阅读说明：本技术 一种煤矿用高聚物基复合阻化剂的制备方法 (Preparation method of high polymer-based composite stopping agent for coal mine ) 是由 黄志安 王冠华 高玉坤 尹义超 宋东鸿 赵新辉 权赛南 张英华 于 2021-07-31 设计创作，主要内容包括：本发明提供了一种煤矿用高聚物基复合阻化剂的制备方法,属于阻化剂制备技术领域。该发明选用物理阻化剂聚丙烯酰胺(PAM)以及纳米材料二氧化硅气凝胶粉末(SA)进行插层复合,再将复合材料PAM/SA与化学阻化剂Ca(OH)-(2)进行复配,制成高聚物基复合阻化剂,提升了阻化剂对煤自燃的全阶段阻化效果。本发明的阻化剂可以有效克服物理类阻化剂后期阻化效果不足以及化学类阻化剂低温阶段抑制作用不明显的问题,能够结合物理类阻化剂和化学类阻化剂各自的优点,对煤的自燃进程起到良好的全阶段阻化效果。(The invention provides a preparation method of a high polymer-based composite stopping agent for coal mines, belonging to the technical field of preparation of stopping agents. The invention adopts physical inhibitor Polyacrylamide (PAM) and nano material silicon dioxide aerogel powder (SA) to carry out intercalation compounding, and then the composite material PAM/SA and chemical inhibitor Ca (OH) 2 The high polymer base composite stopping agent is prepared by compounding, and the full-stage stopping effect of the stopping agent on the spontaneous combustion of coal is improved. The stopping agent can effectively overcome the problems of insufficient stopping effect of a physical stopping agent in the later period and unobvious inhibiting effect of a chemical stopping agent in the low-temperature period, and can combine the advantages of the physical stopping agent and the chemical stopping agent to achieve good full-stage stopping effect on the spontaneous combustion process of coal.)

1. A preparation method of a high polymer-based composite stopping agent for coal mines is characterized by comprising the following steps:

(1) the method comprises the following steps of (1) mixing silicon dioxide aerogel powder with an intercalation agent according to a mass ratio of 1-5: 1-2, adding the mixture into deionized water, uniformly mixing at 60-80 ℃, standing and precipitating for 10-15 hours to obtain a suspension, wherein the intercalation agent is cetyl trimethyl ammonium bromide;

(2) drying the suspension prepared in the step (1) at a constant temperature of 65-75 ℃ to constant weight to obtain aerogel powder after intercalation treatment;

(3) mixing polyacrylamide and deionized water to obtain a polyacrylamide solution, then dissolving the aerogel powder subjected to intercalation treatment in the step (2) in the deionized water, dropwise adding the solution into the polyacrylamide solution, uniformly mixing, and stirring at the rotating speed of 30-35 r/min for 1-2 h at the temperature of 70-80 ℃, wherein the mass ratio of the aerogel powder subjected to intercalation treatment to the polyacrylamide is 1: 3-5, uniformly mixing, then dropwise adding an initiator to perform polymerization reaction, and finally cooling to room temperature to obtain the polyacrylamide/nano-silica composite hydrogel;

(4) drying the polyacrylamide/nano silicon dioxide composite hydrogel at 100-150 ℃ to constant weight, and then crushing;

(5) mixing polyacrylamide/nano material silicon dioxide hydrogel powder with Ca (OH)₂According to the mass ratio of 1-2: 1-2 to prepare the high polymer-based composite stopping agent for coal mine.

2. The preparation method of the high polymer-based composite stopping agent for the coal mine according to claim 1, wherein the drying time in the step (2) is 10-20 hours.

3. The preparation method of the high polymer-based composite stopping agent for the coal mine according to claim 1, wherein the mass volume ratio of the polyacrylamide and the deionized water in the step (3) is 3-5: 140 to 160, and mixing.

4. The method for preparing the high polymer-based composite stopping agent for the coal mine according to claim 1, wherein the mass-to-volume ratio of the aerogel powder subjected to the intercalation treatment in the step (3) to the deionized water is 1: 10.

5. the method for preparing the high polymer-based composite stopping agent for the coal mine according to claim 1, wherein the initiator in the step (3) is potassium persulfate.

6. The preparation method of the high polymer-based composite stopping agent for the coal mine according to claim 1, wherein the polymerization reaction in the step (3) is a constant-temperature sealing polymerization reaction at 70-80 ℃ for 1-2 hours after stirring for 1.5-2.5 hours.

7. A high polymer-based composite inhibitor for coal mine, characterized by being prepared by the method of any one of claims 1 to 4.

8. The application of the high polymer-based composite stopping agent for the coal mine according to claim 7, wherein the high polymer-based composite stopping agent for the coal mine is dissolved in deionized water to prepare a composite stopping agent solution, then the coal mine is soaked in the high polymer-based composite stopping agent solution for 1-24 hours, and the coal mine is taken out and dried to obtain a stopped coal mine.

9. The application of claim 8, wherein the drying manner is natural air drying, and the air drying time is 24-72 h.

Technical Field

The invention relates to the technical field of preparation of stopping agents, in particular to a preparation method of a high polymer-based composite stopping agent for coal mines.

Background

The stopping agent is a medicament for stopping the coal from oxidizing naturally and is also called an oxygen stopping agent. The inhibitor is made into solution or emulsion and sprayed on the surface of coal body, and after absorbing the water in air, the surface of coal body forms water-containing liquid film to play the role of isolating oxygen and inhibiting oxidation, and at the same time the water in the surface liquid film can be evaporated to absorb heat and reduce temperature, so that the coal temperature can be prevented from raising to accelerate the oxidation rate, and the self-heating and self-ignition of coal can be inhibited.

The existing stopping agents mainly comprise a physical stopping agent and a chemical stopping agent, wherein the physical stopping agent mainly solidifies moisture by adjusting limit parameters of coal spontaneous combustion, blocking coal oxygen combination and utilizing good water absorption and moisture retention effects of the physical stopping agent, so that the spontaneous combustion trend of coal is slowed down, the temperature rise rate is reduced, the stopping effect is realized, the stopping agent is suitable for the moisture evaporation and adsorption stage at the initial stage of the coal spontaneous combustion process, and the stopping agent is easily decomposed and failed due to heating at the later stage of the coal spontaneous combustion stage, so that the stopping effect is lost. The chemical inhibitor has the inhibition principle that the inhibitor reacts with active groups on the surface of a coal body to generate a relatively stable chain ring, the activity of a coal oxygen reaction functional group is inactivated, an activation reaction chain is cut off step by step, the coal oxygen chemical reaction is weakened, and the spontaneous combustion process of coal is inhibited.

Xifeng carrier and the like through experiments to discover the halide salt inhibitor MgCl at each stage₂The inhibition effect of (A) is not uniform, and the inhibition effect is good only in the initial stage, and gradually loses the inhibition effect in the later stage. The ammonium salt inhibitor has obvious temperature lowering effect in the initial stage of spontaneous combustion, and can inhibit the self-heating temperature raising rate of coal, capture free radical in coal oxidation chain reaction and inhibit low temperature oxidation of coal. However, according to the research of Chengang et al, it is found that the inhibition efficiency of the ammonium salt type inhibitor is not high, and the inhibition process only prolongs the ignition time.

The gel inhibitor has stronger fluidity and permeability, and experiments show that Wuhuiping and the like have better functions of oxygen isolation, temperature reduction, blocking, wind prevention and the like than the common inhibitor, but the Wuhuiping and the like have the defects that a large amount of ammonia gas is generated in the gelling, the health of human bodies is harmed, the inhibition life is generally short, and the Wuhuiping and the like are not beneficial to large-scale use.

The foam inhibitor is susceptible to temperature and pH, and is easily broken and lost due to large surface free energy, and once the foam is broken, the inhibition performance is lost. Just because the foam inhibitor is difficult to adhere to the surface of the coal body for a long time and is easy to separate from the top and the side of the coal body, how to maintain the continuous inhibition of the foam is a technical difficulty to overcome.

Studies on basic inhibitors such as Suwei et al found Ca (OH)₂The stopping agent has low cost and high stopping rate, but the blocking phenomenon is easy to occur due to low solubility, and the stopping effect is influenced to a certain extent. The sinoland researches the inhibition effect of catechin and polyethylene glycol which are antioxidant inhibitors, and finds that the inhibition efficiency is highest when the content of the inhibition agent is 10%, but the antioxidant inhibitors have the defects of easy decomposition and failure at high temperature, complex process, high cost and easy pollution to the natural environment.

Therefore, the preparation of an efficient stopping agent for stopping the whole spontaneous combustion stage of coal is a problem to be solved at present.

Disclosure of Invention

In view of the above, the invention provides a preparation method of a high polymer-based composite stopping agent for coal mines. Selecting physical inhibitor Polyacrylamide (PAM) and nano material silicon dioxide aerogel powder (SA) to carry out intercalation compounding, and then mixing the composite material PAM/SA with chemical inhibitor Ca (OH)₂The composite inhibitor is compounded and optimized to prepare the high polymer-based composite inhibitor, so that the full-stage inhibition effect of the inhibitor on the spontaneous combustion of coal is improved.

The invention provides a preparation method of a high polymer-based composite stopping agent for coal mines, which comprises the following steps:

(1) the method comprises the following steps of (1-5) mixing silicon dioxide aerogel powder (SA) and an intercalation agent in a mass ratio of: 1-2, adding the mixture into deionized water, uniformly mixing at 60-80 ℃, standing and precipitating for 10-15 hours to obtain a suspension, wherein the intercalation agent is cetyl trimethyl ammonium bromide;

(2) drying the suspension prepared in the step (1) at a constant temperature of 65-75 ℃ to constant weight to obtain aerogel powder (C-SA) subjected to intercalation treatment;

(3) mixing polyacrylamide and deionized water to obtain a polyacrylamide solution, then dissolving the aerogel powder subjected to intercalation treatment in the step (2) in the deionized water, dropwise adding the solution into the polyacrylamide solution, uniformly mixing, and stirring at the rotating speed of 30-35 r/min for 1-2 h at the temperature of 70-80 ℃, wherein the mass ratio of the aerogel powder subjected to intercalation treatment to the polyacrylamide is 1: 3-5, uniformly mixing, then dropwise adding an initiator to perform a polymerization reaction, and finally cooling to room temperature to obtain polyacrylamide/nano-silica (PAM/SA) composite hydrogel;

(4) drying the polyacrylamide/nano silicon dioxide composite hydrogel at 100-150 ℃ to constant weight, and then crushing;

(5) mixing polyacrylamide/nano material silicon dioxide hydrogel powder with Ca (OH)₂According to the mass ratio of 1-2: 1-2 to prepare the high polymer-based composite stopping agent for coal mine.

Preferably, the drying time in the step (2) is 10-20 h.

Preferably, the mass volume ratio of the polyacrylamide and the deionized water in the step (3) is 3-5: 140 to 160, and mixing.

Preferably, the mass-to-volume ratio of the aerogel powder subjected to intercalation treatment in the step (3) to deionized water is 1: 10.

preferably, the initiator in the step (3) is potassium persulfate.

Preferably, the polymerization reaction in the step (3) is a constant-temperature sealing polymerization reaction at 70-80 ℃ for 1-2 hours after stirring for 1.5-2.5 hours.

The invention also aims to provide the coal mine high polymer-based composite stopping agent prepared by the method.

The application method of the high polymer-based composite stopping agent for the coal mine comprises the steps of dissolving the high polymer-based composite stopping agent for the coal mine in deionized water to prepare a composite stopping agent solution, then soaking the coal mine in the high polymer-based composite stopping agent solution for 1-24 hours, taking out and drying to obtain a stopped coal mine.

Preferably, the drying mode is natural air drying, and the air drying time is 24-72 h.

According to the invention, the high temperature resistance of polyacrylamide can be improved by using the silicon dioxide aerogel powder for intercalation treatment, so that the composite material PAM/SA has good heat resistance, and the inhibition time is prolonged. And the PAM/SA surface has a large amount of pores and folds to ensure that the PAM/SA surface has good water absorption and moisture retention performance and stronger overall viscosity, can form a compact curing film at the initial stage of coal spontaneous combustion, tightly covers active centers on the surface of a coal body, plays a role in isolating oxygen and reducing temperature, and delays water evaporation so as to inhibit the spontaneous combustion oxidation process of the coal.

In the later stage of coal spontaneous combustion, PAM/SA is gradually decomposed and failed, which is a defect that the physical stopping agent cannot overcome. At this time, the chemical inhibitor Ca (OH)₂The effect of strong post inhibition performance is highlighted, and the effect can be primarily oxidized with product Fe of pyrite in coal₂(SO₄)₃Oxidation reaction occurs, and further the cyclic oxidation reaction of the pyrite is blocked, and chemical inhibition effect is exerted, so that the handover of inhibition work is completed. The physical and chemical synergistic inhibitor can make up for the chemical inhibitor Ca (OH)₂The weak resistance of the physical inhibitor PAM/SA in the early stage of coal spontaneous combustion overcomes the defect of decomposition failure of the physical inhibitor PAM/SA in the later stage of coal natural combustion, and can inhibit the coal spontaneous combustion to the maximum extent.

Compared with the prior art, the invention has the following beneficial effects:

the invention selects physical inhibitor Polyacrylamide (PAM) and nano material silicon dioxide aerogel powder (SA) to carry out intercalation compounding, and then the composite material PAM/SA and chemical inhibitor Ca (OH)₂And (4) carrying out compound optimization to form the high polymer-based composite inhibitor. The inhibitor of the invention can obviously passivate the oxidation activity of the hydroxyl, aliphatic hydrocarbon and other groups in the coal, improve the temperature of aromatic ring cracking, increase the content of stable structure ether bonds, and greatly improve the inhibitionThe inhibitor has the inhibiting capability on the spontaneous combustion of coal, can effectively overcome the defect of insufficient inhibiting effect of a physical inhibitor in the later period, solves the problem of unobvious inhibiting effect of a chemical inhibitor in the low-temperature stage, and can combine the respective advantages of the physical inhibitor and the chemical inhibitor to achieve good full-stage inhibiting effect on the spontaneous combustion process of coal.

Drawings

FIG. 1 is a microscopic morphology of polyacrylamide PAM under an electron microscope at 1k times magnification;

FIG. 2 is a microscopic morphology of the composite PAM/SA prepared in example 1 under an electron microscope at 1k times magnification;

FIG. 3 is an XRD pattern of the silica aerogel powder of example 1;

FIG. 4 is an XRD pattern of the aerogel powder after intercalation treatment in example 1;

FIG. 5 is an XRD pattern of the PAM/SA composite prepared in example 1;

FIG. 6 is DSC curves of PAM and PAM/SA in example 1;

FIG. 7 is a TG-DTG curve of the hindered coal sample in example 1;

FIG. 8 is a TG-DTG curve of the hindered coal sample in example 2;

FIG. 9 is a TG-DTG curve of the hindered coal sample in example 3;

FIG. 10 is a TG-DTG curve of the hindered coal sample in example 4;

FIG. 11 is a TG-DTG curve of the comparative coal sample in comparative example 1;

FIG. 12 is a TG-DTG curve of the hindered coal sample of comparative example 2;

FIG. 13 is a TG-DTG curve of the hindered coal sample of comparative example 3;

FIG. 14 is a TG-DTG curve of the hindered coal sample of comparative example 4;

FIG. 15 shows 3610cm before and after the inhibition treatment of the coal sample of example 1 and the raw coal of comparative example 1^-1A graph comparing the change in hydroxyl content;

FIG. 16 shows 2889cm before and after the blocking coal sample of example 1 and the raw coal blocking treatment of comparative example 1^-1Comparison graph of the content change of methyl group;

FIG. 17 shows an example1 and 1560cm before and after the inhibition treatment of the raw coal of comparative example 1^-1Graph comparing the content change of aromatic ring;

FIG. 18 shows 1230cm before and after the inhibition treatment of the inhibited coal sample of example 1 and the raw coal of comparative example 1^-1The change in ether linkage content is shown in the graph.

Detailed Description

The present invention will be further described with reference to the following examples.

Example 1

A preparation method of a high polymer-based composite stopping agent for coal mines comprises the following steps:

(1) 100ml of deionized water is measured, poured into a beaker, placed in a water bath heating pot, heated to 70 ℃, and stirred strongly by a magnetic rotor. Adding 4g of silicon dioxide aerogel powder and 1.7498g of intercalation agent cetyl trimethyl ammonium bromide in a stirring state, continuously stirring for 2h at the rotating speed of 30r/min, slowly cooling to room temperature in an environment with the humidity of 30%, standing and precipitating for 12h to obtain stable aerogel powder suspension after intercalation treatment;

(2) pouring the aerogel powder suspension subjected to intercalation treatment prepared in the step (1) into a culture dish, enabling the liquid level of the aerogel powder suspension in the culture dish to be lower than 1mm, putting the culture dish into an electric heating constant-temperature air blowing drying box, setting the drying temperature to be 70 ℃, turning on a fan switch for continuous air supply, drying at constant temperature for 12 hours, enabling an aerogel powder sample subjected to intercalation treatment to reach a constant weight state, obtaining aerogel powder subjected to intercalation treatment, filling the aerogel powder into a brown bottle, sealing, and then placing the aerogel powder suspension in a shade place for keeping out of the sun for later use;

(3) uniformly mixing 4g of polyacrylamide and 150ml of deionized water in a beaker to obtain a polyacrylamide solution, wherein the mass ratio of polyacrylamide to aerogel powder after intercalation treatment is 4: 1, weighing 1g of aerogel powder prepared in the step (2) and subjected to intercalation treatment, dissolving the aerogel powder in 10mL of deionized water, dropwise adding the solution into a polyacrylamide solution, uniformly mixing, stirring at a water bath heating temperature of 75 ℃ for 1h at a rotating speed of 30r/min, dropwise adding 1.3mL of an initiator potassium persulfate solution in a stirring state, continuously stirring for 2h, sealing in a constant-temperature water bath kettle at 75 ℃ for polymerization for 2h, cooling to room temperature to obtain PAM/SA composite hydrogel, and filling the PAM/SA composite hydrogel into a culture dish to form a PAM/SA composite hydrogel film;

(4) placing the PAM/SA composite hydrogel film prepared in the step (3) into an electric heating constant-temperature air blast drying oven, drying for 2h at the temperature of 120 ℃ to constant weight, and then placing the dried sample slice into a mortar for fully grinding to obtain a PAM/SA composite;

(5) weigh 1.0g PAM/SA composite and 1.0g Ca (OH)₂According to the mass ratio of 1:1, fully mixing to prepare the high polymer-based composite stopping agent for coal mines.

PAM/SA-Ca (OH) according to the invention₂Preparing a hindered coal sample by using the composite retardant:

dissolving the composite inhibitor of the invention into 8.0mL deionized water, and fully dissolving to obtain a mixture with a ratio of 1:1 of PAM/SA-Ca (OH)₂And (3) weighing 1ml of the composite stopping agent solution, uniformly mixing the composite stopping agent solution with 1g of the coal sample, fully soaking, and naturally air-drying for 72 hours at normal temperature to form the stopping coal sample.

Examples 2 to 4

A preparation method of a high polymer-based composite stopping agent for coal mines comprises the following steps:

steps (1) to (4) were the same as in example 1

Changing the PAM/SA composite material, Ca (OH) in the step (5)₂Mixing with deionized water to prepare different PAM/SA-Ca (OH)₂Compounding a stopping agent.

The raw materials used in the step (5) of examples 1 to 4 and the prepared composite inhibitor are shown in Table 1:

TABLE 1

PAM/SA-Ca (OH) according to the invention₂Preparing a hindered coal sample by using the composite retardant:

1ml of the stopping agent of the embodiments 2 to 4 is respectively weighed and evenly mixed with 1g of the coal sample, and the stopping coal sample is formed after the stopping agent is fully soaked and naturally dried for 72 hours at normal temperature.

Comparative example 1

Weighing 1.0g of coal sample and 1ml of deionized water, uniformly mixing, fully soaking, and naturally air-drying at normal temperature for 72h to form a comparative coal sample (raw coal).

Comparative example 2

Weighing 1.0g Ca (OH)₂Dissolving in 9.0ml deionized water, and dissolving completely to obtain single Ca (OH)₂A stopping agent; weighing 1ml of stopping agent, uniformly mixing with 1g of coal sample, fully soaking, naturally air-drying at normal temperature for 72h to form Ca (OH)₂Stopping the coal sample.

Comparative example 3

Weighing 1.0g of PAM chemically produced in Tianjin Fuchen, dissolving the PAM with the purity of more than or equal to 90.0% in 9.0ml of deionized water, and fully dissolving the PAM to obtain a single PAM stopping agent; weighing 1ml of stopping agent, uniformly mixing with 1g of coal sample, fully soaking, and naturally air-drying for 72h at normal temperature to form the PAM stopping coal sample.

Comparative example 4

Weighing 1.0g of the PAM/SA composite material prepared in the embodiment 1, dissolving the PAM/SA composite material in 9.0ml of deionized water, and fully dissolving the PAM/SA composite material to obtain a single PAM/SA inhibitor; weighing 1ml of stopping agent, uniformly mixing with 1g of coal sample, fully soaking, and naturally air-drying for 72h at normal temperature to form the PAM/SA stopping coal sample.

The microscopic morphology of polyacrylamide PAM under the magnification of 1k times of an electron microscope is shown in FIG. 1; the microstructure of the PAM/SA composite material prepared in the embodiment 1 of the invention under the magnification of 1k times of an electron microscope is shown in FIG. 2.

As can be seen from fig. 1 and 2, the particles of polyacrylamide are distributed obviously, the edges and corners of the large particles are clear but the wrinkles and holes on the surface of the particles are few, and the small particles are distributed irregularly and are scattered around the large particles; the PAM/SA composite material cannot see obvious granular distribution, the wrinkles on the surface are more dense and distributed in a ripple type diffusion manner, the concave conditions with different degrees can be obviously found on the surface of the PAM/SA composite material, and the number of the scattered cavities is large, the depth is large, so that the contact area of the PAM/SA and water molecules is favorably improved. Therefore, the surface structure of the polyacrylamide is greatly changed after the intercalation treatment of the silicon dioxide aerogel powder, and water molecules are favorably permeated into the gel, so that the water absorption and moisture retention performance of the composite material is effectively improved, and the better inhibition effect is exerted.

X-ray diffraction (XRD) testing

The silica aerogel powder, the intercalated aerogel powder and the PAM/SA composite material in example 1 of the present invention were subjected to X-ray diffraction (XRD) tests, and the XRD curve of the silica aerogel powder is shown in fig. 3, the XRD curve of the intercalated aerogel powder is shown in fig. 4, and the XRD curve of the PAM/SA composite material is shown in fig. 5.

From FIGS. 3-5, the diffraction angle 2 θ, layer spacing, maximum peak height, full width at half maximum, and peak area results for the tests are shown in Table 2:

TABLE 2

As can be seen from Table 2, the positions of the diffraction peaks of the aerogel powder after intercalation treatment are shifted to the left, that is, the value of the diffraction angle 2 theta is reduced from 22.019 degrees to 21.460 degrees, and the reduction is 2.54 percent. The interplanar spacing was increased from 4.0335nm to 4.1373nm, with an increase of 2.51%. Therefore, the interlayer spacing of the silicon dioxide aerogel powder can be enlarged through intercalation treatment, and the monomer can be inserted into the interlayer of the crystal face of the silicon dioxide aerogel powder to form a composite material. And the maximum height of the diffraction peak is increased to 4478 from the original 1858, and the full width at half maximum is reduced to 0.46 from 13.11, which shows that the number of crystal faces of the powder after the intercalation treatment is increased, the grain particles are enlarged, and the crystallinity is better. For the same material, the higher crystallinity means that the molecular chains in the material are arranged more closely, the higher temperature is needed for destruction, and the higher the melting point of the sample is, which is beneficial to improving the high temperature resistance of the material. In fig. 5, the height of the main diffraction peak is greatly reduced as compared with fig. 4, the value of the diffraction angle 2 θ is reduced from 22.019 ° to 21.357 °, and the reduction is 3.01%. The interplanar spacing was increased from 4.0335nm to 4.1569nm with an increase of 3.06%. The maximum peak height is reduced from 4478 to 2104, and the overall trend is more gradual, which indicates that after intercalation treatment, the AM monomer is successfully inserted into the nano-scale lamella of the silicon dioxide aerogel powder to form the PAM/SA composite material, and further verifies the intercalation effect.

Differential Scanning Calorimetry (DSC) test:

measurement of the glass transition temperatures T of PAM and PAM/SA in example 1 by differential scanning calorimetry_gAnd the DSC curves of PAM and PAM/SA are shown in FIG. 6, and in the initial stage of temperature rise, the temperature rise rates of the sample and the reference object are approximately the same, and no obvious thermal effect occurs, so that the DSC curve is a relatively stable straight line. When the temperature is raised enough to make the sample have glass transition, the macromolecular segment in the sample gradually starts to move, the heat capacity thereof will change obviously and need to absorb more heat, so the middle part of the DSC curve will have a region with an obviously increased slope, and the temperature corresponding to the turning point is the glass transition temperature. Then the sample material is changed from a glass state to a high elastic state, the heat capacity of the sample material gradually tends to be stable, and then the DSC curve gradually recovers to be linearly increased at the later stage. Curves (1) and (2) in fig. 6 are DSC curves for PAM and PAM/SA, respectively, where the glass transition temperature of PAM is 159 ℃, the glass transition temperature of PAM/SA is 197 ℃, and the amplification is 23.9%. It can be seen that the glass transition temperature of the silicon dioxide aerogel powder is obviously improved after the silicon dioxide aerogel powder and the polyacrylamide are subjected to intercalation compounding. The PAM macromolecular chain segment has the advantages that after the monomer enters between the sheets of the silicon dioxide aerogel through the intercalation, a large amount of physical crosslinking can be formed between the hydrophilic groups in the PAM and the hydroxyl on the surface of the silicon dioxide aerogel powder, so that strong interaction is realized between the two materials, the energy required by the movement of the PAM macromolecular chain segment is greatly improved, and the moving capability of the chain segment is reduced, so that the movement of the chain segment is limited, and the high-temperature resistance of the composite material PAM/SA is further improved.

Thermogravimetric analysis experiments

Thermogravimetric analysis is carried out on the inhibition coal samples or the comparison coal samples prepared in the examples 1-4 and the comparative examples 1-4, and the analysis method comprises the following steps:

10mg of the coal samples to be tested in the examples and the comparative examples are respectively placed in a crucible, then the crucible is placed in a thermogravimetric analyzer, the temperature rise rate is set to be 10 ℃/min on a computer program, the temperature rise interval is 30 ℃ to 800 ℃, the air flow is 45ml/min, and then the programmed temperature rise is started for thermogravimetric analysis (TG-DTG).

The TG-DTG curves of the coal samples prepared in examples 1 to 4 and comparative examples 1 to 4 are shown in fig. 7 to 14, respectively, and the results of the characteristic temperature points of the thermogravimetric analysis of the coal samples to be measured are shown in table 3, which can be obtained from fig. 7 to 14:

TABLE 3

As can be seen from Table 3, compared with the raw coal sample, the single-type inhibitor PAM has obvious inhibition effect in the low-temperature stage of the coal spontaneous combustion early stage, but fails in the high-temperature stage of the coal spontaneous combustion later stage; single type inhibitor Ca (OH)₂The good inhibition effect can be exerted only in the later high-temperature stage, and the early effect is not prominent; the PAM/SA composite material has better inhibiting effect than PAM, but the inhibiting performance at high temperature is still inferior to Ca (OH)₂. And the composite material PAM/SA and Ca (OH)₂The composite stopping agent formed after compounding can play a more continuous stopping role in the whole stage of the coal spontaneous combustion process, has a promoting role in each characteristic temperature point of the coal sample, makes up the defect of weak stage stopping effect of a single stopping agent, and promotes the full-stage stopping performance of the stopping agent. In the water evaporation and adsorption stage at the initial stage of coal spontaneous combustion reaction, the PAM/SA composite material with good water absorption and moisture retention properties and film forming property can play a certain role in physical reactions such as water evaporation in coal and the likeInhibiting effect. In the pyrolysis and combustion stage in the middle and later period of the spontaneous combustion reaction of coal, the composite material PAM/SA fails due to thermal decomposition caused by the increase of temperature, Ca (OH)₂Gradually highlighting the advantage of strong later-stage inhibition effect, fully exerting chemical inhibition effect, and mixing with Fe product of preliminary oxidation of pyrite in coal₂(SO₄)₃Oxidation reaction is carried out, the cyclic oxidation reaction of the pyrite is interrupted, and CaSO generated by the reaction is generated₄、Fe(OH)₃And Ca (OH) which does not participate in the reaction₂A compact hydrophilic film can be formed on the surface of the coal, and the effect of isolating oxygen is achieved, so that the process of spontaneous combustion oxidation of the coal is further inhibited, and the handover task of inhibition work is completed. The 1:1 proportioning treatment sample resistance except T is seen by combining various evaluation indexes of the coal spontaneous combustion reaction inhibition effect₃(mass maximum temperature) and T₆The 4 characteristic temperature values except the burn-out temperature are the highest in all the mixture ratio treatment resistance samples, so the comprehensive resistance performance of the 1:1 mixture ratio treatment resistance samples is the best in the composite type resistance agent.

Thermogravimetric kinetics experiments

Thermogravimetric experiments are carried out on the inhibition coal sample of the example 1 and the raw coal of the comparative example 1 at the temperature rise rates of 5, 10, 15 and 20 ℃/min respectively, and the T measured in the experimental process is used₂' (temperature of Dry cracking), T₃' (Mass maximum temperature) and T₄' (ignition temperature) as a demarcation point, the thermal oxidation weight loss process of the coal sample is divided into I (low-temperature oxidation stage), II (oxygen uptake weight gain stage) and III (ignition stage), and the activation energy is calculated by adopting a Strink model based on various heating rates.

Thermogravimetric kinetic analysis the activation energy results of the coal samples at various stages are shown in table 4:

TABLE 4

As can be seen from Table 4, the activation energy of the coal sample during the spontaneous combustion oxidation process is increased from 116.47 KJ.mol with the increase of the temperature^-1Gradually increases to 547.67KJ mol^-1And presents the overall trend of three-stage step increasing, which is consistent with the early stage of the coal spontaneous combustion thermogravimetric curve. Compared with raw coal, the coal is processed by PAM/SA-Ca (OH)₂After the composite stopping agent is treated, the activation energy of each stage of the coal sample is improved to different degrees. Wherein the activation energy of the low-temperature oxidation stage is 116.47 KJ.mol^-1Increasing to 169.93KJ mol^-1The amplitude is 31.5%; the activation energy of oxygen uptake weight increasing stage is 316.09 KJ.mol^-1Increasing to 605.35KJ mol^-1The amplitude is 91.5%; the activation energy in the ignition stage is 547.67 KJ.mol^-1Increasing to 757.38KJ mol^-1The amplitude of rise is 38.3%; the average activation energy of each stage is 326.74 KJ.mol^-1Increasing to 510.89KJ mol^-1The rise was 56.4%. The activation energy of each stage is greatly improved, which shows that the inhibition treatment can effectively improve the reaction energy barrier in the spontaneous combustion process of the coal sample, and has the effects of eliminating active groups and improving the stability, so that the spontaneous combustion reaction of the coal is more difficult to carry out.

Infrared diffuse reflection experiment

The hindered coal sample of example 1 and the raw coal of comparative example 1 were subjected to infrared analysis using a seemefly brand Nicolet iS50 fourier transform infrared spectrometer.

The experimental process is provided with the scanning times of 64, the temperature rise interval is 25-700 ℃, the temperature rise rate is5 ℃/min, and the scanning range is 650-4000cm^-1The collection time is 143min, and the air flow is50 ml/min. And (3) analyzing the change trend of the contents of main functional groups, namely hydroxyl, methyl, aromatic ring and ether bond in the temperature rise process of the coal sample in detail.

3610cm before and after the inhibition treatment of the inhibition coal sample of example 1 and the raw coal of comparative example 1^-1The graph comparing the change of hydroxyl content is shown in FIG. 15;

2889cm before and after the blocking coal sample of example 1 and the raw coal blocking treatment of comparative example 1^-1The graph comparing the change in methyl group content is shown in FIG. 16;

sample of hindered coal of example 11560cm before and after the raw coal resistance treatment of comparative example 1^-1The graph comparing the aromatic ring content change is shown in FIG. 17;

1230cm before and after the inhibition treatment of the inhibition coal sample of example 1 and the raw coal of comparative example 1^-1The graph comparing the changes in the ether bond content is shown in FIG. 18.

As can be seen from FIG. 15, the total area of hydroxyl groups in the raw coal is higher than that of the hindered coal sample, and the absorbance of the hydroxyl groups in the raw coal at 25 ℃ is significantly higher than that of the hindered hydroxyl groups, which indicates that a certain amount of hydroxyl groups in the raw coal can be consumed by adding the retardant, and the effect of passivating the active groups and increasing the stability is achieved. Compared with the water evaporation and adsorption stage at 25-150 ℃, the reduction rate of the hydroxyl content in the raw coal is far greater than that of the inhibition coal sample, because PAM/SA in the composite inhibitor has good water absorption and moisture retention effects, the water loss rate of the inhibition sample is far less than that of the raw coal, the loss of the hydroxyl is reduced, and the physical inhibition effect of the inhibitor at the initial stage of the spontaneous combustion reaction of the coal is verified. When the temperature is raised to above 400 ℃, the coal sample enters a pyrolysis and combustion stage, along with a violent oxidation reaction, hydroxyl is taken as a representative active group, the content of the hydroxyl is greatly raised, and after the composition treatment, the temperature point of the sharp increase of the content of the hydroxyl in the sample is obviously lagged behind that of the raw coal, which shows that the flame retardant can effectively improve the ignition temperature point of the coal sample, thereby effectively inhibiting the spontaneous combustion process of the coal.

Methyl is taken as the most representative active group in the aliphatic hydrocarbon, and the content of the methyl can reflect the stability of the coal sample laterally. As can be seen from fig. 16, the total area of methyl groups in the raw coal is higher than that of the inhibition coal sample, which indicates that the addition of the inhibition agent can consume the methyl groups in the raw coal and improve the stability of the coal sample. As carbon element in methyl can be rapidly lost in the pyrolysis and combustion stage of the coal sample, the loss rate can approximately reflect the rate of the spontaneous combustion oxidation process of the coal, and the comparison of the stage at the temperature of more than 300 ℃ in the figure shows that the loss rate of the methyl in the raw coal is far higher than that of the inhibition coal sample, the methyl content of the inhibition coal sample starts to rapidly decrease after reaching a peak at the temperature of about 350 ℃, and the methyl content of the inhibition coal sample is relatively stable in the initial stage of the spontaneous combustion reaction and starts to gradually slide down until the temperature of 430 ℃, which shows that the spontaneous combustion oxidation process of the coal sample is better inhibited after the inhibition treatment.

As can be seen from fig. 17, in the initial stage of spontaneous combustion of coal, the raw coal and the hindered coal sample have approximately the same tendency to change, and the aromatic ring structure gradually increases to a stable value as the internal polycondensation reaction of the coal molecule proceeds. But with the continuous rise of the temperature and the reaching of the ignition point temperature of the coal sample, the overall cracking of the aromatic ring structure in the coal sample can occur, and the C-H bond in the aromatic ring is broken to generate dehydrogenation reaction_nH_2n+2→C_nH_2n+H₂And C-C bond cleavage to cause bond breaking reaction: c_nH_2n+2→C_mH_2m+C_{n- m}H_2(n-m)+2Resulting in a significant drop in the quality of the coal sample. The time when the aromatic ring content greatly slips down is roughly the sign of the coal sample entering the fast pyrolysis and combustion stage. In the figure, the temperature for the aromatic ring in the raw coal to be cracked greatly is about 430 ℃, and the temperature for the aromatic ring in the inhibition coal sample to be cracked greatly is about 450 ℃, which is increased by about 20 ℃, thereby showing that the inhibition treatment can effectively increase the temperature for the coal sample to generate spontaneous combustion.

As can be seen from FIG. 18, the total area of ether bonds in the hindered coal is higher than that of the raw coal sample, and the ether bonds are taken as a functional group with stable properties, and the content of the ether bonds is increased due to the reaction of hydroxyl groups in PAM/SA with alcohol in the coal sample, so that the alcohol is blocked from continuing the oxidation reaction and generating unstable hydrocarbon intermediates and active free radicals, and the chain reaction process is stopped. The increase of the ether bond content shows that the inhibitor can effectively improve the thermal stability of the coal, thereby effectively inhibiting the spontaneous combustion oxidation process of the coal.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.