CO2 refrigeration compression power-saving system

Abstract

The invention relates to the technical field of CO2 aftertreatment, and particularly discloses a CO2 refrigeration compression power-saving system which comprises a propylene compression unit, a CO2 expansion unit and a heat exchange unit, the propylene compression unit comprises a power assembly, a gas compressor and a propylene circulation assembly, and the CO2 expansion unit comprises a CO2 expansion machine, a CO2 primary heat exchange assembly and a CO2 secondary heat exchange assembly. The CO2 expansion machine is connected with the gas compressor through an overrun clutch, the heat exchange unit comprises a propylene heat exchange pipeline and a CO2 heat exchange pipeline, the propylene heat exchange pipeline is connected with the propylene circulation assembly, and the CO2 heat exchange pipeline is connected with the CO2 secondary heat exchange assembly. The medium-pressure CO2 gas generated in the low-temperature methanol washing process is subjected to expansion acting through the CO2 expansion machine, internal energy of the medium-pressure CO2 gas is converted into kinetic energy to be transmitted to the gas compressor, the gas compressor is driven to work, energy consumption of the motor is reduced, utilization of the internal energy of the medium-pressure CO2 gas in the low-temperature methanol washing process is achieved, and resource waste is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of CO2 post-processing, and particularly relates to a CO2 refrigeration compression power-saving system. BACKGROUND

[0002] Gas compression is usually driven by motor or steam turbine, steam turbine driving needs high quality steam, although the operation cost is low, but it is only suitable for steam production process, and the application range is narrow; motor driving is easy to obtain electric energy, but the cost of electric energy consumption is high.

[0003] Low temperature methanol washing uses cold methanol as an absorption solvent, and removes acid gas in raw gas by using the excellent characteristic that methanol has great solubility to acid gas at low temperature. At present, with the improvement of low temperature methanol washing desulfurization and decarburization process, the generated medium pressure CO2 gas is directly decompressed or used for power generation, which causes great waste of energy consumption.

[0004] Therefore, it is necessary to provide a CO2 refrigeration compression power-saving system to overcome the defects of the prior art. SUMMARY

[0005] The purpose of the present application is to solve the problems in the prior art, and provide a CO2 refrigeration compression power-saving system.

[0006] The technical scheme of the present application is: A CO2 refrigeration compression power-saving system, comprising a propylene compression unit, a CO2 expansion unit and a heat exchange unit, the propylene compression unit comprising a power assembly, a gas compressor and a propylene circulation assembly, the power assembly being in transmission connection with the gas compressor, the propylene circulation assembly being arranged between the inlet and the outlet of the gas compressor, the CO2 expansion unit comprising a CO2 expander, a CO2 primary heat exchange assembly and a CO2 secondary heat exchange assembly, the CO2 primary heat exchange assembly being connected with the inlet of the CO2 expander, the CO2 secondary heat exchange assembly being connected with the outlet of the CO2 expander, the CO2 expander being connected with the gas compressor through an overrunning clutch, and the heat exchange unit comprising a propylene heat exchange pipeline and a CO2 heat exchange pipeline, the propylene heat exchange pipeline being connected with the propylene circulation assembly, and the CO2 heat exchange pipeline being connected with the CO2 secondary heat exchange assembly.

[0007] Preferably, the power assembly comprises a motor and a gearbox, the output end of the motor being connected with the input end of the gearbox, and the output end of the gearbox being connected with the input end of the gas compressor.

[0008] Preferably, the propylene circulation assembly comprises a propylene circulation water cooler, a propylene buffer tank, a propylene evaporator and a propylene gas-liquid separation tank which are connected in sequence through pipelines, the propylene heat exchange pipeline is communicated on the propylene evaporator, and a propylene liquid level adjusting valve is arranged on the pipeline between the propylene buffer tank and the propylene evaporator.

[0009] Preferably, an anti-surge valve is arranged between the outlet pipeline of the gas compressor and the inlet pipeline of the gas compressor.

[0010] Preferably, the CO2 primary heat exchange assembly comprises a CO2 separation tank, a CO2 primary heat exchanger and an expander inlet pipeline, the CO2 separation tank and the CO2 primary heat exchanger are sequentially communicated and then connected to the inlet end of the CO2 expander through the expander inlet pipeline, and an expander flow regulating valve is arranged on the expander inlet pipeline.

[0011] Preferably, the CO2 secondary heat exchange assembly comprises an expander outlet pipeline and a CO2 secondary heat exchanger, the CO2 secondary heat exchanger is communicated to the outlet end of the CO2 expander through the expander outlet pipeline, a CO2 flow meter is arranged on the expander outlet pipeline, and a CO2 heat exchange pipeline is communicated to the CO2 secondary heat exchanger.

[0012] Preferably, an expander bypass pipeline is arranged between the expander inlet pipeline and the expander outlet pipeline, and an expander bypass valve is arranged on the expander bypass pipeline.

[0013] Preferably, an expander inlet shut-off valve is arranged on the expander inlet pipeline, and the expander inlet shut-off valve is electrically connected to the gas compressor.

[0014] Preferably, a methanol flow regulating valve one is arranged on the propylene heat exchange pipeline, and a methanol flow regulating valve two is arranged on the CO2 heat exchange pipeline.

[0015] Preferably, a CO2 medium-pressure pipeline is arranged on the CO2 primary heat exchanger, and a medium-pressure gas regulating valve is arranged on the CO2 medium-pressure pipeline.

[0016] Compared with the prior art, the present application has the following beneficial effects: The present application can realize the utilization of the internal energy of the medium-pressure CO2 gas generated in the low-temperature methanol washing process, avoid resource waste, and protect the gas compressor from being damaged by impact. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The figure is a structural schematic diagram of the present application.

[0018] Wherein, 1, motor; 2, gearbox; 3, gas compressor; 4, propylene circulating water cooler; 5, propylene buffer tank; 6, propylene evaporator; 7, propylene gas-liquid separation tank; 8, propylene liquid level regulating valve; 9, anti-surge valve; 10, CO2 expander; 11, CO2 separation tank; 12, CO2 primary heat exchanger; 13, expander inlet pipeline; 14, expander flow regulating valve; 15, expander outlet pipeline; 16, CO2 secondary heat exchanger; 17, CO2 flow meter; 18, expander bypass pipeline; 19, expander bypass valve; 20, expander inlet shut-off valve; 21, overrunning clutch; 22, propylene heat exchange pipeline; 23, CO2 heat exchange pipeline; 24, methanol flow regulating valve I; 25, methanol flow regulating valve II; 26, CO2 medium pressure pipeline; 27, medium pressure gas regulating valve. DETAILED DESCRIPTION

[0019] In order to make the technical means, technical features, purposes and effects of the present application easy to understand, the present application is further described below in combination with specific drawings.

[0020] As shown in Figure 1 , a CO2 refrigeration compression power saving system comprises a propylene compression unit, a CO2 expansion unit and a heat exchange unit, the propylene compression unit is drivingly connected with the CO2 expansion unit through an overrunning clutch 21, and the heat exchange unit is connected in communication with the propylene compression unit and the CO2 expansion unit respectively.

[0021] As shown in Figure 1 , the propylene compression unit comprises a power assembly, a gas compressor 3 and a propylene circulating assembly, the power assembly comprises a motor 1 and a gearbox 2, the output end of the motor 1 is connected with the input end of the gearbox 2, and the output end of the gearbox 2 is connected with the input end of the gas compressor 3; The propylene circulating assembly comprises a propylene circulating water cooler 4, a propylene buffer tank 5, a propylene evaporator 6 and a propylene gas-liquid separation tank 7, the propylene circulating water cooler 4, the propylene buffer tank 5, the propylene evaporator 6 and the propylene gas-liquid separation tank 7 are connected in sequence by pipelines between the outlet of the gas compressor 3 and the inlet of the gas compressor 3, a propylene liquid level regulating valve 8 is installed on the pipeline between the propylene buffer tank 5 and the propylene evaporator 6, and the flow of liquid propylene from the propylene buffer tank 5 into the propylene evaporator 6 is regulated through the propylene liquid level regulating valve 8; The electric motor 1 converts the low speed torque force outputted by the electric motor 1 into high speed torque force outputted by the gearbox 2, drives the gas compressor 3 to rotate at high speed, compresses the propylene gas in the gas compressor 3 by centrifugal force, and the compressed propylene gas enters the propylene circulating water cooler 4, is cooled by the propylene circulating water cooler 4, and is converted into liquid propylene, which is stored in the propylene buffer tank 5, and the amount of liquid propylene entering the propylene evaporator 6 from the propylene buffer tank 5 is controlled by the propylene liquid level regulating valve 8, the liquid propylene is gasified by heat exchange in the propylene evaporator 6, and is converted into gaseous propylene, which enters the propylene gas-liquid separation tank 7, and the separated gaseous propylene is sent to the gas compressor 3 for compression and condensation cycle; The anti-surge valve 9 is arranged between the outlet pipeline of the gas compressor 3 and the inlet pipeline of the gas compressor 3, the flow of propylene is controlled by the anti-surge valve 9, the pressure is adjusted, the surge phenomenon between the outlet and the inlet of the gas compressor 3 due to pressure fluctuation is prevented, and the stable operation and safe production of the gas compressor 3 are ensured.

[0022] As shown in Figure 1 The CO2 expansion unit includes a CO2 expander 10, a CO2 primary heat exchange assembly, and a CO2 secondary heat exchange assembly, the CO2 primary heat exchange assembly is connected with the inlet of the CO2 expander 10, and the CO2 secondary heat exchange assembly is connected with the outlet of the CO2 expander 10; The CO2 primary heat exchange assembly includes a CO2 separation tank 11, a CO2 primary heat exchanger 12, and an expander inlet pipeline 13, the CO2 separation tank 11 and the CO2 primary heat exchanger 12 are sequentially communicated, and then connected with the inlet end of the CO2 expander 10 through the expander inlet pipeline 13, the expander flow regulating valve 14 is installed on the expander inlet pipeline 13, the CO2 medium pressure pipeline 26 is connected with the CO2 primary heat exchanger 12, and the medium pressure gas regulating valve 27 is installed on the CO2 medium pressure pipeline 26; The CO2 secondary heat exchange assembly includes an expander outlet pipeline 15 and a CO2 secondary heat exchanger 16, the CO2 secondary heat exchanger 16 is communicated at the outlet end of the CO2 expander 10 through the expander outlet pipeline 15, the CO2 flow meter 17 is connected with the expander outlet pipeline 15, and the CO2 gas flow is measured by the CO2 flow meter 17 to determine whether it meets the minimum flow requirement of the CO2 expander 10; The expander bypass pipeline 18 is connected between the expander inlet pipeline 13 and the expander outlet pipeline 15, the expander bypass valve 19 is installed on the expander bypass pipeline 18, and the medium pressure CO2 gas pressure is controlled by the expander bypass valve 19 during the non-operation of the CO2 expander 10; The CO2 expander 10 is connected with the gas compressor 3 through the overrunning clutch 21; The medium-pressure, low-temperature CO2 generated by the low-temperature methanol washing process enters the CO2 separator 11 for gas-liquid separation and then enters the CO2 primary heat exchanger 12. The medium-pressure, low-temperature CO2 is heated by heat exchange with the CO2 primary heat exchanger 12 to obtain medium-pressure CO2 gas at approximately 0°C. This prevents the CO2 from sublimating and forming dry ice after entering the CO2 expander 10. The heat exchange medium in the CO2 primary heat exchanger 12 is ambient temperature shift gas or methanol. The medium-pressure CO2 gas at approximately 0°C can be directly delivered to the user through the CO2 medium-pressure pipeline 26. When the flow rate exceeds the user's demand, the expander bypass valve 19 installed on the expander bypass line 18 is opened to control and divert the medium-pressure CO2 gas at around 0°C. When the flow rate of the CO2 flow meter 17 is higher than the minimum flow rate requirement of the CO2 expander 10, the expander flow regulating valve 14 is opened to charge the CO2 expander 10 and expand to do work. At the same time, the expander bypass valve 19 needs to be closed. The medium-pressure CO2 gas at around 0°C converts its internal energy into kinetic energy through the CO2 expander 10 to drive the gas compressor 3, thereby reducing the energy consumption of the motor 1. Since the gas compressor 3 and the CO2 expander 10 are connected by an overrunning clutch 21, when the motor 1 drives the gas compressor 3 to rotate at high speed, the CO2 expander 10 will not rotate due to the action of the overrunning clutch 21. An expander inlet shut-off valve 20 is also installed on the expander inlet pipeline 13. The expander inlet shut-off valve 20 is electrically connected to the gas compressor 3. The opening condition of the expander inlet shut-off valve 20 needs to meet the requirement that the gas compressor 3 reaches a certain speed to prevent the rotation of the CO2 expander 10 from causing damage to the gearbox 2 when the gas compressor 3 is not running. Medium-pressure CO2 gas at around 0℃ is cooled and depressurized in CO2 expander 10 to obtain slightly positive pressure low-temperature CO2 gas. The slightly positive pressure low-temperature CO2 gas enters CO2 secondary heat exchanger 16 through expander outlet pipeline 15. After heat exchange and temperature rise in CO2 secondary heat exchanger 16, it is sent to subsequent processes for use.

[0023] like Figure 1 As shown, the heat exchange unit includes a propylene heat exchange pipeline 22 and a CO2 heat exchange pipeline 23, which are connected in parallel. The propylene heat exchange pipeline 22 is connected to the propylene evaporator 6, and the CO2 heat exchange pipeline 23 is connected to the CO2 secondary heat exchanger 16. In the low-temperature methanol washing process, the cooled methanol is divided into two streams and enters the propylene evaporator 6 and the CO2 secondary heat exchanger 16 respectively. A methanol flow regulating valve 1 24 is installed on the propylene heat exchange pipeline 22, and a methanol flow regulating valve 25 is installed on the CO2 heat exchange pipeline 23. The flow rate of methanol in the two streams is controlled by the methanol flow regulating valve 1 24 and the methanol flow regulating valve 25 respectively, according to the operating status of the CO2 expander 10.

[0024] The working principle of the present application is: In use, the gas compressor 3 is started and each system is ensured to be normal, the anti-surge valve 9 is in full open state, the cylinder of the gas compressor 3 is filled with propylene gas, the motor 1 is started, the motor 1 drives the gas compressor 3 to run through the gearbox 2, when the gas compressor 3 runs normally, the anti-surge valve 9 is gradually closed to increase the outlet pressure of the gas compressor 3, the high-pressure gaseous propylene is cooled by the propylene circulating water cooler 4 to obtain liquid propylene, which is gasified in the propylene evaporator 6 by heat exchange with methanol of the low-temperature methanol washing process and re-enters the gas compressor 3 for recycling; The low-temperature CO2 gas generated by the low-temperature methanol washing process is cooled by the CO2 primary heat exchanger 12 to obtain the medium-pressure CO2 gas above 0℃, the medium-pressure CO2 gas above 0℃ can be directly sent to the user through the CO2 medium-pressure pipeline 26, when the flow of the medium-pressure CO2 gas above 0℃ exceeds the demand of the user, the expander bypass valve 19 is opened to control the pressure of the medium-pressure CO2 gas above 0℃, when the flow of the CO2 flow meter 17 is higher than the minimum flow requirement of the CO2 expander 10, the expander flow regulating valve 14 is opened to drive the CO2 expander 10, and the expander bypass valve 19 is closed, the internal energy of the CO2 expander 10 is converted into kinetic energy to drive the gas compressor 3, thereby reducing the power consumption of the motor 1, and the low-temperature CO2 gas at the outlet of the CO2 expander 10 is cooled in the CO2 secondary heat exchanger 16 to recover the cooling capacity.

[0025] It should be noted that the refrigerant of the gas compressor 3 mentioned in the present application is propylene, and other refrigerants such as ammonia can also be used, the medium-pressure low-temperature CO2 gas refers to the CO2 gas at-40℃ and 0.8MPa generated in the low-temperature methanol washing process, and the low-temperature methanol washing process is a common chemical production process for desulfurization and decarburization in the process of coal-to-gas or oil-to-gas production.

[0026] The above is only the preferred embodiment of the present application, and is not intended to limit the scope of the present application. Any equivalent changes and modifications made within the scope of the present application shall be within the technical scope of the present application.

Claims

1. A CO2 refrigeration compression power saving system characterized by: The propylene compression unit, the CO2 expansion unit and the heat exchange unit, the propylene compression unit comprises a power assembly, a gas compressor (3) and a propylene circulation assembly, the power assembly is in transmission connection with the gas compressor (3), the propylene circulation assembly is arranged between the inlet and the outlet of the gas compressor (3), the CO2 expansion unit comprises a CO2 expander (10), a CO2 primary heat exchange assembly and a CO2 secondary heat exchange assembly, the CO2 primary heat exchange assembly is connected with the inlet of the CO2 expander (10), the CO2 secondary heat exchange assembly is connected with the outlet of the CO2 expander (10), the CO2 expander (10) is connected with the gas compressor (3) through an overrunning clutch (21), the heat exchange unit comprises a propylene heat exchange pipeline (22) and a CO2 heat exchange pipeline (23), the propylene heat exchange pipeline (22) is connected with the propylene circulation assembly, and the CO2 heat exchange pipeline (23) is connected with the CO2 secondary heat exchange assembly.

2. The CO2 refrigeration compression power saving system of claim 1, wherein: The power assembly comprises a motor (1) and a gearbox (2), the output end of the motor (1) is connected with the input end of the gearbox (2), and the output end of the gearbox (2) is connected with the input end of the gas compressor (3).

3. The CO2 refrigeration compression power saving system of claim 1, wherein: The propylene circulation assembly comprises a propylene circulation water cooler (4), a propylene buffer tank (5), a propylene evaporator (6) and a propylene gas-liquid separation tank (7) connected in sequence through pipelines, the propylene heat exchange pipeline (22) is communicated on the propylene evaporator (6), and a propylene liquid level adjusting valve (8) is arranged on the pipeline between the propylene buffer tank (5) and the propylene evaporator (6).

4. The CO2 refrigeration compression power saving system of claim 1, wherein: An anti-surge valve (9) is arranged between the outlet pipeline of the gas compressor (3) and the inlet pipeline of the gas compressor (3).

5. The CO2 refrigeration compression power saving system of claim 1, wherein: The CO2 primary heat exchange assembly comprises a CO2 separation tank (11), a CO2 primary heat exchanger (12) and an expander inlet pipeline (13), the CO2 separation tank (11) and the CO2 primary heat exchanger (12) are sequentially communicated and then connected with the inlet end of the CO2 expander (10) through the expander inlet pipeline (13), and an expander flow adjusting valve (14) is arranged on the expander inlet pipeline (13).

6. The CO2 refrigeration compression power saving system of claim 5, wherein: The CO2 secondary heat exchange assembly comprises an expander outlet pipeline (15) and a CO2 secondary heat exchanger (16), the CO2 secondary heat exchanger (16) is communicated on the outlet end of the CO2 expander (10) through the expander outlet pipeline (15), a CO2 flow meter (17) is arranged on the expander outlet pipeline (15), and the CO2 heat exchange pipeline (23) is communicated on the CO2 secondary heat exchanger (16).

7. The CO2 refrigeration compression power saving system of claim 6, wherein: An expander bypass pipeline (18) is arranged between the expander inlet pipeline (13) and the expander outlet pipeline (15), and an expander bypass valve (19) is arranged on the expander bypass pipeline (18).

8. The CO2 refrigeration compression power saving system of claim 5, wherein: An expander inlet cut-off valve (20) is arranged on the expander inlet pipeline (13), and the expander inlet cut-off valve (20) is electrically connected with the gas compressor (3).

9. The CO2 refrigeration compression power saving system of claim 1, wherein: The propylene heat exchange pipeline (22) is provided with a methanol flow regulating valve one (24), and the CO2 heat exchange pipeline (23) is provided with a methanol flow regulating valve two (25).

10. The CO2 refrigeration compression power saving system of claim 5, wherein: The CO2 primary heat exchanger (12) is provided with a CO2 medium-pressure pipeline (26), and the CO2 medium-pressure pipeline (26) is provided with a medium-pressure gas regulating valve (27).

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