Carbon dioxide separation apparatus and method using carbon dioxide as a refrigerant in a refrigeration circuit

Abstract

A system comprising a heat exchanger in which flue gas containing carbon dioxide is brought into heat exchange flow with a stream of chilled carbon dioxide. The flue gas is cooled and carbon dioxide condensed by the heat exchange is removed from the flue gas. Part of the condensed carbon dioxide is processed in a refrigeration circuit and used as refrigerant in the heat exchanger and part is removed as CO2 product.

Description

[0001] manual Technical Field

[0002] This invention relates to systems, apparatus and methods for separating carbon dioxide (CO2) from flue gas. Background Technology

[0003] CO2 is generated by burning fuels, such as fossil fuels (like natural gas), in several power generation processes. CO2 is a greenhouse gas that negatively impacts the climate and is considered a cause of climate change, particularly global warming. Despite ongoing efforts to reduce electricity generated from burning fossil fuels, these fuels remain one of the primary energy sources.

[0004] Fossil fuels are also used to power fuel cells, where chemical energy is converted into electrical energy through chemical reactions that do not involve combustion. Typical fuel cells, such as solid oxide fuel cells (SOFCs), use hydrogen as fuel. Hydrogen can be produced from fossil fuels, such as methane (CH4), through reforming according to the following reaction:

[0005]

[0006] Hydrogen reacts with oxygen (O2) contained in ambient air in a fuel cell, generating electricity from the reaction.

[0007]

[0008] Flue gas from SOFCs or other fuel cells contains high concentrations of carbon dioxide (CO2) and may also contain residual H2 and CO.

[0009] Reducing the amount of CO2 released into the atmosphere is becoming an important aspect of recent policies aimed at mitigating the climate impacts of human activities. The same applies to flue gas from fuel cells.

[0010] Removing CO2 from flue gas via cryogenic separation has been known for a considerable period of time. See, for example, EP2407741 and EP2365265. According to this known technique, compressed flue gas containing CO2 flows sequentially through one or more heat exchangers (also known as cold boxes), where heat is removed from the flue gas. The temperature decrease causes the CO2 to separate by liquefaction. Liquid CO2 is used as a refrigerant in the heat exchangers. To lower the temperature of the liquefied CO2, it expands in an expander or through an expansion valve. The expanded and partially vaporized CO2 flows through the cold side of the heat exchanger, while the compressed flue gas flows through the hot side. The fully vaporized and heated carbon dioxide exiting the heat exchanger is compressed again by an intercooled CO2 compressor unit and is eventually collected in a storage tank or further transported in pipelines.

[0011] Other CO2 separation systems and methods are disclosed in US2011 / 0271713 and FR2934170.

[0012] Therefore, separating carbon dioxide from CO2-containing flue gas is a power-intensive process, which reduces the overall efficiency of the power generation process.

[0013] Therefore, methods and systems that can reduce the electricity required for carbon dioxide separation will be welcomed in this field. Summary of the Invention

[0014] According to one aspect, this document discloses a system for generating CO2 from flue gas using a refrigerant circuit, wherein carbon dioxide is treated as a refrigerant. The system includes a heat exchanger adapted to receive a compressed inlet flue gas stream and condense at least a portion of its carbon dioxide content; the system also includes at least a first separation drum adapted to receive a quenched flue gas stream containing at least a portion of liquefied CO2 from the heat exchanger and to separate the liquefied CO2 from the quenched flue gas stream. The system also includes a collector line adapted to collect the liquefied carbon dioxide from the liquid outlet of the first separation drum. A liquefied CO2 collection conduit extends from the collector line through the heat exchanger and is adapted to deliver the carbon dioxide to the refrigeration circuit. The liquefied CO2 collection conduit includes a heat exchange section extending through the heat exchanger. Carbon dioxide flowing through the heat exchange section of the liquefied CO2 collection conduit vaporizes by absorbing heat from the flue gas and the hot carbon dioxide flowing through the heat exchanger. The refrigeration circuit includes: a CO2 compressor; a CO2 compressed conduit having an outlet, an inlet connected to the delivery side of the CO2 compressor, and a heat exchange section located between the inlet and the outlet and extending through the heat exchanger. The refrigeration circuit also includes a CO2 return conduit that fluidly connects the outlet of the compressed CO2 conduit to the collector line or the liquefied CO2 collection line, the CO2 return conduit being located upstream of the heat exchange section (71.1) of the liquefied CO2 collection line (71).

[0015] The CO2 outlet pipe is connected to the outlet of the compressed CO2 pipe to remove a portion of the carbon dioxide extracted from the flue gas through condensation.

[0016] According to another aspect, this paper discloses a method for generating liquid CO2 from flue gas, the method comprising the following steps:

[0017] a) A compressed flue gas containing CO2 is conveyed through a heat exchanger that uses a quenched CO2 stream circulating in a refrigeration loop for heat exchange.

[0018] b) The CO2 contained in the compressed flue gas is at least partially condensed by heat exchange using the quenched CO2 circulating in the refrigeration circuit;

[0019] c) Separating liquefied CO2 from the compressed flue gas stream in at least the first separation drum;

[0020] d) Remove liquefied CO2 from the first separation drum;

[0021] e) The liquefied CO2 from the first separation drum is collected in a liquefied CO2 collection pipe, which includes a heat exchange section extending through the heat exchanger;

[0022] f) Evaporate the CO2 flowing through the heat exchange section of the liquefied CO2 collection pipe;

[0023] g) In the CO2 compressor of the refrigeration circuit, the CO2 evaporated in the heat exchange section of the liquefied CO2 collection pipe is compressed and discharged from the heat exchanger.

[0024] h) The compressed CO2 stream from the CO2 compressor is conveyed through a compressed CO2 conduit, which includes a heat exchange section extending through the heat exchanger and cooling the compressed CO2 stream.

[0025] i) At the outlet of the compressed CO2 pipeline, the compressed and quenched CO2 is divided into a first part of the CO2 stream and a second part of the CO2 stream;

[0026] j) The first portion of the CO2 flow is returned to the liquefied CO2 collection pipe upstream of its heat exchange section (71.1);

[0027] k) Remove the second portion of the CO2 stream as a CO2 product from the refrigeration circuit;

[0028] l) Remove lean CO2 flue gas from the heat exchanger.

[0029] Therefore, in the system and method according to this disclosure, liquefied CO2 collected at the collector line and liquefied CO2 from the liquefied CO2 collection pipe are combined in a single liquid CO2 stream, which is fed and vaporized through a heat exchange section of the liquefied CO2 collection pipe. The vaporized CO2 stream at the outlet of the heat exchange section of the collection pipe is then delivered to the compressor in the refrigeration circuit. Thus, compared to other systems and methods in the prior art, which require a single pressure level and a single compressor unit to manage CO2, this significantly simplifies the layout.

[0030] Further features and embodiments of the methods and systems disclosed herein are described below with reference to the accompanying drawings, and are set forth in the appended claims. Attached Figure Description

[0031] Now, please briefly refer to the attached diagram, in which:

[0032] Figure 1 This is a diagram of a system according to this disclosure in one implementation scheme;

[0033] Figure 2 yes Figure 1 The diagram shows enlarged details of the heat exchanger; and

[0034] Figure 3 yes Figure 1 The diagram shows enlarged details in another embodiment. Detailed Implementation

[0035] Figure 1 A schematic diagram of system 1 according to this disclosure is shown in one embodiment. System 1 includes a flue gas pretreatment section 3 and a carbon dioxide separation section 5 (hereinafter referred to as the CO2 separation section). The product CO2 separated from the flue gas in the CO2 separation section can be in a gaseous, liquid, or supercritical state. In the following detailed embodiments, the carbon dioxide separation section 5 will also be referred to as the carbon dioxide liquefaction section 5. However, it should be understood that this does not limit the scope of this disclosure to systems in which the product CO2 is in liquid form.

[0036] System 1 can be used, for example, to remove carbon dioxide from flue gas produced by a fuel cell system, such as a solid oxide fuel cell (SOFC) system using natural gas as fuel. While it is particularly advantageous to treat flue gas from fuel cells with the system according to this disclosure, the use of the systems and methods disclosed herein to treat flue gas from different sources is not excluded given the relatively high CO2 concentration in the flue gas.

[0037] The flue gas pretreatment section 3 includes a flue gas inlet 7, which is fluidly connected to a flue gas source (e.g., a fuel cell layout) or another source of flue gas (e.g., a gas turbine engine).

[0038] The flue gas pretreatment section 3 may include a first liquid-steam or gas-liquid separator 9, which has an inlet 9.1 fluidly connected to the flue gas inlet 7, a liquid outlet 9.2 and a gas outlet 9.3.

[0039] The gas outlet 9.3 of the first gas-liquid separator 9 is fluidly connected to the suction side of the flue gas compressor unit 11 (hereinafter referred to as compressor unit 11).

[0040] For simplicity, compressor unit 11 is referred to as a single compressor. In some embodiments, compressor unit 11 may include an intercooled multi-stage compressor or compressor assembly. The delivery side of compressor unit 11 is connected to aftercooler 15 and a second liquid-vapor or gas-liquid separator 17, which includes an inlet 17.1, a liquid outlet 17.2, and a gas outlet 17.3. Condensate from the liquid outlet 9.2 of the first gas-liquid separator 9 and condensate from the liquid outlet 17.2 of the second gas-liquid separator 17 are collected in condensate removal line 21.

[0041] In some embodiments, the flue gas pretreatment section 3 may include a water-gas shift reactor system 23 (WGS reactor for short), which is adapted to convert carbon monoxide that may be contained in flue gas and steam into carbon dioxide and hydrogen.

[0042] In some embodiments, the water-gas shift reactor system 23 includes a preheater 23.1, a heater 23.2, a reactor 23.3, a cooler 23.4, a water filter 23.5, and a water pump 23.6. The water filter 23.5 and the water pump 23.6 are positioned along a condensate recirculation line 25, which feeds water condensed at the bottom of a third liquid-steam or gas-liquid separator, described below.

[0043] As described above, compressor unit 11 typically includes multiple compressors or compressor stages, each having at least one interstage cooler or intercooler. In such cases, the preferred location of the WGS reactor is after the first stage of compressor unit 11, immediately before the interstage cooler. At this location, the preheater 23.1, and possibly even the heater 23.2, can be avoided when utilizing the heat of compression. Depending on the moisture content of the incoming gas, this location may even allow the avoidance of the pump 23.6.

[0044] The flue gas processed in the water-gas shift reactor system 23 (if present) may be fed through one or more additional components of the flue gas pretreatment section 3.

[0045] exist Figure 1 In one embodiment, the flue gas pretreatment section 3 includes, for example, a mercury absorber 27, followed by a cooler 29. Flue gas can flow through the mercury absorber 27 to remove mercury, and then flow through the hot side of the cooler 29, exchanging heat with a cooling medium flowing through the cold side of the cooler 29. The outlet of the hot side of the cooler 29 is fluidly connected to the inlet 31.1 of a third liquid-vapor or gas-liquid separator 31, which includes a liquid outlet 31.2 and a gas outlet 31.3.

[0046] The third gas-liquid separator 31 is adapted to separate the water condensed after the flue gas in the cooler 29 has been cooled. The condensate collected at the bottom of the third gas-liquid separator 31 can be transported to the water-gas shift reactor system 23 via the condensate recirculation line 25. If the water-gas shift reactor system 23 is not present, the liquid outlet 31.2 of the third gas-liquid separator 31 can be fluidly connected, for example, to the condensate removal line 21.

[0047] The gas outlet 31.3 of the third gas-liquid separator 31 is fluidly connected to a flue gas dryer arrangement 33 adapted to remove moisture from cooled flue gas. This arrangement is schematically shown as a single adsorption-type flue gas dryer section 33.1 containing a desiccant bed 33.2. However, to allow for continuous operation, the flue gas dryer 33 typically comprises two flue gas dryer units, such that while one unit is operating, the other undergoes a regeneration cycle to regenerate the desiccant, for example, via a carbon dioxide stream or another lean water stream (not shown). A filter section 33.3 is arranged downstream of either the flue gas dryer section or each section to prevent adsorbent fines from being conveyed into the downstream section.

[0048] The dehydrated flue gas is transported from the flue gas pretreatment section 3 to the carbon dioxide liquefaction section 5 through the pretreatment flue gas inlet pipeline 35.

[0049] In other embodiments, the water-gas shift reactor system 23 can be omitted. In such cases, the flue gas may be directly delivered from the flue gas inlet 7 to the flue gas cooler 29 and flue gas dryer arrangement 33 after being processed by the compressor unit 11 and the gas-liquid separator 17.

[0050] Carbon dioxide liquefaction section 5 Figure 2 It is shown in more detail below.

[0051] In some embodiments, the carbon dioxide liquefaction section 5 includes a heat exchanger (also called a cold box) 37, a carbon dioxide removal unit 39, and a refrigeration circuit 41. The refrigeration circuit 41 is a refrigeration circuit that uses carbon dioxide separated from the flue gas as a refrigerant fluid and removes a portion of the treated carbon dioxide as a CO2 product therefrom. The CO2 removed from the refrigeration circuit is stored, for example, in a storage container to be described, or transported in a pipeline. Unlike prior art cryogenic carbon dioxide separator systems, the system disclosed herein includes a refrigeration circuit in which the carbon dioxide separated from the flue gas undergoes cyclic thermodynamic transformations, including compression, cooling, expansion, and heating by the heat removed from the flue gas. Thus, the carbon dioxide separated from the flue gas by quenching the expanding carbon dioxide is partly used as a refrigerant in a closed refrigeration circuit and partly removed from the system as a product CO2.

[0052] More specifically, the carbon dioxide removal unit 39 includes a first separation drum 43, another or intermediate separation drum 45, and yet another or final separation drum 47. The intermediate separation drum 45 will also be referred to herein as the second separation drum, and the final separation drum 47 will also be referred to herein as the third separation drum. Similarly, components or devices belonging to or combined with the other or intermediate separation drum 45 and yet another or final separation drum 47 will be referred to as the "second" and "third" components or devices.

[0053] Although Figure 2 In the illustrated embodiment, system 1 includes three separation drums 43, 45, and 47. However, in other embodiments not shown, the number of separation drums may be less than or more than three. For example, in one embodiment, the liquefied carbon dioxide removal unit 39 may include only the first separation drum 43, or only the first separation drum 43 and the second separation drum 45, or only the first separation drum 43 and the third separation drum 47, or additional separation drums arranged sequentially with the first separation drum 43, the second separation drum 45, and the third separation drum 47.

[0054] Generally speaking, the carbon dioxide removal unit 39 includes at least a first separation drum and another separation drum.

[0055] Typically, each separation drum, except for the last separation drum, has a gas outlet that is fluidly connected to the inlet of the next separation drum via a connecting line extending through a heat exchanger or cold box 37.

[0056] Specifically, in Figure 1 In one embodiment, the first separating drum 43 has an inlet 43.1, a liquid outlet 43.2, and a gas outlet 43.3. The second or intermediate separating drum 45 has an inlet 45.1, a liquid outlet 45.2, and a gas outlet 45.3. The third or additional separating drum 47 has an inlet 47.1, a liquid outlet 47.2, and a gas outlet 43.3. The first liquid outlet 43.2, the second liquid outlet 45.2, and the third liquid outlet 47.2 are connected to the collector line 51 via corresponding first control and pressure reducing valves 43.4, second control and pressure reducing valves 45.4, and third control and pressure reducing valves 47.4.

[0057] The inlet 43.1 of the first separation drum 43 is connected to the pretreated flue gas inlet line 35 via a first heat exchange connection 53 extending through the heat exchanger or cold box 37. The flue gas is chilled along this first heat exchange connection by exchanging heat with evaporated carbon dioxide flowing in the cold side of the cold box or heat exchanger 37. The gas outlet 43.3 of the first separation drum 43 is connected to the inlet of the second or intermediate separation drum 45 via a connecting pipe 55, which includes a second heat exchange connection 55.1 extending through the heat exchanger 37. The gas outlet 45.3 of the second or intermediate separation drum 45 is connected to the inlet 47.1 of the third or additional separation drum 47 via a connecting pipe 57, which includes a third heat exchange connection 57.1 extending through the heat exchanger 37.

[0058] The connecting part 57 and the intermediate or second separating drum 45 form a fluid connection between the gas outlet 43.3 of the first separating drum 43 and the inlet 47.1 of the other or third separating drum 47.

[0059] The gas outlet 47.3 of a third or additional separating drum 47 is fluidly connected to a gas discharge conduit 59. The gas discharge conduit 59 has a first heat exchange section 59.1 and a second heat exchange section 59.2 arranged sequentially and extending through a heat exchanger 37. An expansion device, such as an expansion valve or expander, is positioned along the gas discharge conduit 59 between the first heat exchange section 59.1 and the second heat exchange section 59.2. Figure 1 In the schematic diagram, the expansion device includes an expander 59.3. In some embodiments, the expander 59.3 may be drivably coupled to a generator 60 to convert the mechanical power generated by the expander 59.3 into electrical power. In other embodiments, the expander 59.3 may be connected to the CO2 compressor described, or to the flue gas compressor unit 11, or both, to minimize the power requirements of the respective machines. In a simpler embodiment, the expander 59.3 is replaced by a laminating valve or an expansion valve.

[0060] The gas discharge duct 59 can be selectively fluidly connected to an incinerator or a recirculation line adapted to recirculate the gas flowing through it to a flue gas source, such as toward a fuel cell system (not shown).

[0061] The refrigeration circuit 41 includes a CO2 compressor 61. In some embodiments, the CO2 compressor 61 may include one or more stages, or may include a group comprising two or more compressors in sequence. Figure 1 and Figure 2 In the schematic diagram, the CO2 compressor 61 includes two compressors 61.1 and 61.2 connected in series. In some embodiments, the CO2 compressor 61 may be an intercooled compressor. Figure 1 and Figure 2In the schematic diagram, the CO2 compressor 61 includes an intercooler 61.3. To further reduce the temperature of the carbon dioxide processed by the CO2 compressor 61, the CO2 compressor 61 may include an aftercooler 63 or may be used in conjunction with an aftercooler 63. Reference numeral 65 indicates a drive, such as an electric motor, that drives the CO2 compressor or compressor assembly 61 to rotate. Upstream of the suction side of the CO2 compressor 61, a suction drum 67 may be arranged to remove any liquid fractions that may be contained in the CO2 entering the CO2 compressor 61.

[0062] exist Figure 1 and Figure 2 In the illustrated embodiment, refrigeration circuit 41 is an open circuit that processes liquefied carbon dioxide from separators 43, 45, and 47, and only partially recirculates CO2 from the refrigeration circuit. CO2 fractions are removed from the refrigeration circuit as CO2 products, which are collected in a storage container, for example, as will be described in more detail below. The carbon dioxide removed from the system can be liquid, gaseous, or supercritical CO2.

[0063] Specifically, the liquefied CO2 collection conduit 71 extends from the collector line 51 to the suction drum 67 upstream of the CO2 compressor 61. The liquefied CO2 collection conduit 71 includes a heat exchange section 71.1 extending through a heat exchanger or cold box 37.

[0064] The liquefied CO2 collection line 71 collects condensed carbon dioxide from the liquid outlets 43.2, 45.2, and 47.2 of the three separation drums 43, 45, and 47 via control and pressure reducing valves 43.4, 45.4, and 47.4, as will be described in more detail later.

[0065] The delivery side of the CO2 compressor 61 is fluidly connected to the inlet of the CO2 compression line 73. The CO2 compression line 73 extends from the inlet to the outlet 85 and includes heat exchange sections 73.1, between which a cold box or heat exchanger 37 extends. The outlet 85 of the CO2 compression line is fluidly connected to a CO2 return line 75, which connects the outlet 85 of the CO2 compression line 73 to the collector line 51. An expansion valve 77 is positioned along the CO2 return line 75 such that the compressed and quenched CO2 delivered from the CO2 compression line 73 to the CO2 return line 75 expands at least partially and its temperature decreases.

[0066] The compressed CO2 conduit 73 is further fluidly connected to a CO2 outlet conduit 79, which includes a heat exchange section 79.1 extending through a heat exchanger or cold box 37, and is configured to deliver carbon dioxide to a carbon dioxide storage tank 81. A pressure regulating unit 83 is positioned along the CO2 outlet conduit 79 between its heat exchange section 71.1 extending through the heat exchanger 37 and the outlet 85 of the compressed CO2 conduit 73. Figure 1 and Figure 2 In the implementation scheme, the pressure regulating unit 83 includes a pressure reducing valve.

[0067] System 1 operates as follows.

[0068] CO2-rich flue gas is fed into system 1 through flue gas inlet 7. This CO2-rich flue gas may be generated by a fuel cell configuration (such as an SOFC configuration) and may contain carbon dioxide (CO2) combined with other substances such as steam (H2O), carbon monoxide (CO), hydrogen (H2), and possible contaminants. The flue gas is compressed in flue gas compressor unit 11 and cooled in aftercooler 15 to remove water. Condensate is removed from the compressed flue gas in first gas-liquid separator 17 and collected in condensate removal line 21.

[0069] If necessary, the compressed flue gas from the first gas-liquid separator 17 is then processed in the water-gas shift reactor system 23, for example, to convert carbon monoxide and water into carbon dioxide and hydrogen.

[0070] Following the water-gas shift conversion (if provided), the flue gas flows through an optional mercury absorber 27 and then through a cooler 29. The flue gas is pre-cooled in the cooler 29. The condensate (water) separated from the flue gas by cooling in the cooler 29 is removed from the flue gas in a second gas-liquid separator 31. After condensate removal, the flue gas is treated by a dryer 33.1 to remove residual moisture and is finally fed from the flue gas pretreatment section 3 to the carbon dioxide liquefaction section 5.

[0071] In the carbon dioxide liquefaction section 5, the flue gas first flows through the first heat exchange connection 53, where it is quenched by exchanging heat with CO2 from the refrigeration circuit 41 and the collector line 51, causing the carbon dioxide fractions contained in the flue gas to be liquefied and separated from the flue gas flow in the first separation drum 43.

[0072] The gaseous stage of the flue gas separates from the first separation drum 43 and flows through the connecting pipe 55 and the second heat exchange connection 55.1, which extends through a heat exchanger or cold box 37, in which the flue gas is further quenched by exchanging heat with CO2 from the refrigeration circuit 41 and the collector line 51. The second stage of carbon dioxide is liquefied and separated from the gas flow in the intermediate separation drum 45.

[0073] The airflow from the intermediate separation drum 45 flows through the connecting pipe 57 and the third heat exchange connection 57.1, which extends through the heat exchanger 37, which uses CO2 circulating in the refrigeration circuit 41 and from the collector line 51 for heat exchange. The carbon dioxide liquefied in the heat exchange connection 57.1 is separated from the airflow in another separation drum 47.

[0074] The resulting lean CO2 flue gas flows from a separate separation drum 47 through the heat exchange section 59.1 of the gas exhaust duct 59 and expands in the expander 59.3, thereby generating mechanical power. This mechanical power can be converted into electricity by the generator 60. Therefore, the temperature of the expanded lean CO2 flue gas decreases, and the chilled lean CO2 flue gas flows through the second heat exchange section 59.2 to remove heat from the heat exchanger 37. The expanded lean CO2 flue gas is finally discharged through the gas exhaust duct 59. The resulting lean CO2 flue gas can be processed in different ways depending on its composition. For example, if the flue gas is generated by an SOFC configuration, the lean CO2 flue gas may contain hydrogen and can be fully or partially recycled back to the fuel cell configuration.

[0075] The liquid carbon dioxide collected at the first separation drum 43, the intermediate separation drum 45, and the other separation drum 47 is used as a refrigerant in the refrigeration circuit 41. Specifically, the liquid carbon dioxide is depressurized by control and pressure reducing valves 43.4, 45.4, and 47.4 and is transported through a liquefied CO2 collection pipe 71 extending through the cold box or heat exchanger 37. The carbon dioxide entering the liquefied CO2 collection pipe 71 can be two-phase carbon dioxide and can be evaporated by removing heat from the flue gas flowing in the first heat exchange connection 55.1, the second heat exchange connection 57.1, and the third heat exchange connection 59.1.

[0076] Vaporized carbon dioxide flowing in pipe 71 downstream of heat exchanger 37 enters suction drum 67, and after removing any possible residual liquid carbon dioxide, the vapor or gaseous form of carbon dioxide is repressurized in CO2 compressor 61 and cooled in intercooler 61.3 and aftercooler 63.

[0077] The cooled carbon dioxide is then conveyed through the compressed CO2 conduit 73 and liquefied by heat exchange as it flows through the heat exchange section 73.1 of the compressed CO2 conduit 73, which extends through the heat exchanger 37. The cooling of the carbon dioxide is achieved by heat exchange with the evaporated carbon dioxide flowing through the liquefied CO2 collection conduit 71 and its associated heat exchange section 71.1.

[0078] The liquefied carbon dioxide stream is then divided into: a first stream, which returns to the liquefied CO2 collection stream 71 via the CO2 return pipe 75 and expansion valve 77; and a second stream, representing the CO2 product delivered to the carbon dioxide storage tank 81 via the CO2 outlet pipe 79. Before reaching the carbon dioxide storage tank 81, the portion of the carbon dioxide stream delivered from the outlet 85 of the compressed CO2 pipe 73 to the carbon dioxide storage tank 81 can be expanded to the required pressure in valve 83 and heated via the heat exchange section 79.1 of the CO2 outlet pipe 79 by further heat removal from the heat exchanger 37.

[0079] If the pressure in carbon dioxide reservoir 81 is higher than the carbon dioxide pressure at point 85, the pressure regulating device 83 may include a pressurizing unit, such as a pump, instead of an expansion valve. Figure 3 The diagram illustrates an implementation scheme that uses a booster unit 83 instead of an expansion valve. Figure 3 As shown and used with Figure 2 The remaining parts are labeled with the same reference numerals as those above. Figure 1 and Figure 2 The description is the same and will not be described again.

[0080] Table 1 below summarizes Figure 2 The system shown contains exemplary, not limiting, values ​​for pressure and temperature at several points. Each point is labeled with a letter from A to O. These letters are recorded in the first column of Table 1 and... Figure 2 The text shows:

[0081] Table 1

[0082]

[0083] Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. Those skilled in the art will understand that various changes, omissions, and additions may be made to the specific disclosure herein without departing from the scope of the invention as defined in the following claims.

Claims

1. A system (1) for generating CO2 from flue gas, the system comprising: - Heat exchanger (37), said heat exchanger being adapted to receive compressed inlet flue gas and condense at least a portion of its carbon dioxide content; - A first separation drum (43) is adapted to receive a quenched flue gas stream containing at least a portion of liquefied CO2 from the heat exchanger (37) and to separate liquefied CO2 from the quenched flue gas stream; wherein the first separation drum (43) includes an inlet (43.1), a liquid outlet (43.2) and a gas outlet (43.3). - Collector line (51), the collector line being adapted to collect liquefied carbon dioxide from the first separation drum (43); - A refrigeration circuit (41) and a liquefied CO2 collection pipe (71), the liquefied CO2 collection pipe extending from the collector line (51) through the heat exchanger (37) and adapted to deliver carbon dioxide to the refrigeration circuit (41); wherein the liquefied CO2 collection pipe (71) includes a heat exchange section (71.1) extending through the heat exchanger (37); and wherein the refrigeration circuit includes: CO2 compressor (61); A compressed CO2 conduit (73) having an outlet (85), an inlet connected to the delivery side of the CO2 compressor (61), and a heat exchange section (73.1) located between the inlet and the outlet and extending through the heat exchanger (37); and CO2 return pipeline (75) fluidly connects the outlet (85) of compressed CO2 pipeline (73) to the collector line (51) or the liquefied CO2 collection pipeline (71), the CO2 return pipeline being located upstream of the heat exchange section (71.1) of the liquefied CO2 collection pipeline (71); - and CO2 outlet pipe (79), which is connected to the outlet (85) of the compressed CO2 pipe (73).

2. The system (1) according to claim 1, the system further comprising a first pressure reducing valve (43.4) located between the liquid outlet (43.2) of the first separation drum (43) and the collector line (51).

3. The system (1) according to claim 1 or 2, further comprising: At least one additional separation drum (45; 47), said additional separation drum being adapted to receive a quenched flue gas stream containing at least partially liquefied CO2 from said heat exchanger (37) and to separate liquid CO2 from said quenched flue gas stream; wherein said additional separation drum (45; 47) includes an inlet (45.1; 47.1), a liquid outlet (45.2; 47.2) and a gas outlet (45.3; 47.3), said liquid outlet (45.2; 47.2) being fluidly connected to said collector line (51); and A fluid connection is located between the gas outlet (43.1) of the first separation drum (43) and the inlet (45.1; 47.1) of the other separation drum (45; 47), the fluid connection extending through the heat exchanger (37) and including a heat exchange connection (55.1; 57.1).

4. The system (1) according to claim 3, the system further comprising an additional pressure reducing valve (45.4; 47.4) located between the liquid outlet (45.2; 47.2) of the additional separating drum (45; 47) and the collector line (51).

5. The system (1) according to any one of the preceding claims, the system further comprising an expansion valve (77) located in the CO2 return pipe (75).

6. The system (1) according to any one of the preceding claims, the system further comprising a pressure regulating unit (83) along the CO2 outlet pipe (79).

7. The system (1) according to claim 6, wherein, The pressure regulating unit (83) is selected from the group consisting of: pressure reducing valve; pressure boosting unit.

8. The system (1) according to any one of the preceding claims, wherein, The CO2 compressor (61) is an intercooled compressor.

9. The system (1) according to any one of the preceding claims, wherein, The CO2 compressor (61) is fluidly connected to the aftercooler (63).

10. The system according to any one of the preceding claims, the system further comprising a flue gas pretreatment section (3).

11. The system according to claim 10, wherein, The flue gas pretreatment section (3) includes at least one of the following: -Dryer section (33.1); - Cooler (29), the cooler is arranged upstream of the dryer section (33.1) and is adapted to pre-cool the flue gas; - A gas-liquid separator (31) is located between the cooler (29) and the dryer section (33.1) and is adapted to remove condensates formed in the flue gas by pre-cooling the flue gas in the cooler (29); - The filter section (33.3) located downstream of the dryer section (33.1). -Water-gas shift reactor system (23); - Flue gas compressor (11); - Their combination.

12. A method for generating liquid CO2 from flue gas, the method comprising the steps of: A compressed flue gas containing CO2 is conveyed through a heat exchanger (37), which uses a chilled CO2 stream circulating in a refrigeration circuit (41) for heat exchange. The CO2 contained in the compressed flue gas is at least partially condensed by heat exchange using the quenched CO2 circulating in the refrigeration circuit (41); Liquefied CO2 is separated from the compressed flue gas flow in at least the first separation drum (43); Remove liquefied CO2 from the first separation drum (43); The liquefied CO2 from the first separation drum (43) is collected in a liquefied CO2 collection pipe (71), which includes a heat exchange section (71.1) extending through the heat exchanger (37). The CO2 flowing through the heat exchange section (71.1) of the liquefied CO2 collection pipe (71) is evaporated; In the CO2 compressor (61) of the refrigeration circuit (41), the CO2 evaporated in the heat exchange section (71.1) of the liquefied CO2 collection pipe (71) is compressed and discharged from the heat exchanger (37). The compressed CO2 stream from the CO2 compressor (61) is conveyed through a compressed CO2 conduit (73), which includes a heat exchange section (73.1) extending through the heat exchanger (37) and cooling the compressed CO2 stream. At the outlet (85) of the compressed CO2 pipe (73), the compressed and chilled CO2 is divided into a first part of CO2 flow and a second part of CO2 flow; The first portion of the CO2 flow is returned to the liquefied CO2 collection pipe (71) upstream of the heat exchange section (71.1) of the liquefied CO2 collection pipe (71). The second portion of the CO2 stream is removed from the refrigeration circuit as a CO2 product; Remove lean CO2 flue gas from the heat exchanger (37).

13. The method according to claim 12, further comprising the step of depressurizing the liquefied CO2 removed from the first separation drum (43) upstream of the liquefied CO2 collection pipe (71).

14. The method according to claim 12, further comprising the following step: Further liquefied CO2 is separated from the compressed flue gas flow in a separate separation drum (45; 47) located downstream of the first separation drum; wherein the first separation drum (43) and the separate separation drum (47) are fluidly connected by a fluid connection between the gas outlet (43.1) of the first separation drum (43) and the inlet (45.1; 47.1) of the separate separation drum (45; 47), the fluid connection extending through the heat exchanger (37) and including a heat exchange connection (55.1; 57.1); Removal of liquefied CO2 from the additional separation drums (45; 47); and The liquefied CO2 from the other separation drum (45; 47) is collected in the CO2 collection pipe (71).

15. The method of claim 14, further comprising the step of depressurizing the liquefied CO2 removed from the additional separation drum (45; 47) upstream of the liquefied CO2 collection conduit (71).

16. The method according to any one of claims 12 to 15, the method further comprising the step of expanding the first portion of the CO2 flow between the outlet (85) of the compressed CO2 conduit (73) and the liquefied CO2 collection conduit (71).

17. The method according to any one of claims 12 to 16, the method further comprising the step of adjusting the pressure of the second portion of the CO2 stream removed from the refrigeration circuit as a CO2 product; The steps for adjusting the pressure include: This causes the second part of the CO2 flow to expand; Alternatively, the pressure of the second portion of the CO2 stream can be increased.

18. The method according to any one of claims 12 to 17, the method further comprising the step of expanding the lean CO2 flue gas removed from the heat exchanger (37).

19. The method according to claim 18, wherein, The step of expanding the lean CO2 flue gas includes expanding the lean CO2 flue gas in an expander (59.3) and thereby generating mechanical power.

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