CN115078458A - Coal low-temperature oxidation micro-calorimetric accurate determination method based on phase change reference - Google Patents
Coal low-temperature oxidation micro-calorimetric accurate determination method based on phase change reference Download PDFInfo
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- 239000003245 coal Substances 0.000 title claims abstract description 158
- 230000003647 oxidation Effects 0.000 title claims abstract description 67
- 238000007254 oxidation reaction Methods 0.000 title claims abstract description 67
- 238000000034 method Methods 0.000 title claims abstract description 47
- 239000012071 phase Substances 0.000 claims abstract description 56
- 238000010438 heat treatment Methods 0.000 claims abstract description 53
- 239000012074 organic phase Substances 0.000 claims abstract description 45
- 239000000463 material Substances 0.000 claims abstract description 44
- 230000000694 effects Effects 0.000 claims abstract description 40
- 238000005259 measurement Methods 0.000 claims abstract description 25
- 238000004519 manufacturing process Methods 0.000 claims abstract description 20
- 239000012782 phase change material Substances 0.000 claims abstract description 18
- 238000012360 testing method Methods 0.000 claims abstract description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 36
- 229910052757 nitrogen Inorganic materials 0.000 claims description 18
- 239000007789 gas Substances 0.000 claims description 16
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims description 15
- 239000000126 substance Substances 0.000 claims description 15
- 239000000203 mixture Substances 0.000 claims description 6
- 239000004386 Erythritol Substances 0.000 claims description 5
- UNXHWFMMPAWVPI-UHFFFAOYSA-N Erythritol Natural products OCC(O)C(O)CO UNXHWFMMPAWVPI-UHFFFAOYSA-N 0.000 claims description 5
- 235000019414 erythritol Nutrition 0.000 claims description 5
- UNXHWFMMPAWVPI-ZXZARUISSA-N erythritol Chemical compound OC[C@H](O)[C@H](O)CO UNXHWFMMPAWVPI-ZXZARUISSA-N 0.000 claims description 5
- 229940009714 erythritol Drugs 0.000 claims description 5
- FBPFZTCFMRRESA-KVTDHHQDSA-N D-Mannitol Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-KVTDHHQDSA-N 0.000 claims description 3
- 229930195725 Mannitol Natural products 0.000 claims description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 3
- 238000013329 compounding Methods 0.000 claims description 3
- 235000010355 mannitol Nutrition 0.000 claims description 3
- 239000000594 mannitol Substances 0.000 claims description 3
- 239000001301 oxygen Substances 0.000 claims description 3
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 238000010187 selection method Methods 0.000 claims description 2
- 238000007707 calorimetry Methods 0.000 claims 3
- 239000012188 paraffin wax Substances 0.000 description 29
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 12
- 229910052717 sulfur Inorganic materials 0.000 description 12
- 239000011593 sulfur Substances 0.000 description 12
- 239000003077 lignite Substances 0.000 description 9
- 238000001595 flow curve Methods 0.000 description 7
- 230000007704 transition Effects 0.000 description 7
- 238000002485 combustion reaction Methods 0.000 description 5
- 230000002269 spontaneous effect Effects 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 4
- 238000004364 calculation method Methods 0.000 description 4
- 230000020169 heat generation Effects 0.000 description 4
- 238000000691 measurement method Methods 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 description 2
- 239000003830 anthracite Substances 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000000476 thermogenic effect Effects 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
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- G01—MEASURING; TESTING
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- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
- G01N25/48—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity on solution, sorption, or a chemical reaction not involving combustion or catalytic oxidation
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Abstract
The invention discloses a coal low-temperature oxidation micro-heat accurate determination method based on phase change reference, which comprises the steps of firstly determining the heat flow change of an organic phase change material with a certain specific phase change temperature in the heating process, then setting a heating program for a constant-temperature heat effect or a heating heat effect according to a measurement mode, taking the organic phase change material as a reference and taking a coal sample as a sample for testing, obtaining the complete heat peak of coal low-temperature oxidation and the phase change reference heat release thereof in the constant-temperature or heating process based on the heat flow change, and accurately obtaining the set heat release of coal low-temperature oxidation in the constant-temperature or heating process by subtracting the value of the complete heat peak of the phase change material; the heat production quantity of the low-temperature oxidation of the coal determined by the method takes the single phase-change material as a reference base line, breaks through the limitation that a complete exothermic peak cannot be obtained when a trace thermal analyzer is used for directly determining the heat release quantity of the low-temperature oxidation of the coal, effectively avoids the influence caused by base line errors, and realizes the accurate measurement of the whole process and the stages of the low-temperature oxidation heat release of the coal sample.
Description
Technical Field
The invention relates to a method for measuring low-temperature oxidation heat production of coal, in particular to a coal low-temperature oxidation micro-heat accurate measurement method based on phase change reference, and belongs to the technical field of coal low-temperature oxidation heat production measurement.
Background
Coal spontaneous combustion is one of main disasters existing in the mining process of mines, not only burns a large amount of coal resources to cause huge economic loss, but also generates a large amount of toxic and harmful gas to greatly threaten the life safety of miners. The goaf is a dangerous area most prone to coal spontaneous combustion, a large number of cracks and air leakage channels exist, coal gradually generates low-temperature oxidation heat under certain conditions, heat generated by oxidation in spontaneous combustion zones in three zones of the goaf cannot be dissipated timely, and the possibility of coal spontaneous combustion is greatly increased.
Many scientists have studied on low-temperature oxidation of coal, however, most studies are limited in aspects of gas production characteristics, functional group change, kinetic parameter measurement, pyrolysis product analysis and the like of coal, and the research on heat production characteristics of low-temperature oxidation of coal involves a small amount, and known measurement methods are mainly a TG-DSC method, namely a thermal-gravity-differential thermal method, but the method has the disadvantages of insufficient scanning precision, high temperature rise rate, small amount of coal samples (generally about 10mg), and difficulty in embodying oxidation heat production characteristics of coal samples in a broken and stacked state in a large amount in a well. In addition, the existing micro thermal analyzer can accurately measure the heat production characteristic of coal during low-temperature oxidation by using the principle of differential thermal compensation, has high sensitivity, high temperature rise rate of 0.001 ℃/min, good signal stability and large sample pool volume, can hold more coal samples, and is in relatively accordance with the process of low-temperature oxidation of underground coal. However, under the condition of no reference, the baseline of the low-temperature oxidation heat flow change curve of the coal measured by the existing instrument is not accurate, and a certain deviation exists when the baseline is used for calculating and solving the heat change of the coal sample, especially when the coal sample is oxidized and released at a lower temperature, the complete heat peak of the coal sample cannot be displayed, and the measurement is more difficult under the condition of continuous heat release; at present, a coal sample is put into a sample cell and oxygen is introduced, and nitrogen is introduced into the coal sample with the same quality as a reference, but the coal sample as the reference still generates a heat effect due to chemical change caused by temperature rise under the inert gas atmosphere, and the heat effect also affects a test result; moreover, the current thermal measurement method cannot effectively measure the heat production amount of the low-temperature oxidation of the coal sample within a certain set temperature change range, and further cannot perform subsequent analysis on the low-temperature oxidation heat production condition of the coal sample within a specific temperature change interval, so how to provide a method, under the condition of measurement based on a micro thermal analyzer, not only can the low-temperature oxidation heat production characteristic of the coal sample be accurately measured, but also the low-temperature oxidation heat production amount can be measured on a complete exothermic peak within the set temperature change range of the measured coal sample, so that accurate data can be provided for subsequent analysis of the coal sample, and the method is one of research directions of the industry.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the coal low-temperature oxidation micro-heat accurate determination method based on the phase change reference, which not only can realize accurate determination of the low-temperature oxidation heat generation characteristic of the coal sample, but also can perform complete heat release peak determination of the low-temperature oxidation heat generation amount in the set temperature change range of the measured coal sample, thereby providing accurate data for the subsequent analysis of the coal sample.
In order to achieve the purpose, the invention adopts the technical scheme that: the coal low-temperature oxidation micro-calorimetric accurate determination method based on phase change reference comprises 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 during the subsequent coal sample measurement test, wherein the heating condition is a constant-temperature thermal effect or a heating thermal effect, and selecting a corresponding heating 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, taking the organic phase change material heat flow change curve obtained in the step two, the organic phase change material obtained in the step three as a reference raw coal heat flow change curve and the raw coal heat flow change curve obtained in the step four, and respectively calculating according to the temperature change interval selected in the step one to obtain specific numerical values of heat change of the three in the temperature change interval, namely Q 1 、Q 2 And Q 3 J/g; wherein Q 3 Namely the raw coal obtained by the traditional measuring method is in the selected temperature rangeOxidation exotherm of (a); 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.
Further, the phase transition temperature of the organic phase change material is 30-200 ℃, and the organic phase change material comprises mannitol with the phase transition temperature of 165 ℃, erythritol with the phase transition temperature of 116 ℃ and a plurality of phase transition paraffins with the phase transition 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, wherein the single phase change material can realize the measurement of the heat of the coal in the low-temperature oxidation stage, and the compounding of the plurality of organic phase change materials can realize the measurement of the heat of the coal in the whole low-temperature oxidation process.
Further, the temperature rise procedure of the constant temperature heat 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. By adopting the parameters, the constant temperature heat effect can be ensured to be stably carried out, and the data precision of subsequent test measurement is further ensured.
Further, the temperature rise procedure of the temperature rise thermal effect is as follows: 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 The phase change temperature value T corresponding to the organic phase change material with the minimum phase change temperature in the n organic phase change materials 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 respectively the half-peak width of the phase change peak of the organic phase change material with the minimum phase change temperature and the half-peak width of the phase change peak of the organic phase change material with the maximum phase change temperature. The parameters can ensure that the temperature change interval of the heating effect can cover all phase change peaks of the compound phase change material, and further ensure the data precision of the subsequent test measurement。
Further, the usage amount of the raw coal sample is 1-2 g, the usage amount of the organic phase change material is 1-8 g, and the usage amount 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. The use of the dosage ratio can ensure that the heat peak of the coal sample can be covered by the heat peak of the phase-change material as much as possible, thereby further ensuring the data accuracy of the subsequent test measurement.
Further, 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.
Compared with the prior art, the coal low-temperature oxidation micro-calorimetric accurate determination method based on the phase-change reference provides a coal low-temperature oxidation micro-calorimetric accurate determination method based on the phase-change reference, aiming at the defects that the heat generation condition of a coal sample in a certain set temperature change range in the low-temperature oxidation process of the coal sample cannot be accurately measured in the field and the heat generation deviation of the coal sample cannot be measured due to the fact that a complete exothermic peak cannot be displayed because of the change of a test base line of a micro-calorimetric analyzer, firstly, the heat flow change of an organic phase-change material or a composite organic phase-change material at a certain phase-change temperature in the temperature-rising process is measured, then, a temperature-rising program is set for a constant-temperature heat effect or a temperature-rising heat effect according to the measurement mode, the organic phase-change material is used as the reference, and the coal sample is used for testing, and calculating the two curves and accurately subtracting the two curves to obtain the total heat production amount within a certain temperature range in the low-temperature oxidation process of the coal sample. The heat yield of the low-temperature oxidation of the coal measured by the method takes the single phase-change material as a reference baseline, breaks through the limitation that a complete exothermic peak cannot be obtained when the trace thermal analyzer is used for directly measuring the exothermic quantity of the low-temperature oxidation of the coal, can display the complete exothermic peak of the oxidation of the coal sample, and effectively avoids the influence caused by the baseline error of the heat flow curve of the incomplete exothermic peak when the trace thermal analyzer is used for measuring the exothermic quantity; the single organic phase change material or the composite organic phase change material within the phase change temperature can be selected according to the heat production quantity of the coal sample in different temperature ranges, the whole process and the staged measurement of the low-temperature oxidation heat release of the coal sample are realized, the heat release level of the constant-temperature oxidation of the coal sample can be accurately evaluated, and the method has important theoretical values for evaluating the oxidation capacity of the coal sample and predicting the natural ignition characteristics of the coal; the method is simple and convenient to operate, accurate in measurement and small in deviation, and provides data support for the follow-up research of the continuous characteristic of the low-temperature oxidation heat production of the coal and the spontaneous combustion of the coal, particularly the low-temperature oxidation heat production of the coal sample.
Drawings
FIG. 1 is a flow chart of the overall implementation of the present invention;
FIG. 2 is a schematic diagram showing the temperature range selection of a program corresponding to the heating effect of the present invention;
FIG. 3 is a heat flow curve and calculation range of phase change paraffin wax with a phase change temperature of 80 ℃ in example 1;
FIG. 4 is a sulfur ditch long flame coal heat flow curve and a calculation range with phase transition paraffin as a reference, wherein the phase transition temperature of the sulfur ditch long flame coal heat flow curve is 80 ℃ in example 1;
FIG. 5 is a plot of the heat flow of the sulfur channel long flame coal of example 1 and the calculated range;
FIG. 6 is a heat flow curve and calculation range of phase change paraffin wax with a phase change temperature of 120 ℃ in example 2;
FIG. 7 is a heat flow curve and a calculation range of eastern open gas coal with reference to phase-change paraffin wax having a phase-change temperature of 120 ℃ in example 2;
FIG. 8 is a graph showing the heat flow curves and the calculated ranges of the coal in the middle east open gas of example 2.
Detailed Description
The present invention will be further described below.
Example 1: the method comprises the following specific steps:
firstly, selecting sulfur ditch long flame coal as a raw coal sample, then selecting the temperature change interval of the raw coal sample to be 48-83 ℃, subsequently measuring the low-temperature oxidation heat production quantity in the temperature change interval, selecting 2g of phase change paraffin with the phase change temperature of 80 ℃ according to the set temperature change interval for standby, taking 2g of the sulfur ditch long flame coal sample for standby, then determining the heating condition during the subsequent coal sample measurement test as the heating effect, and the corresponding heating program is as follows: firstly, rapidly heating the mixture from room temperature to 48 ℃ at a heating rate of 5 ℃/min, and then heating the mixture from 48 ℃ to 115 ℃ at a heating rate of 0.1 ℃/min;
step two, adding no substance into the sample cell and continuously introducing pure oxygen, adding 1g of phase-change paraffin with the phase-change temperature of 80 ℃ in the step one into the reference cell and introducing pure nitrogen, wherein the rates of the two are both 50mL/min, and measuring by using a micro thermal analyzer according to the heating condition determined in the step one and adopting a corresponding heating program to obtain a change curve of the heat flow of the phase-change paraffin along with the temperature, wherein the change curve is shown in figure 3;
step three, adding 1g of the sulfur ditch long flame coal sample selected in the step one into a sample tank, continuously introducing pure oxygen, adding 1g of phase change paraffin with the phase change temperature of 80 ℃ in the step one into a reference tank, introducing pure nitrogen at the speed of 50mL/min, selecting the heating condition same as that in the step two, and determining by using a micro thermal analyzer by adopting a set temperature-raising program to obtain a change curve of the heat flow of the sulfur ditch long flame coal as the reference, wherein the change curve is shown in FIG. 4;
step four, adding 1g of sulfur ditch long flame coal sample to be measured into a sample pool, continuously introducing pure oxygen, adding no substance into a reference pool, introducing pure nitrogen at the rate of 50mL/min, selecting the heating condition same as that in the step two, and measuring by using a micro thermal analyzer by using a corresponding temperature rise program to obtain a change curve of the heat flow of the sulfur ditch long flame coal along with the temperature, wherein the change curve is shown in FIG. 5;
step five, calculating the heat flow change curve of the phase-change paraffin obtained in the step two, the heat flow change curve of the sulfur ditch long flame coal obtained in the step three as a reference and the heat flow change curve of the sulfur ditch long flame coal obtained in the step four according to the temperature change interval of 48 ℃ to 83 ℃ selected in the step one, and obtaining specific numerical values of the heat change of the phase-change paraffin, the heat flow change curve of the sulfur ditch long flame coal in the temperature change interval; wherein, the calculated thermal effect change value in fig. 5 is the oxidation heat release (i.e. the temperature-rise thermal effect) of the raw coal in the selected temperature range obtained by the traditional measuring method; and subtracting the thermal effect change value in the figure 3 from the calculated thermal effect change value in the figure 4 to obtain the actual oxidation heat release (namely the heating effect) of the raw coal in the selected temperature change interval.
Example 2: the method comprises the following specific steps:
firstly, selecting Dongpeng gas coal as a raw coal sample, then selecting the temperature change interval of the raw coal sample to be 90-128 ℃, subsequently measuring the low-temperature oxidation heat production quantity in the temperature change interval, selecting 4g of phase-change paraffin with the phase-change temperature of 120 ℃ according to the set temperature change interval for standby, taking 2g of the Dongpeng gas coal sample for standby, then determining the heating condition during the subsequent coal sample measurement test as the heating effect, and the corresponding heating program is as follows: firstly, rapidly heating the mixture from room temperature to 90 ℃ at a heating rate of 5 ℃/min, and then heating the mixture from 90 ℃ to 150 ℃ at a heating rate of 0.2 ℃/min;
step two, adding no substance into the sample cell and continuously introducing pure oxygen, adding 2g of phase-change paraffin with the phase-change temperature of 120 ℃ in the step one into the reference cell and introducing pure nitrogen, wherein the rates of the two are both 80mL/min, and measuring by using a micro thermal analyzer according to the heating condition determined in the step one and adopting a corresponding heating program to obtain a change curve of the heat flow of the phase-change paraffin along with the temperature, wherein the change curve is shown in figure 6;
step three, adding 1g of the eastern open-air gas coal sample selected in the step one into a sample tank, continuously introducing pure oxygen, adding 2g of phase-change paraffin with the phase-change temperature of 120 ℃ in the step one into a reference tank, introducing pure nitrogen, wherein the rates of the two are both 80mL/min, selecting the heating condition same as that in the step two, and measuring by using a micro thermal analyzer by adopting a set temperature-rise program to obtain a heat flow change curve of the eastern open-air gas coal with the phase-change paraffin as reference, wherein the heat flow change curve is shown in FIG. 7;
step four, adding 1g of eastern open-air coal sample to be measured into the sample tank, continuously introducing pure oxygen, adding no substance into the reference tank, introducing pure nitrogen at the rate of 80mL/min, selecting the heating condition same as that in the step two, and measuring by using a micro thermal analyzer by using a corresponding temperature rise program to obtain a change curve of the heat flow of the eastern open-air coal along with the temperature, wherein the change curve is shown in FIG. 8;
step five, calculating the phase-change paraffin heat flow change curve obtained in the step two, the phase-change paraffin obtained in the step three as a reference eastern open gas coal heat flow change curve and the eastern open gas coal heat flow change curve obtained in the step four according to the temperature change interval from 90 ℃ to 128 ℃ selected in the step one, and obtaining specific numerical values of heat change of the three in the temperature change interval; wherein, the calculated thermal effect variation value in fig. 8 is the oxidation heat release (i.e. heating effect) of the raw coal in the selected temperature range obtained by the traditional measuring method; and subtracting the thermal effect change value in the figure 6 from the calculated thermal effect change value in the figure 7 is the actual oxidation heat release (namely the heating effect) of the raw coal in the selected temperature change interval.
Example 3: the method comprises the following specific steps:
firstly, selecting victory lignite as a raw coal sample, then selecting a temperature change interval of the raw coal sample to be 75-85 ℃, subsequently measuring the low-temperature oxidation heat production quantity in the temperature change interval, selecting 2g of phase-change paraffin with the phase-change temperature of 80 ℃ according to the set temperature change interval for standby, taking 2g of the victory lignite coal sample for standby, then determining the heating condition during the subsequent coal sample measurement test as a constant-temperature heat effect, and the corresponding temperature rise program is as follows: firstly, keeping the temperature at 30 ℃ for 1h, then heating the temperature from 30 ℃ to 80 ℃ at the speed of 0.5 ℃/min, and then keeping the temperature at the temperature for 2 h;
step two, adding no substance into the sample cell and continuously introducing pure oxygen, adding 1g of phase-change paraffin with the phase-change temperature of 80 ℃ in the step one into the reference cell and introducing pure nitrogen, wherein the rates of the two are both 50mL/min, and measuring by using a micro thermal analyzer according to the heating condition determined in the step one and adopting a corresponding temperature-rise program to obtain a change curve of the heat flow of the phase-change paraffin along with the temperature;
step three, adding 1g of the coal sample of the victory lignite selected in the step one into a sample tank, continuously introducing pure oxygen, adding 1g of phase-change paraffin with the phase-change temperature of 80 ℃ in the step one into a reference tank, introducing pure nitrogen at the speed of 50mL/min, selecting the heating condition same as that in the step two, and determining by using a micro thermal analyzer by adopting a set heating program to obtain a change curve of heat flow of the victory lignite with the phase-change paraffin as the reference along with the temperature;
step four, adding 1g of the coal sample of the victory lignite to be measured into a sample tank, continuously introducing pure oxygen, adding no substance into a reference tank, introducing pure nitrogen at a rate of 50mL/min, selecting the heating condition same as that in the step two, and measuring by using a micro thermal analyzer by using a corresponding temperature rise program to obtain a change curve of the heat flow of the victory lignite along with the temperature;
step five, calculating the phase-change paraffin heat flow change curve obtained in the step two, the phase-change paraffin obtained in the step three as a reference victory lignite heat flow change curve and the victory lignite heat flow change curve obtained in the step four according to the temperature change interval of 75-85 ℃ selected in the step one, and obtaining specific numerical values of heat changes of the phase-change paraffin heat flow change curve, the phase-change paraffin obtained in the step three in the temperature change interval; wherein the heat effect change value obtained by calculating the heat flow change curve of the victory lignite is the oxidation heat release (namely constant temperature heat effect) of the raw coal in a selected temperature range obtained by a traditional measuring method; the actual oxidation heat release (namely constant temperature heat effect) of the raw coal in the selected temperature change interval is accurately measured by subtracting the heat effect change value obtained by calculating the phase change paraffin wax heat flow change curve from the heat effect change value obtained by calculating the phase change paraffin wax heat flow change curve serving as the reference.
Example 4: selecting new anthracite as a raw coal sample, and measuring the characteristic of low-temperature oxidation heating effect rule of the sample in the temperature change range of 75-175 ℃; the consumption of the raw coal sample is 2 g; the selected organic phase change material is mannitol with the phase change temperature of 165 ℃, erythritol with the phase change temperature of 116 ℃ and phase change paraffin with the phase change temperature of 95 ℃ according to the mass ratio of 1: 1: 1 in an amount of 8 g; in this example, T 1 At 95 ℃ and x 1 At 20 ℃ and T n At 165 ℃ and x n Is 15 ℃; as shown in fig. 2, the temperature-raising program is set as follows: the temperature is rapidly raised to 75 ℃ from room temperature at the heating rate of 5 ℃/min, and then is rapidly raised to 0.2 ℃/min from 75 DEG CThe temperature is increased to 180 ℃ at a speed; the subsequent measurement process is the same as that in example 1 (the amount of the raw coal sample is 1g each time, and the amount of the organic phase change material is 4g each time in the measurement process), so that the actual oxidation heat release (namely the heating effect) of the new-bridge anthracite in the temperature change range of 75-175 ℃ is accurately measured.
Example 5: selecting Dongpeng gas coal as a raw coal sample, and measuring the characteristic of low-temperature oxidation constant-temperature thermal effect rule in a temperature change range of 110-120 ℃; the consumption of the raw coal sample is 3 g; the selected organic phase change material is erythritol with the phase change temperature of 116 ℃, and the dosage of the erythritol is 6 g; the temperature-raising program is set as follows: firstly, keeping the temperature at 30 ℃ for 1h, then heating the temperature from 30 ℃ to 116 ℃ at the speed of 1 ℃/min, and then keeping the temperature at the temperature for 2 h; the subsequent measurement implementation process is the same as that in example 3 (the amount of the raw coal sample is 1.5g each time, and the amount of the organic phase change material is 3g each time in the measurement process), so that the actual oxidation heat release (namely the constant temperature heat effect) in the temperature change range of 110 ℃ to 120 ℃ of the eastern open-air gas coal is accurately measured.
The results of the measurements of the above five examples are shown in table 1.
Table 1 specific parameters of the low-temperature oxidation thermogenic thermal effect of the coal samples of the five examples:
according to the data of the test and the attached figures 3 to 8, the calorimetric value of the traditional calorimetric method is low in measurement precision under the low-temperature condition, cannot display the calorimetric peak in the coal sample oxidation process, and is difficult to measure a specific value.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the 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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