PA / CS / TA inhibitor for inhibiting spontaneous combustion of coal and preparation method thereof

Abstract

This invention provides a PA / CS / TA inhibitor for suppressing coal spontaneous combustion and its preparation method, belonging to the field of inhibitor technology. This invention employs aqueous phase electrostatic self-assembly technology to prepare the PA / CS / TA inhibitor. The PA / CS / TA inhibitor can eliminate free radicals and reduce the activity of the coal-oxygen reaction system from the essence of the coal oxidation reaction, thus preventing the occurrence of a chain reaction of coal oxidation spontaneous combustion to a certain extent. From the perspective of chain reaction propagation, the inhibitor can effectively capture the key group -OH, reducing the rate of the coal-oxygen reaction and slowing down its progress. PA, CS, and TA act as acid source, carbon source, and gas source, respectively, and play a mutually promoting role during thermal decomposition. CS and TA, under the promoting effect of the acid source PA, form an encapsulating carbon layer on the coal surface, while simultaneously releasing inert gases. This causes the carbon layer to expand and dilutes the oxygen concentration around the coal, resulting in a significant inhibitory effect on coal oxidation spontaneous combustion.

Description

Technical Field

[0001] This invention relates to the field of inhibitor technology, and in particular to a PA / CS / TA inhibitor for inhibiting spontaneous combustion of coal and its preparation method. Background Technology

[0002] Coal is my country's primary energy source, and its mining, transportation, and storage all face serious threats from spontaneous combustion. To suppress spontaneous combustion, scholars both domestically and internationally have proposed various fire prevention and extinguishing technologies, including grouting, inert injection, and spraying of inhibitors. These methods have played a crucial role in preventing spontaneous combustion and ensuring mine safety, achieving good results. However, they also have several shortcomings: due to the chemical properties of the materials themselves, they release toxic and harmful gases during use under temperature changes, threatening the lives and health of underground personnel; inert injection technology requires high airtightness and stringent conditions, and is greatly affected by airflow, posing a risk of asphyxiation and making it difficult to achieve long-term inertization; while chemical inhibitors, primarily antioxidants, chemically inhibit spontaneous combustion, the antioxidants themselves release heat during oxidation, potentially promoting spontaneous combustion to some extent, and are also costly and difficult to apply.

[0003] Therefore, how to improve the inhibition effect of inhibitors and thus effectively suppress coal spontaneous combustion has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to provide a PA / CS / TA inhibitor for suppressing coal spontaneous combustion and its preparation method. The PA / CS / TA inhibitor prepared by the method provided by this invention can capture free radicals in coal, release inert gases, and form an expanding oxygen-barrier and heat-insulating layer on the coal surface, thereby exhibiting excellent inhibitory effects and effectively suppressing coal spontaneous combustion.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a PA / CS / TA inhibitor to suppress spontaneous combustion of coal, comprising the following steps:

[0007] (1) Mix chitosan solution with phytic acid solution and perform first aqueous phase electrostatic self-assembly to obtain PA / CS solution;

[0008] (2) The PA / CS solution obtained in step (1) is mixed with tannic acid solution and subjected to second aqueous phase electrostatic self-assembly to obtain PA / CS / TA inhibitor for inhibiting coal spontaneous combustion.

[0009] Preferably, the mass concentration of the chitosan solution in step (1) is 0.5 wt% to 1.5 wt%.

[0010] Preferably, the phytic acid solution in step (1) has a mass concentration of 0.1 wt% to 1 wt%.

[0011] Preferably, in step (1), the mass ratio of chitosan solution to phytic acid solution is 1:1.

[0012] Preferably, the first aqueous phase electrostatic self-assembly in step (1) and the second aqueous phase electrostatic self-assembly in step (2) are carried out independently and sequentially under stirring and standing conditions.

[0013] Preferably, the stirring time is 10 min to 30 min.

[0014] Preferably, the settling time is 10 min to 30 min.

[0015] Preferably, the mass concentration of the tannic acid solution in step (2) is 0.5wt% to 2.5wt%.

[0016] Preferably, the mass ratio of the tannic acid solution in step (2) to the phytic acid solution in step (1) is 1:1.

[0017] The present invention also provides a PA / CS / TA inhibitor for inhibiting spontaneous combustion of coal prepared by the preparation method described in the above technical solution.

[0018] This invention provides a method for preparing a PA / CS / TA inhibitor to suppress spontaneous combustion of coal, comprising the following steps: mixing a chitosan solution with a phytic acid solution to perform a first aqueous phase electrostatic self-assembly to obtain a PA / CS solution; mixing the PA / CS solution with a tannic acid solution to perform a second aqueous phase electrostatic self-assembly to obtain a PA / CS / TA inhibitor to suppress spontaneous combustion of coal. This invention employs aqueous electrostatic self-assembly technology. A PA / CS solution is prepared by electrostatic self-assembly of anions in a phytic acid (PA) solution with cations in a chitosan (CS) solution. Then, a PA / CS / TA inhibitor is prepared by electrostatic self-assembly of anions in a tannic acid (TA) solution with cations in the CS solution. The PA / CS / TA inhibitor eliminates free radicals and reduces the activity of the coal-oxygen reaction system, thus preventing the chain reaction of coal oxidation and spontaneous combustion to a certain extent. Simultaneously, from the perspective of chain reaction propagation, the PA / CS / TA inhibitor effectively captures the key group -OH, reducing the rate of the coal-oxygen reaction and slowing its progress. PA, CS, and TA act as acid source, carbon source, and gas source, respectively, mutually promoting each other during thermal decomposition. Under the promoting effect of the acid source PA, CS and TA form a protective carbon layer on the coal surface, while simultaneously releasing inert gases. This causes the carbon layer to expand, diluting the oxygen concentration around the coal and thus inhibiting the coal's reactivity, exhibiting a significant inhibitory effect on coal oxidation and spontaneous combustion. Experimental results show that lignite and gas coal treated with PA / CS / TA inhibitors release significantly less CO gas products during low-temperature oxidation than raw coal. Under the same experimental conditions, the six characteristic temperature points of coal samples treated with PA / CS / TA inhibitors are all higher than those of raw coal. Attached Figure Description

[0019] Figure 1 Top view of the PA / CS / TA inhibitor for inhibiting coal spontaneous combustion prepared in Example 1 before and after the oxidation reaction;

[0020] Figure 2 Side view of the PA / CS / TA inhibitor for inhibiting coal spontaneous combustion prepared in Example 1 before and after the oxidation reaction;

[0021] Figure 3 To compare the CO gaseous products of raw lignite prepared in Example 1 and lignite samples prepared in Example 1 after inhibition treatment with temperature.

[0022] Figure 4 To compare the CO gaseous products of the raw gas coal prepared in Example 2 and the inhibited gas coal sample prepared in Example 2 with temperature variation.

[0023] Figure 5To compare the TG-DTG curves of the lignite raw coal prepared in Example 3;

[0024] Figure 6 The TG-DTG curve of the inhibited lignite sample prepared in Example 3 is shown.

[0025] Figure 7 To compare the TG-DTG curves of the raw gas coal prepared in Example 4;

[0026] Figure 8 The TG-DTG curve of the inhibited gas coal sample prepared in Example 4 is shown.

[0027] Figure 9 The infrared spectra of raw lignite prepared in Example 3 and lignite samples prepared in Example 3 after inhibition treatment are compared.

[0028] Figure 10 To compare the infrared spectra of the main functional groups in the raw lignite prepared in Example 3 and the lignite sample prepared in Example 3 after inhibition treatment, the fitted peak area diagrams of the main functional groups are shown. Detailed Implementation

[0029] This invention provides a method for preparing a PA / CS / TA inhibitor to suppress spontaneous combustion of coal, comprising the following steps:

[0030] (1) Mix chitosan solution with phytic acid solution and perform first aqueous phase electrostatic self-assembly to obtain PA / CS solution;

[0031] (2) The PA / CS solution obtained in step (1) is mixed with tannic acid solution and subjected to second aqueous phase electrostatic self-assembly to obtain PA / CS / TA inhibitor for inhibiting coal spontaneous combustion.

[0032] Unless otherwise specified, the present invention does not impose any special restrictions on the source of each raw material, and commercially available products or well-known preparation methods familiar to those skilled in the art can be used for preparation.

[0033] This invention involves mixing a chitosan solution with a phytic acid solution and performing a first aqueous phase electrostatic self-assembly to obtain a PA / CS solution.

[0034] In this invention, the mass concentration of the chitosan solution is preferably 0.5 wt% to 1.5 wt%, more preferably 0.8 wt% to 1.5 wt%, and even more preferably 1.0 wt% to 1.5 wt%. In this invention, the molecular structure of chitosan is preferably as shown in Formula I. Chitosan is a biomass polycationic electrolyte and the only alkaline polysaccharide carrying a positive charge. Under acidic solution conditions, the chitosan molecule also has a large number of protonated amino groups, with -NH2 protonated to -NH3. +This makes chitosan positively charged in acidic solutions, allowing it to self-assemble with negatively charged phytic acid.

[0035]

[0036] In this invention, the chitosan solution is preferably prepared by dissolving chitosan in an acetic acid solution; the mass concentration of the acetic acid solution is preferably 1 wt% to 3 wt%; the solvent of the acetic acid solution is preferably deionized water; the dissolution of chitosan in the acetic acid solution is preferably carried out under stirring conditions; the stirring temperature is preferably 30℃ to 70℃; the stirring time is preferably 4 h to 8 h; and the stirring rate is preferably 400 r / min to 600 r / min. In this invention, acetic acid is low in cost, and in acidic solution, the amino groups in the chitosan molecule undergo protonation, making the chitosan positively charged in the solution, thereby enabling electrostatic self-assembly with PA and TA.

[0037] In this invention, the mass concentration of the phytic acid solution is preferably 0.1 wt% to 1 wt%, more preferably 0.5 wt% to 1 wt%, and even more preferably 0.6 wt% to 0.8 wt%. In this invention, the molecular structure of the phytic acid (PA) is preferably as shown in Formula II. It is a polyanionic electrolyte, and the phosphate group ionized in water is a multi-negative ion, giving PA an anionic property, allowing it to electrostatically self-assemble with positively charged substances.

[0038]

[0039] In this invention, the phytic acid solution is preferably prepared by mixing phytic acid and deionized water; the mixing of phytic acid and deionized water is preferably carried out under stirring conditions; the stirring temperature is preferably 30℃~70℃; the stirring time is preferably 1h~2h; and the stirring rate is preferably 400r / min~600r / min.

[0040] In this invention, the mass ratio of the chitosan solution to the phytic acid solution is preferably 1:1.

[0041] In this invention, the mixing of the chitosan solution and the phytic acid solution is preferably carried out by adding the phytic acid solution dropwise to the chitosan solution; the dropwise addition rate is preferably 0.01 mL / s to 0.03 mL / s; the dropwise addition is preferably carried out under stirring conditions; the stirring temperature is preferably 30℃ to 70℃; and the stirring rate is preferably 400 r / min to 800 r / min. This invention does not have a specific limitation on the stirring time; it is sufficient to add the phytic acid solution completely. The dropwise addition method used in this invention ensures that the inhibitor PA / CS / TA particles are uniform.

[0042] In this invention, the first aqueous phase electrostatic self-assembly is preferably carried out sequentially under stirring and settling conditions; the stirring time is preferably 10 min to 30 min, more preferably 20 min to 30 min; the stirring temperature is preferably 30℃ to 70℃; the stirring rate is preferably 400 r / min to 800 r / min; and the settling time is preferably 10 min to 30 min, more preferably 10 min to 20 min. By controlling the process parameters of the first aqueous phase electrostatic self-assembly, this invention can further ensure the uniformity of the inhibitor PA / CS / TA particles.

[0043] After obtaining the PA / CS solution, the present invention mixes the PA / CS solution with a tannic acid solution and performs electrostatic self-assembly in the second aqueous phase to obtain a PA / CS / TA inhibitor that inhibits spontaneous combustion of coal.

[0044] In this invention, the mass concentration of the tannic acid solution is preferably 0.5 wt% to 2.5 wt%, more preferably 0.5 wt% to 2.0 wt%, and even more preferably 0.5 wt% to 1.5 wt%. In this invention, tannic acid (TA) is a natural polyphenol with abundant sources. The tannic acid structure contains highly reactive ortho-phenolic hydroxyl groups (preferably as shown in Formula III). The -OH in the TA solution reacts with the -NH3 in the CS solution. + Using electrostatic self-assembly technology, TA molecules are adsorbed onto the main chain of CS molecules to form a supramolecular structure.

[0045]

[0046] In this invention, the tannic acid solution is preferably prepared by mixing tannic acid and deionized water; the mixing of tannic acid and deionized water is preferably carried out under stirring conditions; the stirring temperature is preferably 30℃~70℃; the stirring time is preferably 1h~2h; and the stirring rate is preferably 400r / min~600r / min. This invention does not impose any special limitation on the stirring rate, as long as the raw materials are mixed evenly.

[0047] In this invention, the mass ratio of the tannic acid solution to the phytic acid solution is preferably 1:1.

[0048] In this invention, the mixing of the PA / CS solution and the tannic acid solution is preferably carried out by adding the tannic acid solution dropwise to the PA / CS solution; the preferred dropping rate is 0.01 mL / s to 0.03 mL / s; the dropping is preferably carried out under stirring conditions; the preferred stirring temperature is 30℃ to 70℃; and the preferred stirring rate is 400 r / min to 800 r / min. This invention does not have a specific limitation on the stirring time; it is sufficient to add the tannic acid solution completely. The dropwise addition method used in this invention ensures that the inhibitor PA / CS / TA particles are uniform.

[0049] In this invention, the second aqueous phase electrostatic self-assembly is preferably carried out sequentially under stirring and settling conditions; the stirring time is preferably 10 min to 30 min, more preferably 20 min to 30 min; the stirring temperature is preferably 30℃ to 70℃; the stirring rate is preferably 400 r / min to 800 r / min; and the settling time is preferably 10 min to 30 min, more preferably 10 min to 20 min. By controlling the process parameters of the second aqueous phase electrostatic self-assembly, this invention can further ensure the uniformity of the inhibitor PA / CS / TA particles.

[0050] After the second aqueous phase electrostatic self-assembly is completed, the present invention preferably performs centrifugal filtration, deionized water washing, collection of precipitate and vacuum freeze drying on the product obtained by the second aqueous phase electrostatic self-assembly to obtain PA / CS / TA inhibitors that inhibit coal spontaneous combustion.

[0051] In this invention, the centrifugation speed is preferably 5000 r / min to 6000 r / min; the centrifugation time is preferably 20 min to 30 min.

[0052] The present invention does not impose any special limitations on the operation of washing with deionized water and collecting the precipitate; any operation known to those skilled in the art can be used.

[0053] In this invention, the vacuum freeze-drying time is preferably 70-72 hours. This invention does not impose specific limitations on other process parameters for the vacuum freeze-drying; operations familiar to those skilled in the art can be used.

[0054] The stepwise feeding method of this invention can ensure that the prepared inhibitor PA / CS / TA particles are uniform.

[0055] This invention employs aqueous electrostatic self-assembly technology to prepare PA / CS solutions through the electrostatic self-assembly of anions in phytic acid (PA) solution and cations in chitosan (CS) solution. Then, a PA / CS / TA solution is prepared through the electrostatic self-assembly of anions in tannic acid (TA) solution and cations in CS solution. The PA / CS / TA inhibitor is then obtained through centrifugation, filtration, and freeze-drying. To improve the inhibitory effect, a low-cost, environmentally friendly inhibitor capable of capturing free radicals in coal, releasing inert gases, and forming an expanding oxygen-barrier and heat-insulating layer on the coal surface, with multiple inhibitory functional elements, is prepared using this cost-effective and safe aqueous electrostatic self-assembly technology to inhibit spontaneous combustion of coal.

[0056] Aqueous electrostatic self-assembly technology is based on the electrostatic attraction between the positive and negative charges of polyelectrolytes. An aqueous solution of polyelectrolytes with opposite charges is dropwise added and mixed. As the two solutions mix, molecules self-assemble in the aqueous phase through electrostatic forces, forming a polyelectrolyte complex that precipitates out, yielding the target product. This method can be operated under mild conditions, is inexpensive, simple, environmentally friendly, and requires no complex chemical treatment.

[0057] The present invention also provides a PA / CS / TA inhibitor for inhibiting spontaneous combustion of coal prepared by the preparation method described in the above technical solution.

[0058] The PA / CS / TA inhibitor provided by this invention can capture free radicals in coal, release inert gases, and form an expanding oxygen-barrier and heat-insulating layer on the surface of the coal, thereby exhibiting excellent inhibition effect and effectively suppressing spontaneous combustion of coal.

[0059] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0060] Example 1

[0061] The preparation method of PA / CS / TA inhibitor for suppressing coal spontaneous combustion includes the following steps:

[0062] (1) Weigh CS powder and dissolve it in acetic acid solution with a mass concentration of 1 wt%. Place the solution in a magnetic stirrer and stir to obtain a CS solution with a mass concentration of 1.0 wt%. The stirring temperature is 30℃, the stirring time is 8 h, and the stirring speed is 600 r / min.

[0063] (2) Weigh PA and deionized water, mix them, and place them in a magnetic stirrer. Stir at 30°C for 1 hour to obtain a PA solution with a mass concentration of 0.7wt%; wherein the stirring rate is 600r / min.

[0064] (3) The PA solution obtained in step (2) is added dropwise at a rate of 0.01 mL / s to the CS solution placed in a magnetic stirrer using a syringe pump. After the addition is complete, the mixture is stirred for 30 min and then allowed to stand for 10 min to obtain a PA / CS solution. The mass ratio of PA solution to CS solution is 1:1. The stirring temperature is 30°C and the stirring rate is 400 r / min.

[0065] (4) Weigh TA powder and mix it with deionized water, place it in a magnetic stirrer and stir at 30°C for 1 hour to obtain a TA solution with a mass concentration of 0.5wt%; wherein, the stirring speed is 600r / min;

[0066] (5) Weigh out the same mass of TA solution as PA solution, and use a syringe pump to add the TA solution dropwise to the PA / CS solution placed in a magnetic stirrer at a rate of 0.01 mL / s. After the addition is complete, continue stirring for 30 min, and then let it stand for 10 min to obtain PA / CS / TA solution. The stirring temperature is 30℃ and the stirring rate is 400 r / min.

[0067] (6) The obtained PA / CS / TA solution was centrifuged and filtered, the precipitate was collected, the filtrate was retained, and the precipitate was washed three times with deionized water. The precipitate was then freeze-dried under vacuum for 72 hours to obtain the PA / CS / TA inhibitor that inhibits spontaneous combustion of coal. The centrifugation speed was 6000 r / min and the centrifugation time was 30 min.

[0068] A thermal oxidation experiment was conducted on the PA / CS / TA inhibitor prepared in Example 1 to inhibit spontaneous combustion of coal under an alcohol lamp at room temperature. The morphology of the carbon layer of the inhibitor during the thermal oxidation process was observed, and the expansion performance of the inhibitor was analyzed. The top view and side view of the PA / CS / TA inhibitor before and after the oxidation reaction are shown in the figures below. Figure 1 and 2 As shown.

[0069] from Figure 1 and 2It can be seen that the PA / CS / TA inhibitor exhibits significant expansion behavior after heating. The expansion effect of PA / CS / TA is as follows: First, PA, as an acid source, contains phosphate groups, which can promote the dehydration and carbonization of CS, the carbon source. At the same time, due to the large number of hydroxyl and benzene ring structures of TA, it has excellent carbonization ability and forms a dense carbon layer on the coal surface. CS and TA, as gas sources, generate non-combustible gases such as nitrogen and carbon dioxide respectively during heating, which can promote the expansion and foaming of the carbon layer. Finally, an expanded foamed carbon layer structure is formed on the coal surface. This carbon layer structure can block oxygen and reduce the heat transferred from the heat source to the coal, thereby achieving a synergistic inhibition effect of PA, CS and TA, and inhibiting further oxidation and spontaneous combustion of coal.

[0070] Application Example 1

[0071] The PA / CS / TA inhibitor prepared in Example 1 was mixed with deionized water to prepare a PA / CS / TA solution with a concentration of 10wt%. Then, 20g of the PA / CS / TA solution was weighed and mixed evenly with 80g of lignite sample. The mixture was then placed in a vacuum drying oven and dried at a constant temperature of 45°C until the weight of the coal sample remained unchanged, resulting in a lignite sample with a particle size of 60-80 mesh after inhibition treatment.

[0072] Comparative Application Example 1

[0073] Weigh 80g of raw lignite and place it in a vacuum drying oven at 45℃ for constant drying until the weight of the coal sample remains unchanged, thus obtaining raw lignite with a particle size of 60-80 mesh.

[0074] Application Example 2

[0075] The PA / CS / TA inhibitor prepared in Example 1 was mixed with deionized water to prepare a PA / CS / TA solution with a concentration of 10wt%. Then, 20g of the PA / CS / TA solution was weighed and mixed evenly with 80g of gas coal sample. The mixture was then placed in a vacuum drying oven and dried at a constant temperature of 45℃ until the weight of the coal sample remained unchanged, resulting in a gas coal sample with a particle size of 60-80 mesh after inhibition treatment.

[0076] Comparative Application Example 2

[0077] Weigh 80g of raw gas coal and place it in a vacuum drying oven at 45℃ for constant drying until the weight of the coal sample remains unchanged, thus obtaining raw gas coal with a particle size of 60-80 mesh.

[0078] A programmed temperature rise-gas chromatography (PCC) system was used. The furnace heating rate was set to 0.5 °C / min, the gas flow rate was set to 120 mL / min, and the test temperature was heated from room temperature to 250 °C. Gases produced by the oxidation of coal samples from Application Examples 1-2 and Application Examples 1-2 at different temperatures were collected, and CO was detected by gas chromatography.

[0079] The curves showing the change of CO gaseous products with temperature between the raw lignite prepared in Example 1 and the lignite sample prepared in Example 1 after inhibition treatment are shown below. Figure 3 As shown; the curves of CO gaseous products versus temperature for the gas coal sample prepared in Example 2 and the gas coal sample prepared in Example 2 after inhibition treatment are shown in Figure 2. Figure 4 As shown.

[0080] from Figure 3 and 4 It can be seen that the amount of CO gas produced during the low-temperature oxidation process of lignite and gas coal treated with PA / CS / TA inhibitors is significantly lower than that of raw coal. From the curve slope, it can be seen that the CO generation rate of raw lignite and gas coal is higher than that of the inhibited coal samples during the coal oxidation and spontaneous combustion process, while the CO generation rate of the coal sample treated with PA / CS / TA inhibitors is the lowest. This is because PA, CS, and TA in the inhibitors act as acid source, carbon source, and gas source, respectively, and they mutually promote each other during the thermal decomposition process. CS and TA form a protective carbon layer on the coal surface under the promoting effect of the acid source PA, while simultaneously releasing inert gases. This causes the carbon layer to expand and dilutes the oxygen concentration around the coal, thereby inhibiting the reactivity of the coal and significantly suppressing the oxidative spontaneous combustion of coal.

[0081] Application Example 3

[0082] The PA / CS / TA inhibitor prepared in Example 1 was mixed with deionized water to prepare a PA / CS / TA solution with a concentration of 10wt%. Then, 1g of the PA / CS / TA solution was weighed and mixed evenly with 4g of lignite sample. The mixture was then placed in a vacuum drying oven and dried at a constant temperature of 45°C until the weight of the coal sample remained unchanged, resulting in a lignite sample with a particle size of less than 200 mesh after inhibition treatment.

[0083] Comparative Application Example 3

[0084] Weigh 4g of raw lignite and place it in a vacuum drying oven at 45℃ for constant drying until the weight of the coal sample remains unchanged, thus obtaining raw lignite with a particle size of less than 200 mesh.

[0085] Application Example 4

[0086] The PA / CS / TA inhibitor prepared in Example 1 was mixed with deionized water to prepare a PA / CS / TA solution with a concentration of 10wt%. Then, 1g of the PA / CS / TA solution was weighed and mixed evenly with 4g of gas coal sample. The mixture was then placed in a vacuum drying oven and dried at a constant temperature of 45°C until the weight of the coal sample remained unchanged, thus obtaining a gas coal sample with a particle size of less than 200 mesh after inhibition treatment.

[0087] Comparative Application Example 4

[0088] Weigh 4g of raw gas coal and place it in a vacuum drying oven at a constant temperature of 45℃ until the weight of the coal sample remains unchanged, thus obtaining raw gas coal with a particle size of less than 200 mesh.

[0089] 10 mg of coal samples prepared in Comparative Application Examples 3-4 and Application Examples 3-4 were placed in crucibles, and the heating rate was set to 10 K / min. The coal samples were heated from room temperature to 800 °C, and thermogravimetric analysis (TGA) was performed to obtain the TG and DTG curves of the coal samples during the oxidation and heating process. Based on the TG-DTG curves, six characteristic temperature points of the coal samples were determined.

[0090] Coal spontaneous combustion is an extremely complex process involving interaction with oxygen. The weight of coal changes under oxidative conditions. By measuring the relationship between coal weight and temperature and analyzing the experimentally obtained TG-DTG curves, we can identify the characteristic temperature points at different stages of coal oxidation and spontaneous combustion, reflecting the macroscopic changes in coal oxidation and spontaneous combustion. This allows us to infer the degree of coal spontaneous combustion hazard and can also serve as a basis for judging the effectiveness of inhibitors in suppressing coal spontaneous combustion.

[0091] The critical temperature point T1 is the first minimum value on the DTG curve, representing the temperature at which the coal sample experiences its maximum water loss rate. The drying cracking temperature point T2 is the first minimum weight value that occurs during the oxidation process of the coal sample. The activation temperature point T3 indicates that the oxygen uptake of the coal gradually increases, the dynamic balance of the coal sample weight is broken, and the coal sample begins to enter the oxygen uptake and weight gain stage. The thermal decomposition temperature point T4 is the maximum value on the TG curve. After this temperature point, the coal sample enters the thermal decomposition stage, the weight of the coal sample begins to decrease rapidly, the coal oxidation reaction intensifies, and the coal body temperature further increases. The ignition point temperature T5 is the ignition point of the coal. The maximum thermal weight loss rate temperature point T6 indicates that the coal enters the intense combustion stage and is the point of maximum weight loss rate, the peak value on the DTG curve.

[0092] The characteristic temperature points of the coal samples from Application Example 3 and Application Example 3 are shown in Table 1. The TG-DTG curves of the lignite raw coal prepared in Application Example 3 are shown in Table 1. Figure 5 As shown, the TG-DTG curve of the inhibited lignite sample prepared using Example 3 is as follows. Figure 6 As shown.

[0093] Table 1 compares the characteristic temperature points of coal samples in Application Example 3 and Application Example 4.

[0094] sample <![CDATA[T1]]> <![CDATA[T2]]> <![CDATA[T3]]> <![CDATA[T4]]> <![CDATA[T5]]> <![CDATA[T6]]> Lignite raw coal 48.4 102.1 153.2 278.1 440.1 487 Lignite samples after inhibition treatment 54.7 117.6 200.7 294.8 465.6 530.8

[0095] From Table 1, Figure 5 and 6It can be seen that, under the same experimental conditions, the six characteristic temperature points of the coal sample treated with PA / CS / TA inhibitors are all higher than those of raw lignite. Among them, the critical temperature point T1 is 3.8℃ higher than that of raw lignite; the active temperature point T3 is significantly higher, 42.5℃ higher than that of raw lignite; and the ignition point T5 is 23.3℃ higher than that of raw lignite. This indicates that the oxidation reaction of lignite treated with PA / CS / TA inhibitors requires higher temperature conditions. Therefore, PA / CS / TA inhibitors have excellent ability to inhibit the spontaneous combustion of lignite oxidation.

[0096] Table 2 shows the characteristic temperature points of the coal samples from Application Example 4 and Application Example 4, and the TG-DTG curves of the raw gas coal prepared in Application Example 4 are shown in Table 2. Figure 7 As shown, the TG-DTG curve of the inhibited gas coal sample prepared using Example 4 is as follows. Figure 8 As shown.

[0097] Table 2 compares the characteristic temperature points of coal samples in Application Example 4 and Application Example 5.

[0098] sample <![CDATA[T1]]> <![CDATA[T2]]> <![CDATA[T3]]> <![CDATA[T4]]> <![CDATA[T5]]> <![CDATA[T6]]> Gas coal raw coal 55.6 119.8 176.1 291.9 458.7 519.6 Gas coal samples after inhibition treatment 61.2 125.5 196.2 306.8 473.8 539.4

[0099] From Table 2, Figure 7 and 8 It can be seen that, under the same experimental conditions, the six characteristic temperature points of the coal sample treated with PA / CS / TA inhibitors are all higher than those of the raw gas coal. Among them, the critical temperature point T1 is 5.6℃ higher than that of the raw gas coal; the active temperature point T3 is significantly higher, 20.1℃ higher than that of the raw gas coal; and the ignition point T5 is 15.1℃ higher than that of the raw gas coal. This indicates that the oxidation reaction of gas coal treated with PA / CS / TA inhibitors requires higher temperature conditions. Therefore, PA / CS / TA inhibitors have excellent ability to inhibit the spontaneous combustion of gas coal oxidation.

[0100] By analyzing the effect of PA / CS / TA inhibitors on coal functional groups at their activation temperature, the inhibitory effect of PA / CS / TA inhibitors on the chain reaction process of functional groups and oxygen in the coal oxidation and spontaneous combustion process can be determined.

[0101] Fourier transform infrared spectroscopy was used to compare and analyze the functional groups at the active temperature point of the raw lignite prepared in Comparative Application Example 3 and the lignite sample prepared in Comparative Application Example 3 and inhibited by PA / CS / TA inhibitor. The spectral scanning wavenumber range was 4000–500 cm⁻¹. -1 32 scans, 4cm resolution -1 Infrared spectrum as follows Figure 9 As shown.

[0102] according to Figure 9And the peak positions of the main functional groups in coal were assigned, and the corresponding fitted infrared absorption peak areas of each functional group were obtained. Based on the fitted peak areas of the main functional groups in the infrared spectra of raw lignite and inhibited lignite samples (such as...), Figure 10 As shown, the oxidation degree of different coal samples can be quantitatively analyzed.

[0103] from Figure 10 It can be seen that, compared with raw lignite, the coal sample treated with PA / CS / TA inhibitors showed a significant decrease in the normalized peak areas corresponding to aromatic hydrocarbons, aliphatic hydrocarbons, and oxygen-containing functional groups at the active temperature point, indicating a significant reduction in the concentration of these functional groups. In the coal oxidation-ignition chain reaction, aliphatic hydrocarbons are key exothermic groups. The results show that the concentration of aliphatic hydrocarbons in the inhibited coal sample was significantly reduced, indicating that the inhibitor can reduce the amount of aliphatic hydrocarbons in the coal. Compared with raw lignite, the number of aliphatic hydrocarbons decreased by 68.7%, which can reduce the heat released by coal oxidation to a certain extent. Hydroxyl groups are key linking groups in the coal oxidation-ignition chain reaction, promoting the exothermic reaction process of coal oxidation. The results show that the number of free hydroxyl groups in the inhibited coal sample was significantly reduced, decreasing by 71% compared with raw lignite. Furthermore, due to the low activation energy of free hydroxyl groups, they are easily captured, consumed, and removed by phytic acid and tannic acid in the inhibitor. Compared to raw lignite, the peak area corresponding to associated hydroxyl groups in the inhibited coal sample increased rather than decreased, further indicating that PA and TA in the inhibitor combined with free hydroxyl groups in the coal to produce H2O, thus increasing the concentration of associated hydroxyl groups in the inhibited coal sample, which in turn can cool the coal. Therefore, PA / CS / TA inhibitors can eliminate free radicals and reduce the activity of the coal-oxygen reaction system from the essence of the coal oxidation reaction, and can prevent the occurrence of the coal oxidation spontaneous combustion chain reaction to a certain extent. Simultaneously, from the perspective of chain reaction transmission, PA / CS / TA inhibitors can effectively capture the key group -OH, reducing the rate of the coal-oxygen reaction and slowing down its progress.

[0104] As can be seen from the above embodiments, the PA / CS / TA inhibitor prepared by the preparation method provided by the present invention can capture free radicals in coal, release inert gases, and form an expanding oxygen-barrier and heat-insulating layer on the surface of the coal body, thereby having excellent inhibition effect and effectively suppressing coal spontaneous combustion.

[0105] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a PA / CS / TA inhibitor to suppress spontaneous combustion of coal, comprising the following steps: (1) Mix chitosan solution and phytic acid solution to perform first aqueous phase electrostatic self-assembly to obtain PA / CS solution; (2) The PA / CS solution obtained in step (1) is mixed with tannic acid solution and subjected to second aqueous phase electrostatic self-assembly to obtain PA / CS / TA inhibitor for inhibiting coal spontaneous combustion. In step (1), the mass concentration of the chitosan solution is 0.5wt%~1.5wt%; The phytic acid solution in step (1) has a mass concentration of 0.1 wt% to 1 wt%. The mass concentration of the tannic acid solution in step (2) is 0.5wt%~2.5wt%.

2. The production method according to claim 1, characterized by, In step (1), the mass ratio of chitosan solution to phytic acid solution is 1:

1.

3. The preparation method according to claim 1, characterized in that, The first aqueous phase electrostatic self-assembly in step (1) and the second aqueous phase electrostatic self-assembly in step (2) are carried out independently and sequentially under stirring and standing conditions.

4. The preparation method according to claim 3, characterized in that, The stirring time is 10 min to 30 min.

5. The preparation method according to claim 3, characterized in that, The settling time is 10 min to 30 min.

6. The preparation method according to claim 1, characterized in that, The mass ratio of the tannic acid solution in step (2) to the phytic acid solution in step (1) is 1:

1.

7. The PA / CS / TA inhibitor for inhibiting spontaneous combustion of coal prepared by the preparation method according to any one of claims 1 to 6.

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