CN116151612A - Method for classifying spontaneous combustion dangerous grades of coals with different metamorphism degrees - Google Patents

Abstract

The invention discloses a method for classifying coal spontaneous combustion danger grades with different metamorphism degrees, which comprises the following steps: selecting multiple groups of coal samples with different varieties and different deterioration degrees, and respectively performing low-temperature oxidation temperature programming experiments on the coal to obtain CO and C ₂ H ₄ Obtaining the initial temperatures of two gases according to the change curve of the temperature; then fitting by using a Logistic regression function respectively; furthermore, normal inspection is carried out on the initial temperature and fitting parameters of the coal sample respectively to obtain median or average value; obtaining a first inflection point temperature and a second inflection point temperature of CO according to the Logistic functionAnd a third inflection point temperature; finally, the initial temperature of CO and C ₂ H ₄ The 5 characteristic temperatures of the initial temperature, the CO first inflection point temperature, the CO second inflection point temperature and the CO third inflection point temperature are critical values, and the coal spontaneous combustion dangerous grade state is divided. The invention provides a coal spontaneous combustion danger grade classification method aiming at coal samples with different deterioration degrees for the first time, and provides a new thought for guiding the accurate control of spontaneous combustion of working face coal.

Description

A method for the classification of coal spontaneous combustion hazard levels with different degrees of metamorphism

technical field

The invention relates to the field of coal spontaneous combustion early warning, in particular to a method for classifying coal spontaneous combustion hazard levels with different metamorphic degrees.

Background technique

In underground coal mines, coal spontaneous combustion is one of the main disasters that affect the safe recovery of working faces, and the degree of coal deterioration has a significant impact on the change law of coal spontaneous combustion early warning indicators. The existing coal spontaneous combustion early warning mostly uses CO and _O2 concentrations as indicators to determine the risk of coal spontaneous combustion, but the change of gas concentration is affected by many factors, including whether the ventilation system is stable, mining speed, roof collapse, etc., the probability of misjudgment larger. Temperature is the most direct factor that characterizes the degree of coal spontaneous combustion, and is less affected by the outside world. At present, the early warning of coal spontaneous combustion has not considered the influence of the degree of coal deterioration on the early warning indicators, which limits the application range of the existing early warning system. In view of the above problems, it is necessary to propose a more reasonable and effective method to construct a coal spontaneous combustion hazard classification method for coal samples with different degrees of metamorphism, so as to ensure the high efficiency and effectiveness of coal spontaneous combustion early warning.

Contents of the invention

The purpose of the present invention is to provide a method for classifying coal spontaneous combustion hazard levels with different degrees of metamorphism, so as to improve coal spontaneous combustion early warning.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows: a method for classifying coal spontaneous combustion hazard levels with different metamorphic degrees, comprising the following steps:

Step 1. Select multiple groups of coal samples of different types and different degrees of deterioration, and carry out temperature-programmed experiments on low-temperature oxidation of coal, respectively, to obtain the change curves of the marker gases CO and C ₂ H ₄ with coal temperature, and to obtain the initial appearance of CO and C ₂ H ₄ temperature;

Step 2. Carry out a normality test on the CO and C ₂ H ₄ onset temperatures of each group of coal samples, respectively, and obtain the average values of the CO and C ₂ H ₄ onset temperatures;

Step 3, using the Logistic regression function to fit the curve of CO changing with temperature to obtain the fitting equation;

Step 4, according to the fitting equation, each group of coal samples determines three characteristic temperatures: the first inflection point temperature, the second inflection point temperature and the third inflection point temperature;

Step 5. Carry out normality test respectively to the first inflection point temperature, the second inflection point temperature and the third inflection point temperature of each group of coal samples, and the average value of three inflection point temperatures is obtained for each metamorphic degree coal sample;

Step 6. Using the five characteristic temperatures of the initial appearance temperature of CO, the initial appearance temperature of C ₂ H ₄ , the first inflection point temperature of CO, the second inflection point temperature of CO, and the third inflection point temperature of CO as critical values, classify the coal spontaneous combustion hazard level status: safe , low risk, medium risk, high risk, and catastrophic states.

As a preference of the present invention, the indicators of the coal spontaneous combustion hazard level state described in step 6 are: less than the initial _temperature of CO, safe; greater than or equal to the initial temperature of CO and less than the initial temperature of _C2H4 , low risk; greater than or equal to C The initial temperature of ₂ H ₄ and less than the first inflection point temperature of CO, medium risk; greater than or equal to the first inflection point temperature of CO and less than the second inflection point temperature of CO, high risk; greater than or equal to the third inflection point temperature of CO, catastrophic state.

As a preference of the present invention, in Step 1, three groups of coal samples with a low degree of metamorphism, coal samples with a moderate degree of metamorphism, and coal samples with a high degree of metamorphism are selected.

As a preference of the present invention, the fitting process of the fitting equation in step 3 is: (1) determine the four parameters A ₁ , A ₂ , x ₀ , p ₀ of the Logistic function based on statistics; (2) for the four parameters Normality test was carried out to obtain the respective average values; (3) The average values were substituted into the Logistic regression function to obtain the model of CO concentration changing with temperature.

As a preference of the present invention, the specific steps of the coal low-temperature oxidation temperature programming experiment described in step one are: (1) place the broken coal sample in the coal sample tank in the temperature programming box, connect the gas circuit and the temperature probe, and Check the air tightness, and feed 50mL/min of dry air; (2) start to heat up, when the temperature in the coal sample tank reaches the specified test temperature, take a gas sample after a constant temperature, and use a gas chromatograph to analyze the gas composition and concentration. analyze.

Compared with the prior art, the present invention proposes for the first time a coal spontaneous combustion risk classification method for coal samples with different metamorphism degrees, which provides a new idea for guiding the precise prevention and control of coal spontaneous combustion in working faces, and ensures the effectiveness of early warning of coal spontaneous combustion.

Description of drawings

Figure 1 shows the variation of CO concentration with temperature and the fitting curves of three groups of coal samples with low degree of metamorphism.

Figure 2 shows the variation of C ₂ H ₄ concentration with temperature and the fitting curves of three groups of coal samples with low metamorphic degree.

Fig. 3 is a normality test diagram of the first appearance temperature of C ₂ H ₄ in coal samples with low degree of metamorphism.

Fig. 4 is the normality test diagram of four sets of parameters fitted to the CO concentration of low metamorphic degree coal samples.

Fig. 5 is a curve diagram of the Logistic fitting equation for low metamorphic degree coal samples.

Fig. 6 is a classification diagram of spontaneous combustion grades of coal samples with low degree of metamorphism.

Figure 7 is a classification diagram of spontaneous combustion grades of coal samples with a moderate degree of metamorphism.

Figure 8 is a classification diagram of spontaneous combustion grades of coal samples with a high degree of metamorphism.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

The present invention provides a method for classifying coal spontaneous combustion hazards with different metamorphic degrees, aiming at three kinds of coal samples with different metamorphic degrees: low (long-flame coal: D1, D2, D3), medium (fat coal, coking coal, fat coal: Z1) , Z2, Z3) and high (lean coal, lean coal, lean coal: G1, G2, G3), were tested separately.

Example 1: Coal sample with low degree of metamorphism

Step 1: The variation curve of CO with temperature obtained from the low temperature oxidation temperature program experiment of coal is shown in Fig. 1, and the variation of C ₂ H ₄ concentration with temperature is shown in Fig. 2 respectively.

The specific steps of the coal low-temperature oxidation temperature programming experiment are: (1) put the broken coal sample (50-80 mesh) in the coal sample tank in the temperature programming box, connect the gas circuit and the temperature probe, and check the air tightness (2) Start to heat up, when the temperature in the coal sample tank reaches the specified test temperature, take a gas sample after 5 minutes at a constant temperature, and use a gas chromatograph to analyze the gas composition and concentration.

Step 2: In Fig. 1, it can be obtained that the CO onset temperature corresponding to the coal sample with low metamorphism degree is 30°C, and in Fig. 2, the onset temperature of C ₂ H ₄ can be obtained as 110°C, 120°C and 120°C respectively. The normality test of the initial temperature of C ₂ H ₄ is shown in Figure 3, and the average temperature is 117°C.

Step 3: The Logistic function equation is:

In the formula, y is the volume fraction of the marker gas, %; A ₂ is the maximum value corresponding to the model; A ₁ is the minimum value corresponding to the model; x is the coal temperature, °C; x ₀ is the inflection point of the curve; p ₀ is the inflection point of the curve Quantity related to the slope of the curve.

CO was fitted according to the Logistic function in Figure 1, and the fitting parameters are shown in Table 1.

Table 1 Fitting parameters of CO concentration in coal samples with low degree of metamorphism

A ₁ A ₂ x ₀ p ₀ 79.76619 13651.47 257.98 11.9711 42.49296 12881.27 269.83 11.57086 34.18399 15379.8 270.88 10.24304

The normality test was performed on the four groups of parameters (A ₁ , A ₂ , x ₀ , p ₀ ), as shown in Figure 4, and the average values of the four groups of parameters were 52, 13971, 266 and 11, respectively. Then the equation of CO change with temperature in low metamorphic degree coal sample is:

Among them, 266°C is the second inflection point temperature of CO.

Step 4: Use the Origin drawing software to perform local peak-finding on the curve of equation (2), as shown in Figure 5, the first inflection point temperature of CO is 212°C, and the third inflection point temperature is 318°C.

Step 5. Select CO initial appearance temperature (30°C), C ₂ H ₄ initial appearance temperature (117°C), CO first inflection point temperature (212°C), second inflection point temperature (266°C), CO third inflection point temperature ( 318°C) as the index to classify coal spontaneous combustion, and the classification results are shown in Figure 6. It can be seen that below 30°C is a safe zone, 30°C-117°C is a low risk, 117°C-212°C is a medium risk, 212°C-266°C is a high risk, and 266°C-318°C is a catastrophic state.

Example 2: Coal sample with moderate metamorphism

The method for classifying coal spontaneous combustion grades of medium metamorphic coal samples is the same as in Example 1, and the classification results of coal spontaneous combustion hazard grades are shown in FIG. 7 . It can be seen that below 30°C is a safe zone, 30°C-123°C is a low risk, 123°C-232°C is a medium risk, 232°C-281°C is a high risk, and 281°C-328°C is a catastrophic state.

Example 3: Coal sample with high degree of metamorphism

The coal spontaneous combustion grade classification method of the high metamorphic degree coal sample is the same as that in Example 1, and the classification result of the coal spontaneous combustion hazard grade is shown in FIG. 8 . It can be seen that below 30°C is a safe zone, 30°C-137°C is a low risk, 137°C-267°C is a medium risk, 267°C-327°C is a high risk, and 327°C-386°C is a catastrophic state.

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 modifications and variations.

Claims (5)

1. A method for classifying coal spontaneous combustion hazards of different metamorphic degrees, is characterized in that, comprises the following steps: Step 1. Select multiple groups of coal samples of different types and different degrees of deterioration, and carry out temperature-programmed experiments on low-temperature oxidation of coal, respectively, to obtain the change curves of the marker gases CO and C ₂ H ₄ with coal temperature, and to obtain the initial appearance of CO and C ₂ H ₄ temperature; Step 2. Carry out a normality test on the CO and C ₂ H ₄ onset temperatures of each group of coal samples, respectively, and obtain the average values of the CO and C ₂ H ₄ onset temperatures; Step 3, using the Logistic regression function to fit the curve of CO changing with temperature to obtain the fitting equation; Step 4, according to the fitting equation, each group of coal samples determines three characteristic temperatures: the first inflection point temperature, the second inflection point temperature and the third inflection point temperature; Step 5. Carry out normality test respectively to the first inflection point temperature, the second inflection point temperature and the third inflection point temperature of each group of coal samples, and the average value of three inflection point temperatures is obtained for each metamorphic degree coal sample; Step 6. Using the five characteristic temperatures of CO initial appearance temperature, C ₂ H ₄ initial appearance temperature, CO first inflection point temperature, CO second inflection point temperature, and CO third inflection point temperature as critical values, classify coal spontaneous combustion hazard levels. 2. A method for classifying coal spontaneous combustion hazard levels with different metamorphic degrees according to claim 1, characterized in that the index of the coal spontaneous combustion hazard level state described in step 6 is: less than CO initial appearance temperature, safe; greater than Equal to the initial temperature of CO and less than the initial temperature of C ₂ H ₄ , low risk; greater than or equal to the initial temperature of C ₂ H ₄ and less than the first inflection point temperature of CO, medium risk; greater than or equal to the first inflection temperature of CO and less than the second inflection point of CO Inflection point temperature, high risk; greater than or equal to the third inflection point temperature of CO, catastrophic state. 3. A method for classifying coal spontaneous combustion hazards with different degrees of metamorphism according to claim 1, characterized in that, in step 1, each of the coal samples with low metamorphic degree, the coal samples with medium metamorphic degree and the coal samples with high metamorphic degree are selected. 3 groups. 4. according to claim 1, a kind of method for classifying coal spontaneous combustion hazards with different degrees of metamorphism, is characterized in that, the fitting process of fitting equation in step 3 is: (1) determine the four-dimensional function of Logistic function based on statistics parameters A ₁ , A ₂ , x ₀ , p ₀ ; (2) Carry out normality test on the four parameters to get their average values; (3) Substitute the average values into the Logistic regression function to get the CO concentration change with temperature Model. 5. A method for classifying coal spontaneous combustion hazards with different degrees of metamorphism according to claim 1, characterized in that, the specific steps of the coal low-temperature oxidation temperature programming experiment described in step 1 are: (1) crushing the broken coal Place the sample in the coal sample tank in the programmed temperature riser, connect the gas circuit and temperature probe, check the airtightness, and feed 50mL/min of dry air; (2) start to heat up, when the temperature in the coal sample tank reaches the specified When testing the temperature, take a gas sample after the temperature is constant, and use a gas chromatograph to analyze the gas composition and concentration.

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