JP2023081775A - Evaluation method for spontaneous heat build up property of coal - Google Patents

Abstract

To evaluate spontaneous heat buildup property of stored coals without pulverizing the stored coals.SOLUTION: Of stored coals, heat buildup rate (V_par) of coal having particle size equal to or below a predetermined particle size (Dth) is measured. According to the heat buildup rate (V_par) and a correction coefficient (k), heat buildup rate (V_all) for evaluating a spontaneous heat buildup property of the entire coal is obtained. The correction coefficient (k) is a ratio of the relative heat buildup rate (Vr_all) of a coal belonging to all particle size scales with respect to a relative heat buildup rate (Vr_par) of a coal belonging to the particle size scale equal to or below the predetermined particle size (Dth). The relative heat buildup rate (Vr_par) is value weighting and averaging relative heat buildup rate (Vrn) of each particle size scale equal to or below the predetermined particle size (Dth) by a mass ratio (Wn_par) of a coal of each particle size scale equal to or below the predetermined particle size (Dth). The relative heat buildup rate (Vr_all) is a weighted average value with a mass ratio (Wn_all) of a coal particle size scale of a relative heat buildup rate (Vrn) of each particle size scale of the all particle size scales.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for assessing the self-heating properties of coal in a stored state.

Patent Literature 1 describes a method for evaluating spontaneous heat generation of coal in a short time using a small amount of coal sample. This evaluation method will be specifically described below.

20 to 80 g of pulverized coal sample is placed in an inner container, and this inner container is placed in a heating tank. By supplying oxygen gas to the inside of the heating tank, the pulverized coal sample in the heating tank is spontaneously heated. The temperature of the pulverized coal sample is measured, and the temperature inside the heating tank is increased so as to follow the temperature rise of the pulverized coal sample due to spontaneous heat generation. The time required for the temperature of the pulverized coal sample to rise from a predetermined initial temperature to a predetermined final temperature is measured, and the self-heating property of the coal is evaluated based on this measurement time. Here, the longer the measurement time, the less likely the coal is to generate spontaneous heat.

JP 2019-066296 A

In Patent Document 1, in order to prepare a pulverized coal sample, coal is pulverized to prepare coal having a predetermined particle size or less. Here, the self-heating property when using pulverized coal tends to be evaluated higher than the self-heating property when using unpulverized coal. The reason for this is that pulverized coal exposes the pulverized surface to the outside air, so that it is more likely to generate heat spontaneously than non-pulverized coal.

Coal to be evaluated for spontaneous heat generation is coal stored in a yard or the like. overestimate. For this reason, it is preferable to evaluate the self-heating property of coal in a stored state in order to evaluate the heat-generating property. On the other hand, if the coal is not pulverized, it is difficult to measure the self-heating property of many coals, and it is impossible to measure the self-heating property of all coals.

In Table 1 below, for each of three types of coal A to C with different brands, coal that is pulverized and has a particle size of 3 mm or less, and non-pulverized coal that has a particle size of 3 mm or less. After dividing into 2, the result of having evaluated spontaneous heat generation by the method of the Example mentioned later is shown. Here, the exothermic rate [°C/day] was used as an evaluation value of spontaneous heat generation.

According to Table 1 above, it can be seen that pulverizing coal increases the heat release rate more than non-pulverized coal, regardless of whether coals A to C are used. Therefore, as described above, if pulverized coal is used to evaluate the self-heating property, the self-heating property will be overestimated compared to the stored coal (non-pulverized).

In pulverized coal, the heat generation rate increases in the order of coal A, coal B, and coal C. In non-pulverized coal, the heat generation rate of coal A and coal C is the same, and the heat generation rate of coal B is the same. highest speed. In this way, pulverized coal and non-pulverized coal have different heat generation rates. It becomes difficult to determine the superiority or inferiority of sex.

The present invention is a method for evaluating the spontaneous heat generating property of coal, which includes the steps of: performing a heat generating test for measuring the heat generation rate of coal having a predetermined particle size or less among stored coal; a step of obtaining a heat release rate for evaluating the spontaneous heat generation of the entire coal in a stored state based on the heat release rate measured in the property test and a previously determined correction factor. The correction coefficient is the ratio of the relative heat generation rate of coal belonging to all particle size categories to the relative heat generation rate of coal belonging to particle size categories equal to or smaller than a predetermined particle size when coal in a stored state is divided into a plurality of particle size categories. is.

The relative heat release rate of coal belonging to a particle size class of a predetermined particle size or less is calculated by the ratio of the mass of coal in each particle size class to the total mass of coal of a predetermined particle size or less. This is a weighted average value. The relative heat release rate of coal belonging to all particle size classes is the weighted average value of the relative heat release rates of each particle size class in all particle size classes by the ratio of the mass of coal in each particle size class to the total mass of coal in all particle size classes. .

The predetermined particle size can be a particle size that allows measurement of the heat release rate in the heat generation test.

The correction coefficients described above can be obtained as follows. First, coal in a stored state is classified into a plurality of particle size categories, and the heat generation rate of coal belonging to each particle size category is measured by a heat generation test. Then, based on the measured heat release rate, the relative heat release rate of each particle size classification is obtained with reference to a predetermined heat release rate, and the correction coefficient is obtained based on the relative heat release rate of each particle size classification and the mass ratio. can be done.

The coal used for determining the correction coefficient can be the same brand as the coal for determining the heat release rate for evaluating the spontaneous heat generation.

Advantageous Effects of Invention According to the present invention, it is possible to appropriately grasp the heat generation rate for evaluating the spontaneous heat generating property of coal in a stored state without pulverizing the coal.

4 is a flowchart for explaining how to obtain a correction coefficient k; It is a schematic diagram showing the configuration of a measuring device used in the exothermic test. It is a flowchart explaining the process which calculates|requires the heating rate of the coal used as evaluation object of spontaneous heat generation. FIG. 4 is a graph showing changes over time in the temperature of a constant temperature and humidity bath and the temperature of coal in a heat generation test. It is a figure which shows the relationship between the particle size of coal, and a heat release rate and a relative heat release rate. It is a figure which shows the particle size distribution of five types of coal.

In this embodiment, coal in a stored state is evaluated for spontaneous heat generation. Among the coal, the heat generation rate is measured for the coal having a predetermined particle size or less, and based on this heat generation rate and the correction coefficient k described later, the coal in the stored state (in other words, including all particle sizes) Coal) heat generation rate is calculated. Based on this heat generation rate, the spontaneous heat generating property of coal in a stored state can be evaluated. A specific description will be given below.

Coal to be evaluated for self-heating property may be coal in a stored state, and the type of coal is not particularly limited. Here, if the coal stored in a yard or the like is coal that easily generates heat spontaneously, it is necessary to manage the spontaneous heat generation. Therefore, such coal can be evaluated for spontaneous heat generation. For example, coal having an oxygen content of 8 [mass%, dry base] or more can be evaluated for self-heating property. In addition, even if the coal is of the same brand, it is preferable to evaluate the self-heating property of each coal of different lots.

(correction coefficient k)
The correction coefficient k described above is obtained in advance. A method for obtaining the correction coefficient k will be described below with reference to the flowchart shown in FIG.

In step S101, coal in a stored state is divided into a plurality of particle size categories. Here coal is used as it is stored without crushing it. Since the coal in the stored state includes coal having various particle sizes, a plurality of particle size categories are set and the coal belonging to each particle size category is selected. For example, sieving can sort coal belonging to each particle size category. The total number of particle size divisions and the range of particle diameters defining each particle size division can be determined as appropriate. After dividing the coal into multiple grain size classes, the mass of coal belonging to each grain size class is measured, and for each grain size class, the ratio of the mass of coal belonging to each grain size class to the total mass of coal belonging to all grain size classes ( Mass ratio) [mass%] is obtained.

In step S102, heat release rate Vn [°C/day] is measured for coal belonging to each particle size category. The subscript n (n is a natural number) of the heat generation rate Vn means each particle size division. According to the examples described later, the larger the coal particle size, the smaller the heat release rate Vn. The exothermic rate Vn can be measured, for example, by the exothermicity test described below.

FIG. 2 shows a schematic configuration of a measuring device used in the exothermic test. In the exothermic test, a coal sample is stored in a constant temperature and humidity tank 1, and the internal temperature of the constant temperature and humidity tank 1 is set so as to follow the temperature rise of the coal sample due to low-temperature oxidation heat in an air atmosphere. It measures the speed (heat release rate V).

A constant temperature and humidity chamber 1 having a predetermined internal volume (eg, 225 [L]) contains a pail can 2 (eg, an outer diameter of 300 [mm] and a height of 220 [mm]), which is a cylindrical steel container. is installed. The pail can 2 is filled with a coal sample. Here, a coal sample layer having a predetermined height (for example, about 100 [mm]) may be formed by laying a heat insulating material under the pail can 2 and filling the coal sample on the heat insulating material. good. In addition, as a heat insulating material, for example, a ceramic fiber board or the like can be used. A heat-insulating container (for example, a vacuum heat-insulating container) can be used instead of the pail can 2 as the container filled with the coal sample. By using an insulated container, heat transfer through the container can be suppressed from adversely affecting the exothermic test.

A temperature sensor 3a is arranged inside the coal sample layer, and the temperature of the coal sample can be measured by the temperature sensor 3a. For example, a temperature sensor 3a can be arranged at a depth of 70 [mm] from the upper surface of the coal sample layer, and the temperature measured by this temperature sensor 3a can be used as the representative temperature of the coal sample. On the other hand, outside the pail 2, a temperature sensor 3b for measuring the internal temperature of the thermo-hygrostat 1 is arranged.

A water tank 4 is arranged inside the constant temperature and humidity chamber 1, and the water tank 4 is used to maintain the internal humidity of the constant temperature and humidity chamber 1 at a constant humidity (eg, 50%). Further, the constant temperature and humidity chamber 1 is supplied with gas through a gas supply pipe, and the gas is heated by the heater 5 . The internal temperature of the thermo-hygrostat 1 can be adjusted by the temperature of the gas supplied to the thermo-hygrostat 1 . Specifically, the control unit 6 controls the heating by the heater 5 based on the measurement results of the temperature sensors 3a and 3b, thereby adjusting the temperature of the gas supplied to the thermo-hygrostat 1. The internal temperature of the constant humidity chamber 1 can be adjusted. The gas supplied to the constant temperature and humidity chamber 1 is discharged from the constant temperature and humidity chamber 1 .

When conducting the exothermic test, first, in the constant temperature control mode, nitrogen gas is supplied to the constant temperature and humidity chamber 1 at a predetermined flow rate (for example, 30 [L / min]), so that the internal temperature and The temperature of the coal sample is maintained at the initial temperature (eg, 60[°C]). After the internal temperature of the thermo-hygrostat 1 and the temperature of the coal sample are maintained at the initial temperatures, the constant temperature control mode is switched to the temperature follow-up control mode.

In the temperature follow-up control mode, the internal temperature of the thermo-hygrostat 1 follows the temperature of the coal sample. Here, the control temperature of the constant temperature and humidity chamber 1 is set by setting a bias value for the temperature of the coal sample so that the control target temperature (for example, 60.0 [° C.]) of the constant temperature and humidity chamber 1 does not change. , while supplying nitrogen gas to the constant temperature and humidity chamber 1, wait for a predetermined period (for example, half a day or longer). This predetermined period is set so as to make it easier to grasp the temperature rise of the coal sample due to the low-temperature oxidation reaction after switching the gas supplied to the constant temperature and humidity chamber 1 from nitrogen gas to oxygen-containing gas (for example, air). there is

After a predetermined period of time has passed, the gas supplied to the thermo-hygrostat 1 is switched from nitrogen gas to oxygen-containing gas (for example, air). By supplying the oxygen-containing gas at a predetermined flow rate (for example, 30 [L/min]) to the thermo-hygrostat 1, a low-temperature oxidation reaction proceeds in the coal sample and the temperature of the coal sample rises. Here, in the temperature follow-up control mode, the internal temperature of the thermo-hygrostat 1 follows the temperature of the coal sample, so the internal temperature of the thermo-hygrostat 1 rises as the temperature of the coal sample rises.

Changes in the internal temperature of the thermo-hygrostat 1 are recorded while the temperature follow-up control mode is set. This temperature change includes a temperature change while supplying nitrogen gas and a temperature rise while supplying oxygen-containing gas. A rate is determined, and the rate of temperature rise is determined from the temperature rise during the supply of the oxygen-containing gas. Here, the difference between the temperature change rate when nitrogen gas is supplied and the temperature increase rate when oxygen-containing gas is supplied can be used as the temperature increase rate (that is, heat generation rate V) due to the low-temperature oxidation reaction. .

By measuring the heat release rate Vn as described above for each particle size classification set in the process of step S101, the relationship between each particle size classification and the relative heat release rate Vrn can be obtained. The relative heat release rate Vrn is a relative value with respect to any one heat release rate Vn among the heat release rates Vn in all the measured particle size classes. Specifically, the heat release rate of each particle size class It is a value obtained by dividing Vn by the reference heat release rate Vn. For example, the reference heat release rate Vn may be the highest heat release rate Vn or the lowest heat release rate Vn.

In the case of obtaining the relative heat release rate Vrn, in order to reduce the influence of measurement variations in the heat release rate Vn, the relationship between an arbitrary particle size classification and the relative heat release rate Vrn is obtained, and based on this relationship, a predetermined particle size classification (measured The relative heat generation rate Vrn of the particle size category (which may be different from the particle size category) may be determined. In addition, in a particle size category in which the heat release rate Vn cannot be measured, the heat release rate Vn can be obtained by extrapolating the relationship described above.

Returning to FIG. 1, in step S103, a relative heat release rate Vr_par, which will be described below, is obtained for coal that belongs to a particle size category equal to or smaller than a predetermined particle size Dth. The particle size classifications of the predetermined particle size Dth or less are part of all the particle size classifications set in the process of step S101. Although the predetermined particle size Dth can be determined as appropriate, it may be any particle size of coal that is easy to use with the measuring device described with reference to FIG. good. For example, the predetermined particle size Dth can be 20 [mm], 15 [mm], 10 [mm] or 3 [mm].

The relative heat release rate Vr_par is obtained by multiplying the relative heat release rate Vrn[-] of each of a plurality of particle size divisions within the range of a predetermined particle diameter Dth or less by the mass ratio Wn_par [mass% of each particle size division of a predetermined particle diameter Dth or less. ] and is represented by the following formula (1). Here, the suffix n (n is a natural number) in the relative heat release rate Vrn and the mass ratio Wn_par means each particle size division of a predetermined particle size Dth or less.

In the above formula (1), the relative heat release rate Vrn is obtained from the heat release rate Vn of each particle size category measured in the process of step S102, as described above. The mass ratio Wn_par is the ratio [mass%] of the mass of coal belonging to each particle size class having a predetermined particle size Dth or less to the total mass of coal having a predetermined particle size Dth or less. The mass ratio Wn_par can be obtained from the mass of coal belonging to each particle size category measured in the process of step S101.

In step S104, a relative heat release rate Vr_all, which will be described below, is obtained for all particle size categories. All granularity divisions are all granularity divisions set in the process of step S101. The relative heat release rate Vr_all is a value obtained by weighting and averaging the relative heat release rates Vrn [-] of all particle size categories by the mass ratio Wn_all [mass%] of all particle size categories, and is obtained by the following formula (2): expressed. Here, the subscript n (n is a natural number) in the relative heat release rate Vrn and the mass ratio Wn_all means each particle size division.

In the above formula (2), the relative heat release rate Vrn is obtained from the heat release rate Vn of each particle size category measured in the process of step S102, as described above. The mass ratio Wn_all is the ratio [mass%] of the mass of coal belonging to each particle size classification to the total mass of coal belonging to all particle size classifications. The relative heat release rate Vr_all targets all particle size categories, whereas the above-described relative heat release rate Vr_par targets particle size categories equal to or smaller than a predetermined particle size Dth. That is, the denominator of the mass ratio Wn_all used to calculate the relative heat release rate Vr_all (total mass of coal belonging to all particle size classes) is the denominator of the mass ratio Wn_par used to calculate the relative heat release rate Vr_par (predetermined particle size Dth or less). is the total mass of coal).

In step S105, a correction coefficient k[-] is obtained based on the relative heat generation rate Vr_par obtained in the processing of step S103 and the relative heat generation rate Vr_all obtained in the processing of step S104. The correction coefficient k is the value of the relative heat release rate Vr_all with respect to the relative heat release rate Vr_par, and is represented by the following formula (3). As will be described later, the correction coefficient k is used when obtaining the heat generation rate of coal to be evaluated for spontaneous heat generation.

(Evaluation of spontaneous heat generation of coal)
Next, a method for evaluating the self-heating property of coal will be described. In the evaluation of spontaneous heat generation, the heat generation rate V_all of coal to be evaluated is obtained as described below. Then, based on this heat generation rate V_all, it is evaluated whether or not the coal to be evaluated is likely to generate heat spontaneously, and the order in which multiple types of coal tend to generate heat spontaneously or is difficult to generate heat spontaneously is evaluated. be able to. FIG. 3 is a flowchart for explaining the process of obtaining the heat release rate V_all of coal to be evaluated.

In step S201, coal having a predetermined particle size Dth or less is selected from coal to be evaluated. Coal to be evaluated is coal stored in a yard or the like, and is coal that has not been pulverized. Here, the predetermined particle size Dth is the same as the predetermined particle size Dth described in the process of step S103. For example, by sieving coal to be evaluated, coal having a predetermined particle size Dth or less can be selected.

In step S202, the exothermic rate V_par is measured by performing the heat generation test described above on the coal selected in step S201 (coal having a predetermined particle size Dth or less). In step S203, based on the heat generation rate V_par measured in the process of step S202 and the correction coefficient k previously obtained in the process shown in FIG. Obtain the heat release rate V_all of the coal including the diameter. The heat release rate V_all is a value obtained by multiplying the heat release rate V_par by a correction coefficient k, and is expressed by the following formula (4). Based on this heat generation rate V_all, it is possible to evaluate the spontaneous heat generation of coal stored in a yard or the like.

In the present embodiment, the coal for determining the correction coefficient k and the coal for evaluating the self-heating property may be coal of the same brand or coal of different brands. Coal of the same brand may be coal of the same lot or coal of different lots. If coal of the same brand or coal of the same brand and lot is used, the accuracy of evaluating spontaneous heat generation can be improved.

On the other hand, even coals of different brands can be evaluated for spontaneous heat generation based on the heat generation rate V_all obtained from the above equation (4). Here, as described above, the correction coefficient k for obtaining the heat release rate V_all is the relative heat release rate Vr_par of coal belonging to the particle size divisions equal to or smaller than the predetermined particle size Dth, and the relative heat release rate Vr_all of coal belonging to all particle size divisions. and is required. Even coals of different brands have the same maximum particle size (for example, about 50 [mm]) and the same particle size range. Therefore, the particle size ranges that define the relative heat generation rates Vr_par and Vr_all are common even for coals of different brands. Therefore, even if the brands of coal are different from each other, the heat generation rate V_all can be obtained using the common correction coefficient k, and the spontaneous heat generation can be evaluated based on this heat generation rate V_all.

By evaluating the spontaneous heat generating property of coal based on the heat release rate V_all, heat generation countermeasures for coal stored in a yard or the like can be considered. For example, for coal that has been evaluated as having relatively high self-heating properties, the period of coal storage in yards, etc. should be shortened, water should be sprinkled more strongly to remove heat from the coal, and air should be less likely to enter. The coal can be compacted in such a way as to prevent excessive heat build-up, or the coal can be sprayed with chemicals to suppress excessive heat generation.

Examples will be described below, but the present invention is not limited to these examples.

(Specification of correction coefficient k)
Five coals A to D (2) with different oxygen contents were prepared. These coals are yard-stored coals that are not pulverized. Table 2 below shows the oxygen content of the five coals. Coals D(1) and D(2) shown in Table 2 below are coals of the same brand but of different lots. As shown in Table 2 below, different lots of coal D(1) and D(2) have different oxygen contents. The coals A, B, and C shown in Table 2 below are the same as the coals A, B, and C shown in Table 1 above.

The coal D(1) was classified into a plurality of particle size categories, and the heat generation rate Vn of the coal D(1) belonging to each particle size category was measured using the above-described measuring device (see FIG. 2).

The method for measuring the heat release rate Vn is as described above, and FIG. 4 schematically shows an example of temporal changes in the internal temperature of the constant temperature and humidity tank 1 and the temperature of coal in the measurement of the heat release rate Vn. In FIG. 4, the left vertical axis is the internal temperature [° C.] of the thermo-hygrostat 1, the right vertical axis is the coal temperature [° C.], and the horizontal axis is time [days]. In FIG. 4, the temperature on the left vertical axis and the right vertical axis are shifted in order to make it easier to understand the temperature change in the thermo-hygrostat 1 and the temperature change in the coal.

As shown in FIG. 4, from the start of measurement at time t0 to time t1, control is performed in the constant temperature control mode, and after time t1, control is performed in the temperature follow-up control mode. Here, nitrogen gas was supplied to the constant temperature and humidity chamber 1 from time t0 to time t2, and oxygen-containing gas (air gas) was supplied to the constant temperature and humidity chamber 1 after time t2.

FIG. 5 and Table 3 below show the measurement results of the heat release rate described above. In FIG. 5, the left vertical axis is the measured heat release rate Vn [°C/day], the right vertical axis is the relative heat release rate Vrn [−], and the horizontal axis is the particle size of coal D (1) [mm ]. The particle diameter on the horizontal axis is the geometric mean diameter of the particle size division. In this embodiment, the relative heat release rate Vrn is the ratio (Vn/Vn_max) of the heat release rate Vn of each particle size category to the highest heat release rate Vn_max among the heat release rates Vn of all particle size categories. Here, the relative heat release rate Vrn of the heat release rate Vn_max is 1.0, and the relative heat release rate Vrn can take a value within the range of 0 or more and 1.0 or less.

Table 3 below shows the relative heat release rate Vrn[-] for each particle size category. As can be seen from Table 3 below, the larger the particle size of the coal D(1), the lower the relative heat release rate Vrn (in other words, the heat release rate Vn). For particle size categories with a particle size of 25 [mm] or more, the heat release rate Vn could not be measured and the relative heat release rate Vrn could not be obtained, so extrapolation based on the relationship shown in FIG. A relative heat release rate Vrn was determined.

Next, relative heat release rate Vr_par and relative heat release rate Vr_all are calculated based on the relative heat release rate Vrn of each particle size classification shown in Table 3 above and the mass ratios Wn_par and Wn_all of the coal D(1) belonging to each particle size classification. asked. The relative heat release rate Vr_par is obtained from the above formula (1), and the relative heat release rate Vr_all is obtained from the above formula (2).

Table 4 below shows, for coal D (1), the mass ratio Wn_all of each particle size classification for all particle size classifications, and the mass ratio Wn_all of each particle size classification for particle size classifications of a predetermined particle size Dth or less. and the mass ratio Wn_par. In this example, the predetermined particle diameter Dth was set to 3 [mm]. FIG. 6 shows the relationship (particle size distribution) between particle size [mm] and accumulated mass under sieves (mass%) for coals A to D (2).

The mass ratio Wn_all is the ratio of the mass of coal D(1) belonging to each particle size category to the total mass of coal D(1) in all particle size categories. Used to determine Vr_all. The mass ratio Wn_par is the coal D(1) belonging to each particle size class having a predetermined particle size Dth (3 [mm]) or less with respect to the total mass of the coal D(1) having a predetermined particle size Dth (3 [mm]) or less. , and is used to determine the relative heat release rate Vr_par as shown in the above equation (1). The mass ratio Wn_par can be obtained from the mass ratio Wn_all of each particle size class.

Table 5 below shows the relative heat release rate Vr_par, the relative heat release rate Vr_all, and the correction coefficient k obtained from the above equation (3) for the coal D(1). Further, for each of the coals A to C and D(2), the relative heat release rate Vr_par and the relative heat release rate Vr_all were determined by the same method as for the coal D(1) described above, and the correction coefficient k was determined. The results are also shown in Table 5 below.

(Evaluation of spontaneous heat generation)
For each of the coals A to D(2), coal having a particle size equal to or smaller than a predetermined particle size Dth (=3 [mm]) was selected by sieving. The heat release rate V_par of the sorted coal was measured using the above-described measuring device (see FIG. 2). Further, based on the measured heat release rate V_par and the correction coefficient k shown in Table 5 above, the heat release rate V_all was obtained as an evaluation value. The heat release rate (evaluation value) V_all is the value obtained by multiplying the measured heat release rate V_par by the correction coefficient k, and is the heat release rate (estimated value) of each coal A to D (2) including all particle sizes. The results are shown in Table 6 below.

On the other hand, Table 6 below also shows the heat release rate (measured value) V_all measured by the above-described measuring device (see FIG. 2) using coal containing all particle sizes for each of coals A to D (2). . Here, the coals B, D(1), and D(2) cannot be uniformly filled in the pail 2 (see FIG. 2), and the temperature sensor 3a cannot be properly arranged inside the coal sample bed. Therefore, the heat release rate (measured value) V_all could not be measured.

According to Table 6 above, for each of the coals A and C, no large deviation was found in the heat release rate (evaluation value) V_all and the heat release rate (measurement value) V_all. Therefore, it was found that if the correction coefficient k is obtained in advance and the heat release rate V_par of coal (non-pulverized) having a predetermined particle size Dth or less is measured, the heat release rate V_all of coal including all particle sizes can be grasped. In particular, for coals B, D (1), and D (2), as described above, the heat release rate (measured value) V_all of all particle size categories could not be measured, but the heat release rate of all particle size categories was evaluated. I was able to

If the heat generation rate (evaluation value) V_all is obtained as in this embodiment, it is possible to grasp the level relationship of the heat generation rate (spontaneous heat generation). Specifically, it was found that coal D(2) has a higher self-heating property than coal D(1), and coal D(1) has a higher self-heating property than coals AC. In addition, it was found that coals A to C have the same degree of spontaneous heat generation.

Focusing on the heat release rate V_par of coal with a particle size of 3 mm or less, coal A has a lower heat release rate than coal B, but according to the particle size distribution shown in FIG. It was found that coal A and coal B have similar heat generation rate (evaluation value) V_all because of their small particle size. In addition, although the coals D(1) and D(2) differ only in lot, the heat generation rate (evaluation value) V_all differs greatly, so it was found that it is necessary to evaluate the spontaneous heat generation for each lot. .

1: constant temperature and humidity chamber, 2: pail, 3a, 3b: temperature sensor, 4: water tank, 5: heater,
6: Control unit

Claims (4)

A step of performing a heat generation test for measuring a heat generation rate for coal having a predetermined particle size or less among the coal in a stored state;
determining a heat release rate for evaluating the spontaneous heat generation of the entire coal in a stored state based on the heat release rate measured in the heat release test and a previously obtained correction coefficient;
The correction coefficient is the relative heat generation rate of coal belonging to all particle size categories with respect to the relative heat generation rate of coal belonging to particle size categories equal to or smaller than the predetermined particle size when coal in a stored state is divided into a plurality of particle size categories. is the ratio of
The relative heat generation rate of the coal belonging to the particle size classification of the predetermined particle size or less is calculated by dividing the relative heat generation rate of each particle size classification of the predetermined particle size or less into the mass of the coal of each particle size classification with respect to the total mass of the coal of the predetermined particle size or less. is the weighted average value with the ratio of
The relative heat release rate of coal belonging to all particle size classes is the weighted average value of the relative heat release rates of each particle size class in all particle size classes by the ratio of the mass of coal in each particle size class to the total mass of coal in all particle size classes. A method for evaluating the self-heating property of coal, characterized by: 2. The method for evaluating spontaneous heat generation of coal according to claim 1, wherein the predetermined particle size is a particle size that enables measurement of a heat generation rate in the heat generation test. Classifying coal in a stored state into multiple particle size categories,
For coal belonging to each particle size category, the heat generation rate is measured by the heat generation test,
Based on the measured heat release rate, determine the relative heat release rate of each particle size classification based on the predetermined heat release rate,
3. The method for evaluating spontaneous heat generation of coal according to claim 1 or 2, wherein the correction coefficient is obtained based on the relative heat generation rate of each particle size division and the ratio of the mass. Coal according to any one of claims 1 to 3, wherein the coal used for obtaining the correction coefficient is the same brand as the coal for obtaining the heat generation rate for evaluating spontaneous heat generation. Spontaneous heat generation evaluation method.

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