Carbon dioxide coupling trapping method

Abstract

The invention relates to a carbon dioxide coupling trapping method, which comprises the following steps: trapping carbon-containing gas for at least two times, in all carbon dioxide trapping operations, at least comprising one pressure swing adsorption trapping and one membrane separation trapping; wherein the pressure swing adsorption trapping is performed before the membrane separation trapping according to the trapping process sequence. At least two different modes of carbon dioxide capture and first pressure swing adsorption capture are arranged, no three wastes are generated in the capture process, high automation and second carbon dioxide capture can be realized, and due to the fact that one-time carbon dioxide capture is adopted before, the concentration and the cleanliness of carbon-containing gas are greatly improved, and the carbon dioxide capture efficiency is improved. Therefore, the treatment requirement of membrane separation trapping on the carbon-containing gas is met. According to the invention, two different carbon dioxide trapping modes are adopted and reasonably coupled, so that the service life of the system is ensured, the occupied area and the maintenance cost are saved, and the carbon dioxide trapping efficiency and the product gas quality are also ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field related to carbon dioxide capture and recovery, and more specifically, particularly relates to a carbon dioxide coupled capture method. Background Art

[0002] Coal-fired boiler flue gas, kiln tail gas and other exhaust gases contain a certain concentration of carbon dioxide, ranging from 8% to 80%, which is a medium-low concentration gas. Carbon dioxide gas of this concentration cannot be used directly and needs to be captured, separated, and concentrated before it can be further purified into a high-purity carbon dioxide product.

[0003] Among the traditional carbon dioxide capture methods, conventional capture methods include chemical solvent method, physical adsorption method (also known as PSA method), membrane separation method and physical absorption method. Physical absorption method, namely low-temperature methanol washing, is generally applicable to occasions where methanol products are available in the coal-to-hydrogen industry. The membrane separation method has a narrow application range and is generally used for gas clean natural gas decarbonization. The membrane cartridge in the membrane separation method has very high gas cleanliness requirements. Although it is currently also used in the field of oilfield tail gas recovery of carbon dioxide, it is limited to the experimental stage. In addition, the energy consumption of membrane separation is relatively high, the recovery rate is low, and the operating stability needs to be verified. The more mature carbon dioxide capture methods in the market are chemical solvent method and physical adsorption method. The chemical solvent method uses steam desorption. Although this method is highly efficient, the absorption liquid needs to be replenished regularly, and waste residue will also be generated. The physical adsorption method, namely the PSA method, does not produce three wastes and has a high degree of automation, but the system occupies a large area. When the scale is large, the requirements for project land will become higher accordingly. Summary of the invention

[0004] 1. Technical issues

[0005] In summary, how to provide a new type of carbon dioxide capture process to realize the coupled application of the above-mentioned multiple processes to improve the carbon dioxide capture efficiency, reduce the system scale, ensure the service life of the device, and adapt to industrial production applications has become a problem that needs to be urgently solved by technical personnel in this field.

[0006] (II) Technical solution

[0007] The present invention provides a carbon dioxide coupled capture method. In the present invention, the carbon dioxide coupled capture method comprises:

[0008] The carbon-containing gas is captured at least twice, including at least one pressure swing adsorption capture and one membrane separation capture in the entire carbon dioxide capture operation;

[0009] Among them, according to the capture process sequence, pressure swing adsorption capture is placed before membrane separation capture.

[0010] In the carbon dioxide coupled capture method provided by the present invention, the present invention is provided with at least two different modes of carbon dioxide capture. In the first (first stage) carbon dioxide capture, the present invention adopts physical pressure swing adsorption capture, which does not produce three wastes during the capture process, and can achieve a high degree of automation. Since the present invention adopts at least two different modes of capture, the scale of the pressure swing adsorption capture equipment adopted by the present invention can be appropriately reduced to half the scale of the original equipment. In the second (second stage) carbon dioxide capture, since one carbon dioxide capture was adopted before, the concentration and cleanliness of the carbon-containing gas have been greatly improved, thus meeting the requirements of membrane separation capture for the treatment of carbon-containing gas. The present invention adopts two different carbon dioxide capture modes and performs reasonable coupling, which not only ensures the life of the system, but also saves land and maintenance costs, while also ensuring the carbon dioxide capture efficiency and product gas quality.

[0011] Preferably, in the carbon dioxide coupled capture method provided by the present invention, the gas needs to be compressed before each capture operation. After the compression process, the gas pressure of the carbon-containing gas increases, which can better perform each carbon dioxide capture.

[0012] Preferably, in the carbon dioxide coupled capture method provided by the present invention, the gas is further subjected to cooling and impurity removal treatment before the gas is subjected to the capture operation. The present invention provides a pre-treatment, i.e., cooling and impurity removal treatment of the carbon-containing gas, which can make the original carbon-containing gas meet the gas processing requirements of the first stage carbon dioxide capture equipment.

[0013] Preferably, in the carbon dioxide coupled capture method provided by the present invention, product gas and other gases are generated after each capture operation. According to the capture process sequence, the product gas enters the next process, and the other gases are returned to the previous process for reprocessing, or other gases are used for nitrogen purification. After each capture process of the carbon-containing gas, the tail gas can be recycled and released to improve the capture rate of carbon dioxide.

[0014] Preferably, in the carbon dioxide coupled capture method provided by the present invention, a liquefaction and distillation operation of the product gas is further included after the membrane separation and capture process.

[0015] Preferably, in the carbon dioxide coupled capture method provided by the present invention, carbon dioxide product and pressure-side permeate gas are generated after the liquefaction and rectification operation, wherein the pressure-side permeate gas is returned to the first pressure swing adsorption capture for reprocessing.

[0016] Preferably, in the carbon dioxide coupled capture method provided by the present invention, the cooling and impurity removal treatment is water washing, cooling and impurity removal.

[0017] Preferably, in the carbon dioxide coupled capture method provided by the present invention, the gas is dried after the cooling and impurity removal treatment. After water washing, cooling and impurity removal, the carbon-containing gas will inevitably contain moisture, and the drying treatment can reduce the damage of moisture to the equipment.

[0018] Preferably, in the carbon dioxide coupled capture method provided by the present invention, the specific steps of the capture method include:

[0019] Step 1: Input the carbon-containing gas into the pretreatment unit, and the gas containing carbon dioxide is cooled and impurity-removed in the pretreatment unit;

[0020] Step 2: compressing and increasing the pressure of the gas, using the first compression system to increase the pressure of the pretreated carbon-containing gas to 0.08-1.0 MPaG;

[0021] Step 3: introducing the pressurized carbon-containing gas into a pressure swing adsorption device to capture carbon dioxide for the first carbon capture;

[0022] Step 4: The carbon-containing gas coming out of the pressure swing adsorption device (the carbon-containing gas in this step is the carbon-rich gas after being concentrated by pressure swing adsorption) is introduced into the second compression system and the pressure is increased to 0.1-1.0 MPaG;

[0023] Step 5: introducing the pressurized carbon-containing gas (the carbon-containing gas in this step is carbon-rich gas) into the membrane group to capture carbon dioxide for the second carbon capture;

[0024] Step 6: The high-concentration carbon dioxide gas obtained from the second carbon capture is introduced into the compression liquefaction distillation section to further obtain a higher purity carbon dioxide product. After the liquefaction distillation operation, the pressurized side permeate gas is returned to the first carbon capture inlet for cyclic capture.

[0025] (III) Beneficial effects

[0026] As can be seen from the above, the present invention provides a carbon dioxide coupled capture method. Specifically, the carbon dioxide coupled capture method includes: capturing carbon-containing gas at least twice, and in all carbon dioxide capture operations, at least one pressure swing adsorption capture and one membrane separation capture are included; wherein, according to the capture process sequence, the pressure swing adsorption capture is located before the membrane separation capture. The present invention is provided with at least two different modes of carbon dioxide capture. In the first pressure swing adsorption capture, no three wastes are generated during the capture process, and a high degree of automation can be achieved. In the second carbon dioxide capture, since one carbon dioxide capture is used before, the concentration and cleanliness of the carbon-containing gas are greatly improved, thus meeting the requirements for membrane separation capture to process carbon-containing gas. The present invention adopts two different carbon dioxide capture modes and couples them reasonably, which not only ensures the life of the system, but also saves land occupation and maintenance costs, while also ensuring the carbon dioxide capture efficiency and product gas quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A flowchart of the steps of a carbon dioxide coupled capture method in one embodiment of the present invention;

[0028] Figure 2 It is a system block diagram corresponding to each step of the carbon dioxide coupled capture method in one embodiment of the present invention. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] In addition, in the description of the present invention, the terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention. The terms "connected" and "connected" used in the present invention should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate component. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0031] Please refer to Figure 1 and Figure 2 ,in, Figure 1 A flowchart of the steps of a carbon dioxide coupled capture method in one embodiment of the present invention; Figure 2 It is a system block diagram corresponding to each step of the carbon dioxide coupled capture method in one embodiment of the present invention.

[0032] The object of the present invention is to provide a carbon dioxide coupled capture method to solve or alleviate the problems existing in the prior art.

[0033] In order to achieve the above object, the present invention provides the following technical solutions:

[0034] A carbon dioxide coupled capture method comprises the following steps:

[0035] The carbon-containing tail gas is input into the pretreatment unit to cool down and remove impurities, and then enters the first compression system to increase the pressure to 0.08-1.0MPaG;

[0036] The pressurized carbon-containing gas is introduced into a pressure swing adsorption device to capture carbon dioxide (first stage carbon capture);

[0037] The crude carbon dioxide gas from the pressure swing adsorption device enters the second compression system and is pressurized to 0.1-1.0 MPaG;

[0038] The pressurized crude carbon dioxide gas is introduced into the membrane group to further capture carbon dioxide (second stage carbon capture);

[0039] The high-concentration carbon dioxide gas obtained by the second stage carbon capture is introduced into the compression liquefaction distillation section to further obtain a higher purity carbon dioxide product, and the pressurized side permeate gas is returned to the first stage carbon capture inlet for cyclic capture.

[0040] In the pretreatment unit, the carbon-containing gas is cooled by water washing or heat exchange, and then enters a water removal and drying tower group composed of multiple adsorption towers. The adsorption tower is filled with desiccant, which can be molecular sieve, alumina, silica gel, etc. The incoming water-containing raw gas passes through the desiccant, and the moisture is adsorbed in the micropores of the desiccant, and the gas is dried.

[0041] The first compression system and the second compression system have basically the same structure, including a compressor and a gas-liquid separator. The compressor can be a centrifugal compressor, a blower, a screw machine or a reciprocating compressor. The gas-liquid separator adopts a device capable of gas-liquid separation, and the gas-liquid separator also has a built-in defoaming device.

[0042] In the first stage carbon capture unit, the pressurized carbon-containing gas is adsorbed. The first stage carbon capture unit consists of multiple adsorption towers filled with adsorbents to remove N2, O2, and H2O from the carbon-containing gas, and the gas is discharged from the top of the tower as vent gas and used as regeneration gas in the pretreatment stage. The product gas is naturally decompressed and desorbed or vacuum desorbed.

[0043] The first stage of carbon capture includes an adsorption tower group, valve pipelines and electronic control instruments. The adsorption tower group includes multiple parallel adsorption towers, each of which is filled with adsorbent. The valve pipeline includes multiple programmable valves, solenoid valves and flange pipelines. The electronic control instruments include temperature sensors, pressure sensors, flow meters and analyzers. The inlet of the adsorption tower group is connected to the first compression system, and the adsorption tower is connected to other parallel adsorption towers through the valve pipeline system. The top outlet of the adsorption tower is vented air, and the bottom outlet is product gas (i.e., carbon dioxide-rich gas). The bottom of the adsorption tower is connected to the carbon dioxide desorption system through the valve pipeline system.

[0044] The second stage of carbon capture includes membrane group, valve pipeline and electronic control instrument. The membrane group includes multiple parallel membrane cylinders. The valve pipeline includes multiple programmable valves, solenoid valves and flange pipelines. The electronic control instrument includes temperature sensor, pressure sensor, flow meter and analyzer. The inlet of the membrane group is connected to the second compression system, and the membrane cylinder is connected to other parallel membrane cylinders through the valve pipeline system. The permeate side of the membrane group is vented air, which returns to the first carbon capture inlet, and the retentate side of the membrane group is high-purity carbon dioxide gas. The permeate side can be output by natural gas production or vacuum extraction.

[0045] Through the above process design, the beneficial effects of the present invention are as follows:

[0046] 1. A two-stage capture method is adopted. According to the actual situation of the gas source, the first stage adopts pressure swing adsorption carbon capture, and the second stage adopts membrane separation capture. Compared with the traditional two-stage PSA carbon capture, the present invention not only ensures the life of the system, but also saves land occupation and maintenance costs;

[0047] 2. The application of valves, pipelines and electronic control instruments can make this process highly automated and produce no three wastes;

[0048] 3. The present invention can adopt natural desorption or vacuum desorption. According to the gas source conditions, the operation modes are diverse, and the recovery rate and energy consumption of carbon dioxide can be fully considered.

[0049] The specific embodiments of the present invention in the experimental stage are as follows:

[0050] It is applied to the flue gas of coal-fired boilers to capture and recover the gas with a carbon dioxide concentration of 12-14%, and the carbon dioxide gas is used to make dry ice. The composition of the flue gas is shown in Table 1.

[0051] Table 1 Composition of flue gas from coal-fired boilers

[0052] Element carbon dioxide Nitrogen oxygen water temperature Measured value 12.5％ 68.5％ 6.7％ 12.3％ 50℃

[0053] The flue gas of a coal-fired boiler at about 50°C enters the pretreatment system after induced draft, removes impurities and cools to below 40°C, and then enters the first compression system and the first carbon capture system. Under the operation of multiple adsorption towers in the first carbon capture system, the bottom of the tower continuously produces carbon dioxide-rich gas with a concentration of 40-50%, and then enters the second compression system and the second carbon capture system. After the pressurized carbon dioxide-rich gas enters the membrane group, the permeate side flows out pressurized carbon-containing venting air, which is returned to the inlet of the first carbon capture system for recycling and utilization, and the membrane cylinder retentate side produces normal pressure high-concentration carbon dioxide gas with a purity of ≥90%. In this embodiment, the carbon dioxide capture system adopts adsorption at a low pressure of 0.3MPa, and the desorbed gas adopts a vacuum pump for desorption, which not only reduces energy consumption but also improves the recovery rate of carbon dioxide.

[0054] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

Claims

1. A carbon dioxide coupled capture method, characterized in that: include: The carbon-containing gas is captured at least twice, including at least one pressure swing adsorption capture and one membrane separation capture in the entire carbon dioxide capture operation; Among them, according to the capture process sequence, pressure swing adsorption capture is placed before membrane separation capture.

2. The carbon dioxide coupled capture method according to claim 1, characterized in that: The gas needs to be compressed before each capture operation.

3. The carbon dioxide coupled capture method according to claim 1, characterized in that: Before the gas is captured, the gas is cooled and impurity removed.

4. The carbon dioxide coupled capture method according to claim 1, characterized in that: After each capture operation, product gas and other gases are generated. According to the capture process sequence, the product gas enters the next process, and other gases are returned to the previous process for reprocessing, or other gases are used for nitrogen purification.

5. The carbon dioxide coupled capture method according to claim 1, characterized in that: After the membrane separation and capture process, the product gas is also subjected to liquefaction and distillation operations.

6. The method for coupled capture of carbon dioxide according to claim 5, characterized in that: After the liquefaction and rectification operation, a carbon dioxide product and a pressure-side permeate gas are generated, wherein the pressure-side permeate gas is returned to the first pressure swing adsorption capture for reprocessing.

7. The method for coupled capture of carbon dioxide according to claim 3, characterized in that: The cooling and impurity removal treatment is water washing, cooling and impurity removal.

8. The method for coupled capture of carbon dioxide according to claim 7, characterized in that: After cooling and removing impurities, the gas is also dried.

9. The method for coupled capture of carbon dioxide according to any one of claims 1 to 8, characterized in that: include: Step 1: Input the carbon-containing gas into the pretreatment unit, and the gas containing carbon dioxide is cooled and impurity-removed in the pretreatment unit; Step 2: compressing and increasing the pressure of the gas, using the first compression system to increase the pressure of the pretreated carbon-containing gas to 0.08-1.0 MPaG; Step 3: introducing the pressurized carbon-containing gas into a pressure swing adsorption device to capture carbon dioxide for the first carbon capture; Step 4: The carbon-containing gas from the pressure swing adsorption device is introduced into the second compression system and the pressure is increased to 0.1-1.0 MPaG; Step 5: Introduce the pressurized carbon-containing gas into the membrane group to capture carbon dioxide for the second carbon capture.

10. The method for coupled capture of carbon dioxide according to claim 9, characterized in that: Also includes: Step 6: The high-concentration carbon dioxide gas obtained from the second carbon capture is introduced into the compression liquefaction distillation section to further obtain a higher purity carbon dioxide product. After the liquefaction distillation operation, the pressurized side permeate gas is returned to the first carbon capture inlet for cyclic capture.

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