High-concentration carbon dioxide feed gas trapping system and trapping method

Abstract

The invention discloses a high-concentration carbon dioxide feed gas trapping system and trapping method, and belongs to the technical field of carbon dioxide trapping. Which comprises a compression device (4), carbon dioxide raw material gas is introduced into an inlet of the compression device (4), an outlet of the compression device (4) is connected with a liquefaction and purification unit, and is characterized in that the liquefaction and purification unit comprises a purification tower (15) and a carbon dioxide liquefier (20) arranged at the inlet of the purification tower (15), and is also provided with a refrigerating unit connected with the liquefaction and purification unit; a top outlet of the purifying tower (15) is connected to a high-temperature medium inlet of the tower top condenser (11); and the water chilling unit is connected to a low-temperature medium inlet of the tower top condenser (11). According to the high-concentration carbon dioxide feed gas trapping system and trapping method, the overhead condenser is arranged, and the refrigerant of the refrigerating unit is used for carrying out secondary carbon dioxide recovery on the non-condensable gas output from the top of the purifying tower, so that the recovery rate of carbon dioxide is increased.

Description

Technical Field

[0001] A high-concentration carbon dioxide raw gas capture system and capture method belong to the technical field of carbon dioxide capture. Background Art

[0002] Carbon dioxide is a gas emitted in large quantities by gas-fired power plants, coal-fired power plants, coal chemical industry and other industries. As a greenhouse gas, excessive emissions of carbon dioxide have caused the global environment to continue to warm. However, carbon dioxide is also an important chemical raw material. If the carbon dioxide in the tail gas can be captured, recycled and utilized, it can not only reduce greenhouse gas emissions, but also improve the recycling of carbon resources.

[0003] In the prior art, there are several technical solutions for capturing carbon dioxide. Among these technical solutions, a distillation tower (purification tower) is generally used to purify carbon dioxide, such as the technical solution disclosed in the Chinese invention patent with application number 202211470815.7, application date November 23, 2022, and patent name "Carbon dioxide compression device and process based on low-temperature methanol carbon washing capture process"; the technical solution disclosed in the Chinese utility model patent with application number 202122458330.3, application date October 12, 2021, and patent name "A carbon dioxide liquefaction device for carbon capture system"; and the technical solution disclosed in the Chinese invention patent with application number 202210108897.4, application date January 28, 2022, and patent name "Coal chemical carbon dioxide tail gas low-temperature capture, purification, liquefaction and separation system and method".

[0004] In the purification schemes including the above scheme, there will still be a certain concentration of carbon dioxide in the non-condensable gas output from the top of the distillation tower. If it is directly discharged, it will affect the final recovery efficiency of carbon dioxide and aggravate the greenhouse effect to a certain extent. Therefore, designing a technical solution for secondary recovery of the non-condensable gas output from the distillation tower and further utilization of the non-condensable gas has become an urgent problem to be solved in this field. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a high-concentration carbon dioxide raw gas capture system and capture method, which improves the carbon dioxide recovery rate by setting a tower top condenser and utilizing the refrigerant of a refrigeration unit to perform secondary recovery of carbon dioxide from the non-condensable gas output from the top of a purification tower.

[0006] The technical solution adopted by the present invention to solve the technical problem is: the high-concentration carbon dioxide raw gas capture system includes a compression device, the carbon dioxide raw gas is connected to the inlet of the compression device, and the outlet of the compression device is connected to the liquefaction and purification unit, characterized in that: the liquefaction and purification unit includes a purification tower and a carbon dioxide liquefier arranged at the inlet of the purification tower, and a refrigeration unit connected to the liquefaction and purification unit is also provided, the top outlet of the purification tower is connected to the high-temperature medium inlet of the tower top condenser, and the refrigeration unit is connected to the low-temperature medium inlet of the tower top condenser; The high-temperature medium outlet of the tower top condenser is connected to the expander through the tower top reflux tank, the outlet of the expander is connected to the low-temperature medium inlet of the non-condensable gas supercooler, and the low-temperature medium outlet of the non-condensable gas supercooler is connected to the low-temperature medium inlet of the carbon dioxide precooler.

[0007] Preferably, the outlet of the compression device is connected to the high-temperature medium inlet of the carbon dioxide precooler, and the high-temperature medium outlet of the carbon dioxide precooler is connected to the carbon dioxide liquefier.

[0008] Preferably, a water chiller and a drying and dehydration unit are further provided, the outlet of the compression device is connected to the inlet of the water chiller, and the outlet of the water chiller is connected to the inlet of the drying and dehydration unit.

[0009] Preferably, the outlet of the drying and dehydration unit is connected to the liquefaction and purification unit, the drying and dehydration unit includes a molecular sieve dehydration tower, the outlet of the chiller is connected to the inlet of the molecular sieve dehydration tower, the outlet of the molecular sieve dehydration tower is connected to the inlet of the dust filter, and the outlet of the dust filter is connected to the liquefaction and purification unit.

[0010] Preferably, a pipeline leads out from the inlet of the molecular sieve dehydration tower to the high-temperature medium inlet of the regeneration water cooler, the high-temperature medium outlet of the regeneration water cooler is connected to the high-temperature medium inlet of the regeneration heat exchanger, the high-temperature medium outlet of the regeneration heat exchanger is connected to the input end of the regeneration separator, and the output end of the regeneration separator is connected to the inlet of the molecular sieve dehydration tower.

[0011] Preferably, the chiller comprises a lithium bromide chiller for cooling the carbon dioxide feed gas.

[0012] Preferably, the outlet of the dust filter is divided into two routes: the first route is connected to the carbon dioxide liquefier, and the other route is connected to the first route through the heat exchange tube at the bottom of the purification tower. The low-temperature medium outlet of the carbon dioxide liquefier returns to the refrigeration unit, and the refrigerant output by the refrigeration unit is connected to the low-temperature medium inlet of the carbon dioxide liquefier.

[0013] A method for capturing high-concentration carbon dioxide raw gas, characterized in that it includes the following process: Step a: The carbon dioxide raw gas from the raw gas pipeline enters the compression device and is pressurized to medium pressure, and then sent to the liquefaction and purification unit; Step b, the carbon dioxide raw gas entering the liquefaction and purification unit is divided into two streams at the carbon dioxide liquefier: one stream enters the internal heat exchange coil at the bottom of the purification tower for tower bottom heating, and after coming out of the heat exchange coil, it is mixed with the other raw gas and then enters the carbon dioxide precooler, and the precooled raw gas enters the carbon dioxide liquefier for condensation and liquefaction; The condensed carbon dioxide gas-liquid mixed phase first enters the tower separator for gas-liquid separation, and the separated gas phase and liquid phase enter the purification tower in stages; the top condenser set at the top of the purification tower recovers the carbon dioxide in the non-condensable gas output from the top of the purification tower; the carbon dioxide liquid product with a purity of more than 99% is obtained at the bottom of the purification tower, and then it is supercooled by the non-condensable gas supercooler and output by the bottom delivery pump; Step c, the non-condensable gas output from the top of the purification tower is recovered in the top condenser and then enters the expander through the top reflux tank. The non-condensable gas converts its internal energy into mechanical energy in the expander to perform external work, thereby driving the generator set to generate electricity.

[0014] Preferably, after executing step a, the raw gas is also cooled before drying: the carbon dioxide raw gas output by the compression device is cooled to below 10° C. by a lithium bromide chiller.

[0015] Preferably, the temperature of the non-condensable gas output from the expander reaches below -50°C, and then the low-temperature non-condensable gas first enters the non-condensable gas supercooler as a low-temperature medium to cool the carbon dioxide at the bottom output end of the purification tower, and then enters the carbon dioxide precooler as a low-temperature medium to precool the carbon dioxide raw gas, and then enters the regeneration heat exchanger as a low-temperature medium to recover cold energy, and finally is connected to the exhaust gas buffer tank for exhaust gas treatment.

[0016] Compared with the prior art, the present invention has the following beneficial effects: In the high-concentration carbon dioxide raw gas capture system and capture method, a tower top condenser is provided and the refrigerant of the refrigeration unit is used to perform secondary recovery of carbon dioxide from the non-condensable gas output from the top of the purification tower, thereby improving the recovery rate of carbon dioxide.

[0017] In the present high-concentration carbon dioxide raw gas capture system and capture method, the non-condensable gas output from the top of the purification tower is first used to generate electricity through an expander, and then its low temperature is used as the low-temperature medium of the non-condensable gas supercooler, the carbon dioxide precooler and the regeneration heat exchanger in turn, thereby maximizing the utilization rate of the non-condensable gas.

[0018] The compressed and cooled carbon dioxide raw gas passes through the molecular sieve inlet buffer tank to remove mechanical impurities that may be carried in the medium, and then passes through the molecular sieve dehydration tower for adsorption and dehydration. After dehydration, the dry gas enters the post-dust filter to remove solid particles and dust that may be carried, ensuring that the impurity removal rate is 99%, and then it is output. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a process flow diagram of the high-concentration carbon dioxide raw gas capture system.

[0020] Figure 2 This is a connection diagram of the high-concentration carbon dioxide raw gas capture system.

[0021] Among them: 1. Raw gas pipeline 2, raw gas buffer tank 3, lithium bromide chiller 4, compression device 5, molecular sieve inlet buffer tank 6, molecular sieve dehydration tower 7, dust filter 8, regeneration water cooler 9, regeneration heat exchanger 10, regeneration separator 11, top condenser 12, tail gas buffer tank 13, tail gas pipeline 14, top reflux tank 15, purification tower 16, expander 17, non-condensable gas subcooler 18, bottom delivery pump 19, tower inlet separator 20, carbon dioxide liquefier 21, carbon dioxide precooler 22, carbon dioxide storage tank 23, carbon dioxide output pump. DETAILED DESCRIPTION

[0022] Figure 1~2 The best embodiment of the present invention is shown below in conjunction with the attached Figure 1~2 The present invention is further described.

[0023] like Figure 1 As shown, a high-concentration carbon dioxide raw gas capture system (hereinafter referred to as the capture system) includes a carbon dioxide compression unit, the output end of the carbon dioxide compression unit is connected to the input end of the drying and dehydration unit, the output end of the drying and dehydration unit is connected to the input end of the liquefaction and purification unit, and a lithium bromide chiller 3 is arranged between the carbon dioxide compression unit and the liquefaction and purification unit. The output end of the liquefaction and purification unit is connected to the carbon dioxide storage unit. A propylene refrigeration unit is also provided, which provides liquid or gaseous propylene for condensing carbon dioxide to the liquefaction and purification unit, and propylene circulates between the propylene refrigeration unit and the liquefaction and purification unit. The liquefaction and purification unit is also connected to the expander power generation unit, and after passing through the expander power generation unit, it is merged into the exhaust gas treatment unit together with the fresh air system.

[0024] The carbon dioxide raw gas first enters the carbon dioxide compression unit for pressurization, and then recovers waste heat and refrigerates through the lithium bromide chiller 3, and then enters drying and dehydration, liquefaction and purification in sequence, condenses and liquefies under low temperature conditions, and obtains liquid carbon dioxide products after distillation and purification. A purification tower 15 is set in the liquefaction and purification unit. The non-condensable tail gas at the top output end of the purification tower 15 first enters the expander power generation unit for expansion and power generation, and is finally discharged to the fresh air system, and enters the subsequent tail gas treatment unit with the wind discharged from the fresh air system; the qualified liquid carbon dioxide product produced at the bottom of the purification tower 15 enters the carbon dioxide storage unit for storage.

[0025] Combination Figure 2The raw gas pipeline 1 for inputting carbon dioxide raw gas is connected to the input end of the raw gas buffer tank 2, and the output end of the raw gas buffer tank 2 is connected to the input end of the compression device 4. The compression device 4 is the above-mentioned carbon dioxide compression unit, and the output end of the compression device 4 is connected to the above-mentioned lithium bromide chiller 3.

[0026] The lithium bromide chiller 3 includes a multi-stage cooler. The carbon dioxide raw gas compressed at the output end of the compression device 4 is connected to the input end of the molecular sieve inlet buffer tank 5 after multi-stage cooling. The input end of the molecular sieve inlet buffer tank 5 is connected to the molecular sieve dehydration tower 6. The outlet of the molecular sieve dehydration tower 6 is connected to the inlet of the dust filter 7.

[0027] The output end of the molecular sieve inlet buffer tank 5 is connected to the inlet of the molecular sieve dehydration tower 6, and the inlet of the molecular sieve dehydration tower 6 is connected to the regeneration water cooler 8. The gas therein is used as a high-temperature medium and is cooled for the first time in the regeneration water cooler 8. The high-temperature medium outlet of the regeneration water cooler 8 is connected to the high-temperature medium inlet of the regeneration heat exchanger 9, and the high-temperature medium outlet of the regeneration heat exchanger 9 is connected to the input end of the regeneration separator 10, and the output end of the regeneration separator 10 is connected to the inlet of the molecular sieve dehydration tower 6.

[0028] The outlet of the dust filter 7 is divided into two paths: the first path is connected to the high-temperature medium inlet of the carbon dioxide precooler 21, and the other path is connected to the heat exchange tube at the bottom of the purification tower 15 (distillation tower), and then returns to the high-temperature medium inlet of the carbon dioxide precooler 21 after being output through the heat exchange tube at the bottom of the purification tower 15. The high-temperature medium of the carbon dioxide precooler 21 is connected to the high-temperature medium inlet of the carbon dioxide liquefier 20.

[0029] The carbon dioxide gas-liquid mixed phase medium outputted from the high temperature medium outlet of the carbon dioxide liquefier 20 is connected to the inlet of the tower separator 19, and the tower separator 19 performs gas-liquid separation on the carbon dioxide gas-liquid mixed phase medium and enters the purification tower 15. A tower top condenser 11 and a tower top reflux tank 14 are arranged at the top of the purification tower 15. The tower top outlet of the purification tower 15 is connected to the high temperature medium inlet of the tower top condenser 11, and the high temperature medium outlet of the tower top condenser 11 is connected to the inlet of the tower top reflux tank 14. The outlet of the tower top reflux tank 14 is connected to the inlet of the expander 16, and the outlet of the expander 16 is connected to the low temperature medium inlet of the non-condensable gas supercooler 17. The high purity carbon dioxide outputted from the bottom of the purification tower 15 is connected to the high temperature medium inlet of the non-condensable gas supercooler 17, and the high temperature medium outlet of the non-condensable gas supercooler 17 is connected to the inlet of the tower bottom delivery pump 18, and the outlet of the tower bottom delivery pump 18 is connected to the carbon dioxide storage unit.

[0030] The low-temperature medium outlet of the non-condensable gas subcooler 17 is connected to the low-temperature medium inlet of the carbon dioxide precooler 21, and the low-temperature medium inlet of the carbon dioxide precooler 21 is connected to the low-temperature medium inlet of the regeneration heat exchanger 9. The low-temperature medium outlet of the regeneration heat exchanger 9 and the output end of the fresh air system are simultaneously connected to the inlet of the exhaust buffer tank 12, and the outlet of the exhaust buffer tank 12 leads to the exhaust pipeline 13 for exhaust treatment.

[0031] The carbon dioxide storage unit includes a carbon dioxide storage tank 22. The outlet of the tower bottom delivery pump 18 is connected to the inlet of all carbon dioxide storage tanks 22 at the same time. The outlet of all carbon dioxide storage tanks 22 is connected to the inlet of a carbon dioxide output pump 23. The carbon dioxide output pump 23 outputs the high-purity liquid carbon dioxide in the carbon dioxide storage tank 22.

[0032] The specific working process and working principle are as follows: Process 1: Compression of raw gas.

[0033] The carbon dioxide raw gas sent from the raw gas pipeline first enters the raw gas buffer tank 2 for filtration to remove solid particles that may be entrained in the incoming gas; then enters the compression device 4 for pressurization. The heat generated when the gas is compressed in the compression device 4 is taken away by the intermediate cooler matched with the compressor in the compression device 4; the terminal outlet of the compressor is connected to the lithium bromide chiller 3 for waste heat recovery.

[0034] Process 2: Cooling of raw gas before drying.

[0035] The raw gas output from the compression device 4 is cooled to below 10°C through multiple stages.

[0036] Scheme 3, adsorption process.

[0037] The compressed and cooled carbon dioxide raw gas passes through the molecular sieve inlet buffer tank 5 to remove mechanical impurities that may be carried in the medium, and then passes through the molecular sieve dehydration tower 6 for adsorption and dehydration. The dehydrated dry gas enters the post-dust filter 7 to remove solid particles and dust that may be carried, and then is output.

[0038] Process 4: Liquefaction and purification of carbon dioxide.

[0039] The carbon dioxide tail gas from the output end of the dust filter 7 is divided into two streams. One stream enters the internal heat exchange coil at the bottom of the purification tower 15 for tower bottom heating. After coming out of the heat exchange coil, it is mixed with the other raw gas and enters the carbon dioxide precooler 21. The precooled raw gas enters the carbon dioxide liquefier 20 for condensation and liquefaction.

[0040] The condensed carbon dioxide gas-liquid mixed phase first enters the tower separator 19 for gas-liquid separation, and the separated gas phase and liquid phase enter the purification tower 15 in stages. The top condenser 11 arranged at the top of the purification tower 15 further recovers the carbon dioxide in the non-condensable gas output from the top of the purification tower 15. The above-mentioned propylene refrigeration unit is a refrigeration unit that provides low-temperature medium for the carbon dioxide liquefier 20 and the top condenser 11. A carbon dioxide liquid product with a purity of more than 99% (mol) is obtained at the bottom of the purification tower 15, and is delivered to the subsequent carbon dioxide storage unit by the bottom delivery pump 18.

[0041] Process 5: Secondary utilization of non-condensable gas.

[0042] The non-condensable gas output from the top of the purification tower 15 is further recovered in the top condenser 11 and then enters the expander 16 through the top reflux tank 14. In the expander 16, the non-condensable gas expands and the pressure drops, converting the internal energy into mechanical energy to do external work, thereby driving the generator set to generate electricity.

[0043] The temperature and pressure of the non-condensable gas output from the expander 16 are reduced to below -50°C, and then the low-temperature non-condensable gas first enters the non-condensable gas supercooler 17 as a low-temperature medium to cool the carbon dioxide product output from the bottom of the purification tower 5, and then enters the carbon dioxide precooler 21 as a low-temperature medium to precool the carbon dioxide raw gas, and then enters the regeneration heat exchanger 9 as a low-temperature medium to recover cold energy, and finally connects to the outlet of the fresh air system and enters the exhaust gas buffer tank 12 for exhaust gas treatment.

[0044] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A high-concentration carbon dioxide raw gas capture system, comprising a compression device (4), wherein the carbon dioxide raw gas is connected to the inlet of the compression device (4), and the outlet of the compression device (4) is connected to a liquefaction purification unit, characterized in that: The liquefaction and purification unit comprises a purification tower (15) and a carbon dioxide liquefier (20) arranged at the inlet of the purification tower (15), and a refrigeration unit connected to the liquefaction and purification unit is also provided, the top outlet of the purification tower (15) is connected to the high-temperature medium inlet of the tower top condenser (11), and the refrigeration unit is connected to the low-temperature medium inlet of the tower top condenser (11); The high-temperature medium outlet of the tower top condenser (11) is connected to the expander (16) through the tower top reflux tank (14), the outlet of the expander (16) is connected to the low-temperature medium inlet of the non-condensable gas supercooler (17), and the low-temperature medium outlet of the non-condensable gas supercooler (17) is connected to the low-temperature medium inlet of the carbon dioxide precooler (21).

2. The high-concentration carbon dioxide raw gas capture system according to claim 1, characterized in that: The outlet of the compression device (4) is connected to the high-temperature medium inlet of the carbon dioxide precooler (21), and the high-temperature medium outlet of the carbon dioxide precooler (21) is connected to the carbon dioxide liquefier (20).

3. The high-concentration carbon dioxide raw gas capture system according to claim 1, characterized in that: A water chiller and a drying and dehydration unit are also provided, the outlet of the compression device (4) is connected to the inlet of the water chiller, and the outlet of the water chiller is connected to the inlet of the drying and dehydration unit.

4. The high-concentration carbon dioxide raw gas capture system according to claim 3, characterized in that: The outlet of the drying and dehydration unit is connected to the liquefaction and purification unit, the drying and dehydration unit comprises a molecular sieve dehydration tower (6), the outlet of the chiller is connected to the inlet of the molecular sieve dehydration tower (6), the outlet of the molecular sieve dehydration tower (6) is connected to the inlet of the dust filter (7), and the outlet of the dust filter (7) is connected to the liquefaction and purification unit.

5. The high-concentration carbon dioxide raw gas capture system according to claim 4, characterized in that: The outlet pipe at the inlet of the molecular sieve dehydration tower (6) is connected to the high-temperature medium inlet of the regeneration water cooler (8), the high-temperature medium outlet of the regeneration water cooler (8) is connected to the high-temperature medium inlet of the regeneration heat exchanger (9), the high-temperature medium outlet of the regeneration heat exchanger (9) is connected to the input end of the regeneration separator (10), and the output end of the regeneration separator (10) is connected to the inlet of the molecular sieve dehydration tower (6).

6. The high-concentration carbon dioxide raw gas capture system according to claim 3, characterized in that: The chiller includes a lithium bromide chiller (3) for cooling the carbon dioxide raw gas.

7. The high-concentration carbon dioxide raw gas capture system according to claim 4, characterized in that: The outlet of the dust filter (7) is divided into two paths: the first path is connected to the carbon dioxide liquefier (20), and the other path is connected to the first path through the heat exchange pipe at the bottom of the purification tower (15). The low-temperature medium outlet of the carbon dioxide liquefier (20) returns to the refrigeration unit, and the refrigerant output by the refrigeration unit is connected to the low-temperature medium inlet of the carbon dioxide liquefier (20).

8. A capture method using the high-concentration carbon dioxide raw gas capture system according to any one of claims 1 to 7, characterized in that: The process includes: Step a: The carbon dioxide raw gas from the raw gas pipeline enters the compression device (4) to be pressurized to medium pressure and then sent to the liquefaction purification unit; Step b, the carbon dioxide raw gas entering the liquefaction and purification unit is divided into two streams at the carbon dioxide liquefier (20): one stream enters the internal heat exchange coil at the bottom of the purification tower (15) for tower bottom heating, and after exiting the heat exchange coil, it is mixed with the other stream of raw gas and then enters the carbon dioxide precooler (21). The precooled raw gas enters the carbon dioxide liquefier (20) for condensation and liquefaction; The condensed carbon dioxide gas-liquid mixed phase first enters the tower separator (19) for gas-liquid separation, and the separated gas phase and liquid phase enter the purification tower (15) in stages; the top condenser (11) arranged at the top of the purification tower (15) recovers the carbon dioxide in the non-condensable gas output from the top of the purification tower (15); the carbon dioxide liquid product with a purity of more than 99% is obtained at the bottom of the purification tower (15), and then is supercooled by the non-condensable gas supercooler (17) and output by the bottom delivery pump (18); In step c, the non-condensable gas output from the top of the purification tower (15) is recovered in the top condenser (11) and then enters the expander (16) through the top reflux tank (14). The non-condensable gas converts its internal energy into mechanical energy in the expander (16) to perform external work, thereby driving the generator set to generate electricity.

9. The capture method according to claim 8, characterized in that: After executing step a, the raw gas is further cooled before drying: the carbon dioxide raw gas output by the compression device (4) is cooled to below 10° C. by the lithium bromide chiller (3).

10. The capture method according to claim 8, characterized in that: The temperature of the non-condensable gas output from the expander (16) reaches below -50°C, and then the low-temperature non-condensable gas first enters the non-condensable gas supercooler (17) as a low-temperature medium to cool the carbon dioxide at the bottom output end of the purification tower (15), and then enters the carbon dioxide precooler (21) as a low-temperature medium to precool the carbon dioxide raw gas, and then enters the regeneration heat exchanger (9) as a low-temperature medium to recover the cold energy, and finally connects to the tail gas buffer tank (12) for tail gas treatment.

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