A goaf spontaneous combustion active inerting device and method based on heat-triggered solid-liquid reaction

Abstract

The application discloses a kind of based on heat trigger solid-liquid reaction's goaf spontaneous combustion initiative inerting device and method, belong to coal mine fire prevention technical field, first based on experimental data, goaf beam tube monitoring and numerical simulation determine goaf high temperature prevention area, under the influence of setting safety margin and considering the maximum thickness of residual coal determine the starting temperature of adaptive inerting device, then according to goaf residual coal thickness, porosity, oxygen concentration field and high temperature prevention area area calculate out initiative inerting device size and reagent filling amount, finally combine the effective coverage area of single device and honeycomb grid generation algorithm, design initiative inerting device dynamic pre-buried point, and pre-bury initiative inerting device in coal mining face, when device reaches the high temperature protection area of goaf deep, temperature sensing guide column paraffin melt, aluminum sulfate solution in liquid reagent storage tank flows into solid reaction bin and sodium bicarbonate reaction along guide column, generate a large amount of CO2 from exhaust port, rapidly reduce local oxygen concentration, eliminate goaf spontaneous combustion hazard.The core innovation of the application is to abandon the traditional passive prevention mode relying on gas diffusion, and instead adopt the initiative control mechanism of "temperature sensing trigger-in-situ reaction-directional release", so that CO2 directly acts on the high temperature area through the directional exhaust port, rapidly reduces the local oxygen concentration, cuts off the necessary condition of coal spontaneous combustion from the source, realizes the initiative identification and accurate inerting of goaf high temperature area, and ensures the safety production of coal mining face.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mine goaf fire prevention and extinguishing, in particular to a goaf spontaneous combustion active inerting device and method based on a heat-triggered solid-liquid reaction. BACKGROUND

[0002] Mine fire is one of the disasters that seriously threaten the safety production of coal mines, which is divided into endogenous fire and exogenous fire. The endogenous fire, i.e. coal spontaneous combustion, is one of the main causes of coal mine accidents. According to statistics, the fire caused by coal spontaneous combustion accounts for more than 90% of the total number of mine fires. The residual coal in the goaf is extremely easy to cause spontaneous combustion under the action of oxidation and heat accumulation. However, the internal space of the goaf is complex and has strong concealment, and the traditional fire prevention and extinguishing means is difficult to directly act on the high-temperature hidden danger area. At the same time, the goaf fire has the risk of burning the working face, and the secondary disasters such as coal dust and gas explosion caused by the goaf fire are more serious, which brings great challenges to the safe and efficient mining of coal mines.

[0003] At present, the nitrogen injection inerting technology is one of the main methods for preventing and controlling coal spontaneous combustion in the goaf. It reduces the oxygen concentration by injecting nitrogen into the goaf to inhibit the coal-oxygen complex reaction. However, the existing nitrogen injection technology has significant limitations in practical application. Especially in the single-sided nitrogen injection mode, the air leakage is large on the air inlet side, which causes the oxidation zone to extend to the deep part, and the high-temperature hidden danger point is often formed on the air return side due to the nitrogen injection blind area. More importantly, the existing nitrogen injection mechanism cannot ensure that the nitrogen gas accurately covers the high-temperature area, or the nitrogen gas concentration is significantly reduced when it reaches the target position due to problems such as gas diversion and uneven diffusion, which cannot meet the inerting requirements.

[0004] In recent years, although some patent technologies have tried to optimize the inert injection pipeline arrangement or increase the inert injection pressure to improve the inerting effect, these schemes still belong to passive prevention and control, and cannot fundamentally solve the matching problem of inert injection blind area and dynamic high-temperature area. In addition, although the double-lane nitrogen injection can expand the coverage range, it is high in cost and greatly interferes with the production layout of the mine, which is difficult to be popularized on a large scale. In addition to the nitrogen injection technology, traditional fire prevention and extinguishing means such as grouting and gel sealing also have the problems of being difficult to penetrate into the deep high-temperature area of the goaf and being easily affected by the geological conditions and losing effectiveness. Therefore, how to realize the active identification and accurate inerting of the high-temperature area of the goaf has become a technical problem that needs to be broken through in the field of mine fire prevention and extinguishing.

[0005] In view of the above problems, the present application provides a goaf spontaneous combustion active inerting device and method based on a heat-triggered solid-liquid reaction. The core innovation is to abandon the traditional passive prevention and control mode which relies on gas diffusion, and instead adopt an active prevention and control mechanism of "temperature-sensitive triggering-in-situ reaction-directional release". The device and method can make CO2 directly act on the high-temperature area through the directional exhaust port, rapidly reduce the local oxygen concentration, and cut off the necessary conditions for coal spontaneous combustion from the source. SUMMARY

[0006] The application aims to provide a goaf spontaneous combustion active inerting device and method based on heat-triggered solid-liquid reaction, which adopts a "temperature-sensitive triggering-in-situ reaction-directional release" active prevention and control mechanism to solve the problem that the high-temperature area generated by the oxidation and heat accumulation of residual coal in the goaf is difficult to prevent and control.

[0007] The goaf spontaneous combustion active inerting device based on heat-triggered solid-liquid reaction comprises a protective cage (1), a solid reaction bin (2), a liquid reagent storage tank (3), and a temperature-sensitive guide column body (4).

[0008] The protective cage (1) is located at the outermost layer of the whole device and provides a protection for the internal modular temperature-sensitive triggering reaction system, which is connected from bottom to top by the solid reaction bin (2), the temperature-sensitive guide column (4), and the liquid reagent storage tank (3).

[0009] The reaction device solid reaction bin (2) has a three-layer structure, the inner layer is a high-temperature-resistant and corrosion-resistant polyethylene (7), the middle layer is heat insulation cotton (8), and the outermost layer is a stainless steel shell (9) for protection, the cavity is internally provided with solid powder sodium bicarbonate (17) and catalyst sodium chloride (18), the cavity side has four heat-absorbing exhaust ports (5), the exhaust ports contain one-way valves (10), the inner wall of the exhaust ports is attached with heat-absorbing coating (11), and the cavity top has four hollow threaded rod interfaces (12).

[0010] The liquid reagent storage tank (3) has a three-layer structure, the inner layer is a high-temperature-resistant and corrosion-resistant polyethylene (7), the middle layer is heat insulation cotton (8), and the outermost layer is a stainless steel shell (9) for protection, the cavity top has a vent pipe (6) containing a one-way valve (10) to keep the internal and external pressure the same, the cavity is internally provided with aluminum sulfate solution (19), and the cavity bottom has four hollow threaded rod interfaces (12).

[0011] The temperature-sensitive guide column body (4) is an irregular column body, internally containing paraffin (14), a drainage needle (13), and a drainage needle fixator (15), and the sleeve nuts (16) at both ends of the column body can connect the solid reaction bin (2) and the liquid reagent storage tank (3).

[0012] The method comprises the following five steps:

[0013] S1: Determine the high-temperature prevention and control area of the goaf:

[0014] Determine the spontaneous combustion critical temperature (T c), combined with COMSOL numerical simulation software, a dynamic model of the temperature field in the goaf is constructed, and through multi-parameter coupling analysis, the spatial distribution of the spontaneous combustion hazard point is determined, and the high-temperature area of oxidation and heat storage is accurately positioned;

[0015] S2: Determine the starting temperature of the active inerting device:

[0016] The melting point of paraffin wax (T m ) is generally equal to the critical temperature of coal spontaneous combustion (T c ) minus a safety margin ΔT as (ΔT as is usually 2℃~4℃), but the thicker the residual coal (h), the stronger the heat storage capacity, and the faster the temperature rise in the coal body, the lower the ambient temperature required to reach the critical temperature of spontaneous combustion. Therefore, under the same external conditions, a lower paraffin wax melting point needs to be set in the thick coal area to trigger the device before the actual temperature of the coal body reaches the dangerous value, so a correction factor α (generally 0.5℃ / m ~ 2℃ / m) is added. The final formula for calculating the starting temperature of the active inerting device (paraffin wax melting point) is: T m =T c −ΔT as −αh;

[0017] S3: Determine the size of the active inerting device and the amount of reagent filled:

[0018] Considering the thickness of residual coal in the goaf, porosity, oxygen concentration field and high-temperature prevention and control area, a pre-designed amount of sodium bicarbonate reagent is filled, the amount of other reagents, the volume occupied by the reagent, the amount of CO2 generated by a single device and the size of the device are determined according to the reaction equation, and then the amount of CO2 (V CO2需 ) required to reduce the oxygen concentration (C i ) in the high-temperature area to the critical oxygen concentration (C L ) and the number of devices under this design condition are calculated to determine the rationality of the device density, thereby determining the amount of reaction reagent filled and the size of the device;

[0019] S4: Determine the dynamic layout point of the active inerting device pre-embedded in the goaf:

[0020] According to the porosity (μ) of the goaf, the thickness (h) of the residual coal and the CO2 diffusion efficiency (ϵ usually 0.5~0.7), the effective coverage area (S a ) and the effective coverage radius (R) of CO2 generated by a single device are calculated, then the honeycomb structure with the optimal coverage efficiency is adopted, and the honeycomb grid generation algorithm is used to generate an adaptive hexagonal honeycomb grid in the irregular high-temperature prevention and control area, and then the device pre-embedded dynamic layout point is designed to ensure that the coverage range of each device accurately matches the CO2 diffusion capacity;

[0021] S5: Assembly, pre-installation, and dynamic adjustment of the active inerting device:

[0022] Sodium bicarbonate and aluminum sulfate reagents are respectively loaded into a solid reaction chamber and a liquid reagent storage tank. Then, the temperature-sensitive paraffin guide column, solid reaction chamber, liquid reagent storage tank and protective cage are assembled. The device is pre-buried at the dynamic layout points in the coal mining face. When the device reaches the high temperature protection area of ​​the goaf, if the temperature reaches the set temperature, the paraffin in the temperature-sensitive guide column melts when heated. The aluminum sulfate solution in the liquid reagent storage tank flows into the solid reaction chamber along the guide column and reacts with sodium bicarbonate to generate a large amount of CO2 which is discharged from the exhaust port, quickly reducing the local oxygen concentration and eliminating the risk of spontaneous combustion in the goaf.

[0023] Furthermore, the temperature at which the high-temperature zone in the goaf is divided in step S1 should be based on the critical temperature for coal spontaneous combustion (T). c However, to avoid device trigger hysteresis, the cut-off temperature should be lower than the critical temperature and combined with a safety margin ΔT. bs Set (ΔT) bs (usually taken as 6℃~10℃), the actual temperature is T. h = T c −ΔT bs Based on this, the area of ​​the high-temperature region is divided into S. t However, the actual conditions inside the goaf are complex and variable. To effectively eliminate the problems of delayed equipment start-up or incomplete CO2 coverage caused by the differences within the goaf, a safety redundancy factor (f) is introduced, and the high-temperature zone prevention area S f =S t ×f (f takes values ​​of 1.3 to 2.3 in general regions; f takes values ​​of 2.3 to 3 in constructed regions).

[0024] Furthermore, after determining the melting point of paraffin in step S2, the melting point of paraffin is adjusted by adding high-melting-point carnauba wax (melting point 80~86℃) or low-melting-point mineral wax (45~55℃) at a mass ratio of 5%~30% to adjust the paraffin mixing ratio, and adding 1%~3% dibutyl phthalate (plasticizer) to optimize the fluidity of the temperature-sensitive paraffin.

[0025] Further, in step S3, the mass of sodium bicarbonate, aluminum sulfate, and sodium chloride reagents is determined according to... The mass relationship between aluminum sulfate and sodium bicarbonate can be derived: m Al2(SO4)3 =(m NaHCO3 / 6)×(M NaHCO3 / M Al2(SO4)3 =0.679×m NaHCO3 The mass m of sodium chloride catalyst NaCl =5%×m NaHCO3 When the bulk density of sodium bicarbonate solid reagent is taken as ρ NaHCO3=1.5 g / cm³, the bulk density of the catalyst sodium chloride is taken as p NaCl =2.16 g / cm³, the density of the aluminum sulfate solution with a concentration of 30% is taken as p Al2(SO4)3 =1.3 g / cm³, the volume V of sodium bicarbonate is calculated NaHCO3 = m NaHCO3 / p NaHCO3 (unit: L), the volume V of sodium chloride NaCl = (5% x m NaHCO3 ) / p NaCl =0.023 m NaHCO3 (unit: L), the volume V of the aluminum sulfate solution Al2(SO4)3 = m Al2(SO4)3 / (30% x p Al2(SO4)3 )=1.74 m NaHCO3 (unit: L), the relationship between the total volume occupied by the reagents and the mass of sodium bicarbonate is: V 总试剂 =0.667 m NaHCO3 +0.023 m NaHCO3 +1.74 m NaHCO3 =2.43 m NaHCO3 (unit: L);

[0026] Further, the relationship between the reagent sodium bicarbonate and CO2 in step S3 is: V CO2生 = (m NaHCO3 / M NaHCO3 ) x 22.4 x k = m NaHCO3 x 0.267 x k (m NaHCO3 is the mass of the sodium bicarbonate reagent, M NaHCO3 is the molar mass of sodium bicarbonate, and k is the reaction efficiency number, taken as 0.8-0.9), the formula for the volume of CO2 required to reduce the oxygen concentration (C i ) in the high-temperature area of the goaf to the critical oxygen concentration (C L ): V CO2需 = (S f x h x m) (C i / C L -1), the number N of active inertization devices embedded in the high-temperature control area i = V CO2需 / V CO2生 , and then the rationality of the reagent loading amount is determined by judging whether the density of the embedded devices is reasonable;

[0027] Further, the size of the active inertization device is determined in step S3, and the sum of the volume (V 内 ) of the solid reaction bin and the liquid reagent tank is the volume (V 外50%~60%, under the condition of reserving 10% flow space, 1.1 times of the volume of the aluminum sulfate solution is less than or equal to the volume of the liquid reagent storage tank, under the condition of reserving 100% reaction space, 2 times of the volume of all reagents is less than or equal to the volume of the solid reaction bin, when the device size and the reagent filling amount are determined, the inequality relation of the reagent volume and the device volume needs to be met: V Al2(SO4)3 ×1.1 + V 总试剂 ×2≤50%V 外 ;

[0028] Further, the effective coverage area S a =(ϵ×V CO2生 ) / (η×h) of a single device in the step S4 is effective coverage radius Since the side length of the regular hexagon is equal to the radius of the circumscribed circle, when the honeycomb grid generation algorithm is adopted, the side length r=R of the regular hexagon is equal to the radius of the circumscribed circle.

[0029] Further, the dynamic adjustment in the step S5 refers to flexibly adjusting the device size, the reaction reagent filling amount, the paraffin melting point and the honeycomb grid side length according to the actual change of the goaf and the possible change of the high-temperature protection area, and comprehensively preventing and controlling the potential high-temperature area of the goaf.

[0030] Compared with the prior art, the self-combustion active inerting device and method for goaf based on the heat-triggered solid-liquid reaction disclosed in the application have the following advantages:

[0031] (1) The application pre-buries the active inerting device for heat-triggered solid-liquid reaction, monitors the coal temperature in real time, and when the temperature reaches a preset threshold, the paraffin melts to trigger a chemical reaction, and high-concentration CO2 is generated in situ to directly cover the high-temperature area. This mechanism avoids the concentration loss of long-distance diffusion of gas, shortens the response time to minutes, and only starts at the hidden danger point, effectively improving the resource utilization rate.

[0032] (2) The device of the application generates CO2 through the chemical reaction of sodium bicarbonate and aluminum sulfate, and the cost of a single device is very low, and it does not need continuous energy supply. The device adopts a detachable modular design, supports quick assembly and flexible pre-burial underground, and is especially suitable for small and medium-sized mines or complex geological areas. In addition, the reagent filling amount, trigger temperature and device arrangement density can be dynamically adjusted according to the characteristics of the coal, realizing the customized prevention and control of "one mine one strategy", and the comprehensive operation and maintenance cost is significantly reduced.

[0033] (3) The application expands the prevention and treatment area by introducing a safety redundancy factor (f) to ensure that the high-temperature core area and potential risk zone are covered by CO2 inerting. The device adopts a three-layer composite structure (corrosion-resistant polyethylene lining + thermal insulation layer + stainless steel shell) and can operate stably for a long time in a high-humidity, high-pressure and coal ash impact environment. The device layout adopts a dynamic layout method based on a honeycomb grid generation algorithm, the hexagonal structure more effectively covers the blind area, ensuring uniform diffusion of CO2, the grid density can be automatically adjusted according to the temperature gradient, supporting local grid deformation in irregular areas such as faults and fractures, and accurately matching the risk distribution. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A flowchart of the self-combustion active inerting device and method of goaf based on heat-triggered solid-liquid reaction disclosed in the embodiments of the application.

[0035] Figure 2 A structural schematic diagram of the self-combustion active inerting device and method of goaf based on heat-triggered solid-liquid reaction in the embodiments of the application.

[0036] Figure 3 A sectional view structural schematic diagram of the solid reaction bin in the self-combustion active inerting device and method of goaf based on heat-triggered solid-liquid reaction in the embodiments of the application.

[0037] Figure 4 A sectional view structural schematic diagram of the liquid reagent storage tank in the self-combustion active inerting device and method of goaf based on heat-triggered solid-liquid reaction in the embodiments of the application.

[0038] Figure 5 A sectional view structural schematic diagram of the temperature-sensitive guide column in the self-combustion active inerting device and method of goaf based on heat-triggered solid-liquid reaction in the embodiments of the application.

[0039] Figure 6 A dynamic layout method schematic diagram of the self-combustion active inerting device of goaf based on heat-triggered solid-liquid reaction based on the honeycomb grid algorithm in the embodiments of the application.

[0040] Figures 2 to 5 The names of the components and reagents represented by the numbers in the above table are as follows:

[0041] In the figure: 1, protective cage; 2, solid reaction bin; 3, liquid reagent storage tank; 4, temperature-sensitive guide column; 5, heat-absorbing exhaust port; 6, air pipe; 7, corrosion-resistant polyethylene; 8, thermal insulation cotton; 9, stainless steel shell; 10, one-way valve; 11, heat-absorbing coating; 12, hollow threaded rod; 13, drainage needle; 14, temperature-sensitive paraffin; 15, drainage needle fixator; 16, sleeve nut; 17, sodium bicarbonate; 18, sodium chloride; 19, aluminum sulfate solution. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0043] Figure 1 The flowchart provided for the embodiments of the present application; Figure 2 The overall structure schematic diagram of the device provided for the embodiments of the present application; Figure 3 The cross-sectional structure schematic diagram of the solid-state reaction bin provided for the embodiments of the present application; Figure 4 The cross-sectional structure schematic diagram of the liquid reagent storage tank provided for the embodiments of the present application; Figure 5 The cross-sectional structure schematic diagram of the temperature-sensing flow guide column provided for the embodiments of the present application; Figure 6 The arrangement method schematic diagram provided for the embodiments of the present application.

[0044] S1: determining a goaf high-temperature prevention area:

[0045] The critical temperature of the coal sample and the critical oxygen concentration of the goaf are obtained by analyzing the programmed temperature experiment of the coal sample, and the goaf spontaneous combustion index gas is determined. The parameters of the goaf of the coal mine are surveyed on site, a numerical simulation model of the target goaf is constructed in combination with the COKSOL numerical simulation software, a dynamic model of the temperature field and the oxygen concentration field of the goaf is established, the real-time collected gas temperature data of the goaf beam monitoring system are analyzed, and the goaf high-temperature prevention area is plotted in combination with the experiment, simulation and on-site multi-parameter coupling analysis.

[0046] The goaf coal sample is subjected to programmed temperature experiment to determine the spontaneous combustion critical temperature T c = 70℃, the safety margin ΔT bs = 8℃, the actual division temperature T h = 62℃, in the established temperature field model of the goaf, the isotherm is used to plot the high-temperature area of 62℃, after the demarcation, there may be a high-temperature area of 600㎡ at a section close to the return air side, about 90 meters away from the working face, since there is no structure in the first 300 meters of the target mine goaf, the safety redundancy coefficient f is taken as 1.8, the high-temperature area prevention area S f = 1080㎡ is calculated, and the high-temperature prevention area graph is plotted in the actual proportion.

[0047] S2: determining the starting temperature of the active inerting device:

[0048] The maximum value of the residual coal thickness h of the goaf is 0.5, since there is no structure in the first 300 meters, the safety margin ΔT asTake 3℃, the correction coefficient a is taken 1℃ / m, the device start temperature T m =66.5℃. From S1 step, T h =62℃, T c =70℃, the device start temperature is between the actual division temperature and the critical temperature, in the case of completely covering the high temperature prevention area, prevent the device from starting too early, unable to effectively prevent the high temperature area, the parameter design is reasonable.

[0049] After determining the device start temperature, the melting point of the ordinary paraffin of the same production batch is measured to be 55℃, which is lower than the device start temperature. The melting point of the ordinary paraffin is raised by adding 25%-30% of the Brazil palm wax with a melting point of 80℃ to the quantitative ordinary paraffin, so that the melting point of the paraffin is raised to 66.5℃, and 2% of dibutyl phthalate (plasticizer) is added to optimize the flowability of the paraffin, and then the temperature sensing paraffin (14) is filled into the temperature sensing guide column body (4) to form the temperature sensing device of the active inerting device.

[0050] S3: Determine the size of the active inerting device and the filling amount of the reagent:

[0051] Considering the thickness of the residual coal in the goaf, porosity, oxygen concentration field and high temperature prevention area, a filling amount of sodium bicarbonate (17) is designed in advance, the filling amount of other reagents, the volume occupied by the reagents, the CO2 generation amount of a single device and the device size are determined according to the reaction equation, and then the oxygen concentration (C i ) in the high temperature area is calculated to reduce to the critical oxygen concentration (C L ), the CO2 volume (V CO2需 ) required and the number of pre-embedded thermal active inerting devices under this design condition are calculated to determine the rationality of the device density, thereby determining the filling amount of the reaction reagent and the size of the pre-embedded device.

[0052] Assuming that the filling amount of sodium bicarbonate (17) reagent of a single device is designed to be 20kg, the filling amount of aluminum sulfate (19) reagent can be obtained according to the chemical reaction equation to be 13.58kg, and the filling amount of catalyst sodium chloride (18) is 1kg, the bulk density of sodium bicarbonate (17) solid reagent is taken as ρ NaHCO3 =1.5 g / cm³, the bulk density of catalyst sodium chloride (18) is taken as ρ NaCl =2.16 g / cm³, and the density of 30% aluminum sulfate (19) solution is taken as ρ Al2(SO4)3 =1.3 g / cm³, the volume of all reagents is calculated to be 48.6L, and in the case of reserving 100% of the reaction space, the total volume in the device is 132L, from the inequality V Al2(SO4)3 ×1.1+V 总试剂 ×2≤50%V 外 , it can be deduced that V 外≥264L, thus the device protection cage (1) is designed as a cube with a side length of 0.65m.

[0053] When the reaction efficiency number is 0.9, the V CO2生 =4.8L, the oxygen concentration in the high-temperature area is taken as the maximum value of 13.5%, the critical oxygen concentration is 8%, the maximum thickness of the residual coal in the goaf is 0.5m, the actual measured porosity is 0.4, and the calculated CO2 required for the high-temperature area is V CO2需 = (S f ×h×μ)(C i / C L −1)=148.5L, the number of devices required for prevention and control of the high-temperature area is expected to be N i = V CO2需 / V CO2生 =31, and the sodium bicarbonate (17) reagent filling amount in the device with a side length of 0.65m is 20kg, which is reasonably designed.

[0054] S4: Determine the arrangement point of the active inerting device pre-buried in the goaf:

[0055] According to the porosity (μ) of the goaf, the residual coal thickness (h), and the CO2 diffusion efficiency (ϵ, usually taken as 0.5~0.7), the effective coverage area (S a ) and the effective coverage radius (R) of the CO2 generated by a single device are calculated, then the honeycomb structure with the optimal coverage efficiency is adopted, the honeycomb grid generation algorithm is used to generate the adaptive hexagonal honeycomb grid in the irregular high-temperature prevention and control area, and the dynamic arrangement of the pre-buried point of the active inerting device is determined according to the hexagonal honeycomb grid generated by the algorithm and the real-time dynamic situation of the goaf, so as to ensure that the coverage range of each device accurately matches the CO2 diffusion capacity.

[0056] The CO2 generation amount of a single device is V CO2生 =4.8L, the CO2 diffusion efficiency is taken as 0.7, the effective coverage area S a of a single device is (ϵ×V CO2生 ) / (η×h) =16.8㎡, the effective coverage radius =2.3, since the side length of the regular hexagon is equal to the radius of the circumscribed circle, the side length r of the regular hexagon is R=2.3, the honeycomb grid generation algorithm is used to draw the honeycomb grid in the goaf high-temperature prevention and control area, and then the dynamic laying point of the device is designed according to the generated honeycomb grid and the real-time dynamic situation of the goaf, starting from the pre-buried point near the return air side of the high-temperature prevention and control area, the first row of devices is spaced 4m apart left and right, and the rows are spaced 2.3m apart.

[0057] S5: Assembly, pre-burial, and dynamic adjustment of the device:

[0058] Quantitative sodium bicarbonate (17) and aluminum sulfate (19) reagent are loaded into solid-state reaction chamber (2) and liquid reagent storage tank (3) respectively, then the device is assembled through the reserved hollow threaded rod (12) and the sleeve nut (16) at both ends of the temperature-sensitive paraffin guide column (4) on the solid-state reaction chamber (2) and the liquid reagent storage tank (3), and fixed in the protective cage (1). The device is pre-buried at the designed dynamic laying point on the coal mining face. When the active inerting device reaches the deep part of the goaf with the advancement of the working face, if the temperature of the prevention area reaches the set temperature, the paraffin (14) in the temperature-sensitive guide column (4) melts when heated, the one-way valve (10) in the air pipe (6) of the liquid reagent storage tank (3) opens under negative pressure, and the aluminum sulfate (19) solution in the storage tank flows quickly into the solid-state reaction chamber (2) along the drainage needle (13) and reacts with sodium bicarbonate (17). A large amount of CO2 is generated in a short time under the catalysis of sodium chloride (18) and is discharged from the exhaust port (5), quickly reducing the local oxygen concentration and eliminating the spontaneous combustion hazard in the goaf.

[0059] According to the actual changes of the goaf and the possible changes of the high temperature protection area, the size of the device, the filling amount of the reaction reagent, the melting point of the paraffin and the edge length of the honeycomb grid are flexibly adjusted to comprehensively prevent and control the potential high temperature area of the goaf.

[0060] Finally, it should be noted that the above examples are only used to illustrate the method of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the method described in the foregoing examples, or make equivalent replacement for part or all of the technical features thereof; and these modifications or replacements do not make the essence of the corresponding method deviate from the scope defined by the claims of the present application.

Claims

1. A goaf spontaneous combustion active inerting method based on heat-triggered solid-liquid reaction, which adopts an active prevention and control mechanism of "temperature-sensitive trigger-in-situ reaction-directional release" to solve the problem that the high-temperature area generated by the oxidation and heat accumulation of residual coal in the goaf is difficult to prevent and control due to its spontaneous combustion; The method is based on a goaf spontaneous combustion active inerting device based on heat-triggered solid-liquid reaction, which comprises a protective cage (1), a solid reaction bin (2), a liquid reagent storage tank (3), and a temperature-sensitive guide column body (4); The protective cage (1) is located at the outermost layer of the whole device and provides protection for the internal modular heat-triggered solid-liquid reaction system, which is connected from bottom to top by the solid reaction bin (2), the temperature-sensitive guide column body (4), and the liquid reagent storage tank (3); The solid reaction bin (2) has a three-layer structure, the inner layer is a high-temperature-resistant and corrosion-resistant polyethylene (7), the middle layer is heat insulation cotton (8), and the outermost layer is a stainless steel shell (9) for protection, the bin body is filled with solid powdered sodium bicarbonate (17) and catalyst sodium chloride (18), the cavity side has four heat-absorbing exhaust ports (5), the exhaust ports contain one-way valves (10), the inner wall of the exhaust port is coated with a heat-absorbing coating (11), and the top of the cavity has four hollow threaded rod interfaces (12); The liquid reagent storage tank (3) has a three-layer structure, the inner layer is a high-temperature-resistant and corrosion-resistant polyethylene (7), the middle layer is heat insulation cotton (8), and the outermost layer is a stainless steel shell (9) for protection, the top of the cavity has a vent pipe (6) containing a one-way valve (10) to maintain the same internal and external pressure, the cavity is filled with aluminum sulfate solution (19), and the bottom of the cavity has four hollow threaded rod interfaces (12); The temperature-sensitive guide column body (4) is an irregular column body containing paraffin (14), a drainage needle (13), and a drainage needle holder (15), and the sleeve nuts (16) at both ends of the column body can connect the solid reaction bin (2) and the liquid reagent storage tank (3); The method comprises the following five steps: S1: Determine the high-temperature prevention and control area of the goaf: Based on the real-time collection of gas temperature data by the goaf beam monitoring system and the determination of the spontaneous combustion critical temperature T of the goaf coal sample by programmed temperature experiment c , combined with COMSOL numerical simulation software, a dynamic model of the temperature field in the goaf is constructed, and through multi-parameter coupling analysis, the spatial distribution of the spontaneous combustion hidden danger point is determined, and the high-temperature area of oxidation heat accumulation is accurately located; S2: Determine the starting temperature of the active inerting device: Paraffin wax melting point T m Equal to the critical temperature of coal spontaneous combustion T c Subtract safety margin ΔT as And ΔT as Take 2 ℃~4 ℃, but the thicker the residual coal thickness h, the stronger the heat storage capacity, the faster the internal temperature of the coal body rises, and the lower the ambient temperature required to reach the critical temperature of spontaneous combustion. Therefore, under the same external conditions, the thick coal area needs to set a lower paraffin wax melting point to trigger the device before the actual temperature of the coal body reaches the dangerous value, so a correction factor α is added, and α takes 0.5 ℃ / m~2 ℃ / m, and finally the calculation formula of the active inerting device starting temperature, i.e. the paraffin wax melting point is: T m =T c −ΔT as −αh; S3: Determine the size and reagent filling amount of the active inerting device: Considering the thickness of residual coal, porosity, oxygen concentration field and high temperature prevention area of goaf, a reagent filling amount of sodium bicarbonate is designed in advance, and the filling amount of other reagents, the volume occupied by the reagents, the CO2 generation amount of a single device and the device size are determined according to the reaction equation. Then, the oxygen concentration C i in the high temperature area is calculated L , and the CO2 volume V CO2需 required is calculated. The rationality of the device density is judged according to the device number under the design condition, so as to determine the reaction reagent filling amount and the device size. S4: Determine the dynamic arrangement point of the active inerting device in the goaf: According to the porosity μ of the goaf, the residual coal thickness h and the CO2 diffusion efficiency ϵ, the effective coverage area S of the CO2 generated by a single device is calculated a and the effective coverage radius R, and ϵ is 0.5-0.7, then the honeycomb structure with the optimal coverage efficiency is adopted, the adaptive hexagonal honeycomb grid is generated in the irregular high-temperature control area by using a honeycomb grid generation algorithm, and then the device pre-embedded dynamic arrangement points are designed to ensure that the coverage range of each device accurately matches the CO2 diffusion capacity; S5: Assembly, pre-burial, and dynamic adjustment of the active inerting device: Fill sodium bicarbonate and aluminum sulfate reagents into the solid reaction bin and the liquid reagent storage tank, respectively, then assemble the temperature-sensitive paraffin guide column, the solid reaction bin, the liquid reagent storage tank, and the protective cage, pre-burial the device at the dynamic arrangement point in the coal mining face, when the device reaches the high-temperature prevention and control area of the goaf, if the temperature reaches the set temperature, the paraffin in the temperature-sensitive guide column melts, the aluminum sulfate solution in the liquid reagent storage tank flows into the solid reaction bin along the guide column, reacts with the sodium bicarbonate, generates a large amount of CO2, and is discharged from the exhaust port, rapidly reduces the local oxygen concentration, and eliminates the spontaneous combustion hazard in the goaf.

2. The method of claim 1, wherein the method is characterized by, The division temperature of the high temperature area in the step S1 should be based on the critical temperature T of coal spontaneous combustion c However, in order to avoid device triggering lag, the division temperature should be lower than the critical temperature and combined with a safety margin ΔT bs Set, and ΔT bs Take 6 ℃~10 ℃, the actual division temperature is T h =T c −ΔT bs On this basis, the area of the high temperature area obtained by division is S t However, the actual situation inside the goaf is complex and variable, in order to ensure that the device starting lag or CO2 coverage is not comprehensive caused by the difference inside the goaf is effectively eliminated, the safety redundancy factor f is introduced, the prevention and control area of the high temperature area S f =S t ×f, and f takes the value of 1.3~2.3, the value of the construction area f is 2.3~3.

3. A method for gob self-heating active inerting based on heat-triggered solid-liquid reaction according to claim 1, characterized in that, Further, after determining the paraffin melting point in step S2, the paraffin melting point is adjusted by adding high melting point Brazil palm wax and low melting point mineral earth wax. The melting point of the Brazil palm wax is 80-86℃, the melting point of the mineral earth wax is 45-55℃, the mass ratio of the paraffin is adjusted to 5%-30%, and 1%-3% of a plasticizer, dibutyl phthalate, is added to optimize the flowability of the temperature-sensitive paraffin.

4. The method of claim 1, wherein the method is characterized by, The step S3 determines the quality of sodium bicarbonate, aluminum sulfate and sodium chloride reagent, according to , the quality relationship of aluminum sulfate and sodium bicarbonate can be obtained: m Al2(SO4)3 =(m NaHCO3 / 6)×(M NaHCO3 / M Al2(SO4)3 )=0.679×m NaHCO3 , wherein m Al2(SO4)3 is the quality of aluminum sulfate reagent, M Al2(SO4)3 is the molar mass of aluminum sulfate, m NaHCO3 is the quality of sodium bicarbonate reagent, M NaHCO3 is the molar mass of sodium bicarbonate, and the quality of catalyst sodium chloride is m NaCl =5%×m NaHCO3 , when the bulk density of sodium bicarbonate solid reagent is ρ NaHCO3 =1.5 g / cm³, the bulk density of catalyst sodium chloride is ρ NaCl =2.16g / cm³, and the density of 30% aluminum sulfate solution is ρ Al2(SO4)3 =1.3 g / cm³, the volume V NaHCO3 of sodium bicarbonate is calculated as m NaHCO3 / ρ NaHCO3 (unit: L), the volume V NaCl of sodium chloride is (5%×m NaHCO3 ) / ρ NaCl =0.023m NaHCO3 (unit: L), the volume V Al2(SO4)3 of aluminum sulfate solution is m Al2(SO4)3 / (30%×ρ Al2(SO4)3 )=1.74 m NaHCO3 (unit: L), and the relationship between the total volume occupied by the reagents and the quality of sodium bicarbonate is V 总试剂 =0.667m NaHCO3 +0.023m NaHCO3 +1.74m NaHCO3 =2.43m NaHCO3 (unit: L).

5. A method for gob self-heating active inerting based on heat-triggered solid-liquid reaction according to claim 1, characterized in that, The relationship between the formation of sodium bicarbonate and CO2 in step S3 is as follows: V CO2生 =(m NaHCO3 / M NaHCO3 ) × 22.4 × k = m NaHCO3 ×0.267×k, where m NaHCO3 M represents the mass of sodium bicarbonate reagent. NaHCO3 The molar mass of sodium bicarbonate, k is the reaction efficiency number, taken as 0.8~0.9, and the oxygen concentration C in the high-temperature area of ​​the goaf. i Reduced to the critical oxygen concentration C L Formula for the required CO2 volume: V CO2需 =(S f ×h×μ)(C i / C L -1), the number of active inerting devices pre-embedded in the high-temperature prevention area N i = V CO2需 / V CO2生 Then, by judging whether the density of the pre-embedded device is reasonable, the rationality of the reagent filling amount is determined.

6. A method for gob self-heating active inerting based on heat-triggered solid-liquid reaction according to claim 1, characterized in that, The sum of the volume of the solid reaction chamber and the liquid reagent storage tank is 50%~60% of the volume of the protective cage of the device V 外 Under the condition of reserving 10% of the flow space, 1.1 times the volume of the aluminum sulfate solution is less than or equal to the volume of the liquid reagent storage tank, and under the condition of reserving 100% of the reaction space, 2 times the volume of all reagents is less than or equal to the volume of the solid reaction chamber. When determining the size of the device and the amount of reagent to be filled, the inequality relationship between the volume of the reagent and the volume of the device needs to be satisfied: V Al2(SO4)3 ×1.1 + V 总试剂 ×2≤50%V 外 .

7. A method for gob self-heating active inerting based on heat-triggered solid-liquid reaction according to claim 1, characterized in that, The single device effective coverage area S in the step S4 a = (e x V CO2生 ) / (η x h), the effective coverage radius Since the edge length of the regular hexagon is equal to the radius of the circumscribed circle, when the cellular grid generation algorithm is used, the edge length r of the regular hexagon is R.

8. A method for gob self-heating active inerting based on heat-triggered solid-liquid reaction according to claim 1, characterized in that, The dynamic adjustment in step S5 refers to flexible adjustment of the device size, the reaction reagent filling amount, the paraffin melting point and the honeycomb grid side length according to the actual change of the goaf and the possible change of the high-temperature protection area, so as to comprehensively prevent and control the potential high-temperature area of the goaf.

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