JP2020106405A - Coal spontaneous heating character evaluation method, and coal spontaneous heating character evaluation device - Google Patents

Abstract

To provide a coal spontaneous heating character evaluation method and a coal spontaneous heating character evaluation device each of which enables a coal heating character to be evaluated with a high degree of accuracy in an environment close to an actual coal stock pile.SOLUTION: The coal spontaneous heating character evaluation method is provided that includes the steps of: acquiring a wet air flow from mixed gas obtained by mixing an O2 gas and an N2 gas or acquiring a wet air steam from air: acquiring a wet inert gas flow from at least a kind of inert gas selected from an N2 gas, an Ar gas and an He gas; increasing the temperature of coal filled in a reaction vessel to a predetermined temperature under the wet inert gas flow; switching the wet inert gas flow to the wet air steam after increasing the temperature; wet-oxidizing the coal in the switched wet air flow; quantitatively measuring a CO2 production rate by measuring the time of wet oxidization and the amount of CO2 generated from the coal in a step of performing wet oxidization; determining a coal spontaneous heating character on the basis of the CO2 production rate.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for evaluating the spontaneous heat generation of coal and a device for evaluating the spontaneous heat generation of coal.

The proportion of coal in the world's primary energy supply is second only to oil. In addition, the growth rate of supply in the past 14 years has greatly exceeded that of oil and natural gas, and it is expected that demand will continue to grow. The supply of bituminous coal is likely to be tight due to the increase in domestic and overseas coal demand.
Therefore, in order to meet the future increase in coal demand, it is necessary to establish a technology for utilizing low-grade coal, which accounts for about half of the recoverable reserves of coal such as subbituminous coal and lignite coal.
An obstacle to the use of low-grade coal is the spontaneous heat generation phenomenon of coal. Coal generates heat due to the reaction with oxygen (O ₂ ) in the air, and if the heat generation temperature continues to be higher than the heat radiation temperature, it eventually ignites. In order to properly handle the stored coal and prevent spontaneous ignition, it is necessary to have a technique to evaluate the spontaneous heat generation property of the coal in advance.

For example, in Patent Document 1, a case (2) having a space (1) filled with pulverized coal (S), a heating device (4) mounted on a lower end surface (3) of the case (2), An apparatus for spontaneously igniting pulverized coal, comprising: a closed container (5) for containing these and a heater (6) for heating an atmosphere (A) in the closed container (5). It is disclosed.

Further, in Patent Document 2, a step of heating the low-grade coal in a stream of air obtained by supplying air, and carbon monoxide (CO) and carbon dioxide (CO) generated from the low-grade coal at the time of temperature rise ( CO ₂ ), and a step of evaluating the spontaneous combustion of the low-grade coal from the continuously measured changes in the amounts of CO and CO ₂ generated. An ignitability evaluation method is disclosed.

Moreover, in patent document 3, the atmospheric temperature is a predetermined temperature of 60° C. or less, and the weight increase amount of coal is measured by a thermobalance in an atmosphere in which the atmospheric gas is pure oxygen gas, and the weight of the coal increases. Based on the amount of weight increase of the coal at a predetermined timing from the beginning until a predetermined time elapses, an evaluation regarding the level of spontaneous combustion of the coal is performed, and the predetermined time is the amount of weight increase of the brown coal in the atmosphere. Is a time until it decreases to 90% of the peak value, and a method for evaluating spontaneous combustion of coal is disclosed.

JP, 11-344456, A JP, 2014-126541, A JP, 2017-58203, A

In actual coal storage piles, it has been confirmed that the oxidation reaction of coal proceeds at a low temperature and in a wet state. In addition, it has been reported that the oxidation behavior of coal is different between a high temperature region and a low temperature region, and that water has a physical and chemical effect on the oxidation reaction.
However, since the evaluation method of Patent Document 1 is a test in a closed system, it is considered that there is a difference from the actual coal storage condition in that the O ₂ concentration decreases as the test progresses.
In addition, the evaluation method of Patent Document 2 is considered to be a test under conditions that deviate from the actual coal storage environment because the maximum atmospheric temperature is a high temperature of 600° C. and a dry atmosphere.
In addition, the evaluation method of Patent Document 3 is considered to be a test under conditions that deviate from the actual coal storage environment, because it is in a dry atmosphere in addition to the flow of pure oxygen.

As described above, a method for evaluating the spontaneous heat generation property of coal is known, but in recent years, more accurate evaluation of the spontaneous heat generation property is required.
Therefore, it is necessary to construct an evaluation method that considers the environment close to the actual coal storage pile, specifically, the low temperature and wet condition.
An object of the present invention is to provide a natural exothermic evaluation method of coal and an apparatus for spontaneous exothermic evaluation of coal which can accurately evaluate the natural exothermic property of coal in an environment close to an actual coal storage pile. ..

According to one aspect of the invention,
Obtaining a wet air stream from a mixed gas obtained by mixing oxygen gas and nitrogen gas, or obtaining a wet air stream from air;
Obtaining a wet inert gas stream from at least one inert gas selected from the group consisting of nitrogen gas, argon gas, and helium gas;
Under the wet inert gas flow, a step of heating the coal filled in the reactor to a predetermined temperature,
After the coal is heated to a predetermined temperature, the step of switching the wet inert gas flow to the wet air flow,
Under the switched wet air flow, wet oxidizing the coal,
In the step of wet oxidation, a step of quantifying the production rate of the carbon dioxide by measuring the time of the wet oxidation, and the amount of carbon dioxide generated from the coal,
And a step of determining the spontaneous heat generation of the coal based on the quantified production rate of the carbon dioxide.

In the method for evaluating the spontaneous heat build-up of coal according to one aspect of the present invention, it is preferable that the absolute humidity of the moist airflow is 3 vol% or more and 4 vol% or less.

In the method for evaluating the spontaneous heat generation of coal according to one aspect of the present invention, it is preferable that the step of obtaining the wet airflow is a step of passing the mixed gas or the air through a first bubbling tank.

In the method for evaluating the spontaneous heat build-up of coal according to one aspect of the present invention, it is preferable that the step of obtaining the wet inert gas flow is a step of passing the inert gas through a second bubbling tank.

In the self-heating evaluation method for coal according to an aspect of the present invention, the inert gas is preferably nitrogen gas.

In the method for evaluating the spontaneous heat build-up of coal according to one aspect of the present invention, it is preferable that the step of raising the temperature is a step of raising the temperature of the coal to 80°C.

In the method for evaluating spontaneous heating of coal according to one aspect of the present invention, the step of determining the spontaneous heating is the maximum value of the production rate of carbon dioxide generated from the coal, the equilibrium value of the production rate of carbon dioxide, And a step of determining the spontaneous heat generation property of the coal based on any one or more of integrated values obtained by multiplying the wet oxidation time by the carbon dioxide production rate.

In the self-heating evaluation method for coal according to one aspect of the present invention, the maximum value of the carbon dioxide production rate measured when the coal is at 80° C. is 2.04 per 1 mol of carbon in the coal. It is preferable to determine that the coal has a high spontaneous heat generation when it is ×10 ⁻⁴ mol/sec or more.

In the self-heating evaluation method for coal according to one aspect of the present invention, the equilibrium value of the production rate of carbon dioxide measured when the coal is at 80° C. is 1.61 per 1 mol of carbon in the coal. It is preferable to determine that the coal has a high spontaneous heat generation when it is ×10 ⁻⁴ mol/sec or more.

In the self-heating evaluation method for coal according to one aspect of the present invention, the integrated value obtained by multiplying the time for the wet oxidation by the generation rate of the carbon dioxide, which is measured when the coal is at 80° C., is When it is 4.13×10 ⁻² mol/sec or more per mol of carbon, it is preferable to determine that the coal has a high self-heating property.

In the method for evaluating the spontaneous heat build-up of coal according to an aspect of the present invention, the step of determining the spontaneous heat build-up is performed by changing the temperature of the coal in the step of performing the wet oxidation to generate the carbon dioxide at each temperature. It is preferable that it is a step of calculating an equilibrium value of the velocity and determining the spontaneous heat generation property of the coal at an arbitrary temperature based on a prediction formula derived from the calculated equilibrium value.

In the method for evaluating the spontaneous heat build-up of coal according to an aspect of the present invention, the carbon dioxide production rate is the carbon dioxide production rate when the coal is wet-oxidized under the moist air stream, and the wet impermeability. It is preferable that the difference is the rate of generation of carbon dioxide when the coal is wet-oxidized under an active gas stream.

In the spontaneous heat generation evaluation method for coal according to an aspect of the present invention,
The coal is preferably bituminous coal, sub-bituminous coal, or lignite coal.

According to one aspect of the invention,
Wet air stream obtained from mixed gas obtained by mixing oxygen gas and nitrogen gas, wet air stream obtained from air, and at least one selected from the group consisting of nitrogen gas, argon gas, and helium gas A wet airflow gas generation device for generating a wet inert gas airflow obtained from an inert gas,
A reactor having a first opening, a second opening, a coal filling section that is provided between the first opening and the second opening, and that fills coal with the first opening;
A measuring device for measuring the amount of carbon dioxide generated from the coal,
The wet air stream or the wet inert gas stream is circulated from the first opening of the reactor through the coal filling section to the second opening,
A spontaneous coal heat generation evaluation apparatus is provided, wherein the reactor wet oxidizes the coal when the wet air stream flows through the coal filling portion.

According to one aspect of the present invention, in an environment close to an actual coal storage pile, a natural exothermic evaluation method for coal that can accurately evaluate the spontaneous exothermic property of coal, and a natural exothermic evaluation device for coal are provided. be able to.

Schematic which shows one Embodiment of the self-heating property evaluation apparatus of the coal used for the evaluation method of this embodiment. The schematic sectional drawing which shows one Embodiment of the reactor used for the evaluation method of this embodiment. Graph showing coal A, coal B, and when the coal C respectively by wet oxidation, the relationship between the time and the CO ₂ production rate in the moist air stream. When each wetted oxidizing coal A in moist air stream and under humid nitrogen gas flow, the relationship between the time and the CO ₂ production rate, and a graph showing the difference of the relation. When each wetted oxidizing coal B in moist air stream and under humid nitrogen gas flow, the relationship between the time and the CO ₂ production rate, and a graph showing the difference of the relation. When coal C wetted oxidized in moist air stream and under humid nitrogen gas stream, a graph showing the relationship between time and CO ₂ production rate. Dry air stream and under dry nitrogen gas stream under coal A, coal B, and when the coal C was oxidized respectively, graphs showing the relationship between time and CO ₂ production rate. The graph which shows the Arrhenius plot of coal A. The graph which shows the Arrhenius plot of coal B.

[Coal spontaneous heat generation evaluation method]
The spontaneous heat generation evaluation method for coal of the present embodiment (hereinafter, also referred to as “evaluation method of the present embodiment”) is
Obtaining a wet air stream from a mixed gas obtained by mixing oxygen gas and nitrogen gas, or obtaining a wet air stream from air;
Obtaining a wet inert gas stream from at least one inert gas selected from the group consisting of nitrogen gas, argon gas, and helium gas;
Under the wet inert gas flow, a step of heating the coal filled in the reactor to a predetermined temperature,
After the coal is heated to a predetermined temperature, the step of switching the wet inert gas flow to the wet air flow,
Under the switched wet air flow, wet oxidizing the coal,
In the step of wet oxidation, a step of quantifying the production rate of the carbon dioxide by measuring the time of the wet oxidation, and the amount of carbon dioxide generated from the coal,
Determining the spontaneous heating of the coal based on the quantified production rate of the carbon dioxide.

The spontaneous heat generation evaluation method for coal of the present embodiment (hereinafter, also referred to as “evaluation method of the present embodiment”) is a method for evaluating natural heat generation of various types of coal.
Specifically, in the evaluation method of the present embodiment, the influence of the air flow and moisture that actually occur in the coal storage pile and the low temperature environment (for example, an environment of 30° C. or higher and 80° C. or lower) in the coal storage pile are taken into consideration, A stream of air is passed through the coal at a predetermined temperature to wet and oxidize the coal. Then, based on the generation rate of carbon dioxide generated from coal, it is determined whether the coal easily or naturally does not generate heat. A sample (for example, crushed coal) is used as the coal.
Since coal contains various components, for example, when the components react with water present in the coal storage pile (for example, when a hydrolysis reaction occurs), the reaction triggers the coal to easily generate heat spontaneously. It is considered to be.
In the evaluation method of the present embodiment, in consideration of such a reaction between components contained in coal and moisture, “wet air flow” is selected as an air flow for oxidizing coal and evaluation is performed.
Therefore, according to the evaluation method of the present embodiment, compared to the evaluation in the closed system described in Patent Documents 1 to 3, the evaluation using pure oxygen, and the evaluation under a dry air flow, the actual coal storage pile In an environment close to, it is possible to accurately evaluate the spontaneous heat generation property of coal.
Further, according to the evaluation method of the present embodiment, the spontaneous heat generation of coal can be known in advance, so that spontaneous heat generation of coal can be prevented in advance. Further, by knowing the spontaneous heat generation property of coal in advance, for example, for coal having high heat generation property, spontaneous heat generation can be suppressed by sprinkling water, rolling pressure, and the like. Also, for coal with high heat generation, strengthening the temperature monitoring will enable it to be used early. That is, even low-grade coal can be effectively used.
Further, according to the evaluation method of the present embodiment, since the evaluation is performed using the sample, the evaluation can be performed by a simple method.

Here, the "mixed gas" refers to a mixed gas obtained by mixing oxygen gas and nitrogen gas so that the composition is close to that of air. The composition close to air means that the mixing ratio of oxygen gas and nitrogen gas (O ₂ :N ₂ (volume ratio)) is preferably 21:79. In this embodiment, a mixed gas in which oxygen gas and nitrogen gas are mixed at a ratio of O ₂ :N ₂ (volume ratio)=21:79 is used.
The “air flow” in the wet air flow is a concept including both an air flow obtained from a mixed gas obtained by mixing oxygen gas and nitrogen gas and an air flow obtained from air.

"Wet" in the wet inert gas flow and the wet air flow means that the absolute humidity is preferably 3 vol% or more and 4 vol% or less.
Absolute humidity of 3 vol% or more and 4 vol% or less represents humidity close to the actual humidity in the coal storage pile.
The coal (sample) to be evaluated is not particularly limited. In the evaluation method of the present embodiment, the entire coal can be evaluated, but in JIS M 1002 (1978), it is preferable to evaluate coal classified into the following bituminous coal, subbituminous coal, or lignite. ..
Further, the coal to be evaluated is more preferably subbituminous coal or lignite coal, which is a low-grade coal, from the viewpoint that the spontaneous heat generation property can be accurately evaluated.
-Bituminous coal: coal having a calorific value of 8,100 kcal/kg or more and less than 8,400 kcal/kg based on the anhydrous ashless standard-subbituminous coal... Coal/lignite less than kg: Coal having a calorific value of at least 5,800 kcal/kg and less than 7,300 kcal/kg on an anhydrous ashless basis.

[Spontaneous exothermic index]
The exothermicity of coal was measured by using a spontaneous combustion measuring device (SIT-2, manufactured by Shimadzu Corporation) under a flow of oxygen, and the temperature of a coal sample (air-dried state, particle size 0.212 mm or less, 1 g) was 110°C. It is said that it is possible to measure the time T ₁₈₀ (minutes) required to raise the temperature from ˜180° C. to 180° C. and to judge by the time T ₁₈₀ (minutes).
The present inventor has noticed that the time T ₁₈₀ according to the determination method using this spontaneous combustion measurement device and the amount of carbon dioxide (CO ₂ ) generated when wet oxidizing the coal are correlated, and The CO ₂ generation rate was adopted as an index of spontaneous heat generation.
However, since the determination method based on the time T ₁₈₀ using the spontaneous combustion measurement device is a test under oxygen flow, it can be considered to be a test under a condition different from the actual environment in the coal storage pile.

Furthermore, since the time T ₁₈₀ and the production rate of CO ₂ correlate with each other, the inventor of the present invention uses the index (1) the maximum value of the production rate of CO ₂ (hereinafter, simply “ "Maximum value"), index (2) equilibrium value of CO ₂ generation rate (hereinafter also simply referred to as "equilibrium value"), and index (3) integration obtained by multiplying the time of wet oxidation by the CO ₂ generation rate. It has been found that any one or more of the values (hereinafter, also simply referred to as “integral value”) is adopted. In addition, the maximum value, the equilibrium value, and the integrated value of the CO ₂ generation rate are values per 1 mol of carbon in the coal.
By adopting any one or more of the indexes (1) to (3), it is possible to more accurately evaluate the spontaneous heat generation property of coal.
That is, the “step of determining the spontaneous heat generation” in the present embodiment includes the maximum value, the equilibrium value, and the integral value of the generation rate of CO ₂ generated from the coal, from the viewpoint of accurately evaluating the spontaneous heat generation of coal. Of these, it is preferable to determine the spontaneous heat generation property of coal based on any one or more.

For example, based on the time T ₁₈₀ , the maximum value of CO ₂ production rate, the equilibrium value, and the integral value, which are measured when the temperature of the coal is 80° C., are each divided into three stages, and the coals shown in Table 1 below. It is possible to obtain the criteria for spontaneous heat generation of
Table 1 shows the relationship between the determination criteria based on the time T ₁₈₀ and the determination criteria of the indexes (1) to (3). The unit in Table 1 is a unit per mol of carbon in coal.
In addition, although Table 1 is a determination standard when the temperature of coal is 80° C., it can be similarly created at the temperature of other coal (for example, 40° C. or higher and lower than 80° C.).
Here, the temperature of coal is synonymous with the "predetermined temperature" in the "step of raising the temperature of the coal to a predetermined temperature". That is, the temperature of the coal is the temperature at which the coal is wet-oxidized and is the evaluation temperature.

Specifically, the following criteria were used to derive the criteria for spontaneous heat generation of coal shown in Table 1 from the time T ₁₈₀ .
From the correlation diagram of the production rate (any one of the maximum value, the equilibrium value, and the integrated value) of CO ₂ of coal A, coal B, and coal C used in the examples described later and T ₁₈₀ , from the correlation of T ₁₈₀ and CO ₂ . A first-order approximation formula showing the relationship with the generation rate (any of the maximum value, the equilibrium value, and the integral value) is derived. Using the obtained first-order approximation formula, the CO ₂ generation rate (either the maximum value, the equilibrium value, or the integrated value) at the reference value of T ₁₈₀ of 70 minutes or 85 minutes was derived, and the derived value was derived. Is the standard value.

When the criteria of Table 1 are used, the maximum value of the CO ₂ generation rate measured when the coal is at 80° C. is 2.04×10 ⁻⁴ mol/sec or more per 1 mol of carbon in the coal. When it is, it can be determined that the spontaneous heating of coal is high.

When using the criteria of Table 1, the equilibrium value of the CO ₂ generation rate measured when the coal is at 80° C. is 1.61×10 ⁻⁴ mol/sec or more per 1 mol of carbon in the coal. When it is, it can be determined that the spontaneous heating of coal is high.

When using the criteria of Table 1, the integrated value of the CO ₂ generation rate measured when coal is 80° C. is 4.13×10 ⁻² mol or more per 1 mol of carbon in the coal. At this time, it can be determined that the spontaneous heating of coal is high.

Next, the spontaneous coal heat generation evaluation apparatus used in the evaluation method of the present embodiment will be described.

<Spontaneous heat generation evaluation device>
FIG. 1 is a schematic diagram showing an embodiment of a spontaneous heat generation evaluation apparatus for coal.
The evaluation device 100 measures the amount of carbon dioxide generated from the coal by the wet airflow gas generation device 30 that generates the wet air flow and the wet inert gas flow, the reaction device 40 that wet-oxidizes the coal, and the wet oxidation. The measuring device 50 is provided.
The wet airflow gas generation device 30 of the present embodiment generates a wet airflow from a mixed gas obtained by mixing oxygen (O ₂ ) gas and nitrogen (N ₂ ) gas, and a wet inert gas from N ₂ gas. A wet nitrogen gas stream is generated as the stream.

(Moist gas generator)
The wet airflow gas generation device 30 includes a gas supply unit 301 and a wet airflow gas generation unit 302.
The gas supply unit 301 includes an O ₂ cylinder 1, an N ₂ cylinder 2, mass flow controllers (hereinafter, also referred to as “MFC”) 3, 4, 5, pressure control valves 3a, 4a, 5a, and joints 31, 32. ..
The gas supply unit 301 of the present embodiment can supply a mixed gas of N ₂ gas and O ₂ gas (nitrogen gas:oxygen gas (volume ratio)=79:21) and nitrogen gas (an example of an inert gas). Is configured.
The oxygen gas supplied from the O ₂ cylinder 1 is pressure-controlled by the pressure regulating valve 3a and supplied to the MFC 3. The MFC 3 adjusts the flow rate of oxygen gas so that an air flow is generated when N ₂ gas and O ₂ gas merge at the joint 32.
The nitrogen gas supplied from the N ₂ cylinder 2 is supplied to the MFC 4 through the joint 31, the pressure of which is adjusted by the pressure regulating valve 4a. The MFC 4 adjusts the flow rate of nitrogen gas so that an air flow (a mixed gas of N ₂ gas and O ₂ gas) is generated when N ₂ gas and O ₂ gas join together at the joint 32.
The nitrogen gas supplied from the N ₂ cylinder 2 is pressure-controlled by the pressure regulating valve 5a via the joint 31 and is also supplied to the MFC 5.
The MFC 5 adjusts the flow rate of nitrogen gas in the second bubbling tank 8 so that a desired amount of wet nitrogen gas flow is generated.

The wet airflow gas generation unit 302 includes a constant temperature bath 6, a first bubbling bath 7 that produces a wet air flow, a second bubbling bath 8 that produces a wet nitrogen gas flow, and cocks 9 and 10. The first bubbling tank 7 and the second bubbling tank 8 are triple bubbling tanks, but are not limited thereto. Water (Water in FIG. 1) is stored in each bubbling tank.
The air flow supplied from the MFCs 3 and 4 to the first bubbling tank 7 via the joint 32 and the check valve (not shown) is bubbled and becomes a wet air flow, which can be supplied to the pipe 35 by operating the cock 9. ..
The nitrogen gas flow supplied from the MFC 5 to the second bubbling tank 8 via the check valve (not shown) is bubbled and becomes a wet nitrogen gas flow, which can be supplied to the pipe 35 by operating the cock 10.
The tape heater 12 is wound around the pipe 35 as a heater. The tape heater 12 is connected to the temperature controller 14. Further, a thermocouple 121 is provided on the side of the pipe 35 on the side of the reaction device 40.
The temperature of the pipe 35 is measured by the thermocouple 121 and adjusted to a predetermined temperature by the tape heater 12 and the temperature controller 14.
The temperatures of the wet air flow and the wet nitrogen gas flow are adjusted to a predetermined temperature by flowing through the pipe 35 adjusted to a predetermined temperature by heating the pipe 35.
The temperatures of the wet air stream and the wet nitrogen gas stream are preferably adjusted to the temperature of the coal 174 (see FIG. 2) in the reactor 17 from the viewpoint of maintaining the temperature of the coal sample at a predetermined temperature.
The pressure gauge 11 is connected to the pipe 35. The pressure gauge 11 measures the pressure of the wet air stream and the wet nitrogen gas stream flowing through the pipe 35.
Below, when viewed in the flow direction of the wet air flow and the wet nitrogen gas flow, the side of the wet air flow gas generation unit 302 is referred to as the “upstream side”, and the side away from the wet air flow gas generation unit 302 is referred to as the “downstream side”. It may be called.
One of the wet air flow and the wet nitrogen gas flow generated by the wet air flow gas generation unit 302 is supplied to the reaction device 40 by operating the cocks 9 and 10.

(Reactor)
The reaction device 40 includes a reactor 17 for charging coal as a sample, a heater 13 arranged outside the reactor 17 for heating coal, and a temperature controller 15 connected to the heater 13. ..
A thermocouple 26 inserted in coal 174 (see FIG. 2) is provided on the downstream side of the reactor 17. The temperature of the coal 174 is measured by the thermocouple 26 and adjusted to a predetermined temperature by the heater 13 and the temperature controller 15.
A temperature indicator 16 is provided on the downstream side of the reactor 17. The temperature indicator 16 monitors the temperature of the coal 174.

FIG. 2 is a schematic sectional view showing an embodiment of the reactor.
The reactor 17 has a first opening 171, a second opening 172, and a coal filling portion 173 that is filled with coal 174. The coal filling unit 173 is provided between the first opening 171 and the second opening 172.
The shape of the reactor 17 is not particularly limited. The reactor 17 of the present embodiment has a cylindrical shape and includes a main body member 175 and a downstream member 176.
The moist air flow or the moist nitrogen gas flow generated in the moist air flow gas generation unit 302 flows from the first opening 171 of the reactor 17 through the inside of the coal filling unit 173 in the direction of arrow 177 in FIG. It is circulated to the second opening 172 and sent to the measuring device 50.
The reactor 17 wet-oxidizes the coal 174 by bringing the wet-air flow and the coal 174 into contact with each other when the wet-air flow passes through the coal filling portion 173.
The sample is ground coal. The reactor 17 holds the coal 174 in a state of being filled with the coal 174 so that the coal 174 does not leak from the reactor 17 due to the pressure of the wet air flow or the wet nitrogen gas flow. In the present embodiment, the coal 174 is held by the glass wool filled in the downstream member 176 described later.
The inner diameter of the downstream member 176 of the reactor 17 is smaller than the inner diameter of the main body member 175, and has a convex shape projecting to the downstream side. On the other hand, the inner diameter of the main body member 175 of the reactor 17 is larger than the inner diameter of the downstream member 176, and the inner diameter increases toward the first opening 171. The coal filling unit 173 is provided in the main body member 175.
The material of the reactor 17 is not particularly limited, but is preferably formed of a material having heat resistance and thermal conductivity from the viewpoint of safety management and keeping the coal sample at a predetermined temperature, for example, stainless steel or the like. Is more preferable. The reactor 17 of the present embodiment is made of stainless steel, and the downstream member 176 is filled with glass wool so that the coal 174 does not leak out.

(measuring device)
Measuring device 50 is provided with a CO ₂ containing water calcium chloride tube 18 for removing the gas generated by the wet oxidation of coal, and Men Buremu filter 19, the analyzer for measuring the production rate of the amount and CO ₂ CO _2, etc. 20 and 20 are provided.
The analyzer 20 is connected to the reactor 40 via the calcium chloride tube 18 and the membrane filter 19. Analyzer 20, in reactor 17, to quantify the production rate of the amount and CO ₂ CO ₂ generated from the coal 174 by wet oxidation.
The moist air flow discharged from the reactor 17 is supplied to the exhaust pipe 21, passes through the calcium chloride pipe 18 and the membrane filter 19, and is partially supplied to the analyzer 20, and the rest is indicated by an arrow in FIG. It is exhausted in the direction of 22.
Analyzer 20 of the present embodiment is a micro-gas chromatograph, in addition to the production rate of the amount and CO ₂ CO ₂ generated from the coal 174 by wet oxidation, the largest value of the production rate of CO _2, the equilibrium value, and Measure the integrated value.
In the evaluation device 100 of this embodiment, a wet nitrogen gas stream is supplied to the reactor 17 before the start of evaluation. The wet nitrogen gas flow discharged from the reactor 17 is supplied to the exhaust pipe 21, and a part thereof is supplied to the analyzer 20 as needed. Analyzer 20, by passage of the wet nitrogen gas stream to the coal packed portion 173 in the reactor 17, measuring the production rate of the amount and CO ₂ CO ₂ generated from the coal 174 and the like.

Hereinafter, preferable aspects of the evaluation method of the present embodiment will be described. Hereinafter, the description of the reference numerals may be omitted.
The evaluation method of the present embodiment includes a step of obtaining a moist air flow, a step of obtaining a moist inert gas flow, a step of raising the temperature of coal to a predetermined temperature (hereinafter, also referred to as a “temperature raising step”), and a wet impregnation. A step of switching the active gas flow to a wet air flow (hereinafter, also referred to as "switching step"), a step of wet oxidizing coal (hereinafter, also referred to as "wet oxidation step"), and a step of quantifying the production rate of carbon dioxide (Hereinafter, also referred to as “quantification step”) and a step of determining the spontaneous heat generation property of coal (hereinafter, also referred to as “determination step”).

<Process of obtaining wet air flow>
The step of obtaining a wet air flow is a step of obtaining a wet air flow from a mixed gas obtained by mixing oxygen gas and nitrogen gas, or obtaining a wet air flow from air.
The “air” in the wet air flow may be air in the atmosphere or a mixed gas of oxygen gas and nitrogen gas.
The method for obtaining the moist air flow is not particularly limited, and examples thereof include a method of bubbling a mixed gas of oxygen gas and nitrogen gas or air in a bubbling tank, a method of using a moist air generator, and the like.
As a method for obtaining a moist air flow, a method using a bubbling tank is preferable from the viewpoint of easily forming a humidity (absolute humidity of 3 vol% or more and 4 vol% or less).
The temperature of the moist air stream is preferably adjusted to the temperature of coal (that is, the evaluation temperature). As a method of adjusting the temperature of the wet air flow, for example, as shown in the examples described below, a method of adjusting the temperature of the constant temperature bath, a method of adjusting the temperature of the pipe through which the wet air flow flows, and filling a coal sample. Examples of the method include adjusting the temperature in the reactor.

<Step of obtaining a wet inert gas flow>
The step of obtaining a wet inert gas flow is a step of obtaining a wet inert gas flow from at least one inert gas selected from the group consisting of nitrogen gas, argon gas, and helium gas.
The method for obtaining the wet inert gas flow is not particularly limited, and examples thereof include a method of bubbling an inert gas in a bubbling tank and a method of using a wet air generator.
As a method of obtaining a wet inert gas stream, a method of circulating an inert gas in a bubbling tank is preferable from the viewpoint of easily forming wetness (absolute humidity of 3 vol% or more and 4 vol% or less).
The "inert gas" of the inert gas stream is preferably nitrogen gas.
The temperature of the wet nitrogen gas flow is preferably adjusted to the temperature of coal (that is, the evaluation temperature). As a method for adjusting the temperature of the wet nitrogen gas flow, for example, a method of adjusting the temperature of the constant temperature bath, a method of adjusting the temperature of the pipe through which the wet nitrogen gas flow flows, and the temperature in the reactor filled with the coal sample The method of adjusting etc. are mentioned.

<Temperature raising step>
The temperature raising step is a step of raising the temperature of the coal filled in the reactor to a predetermined temperature under a wet inert gas flow.
As a result, wet oxidation of coal is suppressed before the start of evaluation, and the amount of CO ₂ generated by wet oxidation can be accurately quantified.

The "predetermined temperature" in the temperature raising step is a temperature at which the coal is wet-oxidized and is an evaluation temperature.
The “predetermined temperature” in the temperature raising step is preferably 30° C. or higher and 80° C. or lower, more preferably 40° C. or higher and 80° C. or lower, further preferably 50° C. or higher and 80° C. or lower, further preferably 60° C. or higher and 80° C. or lower, and It is preferably 70° C. or higher and 80° C. or lower, and more preferably 80° C.
The predetermined temperature (the temperature at which the coal is wet-oxidized) represents a temperature close to the actual temperature in the coal storage pile.
The sample coal is preferably crushed coal.
The particle size of coal (sample) is usually 1 mm or less, preferably 0.050 mm or more and 0.853 mm or less, and more preferably 0.050 mm or more and 0.212 mm or less.
The particle size of coal can be determined, for example, by crushing using a crushing device and then classifying with a sieve using a plurality of openings.
The amount of coal charged in the reactor depends on the volume of the reactor, but from the viewpoint of accurately quantifying the amount of CO ₂ generated from coal by wet oxidation, preferably 25 g or more and 75 g or less, more preferably 50 g. ±0.5 g.

<Switching process>
The switching to the moist air flow in the switching step is preferably performed after the temperature of the coal has been raised to a predetermined temperature and then stabilized in the temperature raising step.
The stabilization time of the temperature after the temperature of the coal is raised is preferably 30 minutes or longer. The upper limit of the temperature stabilization time after the temperature of the coal is raised is not particularly limited, but is preferably 18 hours or less.

<Wet oxidation step>
In the case of FIG. 2, in the wet oxidation step, the wet air flow is made to flow from the first opening 171 of the reactor 17 through the coal filling portion 173 to the second opening 172, and the coal 174 and the wet air flow are flown. Is a step of wet-oxidizing the coal by contacting with.
The flow rate of the moist air stream in the wet oxidation step is preferably 50 mL/min or more and 100 mL/min or less.
When the flow rate of the moist air flow is 50 mL/min or more, the influence of the error in the mass flow controller becomes small.
When the flow rate of the moist air flow is 100 mL/min or less, gas leakage is less likely to occur at the connecting portion of the pipe or the like.
In addition, the flow rate in this specification means the flow rate under the conditions of 0° C. and 1 atm. The same applies hereinafter.
The wet oxidation time is preferably 40 minutes or more from the viewpoint of easily reaching the maximum value of the CO ₂ generation rate. The wet oxidation time is more preferably 240 minutes or more from the viewpoint of facilitating convergence of the CO ₂ generation rate. The upper limit of the wet oxidation time is not particularly limited, but is preferably 28 hours or less.

<Quantitative process>
The quantification step is a step of quantifying the generation rate of CO ₂ by measuring the time of wet oxidation and the amount of CO ₂ generated from coal in the step of performing wet oxidation.
CO ₂ generated from coal is preferably dehumidified with a calcium chloride tube or the like and measured. Device for measuring the formation rate of the amount and CO ₂ CO ₂ is not particularly limited. In the present embodiment, as a device for measuring the formation rate of the amount and CO ₂ CO _2, it is used a micro-gas chromatograph.

<Judgment process>
The determination step is a step of determining the spontaneous heat generation property of coal based on the quantified CO ₂ generation rate.
As described above, the determination step is based on any one or more of the maximum value, the equilibrium value, and the integral value of the generation rate of CO ₂ generated from the coal, from the viewpoint of accurately evaluating the spontaneous heat generation property of the coal. It is preferable to determine the spontaneous heating of coal.
By applying the maximum value, the equilibrium value, or the integrated value of the measured CO ₂ generation rate, for example, to the criteria shown in Table 1, the spontaneous heat generation property of coal can be determined.

The determination step is performed by changing the temperature of the coal in the step of performing wet oxidation, calculating the equilibrium value of the production rate of CO ₂ at each temperature, and based on the prediction formula derived from the calculated equilibrium value, at any temperature. It is preferable to determine the spontaneous heat generation of coal.
In the determination step, the temperature (evaluation temperature) of the coal when changing the temperature of the coal is preferably 40° C. or higher and 80° C. or lower, more preferably 60° C. or higher and 80° C. or lower.
Thereby, the spontaneous heat generation property of coal can be evaluated more accurately.
In the determination step, an Arrhenius plot (see FIGS. 8 and 9) is created from the relationship between each temperature and the equilibrium value of the CO ₂ generation rate at each temperature, and based on the prediction formula by this Arrhenius plot, It is more preferable to determine the spontaneous heat generation property of coal.
The “arbitrary temperature” in the determination step is not particularly limited as long as it is a temperature that can be applied to the prediction formula, but a temperature in an actual temperature region within the coal storage pile (for example, 30° C. or higher and 80° C. or lower) is preferable. The “arbitrary temperature” may be a temperature different from the temperature (evaluation temperature) at which the coal is wet-oxidized.

In the evaluation method of the present embodiment, the CO ₂ generation rate is the CO ₂ generation rate when the coal is wet-oxidized under a wet air stream, and the coal is wet-oxidized under a wet inert gas stream. It is preferable that the difference is from the CO ₂ generation rate at that time.
As a result, the amount of net CO ₂ generated by the wet oxidation of coal under a humid air flow can be quantified, so that the spontaneous heat generation property of coal can be evaluated more accurately.
The net amount of CO ₂ means that it can be substantially regarded as the amount of CO ₂ .

[Implementation of evaluation method]
The evaluation method of the present embodiment is carried out as follows using the evaluation device 100 shown in FIG. 1, for example.
First, in the gas supply unit 301 of the wet gas flow generator 30, a mixed gas of nitrogen gas and oxygen gas is generated as an air flow. This mixed gas passes through the first bubbling tank 7 of the wet airflow gas generation unit 302 to become a wet airflow (step of obtaining a wet airflow). The generated moist air flow is supplied to a pipe (not shown) different from the pipe 35 and is not supplied to the reactor 17 until the switching step.
Further, in the gas supply unit 301, nitrogen gas is generated as an inert gas flow. This nitrogen gas passes through the second bubbling tank 8 of the wet airflow gas generation unit 302 to become a wet nitrogen gas airflow (step of obtaining a wet inert gas airflow). The wet nitrogen gas stream flows through the pipe 35 by the operation of the cock 10 and is supplied to the reactor 17 of the reaction device 40.
In the reactor 17, the coal 174 (see FIG. 2) is heated to a predetermined temperature under a wet nitrogen gas stream (heating process).
After the temperature of the coal 174 is stabilized, the cock 9 and the cock 10 are operated to switch the supply gas to the reactor 17 from the wet nitrogen gas flow to the wet air flow (switching step).
After the switching step, in the reactor 17, the coal 174 is wet-oxidized by the flow of the moist air flow (wet oxidation step).
The gas discharged from the reactor 17 is sent to the measuring device 50. In the measuring device 50, the analyzer 20, the amount and CO ₂ production rate of CO ₂ contained in the exhaust gas is quantified (quantitative step).
The spontaneous heat generation property of the coal 174 is determined based on the quantified CO ₂ production rate (determination step).

[Modification of Embodiment]
It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. within the scope of achieving the object of the present invention are included in the present invention.

Examples of the present invention will be described below. The invention is in no way limited by these examples.

[Absolute humidity of moist air flow]
The evaluation apparatus shown in FIG. 1 does not include the reactor 17, the thermocouple 26, the temperature controller 15, the heater 13, the calcium chloride tube 18, the temperature indicator 16, and the membrane filter 19 except that the evaluation apparatus shown in FIG. The absolute humidity of the moist air stream was measured using an evaluation device having the same configuration as the device (hereinafter, also referred to as “test device”).
The test apparatus has a configuration in which the pipe 35 in the evaluation apparatus of FIG. 1 is connected to a micro gas chromatograph (analyzer 20 in FIG. 1). The micro gas chromatograph measures the absolute humidity of the wet air flow discharged from the pipe 35.
As shown in Table 2, the temperature of the constant temperature bath 6 and the temperature of the tape heater 12 wound around the pipe 35 were changed, and the absolute humidity of the moist air stream was measured using a micro gas chromatograph.
Note that the moist air flow was obtained by mixing the O ₂ flow rate of 21 mL/min and the N ₂ flow rate of 79 mL/min (N ₂ :O ₂ (volume ratio)=79:21) in the same manner as in Example 1 described later. Generated. The flow rate is a flow rate under the condition of 0° C. and 1 atm.
The absolute humidity [vol%] of the moist air flow is defined as "mixed gas D" which is "mixed gas of nitrogen and oxygen that does not pass through a bubbling tank", and "mixed gas of nitrogen and oxygen that is moistened by bubbling". Can be calculated by using the following mathematical formula (Equation 11).
The results are shown in Table 2. The absolute humidity [vol%] of the moist air flow in Table 2 is a value calculated using the mathematical formula (Equation 11).

Absolute humidity [vol%] of wet air flow = ("N ₂ concentration in mixed gas D" + "O ₂ concentration in mixed gas D")-("N ₂ concentration in mixed gas W" + "mixed gas O ₂ concentration in W”)... (Equation 11)
In the mathematical formula (Equation 11), the units of the N ₂ concentration and the O ₂ concentration are [vol %].

As shown in Table 2, by heating the temperature of the constant temperature bath 6 and the tape heater 12 to 40° C., 50° C., 60° C., 70° C. or 80° C., a humid air flow having an absolute humidity of 3 vol% or more and 4 vol% or less is obtained. It can be seen that

[Spontaneous heat generation evaluation method]
<Example 1>
Using the evaluation device shown in FIG. 1, the spontaneous heat generation property of coal A was evaluated by the following method.
The coal A corresponds to the coal 174 filled in the reactor 17 (coal filling unit 173) in FIG. 2.
After air-drying, 50 g of coal A (Indonesian subbituminous coal) pulverized to a particle size of 0.212 mm or less was charged into the reactor 17. Coal A was sieved with a sieve having an opening of 0.20 mm to have a particle size of 0.212 mm or less.

Step of obtaining a moist air flow The O ₂ gas supplied from the O ₂ cylinder 1 is adjusted to a flow rate of 21 mL/min (0° C., 1 atm) with the MFC 3, and the N ₂ gas supplied from the N ₂ cylinder 2 is MFC 4. Then, after adjusting the flow rate to 79 mL/min (0° C., 1 atm) (N ₂ :O ₂ (volume ratio)=79:21), they are merged at the joint 32 to form a mixed gas, and triple gas in the constant temperature bath 6 is used. Bubbling was performed in a bubbling tank (first bubbling tank 7 in FIG. 1) to humidify. As a result, a moist air flow (air flow generated from a mixed gas of N ₂ and O ₂ ) was generated. The generated moist air flow is supplied to a pipe (not shown) different from the pipe 35 and is not supplied to the reactor 17 until the switching step.

Step of obtaining a wet inert gas flow After adjusting the N ₂ gas supplied from the N ₂ cylinder 2 with the MFC 5 to a flow rate of 100 mL/min (0° C., 1 atm), the triple bubbling tank in the constant temperature tank 6 ( In FIG. 1, bubbling and humidification were performed in a second bubbling tank 8). This produced a wet nitrogen gas stream.

-The temperature raising step The cock 10 was operated to supply the generated wet nitrogen gas flow from the first opening 171 of the reactor 17, and the atmosphere of the reactor 17 was replaced with the wet nitrogen gas flow. After 30 minutes, the temperature of the coal A in the reactor 17 was raised to 80° C. under a wet nitrogen gas stream by the constant temperature bath 6, the tape heater 12, and the heater 13, and the temperature of the coal A was stabilized over 30 minutes. It was
The temperature of the coal A was confirmed by the thermocouple 26 and the temperature indicator 16.
The temperature of the tape heater 12 was adjusted by the temperature controller 14. The temperature of the heater 13 was adjusted by the temperature controller 15.

-Switching step After the temperature of the coal A was raised to 80°C, and further 30 minutes later, the cock 9 and the cock 10 were operated to switch the supply gas to the reactor 17 from the wet nitrogen gas flow to the wet air flow.

Wet oxidation step Coal A was wet-oxidized under a moist air flow. Specifically, the wet air flow is made to flow from the first opening 171 through the coal filling portion 173 to the second opening 172, and the coal 174 and the wet air flow are brought into contact with each other. Was wet oxidized.

Quantitative Step The exhaust gas (CO ₂ -containing gas) from the reactor 17 is dried with a calcium chloride pipe 18, passed through a membrane filter 19, and then analyzed using a micro gas chromatograph to be included in the exhaust gas. measuring the amount of CO _2, it was quantified CO ₂ production rate from the amount of CO _2.

-Judgment step The spontaneous heat generation property of coal A was judged as follows. Hereinafter, the wet oxidation of coal A may be referred to as a “wet oxidation test”.
Wet Oxidation of Coal A under Wet Air Flow FIG. 3 shows the change over time in the CO ₂ generation rate of coal A after the start of the wet oxidation test. FIG. 3 also shows changes over time in the CO ₂ production rates of coal B and coal C described later.
As shown in FIG. 3, Coal A gradually increased after increasing the CO ₂ generation rate after a sufficient number of test starts, and then became almost in equilibrium.

Wet oxidation of Coal A under wet nitrogen gas flow Under the wet nitrogen gas flow before the start of the wet oxidation test, the temperature of Coal A was raised to 80° C. and the wet nitrogen gas flow was maintained even after the temperature was stabilized. The CO ₂ generation rate when coal A was wet-oxidized under a wet nitrogen gas stream was also quantified.
In Example 1, the difference between the CO ₂ generation rate when the coal A was wet-oxidized under the wet air flow and the CO ₂ generation rate when the coal A was wet-oxidized under the wet nitrogen gas flow was calculated. , And the net production rate of CO ₂ generated by wet oxidation.
FIG. 4 shows the relationship between the time and the CO ₂ generation rate when the coal A was wet-oxidized under the wet air flow and the wet nitrogen gas flow, and the coal A was wet-oxidized under the wet air flow. shows the CO ₂ generation rate, a graph showing the difference between the CO ₂ production rate of when wetted oxidizing coal a in a humidified nitrogen gas flow of time.
In FIG. 4, the signs of A _air , A _air −A _N2 , A _N2 , S _A , prep, and test are as follows.
· _{A air:} CO ₂ generation rate · _A coal A in the moist air stream _N2: wet nitrogen gas flow CO ₂ production rate _· A _air coal A under -A _N2: difference · S between _{A air} and _{A N2 A} : integrated value of CO ₂ generation rate of coal A ・prep: temperature rising and stabilization process under wet nitrogen gas flow ・test: wet oxidation test time (evaluation time) of coal A under wet air flow

From FIGS. 3 and 4, the maximum value, the equilibrium value, and the integrated value of the CO ₂ generation rate when the coal A is at 80° C. are applied to the criteria shown in Table 1 above to determine the spontaneous heat generation of the coal A. did.
In Table 1, "high spontaneous heat generation" was determined as "3", "medium spontaneous heat generation" was determined as "2", and "low spontaneous heat generation" was determined as "1". The same applies below.
The results are shown in Table 3.

[Example 2]
The spontaneous exothermic property of coal B was evaluated in the same manner as the spontaneous exothermic property evaluation of coal A except that coal B (Australian bituminous coal) was used instead of coal A.
In Example 2, in the same manner as in Example 1, the CO ₂ generation rate when coal B was wet-oxidized under a moist air stream and the time when coal B was wet-oxidized under a wet nitrogen gas stream. It was determined as the net rate of production of CO ₂ generated by wet oxidation.
As shown in FIG. 3, Coal B was in an equilibrium state after the CO ₂ generation rate increased after a sufficient number of test starts.
FIG. 5 shows the relationship between the time and the CO ₂ generation rate when the coal B was wet-oxidized under the wet air flow and the wet nitrogen gas flow, and the coal B was wet-oxidized under the wet air flow. shows the CO ₂ generation rate, a graph showing the difference between the CO ₂ production rate of when wetted oxidizing coal B in a humidified nitrogen gas flow of time.
In FIG. _5, showing _{B air, B air -B N2,} B N2, S B, prep, and test the code below.
- _{B air:} wet air stream CO ₂ production rate, coal B under _{B N2:} wet nitrogen gas flow CO ₂ production _rate, coal B under B _air -A _N2: difference · S between _{B air} and _{B N2 B} : integrated value of CO ₂ production rate of coal B prep: temperature rising and stabilizing process under wet nitrogen gas flow test: test: wet oxidation test time (evaluation time) of coal B under wet air flow

From FIG. 3 and FIG. 5, similarly to coal A, the maximum value, the equilibrium value, or the integrated value of the CO ₂ generation rate when coal B is 80° C. is applied to the criterion shown in Table 1 above, The spontaneous heat generation property of coal B was determined.
The results are shown in Table 3.

[Example 3]
The spontaneous exothermic property of coal C was evaluated in the same manner as the spontaneous exothermic property evaluation of coal A, except that coal C (Australian bituminous coal) was used instead of coal A. The coal C is coal produced from a mine different from the coal B.
In Example 3, the CO ₂ production rate when the coal C was wet-oxidized under a wet air stream was determined as a net CO ₂ production rate.
As shown in FIG. 3, Coal C was in an equilibrium state after the CO ₂ generation rate increased after a sufficient number of test starts.
FIG. 6 shows a graph showing the relationship between time and CO ₂ generation rate when the coal C is wet-oxidized under a wet air flow and a wet nitrogen gas flow.
Coal C could not detect CO ₂ under a wet nitrogen gas flow during the wet oxidation test, and therefore the CO ₂ generation rate under a wet nitrogen gas flow could not be calculated.
In FIG. 6, the symbols of C _air , S _C , prep, and test are as follows.
· _{C air:} wet coal C in an air stream CO ₂ production rates · _{S C:} integral value of CO ₂ production rate of coal C · prep: heating under wet nitrogen gas stream and stabilization process · test: wet Wet oxidation test time (evaluation time) of coal C under air flow

From FIG. 3 and FIG. 6, the spontaneous heat generation property of the coal C was determined based on the maximum value of CO ₂ generation rate, the equilibrium value, and the integrated value when the coal C was at 80° C.
The results are shown in Table 3.

By the evaluation methods of Examples 1 to 3, it is possible to determine that coal A has high spontaneous heat generation and coal B and coal C have low spontaneous heat generation.

[Comparative Example 1]
As an evaluation device, shown in FIG. 1 except that the evaluation device shown in FIG. 1 does not include the first bubbling tank 7, the second bubbling tank 8, the constant temperature tank 6, the calcium chloride tube 18, and the membrane filter 19. An evaluation device similar to the evaluation device was used.
Then, the spontaneous heating properties of the coals A to C were evaluated in the same manner as in Examples 1 to 3 except that the dry air flow was used instead of the wet air flow.
FIG. 7 shows a graph showing the relationship between time and CO ₂ generation rate when coal A, coal B, and coal C were respectively oxidized under a dry air flow and a dry nitrogen gas flow.
Comparing FIG. 7 and FIG. 3, although the CO ₂ generation rate of coal A is slower than that when the coal A is oxidized under a moist air stream, the coal A shows a CO ₂ generation rate after a sufficient number of test starts. And then equilibrated.
On the other hand, regarding coals B and C, generation of CO ₂ could not be confirmed.

From the results of Examples 1 to 3 and Comparative Example 1, the evaluation method of Comparative Example using the dry air flow may not be able to evaluate the spontaneous heat generation property of the coal (Coal B and Coal C) which is difficult to be wet-oxidized. all right.

<Evaluation method of spontaneous heat generation by a prediction formula of CO ₂ generation rate>
[Example 4]
In the temperature raising step of Example 1, the CO ₂ generation rate of coal A (hereinafter, also referred to as “coal A ₇₀ ”) was elapsed with the same method as in Example 1 except that the temperature of the coal A was raised to 70° C. The change was measured, and the maximum value, the equilibrium value, and the integrated value of the CO ₂ generation rate of coal A ₇₀ were obtained.
Similarly, in the temperature raising step of Example 1, CO ₂ production of coal A (hereinafter, also referred to as “coal A ₆₀ ”) was performed in the same manner as in Example 1 except that the temperature of coal A was raised to 60° C. The change with time of the rate was measured, and the maximum value, the equilibrium value, and the integrated value of the CO ₂ generation rate of coal A ₆₀ were obtained.
In Example 4, in the same manner as in Example 1, with humid air stream, the CO ₂ production rate at the time of the coal A ₇₀ is wet oxidation under wet nitrogen gas stream, when coal A ₇₀ wetted oxide The CO ₂ production rate was calculated as the net CO ₂ production rate generated by wet oxidation. The same applies to coal A ₆₀ .

Both the coal A ₇₀ and the coal A ₆₀ were in an almost equilibrium state after the CO ₂ generation rate increased after a sufficient number of test starts. At the end of the test, the CO ₂ generation rate was almost constant under all conditions. Therefore, using the following mathematical formula (equation 1), the equilibrium value of CO ₂ at 70° C. and 60° C. and the equilibrium value of CO ₂ at 80° C. were used. The Arrhenius plot shown in FIG. 8 was created from the values (Example 1). Based on this Arrhenius plot, the frequency factor and the activation energy were each calculated, and the prediction formula of the CO ₂ generation rate of the following mathematical formula (Formula 2) was constructed.

R _CO2 =A _CO2 ·exp(-E _CO2 /RT) (Equation 1)
R _CO2 : CO ₂ generation rate per mol of carbon in coal (mol/sec)
A _CO2 : Frequency factor of CO ₂ production reaction (mol/sec)
E _CO2 : Activation energy of CO ₂ production reaction (kJ/mol)
R: Gas constant (kJ/K/mol)
T: Temperature (K)

_RA(CO2) =2.98×10 ³ ·exp(−47.6/RT) (Equation 2)
_RA(CO2) : CO ₂ generation rate per mol of carbon in coal A (mol/sec)
R: Gas constant (kJ/K/mol)
T: Temperature (K)

[Example 5]
CO ₂ equilibrium values at 70° C. and 60° C., and 80° C. were used in the same manner as in Example 4 except that coal B (Australian bituminous coal) was used instead of coal A. The Arrhenius plot shown in FIG. 9 was created from the equilibrium value of CO ₂ in Example 2 (Example 2). Based on this Arrhenius plot, the frequency factor and the activation energy were respectively calculated, and a prediction formula for the equilibrium value of the CO ₂ generation rate of the following mathematical formula (Formula 3) was constructed.

RB _(CO2) =5.61×10 ¹³ ·exp(-94.3/RT) (Equation 3)
RB _(CO2) : CO ₂ generation rate per mol of carbon in coal B (mol/sec)
R: Gas constant (kJ/K/mol)
T: Temperature (K)

Table 4 shows the results of Examples 4 and 5.

By using the mathematical formulas (2) and (3), it is possible to relatively evaluate the spontaneous heat generation properties of the coal A and the coal B in the actual temperature range (for example, 30° C. or higher and 80° C. or lower) in the coal storage pile. it can.
For example, the CO ₂ generation rate per 1 mol of carbon in coal A at 30° C. is calculated as 1.8×10 ⁻⁵ mol/sec from the mathematical expression (Equation 2).
Further, from the mathematical expression (Formula 3), the CO ₂ generation rate per mol of carbon in coal B at 30° C. is calculated to be 2.4×10 ⁻⁷ mol/sec.
That is, in the evaluation methods of Examples 4 and 5, it can be determined that the spontaneous heat generation property at a low temperature (30° C.) is coal A>coal B (coal A is more likely to spontaneously generate heat).

INDUSTRIAL APPLICABILITY The present invention, for example, can prevent spontaneous heat generation of coal that may occur in a coal storage pile such as a thermal power generation facility, and the timing of using various types of coal (for example, preferentially use coal having a high heat generation value). Etc.) can be predicted, so it can be used for effective utilization of various types of coal.

1... O ₂ cylinder, 2... N ₂ cylinder, 3, 4, 5... Mass flow controller, 3a, 4a, 5a... Pressure regulating valve, 6... Constant temperature tank, 7... First bubbling tank, 8... Second bubbling tank , 9, 10... Cock, 11... Pressure gauge, 12... Tape heater, 13... Heater, 14, 15... Temperature controller, 16... Temperature indicator, 17... Reactor, 18... Calcium chloride tube, 19... Membrane Filter, 20... Analysis device, 21... Exhaust pipe, 26... Thermocouple, 30... Wet airflow gas generation device, 31, 32... Joint, 35... Piping, 40... Reactor, 50... Measuring device, 100... Evaluation device, 121... Thermocouple, 171... 1st opening part, 172... 2nd opening part, 173... Coal filling part, 174... Coal, 175... Main body member, 176... Downstream side member, 301... Gas supply part, 302... Wet gas flow generator.

Claims (14)

Obtaining a wet air stream from a mixed gas obtained by mixing oxygen gas and nitrogen gas, or obtaining a wet air stream from air;
Obtaining a wet inert gas stream from at least one inert gas selected from the group consisting of nitrogen gas, argon gas, and helium gas;
Under the wet inert gas flow, a step of heating the coal filled in the reactor to a predetermined temperature,
After the coal is heated to a predetermined temperature, the step of switching the wet inert gas flow to the wet air flow,
Under the switched wet air flow, wet oxidizing the coal,
In the step of wet oxidation, a step of quantifying the production rate of the carbon dioxide by measuring the time of the wet oxidation, and the amount of carbon dioxide generated from the coal,
And a step of determining the spontaneous heat generation property of the coal based on the quantified production rate of the carbon dioxide. In the method for evaluating the spontaneous heat generation of coal according to claim 1,
The method for evaluating the spontaneous heat build-up of coal, wherein the absolute humidity of the wet airflow is 3 vol% or more and 4 vol% or less. In the method for evaluating spontaneous combustion of coal according to claim 1 or 2,
The step of obtaining the moist air flow is a method for evaluating spontaneous heat generation of coal, which is a step of passing the mixed gas or the air through a first bubbling tank. In the coal self-heating evaluation method according to any one of claims 1 to 3,
The step of obtaining the wet inert gas flow is a method for evaluating spontaneous heat generation of coal, which is a step of passing the inert gas through a second bubbling tank. The self-heating evaluation method for coal according to any one of claims 1 to 4,
The inert gas is a nitrogen gas. The self-heating evaluation method for coal according to any one of claims 1 to 5,
The step of raising the temperature is a method for evaluating the spontaneous heat generation of coal, which is a step of raising the temperature of the coal to 80°C. The method for evaluating spontaneous combustion of coal according to any one of claims 1 to 6,
The step of determining the spontaneous exothermicity is the maximum value of the production rate of carbon dioxide generated from the coal, the equilibrium value of the production rate of the carbon dioxide, and the wet oxidation time multiplied by the production rate of the carbon dioxide. A method for evaluating the spontaneous heat generation of coal, which is a step of determining the spontaneous heat generation of the coal based on any one or more of the integrated values. In the self-heating evaluation method of coal according to claim 7,
When the maximum value of the generation rate of the carbon dioxide measured when the coal is at 80° C. is 2.04×10 ⁻⁴ mol/sec or more per mol of carbon in the coal, the natural nature of the coal. A method for evaluating the spontaneous heat generation of coal, which determines that the heat generation is high. In the method for evaluating the spontaneous heat generation of coal according to claim 7 or 8,
When the equilibrium value of the carbon dioxide production rate measured when the coal is at 80° C. is 1.61×10 ⁻⁴ mol/sec or more per 1 mol of carbon in the coal, the natural nature of the coal A method for evaluating the spontaneous heat generation of coal, which determines that the heat generation is high. The spontaneous heat generation evaluation method for coal according to any one of claims 7 to 9,
An integral value obtained by multiplying the time of the wet oxidation by the generation rate of the carbon dioxide, measured when the coal is at 80° C., is 4.13×10 ⁻² mol/sec or more per mol of carbon in the coal. When it is, it is judged that the spontaneous heat generation property of the coal is high, and the spontaneous heat generation evaluation method of the coal. In the self-heating evaluation method of coal according to claim 7,
The step of determining the spontaneous exothermicity is performed by changing the temperature of the coal in the step of performing wet oxidation, calculating an equilibrium value of the production rate of the carbon dioxide at each temperature, and deriving from the calculated equilibrium value. A method for evaluating the spontaneous heat generation of coal, which is a step of determining the spontaneous heat generation of the coal at an arbitrary temperature based on the prediction formula. The spontaneous heat generation evaluation method for coal according to any one of claims 1 to 11,
The carbon dioxide production rate is the carbon dioxide production rate when the coal is wet-oxidized under the wet air stream and the carbon dioxide production rate when the coal is wet-oxidized under the wet inert gas stream. A method for evaluating the spontaneous heat generation of coal, which is the difference from the rate of carbon production. The spontaneous heat generation evaluation method for coal according to any one of claims 1 to 11,
The above-mentioned coal is a bituminous coal, a sub-bituminous coal, or a lignite coal, The natural exothermic property evaluation method of coal. Wet air stream obtained from mixed gas obtained by mixing oxygen gas and nitrogen gas, wet air stream obtained from air, and at least one selected from the group consisting of nitrogen gas, argon gas, and helium gas A wet airflow gas generation device for generating a wet inert gas airflow obtained from an inert gas,
A reactor having a first opening, a second opening, a coal filling section that is provided between the first opening and the second opening, and that fills coal with the first opening;
A measuring device for measuring the amount of carbon dioxide generated from the coal,
The wet air stream or the wet inert gas stream is circulated from the first opening of the reactor through the coal filling section to the second opening,
The said reactor is a spontaneous exothermic evaluation apparatus of the coal which wet-oxidizes the said coal, when the said humid air flow flows through the said inside of the said coal filling part.