Carbon dioxide dehydration

Abstract

A method and system for purifying a carbon dioxide feed stream, wherein the carbon dioxide feed stream is subcooled and partially condensed to remove water upstream of an adsorber to produce a dry carbon dioxide stream. The dry carbon dioxide stream is further subcooled and partially condensed in a carbon dioxide purification unit to form a carbon dioxide product stream. Excess refrigeration duty from the carbon dioxide purification unit is used to subcool the carbon dioxide feed stream.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to U.S. Nonprovisional Patent Application No. 17 / 856,010, filed July 1, 2022. BACKGROUND

[0003] The present disclosure relates generally to the purification and dehydration of carbon dioxide, and more specifically to systems and methods that integrate partial condensation and temperature swing adsorption to remove water from a carbon dioxide stream.

[0004] Existing industrial processes such as power generation require the capture of carbon dioxide (CO2) to mitigate the effects of climate change. The captured CO2 stream often requires removal of water and light components such as nitrogen prior to utilization or sequestration. In particular, water must be removed to prevent the formation of a solid hydrate phase at higher pressures and / or lower temperatures.

[0005] Stallman et al. (US 9,429,359) teaches a method of drying a CO2 stream by compressing and cooling the CO2 stream, which partially condenses to form a carbon dioxide-rich gas phase and an aqueous liquid phase. The carbon dioxide-rich gas phase is then further dehydrated using temperature swing adsorption.

[0006] Buijs et al. (US 8,931,306) teaches a method of cooling a natural gas feed prior to dehydration, where the natural gas feed is cooled using a dehydrated natural gas stream.

[0007] White et al. (US 8,257,476) teaches a method of dehydrating and purifying CO2 by adsorption followed by partial condensation, also known as a CO2 purification unit (CPU). The cooling duty required to cool the CO2 stream is provided by expanding one or more carbon dioxide-rich streams.

[0008] The cooling duty required to cool the CO2 stream requires some form of power, so there is a need in the industry to reduce the power requirements for CO2 dehydration through improved heat integration. SUMMARY

[0009] The present disclosure relates to a process of dehydrating a flue gas stream to allow the capture of CO2 by partial condensation. The flue gas stream is first cooled to condense a portion of the water vapor present, then further dehydrated by adsorption. The resulting dry carbon dioxide stream is cooled and partially condensed to produce a carbon dioxide product stream and an exhaust stream depleted in CO2. The purification system can be configured to produce an additional refrigeration duty that can be used to cool the flue gas stream.

[0010] Aspect 1 : A method for purifying a carbon dioxide feed stream, comprising: subcooling and partially condensing a carbon dioxide feed stream to a first temperature to produce a subcooled carbon dioxide stream; separating the subcooled carbon dioxide stream to produce an overhead vapor stream and an aqueous bottoms stream; passing the overhead vapor stream through an in-line adsorber to produce a dry carbon dioxide stream and a loaded adsorber; subcooling and partially condensing the dry carbon dioxide stream or a stream derived from the dry carbon dioxide stream to produce a cold carbon dioxide stream; separating the cold carbon dioxide stream to produce a cold vent stream and a cold carbon dioxide liquid stream; expanding at least a portion of the cold carbon dioxide liquid stream to produce a low pressure carbon dioxide stream; wherein the carbon dioxide feed is subcooled by one or more of: at least a portion of the cold carbon dioxide liquid stream, at least a portion of the cold vent stream, and at least a portion of the low pressure carbon dioxide stream.

[0011] Aspect 2: A method for purifying a carbon dioxide feed stream, the process comprising: subcooling and partially condensing a carbon dioxide feed stream to a first temperature to produce a subcooled carbon dioxide stream; separating the subcooled carbon dioxide stream to produce an overhead vapor stream and an aqueous bottoms stream; passing the overhead vapor stream through an in-line adsorber to produce a dry carbon dioxide stream and a loaded adsorber; subcooling and partially condensing the dry carbon dioxide stream or a stream derived from the dry carbon dioxide stream to produce an intermediate carbon dioxide stream; separating at least a portion of the intermediate carbon dioxide stream to produce a first carbon dioxide vapor stream and a first carbon dioxide liquid stream; expanding at least a portion of the first carbon dioxide liquid stream to produce a medium pressure carbon dioxide stream; subcooling and partially condensing at least a portion of the first carbon dioxide vapor stream to produce a cold carbon dioxide stream; separating at least a portion of the cold carbon dioxide stream to produce a cold vent stream and a cold carbon dioxide liquid stream; wherein the carbon dioxide feed is cooled by one or more of: at least a portion of the first carbon dioxide liquid stream, at least a portion of the medium pressure carbon dioxide stream, at least a portion of the cold vent stream, at least a portion of the cold carbon dioxide liquid stream, and at least a portion of the low pressure carbon dioxide stream.

[0012] Aspect 3: The method of aspect 2, wherein the carbon dioxide feed stream is subcooled by direct contact with at least a portion of the first carbon dioxide liquid stream.

[0013] Aspect 4: The method of any one of aspects 1 to 3, wherein the first temperature is less than about 12 °C.

[0014] Aspect 5: The method of any one of aspects 1 to 4, wherein at least a portion of the subcooling duty for subcooling and partially condensing the carbon dioxide feed is provided by a waste heat cooler powered by a heat source.

[0015] Aspect 6: The method of aspect 5, further comprising compressing the low pressure carbon dioxide stream to produce a carbon dioxide product; wherein at least a portion of the heat source is provided by the compression of the low pressure carbon dioxide stream.

[0016] Aspect 7: The method of aspect 5 or aspect 6, further comprising compressing the carbon dioxide feed stream prior to the subcooling and partial condensation; wherein at least a portion of the heat source is provided by the compression of the carbon dioxide feed stream.

[0017] Aspect 8: The method of any one of aspects 5 to 7, further comprising reacting the oxygen enriched stream with a fuel to produce the carbon dioxide feed stream; wherein at least a portion of the heat source is provided by the reaction of the oxygen enriched stream with the fuel.

[0018] Aspect 9: The method of any one of aspects 5 to 8, wherein at least a portion of the heat source is provided by a stream of steam.

[0019] Aspect 10: The method of any one of aspects 1 to 9, further comprising passing a regeneration gas stream through the loaded adsorber to regenerate the loaded adsorber and produce a spent regeneration gas; wherein the regeneration gas comprises at least 50% nitrogen.

[0020] Aspect 11 : The method of any one of aspects 1 to 10, wherein the carbon dioxide feed is subcooled and partially condensed in a heat exchanger comprising a metal; wherein the minimum temperature of the metal is greater than the hydrate formation temperature of the carbon dioxide feed stream.

[0021] Aspect 12: The method of any one of aspects 1 to 11, further comprising compressing the low pressure carbon dioxide stream to produce a carbon dioxide product stream; expanding at least a portion of the carbon dioxide product stream to produce a carbon dioxide refrigerant stream; and heating the carbon dioxide refrigerant stream with the carbon dioxide feed stream.

[0022] Aspect 13: The method of any one of aspects 1 to 12, further comprising heating the dry carbon dioxide stream by indirect heat exchange with the carbon dioxide feed stream.

[0023] Aspect 14: The method of aspect 13, further comprising subcooling the dry carbon dioxide stream prior to heating the dry carbon dioxide stream by indirect heat exchange.

[0024] Aspect 15: The method of any one of aspects 1 to 14, wherein the carbon dioxide feed stream is subcooled by direct contact with a cold water stream.

[0025] Aspect 16: The method of any one of aspects 1 to 15, wherein the carbon dioxide feed stream is subcooled by direct contact with at least a portion of a cold carbon dioxide liquid stream.

[0026] Aspect 17: The method of any one of aspects 1-16, wherein the carbon dioxide feed stream is subcooled by indirect heat exchange.

[0027] Aspect 18: A system for purifying a carbon dioxide feed stream, comprising: a first heat exchanger configured to receive a carbon dioxide feed stream and produce a subcooled carbon dioxide stream; a first separator configured to receive the subcooled carbon dioxide stream and produce an overhead vapor stream and an aqueous bottoms stream; an adsorber configured to receive the overhead vapor stream and produce a dry carbon dioxide stream; a second heat exchanger configured to receive the dry carbon dioxide stream and produce a cold carbon dioxide stream; a cold separator configured to receive the cold carbon dioxide stream and produce a cold exhaust stream and a cold carbon dioxide liquid stream; a pressure letdown configured to receive at least a portion of the cold carbon dioxide liquid stream and produce a low pressure carbon dioxide stream; wherein the first heat exchanger and the second heat exchanger are in fluid flow communication with one or more of: at least a portion of the cold carbon dioxide liquid stream, at least a portion of the cold exhaust stream, and at least a portion of the low pressure carbon dioxide stream.

[0028] Aspect 19: The system of aspect 18, wherein the first heat exchanger comprises a direct contact heat exchanger in fluid flow communication with a cold water stream.

[0029] Aspect 20: The system of aspect 18 or aspect 19, further comprising a product compressor configured to receive the low pressure carbon dioxide stream to produce a carbon dioxide product stream; a pressure letdown configured to receive at least a portion of the carbon dioxide product stream to produce a carbon dioxide refrigerant stream; wherein the first heat exchanger is in fluid flow communication with the carbon dioxide refrigerant stream.

[0030] Aspect 21: The system of any one of aspects 18-20, wherein the first heat exchanger comprises a cold side inlet in fluid flow communication with the dry carbon dioxide stream.

[0031] Aspect 22: The system of aspect 21, further comprising a third heat exchanger configured to receive the dry carbon dioxide stream and subcool it; wherein the third heat exchanger is upstream of the cold side inlet of the first heat exchanger.

[0032] Aspect 23: The system of any one of aspects 18-22, further comprising a waste heat cooler configured to receive a heat source and produce a refrigerant stream; wherein the first heat exchanger comprises a cold side inlet in fluid flow communication with the refrigerant stream.

[0033] Aspect 24: The system of aspect 23, further comprising a product compressor configured to receive the low pressure carbon dioxide stream to produce a carbon dioxide product; wherein at least a portion of the heat source is provided by the product compressor.

[0034] Aspect 25: The system of either Aspect 23 or Aspect 24, further comprising a feed compressor configured to receive the carbon dioxide feed stream upstream of the first heat exchanger; wherein at least a portion of the heat source is provided by the feed compressor.

[0035] Aspect 26: The system of any one of Aspects 23-25, further comprising an oxy- fuel combustor configured to receive an oxygen-rich stream and a fuel and produce the carbon dioxide feed stream; wherein at least a portion of the heat source is provided by the oxy-fuel combustor.

[0036] Aspect 27: The system of any one of Aspects 23-26, wherein at least a portion of the heat source is provided by a steam stream. BRIEF DESCRIPTION OF DRAWINGS

[0037] The application will be described below with reference to the attached drawings, in which like elements are indicated by like reference numerals:

[0038] Figure 1 is a diagram depicting an embodiment of an oxy-fuel combustion process with carbon capture.

[0039] Figure 2 is a detailed flow diagram depicting a CO2 purification system.

[0040] Figure 3 is a diagram depicting a modification of Figure 2 in which a single combined heat exchanger is used to both chill and partially condense the carbon dioxide feed stream.

[0041] Figure 4 is a diagram depicting a modification of Figure 2 in which expansion of a portion of the carbon dioxide product provides refrigeration to chill the compressed carbon dioxide feed stream.

[0042] Figure 5 is a diagram depicting a modification of Figure 4 in which a dry carbon dioxide stream provides refrigeration to chill the compressed carbon dioxide feed stream.

[0043] Figure 6 is a diagram depicting a modification of Figure 5 in which a dry carbon dioxide stream is chilled prior to providing refrigeration.

[0044] Figure 7 is a diagram depicting a modification of Figure 5 in which a micro-cooled exhaust stream provides refrigeration to chill the compressed carbon dioxide feed stream.

[0045] Figure 8 is a diagram depicting a modification of Figure 3a variant of FIG. 1 in which the compressed carbon dioxide feed stream is combined with a cold water stream to cool and partially condense the water.

[0046] Figure 9 is a variant of FIG. 1 in which the compressed carbon dioxide feed stream is combined with a liquid carbon dioxide stream. Figure 8

[0047] Figure 10 is a variant of FIG. 1 in which the liquid carbon dioxide stream is obtained from a cold end of a CO2 purification system. Figure 9

[0048] Figure 11 is a variant of FIG. 1 in which a portion of the first liquid carbon dioxide stream is pumped and used as a refrigerant. Figure 2

[0049] Figure 12 is a variant of FIG. 1 in which a portion of the first liquid carbon dioxide stream is pumped and used as a refrigerant. Figure 7

[0050] Figure 13 is a variant of FIG. 1 in which a portion of the first liquid carbon dioxide stream is pumped and used as a refrigerant. Figure 6

[0051] Figure 14 is a variant of FIG. 1 in which the carbon dioxide feed stream is not cooled prior to dehydration. Figure 2 DETAILED DESCRIPTION

[0052] The following detailed description provides preferred exemplary embodiments, and is not intended to limit the scope, applicability or configuration of the invention as set forth in the accompanying claims. Rather, the following detailed description will provide enabling descriptions for one of ordinary skill in the art to practice the preferred exemplary embodiments of the invention. Various changes can be made to the function and arrangement of elements without departing from the spirit and scope of the invention as set forth in the appended claims.

[0053] As used herein, the articles "a" and "an" are intended to mean one or more of the items that they describe, unless otherwise indicated. The use of the terms "first," "second," and the like does not imply any particular order, but they are used to denote one of multiple things. The use of the terms "at least one of," "one or more of," and the like is intended to mean one or more of the items that they describe, unless otherwise indicated. The use of the term "or" is intended to mean "and / or" unless otherwise indicated. The use of the term "based on" is intended to mean "based, at least in part, on" unless otherwise indicated.

[0054] ​​​​​​The phrase "at least a portion" means "a part or all." "At least a portion of a stream" has the same composition as the stream from which it is derived, with each species having the same concentration.

[0055] The term "and / or" placed between the last two entities in a list of 3 or more entities means that at least one of the entities, including any specific combination of the entities in the list, is included in the list. For example, "A, B, and / or C" has the same meaning as "A and / or B and / or C" and includes the following combinations of A, B, and C: (1) only A, (2) only B, (3) only C, (4) A and B but not C, (5) A and C but not B, (6) B and C but not A, and (7) A and B and C.

[0056] The adjective "any" means one, some, or all, as appropriate.

[0057] The term "depleted" or "lean" means that the mole percent concentration of a specified component is less than the mole percent concentration of the original stream from which it was formed. "Depleted" or "lean" does not mean that the stream is completely devoid of the specified component.

[0058] The term "enriched" or "rich" means that the mole percent concentration of a specified component is greater than the mole percent concentration of the original stream from which it was formed.

[0059] "Downstream" and "upstream" refer to the intended flow direction of the process fluid being conveyed. If the intended flow direction of the process fluid is from a first device to a second device, the second device is downstream of the first device. In the case of a recycle stream, downstream and upstream refer to the first pass of the process fluid.

[0060] The term "indirect heat exchange" means a process in which sensible and / or latent heat is transferred between two or more fluids without the fluids in question coming into physical contact with each other. The heat can be transferred through the walls of a heat exchanger or using an intermediate heat transfer fluid. The term "hot stream" means any stream that exits a heat exchanger at a lower temperature than it entered. Conversely, a "cold stream" is a stream that exits a heat exchanger at a higher temperature than it entered. Hot streams enter the hot side inlets of a heat exchanger, while cold streams enter the cold side inlets of a heat exchanger. A heat exchanger can have any number of hot side inlets and cold side inlets.

[0061] Figure 1An embodiment of a process 1 for oxy-fuel combustion with carbon capture is shown. An oxygen plant 10 produces an oxygen-rich stream 12 that is combusted with a fuel 22 in an oxy-fuel combustor 20 to produce heat and a flue gas 24. "Oxygen-rich" is defined as any composition greater than 21% ambient concentration by volume. The oxy-fuel combustor can be associated with any industrial process that requires heat, such as power generation, lime production, and cement production. In at least some embodiments, the flue gas 24 contains carbon dioxide that is generated by the reaction of a feedstock, such as limestone, due to the heat generated by the oxy-fuel combustor. If desired, particulate matter 32 can be removed from the flue gas 24 in a particulate removal system 30, leaving a carbon dioxide feed stream 34. The carbon dioxide feed stream 34 next enters a purification section PS. If desired, the carbon dioxide feed stream 34 can be compressed in a compression system 40. The compression system 40 can include multiple compression stages, and can also include inter-stage coolers and / or a post-cooler. The compression and cooling can result in the formation of a condensate phase 42, which can contain nitrogen- and sulfur-containing species due to dissolved NOx and SOx. The compressed carbon dioxide feed stream 44 enters a dehydration system 50, where water is removed to form a dry carbon dioxide stream 52. The concentration of water in the dry carbon dioxide stream 52 can be less than 5 ppm, less than 3 ppm, or less than 1 ppm, such that the dry carbon dioxide stream 52 can be further cooled without forming an ice phase and / or a hydrate phase. The dry carbon dioxide stream 52 is next cooled and partially condensed in a carbon dioxide purification unit 60. The carbon dioxide purification unit 60 separates the dry carbon dioxide stream 52 into an exhaust stream 64 and a purified carbon dioxide stream 62. In at least some embodiments, the purified carbon dioxide stream 62 can next enter a final purification system 70 to produce a carbon dioxide product stream 72. Depending on the end use of sequestration or utilization and / or transportation requirements, the final purification system 70 can include one or more of the following: liquefaction, trace impurity removal such as oxygen and / or sulfur removal, dehydration, and compression.

[0062] In at least some embodiments, the exhaust stream 64 can be separated in a membrane separation system 80, which can include a single membrane stage or multiple membrane stages in series and / or in parallel. The exhaust stream 64 is separated into a carbon dioxide-rich permeate stream 82 and a carbon dioxide-lean retentate stream 84 by selective permeation. Carbon dioxide selectively permeates the membrane compared to slower species such as nitrogen. In at least some example implementations, the higher solubility of carbon dioxide in the membrane material results in a faster permeation rate than similar-sized molecules with lower solubility, such as nitrogen.

[0063] Sanders et al. (Polymer; Vol. 54; pp. 4729-4761; 2013) provide a handy review of current membrane technology. They describe the physical parameters and performance characteristics of polymeric membranes including polystyrene, polysulfone, polyethersulfone, polyvinylfluoride, polyvinylidene fluoride, polyether ether ketone, polycarbonate, polyphenylene oxide, polyethylene, polypropylene, cellulose acetate, polyimide (such as Matrimid 5218 or P-84), polyamide, polyvinyl alcohol, polyvinyl acetate, polyethylene oxide, polydimethylsiloxane, copolymers, block copolymers, or polymer blends. Existing industrially useful gas separations are carried out primarily with polymers such as those listed above or rubbery materials such as siloxanes. Additional membrane materials can include mixed matrix membranes, perfluoropolymers, thermally rearranged polymers, facilitated transport membranes, metal-organic frameworks, zeolite-imidazolate frameworks, electrochemical membranes, metallic membranes, and carbon molecular sieves. The membrane material in the membrane separation system 80 can be any of those listed above, or any other material that has a faster permeation rate for some compounds, such as carbon dioxide, and a slower permeation rate for some compounds, such as nitrogen.

[0064] Suitable membrane materials can be manufactured as hollow fibers and packaged as membrane bundles, or as flat sheets, packaged as spiral-wound or plate-and-frame units, in order to provide a larger surface area to volume ratio and to be housed in a module. The gas entering the module contacts the membrane, a portion of the gas permeates the membrane and exits the module as a low pressure permeate stream. The permeate will be enriched in the faster permeating gas relative to the slower permeating gas. The portion of the gas that does not permeate the membrane exits the module as an unpermeated or retentate stream, which is enriched in the slower permeating gas relative to the faster permeating gas. A membrane stage is defined as one or more membrane modules arranged such that each feed inlet is in fluid flow communication with each other feed inlet, each permeate outlet is in fluid flow communication with each other permeate outlet, and each retentate outlet is in fluid flow communication with each other retentate outlet.

[0065] The carbon dioxide enriched permeate stream 82 can be recycled by combination with the oxygen enriched stream 12 and / or the carbon dioxide feed stream 34 via line 86. In at least some embodiments, the dehydration system 50 includes an adsorption system. The carbon dioxide depleted retentate stream 84 can be used to regenerate the adsorption system, producing a waste regeneration stream 88 that can be recycled or vented. In at least some embodiments, the adsorption system can be regenerated with at least a portion of the vent stream 64, the compressed dry air, and / or an inert gas such as nitrogen. In at least some embodiments, the vent stream 64 and the carbon dioxide depleted retentate stream 84 contain at least 50% nitrogen by volume.

[0066] Figure 2An embodiment of process 2 is shown, which shows the purification section PS in more detail. In at least some embodiments, carbon dioxide feed stream 34 is compressed in feed compressor K1. Compressed carbon dioxide feed stream 44 is cooled and at least partially condensed in first heat exchanger E1 to produce cooled carbon dioxide stream 114. Cooled carbon dioxide stream 114 is separated in first separator C1 to produce water-containing bottoms stream 116 and overhead vapor stream 118. Overhead vapor stream 118 is passed through on-line adsorber A1, which removes water and allows dry carbon dioxide stream 52 to exit. On-line adsorber A1 can utilize one or more high surface area adsorbents, including but not limited to zeolites, metal organic frameworks (MOFs), alumina, silica gel, silicalite, activated carbon, Engelhard titanosilicates (ETS), and metal oxides.

[0067] Dry carbon dioxide stream 52 is cooled and at least partially condensed in second heat exchanger E2 to produce intermediate carbon dioxide stream 122. Intermediate carbon dioxide stream 122 is separated in intermediate separator C2 to produce first carbon dioxide liquid stream 124 and first carbon dioxide vapor stream 126. First carbon dioxide liquid stream 124 is then expanded over a pressure letdown device such as valve V1 to produce medium pressure carbon dioxide stream 128, which provides refrigeration to second heat exchanger E2.

[0068] First heat exchanger E1 and second heat exchanger E2 represent a heat exchanger system, which can be a single heat exchanger or divided into two or more heat exchangers in series or in parallel. For example, second heat exchanger E2 can be divided into two separate heat exchangers between the location where intermediate carbon dioxide stream 122 exits and the location where first carbon dioxide vapor stream 126 enters.

[0069] First carbon dioxide vapor stream 126 is further cooled and partially condensed in second heat exchanger E2 to produce cold carbon dioxide stream 130. Cold carbon dioxide stream 130 is then separated in cold separator C3, which can include a flash vessel and / or a column including trays and / or packing, to produce cold purge stream 132 and cold carbon dioxide liquid stream 134. Cold purge stream 132 provides refrigeration to second heat exchanger E2. Cold carbon dioxide liquid stream 134 can optionally be warmed in second heat exchanger E2 prior to expansion over a pressure letdown device such as valve V2 to produce low pressure carbon dioxide stream 138, which provides refrigeration to second heat exchanger E2. Second heat exchanger E2, intermediate separator C2, and cold separator C3 form a CPU.

[0070] The intermediate pressure carbon dioxide stream 128, the cold reject stream 132, and the low pressure carbon dioxide stream 138 exit the second heat exchanger E2 as a micro-cooled intermediate pressure carbon dioxide stream 140, a micro-cooled reject stream 142, and a micro-cooled low pressure carbon dioxide stream 144, respectively. The micro-cooled intermediate pressure carbon dioxide stream 140, the micro-cooled reject stream 142, and the micro-cooled low pressure carbon dioxide stream 144 provide refrigeration to the first heat exchanger El, which cools the compressed carbon dioxide feed stream 112, exiting the first heat exchanger as a warmed intermediate pressure carbon dioxide stream 146, a reject stream 64, and a warmed low pressure carbon dioxide stream 150, respectively. For embodiments in which the first heat exchanger El and the second heat exchanger E2 are combined into a single heat exchanger, the intermediate pressure carbon dioxide stream 128, the cold reject stream 132, and the low pressure carbon dioxide stream 138 provide refrigeration to cool the compressed carbon dioxide feed stream 112, the dry carbon dioxide stream 52, and the first carbon dioxide vapor stream 126.

[0071] In at least some embodiments, the intermediate pressure carbon dioxide stream 128, the cold reject stream 132, and the low pressure carbon dioxide stream 138 are cool enough to provide refrigeration to both the dry carbon dioxide stream 52 and the compressed carbon dioxide feed stream 44. This is unexpected because in a typical auto-refrigeration CPU process, the cold streams would only have enough refrigeration to partially condense the dry carbon dioxide stream 52. However, in the present disclosure, the overhead vapor stream 118 from the feed on-stream adsorber Al has already had most of the water removed in the first separator Cl. This in turn reduces the amount of water that the on-stream adsorber Al has to adsorb, and since adsorption is an exothermic process, the temperature rise over the on-stream adsorber is reduced. As a result, the dry carbon dioxide stream 52 exits the on-stream adsorber at a lower temperature than expected, requiring less refrigeration load in the second heat exchanger E2. Therefore, the excess refrigeration load provided by the cold streams can be used to cool the compressed carbon dioxide feed stream 44 without having to expand the cold carbon dioxide liquid stream 134 to a lower pressure (which would increase the amount of refrigeration available at the cost of higher total power requirements).

[0072] The warmed low pressure carbon dioxide stream 150 is compressed in the first product compressor K2 and combined with the warmed intermediate pressure carbon dioxide stream 146 to form a combined carbon dioxide product stream 154, which is in turn compressed in the second product compressor K3 to form the carbon dioxide product stream 72. The carbon dioxide product stream 72 can also be formed by a single multi-stage product compressor, with the warmed low pressure carbon dioxide stream 150 entering the feed stage and the warmed intermediate pressure carbon dioxide stream 146 entering the intermediate stage.

[0073] Figure 3An embodiment of process 3 is shown, wherein the first heat exchanger E1 and the second heat exchanger E2 of process 2 are combined to form a combined heat exchanger E1'. A cooled carbon dioxide stream 114 is drawn from the combined heat exchanger E1', and a dried carbon dioxide stream 52 is returned to the combined heat exchanger E1'. A medium-pressure carbon dioxide stream 128, a cold exhaust stream 132, and a low-pressure carbon dioxide stream 138 are heated in the combined heat exchanger E1' to produce a heated medium-pressure carbon dioxide stream 146, an exhaust stream 64, and a heated low-pressure carbon dioxide stream 150, respectively.

[0074] Figure 4 An embodiment of process 4 is shown, which uses a portion of the carbon dioxide product stream 72 as a refrigerant. A portion of the carbon dioxide product stream 72 is diverted to form a high-pressure return stream 472, which is then expanded at valve V3 to produce a product carbon dioxide refrigerant stream 474. The product carbon dioxide refrigerant stream 474 is heated in a first heat exchanger E1 through indirect heat exchange with the compressed carbon dioxide stream 44. In at least some embodiments, the heated product carbon dioxide refrigerant stream 476 is then compressed in a second product compressor K3. Those skilled in the art will understand that the pressure of the carbon dioxide refrigerant stream 474 can be selected to balance the cooling demand of the first heat exchanger E1 with the suction pressure of the product compressor to which the heated carbon dioxide refrigerant stream 476 can be returned.

[0075] In at least some embodiments, a slightly cooled, low-pressure carbon dioxide stream 144 is drawn from the second heat exchanger E2 and compressed in the first product compressor K2, while a slightly cooled, medium-pressure carbon dioxide stream 140 is drawn from the second heat exchanger E2 and compressed in the second product compressor K3. Compression of the slightly cooled streams improves the overall compressor efficiency and balances the increased volumetric flow rate through the product compressor due to the return of heated product carbon dioxide refrigerant. The slightly cooled discharge stream 142 can be used for refrigeration in E1 or can be directly sent to the membrane separation system 80. For some membrane materials, carbon dioxide separation is improved at lower temperatures due to the higher solubility of CO2 in the membrane.

[0076] Figure 5 It shows Figure 4 A variation thereof, wherein the first heat exchanger is cooled by a dry carbon dioxide stream 52 exiting the online adsorber A1. The dry carbon dioxide stream 52 is cooled in the second heat exchanger E2 to produce a sufficiently cold dry carbon dioxide refrigerant stream 522 to provide cooling to the first heat exchanger E1. The heated dry carbon dioxide refrigerant stream 552 exits the first heat exchanger E1 and enters the second heat exchanger E2 for cooling and partial condensation to produce an intermediate carbon dioxide stream 122, such as... Figure 2 As in process 2.

[0077] Because the second heat exchanger E2 must provide a refrigeration duty to both the dry carbon dioxide stream 52 and the warmed dry carbon dioxide refrigerant stream 552, the medium pressure carbon dioxide stream 128, the cold reject stream 132, and the low pressure carbon dioxide stream 138 are heated in the second heat exchanger E2 to produce a warmed medium pressure carbon dioxide stream 146, a reject stream 64, and a warmed low pressure carbon dioxide stream 150.

[0078] Figure 6 A variation of Figure 5 is shown, where the dry carbon dioxide stream 52 is cooled by a chiller E3 to produce a dry carbon dioxide refrigerant stream 522. The chiller E3 can be any type of chiller designed to achieve a temperature below ambient. In at least some embodiments, the chiller E3 can include a waste heat chiller, such as an absorption chiller or an adsorption chiller. In the simplest form, a waste heat chiller boils a refrigerant to provide cooling. The evaporated refrigerant is absorbed or adsorbed and then released by regeneration using low grade waste heat to release the refrigerant that can then be condensed. Askalany et al. (Renewable and Sustainable Energy Reviews, 16:493-500, 2012) and Srikhirin et al. (Renewable and Sustainable Energy Reviews, 5:343-372, 2001) describe adsorption and absorption chillers, respectively. The low grade heat source can be the oxy-fuel combustor 20, the feed compressor K1, the first product compressor K2, and / or the second product compressor K3. In at least some embodiments, the low grade heat source can be provided by steam.

[0079] Figure 7 A variation of Figure 6 is shown, where the micro cold reject stream 142 provides additional refrigeration to the first heat exchanger E1. In at least some embodiments, the additional refrigeration provided by the micro cold reject stream 142 eliminates the need for the chiller E3.

[0080] Figure 8 A process 8 is shown, where the compressed carbon dioxide feed stream 44 is cooled by contact with a cold water stream 808. The temperature of the cold water stream 808 can be maintained above the hydrate formation temperature. In at least some embodiments, the compressed carbon dioxide feed stream 44 is contacted with the cold water stream 808 in a column C4 containing packing or trays to improve gas-liquid contact. A waste water stream 810 exits the column C4 and can be recycled and / or treated. The cooled compressed carbon dioxide feed stream 818 flows to an in-line adsorber Al where it is dehydrated, as shown in process 9. Figure 2As shown. Note that the cooled, compressed carbon dioxide feed stream 818 is saturated with water vapor, but the stream temperature has been reduced to achieve the same level as... Figure 2 The same degree of dehydration is observed in the first separator C1.

[0081] Figure 9 It shows Figure 8 A variation thereof, wherein the compressed carbon dioxide feed stream 44 is cooled by combining it with a liquid carbon dioxide recirculation stream 924. In at least some embodiments, the liquid carbon dioxide recirculation stream 924 can be formed by diverting a portion of the first liquid carbon dioxide stream 124. If desired, the liquid carbon dioxide recirculation stream 924 can be pumped. The combined streams are separated in separator C5 to produce a water-containing bottom stream 916 and a top vapor stream 918.

[0082] Figure 10 It shows Figure 9 A variation thereof, wherein the liquid carbon dioxide recirculation flow 1034 is formed by diverting a portion of the second liquid carbon dioxide flow 134. The liquid carbon dioxide recirculation flow 1034 may be pumped if necessary.

[0083] Figure 11 It shows Figure 2 A variation thereof, wherein the first liquid carbon dioxide flow 124 is split to form a first liquid carbon dioxide portion 1124 and a second liquid carbon dioxide portion 1182. The first liquid carbon dioxide portion 1124 expands at valve V1 to form a medium-pressure carbon dioxide flow 128 that provides cooling to the second heat exchanger E2, as shown below. Figure 2 As described above. The second liquid carbon dioxide fraction 1182 is pumped in pump P1 to produce a pumped second liquid carbon dioxide fraction 1184, which is heated in the second heat exchanger E2 to produce a slightly cooled second liquid carbon dioxide fraction 1186. The slightly cooled second liquid carbon dioxide fraction 1186 expands at valve V3 to produce an expanded second liquid carbon dioxide fraction 1188. The expanded second liquid carbon dioxide fraction 1188 can then provide cooling to the first heat exchanger E1 to produce a heated second liquid carbon dioxide fraction 1190. Depending on the pressure of the heated second liquid carbon dioxide fraction 1190, it can be combined with a heated low-pressure carbon dioxide stream 150 and fed into the feed stage or interstage of the first product compressor K2, combined with a heated medium-pressure carbon dioxide stream 146, or fed into the feed stage or interstage of the second product compressor K3.

[0084] Figure 12 It shows Figure 7 The variant, in which the first liquid carbon dioxide flow 124, is as follows Figure 11The expanded second liquid carbon dioxide fraction 1188 provides cooling to the first heat exchanger E1, which allows the slightly cooled exhaust stream 142 to be discharged or separated in the membrane separation system at a lower temperature. This allows for higher selectivity for carbon dioxide compared to slower gases such as nitrogen for most membrane materials.

[0085] Figure 13 It shows Figure 6 The variant, in which the first liquid carbon dioxide flow 124, is as follows Figure 11 The flow is split as described above. The pumped second liquid carbon dioxide stream 1184 is directly combined with the dry carbon dioxide stream 52 to produce a dry carbon dioxide refrigerant stream 522. In at least some embodiments, the cooler pumped second liquid carbon dioxide stream 1184 may allow the elimination of cooler E3.

[0086] Figure 14 A comparative example is shown in which the feed to the online adsorber A1 is not cooled.

[0087] Example 1

[0088] Use Aspen, which is available from Aspen Technology Inc. Process simulation software for Figure 2 The process and Figure 14 Computer simulations of the process were compared. In both cases, the compressed carbon dioxide stream 44 was saturated with water vapor at 33°C and 29.6 bar. All pressures listed are absolute pressures. The cooling effect of the feed to the online adsorber A1 can be seen in Table 1. Figure 2 In the process, the feed to the online adsorber A1 is the overhead vapor stream 118, which has a temperature of 12°C and is higher than the inlet vapor stream. Figure 14 The compressed carbon dioxide stream 44 in the inline adsorber A1 retains significantly less water. Figure 2 In the process, the first-stage dehydration prior to TSA reduced the temperature rise in the online adsorber A1 by more than two-thirds, which in turn reduced the cooling capacity required in the CPU. Overall, in Figure 2 With cooled TSA feed, power consumption decreased by 0.2%. Figure 14 In comparison, Figure 2 The additional path through the heat exchanger requires a larger heat exchanger surface area.

[0089] Table 1

[0090]

[0091] Example 2

[0092] Use Aspen Plus software toFigure 2 The process and Figure 4 The process was compared using computer simulations. The compressed carbon dioxide stream 44 was under the same conditions as in Example 1. Figure 4 The feed to the online adsorber A1 is cooled using product carbon dioxide refrigerant stream 474. Figure 2 In comparison, expanding a portion of the product carbon dioxide and then recompressing it increased the total power by 2.6%, although the total heat exchanger area was lower than that of the product. Figure 2 1.4% lower. Using CPU-based cooling reduces operating costs due to a slight increase in heat exchanger area.

[0093] Example 3

[0094] Use Aspen Plus software to Figure 2 The process and Figure 6 The process was compared using computer simulations. The compressed carbon dioxide stream 44 was under the same conditions as in Example 1. Table 2 compares the hot and cold flows entering and leaving the first heat exchanger E1. It can be seen that... Figure 6 The cold flow in the middle is compared to Figure 2 The colder flow, at a higher temperature, enters the first heat exchanger E1. Therefore, Figure 6 It has a narrower cooling curve, in which the temperatures of the hot and cold flows are closer, thereby reducing the risk of carbon dioxide freezing and / or forming solid carbon dioxide hydrates on the metal surface of the first heat exchanger E1.

[0095] The cooling load of cooler E3 is 465 kW. This can be easily provided by a waste heat cooler driven by the heat generated by the second product compressor K3. In at least some embodiments, the waste heat cooler requires heat at a temperature above 130°C and has a coefficient of performance (COP) in the range of 0.7 to 2.0. The COP is defined as the ratio of the cooling load provided by the waste heat cooler to the heating load provided to the waste heat cooler. Figure 6 In this case, there is an order of magnitude more available heating load above 130°C, which allows external cooling to be provided through the compression required by the process.

[0096] Table 2

[0097]

[0098] Example 4

[0099] Use Aspen Plus software to Figure 8The process was simulated using a computer. The compressed carbon dioxide stream 44 was at the same conditions as in Example 1 and combined with a cold water stream 808 at 10°C and 30 bar. The cold water stream 808 was saturated with carbon dioxide to reflect the recycle of the water stream after contact with the compressed carbon dioxide stream 44. The chilled compressed carbon dioxide feed stream 818 left column C4 at 12°C and 29.6 bar with 710 ppmv water, similar to Figure 2 the overhead vapor stream 118 of Example 1 and Example 2 in Example 3.

[0100] While the principles of this application have been described above in connection with preferred embodiments, it is to be clearly understood that this description is made only by way of example and not as a limitation of the scope of the application.

Claims

1. A method for purifying a carbon dioxide feed stream comprising: Chilling and partially condensing the carbon dioxide feed stream to a first temperature to produce a chilled carbon dioxide stream comprising a vapor portion and an aqueous liquid portion; Separating the chilled carbon dioxide stream to produce an overhead vapor stream and an aqueous bottoms stream; Passing the overhead vapor stream through an in-line adsorber to produce a dry carbon dioxide stream and a loaded adsorber; Chilling and partially condensing the dry carbon dioxide stream or a stream derived from the dry carbon dioxide stream to produce a cold carbon dioxide stream; Separating the cold carbon dioxide stream to produce a cold exhaust stream and a cold carbon dioxide liquid stream; Expanding at least a portion of the cold carbon dioxide liquid stream to produce a low pressure carbon dioxide stream; wherein the carbon dioxide feed is chilled by one or more of: at least a portion of the cold carbon dioxide liquid stream, at least a portion of the cold exhaust stream, and at least a portion of the low pressure carbon dioxide stream.

2. The method of claim 1, wherein the first temperature is less than 12°C.

3. The method of claim 1, wherein at least a portion of the chilling duty for chilling and partially condensing the carbon dioxide feed stream is provided by a waste heat cooler powered by a heat source.

4. The method of claim 3, further comprising: compressing the carbon dioxide feed stream prior to chilling and partial condensation; and compressing the low pressure carbon dioxide stream to produce a carbon dioxide product; wherein at least a portion of the heat source is provided by at least one of the compression of the carbon dioxide feed stream and the compression of the low pressure carbon dioxide stream.

5. The method of claim 3, further comprising reacting an oxygen rich stream with a fuel to produce the carbon dioxide feed stream; wherein at least a portion of the heat source is provided by the reaction of the oxygen rich stream with the fuel.

6. The method of claim 1, wherein the carbon dioxide feed is chilled and partially condensed in a heat exchanger comprising a metal; wherein the lowest temperature of the metal is greater than the hydrate formation temperature of the carbon dioxide feed stream.

7. The method of claim 1, further comprising compressing the low pressure carbon dioxide stream to produce a carbon dioxide product stream; expanding at least a portion of the carbon dioxide product stream to produce a carbon dioxide refrigerant stream; and using the carbon dioxide feed stream to heat the carbon dioxide refrigerant stream.

8. The method of claim 1, further comprising heating the dry carbon dioxide stream by indirect heat exchange with the carbon dioxide feed stream.

9. The method of claim 8, further comprising chilling the dry carbon dioxide stream prior to heating the dry carbon dioxide stream by indirect heat exchange.

10. The method of claim 1, wherein the carbon dioxide feed stream is chilled by direct contact with a cold water stream.

11. The method of claim 1, wherein the carbon dioxide feed stream is chilled by direct contact with at least a portion of the cold carbon dioxide liquid stream. ​ 12. The method of claim 1, wherein the carbon dioxide feed stream is subcooled by indirect heat exchange.

13. A system for purifying a carbon dioxide feed stream, comprising: a first heat exchanger configured to receive the carbon dioxide feed stream and produce a subcooled carbon dioxide stream comprising a vapor portion and an aqueous liquid portion; a first separator configured to receive the subcooled carbon dioxide stream and produce an overhead vapor stream and an aqueous bottoms stream; a sorber configured to receive the overhead vapor stream and produce a dry carbon dioxide stream; a second heat exchanger configured to receive the dry carbon dioxide stream and produce a cold carbon dioxide stream; a cold separator configured to receive the cold carbon dioxide stream and produce a cold exhaust stream and a cold carbon dioxide liquid stream; a pressure letdown configured to receive at least a portion of the cold carbon dioxide liquid stream and produce a low pressure carbon dioxide stream; wherein the first heat exchanger and the second heat exchanger are in fluid flow communication with one or more of: at least a portion of the cold carbon dioxide liquid stream, at least a portion of the cold exhaust stream, and at least a portion of the low pressure carbon dioxide stream.

14. The system of claim 13, wherein the first heat exchanger comprises a direct contact heat exchanger in fluid flow communication with a cold water stream.

15. The system of claim 13, further comprising a product compressor configured to receive the low pressure carbon dioxide stream to produce a carbon dioxide product stream; a pressure letdown configured to receive at least a portion of the carbon dioxide product stream to produce a carbon dioxide refrigerant stream; wherein the first heat exchanger is in fluid flow communication with the carbon dioxide refrigerant stream.

16. The system of claim 13, wherein the first heat exchanger comprises a cold side inlet in fluid flow communication with a dry carbon dioxide stream.

17. The system of claim 16, further comprising a third heat exchanger configured to receive the dry carbon dioxide stream and subcool it; wherein the third heat exchanger is upstream of the cold side inlet of the first heat exchanger.

18. The system of claim 13, further comprising a waste heat cooler configured to receive a heat source and produce a refrigerant stream; wherein the first heat exchanger comprises a cold side inlet in fluid flow communication with the refrigerant stream.

19. The system of claim 18, further comprising: a feed compressor configured to receive the carbon dioxide feed stream upstream of the first heat exchanger; and a product compressor configured to receive the low pressure carbon dioxide stream to produce a carbon dioxide product; wherein at least a portion of the heat source is provided by at least one of the feed compressor and the product compressor.

20. The system of claim 18, further comprising an oxy-fuel combustor configured to receive an oxygen rich stream and a fuel and produce a carbon dioxide feed stream; wherein at least a portion of the heat source is provided by the oxy-fuel combustor. ​

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