An integrated device and method for underground residual coal gasification and solid waste backfilling

Abstract

The present invention provides a device and method for integrating underground residual coal gasification and solid waste backfilling, belonging to the technical field of underground coal gasification. It includes a gob area, where there is gangue in each gob area. Above each gob area, a number of vertical wells are horizontally arranged. The lower end of the vertical well communicates with the gob area. There is remaining coal at the top of the gob area. There are roadway safety coal pillars on both the left and right sides of the gob area. An injection gas pipeline is buried on the side of the roadway safety coal pillar, and a number of ignition nodes are installed in the injection gas pipeline. In the present invention, the stability of the overlying strata of the gob area is ensured by gangue filling, thereby maintaining the effective combustion of in-well underground coal gasification and ensuring that the gas generated by gasification is collected according to the set channels. On the other hand, through the combustion of the remaining underground coal resources, the high temperature generated promotes the pyrolysis and cracking of the organic matter in the gangue in the filling body into available combustible gas, enabling it to be synchronously converted and utilized during the gasification process.

Description

Technical Field

[0001] The invention belongs to the technical field of underground coal gasification, and particularly relates to a device and method for integrating underground residual coal gasification and solid waste backfilling. Background Art

[0002] Generally, in the underground mining of coal resources, a large amount of difficult-to-mine resources often remain underground and cannot be exploited and utilized. The loss of these coal resources causes a large amount of waste of coal resources. Well-type underground coal gasification is a method of controlling combustion. After injecting a mixed gas such as O2, CO2, H2O, N2, etc. into the remaining difficult-to-mine resources underground, it is ignited to form high-temperature gas, and then the remaining coal resources are controllably oxidized to produce combustible gases such as CO, CH4, H2, etc. for development and utilization. However, this method is greatly restricted by the stability of the overlying strata in the goaf and the water content of the strata. If the overlying strata collapse and sink and communicate with the surface after underground gasification, the formation sealing will be damaged, and the gas produced by gasification may not be extracted through the predetermined extraction wells; when the water content of the strata is too high, it may be difficult to ignite the coal seam. The gob filling with gangue, fly ash, and construction waste is an effective method to dispose of solid wastes such as gangue and prevent the subsidence of the gob, and is usually completed by methods such as underground filling, continuous mining and filling, and surface drilling filling. However, gangue itself also enriches a certain amount of organic matter, and when it cannot be directly utilized, filling it into the gob will also cause a certain degree of waste of resources. Therefore, a device and method for integrating underground residual coal gasification and solid waste backfilling are needed to solve this problem. Summary of the Invention

[0003] The purpose of the invention is to provide a device and method for integrating underground residual coal gasification and solid waste backfilling.

[0004] To achieve the above object, the invention provides a device and method for integrating underground residual coal gasification and solid waste backfilling, including a plurality of gob areas horizontally arranged from right to left in the underground coal seam. Each gob area is filled with gangue. Above each gob area, a plurality of vertical wells are horizontally arranged from front to back in sequence. The lower ends of the plurality of vertical wells are inserted into the underground coal seam and communicate with the gob area. There is remaining coal at the top of the gob area. There are roadway safety coal pillars on both the left and right sides of the gob area. An injection pipeline is buried on the side of the roadway safety coal pillar, and a plurality of ignition nodes are installed in the injection pipeline.

[0005] Further, the distance between the vertical wells is equal to 2 times the diffusion radius of the solid waste filled in the vertical wells.

[0006] Further, temperature sensors are installed both in the injection pipeline and at the bottom of the vertical wells.

[0007] A method for integrating underground residual coal gasification and solid waste backfilling, comprising the following steps:

[0008] S1: Construct a number of vertical wells. A municipal heating and power generation system and a waste heat utilization system are arranged at the upper ends of the vertical wells. The lower ends of the vertical wells drill into the coal seam in the ground. After the coal seam is mined, a goaf is formed. The lower ends of the vertical wells are connected to the goaf. There are remaining coal in the goaf, and there are roadway safety coal pillars on both sides of the left and right walls of the goaf. After the coal mining operation at the working face is completed, fill the goaf with gangue through the vertical wells. After the filling is completed, seal all the vertical wells to form injection wells and production wells for gasification;

[0009] S2: After the vertical wells are sealed, in the direction of the working face, open a vertical well at one end of the working face as an injection well, inject gas into the injection pipeline, and the injection direction is from front to back. During the injection process, open the vertical well at the rearmost end of the working face to form a gas production well, so that a first circulation path is formed from the injection well through the injection pipeline to the vertical well at the rearmost end;

[0010] S3: After the first circulation path is formed, ignite the roadway safety coal pillar through the ignition node at the rearmost end in the injection pipeline. After ignition, the heat generated by the combustion of the roadway safety coal pillar flows from the roadway to the vertical well under the action of the air flow, and a gasification and pyrolysis zone of the remaining coal and gangue is formed between the roadway safety coal pillar and the vertical well;

[0011] S4: After the pyrolysis gas is produced from the gas production well, it is a high-temperature gas, and the heat carried by the gas can be used to supply energy to the municipal heating and power generation system and the waste heat utilization system at the upper end of the vertical well;

[0012] S5: After the gas heat is extracted, through the gas separation and purification system, the gas generated by gasification is separated and extracted, and the combustible gases H2, CH4 and CO rich in the gas are extracted and recovered;

[0013] S6: As the roadway safety coal pillar burns and gasifies, the combustion zone gradually moves from back to front. When the temperature of the next ignition node counted from back to front reaches 400 °C, open the next vertical well counted from back to front in turn, and close the previous vertical well to form a second circulation path. After the second circulation path is formed, carry out an ignition operation on the roadway safety coal pillar in the second circulation path to make the entire gasification cycle gradually move forward;

[0014] S7: Repeat step S6 to complete the subsequent gasification and pyrolysis work.

[0015] Furthermore, the temperature of the gasification and pyrolysis zone is the temperature at the burning place of the roadway safety coal pillar.

[0016] Furthermore, the temperature of the gasification and pyrolysis zone is 1100°C, the temperature of the gasification and pyrolysis zone gradually decreases toward the front and rear sides, and the temperature at the vertical well is 400°C.

[0017] Furthermore, the gas injected into the gas injection pipeline is composed of a mixture of O2, CO2, H2O, and N2.

[0018] The advantages of the present invention are as follows: the present invention ensures the stability of the overlying rock strata in the goaf through gangue filling, thereby maintaining the effective combustion of the well-type underground coal gasification and ensuring that the gas generated by the gasification is collected according to the set channel; on the other hand, the high temperature generated by the combustion of the remaining underground coal resources causes the gangue organic matter in the filling body to be pyrolyzed and cracked into usable combustible gas, so that it is converted and utilized synchronously with the progress of the gasification process.

[0019] The present invention is described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the present invention.

[0021] Figure 2 It is a cross-sectional view of the top structure of the goaf area of the present invention.

[0022] Figure 3 It is a schematic diagram of the pre-buried gas injection pipeline in the goaf area of the present invention.

[0023] Figure 4 It is an integrated flow chart of underground coal gasification and solid waste backfilling of the present invention.

[0024] Explanation of the accompanying reference numerals: 1. Goaf; 2. Vertical well; 3. Legacy coal; 4. Tunnel safety coal pillar; 5. Gas injection pipeline; 6. Ignition node. DETAILED DESCRIPTION

[0025] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose, the specific implementation methods, structural features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and embodiments.

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "aligned", "overlapped", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0028] The terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features; in the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0029] Embodiment 1

[0030] This embodiment provides a device for integrating underground residual coal gasification and solid waste backfilling as shown in Figures 1 to 4 Figure. The device includes a number of gob areas 1 horizontally arranged from right to left in the underground coal seam. Each gob area 1 is filled with coal gangue. Above each gob area 1, a number of vertical wells 2 are horizontally arranged in sequence from front to back. The lower ends of the number of vertical wells 2 are inserted into the underground coal seam to communicate with the gob area 1. There is residual coal 3 at the top of the gob area 1. There are roadway safety coal pillars 4 on both the left and right sides of the gob area 1. An injection pipeline 5 is buried on the side of the roadway safety coal pillar 4, and a number of ignition nodes 6 are installed in the injection pipeline 5.

[0031] Furthermore, the spacing between the vertical wells 2 is equal to twice the diffusion radius of the solid waste filled in the vertical wells 2.

[0032] Furthermore, temperature sensors are installed both in the injection pipeline 5 and at the bottom of the vertical wells 2.

[0033] A method for integrating underground residual coal gasification and solid waste backfilling includes the following steps:

[0034] S1: Construct a number of vertical wells 2. The upper ends of the number of vertical wells 2 are provided with a municipal heating and power generation system and a waste heat utilization system. The lower ends of the number of vertical wells 2 are drilled into the coal seam in the ground. After the coal seam is mined, gob areas 1 are formed. The lower ends of the vertical wells 2 communicate with the gob areas 1. There is residual coal 3 at the top of the gob areas 1. There are roadway safety coal pillars 4 on both the left and right side walls of the gob areas 1. After the coal mining operation at the working face is completed, fill the gob areas 1 with coal gangue through the vertical wells 2. After the filling is completed, seal all the vertical wells 2 to form injection wells and production wells for gasification.

[0035] S2: After the completion of the sealing of the vertical well 2, in the direction of the working face, a vertical well is opened at one end of the working face as the gas injection well, and gas is injected into the gas injection pipeline 5. The gas injection direction is from front to back. During the gas injection process, the vertical well 2 at the rearmost end of the working face is opened to form a gas production well, so that a first circulation path is formed from the gas injection well and the gas injection pipeline 5 to the vertical well 2 at the rearmost end;

[0036] S3: After the formation of the first circulation path, the roadway security coal pillar 4 is ignited through the ignition node 6 at the rearmost part in the gas injection pipeline 5. After ignition, the heat generated by the combustion of the roadway security coal pillar 4 flows from the roadway to the vertical well 2 under the action of the air flow, and a gasification and pyrolysis zone of the remaining coal 3 and coal gangue is formed between the roadway security coal pillar 4 and the vertical well 2;

[0037] S4: After the pyrolysis gas is produced from the gas production well, it is a high-temperature gas, and the heat carried by the gas can be used for energy supply by the municipal heating and power generation system and the waste heat utilization system at the upper wellhead of the vertical well 2;

[0038] S5: After the extraction of the gas heat is completed, through the gas separation and purification system, the gas generated by gasification is separated and extracted, and the combustible gases H2, CH4 and CO rich in the recovered gas are extracted;

[0039] S6: As the roadway security coal pillar 4 burns and gasifies, the combustion zone gradually moves from back to front. When the temperature of the next ignition node 6 counted from back to front reaches 400 °C, the next vertical well 2 counted from back to front is opened in turn, and the previous vertical well 2 is closed to form a second circulation path. After the second circulation path is formed, the roadway security coal pillar 4 in the second circulation path is ignited, so that the whole gasification cycle gradually moves forward;

[0040] S7: Repeat step S6 to complete the subsequent gasification and pyrolysis work.

[0041] Furthermore, the temperature of the gasification and pyrolysis zone is the temperature at the burning part of the roadway security coal pillar 4.

[0042] Furthermore, the temperature of the gasification and pyrolysis zone is 1100 °C, and the temperature of the gasification and pyrolysis zone gradually decreases towards the front and back sides, and the temperature at the vertical well 2 is 400 °C.

[0043] Furthermore, the gas injected into the gas injection pipeline 5 is a mixed gas of O2, CO2, H2O and N2.

[0044] Working process:

[0045] After underground mining, the residual coal resources in the goaf 1 include the roadway safety coal pillar 4 and the remaining coal 3 at the top. At the same time, there is still a certain amount of residual coal in the goaf 1. During underground mining, as the working face advances, an air injection pipeline 5 is pre-buried on the side of the roadway safety coal pillar 4. The pipeline is pre-installed with a temperature sensor and an ignition node 6. The ignition method of the ignition node 6 is electric ignition. As the working face advances, vertical wells 2 are constructed along the working face trend at a certain interval above the goaf 1. At this time, the vertical wells 2 are coal gangue filling wells. The spacing of the vertical wells 2 is determined according to the coal gangue filling process. When the hydraulic filling process is selected, the well spacing is determined by the fluidity of the gangue slurry and its diffusion radius. Usually, the well spacing of the vertical wells 2 is twice the diffusion radius of the gangue slurry. After the coal mining operation of the working face is completed, coal gangue is filled into the goaf 1 through the vertical wells 2 above the goaf 1.

[0046] After the filling operation is completed, a temperature sensor is installed at the bottom of the vertical well 2 and the well is sealed. At this time, the vertical well 2 is changed to a gas production well. After the transformation of the vertical well 2 is completed, air injection starts into the air injection pipeline 5. The gas composition is a mixture of O2, CO2, H2O, and N2. The air injection direction is as Figure 2 shown by the arrow from front to back. During the air injection process, keep Figure 2 the front vertical well 2 closed in Figure 2 and keep the last vertical well 2 open, so that the gas forms a passage underground, which is called the first circulation passage. After the passage is formed, keep the gas continuously injected, and through the ignition node 6 in the frontmost air injection pipeline 5 in

[0047] ignite the roadway safety coal pillar 4. The heat generated by the combustion of the roadway safety coal pillar 4 after ignition flows from the roadway to the vertical well 2 under the action of the air flow, forming a gasification and pyrolysis zone of the residual coal and coal gangue underground between the roadway and the vertical well 2.

[0048] With the combustion and gasification of the roadway safety coal pillar 4 underground, the combustion zone gradually moves from Figure 2It moves forward to the front side. When the temperature of the second ignition node 6 (starting from the rear as the first) reaches 400 °C, the second vertical well 2 is opened and the first vertical well 2 is closed. At this time, the second circulation path is formed. After the second circulation path is formed, ignition operation is carried out on the coal pillar in the second node roadway, so that the entire gasification cycle gradually moves to the left. After the pyrolysis gas is extracted, it is still a high-temperature gas on the ground. At this time, a waste heat utilization system such as municipal heating and power generation can be set at the extraction wellhead; among them, the solid waste filled into the vertical well 2 can also be replaced with fly ash, construction solid waste and a certain amount of agricultural and forestry waste mixed, further expanding the applicable scope of this method and increasing the application potential of this method for treating solid waste.

[0049] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. An integrated method for underground residual coal gasification and solid waste backfilling, characterized in that: It includes the following steps: S1: Construct a number of vertical wells (2). At the upper ends of the number of vertical wells (2), there are a municipal heating and power generation system and a waste heat utilization system. The lower ends of the number of vertical wells (2) are drilled into the coal seam in the ground. After the coal seam is mined, a number of gob areas (1) are formed. The number of gob areas (1) are horizontally arranged in sequence from right to left in the underground coal seam. Each gob area (1) is filled with gangue. Above each gob area (1), a number of vertical wells (2) are horizontally arranged in sequence from front to back. The lower ends of the number of vertical wells (2) are inserted into the underground coal seam to communicate with the gob area (1). There is residual coal (3) at the top of the gob area (1). There are roadway safety coal pillars (4) on both the left and right sides of the gob area (1). An injection pipeline (5) is buried on the side of the roadway safety coal pillar (4). A number of ignition nodes (6) are installed in the injection pipeline (5). After the coal mining operation at the working face is completed, gangue is filled into the gob area (1) through the vertical well (2). After the filling is completed, all the vertical wells (2) are sealed to form injection wells and production wells for gasification; S2: After the vertical wells (2) are sealed, in the direction of the working face, one vertical well is opened at one end of the working face as an injection well, and gas is injected into the injection pipeline (5). The injection direction is from front to back. During the injection process, the vertical well (2) at the rearmost end of the working face is opened to form a gas production well, so that a first circulation path is formed from the injection well, through the injection pipeline (5) to the vertical well (2) at the rearmost end; S3: After the first circulation path is formed, the roadway safety coal pillar (4) is ignited by the ignition node (6) at the rearmost end in the injection pipeline (5). After ignition, the heat generated by the combustion of the roadway safety coal pillar (4) flows from the roadway to the vertical well (2) under the action of the air flow, and a gasification and pyrolysis zone of the residual coal (3) and gangue is formed between the roadway safety coal pillar (4) and the vertical well (2); S4: After the pyrolysis gas is produced from the gas production well, it is a high-temperature gas, and the heat carried by the gas can be used to supply energy to the municipal heating and power generation system and the waste heat utilization system at the upper wellhead of the vertical well (2); S5: After the gas heat is extracted, through a gas separation and purification system, the gas generated by gasification is separated and extracted, and the combustible gases H2, CH4 and CO rich in the recovered gas are extracted; S6: As the roadway safety coal pillar (4) burns and gasifies, the combustion zone gradually moves from back to front. When the temperature of the next ignition node (6) counted from back to front reaches 400 °C, the next vertical well (2) counted from back to front is opened in sequence, and the previous vertical well (2) is closed to form a second circulation path. After the second circulation path is formed, ignition operation is carried out on the roadway safety coal pillar (4) in the second circulation path, so that the entire gasification cycle gradually moves forward; S7: Repeat step S6 to complete the subsequent gasification and pyrolysis work.

2. The integrated method for underground residual coal gasification and solid waste backfilling according to claim 1, wherein: The spacing between the vertical wells (2) is equal to 2 times the diffusion radius of the gangue filling body in the gob area (1).

3. A method for integrating underground residual coal gasification and solid waste backfilling as described in claim 1, characterized in that: Temperature sensors are installed both in the injection pipeline (5) and at the bottom of the vertical well (2).

4. A method for integrating underground residual coal gasification and solid waste backfilling as described in claim 1, characterized in that: The temperature of the gasification and pyrolysis zone is the temperature at the combustion site of the roadway safety coal pillar (4).

5. A method for integrating underground residual coal gasification and solid waste backfilling as described in claim 4, characterized in that: The temperature of the gasification and pyrolysis zone is 1100 °C, and the temperature of the gasification and pyrolysis zone gradually decreases towards the front and back sides, and the temperature at the vertical well (2) is 400 °C.

6. A method for integrating underground residual coal gasification and solid waste backfilling as described in claim 1, characterized in that: The gas injected into the gas injection pipeline (5) is a mixed gas of O2, CO2, H2O, and N2.

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