Carbon dioxide capture system

Abstract

The present invention relates to a system for cooling cleaning water or an absorption liquid used in a process of capturing carbon dioxide contained in by-product gas generated in an ironmaking process. Provided is a carbon dioxide capture system wherein a heat pump (100) is installed in place of a conventional cooling tower method that cools cleaning water using vaporization of water, so that the cleaning water or the absorption liquid can be cooled with high efficiency, and high-temperature steam or high-temperature water is produced as a by-product and is used to heat the cleaning water or the absorption liquid.

Description

carbon dioxide capture system

[0001] The present invention relates to a carbon dioxide capture system capable of efficiently capturing carbon dioxide contained in byproduct gases and flue gases generated during a steelmaking process, while minimizing total energy consumption by utilizing waste heat generated during the carbon dioxide capture process for a carbon dioxide separation process contained in ammonia water.

[0002]

[0003] As interest in carbon dioxide grows due to issues such as global warming, research aimed at effectively separating and capturing carbon dioxide is continuously being conducted, focusing on major carbon dioxide emission sources such as power plants and steel mills.

[0004] Among the various methods for capturing carbon dioxide, chemical absorption is known to be the most suitable technology for the commercialization stage. Chemical absorption is a technology that captures carbon dioxide using alkaline absorption solutions, and the absorption solution that has absorbed carbon dioxide is regenerated by heat supplied from an external source. Representative carbon dioxide absorption solutions used in chemical absorption include amine-based absorption solutions such as MEA (monoethanolamine), DEA (diethanolamine), MDEA (methyldiethanolamine), and AMP (2-amino 2-methyl 1-propanol), in addition to which various other absorption solutions, such as potassium carbonate solution and ammonia water, are being developed.

[0005] Technologies capable of increasing the efficiency of the carbon dioxide capture method using the chemical absorption method described above include heat exchange network optimization, additive injection, and absorption tower cooling. Additionally, as disclosed in Patent Publication No. 2012-0074139, research is being conducted to suppress the volatilization of ammonia or increase the absorption rate of ammonia and carbon dioxide by injecting metal salts as additives into the absorption solution.

[0006] As illustrated in FIG. 1, the adsorption system for absorbing carbon dioxide comprises an absorption tower (10) that produces flue gas from which carbon dioxide has been removed by introducing an absorption liquid into a target gas containing carbon dioxide, and a regeneration tower (20) that removes carbon dioxide by heating the absorption liquid that has captured the carbon dioxide.

[0007] A process may be included in which the gas is exposed to low-temperature washing water (around 30°C) to remove residual absorbent liquid contained in the gas before the final exhaust gas and carbon dioxide are discharged from the absorption tower (10) and the regeneration tower (20).

[0008] The cleaning water introduced to remove the above residual absorbent liquid can be heated in a concentration tower (30) for reuse to recover the absorbent liquid and then discharged to the bottom of the concentration tower (300).

[0009] Since the cleaning water discharged from the bottom of the above concentration tower (300) is in a high temperature state (about 70°C) due to receiving thermal energy during the heating process, a process of cooling it by exchanging heat with the cooling water of the cooling tower (40) and the seventh heat exchanger (77) was absolutely necessary to restore the ability to collect residual absorbent liquid.

[0010] However, the above method may have the following disadvantages because it necessarily requires the cooling tower (40) and a separate seventh heat exchanger (77), etc.

[0011] First, there is a need to continuously supply cooling water that is evaporated and consumed during the above process; second, there is a need to continuously maintain the nozzle that sprays the cooling water; third, a large site is required because the size of the cooling tower (40) must be secured to a certain size or larger in order to continuously supply low-temperature cleaning water to the carbon dioxide absorption process; fourth, there is a need for continuous maintenance because contamination may occur during the process of the cooling water coming into contact with air and the contaminated cooling water reduces cooling efficiency; fifth, there is a significant amount of noise and power consumption because a large fan is installed in the cooling tower (40) for rapid cooling of the cooling water; and sixth, there may be a problem that the cooling tower has multiple complex pipes connected to it, which may result in high costs for corrosion management.

[0012] Therefore, it is necessary to introduce a cleaning water cooling method that can compensate for the disadvantages of the cooling tower (40) in the carbon dioxide capture process.

[0013]

[0014] The present invention has been devised to solve the aforementioned problems and provides a method to minimize the scale of a plant for capturing carbon dioxide contained in byproduct gas or flue gas containing carbon dioxide.

[0015] In addition, the present invention provides a method to minimize the energy required to separate carbon dioxide from the absorption liquid used to capture carbon dioxide from byproduct gas.

[0016] In addition, the present invention provides a method to minimize the energy required to separate the absorbent solution from the washing water used to capture the absorbent solution remaining in the gas from which the carbon dioxide has been removed.

[0017] In addition, the present invention provides a method to minimize the energy required to separate carbon dioxide from the absorption solution in which the carbon dioxide has been captured.

[0018] In addition, the present invention presents a method for recycling waste heat discarded in a process of capturing carbon dioxide from gas.

[0019] In addition, the present invention provides a method to maximize cooling efficiency and the energy efficiency of the carbon dioxide capture process by using a heat pump system when cooling the cleaning water.

[0020] In addition, the present invention provides a method to minimize the cost and time required to remove contaminants from the cooling water by preventing the cooling water from being exposed to the outside.

[0021]

[0022] The objects of the present invention are not limited to those mentioned above, and other unmentioned objects and advantages of the present invention may be understood from the following description and will be more clearly understood by the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0023]

[0024] To solve the above-mentioned problem, the present invention comprises: an absorption tower (10) that, when a gas containing carbon dioxide is supplied to a lower inlet, exposes it to ammonia water to absorb carbon dioxide and produce exhaust gas, and then exposes the exhaust gas to washing water to collect ammonia before it is discharged to an upper outlet; a regeneration tower (20) that heats the ammonia water in which carbon dioxide has been collected in the absorption tower (10) to separate the carbon dioxide, and then exposes the separated carbon dioxide to washing water to collect ammonia before it is discharged to an upper outlet; and a concentration tower (30) that heats the washing water in which ammonia has been absorbed in the absorption tower (10) or the regeneration tower (20) to separate it into washing water and ammonia water, and then supplies the separated ammonia water to the regeneration tower (20). It may be characterized by being composed of piping connecting an evaporator (101), a compressor (103), a condenser (102), and an expansion valve (104), and a refrigerant circulating through said piping, wherein the high-temperature cleaning water separated from said concentration tower (30) is cooled into low-temperature cleaning water by heat exchange with said evaporator (101), and the steam condensate is heated into high-temperature steam or high-temperature water by heat exchange with said condenser (102).

[0025] In one embodiment of the present invention, the ammonia water supplied to the regeneration tower (20) is heated by a first reboiler (81) installed at the bottom of the regeneration tower (20) to extract carbon dioxide, and high-temperature steam or high-temperature water heated by the condenser (102) is supplied to one side of the first reboiler (81).

[0026] In one embodiment of the present invention, the cleaning water supplied to the concentration tower (30) is heated by a second reboiler (82) installed at the bottom of the concentration tower (30) to extract ammonia water, and high-temperature steam heated by the condenser (102) is supplied to one side of the second reboiler (82).

[0027] In one embodiment of the present invention, the washing water that has absorbed ammonia in the absorption tower (10) or the regeneration tower (20) may be characterized by being stored in a washing water drum (50) and then supplied to the top of the concentration tower (30).

[0028] In one embodiment of the present invention, the cleaning water of the cleaning water drum (50) may be characterized by being heated by heat exchange with the cleaning water heated by the second reboiler (82) through the sixth heat exchanger (76) and then supplied to the top of the concentration tower (30).

[0029] In one embodiment of the present invention, the high-temperature ammonia water from which carbon dioxide has been extracted in the regeneration tower (20) may be characterized by being cooled by heat exchange with cooling water supplied from the cooling tower (40) through the fourth heat exchanger (74) and then being supplied back into the absorption tower (10).

[0030] In one embodiment of the present invention, the cooling water that has obtained thermal energy through the fourth heat exchanger (74) is supplied to the cooling tower (40) to recover thermal energy and cool.

[0031] In one embodiment of the present invention, the ammonia water that has captured carbon dioxide in the absorption tower (10) is heated in the first reboiler (81), and then heat-exchanged with the high-temperature ammonia water from which carbon dioxide has been extracted in the third heat exchanger (73) and supplied to the top of the regeneration tower (20).

[0032] In one embodiment of the present invention, a portion of the ammonia water discharged after carbon dioxide is captured in the absorption tower (10) may be supplied back to the bottom of the absorption tower (10).

[0033] In one embodiment of the present invention, the ammonia water supplied to the bottom of the absorption tower (10) may be characterized by being cooled by heat exchange with the cooling water supplied from the cooling tower (40) before being supplied through the first heat exchanger (71).

[0034] In one embodiment of the present invention, the high-temperature steam supplied with thermal energy to the first reboiler (81) and the second reboiler (82) may be characterized by repeating the process of changing phases into condensate and then exchanging heat with the condenser (102) to change phases back into high-temperature steam.

[0035] To solve the above-mentioned problem, the present invention comprises: an absorption tower (10) that, when a gas containing carbon dioxide is supplied to a lower inlet, exposes it to ammonia water to absorb carbon dioxide and produce exhaust gas, and then exposes the exhaust gas to washing water to collect ammonia before it is discharged to an upper outlet; a regeneration tower (20) that heats the ammonia water in which carbon dioxide has been collected in the absorption tower (10) to separate the carbon dioxide, and then exposes the separated carbon dioxide to washing water to collect ammonia before it is discharged to an upper outlet; and a concentration tower (30) that heats the washing water in which ammonia has been absorbed in the absorption tower (10) or the regeneration tower (20) to separate it into washing water and ammonia water, and then supplies the separated ammonia water to the regeneration tower (20). The heat pump (100), which consists of a pipe connecting an evaporator (101), a compressor (103), a condenser (102), and an expansion valve (104) and a refrigerant circulating through the pipe, may be characterized by exchanging heat with the high-temperature washing water separated from the evaporator (101) and the concentration tower (30), the high-temperature ammonia water supplied to the absorption tower (10) and the regeneration tower (20), and cooling them into low-temperature washing water and low-temperature ammonia water, respectively, and the condenser (102) may be characterized by exchanging heat with the condensate to produce high-temperature steam or high-temperature water.

[0036]

[0037] According to various embodiments of the present invention, the overall cost can be reduced by using a heat pump instead of a cooling tower that occupies a large area, thereby reducing the total plant usage area and decreasing the heat energy consumption required for carbon dioxide removal.

[0038] According to various embodiments of the present invention, heat generated in the heat pump condenser can be used to separate carbon dioxide from the carbon dioxide-captured absorption solution, thereby reducing the load on the reboiler while increasing overall process energy efficiency.

[0039] According to various embodiments of the present invention, heat generated in the heat pump condenser is used to separate the absorbent from the cleaning solution in which the absorbent is collected, thereby reducing the load on the reboiler while increasing the overall process energy efficiency.

[0040] According to various embodiments of the present invention, the cleaning water is supplied to the top of the absorption tower and the top of the regeneration tower in a cooled state after heat exchange with the heat pump evaporator, thereby allowing the absorption liquid contained in the gas to be captured more efficiently.

[0041] According to various embodiments of the present invention, by cooling the cleaning water and ammonia water using a heat pump system instead of a cooling tower, an additional cooling water replenishment process can be omitted.

[0042] According to various embodiments of the present invention, by cooling the cleaning water and ammonia water using a heat pump system, the process piping can be simplified, thereby improving maintainability.

[0043] According to various embodiments of the present invention, by cooling the cleaning water and ammonia water using a heat pump system, the fan noise generated during cooling water cooling by a cooling tower can be eliminated, thereby minimizing the possibility of complaints.

[0044] According to various embodiments of the present invention, the size of the cooling tower can be minimized even when the heat pump system and the cooling tower are used simultaneously, thereby providing design flexibility to the plant manager.

[0045]

[0046] The objects of the present invention are not limited to those mentioned above, and other unmentioned objects and advantages of the present invention may be understood from the following description and will be more clearly understood by the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0047]

[0048] Figure 1 is a schematic diagram of a conventional carbon dioxide capture process.

[0049] FIG. 2 is a schematic diagram of a first embodiment of the carbon dioxide capture process of the present invention.

[0050] Figure 3 is a schematic diagram illustrating the operation sequence of the carbon dioxide capture process of Figure 2.

[0051] FIG. 4 is a schematic diagram of a second embodiment of the carbon dioxide capture process of the present invention.

[0052] FIG. 5 is a schematic diagram of the heat pump system of the present invention.

[0053]

[0054] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0055] Although terms such as "first," "second," etc., are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless specifically stated otherwise, the first component may also be the second component.

[0056] Throughout the specification, unless specifically stated otherwise, each component may be singular or plural.

[0057] In the following, the statement that any configuration is placed on the "upper (or lower)" of a component or on the "upper (or lower)" of a component may mean not only that any configuration is placed in contact with the upper (or lower) surface of said component, but also that another configuration may be interposed between said component and any configuration placed on (or below) said component.

[0058] In addition, where it is stated that one component is "connected," "combined," or "connected" to another component, it should be understood that while the components may be directly connected or connected to each other, another component may be "interposed" between each component, or each component may be "connected," "combined," or "connected" through another component.

[0059] Singular expressions used in this specification include plural expressions unless the context clearly indicates otherwise. In this application, terms such as "composed of" or "comprising" should not be interpreted as necessarily including all of the various components or steps described in the specification, and should be interpreted as meaning that some of the components or steps may be omitted or additional components or steps may be included.

[0060] Throughout the specification, "A and / or B" means A, B, or A and B unless specifically stated otherwise, and "C to D" means C or more and D or less unless specifically stated otherwise.

[0061]

[0062] Hereinafter, carbon dioxide capture systems according to various embodiments will be described with reference to the attached drawings.

[0063]

[0064] Figure 1 illustrates a schematic diagram of a process for capturing carbon dioxide contained in byproduct gas and flue gas in existing technology.

[0065] The above-mentioned conventional carbon dioxide capture process is basically composed of an absorption tower (10), a regeneration tower (20), a concentration tower (30), and a cooling tower (40).

[0066] The absorption tower (10) performs the function of exposing the absorption liquid to a carbon dioxide-containing gas to capture carbon dioxide from the carbon dioxide-containing gas, and then exposing it to washing water to capture the absorption liquid remaining in the exhaust gas from which carbon dioxide has been removed.

[0067] The above regeneration tower (20) heats the absorption liquid that has captured carbon dioxide to separate the absorption liquid and carbon dioxide, and performs the function of exposing the separated carbon dioxide to washing water to capture the remaining absorption liquid.

[0068] The above concentration tower (30) heats the washing water used to collect the absorbent liquid remaining in the gas discharged from the absorption tower (10) and the regeneration tower (20) to separate it into the absorbent liquid and the washing water, and supplies the separated absorbent liquid back to the regeneration tower (20) while simultaneously supplying the washing water from which the absorbent liquid has been removed to the absorption tower (10) and the regeneration tower (20).

[0069] The above cooling tower (40) serves to supply cooling water for cooling the ammonia water used in the absorption tower (10) and the regeneration tower (20) and the cleaning water generated in the concentration tower (30).

[0070] However, since the above-mentioned cooling tower (40) has many problems in use for the reasons mentioned above, the present invention proposes a method to replace it with a heat pump (100) system or to utilize the cooling tower (40) on a minimum scale.

[0071]

[0072] [First Example]

[0073] FIG. 2 illustrates a first embodiment of a carbon dioxide capture process using the heat pump (100) system in the present invention.

[0074] In the present invention, the absorbent solution is described based on ammonia water for convenience of explanation, but the absorbent solution is by no means limited to ammonia water.

[0075] First, a plurality of packings (90) may be provided inside the absorption tower (10).

[0076] It is obvious that the type and number of the above packing (90) can be adjusted according to the usage environment and purpose.

[0077] The above packing (90) can serve to increase the contact area between the ammonia water and the gas containing carbon dioxide.

[0078] By-product gas containing carbon dioxide and gas containing carbon dioxide can be supplied to the bottom inlet of the absorption tower (10).

[0079] Carbon dioxide can be absorbed in the first stage by spraying room temperature ammonia water onto the upper part of the above byproduct gas.

[0080] The ammonia water sprayed above can be cooled by exchanging heat with air or cooling water supplied from the cooling tower (40) and the first heat exchanger (71).

[0081] The gas from which the primary carbon dioxide has been removed can be discharged through the top of the absorption tower (10) via the first packing (91) to the fourth packing (94) at the top.

[0082] It is obvious that the number and configuration of the packings described in the above example are merely for the purpose of explaining the mechanism of the present invention as described above, and that the actual scope of rights is not limited thereto.

[0083] During the above process, carbon dioxide contained in the gas passing through the second packing (92) can be secondarily captured by contacting the ammonia water, which has been cooled by heat exchange with air or cooling water and the second heat exchanger (72), through the second packing (92).

[0084] Carbon dioxide contained in the gas that passes through the second packing (92) and the third packing (93) can be tertiarily captured by contacting the ammonia water, which is cooled by heat exchange with the cooling water and the fourth heat exchanger (74), through the third packing (93).

[0085] The ammonia water cooled by the above-mentioned fourth heat exchanger (74) can be supplied at 30°C to 60°C, and preferably at 30°C to 40°C.

[0086] The temperature of the ammonia water supplied to the fourth heat exchanger (74) can be set lower than the temperature of the ammonia water supplied to the first heat exchanger (71).

[0087] This is to obtain higher efficiency by lowering the temperature of the ammonia water, since the carbon dioxide concentration in the gas to be captured by the third packing (93) is lower than the carbon dioxide concentration contained in the byproduct gas supplied to the absorption tower (10).

[0088] The exhaust gas, which is the result of removing all carbon dioxide from the gas through the above process, can be discharged to the outside after coming into contact with washing water (about 30°C) at the top of the absorption tower (10) to remove the ammonia water contained inside.

[0089] The ammonia water that has captured all the carbon dioxide in the absorption tower (10) can be heated (about 63°C) by heat exchange with the ammonia water (about 77°C) heated in the regeneration tower (20) through the third heat exchanger (73) and then supplied to the top of the regeneration tower (20).

[0090] In the present invention, fifth packings (95) to seventh packings (97) may be sequentially interposed inside the regeneration tower (20).

[0091] Ammonia water in which carbon dioxide has been captured can be separated from the captured carbon dioxide when subjected to thermal energy.

[0092] The supplied ammonia water is sprayed onto the top of the sixth packing (96), receives thermal energy produced by the first reboiler (81) installed at the bottom of the regeneration tower (20), falls to the bottom, and can be separated from carbon dioxide.

[0093] The ammonia water from which carbon dioxide has been separated in the first step above can be cooled by heat exchange with cooling water through the fifth heat exchanger (75) via the fourth pump (64) before being transferred from the sixth packing (96) to the top of the seventh packing (97), and then sprayed back onto the top of the sixth packing (96).

[0094] After going through the above repetition process, the ammonia water passing through the 7th packing (97) can be separated from carbon dioxide by receiving thermal energy from the 1st reboiler (81) and then discharged to the bottom of the regeneration tower (20).

[0095] The ammonia water that has been separated from carbon dioxide in the regeneration tower (20) can be cooled first by exchanging heat with the ammonia water discharged from the absorption tower (10) in the third heat exchanger (73) as described above.

[0096] The above primary cooled ammonia water can be supplied to the top of the absorption tower (10) in a secondary cooled state by exchanging heat with air or cooling water through the fourth heat exchanger (74).

[0097] In addition, ammonia water supplied from the concentration tower (30) can be supplied to the top of the seventh packing (97).

[0098] The carbon dioxide separated through the above regeneration tower (20) process passes through the fifth packing (95) and can come into contact with the washing water, and after separating the residual ammonia water contained inside through the process, it can be discharged through the top of the above regeneration tower (20) and stored separately.

[0099] The cleaning water that captures the residual ammonia water contained in the exhaust gas in the fourth packing (94) and the residual ammonia water contained in the carbon dioxide in the fifth packing (95), and the cooling water used to cool the ammonia water in the first heat exchanger (71), second heat exchanger (72), fourth heat exchanger (74), and fifth heat exchanger (75) have received thermal energy during the heat exchange process, so they are supplied back to the cooling tower (40) to be cooled, and the cooling water cooled in the cooling tower (40) can undergo a circulation process in which it is supplied back to the first heat exchanger (71), second heat exchanger (72), fourth heat exchanger (74), and fifth heat exchanger (75).

[0100] The washing water, which captures residual ammonia while passing through the top of the absorption tower (10) and the regeneration tower (20), can be stored in a washing water drum (50) and then supplied to the concentration tower (30) to remove the captured ammonia water.

[0101] The above washing water can be preheated by exchanging heat with the washing water heated in the second reboiler (82) from the concentration tower (30) through the sixth heat exchanger (76) before being supplied to the concentration tower (30).

[0102] The above preheating process has a primary purpose of reducing the time required for the washing water to be heated to the second reboiler (82) to remove ammonia water and the heat energy supplied through the second reboiler (82), and a secondary purpose of removing heat energy to restore the ammonia capture capacity before the washing water, from which ammonia components have been removed by heating in the concentration tower (30), is supplied back to the absorption tower (10) and the regeneration tower (20).

[0103] In an embodiment of the present invention, the high-temperature cleaning water that has passed through the concentration tower (30) has a mechanism in which it is first cooled through the sixth heat exchanger (76) and then transferred to the heat pump (100) system.

[0104] The above heat pump (100) system is a technology that recovers relatively low-temperature waste heat, vaporizes a heat medium while recovering the heat contained in the waste heat, compresses the vaporized heat medium using electrical energy to raise its temperature, and produces steam using the heat contained in the heat medium with the increased temperature.

[0105] It is known that in the fluid temperature range used in the present invention, the COP (coefficient of performance) can be practically operated up to 2.0 to 2.5, but in the case of a recent heat pump (100) with increased refrigerant and compression efficiency, it is also possible to increase the COP to 3.5 within the fluid operating temperature range of the present invention.

[0106] Therefore, when cooling the cleaning water that has passed through the concentration tower (30) and the sixth heat exchanger (76) using a heat pump (100) system as in the present invention, the amount of cooling and the amount of heat that can be recovered can be increased proportionally according to the size of the COP, and the thermal energy of the condenser can be utilized for steam production. This has the advantage of increasing energy efficiency compared to the existing technology that supplies all of the externally produced steam to the reboiler (80) as shown in FIG. 1, and also has the advantage of achieving substantial carbon dioxide reduction when viewed as the entire steelmaking process rather than just the carbon dioxide capture process.

[0107] FIG. 5 schematically illustrates the operation of the heat pump (100) system used in the present invention.

[0108] In this embodiment, a method is presented in which the cooling tower (40) and the heat pump (100) system are used in parallel.

[0109] The refrigerant circulating inside the heat pump (100) can absorb thermal energy through the evaporator (101), be compressed and heated through the compressor (103), and then release thermal energy through the condenser (102).

[0110] The refrigerant that has released thermal energy in the condenser (102) passes through the expansion valve (104) and has an operating cycle in which it is cooled by throttling expansion.

[0111] In this embodiment, the cleaning water that has passed through the concentration tower (30) and the sixth heat exchanger (76) can be heat-exchanged again with the evaporator (101), thereby easily lowering the temperature of the cleaning water to 30°C.

[0112] In addition, during this process, the condensate can be heated with the thermal energy of the condenser (102) to convert it into high-temperature steam of about 120°C.

[0113] The above high-temperature steam can be transferred to the first reboiler (81) and the second reboiler (82) to heat the ammonia water and washing water and used to separate the residual carbon dioxide or residual ammonia components inside.

[0114] Through the above process of the present embodiment, the cooling of the cleaning water and the heating of the reboiler (80) are processed by a single device (heat pump system), thereby maximizing thermal efficiency and simplifying the equipment introduced into the process.

[0115] In addition, since a high COP can be obtained when using the above heat pump (100) system, the carbon dioxide capture capacity for the entire gas can be increased by cooling the first heat exchanger (71), second heat exchanger (72), fourth heat exchanger (74), and fifth heat exchanger (75), which were previously cooled with some air or cooling water, with low-temperature cleaning water. Furthermore, the problem of having to continuously replenish cleaning water when using the existing cooling tower (40) can be solved.

[0116] FIG. 3 shows the operating sequence of the fluids used in this embodiment, numbered and Table 1 below is the result of comparing the performance when only the cooling tower (40) is used in the conventional process according to the fluid operating sequence of FIG. 3, and when the cooling tower (40) and the heat pump (100) system are used in parallel as in this embodiment.

[0117] In this embodiment, the results obtained in Table 1 above are all results obtained when the COP of the heat pump (100) system is conservatively set to 2.

[0118] In addition, the recoverable heat (kcal / h) Q used for the above performance comparison can be calculated from the following mathematical formula.

[0119]

[0120] [Mathematical Formula]

[0121]

[0122] Here, M is the mass of the fluid, Cp is the specific heat, and △T is the temperature difference between the fluids entering and exiting.

[0123]

[0124] Existing Process Implementation Example Flow Rate stream #Temperature (°C)Temperature (°C)Flow Rate (kg / hr)①44448,916②63638,916③77779,296③54549,296④35359,296⑤30301,550⑥3030800⑦48481,550⑧6969800⑨-120287⑩-120287⑪56562,330⑫80802,330⑬-702,156⑭-352,156Recoverable Heat (Kcal / hr)75,460150,920Produced Steam Amount (ton / hr)-0.287

[0125]

[0126]

[0127] As can be seen from Table 1 above, when the configuration presented in the present invention is used, the amount of recovered heat is about twice as high as when using a conventional cooling tower (40), and additionally, 0.287 tons of 120 °C high-temperature steam can be produced per hour, so it can be seen that the energy efficiency and productivity of the entire process can be improved for the reasons mentioned above.

[0128] It is obvious that if the above COP is set to a maximum of 3.5, the performance difference described above will become even greater.

[0129]

[0130] [2nd Example]

[0131] In this embodiment, a method of replacing the first heat exchanger (71), second heat exchanger (72), fourth heat exchanger (74), and fifth heat exchanger (75) with the heat pump (100) system of the first embodiment is described.

[0132] FIG. 4 illustrates a schematic diagram of the configuration layout of the present embodiment.

[0133] The heat pump (100) system installed at the locations of the first heat exchanger (71), second heat exchanger (72), fourth heat exchanger (74), and fifth heat exchanger (75) can be operated in a circulation manner, as in the first embodiment, by cooling the ammonia water and simultaneously heating the condensate to change its phase into high-temperature steam, and then supplying it back to the reboiler (81, 82).

[0134] To verify the energy saving effect in this embodiment, the energy saving effect can be compared with the carbon dioxide capture process used in the first embodiment.

[0135] As described in Table 1 above, the flow rate of ammonia water passing through the multiple heat pump (100) system applied in this embodiment is 9,296 kg / hr and the temperature difference of the ammonia water heat-exchanged by the heat pump (100) is 19°C, so if the COP is set to 2, the recoverable heat amount is 353,248 kcal / hr and the total heat amount recoverable in the entire ammonia capture process can be calculated as 504,168 kcal / hr, which is the sum of the heat amount recoverable from the washing water, which is 150,920 kcal / hr.

[0136] Accordingly, in this embodiment, when a plurality of heat pump (100) systems are applied, compared to a process using only the cooling tower (40) as in the conventional method, 504,168 kcal / hr of heat can be recovered and used in the carbon dioxide capture process, thereby improving the efficiency of the carbon dioxide capture process.

[0137] However, in the case of the present embodiment, the size of the heat pump (100) system must be large enough to accommodate the flow rate of ammonia water passing through the first heat exchanger (71), the second heat exchanger (72), the fourth heat exchanger (74), and the fifth heat exchanger (75), and in some cases, a result contrary to the problem of the present invention of minimizing the area occupied by the cooling tower (40) in the plant in the existing carbon dioxide capture process may result.

[0138] In addition, there may also be a constraint that the pump and piping must be enlarged to operate the above-mentioned heat pump (100) system.

[0139] Therefore, it is desirable to apply the heat pump system (100) presented in this embodiment by comprehensively considering the scale of the carbon dioxide capture process, the plant structure, and the flow rate and physical properties of the working fluids used (absorbent liquid, cleaning water, cooling water).

[0140] The reaction equation applied to the entire process of capturing carbon dioxide from the aforementioned byproduct gas and separately concentrating the captured carbon dioxide is as follows.

[0141]

[0142] First, the relationship for collecting residual ammonia water with washing water in the absorption tower (10) is as in Equation (1).

[0143] (1)

[0144]

[0145]

[0146]

[0147] In addition, the relationship for capturing carbon dioxide by contacting the byproduct gas with ammonia water in the absorption tower (10) is as shown in Equation (2).

[0148]

[0149] (2)

[0150]

[0151]

[0152]

[0153] In addition, the relationship for collecting residual ammonia water in carbon dioxide in the regeneration tower (20) as washing water is given by Equation (3).

[0154]

[0155] (3)

[0156]

[0157]

[0158]

[0159] In addition, the relationship for removing carbon dioxide remaining in the ammonia water in the above-mentioned regeneration tower (20) is given by Equation (4).

[0160]

[0161] (4)

[0162]

[0163]

[0164]

[0165] Although the present invention has been described above with reference to the illustrated drawings, the present invention is not limited by the embodiments and drawings disclosed in this specification, and it is obvious that various modifications can be made by a person skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention were not explicitly described while describing the embodiments of the present invention above, it is natural to acknowledge that the effects predictable by said configuration should also be recognized.

Claims

1. An absorption tower (10) that, when a gas containing carbon dioxide is supplied to the lower inlet, exposes it to ammonia water to absorb carbon dioxide and produce exhaust gas, and then exposes the exhaust gas to washing water to capture ammonia before it is discharged to the upper outlet; A regeneration tower (20) that heats the ammonia water in which carbon dioxide has been captured in the absorption tower (10) to separate the carbon dioxide, and then exposes the separated carbon dioxide to washing water to capture ammonia before it is discharged through the upper outlet; A concentration tower (30) that heats the washing water that has absorbed ammonia in the absorption tower (10) or regeneration tower (20) to separate it into washing water and ammonia water, and supplies the separated ammonia water to the regeneration tower (20); and A carbon dioxide capture system comprising a heat pump (100) composed of piping connecting an evaporator (101), a compressor (103), a condenser (102), and an expansion valve (104), and a refrigerant circulating through said piping, wherein high-temperature washing water separated from the evaporator (101) and the concentration tower (30) is cooled into low-temperature washing water through heat exchange, and the condenser (102) produces high-temperature steam or high-temperature water through heat exchange with the condensed water.

2. In Claim 1, A carbon dioxide capture system characterized in that the ammonia water supplied to the regeneration tower (20) is heated by a first reboiler (81) installed at the bottom of the regeneration tower (20) to extract carbon dioxide, and high-temperature steam heated by the condenser (102) is supplied to one side of the first reboiler (81).

3. In Claim 1, A carbon dioxide capture system characterized in that the cleaning water supplied to the concentration tower (30) is heated by a second reboiler (82) installed at the bottom of the concentration tower (30) to extract ammonia water, and high-temperature steam heated by the condenser (102) is supplied to one side of the second reboiler (82).

4. In Claim 3, A carbon dioxide capture system characterized in that the washing water that has absorbed ammonia in the absorption tower (10) or regeneration tower (20) is stored in a washing water drum (50) and then supplied to the top of the concentration tower (30).

5. In Claim 4, A carbon dioxide capture system characterized in that the washing water in the washing water drum (50) is heated by heat exchange with the washing water heated by the second reboiler (82) through the sixth heat exchanger (76) and then supplied to the top of the concentration tower (30).

6. In Claim 2, A carbon dioxide capture system characterized in that the high-temperature ammonia water from which carbon dioxide is extracted in the regeneration tower (20) is cooled by heat exchange with cooling water supplied from the cooling tower (40) through the fourth heat exchanger (74) and then supplied back into the absorption tower (10).

7. In Claim 6, A carbon dioxide capture system characterized in that the cooling water, which has obtained thermal energy through the fourth heat exchanger (74), is supplied to the cooling tower (40) to recover thermal energy and cool.

8. In Claim 2, A carbon dioxide capture system characterized by the ammonia water that has captured carbon dioxide in the absorption tower (10) being heated in the first reboiler (81), then heat-exchanged with the high-temperature ammonia water from which carbon dioxide has been extracted in the third heat exchanger (73) and then supplied to the top of the regeneration tower (20).

9. In Claim 1, A carbon dioxide capture system characterized in that a portion of the ammonia water discharged after capturing carbon dioxide in the absorption tower (10) is supplied back to the bottom of the absorption tower (10).

10. In Claim 9, A carbon dioxide capture system characterized in that the ammonia water supplied to the bottom of the absorption tower (10) is cooled by heat exchange with the cooling water supplied from the cooling tower (40) before being supplied through the first heat exchanger (71).

11. In either Claim 2 or Claim 3 A carbon dioxide capture system characterized by the process in which high-temperature steam, which has transferred thermal energy to the first reboiler (81) or the second reboiler (82), undergoes a phase change into condensate and then repeats the process of changing into high-temperature steam again by exchanging heat with the condenser (102).

12. An absorption tower (10) that, when a gas containing carbon dioxide is supplied to the lower inlet, exposes it to ammonia water to absorb carbon dioxide and produce exhaust gas, and then exposes the exhaust gas to washing water to capture ammonia before it is discharged to the upper outlet; A regeneration tower (20) that heats the ammonia water in which carbon dioxide has been captured in the absorption tower (10) to separate the carbon dioxide, and then exposes the separated carbon dioxide to washing water to capture ammonia before it is discharged through the upper outlet; A concentration tower (30) that heats the washing water that has absorbed ammonia in the absorption tower (10) or regeneration tower (20) to separate it into washing water and ammonia water, and supplies the separated ammonia water to the regeneration tower (20); and A carbon dioxide capture system comprising a heat pump (100) composed of piping connecting an evaporator (101), a compressor (103), a condenser (102), and an expansion valve (104), and a refrigerant circulating through said piping, wherein the high-temperature washing water separated from the evaporator (101) and the concentration tower (30), and the high-temperature ammonia water supplied to the absorption tower (10) and the regeneration tower (20) are cooled into low-temperature washing water and low-temperature ammonia water, respectively, and the condenser (102) exchanges heat with the condensate to produce high-temperature steam or high-temperature water.

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