An integrated utilization method for absorbing and fixing CO2 with alkaline solid waste and preventing spontaneous combustion of coal

Abstract

The present invention discloses an integrated utilization method for alkaline solid waste to absorb and fix CO2 and prevent and control coal spontaneous combustion. Two kinds of alkaline industrial solid waste are used as raw materials, and mountain sand is used as a grinding aid. Pre-fixed carbon powder is obtained by mechanical grinding to stimulate activity; the powder is mixed with water and a chloride salt leaching agent and allowed to stand, and then solid-liquid separation is performed to obtain alkaline leaching liquid, solid waste and mountain sand leaching ash, wherein the alkaline leaching liquid is used to absorb and fix carbon dioxide greenhouse gas emitted by coal-fired power plants to obtain a mixed suspension of nano-carbonate particles, leaching agent and water, which is sprayed on the surface of the residual coal in the easily oxidized spontaneous combustion area of ​​the coal mine as an inhibitor; the leaching ash is used as a raw material to prepare an inorganic low-exothermic plugging material, which is poured and filled into the air leakage area of ​​the coal mine. The present invention utilizes alkaline industrial solid waste, which can not only absorb and fix carbon dioxide in flue gas to achieve the carbon reduction target, but also produce a mining inhibitor and an inorganic low-exothermic plugging material, realizing the dual high-value utilization of alkaline industrial solid waste.

Description

Technical Field

[0001] The present invention relates to the field of solid waste resource utilization and coal spontaneous combustion prevention and control, and in particular to an integrated utilization method for alkaline solid waste to absorb and fix CO2 and prevent coal spontaneous combustion. Background Art

[0002] Coal-fired power plants produce a large amount of greenhouse gas CO2 during the power generation process. Long-term and large-scale emissions of greenhouse gases lead to global warming and frequent extreme weather. Carbon emission reduction from coal-fired power plants is the key to achieving my country's carbon neutrality goal. Compared with traditional natural mineral raw materials, the use of alkaline solid waste rich in calcium and magnesium to absorb and fix CO2 not only has higher reactivity, but can also react with its own CO2 emissions to achieve low-cost on-site CO2 emission reduction. However, at this stage, after solid waste absorbs and fixes CO2, there is a lack of resource utilization and efficient treatment methods for carbon fixation products.

[0003] Air leakage in mines is the main cause of spontaneous combustion of coal in goafs, and spontaneous combustion of coal caused by air leakage is one of the important factors that induce gas explosions. If the product of absorbing and fixing CO2 can be used to prevent spontaneous combustion of coal underground, it can not only solve the problem of CO2 and solid waste, but also achieve low-cost inhibition of spontaneous combustion of coal and blockage of air leakage channels; in addition, it can also promote the resource utilization of alkaline industrial solid waste, achieve waste treatment with waste, and produce high value-added products, so that industrial solid waste can be harmlessly disposed of and resourced.

[0004] At present, there are many patents related to alkaline solid waste capture of CO2, such as:

[0005] 1. CN114856689 A discloses an "integrated method for fly ash, CO2 mineralization storage and goaf filling". Fly ash is stirred into loose fly ash by a stirring device, dissolved in water and then filled into a selected goaf together with coal gangue. The effective flow radius of carbon dioxide is used to reasonably set the vertical drilling step, and CO2 is transported into the goaf through a conveying pipeline borehole to react with gangue and loose fly ash for mineralization. The invention uses fly ash and gangue to fill the goaf, realizes the effective utilization of coal-based solid waste, and can use closed goaf to seal part of carbon dioxide. However, the efficiency of mineralization and sealing of CO2 by the filler is not considered. Only a small amount of calcium and magnesium ions in the fly ash can be leached out by water alone, and the sealing rate of CO2 by the filler is low. Most of the carbon dioxide is directly injected into the goaf, which increases the risk of escape, and the solid waste utilization efficiency is low, and the product value is reduced.

[0006] 2. CN111298616A discloses a "method for regenerating CO2 capture solvent from desulfurization slag". The desulfurization slag is reacted with a capture solvent loaded with CO2. The CO2 in the capture solvent will mineralize with the calcium-containing components in the desulfurization slag to react and generate calcium carbonate and fresh capture solvent. Although the effective utilization of the calcium-containing components in the desulfurization slag of solid waste is achieved, the capture solvent used in this method is an organic amine, including one or more of ethanolamine, diethanolamine, methyldiethanolamine, and 2-amino-2-methyl-1-propanol, which are hazardous chemicals with certain toxicity and corrosiveness and poor environmental friendliness. Summary of the invention

[0007] The purpose of the present invention is to provide an integrated utilization method for alkaline solid waste to absorb and fix CO2 and prevent spontaneous combustion of coal. The method can not only increase the amount of CO2 absorbed and fixed, but also realize the dual utilization of alkaline industrial solid waste: the suspension is sprayed to inhibit the coal body, and the leached ash is used to prepare plugging materials to plug cracks.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows: an integrated utilization method of alkaline solid waste to absorb and fix CO2 and prevent spontaneous combustion of coal, comprising the following steps:

[0009] Step 1, mechanical grinding: put the alkaline solid waste compound material and the mountain sand grinding aid into a ball mill and grind for 30 to 60 minutes to increase the specific surface area of ​​the material and improve the reaction activity to obtain pre-solidified carbon powder;

[0010] Step 2, leaching ions: mixing the pre-solidified carbon powder in step 1 with water and a chloride salt leaching agent to form a composite slurry, and standing the slurry for 12 hours;

[0011] Step 3, solid-liquid separation: filtering the composite slurry in step 2 to obtain alkaline leaching solution, solid waste and mountain sand leaching ash respectively;

[0012] Step 4, alkaline leachate absorbs and fixes CO2: the carbon dioxide gas discharged from the coal-fired power plant is introduced into the alkaline leachate described in step 3, and the calcium, magnesium ions leached from the alkaline solid waste compound materials and the mountain sand grinding aid in the solution react with CO2 to form nano carbonate particles, which are mixed with the chloride leaching agent and water to form an inhibitory suspension;

[0013] Step 5, preparing an inorganic low-exothermic plugging material from solid waste and mountain sand leaching ash: collecting the solid waste and mountain sand leaching ash described in step 3, adding sulphoaluminate cement clinker, lime, gypsum and water, mixing and stirring to obtain an inorganic low-exothermic plugging material.

[0014] Preferably, the alkaline solid waste compound material described in step 1 is a mixture of fly ash and carbide slag, which is obtained by stirring and mixing at a mass ratio of 1 to 3:1.

[0015] Preferably, the particle size of the mountain sand grinding aid described in step 1 is 0.5 mm to 2 mm, and the mass ratio of the mountain sand grinding aid to the alkaline solid waste mixing material is 1:8 to 10.

[0016] Preferably, the chloride salt leaching agent described in step 2 is at least one of calcium chloride, magnesium chloride, sodium chloride or ammonium chloride.

[0017] Preferably, the mass ratio of the pre-solidified carbon powder described in step 2 to water and chloride salt leaching agent is 3-7:10:2-5.

[0018] More preferably, the mass ratio of the pre-solidified carbon powder to water and chloride salt leaching agent described in step 2 is 5:10:2-5.

[0019] Preferably, the mass ratio of solid waste to mountain sand leaching ash, sulphoaluminate cement clinker, lime, gypsum and water in the inorganic low-exothermic plugging material described in step 5 is 0.5-1:1-3:0.4-0.8:2:4-8.

[0020] More preferably, the mass ratio of solid waste to mountain sand leaching ash, sulphoaluminate cement clinker, lime, gypsum and water in the inorganic low-exothermic plugging material described in step 5 is 0.7:2:0.6:2:6.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention provides an integrated utilization method of alkaline solid waste to absorb and fix CO2 and prevent and control coal spontaneous combustion. The utilization of alkaline industrial solid waste can not only absorb and fix carbon dioxide in flue gas to achieve the carbon reduction target, but also produce mining inhibitors and inorganic low-exothermic plugging materials, realizing the dual high-value utilization of alkaline industrial solid waste.

[0023] 2. Using mountain sand as a grinding aid, after mixing with alkaline solid waste and undergoing mechanical grinding, can stimulate the mineralization reaction activity of alkaline solid waste; in addition, under the action of chloride leaching agent, it can enhance the leaching intensity of calcium and magnesium ions of solid waste, increase the concentration of calcium and magnesium ions in the leachate, and increase the absorption and fixation amount of CO2 gas and carbon fixation efficiency of unit mass of alkaline solid waste compound materials. At the same time, in the process of making mountain sand into slurry, a large amount of calcium ions will be continuously dissolved, which can also achieve the absorption and fixation of CO2 and increase the carbon fixation amount of the entire leachate.

[0024] 3. The alkaline leachate reacts with CO2 to generate nano-carbonate particles, which are mixed with a chloride leachate and water to form a retardant suspension. Among them, the nano-carbonate particles in the retardant suspension can block the tiny pores on the surface of the coal body, block the contact between the active chemical functional groups on the coal surface and oxygen, and inhibit the oxidation temperature rise and heat storage spontaneous combustion of the coal; the chloride leachate will not react with the carbon dioxide gas emitted by the power plant, so the retardant suspension can retain the chloride salt, and the retardant suspension can directly retard the coal body after being sprayed on the surface of the coal body, achieving the effect of directly using calcium chloride, sodium chloride, magnesium chloride, etc. as the retardant solution, thereby achieving the dual effect of increasing the calcium and magnesium leaching rate in alkaline solid waste and retardant coal spontaneous combustion by using calcium chloride, sodium chloride, magnesium chloride and other substances. In addition, the present invention uses leached ash, and is configured with sulphoaluminate cement clinker, lime, gypsum and water to obtain an inorganic low-exothermic plugging material for plugging air leakage cracks in coal mines. It can be seen that the integrated utilization method of alkaline solid waste for absorbing and fixing CO2 and preventing and controlling coal spontaneous combustion proposed in the present invention not only realizes the absorption and fixation of flue gas CO2 greenhouse gas, but also realizes the dual fire prevention and extinguishing effects of liquid product inhibiting coal body and solid product underground filling and sealing.

[0025] 4. The present invention does not require high-energy consumption such as high temperature and high pressure or high-cost pretreatment such as strong acid and strong alkali on the raw materials before preparing the mineralizer. It has low cost, low energy consumption, no toxic and hazardous chemicals, is environmentally friendly, and has high calcium and magnesium utilization rates.

[0026] 5. Using alkaline solid waste produced by coal-fired power plants as raw materials to fix the carbon dioxide greenhouse gas emitted by coal-fired power plants has achieved the goals of on-site emission reduction, waste treatment, and production of high value-added products. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the integrated utilization process of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Example 1

[0030] like Figure 1 As shown, an integrated utilization method of alkaline solid waste to absorb and fix CO2 and prevent spontaneous combustion of coal, the steps are as follows:

[0031] Step 1, mechanical grinding: fly ash and carbide slag are mixed in a ratio of 3:1, and after mixing, a sand grinding aid with a particle size of about 1 mm is added, and the mixture is put into a ball mill for grinding for 30 minutes, and the powder is ground to a particle size of less than 40 μm to obtain a pre-solidified carbon powder; wherein the mass ratio of the sand grinding aid to the alkaline solid waste compound material is 1:8;

[0032] Step 2, leaching ions: mixing the pre-solidified carbon powder with water and chloride salt leaching agent in a mass ratio of 5:10:2 to form a composite slurry, and standing for leaching for 12 hours;

[0033] Step 3, solid-liquid separation: filtering the composite slurry to obtain alkaline leaching solution, solid waste and mountain sand leaching ash respectively;

[0034] Step 4, alkaline leachate absorbs and fixes CO2; the carbon dioxide gas emitted by the coal-fired power plant is introduced into the alkaline leachate, and the calcium, magnesium ions leached from the alkaline solid waste compound materials and the mountain sand grinding aid in the solution react with CO2 to form nano-carbonate particles, which are mixed with the chloride leaching agent and water to form an inhibitory suspension; wherein the chloride leaching agent is selected from calcium chloride;

[0035] Step 5, preparing an inorganic low-exothermic plugging material from solid waste and mountain sand leaching ash; collecting solid waste and mountain sand leaching ash, adding sulphoaluminate cement clinker, lime, gypsum and water, mixing and stirring to obtain an inorganic low-exothermic plugging material, wherein the mass ratio of leaching ash, sulphoaluminate cement clinker, lime, gypsum and water is 0.7:2:0.6:2:6.

[0036] Example 2

[0037] The method is the same as that of Example 1, except that the mass ratio of the mountain sand grinding aid to the alkaline solid waste compounding material in step 1 is 1:9; the mass ratio of the pre-solidified carbon powder to water and chloride salt leaching agent in step 2 is 5:10:2.

[0038] Example 3

[0039] The method is the same as that of Example 1, except that the mass ratio of the mountain sand grinding aid to the alkaline solid waste compounding material in step 1 is 1:10; the mass ratio of the pre-solidified carbon powder to water and chloride salt leaching agent in step 2 is 5:10:2.

[0040] Example 4

[0041] The method is the same as that of Example 1, except that the mass ratio of the mountain sand grinding aid to the alkaline solid waste compounding material in step 1 is 1:8; the mass ratio of the pre-solidified carbon powder to water and chloride salt leaching agent in step 2 is 5:10:3.

[0042] Example 5

[0043] The method is the same as that of Example 1, except that the mass ratio of the sand grinding aid to the alkaline solid waste compounding material in step 1 is 1:8; the mass ratio of the pre-solidified carbon powder to water and chloride salt leaching agent in step 2 is 5:10:4.

[0044] Example 6

[0045] The method is the same as that in Example 1, except that the mass ratio of the sand grinding aid to the alkaline solid waste compounding material in step 1 is 1:8; the mass ratio of the pre-solidified carbon powder to water and chloride salt leaching agent in step 2 is 5:10:5.

[0046] In order to analyze the influence of different raw material ratios on the carbon fixation amount, the present invention selects fly ash from a power generation company in Jiangsu Province and carbide slag from an environmental protection technology company in Henan Province as raw materials, collects the alkaline leachates in the above embodiments 1-6, takes 50 mL of each and puts it in a beaker for standby use, and adds the prepared leachates into a homemade high-pressure reactor respectively, and measures the carbon fixation amount by the pressure drop method. The test results are shown in Table 1, and the inhibitory suspension corresponding to each embodiment is obtained.

[0047] In order to analyze the inhibitory effect of the inhibitory suspension on coal spontaneous combustion, the present invention selects coal samples from the Sixth Mine of Pingmei Co., Ltd., crushes and grinds the coal samples to 40-80 meshes, and divides the coal powder into 7 groups numbered 0-6, with each group of coal samples weighing 50g; among them, No. 0 coal sample is raw coal, serving as the control group; the remaining 1-6 groups are respectively mixed with the inhibitory suspension obtained in Examples 1-6 (the addition amount is 10% of the coal sample), mixed evenly and placed at room temperature for 120h, and these 6 groups are treated with the inhibitory suspension. Finally, using the coal spontaneous combustion characteristic test system, the temperature rise rate is preset to 0.8℃ / min and the air flow rate is 100mL / min, and the CO generation during the oxidation process of the 7 groups of coal samples is tested. The inhibition rate is used to characterize the inhibition effect of the inhibitory suspension on coal, that is, the ratio of the volume fraction of CO generated by the inhibitory suspension during the programmed temperature rise process at 100°C and the volume fraction of CO generated by the raw coal to the volume fraction of CO in the raw coal is used to express it. The carbon fixation amount of the alkaline leaching solution obtained with different raw material ratios and the inhibition rate of its product are measured, as shown in Table 1.

[0048] In order to analyze the plugging properties of inorganic low-exothermic plugging materials prepared by using leached ash as raw material for cracks, it is necessary to test the compressive strength of the material after curing. Therefore, the plugging material is prepared into a sample with a size of 100mm×100mm×100mm according to the above ratio, and the shrinkage rate of the sample at 28 days of age is obtained by static compression test method; in order to analyze the temperature change in the preparation process of the plugging material, the maximum reaction temperature test method of AQ1090-2011 is adopted to obtain the maximum reaction temperature of each embodiment. The specific test results are shown in Table 2.

[0049] Table 1 Carbon fixation in alkaline leaching solution obtained by different raw material ratios and the inhibition rate of the product

[0050]

[0051] Table 2 Performance test of plugging materials prepared from solid waste and mountain sand leaching ash

[0052]

[0053] As can be seen from Table 1, Examples 1, 2, and 3, in the present invention, a method for comprehensive utilization of alkaline solid waste for fixed absorption of CO2 and prevention of coal spontaneous combustion, the amount of carbon fixed in the pre-fixed carbon powder increases with the increase of the content of the mountain sand grinding aid. The increase of the content of the mountain sand grinding aid can enhance the grinding effect of the alkaline solid waste compound material and promote the leaching of calcium and magnesium ions. On the other hand, the mountain sand also contains a certain amount of calcium ions, which will also be leached with the leachate, increasing the concentration of calcium ions in the leachate. Therefore, the increase of the content of the mountain sand grinding aid will increase the amount of carbon fixed per unit of pre-fixed carbon powder. As can be seen from Table 1, Examples 3, 4, 5, and 6, the inhibition rate of the inhibitory suspension in the present invention increases with the increase of the content of the chloride salt leaching agent. The component of the leaching agent is calcium chloride, which will not react with the carbon dioxide gas discharged by the power plant. After leaching the calcium and magnesium ions, the calcium chloride is retained. After the inhibitory suspension is sprayed on the surface of the coal body, the coal body can be directly inhibited. Therefore, the increase of the calcium chloride content will enhance the inhibitory effect. In addition, as the amount of carbon fixation increases, the inhibition rate will also increase, because the nano-carbonate particles generated by the reaction can block the tiny pores on the surface of the coal, block the contact between the active chemical functional groups on the surface of the coal and oxygen, and inhibit the oxidation temperature rise and heat storage spontaneous combustion of the coal.

[0054] As can be seen from Table 2 Examples 1, 2, and 3, with the increase of the mountain sand content, the compressive strength of the plugging material increases, which is mainly due to the presence of mountain sand increasing the density of the plugging material, ensuring the uniformity of the material, thereby making the compressive strength of the plugging material higher, and showing excellent resistance to external forces in the process of plugging underground air leakage fissures; at the same time, mountain sand particles and cement clinker, fly ash, carbide slag and other gelling components form a mechanical connection, which increases the cohesion and compressive strength of the plugging material and enhances the volume stability of the plugging material. Therefore, the increase in mountain sand content reduces the compressive strength of the plugging material, which is more conducive to the plugging of underground fissures. As can be seen from Table 2 Examples 3, 4, 5, and 6, with the increase of the chloride salt leaching agent (calcium chloride) content, the compressive strength of the plugging material shows a certain growth trend, which is because calcium chloride can accelerate the hydration reaction of the plugging material and reduce its internal pore structure, thereby improving the compressive strength of the plugging material to a certain extent. In addition, according to the test results of Examples 1-6, it can be seen that the maximum reaction temperature of each sample is lower than 30°C, which meets the relevant requirements of standards such as "Polymer Foaming Materials for Coal Mine Filling and Sealing", "Polymer Materials for Coal Mine Reinforcement of Coal Rock Mass", and "Technical Conditions for Polymer Materials for Spraying and Sealing Air Leakage in Coal Mines", and can achieve low-exothermic and safe sealing of air leakage cracks in underground coal mines.

[0055] In summary, the inhibitory suspension described in step 4, comprising nano-carbonate particles, chloride leaching agent and water, can be directly used as an inhibitor to inhibit coal oxidation and spontaneous combustion in coal mines. It can be sprayed on the surface of the residual coal in the easily oxidized and spontaneously combusted areas in coal mines to inhibit the oxidation and spontaneous combustion of the loose residual coal, thereby playing an inhibitory role.

[0056] The inorganic low-exothermic plugging material described in step 5 is used to fill and fill the coal pillar cracks, high-risk areas and other air leakage areas in the coal mine, plug the air leakage channel, isolate oxygen, and play a role in filling and plugging.

[0057] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. An integrated utilization method for alkaline solid waste to absorb and fix CO2 and prevent spontaneous combustion of coal, characterized in that: The following steps are involved: Step 1, mechanical grinding: put the alkaline solid waste mixed material and the mountain sand grinding aid into a ball mill and grind for 30 to 60 minutes to increase the specific surface area of ​​the material, improve the reaction activity, and obtain a pre-solidified carbon powder; the alkaline solid waste mixed material is a mixture of fly ash and carbide slag, which is obtained by stirring and mixing at a mass ratio of 1 to 3:1; Step 2, leaching ions: mixing the pre-solidified carbon powder in step 1 with water and a chloride salt leaching agent to form a composite slurry, and standing the slurry for 12 hours; Step 3, solid-liquid separation: filtering the composite slurry in step 2 to obtain alkaline leaching solution, solid waste and mountain sand leaching ash respectively; Step 4, alkaline leaching solution absorbs and fixes CO2: the carbon dioxide gas discharged from the coal-fired power plant is introduced into the alkaline leaching solution described in step 3, and the calcium and magnesium ions leached from the alkaline solid waste compounding materials and the mountain sand grinding aid in the solution react with CO2 to form nano carbonate particles, which are mixed with the chloride leaching agent and water to form an inhibitory suspension; Step 5, preparing an inorganic low-exothermic plugging material from solid waste and mountain sand leaching ash: collecting the solid waste and mountain sand leaching ash described in step 3, adding sulphoaluminate cement clinker, lime, gypsum and water, mixing and stirring to obtain an inorganic low-exothermic plugging material.

2. The integrated utilization method of alkaline solid waste for absorbing and fixing CO2 and preventing spontaneous combustion of coal according to claim 1 is characterized in that: The particle size of the mountain sand grinding aid described in step 1 is 0.5mm-2mm, and the mass ratio of the mountain sand grinding aid to the alkaline solid waste mixed material is 1:8-10.

3. The integrated utilization method of alkaline solid waste for absorbing and fixing CO2 and preventing spontaneous combustion of coal according to claim 1, characterized in that: The chloride salt leaching agent described in step 2 is at least one of calcium chloride, magnesium chloride, sodium chloride or ammonium chloride.

4. The integrated utilization method of alkaline solid waste for absorbing and fixing CO2 and preventing spontaneous combustion of coal according to claim 1, characterized in that: The mass ratio of the pre-solidified carbon powder to water and chloride salt leaching agent described in step 2 is 3-7:10:2-5.

5. The integrated utilization method of alkaline solid waste for absorbing and fixing CO2 and preventing spontaneous combustion of coal according to claim 4 is characterized in that: The mass ratio of the pre-solidified carbon powder to water and chloride salt leaching agent described in step 2 is 5:10:2-5.

6. The integrated utilization method of alkaline solid waste for absorbing and fixing CO2 and preventing spontaneous combustion of coal according to claim 1, characterized in that: The mass ratio of solid waste to mountain sand leaching ash, sulphoaluminate cement clinker, lime, gypsum and water in the inorganic low-exothermic plugging material described in step 5 is 0.5-1:1-3:0.4-0.8:2:4-8.

7. The integrated utilization method of alkaline solid waste for absorbing and fixing CO2 and preventing spontaneous combustion of coal according to claim 6, characterized in that: The mass ratio of solid waste to mountain sand leaching ash, sulphoaluminate cement clinker, lime, gypsum and water in the inorganic low-exothermic plugging material described in step 5 is 0.7:2:0.6:2:6.

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