CN115078458A - A method for precise determination of coal low temperature oxidation microcalorimetry based on phase transition reference - Google Patents

Abstract

The invention discloses an accurate measurement method of low temperature oxidation microcalorimetry of coal based on phase change reference. First, the heat flow change of an organic phase change material with a specific phase change temperature during the heating process is measured, and then according to the measurement method, constant temperature thermal effect or The heating program is set for the heating effect, and the organic phase change material is used as a reference and the coal sample is used as the sample for testing. By subtracting the value of the complete calorimetric peak of the phase change material, the heat release of the coal low temperature oxidation during the set constant temperature or heating process can be accurately obtained; the heat production of the low temperature oxidation of coal measured by this method is taken as the phase change material alone. The reference baseline breaks through the limitation that a complete exothermic peak cannot be obtained when using a microcalorimeter to directly measure the exothermic heat of coal low-temperature oxidation, effectively avoids the influence of the baseline error, and realizes the whole process of low-temperature oxidation exothermic of coal samples. Accurate measurement in stages.

Description

A method for precise determination of coal low temperature oxidation microcalorimetry based on phase transition reference

technical field

The invention relates to a method for measuring the heat production by low temperature oxidation of coal, in particular to a method for accurate measurement of the microcalorimetry of coal low temperature oxidation based on phase transition reference, and belongs to the technical field of low temperature oxidation heat production measurement of coal.

Background technique

Coal spontaneous combustion is one of the main disasters in the process of mine mining. It not only burns a large amount of coal resources and causes huge economic losses, but also produces a large amount of toxic and harmful gases, posing a great threat to the safety of miners. The mined-out area is the most prone to coal spontaneous combustion dangerous area. There are a lot of cracks and air leakage channels. Under certain conditions, the coal gradually undergoes low-temperature oxidation to generate heat, while the spontaneous combustion zone in the three-zone of the mined-out area cannot be heated due to oxidation. If it is lost in time, the possibility of spontaneous combustion of coal is greatly increased.

Many scientists have done research on the low temperature oxidation of coal, but most of the research stays in the aspects of coal gas production characteristics, functional group changes, kinetic parameter determination, pyrolysis product analysis, etc. The known determination method is mainly TG-DSC method, that is, thermogravimetric-differential thermal method, but this method has insufficient scanning accuracy, fast heating rate, and uses a small amount of coal sample (generally about 10 mg), which is difficult to reflect the coal sample. Oxidative heat production characteristics in the state of broken accumulation and large occurrences in wells. In addition, the existing microcalorimeter also uses the principle of differential thermal compensation, which can accurately measure the heat production characteristics of coal during low temperature oxidation. It has high sensitivity, the heating rate can reach 0.001 °C/min, the signal stability is good, and the sample cell volume is large. , which can accommodate more coal samples, which is more in line with the low-temperature oxidation process of underground coal. However, in the absence of a reference, the existing baseline of the coal low temperature oxidation heat flow change curve measured by this instrument is not accurate, and there is a certain deviation when using this baseline to calculate and solve the heat change of the coal sample, especially when the coal sample is at a lower temperature When oxidizing and exothermic at high temperature, the complete calorimetric peak of the coal sample cannot be displayed, and it is more difficult to measure in the case of continuous exothermicity. At present, there are also studies in which coal samples are placed in the sample pool and oxygen is introduced, and coal samples of the same quality are used. Nitrogen gas is used as a reference, but because the coal sample used as a reference is heated up in an inert gas atmosphere and chemical changes will still produce thermal effects, this part of the thermal effect will also have an impact on the test results; moreover, the current thermal measurement methods are not effective. Measure the heat production of low-temperature oxidation of coal samples within a certain temperature range, which makes it impossible to carry out subsequent analysis on the low-temperature oxidation heat production of coal samples in a specific temperature range. Therefore, how to provide a method based on When the microcalorimeter is used for measurement, it can not only accurately measure the low-temperature oxidation heat production characteristics of coal samples, but also measure the complete exothermic peaks within the set temperature variation range of the measured coal samples. The analysis of coal samples to provide accurate data is one of the research directions of the industry.

SUMMARY OF THE INVENTION

In view of the problems existing in the above-mentioned prior art, the present invention provides a method for accurate determination of low temperature oxidation microcalorimetry of coal based on phase transition reference, which can not only accurately measure the low temperature oxidation heat production characteristics of coal samples, but also set the The complete exothermic peak is measured within a certain temperature range for low temperature oxidation heat production, thereby providing accurate data for subsequent analysis of coal samples.

In order to achieve the above purpose, the technical solution adopted in the present invention is: a method for accurate determination of low temperature oxidation microcalorimetry of coal based on phase transition reference, the specific steps are:

Step 1: First select the raw coal sample, then set the temperature change interval of the raw coal sample, then measure its low-temperature oxidation heat production within the temperature change interval, and select the phase transition temperature corresponding to the temperature interval according to the set temperature change interval. The adapted organic phase change material, and then determine the heating conditions during the subsequent coal sample measurement test, the heating conditions are constant temperature thermal effect or heating thermal effect, and a corresponding heating program is selected in the microcalorimeter according to the heating conditions;

Step 2: No substance is added to the sample cell and pure oxygen is continuously fed. The organic phase change material selected in Step 1 is added to the reference cell and pure nitrogen is fed into the reference cell. The change curve of the heat flow of the organic phase change material with the temperature is obtained by the determined heating program;

Step 3: Add the raw coal sample selected in step 1 to the sample pool and continuously feed pure oxygen, add organic phase change material to the reference pool and feed pure nitrogen gas, select the same heating conditions as step 2, and use a microcalorimeter analyzer. The change curve of raw coal heat flow with temperature with organic phase change material as a reference is obtained by using the set heating program;

Step 4. Add the raw coal sample to be measured into the sample pool and continuously feed pure oxygen. The reference pool does not add substances and feeds pure nitrogen. Select the same heating conditions as step 2, and use the microcalorimeter to set the The curve of the heat flow of the raw coal with the temperature was obtained by measuring the heating program;

Step 5. Use the organic phase change material heat flow change curve obtained in step 2, the organic phase change material obtained in step 3 as a reference heat flow change curve of raw coal, and the heat flow change curve of raw coal obtained in step 4, according to the temperature change selected in step 1. The specific values of the three heat changes in the temperature change range are respectively Q ₁ , Q ₂ and Q ₃ J/g; among them Q ₃ is the raw coal obtained by the traditional measurement method within the selected temperature range. The difference between the Q ₂ value and the Q ₁ value is to accurately measure the actual oxidation heat release of the raw coal in the selected temperature change interval.

Further, the phase transition temperature of the organic phase change material is between 30°C and 200°C, and the organic phase change material includes mannitol with a phase transition temperature of 165°C, erythritol with a phase transition temperature of 116°C, and a phase transition temperature of 116°C. A variety of phase change paraffin waxes from 30°C to 200°C; organic phase change materials are selected according to the temperature change interval and are formed from the above single substance or a variety of substances with different phase change temperatures, wherein a single phase change material can realize the low temperature oxidation of coal. The measurement of stage heat and the combination of various organic phase change materials can realize the measurement of heat in the whole process of low temperature oxidation of coal.

Further, the heating procedure of the constant temperature thermal effect is as follows: firstly, the temperature is kept constant at 30 °C for 1 h, and then the temperature is increased from 30 °C to the phase change temperature of the selected organic phase change material, and the heating rate is 0.1 °C/min, 0.2 °C/min, One of 0.5°C/min and 1°C/min, and then kept at this temperature for 2h at a constant temperature. Adopting this parameter can ensure the stable heating effect of constant temperature, and further ensure the data accuracy of subsequent test measurements.

Further, the heating program of the heating effect is as follows: for the phase change reference compounded by n kinds of organic phase change materials, firstly, the temperature is rapidly raised from room temperature to (T ₁ -x ₁ )° C. at a heating rate of 5° C./min, and then From (T ₁ -x ₁ )°C to (T _n +x _n )°C, the temperature rise rate is one of 0.1°C/min, 0.2°C/min, 0.5°C/min, ₁ °C/min, the T1 is the phase transition temperature value corresponding to the organic phase change material with the smallest phase transition temperature among the n organic phase change materials, T _n is the phase transition temperature value corresponding to the organic phase change material with the largest phase transition temperature among the n organic phase change materials, x ₁ and x _n are the temperature change values of the half-peak widths of the respective phase transition peaks of the organic phase change material with the smallest phase transition temperature and the organic phase change material with the largest phase transition temperature, respectively. The use of this parameter can ensure that the temperature change interval of the heating effect can cover all the phase change peaks of the composite phase change material, and further ensure the data accuracy of subsequent test measurements.

Further, the dosage of the raw coal sample is 1-2 g, the dosage of the organic phase change material is 1-8 g, and the dosage ratio of the raw coal sample and the organic phase change material is one of 1:1, 1:2, and 1:4. The method for selecting the dosage ratio is: when the maximum temperature interval to be measured is less than 85°C, the dosage ratio of the raw coal sample to the organic phase change material is 1:1; when the maximum temperature interval to be measured is located at ( 85,T _cpt ] ℃, the dosage ratio of raw coal sample and organic phase change material is 1:2; when the maximum temperature interval to be measured is greater than T _cpt ℃, the dosage ratio of raw coal sample and organic phase change material is: 1:4, the T _cpt is the temperature value of the intersection point of the raw coal sample. Using this dosage ratio can ensure that the calorimetric peak of the coal sample can be covered by the calorimetric peak of the phase change material as much as possible, thereby further ensuring the subsequent test measurement data precision.

Further, the gas flow rates of the nitrogen gas and the oxygen gas are kept the same, which is any value between 50 and 100 mL/min, and the gas flow rates are controlled by a mass flow meter.

Compared with the prior art, the present invention is based on the phase-change reference-based method for accurate determination of microcalorimetry of coal low-temperature oxidation, aiming at the inability to accurately measure the heat production of coal samples in a set temperature change range during the low-temperature oxidation process of coal samples in the art and The change of the test baseline of the microcalorimeter analyzer leads to the defect that the complete exothermic peak cannot be displayed, resulting in the deviation of the determination of its heat production. An accurate measurement method of the low temperature oxidation microcalorimetry of coal based on the phase change reference is provided. The heat flow change of the organic phase change material or composite organic phase change material at the phase change temperature during the heating process, and then set the heating program for the constant temperature thermal effect or the heating thermal effect according to the measurement method, and the organic phase change material is used as a reference. The samples are tested, and the two curves are calculated and subtracted to accurately obtain the total heat production in a certain temperature range during the low-temperature oxidation of coal samples. The heat production of coal low-temperature oxidation determined by this method uses a separate phase change material as a reference baseline, which breaks through the limitation that a complete exothermic peak cannot be obtained when using a microcalorimeter to directly measure the heat of coal low-temperature oxidation. The complete exothermic peak of coal sample oxidation can effectively avoid the influence of the baseline error of the heat flow curve of the incomplete exothermic peak measured by the microcalorimeter; and the phase can be selected according to the heat production of coal samples in different temperature ranges. The single organic phase change material or composite organic phase change material in the variable temperature can realize the whole process and stage measurement of the low temperature oxidation heat release of coal samples, and can also accurately evaluate the heat release level of the constant temperature oxidation of coal samples. It has important theoretical value in predicting the oxidative capacity of coal samples and predicting the spontaneous combustion characteristics of coal; this method is easy to operate, accurate in measurement and has minimal deviation. The research provides data support.

Description of drawings

Fig. 1 is the overall implementation flow chart of the present invention;

Fig. 2 is the temperature range selection schematic diagram of the program corresponding to the heating effect of the present invention;

Fig. 3 is the heat flow curve and calculation range of the phase change paraffin wax when the phase transition temperature is 80°C in Example 1;

Fig. 4 is the heat flow curve and the calculation range of the sulfur ditch long-flame coal with the phase change temperature of 80°C as the reference in Example 1;

Fig. 5 is sulfur ditch long flame coal heat flow curve and calculation range in embodiment 1;

Fig. 6 is the heat flow curve and the calculation range of the phase change paraffin wax when the phase transition temperature is 120°C in Example 2;

Fig. 7 is the heat flow curve and calculation range of the open-air coal in Example 2 where the phase transition temperature is 120°C and the phase transition paraffin is used as a reference;

Fig. 8 is the heat flow curve and calculation range of coal in the open air in the middle of Example 2.

Detailed ways

The present invention will be further described below.

Embodiment 1: Concrete steps are:

Step 1. First select Sushuanggou long-flame coal as the raw coal sample, and then select the temperature change range of the raw coal sample to be 48°C to 83°C, and then measure its low-temperature oxidation heat production within this temperature range. In the temperature change interval, 2 g of phase-change paraffin with a phase transition temperature of 80°C was selected for use, and 2 g of sulfuric ditch long-flame coal sample was taken for use. Then, the heating condition in the subsequent coal sample measurement test was determined as the heating effect, and the corresponding heating program It is: firstly from room temperature to 48°C at a heating rate of 5°C/min, and then from 48°C to 115°C at a rate of 0.1°C/min;

Step 2. No substance is added to the sample cell and pure oxygen is continuously fed. In the reference cell, 1 g of phase-change paraffin with a phase transition temperature of 80°C in step 1 is added and pure nitrogen is fed. Both rates are 50 mL/min. The heating conditions determined in step 1 are measured by a microcalorimeter using a corresponding heating program to obtain the heat flow curve of the phase change paraffin as a function of temperature, as shown in Figure 3;

Step 3: Add 1 g of the sulfur ditch long-flame coal sample selected in step 1 to the sample pool and continuously inject pure oxygen. Add 1 g of phase change paraffin with a phase transition temperature of 80°C in the reference pool and inject pure nitrogen into the reference pool. , the rate of both is 50mL/min, select the same heating conditions as step 2, and use the microcalorimeter to measure the temperature change of the long-flame coal with the phase change paraffin as a reference. curve, as shown in Figure 4;

Step 4. Add 1 g of the sulfur ditch long-flame coal sample to be measured into the sample pool and continuously feed pure oxygen. The reference pool does not add substances and feeds pure nitrogen. The rate of both is 50mL/min. 2. Under the same heating conditions, use a microcalorimeter to measure the change curve of the heat flow with temperature of the long-flame coal in the Sushuanggou, as shown in Figure 5;

Step 5, take the phase change paraffin heat flow change curve obtained in step 2, the phase change paraffin obtained in step 3 as the reference heat flow change curve of sulfur ditch long flame coal and the heat flow change curve of sulfur ditch long flame coal obtained in step 4, according to the steps A selected temperature change interval of 48°C to 83°C is calculated separately, and the specific value of the heat change of the three in this temperature change interval is obtained; among them, the heat effect change value calculated in Fig. 5 is the raw coal obtained by the traditional measurement method. Oxidation heat release (i.e. heating effect) within the selected temperature range; subtracting the thermal effect change value calculated in Figure 4 from the thermal effect change value in Figure 3 is the present invention to accurately measure the actual oxidation heat release (i.e. heating effect) of raw coal in the selected temperature change interval Thermal effect).

Embodiment 2: Concrete steps are:

Step 1. First select the Donglu weather coal as the raw coal sample, and then select the temperature range of the raw coal sample to be 90°C to 128°C, and then measure its low-temperature oxidation heat production within the temperature range, according to the set temperature. In the change interval, 4g of phase change paraffin with a phase transition temperature of 120°C was selected for use, and 2g of coal sample from Donglu weather was used for use. Then, the heating condition in the subsequent coal sample measurement test was determined as the heating effect, and the corresponding heating program was: First, the temperature is rapidly heated from room temperature to 90°C at a rate of 5°C/min, and then from 90°C to 150°C at a rate of 0.2°C/min;

Step 2: No substance is added to the sample cell and pure oxygen is continuously fed. The reference cell is added with 2g of phase change paraffin with a phase transition temperature of 120°C in step 1 and pure nitrogen gas is fed into the reference cell. The rate of both is 80mL/min. The heating conditions determined in step 1 are measured by a microcalorimeter using a corresponding heating program to obtain the heat flow curve of the phase change paraffin as a function of temperature, as shown in Figure 6;

Step 3: Add 1g of Donglu weather coal sample selected in step 1 to the sample pool and continuously inject pure oxygen, add 2g of phase change paraffin with a phase transition temperature of 120°C in the reference pool and inject pure nitrogen gas into the reference pool, The rate of both is 80mL/min, and the same heating conditions as in step 2 are selected, and the heat flow curve of Donglu weather coal with the phase change paraffin as a reference is obtained by using a microcalorimeter and a set heating program to measure the change curve of heat flow with temperature. , as shown in Figure 7;

Step 4. Add 1 g of the Donglu weather coal sample to be measured into the sample pool and continuously feed pure oxygen. The reference pool does not add substances and feeds pure nitrogen. The rate of both is 80mL/min. The selection is the same as that of step 2. Under the same heating conditions, the variation curve of heat flow with temperature of coal in the open weather was obtained by using a microcalorimeter and a corresponding heating program, as shown in Figure 8;

Step 5, take the phase change paraffin heat flow change curve obtained in step 2, the phase change paraffin obtained in step 3 as the reference heat flow change curve of Donglu weather coal and the heat flow change curve of Donglu weather coal obtained in step 4, select according to step one Calculate the temperature change interval between 90°C and 128°C, respectively, and obtain the specific value of the heat change of the three in this temperature change interval; among them, the heat effect change value calculated in Figure 8 is the raw coal obtained by the traditional measurement method at the selected temperature. Oxidation heat release within the range (i.e. heating effect); subtracting the thermal effect change value calculated in Figure 7 from the thermal effect change value in Figure 6 is the present invention to accurately measure the actual oxidation heat release (i.e. heating effect) of raw coal in the selected temperature change interval .

Embodiment 3: Concrete steps are:

Step 1. First select Shengli lignite as the raw coal sample, and then select the temperature variation range of the raw coal sample to be 75°C to 85°C, and then measure its low-temperature oxidation heat production within this temperature variation range. According to the set temperature variation range Select 2 g of phase change paraffin with a phase transition temperature of 80 °C for use, and take 2 g of Shengli lignite sample for use. The temperature was kept at a constant temperature for 1 h, then the temperature was increased from 30 °C to 80 °C at a rate of 0.5 °C/min, and then the temperature was maintained at a constant temperature for 2 h;

Step 2. No substance is added to the sample cell and pure oxygen is continuously fed. In the reference cell, 1 g of phase-change paraffin with a phase transition temperature of 80°C in step 1 is added and pure nitrogen is fed. Both rates are 50 mL/min. For the heating conditions determined in step 1, use a microcalorimeter to measure a curve of the heat flow of the phase change paraffin with temperature by using a corresponding heating program;

Step 3. Add 1 g of Shengli lignite sample selected in step 1 to the sample pool and continuously feed pure oxygen. Add 1 g of phase change paraffin with a phase change temperature of 80°C in the reference pool and feed pure nitrogen into the reference pool. The rate is all 50mL/min, and the same heating conditions as in step 2 are selected, and the heat flow curve of Shengli lignite with the phase change paraffin as a reference is obtained by using a microcalorimeter analyzer to measure the temperature rise program;

Step 4. Add 1g of Shengli lignite sample to be measured into the sample pool and continue to feed pure oxygen. No substance is added to the reference pool and pure nitrogen is fed. Both rates are 50mL/min. Select the same as step 2. Heating conditions, the curve of the heat flow of Shengli lignite with temperature was obtained by using a microcalorimeter and a corresponding heating program to measure;

Step 5. Use the phase change paraffin heat flow change curve obtained in step 2, the phase change paraffin obtained in step 3 as the reference Shengli lignite heat flow change curve and the Shengli lignite heat flow change curve obtained in step 4, according to the selected 75 ℃ in step 1. The temperature change interval to 85°C is calculated separately, and the specific value of the heat change of the three in the temperature change interval is obtained; among them, the heat effect change value calculated from the heat flow change curve of Shengli lignite is the raw coal obtained by the traditional measurement method. Oxidation heat release in the temperature range (that is, constant temperature thermal effect); the thermal effect change value calculated from the heat flow change curve of Shengli lignite with phase change paraffin as the reference minus the heat effect change value calculated from the phase change paraffin heat flow change curve is the present invention Accurately measure the actual oxidative heat release (ie constant temperature thermal effect) of raw coal in the selected temperature variation range.

Example 4: Xinqiao anthracite was selected as the raw coal sample, and its characteristics of the thermal effect of low temperature oxidation and heating in the temperature range of 75°C to 175°C were determined; the amount of raw coal sample was 2g; the selected organic phase change material was the phase change temperature It is a mixture of mannitol at 165°C, erythritol at a phase transition temperature of 116°C, and phase change paraffin at a phase transition temperature of 95°C in a mass ratio of 1:1:1, and the dosage is 8g; , T ₁ is 95°C, x ₁ is 20°C, Tn _is 165°C, and xn _is 15°C; as shown in Figure 2, the heating program is set as: firstly from room temperature at a heating rate of 5°C/min The temperature was raised to 75°C, and then increased from 75°C to 180°C at a rate of 0.2°C/min; the subsequent measurement implementation process was the same as that of Example 1 (the raw coal sample was 1 g each time during the measurement, and the organic phase change material was used each time. 4g), so as to accurately measure the actual oxidation heat release (ie heating effect) of Xinqiao anthracite in the temperature range of 75°C to 175°C.

Example 5: The Donglu weather coal was selected as the raw coal sample, and its low-temperature oxidation constant temperature thermal effect law characteristics in the temperature range of 110°C to 120°C were determined; the amount of the raw coal sample was 3 g; the selected organic phase change material was phase change The temperature of erythritol is 116 °C, and the dosage is 6 g; the heating program is set as follows: first, keep constant temperature at 30 °C for 1 h, then increase the temperature from 30 °C to 116 °C at a rate of 1 °C/min, and then at this temperature The constant temperature was maintained for 2 hours; the subsequent measurement implementation process was the same as that of Example 3 (the amount of raw coal sample was 1.5g each time during the measurement process, and the amount of organic phase change material was 3g each time), so as to accurately determine the temperature of Donglu weather coal from 110 °C to 120 °C The actual oxidative heat release in the temperature range (ie constant temperature thermal effect).

The measurement results of the above five examples are shown in Table 1.

The specific parameters of the thermal effect of low temperature oxidation of coal samples in the five embodiments of table 1:

It can be seen from the data of the above test and accompanying drawings 3 to 8 that the calorimetric value of the traditional calorimetric method has a low measurement accuracy under low temperature conditions, and cannot show the calorimetric peak during the oxidation process of the coal sample, and it is difficult to measure the specific value. The method of the invention can accurately measure the actual thermal effect of the coal sample in the process of low-temperature oxidation after selecting an organic phase-change material with a suitable phase-transition temperature, amplify the thermal effect change of the coal sample in the process, and show a complete The exothermic peak can also measure the heating effect or the constant temperature heating effect according to the heating effect, so as to realize the accurate measurement of the thermal effect change of the coal sample in stages or in the whole process.

The above is only the preferred embodiment of the present invention, it should be pointed out that: for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.

Claims (6)

1. A coal low-temperature oxidation micro-heat accurate determination method based on phase change reference is characterized by comprising the following specific steps:

firstly, selecting a raw coal sample, then setting a temperature change interval of the raw coal sample, subsequently measuring the low-temperature oxidation heat production quantity of the raw coal sample in the temperature change interval, selecting an organic phase change material with a phase change temperature corresponding to the temperature interval according to the set temperature change interval, then determining the heating condition of the subsequent coal sample during measurement test, wherein the heating condition is a constant-temperature heat effect or a heating-up heat effect, and selecting a corresponding heating-up program in a micro thermal analyzer according to the heating condition;

step two, adding no substance into the sample tank and continuously introducing pure oxygen, adding the organic phase change material selected in the step one into the reference tank and introducing pure nitrogen, and determining by using a trace thermal analyzer according to the heating condition determined in the step one and a set temperature rise program to obtain a change curve of the heat flow of the organic phase change material along with the temperature;

step three, adding the raw coal sample selected in the step one into a sample tank, continuously introducing pure oxygen, adding an organic phase change material into a reference tank, introducing pure nitrogen, selecting the heating condition same as that in the step two, and determining by using a trace thermal analyzer by adopting a set heating program to obtain a change curve of the heat flow of the raw coal as the reference, wherein the change curve of the heat flow of the raw coal is taken as the reference;

step four, adding a raw coal sample to be measured into a sample tank, continuously introducing pure oxygen, adding no substances into a reference tank, introducing pure nitrogen, selecting the heating condition same as that in the step two, and determining by using a trace thermal analyzer by adopting a set temperature-rising program to obtain a change curve of the heat flow of the raw coal along with the temperature;

step five, using the organic phase change material heat flow change curve obtained in the step two and the organic phase change material obtained in the step three as reference raw coal heat flowThe change curve and the heat flow change curve of the raw coal obtained in the fourth step are respectively calculated according to the temperature change interval selected in the first step, and the specific numerical values of the heat change of the raw coal, the heat flow change curve and the temperature change interval are respectively Q ₁ 、Q ₂ And Q ₃ J/g; wherein Q ₃ Namely the oxidation heat release of the raw coal in the selected temperature range obtained by the traditional measuring method; will Q ₂ Value and Q ₁ And (4) making a difference, namely accurately measuring the actual oxidation heat release of the raw coal in the selected temperature change interval.

2. The coal low-temperature oxidation micro-calorimetry accurate determination method based on phase-change reference according to claim 1, wherein the phase-change temperature of the organic phase-change material is 30-200 ℃, the organic phase-change material comprises mannitol with a phase-change temperature of 165 ℃, erythritol with a phase-change temperature of 116 ℃, and a plurality of phase-change paraffins with a phase-change temperature of 30-200 ℃; the organic phase-change material is selected according to the temperature change interval and is formed by compounding the single substance or a plurality of substances with different phase-change temperatures.

3. The coal low-temperature oxidation micro-calorimetry accurate determination method based on phase-change reference according to claim 1, wherein the temperature rise program of the constant-temperature thermal effect is as follows: firstly keeping the temperature at 30 ℃ for 1h, then heating the temperature from 30 ℃ to the phase change temperature of the selected organic phase change material, wherein the heating rate is one of 0.1 ℃/min, 0.2 ℃/min, 0.5 ℃/min and 1 ℃/min, and then keeping the temperature at the constant temperature for 2 h.

4. The coal low-temperature oxidation micro-calorimetry accurate determination method based on phase change reference according to claim 1, wherein the temperature rise thermal effect is obtained by the following temperature rise program: for the phase change reference compounded by n organic phase change materials, the temperature is quickly raised from room temperature to (T) at the temperature rise rate of 5 ℃/min ₁ -x ₁ ) DEG C, then is prepared from (T) ₁ -x ₁ ) Raising the temperature to (T) _n +x _n ) The temperature rise rate is one of 0.1 ℃/min, 0.2 ℃/min, 0.5 ℃/min and 1 ℃/min, and the T is ₁ Is n kinds of organicPhase change temperature value, T, corresponding to the organic phase change material with the minimum phase change temperature in the phase change material _n The phase change temperature value, x, corresponding to the organic phase change material with the maximum phase change temperature in the n organic phase change materials ₁ And x _n The temperature change values are the half-peak widths of the phase change peak of the organic phase change material with the minimum phase change temperature and the phase change material with the maximum phase change temperature respectively.

5. The coal low-temperature oxidation micro-heat accurate determination method based on phase change reference as claimed in claim 1, wherein the raw coal sample is 1-2 g, the organic phase change material is 1-8 g, and the ratio of the raw coal sample to the organic phase change material is 1: 1. 1: 2. 1: 4, one of the compositions; the selection method of the dosage ratio comprises the following steps: when the maximum value of the temperature interval needing to be measured is less than 85 ℃, the usage ratio of the raw coal sample to the organic phase change material is 1: 1; when the maximum value of the temperature interval needing to be measured is positioned at (85, T) _cpt ]At the time of DEG C, the dosage ratio of the raw coal sample to the organic phase-change material is 1: 2; when the maximum value of the temperature interval needing to be measured is more than T _cpt At the time of DEG C, the dosage ratio of the raw coal sample to the organic phase-change material is 1: 4, said T _cpt The cross point temperature value of the raw coal sample is shown.

6. The method for accurately measuring the coal low-temperature oxidation micro heat based on the phase change reference according to claim 1, wherein the gas flow rates of the nitrogen and the oxygen are kept consistent and are any value of 50-100 mL/min, and the gas flow rate is controlled by a mass flow meter.

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