Modified gel foam for inhibiting spontaneous combustion of coal as well as preparation method and application of modified gel foam

Abstract

The invention belongs to the technical field of preparation of composite inhibitors, and particularly relates to modified gel foam for inhibiting spontaneous combustion of coal as well as a preparation method and application of the modified gel foam. The modified gel foam is prepared from the following components in percentage by mass: 0.5-3% of a hydrophobic modified composite thickener, 1-5% of a foaming agent, 0.1-2% of a foam stabilizer, 1-5% of an antioxidant and the balance of water, and the sum of the mass percentages of the raw materials is 100%; wherein the hydrophobic modified composite thickening agent is hydrophobic modified guar gum-konjac glucomannan composite gel. The guar gum and the konjac glucomannan react to form a three-dimensional structure, the water-retaining property and the stability of the gel foam are improved, hydrophobic groups are grafted on molecular chains of the three-dimensional structure, the hydrophobic property and the coal surface binding property of the modified gel foam are improved, the defects that traditional gel foam is poor in oxygen isolation effect and the like are overcome, and the coal surface binding property of the modified gel foam is improved. And the coal spontaneous combustion inhibition effect is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite inhibitor preparation, and particularly relates to a modified gel foam for inhibiting coal spontaneous combustion, a preparation method thereof, and an application thereof. Background Art

[0002] At present, the prevention and control of coal spontaneous combustion mainly adopt grouting, injecting inert gas, injecting three-phase foam, etc., but these technologies also have some defects. For example, in grouting, the slurry injected into the coal seam fissures only flows along the low-lying areas and is difficult to accumulate, and it has no effect on the coal body at high positions; injecting inert gas requires a high requirement for space sealing. If there is air leakage, the gas is extremely easy to leak out with the air flow, which will greatly reduce its inhibition effect; injecting three-phase foam has the advantages of wide application range and easy to block the air leakage of broken coal, but the foam is not stable enough and cannot effectively prevent coal spontaneous combustion for a long time.

[0003] Gel foam is a new type of material for inhibiting coal spontaneous combustion. Before gelling, the gel foam presents a foam state and has good flow and diffusion performance; after gelling, the viscosity of the gel foam increases, the fluidity weakens, and it presents a gel state, showing good water retention and oxygen isolation performance. At present, common hydrogel foams are mainly prepared with sodium silicate as the main base material, and hydrophilic water-soluble starch, cyclodextrin, fiber hydrolysis solution, etc. are used to modify sodium silicate to form the gelling or gel foam of sodium silicate. Its binding property with the coal surface is poor, resulting in poor oxygen isolation effect of the gelling or gel foam and poor effect of inhibiting coal spontaneous combustion. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a modified gel foam for inhibiting coal spontaneous combustion, a preparation method thereof, and an application thereof. The provided modified gel foam forms a stable three-dimensional structure through the composite reaction of guar gum and konjac gum for the hydrophobic modified composite thickener, so that the modified gel foam has better water retention and stability, and a hydrophobic group is grafted on the molecular chain, so that the modified gel foam has excellent hydrophobic properties, thereby being able to better combine with the coal surface, improving the disadvantage of poor oxygen isolation effect of the traditional gel foam, and improving the effect of inhibiting coal spontaneous combustion.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] The present invention is designed at the molecular level to develop a gel foam system with high efficiency in inhibiting coal spontaneous combustion, and the materials are green, environmentally friendly and pollution-free. On the one hand, the first object of the present invention is to provide a modified gel foam for inhibiting coal spontaneous combustion, which is prepared from the following components by mass percentage: 0.5% - 3% of a hydrophobic modified composite thickener, 1% - 5% of a foaming agent, 0.1% - 2% of a foam stabilizer, 1% - 5% of an antioxidant, and the balance is water, and the sum of the mass percentages of the raw materials is 100%; wherein, the hydrophobic modified composite thickener forms a three-dimensional structure through the reaction of guar gum and konjac gum, improves the water retention and stability of the modified gel foam, and grafts hydrophobic groups on the molecular chain of the three-dimensional structure to increase the hydrophobicity characteristics of the modified gel foam and the binding property with the coal surface.

[0007] For the modified gel foam provided by the present invention, the hydrophobic modified composite thickener forms a stable three-dimensional structure through the composite reaction of guar gum and konjac gum, making the modified gel foam have better water retention and stability, and having hydrophobic groups grafted on the molecular chain, so that the modified gel foam has excellent hydrophobicity characteristics, and thus can better bind to the coal surface and form a dense isolation layer on the coal surface, improving the oxygen isolation property of the gel foam and overcoming the disadvantages such as poor oxygen isolation effect of the traditional gel foam, and improving its effect of inhibiting coal spontaneous combustion. The hydrophobic modified composite thickener is stirred and foamed by the foaming agent, and an antioxidant component is added, so that the material can also scavenge active free radicals in coal, block the coal-oxygen chain reaction, enhance the chemical inhibition effect of the gel foam, and has the effect of efficiently inhibiting coal spontaneous combustion. It can not only isolate the contact between coal and oxygen for a long time with strong stability, but also the antioxidant therein has the function of scavenging active free radicals in coal, and the two cooperate to effectively inhibit coal spontaneous combustion.

[0008] Furthermore, the modified gel foam includes the following components by mass percentage: 1% - 3% of a hydrophobic modified composite thickener, 1% - 4% of a foaming agent, 0.1% - 1% of a foam stabilizer, 1% - 4% of an antioxidant, and the balance is water, and the sum of the mass percentages of the raw materials is 100%.

[0009] Furthermore, the preparation method of the hydrophobic modified composite thickener includes the following steps: Mix guar gum and konjac gum, add them to water and stir to undergo a hydrogen bond reaction to obtain a guar gum-konjac gum composite gel; add a sodium hydroxide solution to the guar gum-konjac gum composite gel to carry out alkali modification to obtain an alkaline guar gum-konjac gum composite gel.

[0010] Add a hydrophobic modifier to the alkaline guar gum-konjac gum composite gel to carry out graft polymerization reaction to obtain a modified hydrophobic composite thickener.

[0011] It should be noted that in the present invention, guar gum is a polysaccharide polymer and a natural thickener. To improve the stability of the thickener, konjac gum is a water-soluble colloid. During the dissolution process, the diffusion and migration rate of water molecules is fast. When konjac gum swells in water, a stable three-dimensional structure is formed through the composite reaction of guar gum and konjac gum, making the modified gel foam have better water retention and stability. And hydrophobic groups are grafted on the molecular chain, making the modified gel foam have excellent hydrophobic properties.

[0012] Furthermore, the mass ratio of the guar gum to the konjac gum is (2 - 10):(1 - 7). It should be noted that the guar gum and konjac gum used in the present invention form a stable three-dimensional structure. Therefore, when the dosage of guar gum or konjac gum increases, the formed thickener degree is too large, which will lead to problems such as low foaming multiple.

[0013] Furthermore, the solid-liquid ratio of the guar gum-konjac gum composite gel to the sodium hydroxide solution is 3g - 7g:1mL - 5mL. The sodium hydroxide solution is an aqueous sodium hydroxide solution with a mass concentration of 80wt%. The temperature of the alkali modification is 50°C, and the time is 3h - 5h. It should be noted that the purpose of alkali-treating the guar gum-konjac gum composite gel is to destroy its molecular structure, so that polystyrene molecules can be better grafted onto the guar gum-konjac gum composite gel molecules.

[0014] Furthermore, the mass ratio of the alkaline guar gum-konjac gum composite gel to the hydrophobic modifier is 1 - 4:1 - 6. The hydrophobic modifier is polystyrene. The temperature of the graft polymerization reaction is 60°C, and the time is 1h. It should be noted that the alkaline guar gum-konjac gum composite gel has a stable three-dimensional structure. Through the grafting reaction, polystyrene molecules will be grafted onto the main chain of its molecular structure, so that the alkaline guar gum-konjac gum exhibits hydrophobic properties.

[0015] Furthermore, the foaming agent is at least one of sodium dodecyl sulfate, α-olefin sulfonate, cetyltrimethylammonium bromide, and octanoyl glucoside. It should be noted that the foaming agent used in the present invention has better foaming performance.

[0016] Furthermore, the foam stabilizer is at least one of xanthan gum, polyvinyl alcohol, and alkylolamide. It should be noted that the preferred foam stabilizer is xanthan gum. Xanthan gum is an environmentally friendly material and is inexpensive and easy to obtain.

[0017] Furthermore, the antioxidant is one or more of tea polyphenols, anthocyanins, tert-butylhydroquinone, and propyl gallate.

[0018] On the other hand, the present invention provides a method for preparing the modified gel foam for inhibiting coal spontaneous combustion, comprising the following steps: under dry conditions at room temperature, weighing a modified hydrophobic composite thickener, a foaming agent, a foam stabilizer and an antioxidant in proportion in sequence, mixing them thoroughly, then adding water in proportion, stirring and foaming at a speed of more than 1500r / min, to obtain the gel foam. The modified gel foam prepared by the present invention not only has the advantages of stable structure, wide application range, good stability, good oxygen isolation effect, good water solidification, etc., but also has stronger retardant performance and wider application range than traditional materials for inhibiting coal spontaneous combustion, which is of great significance for safe coal mining.

[0019] The present invention also provides the use of the modified gel foam for inhibiting coal spontaneous combustion in inhibiting coal spontaneous combustion, wherein the modified gel foam is sprayed onto the surface of a coal sample or injected into a coal layer, wherein the mass ratio of the modified gel foam to the coal is 2: 1. The gel foam affects the oxidation stage of the coal through the synergistic physical and chemical inhibition, increases the characteristic temperature point of the coal, and has a significant effect on inhibiting coal spontaneous combustion.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) The modified gel foam provided by the present invention, wherein the hydrophobic modified composite thickener is formed by a composite reaction of guar gum and konjac gum to have a stable three-dimensional structure, so that the modified gel foam has better water holding property and stability, and a hydrophobic group is grafted on the molecular chain, so that the modified gel foam has excellent hydrophobic properties, so that it can better combine with the coal surface and form a high-density isolation layer on the coal surface, thereby improving the disadvantage of poor oxygen isolation effect of traditional gel foam and improving its effect of inhibiting coal spontaneous combustion.

[0021] (2) The modified gel foam provided by the present invention is prepared by stirring and foaming the hydrophobic modified composite thickener with a foaming agent, and adding an antioxidant component, so that the material can remove active free radicals in coal, block the coal-oxygen chain reaction, and enhance the chemical inhibition effect of the gel foam. It has the effect of effectively inhibiting the spontaneous combustion of coal. It can not only isolate the contact between coal and oxygen for a long time and has strong stability, but also the antioxidant therein has the effect of removing active free radicals in coal. The two work synergistically to effectively inhibit the spontaneous combustion of coal. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a graph showing the contact angle test results between the hydrophobically modified composite thickener of Example 1 and the coal surface of the present invention.

[0023] Figure 2 This is a graph showing the contact angle test results between the hydrophobically modified composite thickener of Example 2 of the present invention and the coal surface.

[0024] Figure 3This is the test result diagram of the contact angle between the hydrophobic modified composite thickener in Example 3 of the present invention and the coal surface.

[0025] Figure 4 This is the test result diagram of the contact angle between the composite thickener in Comparative Example 1 of the present invention and the coal surface.

[0026] Figure 5 This is the test result diagram of the contact angle between the single modified guar gum in Comparative Example 2 of the present invention and the coal surface.

[0027] Figure 6 This is the test result diagram of the contact angle between the single modified konjac gum in Comparative Example 3 of the present invention and the coal surface.

[0028] Figure 7 This is the test result diagram of the contact angle between the hydrophobic modified composite gel in Comparative Example 4 of the present invention and the coal surface.

[0029] Figure 8 This is the thermogravimetric curve of the raw coal of the present invention.

[0030] Figure 9 This is the thermogravimetric curve of the coal sample inhibited by the present invention. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0032] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be obtained through the market or prepared by existing methods.

[0033] Example 1 A modified guar gum gel foam for inhibiting coal spontaneous combustion is prepared from the following components by mass percentage: 1.5% of hydrophobic modified composite thickener, 1.2% of foaming agent α-olefin sulfonate, 0.3% of foam stabilizer xanthan gum, 2% of antioxidant propyl gallate, and the balance is water, and the sum of the mass percentages of each raw material is 100%.

[0034] The preparation method of the above-mentioned modified guar gum gel foam for inhibiting coal spontaneous combustion includes the following steps: S1. Prepare a hydrophobic modified composite thickener: After thoroughly mixing guar gum and konjac gum in a mass ratio of 2:1, it is then slowly added to water. After mixing evenly, stirring is stopped to allow the formation of hydrogen bonds between guar gum and konjac gum. The resulting product is dried at 40 °C and ground to obtain a guar gum-konjac gum composite gel.

[0035] Place 30 mL of acetone and 5 mL of an 80% sodium hydroxide aqueous solution by mass in a 100 mL three-necked flask. Add 4 g of the guar gum-konjac gum composite gel to the three-necked flask and reflux and condense with stirring at 50 °C for 4 h for alkali modification. Then, after cooling to room temperature, the resulting product is filtered to obtain an alkaline guar gum-konjac gum composite gel.

[0036] Add 30 mL of acetone to a 100 mL three-necked flask, then add 4 g of the alkaline guar gum-konjac gum composite gel. Reflux and condense with stirring at 50 °C for 1 h, and then slowly drop 3 g of the hydrophobic modifier polystyrene into the three-necked flask for graft polymerization reaction. After the reaction is completed, the resulting product is washed with ethanol, filtered, dried, and ground to obtain a modified hydrophobic composite thickener.

[0037] S2. Weigh 1.5 g of the modified hydrophobic composite thickener, 1.2 g of the foaming agent α-olefin sulfonate, 0.3 g of the foam stabilizer xanthan gum, 2 g of the antioxidant propyl gallate, and 95 g of water by mass. Under normal temperature and dry conditions, the modified hydrophobic composite thickener, α-olefin sulfonate, xanthan gum, and propyl gallate are thoroughly mixed in sequence, and then water is added in proportion and stirred to foam at a speed of more than 1500 r / min for 5 min to prepare the gel foam.

[0038] Example 2 A modified guar gum gel foam for inhibiting coal spontaneous combustion is prepared from the following components by mass percentage: 3% of the modified hydrophobic composite thickener, 4% of the foaming agent sodium dodecyl sulfate, 1% of the foam stabilizer xanthan gum, 4% of the antioxidant tert-butylhydroquinone, and the balance is water, and the sum of the mass percentages of each raw material is 100%.

[0039] The preparation method of the above-mentioned modified guar gum gel foam for inhibiting coal spontaneous combustion includes the following steps: S1. Prepare the modified hydrophobic composite thickener: After thoroughly mixing guar gum and konjac gum in a mass ratio of 1:1, it is then slowly added to water. After mixing evenly, stirring is stopped to allow the formation of hydrogen bonds between guar gum and konjac gum. The resulting product is dried at 40 °C and ground to obtain a guar gum-konjac gum composite gel.

[0040] 30 mL of acetone and 5 mL of 80% sodium hydroxide aqueous solution were placed in a 100 mL three-necked flask, 4 g of guar gum-konjac gum composite gel was added to the three-necked flask, refluxed and condensed at 50° C. and stirred for 4 h for alkali modification, and then cooled to room temperature, and the obtained product was filtered to obtain an alkaline guar gum-konjac gum composite gel.

[0041] Add 30 mL of acetone to a 100 mL three-necked flask, then add 4 g of alkaline guar gum-konjac gum composite gel, reflux and condense with stirring at 50°C for 1 hour, then slowly add 3 g of hydrophobic modifier polystyrene into the three-necked flask to carry out graft polymerization reaction. After the reaction, wash the obtained product with ethanol, filter, dry, and grind to obtain a hydrophobic composite thickener.

[0042] S2. Weigh 3 g of a hydrophobic modified composite thickener, 4 g of sodium dodecyl sulfate, 1 g of xanthan gum, 4 g of tert-butylhydroquinone, and 88 g of water by mass; under dry conditions at room temperature, fully mix the modified hydrophobic composite thickener, sodium α-olefin sulfonate, xanthan gum, and propyl gallate in turn, then add water in proportion, and stir and foam at a speed of more than 1500 r / min for 5 minutes to obtain the gel foam.

[0043] Example 3 A modified guar gum gel foam for inhibiting coal spontaneous combustion is prepared from the following components in percentage by mass: 1% of a hydrophobically modified composite thickener, 1% of a foaming agent sodium α-olefin sulfonate, 0.1% of a foam stabilizer xanthan gum, 1% of an antioxidant propyl gallate, and the balance being water, wherein the sum of the percentages by mass of the raw materials is 100%.

[0044] The method for preparing the modified guar gum gel foam for inhibiting coal spontaneous combustion comprises the following steps: S1. Preparation of hydrophobically modified composite thickener: Guar gum and konjac gum are fully and uniformly mixed in a mass ratio of 2:1, and then slowly added into water. After being uniformly mixed, stirring is stopped to allow guar gum and konjac gum to undergo hydrogen bonding reaction. The obtained product is dried at 40° C. and ground to obtain a guar gum-konjac gum composite gel.

[0045] 30 mL of acetone and 5 mL of 80% sodium hydroxide aqueous solution were placed in a 100 mL three-necked flask, 4 g of guar gum-konjac gum composite gel was added to the three-necked flask, refluxed and condensed at 50° C. and stirred for 4 h for alkali modification, and then cooled to room temperature, and the obtained product was filtered to obtain an alkaline guar gum-konjac gum composite gel.

[0046] Add 30 mL of acetone to a 100 mL three-necked flask, then add 3 g of alkaline guar gum-konjac gum composite gel, reflux and condense with stirring at 50°C for 1 hour, then slowly add 3 g of hydrophobic modifier polystyrene into the three-necked flask to carry out graft polymerization reaction. After the reaction, wash the obtained product with ethanol, filter, dry, and grind to obtain a hydrophobic composite thickener.

[0047] S2. Weigh 1 g of a hydrophobic modified composite thickener, 1 g of a foaming agent, sodium α-olefin sulfonate, 0.1 g of a foam stabilizer, xanthan gum, 1 g of an antioxidant, propyl gallate, and 96.9 g of water by mass; under dry conditions at room temperature, fully mix the modified hydrophobic composite thickener, sodium dodecyl sulfate, xanthan gum, and tert-butylhydroquinone in turn, then add water in proportion, and stir and foam at a speed of more than 1500 r / min for 5 minutes to obtain the gel foam.

[0048] Comparative Example 1 A modified guar gum gel foam for inhibiting spontaneous combustion of coal is prepared from the following components in percentage by mass: 1.5% of a composite thickener, 1.2% of a foaming agent, sodium α-olefin sulfonate, 0.3% of a foam stabilizer, 2% of propyl gallate, an antioxidant, and the balance is water, wherein the sum of the percentages by mass of the raw materials is 100%.

[0049] The method for preparing the modified guar gum gel foam for inhibiting coal spontaneous combustion comprises the following steps: S1. Preparation of composite thickener: Guar gum and konjac gum are fully and uniformly mixed in a mass ratio of 2:1, and then slowly added into water. After being uniformly mixed, stirring is stopped to allow guar gum and konjac gum to undergo hydrogen bonding reaction. The obtained product is dried at 40° C. and ground to obtain a guar gum-konjac gum composite gel, which is a composite thickener.

[0050] S2. Weigh 1.5 g of a composite thickener, 1.2 g of sodium α-olefin sulfonate, 0.3 g of xanthan gum, 2 g of propyl gallate, and 95 g of water by mass; under dry conditions at room temperature, fully mix the composite thickener, sodium α-olefin sulfonate, xanthan gum, and propyl gallate in turn, then add water in proportion, and stir and foam at a speed of more than 1500 r / min for 5 minutes to obtain the gel foam.

[0051] Comparative Example 2 A modified guar gum gel foam for inhibiting spontaneous combustion of coal is prepared from the following components in percentage by mass: 1.5% of a hydrophobic modified thickener, 1.2% of a foaming agent sodium α-olefin sulfonate, 0.3% of a foam stabilizer xanthan gum, 2% of an antioxidant propyl gallate, and the balance being water, wherein the sum of the percentages by mass of the raw materials is 100%.

[0052] The method for preparing the modified guar gum gel foam for inhibiting coal spontaneous combustion comprises the following steps: S1. Preparation of hydrophobically modified thickener: 30 mL of acetone and 5 mL of 80% sodium hydroxide aqueous solution were placed in a 100 mL three-necked flask, 4 g of guar gum was added to the three-necked flask, and the mixture was refluxed and condensed at 50° C. and stirred for 4 h for alkali modification. After cooling to room temperature, the obtained product was filtered to obtain alkaline guar gum gel.

[0053] Add 30 mL of acetone to a 100 mL three-necked flask, then add 4 g of alkaline guar gum gel, reflux and condense with stirring at 50°C for 1 hour, then slowly add 3 g of hydrophobic modifier polystyrene into the three-necked flask to carry out graft polymerization reaction. After the reaction, wash the obtained product with ethanol, filter, dry, and grind to obtain a hydrophobic thickener.

[0054] S2. Weigh 1.5 g of a hydrophobic modified thickener, 1.2 g of sodium α-olefin sulfonate, 0.3 g of xanthan gum, 2 g of propyl gallate, and 95 g of water by mass; fully mix the modified hydrophobic thickener, sodium α-olefin sulfonate, xanthan gum, and propyl gallate in turn under dry conditions at room temperature, then add water in proportion, and stir and foam at a speed of more than 1500 r / min for 5 minutes to obtain the gel foam.

[0055] Comparative Example 3 A modified guar gum gel foam for inhibiting spontaneous combustion of coal is prepared from the following components in percentage by mass: 1.5% of a hydrophobic modified thickener, 1.2% of a foaming agent sodium α-olefin sulfonate, 0.3% of a foam stabilizer xanthan gum, 2% of an antioxidant propyl gallate, and the balance being water, wherein the sum of the percentages by mass of the raw materials is 100%.

[0056] The method for preparing the modified guar gum gel foam for inhibiting coal spontaneous combustion comprises the following steps: S1. Preparation of hydrophobically modified thickener: 30 mL of acetone and 5 mL of an aqueous sodium hydroxide solution with a mass concentration of 80% were placed in a 100 mL three-necked flask, 4 g of konjac gum was added to the three-necked flask, and the mixture was refluxed, condensed and stirred at 50° C. for 4 h for alkali modification. After cooling to room temperature, the obtained product was filtered to obtain an alkaline konjac gum gel.

[0057] Add 30 mL of acetone to a 100 mL three-necked flask, then add 4 g of alkaline konjac gum gel, reflux and condense with stirring at 50°C for 1 hour, then slowly add 3 g of hydrophobic modifier polystyrene into the three-necked flask to carry out graft polymerization reaction. After the reaction is completed, the obtained product is washed with ethanol, filtered, dried, and ground to obtain a hydrophobic thickener.

[0058] S2. Weigh 1.5 g of the hydrophobic modified thickener, 1.2 g of α-olefin sulfonate, 0.3 g of xanthan gum, 2 g of propyl gallate, and 95 g of water by mass. Under normal temperature and dry conditions, successively and fully mix the modified hydrophobic thickener, α-olefin sulfonate, xanthan gum, and propyl gallate, and then add water in proportion, and stir and foam at a speed of more than 1500 r / min for 5 min to obtain the gel foam.

[0059] Comparative Example 4 A modified guar gum gel foam for inhibiting coal spontaneous combustion is prepared from the following components by mass percentage: 1.5% of hydrophobic modified composite thickener, 1.2% of foaming agent α-olefin sulfonate, 0.3% of foam stabilizer xanthan gum, 2% of antioxidant propyl gallate, and the balance is water, and the sum of the mass percentages of each raw material is 100%.

[0060] The preparation method of the above-mentioned modified guar gum gel foam for inhibiting coal spontaneous combustion includes the following steps: S1. Prepare a hydrophobic modified composite thickener: Fully mix guar gum and konjac gum evenly at a mass ratio of 2:1, and then slowly add it to water. After mixing evenly, stop stirring to allow the guar gum and konjac gum to undergo a hydrogen bond reaction. Dry the obtained product at 40 °C and grind it to obtain a guar gum-konjac gum composite gel.

[0061] Place 30 mL of acetone and 5 mL of 80% sodium hydroxide aqueous solution by mass concentration in a 100 mL three-necked flask. Add 4 g of the guar gum-konjac gum composite gel to the three-necked flask, reflux and condense and stir at 50 °C for 4 h for alkali modification. Then, after cooling to room temperature, filter the obtained product to obtain an alkaline guar gum-konjac gum composite gel.

[0062] Add 30 mL of acetone to a 100 mL three-necked flask, then add 4 g of the alkaline guar gum-konjac gum composite gel, reflux and condense and stir at 50 °C for 1 h, and then slowly drop 3 g of the hydrophobic modifier styrene into the three-necked flask for graft polymerization reaction. After the reaction is completed, wash the obtained product with ethanol, filter, dry, and grind it to obtain a modified hydrophobic composite thickener.

[0063] S2. Weigh 1.5 g of the modified hydrophobic composite thickener, 1.2 g of α-olefin sulfonate, 0.3 g of xanthan gum, 2 g of propyl gallate, and 95 g of water by mass. Under normal temperature and dry conditions, successively weigh the modified hydrophobic composite thickener, α-olefin sulfonate, xanthan gum, and propyl gallate in proportion and mix them fully, and then add water in proportion, and stir and foam at a speed of more than 1500 r / min for 5 min to obtain the gel foam.

[0064] The hydrophobic properties of the hydrophobically modified composite thickeners prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were tested. 50 g of pulverized coal with a particle size of 80 - 120 mesh that had been prepared was taken. An appropriate amount of pulverized coal was placed into a tablet press mold and pressed for 5 minutes under a pressure of 8 Mpa to obtain the coal blocks required for measuring the contact angle. Solutions of the hydrophobically modified composite thickeners prepared in Examples 1 to 3 and Comparative Examples 1 to 3 with a mass fraction of 2% were respectively prepared, and their contact angles were tested. The results are shown in Table 1 and Figures 1 to 7 as shown below.

[0065] Table 1 Test results of the contact angle between the hydrophobically modified composite thickener and the coal surface As shown in Table 1 and Figures 1 - 7 as shown below, the contact angle between the hydrophobically modified guar gum - konjac gum and the coal is 40.7°, the contact angle between the unmodified composite thickener and the coal is 74.7°, the contact angle between the singly modified guar gum and the coal is 61.1°, the contact angle between the singly modified konjac gum and the coal is 59.7°, the contact angle between the styrene - hydrophobically modified guar gum - konjac gum and the coal is 64.2°. Compared with the hydrophobically modified guar gum - konjac gum, they are respectively reduced by 34°, 20.4°, 19°, 23.5°. This shows that the introduction of hydrophobic groups greatly enhances its hydrophobicity, enabling the gel to better combine with the coal, which can greatly improve the oxygen - isolation property of the gel foam. In addition, it can be seen from Example 1 and Comparative Example 4 that the modification effect of the hydrophobic group - polystyrene is significantly better than that of styrene, indicating that the hydrophobic modifier selected in the present invention has a better effect.

[0066] The gel foams prepared in Example 1 and Comparative Example 1 were used for the test of inhibiting coal spontaneous combustion, including the following steps: Pulverized coal with a particle size of 80 - 120 mesh was selected as the raw coal sample. The modified gel foam material and the coal sample were mixed evenly in a certain proportion, and after standing for a period of time, it was dried at 40 °C for 24 h to obtain the inhibited coal sample.

[0067] The raw coal and the inhibited coal sample were tested using a STA449F5 type synchronous thermal analyzer from Netzsch Instruments Germany. Under an air atmosphere, the test was carried out under the experimental conditions of a gas flow rate of 100 mL / min, a heating rate of 10 °C / min, and a temperature range of 30 °C to 800 °C.

[0068] The results are shown in Table 2, Figure 8 and Figure 9 as shown below.

[0069] Table 2 Characteristic temperatures of the raw coal and the inhibited coal sample From Table 2 and Figure 8 and Figure 9It can be seen that there are obvious differences in the mass percentage and vector heat rate curves of raw coal and inhibited coal samples, namely the TG and DTG curves. Among them, except for T1, the characteristic temperature points of the inhibited coal samples are higher than those of the raw coal. This shows that the gel foam affects the oxidation stage of coal through the synergistic physical and chemical inhibition, increases the characteristic temperature points of coal, and has a significant effect on inhibiting coal spontaneous combustion.

[0070] In summary, for the modified gel foam provided by the present invention, the hydrophobic modified composite thickener forms a stable three-dimensional structure through the composite reaction of guar gum and konjac gum, making the modified gel foam have better water retention and stability, and having hydrophobic groups grafted on the molecular chain, so that the modified gel foam has excellent hydrophobic properties, thus can better combine with the coal surface energy, improve the oxygen barrier property of the gel foam, overcome the disadvantages such as poor oxygen barrier effect of traditional gel foams, and improve its effect of inhibiting coal spontaneous combustion.

[0071] The modified gel foam provided by the present invention is foamed by a foaming agent for the hydrophobic modified composite thickener and an antioxidant component is added, so that this material can also scavenge active free radicals in coal, block the coal-oxygen chain reaction, and enhance the chemical inhibition effect of the gel foam. It has the effect of efficiently inhibiting coal spontaneous combustion. It can not only isolate the contact between coal and oxygen for a long time and has strong stability, but also the antioxidant therein has the function of scavenging active free radicals in coal. The two work together to effectively inhibit coal spontaneous combustion.

[0072] It should be noted that when the present invention involves numerical ranges, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the adopted step methods are the same as those in the embodiments, in order to prevent repetition, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0073] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. A modified gel foam for inhibiting spontaneous combustion of coal, characterized in that: The invention is prepared from the following components in percentage by weight: 0.5% to 3% of a hydrophobically modified composite thickener, 1% to 5% of a foaming agent, 0.1% to 2% of a foam stabilizer, 1% to 5% of an antioxidant, and the remainder being water, wherein the sum of the percentages by weight of each raw material is 100%; wherein the hydrophobically modified composite thickener is formed by reacting guar gum and konjac gum to form a three-dimensional structure, and hydrophobic groups are grafted onto the molecular chains of the three-dimensional structure.

2. The modified gel foam for inhibiting coal spontaneous combustion according to claim 1, characterized in that: The preparation method of the hydrophobically modified composite thickener comprises the following steps: The guar gum and konjac gum are mixed, added into water and stirred to generate hydrogen bonding reaction, thereby obtaining a guar gum-konjac gum composite gel; sodium hydroxide solution is added into the guar gum-konjac gum composite gel, and alkali modification is performed to obtain an alkaline guar gum-konjac gum composite gel; A hydrophobic modifier is added into the alkaline guar gum-konjac gum composite gel to carry out graft polymerization reaction to obtain a hydrophobic composite thickener.

3. The modified gel foam for inhibiting coal spontaneous combustion according to claim 2, characterized in that: The mass ratio of the guar gum to the konjac gum is (2-10):(1-7).

4. The modified gel foam for inhibiting coal spontaneous combustion according to claim 2, characterized in that: The solid-liquid ratio of the guar gum-konjac gum composite gel to the sodium hydroxide solution is 3g-7g:1mL-5mL, the sodium hydroxide solution is a sodium hydroxide aqueous solution with a mass concentration of 80wt%, the temperature of the alkali modification is 50°C, and the time is 3h-5h.

5. The modified gel foam for inhibiting coal spontaneous combustion according to claim 2, characterized in that: The mass ratio of the alkaline guar gum-konjac gum composite gel to the hydrophobic modifier is 1-4:1-6, the hydrophobic modifier is polystyrene, the temperature of the graft polymerization reaction is 60°C, and the time is 1 hour.

6. The modified gel foam for inhibiting coal spontaneous combustion according to claim 1, characterized in that: The foaming agent is at least one of sodium dodecyl sulfate, sodium α-olefin sulfonate, hexadecyltrimethylammonium bromide, and capryl glucoside.

7. The modified gel foam for inhibiting coal spontaneous combustion according to claim 1, characterized in that: The foam stabilizer is at least one of xanthan gum, polyvinyl alcohol and alkyl alcohol amide.

8. The modified gel foam for inhibiting coal spontaneous combustion according to claim 1, characterized in that: The antioxidant is one or more of tea polyphenols, anthocyanidins, tert-butylhydroquinone, and propyl gallate.

9. A method for preparing a modified gel foam for inhibiting spontaneous combustion of coal according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: under dry conditions at room temperature, weighing a modified hydrophobic composite thickener, a foaming agent, a foam stabilizer and an antioxidant in sequence according to proportion, fully mixing them, then adding water in proportion, stirring and foaming, and obtaining the gel foam.

10. Use of the modified gel foam for inhibiting coal spontaneous combustion according to any one of claims 1 to 8 in inhibiting coal spontaneous combustion, characterized in that: The modified gel foam is sprayed onto the surface of the coal sample or injected into the coal pile layer, wherein the mass ratio of the modified gel foam to the coal is 2:1.

Images