A method for preparing a CO2 trapping agent based on a dual solid waste composition of coal gangue and fly ash, and the trapping agent itself.

Abstract

This invention belongs to the field of CO2 trapping agent preparation technology, specifically a method for preparing a CO2 trapping agent from coal gangue and fly ash dual solid wastes, and the CO2 trapping agent itself. The method includes the following steps: S1: Using coal gangue and fly ash as mixed solid waste raw materials, a mixed solution of sodium silicate and sodium aluminate is obtained through ultrasonic-assisted alkali dissolution treatment; S2: The sodium silicate and sodium aluminate mixed solution is mixed with a calcium source and subjected to microwave hydrothermal reaction to obtain a modified hydrated gel carrier; S3: Using ethanol as an azeotropic solvent, polyethyleneimine is loaded onto the dried modified hydrated gel carrier using an azeotropic method, and the CO2 trapping agent is obtained after vacuum drying. This invention uses industrial solid waste as the main raw material, which not only significantly reduces raw material costs but also achieves high-value resource utilization of solid waste, possessing significant environmental benefits and promising prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of CO2 trapping agent preparation technology, specifically a preparation method and trapping agent of a "coal gangue + fly ash" dual solid waste-based CO2 trapping agent. Background Technology

[0002] With the continuous adjustment of the global energy structure and the deepening of industrialization, the large-scale combustion of fossil fuels has led to a sharp increase in carbon dioxide (CO2) emissions, causing severe environmental problems such as the greenhouse effect and ocean acidification. To address this challenge and achieve the goals of "carbon peaking" and "carbon neutrality," carbon capture, utilization, and storage (CCUS) technology has become a core means of industrial emission reduction. Among existing capture technologies, chemical absorption, although a mature process, suffers from drawbacks such as high regeneration energy consumption and severe equipment corrosion; membrane separation is limited by the lifespan and separation efficiency of membrane modules; while pressure swing adsorption (PSA) technology, with its advantages of low energy consumption, minimal modification to existing facilities, and stable product gas quality, has become a capture solution with great application potential. However, the core of PSA technology's effectiveness lies in the capture agent material itself, whose performance directly determines the economics and feasibility of carbon capture.

[0003] Currently, the preparation of mainstream CO2 traps, such as calcium-based, lithium-based oxides, and biomass-derived carbon materials, mainly employs sol-gel methods, high-temperature solid-state methods, hydrothermal synthesis methods, or conventional alkaline dissolution methods. Although these methods have achieved certain results in laboratory and small-scale applications, they still face significant bottlenecks in actual industrial application: low mass transfer efficiency and long reaction times; uneven distribution and agglomeration of active components; structural defects caused by high-temperature treatment; high solvent consumption and insufficient environmental friendliness, among other problems. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a method for preparing a CO2 capture agent based on "coal gangue + fly ash" dual solid waste.

[0005] This invention adopts the following technical solution: a method for preparing a "coal gangue + fly ash" dual solid waste-based CO2 capture agent, comprising the following steps: S1: Using a mixture of coal gangue and fly ash as raw material, the mixture is treated with ultrasonic-assisted alkali dissolution, and after solid-liquid separation, the supernatant is taken to obtain a mixed solution of sodium silicate and sodium aluminate. S2: The sodium silicate and sodium aluminate mixed solution is mixed evenly with a calcium source, the pH value of the system is adjusted to weak alkalinity, and the modified hydration gel is obtained by microwave hydrothermal reaction. After drying, the modified hydration gel carrier is obtained. S3: Using ethanol as an azeotropic solvent, polyethyleneimine is mixed with the modified hydrated gel carrier, and the mixture is subjected to segmented heterogeneous azeotropic distillation for loading treatment, followed by vacuum drying to obtain a CO2 trap.

[0006] In step S1, the mixed solid waste is first pretreated to obtain activated mixed raw materials, and then subjected to ultrasonic-assisted alkali dissolution treatment; The pretreatment specifically involves mixing coal gangue and fly ash at a mass ratio of 3.5:1.5, grinding and sieving until the particle size is less than 200 mesh, and then calcining in air at 700~900℃ for 1~3 hours to remove organic matter, residual carbon and volatile matter, thereby obtaining activated mixed raw materials.

[0007] In step S1, the ultrasound-assisted alkali dissolution treatment specifically involves mixing the activated mixed raw material, sodium hydroxide, and pure water at a ratio of 5g activated mixed raw material, 10g sodium hydroxide, and 40mL pure water, and reacting for 25-35 minutes under the conditions of an ultrasonic frequency of 25-35kHz, an ultrasonic power of 250-350W, and a reaction temperature of 45-55℃.

[0008] In step S2, the calcium source is calcium hydroxide; The microwave hydrothermal reaction is specifically as follows: a mixed solution of sodium silicate and sodium aluminate is diluted with deionized water, mixed evenly with an aqueous solution of calcium hydroxide, the pH value of the system is adjusted to 8.0~9.0, and then transferred to a microwave hydrothermal reactor and reacted at a constant temperature of 75~85℃ for 50~70 minutes.

[0009] The mass ratio of the activated mixed raw material to calcium hydroxide is 5:0.42; the volume ratio of the diluted sodium silicate and sodium aluminate mixed solution to the calcium hydroxide aqueous solution is 1:1.

[0010] In step S3, a 40% (w / w) aqueous solution of polyethyleneimine is used as the active component raw material. The aqueous solution of polyethyleneimine, the modified hydrated gel carrier, and anhydrous ethanol are mixed evenly according to the ratio of (0.25~1.0) g:1 g:(45~55) mL based on the mass of pure polyethyleneimine. The mixture is then placed in a rotary evaporator for segmented heterogeneous azeotropic distillation. The segmented heterogeneous azeotropic distillation is carried out by first distilling at 76~79℃ for 25~35 min, and then raising the temperature to 79~81℃ for 35~45 min. After distillation, the mixture is vacuum dried at 65~75℃ for 1.5~2.5 h.

[0011] In step S3, the ratio of polyethyleneimine aqueous solution, modified hydrated gel carrier, and anhydrous ethanol is 0.67g:1g:50mL; the polyethyleneimine aqueous solution is a 40% mass fraction solution, and correspondingly, the mass of polyethyleneimine aqueous solution fed is 1.675g; the segmented heterogeneous azeotropic distillation is distilled at 78℃ for 30min and at 79℃ for 40min; the vacuum drying is vacuum drying at 70℃ for 2h.

[0012] A CO2 trapping agent, characterized in that it is prepared by the aforementioned preparation method.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention significantly improves the activation efficiency and carrier synthesis rate of silica-alumina components in coal gangue and fly ash through ultrasonic-assisted alkali dissolution and microwave hydrothermal coupling. A one-step ethanol azeotropic method is used to achieve polyethyleneimine loading and pore structure control, resulting in a substantial increase in porosity and pore connectivity. The prepared trapping agent achieves optimized matching of pore volume, specific surface area, and active sites at a polyethyleneimine loading of 40%, exhibiting a CO2 trapping capacity as high as 157 mg / g at 70℃. Furthermore, using industrial solid waste as the main raw material not only significantly reduces raw material costs but also achieves high-value resource utilization of solid waste, demonstrating significant environmental benefits and promising prospects for industrial application. Attached Figure Description

[0014] Figure 1 This is a detailed flowchart of the preparation method of the carbon capture agent of the present invention.

[0015] Figure 2 Here is a SEM micrograph of the carbon capture agent of this invention; Figure 3 This is a diagram showing the carbon capture and fixation capacity of the carbon capture agent of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] In this invention, unless otherwise specified, the polyethyleneimine loading refers to the percentage of polyethyleneimine in the total mass of the final CO2 scavenger, calculated using the following formula: The specific implementation examples are as follows: Step S1: Select coal gangue and fly ash as solid waste raw materials, mix them in a mass ratio of 3.5:1.5, grind and sieve them to obtain samples with a particle size of less than 200 mesh; place the samples in a muffle furnace and calcine them in air at 800℃ for 2 hours to remove organic matter, residual carbon and volatile matter, to obtain activated mixed raw materials. Take a small amount of activated mixed raw materials and digest them with strong acid. Use inductively coupled plasma atomic emission spectrometry (ICP-MS) to determine the content of each metal in the solid waste and confirm the proportion of silicon and aluminum active components.

[0018] Weigh 5g of the above activated mixed raw materials, mix them with 10g of NaOH and 40mL of pure water, stir evenly, place them in an ultrasonic reaction device, and react for 30min under the conditions of ultrasonic frequency 30kHz, ultrasonic power 300W and reaction temperature 50℃. After the reaction is completed, centrifuge at 4000r / min for 8min, discard the insoluble residue, collect the supernatant, and obtain about 35mL of sodium aluminosilicate mixed solution.

[0019] Step S2: Dilute the above sodium aluminosilicate mixed solution to 250 mL with deionized water; separately dissolve 0.42 g of Ca(OH)2 (the mass ratio of activated mixed raw materials to calcium hydroxide is 5:0.42) in 250 mL of deionized water to prepare a calcium hydroxide aqueous solution; mix the two solutions evenly, add dilute hydrochloric acid dropwise to adjust the pH of the system to 8.0~9.0, transfer to a microwave hydrothermal reactor, turn on microwave heating and intermittent stirring, control the reaction temperature at 80℃, and react at a constant temperature for 60 min to obtain the modified hydrated gel.

[0020] The modified hydrated gel was removed, washed with deionized water until the filtrate was neutral, and then dried at 105°C under normal pressure for 12 hours. After grinding, it was passed through a 200-mesh sieve to obtain the dried modified hydrated gel carrier.

[0021] Step S3: Azeotropic loading of polyethyleneimine was performed. Using a 40% (w / w) polyethyleneimine aqueous solution as the active component, the polyethyleneimine aqueous solution, the dried modified hydrated gel carrier, and ethanol were mixed in a certain proportion. A 40% polyethyleneimine aqueous solution containing 0.67g of pure polyethyleneimine (i.e., 1.675g of solution, 1g of dried modified hydrated gel carrier, and 50mL of anhydrous ethanol) was mixed evenly and ultrasonically dispersed for 8min. Then, it was placed in a rotary evaporator for segmented heterogeneous azeotropic distillation: first, it was distilled at 78℃ for 30min, and then the temperature was raised to 79℃ for 40min. After distillation, the sample was taken out and vacuum dried at 70℃ for 2h to obtain a novel CO2 capture agent for dual solid waste.

[0022] Performance testing: The trap prepared in this embodiment has an average pore size of 34.02 nm, a specific surface area of ​​31.02 m² / g, and a pore volume of 0.147 cm³ / g; the dynamic adsorption capacity for CO2 at 70 °C can reach 157 mg / g.

[0023] The carbon adsorption capacity of the trap was tested, and the adsorption performance of the carrier was characterized by thermogravimetric analysis. First, 10-20 mg of the trap was placed in a 150 μL alumina crucible and heated to 120 °C at a rate of 10 °C / min under N2 flow (50 mL / min⁻¹), and held at 120 °C for 30 min to allow for venting. Subsequently, the temperature was cooled to the target adsorption temperature of 70 °C at a rate of -5 °C / min⁻¹, and an adsorption process was carried out for 60 min under CO2 flow (50 mL / min⁻¹). The adsorption capacity was observed and calculated, and the results are as follows: Figure 3 As shown.

[0024] The CO2 adsorption amount is calculated according to the formula. The value is calculated as ×1000, where: X is the CO2 adsorption capacity, in mg / g; Ma is the mass of the trapping agent at the end of the adsorption process, in mg; and Mf is the mass of the trapping agent after pretreatment under N2 atmosphere, in mg.

Claims

1. A method for preparing a "coal gangue + fly ash" dual solid waste-based CO2 capture agent, characterized in that, Includes the following steps: S1: Using a mixture of coal gangue and fly ash as raw material, the mixture is treated with ultrasonic-assisted alkali dissolution, and after solid-liquid separation, the supernatant is taken to obtain a mixed solution of sodium silicate and sodium aluminate. S2: The sodium silicate and sodium aluminate mixed solution is mixed evenly with a calcium source, the pH value of the system is adjusted to weak alkalinity, and the modified hydration gel is obtained by microwave hydrothermal reaction. After drying, the modified hydration gel carrier is obtained. S3: Using ethanol as an azeotropic solvent, polyethyleneimine is mixed with the modified hydrated gel carrier, and the mixture is subjected to segmented heterogeneous azeotropic distillation for loading treatment, followed by vacuum drying to obtain a CO2 trap.

2. The preparation method of the "coal gangue + fly ash" dual solid waste-based CO2 capture agent according to claim 1, characterized in that, In step S1, the mixed solid waste is first pretreated to obtain activated mixed raw materials, and then subjected to ultrasonic-assisted alkali dissolution treatment; The pretreatment specifically involves mixing coal gangue and fly ash at a mass ratio of 3.5:1.5, grinding and sieving until the particle size is less than 200 mesh, and then calcining in air at 700~900℃ for 1~3 hours to remove organic matter, residual carbon and volatile matter, thereby obtaining activated mixed raw materials.

3. The preparation method of the "coal gangue + fly ash" dual solid waste-based CO2 capture agent according to claim 2, characterized in that, In step S1, the ultrasound-assisted alkali dissolution treatment specifically involves mixing the activated mixed raw material, sodium hydroxide, and pure water at a ratio of 5g activated mixed raw material, 10g sodium hydroxide, and 40mL pure water, and reacting for 25-35 minutes under the conditions of an ultrasonic frequency of 25-35kHz, an ultrasonic power of 250-350W, and a reaction temperature of 45-55℃.

4. The preparation method of the "coal gangue + fly ash" dual solid waste-based CO2 capture agent according to claim 1, characterized in that, In step S2, the calcium source is calcium hydroxide; The microwave hydrothermal reaction is specifically as follows: a mixed solution of sodium silicate and sodium aluminate is diluted with deionized water, mixed evenly with an aqueous solution of calcium hydroxide, the pH value of the system is adjusted to 8.0~9.0, and then transferred to a microwave hydrothermal reactor and reacted at a constant temperature of 75~85℃ for 50~70 minutes.

5. The preparation method of the "coal gangue + fly ash" dual solid waste-based CO2 capture agent according to claim 4, characterized in that, The mass ratio of the activated mixed raw material to calcium hydroxide is 5:0.42; the volume ratio of the diluted sodium silicate and sodium aluminate mixed solution to the calcium hydroxide aqueous solution is 1:

1.

6. The preparation method of the "coal gangue + fly ash" dual solid waste-based CO2 capture agent according to claim 1, characterized in that, In step S3, a 40% (w / w) aqueous solution of polyethyleneimine is used as the active component raw material. The aqueous solution of polyethyleneimine, the modified hydrated gel carrier, and anhydrous ethanol are mixed evenly according to the ratio of (0.25~1.0) g:1 g:(45~55) mL based on the mass of pure polyethyleneimine. The mixture is then placed in a rotary evaporator for segmented heterogeneous azeotropic distillation. The segmented heterogeneous azeotropic distillation is carried out by first distilling at 76~79℃ for 25~35 min, and then raising the temperature to 79~81℃ for 35~45 min. After distillation, the mixture is vacuum dried at 65~75℃ for 1.5~2.5 h.

7. The preparation method of the "coal gangue + fly ash" dual solid waste-based CO2 capture agent according to claim 6, characterized in that, In step S3, the ratio of polyethyleneimine aqueous solution, modified hydrated gel carrier, and anhydrous ethanol is 0.67g:1g:50mL; the polyethyleneimine aqueous solution is a 40% mass fraction solution, and correspondingly, the mass of polyethyleneimine aqueous solution fed is 1.675g; the segmented heterogeneous azeotropic distillation is distilled at 78℃ for 30min and at 79℃ for 40min; the vacuum drying is vacuum drying at 70℃ for 2h.

8. A CO2 trapping agent, characterized in that, It is prepared by any one of claims 1 to 7.

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