Fire preventing and extinguishing method for inhibiting spontaneous combustion of coal in goaf through porous material temperature control desorption inert gas

Abstract

The invention belongs to the field of coal mine goaf fire prevention and extinguishment, and relates to a fire prevention and extinguishment method for inhibiting goaf coal spontaneous combustion through porous material temperature control inert gas desorption, and the method comprises the following steps: step a, putting a porous material into a container, and injecting inert gas into the container by pressure to enable the porous material to reach adsorption equilibrium; the pressure in the container is the optimal adsorption equilibrium pressure of the porous material; b, the porous material reaching the adsorption equilibrium pressure is put into the goaf of the coal mine; c, after the temperature in the goaf rises, the inert gas in the porous material is heated, desorbed and released into the goaf. The stable chemical property of the porous material is utilized, long-term storage of inert gas under the normal temperature condition and controllable release under the temperature rising condition can be achieved, the accuracy and economical efficiency of a conventional inert gas fire preventing and extinguishing technology are improved, and spontaneous combustion of coal in the goaf of a coal mine can be effectively restrained.

Description

Technical Field

[0001] The invention belongs to the field of fire prevention and extinguishing in coal mine goafs, and specifically relates to a fire prevention and extinguishing method for suppressing spontaneous combustion of coal in goafs by temperature-controlled desorption of inert gas by porous materials. Background Art

[0002] Due to the influence of coal seam geological conditions, mining technology, ventilation conditions and coal's own characteristics, coal spontaneous combustion is one of the main disasters that occur during coal mining. The occurrence of coal spontaneous combustion disasters will result in the loss of a large number of mining equipment and high-quality coal resources, seriously endangering the lives and health of underground personnel. In addition, the high-temperature flue gas generated during the coal spontaneous combustion process may cause ventilation system disorders, reverse normal airflow, and even cause gas and coal dust explosion accidents. In response to coal spontaneous combustion disasters, scholars started from the basic conditions of coal spontaneous combustion and successively proposed grouting, equalization, inhibitors, gel and inert gas fire prevention and extinguishing technologies. The research and development of coal mine fire prevention and extinguishing technology is of great significance to reducing resource waste and ensuring safe production in coal mines.

[0003] When spontaneous combustion of coal is detected in the goaf, inert gas is often injected into the mine over a large area to extinguish the fire. Inert gas injected into the goaf can significantly reduce the oxygen concentration in the coal oxidation environment, and has a good control effect on large open flames and high-temperature areas hidden in the goaf. However, due to factors such as the thermal conductivity of the coal body itself, air leakage and coal-rock obstacles, commonly used coal spontaneous combustion monitoring and early warning technologies such as the signature gas method and the temperature measurement method have a lag and can only determine the approximate location of the hidden fire source. If fire prevention and extinguishing technologies are adopted based solely on these coal spontaneous combustion monitoring and early warning technologies, the best time to prevent and control coal spontaneous combustion may be missed. At the same time, inert gas is easy to spread and cannot stay in the dangerous area for a long time. Although large-scale injection of inert gas can overcome the problem of easy diffusion of inert gas, the use of this technology is somewhat blind because the location of the fire source is unknown, which increases the cost of fire prevention and extinguishing work.

[0004] Therefore, a new inert gas fire prevention and extinguishing technology is urgently needed to improve the efficiency and economy of coal spontaneous combustion disaster prevention and control measures in goaf areas. Summary of the invention

[0005] In order to overcome the problems of lag, blindness and high cost in the prior art coal spontaneous combustion disaster prevention and control measures, the present invention provides a fire prevention and extinguishing method for suppressing spontaneous combustion of coal in goaf areas by temperature-controlled desorption of inert gas by porous materials. The porous material used in the method can store inert gas for a long time under normal temperature conditions. When the ambient temperature rises, the porous material is heated to desorb inert gas, which dilutes the oxygen concentration in the environment surrounding the coal and suppresses the coal-oxygen complex reaction, thereby achieving the effect of temperature control to suppress spontaneous combustion of coal in goaf areas, and solving the blindness and high cost of traditional inert gas fire prevention and extinguishing measures.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A fire prevention and extinguishing method for suppressing spontaneous combustion of coal in goaf by temperature-controlled desorption of inert gas by porous materials, comprising the following steps:

[0008] Step a: Place the porous material in a container and inject inert gas into it to make the porous material reach adsorption equilibrium; when the pressure in the container remains unchanged, the porous material is considered to have reached adsorption equilibrium; the pressure in the container is the optimal adsorption equilibrium pressure of the porous material. When the pressure in the container is lower than the optimal adsorption equilibrium pressure of the porous material, the container should be pressurized in time; the optimal adsorption equilibrium pressure of the porous material is determined by adsorption-desorption experiment.

[0009] Step b: placing the porous material that has reached adsorption equilibrium into the coal mine goaf;

[0010] Step c: When the temperature in the goaf increases, the inert gas in the porous material is desorbed by heat and released into the goaf, so as to achieve temperature-controlled release of the inert gas to prevent and extinguish coal spontaneous combustion. Fig. 9 shown.

[0011] Preferably, the porous material is prepared by using coal gangue, NaOH solution and sodium silicate aqueous solution, wherein the sodium silicate aqueous solution is a binder.

[0012] Preferably, the preparation of the porous material comprises the following steps:

[0013] (1) calcining the coal gangue at 600-800°C for 2h, and adjusting the molar ratio of SiO2 to Al2O3 to 2-2.5:1 by adding Al2O3. This step aims to make full use of the silicon in the coal gangue and make the crystallization process more complete;

[0014] (2) Adding a 1.8-3.0 mol / L NaOH solution to the pretreated gangue, with the mass ratio of the pretreated gangue to the NaOH solution being 1:3, placing the two in a 65°C water bath and stirring for 6 hours to obtain a slurry. This step can create the necessary conditions for the subsequent crystallization process;

[0015] (3) transferring the slurry to a Teflon-lined reactor and crystallizing at 80-100°C for 3-12 hours;

[0016] (4) filtering, drying, grinding, and adding a 20%-30% sodium silicate aqueous solution to the crystals to make a paste; the amount of the sodium silicate aqueous solution added is 5%-10% of the mass of the crystals.

[0017] (5) Forming spherical particles in a granulator and drying the formed particles; finally, calcining the granular material at 105° C. for 2 h to remove the binder and improve its stability.

[0018] The porous material prepared above has uniform physical structure, stable chemical properties and high thermal stability. In addition, the porous material prepared has a certain adsorption and desorption capacity for inert gas, can ensure long-term storage of adsorbed gas under normal temperature conditions (below 30°C), and can achieve effective release of adsorbed gas under elevated temperature conditions.

[0019] Preferably, the condition parameters for determining the optimal adsorption equilibrium pressure of the porous material for the inert gas in step a include: the cumulative desorption amount of the inert gas and the desorption rate of the inert gas.

[0020] Preferably, the basis for determining the optimal adsorption equilibrium pressure of the porous material for the inert gas in step a is: comparing the desorption characteristics (including desorption amount and desorption rate values) of the porous material for the inert gas under different adsorption equilibrium pressures, analyzing at which adsorption equilibrium pressure the porous material has the maximum desorption amount or the fastest desorption rate value for the inert gas, and then determining that the adsorption equilibrium pressure is the optimal adsorption equilibrium pressure. Determination of the cumulative desorption amount and desorption rate value of the inert gas: The porous material adsorbs the inert gas at different adsorption equilibrium pressures, and after free desorption for more than 24 hours, the total desorption amount and desorption rate during the period of heating to 75°C are measured.

[0021] Preferably, the inert gas includes carbon dioxide, nitrogen and the like.

[0022] Preferably, the mass ratio of the porous material to the coal in the goaf of the coal mine is above 50%.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention uses porous materials as adsorbents and inert gases such as carbon dioxide as adsorbents. When the ambient temperature rises, the porous materials will release the adsorbed inert gases, thereby achieving temperature-controlled release of the inert gases and reducing waste of the inert gases. The inert gases dilute the oxygen concentration around the fire zone and cut off the coal oxidation reaction process, thereby achieving the purpose of efficiently preventing and controlling spontaneous combustion of coal in goaf areas. Compared with traditional inert gas fire prevention and extinguishing technology, this method provides a new idea for research in the field of preventing and controlling spontaneous combustion of coal. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a graph showing the relationship between the cumulative desorption amount of CO2, temperature, and adsorption equilibrium pressure.

[0026] Figure 2 This is the curve of CO2 concentration changing with temperature for raw coal sample and mixed sample.

[0027] Figure 3 The CO concentration of the raw coal sample and the mixed sample changes with temperature.

[0028] Figure 4This is the curve of O2 concentration changing with temperature for raw coal sample and mixed sample.

[0029] Figure 5 This is the temperature rise characteristic curve of raw coal sample and mixed sample.

[0030] Figure 6 This is a curve of CO2 concentration changing with temperature for samples with different mixing ratios of coal samples and porous materials.

[0031] Figure 7 This is a curve of O2 concentration changing with temperature for samples with different mixing ratios of coal sample and porous material.

[0032] Figure 8 This is the temperature rise characteristic curve of samples with different mixing ratios of coal samples and porous materials.

[0033] Fig. 9 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all 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.

[0035] Example 1

[0036] The preparation of the porous material comprises the following steps:

[0037] (1) First, the coal gangue was calcined at 800 °C for 2 h, and the molar ratio of SiO2 to Al2O3 was adjusted to 2.5:1 by adding additional Al2O3;

[0038] (2) then mixing the pretreated coal gangue with a 1.8 mol / L NaOH solution at a mass ratio of 1:3, and stirring the prepared slurry in a 65° C. water bath for 6 h to obtain a slurry;

[0039] (3) The slurry was then transferred to a Teflon-lined reactor and crystallized at 100 °C for 12 h;

[0040] (4) filtering, drying, grinding, and adding a sodium silicate aqueous solution (20% concentration) to the crystals to make a paste; the amount of the sodium silicate aqueous solution added is 5% of the weight of the crystals.

[0041] (5) Spherical particles are formed in a granulator and the formed particles are dried; finally, the granular material is calcined at a high temperature of 105° C. for 2 hours to remove the binder and improve its stability.

[0042] Example 2

[0043] A method for preventing and extinguishing fire by controlling the temperature of porous materials to desorb inert gas to suppress spontaneous combustion of coal in goaf areas comprises the following steps:

[0044] (1) Fresh bituminous coal was collected on site, sealed and stored, and sent to the laboratory. The bituminous coal and the porous material prepared in Example 1 were ground and crushed using a sample preparation pulverizer, and the particles with a size of 30-80 mesh were sieved and placed in a vacuum drying oven for 24 hours to eliminate the influence of external moisture in the bituminous coal and the porous material.

[0045] (2) The equilibrium pressure of the porous material for adsorbing CO2 is set to 1.0 MPa, 2.0 MPa, 3.0 MPa, 4.0 MPa or 5.0 MPa, and 100 g of the porous material sample is weighed and placed in the adsorption tank, and the excess space is filled with absorbent cotton balls.

[0046] (3) Use the gas booster system to fill the adsorption tank with CO2 gas. When the pressure in the tank reaches the different equilibrium pressures in (1), open the outlet valve to discharge the gas into the atmosphere and allow it to desorb freely for 24 hours. Thereafter, rotate the three-way valve so that the sample tank is directly connected to the automatic gas metering device. Heat the tank to 75°C and record the cumulative desorption amount and desorption rate of CO2 from the porous material at each temperature. The cumulative desorption amount of CO2 is as follows: Figure 1 shown.

[0047] (4) According to step (3), it can be determined that the optimal adsorption equilibrium pressure of the porous material for CO2 is 3MPa. Then, the porous material is placed in an adsorption tank, and CO2 gas at a pressure of 3MPa is injected into it. When the pressure is lower than 3MPa, the adsorption tank should be pressurized in time to allow the porous material to reach adsorption equilibrium.

[0048] (5) After the porous material is taken out, two 20g bituminous coal samples are weighed, one sample is used as the raw coal sample, and the other sample is mixed with 20g of the porous material that adsorbs CO2 and used as the control sample. The two samples are subjected to oxidation heating experiments to analyze the differences in gas product concentration, oxygen consumption law, temperature rise characteristics and coal self-ignition ability during the heating process in each sample. Figures 2 to 5 And as shown in Table 1.

[0049] Table 1 Comprehensive judgment index of coal spontaneous combustion tendency of raw coal samples and mixed samples

[0050] Sample name Raw coal sample Mixed samples Comprehensive judgment index I 1026.1 1346.9

[0051] Combined with the chart analysis, it can be seen that the use of porous materials to control the desorption of inert gas at a temperature shows the following effects on coal spontaneous combustion: (1) diluting the oxygen concentration around the coal body and inhibiting the coal-oxygen reaction process; (2) delaying the coal oxidation temperature rise process, especially the coal accelerated oxidation stage; (3) inerting the coal oxidation spontaneous combustion ability and reducing the risk of coal spontaneous combustion. The results show that the method of the present invention is effective in inhibiting the spontaneous combustion of coal in goaf areas.

[0052] Example 3

[0053] (1) Place the porous material in an adsorption tank and inject CO2 gas at a pressure of 3MPa. When the pressure is lower than 3MPa, the adsorption tank should be pressurized in time to allow the porous material to reach adsorption equilibrium.

[0054] (2) Weigh three 20g bituminous coal samples, and evenly mix 10g of the porous material that absorbs CO2 in one sample as sample 1; evenly mix 20g of the porous material that absorbs CO2 in one sample as sample 2; and evenly mix 40g of the porous material that absorbs CO2 in one sample as sample 3. Perform oxidation heating experiments on the three samples, and analyze the differences in gas product concentration, oxygen consumption law, temperature rise characteristics, and coal self-ignition ability during the heating process in each sample. Figures 6 to 8 And as shown in Table 2.

[0055] Table 2 Comprehensive judgment index of coal spontaneous combustion tendency of three groups of mixed samples

[0056] Sample name Sample 1 Sample 2 Sample 3 Comprehensive judgment index I 1295.9 1346.9 1493.9

[0057] Combined with the analysis of the charts, it can be seen that the use of porous materials to control the temperature of the desorption of inert gas on the spontaneous combustion of coal exhibits the following characteristics: (1) The more porous materials are mixed in the coal, the more CO2 is released during the heating process; (2) The more porous materials are mixed in the coal, the more significant the inhibitory effect of CO2 on the spontaneous combustion of coal.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preventing and extinguishing fire by controlling the temperature of porous materials to desorb inert gas to suppress spontaneous combustion of coal in goafs, characterized in that: The following steps are involved: Step a: placing the porous material into a container and injecting an inert gas into the container to allow the porous material to reach adsorption equilibrium; The pressure in the container is the optimal adsorption equilibrium pressure of the porous material; Step b: placing the porous material that has reached adsorption equilibrium into the coal mine goaf; Step c: When the temperature in the goaf increases, the inert gas in the porous material is desorbed by heat and released into the goaf, thereby achieving temperature-controlled release of the inert gas to prevent and extinguish coal spontaneous combustion.

2. The method according to claim 1, characterized in that: The porous material is made of coal gangue, NaOH solution and sodium silicate aqueous solution.

3. The method according to claim 1, characterized in that The method for preparing a porous material comprises the following steps: (1) calcining the coal gangue at 600-800°C for 2h, adding Al2O3 to adjust the molar ratio of SiO2 to Al2O3 to 2.0-2.5:1; (2) Adding a 1.8-3.0 mol / L NaOH solution to the pretreated gangue, with the mass ratio of the pretreated gangue to the NaOH solution being 1:3, placing the two in a 65°C water bath and stirring for 6 hours to obtain a slurry; (3) crystallizing the slurry at 80-100°C for 3-12 hours; (4) Filter, dry, grind, and add a 20%-30% sodium silicate aqueous solution to the crystals to make a paste; the amount of sodium silicate aqueous solution added is 5%-10% of the mass of the crystals; (5) Granulate, dry, and calcine at 105°C for 2h to obtain the product.

4. The method according to claim 3, characterized in that: The condition parameters for determining the optimal adsorption equilibrium pressure of the porous material for the inert gas in step a include: the cumulative desorption amount of the inert gas and the desorption rate of the inert gas.

5. The method according to claim 4, characterized in that: The basis for determining the optimal adsorption equilibrium pressure of the porous material for inert gas in step a is: comparing the desorption amount and desorption rate values ​​of the porous material for inert gas under different adsorption equilibrium pressures, analyzing at which adsorption equilibrium pressure the porous material has the maximum desorption amount or the fastest desorption rate value for inert gas, and then determining that the adsorption equilibrium pressure is the optimal adsorption equilibrium pressure.

6. The method according to claim 4 or 5, characterized in that: Determination of the cumulative desorption amount and desorption rate of inert gas: The porous material is adsorbed with inert gas at different adsorption equilibrium pressures. After free desorption for more than 24 hours, the total desorption amount and desorption rate during the period of heating to 75°C are measured.

7. The method according to claim 1, characterized in that: The inert gas is carbon dioxide and / or nitrogen.

8. The method according to claim 1, characterized in that: In step b, the mass ratio of the porous material to the coal in the goaf of the coal mine is above 50%.

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