Method and system for evaluating underground gasification conditions of residual coal of closed coal mine

Abstract

The invention discloses a method and a system for evaluating underground gasification conditions of residual coal of a closed coal mine, and relates to the technical field of coal bed gas development, and the method comprises the following steps: constructing a multi-level evaluation system according to a plurality of first-level and second-level evaluation indexes; obtaining the weight of each evaluation index in the evaluation system through an analytic hierarchy process; according to the actual geological parameters of each partition, assigning a plurality of secondary evaluation indexes by using an assignment standard; constructing an evaluation factor set and an evaluation result set; using a membership function to obtain a membership matrix between the evaluation factor set and the evaluation result set; according to the weight and the membership degree matrix, using a multi-level fuzzy evaluation method to obtain the membership degree of the evaluation system; and according to an optimal membership degree principle, evaluating the residual underground coal gasification work of each subarea to obtain an evaluation result. According to the invention, underground gasification work can be accurately researched.

Description

Technical Field

[0001] The present invention relates to the technical field of coalbed methane development, and in particular to a method and system for evaluating underground gasification conditions of residual coal in a closed coal mine. Background Art

[0002] At present, there are still about 42 billion tons of coal resources in my country's closed coal mines, and the remaining coal resources are very rich. Reusing these remaining coal resources can not only reduce resource waste and improve the efficiency of energy resource development and utilization in overcapacity mines, but also provide a strategic path for abandoned mine enterprises to transform and escape difficulties and achieve sustainable development, thereby promoting the transformation and development of resource-depleted cities and bringing huge economic, social and environmental benefits. As a controllable combustion technology, underground coal gasification has the advantages of high safety and low pollution, and is an important method for the reuse of remaining coal resources.

[0003] In the existing technology, the research on underground coal gasification focuses on the underground gasification resource quantity, process parameters, benefit evaluation, etc. However, underground gasification work in closed coal mines is also affected by multiple factors such as geological conditions, coal resources and water resources. Therefore, there is a lack of research, evaluation and effective application of the remaining resources in closed coal mines, especially the consideration and analysis of hydrological conditions such as on-site water resources and prevention and control difficulties, which restricts the sustainable development of underground gasification work.

[0004] In summary, because UCG research lacks comprehensive consideration of the remaining resources in closed coal mines, such as the lack of impact of hydrological conditions on UCG, existing technologies lack a systematic and comprehensive evaluation of whether the remaining resources in closed coal mines are suitable for gasification, resulting in inaccurate research on UCG. Summary of the invention

[0005] The embodiments of the present invention provide a method and system for evaluating the underground gasification conditions of residual coal in closed coal mines, which can solve the problem in the prior art that underground gasification research is inaccurate due to the lack of systematic and comprehensive evaluation of whether the residual resources of closed coal mines are suitable for gasification.

[0006] The embodiment of the present invention provides an evaluation method for the underground gasification conditions of the remaining coal in a closed coal mine, comprising the following steps: zoning the remaining coal resources of the closed coal mine; obtaining a plurality of primary indicators and a plurality of secondary indicators for evaluating the underground gasification of the remaining coal; wherein the plurality of primary evaluation indicators include: geological conditions, coal seam conditions, coal quality conditions and hydrological conditions, the secondary evaluation indicators of the geological conditions include: resource volume, coal seam roof, exploration degree, coal seam fissures and geological structure, the secondary evaluation indicators of the coal seam conditions include: thickness, inclination, burial depth, stability and interlayered gangue, the secondary evaluation indicators of the coal quality conditions include: ash content, fixed carbon, cohesion, ash melting point, CO2 reaction activity, ignition point and sulfur content, the secondary evaluation indicators of the hydrological conditions include: water filling conditions, water filling characteristics, water richness, water resources and difficulty of prevention and control; a multi-layer evaluation system is constructed based on the plurality of primary evaluation indicators and the plurality of secondary evaluation indicators. An evaluation system for evaluating the underground gasification of remaining coal is proposed; the weight of each evaluation index in the evaluation system is obtained by the hierarchical analysis method; according to the actual geological parameters of each sub-area of ​​multiple secondary evaluation indicators in the evaluation system, multiple secondary evaluation indicators are assigned values ​​respectively using an assignment standard that can assign values ​​to the evaluation indicators according to the geological parameters that meet the underground gasification work; a first data set constructed by the primary evaluation indicators and the secondary evaluation indicators is used as an evaluation factor set, and a second data set constructed by the set evaluation results is used as an evaluation result set; according to the assignment results of multiple secondary evaluation indicators, a membership function for evaluating the membership of indicators is used to obtain a membership matrix between the evaluation factor set and the evaluation result set; according to the weight and the membership matrix, a multi-level fuzzy evaluation method is used to obtain the membership of the evaluation system; and according to the optimal membership principle, the underground gasification of remaining coal in each sub-area is evaluated to obtain the evaluation results.

[0007] Furthermore, the use of the value assignment standard capable of assigning values ​​to the evaluation indicators according to the geological parameters that meet the underground gasification work is used to assign values ​​to the multiple secondary evaluation indicators respectively, and the specific steps include: Multiple secondary evaluation indicators are assigned values ​​according to the national standard and industry standard assignment standards, and the assignment standards include: Within the first-level evaluation index of the geological conditions, the production years are set according to the cost and profit budget of the resource volume, and the resource volume is assigned a value; the coal seam roof is divided into extremely difficult to collapse hard roof, difficult to collapse hard roof, weak curved roof, medium collapse roof and easy to collapse loose roof according to its properties, and the coal seam roof is assigned a value according to its properties; the exploration degree is classified into underground work, three-dimensional seismic, geophysical exploration, exploration and below exploration, and the exploration degree is assigned a value according to the classification; the time required for reverse fire penetration between boreholes with an interval of 20 m is used as the standard for the development degree of coal seam fissures, and the coal seam fissures are assigned a value; the geological structure is classified into simple geological structure, medium geological structure, relatively complex geological structure, complex geological structure and extremely complex geological structure, and the geological structure is assigned a value according to the classification; In the first-level evaluation index of the coal seam conditions, the thickness of the lignite seam for gasification must be greater than 2m, and the thickness of the coal seam with a higher degree of coalification than bituminous coal must be greater than 0.8m. The total thickness of the entire coal seam that can be gasified must be greater than 15m. The thickness of the coal seam is assigned according to the thickness value; the inclination of the coal seam is assigned according to the angle of inclination; the burial depth of the coal seam is assigned according to the relationship between the burial depth and environmental protection, economy and sealing; the stability of the coal seam is classified into stable coal seam, relatively stable coal seam, relatively unstable coal seam, unstable coal seam and extremely unstable coal seam, and the stability is assigned according to the classification; when there is no interlayer of coal seam, the gasification process will have no support force and will lead to collapse, which is not conducive to gasification. As the interlayer of coal seam increases, the gasification recovery rate will decrease, and the interlayer of coal seam is assigned according to the amount of interlayer of coal seam; In the first-level evaluation index of the coal quality, when the ash content of coal is between 5% and 30%, it will be beneficial to gasification, and the ash content of coal is assigned according to the ash content; when the fixed carbon content of coal is between 55% and 90%, gasification is effective, and the fixed carbon of the coal seam is assigned according to the fixed carbon content; when the cohesiveness index of coal does not exceed 50%, it is beneficial to gasification, and the cohesiveness of the coal seam is assigned according to the cohesiveness index; when the ash melting point of coal is higher than 1100°C, it is beneficial to gasification, and the ash melting point of the coal seam is assigned according to the value of the ash melting point; for CO2 reaction activity, the gasification index of coal is 1000°C, and the coal seam ash melting point is assigned according to the value of the ash melting point. In terms of properties, the level of reaction activity affects the oxygen consumption, coal gas composition, carbon content of carryover and ash residue, unit gas production rate and gasification thermal efficiency during gasification. The gasification activity of CO2 at different temperatures is different. The CO2 reaction activity of coal seams is assigned according to the CO2 reaction activity at different temperatures; when the ignition point of coal does not exceed 700℃, it is conducive to gasification work, and the ignition point of the coal seam is assigned according to the value of the ignition point; when the upper limit of the sulfur content of coal is between 2% and 4%, it is conducive to gasification work, and the sulfur content of the coal seam is assigned according to the sulfur content; In the first-level evaluation index of the hydrological conditions, coal seams are divided into non-water-filled deposits, indirect water-filled deposits and direct water-filled deposits according to the water-filling conditions, and the water-filling conditions are assigned values ​​according to the classification; according to the water-filling characteristics, the forms of groundwater entering the coal seams are divided into karst, fissures and pores, and the characteristics are extremely uneven, uneven and relatively uniform, respectively, and the characteristics are assigned values ​​according to the characteristics; when the water-richness is less than 0.1L / (s·m) per unit water inflow, it does not affect the gasification work, and the allowable water inflow for bituminous coal gasification is 0.7m 3 / t~1.5 m 3 / t, the allowable water inflow of lignite is 0.3m 3 / t~1.0 m 3 / t, assign values ​​to water richness according to its value; water resources are classified into abundant, relatively abundant, medium, relatively scarce and scarce according to the amount of water, and assign values ​​to water resources according to the classification; prevention and control difficulty is divided into small, relatively small, medium, relatively large and large according to the industry difficulty, and assign values ​​to prevention and control difficulty according to the difficulty classification; According to the assignment results, when the assignment result is between 90 and 100, the evaluation level is "good"; when the assignment result is between 70 and 90, the evaluation level is "good"; when the assignment result is between 50 and 70, the evaluation level is "average"; when the assignment result is between 0 and 50, the evaluation level is "poor".

[0008] Furthermore, the weight of each evaluation indicator in the evaluation system is obtained by the hierarchical analysis method, and the specific steps include: establishing a hierarchical model with multiple first-level evaluation indicators as the target layer and multiple second-level evaluation indicators as the criterion layer; at the criterion layer, comparing each second-level evaluation indicator pairwise and assigning relative importance to each second-level evaluation indicator; constructing a judgment matrix according to the relative importance; obtaining the maximum eigenvalue and the corresponding eigenvector according to the judgment matrix, and performing a consistency test; through the consistency test, using the eigenvector as the weight vector to obtain the weight of each second-level evaluation indicator.

[0009] Furthermore, the use of the membership function for evaluating the membership of the index to obtain the membership matrix between the evaluation factor set and the evaluation result set specifically comprises the following steps: Acquire an evaluation factor set and an evaluation result set, wherein the evaluation factor set includes a primary evaluation factor set and a secondary evaluation factor set, wherein the primary evaluation factor set is composed of a plurality of primary evaluation indicators, and the secondary evaluation factor set is composed of a plurality of secondary evaluation indicators; The evaluation result set Z includes: Z={D≥80, suitable; 60≤D<80, relatively suitable; D<60, unsuitable}; Set the evaluation results and the corresponding membership model: Set the first membership model with the evaluation result as "suitable" , the formula is: The second membership model with the evaluation result set to "relatively suitable" , the formula is: The third membership model with the evaluation result set to "unsuitable" , the formula is: in, Indicates the value assigned to each secondary evaluation indicator; Input the value of each secondary evaluation indicator into the membership model, obtain the membership of the evaluation level corresponding to each evaluation indicator, and establish the membership vector of each evaluation indicator; According to the membership vector of each evaluation index, the membership matrix under each first-level evaluation index is established.

[0010] Furthermore, the use of the multi-level fuzzy evaluation method to obtain the membership of the evaluation system specifically includes: starting from the lowest level of all levels of the evaluation system, fuzzy synthesis of each evaluation indicator and the corresponding weight to obtain the membership of the previous level, until the membership of the highest level of all levels is obtained.

[0011] Furthermore, the remaining underground coal gasification work in each zone is evaluated, and the specific steps include: when the evaluation result corresponding to the membership degree is "suitable", the zone is determined as a "preferred zone"; when the evaluation result corresponding to the membership degree is "relatively suitable", the zone is determined as a "developable zone"; when the evaluation result corresponding to the membership degree is "unsuitable", the zone is determined as a "prospective zone".

[0012] The embodiment of the present invention provides a system for evaluating the conditions of underground gasification of residual coal in a closed coal mine, comprising: An indicator acquisition module is used to divide the remaining coal resources of closed coal mines into zones; to obtain multiple primary indicators and multiple secondary indicators for evaluating the underground gasification of remaining coal; wherein the multiple primary evaluation indicators include: geological conditions, coal seam conditions, coal quality conditions and hydrological conditions; the secondary evaluation indicators of the geological conditions include: resource volume, coal seam roof, exploration degree, coal seam fissures and geological structure; the secondary evaluation indicators of the coal seam conditions include: thickness, inclination, burial depth, stability and interlayer; the secondary evaluation indicators of the coal quality conditions include: ash content, fixed carbon, cohesion, ash melting point, CO2 reaction activity, ignition point and sulfur content; the secondary evaluation indicators of the hydrological conditions include: water filling conditions, water filling characteristics, water richness, water resources and prevention and control difficulty; an evaluation system construction module is used to jointly construct a multi-level evaluation system for evaluating the underground gasification of remaining coal based on multiple primary evaluation indicators and multiple secondary evaluation indicators. An evaluation system for the work; an evaluation system evaluation module, which is used to obtain the weight of each evaluation indicator in the evaluation system through the hierarchical analysis method; according to the actual geological parameters of multiple secondary evaluation indicators in each sub-area in the evaluation system, use the assignment standard that can assign values ​​to the evaluation indicators according to the geological parameters that meet the underground gasification work to assign values ​​to the multiple secondary evaluation indicators respectively; use the first data set constructed by the primary evaluation indicators and the secondary evaluation indicators as the evaluation factor set, and use the second data set constructed by the set evaluation results as the evaluation result set; according to the assignment results of multiple secondary evaluation indicators, use the membership function for evaluating the membership of the indicators to obtain the membership matrix between the evaluation factor set and the evaluation result set; according to the weight and the membership matrix, use the multi-level fuzzy evaluation method to obtain the membership of the evaluation system; and according to the optimal membership principle, evaluate the remaining underground coal gasification work in each sub-area to obtain the evaluation results.

[0013] The embodiment of the present invention provides a method and system for evaluating the underground gasification conditions of residual coal in a closed coal mine. Compared with the prior art, the beneficial effects thereof are as follows: The remaining coal resources of closed coal mines are divided into zones; multiple primary indicators and multiple secondary indicators for evaluating the underground gasification of the remaining coal are obtained; a multi-level evaluation system is jointly constructed based on the multiple primary evaluation indicators and multiple secondary evaluation indicators; the weight of each evaluation indicator in the evaluation system is obtained through the hierarchical analysis method; the multiple secondary evaluation indicators are assigned values ​​using the assignment standard according to the actual geological parameters of the multiple secondary evaluation indicators in each zone in the evaluation system; the first data set constructed by the primary evaluation indicators and the secondary evaluation indicators is used as the evaluation factor set, and the second data set constructed by the set evaluation results is used as the evaluation result set; according to the assignment results of the multiple secondary evaluation indicators, the membership matrix between the evaluation factor set and the evaluation result set is obtained using the membership function; according to the weight and the membership matrix, the membership of the evaluation system is obtained using the multi-level fuzzy evaluation method; and according to the optimal membership principle, the underground gasification of the remaining coal in each zone is evaluated to obtain the evaluation results.

[0014] The evaluation system is composed of multiple first-level indicators and multiple second-level indicators for evaluating the underground gasification of remaining coal, and the second-level indicators are subordinate indicators of the first-level indicators. The first-level evaluation indicators and the second-level evaluation indicators are multiple factors affecting the underground gasification of remaining coal. After quantifying multiple second-level evaluation indicators through the assignment standard, the multi-level fuzzy evaluation method and the optimal membership principle are used to evaluate the underground gasification of remaining coal in each partition according to the weight of each evaluation indicator in the evaluation system. The influence of multiple factors affecting the underground gasification of remaining coal in the evaluation is fully considered, and the gasification work of the remaining resources of closed coal mines can be systematically and comprehensively evaluated to obtain accurate research results of underground gasification work. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flowchart provided for an embodiment of the present invention; Figure 2 A schematic diagram of geological condition indicators provided by an embodiment of the present invention; Figure 3 A schematic diagram of coal seam condition indicators provided by an embodiment of the present invention; Figure 4 A schematic diagram of coal quality indicators provided by an embodiment of the present invention; Figure 5 A schematic diagram of hydrological condition indicators provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0017] See also Figure 1 The embodiment of the present invention provides a method for evaluating the underground gasification conditions of residual coal in a closed coal mine, comprising the following steps: Step 1: Divide the remaining coal resources of closed coal mines into different zones; obtain multiple primary indicators and secondary indicators for evaluating the underground gasification of remaining coal; among them, multiple primary evaluation indicators include: geological conditions, coal seam conditions, coal quality conditions and hydrological conditions; secondary evaluation indicators of geological conditions include: resource volume, coal seam roof, exploration degree, coal seam fissures and geological structure; secondary evaluation indicators of coal seam conditions include: thickness, inclination, burial depth, stability and interlayer; secondary evaluation indicators of coal quality conditions include: ash content, fixed carbon, adhesion, ash melting point, CO2 reaction activity, ignition point and sulfur content; secondary evaluation indicators of hydrological conditions include: water filling conditions, water filling characteristics, water richness, water resources and difficulty of prevention and control.

[0018] Step 2: Based on multiple first-level evaluation indicators and multiple second-level evaluation indicators, jointly construct a multi-level evaluation system for evaluating the remaining underground coal gasification work.

[0019] Step three: obtain the weight of each evaluation indicator in the evaluation system through the hierarchical analysis method; assign values ​​to multiple secondary evaluation indicators respectively according to the actual geological parameters of each sub-area of ​​multiple secondary evaluation indicators in the evaluation system using an assignment standard that can assign values ​​to evaluation indicators according to geological parameters that meet the requirements of underground gasification work; use a first data set constructed by the primary evaluation indicators and the secondary evaluation indicators as an evaluation factor set, and use a second data set constructed by the set evaluation results as an evaluation result set; and use a membership function for evaluating indicator membership to obtain a membership matrix between the evaluation factor set and the evaluation result set according to the assignment results of multiple secondary evaluation indicators.

[0020] Step 4: According to the weight and membership matrix, use the multi-level fuzzy evaluation method to obtain the membership of the evaluation system; and according to the principle of optimal membership, evaluate the remaining underground coal gasification work in each zone to obtain the evaluation results.

[0021] The specific implementation details are as follows: 1. Types of closed coal mines.

[0022] The types of closed coal mines include: Q1, which is relatively economically exhausted type of recoverable resources, and Q2, which is relatively technically exhausted type of recoverable resources. It is characterized by the low production capacity of the coal mine itself and the closure, or the large but relatively scattered total recoverable reserves of the coal mine itself. It is a coal mine with complex geological conditions and incomplete underground engineering conditions, but the remaining coal resources and the remaining coal resources account for a high proportion of the total cumulative resources; Q2, which is closed due to overcapacity, which is characterized by excellent mining conditions, high coal quality and high reserves of the remaining coal in the coal mine, but closed due to market price fluctuations and policy requirements. It is a coal mine with simple geological conditions, complete underground engineering layout, and a high proportion of the remaining coal resources and the remaining resources account for a high proportion of the total cumulative resources; Q3 is the "three-under" coal resource type, which is characterized by being closed due to being located under buildings, water bodies and protected areas, and the covered coal resources account for more than 50% of the total remaining resources. Among them, Q1 and Q2 types of closed coal mines are preferred closed coal mines, which are suitable for underground coal gasification. In the preferred closed coal mines, the underground coal resources are calculated, and the underground coal resources are divided into zones to select the reuse advantage areas.

[0023] 2. Evaluation system.

[0024] The evaluation system U includes two levels of evaluation indicators; among them, there are four first-level evaluation indicators of U, namely geological conditions U1, coal seam conditions U2, coal quality conditions U3, and hydrological conditions U4.

[0025] 1) The secondary evaluation index of geological condition U1 is resource quantity U 11 / 10,000 t, coal seam roof U 12 , exploration degree U 13 , coal seam fissure U 14 / d, geological structure U 15 .

[0026] 2) The secondary evaluation index of coal seam condition U2 is thickness U 21 / m, inclination angle U 22 / (°), burial depth U 23 / m, stability U 24 , U 25 .

[0027] 3) The secondary evaluation index of coal quality condition U3 is ash content U 31 / %,Fixed Carbon U 32 / %, Adhesion U 33 , ash melting point U 34 / ℃, CO2 reaction activity U 35 (900℃), ignition point U 36 / ℃, sulfur content U 37 / %.

[0028] 4) The secondary evaluation index of hydrological condition U4 is the water filling condition U 41 , water filling characteristic U 42, water-rich U 43 , Water Resources 44 , prevention and control difficulty U 45 .

[0029] The above-mentioned primary evaluation indicators and secondary evaluation indicators together constitute a multi-level evaluation system for underground gasification of residual coal in closed coal mines, as shown in Table 1.

[0030] Table 1 Index charts at all levels 3. Grades and values ​​of evaluation indicators.

[0031] The above-mentioned first-level indicators (geological conditions U1, coal seam conditions U2, coal quality conditions U3, hydrological conditions U4) and second-level indicators can all be covered in the closure report of the closed coal mine. Through the actual geological parameters in the report, each second-level indicator is assigned based on the assignment standard (national standard, industry standard) and calculation results.

[0032] The evaluation index levels and values ​​are as follows: good, [90, 100]; better, [70, 90]; average, [50, 70]; poor, [0, 50].

[0033] For the resource volume U in geological condition U1 11 The larger the resource volume, the better the economic efficiency. According to the cost and profit budget, the production period is set and the resource volume is assigned by comprehensive analysis. 12 For the roof properties, they are divided into extremely difficult to collapse and hard, difficult to collapse and hard, weak and curved, moderately collapsed, and easy to collapse and loose. The difficult to collapse and hard roof is conducive to gasification work, and the values ​​are assigned accordingly; for the exploration degree U 13 For the exploration degree, it is divided into underground exploration, 3D seismic, geophysical exploration, exploration, exploration and below. The exploration degree determines the control degree of coal seam and the reliability of resource quantity, and the value is assigned accordingly. For coal seam fracture U 14 In terms of past work experience, the time required for reverse fire penetration between boreholes 20 m apart is used as the standard for the degree of development of coal seam fractures. The longer the time, the slower the gasification channel penetration speed, and the value is assigned accordingly. 15 Generally speaking, geological structures are divided into simple, medium, relatively complex, complex, and extremely complex. The more complex it is, the less conducive it is to gasification work, and values ​​are assigned accordingly.

[0034] For the coal seam case U2, the thickness U 21 The minimum thickness of lignite gasification is 2 m, the minimum thickness of bituminous coal gasification is 0.8 m, and the total thickness of safe coal seams is 15 m. Considering previous work experience and economic efficiency, the values ​​are assigned. 22From a geological perspective, any coal seam can be gasified underground, but a large inclination angle will bring certain difficulties to furnace construction. Generally, the inclination angle should be less than 45°, and the values ​​are assigned in sequence. 23 For the stability U, the burial depth is mainly related to environmental protection, economy, and sealing. The underground gasification technology of deep coal seams (more than 1000 m deep) is not yet mature, so the value is assigned accordingly. 24 For coal seam, it is divided into stable, relatively stable, relatively unstable, unstable and extremely unstable. The stability of coal seam mainly affects the construction and stable operation of furnace, and the value is assigned accordingly. 25 Generally speaking, when there is no gangue in the coal seam, the gasification process has no supporting force and will collapse rapidly in the later stage, which is not conducive to gasification; when there are too many gangue layers in the coal seam, the gasification recovery rate will be reduced, and the value is assigned considering previous work experience.

[0035] For the ash content U in coal quality condition U3 31 For coal, there are certain requirements for the upper and lower limits of ash content. If the ash content is too high, ash will accumulate at the bottom of the hole in the later stage, which is very likely to cause problems such as blockage of furnace holes and channels, and the gasification reaction rate will be affected; if the ash content is too low, it is difficult to form a breathable support body, resulting in roof collapse. Generally speaking, 5% to 30% ash content in coal will be conducive to gasification work, and the value is assigned accordingly. For fixed carbon U 32 In general, the increase of carbon content in coal is conducive to the gasification reaction, but if the carbon content is too high, the consumption of oxygen and water vapor will increase greatly. According to the special requirements of underground gasification, the fixed carbon content of 55% to 90% is the best, and the value is assigned accordingly; for the caking U 33 For the ash melting point U, the higher the coking property, the stronger the coking property, which affects the thermal conductivity and is not conducive to gasification. Considering the economic efficiency, the cohesiveness of gasified coal should be non-cohesive or weakly cohesive, and the cohesive index should not exceed 50%. The value is assigned accordingly. 34 For the ash melting point, the higher it is, the more conducive it is to gasification. On the contrary, the ash is easy to become molten, stick and enter the cracks of the coal seam, affecting gasification. The ash melting point should generally be higher than 1100℃, and the value is assigned accordingly. For the CO2 reaction activity U 35 For gasification, the level of reaction activity affects the oxygen consumption, gas composition, carbon content of carryover and ash residue, unit gas production rate and gasification thermal efficiency and other production indicators during gasification. The gasification activity of CO2 at different temperatures is different. At 900℃, the reaction activity is generally not less than 30, and the value is assigned accordingly. For the ignition point U 36 Generally speaking, the ignition point of coal does not affect the gasification process, but the underground ignition work in the early stage of gasification has certain requirements for the ignition point of coal. Combined with previous engineering tests, the ignition point should not exceed 700℃, and the value is assigned accordingly; for sulfur content U 37For coal, the sulfur content is high, and the gas after gasification is highly corrosive, which affects the service life of the equipment. In addition, the corrosion of equipment such as casing and the discharge of gas are likely to cause the gas to enter the aquifer or the atmosphere, resulting in environmental effects. High-sulfur coal gas will also increase the pressure of the purification system and increase production costs. Domestic and foreign researchers have set limits on the upper limit of sulfur content in coal, and the upper limit ranges from 2% to 4%, and the value is assigned accordingly.

[0036] For the water filling condition U4 in the hydrological condition 41 For the gasification zone, there is no possibility of hydraulic connection under gasification conditions, which is called a non-water-filled deposit (category 1); there is an aquiclude between the gasifier and the aquifer, and hydraulic connection may occur during operation, which is called an indirect water-filled deposit (category 2); the deposit whose direct roof or floor of the gasifier is an aquifer is called a direct water-filled deposit (category 3). Categories 1 and 2 are suitable for gasification work, and are assigned accordingly. For the water-filled characteristic U 42 In general, groundwater enters coal seams in the form of karst, fissures and pores, and its characteristics are extremely uneven, uneven and relatively uniform. Karst and fissure water-filled deposits are generally more suitable for gasification work, and the value is assigned accordingly. 43 For water resources, the unit water inflow is less than 0.1L / (s·m), and the water-richness under this condition basically does not affect the gasification work; water inflow is not allowed in the gasifier during the gasification process of high-water-content coal. The allowable water inflow for bituminous coal gasification is 0.7-1.5 m3 / t, and the allowable water inflow for lignite is 0.3-1.0 m3 / t. The values ​​are assigned accordingly; for water resources U 44 In terms of resource abundance and scarcity, both will have a direct or indirect impact on gasification work. Water resources are divided into abundant, relatively abundant, medium, relatively scarce, and scarce, and replication is carried out accordingly; for the difficulty of prevention and control, U 45 Generally speaking, they are divided into small, smaller, medium, larger and large. The difficulty of prevention and control determines the investment in groundwater prevention and control projects, and they are ranked accordingly.

[0037] All the assignment results obtained by the evaluation system through the above steps are integrated to obtain the evaluation index assignment results.

[0038] 4. Weight of evaluation indicators.

[0039] According to the importance, a judgment matrix is ​​constructed by comparing the importance of each pair. Based on the judgment matrix, the matrix eigenvector is obtained by the sum-product method. The matrix eigenvector is tested for consistency. Based on the test results, the evaluation index weights are obtained.

[0040] 5. The degree of membership of each evaluation level.

[0041] The process of obtaining the membership of each evaluation level includes: establishing an evaluation factor set and an evaluation result set; establishing a membership matrix between the evaluation factor set and the evaluation result set; establishing a membership matrix through a membership function, and the mathematical expression of the membership function corresponding to each evaluation result level is: D1 suitable [80, 100]: D2 is more suitable [60, 80): D3 is not suitable [0, 60]: Substitute the values ​​of each evaluation index of the evaluation unit to obtain the membership of each evaluation index corresponding to each evaluation level, and establish the membership vector R of each evaluation index ij ,Right now: Wherein, i=1, 2, …, n, n is the number of primary indicators, here n=4; j=1, 2, …, m, m is the number of secondary indicators in the primary indicators, here when i=1, 2 and 4, m=5, and when i=3, m=7; k=1, 2, …, x, x is the number of elements in the evaluation result set, here x=4.

[0042] Then establish the membership matrix under each first-level evaluation index Ri ,Right now: Similarly, the membership vectors and matrices of the evaluation units and indicators are obtained.

[0043] 6. Evaluation level.

[0044] The membership of different evaluation levels is judged by the optimal membership principle, and the corresponding evaluation level is selected based on the judgment result. Based on the selected evaluation level, the selection result is obtained, where the selection result includes the preferred area, the developable area, and the prospective area in the order of suitable, relatively suitable, and unsuitable evaluation levels. The evaluation results include 3 subsets, Z={D≥80, suitable; 60≤D<80, relatively suitable; D<60, unsuitable}.

[0045] The present invention also has the following effects: The present invention establishes a multi-level and comprehensive evaluation system for underground gasification of residual coal in closed coal mines, adopts multiple mathematical methods, considers multiple control factors, is progressive and scientific, and has the characteristics of accurate evaluation, easy to obtain evaluation indicators, and simple and easy to operate evaluation process. Through this method, favorable areas for underground gasification of residual coal in closed coal mines are judged, and their development priority and adaptability are determined. The advantages of the evaluation include: (1) the evaluation indicators can directly reflect the potential of underground gasification of residual coal in closed coal mines; (2) the evaluation indicator parameters are easy to obtain; (3) the evaluation indicator parameters are easy to calculate; (4) the evaluation process is scientific and the operation is relatively simple.

[0046] All the assignment results obtained by the evaluation system through the above steps are integrated to obtain the evaluation index assignment results.

[0047] The embodiment of the present invention provides a system for evaluating the conditions of underground gasification of residual coal in a closed coal mine, comprising: The indicator acquisition module is used to divide the remaining coal resources of closed coal mines into zones; to obtain multiple primary indicators and multiple secondary indicators for evaluating the underground gasification of remaining coal; wherein, multiple primary evaluation indicators include: geological conditions, coal seam conditions, coal quality conditions and hydrological conditions; the secondary evaluation indicators of geological conditions include: resource volume, coal seam roof, exploration degree, coal seam fissures and geological structure; the secondary evaluation indicators of coal seam conditions include: thickness, inclination, burial depth, stability and interlayer; the secondary evaluation indicators of coal quality conditions include: ash content, fixed carbon, cohesion, ash melting point, CO2 reaction activity, ignition point and sulfur content; the secondary evaluation indicators of hydrological conditions include: water filling conditions, water filling characteristics, water richness, water resources and prevention and control difficulty. The evaluation system construction module is used to jointly construct a multi-level evaluation system for evaluating the underground gasification of remaining coal based on multiple primary evaluation indicators and multiple secondary evaluation indicators. The evaluation system evaluation module is used to obtain the weight of each evaluation indicator in the evaluation system through the hierarchical analysis method; according to the actual geological parameters of multiple secondary evaluation indicators in each sub-area in the evaluation system, use the assignment standard that can assign values ​​to the evaluation indicators according to the geological parameters that meet the underground gasification work to assign values ​​to the evaluation indicators respectively; use the first data set constructed by the first-level evaluation indicators and the second-level evaluation indicators as the evaluation factor set, and use the second data set constructed by the set evaluation results as the evaluation result set; according to the assignment results of multiple secondary evaluation indicators, use the membership function for evaluating the membership of the indicators to obtain the membership matrix between the evaluation factor set and the evaluation result set; according to the weight and the membership matrix, use the multi-level fuzzy evaluation method to obtain the membership of the evaluation system; and according to the optimal membership principle, evaluate the remaining underground coal gasification work in each sub-area to obtain the evaluation results.

[0048] A specific embodiment is as follows: like Figure 1As shown, this embodiment provides an underground gasification geological condition evaluation system, including: (1) Preliminary selection of closed coal mines, with favorable closed coal mines being prioritized; among the prioritized closed coal mines, underground coal resources are calculated, and the underground coal resources are zoned to select areas with advantages for reuse.

[0049] (2) Construct an evaluation system and assign values ​​to evaluation indicators based on the characteristics of underground remaining coal resources; calculate the evaluation indicators through the analytic hierarchy process to obtain the evaluation indicator weights.

[0050] The evaluation index assignment standard assigns values ​​to each evaluation index and obtains the parameters of the evaluation unit in the evaluation index.

[0051] Parameter acquisition of evaluation unit: 1) Resource volume / 10,000 tons: Obtain remaining coal seam resources from mine closure reports.

[0052] 2) Coal seam roof: Obtain the roof lithology characteristics of the coal seam to be evaluated from the mine closure report.

[0053] 3) Extent of investigation: The extent of coal mining is obtained from the mine closure report.

[0054] 4) Coal seam fissures / d: Obtain coal seam fracture development information from the mine closure report.

[0055] 5) Geological structure: Obtain the geological structure of the mining area from the mine closure report.

[0056] 6) Thickness / m: Obtain the thickness range of the remaining coal seam from the pit closure report.

[0057] 7) Inclination angle / (°): Obtain the dip range of the remaining coal seams from the pit closure report.

[0058] 8) Buried depth / m: Obtain the depth range of the remaining coal seam from the mine closure report.

[0059] 9) Stability: Obtain the remaining coal seam stability information from the mine closure report.

[0060] 10) Gangue inclusions: Obtain the remaining coal seam interlayer situation from the mine closure report.

[0061] 11) Ash content / %: The ash content test method in GB / T212-2008 is obtained.

[0062] 12) Fixed carbon / %: Obtained from the fixed carbon test method in GB / T212-2008.

[0063] 13) Adhesion: Obtained from the adhesion test method in GB / T5447-2014.

[0064] 14) Ash melting point / ℃: Obtained from the ash melting point test method in GB / T219-2008.

[0065] 15) CO2 reactivity: Obtained from the CO2 reactivity test method in GB / T220-2018.

[0066] 16) Ignition point / ℃: Obtained from the fire point test method in GB / T18511-2017.

[0067] 17) Sulfur content / %: Obtained from the sulfur content test method in GB / T214-2007.

[0068] 18) Water filling conditions: Obtain information on water filling conditions from pit closure reports.

[0069] 19) Water filling characteristics: Obtain water filling characteristics from pit closure reports.

[0070] 20) Water-richness: Obtain water richness information from pit closure reports.

[0071] 21) Water resources: Obtain water resource status from pit closure reports.

[0072] 22) Difficulty of prevention and control: Obtain the amount of groundwater inflow from the pit closure report and make a comprehensive assessment of the difficulty of groundwater prevention and control.

[0073] The process of obtaining the evaluation index weights includes: When comparing the importance of two elements, the more important the former is, the larger the value assigned. When the two are equally important, the value assigned is 1. When the latter is more important than the former, the value assigned is the inverse of the previous value. The value assigned does not exceed 9.

[0074] The importance of each indicator at the first level is: U1>U2>U4>U3.

[0075] The importance of each secondary indicator is as follows: Get the relative weight and eigenvalue of the elements: The eigenvalue vector corresponding to the maximum eigenvalue of the judgment matrix is ​​the weight vector, and the weight and eigenvalue vector are obtained according to the "sum-product method". The eigenvalue vector corresponding to the maximum eigenvalue of the judgment matrix is ​​the weight vector, and the weight and eigenvalue vector can be obtained by the "sum-product method". The process is as follows: First, the judgment matrix is ​​normalized by columns: (v, p = 1, 2, ..., n).

[0076] Secondly, add the normalized matrices row by row: (v=1,2,…,n).

[0077] Then, for the vector W s =(w 1a , w 2a ,…,w na ) T For normalization, that is: (v, p = 1, 2,…, n).

[0078] Then the vector W=(W1,W2,…,W n ) T That is, the maximum feature in the corresponding feature matrix.

[0079] Finally, calculate the largest eigenvalue: Where is the vth element of the vector PW, and PW is the judgment matrix Po multiplied by the eigenvector W on the right.

[0080] Consistency check: weights and feature vectors are checked for consistency to obtain evaluation index weights; First, calculate the consistency index CI: .

[0081] Secondly, the consistency ratio CR is obtained: .

[0082] RI can be obtained by looking up the table. When the matrix order is 3, RI = 0.52, and when the matrix order is 4, RI = 0.89. When CR < 0.1, the consistency test passes.

[0083] (3) Based on the evaluation indicators, the evaluation factor set and the evaluation result set are constructed, and based on the evaluation indicator assignment results, the membership matrix between the evaluation factor set and the evaluation result set is obtained.

[0084] The process of obtaining the membership degree of each evaluation level includes: Establish evaluation factor set and evaluation result set: The evaluation factor set includes: the first-level evaluation factor set U = {geological conditions U1, coal seam conditions U2, coal quality conditions U3, hydrological conditions U4}; the second-level evaluation factor set U1 = {resource volume U 11 , coal seam roof U 12 , exploration degree U 13 , coal seam fissure U 14 , geological structure 15}; U2 = {thickness U 21 , inclination angle U 22 , burial depth U 23 , stability U 24 , U 25}; U3={ash content U 31 , fixed carbon U 32 , Adhesion U 33 , ash melting point U 34 , CO2 reactivity U 35 , ignition point U 36 , sulfur content U 37}; U4={water filling condition U 41 , water filling characteristic U 42 , water-rich U 43 , Water Resources 44 , prevention and control difficulty U 45 As shown in Table 2.

[0085] Table 2 Indicator set The evaluation results of each evaluation unit are obtained according to the principle of optimal membership, and the evaluation results include three subsets, Z={D≥80, suitable; 60≤D<80, relatively suitable; D<60, unsuitable}.

[0086] Establish the membership matrix between the evaluation factor set and the evaluation result set: Establish the membership matrix through the membership function. The mathematical expression of the membership function corresponding to each evaluation result level is: D1 suitable [80, 100]: D2 is more suitable [60, 80): D3 is not suitable [0, 60]: Substitute the values ​​of each evaluation index of the evaluation unit to obtain the membership of each evaluation index corresponding to each evaluation level, and establish the membership vector R of each evaluation index ij ,Right now: Wherein, i=1, 2, …, n, n is the number of primary indicators, here n=4; j=1, 2, …, m, m is the number of secondary indicators in the primary indicators, here when i=1, 2 and 4, m=5, and when i=3, m=7; k=1, 2, …, x, x is the number of elements in the evaluation result set, here x=4.

[0087] Then, the membership matrix Ri under each first-level evaluation index is established, namely: Similarly, the membership vectors and matrices of the evaluation units and indicators are obtained.

[0088] First, construct a weight vector with the weights of indicators at all levels. The weight vector for the first-level indicator is W i ={w i1 , w i2 ,…,w ij},but: The weight vector of the first-level indicator: The weight vector W1={} relative to the geological condition U1.

[0089] The weight vector W2={} relative to the coal seam condition U2.

[0090] The weight vector W3={} relative to the coal quality condition U3.

[0091] The weight vector W4={} relative to the hydrological condition U4.

[0092] The weight vector relative to the target layer is W = {w1, w2, w3}.

[0093] Obtain the membership of the target layer relative to each evaluation level.

[0094] Through the principle of multi-level fuzzy evaluation, a single factor judgment matrix R is constructed: .

[0095] Then construct the secondary fuzzy comprehensive judgment result set B: .

[0096] The process of obtaining the evaluation level of the evaluation unit includes: obtaining the evaluation results of each evaluation unit according to the principle of optimal membership, and selecting result D1 as the preferred coal mine suitable for underground gasification, and giving priority to the development of underground gasification; result D2 as the preferred coal mine relatively suitable for underground gasification, and underground gasification development can be carried out; result D3 as the preferred coal mine not suitable for underground gasification, and the underground gasification work is not ideal. As shown in Table 3.

[0097] Table 3 Suitability table The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for evaluating the underground gasification conditions of residual coal in a closed coal mine, characterized in that: The following steps are involved: Zoning remaining coal resources from closed mines; Acquire multiple primary indicators and multiple secondary indicators for evaluating the underground gasification of residual coal; wherein the multiple primary evaluation indicators include: geological conditions, coal seam conditions, coal quality conditions and hydrological conditions; the secondary evaluation indicators of the geological conditions include: resource volume, coal seam roof, exploration degree, coal seam fissures and geological structure; the secondary evaluation indicators of the coal seam conditions include: thickness, inclination, burial depth, stability and interlayer; the secondary evaluation indicators of the coal quality conditions include: ash content, fixed carbon, cohesiveness, ash melting point, CO2 reaction activity, ignition point and sulfur content; the secondary evaluation indicators of the hydrological conditions include: water filling conditions, water filling characteristics, water richness, water resources and difficulty of prevention and control; Based on multiple first-level evaluation indicators and multiple second-level evaluation indicators, a multi-level evaluation system for evaluating the remaining underground coal gasification work is jointly constructed; the weight of each evaluation indicator in the evaluation system is obtained through the hierarchical analysis method; According to the actual geological parameters of each sub-area of ​​the multiple secondary evaluation indicators in the evaluation system, the multiple secondary evaluation indicators are assigned values ​​respectively using an assignment standard that can assign values ​​to the evaluation indicators according to the geological parameters that meet the underground gasification work; A first data set constructed by the primary evaluation index and the secondary evaluation index is used as an evaluation factor set, and a second data set constructed by the set evaluation results is used as an evaluation result set; according to the assignment results of the plurality of secondary evaluation indexes, a membership function for evaluating the membership of the index is used to obtain a membership matrix between the evaluation factor set and the evaluation result set; According to the weight and membership matrix, the membership of the evaluation system is obtained using a multi-level fuzzy evaluation method; and according to the principle of optimal membership, the remaining underground coal gasification work in each zone is evaluated to obtain the evaluation results.

2. The method for evaluating the underground gasification conditions of residual coal in a closed coal mine according to claim 1, characterized in that: The method of using the value assignment standard that can assign values ​​to the evaluation indicators according to the geological parameters that meet the underground gasification work to assign values ​​to the multiple secondary evaluation indicators respectively includes the following specific steps: Multiple secondary evaluation indicators are assigned values ​​according to the national standard and industry standard assignment standards, and the assignment standards include: Within the first-level evaluation index of the geological conditions, the production years are set according to the cost and profit budget of the resource volume, and the resource volume is assigned a value; the coal seam roof is divided into extremely difficult to collapse hard roof, difficult to collapse hard roof, weak curved roof, medium collapse roof and easy to collapse loose roof according to its properties, and the coal seam roof is assigned a value according to its properties; the exploration degree is classified into underground work, three-dimensional seismic, geophysical exploration, exploration and below exploration, and the exploration degree is assigned a value according to the classification; the time required for reverse fire penetration between boreholes with an interval of 20 m is used as the standard for the development degree of coal seam fissures, and the coal seam fissures are assigned a value; the geological structure is classified into simple geological structure, medium geological structure, relatively complex geological structure, complex geological structure and extremely complex geological structure, and the geological structure is assigned a value according to the classification; In the first-level evaluation index of the coal seam conditions, the thickness of the lignite seam for gasification must be greater than 2m, and the thickness of the coal seam with a higher degree of coalification than bituminous coal must be greater than 0.8m. The total thickness of the entire coal seam that can be gasified must be greater than 15m. The thickness of the coal seam is assigned according to the thickness value; the inclination of the coal seam is assigned according to the angle of inclination; the burial depth of the coal seam is assigned according to the relationship between the burial depth and environmental protection, economy and sealing; the stability of the coal seam is classified into stable coal seam, relatively stable coal seam, relatively unstable coal seam, unstable coal seam and extremely unstable coal seam, and the stability is assigned according to the classification; when there is no interlayer of coal seam, the gasification process will have no support force and will lead to collapse, which is not conducive to gasification. As the interlayer of coal seam increases, the gasification recovery rate will decrease, and the interlayer of coal seam is assigned according to the amount of interlayer of coal seam; In the first-level evaluation index of the coal quality, when the ash content of coal is between 5% and 30%, it will be beneficial to gasification, and the ash content of coal is assigned according to the ash content; when the fixed carbon content of coal is between 55% and 90%, gasification is effective, and the fixed carbon of the coal seam is assigned according to the fixed carbon content; when the cohesiveness index of coal does not exceed 50%, it is beneficial to gasification, and the cohesiveness of the coal seam is assigned according to the cohesiveness index; when the ash melting point of coal is higher than 1100°C, it is beneficial to gasification, and the ash melting point of the coal seam is assigned according to the value of the ash melting point; for CO2 reaction activity, the gasification index of coal is 1000°C, and the coal seam ash melting point is assigned according to the value of the ash melting point. In terms of properties, the level of reaction activity affects the oxygen consumption, coal gas composition, carbon content of carryover and ash residue, unit gas production rate and gasification thermal efficiency during gasification. The gasification activity of CO2 at different temperatures is different. The CO2 reaction activity of coal seams is assigned according to the CO2 reaction activity at different temperatures; when the ignition point of coal does not exceed 700℃, it is conducive to gasification work, and the ignition point of the coal seam is assigned according to the value of the ignition point; when the upper limit of the sulfur content of coal is between 2% and 4%, it is conducive to gasification work, and the sulfur content of the coal seam is assigned according to the sulfur content; In the first-level evaluation index of the hydrological conditions, coal seams are divided into non-water-filled deposits, indirect water-filled deposits and direct water-filled deposits according to the water-filling conditions, and the water-filling conditions are assigned values ​​according to the classification; according to the water-filling characteristics, the forms of groundwater entering the coal seams are divided into karst, fissures and pores, and the characteristics are extremely uneven, uneven and relatively uniform, respectively, and the characteristics are assigned values ​​according to the characteristics; when the water-richness is less than 0.1L / (s·m) per unit water inflow, it does not affect the gasification work, and the allowable water inflow for bituminous coal gasification is 0.7m 3 / t~1.5 m 3 / t, the allowable water inflow of lignite is 0.3m 3 / t~1.0 m 3 / t, assign values ​​to water richness according to its value; water resources are classified into abundant, relatively abundant, medium, relatively scarce and scarce according to the amount of water, and assign values ​​to water resources according to the classification; prevention and control difficulty is divided into small, relatively small, medium, relatively large and large according to the industry difficulty, and assign values ​​to prevention and control difficulty according to the difficulty classification; According to the assignment results, when the assignment result is between 90 and 100, the evaluation level is "good"; when the assignment result is between 70 and 90, the evaluation level is "better"; when the assignment result is between 50 and 70, the evaluation level is "average"; when the assignment result is between 0 and 50, the evaluation level is "poor".

3. The method for evaluating the underground gasification conditions of residual coal in a closed coal mine according to claim 1, characterized in that: The weight of each evaluation index in the evaluation system is obtained by the hierarchical analysis method, and the specific steps include: Establish a hierarchical model with multiple first-level evaluation indicators as the target layer and multiple second-level evaluation indicators as the criterion layer; At the criterion level, each secondary evaluation index is compared pairwise and a relative importance is assigned to each secondary evaluation index; a judgment matrix is ​​constructed based on the relative importance; Obtain the maximum eigenvalue and the corresponding eigenvector according to the judgment matrix, and perform consistency check; Through consistency check, the feature vector is used as the weight vector to obtain the weight of each secondary evaluation index.

4. The method for evaluating the underground gasification conditions of residual coal in a closed coal mine according to claim 1, characterized in that: The method of using the membership function for evaluating the membership of the index to obtain the membership matrix between the evaluation factor set and the evaluation result set comprises the following specific steps: Acquire an evaluation factor set and an evaluation result set, wherein the evaluation factor set includes a primary evaluation factor set and a secondary evaluation factor set, wherein the primary evaluation factor set is composed of a plurality of primary evaluation indicators, and the secondary evaluation factor set is composed of a plurality of secondary evaluation indicators; The evaluation result set Z includes: Z={D≥80, suitable; 60≤D<80, relatively suitable; D<60, unsuitable}; Set the evaluation results and the corresponding membership model: Set the first membership model with the evaluation result as "suitable" , the formula is: The second membership model with the evaluation result set to "relatively suitable" , the formula is: The third membership model with the evaluation result set to "unsuitable" , the formula is: in, Indicates the value assigned to each secondary evaluation indicator; Input the value of each secondary evaluation indicator into the membership model, obtain the membership of the evaluation level corresponding to each evaluation indicator, and establish the membership vector of each evaluation indicator; According to the membership vector of each evaluation index, the membership matrix under each first-level evaluation index is established.

5. The method for evaluating the underground gasification conditions of residual coal in a closed coal mine according to claim 3, characterized in that: The multi-level fuzzy evaluation method is used to obtain the membership of the evaluation system, specifically including: Starting from the lowest level of all levels in the evaluation system, each evaluation indicator is fuzzily synthesized with the corresponding weight to obtain the membership of the previous level, until the membership of the highest level of all levels is obtained.

6. The method for evaluating the underground gasification conditions of residual coal in a closed coal mine according to claim 1, characterized in that: The specific steps of evaluating the remaining underground coal gasification work in each zone include: When the evaluation result corresponding to the membership degree is "suitable", the zone is determined as the "optimal zone"; When the evaluation result corresponding to the membership degree is "relatively suitable", the zone is determined as "developable zone"; When the evaluation result corresponding to the membership degree is "unsuitable", the zone is determined as a "prospective zone".

7. A system for evaluating the underground gasification conditions of residual coal in a closed coal mine, characterized in that: include: An indicator acquisition module is used to partition the remaining coal resources of closed coal mines; Acquire multiple primary indicators and multiple secondary indicators for evaluating the underground gasification of residual coal; wherein the multiple primary evaluation indicators include: geological conditions, coal seam conditions, coal quality conditions and hydrological conditions; the secondary evaluation indicators of the geological conditions include: resource volume, coal seam roof, exploration degree, coal seam fissures and geological structure; the secondary evaluation indicators of the coal seam conditions include: thickness, inclination, burial depth, stability and interlayer; the secondary evaluation indicators of the coal quality conditions include: ash content, fixed carbon, cohesiveness, ash melting point, CO2 reaction activity, ignition point and sulfur content; the secondary evaluation indicators of the hydrological conditions include: water filling conditions, water filling characteristics, water richness, water resources and difficulty of prevention and control; An evaluation system construction module is used to construct a multi-level evaluation system for evaluating the remaining underground coal gasification work based on multiple first-level evaluation indicators and multiple second-level evaluation indicators; The evaluation system evaluation module is used to obtain the weight of each evaluation indicator in the evaluation system through the hierarchical analysis method; according to the actual geological parameters of multiple secondary evaluation indicators in each sub-area in the evaluation system, use the assignment standard that can assign values ​​to the evaluation indicators according to the geological parameters that meet the underground gasification work to assign values ​​to the evaluation indicators respectively; use the first data set constructed by the first-level evaluation indicators and the second-level evaluation indicators as the evaluation factor set, and use the second data set constructed by the set evaluation results as the evaluation result set; according to the assignment results of multiple secondary evaluation indicators, use the membership function for evaluating the membership of the indicators to obtain the membership matrix between the evaluation factor set and the evaluation result set; according to the weight and the membership matrix, use the multi-level fuzzy evaluation method to obtain the membership of the evaluation system; and according to the optimal membership principle, evaluate the remaining underground coal gasification work in each sub-area to obtain the evaluation results.

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