CN114397323B - Device and method for measuring shortest natural ignition period of coal - Google Patents
Device and method for measuring shortest natural ignition period of coal Download PDFInfo
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- CN114397323B CN114397323B CN202111524031.3A CN202111524031A CN114397323B CN 114397323 B CN114397323 B CN 114397323B CN 202111524031 A CN202111524031 A CN 202111524031A CN 114397323 B CN114397323 B CN 114397323B
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Abstract
The invention belongs to the technical field of determination of a natural ignition period of coal, and particularly provides a laboratory determination device and a determination method for the shortest natural ignition period of coal. The device for measuring the shortest natural ignition period of the coal mainly comprises a dry air source, an oil storage tank, an oil pump, an oxidation furnace, an air duct, an oil guide pipe, a temperature sensor, a data acquisition unit and a computer; the method for measuring the shortest natural ignition period of the coal comprises the following steps: adopting a coal bed coal sample; preparing and managing a coal sample; measuring the ignition temperature of the coal sample; checking the state of equipment, and loading a coal sample in the checking process; starting an air path and an oil path of the equipment, and measuring and collecting air temperature, oil temperature and coal temperature data; and carrying out operation treatment on the recorded data to obtain the shortest natural ignition period result of the coal sample. The heat balance system of the coal oxidation self-heating process is constructed by adopting the modes of vacuum heat insulation, circulating oil bath and self-adaptive heating, so that the problem of uncontrollable heat dissipation and environmental temperature is solved, and the experimental process has repeatability and high reliability.
Description
Technical Field
The invention belongs to the technical field of determination of a natural ignition period of coal, and particularly provides a laboratory determination device and a determination method for the shortest natural ignition period of coal.
Background
The time from when the coal body contacts air to when spontaneous combustion begins is referred to as the natural ignition period of the coal. The natural ignition period of coal is a measure of the spontaneous combustion risk of coal in time, is an important index for evaluating the natural ignition risk of coal, and is an important parameter for guiding the on-site production of coal mines.
The earliest natural ignition period prediction is roughly estimated mainly by experience and site statistics, usually in units of months, and cannot effectively guide the work on site. Therefore, natural ignition experiment tables are adopted for simulating the natural ignition process of coal in various countries, the natural ignition period of the coal is further predicted, basic data is provided for the fire prevention and extinguishment work in the coal mine site, and good effects are achieved.
The traditional coal natural ignition experiment table approximately simulates the on-site heat dissipation condition, the air leakage condition and the thickness of float coal, takes room temperature as the initial temperature of the experiment, utilizes the oxidation heat release of coal to cause natural temperature rise, continuously monitors the temperature of each characteristic point in the coal and the gas composition change condition, thereby researching the oxidation heat release characteristic of the coal and predicting the natural ignition period of the coal. Since the natural ignition period of coal is long and short for several months or more, and the experimental process may fail, there is a problem that the time and economic cost are too high, regardless of whether the measurement work is performed for research or test analysis. Therefore, a laboratory measurement scheme for the natural ignition period of coal, which has short experimental period, high repeatability and high reliability and can truly restore the natural ignition process, is needed.
Disclosure of Invention
In order to solve the problems, the invention provides a laboratory measuring device and a laboratory measuring method for the shortest natural ignition period of coal.
In order to achieve the above purpose, the invention adopts the following technical scheme: the utility model provides a measuring device of shortest natural ignition period of coal, including dry air source, the oil storage tank, the oil pump, the oxidation oven, the air duct, lead oil pipe, temperature sensor, data collection station, a computer, dry air source passes through the air duct and is connected with the gas circuit of oil storage tank, the gas circuit of oil storage tank is connected through the air duct and is connected with the gas circuit of oxidation oven, the oil pump sets up in the middle part of leading oil pipe through the oil line connection of leading oil pipe and the oil line connection of oxidation oven, the inside of oxidation oven is provided with temperature sensor, temperature sensor passes through data collection station and is connected with the electric motor, the computer passes through the data line respectively with oil storage tank, oil pump electric connection.
Further, the oil storage tank includes box, the agitator, spiral heating pipe, return oil pipe, go out oil pipe, electric heater, the agitator is assembled in the middle part of box top cap, and the blade of agitator extends to the bottom of box inner chamber, spiral heating pipe assembles in the inside of box, and spiral heating pipe's inlet end and the end of giving vent to anger extend to the box outside, return oil pipe, go out oil pipe and run through the top cap of box, return oil pipe's end extends to the top of box inner chamber, go out oil pipe's end and extend to the bottom of box inner chamber, electric heater assembles in the inside of box, dry air source and spiral heating pipe's inlet end intercommunication, the gas circuit of oxidation oven and spiral heating pipe's end intercommunication of giving vent to anger, return oil pipe passes through oil pipe and oxidation oven's oil return line intercommunication, and the oil pump sets up in oxidation oven's oil inlet line, electric heater and computer electric connection.
Further, the oxidation furnace comprises a furnace body, a vacuum cavity, an oil bath cavity, a reaction chamber, a supporting net, an air inlet pipe connector, a spiral air duct, an air outlet pipe connector, an oil return pipe connector and an oil inlet pipe connector, wherein the vacuum cavity and the oil bath cavity are all arranged in the furnace wall of the furnace body, the vacuum cavity is wrapped outside the oil bath cavity, the reaction chamber is a furnace chamber in the furnace body, the two supporting nets are respectively assembled at the top and the bottom of the reaction chamber, the air inlet pipe connector and the air outlet pipe connector are arranged on a top cover of the furnace body, the spiral air duct is arranged in the reaction chamber, the air inlet end of the spiral air duct is communicated with the air inlet pipe connector, the air outlet end of the spiral air duct extends to the bottom of the reaction chamber, the air outlet pipe connector is communicated with the reaction chamber, the oil return pipe connector is arranged at the top of the side wall of the furnace body, the oil inlet pipe connector is arranged on the bottom wall of the furnace body, the oil return pipe connector and the oil inlet pipe connector is communicated with the oil bath cavity, and the oil return pipe connector is communicated with the oil return pipe through the oil guide pipe, and the oil inlet pipe connector is communicated with the oil inlet pipe.
Further, the temperature sensor comprises an oil bath chamber platinum resistor I, an oil bath chamber platinum resistor II, an oil bath chamber platinum resistor III, an oil bath chamber platinum resistor IV, an oil bath chamber platinum resistor V, a reaction chamber platinum resistor II, a reaction chamber platinum resistor III and a reaction chamber platinum resistor IV, wherein the oil bath chamber platinum resistor I and the oil bath chamber platinum resistor I are respectively arranged at opposite side positions of the middle part of the inner side wall of the oil bath chamber, the oil bath chamber platinum resistor III is arranged at the inner wall of the oil inlet pipe interface, the oil bath chamber platinum resistor IV and the oil bath chamber platinum resistor V are respectively arranged at the inner wall of the oil return pipe interface, the reaction chamber platinum resistor I and the reaction chamber platinum resistor V are respectively arranged at opposite side positions of the middle part of the inner side wall of the reaction chamber, the reaction chamber platinum resistor III is arranged at the middle part of the bottom wall of the reaction chamber, the reaction chamber platinum resistor IV is arranged at the inner wall of the air outlet pipe interface, and the nine platinum resistors are electrically connected with the data collector.
Further, the device also comprises a liquid flowmeter, stop valves, a pressure reducing valve, a pressure stabilizing valve and a flow controller, wherein the liquid flowmeter is assembled in an oil inlet pipeline of the oxidation furnace, the two stop valves are respectively assembled at the external interfaces of the oil return pipe and the oil outlet pipe, the pressure reducing valve, the pressure stabilizing valve and the flow controller are sequentially assembled on an air guide pipe outside a drying air source, and the stop valves and the flow controller are respectively electrically connected with the motor.
A method for determining the shortest natural ignition period of coal comprises the following steps:
step 1, adopting a coal bed coal sample;
step 2, preparing and managing the coal sample;
step 3, measuring the ignition temperature of the coal sample;
step 4, checking the state of equipment, and loading a coal sample in the checking process;
step 5, starting an air path and an oil path of the equipment, and measuring and collecting air temperature, oil temperature and coal temperature data;
and step 6, performing operation processing on the recorded data to obtain the shortest natural ignition period result of the coal sample.
Further, in step 2, the process flow of preparing and managing the coal sample is based on the specification related to GB474, and the following requirements should be met at the same time:
1) When the water content of the coal sample is high and the influence on the subsequent experiments is judged, the coal sample is naturally dried, and then all the coal sample is crushed to be less than 10 mm;
2) Dividing the coal sample into 300 g-350 g by using a cone stacking quartering method, and preparing and analyzing the coal sample, and sealing the rest coal samples according to the original package and sealing to obtain a stored coal sample;
3) The crushed coal sample is stored in a jar in a sealing way, and each measurement is completed within 30 days.
Further, in step 4, the equipment status checking and coal sample loading process is as follows:
1) Checking the air tightness of the air path, the oil path and the vacuum cavity of the oxidation furnace, wherein the vacuum degree of the vacuum cavity of the oxidation furnace is not lower than 100kPa;
2) Checking the running states of a temperature sensor, a gas flow controller, a liquid flowmeter and a data collector, and debugging the existing problems;
3) After the air tightness and normal operation of various related instruments are confirmed, loading 100+/-0.1 g of coal sample to be tested into a reaction chamber;
4) After the sample is filled, the air tightness of the instrument should be checked again.
Further, in step 5, the air path and the oil path of the equipment are started, and the flow of collecting the air temperature, the oil temperature and the coal temperature data is measured as follows:
1) Introducing dry air into the reaction chamber at a steady flow rate of 300mL/min, setting the temperature of the oil bath cavity at 40 ℃, and stabilizing the flow rate of the heat conducting oil at 10L/min;
2) After the temperature of the coal sample is stable, recording and calculating the temperature of the coal sample at the temperature of 40 ℃ of the oil bath cavityTemperature difference of oil inlet and return->And air inlet/outlet temperature difference->
3) Setting the temperature of an oil bath cavity to be 1.0 ℃/min for programmed temperature rise, and starting a data acquisition device to acquire data such as air flow, air inlet and outlet temperature, heat conducting oil flow, oil inlet and return temperature, oil bath temperature, coal sample temperature and the like;
4) When the temperature of the coal sample collected by the data collector exceeds the inlet temperature of the oil bath cavity, the temperature of the oil bath cavity is set to be maintained at the current temperature;
5) After the temperature of the coal sample is stable, stopping data acquisition, recording and calculating the temperature of the coal sampleTemperature difference of oil inlet and returnAnd air inlet/outlet temperature difference->
Further, in step 6, the data processing operation steps are as follows:
calculating the shortest natural ignition period of coal
1) Calculating the coal chemical reaction rate parameter k a
2) The shortest natural ignition period tau of the coal is calculated, and the unit is day (d):
representative temperature of the coal sample in the furnace is T 0 When the coal sample generates heat due to self-heating, the unit is J/(m) 3 ·s)：
Representative temperature of the coal sample in the furnace is T 0 At the time, the heat dissipation amount accounts for the proportion of the heat generated by the self-heating effect of the coal sample:
the shortest natural ignition period tau of the coal:
the beneficial effects of using the invention are as follows:
1. the measuring device adopts a vacuum heat insulation, circulating oil bath and self-adaptive heating mode to construct a heat balance system in the coal oxidation self-heating process, solves the problem of uncontrollable heat dissipation and environmental temperature, and ensures that the experimental process has repeatability and high reliability;
2. in the process of measuring the natural ignition period of the coal by using the measuring device for the shortest natural ignition period of the coal, the system detects the oil temperature in the oil bath cavity and the coal temperature in the reaction chamber in real time through the temperature sensor;
the temperature regulation process adopts a feedback mechanism, and when the temperature rise rate of the temperature in the reaction chamber is increased along with the increase of the temperature rise rate of the coal sample, the system can synchronously regulate the temperature rise rate of the oil temperature, so that the effect of dynamic balance of the two is realized; in the temperature rising process of the experimental coal sample, the system records the temperature data of each characteristic point through a temperature sensor; when the temperature of the experimental coal sample rises to the ignition temperature of the coal, substituting the data into a mathematical model established by long-term experimental observation to calculate the natural ignition period of the coal sample; the effects of stabilizing and improving the heating process of the coal body are achieved, and the experimental period is shortened.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention;
fig. 2 is a connection diagram of an electronic component according to the present invention.
The reference numerals include: 1-a drying air source; 2-an oil storage tank; 201-a box body; 202-a stirrer; 203-spiral heating tube; 204, an oil return pipe; 205-an oil outlet pipe; 206-an electric heater; 3-an oil pump; a 4-oxidation furnace; 401-furnace body; 402-vacuum chamber; 403-oil bath chamber; 404-reaction chamber; 405-backing net; 406-an air inlet pipe interface; 407-spiral airway; 408-an outlet pipe interface; 409-an oil return pipe interface; 410-an oil inlet pipe interface; 5-an airway; 6-oil guide pipe; 701-platinum resistance of oil bath chamber I; 702-platinum resistance of the oil bath chamber II; 703-platinum resistance of oil bath chamber three; 704-platinum resistance of the oil bath chamber; 705-platinum resistance of oil bath chamber; 706—reaction chamber platinum resistance one; 707—reaction chamber platinum resistance two; 708—reaction chamber platinum resistance three; 709—a reaction chamber platinum resistance four; 8-a liquid flow meter; 9-a stop valve; 10-a pressure reducing valve; 11-a pressure stabilizing valve; 12-a flow controller; 13-a data collector; 14-computer.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
Referring to fig. 1-2, a measuring device for the shortest natural ignition period of coal comprises a dry air source 1, an oil storage tank 2, an oil pump 3, an oxidation furnace 4, an air duct 5, an oil duct 6, a temperature sensor, a data acquisition device 13 and a computer 14, wherein the dry air source 1 is connected with an air passage of the oil storage tank 2 through the air duct 5, the air passage of the oil storage tank 2 is connected with an air passage of the oxidation furnace 4 through the air duct 5, the oil pump 3 is arranged in the middle of the oil duct 6, the temperature sensor is arranged in the oxidation furnace 4 and is electrically connected with the oil storage tank 2 and the oil pump 3 through the data acquisition device 13, and the computer 14 is electrically connected with the computer 14 through data lines.
The oil storage tank 2 comprises a tank 201, a stirrer 202 and a spiral heating pipe 203, an oil return pipe 204, an oil outlet pipe 205 and an electric heater 206, wherein the stirrer 202 is assembled in the middle of a top cover of the tank 201, blades of the stirrer 202 extend to the bottom of an inner cavity of the tank 201, the spiral heating pipe 203 is assembled in the tank 201, an air inlet end and an air outlet end of the spiral heating pipe 203 extend to the outside of the tank 201, the oil return pipe 204 and the oil outlet pipe 205 penetrate through the top cover of the tank 201, the tail end of the oil return pipe 204 extends to the top of the inner cavity of the tank 201, the tail end of the oil outlet pipe 205 extends to the bottom of the inner cavity of the tank 201, the electric heater 206 is assembled in the tank 201, a drying air source 1 is communicated with the air inlet end of the spiral heating pipe 203, an air path of the oxidation furnace 4 is communicated with the air outlet end of the spiral heating pipe 203, the oil return pipe 204 is communicated with an oil return pipeline of the oxidation furnace 4 through an oil guide pipe 6, the oil outlet pipe 205 is communicated with the oil inlet pipeline of the oxidation furnace 4, and the oil pump 3 is arranged in the oil inlet pipeline of the oxidation furnace 4, and the electric heater 206 is electrically connected with the computer 14.
Preferably, the internal temperature monitoring mode of the oil storage tank 2 is as follows: the electric heater 206 in the oil storage tank 2 is provided with a matched temperature detection component and is used for detecting the temperature in the oil storage tank 2; or a separate temperature sensor is provided in the reservoir 2 for monitoring the internal temperature thereof.
The electric heater 206 controls the heating rate of the heat transfer oil in the box 201, and the heat transfer oil heats the air circulated in the spiral heating pipe 203.
The oxidation furnace 4 comprises a furnace body 401, a vacuum cavity 402, an oil bath cavity 403, a reaction chamber 404, a supporting net 405, an air inlet pipe interface 406, a spiral air duct 407, an air outlet pipe interface 408, an oil return pipe interface 409 and an oil inlet pipe interface 410, wherein the vacuum cavity 402 and the oil bath cavity 403 are both arranged in the furnace wall of the furnace body 401, the vacuum cavity 402 is wrapped outside the oil bath cavity 403, the reaction chamber 404 is a furnace chamber in the furnace body 401, the two supporting nets 405 are respectively assembled at the top and the bottom of the reaction chamber 404, the air inlet pipe interface 406 and the air outlet pipe interface 408 are arranged on the top cover of the furnace body 401, the spiral air duct 407 is arranged in the reaction chamber 404, the air inlet end of the spiral air duct 407 is communicated with the air inlet pipe interface 406, the air outlet end of the spiral air duct 407 extends to the bottom of the reaction chamber 404, the air outlet pipe interface 408 is communicated with the reaction chamber 404, the oil return pipe interface 409 is arranged on the top of the side wall of the furnace body 401, the oil inlet pipe interface 410 is arranged on the bottom wall of the furnace body 401, the oil return pipe interface 409 and the oil inlet pipe interface 410 is communicated with the oil bath cavity 403, the oil return pipe interface 409 is communicated with the oil return pipe 403, the oil inlet pipe interface 409 is communicated with the oil return pipe through an oil guide pipe 6, and the oil inlet pipe 410 is communicated with the oil inlet pipe.
The vacuum chamber 402 can reduce the speed of internal heat dissipation, reduce the influence of environmental factors on the furnace temperature, and provide buffer time for oil temperature adjustment. The oil bath cavity 403 is a loop of a heat conducting oil circulation path, and adjusts the external temperature of the reaction chamber 404 by taking heat conducting oil as a medium, so that the external temperature of the reaction chamber 404 continuously catches up with the internal temperature of the reaction chamber 404 with a very small temperature difference, and a slightly lagging feedback type adjustment steady state is formed. By increasing the external temperature simultaneously, the temperature differential is eliminated to avoid spontaneous heat dissipation from the coal in the reaction chamber 404.
Circulation oil circuit: the oil tank 201, the oil outlet pipe 205, the oil pump 3, the oil inlet pipe connector 410, the oil bath cavity 403, the oil return pipe connector 409, the oil guide pipe 6, the oil return pipe 204 and the tank 201.
And (3) air path: the drying air source 1, the air guide pipe 5, the spiral heating pipe 203, the air inlet pipe interface 406, the spiral air guide pipe 407, the reaction chamber 404, the air outlet pipe interface 408 and the outside.
The temperature of the gas in the gas path is adjusted at the spiral heating pipe 203, and is controlled by the temperature of the heat conducting oil in the box 201, and the temperature of the heat conducting oil is adjusted by controlling the electric heater 206 to heat after the temperature in the reaction chamber 404 is measured by the system.
Dry air is introduced into the reaction chamber 404 through the air path, so that an oxidation environment can be provided for the coal sample in the reaction chamber 404. The air heating in the air path can ensure that the temperature of the air is consistent with the temperature of the reaction chamber, and the heat loss of the coal sample caused by taking away the heat of the coal sample in the process that the air passes through the coal sample is discharged.
The temperature sensor includes an oil bath chamber platinum resistor 701, an oil bath chamber platinum resistor 702, an oil bath chamber platinum resistor 703, an oil bath chamber platinum resistor 704, an oil bath chamber platinum resistor 705, a reaction chamber platinum resistor 706, a reaction chamber platinum resistor 707, a reaction chamber platinum resistor 708, a reaction chamber platinum resistor 709, the oil bath chamber platinum resistor 701, the oil bath chamber platinum resistor 702 are respectively arranged at the opposite side position of the middle part of the inner side wall of the oil bath chamber 403, the oil bath chamber platinum resistor 703 is arranged at the inner wall of the oil inlet pipe interface 410, the oil bath chamber platinum resistor 704 and the oil bath chamber platinum resistor 705 are respectively arranged at the inner wall of the oil return pipe interface 409, the reaction chamber platinum resistor 706 and the reaction chamber platinum resistor 707 are respectively arranged at the opposite side position of the middle part of the inner side wall of the reaction chamber 404, the reaction chamber platinum resistor 708 is arranged at the middle part of the bottom wall of the reaction chamber 404, the reaction chamber platinum resistor 709 is arranged at the inner wall of the air outlet pipe interface 408, and the nine platinum resistors are electrically connected with the data collector 13.
The platinum resistor is abbreviated as platinum thermal resistor, and its resistance value changes with temperature change, and is a common thermal sensor.
The effect of multipoint detection on the temperature in the cavity is achieved by arranging platinum resistors on the inner wall of the container at multiple points. The temperature data in the cavity is obtained by comprehensively evaluating and calculating the temperature data measured by a plurality of detection points, so that the data deviation rate caused by the point selection problem is reduced.
The measuring device further comprises a liquid flowmeter 8, stop valves 9, a pressure reducing valve 10, a pressure stabilizing valve 11 and a flow controller 12, wherein the liquid flowmeter 8 is assembled in an oil inlet pipeline of the oxidation furnace 4, the two stop valves 9 are respectively assembled at external interfaces of an oil return pipe 204 and an oil outlet pipe 205, the pressure reducing valve 10, the pressure stabilizing valve 11 and the flow controller 12 are sequentially assembled on an air guide pipe 5 outside the drying air source 1, and the stop valves 9 and the flow controller 12 are respectively and electrically connected with a computer 14.
Preferably, the reaction chamber 404 is optimally shaped as a cylindrical cylinder 60mm in diameter and 60mm in height, as deduced from lumped parameter theory. The reaction chamber 404 may hold 90g to 120g of coal sample.
The method for measuring the shortest natural ignition period of the coal comprises the following steps:
step 1, adopting a coal bed coal sample;
the standard of the coal bed coal sample is based on the specification of GB/T482.
Step 2, preparing and managing the coal sample;
the process flow of preparing and managing the coal sample is based on the specification related to GB474, and meanwhile, the following requirements are met:
1) When the water content of the coal sample is higher and the influence on the subsequent experiment is judged, the coal sample is naturally dried, then all the coal sample is crushed to be less than 10mm, and the coal sample is divided into 300 g-350 g by a cone stacking quartering method and is used for preparing and analyzing the coal sample, and the rest coal samples are stored and sealed after being packaged and sealed as stored and checked coal samples;
2) When the coal sample is crushed, 300 g-350 g of the coal sample for analysis must be crushed to be less than 0.15mm, and the granularity of 0.10 mm-0.15 mm is required to be more than 70%;
3) Sealing and storing the crushed coal sample in a wide-mouth bottle, and completing each measurement within 30 days;
4) And (5) storing the sample for inspection and the sample for analysis for 6 months after the analysis report is sent.
Step 3, measuring the ignition temperature of the coal sample;
the measurement standard of the ignition temperature of the coal sample is based on the GB/T18511 rule.
Step 4, checking the state of equipment, and loading a coal sample in the checking process;
the equipment state inspection and coal sample loading flow is as follows:
1) Checking the air tightness of the air path, the oil path and the vacuum cavity of the oxidation furnace, wherein the vacuum degree of the vacuum cavity of the oxidation furnace is not lower than 100kPa;
2) Checking the running states of a temperature sensor, a gas flow controller, a liquid flowmeter and a data collector, and debugging the existing problems;
3) After the air tightness and normal operation of various related instruments are confirmed, loading 100+/-0.1 g of coal sample to be tested into a reaction chamber;
4) After the sample is filled, the air tightness of the instrument should be checked again.
Step 5, starting an air path and an oil path of the equipment, and measuring and collecting air temperature, oil temperature and coal temperature data;
the process of starting the gas circuit and the oil circuit of the equipment and measuring and collecting the temperature, the oil temperature and the coal temperature data comprises the following steps:
1) Introducing dry air into the reaction chamber at a steady flow rate of 300mL/min, setting the temperature of the oil bath cavity at 40 ℃, and stabilizing the flow rate of the heat conducting oil at 10L/min;
2) After the coal sample temperature (the units related to the temperature are all degrees centigrade (DEG C)) is stable, the coal sample temperature at the temperature of 40 ℃ of the oil bath cavity is recorded and calculatedTemperature difference of oil inlet and return->(oil inlet pipe interface 410 oil temperature isOil temperature of the oil return pipe interface 409 is +.>) And air inlet/outlet temperature difference->(intake pipe interface 406 air temperature is +.>Air temperature of air outlet pipe interface 408 is->)；
3) Setting the temperature of an oil bath cavity to be 1.0 ℃/min for programmed temperature rise, and starting a data acquisition device to acquire data such as air flow, air inlet and outlet temperature, heat conducting oil flow, oil inlet and return temperature, oil bath temperature, coal sample temperature and the like;
4) When the temperature of the coal sample collected by the data collector exceeds the inlet temperature of the oil bath cavity, the temperature of the oil bath cavity is set to be maintained at the current temperature;
5) After the temperature of the coal sample is stable, stopping data acquisition, recording and calculating the temperature of the coal sampleTemperature difference of oil inlet and returnAnd air inlet/outlet temperature difference->
Step 6, carrying out operation treatment on the recorded data to obtain the shortest natural ignition period result of the coal sample;
the data processing operation steps are as follows:
calculating the shortest natural ignition period of coal
1) Calculating the coal chemical reaction rate parameter k a
2) The shortest natural ignition period tau of the coal is calculated, and the unit is day (d):
representing the inside of the furnaceThe temperature of the coal sample is T 0 When the coal sample generates heat due to self-heating, the unit is J/(m) 3 ·s)：
Representative temperature of the coal sample in the furnace is T 0 At the time, the heat dissipation amount accounts for the proportion of the heat generated by the self-heating effect of the coal sample:
the shortest natural ignition period tau of the coal:
the measuring device adopts a vacuum heat insulation, circulating oil bath and self-adaptive heating mode to construct a heat balance system in the coal oxidation self-heating process.
In the process of measuring the natural ignition period of the coal by using the measuring device for the shortest natural ignition period of the coal by workers, the system detects the oil temperature T in the oil bath cavity 403 in real time through the temperature sensor Oil bath T is equal to the temperature of the coal in the reaction chamber 404 Reaction chamber (two temperature values are respectively obtained through comprehensive consideration of multi-point temperature data in each chamber so as to reduce data errors);
the system adjusts T by controlling the electric heater 206 to adjust the oil temperature Oil bath In the experimental process, the temperature difference between the oil bath cavity 403 and the reaction chamber 404 should be ensured to be more than 0 ℃ and less than 2.5 ℃ (delta T is less than or equal to T) Oil bath -T Reaction chamber ). The temperature regulation process adopts a feedback mechanism, and when the temperature rise rate of the temperature in the reaction chamber is increased along with the increase of the temperature rise rate of the coal sample, the system can synchronously regulate the temperature rise rate of the oil temperature, so that the effect of dynamic balance of the two is realized;
in the temperature rising process of the experimental coal sample, the system records the temperature data of each characteristic point through a temperature sensor;
when the temperature of the experimental coal sample rises to the ignition temperature of the coal, substituting the data into a mathematical model established by long-term experimental observation to calculate the natural ignition period of the coal sample.
The foregoing is merely exemplary of the present invention, and many variations may be made in the specific embodiments and application scope of the invention by those skilled in the art based on the spirit of the invention, as long as the variations do not depart from the gist of the invention.
Claims (5)
1. A measuring device for the shortest natural ignition period of coal is characterized in that: the device comprises a drying air source, an oil storage tank, an oil pump, an oxidation furnace, an air duct, an oil guide pipe, a temperature sensor, a data acquisition unit and a computer, wherein the drying air source is communicated with the oil storage tank through the air duct;
the oil storage tank comprises a tank body, a stirrer, a spiral heating pipe, an oil return pipe, an oil outlet pipe and an electric heater, wherein the stirrer is assembled in the middle of a top cover of the tank body, blades of the stirrer extend to the bottom of an inner cavity of the tank body, the spiral heating pipe is assembled in the tank body, an air inlet end and an air outlet end of the spiral heating pipe extend to the outside of the tank body, the oil return pipe and the oil outlet pipe penetrate through the top cover of the tank body, the tail end of the oil return pipe extends to the top of the inner cavity of the tank body, the tail end of the oil outlet pipe extends to the bottom of the inner cavity of the tank body, the electric heater is assembled in the tank body, a drying air source is communicated with the air inlet end of the spiral heating pipe, a gas path of the oxidation furnace is communicated with the air outlet end of the spiral heating pipe, the oil return pipe is communicated with the oil return pipe of the oxidation furnace through an oil guide pipe, the oil outlet pipe is communicated with the oil inlet pipe of the oxidation furnace, an oil pump is arranged in the oil inlet pipe of the oxidation furnace, and the electric heater is electrically connected with the electric heater;
the oxidation furnace comprises a furnace body, a vacuum cavity, an oil bath cavity, a reaction chamber, a supporting net, an air inlet pipe connector, a spiral air duct, an air outlet pipe connector, an oil return pipe connector and an oil inlet pipe connector, wherein the vacuum cavity and the oil bath cavity are formed in the furnace wall of the furnace body, the vacuum cavity is wrapped outside the oil bath cavity, the reaction chamber is a furnace chamber in the furnace body, the two supporting nets are respectively assembled at the top and the bottom of the reaction chamber, the air inlet pipe connector and the air outlet pipe connector are formed in the top cover of the furnace body, the spiral air duct is arranged in the reaction chamber, the air inlet end of the spiral air duct is communicated with the air inlet pipe connector, the air outlet end of the spiral air duct extends to the bottom of the reaction chamber, the air outlet pipe connector is communicated with the reaction chamber, the oil return pipe connector is formed at the top of the side wall of the furnace body, the oil inlet pipe connector is formed in the bottom wall of the furnace body, the oil return pipe connector and the oil inlet pipe connector are communicated with the oil bath cavity through oil guide pipes, and the oil inlet pipe connector is communicated with the oil inlet pipe;
in the process of measuring the natural ignition period of the coal, the temperature T of the oil in the oil bath cavity is detected in real time through a temperature sensor Oil bath The temperature of the coal in the reaction chamber is T Reaction chamber Wherein T is Oil bath And T Reaction chamber Respectively obtaining the temperature data through comprehensive consideration of multiple points of temperature data in each cavity so as to reduce data errors;
t is adjusted by controlling an electric heater to adjust the oil temperature Oil bath In the experimental process, the temperature difference between the oil bath cavity and the reaction chamber is ensured to be more than 0 ℃ and less than 2.5 ℃, wherein, the delta T is less than or equal to T Oil bath -T Reaction chamber 。
2. The apparatus for measuring the shortest natural ignition period of coal according to claim 1, wherein: the temperature sensor comprises an oil bath chamber platinum resistor I, an oil bath chamber platinum resistor II, an oil bath chamber platinum resistor III, an oil bath chamber platinum resistor IV, an oil bath chamber platinum resistor V, a reaction chamber platinum resistor I, a reaction chamber platinum resistor II, a reaction chamber platinum resistor III and a reaction chamber platinum resistor IV, wherein the oil bath chamber platinum resistor I and the oil bath chamber platinum resistor I are respectively arranged at the opposite side positions of the middle part of the inner side wall of the oil bath chamber, the oil bath chamber platinum resistor III is arranged at the inner wall of the oil inlet pipe interface, the oil bath chamber platinum resistor IV and the oil bath chamber platinum resistor V are respectively arranged at the inner wall of the two oil return pipe interfaces, the reaction chamber platinum resistor I and the reaction chamber platinum resistor III are respectively arranged at the opposite side positions of the middle part of the inner side wall of the reaction chamber, the reaction chamber platinum resistor III is arranged at the middle part of the bottom wall of the reaction chamber, the reaction chamber platinum resistor IV is arranged at the inner wall of the air outlet pipe interface, and the nine platinum resistors are electrically connected with the data collector.
3. The apparatus for measuring the shortest natural ignition period of coal according to claim 1, wherein: the device comprises a drying air source, an oil return pipe, an oil outlet pipe, a liquid flowmeter, a stop valve, a pressure reducing valve, a pressure stabilizing valve and a flow controller, wherein the liquid flowmeter is arranged in the oil inlet pipeline of the oxidation furnace, the two stop valves are respectively arranged at the external interfaces of the oil return pipe and the oil outlet pipe, the pressure reducing valve, the pressure stabilizing valve and the flow controller are sequentially arranged on the air guide pipe outside the drying air source, and the stop valve and the flow controller are respectively electrically connected with the motor.
4. A method for measuring the shortest natural ignition period of coal using the measuring apparatus for the shortest natural ignition period of coal according to claim 1, comprising the steps of:
step 1, adopting a coal bed coal sample;
step 2, preparing and managing the coal sample;
step 3, measuring the ignition temperature of the coal sample;
step 4, checking the state of equipment, and loading a coal sample in the checking process;
and 5, starting an air circuit and an oil circuit of the equipment, measuring and collecting air temperature, oil temperature and coal temperature data, and performing the following steps:
the temperature of the oil inlet isThe temperature of the oil outlet is->The temperature of the air inlet is +.>The temperature of the air outlet is->
1) Introducing dry air into the reaction chamber at a steady flow rate of 300mL/min, setting the temperature of the oil bath cavity at 40 ℃, and stabilizing the flow rate of the heat conducting oil at 10L/min;
2) After the temperature of the coal sample is stable, recording and calculating the temperature of the coal sample at the temperature of 40 ℃ of the oil bath cavityTemperature difference of oil inlet and returnAnd air inlet/outlet temperature difference->
3) Setting the temperature of an oil bath cavity to be 1.0 ℃/min for programmed temperature rise, and starting a data acquisition device to acquire data of air flow, air inlet and outlet temperature, heat conducting oil flow, oil inlet and return temperature, oil bath temperature and coal sample temperature;
4) When the temperature of the coal sample collected by the data collector exceeds the inlet temperature of the oil bath cavity, the temperature of the oil bath cavity is set to be maintained at the current temperature;
5) After the temperature of the coal sample is stable, stopping data acquisition, recording and calculating the temperature of the coal sampleTemperature difference of oil inlet and returnAnd air inlet/outlet temperature difference->The method comprises the steps of carrying out a first treatment on the surface of the Step 6, carrying out operation treatment on the recorded data to obtain the shortest natural ignition period result of the coal sample,
the calculation step of the shortest natural ignition period of the coal is as follows:
1) Calculating the coal chemical reaction rate parameter k a
2) Calculating the shortest natural ignition period tau of the coal, wherein the unit is day:
representative temperature of the coal sample in the furnace is T 0 When the coal sample generates heat due to self-heating, the unit is J/(m) 3 ·s)：
Representative temperature of the coal sample in the furnace is T 0 At the time, the heat dissipation amount accounts for the proportion of the heat generated by the self-heating effect of the coal sample:
the shortest natural ignition period tau of the coal:
。
5. the method for determining the shortest natural ignition period of coal according to claim 4, wherein: in step 2, the process flow of preparing and managing the coal sample is based on the specification related to GB474, and the following requirements should be met at the same time:
1) When the water content of the coal sample is high and the influence on the subsequent experiments is judged, the coal sample is naturally dried, and then all the coal sample is crushed to be less than 10 mm;
2) Dividing the coal sample into 300 g-350 g by using a cone stacking quartering method, and preparing and analyzing the coal sample, and sealing the rest coal samples according to the original package and sealing to obtain a stored coal sample;
3) The crushed coal sample is stored in a jar in a sealing way, and each measurement is completed within 30 days.
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