An efficient coal underground gasification furnace and a method for constructing the same

Abstract

The application discloses a kind of efficient coal underground gasification furnace and its construction method, furnace type construction uses coal seam directional drilling and ground vertical drilling technology, by the docking of gas collection passage, gasification passage and gas outlet channel and vertical drilling in coal seam in ignition area by directional drilling hole construction constructs underground gasification furnace.And using advanced coal seam directional drilling process, while aiming at the coal seam of not with occurrence condition constructs integrated underground gasification furnace and gas collection passage, gas outlet system and ignition area, easy to implement, short construction period.The application structure is reasonable, not only suitable for the new type efficient coal underground gasification furnace of different occurrence scale coal seam, solves the low utilization rate of coal resource gasification and the related problems such as dust, high temperature, high pressure, component is not one and the instability of gas outlet hole bottom of direct product coal gas, ensures stable gas outlet, and easy to implement, short construction period, ensures the long-term stable, efficient operation of gasification furnace.

Description

TECHNICAL FIELD

[0001] The present application relates to coal underground gasification mining technology, belongs to efficient underground gasification mining of coal seams in different occurrence states, and particularly relates to an efficient coal underground gasification furnace and a construction method thereof. TECHNICAL BACKGROUND

[0002] Wellless coal underground gasification is a process of gasification by constructing a geological drilling hole in an original underground coal seam. The occurrence states of original coal seams in different regions are different, and the existing single form of underground gasification furnace cannot achieve effective coverage of coal resources from the economic and reasonable point of view; meanwhile, the ash, high temperature and high pressure of the coal gas directly gasified in the gasification channel will cause the outgas drilling hole to be blocked and deformed; in addition, the conventional underground gasification furnace will form a large combustion empty area at the bottom of the vertical outgas drilling hole, causing stress concentration at the bottom of the drilling hole and affecting the stable outgas of the drilling hole. The present application proposes an efficient coal underground gasification furnace type suitable for different occurrence scale coal seams and a construction method thereof, which fully utilizes the coal seam directional drilling process to construct an integrated underground gasification furnace, gas collection channel and outgas system. The number of gasification channels and the length of the gas collection channel are flexibly adjusted according to different occurrence scales of the coal seam, the gas collection channel is used for dust removal, temperature reduction, pressure stabilization and balancing of the coal gas components, the vertical outgas drilling hole is located outside the stress concentration area, and large-area, continuous and efficient gasification of the coal seam can be realized. SUMMARY

[0003] The present application aims to design an efficient coal underground gasification furnace and a construction method thereof, which has a reasonable structure, is suitable for a new type of efficient coal underground gasification furnace for different occurrence scale coal seams, solves the problems of low utilization rate of coal resource gasification, dust, high temperature, high pressure, different components of direct product coal gas and instability of the outgas hole bottom, ensures stable outgas, is easy to implement, has a short construction period, and can ensure long-term stable and efficient operation of the gasification furnace.

[0004] The purpose of the present application is achieved as follows: an efficient coal underground gasification furnace is composed of at least one gas collection channel, uniformly distributed gasification channels, uniformly distributed outgas holes and an ignition area, the uniformly distributed gasification channels are drilled along the coal seam inclination, the gas collection channel drilled along the strike is located at the upper part of the uniformly distributed gasification channels, the gas collection channel and the gasification channel are cross arranged in plan view, the ignition area is composed of multiple ignition vertical drilling holes, the igniters are respectively lowered after cold fracturing, the gas collection channel is communicated with one of the ignition vertical drilling holes, the uniformly distributed outgas holes are respectively communicated with the corresponding gasification channels, and the generated coal gas is first collected in the gas collection channel and then discharged from the outgas holes.

[0005] The application discloses a construction method of an efficient underground coal gasification furnace.

[0006] The aperture size of the ignition area vertical borehole corresponding to the gas collection channel is determined according to the size of the igniter, double-layer standard petroleum casing anti-high-temperature cement slurry well cementing technology is adopted, the surface casing is lowered to 0-2m above the coal seam roof, the bottom end of the production casing is located 3-5m below the roof, the bottom is expanded and supported, the top end is located in the surface casing and is 2-5m away from the surface casing orifice, a hanger is linked with the surface casing and well cementing is performed, welding is adopted between the two casings, and the vertical borehole can be used for ignition of the gasification furnace, gas discharge of the gasification furnace, water drainage of the gasification furnace and verification of the coal seam fracture development direction.

[0007] The directional drilling of the gas collection channel adopts a three-opening three-section mode, the surface casing and the production casing adopt standard petroleum casings and are welded and connected and are subjected to high-temperature cement slurry well cementing; the three-opening horizontal section is not subjected to well cementing, a support pipe connected with a thread is lowered, the bare hole is supported, and the support pipe and the production casing are connected through an expansion pipe. The appropriate distance of the horizontal section of the directional drilling hole from the coal seam floor is 3.50 to 6m, that is, 3 to 5m above the horizontal section of the gasification channel, the length of the horizontal section of the gas collection channel is determined according to the number of the gasification channel arrangement and the coal seam strike length, and the gas collection channel can be shared by the underground gasification furnace connected in the later period.

[0008] The ignition area vertical borehole of the gas discharge channel is located outside the stress concentration area of the channel, is 15-30m away from the center line of the gas collection channel, adopts double-layer standard petroleum casing anti-high-temperature cement slurry well cementing technology, the surface casing is lowered to 0-2m above the coal seam roof, the bottom end of the production casing is located 1-3m above the floor, the bottom is expanded and supported, the top end is located in the surface casing and is 2-5m away from the surface casing orifice, a hanger is linked with the surface casing and well cementing is performed, welding is adopted between the two casings, the number and aperture size of the ignition area vertical borehole are determined according to the required gas production, the vertical borehole can be used for gas discharge of the gasification furnace and forward and reverse air blowing, and the gas discharge channel can be shared by the underground gasification furnace connected in the later period.

[0009] The appropriate distance of the horizontal section of the coal seam directional drilling hole of the gasification channel from the coal seam floor is 0.50 to 1m, the length of the horizontal section is determined according to the coal seam inclination length and the required gas production, the construction method is consistent with that of the gas collection channel, the number of the gasification channel arrangement can be determined at one time or can be increased in stages according to the product scale. The width of the gasification channel is 2-3 times the thickness of the coal seam, and the protective coal pillar between the gasification channels is 1.50-2 times the thickness of the coal seam.

[0010] Supporting pipes with certain strength are arranged in the horizontal sections of the gas collection channel and the gasification channel, and cross holes with a diameter of 2-5 mm are punched on the wall of the supporting pipe every 1-2 m.

[0011] The gasification channel and the gas collection channel are penetrated by directional drilling, and a separation control gas injection point device is lowered in the channel, and the movement of the gas injection point is controlled by a mechanical device.

[0012] After the construction of each channel and the related system is completed, the ignition is started from the first vertical drilling hole, and the second and third vertical drilling holes are communicated, and the gas collection channel is gradually constructed, and the cross-sectional size of the gas collection channel is controlled within 10*10 m, and the gas outlet hole is cold fractured during the construction of the gas collection channel.

[0013] After the construction of the gas collection channel is completed, the forced oxidation method and the internal high temperature ignition of the gas collection channel are used to gradually form the gasification channel, wherein the cross-sectional area of the gasification channel within the range of 20-30 m on the left side of the center line of the gas collection channel is controlled within 10*10 m, and the first, third and fifth vertical drilling holes at the bottom of the right side boundary of the gas collection channel to the gas outlet hole are not actively burned.

[0014] The present application proposes to use the coal seam directional drilling technology to construct an integrated underground gasification furnace, a gas collection channel and a gas outlet system, which solves the above problems and is a practical invention. The furnace type takes into account the coal gasification and product discharge, and the coal gas is self-treated through the gas collection channel perpendicular to the gasification channel, and the gas outlet hole is arranged outside the stress concentration area, which fundamentally solves the unstable gas outlet problem of the gasification furnace.

[0015] Advantages of the present application

[0016] 1. Improve the utilization rate of coal resources. The underground gasification furnace is constructed according to the occurrence characteristics of different coal resources, the length of the gasification channel and the gas collection channel is flexibly adjusted, the utilization rate of the gasification resources is more than 90%, and the utilization rate of coal resources is greatly improved.

[0017] 2. Improve the comprehensive quality of product coal gas. The product coal gas in each gasification channel is first gathered in the gas collection channel, and the gas collection channel is used for buffering to achieve the effects of dust removal, temperature reduction, pressure stabilization and balanced gas composition, thereby improving the comprehensive quality of the direct product coal gas.

[0018] 3. Improve the stability of the gas outlet system. The gas outlet system composed of vertical drilling holes is arranged outside the stress concentration area, which avoids the shearing effect of the ground movement on the bottom of the gas outlet hole after the underground formation of the empty area, and the certain length of the gas outlet pipeline can reduce the coal gas temperature and the high-temperature dry distillation of the coal resources on both sides, thereby ensuring that the bottom of the gas outlet drilling hole is under stable ground stress and is not affected by high temperature, and improving the stability of the gas outlet system.

[0019] This invention has a reasonable structure and is not only applicable to new high-efficiency underground coal gasification furnaces for coal seams of different occurrence scales, but also solves problems such as low coal resource gasification utilization rate and the dust, high temperature, high pressure, inconsistent composition, and instability at the bottom of the gas outlet of the direct product coal gas. It ensures stable gas output, is easy to implement, has a short construction period, and ensures the long-term stable and efficient operation of the gasification furnace. Attached Figure Description

[0020] Figure 1 This is a three-dimensional structural diagram of the present invention.

[0021] Figure 2 for Figure 1 A-A sectional view of the structure.

[0022] Figure 3 for Figure 1 A top-view structural diagram. Detailed Implementation

[0023] A highly efficient underground coal gasification furnace and its construction method, such as Figure 1 , Figure 2 , Figure 3As shown, it is composed of at least one gas collection channel 2, uniformly distributed gasification channels, uniformly distributed gas outlet channels and ignition area. The uniformly distributed gasification channels are drilled along the coal seam inclination. The gas collection channel 2 located in the upper part of the uniformly distributed gasification channels is drilled along the coal seam strike. The plane projection of the gas collection channel 2 is cross set with the gasification channel. The ignition area is composed of multiple ignition vertical boreholes. After cold fracturing, the igniters are respectively lowered. The gas collection channel 2 is communicated with one of the ignition vertical boreholes. The uniformly distributed gas outlet channels are respectively communicated with the corresponding gasification channels. The generated coal gas is first collected in the gas collection channel 2 and then discharged by the gas outlet channels. The ignition area is composed of first, second and third ignition vertical boreholes 6, 7 and 8. The boreholes penetrate into the coal seam floor 1-1.5 meters. The double-layer casing is cemented. The borehole diameter is determined according to the size of the igniter. The gas outlet channels are composed of first, second, third, fourth, fifth and n-th gas outlet vertical boreholes 9, 10, 11, 12, 13 and n. The boreholes can be drilled to the coal seam floor. The double-layer casing is cemented. The bottom is reamed and supported. The borehole diameter is determined according to the need of gas production. The gas collection channel 2 is communicated with the first ignition vertical borehole 6. The horizontal section of the gas collection channel 2 is drilled along the coal seam strike. The distance from the coal seam floor is 3.5-6 meters. The vertical section and the directional build-up section use oil casing for cementing. The horizontal section lowers the support pipe. The length of the horizontal section can be adjusted or reserved according to the number of gasification channels. The gasification channels are composed of first, second and third gasification channels 3, 4 and 5. They are respectively communicated with the first, third and fifth vertical boreholes 9, 11 and 13. The horizontal section of the gasification channel is drilled along the coal seam inclination. The distance from the coal seam floor is 0.5-1 meter. The vertical section and the directional build-up section use standard oil casing for cementing. The horizontal section lowers the support pipe. The length of the horizontal pipe is determined according to the gasification scale. The gas outlet channels are cold fractured. A construction method of high-efficiency underground coal gasification furnace. The furnace type is constructed by using coal seam directional drilling and ground vertical drilling technology. The gas collection channel 2, the gasification channel and the gas outlet channel are connected with the ignition area vertical borehole in the coal seam to construct the underground gasification furnace. The gasification furnace is composed of multiple coal seam directional boreholes and one or two corresponding ignition area vertical boreholes. The size of the borehole diameter of the corresponding ignition area vertical borehole of the gas collection channel is determined according to the size of the igniter. The double-layer standard oil casing is used for high-temperature cement slurry cementing technology. The surface casing is lowered to 0-2 meters above the coal seam roof. The production casing bottom end is located 3-5 meters below the roof. The bottom is reamed and supported. The top end is located in the surface casing. The distance from the surface casing orifice is 2-5 meters. The hanger is linked with the surface casing and cemented. The two types of casings are welded. The vertical borehole can be used for gasification furnace ignition, gasification furnace gas discharge, gasification furnace drainage and verification of coal seam fracture development direction.The directional drilling of the gas collection channel adopts a three-opening three-section system, the surface casing and the production casing adopt standard oil casings, are welded, and are cemented with high-temperature resistant cement slurry; the three-opening horizontal section is not cemented, a supporting pipe connected with threads is lowered, the naked hole is supported, the supporting pipe and the production casing are connected with an expansion pipe, the appropriate distance between the horizontal section of the directional drilling hole and the coal seam floor is 3.50 to 6 meters, the horizontal section of the gas collection channel 2 is above 3 to 5 meters of the gasification channel, the length of the horizontal section of the gas collection channel 2 is determined according to the number of the gasification channel and the length of the coal seam, and the gas collection channel 2 can be shared with the underground gasification furnace connected later. The ignition area of the gas outlet channel vertical drilling hole is located outside the stress concentration area of the channel, is 15-30 meters away from the center line of the gas collection channel 2, adopts the double-layer standard oil casing high-temperature resistant cement slurry cementing technology, the surface casing is lowered to 0-2 meters above the coal seam roof, the bottom end of the production casing is located 1-3 meters above the floor, the bottom is expanded and supported, the top end is located in the surface casing, is 2-5 meters away from the surface casing hole, is connected with the surface casing by a hanger and is cemented, the two casings are welded, the number and the size of the vertical drilling hole of the ignition area are determined according to the gas production requirement, and the vertical drilling hole can be used for the gas outlet and the positive and reverse air blowing of the gasification furnace respectively, and the gas outlet channel can be shared with the underground gasification furnace connected later. The appropriate distance between the horizontal section of the coal seam directional drilling hole of the gasification channel and the coal seam floor is 0.50 to 1 meter, the length of the horizontal section is determined according to the length of the coal seam and the gas production requirement, the construction method is consistent with that of the gas collection channel 2, and the number of the gasification channel can be determined at one time or can be increased in stages according to the product scale. The width of the gasification channel is 2-3 times of the thickness of the coal seam, and the protective coal pillar between the gasification channels is 1.50-2 times of the thickness of the coal seam. The supporting pipe with a certain strength is placed in the horizontal section of each coal seam gas collection channel 2 and the gasification channel, and the holes with a diameter of 2 to 5 mm are cross drilled on the wall of the supporting pipe every 1 to 2 meters. The gasification channel and the gas collection channel 2 are connected by directional drilling, the separation control gas injection point device is lowered in the channel, and the movement of the gas injection point is controlled by a mechanical device. After the construction of each channel and the related system is completed, the first ignition vertical drilling hole 6 is ignited, and the second and third ignition vertical drilling holes 7 and 8 are connected, the gas collection channel is gradually constructed, the cross-sectional size of the gas collection channel 2 is controlled to be within 10*10 meters, and the gas outlet channel is cold fractured during the construction of the gas collection channel 2. After the construction of the gas collection channel 2 is completed, the forced oxidation method and the internal high-temperature ignition of the gas collection channel 2 are used from the bottom ends of the first, second and third gasification channels 3, 4 and 5 to gradually form the gasification channel, the cross-sectional area of the gasification channel in the range of 20-30 meters to the left of the center line of the gas collection channel 2 is controlled to be within 10*10 meters, and the first, third and fifth vertical drilling holes 9, 11 and 13 from the right boundary of the gas collection channel 2 to the gas outlet channel do not actively burn.

[0024] The working process of the underground coal gasification furnace of the present application is as follows:

[0025] 1. After igniting vertical boreholes 6, 7, 8 cold fracturing, igniting device is lowered in gas collection channel 2, igniting is started from first igniting vertical borehole 6, gas collection channel 2 is gradually constructed, first, second and third igniting vertical boreholes 6, 7, 8 are used as gas outlet holes during the construction of gas collection channel 2, and the development direction of coal seam fracture is verified during cold fracturing or gas outlet process, the cross-sectional area of final gas collection channel 2 is controlled to about 10*10m;

[0026] 2. The gas outlet vertical boreholes 9, 11, 13 and 10, 12 of the gas outlet channel are cold fractured as appropriate;

[0027] 3. The separation and control gas injection point device is lowered in the first, second and third gasification channels 3, 4, 5 or one or two channels to the bottom of the gas collection channel 2, forced oxidation method and internal high temperature of the gas collection channel 2 are used to ignite, the cross-sectional area of the gas collection channel 2 in the range of 20-30m on the left side of the center line is controlled within 10*10m, and the right side of the gas collection channel 2 to the bottom of the first, second and third vertical boreholes 9, 11, 13 of the gas outlet channel does not actively burn;

[0028] 4. After forming the stable gasification zone, gas collection zone and gas outlet system, the first, second and third vertical boreholes 9, 11, 13 of the gas outlet channel can continue to be used as gas outlet holes or be adjusted as drainage holes as appropriate;

[0029] 5. According to the expansion plan of the furnace area, the formed gas collection channel and exhaust system can be used as the supporting system of the second phase gasification furnace.

[0030] The advantages of the present application are that advanced coal seam directional drilling technology is used, and an integrated underground gasification furnace, gas collection channel and gas outlet system are constructed for coal seams with different conditions, which is easy to implement and has a short construction period; the gas collection channel can dust, cool, stabilize and balance the components of the gas of each gasification channel; the gas outlet system is located outside the stress concentration area, which can avoid hole bottom collapse; and the number of gasification channels, the length of the gas collection channel and the number of gas outlet holes can be flexibly adjusted according to different gasification scales. The problems of low utilization rate of coal gasification, dust, high temperature, high pressure, different components and unstable hole bottom of direct product gas are fundamentally solved, and the long-term, stable and efficient operation of the gasification furnace is ensured.

Claims

1. A high-efficiency underground coal gasification furnace, characterized in that: it consists of... It consists of at least one gas gathering channel (2), a uniformly distributed gasification channel, a uniformly distributed gas outlet channel and an ignition area. The uniformly distributed gasification channel is drilled along the dip of the coal seam. The gas gathering channel (2) drilled along the direction is located above the uniformly distributed gasification channel. The gas gathering channel (2) and the gasification channel are intersected by their planar projections. The ignition area consists of multiple vertical ignition boreholes. After cold fracturing, igniters are lowered. The gas gathering channel (2) is connected to one of the vertical ignition boreholes. The uniformly distributed gas outlet channels are connected to the corresponding gasification channels. The generated coal gas is first gathered in the gas gathering channel (2) and then discharged through the gas outlet channel. The ignition zone consists of the first, second, and third vertical ignition boreholes (6, 7, and 8), which penetrate 1-1.5 meters into the bottom of the coal seam. The well is cemented with double-layer casing, and the borehole diameter is determined according to the size of the igniter. The gas outlet channel consists of the first, second, third, fourth, fifth to nth vertical gas outlet boreholes (9, 10, 11, 12, 13, ... to n). The boreholes are drilled to the bottom of the coal seam. Double-layer casing cementing is used, and the bottom hole is enlarged and supported. The borehole diameter is determined according to the gas production requirements. The gas gathering channel (2) is connected to the first ignition vertical borehole (6). The horizontal section of the gas gathering channel (2) is drilled along the coal seam direction and the distance from the bottom plate of the coal seam is 3.5-6 meters. Its vertical section and directional ramping section are cemented with oil casing. The horizontal section is lowered with support pipe. The length of its horizontal section can be adjusted or reserved according to the number of gasification channels. The vertical boreholes in the ignition zone of the gas outlet are located outside the stress concentration zone of the channel, 15-30 meters away from the centerline of the gas gathering channel (2). The double-layer standard oil casing high-temperature cement slurry cementing technology is adopted. The surface casing is lowered to 0-2 meters above the top of the coal seam, and the bottom of the production casing is located 1-3 meters above the bottom plate. The bottom hole is enlarged and supported, and the top is located inside the surface casing, 2-5 meters away from the surface casing orifice. The hanger is used to connect with the surface casing and cement it. Welding is used between the two types of casings. The number and diameter of the vertical boreholes in the ignition zone are determined according to the gas production requirements. The vertical boreholes are used for gasification furnace gas output and forward and reverse air blowing. The gas outlet can be shared with the underground gasification furnace that will be connected later.

2. The high-efficiency underground coal gasification furnace according to claim 1, characterized in that: The gasification channel consists of the first, second, and third gasification channels (3, 4, and 5), which are connected to the first, third, and fifth vertical gas outlet boreholes (9, 11, and 13), respectively. The horizontal section of the gasification channel is drilled along the dip of the coal seam, with a distance of 0.5-1 meter from the bottom of the coal seam. The vertical section and the directional ramping section use standard oil casing cementing. The horizontal section is lowered with support pipe, and the length of the horizontal pipe is determined according to the scale of gasification.

3. The high-efficiency underground coal gasification furnace according to claim 1, characterized in that: Cold fracturing was performed on the spaced-out vent channels.

4. The method for constructing a high-efficiency underground coal gasification furnace according to claim 1, characterized in that: The furnace construction adopts coal seam directional drilling and ground vertical drilling technology. The underground gasification furnace is constructed by connecting the gas collection channel (2), gasification channel and gas outlet channel constructed by directional drilling with the vertical drilling of the ignition area in the coal seam. The gasification furnace consists of multiple coal seam directional drilling holes and one or two corresponding vertical drilling holes in the ignition area.

5. The method for constructing a high-efficiency underground coal gasification furnace according to claim 1, characterized in that: The diameter of the vertical borehole in the ignition area corresponding to the gas gathering channel is determined according to the size of the igniter. The double-layer standard oil casing high-temperature cement slurry cementing technology is adopted. The surface casing is lowered to 0-2 meters above the coal seam roof, and the bottom end of the production casing is located 3-5 meters below the roof. The bottom hole is enlarged and supported, and the top end is located inside the surface casing, 2-5 meters away from the surface casing orifice. A hanger is used to connect the surface casing and cement it. Both types of casing are welded together. The vertical boreholes are used for gasifier ignition, gasifier gas output, gasifier drainage, and verification of coal seam fracture development direction.

6. The method for constructing a high-efficiency underground coal gasification furnace according to claim 1, characterized in that: The directional drilling of the gas gathering channel adopts a three-section system. The surface casing and production casing adopt standard oil casing, which is welded and cemented with high-temperature cement slurry. The horizontal section of the three sections is not cemented. The threaded support pipe is lowered to support the bare hole. The support pipe and the production casing are connected by expansion pipe. The appropriate distance between the horizontal section of the directional drilling and the bottom plate of the coal seam is 3.50 to 6 meters, which is 3 to 5 meters above the horizontal section of the gasification channel. The length of the horizontal section of the gas gathering channel (2) is determined according to the number of gasification channels and the length of the coal seam. The gas gathering channel (2) can be shared with the underground gasifier that will be connected later.

7. The method for constructing a high-efficiency underground coal gasification furnace according to claim 1, characterized in that: The appropriate distance between the horizontal section of the coal seam directional drilling of the gasification channel and the bottom plate of the coal seam is 0.50 to 1 meter. The length of the horizontal section is determined according to the length of the coal seam dip and the gas production requirements. The construction method is the same as that of the gas gathering channel (2). The number of gasification channels can be determined at once or increased in stages according to the product scale.

8. The method for constructing a high-efficiency underground coal gasification furnace according to claim 1, characterized in that: The width of the gasification channel is 2-3 times the thickness of the coal seam, and the protective coal pillar between the gasification channels is 1.50-2 times the thickness of the coal seam.

9. The method for constructing a high-efficiency underground coal gasification furnace according to claim 1, characterized in that: In each coal seam gas gathering channel (2) and gasification channel horizontal section, a support pipe with a certain strength is installed, and holes with a diameter of 2 to 5 mm are drilled crosswise every 1 to 2 meters on the support pipe wall.

10. The method for constructing a high-efficiency underground coal gasification furnace according to claim 1, characterized in that: Both the gasification channel and the gas collection channel (2) are penetrated by directional drilling. The separation control gas injection point device is lowered into the channel, and the movement of the gas injection point is controlled by a mechanical device.

11. The method for constructing a high-efficiency underground coal gasification furnace according to claim 1, characterized in that: After the construction of each channel and related system is completed, the first ignition vertical borehole (6) is used to start the ignition, and the second and third ignition vertical boreholes (7, 8) are connected to gradually construct the gas collection channel (2). The cross-sectional size of the gas collection channel (2) is controlled within 10×10 meters. During the construction of the gas collection channel (2), the gas outlet channels arranged at intervals are subjected to cold fracturing as appropriate.

12. The method for constructing a high-efficiency underground coal gasification furnace according to claim 1, characterized in that: After the gas collection channel (2) is constructed, the gasification channel is gradually formed from the bottom end of the first, second and third gasification channels (3, 4 and 5) by forced oxidation and high temperature ignition inside the gas collection channel (2). The cross-sectional area of ​​the gasification channel within 20-30 meters to the left of the center line of the gas collection channel (2) is controlled within 10×10 meters. The bottom of the first, third and fifth vertical boreholes (9, 11 and 13) from the right boundary of the gas collection channel (2) to the gas outlet is not actively burned.

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