Similar experiment system and method for coal spontaneous combustion dynamic process characteristic determination

Abstract

The invention discloses a similar experiment system and method for coal spontaneous combustion dynamic process characteristic determination, and relates to the field of coal mining. A gas distribution system prepares nitrogen and oxygen into dry air; the dynamic sample adding coal sample tank is used for adding coal samples based on the similar sequence and step size of primary weighting and periodic weighting roof caving filling goaf in the mining process of the coal face, and a goaf residual coal spontaneous combustion dynamic process similar experiment is completed; the temperature programming box adjusts the furnace temperature and sets the temperature programming rate; analyzing a gas sample collected from a tail gas discharge port of the dynamic sample adding coal sample tank by a gas chromatograph; the temperature itinerant detector records the coal sample temperature collected by the temperature sensor after the coal sample is added; the data acquisition host acquires the temperature of coal and the components and concentration of tail gas in the dynamic sample adding process, calculates the oxidation oxygen consumption rate, the heat release rate and the like by adopting an oxidation kinetics method, and judges the dynamic law and process of spontaneous combustion of residual coal in a goaf in the dynamic mining process. According to the invention, coal spontaneous combustion dynamic process characteristic determination of coal sample dynamic addition is realized.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, and more particularly to a similar experimental system and method for measuring dynamic process characteristics of coal spontaneous combustion. Background Art

[0002] The main characteristics of thermal dynamic disasters in goafs are: concealment, coupling, dynamics, and complexity, which lead to the characteristics of high risk, difficult identification, difficult early warning, and difficult prevention and control. The coal mining face is a dynamic system. As the working face advances, the boundary between the working face and the goaf moves, the length of the air inlet and return tunnels shortens, and the length of the goaf increases. Once any area in the goaf is formed, its depth in the goaf increases dynamically as mining continues. Figure 1 , which determines that the goaf and various problems related to it are dynamic. In the process of dynamic change of the mining field, the areas that have been formed in the goaf are gradually compacted repeatedly with the passage of time and the gradual appearance and stabilization of roof collapse and pressure. The crushing coefficient is gradually reduced, which leads to the gradual reduction of the thickness, porosity, and permeability of the coal in any area that has been formed in the goaf with the continuous mining time. The air leakage rate will also decrease, and the concentration of gas such as gas will increase. Figure 1 The red circle marks the area. The changes in the leakage flow field and the accumulation and expansion characteristics of the coal residue lead to changes in the oxygen supply and heat dissipation state of the goaf, as well as changes in the outflow and distribution of toxic and harmful gases, which will inevitably lead to dynamic changes in the spontaneous combustion of the coal residue in the goaf, especially the dynamic changes in the distribution of the "three zones" of spontaneous combustion. During the mining process of the working face, there is a certain distance between the high-temperature area of ​​the coal residue in the goaf and the high-oxygen concentration area, and this distance changes dynamically. During the dynamic advancement process, this distance continues to shrink, and the heating rate of the goaf continues to increase. With the dynamic advancement of the working face and the gradual recovery of the stress in the goaf, the porosity of the coal residue in the goaf is dynamically reduced and the degree of fragmentation is dynamically increased, which will eventually lead to dynamic changes in the air leakage, gas migration, and spontaneous combustion of the coal residue in the goaf. To study the characteristics and process of spontaneous combustion of coal residue in the goaf, a dynamic method is needed to truly describe all the characteristics and processes of spontaneous combustion in the goaf. During the mining process of the working face, the broken coal left in the goaf begins to heat up under appropriate conditions after air leakage and high oxygen concentration, which triggers the beginning of spontaneous combustion. After that, the broken coal left in the goaf is continuously compacted and crushed, the air leakage flow rate decreases, the oxygen concentration decreases, and the concentration of gas and other factors continues to increase. The spontaneous combustion process develops dynamically. This dynamic development process has strong complexity, variability and contingency. The spontaneous combustion of the coal continues to evolve in a transient form during the dynamic coupling process of seepage, heat transfer and mass transfer. Therefore, when studying and preventing the spontaneous combustion of coal left in the goaf during normal mining, it is necessary to pay attention to the dynamic changes of related factors in the goaf.

[0003] As mining continues, the amount of residual coal in the goaf continues to increase. The newly exposed residual coal in the shallow part has a short contact time with oxygen, while the early formed residual coal in the deep part has a long contact time with air. However, as the working face continues to press, the wind flow received by the deep residual coal becomes less and less, and the airflow received gradually evolves into gas that has been oxidized and consumed by the shallow residual coal. The airflow that has been oxidized and consumed by the newly added shallow residual coal not only has a low oxygen content, but also a slightly higher temperature, and the CO, CO2, CH4 and hydrocarbon gases in the gas components gradually increase. The oxidation of deep early residual coal or residual coal along the leakage route will be significantly affected. Therefore, it is necessary to determine the order of adding relevant coal samples and the order of airflow inflow based on the formation sequence of residual coal in the goaf and the pressure law of the roof, combined with the flow route of the leakage airflow in the goaf, so as to obtain a law that is closer to and similar to the actual oxidation and spontaneous combustion of residual coal in the goaf.

[0004] Therefore, how to design a similar experimental system and method for determining the dynamic process characteristics of spontaneous combustion of coal in goafs that can realize dynamic addition of coal samples is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention provides a similar experimental system and method for measuring the dynamic process characteristics of coal spontaneous combustion, which solves the problems pointed out in the background technology.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A similar experimental system for determining the dynamic process characteristics of coal spontaneous combustion comprises: a gas distribution system, a program temperature rise box, a dynamic sample addition coal sample tank, a gas chromatograph, a temperature patrol meter, and a data acquisition host; two air inlets of the gas distribution system are respectively connected to a nitrogen bottle and an oxygen bottle, and the gas outlet of the gas distribution system is connected to the dynamic sample addition coal sample tank; the dynamic sample addition coal sample tank is respectively connected to the gas chromatograph and the temperature patrol meter, and the output ends of the gas chromatograph and the temperature patrol meter are both connected to the data acquisition host;

[0008] A gas distribution system, used to mix nitrogen and oxygen into dry air and input it into the dynamic sampling coal sample tank;

[0009] Dynamic sampling coal sample tank, based on the similar order and step size of the initial pressure and periodic pressure of the roof collapse filling the goaf during the mining process of the coal mining face, adds coal samples to complete the similar experiment of the dynamic process of spontaneous combustion of coal in the goaf;

[0010] Programmable temperature rise box, used to adjust the furnace temperature and set the program heating rate;

[0011] A gas chromatograph, used to analyze and test the gas samples collected from the tail gas outlet of the dynamic sampling coal sample tank;

[0012] A temperature inspection instrument is used to record the temperature of the coal sample of the temperature sensor in the coal sample after the coal sample is added;

[0013] The data acquisition host is used to obtain the temperature of the coal and the composition and concentration of the tail gas during the dynamic sampling process. After the experiment is completed, the oxidation kinetics method is used to calculate the oxidation oxygen consumption rate and heat release rate based on the temperature of the coal and the composition and concentration of the tail gas, so as to determine the dynamic laws and progress of spontaneous combustion of the coal left in the goaf during dynamic mining.

[0014] Optionally, it also includes a gas distribution system output switch valve, a tee, a gas circuit switch valve, and a gas flow meter. The prepared dry air flows through the gas distribution system output switch valve, the tee, and then through the gas circuit switch valve and the gas flow meter into two dynamic sampling coal sample tanks respectively.

[0015] Optionally, the dynamic sample adding coal sample tank includes: a feed funnel, a coal sample tank plug, a 304 stainless steel connecting pipe, a feed pipe switch valve, a temperature sensor, a coal sample tank air inlet pipe, a copper net to prevent coal sample leakage, an air outlet pipe, and a coal sample tank bracket;

[0016] The outlet of the feed funnel is opposite to the plug of the coal sample tank, the plug of the coal sample tank is plugged into the 304 stainless steel connecting pipe, and the 304 stainless steel connecting pipe is plugged into the coal sample tank;

[0017] A feed pipe switch valve is provided on the 304 stainless steel connecting pipe, and several temperature sensors are provided along the depth direction in the coal sample tank;

[0018] The dry air prepared by the gas distribution system flows into the coal sample tank from the top through the coal sample tank air inlet pipe. A copper net and an air outlet pipe are provided near the bottom of the coal sample tank to prevent coal sample leakage, and a coal sample tank bracket is provided at the bottom of the coal sample tank.

[0019] Optionally, the temperature inspection instrument is connected to the temperature sensor via a temperature transmission data line.

[0020] Optionally, the gas outlet pipe is connected to a gas chromatograph.

[0021] A similar experimental method for measuring the dynamic process characteristics of coal spontaneous combustion is applied to the similar experimental system for measuring the dynamic process characteristics of coal spontaneous combustion described above, and comprises the following steps:

[0022] S1. Assume that the natural combustion period of the coal in the goaf is t days, the first pressure time is t1 days, and the periodic pressure time is t r day, and the mining advance speed is vm / d, then as the working face is mined, when the depth or length of the goaf is greater than t v When the coal in the mining area spontaneously combusts;

[0023] S2, nitrogen and oxygen are mixed into dry air according to the nitrogen and oxygen ratio in the air through the two-way gas distribution system, and the prepared dry air flows through the output switch valve of the gas distribution system through the three-way and then through the gas circuit switch valve and the gas flow meter into the two dynamic sample addition coal sample tanks respectively, and the gas distribution and air intake pipelines are closed at this time;

[0024] S3. At the beginning of the experiment, the first coal sample to be pressed is first added to the two dynamic sample adding coal sample tanks. Assuming that the total height of the effective added coal sample in the dynamic sample adding coal sample tank is L, the height of the first added coal sample is simplified to:

[0025] S4. Open the nitrogen bottle, and let the nitrogen flow into the dynamic sample adding coal sample tank through the gas distribution system. Open the heating program of the program heating box and set the program heating rate to h. t ℃ / min, initial ambient temperature is T e The temperature starts to rise from here, and the end temperature is set to T s , then the total time required for similar experiments is: During the experimental period It represents the equivalent conversion quantity of the time of similar experimental process and the actual ignition period t;

[0026] S5. Adjust the nitrogen flow rate, open the oxygen cylinder at a ratio of 21:79 of oxygen and nitrogen according to the gas flow rate required for the experiment, and mix it through the gas distribution system to prepare dry air with a flow rate of Q, which enters the air intake pipeline;

[0027] S6. According to the time required for the experiment, gas samples are collected from the tail gas outlet of the dynamic sample addition coal sample tank and analyzed and tested by gas chromatograph. The actual gas collection is based on the furnace temperature rising by 10°C, starting from the furnace temperature of 40°C to the end of the experiment, and the gas sampling is completed before the periodic pressure coal sample is added;

[0028] S7, start the experiment time At 15 minutes, add the coal sample for the first cycle of pressing. The height of the coal sample added each time is

[0029] S8. After multiple additions, the experiment can be stopped when the number of dynamic additions of coal samples and the amount of coal samples reach the predetermined experimental purpose, and the coal sample addition process and the corresponding position of the temperature sensor are recorded;

[0030] S9. According to the coal oxidation kinetics theory, based on the oxygen concentration, carbon oxide concentration, and hydrocarbon gas concentration of the gas sample test, the height of the coal sample or the height difference between the inlet and outlet ends in the calculation formula is used as the basis for dynamic calculation based on the dynamically changing height of the coal sample;

[0031] S10. According to the oxidation oxygen consumption rate and heat release rate of coal during the dynamic sampling process, determine the index gas generation law and the oxidation kinetic index change law, the coal sample temperature increase law during the dynamic sampling process, and judge the dynamic law and process of spontaneous combustion of coal in the goaf during dynamic mining.

[0032] Optionally, the natural combustion period of the residual coal in the goaf is the time required for the coal temperature in the goaf to rise from the underground temperature to 70°C.

[0033] It can be seen from the above technical scheme that compared with the prior art, the present invention provides a similar experimental system and method for determining the dynamic process characteristics of coal spontaneous combustion, and provides an experimental detection system and method for the oxidation and spontaneous combustion laws of residual coal in the process of dynamic expansion of the goaf and dynamic increase of residual coal as the working face is mined. The main beneficial effects include: the similar experimental system and method can gradually add coal samples according to the actual dynamic expansion law of the goaf, and can achieve effective similar reflection of the differences in oxidation time and oxidation degree of the residual coal in the goaf due to the differences in mining time; the oxidation kinetics calculation results obtained by the dynamic similar experimental system and method can reflect the segmented and average characteristics of the oxidation kinetics of residual coal in different regions or depths formed at different times in the actual goaf, and can significantly improve the prediction accuracy and reliability of the spontaneous combustion state of residual coal in non-uniform, asymmetric and dynamic goafs. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0035] Figure 1 The dynamic distribution diagram of the flow field and concentration field of the coal residue range in the goaf during the mining process provided by the present invention;

[0036] Figure 2 A structural diagram of a similar experimental system for measuring the dynamic process characteristics of coal spontaneous combustion provided by the present invention;

[0037] Figure 3 A schematic diagram of a coal sample adding process for simulating the initial pressure and periodic pressure roof collapse provided by the present invention;

[0038] FIG. 4( a ) and FIG. 4( b ) are schematic diagrams of the temperature change in the constant-height coal sample tank and the temperature change in the dynamic-sampling coal sample tank provided by the present invention, respectively;

[0039] Figure 5 A schematic diagram of oxygen concentration change provided by the present invention;

[0040] Figure 6 A schematic diagram of carbon monoxide concentration change provided by the present invention;

[0041] Figure 7 A schematic diagram of the change of carbon dioxide concentration provided by the present invention;

[0042] Figure 8 A schematic diagram of the change law of oxygen consumption rate provided by the present invention;

[0043] Fig. 9 A schematic diagram of the carbon monoxide generation rule provided by the present invention;

[0044] Fig.10 A schematic diagram of the carbon dioxide generation law provided by the present invention;

[0045] Fig.11 A schematic diagram of the maximum heat release rate variation law provided by the present invention;

[0046] Fig.12 A schematic diagram of the variation law of the minimum heat release rate provided by the present invention;

[0047] Figure markings: 1-oxygen cylinder, 2-nitrogen cylinder, 3-gas distribution system, 4-gas distribution system output switch valve, 5-tee, 6-gas circuit switch valve, 7-gas flow meter, 8-feeding funnel, 9-coal sample, 10-coal sample tank plug (inner thread), 11-304 stainless steel connecting pipe, 12-feeding pipe switch valve, 13-temperature sensor, 14-temperature transmission data line, 15-coal sample tank air inlet pipe, 16-coal sample leakage prevention copper net, 17-air outlet pipe, 18-coal sample tank bracket, 19-programmed temperature rising box, 20-temperature patrol meter, 21-gas chromatograph, 22-data acquisition host. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] The embodiment of the present invention discloses a similar experimental system for measuring the dynamic process characteristics of coal spontaneous combustion, such as Figure 2As shown, it includes: a gas distribution system 3, a program temperature rising box 19, a dynamic sample adding coal sample tank, a gas chromatograph 21, a temperature patrol meter 20, and a data acquisition host 22; the two air inlets of the gas distribution system 3 are respectively connected to the nitrogen cylinder 2 and the oxygen cylinder 1, and the gas outlet of the gas distribution system 3 is connected to the dynamic sample adding coal sample tank; the dynamic sample adding coal sample tank is respectively connected to the gas chromatograph 21 and the temperature patrol meter 20, and the output ends of the gas chromatograph 21 and the temperature patrol meter 20 are both connected to the data acquisition host 22;

[0050] A gas distribution system 3, used for mixing nitrogen and oxygen into dry air and inputting the dry air into the dynamic sampling coal sample tank;

[0051] Dynamically add coal sample tank, add coal sample 9 based on the similar sequence and step size of the initial pressure and periodic pressure of roof collapse filling the goaf during the mining process of the coal mining face, and complete the similar experiment of the dynamic process of spontaneous combustion of coal in the goaf;

[0052] A program heating box 19 is used to adjust the furnace temperature and set the program heating rate;

[0053] A gas chromatograph 21, used for analyzing and testing the gas sample collected from the tail gas discharge port of the dynamic sampling coal sample tank;

[0054] A temperature inspection instrument 20, used to record the temperature of the coal sample collected by the temperature sensor 13 in the coal sample 9 after the addition of the coal sample 9 is completed;

[0055] The data acquisition host 22 is used to obtain the temperature of the coal and the composition and concentration of the tail gas during the dynamic sampling process. After the experiment is completed, the oxidation kinetics method is used to calculate the oxidation oxygen consumption rate, heat release rate, etc. according to the temperature of the coal and the composition and concentration of the tail gas, so as to determine the dynamic law and progress of spontaneous combustion of the coal in the goaf during the dynamic mining process.

[0056] Furthermore, it also includes a gas distribution system output switch valve 4, a tee 5, a gas circuit switch valve 6, and a gas flow meter 7. The prepared dry air flows through the gas distribution system output switch valve 4, the tee 5, and then through the gas circuit switch valve 6 and the gas flow meter 7 to enter the two dynamic sampling coal sample tanks respectively.

[0057] Furthermore, the dynamic sample adding coal sample tank comprises: a feed funnel 8, a coal sample tank plug 10, a 304 stainless steel connecting pipe 11, a feed pipe switch valve 12, a temperature sensor 13, a coal sample tank air inlet pipe 15, a copper mesh to prevent coal sample leakage 16, an air outlet pipe 17, and a coal sample tank bracket 18;

[0058] The outlet of the feed funnel 8 is opposite to the coal sample tank plug 10, the coal sample tank plug 10 is plugged into the 304 stainless steel connecting pipe 11, and the 304 stainless steel connecting pipe 11 is plugged into the coal sample tank;

[0059] A feed pipe switch valve 12 is provided on the 304 stainless steel connecting pipe 11, and a plurality of temperature sensors 13 are provided in the coal sample tank along the depth direction;

[0060] The dry air prepared by the gas distribution system 3 flows into the coal sample tank from the top through the coal sample tank air inlet pipe 15. A copper mesh 16 to prevent coal sample leakage and an air outlet pipe 17 are arranged near the bottom of the coal sample tank, and a coal sample tank bracket 18 is arranged at the lower side of the coal sample tank.

[0061] Furthermore, the temperature inspection instrument 20 is connected to the temperature sensor 13 via a temperature transmission data line 14 .

[0062] Furthermore, the gas outlet pipe 17 is connected to a gas chromatograph 21 .

[0063] This embodiment establishes Figure 2 The similar experimental system for determining the dynamic process characteristics of coal spontaneous combustion shown in the figure has a gas supply system, a programmed temperature system, a dynamic sample adding tank system, a temperature monitoring system, etc., which can realize the dynamic addition of coal sample 9 and the free collection of gas samples. The coal sample 9 can be added in a similar order and step size according to the initial pressure and periodic pressure of the roof collapse and filling of the goaf during the working face mining process. At the same time, the system adopts the method of dynamically adding coal sample 9 with air intake at the upper end and air outlet at the tail end to supply airflow.

[0064] This embodiment also discloses a similar experimental method for measuring the dynamic process characteristics of coal spontaneous combustion, which is applied to the similar experimental system for measuring the dynamic process characteristics of coal spontaneous combustion described above, and includes the following steps:

[0065] S1. Assume that the natural ignition period of the coal in the goaf (the time required for the coal temperature in the goaf to rise from the underground temperature to 70°C) is t days, the initial pressure time is t1 days, and the periodic pressure time is t r day, and the mining advance speed is vm / d, then as the working face is mined, when the depth or length of the goaf is greater than t v When the coal in the mining area spontaneously combusts;

[0066] S2, nitrogen and oxygen are mixed into dry air according to the nitrogen and oxygen ratio in the air through the two-way gas distribution system 3, and the prepared dry air flows through the output switch valve 4 of the gas distribution system, flows through the three-way 5, and then passes through the gas circuit switch valve 6 and the gas flow meter 7 to enter the two dynamic sample addition coal sample tanks respectively, and the gas distribution and air intake pipelines are closed at this time;

[0067] S3. At the beginning of the experiment, the first pressurized coal sample 9 is first added to the two dynamic sample adding coal sample tanks. Assuming that the total height of the effective added coal sample 9 in the dynamic sample adding coal sample tank is L, the height of the first added coal sample is simplified to:

[0068] S4, open the nitrogen bottle 2, the nitrogen flows into the dynamic sample adding coal sample tank through the gas distribution system 3, open the heating program of the program heating box 19, and set the program heating rate to h t ℃ / min, initial ambient temperature is T e The temperature starts to rise from here, and the end temperature is set to T s , then the total time required for similar experiments is: During the experimental period It represents the equivalent conversion quantity of the time (minutes) of similar experimental process and the actual ignition period t (days);

[0069] S5, adjust the nitrogen flow rate, open the oxygen cylinder 1 according to the gas flow rate required by the experiment with a ratio of 21:79 between oxygen and nitrogen, and mix it through the gas distribution system 3 to prepare dry air with a flow rate of Q, and enter the air intake pipeline;

[0070] S6. According to the time required for the experiment, gas samples are collected from the tail gas outlet of the dynamic sample addition coal sample tank and analyzed and tested using a gas chromatograph 21. The actual gas collection is based on the furnace temperature rising by 10°C, starting from the furnace temperature of 40°C to the end of the experiment, and the gas sampling is completed before the periodic pressure coal sample is added;

[0071] S7, start the experiment time At 15 minutes, add the coal sample 9 for the first cycle of pressure, and the height of the coal sample added each time is

[0072] S8. According to the above sequence and procedures, the time increases Minutes, add After multiple additions, the number of dynamic additions of coal samples and the amount of coal samples reach the predetermined experimental purpose, and the experiment can be stopped, and the addition process of the coal sample 9 and the corresponding position of the temperature sensor 13 are recorded. Figure 3 and Table 1;

[0073] S9. According to the coal oxidation kinetics theory, based on the oxygen concentration, carbon oxide concentration, hydrocarbon gas concentration, etc. of the gas sample test, the height of the coal sample or the height difference between the inlet and outlet ends in the calculation formula is used as the basis for dynamic calculation based on the dynamically changing height of the coal sample;

[0074] S10. According to the oxidation oxygen consumption rate and heat release rate of coal during the dynamic sampling process, determine the index gas generation law and the oxidation kinetic index change law, the coal sample temperature increase law during the dynamic sampling process, and judge the dynamic law and process of spontaneous combustion of coal in the goaf during dynamic mining.

[0075] Table 1 Coal sample adding process in the experimental tank

[0076]

[0077] Specifically, taking the mining advance of 6m / d, the ignition period of 30d, the initial pressure distance of 30m, and the periodic pressure step distance of 15m as an example, the spontaneous combustion phenomenon in the goaf should occur after 30 days of mining, that is, after the depth of the goaf is greater than 180m. Therefore, based on the calculation basis of the goaf depth of 180m, deducting the initial pressure of 30m, the remaining 150m, according to the weekly pressure step distance of 15m, 10 subsequent pressures are required. During the experiment, the program heating rate was 0.5℃ / min, the furnace temperature around the experiment was increased from 30℃ to 210℃, and the experiment took 360min. According to the research plan and method of similar experimental system, tank 1 directly added 36cm of coal sample for the first time as the control experimental tank; tank 2 initially added 6cm of coal sample as the coal sample corresponding to the first pressing. During the subsequent cycle pressing, it was considered to merge the two-step cycle pressing into one, that is, merge the two cycle pressing together as a coal sample adding opportunity, that is, add 5 coal samples in the middle. The specific coal sample adding process is shown in Table 2.

[0078] Table 2 Coal sample addition process in experimental tank 2

[0079]

[0080] The temperature variation patterns obtained during the experiment are shown in Figure 4(a) and Figure 4(b). The concentration variation patterns of oxygen, carbon monoxide, and carbon dioxide during the experiment are shown in Figure 4(a) and Figure 4(b). Figure 5-Figure 7 According to the oxidation kinetics theory and method, combined with Figure 5-Figure 7 The obtained oxygen concentration, carbon monoxide concentration, carbon dioxide concentration, etc. are calculated Figure 8-Figure 12 The shown patterns are the changing patterns of oxygen consumption rate, carbon monoxide generation rate, carbon dioxide generation rate, and maximum and minimum heat release rates.

[0081] The results of relevant kinetic calculations show that when the furnace temperature is lower than 160°C, that is, after the fourth addition of coal samples (simulating the 7th-8th cycle pressure), the average oxygen consumption rate and maximum heat release rate of coal in the process of dynamically adding coal samples according to the cycle pressure law of the goaf roof are gradually lower than those of the control group, and the relative difference between the two gradually increases. Before that, the difference between the two was not large. Therefore, it can be judged that the oxygen consumption rate gradually increases during the dynamic increase of coal samples. When the cycle pressure exceeds 8 times, the oxygen consumption rate and maximum heat release rate of the coal left in the goaf gradually increase. Lower than the non-dynamic process. The experimental results show that the dynamic experimental system and experimental method established in this embodiment can obtain the spontaneous combustion process of coal in the dynamic addition process of coal samples.

[0082] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other. The above description of the disclosed embodiments enables professionals and technicians in this field to implement or use the present invention. Various modifications to these embodiments will be obvious to professionals and technicians in this field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown in this article, but will comply with the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A similar experimental system for measuring the dynamic process characteristics of coal spontaneous combustion, characterized in that: include: Gas distribution system, programmed temperature box, dynamic sample addition coal sample tank, gas chromatograph, temperature patrol meter, data acquisition host; the two air inlets of the gas distribution system are connected to the nitrogen cylinder and the oxygen cylinder respectively, and the gas outlet of the gas distribution system is connected to the dynamic sample addition coal sample tank; the dynamic sample addition coal sample tank is connected to the gas chromatograph and the temperature patrol meter respectively, and the output ends of the gas chromatograph and the temperature patrol meter are connected to the data acquisition host; A gas distribution system, used to mix nitrogen and oxygen into dry air and input it into the dynamic sampling coal sample tank; Dynamic sampling coal sample tank, based on the similar order and step size of the initial pressure and periodic pressure of the roof collapse filling the goaf during the mining process of the coal mining face, adds coal samples to complete the similar experiment of the dynamic process of spontaneous combustion of coal in the goaf; Programmable temperature rise box, used to adjust the furnace temperature and set the program heating rate; A gas chromatograph, used to analyze and test the gas samples collected from the tail gas outlet of the dynamic sampling coal sample tank; A temperature inspection instrument is used to record the temperature of the coal sample collected by the temperature sensor in the coal sample after the coal sample is added; The data acquisition host is used to obtain the temperature of the coal and the composition and concentration of the tail gas during the dynamic sampling process. After the experiment is completed, the oxidation kinetics method is used to calculate the oxidation oxygen consumption rate and heat release rate based on the temperature of the coal and the composition and concentration of the tail gas, so as to determine the dynamic laws and progress of spontaneous combustion of the coal left in the goaf during dynamic mining.

2. A similar experimental system for measuring the dynamic process characteristics of coal spontaneous combustion according to claim 1, characterized in that: It also includes a gas distribution system output switch valve, a tee, a gas circuit switch valve, and a gas flow meter. The prepared dry air flows through the gas distribution system output switch valve, the tee, and then through the gas circuit switch valve and the gas flow meter into two dynamic sampling coal sample tanks respectively.

3. A similar experimental system for measuring the dynamic process characteristics of coal spontaneous combustion according to claim 1, characterized in that: The dynamic sample adding coal sample tank includes: feed funnel, coal sample tank plug, 304 stainless steel connecting pipe, feed pipe switch valve, temperature sensor, coal sample tank air inlet pipe, copper net to prevent coal sample leakage, air outlet pipe, coal sample tank bracket; The outlet of the feed funnel is opposite to the plug of the coal sample tank, the plug of the coal sample tank is plugged into the 304 stainless steel connecting pipe, and the 304 stainless steel connecting pipe is plugged into the coal sample tank; A feed pipe switch valve is provided on the 304 stainless steel connecting pipe, and several temperature sensors are provided along the depth direction in the coal sample tank; The dry air prepared by the gas distribution system flows into the coal sample tank from the top through the coal sample tank air inlet pipe. A copper net and an air outlet pipe are provided near the bottom of the coal sample tank to prevent coal sample leakage, and a coal sample tank bracket is provided at the bottom of the coal sample tank.

4. A similar experimental system for measuring the dynamic process characteristics of coal spontaneous combustion according to claim 3, characterized in that: The temperature inspection instrument is connected to the temperature sensor via a temperature transmission data line.

5. A similar experimental system for measuring the dynamic process characteristics of coal spontaneous combustion according to claim 3, characterized in that: The gas outlet pipe is connected to the gas chromatograph.

6. A similarity experiment method for measuring the dynamic process characteristics of coal spontaneous combustion, applied to a similarity experiment system for measuring the dynamic process characteristics of coal spontaneous combustion as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Assume that the natural combustion period of the coal in the goaf is t days, the first pressure time is t1 days, and the periodic pressure time is t r day, and the mining advancement speed is vm / d. Then, with the mining of the working face, when the depth or length of the goaf is greater than tv, the coal left in the mining area will spontaneously combust; S2, nitrogen and oxygen are mixed into dry air according to the nitrogen and oxygen ratio in the air through the two-way gas distribution system, and the prepared dry air flows through the output switch valve of the gas distribution system through the three-way and then through the gas circuit switch valve and the gas flow meter into the two dynamic sample addition coal sample tanks respectively, and the gas distribution and air intake pipelines are closed at this time; S3. At the beginning of the experiment, the first coal sample to be pressed is first added to the two dynamic sample adding coal sample tanks. Assuming that the total height of the effective added coal sample in the dynamic sample adding coal sample tank is L, the height of the first added coal sample is simplified to: S4. Open the nitrogen bottle, and let the nitrogen flow into the dynamic sample adding coal sample tank through the gas distribution system. Open the heating program of the program heating box and set the program heating rate to h. t ℃ / min, initial ambient temperature is T e The temperature starts to rise from here, and the end temperature is set to T s , then the total time required for similar experiments is: During the experimental period It represents the equivalent conversion quantity of the time of similar experimental process and the actual ignition period t; S5. Adjust the nitrogen flow rate, open the oxygen cylinder at a ratio of 21:79 of oxygen and nitrogen according to the gas flow rate required for the experiment, and mix it through the gas distribution system to prepare dry air with a flow rate of Q, which enters the air intake pipeline; S6. According to the time required for the experiment, gas samples are collected from the tail gas outlet of the dynamic sample addition coal sample tank and analyzed and tested by gas chromatograph. The actual gas collection is based on the furnace temperature rising by 10°C, starting from the furnace temperature of 40°C to the end of the experiment, and the gas sampling is completed before the periodic pressure coal sample is added; S7, start the experiment time At 15 minutes, add the coal sample for the first cycle of pressing. The height of the coal sample added each time is S8. After multiple additions, the experiment can be stopped when the number of dynamic additions of coal samples and the amount of coal samples reach the predetermined experimental purpose, and the coal sample addition process and the corresponding position of the temperature sensor are recorded; S9. According to the coal oxidation kinetics theory, based on the oxygen concentration, carbon oxide concentration, and hydrocarbon gas concentration of the gas sample test, the height of the coal sample or the height difference between the inlet and outlet ends in the calculation formula is used as the basis for dynamic calculation based on the dynamically changing height of the coal sample; S10. According to the oxidation oxygen consumption rate and heat release rate of coal during the dynamic sampling process, determine the index gas generation law and the oxidation kinetic index change law, the coal sample temperature increase law during the dynamic sampling process, and judge the dynamic law and process of spontaneous combustion of coal in the goaf during dynamic mining.

7. A similar experimental method for measuring the dynamic process characteristics of coal spontaneous combustion according to claim 6, characterized in that: The spontaneous combustion period of the residual coal in the goaf is the time required for the coal temperature in the goaf to rise from the underground temperature to 70℃.

Images