Separation and purification of carbon dioxide streams

Abstract

A method and system for purifying a carbon dioxide feed stream in which the carbon dioxide feed stream is cooled and partially condensed to remove water upstream of an adsorber to produce a dried carbon dioxide stream. The dried carbon dioxide stream is further cooled and partially condensed in a carbon dioxide purification unit to form a carbon dioxide product stream. The excess refrigeration load from the carbon dioxide purification unit is used to cool the carbon dioxide feed stream.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. non-provisional patent application No. 17 / 856,010, filed on July 1, 2022. Background Art

[0003] The present disclosure relates generally to the purification and dehydration of carbon dioxide and, more particularly, 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 generally requires the removal of water and light components such as nitrogen before utilization or storage. 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) teach a method for drying a CO2 stream by compressing and cooling the CO2 stream, which is partially condensed to form a gas phase rich in carbon dioxide and a water-containing liquid phase. The gas phase rich in carbon dioxide is then further dehydrated using temperature swing adsorption.

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

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

[0008] The temperature reduction 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 of the invention

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

[0010] Aspect 1: A method for purifying a carbon dioxide feed stream, comprising: cooling and partially condensing the carbon dioxide feed stream to a first temperature to produce a cooled carbon dioxide stream; separating the cooled carbon dioxide stream to produce an overhead vapor stream and a water-containing bottoms stream; passing the overhead vapor stream through an online adsorber to produce a dry carbon dioxide stream and a loaded adsorber; cooling 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 cooled 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.

[0011] Aspect 2: A method for purifying a carbon dioxide feed stream, the process comprising: cooling and partially condensing the carbon dioxide feed stream to a first temperature to produce a cooled carbon dioxide stream; separating the cooled carbon dioxide stream to produce an overhead vapor stream and a water-containing bottoms stream; passing the overhead vapor stream through an online adsorber to produce a dry carbon dioxide stream and a loaded adsorber; cooling 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 an intermediate pressure carbon dioxide stream; cooling 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 exhaust 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 intermediate pressure carbon dioxide stream, at least a portion of the cold exhaust 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 according to aspect 2, wherein the carbon dioxide feed stream is cooled by direct contact with at least a portion of the first carbon dioxide liquid stream.

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

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

[0015] Aspect 6: The method according to 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 compression of the low-pressure carbon dioxide stream.

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

[0017] Aspect 8: The method according to any one of aspects 5 to 7, further comprising reacting the oxygen-rich stream with a fuel to produce a 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.

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

[0019] Aspect 10: The method according to any one of aspects 1 to 9, further comprising flowing a regeneration gas 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 according to any one of aspects 1 to 10, wherein the carbon dioxide feed is cooled and partially condensed in a heat exchanger containing 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 according to any one of aspects 1 to 11, further comprising compressing a 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 using a carbon dioxide feed stream.

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

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

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

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

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

[0027] Aspect 18: 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 cooled carbon dioxide stream; a first separator configured to receive the cooled carbon dioxide stream and produce an overhead vapor stream and a water-containing bottom 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 reducer 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 fluidly connected to 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 the cold water stream.

[0029] Aspect 20: The system according to Aspect 18 or Aspect 19, further comprising a product compressor configured to receive a low-pressure carbon dioxide stream to produce a carbon dioxide product stream; a pressure reducer 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 fluidly connected to the carbon dioxide refrigerant stream.

[0030] Aspect 21: The system of any of aspects 18 to 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 according to aspect 21, further comprising a third heat exchanger configured to receive and cool down the dry carbon dioxide stream; wherein the third heat exchanger is located upstream of the cold side inlet of the first heat exchanger.

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

[0033] Aspect 24: The system according to aspect 23, further comprising a product compressor configured to receive a 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 according to 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 according to any one of aspects 23 to 25, further comprising an oxy-fuel burner 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 burner.

[0036] Aspect 27: The system according to any one of aspects 23 to 26, wherein at least a portion of the heat source is provided by a steam flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention will be described below with reference to the accompanying drawings, wherein the same reference numerals represent the same elements:

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

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

[0040] Figure 3 It is a depiction Figure 2 FIG. 1 is a diagram of a variation of FIG. 1 in which a single combined heat exchanger is used to cool and partially condense the carbon dioxide feed stream.

[0041] Figure 4 It is a depiction Figure 2 A variation of the diagram in which a portion of the carbon dioxide product is expanded to provide refrigeration to cool the compressed carbon dioxide feed stream.

[0042] Figure 5 It is a depiction Figure 4 A variation of FIG. 1 in which a dry carbon dioxide stream provides refrigeration to cool a compressed carbon dioxide feed stream.

[0043] Figure 6 It is a depiction Figure 5 FIG. 1 is a diagram of a variation of a process in which the dry carbon dioxide stream is cooled prior to providing refrigeration.

[0044] Figure 7 It is a depiction Figure 5 A variation of FIG. 1 in which a micro-cooled exhaust stream provides refrigeration to cool a compressed carbon dioxide feed stream.

[0045] Figure 8 It is a depiction Figure 3A variation of the diagram in which a compressed carbon dioxide feed stream is combined with a cold water stream to cool and partially condense the water.

[0046] Fig. 9 It is a depiction Figure 8 A variation of the diagram in which a compressed carbon dioxide feed stream is combined with a liquid carbon dioxide stream.

[0047] Fig.10 It is a depiction Fig. 9 A variation of the diagram in which a liquid carbon dioxide stream is obtained from the cold end of the CO2 purification system.

[0048] Fig.11 It is a depiction Figure 2 A variation of the diagram in which a portion of the first carbon dioxide liquid stream is pumped and used as refrigerant.

[0049] Fig.12 It is a depiction Figure 7 A variation of the diagram in which a portion of the first carbon dioxide liquid stream is pumped and used as refrigerant.

[0050] Fig.13 It is a depiction Figure 6 A variation of the diagram in which a portion of the first carbon dioxide liquid stream is pumped and used as refrigerant.

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

[0052] The detailed description that follows provides preferred exemplary embodiments and is not intended to limit the scope, applicability or configuration of the present invention. On the contrary, the detailed description that follows of the preferred exemplary embodiments will provide an enabling description for implementing the preferred exemplary embodiments of the present invention to those skilled in the art. Various changes may be made to the functions and arrangements of the elements without departing from the spirit and scope of the present invention as set forth in the appended claims.

[0053] As used herein, the articles "a" and "an" refer to one or more when applied to any feature in the embodiments of the present invention described in the specification and claims. The use of "a" and "an" does not limit the meaning to a single feature unless such limitation is specifically stated. The article "the" preceding a singular or plural noun or noun phrase refers to one specific particular feature or multiple specific particular features and can have a singular or plural meaning depending on the context in which it is used.

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

[0055] The term "and / or" placed between a first entity and a second entity includes any of the following meanings: (1) only the first entity, (2) only the second entity, and (3) the first entity and the second entity. The term "and / or" placed between the last two entities of a list of 3 or more entities means that at least one of the entities in the list includes any specific combination of the entities 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, in any number.

[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 completely lacks a specified component.

[0058] The terms "enriched" or "rich" refer to a mole percent concentration of a specified component that 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 transferred process fluid. 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 recirculating flow, downstream and upstream refer to the first pass of the process fluid.

[0060] The term "indirect heat exchange" refers to the process of transferring sensible heat and / or latent heat between two or more fluids without the fluids in question coming into physical contact with each other. Heat can be transferred through the walls of the heat exchanger or using an intermediate heat transfer fluid. The term "hot stream" refers to any stream that leaves a heat exchanger at a lower temperature than when it entered. Conversely, a "cold stream" is a stream that leaves a heat exchanger at a higher temperature than when it entered. The hot stream enters the hot side inlet of the heat exchanger, while the cold stream enters the cold side inlet of the 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 oxyfuel combustion with carbon capture is shown. An oxygen plant 10 produces an oxygen-rich stream 12, which is combusted with a fuel 22 in an oxyfuel burner 20 to produce heat and flue gas 24. "Enriched oxygen" is defined as any composition greater than 21% of ambient concentration by volume. The oxyfuel burner can be associated with any industrial process requiring heat, such as power generation, lime production, and cement production. In at least some embodiments, the flue gas 24 contains carbon dioxide generated by the reaction of raw materials such as limestone due to the heat generated by the oxyfuel burner. If desired, particulate matter 32 can be removed from the flue gas 24 in a particle removal system 30, leaving a carbon dioxide feed stream 34. The carbon dioxide feed stream 34 then 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 interstage desuperheaters and / or post-desuperheaters. Compression and cooling can lead to the formation of a condensate phase 42, which can contain nitrogen and sulfur-containing substances 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 5ppm, less than 3ppm, or less than 1ppm, so 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 then 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 a discharge stream 64 and a purified carbon dioxide stream 62. In at least some embodiments, the purified carbon dioxide stream 62 can then enter a final purification system 70 to produce a carbon dioxide product stream 72. Depending on the final use and / or transportation requirements for storage or utilization, the final purification system 70 may 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 effluent 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 parallel. The effluent stream 64 is separated into a permeate stream 82 rich in carbon dioxide and a retentate stream 84 lean in carbon dioxide by selective permeation. Carbon dioxide selectively permeates the membrane compared to slower substances 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 molecules of similar size (such as nitrogen) with lower solubility.

[0063] Sanders et al. (" polymer (Polymer) "; Vol. 54; Pages 4729-4761; 2013) provide a simple review of current membrane technology. They describe the physical parameters and performance characteristics of the following polymer membranes: polystyrene, polysulfone, polyethersulfone, polyvinyl fluoride, polyvinylidene fluoride, polyetheretherketone, polycarbonate, polyphenylene oxide, polyethylene, polypropylene, cellulose acetate, polyimide (such as Matrimid 5218 or P-84), polyamide, polyvinyl alcohol, polyvinyl acetate, polyethylene oxide, polydimethylsiloxane, copolymer, block copolymer or polymer blend. Existing industrially useful gas separation mainly utilizes polymers such as those listed above or rubber materials such as siloxane to carry out. Other membrane materials can include mixed matrix membranes, perfluoropolymers, thermal rearrangement polymers, facilitated transport membranes, metal-organic skeletons, zeolite-imidazole ester skeletons, electrochemical membranes, metal membranes and carbon molecular sieves. The membrane material in membrane separation system 80 may 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 can be manufactured as flat sheets, packaged as spiral wound or plate-and-frame units to provide a greater surface area to volume ratio, and contained in modules. Gas entering the module contacts the membrane, and a portion of the gas permeates the membrane and leaves the module in the form of a low-pressure permeate stream. The permeate will be enriched in faster-permeating gases relative to slower-permeating gases. The portion of the gas that does not permeate the membrane leaves the module in the form of a non-permeate or retentate stream, which is enriched in slower-permeating gases relative to faster-permeating gases. A membrane stage is defined as one or more membrane modules arranged so that each feed inlet is in fluid flow communication with each other, each permeate outlet is in fluid flow communication with each other, and each retentate outlet is in fluid flow communication with each other.

[0065] The carbon dioxide-enriched permeate stream 82 can be recycled via line 86 by combining with the oxygen-enriched stream 12 and / or the carbon dioxide feed stream 34. In at least some embodiments, the dehydration system 50 comprises an adsorption system. The carbon dioxide-depleted retentate stream 84 can be used to regenerate the adsorption system, producing a spent regeneration stream 88 that can be recycled or vented. In at least some embodiments, the adsorption system can be regenerated using at least a portion of the effluent stream 64, compressed dry air, and / or an inert gas such as nitrogen. In at least some embodiments, the effluent 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, the carbon dioxide feed stream 34 is compressed in the feed compressor K1. The compressed carbon dioxide feed stream 44 is cooled and at least partially condensed in the first heat exchanger E1 to produce a cooled carbon dioxide stream 114. The cooled carbon dioxide stream 114 is separated in the first separator C1 to produce a water-containing bottom stream 116 and an overhead vapor stream 118. The overhead vapor stream 118 flows through the online adsorber A1, which removes water and allows the dry carbon dioxide stream 52 to leave. The online adsorber A1 can utilize one or more high surface area adsorbents, including but not limited to zeolites, metal organic frameworks (MOFs), alumina, silica gel, silica zeolites, activated carbon, Engelhard titanosilicates (ETS), and metal oxides.

[0067] The dry carbon dioxide stream 52 is cooled and at least partially condensed in the second heat exchanger E2 to produce an intermediate carbon dioxide stream 122. The intermediate carbon dioxide stream 122 is separated in the intermediate separator C2 to produce a first carbon dioxide liquid stream 124 and a first carbon dioxide vapor stream 126. The first carbon dioxide liquid stream 124 is then expanded on a pressure reducer such as a valve V1 to produce an intermediate pressure carbon dioxide stream 128 that provides refrigeration to the second heat exchanger E2.

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

[0069] The first carbon dioxide vapor stream 126 is further cooled and partially condensed in the second heat exchanger E2 to produce a cold carbon dioxide stream 130. The cold carbon dioxide stream 130 is then separated in a cold separator C3, which may include a flash vessel and / or a tower including trays and / or packing to produce a cold discharge stream 132 and a cold carbon dioxide liquid stream 134. The cold discharge stream 132 provides refrigeration to the second heat exchanger E2. The cold carbon dioxide liquid stream 134 may be optionally warmed in the second heat exchanger E2 before expansion on a pressure reducer such as a valve V2 to produce a low-pressure carbon dioxide stream 138 that provides refrigeration to the second heat exchanger E2. The second heat exchanger E2, the intermediate separator C2 and the cold separator C3 form a CPU.

[0070] The medium-pressure carbon dioxide stream 128, the cold exhaust stream 132, and the low-pressure carbon dioxide stream 138 exit the second heat exchanger E2 as a slightly cooled medium-pressure carbon dioxide stream 140, a slightly cooled exhaust stream 142, and a slightly cooled low-pressure carbon dioxide stream 144, respectively. The slightly cooled medium-pressure carbon dioxide stream 140, the slightly cooled exhaust stream 142, and the slightly cooled low-pressure carbon dioxide stream 144 provide refrigeration to the first heat exchanger E1, which cools down the compressed carbon dioxide feed stream 112, exiting the first heat exchanger as a warmed medium-pressure carbon dioxide stream 146, the exhaust stream 64, and a warmed low-pressure carbon dioxide stream 150, respectively. For embodiments in which the first heat exchanger E1 and the second heat exchanger E2 are combined into a single heat exchanger, the medium-pressure carbon dioxide stream 128, the cold exhaust stream 132, and the low-pressure carbon dioxide stream 138 provide refrigeration to cool down 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 medium-pressure carbon dioxide stream 128, the cold exhaust stream 132, and the low-pressure carbon dioxide stream 138 are cold 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 autorefrigeration CPU process, the cold stream will only have refrigeration sufficient to partially condense the dry carbon dioxide stream 52. However, in the present disclosure, the overhead vapor stream 118 feeding the online adsorber A1 has been removed from most of the water in the first separator C1. This in turn reduces the amount of water adsorbed by the online adsorber A1, and since adsorption is an exothermic process, the temperature rise on the online adsorber is reduced. As a result, the dry carbon dioxide stream 52 leaves the online adsorber at a lower temperature than expected, thereby requiring less refrigeration load in the second heat exchanger E2. Therefore, the excess refrigeration load provided by the cold stream can be used to cool the compressed carbon dioxide feed stream 44 without expanding the cold carbon dioxide liquid stream 134 to a lower pressure (which will increase the amount of available refrigeration at the expense of a higher total power demand).

[0072] The warmed low-pressure carbon dioxide stream 150 is compressed in the first product compressor K2 and combined with the warmed medium-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, in which the warmed low-pressure carbon dioxide stream 150 enters the feed stage and the warmed medium-pressure carbon dioxide stream 146 enters the intermediate stage.

[0073] Figure 3An embodiment of process 3 is shown in which the first heat exchanger E1 and the second heat exchanger E2 of process 2 are combined to form a combined heat exchanger E1'. A reduced-temperature carbon dioxide stream 114 is drawn from the combined heat exchanger E1' and a dry carbon dioxide stream 52 is returned to the combined heat exchanger E1'. An intermediate-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 warmed intermediate-pressure carbon dioxide stream 146, an exhaust stream 64, and a warmed 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 split to form a high-pressure return stream 472, and then expanded on valve V3 to produce a product carbon dioxide refrigerant stream 474. The product carbon dioxide refrigerant stream 474 is heated in the first heat exchanger E1 by 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 the second product compressor K3. It will be appreciated by those skilled in the art that the pressure of the carbon dioxide refrigerant stream 474 can be selected to balance the refrigeration 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 cold low-pressure carbon dioxide stream 144 is drawn from the second heat exchanger E2 and compressed in the first product compressor K2, and a slightly cold medium-pressure carbon dioxide stream 140 is drawn from the second heat exchanger E2 and compressed in the second product compressor K3. Compressing the slightly cold stream improves the overall compressor efficiency and balances the volume flow through the product compressor due to the return of the warmed product carbon dioxide refrigerant. The slightly cold discharge stream 142 can be used as 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 Shows Figure 4 A variation of the invention in which the first heat exchanger is refrigerated by the dry carbon dioxide stream 52 leaving the online adsorber A1. The dry carbon dioxide stream 52 is cooled in the second heat exchanger E2 to produce a dry carbon dioxide refrigerant stream 522 having a temperature sufficiently cold to provide refrigeration to the first heat exchanger E1. The warmed dry carbon dioxide refrigerant stream 552 leaves 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 Just like in process 2.

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

[0078] Figure 6 Shows Figure 5 A variation of the invention, in which the dry carbon dioxide stream 52 is cooled by a cooler E3 to produce a dry carbon dioxide refrigerant stream 522. The cooler E3 can be any type of cooler designed to reach a temperature below ambient. In at least some embodiments, the cooler E3 can include a waste heat cooler, such as an absorption cooler or an adsorption cooler. In the simplest form, the waste heat cooler boils the refrigerant to provide cooling. The evaporated refrigerant is absorbed or adsorbed, and then regenerated 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 coolers, respectively. The low-grade heat source may be the oxyfuel burner 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 may be provided by steam.

[0079] Figure 7 Shows Figure 6 A variation of wherein the micro-cooled exhaust stream 142 provides additional refrigeration to the first heat exchanger E1. In at least some embodiments, the additional refrigeration provided by the micro-cooled exhaust stream 142 eliminates the need for chiller E3.

[0080] Figure 8 Process 8 is shown in which a 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 temperature at which hydrates are formed. 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 wastewater stream 810 exits the column C4 and can be recycled and / or processed. The cooled compressed carbon dioxide feed stream 818 flows through an online adsorber A1, such as a reactor, where it is dehydrated. Figure 2Note that the reduced temperature compressed carbon dioxide feed stream 818 is saturated with water vapor, but the temperature of the stream has been reduced to match that of Figure 2 A similar degree of dehydration is achieved in the first separator C1 in the reactor.

[0081] Fig. 9 Shows Figure 8 A variation of the invention in which the compressed carbon dioxide feed stream 44 is cooled by combining with a liquid carbon dioxide recycle stream 924. In at least some embodiments, the liquid carbon dioxide recycle stream 924 can be formed by diverting a portion of the first carbon dioxide liquid stream 124. If desired, the liquid carbon dioxide recycle stream 924 can be pumped. The combined stream is separated in separator C5 to produce a water-containing bottoms stream 916 and an overhead vapor stream 918.

[0082] Fig.10 Shows Fig. 9 A variation of the present invention, in which the liquid carbon dioxide recycle stream 1034 is formed by diverting a portion of the second carbon dioxide liquid stream 134. If necessary, the liquid carbon dioxide recycle stream 1034 can be pumped.

[0083] Fig.11 Shows Figure 2 A variation of the present invention, in which the first carbon dioxide liquid stream 124 is split to form a first carbon dioxide liquid portion 1124 and a second carbon dioxide liquid portion 1182. The first carbon dioxide liquid portion 1124 is expanded at valve V1 to form a medium-pressure carbon dioxide stream 128 that provides refrigeration to the second heat exchanger E2, such as Figure 2 1. The second carbon dioxide liquid portion 1182 is pumped in pump P1 to produce a pumped second carbon dioxide liquid portion 1184 which is heated in the second heat exchanger E2 to produce a slightly cooled second carbon dioxide liquid portion 1186. The slightly cooled second carbon dioxide liquid portion 1186 is expanded in valve V3 to produce an expanded second carbon dioxide liquid portion 1188. The expanded second carbon dioxide liquid portion 1188 can then provide refrigeration to the first heat exchanger E1 to produce a warmed second carbon dioxide liquid portion 1190. Depending on the pressure of the warmed second carbon dioxide liquid portion 1190, it can be combined with the warmed low-pressure carbon dioxide stream 150, fed to a feed stage or interstage of the first product compressor K2, combined with the warmed medium-pressure carbon dioxide stream 146, or fed to a feed stage or interstage of the second product compressor K3.

[0084] Fig.12 Shows Figure 7 A variation of the present invention, wherein the first liquid carbon dioxide stream 124 is as follows Fig.11The expanded second carbon dioxide liquid portion 1188 provides refrigeration to the first heat exchanger El, which allows the slightly cooled exhaust stream 142 to be discharged or separated in the membrane separation system at a lower temperature, which for most membrane materials allows for a higher selectivity for carbon dioxide compared to slow gases such as nitrogen.

[0085] Fig.13 Shows Figure 6 A variation of the present invention, wherein the first liquid carbon dioxide stream 124 is as follows Fig.11 The pumped second carbon dioxide liquid portion 1184 is directly combined with the dry carbon dioxide stream 52 to produce the dry carbon dioxide refrigerant stream 522. In at least some embodiments, the cooler pumped second carbon dioxide liquid portion 1184 can allow the elimination of chiller E3.

[0086] Fig.14 A comparative example is shown in which the feed to online adsorber A1 is not temperature reduced.

[0087] Example 1

[0088] Using Aspen available from Aspen Technology Inc. Process simulation software Figure 2 process and Fig.14 A computer simulation of the process was 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 The feed to online adsorber A1 is overhead vapor stream 118, which has a temperature of 12°C and is warmer than that entering Fig.14 The compressed carbon dioxide stream 44 of the online adsorber A1 in retains much less water. Figure 2 In the case of the first stage of dehydration before the TSA, the temperature rise in the online adsorber A1 is reduced by more than two thirds, which in turn reduces the required cooling capacity in the CPU. Figure 2 In the case of a cooled TSA feed, the power reduction was 0.2%. Fig.14 In comparison, Figure 2 More heat exchanger surface area is required due to the additional path through the heat exchanger.

[0089] Table 1

[0090]

[0091] Example 2

[0092] Using Aspen Plus software Figure 2 process and Figure 4 The compressed carbon dioxide stream 44 is subjected to the same conditions as in Example 1. Figure 4 The feed to online adsorber A1 is cooled using product carbon dioxide refrigerant stream 474. Figure 2 In comparison, expanding a portion of the product CO2 and then recompressing it increases the total power by 2.6%, although the total heat exchanger area is smaller than Figure 2 1.4% lower. Using cooling for the CPU saves operating costs because the heat exchanger area is slightly increased.

[0093] Example 3

[0094] Using Aspen Plus software Figure 2 process and Figure 6 The compressed carbon dioxide stream 44 is subjected to the same conditions as in Example 1. The hot and cold streams entering and leaving the first heat exchanger E1 are compared in Table 2. It can be seen that Figure 6 The cold flow in Figure 2 The cold stream in the heat exchanger enters the first heat exchanger E1 at a higher temperature. Figure 6 It has a narrower temperature drop curve, in which the temperatures of the hot stream and the cold stream are closer, thereby reducing the risk of freezing carbon dioxide and / or forming solid carbon dioxide hydrate on the metal surface of the first heat exchanger E1.

[0095] The cooling duty 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 in the range of 0.7 to 2.0. The coefficient of performance is defined as the ratio of the cooling duty provided by the waste heat cooler to the heating duty provided to the waste heat cooler. Figure 6 In the case of , there is more than an order of magnitude of available heating duty above 130°C, allowing external refrigeration to be provided by the compression required by the process.

[0096] Table 2

[0097]

[0098] Example 4

[0099] Using Aspen Plus software Figure 8The process was computer simulated. The compressed carbon dioxide stream 44 was at the same conditions as in Example 1 and was 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 reduced temperature 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 Examples 1 and 2 is shown in FIG.

[0100] Although the principles of the present invention have been described above in conjunction with the preferred embodiments, it should be clearly understood that this description is intended as an example only and not as a limitation on the scope of the invention.

Claims

1. A method for purifying a carbon dioxide feed stream, comprising: cooling and partially condensing the carbon dioxide feed stream to a first temperature to produce a cooled carbon dioxide stream; separating the reduced temperature carbon dioxide stream to produce an overhead vapor stream and an aqueous bottoms stream; passing the overhead vapor stream through an online adsorber to produce a dry carbon dioxide stream and a loaded adsorber; cooling 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 effluent stream and a cold carbon dioxide liquid stream; expanding at least a portion of the cold liquid carbon dioxide stream to produce a low pressure carbon dioxide stream; The carbon dioxide feed is cooled 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 below about 12°C.

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

4. The method according to claim 1, further comprising: compressing the carbon dioxide feed stream prior to cooling and partially condensing; compressing the low pressure carbon dioxide stream to produce a carbon dioxide product; reacting the oxygen-rich stream with a fuel to produce the carbon dioxide feed stream wherein a portion of said heat source is provided by at least one of said compression of said carbon dioxide feed stream and said compression of said low pressure carbon dioxide stream, and wherein a portion of said heat source is provided by said reaction of said oxygen-rich stream with said fuel.

5. The process of claim 1, wherein the carbon dioxide feed is cooled 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.

6. 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; heating the carbon dioxide refrigerant stream using the carbon dioxide feed stream comprising heating the dry carbon dioxide stream by indirect heat exchange with the carbon dioxide feed stream, The dry carbon dioxide stream is cooled by indirect heat exchange prior to heating the dry carbon dioxide stream.

7. The process of claim 1, wherein the carbon dioxide feed stream is cooled by direct contact with a cold water stream.

8. The process of claim 1, wherein the carbon dioxide feed stream is cooled by direct contact with at least a portion of the cold carbon dioxide liquid stream.

9. The process of claim 1 wherein the carbon dioxide feed stream is cooled by indirect heat exchange.

10. 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 reduced temperature carbon dioxide stream; a first separator configured to receive the reduced temperature 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 cool 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 reducer 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.

11. The system of claim 10, wherein the first heat exchanger comprises a direct contact heat exchanger in fluid flow communication with a stream of cold water.

12. The system of claim 10, further comprising a product compressor configured to receive the low pressure carbon dioxide stream to produce a carbon dioxide product stream; a pressure reducer 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 flow.

13. The system of claim 10, further comprising a third heat exchanger configured to receive and cool the dry carbon dioxide stream; wherein the third heat exchanger is located upstream of a cold side inlet of the first heat exchanger, Wherein the first heat exchanger includes a cold side inlet in fluid flow communication with the dry carbon dioxide stream.

14. The system of claim 10, further comprising a waste heat cooler configured to receive a heat source and generate a refrigerant flow; 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 the first heat exchanger includes a cold side inlet in fluid flow communication with the refrigerant stream, and Wherein at least a portion of the heat source is provided by at least one of the feed compressor and the product compressor.

15. The system of claim 14, further comprising an oxyfuel burner configured to receive the oxygen-rich stream and the fuel and produce the carbon dioxide feed stream; Wherein at least a portion of the heat source is provided by the oxy-fuel burner.

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