CO2 capture and catalytic conversion integrated process based on fly ash derived catalyst

Abstract

The invention discloses a coal ash derived catalyst-based CO2 capture and catalytic conversion integrated process, which comprises a coal ash derived catalyst preparation module, a CO2 adsorption module, a CO2 desorption module, a CO2 catalytic conversion module and a gas storage tank, the coal ash derived catalyst adsorbs CO2 in flue gas in the CO2 adsorption module, adsorbate enters the CO2 desorption module to remove CO2, and the gas storage tank enters the CO2 catalytic conversion module to adsorb CO2 in the flue gas. The desorbed catalyst is returned to the CO2 adsorption module for recycling; the removed high-purity CO2 enters a CO2 catalytic conversion module to be subjected to catalytic conversion, and a product enters a gas storage tank to be stored. Compared with the prior art, the coal ash derivative catalyst is an adsorbent of an adsorption module and a catalyst of a catalytic conversion module, functional coupling of the adsorbent and the catalyst is achieved, the catalyst can be recycled, secondary pollution is avoided, and the coal ash derivative catalyst has the advantages of being low in cost and environmentally friendly; meanwhile, the energy consumption and the equipment complexity of a traditional CO2 capture and conversion separation system are reduced through process integration, and an efficient solution is provided for carbon emission reduction and recycling of industrial flue gas.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas treatment and resource utilization, and in particular to an integrated process for CO2 capture and catalytic conversion based on a fly ash-derived catalyst. Background Art

[0002] In recent years, excessive emissions of greenhouse gases such as CO2, caused by the massive combustion of fossil fuels, have had a serious impact on global climate change. Carbon dioxide capture, utilization, and storage (CCUS) technology is currently considered an effective CO2 emission reduction technology. Absorption is a relatively mature process, but the absorption process still faces challenges such as corrosion of the reaction equipment, the production of toxic byproducts, and high operating and regeneration costs. Fly ash, a solid waste generated during the combustion of coal in thermal power plants, is alkaline and contains small amounts of CaO and MgO, which react with CO2 to form carbonation. Furthermore, fly ash consists of fine, irregularly spherical powder particles with a loose, porous surface and a small specific surface area, resulting in a certain adsorption capacity. Therefore, after proper processing, fly ash can be used as a low-cost gas adsorbent. While solid adsorbents can effectively capture CO2, they also present another challenge: the adsorbed CO2 cannot be permanently stored. Therefore, timely and appropriate treatment of the adsorbed CO2 is crucial. Furthermore, in existing technologies, the adsorbent and catalyst are often used separately, resulting in bulky equipment and cumbersome operation.

[0003] Taking the above background into consideration, the present invention develops a fly ash-based catalyst that combines CO2 adsorption / desorption and catalytic conversion functions, creating a new integrated approach for CO2 adsorption / desorption and CO2 catalytic conversion into high-value fuels. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides an integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalysts. By modifying fly ash into a material with both adsorption and catalytic functions, efficient capture and resource utilization of CO2 can be achieved.

[0005] To achieve this technical purpose, the present invention adopts the following scheme: The present invention discloses an integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalysts, comprising a fly ash-derived catalyst preparation module, a CO2 adsorption module, a CO2 desorption module, a CO2 catalytic conversion module and a gas storage tank. The fly ash-derived catalyst prepared in the fly ash-derived catalyst preparation module enters the CO2 adsorption module to adsorb CO2 in the flue gas after desulfurization, denitrification and electrostatic precipitator. The adsorbate after CO2 adsorption enters the CO2 desorption module through an adsorbate transmission slide to remove CO2. The desorbed catalyst returns to the CO2 adsorption module through a fly ash-derived catalyst recycling transmission slide for recycling. The removed high-purity CO2 enters the CO2 catalytic conversion module through a high-purity CO2 inlet pipeline. After the CO2 is catalytically converted, the product enters the gas storage tank for storage.

[0006] Furthermore, the fly ash-derived catalyst used in the CO2 adsorption module and the CO2 catalytic conversion module is the same, and the fly ash-derived catalyst is Ni-based fly ash or Mn-based fly ash.

[0007] Furthermore, the preparation method of the fly ash-derived catalyst is as follows: fly ash is mixed with sodium hydroxide solution for alkali modification, filtered and washed with water until neutral, metal salt is added according to the mass ratio of metal to fly ash of 1:4 to 3:7, stirred and ultrasonically impregnated, and calcined at 500°C for 6 hours.

[0008] Furthermore, the adsorption temperature in the CO2 adsorption module is room temperature, and the adsorption capacity is greater than 3.8 mmol / g, where the adsorption capacity refers to the maximum capacity of the catalyst for the first adsorption of CO2.

[0009] Furthermore, the CO2 desorption module includes a heating device and an N2 purge system, which uses N2 to purge and desorb CO2 at 110°C, with a desorption rate of more than 90%.

[0010] Furthermore, the CO2 catalytic conversion module includes a fixed bed reactor, an H2 supply system and a temperature control device. The catalytic conversion reaction temperature is 450°C, the CO2 conversion rate is greater than 90%, the CO2 catalytic conversion products are CH4 or CO, the CH4 selectivity is greater than 84%, and the CO selectivity is greater than 61%.

[0011] Furthermore, the CO2 catalytic conversion module also includes a product separation and purification unit for separating the product and unreacted H2, wherein the product enters the gas storage tank for storage, and the H2 is recycled back to the catalytic conversion unit for reuse.

[0012] Furthermore, the fly ash-derived catalyst is recycled among the modules. The fly ash-derived catalyst used in the CO2 adsorption module can be recycled no less than 15 times, and the performance decay rate is less than 15%; the fly ash-derived catalyst used in the CO2 catalytic conversion module can be recycled no less than 7 times, and the performance decay rate is less than 18%.

[0013] Furthermore, the flue gas intake pipeline is divided into two routes, one of which is: the flue gas enters the first adsorption module through the first flue gas pipeline, the first adsorption module is pre-installed with Ni-based fly ash prepared by the first preparation module, the CO2 in the flue gas is adsorbed by the Ni-based fly ash, and the adsorbate after adsorbing CO2 enters the first desorption module through the first adsorbate transmission slide for desorption treatment, and the desorbed Ni-based fly ash returns to the first adsorption module through the first fly ash-derived catalyst transmission slide for reuse; the CO2 desorbed from the first desorption module enters the first conversion module through the first CO2 intake pipeline for catalytic conversion, the catalyst in the first conversion module is Ni-based fly ash, and the CO2 is converted into CH4 in the first conversion module, and after separation, enters the CH4 gas storage tank through the CH4 intake pipeline for storage.

[0014] Furthermore, another route is: the flue gas enters the second adsorption module through the second flue gas pipeline, the second adsorption module is pre-installed with Mn-based fly ash prepared by the second preparation module, the CO2 in the flue gas is adsorbed by the Mn-based fly ash, and the adsorbate after adsorbing CO2 enters the second desorption module through the second adsorbate transmission slide for desorption treatment, and the desorbed Mn-based fly ash returns to the second adsorption module through the second fly ash-derived catalyst transmission slide for reuse; the CO2 desorbed from the second desorption module enters the second conversion module through the second CO2 inlet pipeline for catalytic conversion, the catalyst in the second conversion module is Mn-based fly ash, and the CO2 is converted into CO in the second conversion module, and after separation, enters the CO gas storage tank through the CO inlet pipeline for storage.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention integrates CO2 capture and catalytic conversion, simplifies the process flow, and reduces equipment investment and operating costs. It utilizes industrial solid waste fly ash as raw material and, by regulating the types of loaded metal active components, achieves both resource utilization and the selective preparation of high-value fuels such as CH4 or CO. The fly ash-derived catalyst has both adsorption and catalytic functions, is recyclable, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the overall industrial process of the integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalysts in an embodiment of the present invention; The following are marked in the figure: 1. Fly ash-derived catalyst preparation module; 101. First preparation module; 102. Second preparation module; 2. CO2 adsorption module; 201. First adsorption module; 202. Second adsorption module; 3. CO2 desorption module; 301. First desorption module; 302. Second desorption module; 4. CO2 catalytic conversion module; 401. First conversion module; 402. Second conversion module; 5. CH4 gas storage tank; 6. CO gas storage tank; 7. Flue gas intake pipe; 701. First flue gas pipe; 702. Second flue gas pipe Road; 8. Fan; 9. Adsorbent transfer slide; 901. First adsorbent transfer slide; 902. Second adsorbent transfer slide; 10. High-purity CO2 inlet pipeline; 1001. First CO2 inlet pipeline; 1002. Second CO2 inlet pipeline; 11. CH4 inlet pipeline; 12. CO inlet pipeline; 13. Fly ash-derived catalyst recycling transfer slide; 1301. First fly ash-derived catalyst transfer slide; 1302. Second fly ash-derived catalyst transfer slide; 14. Electrostatic precipitator; 15. Desulfurization and denitrification tower. DETAILED DESCRIPTION

[0017] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific embodiments, but the present invention is not limited thereto.

[0018] See also Figure 1 The present invention provides an integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalysts, comprising a fly ash-derived catalyst preparation module 1, a CO2 adsorption module 2, a CO2 desorption module 3, a CO2 catalytic conversion module 4, and a gas storage tank. Flue gas generated by a desulfurization and denitrification tower 15 and an electrostatic precipitator 14 enters the CO2 adsorption module 2 via a flue gas inlet pipe 7 via a fan 8. The fly ash-derived catalyst prepared in the fly ash-derived catalyst preparation module 1 enters the CO2 adsorption module 2, adsorbing CO2 from the flue gas after desulfurization, denitrification, and electrostatic precipitator removal. The adsorbate after CO2 adsorption enters the CO2 desorption module 3 via an adsorbate transfer chute 9 for CO2 removal. The desorbed catalyst returns to the CO2 adsorption module 2 for reuse via a fly ash-derived catalyst recycling transfer chute 13. The removed high-purity CO2 enters the CO2 catalytic conversion module 4 via a high-purity CO2 inlet pipe 10. After catalytic conversion, the CO2 product enters the gas storage tank for storage.

[0019] Furthermore, the fly ash-derived catalyst used in CO2 adsorption module 2 and CO2 catalytic conversion module 4 is the same, and is either Ni-based or Mn-based. The fly ash-derived catalyst is prepared by mixing fly ash with a sodium hydroxide solution for alkali modification, filtering, and washing with water until neutral. Nickel acetate or manganese acetate is then added at a metal (Ni or Mn) to fly ash mass ratio of 1:4 to 3:7, followed by stirring and ultrasonic impregnation, and calcination at 500°C for 6 hours.

[0020] Furthermore, the CO2 adsorption module 2 includes an adsorption tower, which is equipped with a constant temperature device to maintain the adsorption temperature at room temperature. The adsorption capacity is greater than 3.8 mmol / g, where the adsorption capacity refers to the maximum capacity of the catalyst for the first adsorption of CO2.

[0021] Furthermore, the CO2 desorption module 3 includes a heating device and an N2 purge system. The fly ash-derived catalyst adsorbed to a saturated state in the CO2 adsorption module 2 is transported to the CO2 desorption module 3 through the adsorbent transfer slide 9. CO2 is desorbed by N2 purge for 10 minutes at 110°C, and the desorption rate is greater than 90%.

[0022] Furthermore, the CO2 catalytic conversion module 4 includes a fixed bed reactor, an H2 supply system and a temperature control device. The reaction temperature in the CO2 catalytic conversion module 4 is 450°C, the CO2 conversion rate is greater than 90%, the CO2 catalytic conversion products are CH4 or CO, the CH4 selectivity is greater than 84%, and the CO selectivity is greater than 61%.

[0023] The CO2 catalytic conversion module 4 also includes a product separation and purification unit for separating the product and unreacted H2, wherein the H2 is recycled back to the catalytic conversion unit for reuse, and the product enters the gas storage tank for storage.

[0024] Furthermore, the fly ash-derived catalyst can be recycled between modules. The fly ash-derived catalyst used in the CO2 adsorption module 2 can be recycled for no less than 15 times, and the performance attenuation rate is less than 15%. The fly ash-derived catalyst used in the CO2 catalytic conversion module 4 can be recycled for no less than 7 times, and the performance attenuation rate is less than 18%.

[0025] In some embodiments, the desulfurization and denitrification tower 15 and the electrostatic precipitator 14 are connected to the flue gas inlet pipeline 7 through the fan 8. The flue gas inlet pipeline 7 is divided into two paths. One path is: the flue gas after desulfurization, denitrification and electrostatic precipitator enters the first adsorption module 201 through the first flue gas pipeline 701. The first adsorption module 201 is pre-installed with Ni-based fly ash prepared by the first preparation module 101. CO2 in the flue gas is adsorbed by the Ni-based fly ash. The adsorbate after adsorbing CO2 enters the first desorption module 301 through the first adsorbate transfer slide 901 for Desorption treatment: the desorbed Ni-based fly ash is returned to the first adsorption module 201 through the first fly ash-derived catalyst transmission slide 1301 for reuse; the CO2 desorbed from the first desorption module 301 enters the first conversion module 401 through the first CO2 inlet pipeline 1001 for catalytic conversion. The catalyst in the first conversion module 401 is Ni-based fly ash. The CO2 is converted into CH4 in the first conversion module 401, and after separation, it enters the CH4 gas storage tank 5 through the CH4 inlet pipeline 11 for storage.

[0026] The other route is: the flue gas after desulfurization, denitrification and electrostatic precipitator enters the second adsorption module 202 through the second flue gas pipeline 702. The second adsorption module 202 is pre-installed with Mn-based fly ash prepared by the second preparation module 102. The CO2 in the flue gas is adsorbed by the Mn-based fly ash. The adsorbate after adsorbing CO2 enters the second desorption module 302 through the second adsorbate transfer slide 902 for desorption treatment. The desorbed Mn-based fly ash is returned to the second adsorption module 202 through the second fly ash-derived catalyst transfer slide 1302 for reuse; the CO2 removed from the second desorption module 302 enters the second conversion module 402 through the second CO2 inlet pipeline 1002 for catalytic conversion. The catalyst in the second conversion module 402 is Mn-based fly ash. The CO2 is converted into CO in the second conversion module 402, and after separation, it enters the CO gas storage tank 6 through the CO inlet pipeline 12 for storage. Example 1

[0027] An appropriate amount of fly ash was weighed and wet-milled in a ball mill. The solid-liquid mixture was dried in a drying oven. Two portions of 7g and 120-mesh ball-milled fly ash powder were sieved and added to 20ml of a pre-prepared 2mol / L NaOH solution. The mixture was stirred at 25°C for 24 hours, washed with deionized water, filtered until neutral, and dried in a drying oven at 100°C for 12 hours. 3g of nickel acetate and manganese acetate were weighed, dissolved in 20ml of deionized water at 25°C for 30 minutes, and then 7g of alkali-modified fly ash was added to each. The mixture was stirred at 25°C for 24 hours and ultrasonically impregnated in an ultrasonicator for 1 hour. The sonicated solution was dried in a drying oven at 100°C for 12 hours. The dried sample was calcined in a muffle furnace at 500°C for 6 hours. After grinding and sieving through a 120-mesh screen, the fly ash-derived catalysts (Ni-based fly ash and Mn-based fly ash) were prepared.

[0028] The fly ash-derived catalyst prepared above is loaded into the CO2 adsorption module 2 and the CO2 catalytic conversion module 4, wherein the Ni-based fly ash is loaded into the first adsorption module 201 and the first conversion module 401, and the Mn-based fly ash is loaded into the second adsorption module 202 and the second conversion module 402. The valve of the flue gas inlet pipe 7 is opened, and the coal-fired flue gas treated by the desulfurization and denitrification tower 15 and the electrostatic precipitator 14 is controlled by a mass flow meter. The CO2 concentration before and after adsorption of the fly ash-derived catalyst in the CO2 adsorption module 2, as well as the CO2 adsorption saturation time are measured using an infrared CO2 analyzer, and the adsorption efficiency of the fly ash-derived catalyst is calculated. After the fly ash-derived catalyst adsorbs CO2 to a saturated state, the valve of the flue gas inlet pipe 7 is closed, and the fly ash-derived catalyst saturated with CO2 adsorption is transported to the desorption CO2 module 3 through the adsorbent transfer slide 9. High-purity N2 is introduced, and the temperature is raised to 110°C. The adsorbent is purged for 10 minutes to remove the adsorbed CO2. The high-purity desorbed catalyst is then High-purity CO2 is introduced into the CO2 catalytic conversion module 4 (CO2 catalytic conversion module 4 is pre-equipped with a fly ash-derived catalyst; the first conversion module 401 is equipped with Ni-based fly ash, and the second conversion module 402 is equipped with Mn-based fly ash) via a high-purity CO2 inlet line 10. H2 is simultaneously introduced and heated to 450°C. The CO2 and H2 flow rates are controlled by flow meters, respectively. The catalytic treatment lasts for 20 minutes. An infrared multi-gas analyzer is used to measure the concentration of generated CH4 or CO, and the selectivity for CH4 or CO, as well as the CO2 conversion rate, is calculated. The generated CH4 is then passed through a CH4 inlet line 11 to a CH4 storage tank 5, and the generated CO is passed through a CO inlet line 12 to a CO storage tank 6. The CO2 conversion rates are all greater than 90%, the CH4 selectivity is greater than 84%, and the CO selectivity is greater than 61%.

[0029] In CO2 adsorption module 2, when the difference between the CO2 concentration at the inlet and the CO2 concentration measured at the outlet reaches zero and remains constant for a period of time, the fly ash-derived catalyst has reached saturation in its adsorption of CO2 from the flue gas. After CO2 is desorbed by CO2 desorption module 3, the fly ash-derived catalyst is returned to CO2 adsorption module 2 via fly ash-derived catalyst recycling transfer slide 13 for reuse. Measurements by an infrared CO2 analyzer show that after 15 adsorption / desorption cycles, the fly ash-derived catalyst maintains a CO2 adsorption capacity of at least 3.3 mmol / g.

[0030] In the CO2 catalytic conversion module 4, the fly ash-derived catalyst after catalysis is purged with 45% H2 / Ar mixed gas at 500°C for 60 minutes and can be reused.

[0031] The temperature, pressure, time and other parameters used in the above embodiments can be appropriately adjusted according to actual needs; the metal loading in the preparation process of the fly ash-derived catalyst can be varied in the range of 1:4 to 7:13; and the gas flow rate can be proportionally scaled up according to the scale of the reactor.

[0032] Finally, it should be noted that the above-listed embodiments are merely preferred embodiments of the present invention. Of course, those skilled in the art may make changes and modifications to the present invention. If these modifications and variations fall within the scope of the claims of the present invention and their equivalents, they should be considered to be within the scope of protection of the present invention.

Claims

1. An integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalysts, comprising a fly ash-derived catalyst preparation module, a CO2 adsorption module, a CO2 desorption module, a CO2 catalytic conversion module, and a gas storage tank, characterized in that: The fly ash-derived catalyst prepared in the fly ash-derived catalyst preparation module enters the CO2 adsorption module to adsorb CO2 in the flue gas after desulfurization, denitrification and electrostatic precipitator. The adsorbate after CO2 adsorption enters the CO2 desorption module through the adsorbate transfer slide to remove CO2. The desorbed catalyst returns to the CO2 adsorption module through the fly ash-derived catalyst recycling transfer slide for reuse; the removed high-purity CO2 enters the CO2 catalytic conversion module through the high-purity CO2 inlet pipeline. After the CO2 is catalytically converted, the product enters the gas storage tank for storage.

2. The integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalyst according to claim 1, characterized in that: The fly ash-derived catalyst used in the CO2 adsorption module and the CO2 catalytic conversion module is the same, and the fly ash-derived catalyst is Ni-based fly ash or Mn-based fly ash.

3. The integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalyst according to claim 2, characterized in that: The preparation method of fly ash-derived catalyst is as follows: fly ash is mixed with sodium hydroxide solution for alkali modification, filtered and washed with water until neutral, metal salt is added according to the mass ratio of metal to fly ash of 1:4 to 3:7, stirred and ultrasonically impregnated, and calcined at 500°C for 6 hours.

4. The integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalyst according to claim 1, characterized in that: The adsorption temperature in the CO2 adsorption module is room temperature, and the adsorption capacity is greater than 3.8 mmol / g.

5. The integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalyst according to claim 1, characterized in that: The CO2 desorption module includes a heating device and an N2 purge system. CO2 is desorbed by N2 purge at 110°C, with a desorption rate of more than 90%.

6. The integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalyst according to claim 1, characterized in that: The CO2 catalytic conversion module includes a fixed bed reactor, an H2 supply system and a temperature control device. The catalytic conversion reaction temperature is 450°C, the CO2 conversion rate is greater than 90%, and the CO2 catalytic conversion products are CH4 or CO. The CH4 selectivity is greater than 84% and the CO selectivity is greater than 61%.

7. The integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalyst according to claim 6, characterized in that: The CO2 catalytic conversion module also includes a product separation and purification unit for separating the product and unreacted H2, wherein the product enters the gas storage tank for storage and the H2 is recycled back to the catalytic conversion unit for reuse.

8. The integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalyst according to claim 1, characterized in that: The fly ash-derived catalyst is recycled among the modules. The fly ash-derived catalyst used in the CO2 adsorption module can be recycled no less than 15 times, and the performance decay rate is less than 15%; the fly ash-derived catalyst used in the CO2 catalytic conversion module can be recycled no less than 7 times, and the performance decay rate is less than 18%.

9. The integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalyst according to claim 1, characterized in that: The flue gas intake pipeline is divided into two routes. One route is: the flue gas enters the first adsorption module through the first flue gas pipeline. The first adsorption module is pre-installed with Ni-based fly ash prepared by the first preparation module. The CO2 in the flue gas is adsorbed by the Ni-based fly ash. The adsorbate after adsorbing CO2 enters the first desorption module through the first adsorbate transmission slide for desorption treatment. The desorbed Ni-based fly ash returns to the first adsorption module through the first fly ash-derived catalyst transmission slide for reuse; the CO2 desorbed from the first desorption module enters the first conversion module through the first CO2 intake pipeline for catalytic conversion. The catalyst in the first conversion module is Ni-based fly ash. CO2 is converted into CH4 in the first conversion module. After separation, it enters the CH4 gas storage tank through the CH4 intake pipeline for storage.

10. The integrated process for CO2 capture and catalytic conversion based on fly ash-derived catalyst according to claim 9, characterized in that: The other route is: the flue gas enters the second adsorption module through the second flue gas pipeline. The second adsorption module is pre-installed with Mn-based fly ash prepared by the second preparation module. The CO2 in the flue gas is adsorbed by the Mn-based fly ash. The adsorbate after adsorbing CO2 enters the second desorption module through the second adsorbate transmission slide for desorption treatment. The desorbed Mn-based fly ash returns to the second adsorption module through the second fly ash-derived catalyst transmission slide for reuse; the CO2 desorbed from the second desorption module enters the second conversion module through the second CO2 inlet pipeline for catalytic conversion. The catalyst in the second conversion module is Mn-based fly ash. The CO2 is converted into CO in the second conversion module. After separation, it enters the CO gas storage tank through the CO inlet pipeline for storage.

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