A system and method for comprehensive utilization of carbon dioxide residual pressure

Abstract

The present invention relates to the technical field of carbon dioxide recovery and utilization, and in particular to a system and method for comprehensive utilization of carbon dioxide residual pressure, including a carbon dioxide emission main line connected to a synthetic ammonia system washed with low-temperature methanol, a waste heat utilization unit, a waste pressure power generation unit and a tail gas emission unit connected to the carbon dioxide emission main line, the waste heat utilization unit includes a carbon dioxide heat exchanger, a flash tank, a medium heat exchanger and a liquid storage tank connected in series in sequence, the waste pressure power generation unit includes a turbo expander, a reducer and a generator, and the tail gas emission device includes a tail gas water washing tower and an exhaust chimney. The present invention adopts the above-mentioned system and method for comprehensive utilization of carbon dioxide residual pressure, which is simple in structure, safe and reliable, easy to use, and realizes the recycling of resources.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide recovery and utilization, and in particular to a system and method for comprehensive utilization of carbon dioxide residual pressure. Background Art

[0002] A large amount of carbon dioxide will be produced in the process of coal-to-gas ammonia synthesis. The direct discharge of carbon dioxide will have an impact on the atmospheric environment. At the same time, carbon dioxide is also a resource. Reasonable use can turn waste into treasure and bring huge benefits. For example, carbon dioxide gas can be liquefied into liquid form under high pressure and low temperature. Liquid carbon dioxide is a refrigerant that can be used to preserve food and for artificial rainfall. It is also an industrial raw material that can be used to make soda ash, urea and soda. However, it can only consume part of the carbon dioxide, and the remaining carbon dioxide can only be released, resulting in a waste of resources.

[0003] At present, in the synthetic ammonia system using the low-temperature methanol washing process, the amount of carbon dioxide tail gas discharged by the low-temperature methanol washing varies according to the system capacity and production adjustment. Carbon dioxide is normally discharged after being decompressed by a pressure reducing valve. During the process of tail gas decompression, due to factors such as throttling loss, friction loss and pressure loss, energy in the tail gas is also wasted. Therefore, it is very necessary for the present invention to provide a system and method for comprehensive utilization of carbon dioxide residual pressure. Summary of the invention

[0004] The purpose of the present invention is to provide a system and method for comprehensive utilization of carbon dioxide residual pressure, which has a simple structure, is safe and reliable, and is easy to use, thereby realizing the recycling of resources.

[0005] To achieve the above-mentioned purpose, the present invention provides a system for comprehensive utilization of carbon dioxide waste pressure, including a carbon dioxide emission main line connected to a synthetic ammonia system washed with low-temperature methanol, a waste heat utilization unit, a waste pressure power generation unit and a tail gas emission unit connected to the carbon dioxide emission main line, the waste heat utilization unit includes a carbon dioxide heat exchanger, a flash tank, a medium heat exchanger and a liquid storage tank connected in series in sequence, the waste pressure power generation unit includes a turbo expander, a reducer and a generator, and the tail gas emission device includes a tail gas water washing tower and an exhaust chimney.

[0006] Preferably, the carbon dioxide emission main line is connected to the air inlet of the carbon dioxide heat exchanger, the side of the carbon dioxide emission main line close to the synthetic ammonia system for low-temperature methanol washing is connected to carbon dioxide bypass 1, and the side of the carbon dioxide emission main line close to the carbon dioxide heat exchanger is connected to carbon dioxide bypass 2.

[0007] Preferably, the carbon dioxide bypass line 1 is connected to the carbon dioxide compressor, the gas outlet line 1 of the carbon dioxide compressor is connected to the liquid carbon dioxide device, and the gas outlet line 2 of the carbon dioxide compressor is connected to the urea device.

[0008] Preferably, the carbon dioxide bypass 2 is connected to the tail gas water washing tower, and a bypass regulating valve is provided on the carbon dioxide bypass 2.

[0009] Preferably, the liquid inlet pipeline of the carbon dioxide heat exchanger is connected to the heat exchange medium storage device, the liquid outlet pipeline 1 of the carbon dioxide heat exchanger is connected to the flash tank, the flash tank is provided with a deaerator, the liquid outlet pipeline 2 of the flash tank is connected to the medium heat exchanger, the liquid outlet pipeline 3 of the medium heat exchanger is connected to the liquid storage tank, and the liquid storage tank is connected to the desalted water device.

[0010] Preferably, a circulating water inlet pipeline and a circulating water outlet pipeline are connected to the medium heat exchanger, and the circulating water outlet pipeline is connected to the heat exchange medium storage device.

[0011] Preferably, an automatic exhaust valve is provided on the side of the first liquid outlet pipeline close to the carbon dioxide heat exchanger, a medium valve is provided on the side of the first liquid outlet pipeline close to the flash tank, and a medium pump is provided on the second liquid outlet pipeline.

[0012] Preferably, the gas outlet pipeline three of the carbon dioxide heat exchanger is connected to the turbo expander, a quick-closing valve is provided on the side of the gas outlet pipeline three close to the carbon dioxide heat exchanger, a main regulating valve is provided on the side of the gas outlet pipeline three close to the turbo expander, the output end of the turbo expander is connected to the reducer, and the output end of the reducer is connected to the generator.

[0013] Preferably, the outlet pipe four of the turbo expander is connected to the side of the carbon dioxide bypass two close to the exhaust gas washing tower, the outlet pipe five of the exhaust gas washing tower is connected to the exhaust chimney, the water inlet pipe on the upper side of the exhaust gas washing tower is connected to the desalting water device, and the drain pipe at the bottom of the exhaust gas washing tower is connected to the sewage treatment device.

[0014] A method for comprehensive utilization of carbon dioxide excess pressure, using the above-mentioned system for comprehensive utilization of carbon dioxide excess pressure, specifically comprises the following steps: carbon dioxide discharged from a synthetic ammonia system washed with low-temperature methanol enters a carbon dioxide heat exchanger through a carbon dioxide emission main line for heating, the heated carbon dioxide enters a turboexpander for expansion and refrigeration, the heat energy and pressure carried by the carbon dioxide during the expansion process are converted into mechanical energy, and then a reducer is used to drive a generator to generate electricity, the heat exchange medium in the carbon dioxide heat exchanger is deoxygenated through a flash tank, and then enters a medium heat exchanger for heat exchange and cooling, the residual heat of the heat exchange medium is recycled, and the cooled heat exchange medium enters a liquid storage tank for storage.

[0015] Beneficial effects of the present invention:

[0016] (1) The system and method for comprehensive utilization of carbon dioxide excess pressure provided by the present invention utilizes an excess pressure power generation unit to replace the tail gas pressure reducing valve, which can convert the energy lost in the throttling process into electricity and recover a portion of high-quality energy, thereby reducing the enterprise's own electricity consumption and achieving the social benefits of energy conservation and emission reduction;

[0017] (2) The system and method for comprehensive utilization of carbon dioxide residual pressure provided by the present invention cooperate with the bypass regulating valve provided on the carbon dioxide bypass line 2 and the quick-closing valve provided on the gas outlet line 3. When the generator is accidentally disconnected, the exhaust gas can be cut off within no more than 1 second to prevent the generator from overspeeding. At the same time, the carbon dioxide exhaust gas can be discharged through the carbon dioxide bypass line 2 without affecting normal production.

[0018] (3) The system and method for comprehensive utilization of residual pressure of carbon dioxide provided by the present invention ensure that the temperature of carbon dioxide gas entering the residual pressure power generation unit is not too low by setting a carbon dioxide heat exchanger and using a heat exchange medium to exchange heat with carbon dioxide. A medium heat exchanger is set to continue to recover the residual temperature of the heat exchange medium through circulating water. At the same time, by setting a medium valve and an automatic exhaust valve, the heat exchange medium of the carbon dioxide heat exchanger is kept at a relatively high pressure to prevent it from being decompressed and vaporized. A small amount of gas can be automatically discharged through the automatic exhaust valve to maintain the normal operation of the carbon dioxide heat exchanger.

[0019] (4) The present invention provides a system and method for comprehensive utilization of carbon dioxide waste pressure, wherein a portion of the carbon dioxide produced by the synthetic ammonia system washed with low-temperature methanol is sent to a carbon dioxide compressor, where it can be used to produce urea and liquid carbon dioxide after conversion by the carbon dioxide compressor, and the other portion of the carbon dioxide is sent to a waste pressure power generation unit, where the heat energy and pressure it carries are converted into mechanical energy to generate electricity, thereby realizing the recovery and utilization of the waste heat and waste pressure of carbon dioxide;

[0020] (5) The system and method for comprehensive utilization of carbon dioxide excess pressure provided by the present invention have reasonable design, simple structure, safety and reliability, and are easy to use, and have great value for promotion and use.

[0021] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of a comprehensive utilization system of carbon dioxide residual pressure of the present invention.

[0023] Reference numerals:

[0024] 1. Low-temperature methanol-washed ammonia synthesis system; 2. Carbon dioxide emission main line;

[0025] 3. Waste heat utilization unit; 31. Carbon dioxide heat exchanger; 32. Flash tank; 33. Medium heat exchanger; 34. Liquid storage tank; 35. Liquid inlet pipeline; 36. Gas outlet pipeline three; 37. Quick closing valve; 38. Main regulating valve; 39. Liquid outlet pipeline one; 310. Automatic exhaust valve; 311. Medium valve; 312. Liquid outlet pipeline two; 313. Medium pump; 314. Liquid outlet pipeline three; 315. Circulating water inlet pipeline; 316. Circulating water outlet pipeline;

[0026] 4. Residual pressure power generation unit; 41. Turbo expander; 42. Speed ​​reducer; 43. Generator; 44. Gas outlet pipeline 4;

[0027] 5. Tail gas emission unit; 51. Tail gas water washing tower; 52. Exhaust chimney; 53. Water inlet pipe; 54. Drain pipe; 55. Exhaust pipe five;

[0028] 6. Carbon dioxide bypass 1; 7. Carbon dioxide compressor; 8. Gas outlet pipeline 1; 9. Gas outlet pipeline 2; 10. Carbon dioxide bypass 2; 11. Bypass regulating valve. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the accompanying drawings and embodiments. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs. The above-mentioned features or features mentioned in the specific examples mentioned in the present invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0030] Example 1

[0031] Figure 1 It is a schematic diagram of a comprehensive utilization system of carbon dioxide residual pressure of the present invention. As shown in the figure, the present invention provides a system for comprehensive utilization of carbon dioxide residual pressure, including a carbon dioxide emission main line 2 connected to a synthetic ammonia system 1 washed with low-temperature methanol, and the carbon dioxide generated by the synthetic ammonia system 1 washed with low-temperature methanol is transported through the carbon dioxide emission main line 2. The carbon dioxide emission main line 2 is connected to a waste heat utilization unit 3, a waste pressure power generation unit 4 and a tail gas emission unit 5. The waste heat utilization unit 3 cooperates with the waste pressure power generation unit 4 to recycle the waste heat and waste pressure carried by the carbon dioxide and convert them into mechanical energy to generate electricity. The setting of the tail gas emission unit 5 can discharge the carbon dioxide after comprehensive utilization, and can also directly vent the carbon dioxide. When the generator 43 is accidentally disconnected, the tail gas can be cut off within no more than 1 second to prevent the generator 43 from overspeeding. At the same time, the carbon dioxide tail gas can be vented through the carbon dioxide bypass 10 without affecting normal production.

[0032] The waste heat utilization unit 3 includes a carbon dioxide heat exchanger 31, a flash tank 32, a medium heat exchanger 33 and a liquid storage tank 34 which are connected in series in sequence. The waste pressure power generation unit 4 includes a turbo expander 41, a reducer 42 and a generator 43. The tail gas emission device includes a tail gas water washing tower 51 and an exhaust chimney 52. ​​The carbon dioxide emission main line 2 is connected to the air inlet of the carbon dioxide heat exchanger 31, and the side of the carbon dioxide emission main line 2 close to the synthetic ammonia system 1 washed with low-temperature methanol is connected to a carbon dioxide bypass 6, and the carbon dioxide bypass 6 is connected to the carbon dioxide compressor 7, and the outlet pipeline 8 of the carbon dioxide compressor 7 is connected to the liquid carbon dioxide device, and the outlet pipeline 9 of the carbon dioxide compressor 7 is connected to the urea device.

[0033] Part of the carbon dioxide produced by the low-temperature methanol-washed ammonia synthesis system 1 is sent to the carbon dioxide heat exchanger 31 through the carbon dioxide emission main line 2, and part of it is sent to the carbon dioxide compressor 7 through the carbon dioxide bypass 6. After the carbon dioxide compressor 7 increases its pressure, most of the carbon dioxide is sent to the urea unit to produce urea, and a small part of the carbon dioxide is sent to the liquid carbon dioxide unit to produce liquid carbon dioxide.

[0034] The liquid inlet pipeline 35 of the carbon dioxide heat exchanger 31 is connected to the heat exchange medium storage device, and the gas outlet pipeline 36 of the carbon dioxide heat exchanger 31 is connected to the turbo expander 41. A quick-closing valve 37 is provided on the side of the gas outlet pipeline 36 close to the carbon dioxide heat exchanger 31. The quick-closing valve 37 can quickly close the gas outlet pipeline 36, so as to quickly cut off the exhaust gas when the generator 43 is accidentally disconnected. A main regulating valve 38 is provided on the side of the gas outlet pipeline 36 close to the turbo expander 41. The main regulating valve 38 is used to adjust the flow rate of carbon dioxide. The output end of the turbo expander 41 is connected to the reducer 42, and the output end of the reducer 42 is connected to the generator 43.

[0035] The heat exchange medium storage device transports high-temperature heat exchange medium into the carbon dioxide heat exchanger 31 to heat up the carbon dioxide entering the carbon dioxide heat exchanger 31. Since the carbon dioxide discharged from the synthetic ammonia system 1 washed with low-temperature methanol has a certain stability, the required temperature can be reached in a relatively short time of heat exchange in the carbon dioxide heat exchanger 31, which reduces the load of the heat exchange medium in the carbon dioxide heat exchanger 31. The heated carbon dioxide enters the turbo expander 41 through the outlet pipe 36 for expansion and refrigeration. During the expansion process, the heat energy and pressure carried by the carbon dioxide are converted into mechanical energy, and then the reducer 42 drives the generator 43 to generate electricity.

[0036] The carbon dioxide bypass 2 10 is connected to the side of the carbon dioxide heat exchanger 31 on the carbon dioxide emission main line 2, and the carbon dioxide bypass 2 10 is connected to the tail gas water washing tower 51. The carbon dioxide bypass 2 10 is provided with a bypass regulating valve 11. The gas outlet pipeline 44 of the turbo expander 41 is connected to the side of the carbon dioxide bypass 2 10 close to the tail gas water washing tower 51, the gas outlet pipeline 55 of the tail gas water washing tower 51 is connected to the exhaust chimney 52, the water inlet pipe 53 on the upper side of the tail gas water washing tower 51 is connected to the desalted water device, and the drain pipe 54 at the bottom of the tail gas water washing tower 51 is connected to the sewage treatment device.

[0037] The pressure and temperature of the carbon dioxide recovered by the turbo expander 41 are reduced, and the low-temperature and low-pressure carbon dioxide enters the tail gas water washing tower 51, where the carbon dioxide is contacted and washed with the desalted water entering from the top of the tower, and the carbon dioxide leaving the tail gas water washing tower 51 is discharged to the exhaust chimney 52 and then vented, and the washing liquid at the bottom of the tail gas water washing tower 51 is sent to a sewage treatment device.

[0038] Open the bypass regulating valve 11 on the carbon dioxide bypass 10, and the carbon dioxide produced by the synthetic ammonia system 1 washed with low-temperature methanol can also go through the carbon dioxide bypass 10 and directly enter the tail gas water washing tower 51, so that when the generator 43 fails, the carbon dioxide entering the residual pressure power generation unit 4 can be cut off and the carbon dioxide can be directly discharged without affecting normal production.

[0039] The liquid outlet pipeline 1 39 of the carbon dioxide heat exchanger 31 is connected to the flash tank 32. An automatic exhaust valve 310 is provided on the side of the liquid outlet pipeline 1 39 close to the carbon dioxide heat exchanger 31. A medium valve 311 is provided on the side of the liquid outlet pipeline 1 39 close to the flash tank 32. By providing the medium valve 311 and the automatic exhaust valve 310, the heat exchange medium of the carbon dioxide heat exchanger 31 is kept at a relatively high pressure so as not to be decompressed and vaporized. A small amount of gas can be automatically discharged through the automatic exhaust valve 310 to maintain the normal operation of the carbon dioxide heat exchanger 31. A deaerator is provided on the flash tank 32. The liquid outlet pipeline 2 312 of the flash tank 32 is connected to the medium heat exchanger 33. A medium pump 313 is provided on the liquid outlet pipeline 2 312. The liquid outlet pipeline 3 314 of the medium heat exchanger 33 is connected to the liquid storage tank 34. The liquid storage tank 34 is connected to the desalted water device. After the heat exchange medium enters the flash tank 32 for exhaust and deoxygenation, it is transported to the medium heat exchanger 33 through the medium pump 313 for heat exchange and cooling. The medium heat exchanger 33 is connected with a circulating water inlet pipeline 315 and a circulating water outlet pipeline 316. The circulating water outlet pipeline 316 is connected with the heat exchange medium storage device. The circulating water exchanges heat with the heat exchange medium. The circulating water after heat exchange can enter the heat exchange medium storage device for heating the heat exchange medium, and the residual heat of the heat exchange medium is recycled. The heat exchange medium after cooling enters the liquid storage tank 34 for storage and can be used as a water source for the desalted water device.

[0040] Example 2

[0041] A method for comprehensive utilization of carbon dioxide residual pressure, using the system for comprehensive utilization of carbon dioxide residual pressure of Example 1, specifically comprising the following steps:

[0042] Part of the carbon dioxide discharged from the low-temperature methanol-washed ammonia system 1 is sent to the carbon dioxide heat exchanger 31 through the carbon dioxide emission main line 2, and part of it is sent to the carbon dioxide compressor 7 through the carbon dioxide bypass 6. After the carbon dioxide compressor 7 increases the pressure, most of the carbon dioxide is sent to the urea unit to produce urea, and a small part of the carbon dioxide is sent to the liquid carbon dioxide unit to produce liquid carbon dioxide.

[0043] The carbon dioxide entering the carbon dioxide heat exchanger 31 exchanges heat with the high-temperature heat exchange medium sent into the carbon dioxide heat exchanger 31 to increase its temperature. The heated carbon dioxide enters the turbo expander 41 to expand and cool. During the expansion process, the heat energy and pressure carried by the carbon dioxide are converted into mechanical energy, and then the reducer 42 drives the generator 43 to generate electricity. The pressure and temperature of the carbon dioxide recycled by the turbo expander 41 are reduced, and the low-temperature and low-pressure carbon dioxide enters the tail gas washing tower 51. In the tail gas washing tower 51, the carbon dioxide is contacted and washed with the desalted water entering the top of the tower. The carbon dioxide leaving the tail gas washing tower 51 is discharged to the exhaust chimney 52 and then emptied. The washing liquid at the bottom of the tail gas washing tower 51 is sent to the sewage treatment device.

[0044] Open the bypass regulating valve 11 on the carbon dioxide bypass 10, and the carbon dioxide produced by the synthetic ammonia system 1 washed with low-temperature methanol can also go through the carbon dioxide bypass 10 and directly enter the tail gas water washing tower 51, so that when the generator 43 fails, the carbon dioxide entering the residual pressure power generation unit 4 can be cut off and the carbon dioxide can be directly discharged without affecting normal production.

[0045] The heat exchange medium after heat exchange in the carbon dioxide heat exchanger 31 enters the flash tank 32 through the liquid outlet pipeline 39, and after exhausting steam and deoxygenating through the flash tank 32, it is transported to the medium heat exchanger 33 through the medium pump 313 for heat exchange and cooling. The medium heat exchanger 33 is connected with a circulating water inlet pipeline 315 and a circulating water outlet pipeline 316, and the circulating water outlet pipeline 316 is connected with the heat exchange medium storage device. Through the heat exchange between the circulating water and the heat exchange medium, the circulating water after heat exchange can enter the heat exchange medium storage device for heating the heat exchange medium, and the residual heat of the heat exchange medium is recycled. The heat exchange medium after cooling enters the liquid storage tank 34 for storage, and can be used as a water source for the desalted water device.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A system for comprehensive utilization of carbon dioxide residual pressure, characterized in that: It includes a carbon dioxide emission main line connected to a synthetic ammonia system washed with low-temperature methanol, and a waste heat utilization unit, a waste pressure power generation unit and a tail gas emission unit are connected on the carbon dioxide emission main line. The waste heat utilization unit includes a carbon dioxide heat exchanger, a flash tank, a medium heat exchanger and a liquid storage tank connected in series in sequence. The waste pressure power generation unit includes a turbo expander, a reducer and a generator. The tail gas emission device includes a tail gas water washing tower and an exhaust chimney; The liquid inlet pipeline of the carbon dioxide heat exchanger is connected to the heat exchange medium storage device, the gas outlet pipeline 3 of the carbon dioxide heat exchanger is connected to the turbo expander, a quick-closing valve is provided on the side of the gas outlet pipeline 3 close to the carbon dioxide heat exchanger, a main regulating valve is provided on the side of the gas outlet pipeline 3 close to the turbo expander, the output end of the turbo expander is connected to the reducer, and the output end of the reducer is connected to the generator; A carbon dioxide bypass 2 is connected to the side of the carbon dioxide heat exchanger on the carbon dioxide emission main line, and the carbon dioxide bypass 2 is connected to the exhaust gas water washing tower. A bypass regulating valve is provided on the carbon dioxide bypass 2. An outlet pipe 4 of the turboexpander is connected to the side of the carbon dioxide bypass 2 close to the exhaust gas water washing tower. An outlet pipe 5 of the exhaust gas water washing tower is connected to the exhaust chimney. The water inlet pipe on the upper side of the exhaust gas water washing tower is connected to the desalting water device, and the drain pipe at the bottom of the exhaust gas water washing tower is connected to the sewage treatment device.

2. A system for comprehensive utilization of carbon dioxide excess pressure according to claim 1, characterized in that: The carbon dioxide emission main line is connected with the air inlet of the carbon dioxide heat exchanger, and a carbon dioxide bypass line 1 is connected on one side of the carbon dioxide emission main line close to the synthetic ammonia system of low-temperature methanol washing.

3. A system for comprehensive utilization of carbon dioxide excess pressure according to claim 2, characterized in that: The carbon dioxide bypass line 1 is connected to the carbon dioxide compressor, the gas outlet line 1 of the carbon dioxide compressor is connected to the liquid carbon dioxide device, and the gas outlet line 2 of the carbon dioxide compressor is connected to the urea device.

4. The system for comprehensive utilization of carbon dioxide excess pressure according to claim 1, characterized in that: The outlet pipe 1 of the carbon dioxide heat exchanger is connected to the flash tank, which is provided with a deaerator. The outlet pipe 2 of the flash tank is connected to the medium heat exchanger. The outlet pipe 3 of the medium heat exchanger is connected to the liquid storage tank, which is connected to the desalted water device.

5. A system for comprehensive utilization of carbon dioxide excess pressure according to claim 4, characterized in that: The medium heat exchanger is connected with a circulating water inlet pipeline and a circulating water outlet pipeline, and the circulating water outlet pipeline is connected with the heat exchange medium storage device.

6. The system for comprehensive utilization of carbon dioxide excess pressure according to claim 4, characterized in that: An automatic exhaust valve is arranged on the side of the first liquid outlet pipeline close to the carbon dioxide heat exchanger, a medium valve is arranged on the side of the first liquid outlet pipeline close to the flash tank, and a medium pump is arranged on the second liquid outlet pipeline.

7. A method for comprehensive utilization of carbon dioxide excess pressure, characterized in that: The system for comprehensive utilization of carbon dioxide residual pressure using any one of claims 1 to 6 specifically comprises the following steps: carbon dioxide discharged from the synthetic ammonia system washed with low-temperature methanol enters the carbon dioxide heat exchanger through the carbon dioxide emission main line for heating, the heated carbon dioxide enters the turboexpander for expansion and refrigeration, the heat energy and pressure carried by the carbon dioxide during the expansion process are converted into mechanical energy, and then the generator is driven by the reducer to generate electricity; the heat exchange medium in the carbon dioxide heat exchanger is deoxygenated through the flash tank, and then enters the medium heat exchanger for heat exchange and cooling, the residual heat of the heat exchange medium is recycled, and the cooled heat exchange medium enters the liquid storage tank for storage.

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