An integrated device and method for underground coal gasification and solid waste pyrolysis

Abstract

The present invention provides an integrated device and method for underground coal gasification and solid waste pyrolysis, belonging to the technical field of underground coal gasification. It includes a coal seam roof, a coal mine layer, and a coal seam floor that are horizontally arranged in sequence from top to bottom. Above the coal seam roof, an injection well and a production well are vertically arranged in sequence from left to right. The lower ends of the injection well and the production well both penetrate the coal seam roof and are inserted into the coal mine layer. A gasification channel is horizontally arranged in the coal mine layer, and the lower end of the injection well is connected to the lower end of the production well through the gasification channel; a number of vertical wells are horizontally arranged at intervals between the injection well and the production well. All the vertical wells vertically penetrate the coal seam roof, and the bottoms of the vertical wells are filled and sealed with cement, so as to extract the useful components in the coal gangue to the ground through pyrolysis gasification, making the most of the underground gasification heat energy. Compared with the existing technical methods, it has the characteristics of low cost and high resource utilization rate.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground coal gasification, and particularly relates to an integrated method for underground coal gasification and solid waste pyrolysis. Background Art

[0002] After underground coal seam gasification and combustion, a combustion-empty area is formed. The overlying strata of the combustion-empty area will collapse, causing damage to the aquifer above the coal seam. The collapse of the combustion-empty area will also cause ground subsidence and affect the safety of ground buildings. At the same time, the gangue separated from coal mining accumulates on the ground to form solid waste, which will pollute the ground environment. The long-term accumulated gangue oxidizes and spontaneously combusts, emitting gases such as carbon dioxide, polluting the environment. The traditional solution is to construct vertical wells above the combustion-empty area and horizontal wells in the coal seam roof to form a filling path, combined with a ground gangue crushing system, and fill the coal gangue into the underground gasification combustion-empty area to prevent ground subsidence.

[0003] However, the existing technical means only use drilling to send coal gangue to the underground gasification combustion-empty area for backfilling. However, the coal gangue backfilled into the combustion-empty area can not only act as a support agent for the overlying strata of the combustion-empty area, but also the high-temperature gas generated during the advancement of the gasification working face will heat the coal gangue, generating pyrolysis gas components for use, which has not been taken seriously in the existing technology. Summary of the Invention

[0004] The purpose of the present invention is to provide an integrated method for underground coal gasification and solid waste pyrolysis.

[0005] To achieve the above object, the present invention provides an integrated device for underground coal gasification and solid waste pyrolysis, including a coal seam roof, a coal mine layer, and a coal seam floor arranged horizontally from top to bottom in sequence. It is characterized in that: an injection well and an outlet well are vertically arranged in sequence from left to right above the coal seam roof. The lower ends of the injection well and the outlet well both penetrate the coal seam roof and are inserted into the coal mine layer. A gasification channel is horizontally arranged in the coal mine layer. The lower end of the injection well is connected to the lower end of the outlet well through the gasification channel. A plurality of vertical wells are horizontally arranged at intervals between the injection well and the outlet well. All the vertical wells vertically penetrate the coal seam roof, and the bottoms of the vertical wells are filled and sealed with cement.

[0006] Further, an intake flowmeter is fixedly connected to the upper end of the injection well, and an outlet flowmeter and a gas on-line analyzer are fixedly connected to the upper end of the outlet well in sequence.

[0007] Further, a gas supply device is connected to the upper end of the injection well.

[0008] Further, it also includes a feeding pipe which can be installed in each of the vertical wells. The lower end of the feeding pipe penetrates through the cement and is located within the coal seam. A rotary nozzle is connected to the lower end of the feeding pipe, and the nozzle of the rotary nozzle is bent.

[0009] Further, a vibration device is provided on the rotary nozzle.

[0010] Further, U-shaped heat conduction pipes are vertically arranged in several of the vertical wells. The U-shaped closed end of the heat conduction pipe is inserted into the cement for fixed connection, and several heat transfer fins are evenly arranged on the outer side wall of the end of the heat conduction pipe located within the cement.

[0011] Further, a coal gangue crushing device and a coal gangue pumping device are provided at the upper end of each vertical well.

[0012] Further, an ignition device is provided within the gasification channel.

[0013] An integrated method for underground coal gasification and coal gangue pyrolysis, characterized by comprising the following steps:

[0014] S1: Construct an injection well, a production well and a gasification channel to form an underground gasification furnace. An intake flowmeter is installed at the wellhead of the injection well, and an outlet flowmeter is installed at the wellhead of the production well;

[0015] S2: Construct several vertical wells on the ground, inject cement into the vertical wells for sealing, and construct a coal gangue crushing device and a coal gangue pumping device on the ground;

[0016] S3: The method adopted for underground coal gasification is injection-retreat gasification. The ignition device within the underground gasification furnace sequentially gasifies the working face of the coal seam below the vertical well in the direction from the production well to the injection well. After the first working face of the coal seam is gasified to form a combustion void area, the cement in the reserved vertical well is drilled;

[0017] S4: Through the coal gangue crushing device and the coal gangue pumping device in step S2, crush the coal gangue and fill it into the combustion void area of the first working face;

[0018] S5: The ignition device retreats to the working face of the coal seam below the second vertical well for gasification. The pyrolysis gas generated flows through the combustion void area formed by gasifying the first working face. The pyrolysis gas undergoes a pyrolysis reaction with the coal gangue filled into the combustion void area to generate gas, which is discharged to the ground along the production well;

[0019] S6: Repeat step S5 to complete the gasification of subsequent working faces and the filling of coal gangue.

[0020] The advantages of the present invention are as follows: The present invention provides an integrated device and method for filling the combustion-empty area in underground coal gasification and pyrolyzing gangue. After the gangue is crushed by a ground device, it is sent into the combustion-empty area. When the underground coal seam is gasified, a large amount of high-temperature gas will heat the gangue to cause pyrolysis gasification reaction. The useful components in the gangue are extracted to the ground through pyrolysis gasification, so that the gangue is transported into the combustion-empty area in the coal seam. This not only reduces pollution, but also plays a role in supporting and fixing to prevent ground subsidence. At the same time, the underground gasification heat energy is utilized to the greatest extent, and the useful components contained in the gangue are reused. Therefore, compared with the existing technical methods, the cost is further reduced, and the resource utilization rate and environmental protection effect are improved.

[0021] The following will describe the present invention in detail with reference to the accompanying drawings and embodiments. Description of the Drawings

[0022] Figure 1 is a schematic structural diagram of the present invention.

[0023] Figure 2 is a flow chart of the integration of underground coal gasification and solid waste pyrolysis of the present invention.

[0024] Description of the reference numerals in the drawings: 1, coal seam roof; 2, coal seam; 3, coal seam floor; 4, gas injection well; 5, gas outlet well; 6, gasification channel; 7, vertical well; 8, cement; 9, intake flowmeter; 10, outlet flowmeter; 11, gas on-line analyzer; 12, rotary spray head; 13, feeding pipe; 14, heat conduction pipe; 15, heat transfer fin. Specific Embodiments

[0025] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined purpose, the following will describe in detail the specific embodiments, structural features and their effects of the present invention with reference to the accompanying drawings and embodiments.

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "alignment", "overlap", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is 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 thus 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] This embodiment provides an integrated device for underground coal gasification and solid waste pyrolysis as shown in Figure 1 and Figure 2 It includes a coal seam roof 1, a coal mine seam 2, and a coal seam floor 3 that are horizontally arranged in sequence from top to bottom. Above the coal seam roof 1, an injection well 4 and a production well 5 are vertically arranged in sequence from left to right. The lower ends of both the injection well 4 and the production well 5 penetrate through the coal seam roof 1 and are inserted into the coal mine seam 2. A gasification channel 6 is horizontally arranged in the coal mine seam 2. The lower end of the injection well 4 is connected to the lower end of the production well 5 through the gasification channel 6; a number of vertical wells 7 are horizontally spaced between the injection well 4 and the production well 5. All the vertical wells 7 vertically penetrate through the coal seam roof 1. The bottoms of the vertical wells 7 are filled and sealed with cement 8. A coal gangue crushing device and a coal gangue pumping device are arranged at the upper end of each vertical well 7. An ignition device is arranged in the gasification channel 6. By constructing boreholes to build the injection well 4, the production well 5, and the gasification channel 6, an underground gasification furnace is formed. At the same time, large-diameter (d = 298 mm) vertical wells 7 are constructed at equal intervals on the ground. The bottom of the vertical well 7 is sealed with cement 8 to prevent the gas generated during the gasification process from flowing out of the ground along the borehole. At the same time, heat pipes are placed in the vertical well 7 to utilize the heat energy during the gasification and pyrolysis processes; the method adopted for underground coal gasification is the injection-retreat gasification method, that is, horizontal wells and vertical wells 7 are constructed from the ground. The horizontal wells are the injection well 4 and the underground gasification channel 6. The horizontal wells are completed with screen pipes. The vertical wells 7 are the production wells 5. The vertical wells 7 are completed with semi-screen pipes. The ignition device in the underground gasification furnace gasifies the working face of the coal mine seam 2 below the vertical well 7 in sequence from the production well 5 to the injection well 4. The first gasified working face is on the side close to the production well 5.

[0030] Send the underground gasification ignition device to the first underground gasification working face for ignition. The ground gas supply device inputs the gasifying agent, and the coal seam is ignited to undergo oxidation-reduction reactions (600°C - 1200°C):

[0031] C + O2 → CO2 + Q

[0032] C + 1 / 2O2 → CO + Q

[0033] CO + 1 / 2O2 → CO2 + Q

[0034] CO2 + C → CO - Q

[0035] H2O(g) + C → H2 + CO + Q

[0036] H2O(g) + CO → H2 + CO2 + Q

[0037] C + H2 → CH4 + Q

[0038] Low-temperature pyrolysis reactions (200°C - 600°C):

[0039] Coal → CH4 + H2O(g) + H2 +......

[0040] The gas components produced by coal gasification include CH4, CO, CO2, H2, H2O(g), hydrocarbons and others.

[0041] After the first underground gasification working face is completed, the ignition device retreats to the second underground gasification working face. Drill open the cement 8 reserved in the large-diameter vertical well 7⑥ above the burned-out area of the first underground gasification working face, and lower the vibration device. The ground solid waste crushing device crushes the ground coal gangue and transports it to the burned-out area by the pumping device. The vibration device reserved in the burned-out area vibrates the coal gangue sent in to make the coal gangue fill the burned-out area as much as possible. After it can no longer be pumped in, lift the vibration device to the ground, and at the same time seal the vertical well 7⑥ with cement 8 to prevent gas leakage.

[0042] Ignite the ignition device of the second underground gasification working face, and at the same time introduce the gasifying agent. The reaction of the coal seam combustion in the second underground gasification working face is similar to the above reaction. The high-temperature gas generated in the second underground gasification working face will flow through the coal gangue filled in the burned-out area of the first underground gasification working face when flowing towards the production well. The coal gangue and the high-temperature gas undergo pyrolysis reactions to produce CH4, CO, CO2, H2 and hydrocarbons, etc. Since the gas produced in the coal seam of the second gasification working face contains CH4 and H2 components, which promote the pyrolysis of the coal gangue. After the second gasification working face is completed, repeat the steps of injecting coal gangue in the first gasification working face to complete the coal gangue filling and pyrolysis of the burned-out areas of the remaining gasification working faces.

[0043] In the present invention, the ground device is used to crush the coal gangue and send it into the combustion-empty area. When the underground coal seam is gasified, a large amount of high-temperature gas will heat the coal gangue to undergo pyrolysis gasification reaction, and extract the useful components in the coal gangue to the ground through pyrolysis gasification. The coal gangue is transported to the combustion-empty area in the coal seam 2, which not only reduces pollution, but also plays a role in supporting and fixing to prevent ground subsidence. At the same time, the underground gasification heat energy is utilized to the maximum extent, and the useful components contained in the coal gangue are reused. Therefore, compared with the existing technical methods, the cost is further reduced, and the resource utilization rate and environmental protection effect are improved.

[0044] Further, an intake flowmeter 9 is fixedly connected to the upper end of the gas injection well 4, and an outlet flowmeter 10 and a gas on-line analyzer 11 are fixedly connected to the upper end of the outlet well 5 in sequence. The upper end of the gas injection well 4 is connected to a gas supply device. An intake flowmeter 9 is connected between the gas supply device and the gas injection well 4. The intake flowmeter 9 is used to record the amount of the gasifying agent input. An outlet flowmeter 10 is arranged at the outlet of the outlet well 5. The outlet flowmeter 10 is used to record the amount of the gas generated by underground gasification, and then connected to the gas on-line analyzer 11 for analyzing the components of the gas generated underground.

[0045] Further, it further includes a feeding pipe 13. The feeding pipe 13 can be installed in each vertical well 7. The lower end of the feeding pipe 13 penetrates through the cement 8 and is located in the coal seam 2. The lower end of the feeding pipe 13 is connected to a rotary nozzle 12. The nozzle of the rotary nozzle 12 is bent, and a vibration device is arranged on the rotary nozzle 12.

[0046] The well spacing L of the large-diameter vertical wells 7 on the ground is the ground diameter D of the coal gangue cone in the combustion-empty area.

[0047] The coal gangue is transported from the large-diameter vertical wells 7 on the ground to form a cone in the combustion-empty area. The calculation method of the volume V of the coal gangue cone is as follows:

[0048] Wherein, h is the height of the cone, approximately equal to the height H of the combustion-empty area; R is the radius of the bottom surface of the cone.

[0049] R = h / tanα

[0050] Wherein, α is the angle of repose of the coal gangue filled into the combustion-empty area in degrees, and the angle α formed by the slope surface and the ground after the coal gangue is naturally stacked and stabilized is α ≤ 50°.

[0051] The weight m of the coal gangue that can be injected is

[0052] m = ρ·V

[0053] Wherein, ρ is the bulk density of the coal gangue, and the value is about 2 t / m³.

[0054] Calculated with α = 50° and h = 10m, the bottom radius R1 of the conical body is 7m, the well spacing L1 of the 7 large-diameter vertical wells on the ground is 14m, the volume V1 of coal gangue that can be injected is 514m3, and the weight m1 of the coal gangue is 1028t.

[0055] Calculated with α = 20° and h = 10m, the bottom radius R2 of the conical body is 28m, the well spacing L2 of the 7 large-diameter vertical wells on the ground is 56m, the volume V2 of coal gangue that can be injected is 8206m3, and the weight m2 of the coal gangue is 16411t.

[0056] It can be seen from the above calculations that when the thickness of the underground coal seam is constant, reducing the angle of repose α is beneficial to the filling of coal gangue. When the coal gangue is injected from the ground into the burned-out area, it is a natural stacking. After the stacking is stable, the maximum angle of repose α does not exceed 50°. In order to reduce the angle of repose α, a rotary nozzle 12 can be used to guide and transport the coal gangue in different directions in the burned-out area during the injection process. The rotary nozzle 12 can adjust the direction by 360°. At the same time, a vibration device can be used during the transportation process to increase the stacking area of the coal gangue and reduce the angle of repose α. By using this method, the angle of repose can be reduced to 20° or even smaller.

[0057] Furthermore, a U-shaped heat conduction tube 14 is vertically arranged in each of the several vertical wells 7. The U-shaped closed end of the heat conduction tube 14 is inserted into the cement 8 and fixedly connected. A number of heat transfer fins 15 are uniformly arranged on the outer side wall of the end of the heat conduction tube 14 located in the cement 8.

[0058] Put the U-shaped heat conduction tube 14 into the large-diameter borehole constructed above the underground gasification working surface. A number of heat transfer fins 15 are embedded in the U-shaped closed part of the heat conduction tube 14. During the pyrolysis of the underground gasification coal seam or coal gangue, the heat in the gasification cavity is transferred to the coal seam roof 1 rock stratum. The heat energy is absorbed and utilized through the heat conduction tube 14 placed in the large-diameter borehole.

[0059] An integrated method for underground coal gasification and coal gangue pyrolysis includes the following steps:

[0060] S1: Construct an injection well 4, an outlet well 5 and a gasification channel 6 to form an underground gasification furnace. An intake flowmeter 9 is installed at the wellhead of the injection well 4, and an outlet flowmeter 10 is installed at the wellhead of the outlet well 5;

[0061] S2: Construct several vertical wells 7 on the ground. The vertical wells 7 are injected with cement 8 for sealing. A coal gangue crushing device and a coal gangue pumping device are constructed on the ground;

[0062] S3: The method adopted for underground coal gasification is injection-retreat gasification. The ignition device in the underground gasification furnace is used to gasify the working surface of the coal seam 2 below the vertical well 7 in sequence from the outlet well 5 to the injection well 4 direction. After the first working surface of the coal seam 2 is gasified, a burned-out area is formed, and the cement 8 in the reserved vertical well 7 is drilled open;

[0063] S4: Through the gangue crushing device and the gangue pumping device in step S2, crush and fill the gangue into the gob area of the first working face;

[0064] S5: The ignition device retreats to the working face of coal seam 2 under the second vertical well 7 for gasification. The pyrolysis gas generated flows through the gob area formed by gasifying the first working face. The pyrolysis gas undergoes a pyrolysis reaction with the gangue filled in the gob area to generate gas, which is discharged to the ground along the gas outlet well 5;

[0065] S6: Repeat step S5 to complete the gasification and gangue filling of subsequent working faces.

[0066] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. 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 pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. An integrated device for underground coal gasification and coal gangue pyrolysis, comprising a coal seam roof (1), a coal seam (2) and a coal seam floor (3) which are horizontally arranged in sequence from top to bottom, and characterized in that: Above the coal seam roof (1), an air injection well (4) and an air outlet well (5) are vertically arranged in sequence from left to right. The lower ends of the air injection well (4) and the air outlet well (5) both penetrate through the coal seam roof (1) and are inserted into the coal seam (2). A gasification channel (6) is horizontally arranged in the coal seam (2). The lower end of the air injection well (4) is connected to the lower end of the air outlet well (5) through the gasification channel (6). An ignition device is arranged in the gasification channel (6). A number of vertical wells (7) are horizontally spaced between the air injection well (4) and the air outlet well (5). All the vertical wells (7) vertically penetrate through the coal seam roof (1). The bottoms of the vertical wells (7) are filled and sealed with cement (8). It further includes a feeding pipe (13). The feeding pipe (13) can be installed in each vertical well (7). The lower end of the feeding pipe (13) penetrates through the cement (8) and is located in the coal seam (2). A rotary spray head (12) is connected to the lower end of the feeding pipe (13). The nozzle of the rotary spray head (12) is bent.

2. The integrated device for underground coal gasification and coal gangue pyrolysis according to claim 1, characterized in that: An intake flowmeter (9) is fixedly connected to the upper end of the air injection well (4). An outlet flowmeter (10) and a gas on-line analyzer (11) are fixedly connected in sequence to the upper end of the air outlet well (5).

3. The integrated device for underground coal gasification and coal gangue pyrolysis according to claim 2, wherein: The upper end of the air injection well (4) is connected to a gas supply device.

4. An integrated device for underground coal gasification and coal gangue pyrolysis according to claim 1, characterized in that: A vibration device is arranged on the rotary spray head (12).

5. The integrated device for underground coal gasification and coal gangue pyrolysis according to claim 1, characterized in that: U-shaped heat conduction pipes (14) are vertically arranged in a number of the vertical wells (7). The U-shaped closed ends of the heat conduction pipes (14) are inserted into the cement (8) and fixedly connected. A number of heat transfer fins (15) are evenly arranged on the outer side wall of the end of the heat conduction pipe (14) located in the cement (8).

6. The integrated device for underground coal gasification and coal gangue pyrolysis according to claim 1, wherein: A coal gangue crushing device and a coal gangue pumping device are arranged at the upper end of each vertical well (7).

7. An integrated method for underground coal gasification and coal gangue pyrolysis, characterized in that: It includes the following steps: S1: Construct the air injection well (4), the air outlet well (5) and the gasification channel (6) to form an underground gasification furnace. Above the coal seam roof (1), an air injection well (4) and an air outlet well (5) are vertically arranged in sequence from left to right. The lower ends of the air injection well (4) and the air outlet well (5) both penetrate through the coal seam roof (1) and are inserted into the coal seam (2). A gasification channel (6) is horizontally arranged in the coal seam (2). The lower end of the air injection well (4) is connected to the lower end of the air outlet well (5) through the gasification channel (6). An ignition device is arranged in the gasification channel (6). An intake flowmeter (9) is installed at the wellhead of the air injection well (4), and an outlet flowmeter (10) is installed at the wellhead of the air outlet well (5). S2: Construct the vertical wells (7) on the ground. A number of vertical wells (7) are horizontally spaced between the air injection well (4) and the air outlet well (5). All the vertical wells (7) vertically penetrate through the coal seam roof (1). The vertical wells (7) are filled with cement (8) for sealing. A coal gangue crushing device and a coal gangue pumping device are constructed on the ground. S3: The method adopted for underground coal gasification is the gas injection and retreat type gasification. The ignition device in the underground gasification furnace gasifies the working face of the coal seam (2) below the vertical well (7) in sequence from the gas outlet well (5) towards the gas injection well (4). After the gasification of the first working face of the coal seam (2) is completed, a combustion-empty zone is formed, and the cement (8) in the reserved vertical well (7) is drilled open; S4: Through the coal gangue crushing device and the coal gangue pumping device in step S2, the coal gangue is crushed and filled into the combustion-empty zone of the first working face; S5: The ignition device retreats to the working face of the coal seam (2) below the second vertical well (7) for gasification. The pyrolysis gas generated flows through the combustion-empty zone formed by gasifying the first working face. The pyrolysis gas undergoes a pyrolysis reaction with the coal gangue filled into the combustion-empty zone to generate gas, which is discharged to the ground along the gas outlet well (5); S6: Repeat step S5 to complete the gasification of subsequent working faces and the filling of coal gangue.

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