: subjecting the partial condenser heat exchanger reject gas to a CO2 selective separation in a reject gas CO2 separation arrangement to obtain a reject gas CO2 separation arrangement CO2 rich outlet stream, containing at least a portion of the CO2 in the partial condenser heat exchanger reject gas, and a reject gas CO2 separation arrangement CO2 depleted outlet stream comprising non-condensable components and having a reduced content of CO2 compared to the partial condenser heat exchanger reject gas (in other words, the reject gas CO2 separation arrangement CO2 depleted outlet stream has a lower concentration of CO2 than the partial condenser heat exchanger reject gas).

[0059] The reject gas CO2 separation arrangement may be any arrangement suitable for selective separation of CO2 from a fluid stream, such as any type of pressure swing adsorption system, systems using a solvent for selective absorption of CO2 from a fluid stream, such as a regenerative amine solvent or a physical absorption solvent, or any type of membrane separator or membrane separation system. Such CO2 separation systems are known in the art and can be implemented by the skilled person having knowledge of the present specification.

[0060] In an embodiment, the reject gas CO2 separation arrangement CO2 depleted outlet stream may be transferred out of the CO2 liquefaction system as the final reject gas.

[0061] The partial condenser heat exchanger reject gas may be termed a reject gas CO2 separation arrangement feed stream to be introduced to the reject gas CO2 separation arrangement.

[0062] In an embodiment, the method may comprise a step of transferring the reject gas CO2 separation arrangement CO2 rich outlet stream to the compressor arrangement to form a portion of the compressor arrangement discharge stream. In other words, the reject gas CO2 separation arrangement CO2 rich outlet stream may be recycled to the compressor arrangement to form a portion of the compressor arrangement discharge stream.

[0063] In an embodiment, the method may comprise the steps of transferring the partial condenser heat exchanger reject gas to a second partial condenser heat exchanger to obtain a second partial condenser heat exchanger CO2 depleted outlet stream having a reduced content of CO2 compared to the partial condenser heat exchanger reject gas (in other words, the second partial condenser heat exchanger CO2 depleted outlet stream has a lower concentration of CO2 than the partial condenser heat exchanger reject gas), and a second recovered liquid, and transferring the second recovered liquid to the stripping column.

[0064] In other words, the partial condenser heat exchanger reject gas may be cooled in a second partial condenser heat exchanger to obtain a second partial condenser heat exchanger CO2 depleted outlet stream and a second recovered liquid.

[0065] The second partial condenser heat exchanger is configured to cool the partial condenser heat exchanger reject gas such that at least a part of the CO2 present in the partial condenser heat exchanger reject gas is condensed to provide at least a portion of the second recovered liquid.

[0066] In an embodiment of the method, the second partial condenser heat exchanger CO2 depleted outlet stream may be transferred out of the CO2 liquefaction system as the final reject gas.

[0067] The second recovered liquid may be transferred to the stripping column either directly, or indirectly via any of the rectification column, the first separator and the second separator.

[0068] In an embodiment of the method, the second recovered liquid is transferred to the stripping column via the rectification column by having the second recovered liquid mixed with the reflux liquid such that the second recovered liquid becomes a portion of the reflux liquid which is introduced to the rectification column.

[0069] In an embodiment of the method, the second recovered liquid is transferred to the stripping column via the first separator, e.g. by introducing the second recovered liquid to the first separator, or by having the second recovered liquid mixed with the recovered CO2 liquid such that the second recovered liquid becomes a portion of the recovered CO2 liquid which is introduced to the first separator or the first intermediate flash stream, or by having the second recovered liquid mixed with the first separator liquid.

[0070] In an embodiment, the method may comprise the step of subjecting the second partial condenser heat exchanger CO2 depleted outlet stream to a CO2 selective separation in a reject gas CO2 separation arrangement to obtain a reject gas CO2 separation arrangement CO2 rich outlet stream, containing at least a portion of the CO2 in the second partial condenser heat exchanger CO2 depleted outlet stream, and a reject gas CO2 separation arrangement CO2 depleted outlet stream comprising non-condensable components and having a reduced content of CO2 compared to the second partial condenser heat exchanger CO2 depleted outlet stream (i.e. the reject gas CO2 separation arrangement CO2 depleted outlet stream has a lower concentration of CO2 than the second partial condenser heat exchanger CO2 depleted outlet stream).

[0071] The reject gas CO2 separation arrangement receiving the second partial condenser heat exchanger CO2 depleted outlet stream may be any arrangement suitable for selective separation of CO2 from a fluid stream, such as any type of pressure swing adsorption system, systems using a solvent for selective absorption of CO2 from a fluid stream, such as a regenerative amine solvent or a physical absorption solvent, or any type of membrane separator or membrane separation system. Such CO2 separation systems are known in the art and can be implemented by the skilled person having knowledge of the present specification.

[0072] In an embodiment, the reject gas CO2 separation arrangement CO2 depleted outlet stream, from the CO2 separation arrangement receiving the second partial condenser heat exchanger CO2 depleted outlet stream, may be transferred out of the CO2 liquefaction system as the final reject gas.

[0073] In an embodiment, the method may comprise a step of obtaining a second partial condenser heat exchanger cold side feed stream by extracting at least a portion of liquid CO2 from any of the stripping column liquid sump section, the second separator and the first separator, and

[0074] - transferring the second partial condenser heat exchanger cold side feed stream to the second partial condenser heat exchanger where it is used to cool the partial condenser heat exchanger reject gas.

[0075] In an embodiment of the method, the partial condenser heat exchanger reject gas is cooled in the second partial condenser heat exchanger by heat exchange with CO2 evaporating at a pressure which is lower than the stripping column pressure but higher than the triple point pressure of CO2. In an embodiment, the method may comprise a step of: controlling the ratio between the first intermediate liquid phase and the first intermediate gas phase by allowing at least a portion of the compressor arrangement discharge stream to bypass the liquefaction inlet cooler before entering the first separator.

[0076] In a second aspect, the present invention provides a carbon dioxide liquefaction system, the system comprises a compressor arrangement, a liquefaction inlet cooler, a first separator, a rectification column, a partial condenser heat exchanger and a stripping column, wherein

[0077] - the compressor arrangement comprises a first compressor arrangement inlet for a CO2 rich stream and a compressor arrangement outlet for a compressor arrangement discharge stream;

[0078] - the liquefaction inlet cooler comprises a liquefaction inlet cooler inlet for the compressor discharge stream, and a liquefaction inlet cooler outlet for a liquefaction inlet stream;

[0079] - the first separator comprises a first separator flash stream inlet in fluid communication with the liquefaction inlet cooler outlet, a first separator liquid outlet for a first separator liquid and at least one first separator gas outlet, wherein the first separator is configured to separate a first intermediate flash stream entering the first separator flash stream inlet into a first intermediate gas phase and a first intermediate liquid phase, and the first separator gas outlet is in fluid communication with a rectification column gas inlet of the rectification column, such that at least a portion of the first intermediate gas phase will flow to the rectification column as a first reject gas during use;

[0080] - the rectification column comprises a rectification mass transfer section, the rectification column gas inlet and a rectification column liquid outlet for a recovered CO2 liquid, the rectification column being configured to receive a reflux liquid and discharge a rectification outlet gas at a level above the rectification mass transfer section, and the rectification mass transfer section is configured to provide counter current contact between the reflux liquid and the first reject gas; the partial condenser heat exchanger has a warm side configured to receive the rectification outlet gas and to discharge the reflux liquid and a partial condenser heat exchanger reject gas, and a cold side configured to receive a partial condenser heat exchanger cold side feed and to discharge a partial condenser heat exchanger cold side outflow, wherein the partial condenser heat exchanger is configured to cool the rectification outlet gas, such that a fraction of a CO2 content of the rectification outlet gas is condensed, the condensed CO2 providing the reflux liquid;

[0081] - the stripping column comprises a stripping column mass transfer section arranged between a stripping column top separation zone and a stripping column liquid sump section (i.e. the stripping column mass transfer section is arranged such that liquid in the top separation zone must pass through the stripping column mass transfer section to reach the stripping column liquid sump section), a stripping column flash stream inlet arranged in the stripping column top separation zone and being in fluid communication with the first separator liquid outlet via at least a final expansion device, a stripping column gas outlet for a stripping column recycle gas, arranged in the stripping column top separation zone and being connected to the compressor arrangement at a compressor arrangement stripping column recycle gas inlet, and a stripping column liquid CO2 product outlet, wherein the stripping column is configured to receive a final intermediate flash stream through the stripping column flash stream inlet, the final intermediate flash stream comprising a final intermediate liquid phase and a final intermediate gas phase, and wherein the stripping column mass transfer section is arranged such that noncondensable components are stripped from the final intermediate liquid phase to yield a stripped CO2 liquid being discharged to the stripping column liquid sump section, and wherein the stripping of noncondensable components from the final intermediate liquid phase is assisted by a stripping gas flowing upwards through the stripping column mass transfer section; wherein the stripping column liquid CO2 product outlet is arranged in the stripping column liquid sump section such that at least a portion of the stripped CO2 liquid may exit the system as a liquid CO2 product during use; and

[0082] - the CO2 liquefaction system comprises an arrangement for providing at least a portion of the stripped CO2 liquid as the partial condenser heat exchanger cold side feed and an arrangement for providing the partial condenser heat exchanger cold side outflow to the stripping column at a position between the stripping column liquid sump section and the stripping column mass transfer section, and wherein the stripping gas comprises a primary stripping gas provided by a gaseous portion of the partial condenser heat exchanger cold side outflow. The rectification outlet gas minus the reflux liquid provides the partial condenser heat exchanger reject gas.

[0083] The term “fluid communication” is intended to mean a connection between two features allowing a fluid to be transferred between them. The connection may e.g. comprise at least one fluid conduit.

[0084] The first separator liquid outlet is configured such that the first separator liquid will comprise the first intermediate liquid phase.

[0085] The first intermediate flash stream entering the first separator flash stream inlet is derived from the liquefaction inlet stream.

[0086] The rectification mass transfer section is configured to provide counter current contact between the reflux liquid and the first reject gas. The rectification column gas inlet and the rectification column liquid outlet are arranged below the mass transfer section. In other words, the rectification column gas inlet is arranged such that the first reject gas may enter and flow through the rectification mass transfer section from below.

[0087] The stripping column liquid CO2 product outlet may be connected to or comprise any suitable conduit arrangement allowing at least a portion of the stripped CO2 liquid to exit the system as a liquid CO2 product. The conduit arrangement may be configured to split the stripped CO2 liquid into a portion used as a partial condenser heat exchanger cold side feed and a portion being the liquid CO2 product.

[0088] The stripping column flash stream inlet may optionally be termed a stripping column top inlet.

[0089] The stripping column gas outlet may optionally be termed a stripping column top gas outlet.

[0090] In an embodiment, the carbon dioxide liquefaction system may comprise a reboiler configured to evaporate a portion of the stripped CO2 liquid to produce a secondary stripping gas forming a portion of the stripping gas during use.

[0091] In an embodiment of the carbon dioxide liquefaction system, the reboiler may be arranged in the stripping column liquid sump section, or the reboiler is arranged external to the stripping column. In an embodiment of the carbon dioxide liquefaction system, the reboiler may comprise a reboiler warm side inlet for a reboiler warm side inlet stream and a reboiler warm side outlet for a reboiler warm side outlet stream, the reboiler warm side inlet is fluidly connected between the liquefaction inlet cooler and the first separator (i.e. fluidly connected to a position between the liquefaction inlet cooler and the first separator), such that a portion of the liquefaction inlet stream constitutes the reboiler warm side inlet stream during use, and the reboiler warm side outlet is fluidly connected downstream an expansion device to a section of the carbon dioxide liquefaction system operating at a pressure lower than the pressure of the liquefaction inlet stream.

[0092] In an embodiment, the carbon dioxide liquefaction system may comprise a first expansion device arranged between the liquefaction inlet cooler and the first separator, i.e. such that the first intermediate flash stream will have a pressure lower than the liquefaction inlet stream. In other words, such that the pressure of the liquefaction inlet stream is lowered before entering the first separator as the first intermediate flash stream.

[0093] In an embodiment of the carbon dioxide liquefaction system, the first separator gas outlet, or a separate first separator recycle gas outlet of the first separator, is in fluid communication with the compressor arrangement to route at least a portion of the first intermediate gas phase to the compressor arrangement as a first recycle gas.

[0094] In an embodiment, the carbon dioxide liquefaction system may comprise one or more additional pressure reduction stages arranged between the first separator liquid outlet and the final expansion device. Each of the one or more additional pressure reduction stages may comprise an additional expansion device and an additional separator configured similar to the first expansion device and the first separator. An additional separator may provide an additional recycle gas via an additional recycle gas outlet and an additional separator liquid via an additional separator liquid outlet.

[0095] In an embodiment of the carbon dioxide liquefaction system, the first expansion device may comprise a first ejector, the first ejector comprises a first ejector motive fluid inlet, a first ejector outlet and a first ejector low-pressure suction inlet, wherein the first ejector motive fluid inlet is configured to receive the liquefaction inlet stream, the first ejector outlet is in fluid communication with the first separator flash stream inlet and the first ejector low-pressure suction inlet is in fluid communication with the stripping column gas outlet, such that at least a portion of the stripping column recycle gas may function as a first ejector suction gas.

[0096] In an embodiment, the carbon dioxide liquefaction system may comprise a second separator, wherein the second separator comprises a second separator flash stream inlet in fluid communication with the first separator liquid outlet via a second expansion device, a second separator gas outlet and a second separator liquid outlet, wherein the second separator is configured to separate a second intermediate flash stream entering the second separator flash stream inlet into a second intermediate gas phase and a second intermediate liquid phase, wherein the second separator gas outlet is in fluid communication with the compressor arrangement to route at least a portion of the second intermediate gas phase to the compressor arrangement as a second recycle gas, and the second separator liquid outlet is in fluid communication with the stripping column flash stream inlet via at least the final expansion device.

[0097] In an embodiment of the carbon dioxide liquefaction system, the one or more additional pressure reduction stages is arranged between the first separator liquid outlet and the second expansion device.

[0098] In an embodiment of the carbon dioxide liquefaction system, the first expansion device may comprise a first ejector, the first ejector comprises a first ejector motive fluid inlet, a first ejector outlet and a first ejector low-pressure suction inlet, wherein the first ejector motive fluid inlet is configured to receive the liquefaction inlet stream, the first ejector outlet is in fluid communication with the first separator flash stream inlet and the first ejector low-pressure suction inlet is in fluid communication with the second separator gas outlet or an additional recycle gas outlet, such that at least a portion of the second intermediate gas phase or at least a portion of an additional recycle gas may function as a first ejector suction gas.

[0099] In an embodiment of the carbon dioxide liquefaction system, the second expansion device may comprise a second ejector, the second ejector comprises a second ejector motive fluid inlet, a second ejector outlet and a second ejector low-pressure suction inlet, wherein the second ejector motive fluid inlet is configured to receive at least a portion of the first separator liquid, the second ejector outlet is in fluid communication with the second separator flash stream inlet, and the second ejector low-pressure suction inlet is in fluid communication with the stripping column gas outlet, such that at least a portion of the stripping column recycle gas may function as a second ejector suction gas.

[0100] In an embodiment of the carbon dioxide liquefaction system, at least one of the first expansion device, the second expansion device and the final expansion device may comprise a valve, e.g. a pressure reducing valve.

[0101] In an embodiment of the carbon dioxide liquefaction system, the rectification column and the partial condenser heat exchanger may be connected together to form a combined column condenser assembly. In an embodiment of the carbon dioxide liquefaction system, the partial condenser heat exchanger may be a vertical shell and tube type heat exchanger, mounted directly at or on the top of the rectification column, such that the rectification column and the partial condenser heat exchanger is a combined column condenser assembly.

[0102] In an embodiment of the carbon dioxide liquefaction system, the stripping column, the first separator and optionally the second separator are mechanically interconnected to form a vertical column structure wherein the stripping column is at a higher elevation than the first separator. By having the stripping column arranged at a higher level than the first separator, it may be possible to arrange the partial condenser heat exchanger such that at least a portion of the stripped CO2 liquid may be transferred to the partial condenser heat exchanger from the stripping column by gravity flow, and at the same time arrange the rectification column or combined column condenser assembly such that the recovered CO2 liquid may be transferred from the rectification column to the first separator by gravity flow. When the vertical column structure comprises the second separator, the second separator may preferably be arranged between the stripping column and the first separator.

[0103] In an embodiment of the carbon dioxide liquefaction system, the arrangement for providing the partial condenser heat exchanger cold side outflow to the stripping column comprises a first heat exchanger conduit connecting the partial condenser heat exchanger cold side outflow to the stripping column at a position between the stripping column liquid sump section and the stripping column mass transfer section, and the arrangement for providing at least a portion of the stripped CO2 liquid as the partial condenser heat exchanger cold side feed comprises a second heat exchanger conduit fluidly connecting the stripping column and the partial condenser heat exchanger cold side feed. In other words, the second heat exchanger conduit is configured to connect the stripping column and the partial condenser heat exchanger cold side, such that the partial condenser heat exchanger cold side feed is in fluid communication with the stripping column, and configured to transfer the partial condenser heat exchanger cold side feed from the stripping column to the partial condenser heat exchanger.

[0104] In other words, the first heat exchanger conduit is configured to connect a partial condenser heat exchanger cold side outflow outlet to the stripping column at a position between the stripping column liquid sump section and the stripping column mass transfer section and the second heat exchanger conduit is configured to provide fluid communication between the stripping column and a partial condenser heat exchanger cold side feed inlet. In an embodiment of the carbon dioxide liquefaction system, the partial condenser heat exchanger may be arranged in the stripping column liquid sump section of the stripping column. When the partial condenser heat exchanger is arranged in the stripping column liquid sump section, the partial condenser heat exchanger may be termed an internal partial condenser heat exchanger.

[0105] In an embodiment of the carbon dioxide liquefaction system, the arrangement for providing a portion of stripped CO2 liquid to the partial condenser heat exchanger comprises a pump, the pump being configured to transfer the portion of stripped CO2 liquid to the partial condenser heat exchanger.

[0106] In an embodiment, the carbon dioxide liquefaction system may comprise a reflux separator, the reflux separator being configured to receive a stream, the stream consisting of the reflux liquid and the partial condenser heat exchanger reject gas discharged from the partial condenser heat exchanger, via a reflux separator inlet to separate the reflux liquid and the partial condenser heat exchanger reject gas, and comprises a reflux liquid outlet, in fluid communication with the rectification column, and a partial condenser heat exchanger reject gas outlet.

[0107] In other words the reflux separator is configured to receive a stream consisting of the reflux liquid and the partial condenser heat exchanger reject gas discharged from the partial condenser heat exchanger, separate the reflux liquid and the partial condenser heat exchanger reject gas, discharge the reflux liquid to the rectification column, i.e. provide the reflux liquid above the mass transfer section of the rectification column, and discharge the partial condenser heat exchanger reject gas to a suitable recipient, when the partial condenser heat exchanger reject gas is a final reject gas, or transfer the partial condenser heat exchanger reject gas to further treatment.

[0108] In an embodiment, the system may comprise a liquefaction inlet cooler bypass arrangement configured such that a portion of the compressor arrangement discharge stream may bypass the liquefaction inlet cooler before entering the first separator. By regulating the ratio between a portion of the compressor arrangement discharge stream being cooled and a portion of the compressor arrangement discharge stream bypassing the liquefaction inlet cooler, the ratio between the first intermediate liquid phase and the first intermediate gas phase may be controlled.

[0109] In an embodiment, the system may comprise a pre-compression and pre-purification system arranged upstream of the compression arrangement. The pre-compression and pre-purification arrangement is arranged for the source of CO2 to be liquefied. The pre-compression and pre-purification arrangement may comprise compression of the source of CO2 to be liquefied. The pre-compression and pre-purification arrangement may comprise a system for removal of water from the source of CO2 to be liquefied.

[0110] In an embodiment, the carbon dioxide liquefaction system may comprise a reject gas CO2 separation arrangement, the reject gas CO2 separation arrangement is configured to receive the partial condenser heat exchanger reject gas during use, and to subject the partial condenser heat exchanger reject gas to a CO2 selective separation to obtain a reject gas CO2 separation arrangement CO2 rich outlet stream, containing at least a portion of the CO2 in the partial condenser heat exchanger reject gas, and a reject gas CO2 separation arrangement CO2 depleted outlet stream comprising non-condensable components and having a reduced content of CO2 compared to the partial condenser heat exchanger reject gas.

[0111] The reject gas CO2 separation arrangement may be any arrangement or assembly suitable for selective separation of CO2 from a fluid stream, such as any type of pressure swing adsorption system, systems using a solvent for selective absorption of CO2 from a fluid stream, such as a regenerative amine solvent, or a physical absorption solvent or any type of membrane separator or membrane separation system. Such CO2 separation systems are known in the art and can be implemented by the skilled person having knowledge of the present specification.

[0112] The reject gas CO2 separation arrangement may be configured to receive the partial condenser heat exchanger reject gas during use, by e.g. having an inlet in fluid communication with an outlet of the partial condenser heat exchanger. The fluid communication may be obtained by a suitable conduit.

[0113] The reject gas CO2 separation arrangement may comprise an inlet for the partial condenser heat exchanger reject gas, an outlet for the reject gas CO2 separation arrangement CO2 rich outlet stream and an outlet for the reject gas CO2 separation arrangement CO2 depleted outlet stream. The inlet for the partial condenser heat exchanger reject gas may be connected to an outlet of the partial condenser heat exchanger.

[0114] The outlet for the reject gas CO2 separation arrangement CO2 depleted outlet stream may provide a final reject gas to be transferred out of the CO2 liquefaction system.

[0115] In an embodiment, the carbon dioxide liquefaction system may comprise at least one conduit arranged to transfer the reject gas CO2 separation arrangement CO2 rich outlet stream to the compressor arrangement to form a portion of the compressor arrangement discharge stream. The reject gas CO2 separation arrangement CO2 rich outlet stream may be transferred directly to, or upstream of, the compressor arrangement. The reject gas CO2 separation arrangement CO2 rich outlet stream may be transferred to the compressor arrangement via the precompression and pre-purification system or a reject gas CO2 separation arrangement CO2 rich outlet stream compressor. The reject gas CO2 separation arrangement CO2 rich outlet stream compressor may be arranged to compress the reject gas CO2 separation arrangement CO2 rich outlet stream before said outlet stream enters the compressor arrangement.

[0116] In other words, the reject gas CO2 separation arrangement CO2 rich outlet stream may be recycled to the compressor arrangement to form a portion of the compressor arrangement discharge stream. The reject gas CO2 separation arrangement CO2 depleted outlet stream may be transferred out of the CO2 liquefaction system as a final reject gas.

[0117] The reject gas CO2 separation arrangement may comprise an outlet for the reject gas CO2 separation arrangement CO2 rich outlet stream and said outlet may be directly or indirectly connected to the compressor arrangement by a conduit such that the reject gas CO2 separation arrangement CO2 rich outlet stream may form a portion of the compressor arrangement discharge stream during use.

[0118] In an embodiment, the carbon dioxide liquefaction system may comprise a second partial condenser heat exchanger, the second partial condenser heat exchanger is configured to receive the partial condenser heat exchanger reject gas during use, and to cool the partial condenser heat exchanger reject gas to obtain a second partial condenser heat exchanger CO2 depleted outlet stream having a reduced content of CO2 compared to the partial condenser heat exchanger reject gas, and a second recovered liquid.

[0119] In an embodiment, the carbon dioxide liquefaction system may comprise a reflux separator (i.e. a second condenser separator being separate from the second partial condenser heat exchanger) configured to receive and separate a second partial condenser heat exchanger 2-phase outlet stream consisting of a mixture of the second partial condenser heat exchanger CO2 depleted outlet stream and the second recovered liquid, the reflux separator comprising a first outlet for the second partial condenser heat exchanger CO2 depleted outlet stream and a second outlet for the second recovered liquid.

[0120] In an embodiment, the second partial condenser heat exchanger CO2 depleted outlet stream may be transferred out of the CO2 liquefaction system as the final reject gas.

[0121] In an embodiment, the carbon dioxide liquefaction system may comprise an arrangement for transfer of the second recovered liquid to the stripping column, directly, or indirectly via any of the rectification column, the first separator and the second separator.

[0122] In an embodiment, the carbon dioxide liquefaction system may comprise a reject gas CO2 separation arrangement, the reject gas CO2 separation arrangement is configured to receive the second partial condenser heat exchanger CO2 depleted outlet stream during use, and to subject the second partial condenser heat exchanger CO2 depleted outlet stream to a CO2 selective separation to obtain a reject gas CO2 separation arrangement CO2 rich outlet stream containing at least a portion of the CO2 in the second partial condenser heat exchanger CO2 depleted outlet stream, and a reject gas CO2 separation arrangement CO2 depleted outlet stream comprising non-condensable components and having a reduced content of CO2 compared to the second partial condenser heat exchanger CO2 depleted outlet stream.

[0123] The reject gas CO2 separation arrangement may comprise an inlet for the second partial condenser heat exchanger CO2 depleted outlet stream, an outlet for the reject gas CO2 separation arrangement CO2 rich outlet stream and an outlet for the reject gas CO2 separation arrangement CO2 depleted outlet stream. The inlet for the second partial condenser heat exchanger CO2 depleted outlet stream may be connected to an outlet of the second partial condenser heat exchanger. The outlet for the reject gas CO2 separation arrangement CO2 depleted outlet stream may provide a final reject gas to be transferred out of the CO2 liquefaction system.

[0124] The reject gas CO2 separation arrangement configured to receive the second partial condenser heat exchanger CO2 depleted outlet stream may be similar to the CO2 separation arrangement configured to receive a partial condenser heat exchanger CO2 depleted outlet stream as described above and may comprise corresponding features for recycling the reject gas CO2 separation arrangement CO2 rich outlet stream, derived from the second partial condenser heat exchanger CO2 depleted outlet stream, to the compressor arrangement to form a portion of the compressor arrangement discharge stream.

[0125] In an embodiment of the carbon dioxide liquefaction system, the rectification column and the first separator may be a combined separator and column device in which the rectification mass transfer section is arranged at a level above the first separator flash stream inlet and the first separator liquid outlet, and a lower end of the rectification mass transfer section provides the rectification column gas inlet and the first separator gas outlet. The combined separator and column device features a single vessel in which the rectification column and the first separator are arranged. In an embodiment, the carbon dioxide liquefaction system may comprise a regasification unit arranged to receive at least parts of the liquid CO2 product, and configured to transform the received liquid CO2 product to a gaseous CO2 product which is in a sub critical gas phase or a supercritical dense gas phase.

[0126] In an embodiment of the carbon dioxide liquefaction system, the regasification unit may comprise an arrangement for heat exchange with any of the liquefaction inlet stream, the first intermediate flash stream, the first separator liquid, the second intermediate flash stream and the second separator liquid. The arrangement for heat exchange may provide heat to the received liquid CO2 product and may comprise at least one liquid CO2 product heat exchanger wherein the received liquid CO2 product is the cold side flow, and the warm side flow is provided by at least a part of any suitable stream of the liquefaction system.

[0127] In an embodiment of the carbon dioxide liquefaction system, the stripping column may comprise two separate pressure vessels; a first pressure vessel comprising the stripping column mass transfer section and a second pressure vessel comprising the stripping column liquid sump section, the first pressure vessel and the second pressure vessel may be connected via a stripped CO2 liquid conduit and a stripping gas conduit.

[0128] The inventive CO2 liquefaction system may comprise a control system to ensure optimal efficiency and performance. The control system may comprise a logic controller communicating with any required sensors, such as temperature sensors, pressure sensors and level sensors, as well as actuators configured to e.g. control any required control valve based on data received from said sensors. The detailed configuration of a suitable control system may easily be conceived by the skilled person having knowledge of the present specification and the common general knowledge within the field of process control systems.

[0129] In embodiments of the first and second aspect of the invention, the CO2 rich stream to be liquefied may consist of at least 50%, at least 70% or at least 90% CO2 in mixture with non-CO2 components, wherein at least a portion of the non-CO2 components are non-condensable components.

[0130] In embodiments of the first and second aspect of the invention, the CO2 rich stream may consist of more than 98 mol% CO2.

[0131] In embodiments of the first and second aspect of the invention, the CO2 rich stream may contain less than 2 mol% non-condensable components. In embodiments of the first and second aspect of the invention, water has been removed from the CO2 rich stream to be liquefied such that the CO2 rich stream is a dry CO2 rich stream.

[0132] The CO2 rich stream may optionally be termed a stream of CO2.

[0133] The dry CO2 rich stream may optionally be termed a stream of dry CO2.

[0134] Description of the drawings

[0135] Embodiments of the invention is described in detail by reference to the following drawings:

[0136] Fig. la is a schematic drawing of an exemplary carbon dioxide liquefaction system according to the invention.

[0137] Fig. lb is a schematic drawing of an exemplary carbon dioxide liquefaction system according to the invention.

[0138] Fig. 1c is a schematic drawing of an exemplary carbon dioxide liquefaction system according to the invention.

[0139] Fig. 2 is a schematic drawing of an exemplary carbon dioxide liquefaction system according to the invention.

[0140] Fig. 3 is a schematic drawing of an exemplary carbon dioxide liquefaction system according to the invention.

[0141] Fig. 4a is a schematic drawing of an exemplary carbon dioxide liquefaction system according to the invention.

[0142] Fig. 4b is a schematic drawing of an exemplary carbon dioxide liquefaction system according to the invention.

[0143] Fig. 4c is a schematic drawing of an exemplary carbon dioxide liquefaction system according to the invention.

[0144] Fig. 4d is a schematic drawing of an exemplary carbon dioxide liquefaction system according to the invention. Figs. 5a-5e are schematic drawings of alternative configurations of the stripping column, the rectification column and the partial condenser heat exchanger, for use in embodiments of the carbon dioxide liquefaction system according to the invention.

[0145] Figs. 5f and 5g are schematic drawings of alternative configurations of the stripping column, for use in embodiments of the carbon dioxide liquefaction system according to the invention.

[0146] Figs. 6a-6d are schematic drawings of alternative configurations of the stripping column, the rectification column and the partial condenser heat exchanger, wherein the partial condenser heat exchanger is arranged within the stripping column.

[0147] Figs. 7a and 7b are schematic drawings of an exemplary carbon dioxide liquefaction system according to the invention, featuring a configuration as shown in fig. 5e.

[0148] Figs. 8a and 8b are schematic drawings of alternative configurations of the stripping column, the first separator and an optional second separator, wherein said elements are interconnected to form a vertical column structure.

[0149] Fig. 9a is a schematic drawing of an alternative configuration of the stripping column, the first separator and an optional second separator, wherein said elements are interconnected to form a vertical column structure and wherein the partial condenser heat exchanger is arranged within the stripping column.

[0150] Fig. 9b and 9c are schematic drawings of alternative configurations of the stripping column, the first separator and an optional second separator, wherein said elements are interconnected to form a vertical column structure and wherein the partial condenser heat exchanger is arranged within the stripping column and the rectification column is integrated with the first separator.

[0151] Figs. 10a and 10b are schematic drawings of exemplary carbon dioxide liquefaction systems according to the invention, featuring a reject gas CO2 separation arrangement.

[0152] Figs. 1 la-1 Id are schematic drawings of exemplary carbon dioxide liquefaction systems according to the invention, featuring a second partial condenser heat exchanger.

[0153] Fig. 12 is a schematic drawing of a section of an exemplary carbon dioxide liquefaction system according to the invention, featuring a second partial condenser heat exchanger and a reject gas CO2 separation arrangement.

[0154] Fig. 13 is a schematic drawing of a section of an exemplary carbon dioxide liquefaction system according to the invention, featuring a first additional expansion device and a first additional separator. Detailed description of embodiments of the invention

[0155] As described above, there is a need for energy efficient processes and systems for the liquefaction of carbon dioxide (CO2).

[0156] The present invention provides a CO2 liquefaction system and a process for liquefaction of a CO2 rich stream 1, see e.g. figs, la and 7a / 7b.

[0157] The CO2 rich stream 1 to be liquefied by the inventive CO2 liquefaction system consists of at least 50% CO2 in mixture with non-CO2 components, wherein at least a portion of the non-CO2 components are non-condensable components.

[0158] The process for liquefaction of the CO2 rich stream 1 produces a liquid CO2 product 5 and a final reject gas 3.

[0159] The liquid CO2 product 5 is saturated (at its boiling point) at a liquid CO2 product pressure above the triple point of CO2, and a liquid CO2 product temperature corresponding to the saturation temperature of the liquid CO2 product 5. In a preferred embodiment, the liquid CO2 product pressure is lower than 25 bar absolute pressure. In a more preferred embodiment, the liquid CO2 product pressure is between 6 bar absolute pressure and 20 bar absolute pressure. The final reject gas 3 includes a major part of the non-condensable components.

[0160] The liquid CO2 product 5 is typically sent to a liquid CO2 storage 150 or transportation device, directly or by using a transfer pump.

[0161] The source of carbon dioxide to be liquefied in the inventive CO2 liquefaction system will normally have to undergo well-known steps of pre-compression from typically a near atmospheric pressure, and any number of optional steps of prepurification, to obtain the CO2 rich stream 1. In a preferred embodiment, water has been removed from the CO2 rich stream 1 to be liquefied such that the CO2 rich stream is dry. In order to obtain the pre-compression and the optional steps of prepurification, a pre-compression and pre-purification system 145 can be arranged upstream the compressor arrangement 100, fig. lb.

[0162] In a preferred embodiment, the CO2 rich stream 1 has a CO2 rich stream pressure which is equal to or higher than the liquid CO2 product pressure. The CO2 rich stream 1 is introduced to the CO2 liquefaction system via a first compressor arrangement inlet 100-1 of a compressor arrangement 100 and is compressed to a compressor arrangement discharge pressure, such that the CO2 rich stream 1 makes up at least a portion of a compressor arrangement discharge stream 2 exiting a compressor arrangement outlet 100-5 at the compressor arrangement discharge pressure. The compressor arrangement discharge stream 2 is cooled to a liquefaction inlet temperature in a liquefaction inlet cooler 131. The resulting stream exiting the liquefaction inlet cooler 131 is a liquefaction inlet stream 10, having a liquefaction inlet pressure essentially equal to the compressor arrangement discharge pressure. The liquefaction inlet stream 10 must be dry (a dry liquefaction inlet stream, the meaning of dry is described in the section for definition of terminology). This implies that if the CO2 rich stream 1 is not dry, or any other streams entering the CO2 liquefaction system and the process for liquefaction of a stream of CO2 are not dry, water removal from one or more of the streams making up the compressor arrangement discharge stream 2, water removal from the compressor arrangement discharge stream 2, or water removal from the liquefaction inlet stream 10, may be required. The location and method for removing water from any of the streams making up the liquefaction inlet stream 10 may be selected as required. Any suitable method known in the art for removal of water from a fluid stream can be used without any inventive effort by the skilled person. Hence, no details related to any water removal is disclosed. For the further description of the CO2 liquefaction system and the process for liquefaction of a stream of CO2, it is assumed that the CO2 rich stream 1 and any other streams entering the process / system are dry.

[0163] If the pressure of the CO2 rich stream 1 is equal to or higher than the compressor arrangement discharge pressure, compression of the CO2 rich stream 1 is not required and it may be directly mixed with the compressor arrangement discharge stream 2 to form a portion of said stream.

[0164] The cooling in the liquefaction inlet cooler 131 can be provided by any available ambient cooling medium, as known in the art, including but not limited to ambient air, evaporative air cooling, direct or indirect cooling by ambient water (seawater or fresh water), geothermal cooling. The cooling in the liquefaction inlet cooler 131 can optionally be provided by any type of refrigeration work cycle as known in the art. This includes but is not limited to, direct or indirect mechanical refrigeration in single or multiple stages, and absorption cooling. The cooling in the liquefaction inlet cooler 131 can also be provided by a combination of using ambient cooling and refrigeration. Optionally, the cooling in the liquefaction inlet cooler 131 can comprise heat exchange with one or more recycle streams in the CO2 liquefaction system, as described herein below.

[0165] The liquefaction inlet stream 10 is routed to a first separator 101 and introduced to the first separator 101, via a first separator flash stream inlet 101-1, as a first intermediate flash stream 12 consisting of a first intermediate liquid phase 12a and a first intermediate gas phase 12b, which are essentially in thermodynamic equilibrium. The first separator 101 operates at a first separator pressure which is equal to or lower than the liquefaction inlet pressure, and higher than the liquid CO2 product pressure. If the first separator pressure is lower than the liquefaction inlet pressure, the liquefaction inlet stream 10 is subjected to a first pressure reduction in a first expansion device 110 from the liquefaction inlet pressure to the first separator pressure, wherein the first expansion device 110 yields the first intermediate flash stream 12. The selection of the first separator pressure is a matter of process optimisations and is dependent on the liquefaction inlet temperature and the liquefaction inlet pressure.

[0166] In the exemplary liquefaction system illustrated in fig. la, the liquefaction inlet stream 10 is subjected to the first pressure reduction in the first expansion device 110 from the liquefaction inlet pressure to the first separator pressure which is lower than the liquefaction inlet pressure and higher than the liquid CO2 product pressure, yielding the first intermediate flash stream 12. The first pressure reduction results in a temperature reduction of the fluid, and that the first intermediate flash stream 12 consists of the first intermediate liquid phase 12a and the first intermediate gas phase 12b, which are essentially in thermodynamic equilibrium.

[0167] In an alternative embodiment of the invention when the compressor arrangement discharge stream 2 is cooled to a liquefaction inlet temperature which enables phase separation at the liquefaction inlet pressure, the liquefaction inlet stream 10 can become the first intermediate flash stream 12 without any substantial pressure reduction, and the first separator pressure is essentially equal to the liquefaction inlet pressure. In the alternative embodiment, any pressure reduction of the liquefaction inlet stream 10 is caused by the flow through a conduit / pipe arranged between the liquefaction inlet cooler 131 and the first separator 101.

[0168] The first intermediate liquid phase 12a and the first intermediate gas phase 12b are separated in the first separator 101 operating at the first separator pressure and a first separator temperature. The first intermediate gas phase 12b comprises CO2 and non-condensable components. At least a portion of the first intermediate gas phase 12b is extracted (split) as a first reject gas 31 via a first separator gas outlet 101-3, while an optional portion of the first intermediate gas phase is a first recycle gas 14 exiting the first separator 101 via an optional first separator recycle gas outlet 101- 2. The first separator gas outlet 101-3 and the first separator recycle gas outlet 101-2 may form a common gas outlet in the first separator 101, wherein the recycle gas 14 and the first reject gas 31 are split downstream of the first separator 101, see fig. la, or the gas outlets may be two separate outlets of the first separator 101, see fig. lb.

[0169] The portion of the first intermediate gas phase 12b which is the first reject gas 31 can comprise 100% of the first intermediate gas phase 12b, such that the first recycle gas 14 is zero. In such case the first recycle gas 14 is non-existent in the configuration of the invention. In embodiments where the first reject gas 31 is lower than 100% of the first intermediate gas phase 12b, the first recycle gas 14 can comprise all of the first intermediate gas phase 12b which is not extracted as the first reject gas 31. The amount of first intermediate gas phase 12b that is extracted (split) as the first reject gas 31 is a matter of process design options and optimisation, and will depend on various process parameters, including but not limited to the amount of non-condensable components in the CO2 rich stream 1 which is fed into the compressor arrangement 100 and becoming a part of the liquefaction inlet stream 10. In the alternative embodiment of the invention when the liquefaction inlet stream 10 can become the first intermediate flash stream 12 without substantial pressure reduction, and the first separator pressure is essentially equal to the liquefaction inlet pressure, the first reject gas 31 will be 100% of the first intermediate gas phase 12b, and the first recycle gas 14 is not present.

[0170] As described above, the split of the first intermediate gas phase 12b into the first recycle gas 14 and the first reject gas 31 can be done inside the first separator 101, resulting in the first recycle gas 14 and the first reject gas 31 flowing out of the first separator 101 as separate streams, or by letting the first intermediate gas phase 12b become a first intermediate gas stream 12c flowing out of the first separator 101, and thereafter splitting the first intermediate gas stream 12c into the first recycle gas 14 and the first reject stream 31. The former alternative is shown in figures lb, 1c, and 7b. These two alternatives may be regarded as equivalent.

[0171] The first recycle gas 14 flows to the compressor arrangement 100 and is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream 2 and the liquefaction inlet stream 10.

[0172] In the exemplary liquefaction system illustrated in fig. la, the first intermediate liquid phase 12a is mixed with a recovered CO2 liquid 35,35a which is introduced to the first separator 101 via a first separator recovered liquid inlet 101-5, for mixing with the first intermediate liquid phase 12a. The first intermediate liquid phase 12a, and any recovered CO2 liquid 35, 35a, is termed a first separator liquid 13. The first separator liquid 13, 13a is directed to a stripping column top separation zone 103a of a stripping column 103 operating at a stripping column pressure which is essentially equal to the liquid CO2 product pressure, by subjecting the first separator liquid 13 to a pressure reduction from the first separator pressure to the stripping column pressure.

[0173] In the exemplary liquefaction system illustrated in fig. la, the first separator liquid 13 is subjected to the pressure reduction from the first separator pressure to the stripping column pressure by leading the first separator liquid 13,13a to a final pressure reduction in a final expansion device 112, yielding a final intermediate flash stream 20. The final intermediate flash stream 20 is introduced to the stripping column 103 via a stripping column flash stream inlet 103-1.

[0174] In an alternative embodiment of the inventive liquefaction system, the first separator liquid 13 is subjected to the pressure reduction from the first separator pressure to the stripping column pressure in two or more pressure reduction stages. The following describes an embodiment of the invention where the first separator liquid 13 is subjected to the pressure reduction from the first separator pressure to the stripping column pressure in two pressure reduction stages, see figs, lb, 1c, 2, 3, 4b and 7a / 7b, however additional pressure reduction stages can be arranged equivalently. The first separator liquid 13,13b is led to a second pressure reduction in a second expansion device 111 from the first separator pressure to a second separator pressure which is lower than the first separator pressure and higher than the stripping column pressure, yielding a second intermediate flash stream 17. The second pressure reduction resulting in a temperature reduction of the fluid and further resulting in that the second intermediate flash stream 17 consists of a second intermediate liquid phase 17a and a second intermediate gas phase 17b, which are essentially in thermodynamic equilibrium. The second intermediate flash stream 17 enters a second separator 102 via a second separator flash stream inlet 102-1.

[0175] The second intermediate liquid phase 17a and the second intermediate gas phase 17b are separated in the second separator 102 operating at the second separator pressure and a second separator temperature. The separation of the second intermediate liquid phase 17a and the second intermediate gas phase 17b yields a second separator liquid 18 and a second recycle gas 19, respectively. The second recycle gas 19 consisting of CO2 and non-condensable components, flows to the compressor arrangement 100 via a second separator gas outlet 102-3 and is recompressed to the liquefaction inlet pressure to form a portion of the compressor arrangement discharge stream 2 and the liquefaction inlet stream 10. The second separator liquid 18 is led to the final expansion device 112 via a second separator liquid outlet 102-2, wherein the pressure is reduced from the second separator pressure to the stripping column pressure, to yield the final intermediate flash stream 20 introduced to the stripping column 103.

[0176] In alternative embodiments of the invention, the first separator liquid 13 may be subjected to the pressure reduction from the first separator pressure to the stripping column pressure in more than two pressure reduction stages, additional pressure reduction stages for the first separator liquid 13 can be arranged between the first separator 101 and the second expansion device 111. Any optional additional separators configured between the first separator 101 and the second expansion device 111 are herein defined as a first additional separator 162, a second additional separator, etc, collectively defined as additional separator. Corresponding additional pressure reductions between the first separator 101 and the first additional separator, and between further additional separators are a first additional pressure reduction, a second additional pressure reduction, etc., collectively defined as additional pressure reductions. The required devices for the respective additional pressure reductions are a first additional expansion device 161, a second additional expansion device, etc., collectively defined as additional expansion device. Any optional additional separator liquids resulting from additional separators are herein defined as a first additional liquid 66, a second additional liquid, etc., collectively defined as additional liquids (i.e. additional liquid streams). Any optional additional separator gas streams resulting from additional separators are herein defined as a first additional recycle gas 67, a second additional recycle gas, etc, collectively defined as additional recycle gases (i.e. additional gas streams). Any optional outlet streams from additional expansion devices are herein defined as a first additional intermediate flash stream 65, a second additional intermediate flash stream, etc., collectively defined as additional intermediate flash streams, and where the additional intermediate flash stream is the inlet streams to the respective additional separator. According to these alternative embodiments, the first separator liquid 13 is led to the first additional expansion device 161, resulting in the first additional intermediate flash stream 65 which is led to the first additional separator 162 to be separated into the first additional recycle gas 67 and the first additional liquid 66, the first additional liquid is thereafter led to the second expansion device 111, optionally via further additional expansion devices and additional separators. The first additional recycle gas 67 and any further additional recycle gases are led to the compressor arrangement 100 and recompressed to the liquefaction inlet pressure to form a portion of the compressor arrangement discharge stream 2.

[0177] For any of the alternatives which are described for the pressure reduction of the first separator liquid 13 from the first separator pressure to the stripping column pressure, the final pressure reduction to the stripping column pressure results in a temperature reduction of the fluid, and further resulting that the final intermediate flash stream 20 consists of a final intermediate liquid phase 20a and a final intermediate gas phase 20b, which are essentially in thermodynamic equilibrium. The final intermediate liquid phase 20a and the final intermediate gas phase 20b are separated in a stripping column top separation zone 103a.

[0178] In the stripping column top separation zone 103a, the final intermediate gas phase 20b mixes with a stripping column outlet stripping gas 24e, forming a stripping column recycle gas 22, see e.g. fig. 5a. The stripping column recycle gas 22 comprising CO2 and non-condensable components exits the stripping column 103 via a stripping column gas outlet 103-3 and is routed to the compressor arrangement 100 and is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream 2 and the liquefaction inlet stream 10. After entering the stripping column top separation zone 103a, the final intermediate liquid phase 20a flows downwards through a stripping column mass transfer section 103b arranged inside the stripping column 103, see e.g. fig. 5a. In the stripping column mass transfer section 103b, non-condensable components are stripped from the final intermediate liquid phase 20a, yielding a stripped CO2 liquid 21. The stripping of non-condensable components from the final intermediate liquid phase 20a is assisted by a stripping gas 24d flowing upwards through the stripping column mass transfer section 103b. The stripping gas 24d is comprising a primary stripping gas 24a and an optional secondary stripping gas 24c. The stripped CO2 liquid 21 has a stripped CO2 liquid temperature substantially equal to the saturation temperature of liquid CO2 at the stripping column pressure. The stripped CO2 liquid 21 consists essentially of CO2; however, traces of non-condensable components and water may be present. The stripped CO2 liquid 21 flows to a stripping column liquid sump section 103c in the bottom of the stripping column 103. The stripped CO2 liquid 21 in the stripping column liquid sump section 103c has a stripping column liquid sump section temperature substantially equal to the saturation temperature of liquid CO2 at the stripping column pressure. The stripping column 103 features a stripping column liquid CO2 product outlet 103-2, and an optional stripping column heat exchange outlet 103-4, for transferring stripped CO2 liquid 21 from the stripping column liquid sump section 103c. At least a portion of the stripped CO2 liquid 21 will be a liquid CO2 product 5.

[0179] The stripping column outlet stripping gas 24e consists of the stripping gas 24d plus any stripped non-condensable components plus the net amount of CO2 evaporating in the stripping column mass transfer section 103b (evaporated CO2 minus condensed CO2 in the stripping column mass transfer section 103b).

[0180] The first reject gas 31 consisting of CO2 and non-condensable components is introduced as a bottom gaseous feed to a rectification column 104 via a rectification column gas inlet 104-1. The rectification column gas inlet 104-1 arranged below a rectification mass transfer section 104a of the rectification column 104. The rectification column 104 with the rectification mass transfer section 104a may be arranged as a separate unit or be a part of an assembly in combination with other units (e.g. combined with the first separator), as described for alternative embodiments herein below. The functionality of the rectification column and the rectification mass transfer section 104a are the same for all embodiments of the invention. The first reject gas 31 has a first reject gas temperature which is essentially equal to the first separator temperature. In the rectification mass transfer section 104a, the first reject gas 31 is in counter current contact with a reflux liquid 34 having a reflux liquid temperature being colder than the first reject gas temperature. The reflux liquid 34 is introduced in the upper part of the rectification column 104, at a level / elevation above the rectification mass transfer section 104a, such that the reflux liquid 34 is flowing from the top of the rectification mass transfer section 104a towards the bottom of the rectification mass transfer section 104a. In the rectification mass transfer section 104a, the first reject gas 31 is subjected to a temperature reduction to a rectification outlet temperature which is lower than the first reject gas temperature but equal to or higher than the reflux liquid temperature. The temperature reduction for the first reject gas 31 causes condensation of a fraction of the CO2 content of the first reject gas 31. A fraction of the reflux liquid 34 is simultaneously evaporated, however the result is a rectification outlet gas 32 having a reduced concentration of CO2 compared to the first reject gas 31. CO2 which is condensed in the rectification mass transfer section 104a is mixed with the non-evaporated fraction of the reflux liquid 34, such that the condensed CO2 plus the non-evaporated fraction of the reflux liquid 34 provides the recovered CO2 liquid 35. The recovered CO2 liquid 35 flows out of the bottom of the rectification mass transfer section 104a, and thereafter out of the rectification column 104 via a rectification column liquid outlet 104-2 in the bottom of the rectification column 104 and is routed to the stripping column 103, directly or indirectly, via one or more pressure reduction stages.

[0181] The rectification outlet gas 32, comprising CO2 and non-condensable components, and having a rectification outlet temperature, flows / is discharged from the rectification column 104 at the level / elevation above the rectification mass transfer section 104a, and is introduced as a warm side feed to a partial condenser heat exchanger 105. The rectification outlet gas 32 is cooled in the partial condenser heat exchanger 105 to a partial condenser heat exchanger outlet temperature which is lower than the rectification outlet temperature but higher or equal to the stripping column liquid sump section temperature. The cooling of the rectification outlet gas 32 in the partial condenser heat exchanger 105 causes a fraction of the CO2 content of the rectification outlet gas 32 to become condensed. CO2 which is condensed in the partial condenser heat exchanger 105 is separated from the rectification outlet gas 32, providing the reflux liquid 34. The rectification outlet gas 32 minus the fraction of condensed CO2 constitutes a partial condenser heat exchanger reject gas 3a. The reflux liquid 34 is routed (recycled) to the rectification column 104.

[0182] The separation of CO2 which is condensed in the partial condenser heat exchanger 105 from the rectification outlet gas 32 can be done inside the partial condenser heat exchanger 105 by any method known in the art, for example by applying a heat transfer surface which separates and drains condensed CO2 liquid “in situ” from the rectification outlet gas 32 as it is being cooled down, where the separated and drained condensed CO2 liquid flows in counter current direction relative to the rectification outlet gas 32. The heat transfer surface may for example be provided by applying a coil or a finned tube assembly, see e.g. figs. 5a and 5d, or by applying a vertical shell and tube heat exchanger, see e.g. fig. 5e. Alternatively, the partial condenser heat exchanger 105 can have an integrated separation arrangement for separation of condensed liquid from the rectification outlet gas 32, where the separated CO2 liquid provides the reflux liquid 34, the reflux liquid 34 being routed back to the rectification column 104. In these embodiments, the partial condenser heat exchanger reject gas 3a leaves the warm side of the partial condenser heat exchanger 105 via a partial condenser heat exchanger outlet 105-1.

[0183] In an alternative embodiment of the invention, a reflux separator 109 which is separate to the partial condenser heat exchanger 105 is arranged for separation of a partial condenser heat exchanger 2-phase outlet stream 33a into the partial condenser heat exchanger reject gas 3a and the reflux liquid 34, which is routed to the rectification column 104, see figs. 5c and 6b. For this embodiment, the partial condenser heat exchanger reject gas 3a is led out via a reflux separator gas outlet 109- 2 of the optional reflux separator 109.

[0184] For all embodiments of the invention, the rectification column 104 is configured to receive the reflux liquid 34 and discharge the rectification outlet gas 32, and the partial condenser heat exchanger 105 is configured to receive the rectification outlet gas 32 and discharge the reflux liquid 34 and the partial condenser heat exchanger reject gas 3a as separate streams or as a mixed (2-phase) stream for separation downstream.

[0185] The specific configuration of the rectification column 104 and the partial condenser heat exchanger 105, and the optional reflux separator 109, may vary in the different embodiments of the inventive CO2 liquefaction system while having the same function and operating principle as disclosed above.

[0186] The rectification column 104 and the partial condenser heat exchanger 105 can e.g. be connected together such that the rectification column 104 and the partial condenser heat exchanger 105 appear as a combined column condenser assembly 107, where the rectification outlet gas 32 and the reflux liquid 34 are streams internal in the combined column condenser assembly 107, see e.g. figs. 5d and 5e.

[0187] In an advantageous embodiment of the invention, the partial condenser heat exchanger 105 is a shell and tube type heat exchanger, as known in the art, configured vertically and mounted directly at the top of the rectification column 104, see e.g. fig. 5e, such that the rectification column 104 and the partial condenser heat exchanger 105 provide the combined column condenser assembly 107.

[0188] Some of the alternatives for routing of the reflux liquid 34 to the rectification column 104 may require the use of one or more valves for the purpose of process control, the detailed configuration of such valves for process control may easily be conceived by the skilled person having knowledge of the present specification and the common general knowledge within the field of process control.

[0189] The partial condenser heat exchanger reject gas 3a has a reduced concentration of CO2, compared to the rectification outlet gas 32. The partial condenser heat exchanger reject gas 3a has a partial condenser heat exchanger outlet pressure which is essentially equal to the first separator pressure and has the partial condenser heat exchanger outlet temperature.

[0190] The partial condenser heat exchanger reject gas 3a contains a major part of the noncondensable components from the CO2 rich stream 1, in mixture with an amount of CO2 which is not condensed in the partial condenser heat exchanger 105. The amount of CO2 in mixture with non-condensable components in the partial condenser heat exchanger reject gas 3a is essentially equal to the concentration of CO2 in thermodynamic equilibrium with the non-condensable components of the partial condenser heat exchanger reject gas 3a, at the partial condenser heat exchanger outlet temperature and partial condenser heat exchanger outlet pressure.

[0191] In the basic embodiment of the invention, the partial condenser heat exchanger reject gas 3a is transferred out of the CO2 liquefaction system without further treatment as the final reject gas 3. I.e. in the basic embodiment of the invention, the partial condenser heat exchanger reject gas 3a is transferred out of the CO2 liquefaction system directly, such that the partial condenser heat exchanger reject gas 3a is the final reject gas 3.

[0192] In an alternative embodiment of the invention, see figs. 10a, 10b, the partial condenser heat exchanger reject gas 3a is subjected to a CO2 selective separation in a reject gas CO2 separation arrangement 141 to obtain a reject gas CO2 separation arrangement CO2 rich outlet stream 4, containing at least a portion of the CO2 in the partial condenser heat exchanger reject gas 3a, and a reject gas CO2 separation arrangement CO2 depleted outlet stream 3e comprising non-condensable components and having a reduced content of CO2 compared to the partial condenser heat exchanger reject gas 3a. In this embodiment, the partial condenser heat exchanger reject gas 3a is introduced to the reject gas CO2 separation arrangement 141 as a reject gas CO2 separation arrangement feed stream 3d. In the reject gas CO2 separation arrangement 141, the reject gas CO2 separation arrangement feed stream 3d is subjected to a CO2 selective separation, resulting in the reject gas CO2 separation arrangement CO2 rich outlet stream 4 which contains at least a portion of the CO2 in the reject gas CO2 separation arrangement feed stream 3d, and the reject gas CO2 separation arrangement CO2 depleted outlet stream 3e comprising non- condensable components and having a reduced content of CO2 compared to the reject gas CO2 separation arrangement feed stream 3d and the partial condenser heat exchanger reject gas 3a. The reject gas CO2 separation arrangement 141 can be any type of separation system which enables a selective separation of CO2 from non-condensable components, as known in the art. For example, the reject gas CO2 separation arrangement 141 can be any type of pressure swing adsorption system, as known in the art, which enables selective adsorption of CO2 from the reject gas CO2 separation arrangement feed stream 3d. In another example, the reject gas CO2 separation arrangement 141 can be a system using a solvent for selective absorption of CO2 from the reject gas CO2 separation arrangement feed stream 3d, such as a regenerative amine solvent, or a physical absorption solvent, as known in the art. In a preferred embodiment, the reject gas CO2 separation arrangement 141 is any type of membrane separator or membrane separation system, as known in the art, which enables selective separation of CO2 from the reject gas CO2 separation arrangement feed stream 3d. The reject gas CO2 separation arrangement 141 may comprise a step of heating of the reject gas CO2 separation arrangement feed stream 3d, using any type of heating as known in the art. The reject gas CO2 separation arrangement CO2 rich outlet stream 4 has a reject gas CO2 separation arrangement CO2 rich outlet stream pressure which is lower than the partial condenser heat exchanger outlet pressure. The reject gas CO2 separation arrangement CO2 rich outlet stream 4 is either recycled to the CO2 liquefaction system (4a, 4b, 4c, 4d, fig. 10a) or transferred out of the CO2 liquefaction system (4e, fig. 10a). The choice of recycling is a matter of process optimisation and is dependent on the reject gas CO2 separation arrangement CO2 rich outlet stream pressure. In a preferred embodiment, the reject gas CO2 separation arrangement CO2 rich outlet stream 4 is transferred to the compressor arrangement 100, such that the reject gas CO2 separation arrangement CO2 rich outlet stream 4 is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream 2 and the liquefaction inlet stream 10. The transferring of the reject gas CO2 separation arrangement CO2 rich outlet stream 4 to the compressor arrangement 100 can be directly to the compressor arrangement 100 (4a), or indirectly to the compressor arrangement 100 via any of the following routes: compressing the reject gas CO2 separation arrangement CO2 rich outlet stream 4, 4b using a reject gas CO2 separation arrangement CO2 rich outlet stream compressor 142, or mixing the reject gas CO2 separation arrangement CO2 rich outlet stream 4, 4c with the CO2 rich stream 1 such that the reject gas CO2 separation arrangement CO2 rich outlet stream 4, 4c forms a portion of the CO2 rich stream 1, or transferring the reject gas CO2 separation arrangement CO2 rich outlet stream 4, 4d to the pre-compression and pre-purification system 145. In an advantageous embodiment, the reject gas CO2 separation arrangement CO2 rich outlet stream pressure is lower than the CO2 rich stream pressure, and the reject gas CO2 separation arrangement CO2 rich outlet stream 4, 4d is transferred to the compressor arrangement 100 via the precompression and pre-purification system 145, fig. 10b. The reject gas CO2 separation arrangement CO2 depleted outlet stream 3e is transferred out of the CO2 liquefaction system as the final reject gas 3. I.e. in this embodiment the reject gas CO2 separation arrangement CO2 depleted outlet stream 3e is transferred out of the CO2 liquefaction system such that the reject gas CO2 separation arrangement CO2 depleted outlet stream 3e is the final reject gas 3.

[0193] In another alternative embodiment of the invention, fig. I la, the partial condenser heat exchanger reject gas 3a is transferred to a second partial condenser heat exchanger 106 to obtain a second partial condenser heat exchanger CO2 depleted outlet stream 3b having a reduced content of CO2 compared to the partial condenser heat exchanger reject gas 3a, and a second recovered liquid 36. The partial condenser heat exchanger reject gas 3a is introduced as a warm side feed to the second partial condenser heat exchanger 106 where the partial condenser heat exchanger reject gas is cooled to a second partial condenser heat exchanger outlet temperature which is lower than the partial condenser heat exchanger outlet temperature. The cooling of the partial condenser heat exchanger reject gas 3 a in the second partial condenser heat exchanger 106 causes a fraction of the CO2 content of the partial condenser heat exchanger reject gas 3a to become condensed. CO2 which is condensed in the second partial condenser heat exchanger 106 is separated from the partial condenser heat exchanger reject gas 3a, providing the second recovered liquid 36. The partial condenser heat exchanger reject gas 3a minus the second recovered liquid 36 constitutes the second partial condenser heat exchanger CO2 depleted outlet stream 3b. The second recovered liquid 36 is transferred to the stripping column 103. The transfer can be directly to the stripping column (36a, this route will require a pressure reduction for the second recovered liquid 36, 36a, e.g. by use of a valve) or indirectly to the stripping column via any of the following routes: via rectification column 104 (36b), or via first separator 101 (e.g. 36d or 36e), or via the second separator 102 (36c, this route will require a pressure reduction, e.g. by use of a valve). In an advantageous embodiment, the transfer of the second recovered liquid 36 to the stripping column 103 is via the rectification column 104, in that the second recovered liquid 36, 36b is mixed with the reflux liquid 34 such that the second recovered liquid 36, 36b becomes a portion of the reflux liquid which is introduced to the rectification column 104, fig. 11c. In another advantageous embodiment, the transfer of the second recovered liquid 36 to the stripping column 103 is via the first separator 101, either directly (as stream 36d), or by mixing the second recovered liquid with the first intermediate flash stream 12, or by mixing the second recovered liquid 36, 36e with the recovered CO2 liquid 35, 35a such that the second recovered liquid 36, 36b becomes a portion of the recovered CO2 liquid 35,35a, which is introduced to the first separator 101 or to the first intermediate flash stream 12, see fig. l id. Routing the second recovered liquid 36 directly to the first separator liquid 13 is also possible according to the method. In any of the embodiments for routing the second recovered liquid 36 to the first separator 101 or rectification column 104, the use of one or more valve for the purpose of process control may be required, the detailed configuration of such valves may easily be conceived by the skilled person having knowledge of the present specification and the common general knowledge within the field of process control. The separation of CO2 which is condensed in the second partial condenser heat exchanger 106 from the partial condenser heat exchanger reject gas 3a can be done inside the second partial condenser heat exchanger 106 by any method known in the art. In an embodiment of the invention, a second condenser separator 106b which is separate to the second partial condenser heat exchanger 106 is arranged for separation of a second partial condenser heat exchanger 2-phase outlet stream 3c into the second partial condenser heat exchanger CO2 depleted outlet stream 3b and the second recovered liquid 36, fig. 11b. The cooling of the partial condenser heat exchanger reject gas 3a in the second partial condenser heat exchanger 106 can be provided by using any type of cooling medium or refrigeration work cycle as known in the art. In an advantageous embodiment, the cooling of the partial condenser heat exchanger reject gas 3a in the second partial condenser heat exchanger 106 is by heat exchange with CO2 evaporating at a pressure which is lower than the stripping column pressure but higher than the triple point pressure of CO2. A second partial condenser heat exchanger cold side feed stream 37 is obtained by extraction of at least a portion of liquid CO2 from the CO2 liquefaction system. In an advantageous embodiment, the second partial condenser heat exchanger cold side feed stream 37 is obtained by extraction of at least a portion of liquid CO2 from any of the stripping column liquid sump section 103 c (as stream 37a, extraction from the liquid CO2 product 5 is equivalent), the second separator 102 (as stream 37b, extraction from the second separator liquid 18 is equivalent), and the first separator 101 (as stream 37c, extraction from the first separator liquid 13 is equivalent), where the second partial condenser heat exchanger cold side feed stream 37 is transferred to the second partial condenser heat exchanger 106 and used to cool the partial condenser heat exchanger reject gas 3a, see fig. 11c. In a preferred embodiment, the second partial condenser heat exchanger cold side feed stream 37 is derived by extracting at least a portion of liquid CO2 from the stripping column liquid sump section 103c (as stream 37a, fig. l id, extraction from the liquid CO2 product 5 is equivalent). The second partial condenser heat exchanger cold side feed stream 37 is introduced to the second partial condenser heat exchanger 106 via a second partial condenser heat exchanger control valve 106c. At least a portion of the second partial condenser heat exchanger cold side feed stream 37 is evaporated in a cold side of the second partial condenser heat exchanger 106, causing a net cooling duty in the second partial condenser heat exchanger 106. The evaporation results in a second partial condenser heat exchanger cold side outflow stream 38, having a second partial condenser heat exchanger cold side outflow stream pressure which is lower than the stripping column pressure. The second partial condenser heat exchanger cold side outflow stream 38 is either transferred back to the CO2 liquefaction system (recycled to the CO2 liquefaction system) or transferred out of the CO2 liquefaction system. In a preferred embodiment, the second partial condenser heat exchanger cold side outflow stream 38 is transferred to the compressor arrangement 100, such that the second partial condenser heat exchanger cold side outflow stream 38 is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream 2 and the liquefaction inlet stream 10. The transferring of the second partial condenser heat exchanger cold side outflow stream 38 to the compressor arrangement 100 can be via any of the following routes (see fig. 11c): compressing the second partial condenser heat exchanger cold side outflow stream 38, 38a using a second partial condenser heat exchanger cold side outflow stream compressor 143, or transferring the second partial condenser heat exchanger cold side outflow stream 38, 38b via the pre-compression and pre-purification system 145. The choice of recycling to the CO2 liquefaction system is a matter of process optimisation. In an advantageous embodiment, the second partial condenser heat exchanger cold side outflow stream 38, 38b is transferred to the compressor arrangement 100 via the pre-compression and pre-purification system 145, fig. l id. In one embodiment of the invention, the second partial condenser heat exchanger CO2 depleted outlet stream 3b is transferred out of the CO2 liquefaction system as the final reject gas 3, i.e. such that the second partial condenser heat exchanger CO2 depleted outlet stream 3b is the final reject gas 3, see figs. I la, 11c, l id.

[0194] In another alternative embodiment, fig. 12, the second partial condenser heat exchanger CO2 depleted outlet stream 3b is subjected to a CO2 selective separation in the reject gas CO2 separation arrangement 141 to obtain the reject gas CO2 separation arrangement CO2 rich outlet stream 4 containing at least a portion of the CO2 in the second partial condenser heat exchanger CO2 depleted outlet stream 3b, and the reject gas CO2 separation arrangement CO2 depleted outlet stream 3e comprising non-condensable components and having a reduced content of CO2 compared to the second partial condenser heat exchanger CO2 depleted outlet stream 3b. In this embodiment of the invention, the partial condenser heat exchanger reject gas 3a is introduced as the warm side feed to the second partial condenser heat exchanger 106, and the second partial condenser heat exchanger CO2 depleted outlet stream 3b is introduced to the reject gas CO2 separation arrangement 141 as the reject gas CO2 separation arrangement feed stream 3d. I.e. the second partial condenser heat exchanger CO2 depleted outlet stream 3b is the reject gas CO2 separation arrangement feed stream 3d. In the reject gas CO2 separation arrangement 141, the reject gas CO2 separation arrangement feed stream 3d, which equals the second partial condenser heat exchanger CO2 depleted outlet stream 3b, is subjected to the CO2 selective separation, resulting in the reject gas CO2 separation arrangement CO2 depleted outlet stream 3e which has a further reduced content of CO2, as compared to the second partial condenser heat exchanger CO2 depleted outlet stream 3b and the reject gas CO2 separation arrangement feed stream 3d. The reject gas CO2 separation arrangement CO2 depleted outlet stream 3e is then transferred out of the CO2 liquefaction system as the final reject gas 3.

[0195] The transfer of the partial condenser heat exchanger reject gas 3a out of the CO2 liquefaction system as the final reject gas 3 may be done directly or via any of the second partial condenser heat exchanger 106 and the reject gas CO2 separation arrangement 141. The transfer may include heating and / or pressure reduction of the final reject gas 3. The optional treatment of the partial condenser heat exchanger reject gas 3a described above may contribute to further optimize the inventive basic CO2 liquefaction system when required.

[0196] The final reject gas 3 has an increased concentration of non-condensable components relative to any of the rectification outlet gas 32 and the first reject gas 31. Specifically, the final reject gas 3 includes a major part of the non-condensable components of the CO2 rich stream 1.

[0197] The use of one or more valves for the purpose of process control may be required for any of the following: the first reject gas 31, the rectification outlet gas 32, the partial condenser heat exchanger reject gas 3a, the second partial condenser heat exchanger CO2 depleted outlet stream 3b, reject gas CO2 separation arrangement feed stream 3d, reject gas CO2 separation arrangement CO2 depleted outlet stream 3e, the final reject gas 3. The detailed configuration of such valves for process control may easily be conceived by the skilled person having knowledge of the present specification and the common general knowledge within the field of process control.

[0198] The rectification outlet gas 32 is cooled in the partial condenser heat exchanger 105 by heat exchange with evaporating CO2 from the stripped CO2 liquid 21 obtained in the stripping column 103. A partial condenser heat exchanger cold side feed 23, see e.g. figs. 5a and 5c, is derived by extraction of at least a portion of the stripped CO2 liquid 21. The partial condenser heat exchanger cold side feed 23 is introduced to the partial condenser heat exchanger 105 via a second heat exchanger conduit 105-3 and the stripping column heat exchange outlet 103-4. In alternative embodiments, see e.g. figs. 5b, the portion of the stripped CO2 liquid 21 may be extracted at a position downstream of the stripping column liquid CO2 product outlet 103-2.

[0199] At least a portion of the partial condenser heat exchanger cold side feed 23, i.e. at least a portion of the stripped CO2 liquid 21 entering the partial condenser heat exchanger 105, is evaporated in a cold side of the partial condenser heat exchanger 105, causing a net cooling duty in the partial condenser heat exchanger 105. The evaporation results in a partial condenser heat exchanger cold side outflow 24 in which at least a portion of the stripped CO2 liquid 21 is evaporated to become a gaseous portion of the partial condenser heat exchanger cold side outflow 24. The partial condenser heat exchanger cold side outflow 24 is returned to the stripping column 103 via a first heat exchanger conduit 105-2 and a stripping column heat exchange inlet 103-5, the stripping column heat exchange inlet 103-5 arranged at a position below the stripping column mass transfer section 103b and above the stripping column liquid sump section 103c. The gaseous portion of the partial condenser heat exchanger cold side outflow 24 is the primary stripping gas 24a, and any non-evaporated liquid portion of the partial condenser heat exchanger cold side outflow 24 is a partial condenser heat exchanger cold side outlet liquid 24b.

[0200] The partial condenser heat exchanger cold side outflow 24 may be returned to the stripping column 103 as a mixed gas and liquid stream, where phase separation will be inside the stripping column 103. Alternatively, the partial condenser heat exchanger cold side outflow 24 can be returned to the stripping column 103 as two separate streams, the partial condenser heat exchanger cold side outlet liquid 24b, and the primary stripping gas 24a, respectively. In the latter alternative, the stripping column heat exchange inlet 103-5 will comprise two separate physical inlets. In an embodiment where the partial condenser heat exchanger cold side is configured to provide complete evaporation of the partial condenser heat exchanger cold side feed 23, the partial condenser heat exchanger cold side outflow 24 is a gaseous stream, providing the primary stripping gas 24a, and the partial condenser heat exchanger cold side outlet liquid 24b is non-existent.

[0201] The secondary stripping gas 24c can optionally be generated by applying a reboiler 103d for evaporation of a portion of the stripped CO2 liquid 21. The heat required for evaporating the portion of the stripped CO2 liquid 21 is by heat exchange with a reboiler warm side inlet stream 41. The reboiler warm side inlet stream 41 is obtained by extracting a portion of the liquefaction inlet stream 10. The extraction of a portion of the liquefaction inlet stream 10 leaves a non-extracted portion of the liquefaction inlet stream 10b which flows to the first expansion device 110. The reboiler warm side inlet stream 41 is cooled to a temperature lower than the liquefaction inlet temperature, but higher or equal than the stripped CO2 liquid temperature, the result being a reboiler warm side outlet stream 42. The cooling of the reboiler warm side inlet stream 41 results in a net heating duty which ensures the evaporation of the portion of the stripped CO2 liquid 21. The use of secondary stripping gas 24c is an optional feature of the invention.

[0202] A reboiler control valve 113a, alternatively 113b, regulates the amount (flow rate) of reboiler warm side inlet stream 41 which is extracted from the liquefaction inlet stream 10, between zero and 100% of the liquefaction inlet stream 10, wherein the amount (flow rate) of reboiler warm side inlet stream 41 is indirectly regulating the amount of heat duty in the reboiler 103d, and thereby regulating the amount of secondary stripping gas 24c. In a preferred embodiment, the reboiler control valve 113a is located at the reboiler warm side outlet side (in the reboiler warm side outlet stream 42). Alternatively, the reboiler control valve 113b can be located at the reboiler warm side inlet side (in the reboiler warm side inlet stream 41). The reboiler control valve 113a, 113b is causing a pressure drop, resulting that the reboiler warm side outlet stream 42 has a reboiler warm side return pressure which is lower than the liquefaction inlet pressure.

[0203] The reboiler warm side outlet stream 42 is introduced to a section of the carbon dioxide liquefaction system operating at a pressure lower than the pressure of the liquefaction inlet stream 10 (i.e. lower than the liquefaction stream pressure).

[0204] In one embodiment of the invention the reboiler warm side outlet stream 42, 42a is introduced downstream of the first expansion device 110, to form a portion of the first intermediate flash stream 12, see e.g. fig. la, or the reboiler warm side outlet stream 42, 42a is introduced to the first separator 101.

[0205] In an alternative embodiment of the invention the reboiler warm side outlet stream 42, 42b is introduced downstream of the second expansion device 111, to form a portion of the second intermediate flash stream 17, see e.g. fig. 2, or the reboiler warm side outlet stream 42, 42b is introduced to the second separator 102.

[0206] Alternatively, in any embodiment of the invention where additional separators are applied, the reboiler warm side outlet stream 42, 42b can be introduced to any of the additional separators or introduced to any of the additional intermediate flash streams.

[0207] In an alternative embodiment of the invention the reboiler warm side outlet stream 42, 42c is introduced downstream of the final expansion device 112 to form a portion of the final intermediate flash stream 20, see e.g. fig. 3, or the reboiler warm side outlet stream 42, 42c is introduced to the stripping column 103.

[0208] The reboiler 103d can be configured as an internal reboiler in the stripping column liquid sump section 103c, see e.g. fig. 5a, or as an external reboiler heat exchanger 103e, see fig. 5b, of any type known in the art, having a reboiler cold side fluid supply 25a from the stripping column liquid sump section 103c, and having a reboiler cold side fluid return 25b from the external reboiler 103e to the stripping column 103. The reboiler cold side fluid return 25b consisting of secondary stripping gas 24c and a reboiler non-evaporated liquid 25c, in mixture or as two separate streams. A portion of the stripped CO2 liquid 21 is extracted as the liquid CO2 product 5, where the liquid CO2 product portion is the stripped CO2 liquid, minus any fluid evaporated from the stripped CO2 liquid by net heat input resulting from heat exchange in the partial condenser heat exchanger 105 and any optional heat exchange in the reboiler 103d or in the external reboiler heat exchanger 103e, and minus any optional fluid extracted from the stripping column liquid sump section, directly or via the stripping column liquid CO2 product outlet 103-2, to become the second partial condenser heat exchanger cold side feed stream 37a. The liquid CO2 product 5 has a liquid CO2 product pressure which is essentially equal to the stripping column pressure, a liquid CO2 product temperature which is essentially corresponding to the saturation temperature of liquid CO2 at the stripping column pressure.

[0209] The liquid CO2 product 5 is either led out of the stripping column 103 from the stripping column liquid sump section 103c via the stripping column liquid CO2 product outlet 103-2, or the liquid CO2 product 5 is optionally derived as a portion of an intermediate stripping column outlet stream 5a, see fig. 5b.

[0210] In the basic embodiment of the invention, the extraction of at least a portion of the stripped CO2 liquid 21, to form the partial condenser heat exchanger cold side feed 23, is obtained by extracting the partial condenser heat exchanger cold side feed 23 from the stripping column liquid sump section 103c, see fig. 5a. In an alternative embodiment of the invention, the extraction of at least a portion of the stripped CO2 liquid 21, to form the partial condenser heat exchanger cold side feed 23, is by extracting the partial condenser heat exchanger cold side feed 23 from the stripped CO2 liquid 21 directly from the stripping column mass transfer section 103b, before the stripped CO2 liquid 21 flows to the stripping column liquid sump section 103c. Any non-extracted stripped CO2 liquid flows to the stripping column liquid sump section 103c. This functionality is enabled by use of column internals and internal fluid conduits as known in the art. In another alternative embodiment of the invention, the extraction of at least a portion of the stripped CO2 liquid 21, to form the partial condenser heat exchanger cold side feed 23, is by extracting the partial condenser heat exchanger cold side feed 23 from the stripped CO2 liquid 21 as a portion of an intermediate stripping column outlet stream 5a, wherein the nonextracted portion of the intermediate stripping column outlet stream 5a is the liquid CO2 product 5, see figs. 5b and 5d. The intermediate stripping column outlet stream 5a is exiting via the stripping column liquid CO2 product outlet 103-2. These alternatives for the extraction of at least a portion of the stripped CO2 liquid 21, to form the partial condenser heat exchanger cold side feed 23, are regarded as equivalent. A pump 114a, 114b can be used to transfer the partial condenser heat exchanger cold side feed 23 to the partial condenser heat exchanger cold side inlet. The pump 114a can be configured in the partial condenser heat exchanger cold side feed 23, see fig. 5c. For the alternative where the extraction of at least a portion of the stripped CO2 liquid 21, to form the partial condenser heat exchanger cold side feed 23, is by extracting the partial condenser heat exchanger cold side feed 23 from the stripped CO2 liquid 21 as a portion of the intermediate stripping column outlet stream 5a, the pump 114b can be configured in the intermediate stripping column outlet stream 5a, see fig. 5d.

[0211] Some of the alternatives for providing the partial condenser heat exchanger cold side feed 23 to the partial condenser heat exchanger cold side inlet, and for returning the partial condenser heat exchanger cold side outflow 24 to the stripping column 103, may require the use of one or more valves for the purpose of process control. The extraction of a portion of the stripped CO2 liquid 21 as the liquid CO2 product 5 may require the use of one or more valves for the purpose of process control. The detailed configuration of such valves for process control may easily be conceived by the skilled person having knowledge of the present specification and the common general knowledge within the field of process control.

[0212] In an advantageous embodiment, the partial condenser heat exchanger 105 is designed and configured such that flow of partial condenser heat exchanger cold side feed 23 to the partial condenser heat exchanger 105, and flow of partial condenser heat exchanger cold side outflow 24 to the stripping column 103 is driven by a reduction in fluid density occurring when a portion of the partial condenser heat exchanger cold side feed 23 is evaporated in the partial condenser heat exchanger 105. Such phenomenon is commonly referred to as natural circulation.

[0213] The compressor arrangement 100 of the inventive CO2 liquefaction system can be any type of compression system as known in the art, consisting of one or more compression sections and any number of interstage cooling and aftercooling, as known in the art.

[0214] Details of an exemplary compressor arrangement 100 are illustrated in figs. 7a and 7b. The compressor arrangement 100 comprises a first compression section 121 having a first compression section inlet stream 51, wherein the compression section inlet stream 51 comprises the stripping column recycle gas 22, and wherein the first compression section inlet stream 51 has a first compression section inlet pressure essentially equal to the stripping column pressure. The compressor arrangement 100 comprises the compressor arrangement discharge stream 2, having the compressor arrangement discharge pressure, which is essentially equal to the liquefaction inlet pressure. Depending on the configuration of the liquefaction system, the compressor arrangement 100 comprises one or more compressor sections in addition to the first compression section 121.

[0215] In embodiments of the invention, where the first recycle gas 14 is non-existent, and where there are no additional separators, the first compressor section 121 has a first compression section discharge stream 52 which has a first compression section discharge pressure essentially equal to the compressor arrangement discharge pressure, and the compressor arrangement discharge stream 2 comprises the first compression section discharge stream 52. Aftercooling at the first compressor section discharge can be applied.

[0216] In embodiments of the invention, where the compressor arrangement 100 is arranged to receive any of the following recycle streams; the first recycle gas 14, the second recycle gas 19, any intermediate recycle gas streams, the compressor arrangement 100 is configured such that each recycle stream is introduced to a compressor section inlet stream where the pressure is essentially equal to the pressure of the respective recycle stream, and such that each recycle stream is recompressed to the compressor arrangement discharge pressure, to form a portion of the compressor arrangement discharge stream 2.

[0217] In any embodiments of the invention, the CO2 rich stream 1, having the CO2 rich stream pressure, is introduced to the compressor arrangement 100, such that the CO2 rich stream 1 makes up at least a portion of the compressor arrangement discharge stream 2 having the compressor arrangement discharge pressure. The position in the compressor arrangement 100 where the CO2 rich stream 1 is introduced, i.e. to be understood as to which compressor section inlet stream the CO2 rich stream 1 is introduced, will be dependent on the CO2 rich stream pressure. The CO2 rich stream pressure shall be at least as high as the first compression section inlet pressure, where the first compression section inlet pressure is essentially equal to the stripping column pressure and the liquid CO2 product pressure.

[0218] In the exemplary liquefaction system illustrated in fig. 7a and 7b, where the first separator liquid 13 is subjected to the pressure reduction from the first separator pressure to the stripping column pressure in two steps, the compressor arrangement 100 has a second compression section 122, arranged between the first compression section 121 and a final compression section 123. The first compression section discharge stream 52 having the first compression section discharge pressure which in this embodiment is essentially equal to the second separator pressure. The second recycle gas 19 is mixed with the first compression section discharge stream 52, such that a second compression section inlet stream 53a, having a second compression section inlet pressure which is essentially equal to the second separator pressure and the first compression section discharge pressure, comprises the first compression section discharge stream 52 and the second recycle gas 19. Further, the second compression section 122 has a second compression section discharge stream 54a having a second compression section discharge pressure which is essentially equal to the first separator pressure. The first recycle gas 14 is mixed with the second compression section discharge stream 54a, such that a final compression section inlet stream 55, having a final compression section inlet pressure which is essentially equal to the first separator pressure and the second compression section discharge pressure, comprises the second compression section discharge stream 54a and the first recycle gas 14. The final compression section 123 has a final compression section discharge stream 56 which has a final compression section discharge pressure essentially equal to the compressor arrangement discharge pressure, and the compressor arrangement discharge stream 2 comprises the final compression section discharge stream 56. Each compression section can have any number of compression stages and compression coolers (aftercooling, intercooling, as known in the art). In a preferred embodiment of the invention, the first compression section 121 and the second compression section 122 have aftercooling. The final compression section 123 can have aftercooling.

[0219] Commonly, the CO2 rich stream pressure is equal to or higher than the first compression section inlet pressure. The CO2 rich stream 1, la is then mixed with the stripping column recycle gas 22, such that the first compression section inlet stream 51 comprises the stripping column recycle gas 22 and the CO2 rich stream la.

[0220] In alternative embodiments, wherein the compressor arrangement 100 features the second compressor section 122, and the CO2 rich stream pressure is equal to or higher than the second compression section inlet pressure, the CO2 rich stream 1, lb may be mixed with the second recycle gas 19 and the first compressor section discharge stream 52, such that the second compression section inlet stream 53a comprises the first compression section discharge stream 52, the second recycle gas 19 and the CO2 rich stream lb.

[0221] In further alternative embodiments, the CO2 rich stream pressure may be equal to or higher than the final compression section inlet pressure. The CO2 rich stream 1, 1c may then be mixed with the first recycle gas 14 and the second compressor section discharge stream 54a, such that the final compression section inlet stream 55 comprises the second compression section discharge stream 54a, the first recycle gas 14 and the CO2 rich stream 1c. When the CO2 rich stream pressure is equal to or higher than the final compression section discharge pressure, the CO2 rich stream 1, Id may be mixed with the final compression section discharge stream 56, such that the compressor arrangement discharge stream 2 comprises the final compression section discharge stream 56 and the CO2 rich stream Id.

[0222] In an exemplary embodiment of the invention, an optional vapour return stream 6 from the liquid CO2 storage 150 may be introduced to the compressor arrangement 100, such that the vapour return stream 6 is compressed in the compressor arrangement 100 and becomes a portion of the compressor arrangement discharge stream 2, and consequently also a portion of the liquefaction inlet stream 10. The vapour return stream 6 consists of CO2 and non-condensable components in gaseous phase. With such a configuration, the vapour return stream 6 is subject to liquefaction along with the CO2 rich stream 1. The vapour return stream 6 may be mixed with the stripping column recycle gas 22, such that the first compressor section inlet stream 51 comprises the vapour return stream 6.

[0223] In an advantageous embodiment of the invention, the recovered CO2 liquid 35 obtained in the rectification column 104 is routed to the stripping column 103 indirectly via the first separator 101, in that the recovered CO2 liquid 35,35a is introduced to the first separator 101 or to the first intermediate flash stream 12, where the recovered CO2 liquid 35,35a is mixed with the first intermediate liquid phase 12a, such that the first separator liquid 13 which is subjected to a pressure reduction from the first separator pressure to the stripping column pressure in one or more pressure reduction stages comprises the first intermediate liquid phase 12a and the recovered CO2 liquid 35,35a. Routing the recovered CO2 liquid 35 directly to the first separator liquid 13 is also possible according to the method. In any of the alternatives for routing the recovered CO2 liquid 35 to the stripping column 103 via the first separator 101, the use of one or more valves for the purpose of process control may be required, the detailed configuration of such valves may easily be conceived by the skilled person having knowledge of the present specification and the common general knowledge within the field of process control.

[0224] In an alternative embodiment of the invention, the recovered CO2 liquid 35, 35b is routed to the stripping column 103 via one or more pressure reduction stages by subjecting the recovered CO2 liquid 35, 35b to a pressure reduction in a recovered CO2 liquid expansion device 116b, forming a recovered CO2 gas phase and a recovered CO2 liquid phase, which is introduced to the second separator 102 or any optional additional separator, see fig. 4b. The following describes an embodiment of the invention where the recovered CO2 liquid 35, 35b is routed to the second separator 102. It is noted that routing to any optional additional separator can be arranged equivalently. The introduction of the recovered CO2 gas phase and the recovered CO2 liquid phase to the second separator 102 can be either to the second intermediate flash stream 17, or directly to the second separator 102 via a dedicated second separator recovered CO2 liquid inlet (not shown in figures). Both alternatives for introduction of the recovered CO2 gas phase and the recovered CO2 liquid phase to the second separator 102 shall be regarded as equivalent, resulting in the recovered CO2 gas phase being mixed with the second intermediate gas phase 17b, such that the second recycle gas 19 comprises the mix of the recovered CO2 gas phase and the second intermediate gas phase 17b, and further resulting in the recovered CO2 liquid phase being mixed with the second intermediate liquid phase 17a, such that the second separator liquid 18 which is subjected to a pressure reduction from the second separator pressure to the stripping column pressure in one or more pressure reduction stages, including at least the final expansion device 112, comprises the recovered CO2 liquid phase and the second intermediate liquid phase 17a.

[0225] In an alternative embodiment of the invention, see fig. 4a, the recovered CO2 liquid 35,35c is subjected to pressure reduction in a recovered CO2 liquid expansion device 116c, forming a recovered CO2 gas phase and a recovered CO2 liquid phase, and introduced to the stripping column 103. In an advantageous embodiment, the introduction of the recovered CO2 gas phase and the recovered CO2 liquid phase to the stripping column 103 is either to the final intermediate flash stream 20 or directly to the stripping column top separation zone 103a via a dedicated stripping column recovered CO2 liquid inlet (not shown). Both alternatives result in the recovered CO2 gas phase being mixed with the final intermediate gas phase 20b and the stripping column outlet stripping gas 24e, such that the stripping column recycle gas 22 comprises the recovered CO2 gas phase, the final intermediate gas phase 20b and the stripping column outlet stripping gas 24e, and further resulting in the recovered CO2 liquid phase becoming mixed with the final intermediate liquid phase 20a, such that the final intermediate liquid phase 20a which flows downwards through the stripping column mass transfer section 103b comprises the recovered CO2 liquid phase.

[0226] In an alternative embodiment of the invention, the first separator 101 and the rectification column 104 may be arranged as a combined separator and column device 101b, see fig. 9b. In this embodiment the rectification mass transfer section 104a is arranged inside the first separator 101, at a level above the first separator flash stream inlet 101-1 and above the level of the first separator recycle gas outlet 101-2 The first reject gas 31 and the recovered CO2 liquid 35 are internal streams in the combined separator and column device 101b, and a lower end of the rectification mass transfer section 104a provides the rectification column gas inlet 104-1 and the first separator gas outlet 101-3. In this embodiment, the rectification outlet gas 32 will come from a rectification gas outlet 101-6 which is located on the combined separator and column device 101b at a level above the rectification mass transfer section 104a, and the reflux liquid 34 may be introduced to the combined separator and column device 101b via a reflux liquid inlet 101-7, also at a level above the rectification mass transfer section 104a. The first recycle gas 14 (if any) will exit via the first separator recycle gas outlet 101-2, which in this embodiment is located at a level below the rectification mass transfer section 104a, and above the first separator flash stream inlet 101-1.

[0227] In an alternative embodiment of the invention, the partial condenser heat exchanger 105 can be arranged inside the stripping column liquid sump section 103c, where the stripping column 103 will include an internal partial condenser heat exchanger inlet 105b-2 for the rectification outlet gas 32, see e.g. fig. 6a, 6b, 6c, 6d.

[0228] The partial condenser heat exchanger 105 can have an integrated separation zone for separation of CO2 which is condensed in the partial condenser heat exchanger 105 from the rectification outlet gas 32, where the separated CO2 liquid is providing the reflux liquid 34, and the rectification outlet gas 32 minus the condensed CO2 constitutes the partial condenser heat exchanger reject gas 3a, see fig. 6a. The reflux liquid 34 is drawn off from the partial condenser heat exchanger 105 and thereafter led out of the stripping column via an internal partial condenser heat exchanger reflux liquid outlet 105b-3 and routed to the rectification column 104, or in the embodiment where the first separator 101 and the rectification column 104 are arranged as a combined separator and column device 101b, routing the reflux liquid 34 to the combined separator and column device 101b reflux liquid inlet 101-7. The partial condenser heat exchanger reject gas 3a is drawn off from the partial condenser heat exchanger 105 and thereafter led out of the stripping column 103 via an internal partial condenser heat exchanger outlet 105b- 1. Alternatively, the partial condenser heat exchanger 105 is configured to provide an internal partial condenser heat exchanger 2-phase outlet stream 33b which is connected to a stripping column integrated reflux separation arrangement 109b arranged inside the stripping column 103. The stripping column integrated reflux separation arrangement 109b is arranged for separation of the internal partial condenser heat exchanger 2-phase outlet stream 33b into the partial condenser heat exchanger reject gas 3a and the reflux liquid 34, see fig 6c. In this alternative, the reflux liquid 34 is led out of the stripping column 103 via a stripping column integrated reflux separation arrangement liquid outlet 109b-3 and routed to the rectification column 104, or in the embodiment where the first separator 101 and the rectification column 104 are arranged as a combined separator and column device 101b, routing the reflux liquid 34 to the combined separator and column device 101b reflux liquid inlet 101-7. The partial condenser heat exchanger reject gas 3a is then led out of the stripping column 103 via a stripping column integrated reflux separation arrangement gas outlet 109b-2. Further in this alternative, the internal partial condenser heat exchanger 2-phase outlet stream 33b is transferred from the partial condenser heat exchanger 105 to the stripping column integrated reflux separation arrangement 109b via a conduit configured internally in the stripping column liquid sump section 103c.

[0229] In another alternative embodiment of the invention, where the partial condenser heat exchanger 105 is arranged inside the stripping column liquid sump section 103c, the partial condenser heat exchanger 105 is configured to provide the partial condenser heat exchanger 2-phase outlet stream 33a, the partial condenser heat exchanger 2-phase outlet stream 33a is led out of the stripping column 103 via an internal partial condenser heat exchanger 2-phase outlet 105b-4. The partial condenser heat exchanger 2-phase outlet stream 33a may be connected to the reflux separator 109 which is separate from the partial condenser heat exchanger 105 and the stripping column 103, see fig. 6b. The reflux separator 109 now being arranged for separation of the partial condenser heat exchanger 2-phase outlet stream 33a into the partial condenser heat exchanger reject gas 3a and the reflux liquid 34, where the reflux liquid 34 is routed to the rectification column 104, or in the embodiment where the first separator 101 and the rectification column 104 are arranged as a combined separator and column device 101b, routing the reflux liquid 34 to the combined separator and column device 101b reflux liquid inlet 101-7.

[0230] In another advantageous embodiment of the invention, see fig. 6d, the partial condenser heat exchanger 105 is arranged inside the stripping column liquid sump section 103c, and the partial condenser heat exchanger 105 is configured to provide the partial condenser heat exchanger 2-phase outlet stream 33a. In this embodiment, the partial condenser heat exchanger 2-phase outlet stream 33a is led out of the stripping column 103 via the internal partial condenser heat exchanger 2-phase outlet 105b-4, and routed to a combined separator and column device reflux separation arrangement 109c which is configured in the top of the combined separator and column device 101b, above the rectification gas outlet 101-6. The combined separator and column device reflux separation arrangement 109c is configured for separation of the partial condenser heat exchanger 2-phase outlet stream 33a into the partial condenser heat exchanger reject gas 3a and the reflux liquid 34. In this embodiment, the combined separator and column device 101b has a combined separator and column device reflux separator inlet 109c-l for the partial condenser heat exchanger 2-phase outlet stream 33a, and a combined separator and column device reject gas outlet 109c-2 for the partial condenser heat exchanger reject gas 3a. The reflux liquid 34 can be transferred from the combined separator and column device reflux separation arrangement 109c to the rectification mass transfer section 104a via a conduit configured internally in the combined separator and column device 101b, in the latter alternative the reflux liquid inlet 101-7 is nonexistent. However, in a preferred embodiment, the reflux liquid 34 is led out of the combined separator and column device reflux separation arrangement 109c via a combined separator and column device reflux outlet 109c-3 and thereafter introduced to the combined separator and column device 101b via the reflux liquid inlet 101-7, at an elevation which is below the combined separator and column device reflux separator arrangement 109c, but above the rectification mass transfer section 104a. See figs. 6d, 9c.

[0231] In all embodiments of the invention where the partial condenser heat exchanger 105 is arranged inside the stripping column liquid sump section 103c, the partial condenser heat exchanger cold side feed and the internal partial condenser heat exchanger cold side outflow will be streams (flows) internal in the stripping column liquid sump section 103 c.

[0232] In alternative embodiments, see figs. 5f and 5g, the stripping column 103 may be configured with two separate units / pressure vessels; a first pressure vessel 103f comprising the stripping column top separation zone 103a and the stripping column mass transfer section 103b and a second pressure vessel 103g comprising the stripping column liquid sump section 103c, the first pressure vessel and the second pressure vessel being connected via a stripped CO2 liquid conduit 21a and a stripping gas conduit 24f. In one of these embodiments, the partial condenser heat exchanger cold side outflow 24 is routed to the first pressure vessel 103f, and the stripped CO2 liquid 21 and the partial condenser heat exchanger cold side outlet liquid 24b are transferred from the bottom of the first pressure vessel 103f to the stripping column liquid sump section 103c in the second pressure vessel 103g via the stripped CO2 liquid conduit 21a, and any vapours from the stripping column liquid sump section 103c, optionally including the secondary stripping gas 24c, are transferred from the top of the second pressure vessel 103 g to the first pressure vessel 103f via the stripping gas conduit 24f and introduced to the first pressure vessel at a position below the stripping column mass transfer section 103b, see fig. 5f. Alternatively, the partial condenser heat exchanger cold side outflow 24 can be routed to the second pressure vessel 103g, in this alternative the stripped CO2 liquid 21 is transferred from the bottom of the first pressure vessel 103f to the stripping column liquid sump section 103c in the second pressure vessel 103g via the stripped CO2 liquid conduit 21a, and the primary stripping gas 24a together with any vapours from the stripping column liquid sump section 103c, and optionally the secondary stripping gas 24c, are transferred from the top of the second pressure vessel 103g to the first pressure vessel via the stripping gas conduit 24f and introduced to the first pressure vessel at a position below the stripping column mass transfer section 103b, see fig. 5g.

[0233] In an alternative embodiment of the invention, see fig. 3, the compressor arrangement discharge stream 2 is cooled to a pre-liquefaction inlet temperature which enables phase separation at the liquefaction inlet pressure. The resulting stream is a pre-liquefaction inlet stream 11, which is introduced to a pre-separator 108 operating at a pressure essentially equal to the liquefaction inlet pressure. The pre-liquefaction inlet stream 11 has a pre-liquefaction gas phase 11b and a preliquefaction liquid phase I la, which are separated in the pre-separator 108, such that the pre-liquefaction liquid phase I la from the pre-separator 108 is the liquefaction inlet stream 10, which in this alternative embodiment of the invention is a liquid and follows the steps as described above.

[0234] The pre-liquefaction gas phase 11b exits the pre-separator 108 as a pre-liquefaction reject gas 31b, comprising CO2 and non-condensable components, the pre- liquefaction reject gas 31b is subject to a pre-liquefaction gas pressure reduction in a pre-liquefaction gas expansion device 115, reducing pressure of the pre- liquefaction reject gas 31b from the liquefaction inlet pressure to essentially the first separator pressure. A resulting pressure reduced pre-liquefaction reject gas 31c is mixed with the first reject gas 31, creating a reject gas mix stream 3 Id which is routed to the rectification column 104.

[0235] In an exemplary embodiment of the invention, see fig. 4a, the first expansion device 110 comprises a first ejector 110b, having a first ejector motive fluid inlet 110b-l, a first ejector outlet 110b-2 and a first ejector low-pressure suction inlet 110b-3, where the liquefaction inlet stream 10 or the non-extracted portion of the liquefaction inlet stream 10b, having essentially the liquefaction inlet pressure, is connected to the first ejector motive fluid inlet 110b-l, and the first ejector outlet 110b-2 provides the first intermediate flash stream 12 having essentially the first separator pressure. The stripping column recycle gas 22 is divided into a first ejector suction gas 15a and optionally a stripping column compressor recycle gas 22a, where the first ejector suction gas 15a is connected to the first ejector low- pressure suction inlet 110b-3. The flow of fluid through the first ejector 110b, from the first ejector motive fluid inlet to the first ejector outlet, goes through a venturi contraction, creating a pressure at the first ejector low-pressure suction inlet which is lower than or equal to the stripping column pressure, enabling inflow of at least a portion of the stripping column recycle gas 22 to the first ejector 110b, as the first ejector suction gas 15a, such that the first ejector suction gas 15a is being recompressed to the first separator 101, having the first separator pressure, and such that the first ejector suction gas 15a makes up a portion of the first intermediate flash stream 12. The portion of the stripping column recycle gas 22 which is not flowing to the first ejector 110b as the first ejector suction gas 15a, if any, flows to the compressor arrangement 100 as the stripping column compressor recycle gas 22a and is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream 2 and the liquefaction inlet stream 10. In another exemplary embodiment of the invention, see figs. 4b, 4c, the first separator liquid 13 is subjected to the pressure reduction from the first separator pressure to the stripping column pressure in two steps. The first expansion device 110 comprises a first ejector 110b, having a first ejector motive fluid inlet 110b-l, a first ejector outlet 110b-2 and a first ejector low-pressure suction inlet 110b-3, similar to the embodiment in fig. 4a. The liquefaction inlet stream 10 or the nonextracted portion of the liquefaction inlet stream 10b, having essentially the liquefaction inlet pressure, is connected to the first ejector motive fluid inlet 110b- 1, and the first ejector outlet 110b-2 is the first intermediate flash stream 12 having essentially the first separator pressure. The second recycle gas 19 is divided into a first ejector suction gas 15b and optionally a second compressor recycle gas 19a, where the first ejector suction gas 15b is connected to the first ejector low-pressure suction inlet 110b-3. The flow of fluid through the first ejector 110b, from the first ejector motive fluid inlet to the first ejector outlet, goes through a venturi contraction, creating a pressure at the first ejector low-pressure suction inlet which is lower than or equal to the second separator pressure, enabling inflow of at least a portion of the second recycle gas 19 to the first ejector 110b, as the first ejector suction gas 15b, such that the first ejector suction gas 15b is being recompressed to the first separator 101, having the first separator pressure, and such that the first ejector suction gas 15b makes up a portion of the first intermediate flash stream 12. The portion of the second recycle gas 19 which is not flowing to the first ejector 110b as the first ejector suction gas 15b, if any, flows to the compressor arrangement 100 as the second compressor recycle gas 19a and is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream 2 and the liquefaction inlet stream 10. In the embodiment of the invention where the first expansion device 110 comprises the first ejector 110b, and where the first separator liquid 13 is subjected to the pressure reduction from the first separator pressure to the stripping column pressure in more than two pressure reduction stages, where at least a first additional pressure reduction stage for the first separator liquid 13 is arranged between the first separator 101 and the second expansion device 111, such that the first separator liquid 13 is led to the first additional expansion device, resulting in the first additional intermediate flash stream which is led to the first additional separator to be separated into the first additional recycle gas and the first additional liquid, the first additional recycle gas is in fluid communication with the first ejector low-pressure suction inlet 110b-3, enabling inflow of at least a portion of the first additional recycle gas to the first ejector such that the said portion of the first additional recycle gas is being recompressed to the first separator 101, having the first separator pressure, and such that the said portion of the first additional recycle gas makes up a portion of the first intermediate flash stream 12. The portion of the first additional recycle gas which is not flowing to the first ejector low-pressure suction inlet 110b-3, if any, flows to the compressor arrangement 100 and is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream 2 and the liquefaction inlet stream 10. That is, depending on the number of pressure reduction stages between the first separator 101 and the second expansion device 111, the first ejector 110b is enabling inflow of at least a portion of the second recycle gas 19 or at least a portion of the first additional recycle gas to the first ejector low-pressure suction inlet 110b-3, for recompression to the first separator, and wherein any portion of the second recycle gas or any portion of the first additional recycle gas which is not flowing to the first ejector 110b, flows to the compressor arrangement 100 to form a portion of the compressor arrangement discharge stream 2 and the liquefaction inlet stream 10.

[0236] In another exemplary embodiment of the invention, see figs. 4b, 4d, the first separator liquid 13 is subjected to the pressure reduction from the first separator pressure to the stripping column pressure in two or more steps, the second expansion device 111 comprises a second ejector 111b, having a second ejector motive fluid inlet l l lb-1, a second ejector outlet l l lb-2 and a second ejector low- pressure suction inlet 11 lb-3, where at least a portion of the first separator liquid 13 is connected to the second ejector motive fluid inlet 11 lb- 1 directly, or indirectly via one or more additional expansion devices and corresponding additional separators, and the second ejector outlet 11 lb-2 is the second intermediate flash stream 17 having essentially the second separator pressure. The stripping column recycle gas 22 is divided into a second ejector suction gas 16 and optionally a stripping column compressor recycle gas 22a, where the second ejector suction gas 16 is connected to the second ejector low-pressure suction inlet 11 lb-3. The flow of fluid through the second ejector 11 lb, from the second ejector motive fluid inlet to the second ejector outlet, goes through a venturi contraction, creating a pressure at the second ejector low-pressure suction inlet which is lower than or equal to the stripping column pressure, enabling inflow of at least a portion of the stripping column recycle gas 22 to the second ejector 11 lb, as the second ejector suction gas 16, such that the second ejector suction gas 16 is being recompressed to the second separator 102, having the second separator pressure and such that the first ejector suction gas 16 makes up a portion of the second intermediate flash stream 17. The portion of the stripping column recycle gas 22 which is not flowing to the second ejector 111b as the second ejector suction gas 16, if any, flows to the compressor arrangement 100 as the stripping column compressor recycle gas 22a and is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream 2 and the liquefaction inlet stream 10.

[0237] The first ejector 110b can have an integrated device for adjusting the flow of fluid throughput. Alternatively, a valve device is applied in the first expansion device 110, in conjunction with the first ejector 110b, the valve device located either upstream of the first ejector motive fluid inlet 110b-l, or downstream of the first ejector outlet 110b-2, to control the flow of fluid through the first ejector 110b. The overall pressure drop across the first expansion device 110 is then the sum of the pressure drops across the valve device and the first ejector 110b.

[0238] The second ejector 111b can have an integrated device for adjusting the flow of fluid throughput. Alternatively, a valve device is applied in the second expansion device 111, in conjunction with the second ejector 11 lb, the valve device located either upstream of the second ejector motive fluid inlet 11 lb- 1 , or downstream of the second ejector outlet 11 lb-2, to control the flow of fluid through the second ejector 111b. The overall pressure drop across the second expansion device 111 is then the sum of the pressure drops across the valve device and the second ejector 111b.

[0239] In an exemplary embodiment, the liquefaction inlet cooler is a multi-stream heat exchanger 131b with a warm side and at least one cold side, see fig. 1c. The liquefaction inlet cooler 131b is configured to cool the compressor arrangement discharge stream 2 in heat exchange with at least one of the following streams; the first recycle gas 14, the second recycle gas 19, any intermediate recycle gas streams, the stripping column recycle gas 22, any available ambient cooling medium stream, a refrigerant stream provided by a refrigeration work cycle (refrigerant feed stream 61 and the refrigerant return stream 62). The solution provides an increased energy efficiency by enabling cold recovery from the recycle streams. The cooled compressor discharge stream exiting the liquefaction inlet cooler is the liquefaction inlet stream 10. In any embodiment, the compressor arrangement 100 can comprise an after cooler for cooling of the compressor arrangement discharge stream 2 upstream of the liquefaction inlet cooler 131b.

[0240] For any embodiment of the invention, any of the first recycle gas 14, the second recycle gas 19, and the stripping column recycle gas 22 can optionally exchange heat with one or more external process streams, heat sources or heat sinks. Such heat transfer may affect the compressor work by removing heat from or adding heat to one or more gas streams which will be subject to compression in the compressor arrangement 100.

[0241] Alternative configurations, wherein at least two of the stripping column 103, the first separator 101, the second separator 102, the rectification column 104 and the partial condenser heat exchanger 105 are connected to form a vertical column structure, are shown in figs. 8a, 8b, 9a, 9b and 9c.

[0242] For the alternative configurations shown in fig. 8a, 9a, 9b and 9c, the stripping column 103, the first separator 101 and optionally the second separator 102, are pressure vessels that can be welded together as one pressure vessel assembly providing a vertical column structure.

[0243] For the alternative configuration shown in fig. 8b, the stripping column 103, the first separator 101 and optionally the second separator 102 can be assembled to form the vertical column structure by using distance pieces / spacers, and where the connections are either welded or bolted.

[0244] The compressor arrangement discharge pressure can be any pressure above the liquid CO2 product pressure. However, the compressor arrangement discharge pressure minimum value is such that the first intermediate flash stream 12 is a two- phase fluid consisting of the first intermediate liquid phase 12a and the first intermediate gas phase 12b. This implies that the compressor arrangement discharge pressure minimum value is dependent on the liquefaction inlet temperature and the first separator pressure. In a preferred embodiment of the invention, the compressor arrangement discharge pressure is higher than 25 bar absolute pressure but not higher than 100 bar absolute pressure. In a more preferred embodiment of the invention, when cooling in the liquefaction inlet cooler 131 is by ambient cooling medium, cooling the liquefaction inlet stream 10 to a liquefaction inlet temperature between 15°C and 35°C, the compressor arrangement discharge pressure is between 45 bar absolute pressure and 90 bar absolute pressure. In another preferred embodiment of the invention, when cooling in the liquefaction inlet cooler 131 is by refrigeration work cycle, cooling the liquefaction inlet stream 10 to a liquefaction inlet temperature between -15°C and 15°C the compressor arrangement discharge pressure is between 35 bar absolute pressure and 55 bar absolute pressure.

[0245] In the disclosed embodiments of the CO2 liquefaction system according to the invention, the final product is liquid phase CO2 (i.e. the liquid CO2 product 5). However, in some cases it may be desirable to provide the final product in gaseous form, e.g. when the CO2 product is to be transported from the CO2 liquefaction system via a gas pipeline. In such cases, the CO2 liquefaction system according to the invention may comprise a regasification unit 151 to which at least a portion of the liquid CO2 product 5 may be transferred, e.g. via a conduit. The regasification unit 151 may transform the liquid CO2 product 5 to a gaseous CO2 product 7, where the gaseous CO2 product 7 may be in a sub critical gas phase or a supercritical dense gas phase. The regasification unit 151 may include pressure reduction or pressure increase (e.g. by use of a CO2 product pump). See fig. 1c. The regasification unit 151 may include an arrangement for heat exchange with various streams of the CO2 liquefaction system, for example an arrangement for heat exchange with any of the following streams; the liquefaction inlet stream 10, the first intermediate flash stream 12, the first separator liquid 13, the second intermediate flash stream 17 and the second separator liquid 18, such that any portion of the heat required to convert the liquid CO2 product 5 to the gaseous CO2 product 7 can be provided from the CO2 liquefaction system, and thereby further optimizing the CO2 liquefaction system.

[0246] In any embodiment of the invention, a liquefaction inlet cooler bypass arrangement (not shown) can optionally be arranged such that a portion of the compressor arrangement discharge stream 2 is bypassing the liquefaction inlet cooler 131 (or 131b) and led to the first separator 101, directly or indirectly, in order to improve process control of the ratio between the first intermediate liquid phase 12a and the first intermediate gas phase 12b. The use of the liquefaction inlet cooler bypass arrangement is particularly relevant when heat duty control for the liquefaction inlet cooler 131 / 13 lb is challenging. The use of the liquefaction inlet cooler bypass arrangement is also relevant if the amount of non-condensable components in the CO2 rich stream 1 is low, which also leads to a challenging heat duty control for the liquefaction inlet cooler 131 / 13 lb. For any given heat duty in the liquefaction inlet cooler 131 / 13 lb, the overall result when using the liquefaction inlet cooler bypass arrangement will be the same as in any embodiment not having or not using the liquefaction inlet cooler bypass arrangement.

[0247] CO2 liquefaction process

[0248] An exemplary liquefaction process is described in the following by reference to the CO2 liquefaction system illustrated in figs. 7a / 7b and 5e.

[0249] A CO2 rich stream 1 is obtained by pre-compressing and removal of water from raw / untreated CO2 from a system capturing CO2, e.g. from a flue gas. The steps of pre-compression and water removal are well known in the art.

[0250] The CO2 rich stream 1, consisting of 99.9915 mol% CO2, 370 ppm (parts per million on molar basis) Nitrogen (N2), 100 ppm Oxygen (02), 10 ppm Water vapour (H2O), and 5 ppm Argon (Ar), and having a flow rate of 100,000 kg / h, is introduced to a compressor arrangement 100 at a pressure of 16 bar (absolute pressure). The stream has a temperature of 30°C.

[0251] In the compressor arrangement 100, the CO2 rich stream 1 is mixed with a vapour return stream 6 from a liquid CO2 storage 150 having an operating pressure of slightly above 16 bar, and a stripping column recycle gas 22 from a stripping column 103. The vapour return stream 6 consists of 99.8 mol% CO2, 820 ppm N2, 1000 ppm 02, 180 ppm Ar, and less than 1 ppm H2O, and has a flow rate of 2,000 kg / h and a temperature of approximately -26.6°C. The stripping column recycle gas 22 comprises 99.786 mol% CO2 and has a flow rate of 27,253 kg / h and a temperature of -26.6°C.

[0252] The resulting mix of the CO2 rich stream 1, the vapour return stream 6, and the stripping column recycle gas 22, is a first compressor section inlet stream 51, which is compressed in a first compression section 121 comprising a first compression stage and a first after cooler. The first compression section discharge stream 52, having a pressure of 30 bar and a temperature of 30°C, is mixed with a second recycle gas 19 from a second separator 102. The second recycle gas 19 comprises 99.477 mol% CO2 and has a flow rate of 31,000 kg / h and a temperature of -6.5°C. The resulting mix is a second compression section inlet stream 53a, which is compressed in a second compression section 122 comprising a second compression stage and a second after cooler. The second compression section discharge stream 54a, having a pressure of 50 bar and a temperature of 30°C, is mixed with a first recycle gas 14 from a first separator 101. The first recycle gas 14 comprises 99.334 mol% CO2 and has a flow rate of 59,450 kg / h and a temperature of 13.3°C. The resulting mix is a final compression section inlet stream 55, which is compressed in a final compression section 123 comprising a final compression stage and a final after cooler. The final compression section outlet is a final compression section discharge stream 56, which has a pressure of 76 bar and a temperature of 50°C, and the flow rate is 219,700 kg / h.

[0253] The final compression section discharge stream 56 leaves the compressor arrangement 100 as a compressor arrangement discharge stream 2, which is cooled to 30°C in a liquefaction inlet cooler 131, yielding a liquefaction inlet stream 10 from where a portion of 2.5% is extracted as a reboiler warm side inlet stream 41. The non-extracted portion of the liquefaction inlet stream 10b is pressure-reduced to approximately 50 bar in a first expansion device 110 (valve), resulting in a temperature decrease to 13.4°C, and approximately 67% of the fluid being a liquid phase. The reboiler warm side inlet stream 41 is cooled in a reboiler 103d, thereafter pressure reduced to approximately 50 bar in a reboiler control valve 113a. The resulting reboiler warm side outlet stream 42 has a temperature of -15°C and is a liquid. The reboiler warm side outlet stream 42 is mixed with the non-extracted portion of the liquefaction inlet stream downstream of first expansion device outlet, the mix being a first intermediate flash stream 12 consisting of a first intermediate gas phase 12b and a first intermediate liquid phase 12a, is introduced to the first separator 101, operating at approximately 50 bar.

[0254] A first reject gas 31 having a flow rate of 10,485 kg / h is extracted from the first intermediate gas phase 12b, while the non-extracted portion of the first intermediate gas phase 12b is the first recycle gas 14, which is recycled to the compressor arrangement 100. A recovered CO2 liquid 35, 35a, flowing from a rectification column 104, and having a flow rate of 10,400 kg / h is also introduced to the first separator 101. The first intermediate liquid phase 12a and the recovered CO2 liquid is flowing out of the first separator 101 as a first separator liquid 13, 13b, and has a flow rate of 160,165 kg / h. The first separator liquid 13, 13b is pressure-reduced to approximately 30 bar in a second expansion device 111 (valve), resulting in a temperature decrease to -6.5°C, and approximately 80% of the fluid being a liquid phase. The pressure-reduced first separator liquid 13, 13b is a second intermediate flash stream 17 consisting of a second intermediate gas phase 17b and a second intermediate liquid phase 17a, and is introduced to the second separator 102, operating at approximately 30 bar.

[0255] The second intermediate gas phase 17b is exiting the second separator 102 as the second recycle gas 19, which is recycled to the compressor arrangement 100. The second intermediate liquid phase 17a exits the second separator 102 as a second separator liquid 18 and has a flow rate of 129,165 kg / h. The second separator liquid 18 is pressure-reduced to approximately 16 bar in a final expansion device 112 (valve), resulting in a temperature decrease to -26.6°C, and approximately 86% of the fluid being a liquid phase. The pressured reduced second separator liquid 18 is a final intermediate flash stream 20 which is introduced to the stripping column 103, operating at approximately 16 bar.

[0256] The final intermediate flash stream 20, consisting of a final intermediate gas phase 20b and a final intermediate liquid phase 20a, is separated in a stripping column top separation zone 103a inside the stripping column 103. The final intermediate liquid phase 20a is stripped in a stripping column mass transfer section 103b in counter current contact with a stripping gas 24d having a flow rate of 8900 kg / h, yielding a stripped CO2 liquid 21 with a flow rate of 110,815 kg / h which flows to a stripping column liquid sump section 103 c located in the lower part of the stripping column 103, and a stripping column outlet stripping gas 24e, the stripping column outlet stripping gas 24e is mixing with the final intermediate gas phase 20b in the stripping column top separation zone 103a, and the resulting mix is exiting the stripping column 103 as the stripping column recycle gas 22, which is recycled to the compressor arrangement 100. The stripped CO2 liquid 21 has a stripping column liquid sump section temperature of approximately -26.6°C.

[0257] Around 15,000 kg / h of the stripped CO2 liquid 21 is extracted from the stripping column liquid sump section 103c as a partial condenser heat exchanger cold side feed 23, and routed to the cold side of a partial condenser heat exchanger 105 where it is heated such that 6500 kg / h evaporates to a gaseous phase, and providing around 540 kW of cooling duty. The resulting stream is returned to the stripping column 103 as a partial condenser heat exchanger cold side outflow 24, and separated in the stripping column 103, such that the evaporated portion of the partial condenser heat exchanger cold side outflow 24 is a primary stripping gas 24a. The stripping column 103 has a reboiler 103d providing a heating duty of 200 kW which is obtained by the cooling of the reboiler warm side inlet stream 41. The reboiler 103d evaporates 2400 kg / h of the stripped CO2 liquid 21, the evaporated portion is a secondary stripping gas 24c, which mixes with the primary stripping gas 24a to form the stripping gas 24d. The residual stripped CO2 liquid 21 (i.e. the portion which is not evaporated to become the stripping gas 24d) is a liquid CO2 product 5 having a flow rate of 101,915 kg / h, and consists of 99.999 mol% CO2, less than 10 ppm of H2O, and less than 1 ppm 02, N2 and Ar. The liquid CO2 product has a liquid CO2 product pressure of approximately 16 bar absolute pressure and a liquid CO2 product temperature of approximately -26.6°C. The liquid CO2 product 5 is routed to the liquid CO2 storage 150.

[0258] The first reject gas 31 (10,485 kg / h, 50 bar, 13.3°C) is introduced to the rectification column 104 having a rectification mass transfer section 104a, where the first reject gas 31 is cooled in counter current contact with a reflux liquid 34. The resulting bottom liquid is the recovered CO2 liquid 35, while the resulting overhead gas (7800 kg / h, 9°C) is a rectification outlet gas 32 which is further cooled to -21.5°C in the warm side of the partial condenser heat exchanger 105, to yield a partial condenser heat exchanger reject gas 3a having a flow rate of 85 kg / h, and consisting of 51 kg / h CO2, 24.6 kg / h N2, 8.7 kg / h 02, and 0.75 kg / h Ar, and the reflux liquid 34 (7715 kg / h, -21.5°C) which is recycled to the rectification column 104. The partial condenser heat exchanger reject gas 3a can be discharged to ambient air as a final reject gas 3, or recycled to the CO2 capture system as described above. In this example, the CO2 conservation (ratio of liquid CO2 product to CO2 content in the CO2 rich stream 1) of the liquefaction system is approximately 99.95%.

[0259] Definition of terminology

[0260] In the above description the terms are intended to have the following meanings:

[0261] Dry (as in a dry stream, e.g. dry CO2 rich stream, dry liquefaction inlet stream) shall mean that water has been removed from the stream, resulting in a dry stream having a residual water concentration which does not exceed the limit of solubility of water in liquid CO2 at any pressure between the triple point of CO2 (as known in the art) and the highest operating pressure in the CO2 liquefaction system. In a preferred embodiment of the invention, the water content of any dry dry stream shall be lower than 100 parts per million on volumetric basis (ppm, also termed ppmv), and more preferably the water content of any dry stream shall be lower than 30 ppm. Non-condensable components shall in this context mean any molecules other than CO2 and water, which can co-exist in gaseous phase with CO2, however where the amount of non-condensable components that can be dissolved in liquefied CO2, as determined by physical vapour-liquid equilibrium, is low (traces). This definition implies that in any thermodynamic equilibrium flash of CO2 and non-condensable components at such conditions that both a gaseous and liquid phase can co-exist, a majority of non-condensable components in the overall fluid which is subject to equilibrium flash will be present in gaseous phase, and a minority of the non- condensable components will be present in the liquid phase. In the context of this invention, non-condensable components include, but are not limited to, Oxygen, Nitrogen, Carbon Monoxide, Hydrogen, Argon, light hydrocarbons (e.g. methane, ethane, ethylene).

[0262] Non-CO2 components include non-condensable components and any other components which can co-exist in gaseous phase with CO2, including but not limited to, Oxygen, Nitrogen, Argon, noble gases other than Argon, Carbon Monoxide, Hydrogen, Nitrous Oxides, Sulphur Oxides, Hydrogen Sulphide, Carbonyl Sulphide, Mercaptans, Carbon Disulphide, Formaldehyde, Acetaldehyde, Ammonia, hydrocarbons, alcohols, vapour of amine, vapour of glycol.

[0263] The term “liquid CO2” shall mean that the molar composition is predominantly CO2 however with traces of non-condensable components which can thermodynamically be dissolved in the liquid CO2 at the prevailing liquid CO2 temperature and pressure.

[0264] Essentially equal pressures shall mean that the pressure difference is such that it does not materially affect the basic and novel characteristics of the claimed invention. For example, as a result of pressure drop in equipment (e.g. a column, a heat exchanger, a separator), flow momentum loss in equipment inlets and outlets, effect of liquid static head (elevation difference), frictional pressure drop in a stream or flowline.

[0265] Essentially in thermodynamic equilibrium shall mean that the compositions of the vapour and liquid phases of the referenced fluid are equal to thermodynamic equilibrium at the prevailing pressure and temperature, or having vapour and liquid compositions which deviate to the vapour and liquid compositions associated with thermodynamic equilibrium at the prevailing pressure and temperature, however the said deviations being sufficiently insignificant such that the deviations do not materially affect the basic and novel characteristics of the claimed invention. Ambient cooling medium shall mean any cooling medium fluid as known in the art (including air, water, seawater) having a temperature suitable for providing cooling, obtained without the use of any work cycle to reduce the temperature of the fluid. This implies that the cooling is based on direct use of an available ambient fluid holding a temperature governed by the prevailing ambient conditions (for example air, water or seawater) such that the available ambient fluid is the cooling medium (direct cooling), or indirect use of an available ambient fluid holding a temperature governed by the prevailing ambient conditions (for example air, water or seawater) which is heat exchanged by another suitable fluid which is the cooling medium (indirect cooling). In the latter case, the cooling medium can be any fluid suitable as an indirect cooling medium, as known in the art.

[0266] Refrigeration work cycle shall mean any process applying energy input (heat or mechanical work) to provide a cooling medium having a temperature which is lower than prevailing ambient conditions. Refrigeration work cycle includes any known refrigeration work cycle, as known in the art, including but not limited to direct or indirect mechanical refrigeration (vapour compression cycle) in single or multiple stages, and absorption cooling.

[0267] Liquid sump (as in stripping column liquid sump) as known in the art, shall mean a section which holds a volume of liquid inside an equipment, before the liquid is diverted out of the equipment. The liquid volume in the liquid sump can have several functions, including but not limited to; providing volume for level regulation, providing a retention volume (buffer) for downstream equipment / process, ensuring sufficient static liquid head, ensuring that any items installed in the liquid sump are covered by liquid, or any combination of these.

[0268] A mass transfer section (as in stripping column mass transfer section, rectification mass transfer section) as known in the art, shall mean a section inside an equipment which holds any suitable mass transfer device that promotes mass and heat transfer between downwards flowing liquid and upwards flowing vapour. Mass transfer device includes but is not limited to structured packing, random packing, fractionation trays, and all required auxiliaries e.g. gas distribution, liquid distribution, etc.

[0269] An expansion device shall mean any device, as known in the art, for reducing the pressure of a flowing fluid. This includes, but is not limited to, any types of valves, ejectors / jet pumps, and any types of expansion machines such as radial or axial flow turbines (expanders), and reciprocating expansion machines.

[0270] As known in the art, a heat exchanger shall mean a device for exchange of heat between at least two streams, the heat exchanger having at least one cold side and at least one warm side. The cold side having at least one cold side inlet stream (or feed stream) and at least one cold side outlet stream, and the warm side having at least one warm side inlet stream (or feed stream) and at least one warm side outlet stream, and such that the warm side feed stream releases heat, causing the warm side outlet stream to have a reduced temperature compared to the warm side feed stream temperature, and the cold side feed stream absorbs heat, causing the cold side outlet stream to have an increased temperature compared to the cold side feed stream temperature.

[0271] As known in the art, an ejector (also known as jet pump) shall mean a static device that use the energy within a high-pressure motive fluid (gas or liquid) to entrain and compress a low-pressure suction fluid (gas or liquid) to an intermediate discharge pressure which is lower than the pressure of the high-pressure motive fluid but higher than the pressure of the low-pressure suction fluid. The discharge of the ejector is a mix of the motive fluid and the low-pressure suction fluid.

[0272] As known in the art, gravity flow shall mean that a fluid flows from one position (source) to another position (designation) by an elevation difference between the source (highest elevation) and designation (lowest elevation), the elevation difference resulting in a static fluid pressure difference between the source and the designation.

[0273] Reference numbers

[0274] Equipment

[0275] Streams

[0276] Temperatures and pressures

Claims

1. Claims1. A method of liquefying a CO2 rich stream (1) to a liquid CO2 product (5), stripped of non-condensable components, in a carbon dioxide liquefaction system, the method comprising the steps of: introducing the CO2 rich stream (1) to a compressor arrangement (100) to obtain a compressor arrangement discharge stream (2) where the CO2 rich stream (1) makes up a portion of the compressor arrangement discharge stream (2); cooling the compressor arrangement discharge stream (2) in a liquefaction inlet cooler (131) to obtain a liquefaction inlet stream (10) having a liquefaction inlet pressure and a liquefaction inlet temperature; providing the liquefaction inlet stream (10) to a first separator (101) as a first intermediate flash stream (12) at a first separator pressure which is equal to or lower than the liquefaction inlet pressure, the first intermediate flash stream (12) comprising a first intermediate liquid phase (12a) and a first intermediate gas phase (12b); routing the first intermediate liquid phase (12a) from the first separator (101) as at least a portion of a first separator liquid (13), and subjecting the first separator liquid (13) to a pressure reduction from the first separator pressure to a stripping column pressure via one or more pressure reduction stages, resulting in a final intermediate flash stream (20) comprising a final intermediate liquid phase (20a) and a final intermediate gas phase (20b); introducing the final intermediate flash stream (20) to a stripping column top separation zone (103a) of a stripping column (103) operating at the stripping column pressure; flowing the final intermediate liquid phase (20a) downwards through a stripping column mass transfer section (103b) inside the stripping column (103) to strip non-condensable components from the final intermediate liquid phase (20a), the stripping of non-condensable components being assisted by a stripping gas (24d) flowing upwards through the stripping column mass transfer section (103b), to obtain a stripped CO2 liquid (21) having a stripped CO2 liquid temperature, the stripping gas (24d) comprising a primary stripping gas (24a);extracting a portion of the stripped CO2 liquid (21) as the liquid CO2 product (5), the liquid CO2 product (5) has a liquid CO2 product pressure which is essentially equal to the stripping column pressure; extracting at least a portion of the first intermediate gas phase (12b) from the first separator (101) as a first reject gas (31); introducing the first reject gas (31) as a bottom gaseous feed to a rectification column (104) having a rectification mass transfer section (104a), where the first reject gas (31) is in counter current contact with a reflux liquid (34) which is colder than the first reject gas (31), and where the first reject gas (31) is subjected to a temperature reduction that causes a fraction of the CO2 content of the first reject gas (31) to become condensed to provide a rectification outlet gas (32) having a reduced concentration of CO2 relative to the first reject gas (31), and a recovered CO2 liquid (35); and cooling the rectification outlet gas (32) in a partial condenser heat exchanger (105) such that a fraction of the CO2 content of the rectification outlet gas (32) becomes condensed, the CO2 which is condensed is separated from the rectification outlet gas (32) to form the reflux liquid (34) which is recycled to the rectification column (104), and such that the rectification outlet gas (32) minus the reflux liquid (34) is a partial condenser heat exchanger reject gas (3a) having a reduced concentration of CO2 relative to the rectification outlet gas (32).

2. A method according to claim 1, comprising the step of routing the recovered CO2 liquid (35) from the rectification column (104) to the stripping column (103) via one or more pressure reduction stages.

3. A method according to claim 1 or 2, wherein the rectification outlet gas (32) is cooled in the partial condenser heat exchanger (105) by heat exchange with evaporating CO2.

4. A method according to claim 3, wherein the rectification outlet gas (32) is cooled in the partial condenser heat exchanger (105) by heat exchange with evaporating CO2 from the stripped CO2 liquid (21), comprising the steps ofobtaining a partial condenser heat exchanger cold side feed (23) by extracting at least a portion of the stripped CO2 liquid (21); evaporating at least a portion of the partial condenser heat exchanger cold side feed (23) in the partial condenser heat exchanger (105), causing a net cooling duty in the partial condenser heat exchanger (105); and returning a partial condenser heat exchanger cold side outflow (24) to the stripping column (103), in the partial condenser heat exchanger cold side outflow (24) at least a portion of the stripped CO2 liquid (21) of the partial condenser heat exchanger cold side feed (23) is evaporated to become a gaseous portion.

5. A method according to claim 4, wherein the gaseous portion of the partial condenser heat exchanger cold side outflow (24) is the primary stripping gas (24a).

6. A method according to claim 4 or 5, wherein the flow of the partial condenser heat exchanger cold side feed (23) to the partial condenser heat exchanger (105), and the flow of the partial condenser heat exchanger cold side outflow (24) to the stripping column (103) is driven by a reduction in fluid density occurring for the condenser cold side feed when a portion of the condenser cold side feed is evaporated in the partial condenser heat exchanger (105).

7. A method according to any of the preceding claims, wherein the first separator pressure is lower than the liquefaction inlet pressure, and wherein the liquefaction inlet stream (10) is subjected to a first pressure reduction in a first expansion device (110) from the liquefaction inlet pressure to the first separator pressure, and wherein the first expansion device (110) yields the first intermediate flash stream (12).

8. A method according to claim 7, comprising the steps of extracting a portion of the first intermediate gas phase (12b) from the first separator (101) as a first recycle gas (14); routing the first recycle gas (14) to the compressor arrangement (100); and recompressing the first recycle gas (14) to the liquefaction inlet pressure to form a portion of the compressor arrangement discharge stream (2) and the liquefaction inlet stream (10).

9. A method according to any of claims 1-6, wherein the first separator (101) operates at essentially the liquefaction inlet pressure, and wherein theliquefaction inlet stream (10) is routed to the first separator (101) and introduced to the first separator (101) as the first intermediate flash stream (12) consisting of the first intermediate liquid phase (12a) and the first intermediate gas phase (12b), and wherein the portion of the first intermediate gas phase (12b) which is the first reject gas (31) is 100% of the first intermediate gas phase (12b).

10. A method according to any of the preceding claims, wherein the first separator liquid is subjected to the pressure reduction from the first separator pressure to the stripping column pressure in two pressure reduction stages, the method comprising the steps of; routing the first separator liquid (13, 13b) to a second pressure reduction in a second expansion device (111) to reduce the pressure from the first separator pressure to a second separator pressure, the second separator pressure being lower than the first separator pressure and higher than the stripping column pressure; obtaining a second intermediate flash stream (17) consisting of a second intermediate liquid phase (17a) and a second intermediate gas phase (17b); separating the second intermediate liquid phase (17a) and the second intermediate gas phase (17b) in a second separator (102) operating at the second separator pressure to obtain a second separator liquid (18) and a second recycle gas (19); routing the second separator liquid (18) to a final expansion device (112), wherein the pressure is reduced from the second separator pressure to the stripping column pressure to provide the final intermediate flash stream (20); routing the second recycle gas (19) to the compressor arrangement (100); and recompressing the second recycle gas (19) to the liquefaction inlet pressure to form a portion of the compressor arrangement discharge stream (2) and the liquefaction inlet stream (10).

11. A method according to any of the preceding claims, wherein the recovered CO2 liquid (35) is routed to the stripping column by the step of mixing the recovered CO2 liquid (35, 35a) with the first intermediate flash stream (12) upstream of the first separator or with the first intermediate liquid phase (12a) in the first separator.; or routing the recovered CO2 liquid (35, 35c) to the stripping column via a recovered CO2 liquid expansion device (116c).

12. A method according to claim 10, wherein the recovered CO2 liquid (35) is routed to the stripping column (103) by the step of: routing the recovered CO2 liquid (35, 35b) to the second separator (102) via a recovered CO2 liquid expansion device (116b).

13. A method according to any of the preceding claims, comprising the steps of: mixing the final intermediate gas phase (20b) with a stripping column outlet stripping gas (24e) to obtain a stripping column recycle gas (22); routing the stripping column recycle gas (22) to the compressor arrangement (100); and recompressing the stripping column recycle gas (22) to the liquefaction inlet pressure to form a portion of the compressor arrangement discharge stream (2) and the liquefaction inlet stream (10).

14. A method according to any of the preceding claims, wherein a secondary stripping gas (24c) is generated by applying a reboiler (103d) for evaporation of a portion of the stripped CO2 liquid (21), and wherein the heat required for evaporating the portion of the stripped CO2 liquid (21) is by heat exchange with a reboiler warm side inlet stream (41), the method comprising the steps of obtaining the reboiler warm side inlet stream (41) by extracting a portion of the liquefaction inlet stream (10), leaving a non-extracted portion of the liquefaction inlet stream (10b) which flows to the first expansion device (110), cooling the reboiler warm side inlet stream (41) to a temperature lower than the liquefaction inlet temperature, but higher than or equal to the stripped CO2 liquid temperature, providing a reboiler warm side outlet stream (42) regulating the flow of the reboiler warm side inlet stream (41) by a reboiler control valve (113a, 113b), the reboiler control valve being located at the reboiler warm side inlet (113b) or at the reboiler warm side outlet (113a); and introducing the reboiler warm side outlet stream (42) to a section of the carbon dioxide liquefaction system operating at a pressure lower than the pressure of the liquefaction inlet stream (10).

15. A method according to claim 14, wherein the reboiler warm side outlet stream (42) is introduced to the section of the carbon dioxide liquefactionsystem operating at a pressure lower than the pressure of the liquefaction inlet stream (10),- by introducing the reboiler warm side outlet stream (42a) downstream of the first expansion device (110,110b) to form a portion of the first intermediate flash stream (12); or- by introducing the reboiler warm side outlet stream (42a) to the first separator (101).

16. A method according to claim 10 and 14, wherein the reboiler warm side outlet stream (42) is introduced to the section of the carbon dioxide liquefaction system operating at a pressure lower than the pressure of the liquefaction inlet stream (10), by introducing the reboiler warm side outlet stream (42b) downstream of the second expansion device (111) to form a portion of the second intermediate flash stream (17); or introducing the reboiler warm side outlet stream (42b) to the second separator (102).

17. A method according to claim 14, wherein the reboiler warm side outlet stream (42) is introduced to the section of the carbon dioxide liquefaction system operating at a pressure lower than the pressure of the liquefaction inlet stream (10), by introducing the reboiler warm side outlet stream (42c) downstream of the final expansion device (112) to form a portion of the final intermediate flash stream (20); or introducing the reboiler warm side outlet stream (42c) to the stripping column (103).

18. A method according to any of the preceding claims, wherein the cooling in the liquefaction inlet cooler (131) is provided by any type of refrigeration work cycle.

19. A method according to any of the preceding claims, wherein the liquefaction inlet cooler is a multi-stream heat exchanger (131b) having a warm side and at least one cold side, and wherein the liquefaction inlet cooler (131b) is configured to cool the compressor arrangement discharge stream (2) by heat exchange with any of the first recycle gas (14), the second recycle gas (19), an intermediate recycle gas stream, the stripping column recycle gas (22), any available ambient cooling medium stream, and a refrigerant streamprovided by a refrigeration work cycle (61,62), and wherein the cooled compressor discharge stream exiting the liquefaction inlet cooler is the liquefaction inlet stream (10).

20. A method according to claim 18 or 19, wherein the compressor arrangement comprises an after cooler for cooling of the compressor arrangement discharge stream (2).

21. A method according to any of claims 1-8 or 10-20, wherein the compressor arrangement discharge stream (2) is cooled to a pre-liquefaction inlet temperature which enables phase separation at the liquefaction inlet pressure, and wherein the resulting stream is a pre-liquefaction inlet stream (11), which is introduced to a pre-separator (108) operating at a pressure essentially equal to the liquefaction inlet pressure, comprising the steps of separating a pre-liquefaction gas phase (1 lb) and a pre-liquefaction liquid phase (I la) of the pre-liquefaction inlet stream (11) in the preseparator (108);- the pre-liquefaction liquid phase (I la) from the pre-separator (108) is the liquefaction inlet stream (10);- the pre-liquefaction gas phase (1 lb) from the pre-separator (108) is a pre- liquefaction reject gas (31b) comprising CO2 and non-condensable components, which is subject to a pre-liquefaction gas pressure reduction in a pre-liquefaction gas expansion device (115), reducing pressure of the pre-liquefaction reject gas (31b) from the liquefaction inlet pressure to essentially the first separator pressure; and mixing the resulting pressure reduced pre-liquefaction reject gas (31c) with the first reject gas (31), creating a reject gas mix stream (3 Id) which is routed to the rectification column (104).

22. A method according to claim 7, wherein the first expansion device comprises a first ejector (110b), where the liquefaction inlet stream (10,10b) having essentially the liquefaction inlet pressure, is connected to a first ejector motive fluid inlet (110b-l), and a first ejector outlet (11 Ob-2) providing the first intermediate flash stream (12) having essentially the first separator pressure, and wherein the flow of fluid through the first ejector (110b) from the first ejector motive fluid inlet to the first ejector outlet is creating a pressure at a first ejector low-pressure suction inlet (110b-3) which is lower than or equal to the stripping column pressure, enabling inflow of at least a portion of the stripping column recycle gas (22) to the first ejector (110b), as the first ejector suction gas (15a), such that the first ejector suction gas (15a) is being recompressed to the first separator, and wherein any portion of thestripping column recycle gas which is not flowing to the first ejector (110b) as the first ejector suction gas (15a), flows to the compressor arrangement and is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream (2) and the liquefaction inlet stream (10).

23. A method according to claim 7 and 10, wherein the first expansion device comprises a first ejector (110b), where the liquefaction inlet stream (10,10b) having essentially the liquefaction inlet pressure, is connected to a first ejector motive fluid inlet (110b-l), and a first ejector outlet (11 Ob-2) provides the first intermediate flash stream (12) having essentially the first separator pressure, and wherein the flow of fluid through the first ejector (110b) from the first ejector motive fluid inlet to the first ejector outlet is creating a pressure at a first ejector low-pressure suction inlet (110b-3) which enables inflow of at least a portion of the second recycle gas (19), or at least a portion of an additional recycle gas, to the first ejector (110b), as the first ejector suction gas (15b), such that the first ejector suction gas (15b) is being recompressed to the first separator, and wherein any portion of the second recycle gas or any portion of the additional recycle gas which is not flowing to the first ejector (110b) as the first ejector suction gas (15b), flows to the compressor arrangement and is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream (2) and the liquefaction inlet stream (10).

24. A method according to claim 10 or 23, wherein the second expansion device comprises a second ejector (11 lb), where at least a portion of the first separator liquid (13) is connected directly or indirectly to a second ejector motive fluid inlet (l l lb-1), and a second ejector outlet (l l lb-2) providing the second intermediate flash stream (17) having essentially the second separator pressure, and wherein the flow of fluid through the second ejector (11 lb) from the second ejector motive fluid inlet to the second ejector outlet is creating a pressure at a second ejector low-pressure suction inlet (11 lb-3) which is lower than or equal to the stripping column pressure, enabling inflow of at least a portion of the stripping column recycle gas (22) to the second ejector (11 lb), as the second ejector suction gas (16), such that the second ejector suction gas (16) is being recompressed to the second separator, having the second separator pressure, and wherein any portion of the stripping column recycle gas which is not flowing to the second ejector (11 lb) as the second ejector suction gas (16), flows to the compressor arrangement and is recompressed to the liquefaction inlet pressure, to form a portion of the compressor arrangement discharge stream (2) and the liquefaction inlet stream (10).

25. A method according to claim 22 or 23, wherein the first ejector (110b) has an integrated device for adjusting the flow of fluid throughput, or wherein a valve device is applied in conjunction with the first ejector (110b), to control the flow of fluid through the first ejector (110b).

26. A method according to claim 24, wherein the second ejector (11 lb) has an integrated device for adjusting the flow of fluid throughput, or wherein a valve device is applied in conjunction with the second ejector (11 lb), to control the flow of fluid through the second ejector (11 lb).

27. A method according to any of the preceding claims, comprising the steps of introducing a vapour return stream (6) from a liquid CO2 storage (150) to the compressor arrangement (100); and compressing the vapour return stream (6) in the compressor arrangement (100) to become a portion of the compressor arrangement discharge stream (2), and consequently also a portion of the liquefaction feed stream (10).

28. A method according to claim 27, comprising the step of mixing the vapour return stream (6) with the stripping column recycle gas (22).

29. A method according to any of the preceding claims, wherein the CO2 rich stream (1) is introduced to the compressor arrangement (100) to make up a portion of the compressor arrangement discharge stream (2) by: mixing the CO2 rich stream (1) with the stripping column recycle gas (22,22a) and compressing the resulting mix in the compressor arrangement; or mixing the CO2 rich stream (1) with the compressor arrangement discharge stream (2).

30. A method according to claim 10, wherein the CO2 rich stream (1) is introduced to the compressor arrangement to make up a portion of the compressor arrangement discharge stream (2) by: mixing the CO2 rich stream (1) with the second recycle gas (19,19a) and compressing the resulting mix in the compressor arrangement.

31. A method according to claim 8, wherein the CO2 rich stream (1) is introduced to the compressor arrangement to make up a portion of the compressor arrangement discharge stream (2) by:mixing the CO2 rich stream (1) with the first recycle gas (14) and compressing the resulting mix in the compressor arrangement.

32. A method according to any of the preceding claims, comprising a step of: subjecting the partial condenser heat exchanger reject gas (3a) to a CO2 selective separation in a reject gas CO2 separation arrangement (141) to obtain a reject gas CO2 separation arrangement CO2 rich outlet stream (4), containing at least a portion of the CO2 in the partial condenser heat exchanger reject gas (3a), and a reject gas CO2 separation arrangement CO2 depleted outlet stream (3e) comprising non-condensable components and having a reduced content of CO2 compared to the partial condenser heat exchanger reject gas (3a).

33. A method according to claim 32, comprising a step of:- transferring the reject gas CO2 separation arrangement CO2 rich outlet stream (4) to the compressor arrangement (100) to form a portion of the compressor arrangement discharge stream (2).

34. A method according to any of claims 1-31, comprising a step of:- transferring the partial condenser heat exchanger reject gas (3a) to a second partial condenser heat exchanger (106) to obtain a second partial condenser heat exchanger CO2 depleted outlet stream (3b) having a reduced content of CO2 compared to the partial condenser heat exchanger reject gas (3a), and a second recovered liquid (36); and- transferring the second recovered liquid (36) to the stripping column (103), either directly, or indirectly via any of the rectification column, the first separator and the second separator.

35. A method according to claim 34 comprising the step of: subjecting the second partial condenser heat exchanger CO2 depleted outlet stream (3b) to a CO2 selective separation in a reject gas CO2 separation arrangement (141) to obtain a reject gas CO2 separation arrangement CO2 rich outlet stream (4), containing at least a portion of the CO2 in the second partial condenser heat exchanger CO2 depleted outlet stream (3b), and a reject gas CO2 separation arrangement CO2 depleted outlet stream (3e) comprising non-condensable components and having a reduced content of CO2 compared to the second partial condenser heat exchanger CO2 depleted outlet stream (3b).

36. A method according to claim 34 or 35, comprising the steps of: obtaining a second partial condenser heat exchanger cold side feed stream (37) by extracting at least a portion of liquid CO2 from any of thestripping column liquid sump section, the second separator and the first separator, and- transferring the second partial condenser heat exchanger cold side feed stream to the second partial condenser heat exchanger (106) where it is used to cool the partial condenser heat exchanger reject gas (3a).

37. A carbon dioxide liquefaction system, the system comprises a compressor arrangement (100), a liquefaction inlet cooler (131), a first separator (101), a rectification column (104), a partial condenser heat exchanger (105) and a stripping column (103), wherein- the compressor arrangement comprises a first compressor arrangement inlet (100-1) for a CO2 rich stream (1) and a compressor arrangement outlet (100-5) for a compressor arrangement discharge stream (2);- the liquefaction inlet cooler (131) comprises a liquefaction inlet cooler inlet (131-1) for the compressor discharge stream (2), and a liquefaction inlet cooler outlet (131-2) for a liquefaction inlet stream (10);- the first separator (101) comprises a first separator flash stream inlet (101-1) in fluid communication with the liquefaction inlet cooler outlet, a first separator liquid outlet (101-4) for a first separator liquid (13) and at least one first separator gas outlet (101-3), wherein the first separator is configured to separate a first intermediate flash stream (12) entering the first separator flash stream inlet into a first intermediate gas phase (12b) and a first intermediate liquid phase (12a), and the first separator gas outlet is in fluid communication with a rectification column gas inlet (104-1) of the rectification column (104), such that at least a portion of the first intermediate gas phase (12b) will flow to the rectification column (104) as a first reject gas (31) during use;- the rectification column (104) comprises a rectification mass transfer section (104a), the rectification column gas inlet (104-1) and a rectification column liquid outlet (104-2) for a recovered CO2 liquid (35), the rectification column (104) being configured to receive a reflux liquid (34) and discharge a rectification outlet gas (32) at a level above the rectification mass transfer section, and the rectification mass transfer section is configured to provide counter current contact between the reflux liquid (34) and the first reject gas (31);- the partial condenser heat exchanger (105) has a warm side configured to receive the rectification outlet gas (32) and to discharge the reflux liquid (34) and a partial condenser heat exchanger reject gas (3a), and a cold side configured to receive a partial condenser heat exchanger cold side feed (23) and to discharge a partial condenser heat exchanger cold side outflow (24), wherein the partial condenser heat exchanger (105) is configured to cool the rectification outlet gas (32), such that a fraction of a CO2 content of the rectification outlet gas (32) is condensed, the condensed CO2 providing the reflux liquid (34);- the stripping column (103) comprises a stripping column mass transfer section (103b) arranged between a stripping column top separation zone (103a) and a stripping column liquid sump section (103c), a stripping column flash stream inlet (103-1) arranged in the stripping column top separation zone (103 a) and being in fluid communication with the first separator liquid outlet (101-4) via at least a final expansion device (112), a stripping column gas outlet (103-3) for a stripping column recycle gas (22), arranged in the stripping column top separation zone (103 a) and being connected to the compressor arrangement (100) at a compressor arrangement stripping column recycle gas inlet (100-2), and a stripping column liquid CO2 product outlet (103-2), wherein the stripping column is configured to receive a final intermediate flash stream (20) through the stripping column flash stream inlet, the final intermediate flash stream (20) comprising a final intermediate liquid phase (20a) and a final intermediate gas phase (20b), and wherein the stripping column mass transfer section (103b) is arranged such that non-condensable components are stripped from the final intermediate liquid phase (20a) to yield a stripped CO2 liquid (21) being discharged to the stripping column liquid sump section (103 c), and wherein the stripping of non-condensable components from the final intermediate liquid phase (20a) is assisted by a stripping gas (24d) flowing upwards through the stripping column mass transfer section (103b); wherein the stripping column liquid CO2 product outlet (103-2) is arranged in the stripping column liquid sump section (103c) such that at least a portion of the stripped CO2 liquid (21) may exit the system as a liquid CO2 product (5) during use; and the CO2 liquefaction system comprises an arrangement for providing at least a portion of the stripped CO2 liquid (21) as the partial condenser heat exchanger cold side feed (23) and an arrangement for providing the partial condenser heat exchanger cold side outflow (24) to the stripping column (103) at a position between the stripping column liquid sump section (103c) and the stripping column mass transfer section (103b), and wherein thestripping gas (24d) comprises a primary stripping gas (24a) provided by a gaseous portion of the partial condenser heat exchanger cold side outflow (24).

38. A carbon dioxide liquefaction system according to claim 37, comprising a reboiler (103d) configured to evaporate a portion of the stripped CO2 liquid (21) to produce secondary stripping gas (24c) forming a portion of the stripping gas (24d) during use.

39. A carbon dioxide liquefaction system according to claim 38, wherein the reboiler (103d) is arranged in the stripping column liquid sump section (103c), or the reboiler is arranged external to the stripping column.

40. A carbon dioxide liquefaction system according to claim 38 or 39, wherein the reboiler comprises a reboiler warm side inlet (103d-l) for a reboiler warm side inlet stream (41) and a reboiler warm side outlet (103d-2) for a reboiler warm side outlet stream (42), the reboiler warm side inlet is fluidly connected between the liquefaction inlet cooler (131) and the first separator (101), such that a portion of the liquefaction inlet stream (10) constitutes the reboiler warm side inlet stream (41) during use, and the reboiler warm side outlet is fluidly connected downstream an expansion device (110,111,112) to a section of the carbon dioxide liquefaction system operating at a pressure lower than the pressure of the liquefaction inlet stream (10).

41. A carbon dioxide liquefaction system according to any of claims 37-40, comprising a first expansion device (110) arranged between the liquefaction inlet cooler (131) and the first separator (101).

42. A carbon dioxide liquefaction system according to any of claims 37-41, wherein the first separator gas outlet, or a separate first separator recycle gas outlet (101-2) of the first separator, is in fluid communication with the compressor arrangement to route at least a portion of the first intermediate gas phase (12b) to the compressor arrangement as a first recycle gas (14).

43. A carbon dioxide liquefaction system according to claim 41 and 42, wherein the first expansion device (110) comprises a first ejector (110b), the first ejector comprises a first ejector motive fluid inlet (110b-l), a first ejector outlet (11 Ob-2) and a first ejector low-pressure suction inlet (110b-3), wherein the first ejector motive fluid inlet (110b-l) is configured to receive the liquefaction inlet stream (10), the first ejector outlet (11 Ob-2) is in fluid communication with the first separator flash stream inlet (101-1) and the firstejector low-pressure suction inlet (110b-3) is in fluid communication with the stripping column gas outlet (103-3), such that at least a portion of the stripping column recycle gas (22) functions as a first ejector suction gas (15a).

44. A carbon dioxide liquefaction system according to any of claims 37-43, comprising a second separator (102), wherein the second separator (102) comprises a second separator flash stream inlet (102-1) in fluid communication with the first separator liquid outlet (101-4) via a second expansion device (H I), a second separator gas outlet (102-3) and a second separator liquid outlet (102-2), wherein the second separator is configured to separate a second intermediate flash stream (17) entering the second separator flash stream inlet into a second intermediate gas phase (17b) and a second intermediate liquid phase (17a), wherein the second separator gas outlet (102-3) is in fluid communication with the compressor arrangement to route at least a portion of the second intermediate gas phase (17b) to the compressor arrangement as a second recycle gas (19), and the second separator liquid outlet (102-2) is in fluid communication with the stripping column flash stream inlet (103-1) via at least the final expansion device (H2).

45. A carbon dioxide liquefaction system according to claim 41 or 42, and 44, wherein the first expansion device (110) comprises a first ejector (110b), the first ejector (110b) comprises a first ejector motive fluid inlet (110b-l), a first ejector outlet (11 Ob-2) and a first ejector low-pressure suction inlet (110b-3), wherein the first ejector motive fluid inlet (110b-l) is configured to receive the liquefaction inlet stream (10), the first ejector outlet (110b-2) is in fluid communication with the first separator flash stream inlet (101-1) and the first ejector low-pressure suction inlet (110b-3) is in fluid communication with the second separator gas outlet (102-3), such that at least a portion of the second intermediate gas phase (17b) functions as a first ejector suction gas (15b).

46. A carbon dioxide liquefaction system according to claim 44 or 45, wherein the second expansion device (111) comprises a second ejector (11 lb), the second ejector comprises a second ejector motive fluid inlet (l l lb-1), a second ejector outlet (11 lb-2) and a second ejector low-pressure suction inlet (11 lb-3), wherein the second ejector motive fluid inlet (11 lb- 1) is configured to receive at least a portion of the first separator liquid (13), the second ejector outlet (11 lb-2) is in fluid communication with the second separator flash stream inlet (102-1) and the second ejector low-pressure suction inlet (11 lb-3) is in fluid communication with the stripping columngas outlet (103-3), such that at least a portion of the stripping column recycle gas (22) functions as a second ejector suction gas (16).

47. A carbon dioxide liquefaction system according to any of claims 37-46, wherein at least one of the first expansion device, the second expansion device and the final expansion device comprises a valve (110,111,112).

48. A carbon dioxide liquefaction system according to any of claims 37-47, wherein the rectification column (104) and the partial condenser heat exchanger (105) are connected to form a combined column condenser assembly (107).

49. A carbon dioxide liquefaction system according to claim 48, wherein the partial condenser heat exchanger (105) is a vertical shell and tube type heat exchanger, mounted directly at the top of the rectification column (104), such that the rectification column (104) and the partial condenser heat exchanger (105) is a combined column condenser assembly (107).

50. A carbon dioxide liquefaction system according to any of claims 37-49, wherein the stripping column (103), the first separator (101) and optionally the second separator (102) are mechanically interconnected to form a vertical column structure wherein the stripping column is at a higher elevation than the first separator.

51. A carbon dioxide liquefaction system according to any of claims 37-50, wherein the arrangement for providing the partial condenser heat exchanger cold side outflow (24) to the stripping column comprises a first heat exchanger conduit (105-2) connecting the partial condenser heat exchanger cold side outflow (24) to the stripping column heat exchange inlet (103-5) at a position between the stripping column liquid sump section (103c) and the stripping column mass transfer section (103b), and wherein the arrangement for providing at least a portion of the stripped CO2 liquid (21) as the partial condenser heat exchanger cold side feed (23) comprises a second heat exchanger conduit (105-3) fluidly connecting the stripping column and the partial condenser heat exchanger cold side feed (23).

52. A carbon dioxide liquefaction system according to any of claims 37-47 and 50, wherein the partial condenser heat exchanger (105) is arranged in the stripping column liquid sump section (103).

53. A carbon dioxide liquefaction system according to any of claims 37-51, wherein the arrangement for providing a portion of stripped CO2 liquid (21)to the partial condenser heat exchanger (105) comprises a pump (114a, 114b), the pump configured to transfer the portion of stripped CO2 liquid (21) to the partial condenser heat exchanger (105).

54. A carbon dioxide liquefaction system according to any of claims 37-48 and 51-53, comprising a reflux separator (109), the reflux separator (109) being configured to receive a stream consisting of the reflux liquid (34) and the partial condenser heat exchanger reject gas (3a) discharged from the partial condenser heat exchanger (105) via a reflux separator inlet (109-1) to separate the reflux liquid (34) and the partial condenser heat exchanger reject gas (3a)?and comprises a reflux liquid outlet (109-3) in fluid communication with the rectification column (104) and a reflux separator gas outlet (109-2).

55. A carbon dioxide liquefaction system according to any of claims 37-54, comprising a reject gas CO2 separation arrangement (141), the reject gas CO2 separation arrangement (141) is configured to receive the partial condenser heat exchanger reject gas (3a) during use, and to subject the partial condenser heat exchanger reject gas (3a) to a CO2 selective separation to obtain a reject gas CO2 separation arrangement CO2 rich outlet stream (4), containing at least a portion of the CO2 in the partial condenser heat exchanger reject gas (3a), and a reject gas CO2 separation arrangement CO2 depleted outlet stream (3e) comprising non-condensable components and having a reduced content of CO2 compared to the partial condenser heat exchanger reject gas (3a).

56. A carbon dioxide liquefaction system according to claim 55, comprising at least one conduit arranged to transfer the reject gas CO2 separation arrangement CO2 rich outlet stream (4) to the compressor arrangement (100) to form a portion of the compressor arrangement discharge stream (2).

57. A carbon dioxide liquefaction system according to any of claims 37-54, comprising a second partial condenser heat exchanger (106), the second partial condenser heat exchanger (106) is configured to receive the partial condenser heat exchanger reject gas (3a) during use, and to cool the partial condenser heat exchanger reject gas (3a) to obtain a second partial condenser heat exchanger CO2 depleted outlet stream (3b) having a reduced content of CO2 compared to the partial condenser heat exchanger reject gas (3a), and a second recovered liquid (36).

58. A carbon dioxide liquefaction system according to claim 57, comprising an arrangement for transfer of the second recovered liquid (36) to the strippingcolumn (103), directly or indirectly via any of the rectification column (104), the first separator (101), the second separator (102).

59. A carbon dioxide liquefaction system according to claim 57 or 58, comprising a reject gas CO2 separation arrangement (141), the reject gas CO2 separation arrangement (141) is configured to receive the second partial condenser heat exchanger CO2 depleted outlet stream (3b) during use, and to subject the second partial condenser heat exchanger CO2 depleted outlet stream (3b) to a CO2 selective separation to obtain a reject gas CO2 separation arrangement CO2 rich outlet stream (4), containing at least a portion of the CO2 in the second partial condenser heat exchanger CO2 depleted outlet stream (3b), and a reject gas CO2 separation arrangement CO2 depleted outlet stream (3e) comprising non-condensable components and having a reduced content of CO2 compared to the second partial condenser heat exchanger CO2 depleted outlet stream (3b).

60. A carbon dioxide liquefaction system according to any of claims 37-47 and 50-59, wherein the rectification column (104) and the first separator (101) is a combined separator and column device (101b) in which the rectification mass transfer section (104a) is arranged at a level above the first separator flash stream inlet (101-1) and the first separator liquid outlet (101-4), and a lower end of the rectification mass transfer section (104a) provides the rectification column gas inlet (104-1) and the first separator gas outlet (101- 3).

61. A carbon dioxide liquefaction system according to any of claims 37-60, comprising a regasification unit (151) arranged to receive at least parts of the liquid CO2 product (5), and configured to transform the received liquid CO2 product (5) to a gaseous CO2 product (7) which is in a sub critical gas phase or a supercritical dense gas phase.

62. A carbon dioxide liquefaction system according to claim 61, wherein the regasification unit (151) comprises an arrangement for heat exchange with any of the liquefaction inlet stream 10, the first intermediate flash stream 12, the first separator liquid 13, the second intermediate flash stream 17 and the second separator liquid 18.

63. A carbon dioxide liquefaction system according to any of claims 37-62, comprising at least one additional pressure reduction stage arranged between the first separator liquid outlet and the final expansion device, the additional pressure reduction stage comprises an additional expansion device and an additional separator configured similar to the first expansion device and thefirst separator, wherein the additional separator is configured to provide an additional recycle gas via an additional recycle gas outlet and an additional separator liquid via an additional separator liquid outlet.

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