Processes and systems for removal of components from mixed gas streams

Abstract

The present disclosure relates to processes and systems useful for removing carbon dioxide (CO2) from a mixed gas stream, such as a syngas stream or a flue gas stream. The processes and systems can utilize a low temperature CO2 purification column in combination with a plurality of upstream separators that are effective for bulk removal of impurities so that the low temperature CO2 purification column can operate with greater efficiency in producing a liquid CO2 bottom stream that is substantially pure CO2. Overhead gas from the low temperature CO2 purification column can be further processed to achieve near 100% carbon capture by the process and system.

Description

[0001] AttyDkt.No. P62622 2420WO (01250)

[0002] PROCESSES AND SYSTEMS FOR REMOVAL OF

[0003] COMPONENTS FROM MIXED GAS STREAMS

[0004] FIELD OF THE INVENTION

[0005] The present disclosure provides processes and systems for separating components, such as carbon dioxide, from a mixed gas stream.

[0006] BACKGROUND

[0007] Mixed gas streams (MGS) are known to arise from many sources, both naturally and man-made. Natural sources, such as natural gas, may also include one or more of the so-called “acid” gases, such as carbon dioxide (CO2) and hydrogen sulfide (H2S), and so-called “inert” gases, such as nitrogen (N2) and argon (Ar). Mixed gas streams from industrial processes, such as synthesis gas (“syngas”), often comprises one or more of molecular hydrogen (H2), carbon monoxide (CO), CO2, methane, and water. Processes that produce a flue gas, such as from combustion of a carbonaceous fuel, may comprise one or more of CO, CO2, oxygen (02), water, N2, and Ar.

[0008] SUMMARY OF THE INVENTION

[0009] The present disclosure relates to processes and systems for purification of mixed gas streams, and particularly for the removal of CO2 from mixed gas streams. The processes and systems may utilize auto-refrigeration to improve efficiency and reduce cost of CO2 removal. The processes and systems also may use a plurality of single stage separation units in combination with a low temperature (LT) CO2 purification unit configured to provide a stream of substantially pure liquid CO2. The substantially pure liquid CO2 produced may comprise a majority of the CO2 originally introduced with the MGS; therefore, not only is the substantially pure liquid CO2 produced of high purity but also comprises a significant quantity of the CO2 introduced with the MGS. The system may be configured to produce one or more overhead gas streams comprising a minority of the CO2 present in the introduced mixed gas stream (MGS). The overhead gas streams may be subject to additional processing to boost CO2 separation efficiency and quantity capture, such as up to about 100% of the introduced and formed CO2. The present processes and systems configurations may also be effective to minimize the power requirement for low temperature LT CO2 separation versus other systems that separate CO2 from a mixed gas stream.

[0010] In one or more embodiments, which can be combined with other embodiments, the present processes and systems are effective to remove and recover about 90 mol% (mole percent) or greater, such as about 95 mol% or greater, such as about 98 mol% or greater, such as about 99 mol% or greater, such as AttyDkt.No. P62622 2420WO (01250) about 99.5 mol% or greater, or such as about 99.9 mol% of the CO2 introduced through the mixed gas stream. The recovery efficacy can be achieved by utilizing one or more multi-stage phase separations carried out in a plurality of separate separation vessels, where a LT CO2 purification column with one or a plurality of reflux streams is utilized to increase the single pass CO2 recovery efficiency over other processes. As part of embodiment processes, heat is exchanged with the vapor streams of the various phase separations units, including the pre-LT CO2 purification column separators and the LT CO2 purification column itself and the feed stream(s) to remove heat from the feed streams. In other configurations of embodiment systems, the addition of further CO2 recovery systems, such as a CO2 pressure swing adsorption unit (CO2 PSA), a CO2 vacuum pressure swing adsorption unit (CO2 VPSA), a solvent-based CO2 separation unit, or a CO2 temperature swing adsorption unit (CO2 TSA), produce a CO2 rich stream and further enhance CO2 recovery. This CO2 rich stream, in whole or in part, may be recycled back to the LT CO2 recovery process and system. This CO2 rich stream, in whole or in part, may be combined and produced as part of the product CO2 from the LT CO2 recovery process and system. The present processes and systems may meet any cooling requirements through autothermal refrigeration, such as by pressure letdown of liquid CO2 from the LT CO2 purification column.

[0011] In one or more embodiments, which can be combined with other embodiments, the mixed gas stream that also comprises hydrogen and optionally other fuel materials is introduced into a system as part of a process to separate CO2 therefrom. Example mixed gas streams suitable for CO2 removal includes syngas and “tail gas” from an H2 PSA, for example, a PSA purge gas. These mixed gas streams can be enriched, that is the hydrogen or hydrocarbon concentration is relatively increased versus what is in the introduced MGS by extracting the CO2 from the MGS. For example, one or more single or multiple stage separation vessels may be fluidly coupled and positioned upstream of the LT CO2 purification column to process the MGS, and bottom liquid stream(s) from each of the one or more single or multiple stage separators may be introduced into the LT CO2 purification column. In one or more embodiments, which may be combined with other embodiments, at least about 80 mol%, such as at least 85 mol%, or such as in a range of from about 80 mol% to about 95 mol%, of the CO2 introduced with the mixed gas stream is produced as the bottom liquid stream of the LT CO2 purification column.

[0012] The top vapor streams passing from the LT CO2 purification column and the final separator upstream of the LT CO2 purification column can be maintained separately or combined and then further processed through one or more pressure swing absorption (PSA) units, such as a second H2 PSA, to extract any hydrogen, hydrocarbons, or both, remaining in the stream(s).

[0013] A tail gas from a second H2 PSA can be used as a low-calorific value fuel, such as for a combustion process, such as for an oxy-fired or air-fired combustor, to form a combustion gas product. The combustion gas product from such a combustor, in whole or in part, can be directed to and processed AttyDkt.No. P62622 2420WO (01250) by separation vessels and a LT CO2 purification unit for recovery of the CO2 produced by the combustion process. In one or more embodiments, which may be combined with other embodiments, about 95% or greater, such as about 97% or greater, such as about 98% or greater, of the total CO2 introduced into and produced within the system is produced as one or more system CO2 products.

[0014] In one or more embodiments, which can be combined with other embodiments, the disclosure provides a process for separating carbon dioxide (CO2) from a mixed stream. The process may comprise: introducing a mixed gas stream to a first separator, which may be a single stage separator, the mixed gas stream comprising CO2 and at least one further component; processing at least a portion of a first top vapor stream from the first separator in a second separator, which may be a single stage separator; processing a second top vapor stream from the second separator in one or more components to form a gas stream that is substantially free of CO2; and processing a first bottom liquid stream from the first separator and a second bottom liquid stream from the second separator in a CO2 purification column to form a liquid CO2 product stream. The process may be further defined in relation to any one or more of the following statements, which may be combined in any number and order.

[0015] Prior to introducing the mixed gas stream to the first separator, the mixed gas stream may be processed in one or more of a compressor, a drier, and a heat exchanger.

[0016] The process further may comprise combining a top vapor stream from the CO2 purification column with the second top vapor stream from the second separator.

[0017] The process further may comprise introducing one or both of the top vapor stream from the CO2 purification column and the second top vapor stream from the second separator into a heat exchanger for use in cooling one or more further streams entering the heat exchanger.

[0018] Processing the second top vapor stream from the second separator in one or more components may comprise combusting the second top vapor stream in a combustor.

[0019] At least a portion of the flue gas from the combustor may be processed through a plurality of separators configured to provide a top gas stream that is substantially free of CO2 and provide a bottom liquid CO2 stream.

[0020] Processing the second top vapor stream from the second separator in one or more components may comprise processing the second top vapor in a third separator, which may be a single stage separator. The processing also may comprise operating the third separator such that a third top vapor stream forms.

[0021] The process further may comprise processing the third top vapor stream from the third separator in a CO2 enriching system. The CO2-enriching system may be operated such that a CO2-rich gas forms.

[0022] The process further may comprise passing the CO2-rich gas from the CO2 enriching system to the mixed gas stream. AttyDkt.No. P62622 2420WO (01250)

[0023] The process further may comprise passing a stream of substantially pure CO2 gas from the CO2 enriching system.

[0024] The process further may comprise processing a third bottom liquid stream from the third separator in the CO2 purification column.

[0025] Forming the liquid CO2 product stream may include cooling at least a portion of a bottom stream from the CO2 purification column in a heat exchanger.

[0026] The process may comprise splitting the at least a portion of the bottom stream from the CO2 purification column into a plurality of separate streams that are individually cooled in the heat exchanger.

[0027] The process may comprise, after said cooling, compressing the at least a portion of the bottom stream from the CO2 purification column in one or more compressors or in one or more compression stages.

[0028] In one or more embodiments, which may be combined with other embodiments, the disclosure provides a process for separating carbon dioxide (CO2) from a syngas stream. The process may comprise: processing a shifted syngas stream in a first hydrogen pressure swing adsorber (H2 PSA 1); processing a tail gas from H2 PSA 1 in a first low temperature CO2 removal envelope to provide a CO2 export stream and a syngas stream reduced in CO2 content; processing the syngas stream reduced in CO2 content in a second hydrogen pressure swing adsorber (H2 PSA 2); combusting a hydrogen-lean syngas from H2 PSA 2 in a combustor to form a flue gas; and processing the flue gas in a second low temperature CO2 removal envelope to provide a further CO2 export stream and a gas stream reduced in CO2 content. In one or more embodiments, one or both of the syngas stream reduced in CO2 content and the gas stream reduced in CO2 content may be substantially free of CO2.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Having thus described the disclosure in the foregoing general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0031] FIG. 1 is a flow diagram illustrating components of a low temperature CO2 removal system useful for carrying out a low temperature CO2 removal process according to one or more embodiments of the disclosure.

[0032] FIG. 2 is a flow diagram illustrating process stream flows according to one or more embodiments of the disclosure.

[0033] FIG. 3 is a flow diagram illustrating components of a low temperature CO2 removal system useful for carrying out a low temperature CO2 removal process according to one or more embodiments of the disclosure. AttyDkt.No. P62622 2420WO (01250)

[0034] FIG. 4 is a flow diagram illustrating process stream flows according to one or more embodiments of the disclosure.

[0035] FIG. 5 is a flow diagram illustrating components of a low temperature CO2 removal system useful for carrying out a low temperature CO2 removal process according to one or more embodiments of the disclosure.

[0036] FIG. 6 is a flow diagram illustrating components of a low temperature CO2 removal system useful for carrying out a low temperature CO2 removal process according to one or more embodiments of the disclosure.

[0037] FIG. 7 is a flow diagram illustrating process stream flows according to one or more embodiments of the disclosure.

[0038] Like numbers refer to identical, like or similar elements throughout, although such numbers may be referenced in the context of different embodiments.

[0039] DETAILED DESCRIPTION

[0040] The present subject matter is described more fully with reference to the one or more embodiments. These embodiments are described so that this disclosure will be thorough, complete, and will fully convey the scope of the subject matter to those skilled in the art. Indeed, the subject matter can be embodied in many different forms and should not be construed as limited to the embodiments set forth; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. As used in the specification and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0041] One may desire to purify a mixed gas stream (MGS) by removing carbon dioxide (CO2). This can be due to regulations around carbon emissions, such as its release into the atmosphere or water. One may have a desire to upgrade the calorific value of a gas, such as a fuel gas, such as a natural gas or a syngas. CO2 is known to act as a diluent given its non-combustion value. Although a variety of methods are known for purifying mixed gas streams, including removal of carbon dioxide, purification of mixed gas streams to a level that approaches removal of about 100% of the CO2 from a given mixed gas stream is not only technically difficult but also may be energy or capital intensive.

[0042] The embodiment processes and systems that are generally described in relation to FIG. 1 can define a low temperature (LT) CO2 removal envelope that can be integrated with existing processes and systems that produce one or more mixed gas streams where CO2 removal from the MGS is needed, wanted, or desired. The term “envelope” indicates a plurality of separate components that are coupled together, such as in a fluid, thermal, or other manner where there is a transversal of physical, thermal, electrical, or signal flow between each, to operate while also being physically separate for achieving a AttyDkt.No. P62622 2420WO (01250) common purpose. A “low temperature CO2 removal envelope” is a plurality of components that are configured to operate as a system to provide removal and recovery of CO2 from an introduced MGS. The system may be integrated, as a unit or envelope, with existing processes, such as a subsystem, that may produce one or more MGSs from which CO2 removal and recovery is needed, wanted, or desired.

[0043] The LT CO2 removal envelope can be modified to accommodate a variety of gas mixtures as the incoming stream for purification. The LT CO2 removal envelope can provide a stream of substantially pure liquid CO2. For the purposes of this disclosure, “substantially pure” means a material or stream comprises about 97 mol% or greater, such as about 98 mol% or greater, or such as about 99 mol% or greater concentration of the material described, for example, CO2 as the liquid product produced from the LT CO2 removal envelope. Such a substantially pure liquid CO2 product may be suitable for chemical processing, downhole sequestration or other uses outside of the scope of this matter.

[0044] The LT CO2 removal envelope can provide a gas stream that is of substantially “low” CO2 concentration, which is a “reduced concentration” CO2 gas. The reduced concentration CO2 gas can be further treated to provide a desired end gas product, such as a gas product that is substantially free of CO2. A stream that is “substantially free” of a material means that the gas stream comprises about 3 mol% or less, such as about 2 mol% or less, such as about 1 mol% or less, such as about 0.5 mol% or less, concentration of the material, for example, CO2. Treatment can include processing of the low CO2 gas stream in one or more CO2-enriching units that are selective for removal of CO2 from a gas stream. The treatment can include use of the reduced concentration CO2 gas stream as at least a portion of a fuel gas in a combustor to produce a flue gas that can be processed through a LT CO2 removal process and system, such as generally described relative to FIG. 1. Processing such a flue gas in the LT CO2 removal process and system may result in substantially all the CO2 introduced with the flue gas being stripped and produced as a liquid CO2 product stream and a vent gas that is substantially free of CO2.

[0045] The present disclosure provides processes and systems for purifying an introduced MGS, which is understood to mean a stream where greater than 50% by weight (weight percent; wt%), such as about 60 wt% or greater, such as about 75 wt% or greater, such as about 90 wt% or greater, such as about 95 wt% or greater, such as about 98 wt%% or greater, of the components of the stream at least in part gaseous at standard temperature and pressure (STP) conditions, such as about 20 °C and about 1 bar (0.1 MPa (Megapascal)). In one or more embodiments, which can be combined with other embodiments, the processes and systems can be configured to separate CO2 from a mixed gas stream and produce CO2 as a fluid product, such as in the form of a liquid, a gas, a critical fluid, a supercritical fluid, and combinations thereof. The mixed gas stream is a stream that comprises CO2 and at least one other gaseous material, which may include, but is not limited to, methane, one or more hydrocarbons, H2, CO, N2, and Ar. AttyDkt.No. P62622 2420WO (01250)

[0046] One or more embodiments of the processes and systems are provided, and the one or more embodiments are described individually only for ease of disclosure and understanding. The one or more embodiments, however, are expressly intended to be useful either individually or in any combination of with one another. It is understood that each embodiment provides improvements in purification of a MGS arising from the specific features of the individual embodiment. Individual embodiments arise from a recognition of one or more shortcomings in existing methods, processes, systems, and equipment, used for the purification of mixed gas streams. Each individual embodiment provides a useful improvement and advantage in purification of mixed gas streams. The improvements and advantages can be multiplied through combinations of individual embodiments. The unique features of each embodiment are evidence that the improvements achieved with the combinations of the embodiments are not an expected, cumulative effect, but rather may demonstrate synergistic effects arising from the various combinations of the individual embodiments.

[0047] In one or more embodiments, which can be combined with other embodiments, the processes and systems can utilize one or more separation vessels (separators) in combination with a low-temperature (LT) CO2 purification column to provide improved CO2 separation from a MGS. The one or more separators are useful to perform bulk impurity removal so that the LT CO2 purification column can be operated to efficiently strip CO2 from the introduced mixed gas streams or portions thereof and form a purified liquid bottom stream.

[0048] The use of one or more separation vessels also makes it possible to approach temperatures in the LT CO2 purification column that are at or proximate to but greater than the CO2 triple point.

[0049] Labels such as “first,” “second,” “third,” and so on are used for ease of identifying components or streams in describing the processes and systems relative to the various figures and are not intended to necessarily indicate a specific order unless otherwise specified.

[0050] A simplified flowchart of an embodiment process and system for purifying an introduced MGS by extracting CO2 therefrom and forming a purified liquid CO2 stream is illustrated in FIG. 1 as system 100. Introduced into system 100 is a mixed gas stream 101 that includes CO2 and at least one additional component, such as, but not limited to, methane, one or more higher-order hydrocarbons, molecular hydrogen, carbon monoxide, water, or oxygen, is optionally processed in block 102, which produces an optional product stream 105. Optional processing in block 102 can include compression in one or more compressors, dewatering in one or more dryers or water separators, cooling in one or more heat exchangers or coolers, and combinations thereof. Examples of such components are illustrated in other figures of the present application to be discussed forthcoming. In one or more embodiments, which can be combined with other embodiments, prior to introducing the mixed gas stream to the first separator vessel, the mixed gas stream is processed in a compressor, a dryer, and a heat exchanger. AttyDkt.No. P62622 2420WO (01250)

[0051] Stream 101 or optionally 105 is introduced to a first separator vessel, such as first separator vessel 110. First separator vessel is positioned upstream from the LT CO2 purification column and acts as a “pre-treater” or “pre-separator” for the column. First separator vessel is configured to separate a vapor and a liquid from the introduced MGS, forming a first top vapor and a first bottom liquid. The first top vapor passes from the first separator vessel 110 as first top vapor stream 111. The remainder of the material passes from the first separator vessel as a liquid, such as first liquid bottoms stream 113. In one or more embodiments, which may be combined with other embodiments, the first liquid bottom streams from the first separator can comprise about 80 mol% or greater, such as about 85 mol% or greater, such as about 90 mol% or greater, such as about 95 mol% or greater, such as about 97 mol% or greater, concentration of CO2.

[0052] Optionally, the first top vapor is processed in block 112. Optional processing in block 112 can include expanding in one or more turboexpanders or expansion valves or cooling in one or more heat exchangers or coolers, providing a stream 115 that is cooled and potentially reduced pressured versus the stream in line 111.

[0053] Stream 111 or optionally 115 is introduced into a second separator vessel, such as separator vessel 120. Second separator vessel is also positioned upstream from the LT CO2 purification column and acts as a “pre-treater” or “pre-separator” for the column. Second separator vessel is configured to separate a vapor and a liquid from the introduced overhead stream from the first separator, forming a second top vapor, such as second top vapor stream 121 and a second bottom liquid 123. The remainder of the material passes from the second separator vessel as a liquid, such as second liquid bottoms stream 123. In one or more embodiments, which may be combined with other embodiments, the second liquid bottom streams from the second separator can comprise about 80 mol% or greater, such as about 85 mol% or greater, such as about 90 mol% or greater, such as about 95 mol% or greater, such as about 97 mol% or greater, concentration of CO2. In one or more embodiments, which may be combined with other embodiments, the concentration of CO2 in both the first and the second liquid bottoms streams are similar.

[0054] Optionally, the second top vapor is processed in block 122. Optional processing in block 122 may include expanding in one or more turboexpanders or expansion valves or cooling in one or more heat exchangers or coolers, providing a stream 125 that is cooled and potentially reduced pressured versus the stream in line 122.

[0055] After processing through two pre-LT CO2 purification column separation vessels, the second top vapor, either further untreated as stream 115 or optional stream 125, may be regarded as a “reduced CO2 concentration” stream, that is low in concentration of CO2 versus the mixed gas stream and the first top vapor stream. A stream can be considered to be reduced CO2 concentration stream by comprising less AttyDkt.No. P62622 2420WO (01250) than about 30 mol%, such as about 25 mol% or less, such as about 20 mol% or less, such as about 15 mol% or less, or comprise in a range of from about 5 mol% to about 30 mol%, such as a range of from about 10 mol% to about 28 mol%, such as a range of from about 15 mol% to about 25 mol%, concentration of CO2.

[0056] Referring back to FIG. 1, the first liquid bottom stream and a second liquid bottom stream, such as first liquid bottom stream 113 and second liquid bottom stream 123, respectively, are introduced separately into LT CO2 purification column 130. Although shown introduced into the LT CO2 purification column separately, the two or more streams may be pre-combined and introduced as a single feed stream into the LT CO2 purification column.

[0057] The use of multiple separation vessels before processing through the LT CO2 purification column can be effective so that the temperature of one or more of the separate liquid bottom streams or a combined liquid bottom stream may be managed before introduction into the LT CO2 purification column, enhancing its performance and reducing its energy requirements for separations. In one or more embodiments, which may be combined with other embodiments, the temperature of one or more separate liquid bottom streams or a combined liquid bottom stream introduced into the LT CO2 purification column may have a temperature in a range of from about -56°C to about 0°C, such as from about -55°C to about -5°C, such as from about -54°C to about -40°C. In one or more embodiments, which may be combined with other embodiments, the temperature of one or more separate liquid bottom streams or a combined liquid bottom stream introduced into the LT CO2 purification column may have a temperature in a range of from about -50°C to about 0°C, such as from about -45°C to about -10°C, such as from about -40°C to about -20°C. In one or more embodiments, which may be combined it other embodiments, the temperature of one or more separate liquid bottom streams or a combined liquid bottom stream introduced into the LT CO2 purification column may have a temperature differential in a range that is upon to but no greater than about 5°C , such as no greater than 4°C, such as no greater than 3°C, such as no greater than 2°C , such as no greater than 1°C the freezing point of pure CO2 (that is, 100% carbon dioxide) at the operating pressure of the LT CO2 purification column at the point of introduction of the one or more separate liquid bottom streams or the combined liquid bottom stream.

[0058] In one or more embodiments, which may be combined it other embodiments, the temperature of the one or more separate liquid bottom streams introduced into the LT CO2 purification column each has a different temperature. For example, as shown in FIG. 1, stream 123 is shown introduced into the LT CO2 purification column at a higher position relative to stream 113. If stream 123 has a reduced temperature relative to stream 113, then the cooler 123 stream may be utilized to facilitate in part the stripping of CO2 from the vapor components rising from the introduction of fluid from stream 113 in the AttyDkt.No. P62622 2420WO (01250)

[0059] LT CO2 purification column. This may, in turn, reduce the overall energy requirements for the polishing action occurring within the LT CO2 purification column.

[0060] The LT CO2 purification column can be operated at pressures greater than the triple point pressure of CO2. In one or more embodiments, which may be combined with other embodiments, the operating pressure of the LT CO2 purification column is in a range of from about 6 bar (0.6 MPa) to about 100 bar (10 MPa), such as about 8 bar (0.8 MPa) to about 80 bar (8 MPa), such as about 10 bar (1 MPa) to about 60 bar (6 MPa). Operating pressure may be as measured in an upper operating section of the column or approximately at the top of the column.

[0061] The LT CO2 purification column is configured to separate the one or more separately introduced or combined liquid bottom stream(s) into an LT CO2 column vent gas and a liquid CO2 product stream. The LT CO2 column vent gas, shown in FIG. 1 as passing through line 131, will include a relatively high concentration of non-CO2 containing species. In one or more embodiments, which may be combined with other embodiments, the LT CO2 column vent gas has a temperature in a range that is , less than the CO2 triple point temperature, such as in a range of from about -80°C to about -56°C, such as in a range of from about -75°C to about -60°C.

[0062] In one or more embodiments, which may be combined with other embodiments, the liquid CO2 product stream passing from the LT CO2 purification column, such as stream 133 from column 130, has a CO2 concentration of at least about 95 mol% or greater, such as about 98 mol% or greater, such as about 99.5 mol% or greater, CO2. The systems particularly may be configured so that the stream leaving the LT CO2 purification column has a greater CO2 purity (in mol%) than the stream(s) leaving the separator vessel(s). The difference in CO2 purity may be, for example, at least 1 mol%, at least 2 mol%, at least 3 mol%, or at least 4 mol%. The bottoms stream passing from LT CO2 purification column is a liquid CO2 product that is ready for use in chemical production, enhanced oil recovery (EOR), sequestration, mineralization, or other use.

[0063] Optionally, The LT CO2 column vent gas is processed in block 132. Optional processing block 132 may include expanding in one or more turboexpanders or expansion valves or cooling in one or more heat exchangers or coolers, providing a stream 135 that is cooled and potentially reduced pressured versus the stream in line 132. As shown in FIG. 1, stream 135 may be combined with stream 125 and further processed, purged, or both.

[0064] Although not shown in FIG. 1, one of ordinary skill in the art appreciates that if more than two pre-LT CO2 purification column separation vessels are used upstream of the LT CO2 purification column, the LT CO2 column vent gas stream, such as line 135, may be combined with the top vapor stream line from the final or last pre-separation vessel, such as a third or even fourth separation vessel. In doing so, additional CO2 and other non-condensable recovery may occur. AttyDkt.No. P62622 2420WO (01250)

[0065] The process and system that is generally described in relation to FIG. 1 can define a low temperature CO2 removal envelope that can be integrated with existing processes and systems that produce a mixed gas and where CO2 removal from the mixed gas stream is needed or desired. The low temperature CO2 removal envelope may be modified to accommodate a variety of gas mixtures as the incoming stream for purification. The LT CO2 removal envelope may provide both a stream of substantially pure liquid CO2 that is suitable for sequestration or other use and a gas stream that is of substantially low CO2 concentration, which is a “low CO2” gas. The low CO2 gas may be treated to provide a desired end gas product that is substantially free of CO2. Treatment may include processing of the low CO2 gas stream in one or more CO2 enriching units that are selective for removal of CO2 from a gas stream. The treatment may include use of the low CO2 gas stream as at least a portion of a fuel gas in a combustor to produce a flue gas that can be processed through a low temperature CO2 removal process and system, such as generally described relative to FIG. 1, so that substantially all of the CO2 in the flue gas is removed with the liquid CO2 product stream and a vent gas that is substantially free of CO2 is provided. A gas stream that is substantially free of CO2 may mean that the gas stream contains about 3 mol% or less, such as about 2 mol% or less, such as about 1 mol% or less, or such as about 0.5 mol% or less concentration of CO2.

[0066] In one or more embodiments, which can be combined with other embodiments, processes and systems can be configured to remove CO2 from an introduced MGS, such as an introduced mixed gas stream comprising a syngas, and produce a product stream of a modified syngas that is substantially free of CO2. Although for the purposes of providing an enabling description of embodiment systems and processes a syngas is utilized as an example mixed gas stream, one of ordinary skill in the art appreciates that embodiment processes and systems, either alone or in combination, can remove, extract, or strip CO2 from the introduced stream to modify, alter, or purify other raw, refined, or partially-processed fuel gas streams, such as natural gas, or industrial streams, such as a tail gas.

[0067] With reference now to FIG. 2, a block diagram is provided and illustrates embodiments of a mixed gas treatment system, such as mixed gas treatment system (MGTS) 200. As provided, a “shifted” syngas is shown introduced into MGTS 200 through line 201 and initially processed in H2 PSA 205.

[0068] The H2 PSA, such as H2 PSA 205, is configured to provide as products from the introduced shifted syngas a stream of substantially pure H2 gas, passing from MGTS 200 through line 207, and a tail gas stream through line 209. In one or more embodiments, which may be combined with other embodiments, the tail gas stream may have a CO2 concentration of about 60 mol% or greater, such as about 70 mol% or greater, such as about 75 mol% or greater, such as about 80 mol% or greater, concentration of CO2. AttyDkt.No. P62622 2420WO (01250)

[0069] The tail gas stream passing from an H2 PSA, such as H2 PSA, 205, can be introduced into an LT CO2 removal envelope, such as LT CO2 removal envelope 1000, illustrated as Block 1. In one or more embodiments, which may be combined with other embodiments, LT CO2 removal envelope may be similar or the same in configuration and operation as the LT CO2 removal envelope described in association with FIG. 1, that is system 100. In one or more embodiments, which may be combined with other embodiments, LT CO2 removal envelope of Block 1 may be similar or the same in configuration and operation as the LT CO2 removal envelope described in association with FIG. 3, that is envelope 1000A, the detailed description of which is forthcoming.

[0070] The tail gas stream passing from an H2 PSA, such as the tail gas stream traversing line 209 and introduced into LT CO2 removal envelope, such as LT CO2 removal envelope 1000, is processed within LT CO2 removal envelope through one or more units, of which some are optional, such as one or more compressors, one or more dewatering units, one or more heat exchangers, one or more coolers, one or more turboexpanders, one or more expansion valves, one or more pumps, one or more single or multistage pre-LT CO2 purification column separation vessels, one or more LT CO2 purification columns, and one or more CO2-enriching units. Although not shown in detail in FIG. 2, the LT CO2 removal envelope produces one or more top gas streams from the one or more pre-LT CO2 single or multi-stage separators and the one or more LT CO2 purification columns. In some instances, the top gas streams may be further cooled within the LT CO2 removal envelope 1000 to produce a plurality of two-phase, gas / liquid streams that are then separated by phase in a similar manner to the processes described previously, such as for system 100, and to be further described.

[0071] The liquid streams that are the resultant of the one or more single or multi-stage pre-LT CO2 purification column(s) are directed to at least one LT CO2 purification column, which as previously described, configured to produce a liquid bottoms stream of substantially pure CO2. For system 200, such a product stream is provided for as CO2 export stream 1375.

[0072] The top gas from a final single or multi-state pre-LT CO2 purification column(s) and the LT CO2 column vent gas stream(s) from the one or more LT CO2 purification column(s) may be further processed in an optional CO2 enrichment unit before passing from the LT CO2 removal envelope as a product gas stream. See CO2 enrichment unit 1410 in FIG. 3 and the associated disclosure following. The CO2 enrichment unit provides a product gas stream, such as modified syngas through line 1417, that in one or more embodiments, which may be combined with other embodiments, is substantially free of CO2. Although also not specifically illustrated in FIG. 2, the CO2 enrichment unit is configured to provide a stream that comprises CO2 recovered from the top gas and vent gas stream(s) introduced (either precombined or separately) into the CO2 enrichment unit such that the product stream is substantially free of CO2. AttyDkt.No. P62622 2420WO (01250)

[0073] In one or more embodiments, which may be combined with other embodiments, the product stream from the optional CO2 enrichment unit is not substantially free of CO2. One of ordinary skill in the art may appreciate that the composition of gas product stream of LT CO2 removal envelope can vary based upon the composition of the introduced MGS.

[0074] In one or more embodiments, which can be combined with other embodiments, a LT CO2 removal envelope 1000A is illustrated in FIG. 3. The LT CO2 removal envelope 1000A as provided for in FIG. 3 and the forthcoming description, in one or more embodiments, which may be combined with other embodiments, is configured and operable with system 200, as previously described, and may be substituted into system 200 in place of LT CO2 removal envelope 1000. A person of skill in the art recognizes any adjustments or modifications to system 200 or LT CO2 removal envelope 1000A that permits each to operate with the other per the disclosed scope.

[0075] As shown in FIG. 3, LT CO2 removal envelope 1000A comprises three pre-LT CO2 purification column separation vessels (1210, 1230, 1250); however, in one or more embodiments, the LT CO2 removal envelope may provide for a different number of pre-LT CO2 purification column separation vessels, including two, four, five, or more. In one or more embodiments, which may be combined with other embodiments, each of the separation vessels may be configured either as a single or a multi-stage separation vessel, as previously described. Within the LT CO2 removal envelope, in one or more embodiments, which may be combined with other embodiments, a combination of only single stage, only multi-stage, or both single and multi-stage separation vessels may be present, as previously described.

[0076] As shown in FIG. 3, LT CO2 removal envelope 1000A comprises a single LT CO2 purification column (1310) ; however, in one or more embodiments, the LT CO2 removal envelope may provide for a plurality of LT CO2 purification columns, including two, three, four, or more. In instances where there is more than one LT CO2 purification column, in one or more embodiments, which may be combined with other embodiments, the plurality of LT CO2 purification columns may be configured such that each of the LT CO2 purification columns are operationally in series with one another, parallel with one another, or a combination thereof. For example, a first and a second LT CO2 purification columns of an embodiment LT CO2 removal envelope may be configured to be operationally in parallel with one another, and a third LT CO2 purification column within the same LT CO2 removal envelope may be configured downstream (or in other embodiments upstream) of both the first and the second LT CO2 purification columns.

[0077] As shown in FIG. 3, LT CO2 removal envelope 1000A comprises a single, multi-pass heat exchanger (1100). A “multi-pass” heat exchanger means a heat exchanger where multiple streams are introduced into the heat exchanger at a greater temperature, are cooled, and pass from the heat exchanger at a reduced temperature and where multiple streams are introduced into the heat exchanger at a reduced temperature, are heated, and pass from the heat exchanger at a greater temperature. A “single pass” heat AttyDkt.No. P62622 2420WO (01250) exchanger is appreciated to mean a heat exchanger where a single stream is introduced into the heat exchanger at a greater temperature, is cooled, and passes from the heat changes at a reduced temperature, and a single stream is introduced into the heat exchanger a reduced temperature, is heated, and passes from the heat exchanger at an elevated temperature. A person of skill in the art recognizes that embodiment of the LT CO2 removal envelope may alternatively comprise a plurality of multi-pass heat exchangers, a plurality of single pass heat exchangers, and combinations thereof.

[0078] As shown in FIG. 3, LT CO2 removal envelope 1000A is configured to cool one or more streams by use of flashing or expansion equipment, such as through one or more turboexpanders, one or more inline expansion valves, such as Joule-Thomson valves (J-T valves), and combinations thereof.

[0079] Turning specifically to the embodiment of the LT CO2 removal envelope provided in FIG. 3, a tail gas, such as from an H2 PSA, or other MGS, is introduced into the CO2 removal envelope 1000A through line 1009. The tail gas may comprise, for example, H2, CO, and CO2, as well as small amounts of CH4, N2, water, and Ar. The tail gas in line 1009 is directed into a compressor 1011, which compresses the tail gas a pressure that is less than the CO2 supercritical pressure at the operating temperature of the LT CO2 purification column, such as LT CO2 purification column 1310, but is sufficiently elevated such that the LT CO2 purification column is able to recover about 80% or greater CO2 introduced into the LT CO2 purification column as liquid CO2 on a single pass basis. In one or more embodiments, which may be combined with other embodiments, the compressed tail gas is discharged from the compressor at a pressure in a range of from about 30 bar (3 MPa) to about 80 bar (8 MPa), such as about 35 bar (3.5 MPa) to about 70 bar (7 MPa), such as about 30 bar (4 MPa) to about 60 bar (6 MPa). The compressed tail gas is discharged from compressor 1011 into line 1013.

[0080] The compressed tail gas is introduced into a dryer, such as dryer 1020, to desiccate the stream. In one or more embodiments, which may be combined with other embodiments, the desiccated, compressed tail gas comprises an amount of water of about 10 ppm or less, such as about in a range of about such as about 5 ppm or less concentration of water. Dryer in one or more embodiments may be configured as a drying bed packed with a desiccant material, such as molecular sieves or zeolites. The compressed, desiccated tail gas passes from the dryer 1020 via line 1022.

[0081] The compressed, desiccated tail gas in line 1022 is introduced into and cooled during passage through the multi-pass heat exchanger 1100. The cooled tail gas passing from the multi-pass heat exchanger 1100 is at a pressure and temperature that is less than the carbon dioxide dew point, resulting in a dual-phase stream in line 1101.

[0082] The cooled stream in line 1101 is introduced into a first separation vessel 1210 configured for liquid / vapor separation. First separation vessel is configured to separate the introduced dual-phase material into a first top vapor, which passes from the first separation vessel 1210 through line 1213, and a AttyDkt.No. P62622 2420WO (01250) first CO2-rich liquid stream, which passes via bottoms line 1212. In one or more embodiments, which may be combined with other embodiments, the CO2 concentration of the first CO2-rich liquid stream may be about 90 mol% or greater, such as about 92 mol% or greater, such as about 95 mol% or greater, CO2.

[0083] Following the vapor pathway, the first top vapor passing through line 1213 traverses through the multi-pass heat exchanger 1100, where its temperature is reduced towards a minimum approach to the CO2 solidification temperature, forming a chilled first top vapor stream. First top vapor stream is a two- phase stream with a CO2-rich liquid portion and a CO2-lean vapor portion that passes from the heat exchanger via line 1113. To achieve bulk separation in the separation vessels upstream of the LT CO2 purification column and to reduce overall cryogenic cooling demand for the envelope, one may find that it is useful to process the vapor streams such that a temperature less the dew point of carbon dioxide is reached for each stream entering the multi-pass heat exchanger by maintaining a narrow temperature approach between the hot and cold composite curves. In one or more embodiments, which may be combined with other embodiments, the chilled first top vapor stream is at a temperature that is about 5 °C greater, such as up to about 3 °C greater, such as up to about 1 °C greater, than the CO2 solidification temperature of the composition of the first top vapor stream.

[0084] The chilled first top vapor stream from line 1113 is introduced to a second separation vessel 1230. Second separation vessel is configured to separate the introduced dual-phase material into a second top vapor, which passes from the second separation vessel 1230 through line 1233, and a second CO2- rich liquid stream, which passes via bottoms line 1232. In one or more embodiments, which may be combined with other embodiments, the CO2 concentration of the second CO2-rich liquid stream may be about 90 mol% or greater, such as about 92 mol% or greater, such as about 95 mol% or greater, CO2.

[0085] The second top vapor passing through line 1233 traverses through the multi-pass heat exchanger 1100 again and is cooled and maintained at a temperature with a minimum approach to the CO2 solidification temperature, forming a chilled second top vapor stream. Second top vapor stream is a two- phase stream with a CO2-rich liquid portion and a CO2-lean vapor portion, that passes from the heat exchanger via line 1133. In one or more embodiments, which may be combined with other embodiments, the chilled second top vapor stream is at a temperature that is in a range of from about 1°C to about 15°C, such as a range of from about 1°C to about 10°C, such as a range of from about 1°C to about 5°C, greater than the CO2 solidification temperature of the composition of the second top vapor stream.

[0086] The chilled second top vapor stream from line 1133 is introduced to a third separation vessel 1250. Third separation vessel is configured to separate the introduced dual-phase material into a third top vapor, which passes from the third separation vessel 1250 through line 1261, and a third CO2-rich liquid stream, which passes via bottoms line 1252. In one or more embodiments, which may be combined with AttyDkt.No. P62622 2420WO (01250) other embodiments, the CO2 concentration of the third CO2-rich liquid stream may be about 90 mol% or greater, such as about 92 mol% or greater, such as about 95 mol% or greater, CO2.

[0087] As shown in FIG. 3, the third top vapor stream passes through line 1261 from the overhead of the third separation vessel 1250 and traverses across expansion valve 1262, which expands the gas and reduces its pressure and temperature. The expanded third top vapor stream in line 1263 is introduced into the multi-pass heat exchanger 1100. The expanded third top vapor stream provides heat absorption capacity against the introduced tail gas from line 1022, cooling the introduced tail gas. The now warmed, expanded third top vapor stream passes from the multi-pass heat exchanger 1100 via line 1163 and is directed within envelope 1000 to be combined with an LT CO2 column vent gas from the LT CO2 purification column, to be described.

[0088] As previously described, separately the first CO2-rich liquid stream in line 1212, the second CO2-rich liquid stream in line 1232, and the third CO2-rich liquid stream in line 1252, are directed separately towards a LT CO2 purification column, such as LT CO2 purification column 1310.

[0089] As shown in FIG. 3, optionally, the CO2-rich liquid stream lines 1212, 1232, 1252, each may traverse across an in-line expansion valves (1215, 1235, 1255, respectively) or other forms of fluid restrictors before introduction into the LT CO2 purification column 1310. Traversing across an expansion valve or fluid restrictor, such as orifice plates, at an accelerated flow rate may cause fluid to depressurize and expand through spot flashing and formation of a partial vapor phase before introduction into the LT CO2 purification column. In instances where some or all the CO2-rich liquid streams are combined before introduction into the LT CO2 purification column, the combined stream may pass through such an expander or flow restriction to cause the same expansive cooling effect. One skilled in the art may envision that the optional expanders may be present in one, some, all, or none of the lines through which liquid CO2-rich streams traverse to modify the super-cooling effect given the relative volumes of the liquid CO2-rich streams to one another. As well, the presence of and its configuration or lack thereof entirely may be based upon impact upon the particular stream, for example, one may find it desirable to have the relatively coolest of the liquid CO2-rich streams introduced at the highest position of the LT CO2 purification column relative to the other streams to facilitate CO2 stripping LT CO2 purification column, and therefore undergo relatively the most severe expansion process.

[0090] The LT CO2 purification column 1310 is configured to polish the CO2-rich liquid bottom streams from the separation vessels, which means that relatively small amounts of CO2 remaining in the liquid streams are readily removed via stripping. The LT CO2 purification column can be configured with a stripping section and a rectifying section. The stripping section can produce a substantially pure liquid CO2 product and the rectifying section can product the top vapor gas product. The LT CO2 purification column can be packed with packing material (for example, random packing, structured packing, AttyDkt.No. P62622 2420WO (01250) distillation trays, and combinations thereof) to enhance mass transfer within the column and produce the substantially pure liquid CO2 bottoms product. The bottoms liquid CO2 product stream passes from the LT CO2 purification column 1310 through line 1312. The overhead vapor LT CO2 column vent gas stream passes from the LT CO2 purification column through line 1381.

[0091] In one or more embodiments, which can be combined with other embodiments, the LT CO2 purification column, such as LT CO2 purification column 1310, is fluidly coupled to a multi-pass heat exchanger, such as multi-pass heat exchanger 1100, such that the multi-pass heat exchanger provides heat and operates as a reboiler for the LT CO2 purification column. As illustrated in FIG. 3, in such a configuration, a reboiler draw stream can pass from LT CO2 purification column 1310 through line 1302 and be introduced into the multi-pass heat exchanger 1100 to be heated. The now heated reboiler draw passes from the multi-pass heat exchanger 1100 using line 1304 and is introduced back into the LT CO2 purification column 1310, providing reboiling duty for the column.

[0092] Although not shown in FIG. 3, in one or more embodiments, which can be combined with other embodiments, the LT CO2 purification column may be fluidly coupled with a stand-alone reboiler or heating unit, where at least a portion of the first CO2-rich liquid stream passing to the LT CO2 purification column is routed first through the stand-alone reboiler, is heated, such as with another process stream or a utility stream, and then is directed into the LT CO2 purification column either as a combined stream, such as being recombined with a remaining portion of the first CO2-rich liquid stream, or as an independent stream, into the rectifying section of the column.

[0093] The bottoms liquid CO2 product stream may pass from the LT CO2 purification column at approximately the column pressure. The LT CO2 purification column can be operated at pressures greater than the triple point pressure of CO2, which is 5.18 bar (0.518 MPa). In one or more embodiments, which may be combined with other embodiments, the operating pressure of the LT CO2 purification column is in a range of from about 6 bar (0.6 MPa) to about 100 bar (10 MPa), such as about 8 bar (0.8 MPa) to about 80 bar (8 MPa), such as about 10 bar (1 MPa) to about 60 bar (6 MPa).

[0094] As shown in FIG. 3, the liquid CO2 product passing via line 1312 from the bottom of the LT CO2 purification column 1310 is apportioned into a plurality of streams (1312a, 1312b). The first liquid CO2 product stream 1312a is drawn into pump 1320, pressurized, and readied for export through line 1323.

[0095] The second liquid CO2 product stream 1312b is further split into three separate CO2 coolant stream lines (1313, 1314, and 1315), each of which are independently reduced in pressure by expansion across valves or restrictions 1324, 1325, and 1326, respectively, to provide auto-refrigeration for the multi-pass heat exchanger 1100. “Auto -refrigeration” can mean that a dedicated coolant that is not otherwise one of the process streams is not utilized, and this can exclude refrigerants such as freon, liquid nitrogen, liquid propane, and ammonia. Since liquid CO2 is an effective refrigerant, a portion of the AttyDkt.No. P62622 2420WO (01250) liquid CO2 product can be used to increase overall system process efficiency by providing at least some if not all of the refrigeration duty for the pre-LT CO2 purification column separation vessels and the LT CO2 purification column through the multi-pass heat exchanger.

[0096] Upon passing through the flow restrictions or expansion valves 1324, 1325, and 1326, a portion of the liquid CO2 flashes into the vapor phase, forming a dual-phase, chilled substantially pure CO2 fluids in each of lines 1333, 1334, and 1335, respectively, that each may be referred to as an “autorefrigerant stream”. In one or more embodiments, which may be combined with other embodiments, each of the auto-refrigerant streams may have a different pressure, a different temperature, or both, relative to the other auto -refrigerant streams. Each of the three separate CO2 coolant streams in lines 1313, 1314, and 1315, may in such embodiment may undergo different pressure differentials across the flow restrictions or expansion valves, such that each have different physical and thermal properties from one another, and thereby capable of providing different levels of refrigeration within the multi-stream heat exchanger. For example, the streams in lines 1333, 1334, and 1335, may exhibit a single, two, or three different temperatures.

[0097] The auto-refrigerant streams of lines 1333, 1334, and 1335, as shown in FIG. 3, are introduced into the multi-pass heat exchanger 1100. The introduced streams are utilized within the multi-pass heat exchanger to absorb latent heat from the streams introduced into the multi-pass heat exchanger, cooling the compositions introduced via lines 1022, 1213, 1233, 1257, 1345, and 1362, which have been previously described, and vaporizing the remainder of the substantially pure CO2 introduced through lines 1333, 1334, and 1335. The vaporized auto-refrigerant fluid streams pass as CO2-rich vapor streams though lines 1143, 1144, and 1145, respectively.

[0098] Adding cooling for the tail gas introduced into the envelope, such as envelope 1000A, by way of utilizing the auto -refrigerant fluids, is achieved by letting down the second portion of the bottoms liquid stream from the LT CO2 purification column. In addition, the temperatures of the auto -refrigerant fluids maintain a relatively small temperature approach between the hot and cold composite streams within the multi-pass heat exchanger without reaching a pinch point within the exchanger. In one or more embodiments, which may be combined with other embodiments, the “relatively small” temperature approach may be in a range of from about 2 °F or less.

[0099] Although each vaporized auto-refrigerant fluid stream is substantially pure CO2, each is at an insufficient pressure and phase for export from envelope 1000A, especially if, as shown in FIG. 3, such substantially pure CO2 streams are to be combined and passed as an export-grade, liquid CO2 stream, such as the liquid CO2 product in line 1323. The vaporized auto-refrigerant fluid in line 1143 is introduced into first compressor 1350 and compressed to a first discharge pressure. The compressed fluid is discharged from first compressor 1350 via line 1351 and passes through first intercooler 1353, which AttyDkt.No. P62622 2420WO (01250) cools down the compressed stream and passes it through line 1355. The process continues by combining the vaporized auto-refrigerant fluid in line 1144 with the cooled compressed fluid in line 1355. The combined fluid is introduced into a second compressor 1360, where the fluid is compressed to a second discharge pressure. The compressed fluid is discharged from second compressor 1360 via line 1361 and passes through second intercooler 1353, which cools down the compressed stream and passes it through line 1365. The process continues by combining the vaporized auto-refrigerant fluid in line 1145 with the cooled compressed fluid in line 1365. The combined fluid is introduced into a final compressor 1370, where the fluid is compressed to a final discharge pressure. Although a plurality of compressors are illustrated, one or more multi-stage compressors may be utilized, and intercooling may be carried between two or more of the stages of compression in a multi-stage compressor. The compressed fluid is discharged from final compressor 1370 via line 1371 and passes through aftercooler 1373, which cools down the compressed stream and passes it through line 1375. Envelope 1000A produces a liquid CO2 product that is suitable for export by combining the liquid CO2 streams of lines 1323 and 1375.

[0100] The overhead gas of the LT CO2 purification column, such as LT CO2 purification column 1310, passes through line 1381 as LT CO2 column vent gas stream, as previously described. The LT CO2 column vent gas stream is expanded through expansion valve 1382, which expands the gas and reduces its pressure and temperature. The expanded LT CO2 column vent gas in line 1383 is then directed into the multi-pass heat exchanger 1100 to provide heat absorption capacity against the introduced tail gas from line 1022, cooling the introduced tail gas. The now warmed, expanded LT CO2 column vent gas passes from the multi-pass heat exchanger 1100 via line 1183.

[0101] Downstream of the multi-pass heat exchanger 1100, the warmed, expanded third top vapor stream from stream 1163 and the warmed, expanded LT CO2 column vent gas are combined in line 1183. In one or more embodiments, which may be combined with other embodiments, the combined stream is a “reduced CO2 concentration” gas stream.

[0102] As provided in FIG. 3, the stream in line 1183 is introduced into a CO2-enriching unit, such as CO2-enriching unit 1410, for further processing. In one or more embodiments, which may be combined with other embodiments, the CO2-enriching unit is configured such that the introduced reduced CO2 concentration gas stream is separated into a tail gas stream and a gas stream that is substantially free of CO2. The gas stream that is substantially free of CO2, which comprises at least some if not all the non- CO2 components introduced with the reduced CO2 concentration gas stream, is shown in FIG. 3 as passing from CO2-enriching unit 1410 via line 1417, and in some instances from envelope 1000A, as a product stream. The substantially free of CO2 gas may be used as a relatively low heating value fuel or may be further processed to obtain a higher heating value product outside the bounds of the envelope 1000A. AttyDkt.No. P62622 2420WO (01250)

[0103] The tail gas produced by the CO2-enriching unit is rich in CO2. The tail gas from the CO2- enriching unit may comprise substantially all the CO2 introduced into the CO2-enriching unit via the reduced CO2 concentration gas stream. In one or more embodiments, the CO2-rich tail gas can comprise H2 in a range of from about 5 mol% to about 10 mol% concentration of H2.

[0104] In one or more embodiments, the envelope may be configured such that the tail gas from the CO2-enriching unit is directed to the first pre-LT CO2 purification column separation vessels. As shown in FIG. 3, line 1413, which is the line directing the tail gas produced by the CO2-enriching unit, is routed to merge with the tail gas in line 1009 upstream of compressor 1011. In such a configuration, the LT CO2 removal envelope is configured to not only recover CO2 from the introduced tail gas but also retain and concentrate the CO2 within the LT CO2 removal envelope until it is produced as a liquid product from the bottom of the LT CO2 purification column.

[0105] Examples of useful configurations of CO2-enriching units may include, but are not limited to, one or more of a CO2 PSA, a VPSA, a CO2 TSA, a reversing heat exchanger system using a heat exchanger to freeze the CO2 and a regeneration cycle to re-heat and recover the CO2, or a solvent-based CO2 removal unit.

[0106] In one or more embodiments, which can be combined with other embodiments, the CO2- enriching unit 1410 can be configured as a CO2 TSA that utilizes CH4-rich gas or natural gas as a regeneration gas. Such arrangement can comprise one or more of the following process steps: processing the introduced reduced CO2 concentration gas stream, such as the heated vapor streams from the LT CO2 purification column 1310 and the third separation unit 1250 in the CO2 TSA; separating the CO2 from one or more remaining components by capturing the CO2 selectively in an adsorbent bed; using a heated natural gas or a CH4-rich stream as a regeneration gas to recover the adsorbed CO2; utilizing the CO2- bome natural gas or CH4-rich stream either in a combustor with a backend CO2 capture or a reformer, or recycling the stream back to the low temperature CO2 removal system to recover the CO2; separating the H2 from one or more components from the CO2-free stream leaving the CO2 TSA unit using adsorbent systems while utilizing the CH4-rich gas for reforming or combustion with a backend CO2 capture system.

[0107] In one or more embodiments, which can be combined with other embodiments, the CO2- enriching unit 1410 can be configured to separate the H2 content from the introduced reduced CO2 concentration gas stream and produce an H2 stream that is sent for polishing to remove CO, CH4, and inert components that may be present. In such one or more embodiments, which can be combined with other embodiments, the CO2-enriching unit 1410 can be configured to produce a CO2-rich tail gas and a CO2-lean tail gas with a pure H2 stream, where the CO2-lean stream can be used as a fuel in an oxy-fired or an air-fired heater. AttyDkt.No. P62622 2420WO (01250)

[0108] In one or more embodiments, which can be combined with other embodiments, the CO2- enriching unit 1410 can be configured to produce a substantially pure stream of CO2. In such instances, the substantially pure stream of CO2 may be treated, such as pressurized and then mixed with the liquid product CO2 from the LT CO2 purification column 1310 and exported.

[0109] The process and system illustrated in FIG. 3 is configured to achieve near 100% CO2 recovery from the introduced mixed gas stream entering the LT CO2 removal envelope 1000 while minimizing the total electrical energy demand and the total thermal energy demand for the low temperature CO2 separation system. This is achieved at least in part by concentrating the thermal load of the system into a multi-pass heat exchanger, such as the multi-pass heat exchanger 1100, to generate concentrated CO2 bottom streams from the plurality of pre-LT CO2 purification column separation vessels, such as separation vessels 1210, 1230, 1250. These bottoms liquid streams can be used as reflux feed streams back into the LT CO2 purification column 1310 so the column can function as a trim purification system, which improves efficiency in the low-temperature CO2 removal process and system.

[0110] The use of separation vessels upstream of the LT CO2 purification column also reduces overall energy consumption for refrigeration. The plurality of pre-LT CO2 purification column separation vessels (1210, 1230, 1250) are configured to perform bulk impurity removal upstream of the LT CO2 purification column. Removing CO2 from portions of the introduced stream before reducing the remainder of the stream to cryogenic temperatures mitigates having to cool the entire introduced volume of tail gas or flue gas initially, saving energy. Further, use of multiple separation vessels makes it possible to achieve operating temperatures near the CO2 freezing temperature, which improves CO2 recovery The plurality of separator vessels produce bottom liquid streams that are already relatively pure streams of CO2. Introducing the relatively pure CO2 streams into the lower stages of the LT CO2 purification column 1310 boosts the single-pass CO2 recovery in the LT CO2 purification column 1310.

[0111] Adjusting where certain liquid bottoms from the separation vessels are introduced reduces cooling load. In the instance provided for in LT CO2 removal envelope 1000A, the third CO2-rich liquid stream from the third separation vessel 1250 has a relatively small volume compared to the first and second CO2-rich liquid streams. In such instances, introduction of the third CO2-rich liquid stream proximate to the top of the LT CO2 purification column allows it to act as a stripping fluid to the upflowing vapor, resulting in deep removal of non-CO2 “impurities” from the bottoms of the first and second separation vessels while also reducing reflux cooling load for the LT CO2 purification column.

[0112] By expanding the overhead streams that are to be processed to extract the final amounts of CO2 not recovered during the prior cryogenic processes, such as expanding the third top vapor stream in line 1261 and the LT CO2 column vent gas stream in line 1381, additional refrigeration can be generated in process and utilized to cool inbound streams, such as those streams introduced into the multi-pass heat AttyDkt.No. P62622 2420WO (01250) exchanger 1100, thereby further lowering the net energy required for operation of the LT CO2 removal envelope 1000A.

[0113] Several process conditions for a prophetic example of a process using a similar configuration of the LT CO2 removal envelope as provided for in FIG. 3 and as described are given in T able 1. T able 1 provides several inlet and outlet conditions for the introduced tail gas stream (line 1009), the CO2 export stream (line 1375), the warmed, expanded LT CO2 column vent gas stream post-multi-pass heat exchanger (line 1183), and , and the warmed, expanded third top vapor stream post-multi-pass heat exchanger (line 1163).

[0114] Table 1 : Prophetic calculations for several streams associated with the embodiment LT CO2 removal envelope shown in FIG. 3.

[0115] Utilizing the data provided in Table 1, it is evident that the vent streams from both the final pre- LT CO2 purification column separation vessel (third separation vessel) and the LT CO2 purification column itself contain both a significant amount and concentration of CO2. The single pass CO2 recovery for a LT CO2 removal envelope that is similar in configuration to that shown in FIG. 3 but without taking into consideration any CO2 recovered by the CO2-enriching unit is about 88.7 mol%. However, when a configuration of an embodiment LT CO2 removal envelope includes the internal recovery of CO2 from both the LT CO2 column vent gas and third top vapor streams by a CO2-enriching unit and an embodiment process recycles the recycle of CO2-rich tail gas from the CO2-enriching unit to upstream of the first pre- LT CO2 purification column separation vessel, such as provided for in the embodiment LT CO2 removal envelope 1000A of FIG. 3, the overall CO2 recovery increases to about 100 mol%. AttyDkt.No. P62622 2420WO (01250)

[0116] In one or more embodiments, which can be combined with other embodiments, a process and system can be configured to remove CO2 from an introduced flue gas stream. Such an embodiment system and process can be effective to purify the introduced flue gas stream and produce both a stream of substantially pure CO2 and a stream of inert gas. Embodiment processes and systems can be coupled to a process and system where a carbonaceous fuel, such as methane, is introduced into and combusted in a combustor with an oxidant to produce a stream of flue gas that includes CO2. Embodiment processes and systems can be coupled to other processes and systems that produce a MGS where CO2 may be removed, recovered, and separately produced therefrom.

[0117] With reference to FIG. 4, a block diagram of an embodiment mixed gas treatment system, such as mixed gas stream 400, is shown. Within the mixed gas treatment stream, a flue gas passing from a combustor can be introduced into an embodiment LT CO2 removal envelope. For system 400, a carbonaceous fuel and an oxidant are introduced through lines 401 and 402, respectively, into a combustor 405. Within the combustor, the fuel and oxygen are combined and combusted to form a flue gas that comprises in part carbon dioxide. The flue gas in system 400 passes from the combustor 405 through line 409.

[0118] The stream of flue gas passing from the combustor is introduced into a LT CO2 removal envelope. Within the LT CO2 removal envelope, the flue gas is processed through a plurality of units, such as one or more compressors, one or more dewatering units, one or more heat exchangers, one or more coolers, one or more turboexpanders, one or more expansion valves, one or more pumps, one or more pre-LT CO2 purification column separation vessels, and one or more LT purification columns. In one or more embodiments, which may be combined with other embodiments, the LT CO2 removal envelope is configured as provided for previously in FIG. 3 and as described previously as envelope 1000A. In one or more embodiments, which may be combined with other embodiments, the LT CO2 removal envelope is configured as provided for previously in FIG. 5 and as to be described as envelope 2000A. In one or more embodiments, which may be combined with other embodiments, the LT CO2 removal envelope is configured as provided for previously in FIG. 6 and as to be described as envelope 3000A. System 400 as provided for in FIG. 4 may utilize an LT CO2 removal envelope 2000 or 3000. As such, FIG. 4 can reference embodiments where the flue gas stream in line 409 is introduced into either LT CO2 removal envelope 2000A of FIG. 5 or LT CO2 removal envelope 3000A of FIG. 6.

[0119] The flue gas, such as flue gas stream 409 of system 400, which is a MGS, may be processed in embodiment systems and processes to produce one or more top gas streams from the pre- LT CO2 purification column separation vessels that can then be cooled to produce a plurality of two-phase, gas / liquid streams that are then phase separated in either series or parallel downstream single or multistage separation vessels, as previously described. The two-phase streams may be processed such that all AttyDkt.No. P62622 2420WO (01250) the bottoms liquid streams are processed through the LT CO2 purification column to produce a bottoms stream that is a CO2-rich liquid. The CO2-rich liquid stream may be in part further processed and then passed from the system as a liquid CO2 product stream, such as via line 1375, as previously described. The two-phase streams may be processed such that a top gas from a final pre-LT CO2 purification column separation vessel along with the overhead stream from the LT CO2 purification column are provided to a further process that performs CO2 enrichment, forming a stream of gas that is substantially free of CO2 that passes through line 1418 . In instances where the stream in 1418 is an otherwise an inert gas, such as one containing nitrogen, oxygen, or noble gases, the stream may be vented to the atmosphere.

[0120] In FIG. 4, Block 2 / Block 3 represents two configurations of a low temperature CO2 removal envelope. As such, FIG. 4 can reference embodiments where the flue gas in line 409 enters Block 2, which is low temperature CO2 removal envelope 2000, or FIG. 4 can reference embodiments where the flue gas in line 409 enters Block 3, which is low temperature CO2 removal envelope 3000.

[0121] In one or more embodiments, which can be combined with other embodiments, LT CO2 removal envelope 2000A as illustrated in FIG. 5, which may correspond with LT CO2 removal envelope 2000 of FIG. 4, includes three separation vessels, which in one or more embodiments may be combined with other embodiments may comprise single or multiple-stage separation vessels, and combinations thereof; however, one may appreciate that in one or more embodiments, which may be combined with other embodiments, the number of separation vessels upstream of the LT CO2 purification column may encompass a single, two, four, five, or more, as previously described.

[0122] The LT CO2 removal envelope 2000A shown in FIG. 5 utilizes a single LT CO2 purification column; however, in one or more embodiment, which may be comprised of other embodiments, a plurality of CO2 purification columns, such as two, three, or more LT CO2 purification columns may be used, as previously described. In instances where a plurality of LT CO2 purification columns are utilized, the relative configuration of each of the LT CO2 columns to one another may be in series, in parallel, or combinations thereof, as previously described.

[0123] The LT CO2 removal envelope 2000A shown in FIG. 5 utilizes a single, multi-pass heat exchanger for systemwide heat exchange; however, it is understood that a plurality of multi-pass heat exchangers may be used, or a plurality of single pass heat exchangers may be used, a single pass heat exchanger meaning a heat exchanger where a single stream is cooled during passage through the heat exchanger and a single stream is heated during passage through the heat exchanger, as previously described.

[0124] Additional stream-specific cooling in the LT CO2 removal envelope 2000A may be achieved by passing one or more streams through one or more turboexpanders or expansion valves, as previously described. AttyDkt.No. P62622 2420WO (01250)

[0125] Tuming specifically to FIG. 5, the configuration of the LT CO2 removal envelope shown - LT CO2 removal envelope 2000A - is substantially similar to the LT CO2 removal envelope 1000A as previously described in association with FIG. 3. Any system components or process steps described previously with reference to the embodiment LT CO2 removal envelope 1000A or associated therewith that are not expressly described following with reference to LT CO2 removal envelope 2000A in FIG. 5 are optionally or expressly incorporated.

[0126] In LT CO2 removal envelope 2000A, a flue gas is introduced through line 1010 into dryer 1020 to dewater the stream. The flue gas is optionally compressed in compressor 1011 before passing through line 1101 and traversing dryer 1020. The dried flue gas passes through the multi-pass heat exchanger 1100 and through each of the plurality of pre-LT CO2 purification column separation vessels (1210, 1230, 1250) in series, where each separation vessel produces a liquid bottoms CO2-rich liquid stream and a gaseous overheads stream. The gaseous overheads stream from each separation vessel is passed to the next separation vessel in series, except where the third separation vessel 1250 produces a third top vapor stream 1261.

[0127] From the first, second, and third separation vessels (1210, 1230, 1250), a first CO2-rich liquid stream, a second CO2-rich liquid stream, and a third CO2-rich liquid stream, respectively, passes through lines 1212, 1232, and 1252, respectively, and are each directed and introduced separately into the LT CO2 purification column 1310.

[0128] In one or more of the embodiments, which may be combined with other embodiments, the third CO2-rich liquid stream is introduced into the LT CO2 purification column proximate to the top of the column. The third CO2-rich liquid acts to strips CO2 from the upflowing vapor from the first and second CO2-rich liquids introduced into the bottom of the LT CO2 purification.

[0129] A bottom liquid stream comprising substantially pure liquid CO2 forms within and passes from the LT CO2 purification column 1310 via line 1312. In envelope 2000A, a portion of the substantially pure liquid CO2 is used for auto-refrigeration. The portion used for auto-refrigeration is expanded, directed through the multi-pass heat exchanger, recompressed, and then combined with the remainder of the substantially pure liquid CO2 before passing from the LT CO2 removal envelope 2000A as liquid CO2 export in line 1375.

[0130] The LT CO2 column vent gas stream from the overhead of the LT CO2 purification column 1310 combines with the third top vapor stream from the third separation vessel 1250 after each is expanded and each pass through the multi-pass heat exchanger 1100, forming a combined vapor stream 1183, which again is a low-CO2 vapor stream.

[0131] The combined vapor stream, such as the contents of line 1414, which has been previously warmed and expanded, is introduced into the CO2-enriching unit 1410. As previously described, the AttyDkt.No. P62622 2420WO (01250)

[0132] C02-enriching unit may comprise one or more of a CO2 PSA, a VPSA, a CO2 TSA, a reversing heat exchanger system, or a solvent-based CO2 removal unit, and combinations thereof.

[0133] The CO2-enriching unit produces a tail gas rich in CO2, containing substantially all of the CO2 not produced from the bottom of the LT CO2 purification column 1310, representing the remaining CO2 introduced into the LT CO2 removal envelope through the flue gas stream 1010. The CO2-enriching unit also produces a top gas that is substantially free of CO2, which in some instances as previously described may be vented to the atmosphere or further processed to capture nitrogen or noble gases for further processing.

[0134] As shown in FIG. 5, the CO2-rich tail gas in line 1414 may be compressed in an optional compressor 1415 and recycled back to a position within the LT CO2 removal envelope 2000A upstream of the multi-pass heat exchanger 1100, where it is shown combining with the introduced flue gas in line 1009 before optional compression in compressor 1011.

[0135] Table 2: Prophetic calculations for several streams associated with the embodiment LT CO2 rem ova envelope shown in FIG. 5.

[0136] As shown in FIG. 5 using envelope 2000A and the prophetic calculations provided for in Table 2, which are similar to the determinations made for envelope 1000A and in Table 1, all the CO2 introduced into the system via the flue gas not produced initially as a liquid CO2 product via the bottom of the LT AttyDkt.No. P62622 2420WO (01250)

[0137] CO2 purification column is recovered and recycled until it is ultimately produced through the LT CO2 purification column liquid bottoms. The single-pass CO2 recovery efficiency for envelope 2000A without the recycle from the CO2-enriching unit at the conditions presented in Table 2 is about 59.6 mol% of the CO2 introduced with the flue gas; however, with the internal recycle, nearly 100 mol% of the CO2 may be recovered and controllably produced as a liquid product, avoiding further processing or discharge to the atmosphere.

[0138] In one or more embodiments, which can be combined with other embodiments, LT CO2 removal envelope 3000A as illustrated in FIG. 6, which may correspond with LT CO2 removal envelope 3000 of FIG. 4, includes three separation vessels, which in one or more embodiments may be combined with other embodiments may comprise single or multiple-stage separation vessels, and combinations thereof; however, one may appreciate that in one or more embodiments, which may be combined with other embodiments, the number of pre-LT CO2 purification column separation vessels may encompass a single, two, four, five, or more, as previously described.

[0139] The LT CO2 removal envelope 3000A shown in FIG. 5 utilizes a single LT CO2 purification column; however, in one or more embodiments, which may be comprised of other embodiments, a plurality of CO2 purification columns, such as two, three, or more LT CO2 purification columns may be used, as previously described. In instances where a plurality of LT CO2 purification columns are utilized, the relative configuration of each of the LT CO2 columns to one another may be in series, in parallel, or combinations thereof, as previously described.

[0140] The LT CO2 removal envelope 3000A shown in FIG. 6 utilizes a single, multi-pass heat exchanger for systemwide heat exchange; however, it is understood that a plurality of multi-pass heat exchangers may be used, or a plurality of single pass heat exchangers may be used, a single pass heat exchanger meaning a heat exchanger where a single stream is cooled during passage through the heat exchanger and a single stream is heated during passage through the heat exchanger, as previously described.

[0141] Additional stream-specific cooling in the LT CO2 removal envelope 3000A may be achieved by passing one or more streams through one or more turboexpanders or expansion valves, as previously described.

[0142] Turning specifically to FIG. 6, the configuration of the LT CO2 removal envelope shown - LT CO2 removal envelope 3000A - is substantially similar to the LT CO2 removal envelope 1000A as previously described in association with FIG. 3 and LT CO2 removal envelope 2000A as previously described in association with FIG. 5. Any system components or process steps described previously with reference to the embodiment LT CO2 removal envelopes 1000A, 2000A or associated therewith that are AttyDkt.No. P62622 2420WO (01250) not expressly described following with reference to LT CO2 removal envelope 3000 A in FIG. 6 are optionally or expressly incorporated.

[0143] In LT CO2 removal envelope 3000A, a flue gas is introduced through line 1010 into dryer 1020 to dewater the stream. The flue gas is optionally compressed in compressor 1011 before traversing dryer 1020. The dried flue gas passes through the multi-pass heat exchanger 1100 and through each of the plurality of separation vessels (1210, 1230, 1250) in series upstream of the LT CO2 purification column, where each separation vessel produces a liquid bottoms CO2-rich liquid stream and a gaseous overheads stream. The gaseous overheads stream from each separation vessel is passed to the next separation vessel in series, except where the third separation vessel 1250 produces a third top vapor stream 1261.

[0144] In one or more of the embodiments, which may be combined with other embodiments, the third CO2-rich liquid stream is introduced into the LT CO2 purification column proximate to the top of the column. The third CO2-rich liquid acts to strips CO2 from the upflowing vapor from the first and second CO2-rich liquids introduced into the bottom of the LT CO2 purification.

[0145] A bottom liquid stream comprising substantially pure liquid CO2 forms within and passes from the LT CO2 purification column 1310 via line 1312. In envelope 3000A, a portion of the substantially pure liquid CO2 is used for auto-refrigeration. The portion used for auto-refrigeration is expanded, directed through the multi-pass heat exchanger, recompressed, and then combined with the remainder of the substantially pure liquid CO2 before passing from the LT CO2 removal envelope 3000A as liquid CO2 export in line 1375.

[0146] The LT CO2 column vent gas stream from the overhead of the LT CO2 purification column 1310 combines with the third top vapor stream from the third separation vessel 1250 after each is expanded and each pass through the multi-pass heat exchanger 1100, forming a combined vapor stream 1183, which again is a low-002 vapor stream. The combined vapor streams in line 1183 pass from the LT CO2 removal envelope 3000A through line 1183 for venting to the atmosphere.

[0147] As noted, the LT CO2 removal envelope 3000A does not include a CO2-enriching unit, such as CO2-enriching units 1410 as shown in FIGs 3, 5 for envelopes 1000A, 2000A, respectively. Such a unit may be expressly excluded when the LT CO2 removal envelope operates under conditions where near 100 mol% CO2 capture is not required, such as when a relatively small concentration of CO2 is acceptable to vent to the atmosphere or the CO2 may be passed as part of the stream to a different process.

[0148] Although shown in FIG. 6 as two lines that combine into a single vent line (lines 1163, 1183), one appreciates that each stream (LT CO2 column vent gas stream, third top vapor stream) may be directed and utilized separately. For example, the LT CO2 column vent gas stream provided through line 1183 may be used as a blanket or inert gas in the upstream processing while the third top vapor stream in AttyDkt.No. P62622 2420WO (01250) line 1163 may be vented to the atmosphere after heat exchange to avoid inert buildup within the LT CO2 removal envelope 3000A.

[0149] In one or more embodiments, which can be combined with other embodiments, a mixed gas treatment system, such as mixed gas treatment system 700 in FIG. 7, receives an introduced “shifted” syngas via line 701. A “shifted” syngas is one that has relatively greater amounts of carbon dioxide and hydrogen and relatively reduced amounts of carbon monoxide and water, although each component is present. The shifted syngas is introduced into a first H2 PSA, such as H2 PSA 705, that is configured to separate the shifted syngas into a stream of substantially pure H2 passing via line 707 and a tail gas stream passing via line 709. The substantially pure H2 in line 707 passes from the mixed gas treatment system 700 as a product. The tail gas stream is a MGS that includes CO2 and one or more further gases, such as H2, CO, CH4, or water.

[0150] The tail gas stream is introduced into a first LT CO2 removal envelope 1000, such as LT CO2 removal envelope 1000A, as described previously and illustrated as Block 1, to produce a liquid CO2 export stream and a CO2-free syngas. The liquid CO2 export stream 1375 is directed from the mixed gas treatment system 700 as a product.

[0151] The CO2-free syngas passes using line 1417 to a second H2 PSA, such as H2 PSA 715, that is configured to separate the CO2-free syngas into a stream of substantially pure H2 and a H2-lean syngas. In FIG. 7, the substantially pure H2 passes from the H2 PSA 715 via line 717 and combines with the substantially pure H2 passing via line 707.

[0152] The H2-lean syngas material is a low-grade fuel that has value once combusted to recover additional carbon dioxide. The H2-lean syngas in line 719 may be introduced to a combustor 1510. In one or more embodiments, which may be combined with other embodiments, an oxidant may be introduced along with the H2-lean syngas into the combustor. In one or more embodiments, which may be combined with other embodiments, an oxidant and supplemental fuel may be introduced along with the H2-lean syngas into the combustor. In mixed gas treatment system 700, oxidant and optionally additional fuel in line 1501 are combined with the H2-lean syngas in line 719 and introduced into a combustor, which is configured to combust the syngas and optional addition fuel in the presence of the oxidant to form a flue gas product.

[0153] The flue gas product passes a stream 1010 from the combustor 1510. The stream of flue gas product is introduced and processed in a second LT CO2 removal envelope 2000, 3000, such as LT CO2 removal envelope 2000A or LT CO2 removal envelope 3000A, illustrated as Block 2 / Block 3, each described previously, to produce a second liquid CO2 export stream and a CO2-free inert gas. The second liquid CO2 export stream is shown in combined with line 1375 and directed from system 700 as a AttyDkt.No. P62622 2420WO (01250) product. The CO2-free inert gas is directed from system 700 through line 1418, such as to the atmosphere as a system vent.

[0154] The embodiment LT CO2 removal envelope processes and systems provide the ability to introduce and process a variety of different mixed gases such that nearly almost all the CO2 is removed therefrom. This may result in the production of not only a MGS product that is substantially free of CO2 but also a substantially pure liquid CO2 stream product.

[0155] The terms “about” or “substantially” as used herein can indicate that certain recited values or conditions are intended to be read as encompassing the expressly recited value or condition and values that are relatively close thereto or conditions that are recognized as being relatively close thereto. For example, unless otherwise indicated herein, a value of “about” a certain number or “substantially” a certain value can indicate the specific number or value as well as numbers or values that vary therefrom (±) by 10% or less, such as 5% or less, such as 4% or less, such as 3% or less, such as 2% or less, or such as 1% or less, and any one of such values may be used interchangeably with the words “about” or “substantially” as needed for clarity. Similarly, unless otherwise indicated, a condition that substantially exists can indicate the condition is met exactly as described or claimed or is within typical manufacturing tolerances or would appear to meet the required condition upon casual observation even if not perfectly meeting the required condition. In some embodiments, the values or conditions can be defined as being express and, as such, the term “about” or “substantially” (and thus the noted variances) can be excluded from the express value.

[0156] Many modifications and other embodiments of the presently disclosed subject matter will come to mind to one skilled in the art to which this subject matter pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the present disclosure is not to be limited to the specific embodiments described herein and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

AttyDkt.No. P62622 2420WO (01250)CLAIMS:

1. A process for separating carbon dioxide (CO2) from a mixed gas stream, the process comprising: introducing a mixed gas stream to a first separator, the mixed gas stream comprising CO2 and at least one further component; processing at least a portion of a first top vapor stream from the first separator in a second separator; processing a second top vapor stream from the second separator in one or more components to form a gas stream that is substantially free of CO2; processing a first bottom liquid stream from the first separator and a second bottom liquid stream from the second separator in at least a CO2 purification column and thereby forming a liquid CO2 product stream.

2. The process of claim 1, wherein prior to introducing the mixed gas stream to the first separator, the mixed gas stream is processed in one or more of a compressor, a drier, and a heat exchanger.

3. The process of claim 1, further comprising combining a top vapor stream from the CO2 purification column with the second top vapor stream from the second separator.

4. The process of claim 3, further comprising introducing one or both of the top vapor stream from the CO2 purification column and the second top vapor stream from the second separator into a heat exchanger for use in cooling one or more further streams entering the heat exchanger.

5. The process of claim 1, wherein processing the second top vapor stream from the second separator in one or more components comprises combusting the second top vapor stream in a combustor.

6. The process of claim 5, wherein at least a portion of the flue gas from the combustor is processed through a plurality of separators configured to provide a top gas stream that is substantially free of CO2 and provide a bottom liquid CO2 stream.

7. The process of claim 1, wherein processing the second top vapor stream from the second separator in one or more components comprises processing the second top vapor in a third separator.AttyDkt.No. P62622 2420WO (01250)8. The process of claim 7, further comprising processing a third bottom liquid stream from the third separator in the CO2 purification column.

9. The process of claim 7, further comprising processing a third top vapor stream from the third separator in a CO2-enriching system.

10. The process of claim 7, further comprising passing a CO2-rich gas from the CO2- enriching system to the mixed gas stream.

11. The process of claim 7, further comprising passing a stream of substantially pure CO2 gas from the CO2-enriching system.

12. The process of claim 1, wherein forming the liquid CO2 product stream includes cooling at least a portion of a bottom stream from the CO2 purification column in a heat exchanger.

13. The process of claim 12, comprising splitting the at least a portion of the bottom stream from the CO2 purification column into a plurality of separate streams that are individually cooled in the heat exchanger.

14. The process of claim 12, further comprising, after said cooling, compressing the at least a portion of the bottom stream from the CO2 purification column in one or more compressors or in one or more compression stages.

15. A process for separating carbon dioxide (CO2) from a syngas stream, the process comprising: processing a shifted syngas stream in a first hydrogen pressure swing adsorber (H2 PSA 1); processing a tail gas from H2 PSA 1 in a first low temperature CO2 removal envelope to provide a CO2 export stream and a syngas stream reduced in CO2 content; processing the syngas stream reduced in CO2 content in a second hydrogen pressure swing adsorber (H2 PSA 2); combusting a hydrogen-lean syngas from H2 PSA 2 in a combustor to form a flue gas; processing the flue gas in a second low temperature CO2 removal envelope to provide a further CO2 export stream and a gas stream reduced in CO2 content.AttyDkt.No. P62622 2420WO (01250)16. The process of claim 15, wherein one or both of the syngas stream reduced in CO2 content and the gas stream reduced in CO2 content is substantially free of CO2.

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