A two-factor coal spontaneous combustion tendency comprehensive determination method based on multi-scale data

Abstract

The application discloses a double-factor coal spontaneous combustion tendency comprehensive determination method based on multi-scale data, the method is combined by cross point temperature test and chromatographic oxygen absorption test, and a double-factor coal spontaneous combustion tendency comprehensive index is constructed based on an entropy weight method, the entropy weight method is used for dynamically distributing the weight of a target coal sample in a low-temperature oxidation stage, and the double-factor coal spontaneous combustion tendency comprehensive index is constructed. The deviation problem caused by the fact that the existing single method only focuses on a local oxidation stage is solved, the characterization capability for the whole process of coal spontaneous combustion is obviously improved, the determination basis with scientificity and practicability is provided for the coal spontaneous combustion risk monitoring in a coal mine underground, and the misjudgment risk caused by the limitation of a single index is effectively reduced.

Description

Technical Field

[0001] This application relates to the field of coal mining technology, and in particular to a two-factor comprehensive determination method for coal spontaneous combustion tendency based on multi-scale data. Background Technology

[0002] Currently, different countries around the world have established standards for identifying the tendency of coal to spontaneously combust, based on their specific circumstances. However, these standards are all based on low-temperature or high-temperature experiments on different types of coal, and select one or more parameters as indicators to measure the tendency of coal to spontaneously combust.

[0003] Currently, the mainstream methods for determining the spontaneous combustion tendency of coal include chromatographic oxygen absorption and the Crossing Point Temperature (CPT) method. However, each method has its advantages and disadvantages.

[0004] Chromatographic oxygen uptake, as a method for assessing the spontaneous combustion tendency of coal, primarily uses the amount of oxygen physically adsorbed per gram of dry coal at room temperature and pressure as the main classification criterion to categorize the spontaneous combustion tendency of coal. However, the spontaneous combustion process of coal involves much more than just physical oxygen adsorption; it also involves crucial chemical adsorption processes in the coal sample. Therefore, simply using the amount of oxygen physically adsorbed by coal is insufficient to comprehensively reflect the chemical reactions with oxygen during the spontaneous combustion process. The crossover temperature method, on the other hand, uses the average heating rate of the coal sample from 110℃ to 230℃ as the experimental parameter. This temperature range is relatively late compared to the spontaneous combustion behavior of coal. Summary of the Invention

[0005] This application provides a two-factor comprehensive judgment method for coal spontaneous combustion tendency based on multi-scale data to improve the accuracy of coal spontaneous combustion tendency judgment.

[0006] To achieve the above objectives, the technical solution of this invention is as follows:

[0007] This invention provides a two-factor comprehensive method for determining the spontaneous combustion tendency of coal based on multi-scale data, comprising: acquiring the cross-point temperature and oxygen uptake of a target coal sample; calculating the average heating rate and comprehensive parameters of spontaneous combustion tendency of the target coal sample based on the cross-point temperature; determining the weight of the low-temperature oxidation stage of the target coal sample using the entropy weight method based on the cross-point temperature, oxygen uptake, average heating rate, and comprehensive parameters of spontaneous combustion tendency of the target coal sample, and calculating the two-factor comprehensive index of spontaneous combustion tendency of the target coal sample; and constructing a spontaneous combustion tendency identification model for the target coal sample based on the two-factor comprehensive index of spontaneous combustion tendency of the target coal sample to identify the spontaneous combustion tendency of the coal seam corresponding to the target coal sample.

[0008] In some possible implementations, the formula for calculating the average heating rate of the target coal sample is:

[0009] ;

[0010] in, The average heating rate of the target coal sample. and The reaction times are 110℃ and 230℃, respectively, for the target coal sample; the formula for calculating the comprehensive parameter of the natural tendency of the target coal sample is:

[0011] ;

[0012] in, The comprehensive parameters of the natural tendency of coal for the target coal sample. The crossover temperature of the target coal sample.

[0013] In some possible implementations, the oxygen uptake of the target coal sample is obtained by chromatographic oxygen uptake, calculated using the following formula:

[0014] ;

[0015] in, This refers to oxygen uptake. This is the instrument constant; This is the instrument calibration factor; This refers to the actual carrier gas flow rate in the pipe, in cm³. 3 / min; This refers to the empty tube carrier gas flow rate, in cm³. 3 / min; This is the ratio of the partial pressure of oxygen to atmospheric pressure in a solid tube. This is the ratio of the partial pressure of oxygen to atmospheric pressure when the tube is empty. The actual desorption peak area is expressed in units of... ; The desorption peak area of ​​the air tube is expressed in units of 1000 m². ; This refers to the weight of the coal sample, in grams. The relative density of coal; The volume of the sample tube (standard state) is expressed in cm³. 3 ; This refers to the moisture content of the coal sample.

[0016] In some possible implementations, the formula for calculating the two-factor coal spontaneous combustion tendency composite index of the target coal sample is as follows:

[0017] ;

[0018] in, The two-factor coal spontaneous combustion tendency composite index for the target coal sample. and The oxygen uptake index of the target coal sample at 30℃ is a dimensionless quantity, corresponding to the average heating rate and the comprehensive parameter of the coal's natural tendency, respectively. ; 1.603 and 11.362 are the standardized factors determined experimentally. The weights for the low-temperature oxidation stage of the target coal sample, determined by the entropy weight method, are as follows: As the amplification factor, This represents the saturated oxygen uptake of coal during low-temperature adsorption at 30℃.

[0019] In some possible implementations, the weights of the low-temperature oxidation stage of the target coal sample are determined by the entropy weight method, including: standardizing the comprehensive parameters of oxygen uptake and coal natural tendency to eliminate dimensional differences; calculating the entropy value of the target coal sample based on the standardized data; determining the information utility value of each indicator based on the entropy value; and determining the weights of the low-temperature oxidation stage of the target coal sample based on the information utility value.

[0020] In some possible implementations, the spontaneous combustion tendency of the coal seam corresponding to the target coal sample is identified based on the dual-factor coal spontaneous combustion tendency comprehensive index, including: determining the natural tendency level of the target coal sample according to the dual-factor coal spontaneous combustion tendency comprehensive index, and identifying the spontaneous combustion tendency of the coal seam corresponding to the target coal sample.

[0021] In some possible implementations, the above method also includes analyzing the characteristic temperature points and exothermic characteristics of the target coal sample using simultaneous thermal analysis technology, and establishing an oxidation kinetic model by combining the Achar differential method and the Coats-Redfern integral method to verify the correspondence between the dual-factor coal spontaneous combustion tendency comprehensive index and the activation energy.

[0022] In some possible implementations, the method is applicable to the determination of the spontaneous combustion tendency of lignite, long-flame coal, gas coal, coking coal and anthracite.

[0023] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0024] In this embodiment of the invention, a two-factor coal spontaneous combustion tendency comprehensive index is constructed by combining cross-point temperature testing and chromatographic oxygen uptake testing, and using the entropy weight method to dynamically allocate the weight of the low-temperature oxidation stage of the target coal sample. This solves the identification bias problem caused by existing single methods focusing only on the local oxidation stage, significantly improves the characterization ability of the entire coal spontaneous combustion process, and provides a scientific and practical basis for the risk monitoring of coal spontaneous combustion in underground coal mines, effectively reducing the risk of misjudgment caused by the limitations of a single indicator. Attached Figure Description

[0025] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A schematic flowchart of an embodiment of a two-factor comprehensive determination method for spontaneous combustion tendency of coal based on multi-scale data provided for the implementation of the present invention;

[0027] Figure 2 This is a schematic diagram of the characteristic temperature points and stage divisions in an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of characteristic temperature points of coal samples with different degrees of metamorphism in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the calorific value of different coal samples in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram comparing the activation energy of coal during the combustion and decomposition stage with the comprehensive index of the two-factor coal spontaneous combustion tendency in an embodiment of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0032] In the relevant descriptions of this embodiment, the terms "including," "containing," and "possessing" are all open terms and are generally understood to include but not be limited to; the term "at least one" is generally understood to mean one or more, where "multiple" refers to two or more; the term "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items, for example, "at least one of a, b, or c", or "at least one of a, b, and c", which can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple; the symbol "A / B" is used to describe the selection relationship of associated objects, generally indicating an "or" relationship.

[0033] In the following description of the embodiments, the terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0034] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0035] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Any stated value or intermediate value within a stated range, as well as any other stated value or each smaller range between intermediate values ​​within a range, are also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe the methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0037] To illustrate the technical solution of the present invention, specific embodiments are described below.

[0038] Currently, different countries around the world have established standards for identifying the tendency of coal to spontaneously combust, based on their specific circumstances. However, these standards are all based on low-temperature or high-temperature experiments on different types of coal, and select one or more parameters as indicators to measure the tendency of coal to spontaneously combust.

[0039] Currently, the mainstream methods for determining the spontaneous combustion tendency of coal include chromatographic oxygen absorption and the Crossing Point Temperature (CPT) method. However, each method has its advantages and disadvantages.

[0040] Chromatographic oxygen uptake, as a method for assessing the spontaneous combustion tendency of coal, primarily uses the amount of oxygen physically adsorbed per gram of dry coal at room temperature and pressure as the main classification criterion to categorize the spontaneous combustion tendency of coal. However, the spontaneous combustion process of coal involves much more than just physical oxygen adsorption; it also involves crucial chemical adsorption processes in the coal sample. Therefore, simply using the amount of oxygen physically adsorbed by coal is insufficient to comprehensively reflect the chemical reactions with oxygen during the spontaneous combustion process. The crossover temperature method, on the other hand, uses the average heating rate of the coal sample from 110℃ to 230℃ as the experimental parameter. This temperature range is relatively late compared to the spontaneous combustion behavior of coal.

[0041] Based on this, embodiments of the present invention provide a two-factor comprehensive determination method for coal spontaneous combustion tendency based on multi-scale data, so as to improve the accuracy of coal spontaneous combustion tendency determination.

[0042] Figure 1 A schematic flowchart illustrating an embodiment of the dual-factor coal spontaneous combustion tendency comprehensive determination method based on multi-scale data provided for the implementation of this invention is shown below. Figure 1 As shown, the above-mentioned two-factor comprehensive determination method for coal spontaneous combustion tendency based on multi-scale data can include:

[0043] S101, obtain the cross-point temperature and oxygen uptake of the target coal sample;

[0044] The target coal sample includes, but is not limited to, one of lignite, long-flame coal, gas coal, coking coal, and anthracite. The method of this invention can be applied to determine the spontaneous combustion tendency of these types of coal samples.

[0045] In some embodiments, the specific steps for testing the crossover temperature of the target coal sample include: placing the target coal sample into a wire mesh basket, placing a precision thermocouple in the center of the basket, and placing the basket in a programmed temperature-increasing furnace. The sample mass used in the experiment is 100g, the reaction gas is air, and the flow rate is 100ml / min. After the experiment starts, the programmed temperature is increased from 30℃ to 250℃ at a heating rate of 1℃ / min. The crossover temperature between the furnace temperature and the coal temperature is then measured.

[0046] In some embodiments, the oxygen uptake of the target coal sample can be obtained by chromatographic oxygen uptake, and the calculation formula is as follows:

[0047] ;

[0048] in, This refers to oxygen uptake. This is the instrument constant; This is the instrument calibration factor; This refers to the actual carrier gas flow rate in the pipe, in cm³. 3 / min; This refers to the empty tube carrier gas flow rate, in cm³. 3 / min; This is the ratio of the partial pressure of oxygen to atmospheric pressure in a solid tube. This is the ratio of the partial pressure of oxygen to atmospheric pressure when the tube is empty. The actual desorption peak area is expressed in units of... ; The desorption peak area of ​​the air tube is expressed in units of 1000 m². ; This refers to the weight of the coal sample, in grams. The relative density of coal; The volume of the sample tube (standard state) is expressed in cm³. 3 ; This refers to the moisture content of the coal sample.

[0049] In step S101 above, the crossover temperature of the coal sample during the programmed heating process is experimentally determined, that is, the critical temperature point at which the self-oxidation exothermic rate of the coal sample exceeds the ambient heating rate. This can characterize the initial characteristics of the coal in the high-temperature stage, which changes from slow oxidation to rapid reaction. At the same time, based on the chromatographic oxygen adsorption method, the physical adsorption amount of oxygen by the coal sample at a low temperature of 30℃ is quantitatively determined, reflecting the potential ability of coal to adsorb oxygen in the early stage of oxidation.

[0050] S102, Calculate the average heating rate and comprehensive parameters of the natural tendency of the coal sample based on the temperature at the intersection point;

[0051] In some embodiments, the average heating rate of the target coal sample from 110°C to 230°C can be calculated using the following formula:

[0052] ;

[0053] in, The average heating rate of the target coal sample. and These are the reaction times when the target coal sample reaches 110℃ and 230℃, respectively.

[0054] The formula for calculating the comprehensive parameter of the natural tendency of coal in the target coal sample is as follows:

[0055] ;

[0056] in, The comprehensive parameters of the natural tendency of coal for the target coal sample. The crossover temperature of the target coal sample.

[0057] S103, based on the crossover temperature, oxygen uptake, average heating rate and coal spontaneous combustion tendency comprehensive parameters of the target coal sample, the weight of the low-temperature oxidation stage of the target coal sample is determined by the entropy weight method, and the two-factor coal spontaneous combustion tendency comprehensive index of the target coal sample is calculated.

[0058] In some embodiments, step S103 includes:

[0059] The oxygen saturation index of the target coal sample at 30℃ is determined by the following formula:

[0060] ;

[0061] ;

[0062] in, and The oxygen uptake index of the target coal sample at 30℃ is a dimensionless quantity, corresponding to the average heating rate and the comprehensive parameter of the coal's natural tendency, respectively. 1.603 and 11.362 are experimentally determined standardization factors. Taking lignite, long-flame coal, gas coal, coking coal, and anthracite as examples, 1.603 is the maximum value of the oxygen uptake of the five coal samples at 30℃, used as a calculation factor, with units in cm³. 3 / g; 11.362 represents the temperature of five coal samples when heated from 110℃ to 230℃. and The maximum value of the ratio of values ​​is used as a calculation factor, with the unit being min. -1 , This represents the saturated oxygen uptake of coal during low-temperature adsorption at 30℃.

[0063] In some embodiments, the formula for calculating the two-factor coal spontaneous combustion tendency composite index of the target coal sample is as follows:

[0064] ;

[0065] in, The two-factor coal spontaneous combustion tendency composite index for the target coal sample. The weights for the low-temperature oxidation stage of the target coal sample, determined by the entropy weight method, are as follows: This is the amplification factor.

[0066] In some embodiments, determining the weight of the low-temperature oxidation stage of the target coal sample using the entropy weight method includes:

[0067] The combined parameters of oxygen uptake and coal natural tendency are standardized to eliminate dimensional differences, and the formula is expressed as follows:

[0068] ;

[0069] Based on the standardized data, the entropy value of the target coal sample is calculated, expressed by the formula:

[0070] ;

[0071] The information utility value of each indicator is determined based on the entropy value, expressed by the following formula:

[0072] ;

[0073] The weight of the low-temperature oxidation stage of the target coal sample is determined based on the information utility value, expressed by the following formula:

[0074] .

[0075] in, The standardized values ​​of the data after eliminating dimensional differences. The original data needs to be substituted separately. and Experimental data, and These are the minimum and maximum values ​​in the original data. For the target coal sample and The entropy value of the experimental data, The target coal sample number, For the corresponding target coal sample sequence, Indicators for each coal sample and Information utility value;

[0076] For example, by standardization, the differences in dimensions are eliminated, and the data of each indicator are standardized to [0, 1], resulting in... and ; This represents the saturated oxygen uptake capacity of coal at a low-temperature adsorption rate of 30℃, a standardized value after eliminating dimensional differences. The value is the standardized value of the coal natural tendency comprehensive parameter of the target coal sample after eliminating dimensional differences.

[0077] Based on the standardized data, the entropy value of each coal sample is calculated to obtain... and ; The entropy value is calculated after standardizing the saturated oxygen uptake of coal at a low temperature of 30℃. The entropy value is calculated after standardizing the comprehensive parameters of the natural tendency of coal in the target coal sample.

[0078] Next, determine each coal sample and Information utility value ,get and ; This represents the information utility value of coal during low-temperature adsorption at 30℃. The information utility value of the comprehensive parameters of the natural tendency of coal for the target coal sample.

[0079] Finally, based on the calculated information utility value, the weight of the low-temperature oxidation stage of the target coal sample is calculated, including the weight of the influence of the low-temperature adsorption stage on the spontaneous combustion tendency of coal. The weighting of the impact of the rapid response phase on the tendency of coal to spontaneous combustion. .

[0080] After obtaining the minimum and maximum values ​​from the original data, they are substituted into the calculation formula for the two-factor coal spontaneous combustion tendency comprehensive index of the target coal sample. The two-factor coal spontaneous combustion tendency comprehensive index can be further expressed as:

[0081] ;

[0082] S104, Based on the dual-factor coal spontaneous combustion tendency comprehensive index, the spontaneous combustion tendency of the coal seam corresponding to the target coal sample is identified.

[0083] In some embodiments, step S104 may include: determining the natural tendency level of the target coal sample based on the dual-factor coal spontaneous combustion tendency comprehensive index.

[0084] For example, after obtaining the above-mentioned comprehensive index formula for the two-factor coal spontaneous combustion tendency, the formula is substituted into... and Based on standardized data, calculations were performed. and Two-factor coal spontaneous combustion tendency composite index of parameters The experimental results data in the embodiments of the present invention are shown in Table 1:

[0085] Table 1:

[0086]

[0087] Table 1 lists several parameters for coal samples that identify existing coal types. As shown in Table 1, lignite and bituminous coal... The value increases with increasing metamorphism, with HG having the lowest value at 5.788 and CJG the highest at 9.905. The I value for anthracite... DSP The values ​​are all greater than 9. This pattern is consistent with the conclusions of the chromatographic oxygen absorption method, therefore it is inferred that within a certain coal quality range, The size of the coal is positively correlated with the degree of coal metamorphism; the greater the degree of coal metamorphism, the higher the density of the coal. The larger the coal mass, the less likely it is to spontaneously combust; conversely, the smaller the mass, the more likely the coal is to spontaneously combust. When a coal sample reaches the anthracite stage of metamorphism, it has almost no tendency to spontaneously combust, but the two types of anthracite... The value is less than that of bituminous coal. Value, because by and The influence of the value is analyzed, and it can be seen that the oxygen uptake of coal is not linearly related to the degree of coal metamorphism. It is reasonable that the relationship between anthracite and the degree of metamorphism is not linear. The values ​​are all greater than 9 and less than 9.2, so 9 to 9.2 is taken as the index range for judging whether high-rank coal is not easy to spontaneously combust.

[0088] Based on this, the above step S104 can be specifically classified into natural tendency levels using the following Table 2:

[0089] Table 2:

[0090]

[0091] Understandably, the calculation model for chromatographic oxygen absorption is based on the saturated oxygen absorption capacity of coal at a low-temperature adsorption of 30℃. The method calculates the ease of spontaneous combustion of coal using as the independent variable, while the CPT method uses the rapid reaction stage of coal from 110℃ to 230℃. The index is the independent variable. In this embodiment of the invention, by fusing the two calculation models, a coal spontaneous combustion difficulty determination model can be obtained that considers both the parameters of the low-temperature adsorption stage and the parameters of the rapid reaction stage. Constructing this fused model first requires considering the inherent relationship between these two stages: the low-temperature stage... A higher value means that the coal sample is more likely to adsorb oxygen at low temperatures, initiate an oxidation reaction, and accumulate heat. The values ​​reflect that the reaction becomes more intense when the temperature rises to 110-230℃. Oxygen adsorption in the low-temperature stage provides more reactants or heat accumulation for the high-temperature stage reaction, and there is a synergistic effect between the two. Therefore, compared with the linear model, the product model has the characteristics of expressing a chain-like synergistic relationship and can better capture this relationship of "high oxygen adsorption → oxygen enrichment in coal pores → accelerated low-temperature oxidation exothermic → providing heat and reactant accumulation for the high-temperature stage".

[0092] In some embodiments, the above method may further include: analyzing the characteristic temperature points and exothermic characteristics of the target coal sample using simultaneous thermal analysis technology, and establishing an oxidation kinetic model by combining the Achar differential method and the Coats-Redfern integral method to verify the correspondence between the dual-factor coal spontaneous combustion tendency comprehensive index and the activation energy.

[0093] Specifically, by monitoring the synchronous response of mass change and heat release during the oxidation process of coal samples using simultaneous thermal analysis, a curve showing the change in coal sample mass with programmed temperature rise (TG curve) is obtained, such as... Figure 2 As shown, Figure 2 This is a schematic diagram of the characteristic temperature points and stage divisions in an embodiment of the present invention.

[0094] Differentiating the mass change curve of a coal sample with programmed temperature increase (TG curve) yields the rate of mass change at different temperatures; this rate curve is called the DTG curve. The peak points on the DTG curve essentially correspond to the moments when the mass change of the coal sample is most drastic at each stage of the heating process. By simultaneously analyzing the TG and DTG curves, the characteristic temperature points of coal samples with different degrees of metamorphism can be accurately determined, allowing for a reasonable division of the coal oxidation process into stages based on these characteristic temperature points.

[0095] The characteristic temperature points of coal can be divided into: initial adsorption temperature (Ta), maximum mass temperature (Tp), ignition temperature (Ti), maximum weight loss rate temperature (Tm), and burnout temperature (Tb). For simplicity, we take HG (lignite), YM (long-flame coal), ZSP (gas coal), HH (coking coal), and FHS (coking coal) from some characteristic coal samples in Table 1 above as examples. The characteristic temperature points of coal samples with different metamorphic degrees are as follows: Figure 3 As shown.

[0096] The degree of coal metamorphism is related to its spontaneous combustion characteristics. As the degree of coal metamorphism increases, the critical characteristic temperature of the coal sample increases accordingly, and the initiation of the spontaneous combustion reaction of coal shows a significant lag. This also indicates that the higher the degree of coal metamorphism, the lower its spontaneous combustion tendency.

[0097] As the degree of coal metamorphism increases, the combustion rate shows a significant decreasing trend, while the exothermic capacity shows an increasing trend. After all coal samples have been completely burned, it can be found that the exothermic capacity of HG and YM with lower metamorphism is less than that of HH and FHS. This indicates that low-ratio HG and YM are more likely to spontaneously combust than high-ratio HH and FHS, but high-ratio HH and FHS have a stronger exothermic capacity.

[0098] This further illustrates that the risk of spontaneous combustion of coal depends not only on its stored energy but also on its internal structure's reaction with oxygen. The denser the coal structure, the more heat it accumulates during the oxidation stage, and the more intensely it releases during combustion. This is a key reason why anthracite has a higher risk of spontaneous combustion. The calorific value of different coal samples is shown in the graph. Figure 4 As shown.

[0099] Understandably, the activation energy of coal ignition essentially represents the maximum barrier that coal must overcome to react chemically with oxygen. During coal oxidation, the active groups in coal react with oxygen to generate reactive intermediates. As the temperature continues to rise, energy gradually accumulates, and previously inert groups in the coal are activated to participate in the reaction. Therefore, assessing the spontaneous combustion tendency of coal based on its ignition activation energy is reasonable. This invention uses the activation energy of coal during the combustion decomposition stage as the criterion for determining the spontaneous combustion tendency, thereby verifying the accuracy of the index model. See also... Figure 5 As shown, during the combustion and decomposition stage of coal, HG has the lowest activation energy, while YCW has the highest, with the activation energy gradually increasing from HG to FHS. A higher activation energy indicates more stable coal properties, meaning a lower tendency for spontaneous combustion; conversely, a lower activation energy indicates easier spontaneous combustion and a higher tendency for spontaneous combustion. The activation energies of the coal samples, ranked from lowest to highest, are: HG < FSG < YM < ZSP < MYK < SL < HH < CJG < FHS < YCW. This is consistent with the conclusions obtained from the previously constructed two-factor coal spontaneous combustion tendency comprehensive index model. Therefore, the constructed comprehensive index model can be used as a method for determining the spontaneous combustion tendency of coal.

[0100] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0101] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A comprehensive method for determining the spontaneous combustion tendency of coal based on multi-scale data using two factors, characterized in that it includes: Obtain the cross-point temperature and oxygen uptake of the target coal sample; The average heating rate and the comprehensive parameter of the coal's natural tendency are calculated based on the temperature at the intersection point; the formula for calculating the comprehensive parameter of the coal's natural tendency is as follows: ; in, The comprehensive parameters of the natural tendency of coal for the target coal sample. The crossover temperature of the target coal sample. The average heating rate of the target coal sample; Based on the crossover temperature, oxygen uptake, average heating rate, and comprehensive parameters of the coal's spontaneous combustion tendency of the target coal sample, the weight of the low-temperature oxidation stage of the target coal sample is determined using the entropy weight method, and the two-factor coal spontaneous combustion tendency comprehensive index of the target coal sample is calculated; the calculation formula for the two-factor coal spontaneous combustion tendency comprehensive index of the target coal sample is as follows: ; in, The two-factor coal spontaneous combustion tendency composite index for the target coal sample. and The oxygen uptake index of the target coal sample at 30℃ is a dimensionless quantity, corresponding to the average heating rate and the comprehensive parameter of the coal's natural tendency, respectively. ; ; 1.603 and 11.362 are the standardized factors determined experimentally. The weights for the low-temperature oxidation stage of the target coal sample, determined by the entropy weight method, are as follows: As the amplification factor, This represents the saturated oxygen uptake of coal during low-temperature adsorption at 30℃. The determination of the weight of the low-temperature oxidation stage of the target coal sample using the entropy weight method includes: The combined parameters of oxygen uptake and coal natural tendency are standardized to eliminate dimensional differences, and the formula is expressed as follows: ； Based on the standardized data, the entropy value of the target coal sample is calculated, expressed by the formula: ； The information utility value of each indicator is determined based on the entropy value, expressed by the following formula: ； The weight of the low-temperature oxidation stage of the target coal sample is determined based on the information utility value, expressed by the following formula: ； in, The standardized values ​​of the data after eliminating dimensional differences. The original data needs to be substituted separately. and Experimental data, and These are the minimum and maximum values ​​in the original data. For the target coal sample and The entropy value of the experimental data, The target coal sample number, For the corresponding target coal sample sequence, Indicators for each coal sample and Information utility value; Based on the dual-factor coal spontaneous combustion tendency comprehensive index, the spontaneous combustion tendency of the coal seam corresponding to the target coal sample is identified.

2. The method according to claim 1, characterized in that, The formula for calculating the average heating rate of the target coal sample is as follows: ； in, The average heating rate of the target coal sample. and These are the reaction times when the target coal sample reaches a temperature of 110℃ and 230℃, respectively.

3. The method according to claim 2, characterized in that, The oxygen uptake of the target coal sample was obtained by chromatographic oxygen uptake method, and the calculation formula is as follows: ； in, This refers to oxygen uptake. This is the instrument constant; This is the instrument calibration factor; This refers to the actual carrier gas flow rate in the pipe, in cm³. 3 / min; This refers to the empty tube carrier gas flow rate, in cm³. 3 / min; This is the ratio of the partial pressure of oxygen to atmospheric pressure in a solid tube. This is the ratio of the partial pressure of oxygen to atmospheric pressure when the tube is empty. The actual desorption peak area is expressed in units of... ; The desorption peak area of ​​the air tube is expressed in units of 1000 m². ; This refers to the weight of the coal sample, in grams. The relative density of coal; The volume of the sample tube (standard state) is expressed in cm³. 3 ; This refers to the moisture content of the coal sample.

4. The method according to claim 3, characterized in that, The step of identifying the spontaneous combustion tendency of the coal seam corresponding to the target coal sample based on the dual-factor coal spontaneous combustion tendency comprehensive index includes: The natural tendency level of the target coal sample is determined based on the dual-factor coal spontaneous combustion tendency comprehensive index.

5. The method according to any one of claims 1 to 4, characterized in that, The method also includes analyzing the characteristic temperature points and exothermic characteristics of the target coal sample using simultaneous thermal analysis technology, and establishing an oxidation kinetic model by combining the Achar differential method and the Coats-Redfern integral method to verify the correspondence between the dual-factor coal spontaneous combustion tendency comprehensive index and the activation energy.

6. The method according to claim 5, characterized in that, The method is applicable to the determination of the spontaneous combustion tendency of lignite, long-flame coal, gas coal, coking coal and anthracite.

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