Method for preparing carbon sequestration slurry by modifying fly ash mineralized carbon dioxide and application thereof

Abstract

The application discloses a method for preparing carbon fixation slurry by modifying fly ash and mineralizing carbon dioxide and application thereof. Firstly, the fly ash is modified by using a microwave to break SiO2-Al2O3 polar bonds and break the glass body; then water and a decomposition agent are weighed and poured into a reaction kettle, stirring is conducted and a gel structure is destroyed by using the microwave to promote calcium ion dissolution and prevent the formation of a passivation layer; finally, a leaching agent is weighed and poured into the reaction kettle, carbon dioxide is introduced into the reaction kettle, the carbon dioxide pressure in the kettle is maintained at 10-20 bar, and stirring is conducted to mineralize and form the carbon fixation slurry. The carbon fixation slurry is injected into a mine goaf for preventing and treating coal spontaneous combustion. The method can strengthen the massive leaching of alkali metal ions in the fly ash, mineralize carbon dioxide to form a carbon fixation product, and has the advantages of simple process, easy operation and the carbon fixation product can prevent and treat coal spontaneous combustion in the goaf.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fly ash activation and carbon dioxide mineralization, and in particular to a method for preparing carbon sequestration slurry by modifying fly ash to mineralize carbon dioxide and application thereof. BACKGROUND

[0002] Injecting the carbon sequestration product produced by mineralizing carbon dioxide with fly ash into the goaf of a mine for preventing and treating coal spontaneous combustion is a novel and promising technology, which can realize the organic combination of carbon dioxide sequestration, solid waste utilization and spontaneous combustion prevention of residual coal.

[0003] Currently, the research on leaching calcium and magnesium ions from fly ash to mineralize carbon dioxide adopts an indirect carbonation method, which is a two-step reaction, i.e., first leaching calcium and magnesium ions from fly ash in a leaching solution, and then introducing carbon dioxide into the leaching solution rich in calcium and magnesium ions for mineralization reaction. The fly ash used for mineralizing carbon dioxide is alkaline fly ash containing a large amount of free calcium oxide. SiO2 and Al2O3 in the fly ash gradually dissolve to form [SiO4] and [AlO4] monomers under the action of alkali, and the active components containing calcium will react with them to convert into hydrated calcium aluminate, hydrated calcium silicate and hydrated calcium silicate-aluminate amorphous gel, thereby reducing the leaching rate of calcium ions and causing these gels to deposit on the surface of the amorphous glass body to form a passivation layer, which hinders the continuous leaching of calcium and magnesium ions and the continuous progress of the reaction of mineralizing carbon dioxide.

[0004] The most common method for enhancing the leaching rate of calcium and magnesium ions in fly ash is to add some acidic substances as leaching agents to react with the glass body in fly ash to release calcium and magnesium ions. However, the addition of acidic substances will consume the alkalinity of the leaching solution, which not only reduces the adsorption effect of the leaching solution on carbon dioxide, but also reduces the activity of the leaching agent, thereby making the enhancement of leaching effect very limited. CN 102343199 A proposes a method and device for strengthening mineral carbonation to fix CO2, which uses HCO3 - weak acid solution as a mineral leaching agent, but the HCO3 - acid is too weak, and the effect of enhancing the leaching rate of calcium and magnesium ions is not significant. SUMMARY

[0005] The purpose of the present application is to provide a method for preparing carbon sequestration slurry by modifying fly ash to mineralize carbon dioxide, which can not only enhance the leaching of alkali metal ions in fly ash and mineralize a large amount of carbon dioxide, but also has a simple process and is easy to operate.

[0006] The second purpose of the present application is to provide the application of the carbon sequestration slurry prepared by the above method in the treatment of coal spontaneous combustion disaster in goaf.

[0007] To achieve the above-mentioned purposes, the technical solutions adopted by the present application are as follows:

[0008] In one aspect, the present application provides a method for preparing a carbon sequestration slurry from modified fly ash and carbon dioxide, comprising the following steps:

[0009] Step 1: weigh 20-30 parts of fly ash into a reaction kettle, then place the reaction kettle on the workbench of an industrial microwave device, and turn on the microwave modification for 3-5 min; the fly ash is C-class, grade I or grade II fly ash.

[0010] Step 2: weigh 90-120 parts of water and 1-3 parts of a decomposition agent into the reaction kettle respectively, and microwave heat while stirring for 5-8 min; the decomposition agent is one or more of methanol, ethanol, urea, pure lauryl sodium sulfate, N-hexadecyl-N-ethyl morpholinyl ethyl sodium sulfate, potassium oleate, polyoxyethylene monostearate, and sodium oleate;

[0011] Step 3: weigh 1-2 parts of a leaching agent into the reaction kettle, then introduce carbon dioxide into the reaction kettle, maintain the carbon dioxide pressure in the reaction kettle to 10-20 bar, and stir the slurry for 10-15 min, and obtain a carbon sequestration slurry after the reaction is completed.

[0012] Preferably, in steps 1 and 2, the microwave frequency is 915 MHz, and the power is 80-100 kW.

[0013] Preferably, in step 2, the decomposition agent is pure lauryl sodium sulfate.

[0014] Preferably, in step 3, the leaching agent is one or more of ammonium chloride, ammonium nitrate, ammonium acetate, sodium carbonate, and acetic acid.

[0015] Preferably, in step 1, the fly ash is C-class grade I fly ash or C-class grade II fly ash.

[0016] Preferably, in step 1, the material of the reaction kettle is one of polyvinyl chloride, polypropylene, polycarbonate fiber, and nylon.

[0017] Preferably, the raw material ratio in the carbon sequestration slurry is 30 parts of fly ash, 120 parts of water, 3 parts of a decomposition agent, and 2 parts of a leaching agent.

[0018] Preferably, the stirring rate in steps 2 and 3 is 900-1200 rpm.

[0019] In another aspect, the present application also provides the use of the carbon sequestration slurry prepared by the above method in the management of coal spontaneous combustion disasters in goaf. When used, the carbon sequestration slurry is directly injected into the goaf of a mine to prevent and control coal spontaneous combustion.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] (1) The essence of releasing calcium ions in fly ash glass body is that silicate-aluminate (main component of glass body) reacts with alkali to generate calcium-containing cementitious material, but only a small amount of active silicon aluminum in fly ash can be dissolved by alkali and participate in gel generation; one of the purposes of using microwave to modify fly ash in step 1 is to increase the content of active silicon aluminum in fly ash, and the SiO2-Al2O3 polar bond will absorb microwave energy and break, thereby increasing the dissolution rate of silicate-aluminate and promoting the release of calcium ions; the other purpose is to use the non-thermal effect of microwave to crush and pulverize the glass body, increase the specific surface area of fly ash, and expose more active silicon aluminum and alkali metal ions, so as to promote the efficient leaching of calcium and magnesium ions in step 2.

[0022] (2) The formation of gel is the result of the synergistic driving of hydrogen bond, hydrophobic interaction and other non-covalent interactions, and hydrogen bond plays a crucial role in the formation and transformation of gel aggregate structure; the present application aims to destroy the gel structure, which not only promotes the dissolution of calcium ions in the gel, but also prevents the formation of a passivation layer on the surface of the glass body, which hinders the continuous leaching of alkali metal ions and the continuous reaction of mineralized carbon dioxide. The external energy brought by the microwave used in step 2 destroys the hydrogen bonds in the gel, destroys its three-dimensional network structure, and promotes the dissolution of calcium ions in the gel. The decomposing agent used in step 2 mainly destroys the hydrogen bonds or non-covalent interactions in the gel, promotes the decomposition of the gel, and releases the surfactant therein; the decomposing agent can be divided into two categories, one is low alcohol (methanol, ethanol) and urea, which can provide hydrogen on its own hydroxyl group to form hydrogen bonds and promote the dissociation of hydrogen bonds in the gel; the other is pure lauryl sodium sulfate and other surfactants, which have strong hydrophilicity (HLB>18.0) and can greatly destroy the balance of non-covalent interactions in the gel.

[0023] (3) Most of the currently used reaction kettles are made of metal materials, and microwaves will be reflected by these reaction kettles without penetrating, so they cannot act on fly ash or fly ash slurry, and the preparation method provided by the present application cannot be realized; the reaction kettle used in the present application is made of polyvinyl chloride, polypropylene, polycarbonate fiber and nylon, and microwaves almost penetrate without being absorbed, and their strength can reach more than 10 MPa, meeting the requirements of industrial applications. The industrial microwave frequency in China is only 915 MHz and 2450 MHz, and the selected 915 MHz has stronger penetration ability, and its penetration distance is about three times that of 2450 MHz.

[0024] (4) The leaching agent used in step 3 is selected from an acidic substance, and the reaction of the acidic substance with the glass body is utilized to continuously leach the alkali metal ions in the process of carbon dioxide mineralization, so as to achieve the maximum leaching rate of the alkali metal ions and the amount of carbon dioxide mineralization. The preparation method of the present application uses the preparation method of modification and preparation, and cooperates with physical and chemical methods from the aspects of polar bond, non-covalent interaction, chemical reaction, macroscopic crushing, and the like, so as to promote the leaching of the alkali metal ions such as calcium and magnesium in a multi-scale and whole-process manner.

[0025] (5) The carbon sequestration slurry contains a large amount of nano- and micro-sized calcium carbonate particles due to the carbon dioxide mineralization reaction, and the particles have strong hydrophilicity and water retention performance, can form a liquid water film, and can keep the coal sample in a humid state for a long time, so as to prevent oxygen from contacting with the residual coal and enhance the prevention and control effect of coal spontaneous combustion. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A flow chart of the method for preparing the carbon sequestration slurry by modifying fly ash to mineralize carbon dioxide. DETAILED DESCRIPTION

[0027] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0028] The fly ash used for preparing the carbon sequestration slurry is preferably C-class first-grade fly ash or C-class second-grade fly ash, and the fly ash used in the following embodiments is C-class first-grade fly ash.

[0029] Embodiment 1

[0030] The carbon sequestration slurry is prepared from the following raw materials in mass parts: 30 parts of fly ash, 120 parts of water, 3 parts of a decomposition agent, and 2 parts of a leaching agent; wherein the decomposition agent is pure lauryl sodium sulfate, and the leaching agent is acetic acid.

[0031] A method for preparing a carbon sequestration slurry by modifying fly ash to mineralize carbon dioxide, a route of which is shown in Figure 1 The method comprises the following steps:

[0032] Step 1: weigh the fly ash and pour it into a reaction kettle made of polyvinyl chloride, then place the reaction kettle on an industrial microwave device workbench, and use microwave modification for 5 min, with a microwave frequency of 915 MHz and a power of 80-100 kW;

[0033] Step 2: weigh the decomposition agent solution and pour it into the reaction kettle, stir at a speed of 1200 rpm for 8 min, and keep the industrial microwave device workbench in an open state;

[0034] Step 3: weigh the leaching agent and pour it into the reaction kettle, then introduce carbon dioxide into the reaction kettle, maintain the carbon dioxide pressure in the reaction kettle to 20 bar, stir the slurry at a speed of 1200 rpm for 15 min, and obtain the carbon sequestration slurry after the reaction is completed.

[0035] Example 2

[0036] The solid carbon slurry is made from the following raw materials in mass parts: 30 parts of fly ash, 120 parts of water, 2 parts of decomposing agent, 2 parts of leaching agent; wherein the decomposing agent is pure lauryl sodium sulfate; the leaching agent is acetic acid.

[0037] The method of preparing the solid carbon slurry by mineralizing carbon dioxide with modified fly ash in this example is the same as that in Example 1.

[0038] Example 3

[0039] The solid carbon slurry is made from the following raw materials in mass parts: 30 parts of fly ash, 120 parts of water, 1 part of decomposing agent, 2 parts of leaching agent; wherein the decomposing agent is pure lauryl sodium sulfate; the leaching agent is acetic acid.

[0040] The method of preparing the solid carbon slurry by mineralizing carbon dioxide with modified fly ash in this example is the same as that in Example 1.

[0041] Example 4

[0042] The solid carbon slurry is made from the following raw materials in mass parts: 30 parts of fly ash, 120 parts of water, 3 parts of decomposing agent, 2 parts of leaching agent; wherein the decomposing agent is polyoxyethylene monostearate; the leaching agent is acetic acid.

[0043] The method of preparing the solid carbon slurry by mineralizing carbon dioxide with modified fly ash in this example is the same as that in Example 1.

[0044] Example 5

[0045] The solid carbon slurry is made from the following raw materials in mass parts: 30 parts of fly ash, 120 parts of water, 3 parts of decomposing agent, 2 parts of leaching agent; wherein the decomposing agent is ethanol; the leaching agent is acetic acid.

[0046] The method of preparing the solid carbon slurry by mineralizing carbon dioxide with modified fly ash in this example is the same as that in Example 1.

[0047] Example 6

[0048] The solid carbon slurry is made from the following raw materials in mass parts: 30 parts of fly ash, 120 parts of water, 3 parts of decomposing agent, 1 part of leaching agent; wherein the decomposing agent is pure lauryl sodium sulfate; the leaching agent is acetic acid.

[0049] The method of preparing the solid carbon slurry by mineralizing carbon dioxide with modified fly ash in this example is the same as that in Example 1.

[0050] Example 7

[0051] The solid carbon slurry is made from the following raw materials in mass parts: 30 parts of fly ash, 120 parts of water, 3 parts of decomposing agent, 2 parts of leaching agent; wherein the decomposing agent is pure lauryl sodium sulfate; the leaching agent is ammonium acetate.

[0052] The method for preparing the carbon sequestration slurry by modifying fly ash to mineralize carbon dioxide in this example is the same as that in Example 1.

[0053] Comparative Example 1

[0054] The carbon sequestration slurry is prepared from the following raw materials in mass parts: 30 parts of fly ash, 120 parts of water, 3 parts of a decomposing agent, and 2 parts of a leaching agent; wherein the decomposing agent is pure lauryl sodium sulfate; and the leaching agent is acetic acid.

[0055] The method for preparing the carbon sequestration slurry by modifying fly ash to mineralize carbon dioxide in this example is the same as that in Example 1, wherein step 1 does not use microwave modification.

[0056] Comparative Example 2

[0057] The carbon sequestration slurry is prepared from the following raw materials in mass parts: 30 parts of fly ash, 120 parts of water, 3 parts of a decomposing agent, and 2 parts of a leaching agent; wherein the decomposing agent is pure lauryl sodium sulfate; and the leaching agent is acetic acid.

[0058] The method for preparing the carbon sequestration slurry by modifying fly ash to mineralize carbon dioxide in this example is the same as that in Example 1, wherein step 2 does not start the industrial microwave device workbench.

[0059] The slurry obtained after step 2 in Examples 1-7 and Comparative Examples 1-2 above is subjected to suction filtration, and the ion chromatograph is used to measure the calcium ion concentration in the filtrate; after step 3, the carbon sequestration slurry prepared is subjected to suction filtration, drying, and grinding, and then the simultaneous thermal analyzer is used to obtain the carbon dioxide mineralization amount of the dry powder.

[0060] The specific data are shown in Table 1.

[0061] Table 1 Calcium ion concentration and carbon dioxide mineralization amount of the fly ash slurry prepared in Examples 1-7 and Comparative Examples 1-2

[0062]

[0063]

[0064] In combination with Table 1, it can be seen from Comparative Examples 1-3 that the more the parts of the decomposing agent added, the higher the calcium ion concentration in the slurry, and the highest can reach 15.5 kg / m 3 The increase in the concentration of pure lauryl sodium sulfate can enhance the destruction of the non-covalent interaction balance of sodium oleate in the gel, and promote the dissolution of calcium ions from the gel.

[0065] Comparative Example 1 and 4, it can be seen that: pure lauryl sodium sulfate (HLB = 40) as a decomposing agent leaching of calcium ion concentration than polyoxyethylene monostearate (HLB = 18.8), indicating that the stronger the hydrophilicity, the more intense the destruction of the non-covalent interaction balance in the gel.

[0066] Comparative Example 1 and 5, it can be seen that: pure lauryl sodium sulfate as a decomposing agent leaching of calcium ion concentration than ethanol, indicating that for leaching of calcium ions, the efficiency of destroying the non-covalent interaction balance in the gel is better than promoting the dissociation of hydrogen bonds in the gel itself.

[0067] Comparative Example 1 and 6, it can be seen that: the decrease of the concentration of the leaching agent leads to the decrease of the amount of carbon dioxide mineralization, which is due to the decrease of the reaction intensity of the leaching agent with the glass body, and the decrease of the amount of alkali metal ions leached during the carbon dioxide mineralization.

[0068] Comparative Example 1 and 7, it can be seen that: the amount of carbon dioxide mineralization of acetic acid as a leaching agent is higher than that of ammonium acetate, which is because the acidity of acetic acid is stronger than that of ammonium acetate, and the reaction intensity of acetic acid with the glass body is higher.

[0069] Comparative Example 1 and Comparative Example 1, it can be seen that: step 1 does not modify the fly ash by microwave, which significantly reduces the concentration of calcium ions and the amount of carbon dioxide mineralization, and microwave activation of silicon and aluminum in fly ash glass body is important to increase the dissolution rate of silicate, which affects the subsequent leaching of calcium ions and mineralization of carbon dioxide.

[0070] Comparative Example 1 and Comparative Example 2, it can be seen that: step 2 does not open the industrial microwave device workbench, which has the greatest impact on the concentration of calcium ions and the amount of carbon dioxide mineralization, and the lack of microwave action cannot release a large amount of calcium ions in the gel.

[0071] Example 8

[0072] The carbon sequestration slurry prepared in Example 1 was mixed with anthracite (particle size: 0.18-0.38 mm) at a mass ratio of 1:1, and the filter residue was weighed after suction filtration. Then the filter residue was placed in a drying oven and dried at 50℃ under vacuum for 60min. The filter residue was weighed again and the mass loss rate was calculated. The control group was fly ash slurry without carbon sequestration, and the test data are shown in Table 2.

[0073] As shown in Table 2, the mass loss rate of the carbon sequestration slurry after drying is less than that of the slurry without carbon sequestration, which is because the mineralization reaction generates calcium carbonate particles with good hydrophilicity and water retention, which can effectively prolong the wetting time of residual coal in the early stage of coal spontaneous combustion, prevent residual coal from reacting with oxygen, and enhance the coal spontaneous combustion prevention ability of the slurry.

[0074] Table 2 Mass loss rate of slurry mixed with anthracite after drying

[0075]

[0076] The above-mentioned embodiments are merely preferred technical solutions of the present application, and should not be regarded as a limitation on the present application. The embodiments in the present application and the features in the embodiments can be combined with each other as long as there is no conflict. The protection scope of the present application should be subject to the technical solutions recited in the claims, and include equivalent replacement solutions of the technical features recited in the claims. That is, equivalent replacement improvements within this range are also within the protection scope of the present application.

Claims

1. A method of preparing a carbon sequestration slurry from modified fly ash mineralized carbon dioxide, characterized by, The method comprises the following steps: Step 1: 20-30 parts by mass of fly ash are weighed and put into a reaction kettle, and then the reaction kettle is placed on a workbench of an industrial microwave device, and microwave modification is started for 3-5 minutes; Step 2: 90-120 parts by mass of water and 1-3 parts by mass of a decomposition agent are weighed and put into the reaction kettle, and microwave heating is carried out while stirring for 5-8 minutes; the decomposition agent is pure lauryl sodium sulfate; Step 3: 1-2 parts by mass of a leaching agent are weighed and put into the reaction kettle, then carbon dioxide is introduced into the reaction kettle, the carbon dioxide pressure in the reaction kettle is maintained at 10-20 bar, and the slurry is stirred for 10-15 minutes, and a carbon fixation slurry is obtained after the reaction is completed; the leaching agent is one or more of ammonium chloride, ammonium nitrate, ammonium acetate, sodium carbonate and acetic acid.

2. The method for preparing carbon sequestration slurry by modifying fly ash mineralized carbon dioxide according to claim 1, characterized in that, In steps 1 and 2, the microwave frequency is 915 MHz, and the power is 80-100 kW.

3. The method for preparing carbon sequestration slurry by modifying fly ash mineralized carbon dioxide according to claim 1, characterized in that, In step 1, the fly ash is C-class first-grade fly ash or C-class second-grade fly ash.

4. The method for preparing carbon sequestration slurry by modifying fly ash mineralized carbon dioxide according to claim 1, characterized in that, In step 1, the material of the reaction kettle is one of polyvinyl chloride, polypropylene, polycarbonate fiber and nylon.

5. The method of claim 1, wherein the method of preparing a carbon sequestration slurry from modified fly ash mineralized carbon dioxide is characterized by, The raw material ratio in the carbon fixation slurry is: 30 parts by mass of fly ash, 120 parts by mass of water, 3 parts by mass of a decomposition agent and 2 parts by mass of a leaching agent.

6. The method of claim 1, wherein the method of preparing a carbon sequestration slurry from modified fly ash mineralized carbon dioxide is characterized by, In steps 2 and 3, the stirring rate is 900-1200 rpm.

7. The application of the carbon fixation slurry prepared by the method of any one of claims 1 to 6 in the treatment of coal spontaneous combustion disasters in goaf.

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