Coupling system and method for capturing carbon dioxide in flue gas and converting C4 product

Abstract

The invention discloses a coupling system and method for capturing carbon dioxide in flue gas and converting C4 products. The coupling system comprises a flue gas purification system, a CO2 trapping system and a CO2 catalytic conversion system, a regeneration tower in the trapping system is heated through flue gas waste heat in the purification system, energy is provided for regeneration of absorption liquid in rich liquid, and energy consumption of the regeneration tower is reduced; waste heat of hot barren liquor in a regeneration tower and waste heat of carbon dioxide regeneration gas at an outlet are converted into steam through a second-class absorption heat pump in the trapping system, heat energy needed by reaction is provided for fixed bed reactors in the catalytic conversion system, and finally trapped CO2 is converted into a high-added-value C4 + product in situ through the fixed bed reactors connected in series. And continuous production is realized. The whole coupling system realizes the capture and in-situ conversion of CO2 under the condition of not additionally supplying heat energy, so that the resource utilization value of CO2 is improved, the problems of high cost, high energy consumption and the like of the traditional CCUS technology are solved, and the energy conservation and consumption reduction of the whole capture and conversion system are realized.

Description

Technical Field

[0001] The present invention belongs to the field of carbon dioxide capture and conversion utilization technology and carbon dioxide emission reduction technology, and specifically relates to a coupling system and method for flue gas carbon dioxide capture and C4 product conversion. Background Art

[0002] With the rapid growth of the global population and the continuous development of industries such as power plants, cement plants, steel plants, petrochemical plants and coal chemical plants, the consumption of fossil energy has increased significantly, currently accounting for about 85% of global energy consumption, and the amount of CO2 generated has also continued to increase. CO2 is the main component of greenhouse gases, accounting for 74% of global greenhouse gas emissions. According to the Intergovernmental Panel on Climate Change (IPCC), the global average temperature has risen by about 1°C in 2017 and will rise by 1.5°C in 2040. This has had a significant impact on the high-quality development of human society. Therefore, CO2 emission reduction has become one of the major strategic issues of the international community. Carbon dioxide capture, utilization and storage technology (CCUS) is one of the effective ways to achieve carbon emission reduction in industry. This technology captures CO2 from CO2 emission sources, and then utilizes and stores it through separation, collection and compression, thereby achieving large-scale industrial carbon emission reduction.

[0003] However, the existing CO2 capture and conversion technology has the following disadvantages: In addition, the existing CO2 capture and conversion technology also has the following disadvantages:

[0004] The capture and conversion systems of CCUS technology are independent processes, resulting in high CO2 storage and transportation costs;

[0005] The chemical absorption method and solid adsorption method commonly used in CO2 capture technology both require the high-temperature flue gas to be cooled to 40-50°C before CO2 absorption and capture can be achieved. The CO2 desorption and conversion process requires the creation of a medium-to-high temperature environment (90-120°C), which will generate huge energy and heat losses, resulting in high energy consumption and high costs for CO2 capture.

[0006] The CO2 capture and conversion products are mainly C1 and C2 products. There is a lack of simple technical solutions for converting CO2 into high value-added products. In addition, electrocatalytic technology is usually used, which has complex operations and high costs, and is not conducive to large-scale production. Summary of the invention

[0007] The purpose of the present invention is to provide a coupling system and method for flue gas carbon dioxide capture and C4 product conversion in order to solve the above-mentioned problems.

[0008] The technical solution adopted by the present invention is as follows: a coupled system for flue gas carbon dioxide capture and C4 product conversion, the system comprising a flue gas purification system, a CO2 capture system and a CO2 catalytic conversion system;

[0009] The flue gas purification system is composed of a waste heat recovery device, an electrostatic precipitator and a desulfurization and denitrification tower in series;

[0010] The CO2 capture system comprises an absorption tower, a rich liquid pump, a lean and rich liquid heat exchanger, a regeneration tower, a lean liquid pump, a second type absorption heat pump, a gas-liquid separator, and a purification tower;

[0011] The CO2 catalytic conversion system comprises a raw material tank, a pressure plunger pump, a gas mixer, a fixed bed reactor, a condenser, a condensate collecting tank and a product collecting tank; wherein the fixed bed reactor is composed of a preheating tube and a catalytic reaction tube.

[0012] In a preferred embodiment, the inlet of the waste heat recovery device is connected to the flue gas, and the flue gas outlet of the waste heat recovery device is connected to the electrostatic precipitator.

[0013] In a preferred embodiment, the outlet of the electrostatic precipitator is connected to the desulfurization and denitrification tower, and the treated flue gas enters from the bottom of the absorption tower through the outlet of the desulfurization and denitrification tower, and the CO2 rich liquid flowing out from the bottom of the absorption tower enters the regeneration tower through the rich liquid pump and the lean-rich liquid heat exchanger.

[0014] In a preferred embodiment, the lean liquid outlet of the regeneration tower flows into the lean-rich liquid heat exchanger through the lean liquid pump a to exchange heat with the rich liquid, then flows into the second type absorption heat pump through the lean liquid pump b, and finally flows back to the absorption tower.

[0015] In a preferred embodiment, the regeneration gas outlet at the top of the regeneration tower is also connected to the second type of absorption heat pump, and then enters the purification tower through the gas-liquid separator.

[0016] In a preferred embodiment, the outlet of the purification tower is connected to the gas mixer through a pipeline, and the epoxide in the raw material tank flows into the preheating tube in the fixed bed reactor through a pressure plunger pump, is gasified in the preheating tube, and then enters the gas mixer together with high-purity CO2.

[0017] In a preferred embodiment, the gas mixer outlet is connected to the catalytic converter tube in the fixed bed reactor. The heat energy required by the fixed bed reactor is supplied by the high-temperature steam generated by the second type of absorption heat pump. The product of the reaction between the raw material and CO2 in the catalytic converter tube flows into the product collecting tube, and the gas flowing out with the product is condensed by the condenser and flows into the condensate collection tank.

[0018] In a preferred embodiment, the method for capturing flue gas carbon dioxide and converting C4 products comprises the following steps:

[0019] S1: Recover and purify flue gas waste heat. Most of the heat in the high-temperature flue gas is converted into steam through the waste heat recovery device to heat the rich liquid in the regeneration tower, so that the temperature in the regeneration tower is maintained at 90-120°C. The cooled flue gas after passing through the waste heat recovery device is transported to the electrostatic precipitator and desulfurization and denitrification towers in turn to remove dust and SO x and NO x ;

[0020] S2: The CO2 in the treated flue gas is captured and purified. The treated flue gas enters from the bottom of the absorption tower and is contacted with the absorption liquid entering from the top through countercurrent reaction to capture CO2. The captured cold rich liquid flows out from the bottom of the absorption tower and enters the lean-rich liquid heat exchanger to exchange heat with the hot lean liquid in the desorption regeneration tower. The obtained hot rich liquid enters the desorption regeneration tower for desorption. After desorption, regenerated gas CO2, H2O and hot lean liquid are obtained. The hot lean liquid exchanges heat with the cold rich liquid through the lean liquid pump a, and then is transported to the second type of absorption heat pump through the lean liquid pump b to obtain cold lean liquid, and the cold lean liquid flows back to the absorption tower. The regenerated gas CO2 and H2O are also cooled by the second type absorption heat pump and then pass through the gas-liquid separator to obtain high-concentration CO2. The liquid is then refluxed to the regeneration tower. The high-concentration CO2 enters the purification tower to further remove non-condensable gas and other gas impurities, thereby obtaining high-purity CO2. The second type absorption heat pump uses the heat of the hot lean liquid and the regenerated gas to produce steam with a higher temperature than the heat source, and transports it to the fixed bed reactor in the CO2 catalytic conversion system to maintain the temperature in the fixed bed reactor at around 100°C, thereby realizing the utilization of waste heat in the entire system and reducing the energy consumption of the system.

[0021] S3: CO2 is catalytically converted into high value-added C4+ products. The epoxide raw material is pumped into the preheating tube of the fixed bed reactor for gasification through a pressure plunger pump. The high-purity CO2 and the gasified epoxide gas enter the gas mixer together and are fully mixed. Then, they enter the catalytic conversion tube in the fixed bed reactor for reaction. The catalytic conversion tube is filled with a solid catalyst of SiC-supported ionic liquid. Under the action of the catalyst, the high-purity CO2 reacts with the epoxide to produce cyclic carbonates. The unreacted raw gas is then condensed and recovered through a condenser for recycling.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] 1. In the present invention, the heat of high-temperature flue gas is converted into steam through a waste heat recovery device to maintain the reaction temperature in the desorption regeneration tower, provide energy for the regeneration of the absorption liquid, reduce the energy consumption of CO2 capture, and save the capture cost; the present invention uses a second-class absorption heat pump to convert the waste heat of hot lean liquid and regeneration gas into steam to provide the fixed bed reactor in the catalytic conversion system with the heat energy required for the reaction, thereby realizing the conversion of CO2 without the need for additional energy supply.

[0024] 2. In the present invention, the in-situ production of high value-added C4+ products is achieved by connecting fixed bed reactors in series, which improves the utilization value of CO2 and solves the high cost problem of CO2 storage and transportation caused by the independent capture and conversion of CO2 in traditional CCUS technology, thereby achieving energy saving and consumption reduction of the entire capture and conversion system. The epoxide is heated and gasified by the fixed bed reactor, mixed with CO2 after gasification and then transported to the fixed bed reactor, and thermally catalytically converted into C4+ products under the action of the catalyst, thereby achieving continuous production of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a system process flow chart of the present invention;

[0026] Figure 2 It is a schematic diagram of the coupling system structure in the present invention.

[0027] Markings in the figure: 1-waste heat recovery device; 2-electrostatic precipitator; 3-desulfurization and denitrification tower; 4-absorption tower; 5-rich liquid pump; 6-lean and rich liquid heat exchange pump; 7-regeneration tower; 8-lean liquid pump a; 9-lean liquid pump b; 10-second type absorption heat pump; 11-gas-liquid separator; 12-purification tower; 13-raw material tank; 14-pressure plunger pump; 15-gas mixer; 16-fixed bed reactor; 161-preheating tube; 162-catalytic reaction tube; 17-condenser; 18-condensate collection tank; 19-product collection tank. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] Reference Figure 1-2 ,

[0030] Example:

[0031] The present invention is a coupling system and method for flue gas carbon dioxide capture and C4 product conversion, which includes a flue gas purification system, a CO2 capture system, and a CO2 catalytic conversion system. The flue gas purification system is composed of a waste heat recovery device 1, an electrostatic precipitator 2, and a desulfurization and denitrification tower 3 in series, and the CO2 capture system includes an absorption tower 4, a rich liquid pump 5, a lean and rich liquid heat exchanger 6, a regeneration tower 7, a lean liquid pump 8, a second type absorption heat pump 10, a gas-liquid separator 11, and a purification tower 12;

[0032] The CO2 catalytic conversion system includes a raw material tank 13, a pressure plunger pump 14, a gas mixer 15, a fixed bed reactor 16, a condenser 17, a condensate collecting tank 18 and a product collecting tank 19, wherein the fixed bed reactor is composed of a preheating tube 161 and a catalytic reaction tube 162.

[0033] In the entire coupling system, the flue gas is connected to the inlet of the waste heat recovery device 1, the flue gas outlet of the waste heat recovery device 1 is connected to the electrostatic precipitator 2, the high-temperature steam generated provides heat for the regeneration tower 7 through the pipeline, the outlet of the electrostatic precipitator 2 is connected to the desulfurization and denitrification tower 3, the treated flue gas enters from the bottom of the absorption tower 4 through the outlet of the desulfurization and denitrification tower, and the CO2 rich liquid flowing out from the bottom of the absorption tower enters the regeneration tower 7 through the rich liquid pump 5 and the lean-rich liquid heat exchanger 6.

[0034] The lean liquid outlet of the regeneration tower 7 flows into the lean-rich liquid heat exchanger 6 through the lean liquid pump a 8 to exchange heat with the rich liquid, and then flows into the second type absorption heat pump 10 through the lean liquid pump b 8, and finally enters the absorption tower. The regeneration gas outlet at the top of the regeneration tower 7 is also connected to the second type absorption heat pump 10.

[0035] Then it enters the purification tower 12 through the gas-liquid separator 11 to obtain high-purity CO2. The separated liquid flows back to the regeneration tower from the gas-liquid separator 11. The outlet of the purification tower is connected to the gas mixer 15 through a pipeline. The epoxide in the raw material tank 13 flows into the preheating tube 161 in the fixed bed reactor 16 through a pressure plunger pump. After being gasified in the preheating tube 161, it enters the gas mixer 15 together with the high-purity CO2. The outlet of the gas mixer is connected to the catalytic conversion tube 162 in the fixed bed reactor.

[0036] The heat energy required by the fixed bed reactor 16 is supplied by the high-temperature steam generated by the second type absorption heat pump 10. The product of the reaction between the raw material and CO2 in the catalytic conversion tube 162 flows into the product collecting pipe 19, and the gas flowing out with the product is condensed by the condenser 17 and flows into the condensate collection tank 18.

[0037] Technical solution / working and use process of the coupling system and method for flue gas carbon dioxide capture and C4 product conversion of the present invention:

[0038] The first step is to recover and purify the flue gas waste heat. Most of the heat in the high-temperature flue gas is converted into steam through the waste heat recovery device to heat the rich liquid in the regeneration tower that needs to be heated, so that the temperature in the regeneration tower is maintained at 90-120°C, thereby reducing the energy consumption of the regeneration tower. The flue gas that has been cooled after passing through the waste heat recovery device is transported to the electrostatic precipitator and desulfurization and denitrification towers in turn to remove dust and SO x and NO x .

[0039] In the second step, the CO2 in the treated flue gas is captured and purified. The treated flue gas enters the absorption tower and is mixed with the absorption liquid to capture CO2. The captured cold rich liquid flows out from the bottom of the absorption tower and enters the lean-rich liquid heat exchanger to exchange heat with the hot lean liquid in the desorption regeneration tower. The obtained hot rich liquid enters the desorption regeneration tower for desorption to obtain regenerated gas CO2, H2O and hot lean liquid. The hot lean liquid exchanges heat with the cold rich liquid through the lean liquid pump a, and then is transported to the second type of absorption heat pump through the lean liquid pump b to obtain cold lean liquid. The cold lean liquid returns to the absorption tower to be recycled and reused as a CO2 absorption capture agent. The regenerated gas CO2 and H2O are also cooled by the second type of absorption heat pump and then passed through the gas-liquid separator to obtain high-concentration CO2. The liquid then flows back to the regeneration tower. The high-concentration CO2 enters the purification tower to further remove gas impurities such as non-condensable gas, thereby obtaining high-purity CO2. The second type of absorption heat pump uses the heat of hot lean liquid and regenerated gas to produce steam with a higher temperature than the heat source, and transports it to the fixed bed reactor in the CO2 catalytic conversion system, maintaining the temperature in the fixed bed reactor at around 100°C, thereby realizing the waste heat utilization of the entire system and reducing the system energy consumption.

[0040] In the third step, CO2 is catalytically converted into high value-added C4+ products. The epoxide raw material is pumped into the preheating tube of the fixed bed reactor by a pressure plunger pump for gasification. The high-purity CO2 and the gasified epoxide gas enter the gas mixer together and are fully mixed. Then, they enter the catalytic conversion tube in the fixed bed reactor for reaction. The catalytic conversion tube is filled with a solid catalyst of SiC-supported ionic liquid. Under the action of the catalyst, high-purity CO2 reacts with epoxide to produce cyclic carbonates. The unreacted raw gas is then condensed and recovered through a condenser for recycling.

[0041] In the present invention, the heat of the high-temperature flue gas is converted into steam through a waste heat recovery device to maintain the reaction temperature in the desorption regeneration tower, provide energy for the regeneration of the absorption liquid, reduce the energy consumption of CO2 capture, and save the capture cost; the present invention uses a second-type absorption heat pump to convert the waste heat of the hot lean liquid and the regenerated gas into steam to provide the fixed bed reactor in the catalytic conversion system with the thermal energy required for the reaction, thereby realizing the conversion of CO2 without the need for additional energy supply.

[0042] In the present invention, the in-situ continuous production of high value-added C4+ products is achieved by connecting fixed bed reactors in series, the utilization value of CO2 is improved, and the high cost problem of CO2 storage and transportation caused by the independent capture and conversion of CO2 in traditional CCUS technology is solved, thereby achieving energy saving and consumption reduction of the entire capture and conversion system. The epoxide is heated and gasified by the fixed bed reactor, mixed with CO2 after gasification and then transported to the fixed bed reactor, and thermally catalytically converted into C4+ products under the action of the catalyst, thereby achieving continuous production of the product.

[0043] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0044] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A coupled system for flue gas carbon dioxide capture and C4 product conversion, characterized by: The system includes a flue gas purification system, a CO2 capture system and a CO2 catalytic conversion system; The flue gas purification system is composed of a waste heat recovery device (1), an electrostatic precipitator (2) and a desulfurization and denitrification tower (3) connected in series; The CO2 capture system comprises an absorption tower (4), a rich liquid pump (5), a lean and rich liquid heat exchanger (6), a regeneration tower (7), a lean liquid pump (8), a second type absorption heat pump (10), a gas-liquid separator (11), and a purification tower (12); The CO2 catalytic conversion system comprises a raw material tank (13), a pressure plunger pump (14), a gas mixer (15), a fixed bed reactor (16), a condenser (17), a condensate collection tank (18) and a product collection tank (19); wherein the fixed bed reactor is composed of a preheating tube (161) and a catalytic reaction tube (162).

2. A coupled system for flue gas carbon dioxide capture and C4 product conversion as claimed in claim 1, characterized in that: The inlet of the waste heat recovery device (1) is connected to the flue gas, and the flue gas outlet of the waste heat recovery device (1) is connected to the electrostatic precipitator (2).

3. A coupled system for flue gas carbon dioxide capture and C4 product conversion as claimed in claim 1, characterized in that: The outlet of the electrostatic precipitator (2) is connected to the desulfurization and denitrification tower (3), and the treated flue gas enters from the bottom of the absorption tower (4) through the outlet of the desulfurization and denitrification tower. The CO2 rich liquid flowing out from the bottom of the absorption tower enters the regeneration tower (7) through the rich liquid pump (5) and the lean rich liquid heat exchanger (6).

4. A coupled system for flue gas carbon dioxide capture and C4 product conversion as claimed in claim 1, characterized in that: The lean liquid outlet of the regeneration tower (7) flows into the lean-rich liquid heat exchanger (6) through the lean liquid pump a (8) to exchange heat with the rich liquid, then flows into the second type absorption heat pump (10) through the lean liquid pump b (8), and finally enters the absorption tower.

5. A coupled system for flue gas carbon dioxide capture and C4 product conversion as claimed in claim 1, characterized in that: The regeneration gas outlet at the top of the regeneration tower (7) is also connected to the second type absorption heat pump (10), and then enters the purification tower (12) through the gas-liquid separator (11).

6. A coupled system for flue gas carbon dioxide capture and C4 product conversion as claimed in claim 1, characterized in that: The outlet of the purification tower is connected to the gas mixer (15) through a pipeline, and the epoxide in the raw material tank (13) flows into the preheating tube (161) in the fixed bed reactor (16) through a pressure plunger pump, and then enters the gas mixer (15) together with high-purity CO2 after being gasified in the preheating tube (161).

7. A coupled system for flue gas carbon dioxide capture and C4 product conversion as claimed in claim 1, characterized in that: The outlet of the gas mixer is connected to the catalytic converter tube (162) in the fixed bed reactor. The heat energy required by the fixed bed reactor (16) is supplied by the high-temperature steam generated by the second type absorption heat pump (10). The product of the reaction between the raw material and CO2 in the catalytic converter tube (162) flows into the product collection tube (19), and the gas flowing out with the product is condensed by the condenser (17) and flows into the condensate collection tank (18).

8. The method for capturing flue gas carbon dioxide and converting C4 products according to claim 1, characterized in that: The method comprises the following steps: S1: Recover and purify flue gas waste heat. Most of the heat in the high-temperature flue gas is converted into steam through the waste heat recovery device to heat the rich liquid in the regeneration tower, so that the temperature in the regeneration tower is maintained at 90-120°C. The cooled flue gas after passing through the waste heat recovery device is transported to the electrostatic precipitator and desulfurization and denitrification towers in turn to remove dust and SO x and NO x ; S2: The CO2 in the treated flue gas is captured and purified. The treated flue gas enters from the bottom of the absorption tower and is contacted with the absorption liquid entering from the top through countercurrent reaction to capture CO2. The captured cold rich liquid flows out from the bottom of the absorption tower and enters the lean-rich liquid heat exchanger to exchange heat with the hot lean liquid in the desorption regeneration tower. The obtained hot rich liquid enters the desorption regeneration tower for desorption. After desorption, regenerated gas CO2, H2O and hot lean liquid are obtained. The hot lean liquid exchanges heat with the cold rich liquid through the lean liquid pump a, and then is transported to the second type of absorption heat pump through the lean liquid pump b to obtain cold lean liquid, and the cold lean liquid flows back to the absorption tower. The regenerated gas CO2 and H2O are also cooled by the second type absorption heat pump and then pass through the gas-liquid separator to obtain high-concentration CO2. The liquid is then refluxed to the regeneration tower. The high-concentration CO2 enters the purification tower to further remove non-condensable gas and other gas impurities, thereby obtaining high-purity CO2. The second type absorption heat pump uses the heat of the hot lean liquid and the regenerated gas to produce steam with a higher temperature than the heat source, and transports it to the fixed bed reactor in the CO2 catalytic conversion system to maintain the temperature in the fixed bed reactor at around 100°C, thereby realizing the utilization of waste heat in the entire system and reducing the energy consumption of the system. S3: CO2 is catalytically converted into high value-added C4+ products. The epoxide raw material is pumped into the preheating tube of the fixed bed reactor for gasification through a pressure plunger pump. The high-purity CO2 and the gasified epoxide gas enter the gas mixer together and are fully mixed. Then, they enter the catalytic conversion tube in the fixed bed reactor for reaction. The catalytic conversion tube is filled with a solid catalyst of SiC-supported ionic liquid. Under the action of the catalyst, the high-purity CO2 reacts with the epoxide to produce cyclic carbonates. The unreacted raw gas is then condensed and recovered through a condenser for recycling.

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