Coal low-temperature oxidation trace heat accurate determination method based on phase change reference

Abstract

The invention discloses a phase change reference-based coal low-temperature oxidation trace heat accurate determination method, which comprises the following steps: S1, selecting a raw coal sample, setting a temperature change interval of the raw coal sample, subsequently measuring the low-temperature oxidation heat yield of the raw coal sample in the temperature change interval, and selecting an organic phase change material according to the temperature change interval; s2, acquiring a heat flow curve of the organic phase-change material measured by a set heating program by using a micro-thermal analyzer; s3, collecting a heat flow curve of the raw coal sample with the organic phase-change material as a reference, which is measured by a set heating program, by using a micro-thermal analyzer; s4, acquiring a heat flow curve of the raw coal sample measured by a set heating program by using a micro-thermal analyzer; and S5, respectively calculating according to the temperature change interval to obtain specific heat change values Q1, Q2 and Q3, and subtracting the Q2 value from the Q1 value to obtain the actual oxidation heat release of the raw coal in the selected temperature change interval. According to the invention, the measurement precision of the heat release of low-temperature oxidation of the coal sample can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal low-temperature oxidation heat generation detection, and in particular to a method for accurately measuring coal low-temperature oxidation microcalorimetry based on phase change reference. Background Art

[0002] Coal exposed to air gradually increases in temperature due to oxidation heat release. After reaching 70-80°C, the temperature rise rate suddenly accelerates. When the ignition point of coal (300-350°C) is reached, combustion occurs. This phenomenon is called spontaneous combustion of coal seams. Low-temperature oxidation of coal is an important issue for coal mine safety, and traditional measurement methods have limitations. The measurement method based on phase change reference can effectively avoid baseline errors, provide more accurate measurement results, help to better understand the low-temperature oxidation process of coal, and provide a scientific basis for coal mine safety.

[0003] The accurate determination method of low-temperature oxidation microcalorimetry of coal based on phase change reference is a method that measures the heat flow change of organic phase change materials with specific phase change temperature during the heating process, and uses this material as a reference to test coal samples, thereby accurately measuring the heat release of low-temperature oxidation of coal. This method breaks through the limitation that the complete heat release peak cannot be obtained when directly measuring the heat release of low-temperature oxidation of coal using a microcalorimeter, effectively avoids the influence of baseline error, and realizes the accurate measurement of the heat release of low-temperature oxidation of coal samples in the whole process and in stages.

[0004] At present, there are also studies that place coal samples in the sample pool and introduce oxygen, and use the same mass of coal samples introduced with nitrogen as a reference. However, since the coal sample used as a reference will still produce thermal effects when it is heated up and undergoes chemical changes in an inert gas atmosphere, this part of the thermal effect will also affect the test results. Therefore, it is necessary to improve the research technology of the reference oxidation method for determining the low-temperature oxidation characteristics of coal. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for accurately measuring the microcalorimetry of low-temperature oxidation of coal based on phase change reference.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions: A method for accurately measuring the microcalorimetry of low-temperature oxidation of coal based on phase change reference, comprising the following steps:

[0007] S1. Select a raw coal sample and set a temperature change interval for the raw coal sample. Then measure the heat generated by low-temperature oxidation within the temperature change interval. Select an organic phase change material with a phase change temperature that is compatible with the temperature change interval according to the set temperature change interval. Then determine the heating conditions for the subsequent coal sample measurement test. The heating conditions are a constant temperature thermal effect or a rising temperature thermal effect. Select a corresponding heating program in the microcalorimeter according to the heating conditions.

[0008] S2. Take two coal sample tanks, connect the gas path and temperature sensor, do not add any substance to one of the coal sample tanks and continuously introduce nitrogen, and add organic phase change material to the other coal sample tank as a reference tank and continuously introduce nitrogen. Keep the temperature of each tank constant at 100°C, then dry for 4-5 hours, and then keep the temperature constant at the starting temperature of the experiment. Immediately switch the nitrogen in the reference tank to oxygen, and change the temperature control system to a programmed temperature control mode. Use a microcalorimeter to collect the set temperature program to measure the heat flow curve of the organic phase change material.

[0009] S3. Take two coal sample tanks, connect the gas path and temperature sensor, add the raw coal sample into one of the coal sample tanks and continuously introduce nitrogen, add the organic phase change material into the other coal sample tank as a reference tank and continuously introduce nitrogen, keep the temperature constant at 100°C, then dry for 4h-5h, and then keep the temperature constant at the starting temperature of the experiment, immediately switch the nitrogen in the coal sample tank where the raw coal sample is located to oxygen, and change the temperature control system to the programmed temperature control mode, use the microcalorimeter to collect the set temperature program to measure the heat flow curve of the raw coal sample with the organic phase change material as a reference;

[0010] S4. Take two coal sample tanks, connect the gas path and temperature sensor, add raw coal sample into one of the coal sample tanks and continuously introduce nitrogen, and do not add any substance into the other coal sample tank as a reference tank and continuously introduce nitrogen. Keep the temperature of each tank constant at 100°C, then dry for 4-5 hours, and then keep the temperature constant at the starting temperature of the experiment. Immediately switch the nitrogen in the reference tank to oxygen, and change the temperature control system to a programmed temperature control mode. Use a microcalorimeter to collect the set temperature program to measure the heat flow curve of the raw coal sample.

[0011] S5. Calculate the heat flow curve of the organic phase change material obtained in steps S2, S3, and S4, the heat flow curve of the raw coal sample using the organic phase change material as a reference, and the heat flow curve of the raw coal sample according to the temperature change range selected in step S1, and obtain the specific values ​​of heat changes of the three within the temperature change range as Q1, Q2, and Q3, respectively, where Q3 is the oxidation heat release of the raw coal within the selected temperature range obtained by the traditional measurement method; subtract the Q2 value from the Q1 value to accurately determine the actual oxidation heat release of the raw coal within the selected temperature change range.

[0012] By adopting the above technical scheme, in step S2, both the coal sample tanks with no substance added and the coal sample tanks with organic phase change materials added are initially introduced with inert gas nitrogen, and neither of them is oxidized. Subsequently, the reference tank where the organic phase change material is located is changed to introduce oxygen, and oxidation occurs rapidly, so as to better study the low-temperature oxidation characteristics of the organic phase change material. In step S3, both the coal sample tanks with raw coal added and the coal sample tanks with organic phase change materials added are initially introduced with inert gas nitrogen, and neither of them is oxidized. Subsequently, the coal sample tanks where the raw coal sample is located are changed to introduce oxygen, and oxidation occurs rapidly. In step S4, no oxidation occurs in the coal sample tanks. Step S4 is combined with S3 to better study the low-temperature oxidation characteristics of the raw coal sample with the organic phase change material as a reference. The heat production of low-temperature oxidation of coal measured by this method uses a single phase change material as a reference baseline, breaking through the limitation that a complete exothermic peak cannot be obtained when directly measuring the heat release of low-temperature oxidation of coal using a microcalorimeter. It can display the complete exothermic peak of coal sample oxidation and effectively avoid the influence of the baseline error of the heat flow curve of the incomplete exothermic peak when using a microcalorimeter for actual measurement.

[0013] Furthermore, the raw coal sample is one or more of long flame coal, lignite, gas coal, gas fat coal and anthracite.

[0014] By adopting the above technical scheme, long flame coal, lignite, gas coal, gas-fat coal and anthracite were used as coal samples with different metamorphic degrees. The low-temperature oxidation characteristics of coal samples with different metamorphic degrees were studied, and it was found that the low-temperature oxidation process of coal has obvious stages. In the practice of coal spontaneous combustion prevention and control, coal spontaneous combustion basically proceeds according to these stages.

[0015] Furthermore, the raw coal samples are selected from freshly cut coal blocks at the working face and stored in a sealed manner. Before making the coal samples, the coal particles of 3mm-5mm are crushed and sieved and stored at a low temperature of 0℃-4℃ for experiments.

[0016] By adopting the above technical solution, the fresh-cut coal is stored at low temperature and sealed, which is beneficial to prevent the coal sample from low-temperature oxidation before the experiment and improve the accuracy of the experiment.

[0017] Furthermore, the introduction rates of nitrogen and oxygen in steps S2, S3 and S4 are all 100 mL / min.

[0018] Furthermore, in the programmed temperature control method, the heating rate is one of 0.2°C / min, 0.4°C / min, 0.6°C / min, 0.8°C / min, 1.0°C / min, 1.5°C / min or 2.0°C / min.

[0019] By adopting the above technical scheme, multiple heating rate experiments were carried out under pure oxygen conditions, and the coal sample mass and heat release rate curve in the multiple heating rate experiment and constant temperature experiment were measured. The reaction heat release Q was obtained through the heat release rate curve, which can fully determine the oxidation heat release of the coal sample under low temperature conditions.

[0020] Furthermore, the organic phase change material is selected from one or more of capric acid with a phase change temperature of 30°C, lauric acid with a phase change temperature of 42.6°C-42.7°C, neopentyl glycol with a phase change temperature of 47.3°C, or trimethylolpropane with a phase change temperature of 62.3°C.

[0021] By adopting the above technical scheme, the heat flow change of an organic phase change material or a composite organic phase change material at a certain phase change temperature during the heating process is determined, and then a heating program is set for a constant temperature thermal effect or a heating thermal effect according to the measurement method. The organic phase change material is used as a reference and a coal sample is used as a sample for testing. The two curves are calculated and subtracted to accurately obtain the total heat generation within a certain temperature range during the low-temperature oxidation process of the coal sample.

[0022] Furthermore, the organic phase change material is a mixed system composed of capric acid with a phase change temperature of 30°C and lauric acid with a phase change temperature of 42.6°C-42.7°C in a mass ratio of 2:3, forming a phase change temperature of 20°C-23°C.

[0023] In summary, the present invention has the following beneficial effects:

[0024] 1. In the present application, in step S3, the inert gas nitrogen is introduced into the coal sample tank where the raw coal sample and the coal sample tank where the organic phase change material are added are introduced at the beginning, and neither of them is oxidized. Subsequently, the coal sample tank where the raw coal sample is located is changed to introduce oxygen, and oxidation occurs rapidly. In step S4, no oxidation occurs in the coal sample tank. The combination of step S4 and S3 can better study the low-temperature oxidation characteristics of the raw coal sample with the organic phase change material as a reference;

[0025] 2. In this application, long flame coal, lignite, gas coal, gas fat coal and anthracite are coal samples with different degrees of metamorphism. The low-temperature oxidation characteristics of coal samples with different degrees of metamorphism are studied, and it is found that the low-temperature oxidation process of coal has obvious stages. In the practice of coal spontaneous combustion prevention and control, coal spontaneous combustion basically proceeds according to such stages;

[0026] 3. In this application, multiple heating rate experiments were carried out under pure oxygen conditions, and the coal sample mass and heat release rate curves in the multiple heating rate experiments and constant temperature experiments were measured. The reaction heat release Q was obtained through the heat release rate curve, which can fully determine the oxidation heat release of the coal sample under low temperature conditions. DETAILED DESCRIPTION

[0028] Example 1

[0029] The present application discloses a method for accurately measuring the microcalorimetry of low-temperature oxidation of coal based on phase change reference, comprising the following steps:

[0030] S1. Select a raw coal sample (in this embodiment, the raw coal sample is selected as long flame coal) and set a temperature change interval of the raw coal sample. Subsequently, measure the heat generated by low-temperature oxidation in the temperature change interval. Select an organic phase change material with a phase change temperature that is compatible with the temperature interval according to the set temperature change interval (in this embodiment, the organic phase change material is selected as decanoic acid with a phase change temperature of 30°C). Then determine the heating conditions for the subsequent coal sample measurement test. The heating conditions are a constant temperature thermal effect or a temperature increase thermal effect. Select a corresponding temperature increase program in the microcalorimeter according to the heating conditions.

[0031] The raw coal samples were selected from freshly cut coal blocks at the working face and stored in a sealed container. Before making the coal samples, the coal particles of 3 mm were crushed and sieved and stored at 0°C for the experiment.

[0032] In the programmed temperature control mode, the heating rate is 0.2°C / min;

[0033] S2. Take two coal sample tanks, connect the gas path and temperature sensor, do not add any substance to one of the coal sample tanks and continuously pass 100mL / min of nitrogen, and add organic phase change material to the other coal sample tank as a reference tank and continuously pass 100mL / min of nitrogen. Keep the temperature of each tank constant at 100°C, then dry for 4h, and then keep the temperature constant at the starting temperature of the experiment. Immediately switch the nitrogen in the reference tank to oxygen with a flow rate of 100mL / min, and change the temperature control system to a programmed temperature control mode. Use a microcalorimeter to collect the set temperature program to measure the heat flow curve of the organic phase change material.

[0034] S3. Take two coal sample tanks, connect the gas path and temperature sensor, add the raw coal sample into one of the coal sample tanks and continuously pass 100mL / min of nitrogen, add the organic phase change material into the other coal sample tank as a reference tank and continuously pass 100mL / min of nitrogen, keep the temperature constant at 100°C, then dry for 4h, and then keep the temperature constant at the starting temperature of the experiment, immediately switch the nitrogen in the coal sample tank where the raw coal sample is located to oxygen with a flow rate of 100mL / min, and change the temperature control system to a programmed temperature control mode, use a microcalorimeter to collect and set the temperature program to measure the heat flow curve of the raw coal sample with the organic phase change material as a reference;

[0035] S4. Take two coal sample tanks, connect the gas path and temperature sensor, add the raw coal sample into one of the coal sample tanks and continuously pass 100mL / min of nitrogen, and use the other coal sample tank as a reference tank without adding any substance and continuously pass 100mL / min of nitrogen. Keep the temperature of each tank constant at 100°C, then dry for 4h, and then keep the temperature constant at the starting temperature of the experiment. Immediately switch the nitrogen in the reference tank to pass 100mL / min of oxygen, and change the temperature control system to a programmed temperature control mode. Use a microcalorimeter to collect the heat flow curve of the raw coal sample by setting the temperature rise program.

[0036] S5. Calculate the heat flow curve of the organic phase change material obtained in steps S2, S3, and S4, the heat flow curve of the raw coal sample using the organic phase change material as a reference, and the heat flow curve of the raw coal sample according to the temperature change range selected in step S1, and obtain the specific values ​​of heat changes of the three within the temperature change range as Q1, Q2, and Q3, respectively, where Q3 is the oxidation heat release of the raw coal within the selected temperature range obtained by the traditional measurement method; subtract the Q2 value from the Q1 value to accurately determine the actual oxidation heat release of the raw coal within the selected temperature change range.

[0037] Example 2

[0038] The present application discloses a method for accurately measuring the microcalorimetry of low-temperature oxidation of coal based on phase change reference, comprising the following steps:

[0039] S1. Select a raw coal sample (in this embodiment, the raw coal sample is selected as lignite) and set a temperature change range of the raw coal sample. Subsequently, measure the heat generated by low-temperature oxidation within the temperature change range. Select an organic phase change material with a phase change temperature that is compatible with the temperature range according to the set temperature change range (in this embodiment, the organic phase change material is lauric acid with a phase change temperature of 42.6°C-42.7°C). Then determine the heating conditions for the subsequent coal sample measurement test. The heating conditions are a constant temperature thermal effect or a temperature increase thermal effect. Select a corresponding temperature increase program in the microcalorimeter according to the heating conditions.

[0040] The raw coal samples were selected from freshly cut coal blocks at the working face and stored in a sealed container. Before preparing the coal samples, the coal particles of 5 mm were crushed and sieved and stored at 4°C for the experiment.

[0041] In the programmed temperature control mode, the heating rate is 0.4°C / min;

[0042] S2. Take two coal sample tanks, connect the gas path and temperature sensor, do not add any substance to one of the coal sample tanks and continuously pass 100mL / min of nitrogen, and add organic phase change material to the other coal sample tank as a reference tank and continuously pass 100mL / min of nitrogen. Keep the temperature of each tank constant at 100°C, then dry for 5h, and then keep the temperature constant at the starting temperature of the experiment. Immediately switch the nitrogen in the reference tank to oxygen with a flow rate of 100mL / min, and change the temperature control system to a programmed temperature control mode. Use a microcalorimeter to collect the set temperature program to measure the heat flow curve of the organic phase change material.

[0043] S3. Take two coal sample tanks, connect the gas path and temperature sensor, add the raw coal sample into one of the coal sample tanks and continuously pass 100mL / min of nitrogen, add the organic phase change material into the other coal sample tank as a reference tank and continuously pass 100mL / min of nitrogen, keep the temperature constant at 100°C, then dry for 5h, and then keep the temperature constant at the starting temperature of the experiment, immediately switch the nitrogen in the coal sample tank where the raw coal sample is located to oxygen with a flow rate of 100mL / min, and change the temperature control system to a programmed temperature control mode, use a microcalorimeter to collect and set the temperature program to measure the heat flow curve of the raw coal sample with the organic phase change material as a reference;

[0044] S4. Take two coal sample tanks, connect the gas path and temperature sensor, add raw coal sample to one of the coal sample tanks and continuously pass 100mL / min of nitrogen, and use the other coal sample tank as a reference tank without adding any substance and continuously pass 100mL / min of nitrogen. Keep the temperature of each tank constant at 100°C, then dry for 5h, and then keep the temperature constant at the starting temperature of the experiment. Immediately switch the nitrogen in the reference tank to pass 100mL / min of oxygen, and change the temperature control system to a programmed temperature control mode. Use a microcalorimeter to collect the heat flow curve of the raw coal sample by setting the temperature rise program;

[0045] S5. Calculate the heat flow curve of the organic phase change material obtained in steps S2, S3, and S4, the heat flow curve of the raw coal sample using the organic phase change material as a reference, and the heat flow curve of the raw coal sample according to the temperature change range selected in step S1, and obtain the specific values ​​of heat changes of the three within the temperature change range as Q1, Q2, and Q3, respectively, where Q3 is the oxidation heat release of the raw coal within the selected temperature range obtained by the traditional measurement method; subtract the Q2 value from the Q1 value to accurately determine the actual oxidation heat release of the raw coal within the selected temperature change range.

[0046] Example 3

[0047] The present application discloses a method for accurately measuring the microcalorimetry of low-temperature oxidation of coal based on phase change reference, comprising the following steps:

[0048] S1. Select a raw coal sample (in this embodiment, the raw coal sample is selected as gas fertilizer coal) and set a temperature change interval of the raw coal sample, and then measure the heat generated by low-temperature oxidation in the temperature change interval. According to the set temperature change interval, select an organic phase change material with a phase change temperature that is compatible with the temperature interval (in this embodiment, the organic phase change material is a mixed system of capric acid with a phase change temperature of 30°C and lauric acid with a phase change temperature of 42.6°C-42.7°C in a mass ratio of 2:3, and a phase change temperature of 20°C-23°C), and then determine the heating conditions for the subsequent coal sample measurement test. The heating conditions are constant temperature thermal effect or temperature increase thermal effect. According to the heating conditions, select the corresponding temperature increase program in the microcalorimeter;

[0049] Among them, the raw coal samples were selected from freshly cut coal blocks at the working face and stored in a sealed manner. Before making the coal samples, the coal particles of 4 mm were crushed and sieved and stored at 2°C for the experiment;

[0050] In the programmed temperature control mode, the heating rate is 0.6°C / min;

[0051] S2. Take two coal sample tanks, connect the gas path and temperature sensor, do not add any substance to one of the coal sample tanks and continuously pass 100mL / min of nitrogen, and add organic phase change material to the other coal sample tank as a reference tank and continuously pass 100mL / min of nitrogen. Keep the temperature of each tank constant at 100°C, then dry for 4.5h, and then keep the temperature constant at the starting temperature of the experiment. Immediately switch the nitrogen in the reference tank to oxygen with a flow rate of 100mL / min, and change the temperature control system to a programmed temperature control mode. Use a microcalorimeter to collect the set temperature program to measure the heat flow curve of the organic phase change material.

[0052] S3. Take two coal sample tanks, connect the gas path and temperature sensor, add the raw coal sample into one of the coal sample tanks and continuously pass 100mL / min of nitrogen, add the organic phase change material into the other coal sample tank as a reference tank and continuously pass 100mL / min of nitrogen, keep the temperature constant at 100°C, then dry for 4.5h, and then keep the temperature constant at the starting temperature of the experiment, immediately switch the nitrogen in the coal sample tank where the raw coal sample is located to oxygen with a flow rate of 100mL / min, and change the temperature control system to a programmed temperature control mode, use a microcalorimeter to collect and set the temperature program to measure the heat flow curve of the raw coal sample with the organic phase change material as a reference;

[0053] S4. Take two coal sample tanks, connect the gas path and temperature sensor, add the raw coal sample into one of the coal sample tanks and continuously pass 100mL / min of nitrogen, and use the other coal sample tank as a reference tank without adding any substance and continuously pass 100mL / min of nitrogen. Keep the temperature of each tank constant at 100°C, then dry for 4.5h, and then keep the temperature constant at the starting temperature of the experiment. Immediately switch the nitrogen in the reference tank to pass 100mL / min of oxygen, and change the temperature control system to a programmed temperature control mode. Use a microcalorimeter to collect the heat flow curve of the raw coal sample by setting the temperature rise program.

[0054] S5. Calculate the heat flow curve of the organic phase change material obtained in steps S2, S3, and S4, the heat flow curve of the raw coal sample using the organic phase change material as a reference, and the heat flow curve of the raw coal sample according to the temperature change range selected in step S1, and obtain the specific values ​​of heat changes of the three within the temperature change range as Q1, Q2, and Q3, respectively, where Q3 is the oxidation heat release of the raw coal within the selected temperature range obtained by the traditional measurement method; subtract the Q2 value from the Q1 value to accurately determine the actual oxidation heat release of the raw coal within the selected temperature change range.

[0055] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for accurately measuring the microcalorimetry of low-temperature oxidation of coal based on phase change reference, characterized in that: The steps include: S1. Select a raw coal sample and set a temperature change interval for the raw coal sample. Then measure the heat generated by low-temperature oxidation within the temperature change interval. Select an organic phase change material with a phase change temperature that is compatible with the temperature change interval according to the set temperature change interval. Then determine the heating conditions for the subsequent coal sample measurement test. The heating conditions are a constant temperature thermal effect or a rising temperature thermal effect. Select a corresponding heating program in the microcalorimeter according to the heating conditions. S2. Take two coal sample tanks, connect the gas path and temperature sensor, do not add any substance to one of the coal sample tanks and continuously introduce nitrogen, and add organic phase change material to the other coal sample tank as a reference tank and continuously introduce nitrogen. Keep the temperature of each tank constant at 100°C, then dry for 4-5 hours, and then keep the temperature constant at the starting temperature of the experiment. Immediately switch the nitrogen in the reference tank to oxygen, and change the temperature control system to a programmed temperature control mode. Use a microcalorimeter to collect the set temperature program to measure the heat flow curve of the organic phase change material. S3. Take two coal sample tanks, connect the gas path and temperature sensor, add the raw coal sample into one of the coal sample tanks and continuously introduce nitrogen, add the organic phase change material into the other coal sample tank as a reference tank and continuously introduce nitrogen, keep the temperature constant at 100°C, then dry for 4h-5h, and then keep the temperature constant at the starting temperature of the experiment, immediately switch the nitrogen in the coal sample tank where the raw coal sample is located to oxygen, and change the temperature control system to the programmed temperature control mode, use the microcalorimeter to collect the set temperature program to measure the heat flow curve of the raw coal sample with the organic phase change material as a reference; S4. Take two coal sample tanks, connect the gas path and temperature sensor, add raw coal sample into one of the coal sample tanks and continuously introduce nitrogen, and do not add any substance into the other coal sample tank as a reference tank and continuously introduce nitrogen. Keep the temperature of each tank constant at 100°C, then dry for 4-5 hours, and then keep the temperature constant at the starting temperature of the experiment. Immediately switch the nitrogen in the reference tank to oxygen, and change the temperature control system to a programmed temperature control mode. Use a microcalorimeter to collect the set temperature program to measure the heat flow curve of the raw coal sample. S5. Calculate the heat flow curve of the organic phase change material obtained in steps S2, S3, and S4, the heat flow curve of the raw coal sample using the organic phase change material as a reference, and the heat flow curve of the raw coal sample according to the temperature change range selected in step S1, and obtain the specific values ​​of heat changes of the three within the temperature change range as Q1, Q2, and Q3, respectively, where Q3 is the oxidation heat release of the raw coal within the selected temperature range obtained by the traditional measurement method; subtract the Q2 value from the Q1 value to accurately determine the actual oxidation heat release of the raw coal within the selected temperature change range.

2. According to claim 1, a method for accurately measuring the microcalorimetry of low-temperature oxidation of coal based on phase change reference, characterized in that: The raw coal sample is one or more of long flame coal, lignite, gas coal, gas fat coal and anthracite.

3. The method for accurate determination of low-temperature oxidation microcalorimetry of coal based on phase change reference according to claim 2 is characterized by: The raw coal samples were selected from freshly cut coal blocks at the working face and stored in a sealed container. Before making the coal samples, the coal particles of 3mm-5mm were crushed and sieved and stored at a low temperature of 0℃-4℃ for the experiment.

4. The method for accurately measuring the low-temperature oxidation microcalorimetry of coal based on phase change reference according to claim 3 is characterized by: In steps S2, S3 and S4, the introduction rates of nitrogen and oxygen are all 100 mL / min.

5. The method for accurate determination of low-temperature oxidation microcalorimetry of coal based on phase change reference according to claim 3 is characterized by: In the programmed temperature control mode, the heating rate is one of 0.2°C / min, 0.4°C / min, 0.6°C / min, 0.8°C / min, 1.0°C / min, 1.5°C / min or 2.0°C / min.

6. The method for accurate determination of low-temperature oxidation microcalorimetry of coal based on phase change reference according to claim 1 is characterized by: The organic phase change material is selected from one or more of capric acid with a phase change temperature of 30°C, lauric acid with a phase change temperature of 42.6°C-42.7°C, neopentyl glycol with a phase change temperature of 47.3°C, or trimethylolpropane with a phase change temperature of 62.3°C.

7. The method for accurate determination of low-temperature oxidation microcalorimetry of coal based on phase change reference according to claim 6 is characterized by: The organic phase change material is a mixed system composed of capric acid with a phase change temperature of 30°C and lauric acid with a phase change temperature of 42.6°C-42.7°C in a mass ratio of 2:3, forming a phase change temperature of 20°C-23°C.