Carbon dioxide drying system combining carbon capture with methanol synthesis

Abstract

The utility model discloses a carbon dioxide drying system combining carbon capture and methanol synthesis, which is characterized in that carbon dioxide gas with water vapor is firstly cooled by a heat exchanger, the cooling capacity of the heat exchanger is from heat absorbed by throttling expansion of pressurized carbon dioxide, the primarily dried gas enters a first-stage vortex compressor, the gas is pressurized to about 3MPa, and the pressure of the gas is increased to about 3MPa; according to calculation, a small amount of condensate water can be produced in the pressurization process, the condensate water is stored in a tank and discharged regularly, the pressurized carbon dioxide gas is cooled, enters a heat exchanger and is throttled to 1 MPa through throttling expansion, and it is predicted that the gas can be cooled by about 25 K, and cold energy is provided for cooling the gas in the previous step. After throttling, about 1 MPa of carbon dioxide gas enters the adsorption dryer, and due to the fact that the pressure of the carbon dioxide gas is increased, the dryer can not adopt a mode of compressed air purging regeneration and a mode of replacing air with air supplied by a carbon dioxide gas cylinder, and maintenance steps are saved.

Description

Technical Field

[0001] The utility model relates to the field of mechanical equipment, in particular to a carbon dioxide drying system for carbon capture combined with methanol synthesis. Background Art

[0002] At present, the carbon dioxide drying process used for CCUS chemical carbon capture combined with methanol synthesis in coal-fired power plants. Carbon capture is the primary link of CCUS, which mainly captures carbon dioxide from industrial waste gas and the atmosphere. The higher the carbon dioxide concentration, the lower the capture cost. According to the separation process of carbon dioxide in waste gas, carbon capture technology is mainly divided into physical absorption technology, chemical absorption technology, membrane separation technology, low-temperature separation technology, etc. Among them, membrane separation technology has the problem of high investment and immature technology. Physical absorption technology and low-temperature separation technology are suitable for industries with high carbon dioxide concentrations. The flue gas composition of coal-fired power plants contains carbon dioxide between 10% and 15%, so chemical capture is suitable for CCUS carbon capture in coal-fired power plants. In the process of combined methanol synthesis, a large amount of water vapor will be brought out after carbon dioxide is captured and released. The compressor and synthesis reaction fan in methanol synthesis are very sensitive to carbon dioxide water vapor. The dew point of carbon dioxide gas needs to be controlled below -40°C, so carbon dioxide needs to be dried before entering methanol synthesis.

[0003] The existing carbon dioxide drying adopts the mode of secondary compression of carbon dioxide after drying with a cold dryer and a low-pressure carbon dioxide adsorption dryer. In this mode, the working pressure of the low-pressure carbon dioxide adsorption dryer is low, the drying effect is not ideal, and the maintenance is complicated: cooling water, compressed air, and pure carbon dioxide cylinders need to be provided and replaced frequently, and the production cost is relatively high.

[0004] In summary, a carbon dioxide drying process and system for carbon capture combined with methanol synthesis is needed to address the deficiencies in the prior art. Utility Model Content

[0005] In view of the deficiencies in the prior art, the utility model provides a carbon dioxide drying system for carbon capture combined with methanol synthesis, aiming to solve the above problems.

[0006] To achieve the above-mentioned purpose, the utility model provides the following technical solution: it includes a heat exchanger, a vortex compressor, an adsorption dryer and a secondary compressor, an air outlet pipe is arranged between the heat exchanger and the vortex compressor, and the two ends of the air outlet pipe are respectively fixedly connected to the heat exchanger and the vortex compressor, and a return air inlet is also arranged between the vortex compressor and the heat exchanger, and the return air inlet is respectively connected to the heat exchange pipe side of the vortex compressor and the heat exchanger, a return air outlet pipe is arranged between the adsorption dryer and the heat exchanger, and the two ends of the return air outlet pipe are respectively fixedly connected to the adsorption dryer and the heat exchanger, and the secondary compressor is connected to the adsorption dryer.

[0007] Optionally, an air inlet pipe is also provided on the heat exchanger, and the air inlet pipe is fixedly connected to the heat exchanger.

[0008] Optionally, a drying air outlet pipe is provided on the adsorption dryer, and the drying air outlet pipe is fixedly connected to the adsorption dryer and the secondary compressor.

[0009] Optionally, a throttling expansion valve is provided on the heat exchanger, and the throttling expansion valve is provided between the heat exchanger and the return air inlet pipe, and the throttling expansion valve is detachably connected to the heat exchanger and the return air inlet pipe.

[0010] Optionally, the adsorption dryer includes a primary adsorption drying tank and a secondary adsorption drying tank, the primary adsorption drying tank is communicated with the secondary adsorption drying tank, the return air outlet pipe is connected to the primary adsorption drying tank, and the secondary adsorption drying tank is connected to the drying air outlet pipe.

[0011] Beneficial effects of the utility model:

[0012] 1. In the utility model, the first-stage compressor is improved and transformed to the front of the adsorption dryer and a vortex compressor is used instead, and a heat exchanger is added to replace the function of the freeze dryer;

[0013] 2. In the utility model, the carbon dioxide gas with water vapor is first cooled by the heat exchanger. The cooling capacity of the heat exchanger comes from the heat absorption of the carbon dioxide throttling expansion after pressurization. The gas after preliminary drying enters the first-stage vortex compressor, and the gas is pressurized to about 3MPa. It is calculated that a small amount of condensed water will be produced during the pressurization process, and the condensed water is stored in the tank and discharged regularly;

[0014] 3. In the utility model, the pressurized carbon dioxide gas is cooled and enters the heat exchanger to be throttled to 1MPa through throttling expansion, which is expected to reduce the temperature of the gas by about 25K and provide cold capacity to cool the gas in the previous step. The carbon dioxide gas of about 1MPa after throttling enters the adsorption dryer. Due to the increase in the pressure of carbon dioxide gas, the dryer does not need to use compressed air purge regeneration, and the carbon dioxide cylinder supplies gas to replace air, which saves maintenance steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a system structure diagram of the utility model.

[0016] Figure 2 This is a flow chart of a traditional process.

[0017] Figure 3 The utility model is a flow chart.

[0018] 1. Heat exchanger; 2. Vortex compressor; 3. Adsorption dryer; 4. Secondary compressor; 11. Air inlet pipe; 12. Air outlet pipe; 13. Throttling expansion valve; 21. Return air inlet pipe; 22. Return air outlet pipe; 31. Primary adsorption drying tank; 32. Secondary adsorption drying tank; 33. Drying outlet pipe. DETAILED DESCRIPTION

[0019] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] like Figure 1 As shown, a carbon dioxide drying system for carbon capture combined with methanol synthesis includes a heat exchanger 1, a vortex compressor 2, an adsorption dryer 3 and a secondary compressor 4. The heat exchanger 1 is provided with an air inlet pipe 11 and an air outlet pipe 12, and the air inlet pipe 11 and the air outlet pipe 12 are both fixedly connected to the heat exchanger 1, and the air outlet pipe 12 is connected to the vortex compressor 2. The vortex compressor 2 is provided with a return air inlet pipe 21, and the return air inlet pipe 21 is fixedly connected to the vortex compressor 2 and the heat exchanger 1. The heat exchanger 1 is provided with a return air outlet pipe 22, and the return air outlet pipe 22 is fixedly connected to the heat exchanger 1 and the adsorption dryer 3. The adsorption dryer 3 A drying air outlet pipe 33 is arranged on the heat exchanger 1, and the drying air outlet pipe 33 is fixedly connected to the adsorption dryer 3 and the secondary compressor 4. A throttling expansion valve 13 is arranged on the heat exchanger 1, and the throttling expansion valve 13 is arranged between the heat exchanger 1 and the return air inlet pipe 21. The throttling expansion valve 13 is detachably connected to the heat exchanger 1 and the return air inlet pipe 21. The adsorption dryer 3 includes a primary adsorption drying tank 31 and a secondary adsorption drying tank 32. The primary adsorption drying tank 31 is connected to the secondary adsorption drying tank 32. The return air outlet pipe 22 is connected to the primary adsorption drying tank 31, and the secondary adsorption drying tank 32 is connected to the drying air outlet pipe 33.

[0021] Working principle of the utility model: The carbon dioxide gas with water vapor is first cooled by the heat exchanger. The cooling capacity of the heat exchanger comes from the heat absorption by the throttling expansion of the pressurized carbon dioxide. The gas after preliminary drying enters the first-stage vortex compressor. The gas is pressurized to about 3MPa. After calculation, a small amount of condensed water will be produced during the pressurization process. The condensed water is stored in the tank and discharged regularly. The pressurized carbon dioxide gas is cooled and enters the heat exchanger to be throttled to 1MPa through throttling expansion. It is expected to cool the gas by about 25K and provide cooling capacity to cool the gas in the previous step; the carbon dioxide gas of about 1MPa after throttling enters the adsorption dryer. Due to the increase in the pressure of the carbon dioxide gas, the dryer does not need to use compressed air purge regeneration. The high-pressure carbon dioxide gas supply replaces the compressed air mode, which saves maintenance steps.

[0022] like Figure 3 As shown, a carbon dioxide drying process and system for carbon capture combined with methanol synthesis includes the following steps:

[0023] Step S1: sending the carbon dioxide gas released after carbon capture into a heat exchanger, and cooling the carbon dioxide gas in the heat exchanger;

[0024] Step S2: the carbon dioxide gas after cooling enters the scroll compressor and is pressurized in the scroll compressor. The pressure of the carbon dioxide gas after pressurization by the scroll compressor is greater than or equal to 3 MPa;

[0025] Step S3: the carbon dioxide gas pressurized by the vortex compressor is depressurized to 1 MPa through a throttling expansion valve before entering the heat exchanger, and the pressurized carbon dioxide gas is returned to the heat exchanger for cooling and heat exchange again;

[0026] Step S4: the carbon dioxide gas after cooling and heat exchange enters the adsorption dryer, and is adsorbed and dried in the adsorption dryer. The carbon dioxide after the first adsorption drying enters the second adsorption drying, and the carbon dioxide after the second adsorption drying enters the second compressor;

[0027] Step S5: the carbon dioxide gas after adsorption and drying enters the secondary compressor and is subjected to secondary pressurization and boosting in the secondary compressor;

[0028] Step S6: The carbon dioxide gas that has been pressurized for the second time enters the hydrogenation methanol synthesis reaction device.

[0029] The traditional carbon dioxide drying process is:

[0030] like Figure 2 As shown in the figure, after the chemical capture is completed, the carbon dioxide is released from the capture solvent by heating and other means, and a large amount of water vapor is brought out. The carbon dioxide gas containing water vapor enters the diaphragm compressor, which will cause damage to the compressor diaphragm. The high content of water vapor will also cause the fan of the pipeline to short-circuit and damage, and affect the subsequent methanol synthesis reaction and methanol distillation effect. Therefore, a gas drying device is added to the front end of the compressor, which includes a freeze dryer and a low-pressure adsorption dryer. The carbon dioxide gas released by the capture device at a pressure of about 10kpa is cooled and dried by the freeze dryer, and the condensed water vapor is automatically discharged through the device. The reason for adding a freeze dryer is mainly that the adsorption effect of the adsorption dryer under low pressure conditions is not ideal, and the process gas has a large water content and needs to remove part of the water vapor in advance. The gas after preliminary drying by the freeze dryer then enters the low-pressure adsorption dryer to further remove water to below the dew point of -40℃. The dryer needs to be regenerated by compressed air, and pure carbon dioxide gas needs to be purged after the regeneration stage to remove the air oxygen in the regeneration tower.

[0031] The carbon dioxide drying process of this application is:

[0032] The water content of the carbon dioxide gas after carbon capture is above 5%, and the gas pressure is between 10-20KPa. The carbon dioxide gas enters the heat exchanger, where it undergoes heat exchange and cooling. The cooled carbon dioxide gas enters the vortex compressor, which pressurizes the carbon dioxide gas to 3MPa. The pressurized carbon dioxide gas returns to the heat exchanger, and before entering the heat exchanger, the pressure of the carbon dioxide gas is expanded to 1MPa through the throttling expansion valve on the heat exchanger, where it undergoes heat exchange and cooling again.

[0033] The carbon dioxide gas after secondary heat exchange and cooling in the heat exchanger enters the adsorption dryer. The carbon dioxide first passes through the first adsorption drying tank for the first adsorption drying. The carbon dioxide gas after the first adsorption drying enters the second adsorption drying tank for the second adsorption drying. The carbon dioxide gas after the two adsorption dryings enters the secondary compressor for pressurization again. The pressurized carbon dioxide gas from the secondary compressor enters the hydrogenation synthesis methanol reaction unit.

[0034] Since the pressure of the carbon dioxide gas entering the adsorption dryer is 1MPa, which is higher than the pressure entering the dryer in the traditional process, the dryer does not need to be purged and regenerated by compressed air. In this way, the pressurized carbon dioxide gas is used instead of compressed air to purge and regenerate the adsorption dryer, which saves the maintenance steps of the adsorption dryer, reduces the drying cost of carbon dioxide, and thus saves production costs to a certain extent.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A carbon dioxide drying system for carbon capture combined with methanol synthesis, characterized in that: It includes a heat exchanger, a vortex compressor, an adsorption dryer and a secondary compressor. An air outlet pipe is arranged between the heat exchanger and the vortex compressor, and two ends of the air outlet pipe are fixedly connected to the heat exchanger and the vortex compressor respectively. A return air inlet is also arranged between the vortex compressor and the heat exchanger, and the return air inlet is respectively connected to the heat exchange pipe side of the vortex compressor and the heat exchanger. A return air outlet pipe is arranged between the adsorption dryer and the heat exchanger, and two ends of the return air outlet pipe are respectively fixedly connected to the adsorption dryer and the heat exchanger, and the secondary compressor is connected to the adsorption dryer.

2. The carbon dioxide drying system for carbon capture combined with methanol synthesis according to claim 1, characterized in that: An air inlet pipe is also arranged on the heat exchanger, and the air inlet pipe is fixedly connected to the heat exchanger.

3. The carbon dioxide drying system for carbon capture combined with methanol synthesis according to claim 1, characterized in that: The adsorption dryer is provided with a drying air outlet pipe, and the drying air outlet pipe is fixedly connected to the adsorption dryer and the secondary compressor.

4. The carbon dioxide drying system for carbon capture combined with methanol synthesis according to claim 1, characterized in that: A throttling expansion valve is arranged on the heat exchanger, and the throttling expansion valve is arranged between the heat exchanger and the return air inlet pipe. The throttling expansion valve is detachably connected to the heat exchanger and the return air inlet pipe.

5. The carbon dioxide drying system for carbon capture combined with methanol synthesis according to claim 1, characterized in that: The adsorption dryer comprises a primary adsorption drying tank and a secondary adsorption drying tank, wherein the primary adsorption drying tank is connected to the secondary adsorption drying tank, the return air outlet pipe is connected to the primary adsorption drying tank, and the secondary adsorption drying tank is connected to the dry air outlet pipe.

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