Method for full combustion and monitoring of furnace inner wall deformation in underground coal gasification furnace

Abstract

The present invention relates to a method for fully burning an underground coal gasifier and monitoring the deformation of the inner wall of a furnace, comprising: lowering a gasification pipe along a vertical well to the bottom of the vertical well, the front end of a horizontally arranged underground gasifier is connected to the bottom of the vertical well, a rotatable detection cage is provided at the bottom of the gasification pipe, the detection cage is woven from stress-sensing optical fibers that are staggered horizontally and vertically, the gasification pipe is provided with two gas outlets, both extending into the detection cage, and an igniter is provided at the gas outlet; the detection cage is rotated to a point where one gas outlet faces downward, the detection cage is placed on the bottom surface of the front end of the furnace of the gasifier, ignites and burns, and the stress-sensing optical fiber that contacts the furnace monitors stress data in real time; the detection cage is rotated so that one gas outlet faces one side of the front end of the furnace, the side wall of the detection cage contacts the side wall of the furnace, ignites and burns, and the stress-sensing optical fiber that contacts the side wall of the furnace monitors stress data in real time; according to the previous step, the other side of the gasification furnace is burned; according to the previous step, the top of the gasification furnace is burned.

Description

Technical Field

[0001] The invention belongs to the technical field of underground coal gasification, and in particular relates to a method for fully burning an underground coal gasification furnace and monitoring the deformation of the inner wall of the furnace. Background Art

[0002] Underground gasification technology is to burn and gasify solid fuels such as underground coal under oxygen-deficient or oxygen-rich conditions to generate combustible gas, so as to achieve the purpose of converting solid energy into gaseous energy and realize energy conversion. At present, underground gasification technology is to drill or dig a nearly horizontal tunnel in the underground coal reservoir in advance as the furnace of the gasifier. The gasifier is introduced into the furnace, and after ignition, the coal begins to burn. After a series of redox reactions, the gas produced is mainly methane, which is discharged to the ground and collected. During the gasification process, the cavity wall of the underground gasifier will be affected by multiple factors such as high temperature, high pressure and chemical reaction, resulting in deformation. The full combustion and gasification of coal and the original shape of the inner wall of the furnace are contradictory and cannot be achieved at the same time. After the coal is fully burned, the structure and properties undergo fundamental changes. The remaining coal slag is relatively loose, has low strength, and is very easy to collapse, which affects the subsequent full combustion of coal. At present, technicians in this field can only try to maintain the shape of the inner wall of the furnace as much as possible during the gasification process to prevent collapse accidents, at the cost of partial waste of coal resources. Summary of the invention

[0003] In view of the above problems, the present invention provides a method for achieving full combustion in an underground coal gasification furnace and monitoring deformation of the inner wall of the furnace, comprising the following steps:

[0004] S1: The gasification pipe is lowered along the vertical well to the bottom of the vertical well. The front end of the horizontally arranged underground gasifier is connected to the bottom of the vertical well. A rotatable detection cage is provided at the bottom of the gasification pipe. The detection cage is woven from stress-sensitive optical fibers that are staggered horizontally and vertically. The gasification pipe is provided with two gas outlets, both extending into the detection cage. An igniter is provided at the gas outlet;

[0005] S2: Rotate the detection cage until the two gas outlets are on the same vertical line, then lower the detection cage and place it on the bottom surface of the front end of the gasifier furnace, so that the outer side of the bottom of the detection cage contacts the bottom surface of the furnace, and the first gas outlet at the bottom of the detection cage is ignited to burn the coal layer on the bottom surface of the front end of the furnace;

[0006] During the combustion process, the stress-sensing optical fiber in contact with the furnace monitors stress data in real time. When the optical fiber that could detect stress can no longer detect stress, it means that the area has collapsed downward and no longer supports the optical fiber. When all the optical fibers at the bottom of the detection cage suddenly fail to detect stress, it means that the coal seam below has collapsed after being fully burned, and the detection cage is suspended from the gasification pipe.

[0007] S3: Rotate the detection cage so that the first gas outlet faces the side of the front end of the furnace, and the side wall of the detection cage contacts the side wall of the furnace, and ignites and burns; during the combustion process, the stress sensing optical fiber in contact with the side wall of the furnace monitors the stress data in real time. When the optical fiber that can detect stress can no longer detect stress, it means that the place has collapsed downward and is no longer in contact with the optical fiber; when all stress sensing optical fibers suddenly fail to detect stress, it means that the coal layer on the side wall has collapsed after being fully burned and has fallen to the bottom of the furnace;

[0008] S4: The second gas outlet faces the other side of the front end of the furnace, and the other side wall of the detection cage contacts the other side wall of the furnace, and ignites and burns; during the combustion process, the stress sensing optical fiber in contact with the side wall of the furnace monitors the stress data in real time. When the optical fiber that can detect stress can no longer detect stress, it means that the place has collapsed downward and is no longer in contact with the optical fiber; when all stress sensing optical fibers suddenly fail to detect stress, it means that the coal layer on the other side wall has collapsed after being fully burned and has fallen to the bottom of the furnace;

[0009] S5: Rotate the detection cage so that the first gas outlet or the second gas outlet faces the top wall of the front end of the furnace, and the top of the detection cage contacts the top wall of the furnace, and ignites and burns; during the combustion process, the stress sensing optical fiber in contact with the top wall of the furnace monitors the stress data in real time. When the stress detected by the optical fiber at a certain place suddenly increases, it means that the place has collapsed downward; when the optical fiber at the top of the detection cage detects a sudden increase in stress at the same time, it means that the coal layer on the top wall has collapsed after being fully burned and falls on the detection cage. The detection cage rotates, and the coal slag falls to the bottom of the furnace;

[0010] The detection cage is extended toward the interior of the furnace, and segmented combustion and gasification are performed according to the operations of the above steps S1-S5, with the length of each segment being the length of the detection cage, until the tail end of the furnace.

[0011] Optionally, the gasification pipe includes a vertical part and a horizontal part, the front end of the horizontal part is connected to the bottom of the vertical part, the tail end of the horizontal part is connected to the outlet pipe through a rotating motor, the front end of the outlet pipe is connected to the rotating shaft of the rotating motor, and the tail end of the outlet pipe is divided into two branches to form two outlets, each outlet is provided with a valve to control whether the outlet is exhausted.

[0012] Optionally, the detection cage is cylindrical as a whole, with its central axis horizontal, and the air outlet pipe coincides with the central axis; the detection cage is divided into a front cage, a middle cage and a rear cage along the central axis, and the diameters of the front cage and the rear cage are the same and larger than the diameter of the middle cage, that is, the middle cage is formed by the detection cage being concave inwardly;

[0013] Two outwardly protruding conical combustion corners are arranged on the side wall of the middle cage, which are used to accommodate the air outlets respectively. The two combustion corners are symmetrically arranged with the central axis of the detection cage as the center, and the top ends of the two combustion corners point in opposite directions.

[0014] Further optionally, a plurality of support rods 1 are provided on the outer side of the air outlet pipe for supporting the inner side of the front cage, and the plurality of support rods 1 are evenly distributed along the length direction and circumference direction of the air outlet pipe;

[0015] A central rod is connected to the tail end of the air outlet pipe and the root position where the two air outlets meet. The central rod coincides with the central axis. Several support rods 2 are provided on the outside of the central rod to support the inner side of the rear cage. Several support rods 2 are evenly distributed along the length and circumference of the central rod, so that the air outlet pipe drives the detection cage to rotate through support rods 1 and 2.

[0016] The diameter of the detection cage is smaller than the inner diameter of the furnace, so that the detection cage can move in the furnace. Further optionally, a position adjustment part is provided at the tail of the horizontal part of the gasification tube, and the position adjustment part includes five adjustable position gears, namely, upper, lower, left, right and central. The central position gear corresponds to the horizontal part of the gasification tube, and the upper, lower, left and right four position gears are located around the central position gear. The rotating motor is movably connected to the position adjustment part through the control block, and the control block drives the rotating motor to move along the position adjustment part to realize switching between the five position gears, namely, upper, lower, left, right and central, so that the side wall of the detection cage can contact the top wall, bottom surface, left inner wall and right inner wall of the furnace respectively.

[0017] Optionally, in step S1, the vertical portion of the gasification tube is lowered along the vertical shaft until the horizontal portion reaches the bottom of the vertical shaft; the horizontal portion is then extended toward the interior of the furnace until the detection cage completely enters the furnace; the length of the detection cage is the length of the first section of combustion gasification.

[0018] Optionally, in step S2, the detection cage is rotated by a rotating motor so that the line between the two combustion angles is a vertical line, that is, the two air outlets are arranged up and down; the control block drives the rotating motor to switch from the original central position gear to the lower position gear, so that the bottom surface of the detection cage contacts the bottom surface of the furnace at this time;

[0019] The stress on the stress-sensing optical fiber that can contact the bottom of the furnace is greater than zero, and the data obtained by the detection is transmitted to the data processing device on the ground to record and analyze the data.

[0020] The gasifying agent is a conventional gasifying agent in the art, such as a mixed gas containing oxygen or air. All stress-sensing optical fiber communication connections or lines are connected to a data processing device on the ground.

[0021] Further optionally, in step S2, after the stress on the stress sensing optical fiber is stabilized and the data is substantially unchanged, the valve of the first gas outlet is opened to start releasing the gasifying agent, and at the same time, the corresponding igniter is opened to ignite the coal layer at the bottom of the furnace;

[0022] The stress-sensing optical fiber at the bottom of the front cage and the rear cage continuously monitors stress changes. As the coal seam at the bottom burns, the stress continues to change, reflecting the slight deformation of the coal seam during combustion. If the stress at a certain point of the optical fiber increases, it means that the coal seam at this point is expanding or displacing; if the stress at a certain point of the optical fiber decreases, it means that the coal seam at this point is shrinking.

[0023] As the combustion continues, when the optical fiber at a certain place on the bottom of the detection cage continues to detect no stress, it means that the place has collapsed downward; when all the optical fibers at the bottom of the detection cage detect no stress, it means that the coal seam at the bottom of the furnace of the detection cage has collapsed after full combustion, and the detection cage is supported by the horizontal part of the gasification pipe, and the detection cage is reset to the central position.

[0024] The detection cage of the present invention is used for real-time monitoring of the deformation of the coal seam during combustion. The unburned furnace part is also affected by the gasification process and will deform. The present invention proposes a detector to assist in detecting the deformation of the unburned furnace part.

[0025] Optionally, the tail end of the underground gasifier is connected to another vertical well, and the two vertical wells are parallel to each other; the detector is connected to a rod, and before the gasifier starts gasification, the rod moves the detector along the bottom of another vertical well to the position corresponding to the tail end of the furnace, and then detects the shape of the inner wall of the furnace in sections and batches in the direction of the front end of the furnace.

[0026] Optionally, the detector includes a main rod and a plurality of detection parts, the detection parts include an arc-shaped detection piece and a retractable support rod, the plurality of support rods are evenly arranged along the circumference of the main rod, one end of the support rod is connected to the main rod, and the other end is connected to the inner side surface of the detection piece, so as to push the detection piece to the inner wall of the furnace;

[0027] The detection piece is made of stress-sensitive optical fibers that are staggered horizontally and vertically. Two adjacent optical fibers are in contact with each other but do not squeeze each other. The curvature of each detection piece is the same. The width of the detection piece is the length direction of the furnace, and the detection piece has a certain width.

[0028] The method for the detector to monitor the unburned furnace inner wall is:

[0029] (1) The horizontal rod extends the detector into the rear end of the furnace and stops at the first detection section. The length of the detection section is equal to the width of the detection piece. The main rod coincides with the central axis of the furnace. Several support rods are extended in sequence, so that the outer sides of several detection pieces contact the inner wall of the furnace in sequence. The detection pieces form a circle and monitor the deformation of a circle of the inner wall of the furnace in real time.

[0030] (2) At the beginning, the stress detected by 85-90% of the optical fibers of each detection piece is greater than zero, indicating that most of the optical fibers have contacted the inner wall of the furnace. The position where the detection value is zero is the original depression of the inner wall of the furnace. The greater the stress detected, the more the inner wall of the furnace protrudes toward the detection piece, compressing the flexible detection piece, and recording the detection data at the beginning;

[0031] (3) The support rod is shortened, so that the detection values ​​of all detection pieces return to zero, that is, the detection pieces are separated from the inner wall of the furnace, and the horizontal rod continues to send the detector into the furnace to detect the next detection section; BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic diagram of the structure of the detection cage;

[0033] Figure 2 is a three-dimensional schematic diagram of the detection cage;

[0034] Figure 3 A schematic diagram of the detector.

[0035] In the attached drawings, 1-rotating motor, 2-rotating shaft, 3-exhaust pipe, 4-detection cage, 5-front cage, 6-middle cage, 7-rear cage, 8-exhaust port, 9-combustion angle, 10-stress sensing optical fiber, 11-support rod one, 12-support rod two, 13-center rod, 14-support rod, 15-main rod, 16-detection piece. DETAILED DESCRIPTION

[0036] This embodiment provides a method for achieving full combustion in an underground coal gasification furnace and monitoring deformation of the inner wall of the furnace, comprising the following steps:

[0037] S1: The gasification pipe is lowered along the vertical well to the bottom of the vertical well. The front end of the horizontally arranged underground gasification furnace is connected to the bottom of the vertical well. A rotatable detection cage 4 is provided at the bottom of the gasification pipe. The detection cage 4 is woven by stress-sensing optical fibers 10 that are staggered horizontally and vertically. The gasification pipe is provided with two gas outlets, both extending into the detection cage 4. An igniter is provided at the gas outlet;

[0038] S2: Rotate the detection cage 4 until the two gas outlets are on the same vertical line, then lower the detection cage 4 and place it on the bottom surface of the front end of the gasifier furnace, so that the outer side of the bottom of the detection cage 4 contacts the bottom surface of the furnace, and ignite the first gas outlet at the bottom of the detection cage 4 to burn the coal layer at the bottom surface of the front end of the furnace;

[0039] During the combustion process, the stress sensing optical fiber in contact with the furnace monitors the stress data in real time. When the optical fiber that could detect stress can no longer detect stress, it means that the place has collapsed downward and no longer supports the optical fiber. When all the optical fibers on the bottom of the detection cage 4 suddenly fail to detect stress, it means that the coal seam below has collapsed after being fully burned. The detection cage 4 is suspended by the gasification pipe.

[0040] S3: Rotate the detection cage 4 so that the first gas outlet faces the side of the front end of the furnace, and the side wall of the detection cage 4 contacts the side wall of the furnace, and ignites and burns; during the combustion process, the stress sensing optical fiber in contact with the side wall of the furnace monitors the stress data in real time. When the optical fiber that can detect stress can no longer detect stress, it means that the place has collapsed downward and is no longer in contact with the optical fiber; when all the stress sensing optical fibers suddenly fail to detect stress, it means that the coal layer on the side wall has collapsed after being fully burned and has fallen to the bottom of the furnace;

[0041] S4: The second gas outlet faces the other side of the front end of the furnace, and the other side wall of the detection cage 4 contacts the other side wall of the furnace, and ignites and burns; during the combustion process, the stress sensing optical fiber in contact with the side wall of the furnace monitors the stress data in real time. When the optical fiber that can detect stress can no longer detect stress, it means that the place has collapsed downward and is no longer in contact with the optical fiber; when all stress sensing optical fibers suddenly fail to detect stress, it means that the coal layer on the other side wall has collapsed after being fully burned and has fallen to the bottom of the furnace;

[0042] S5: Rotate the detection cage 4 so that the first gas outlet or the second gas outlet faces the top wall of the front end of the furnace, and the top of the detection cage 4 contacts the top wall of the furnace, and ignites and burns; during the combustion process, the stress sensing optical fiber in contact with the top wall of the furnace monitors the stress data in real time. When the stress detected by the optical fiber at a certain place suddenly increases, it indicates that the place has collapsed downward; when the optical fiber at the top of the detection cage 4 detects a sudden increase in stress at the same time, it indicates that the coal layer on the top wall has collapsed after being fully burned and falls on the detection cage 4. The detection cage 4 rotates, and the coal slag falls to the bottom of the furnace;

[0043] The detection cage 4 is extended toward the interior of the furnace, and segmented combustion and gasification are performed according to the operations of the above steps S1-S5, with the length of each segment being the length of the detection cage 4, until the rear end of the furnace.

[0044] The traditional underground gasification technology does not fully burn the coal seam, and a large amount of unburned coal is left to support the shape of the furnace tunnel to avoid tunnel collapse accidents, bury the gasification pipe, and cannot carry out gasification and combustion of the entire furnace. The present invention completely abandons this method and uses a gasification pipe with a detection cage 4 to carry out segmented gasification treatment. For each section of the furnace, the bottom surface is burned first. After the bottom coal seam collapses, a small pit is left on the bottom surface. According to the geological conditions of the coal seam, the length of the detection cage 4 is reasonably set so that the segmented combustion does not affect the integrity of the entire furnace and other positions of the furnace do not collapse. Then the coal seams on the two sides of the same section are burned separately, and the coal slag that falls after burning falls into the pit below to fill the pit. Finally, the top coal seam of the same section is burned, and the coal slag that falls on the detection cage 4 can be thrown off by rotating the detection cage 4, that is, the coal slag on the top also falls into the pit below. After the coal seams on both sides and the top coal slag are filled, a pit at the bottom of the furnace can be basically filled, or even slightly protruding. This is equivalent to the bottom of the furnace still having solid support, while the sides and top have been expanded and the overall shape of the furnace can still be maintained.

[0045] When the furnace is burning, the temperature reaches hundreds to thousands of degrees Celsius. The deformation detection device that can adapt to such high temperatures is expensive, and it is not realistic to cover the inner wall of the furnace. In addition, the device is easily damaged or buried after the coal seam collapses, making it difficult to recover. Therefore, the traditional deformation measurement method is not suitable for the present invention. The present invention is designed to match the characteristics of segmented combustion, and a detection cage 4 connected to the gasification pipe is designed. The detection cage 4 is woven from high-temperature resistant stress-sensing optical fibers. It not only serves as a shell to protect the gasification pipe to prevent the gasification pipe and its gas outlet from being buried by collapsed coal slag, but also can contact the surface of the coal seam in real time when the coal seam is burning. The real-time morphological changes of the inner wall of the furnace are judged by the detected stress and stress changes. The accuracy is high, and the size and length of the detection cage 4 are controllable, and the cost is controllable.

[0046] Optionally, the gasification pipe includes a vertical part and a horizontal part, the front end of the horizontal part is connected to the bottom of the vertical part, the tail end of the horizontal part is connected to the outlet pipe 3 through the rotating motor 1, the front end of the outlet pipe 3 is connected to the rotating shaft 2 of the rotating motor 1, and the tail end of the outlet pipe 3 is divided into two branches to form two outlets 8, each of which is provided with a valve to control whether the outlet 8 is exhausted.

[0047] Optionally, the gasification tube is hollow inside and used to transport gasifying agent gas. The tail end of the horizontal part is closed and passes through a section of air pipe. The tail end of the air pipe passes through the air outlet pipe 3, so that the gasifying agent transported by the gasification tube skips the motor and is input into the air outlet pipe 3.

[0048] Optionally, a gas delivery pipe is provided on the outside of the gasification pipe, the gas delivery pipe extends along the gasification pipe and finally penetrates into the gas outlet pipe 3, and the gasification agent provided on the ground is directly input into the gas outlet pipe 3 along the gas delivery pipe.

[0049] Optional, such as Figure 1-Figure 2 The detection cage 4 is cylindrical as a whole, with its central axis horizontal, and the air outlet pipe 3 coincides with the central axis; the detection cage 4 is divided into a front cage 5, a middle cage 6 and a rear cage 7 along the central axis, and the diameters of the front cage 5 and the rear cage 7 are the same and larger than the diameter of the middle cage 6, that is, the middle cage 6 is formed by the detection cage 4 being recessed inwardly;

[0050] Two outwardly protruding conical combustion angles 9 are provided on the side wall of the middle cage 6, which are used to accommodate the gas outlets respectively. The two combustion angles 9 are symmetrically arranged with the central axis of the detection cage 4 as the center, and the tops of the two combustion angles 9 point in opposite directions. The two adjacent stress-sensing optical fibers on the detection cage 4 are in contact with each other, but do not squeeze each other, so that the fallen coal slag can only fall on the outer surface of the detection cage 4 and does not enter the interior of the detection cage 4. The middle cage 6 burns the coal seam, and the front cage 5 and the rear cage 7 on both sides of the burning coal seam can better and more comprehensively detect the deformation of the coal seam during combustion.

[0051] Further optionally, the gas outlet extends into the corresponding combustion angle 9 but does not extend out of the combustion angle 9, so as to prevent the collapsed and fallen coal slag from falling on the gas outlet and blocking the gas outlet.

[0052] Further optionally, a plurality of support rods 11 are provided on the outer side of the air outlet pipe 3 to support the inner side of the front cage 5, and the plurality of support rods 11 are evenly distributed along the length direction and circumference direction of the air outlet pipe 3;

[0053] A center rod 13 is connected to the tail end of the air outlet pipe 3 and the root position where the two air outlets meet. The center rod 13 is solid and coincides with the center axis. A plurality of support rods 12 are provided on the outside of the center rod 13 for supporting the inner side surface of the rear section cage 7. The plurality of support rods 12 are evenly distributed along the length direction and circumference direction of the center rod 13, so that the air outlet pipe 3 drives the detection cage 4 to rotate through the support rods 11 and 12.

[0054] The diameter of the detection cage 4 is smaller than the inner diameter of the furnace, so that the detection cage 4 can move in the furnace. Further optionally, a position adjustment part is provided at the tail of the horizontal part of the gasification tube, and the position adjustment part includes five adjustable position gears of upper, lower, left, right and central. The central position gear corresponds to the horizontal part of the gasification tube, and the upper, lower, left and right four position gears are located around the central position gear. The rotating motor 1 is movably connected to the position adjustment part through the control block, and the control block drives the rotating motor 1 to move along the position adjustment part to realize switching between the five position gears of upper, lower, left, right and central, so that the side walls of the detection cage 4 can contact the top wall, bottom surface, left inner wall and right inner wall of the furnace respectively. The position adjustment part can be an electromagnetic control, and the communication is connected to the control device on the ground.

[0055] Optionally, in step S1, the vertical portion of the gasification tube is lowered along the vertical shaft until the horizontal portion reaches the bottom of the vertical shaft; the horizontal portion is then extended toward the interior of the furnace until the detection cage 4 completely enters the furnace; the length of the detection cage 4 is the length of the first stage of combustion gasification.

[0056] Optionally, in step S2, the detection cage 4 is rotated by the rotating motor 1 so that the line between the two combustion angles 9 is a vertical line, that is, the two air outlets are arranged up and down; the control block drives the rotating motor 1 to switch from the original central position gear to the lower position gear, so that the bottom surface of the detection cage 4 contacts the bottom surface of the furnace at this time;

[0057] The stress on the stress-sensing optical fiber that can contact the bottom of the furnace is greater than zero, and the data obtained by the detection is transmitted to the data processing device on the ground to record and analyze the data.

[0058] The gasifying agent is a conventional gasifying agent in the art, such as a mixed gas containing oxygen or air. All stress-sensing optical fiber communication connections or lines are connected to a data processing device on the ground.

[0059] Further optionally, in step S2, after the stress on the stress sensing optical fiber is stabilized and the data is substantially unchanged, the valve of the first gas outlet is opened to start releasing the gasifying agent, and at the same time, the corresponding igniter is opened to ignite the coal layer at the bottom of the furnace;

[0060] The stress sensing optical fiber at the bottom of the front cage 5 and the rear cage 7 continuously monitors stress changes. As the coal seam at the bottom burns, the stress continues to change, reflecting the slight deformation of the coal seam during combustion, such as expansion, contraction, slight displacement, etc. The stress at a certain point of the optical fiber increases, indicating that the coal seam at this point is expanding or displacing; the stress at a certain point of the optical fiber decreases, indicating that the coal seam at this point is contracting. These real-time data are helpful for technicians in the field to study the microscopic process and changes during the combustion process of the underground gasifier;

[0061] As the combustion continues, when the optical fiber at a certain place on the bottom of the detection cage 4 continues to detect no stress, it means that the place has collapsed downward; when all the optical fibers at the bottom of the detection cage 4 detect no stress, it means that the coal seam at the bottom of the furnace of the detection cage 4 has collapsed after full combustion, and the detection cage 4 is supported by the horizontal part of the gasification pipe, and the detection cage 4 is reset to the central position.

[0062] By summarizing and analyzing all stress data from the beginning of combustion to the collapse of the coal seam, we can obtain the qualitative changes in deformation at the same position; before the collapse, the stress increases, indicating that the coal seam squeezes the optical fiber toward the detection cage 4; the stress decreases, indicating that the coal seam shrinks toward its own interior but does not leave the optical fiber; the stress returns to zero and does not recover for a long time, indicating a collapse at this location.

[0063] Optionally, in step S3, the detection cage 4 is rotated by the rotating motor 1 so that the first air outlet faces the left side wall of the furnace and the second air outlet faces the right side wall of the furnace; the control block drives the detection cage 4 to switch to the left position gear, so that the left side of the detection cage 4 contacts the left side wall of the furnace at this time, and the force on the stress-sensing optical fiber on the left side is greater than zero;

[0064] After the stress on the stress-sensing optical fiber is stabilized, it is ignited and burned, and the stress-sensing optical fibers on the left sides of the front cage 5 and the rear cage 7 continue to monitor stress changes;

[0065] As the combustion continues, when the optical fiber at a certain place on the left side of the detection cage 4 continues to detect no stress, it means that the place has collapsed downward; when all the optical fibers on the left side of the detection cage 4 detect no stress, it means that the corresponding coal seam has collapsed after full combustion, and the detection cage 4 is reset to the central position.

[0066] Steps S4 and S5 are similar to step S3. Since the inner wall of the furnace is approximately cylindrical, when the coal slag on the left and right sides of the furnace collapses, it slides down along the curved wall of the furnace, and most of it can fall into the pit formed by the collapse of the bottom surface of the furnace. Moreover, burning the coal layers on the left and right sides first can make the fallen coal slag fill the pit from the left and right sides respectively, which is conducive to more fully filling the pit, avoiding space waste in the pit, and making the coal slag of this section fall into the pit as much as possible, thereby improving the stability of the furnace.

[0067] Optionally, the tail end of the underground gasifier is connected to another vertical well, and the two vertical wells are parallel to each other; the detector is connected to a rod, and before the gasifier starts gasification, the rod moves the detector along the bottom of another vertical well to the position corresponding to the tail end of the furnace, and then detects the shape of the inner wall of the furnace in sections and batches in the direction of the front end of the furnace.

[0068] Optional, such as Figure 3 As shown, the detector includes a main rod 15 and a plurality of detection parts, the detection parts include an arc-shaped detection piece 16 and a retractable support rod 14, the plurality of support rods 14 are evenly arranged along the circumference of the main rod 15, one end of the support rod 14 is connected to the main rod 15, and the other end is connected to the inner side of the detection piece 16, which is used to push the detection piece 16 to the inner wall of the furnace;

[0069] The detection piece 16 is made of stress-sensing optical fibers that are crisscrossed horizontally and vertically. Two adjacent optical fibers are in contact with each other but do not squeeze each other. The curvature of each detection piece 16 is the same. The width of the detection piece 16 is the length direction of the furnace, and the detection piece 16 has a certain width.

[0070] Further optionally, the rod includes a vertical rod and a horizontal rod, one end of the horizontal rod is connected to the bottom of the vertical rod, and the other end is connected to the tail end of the main rod 15, the detection part is arranged near the front end of the main rod 15, and the horizontal rod can be extended and retracted inside the furnace, thereby driving the detector to different positions of the furnace.

[0071] Further optionally, the main rod 15 is horizontal, hollow inside, and is provided with an electromagnetic controller inside for controlling the telescopic length and telescopic time of each support rod 14 .

[0072] Further optionally, the initial state of the detector is: the support rods 14 are in a retracted state, so that the detection pieces 16 surround the main rod 15, and the lengths of the support rods 14 are different. The support rods 14 are sequentially extended or shortened along the circumference of the main rod 15, so that the detection pieces 16 are cross-stacked with each other.

[0073] The method for the detector to monitor the unburned furnace inner wall is:

[0074] (1) The horizontal rod extends the detector into the rear end of the furnace and stops at the first detection section. The length of the detection section is equal to the width of the detection piece 16. The main rod 15 coincides with the central axis of the furnace. Several support rods 14 are extended in sequence, so that the outer sides of several detection pieces 16 contact the inner wall of the furnace in sequence. The detection pieces 16 form a circle to monitor the deformation of a circle of the inner wall of the furnace in real time.

[0075] (2) At the beginning, the stress detected by 85-90% of the optical fibers of each detection piece 16 is greater than zero, indicating that most of the optical fibers have contacted the inner wall of the furnace. The position where the detection value is zero is the original depression of the inner wall of the furnace. The greater the stress detected, the more the inner wall of the furnace protrudes toward the detection piece 16, compressing the flexible detection piece 16, and recording the detection data at the beginning;

[0076] (3) The support rod 14 is shortened, so that the detection values ​​of all the detection pieces 16 return to zero, that is, the detection pieces 16 are separated from the inner wall of the furnace, and the horizontal rod continues to send the detector into the furnace to detect the next detection section;

[0077] Repeat the operations of steps (2) and (3) above to detect the unburned furnace inner wall, and before combustion and gasification, detect from the furnace tail to the furnace front; during the gasification process, the detector detects back and forth along the length of the furnace, and based on the recorded historical data, obtains the qualitative deformation of the same furnace inner wall position during the gasification process. The detection of the unburned furnace by the detector and the combustion and gasification of the detection cage 4 can be performed separately or simultaneously. Although the method provided by the present invention is a qualitative detection method, it has high sensitivity, simple operation, and controllable cost. It can cooperate with the full combustion of the coal layer in the furnace, and provides a new idea and application for this field.

Claims

1. A method for fully burning an underground coal gasifier and monitoring the deformation of the inner wall of the furnace, characterized in that: The following steps are involved: S1: The gasification pipe is lowered along the vertical well to the bottom of the vertical well. The front end of the horizontally arranged underground gasifier is connected to the bottom of the vertical well. A rotatable detection cage is provided at the bottom of the gasification pipe. The detection cage is woven from stress-sensitive optical fibers that are staggered horizontally and vertically. The gasification pipe is provided with two gas outlets, both extending into the detection cage. An igniter is provided at the gas outlet; S2: Rotate the detection cage until the two gas outlets are on the same vertical line, then lower the detection cage and place it on the bottom surface of the front end of the gasifier furnace, so that the outer side of the bottom of the detection cage contacts the bottom surface of the furnace, and the first gas outlet at the bottom of the detection cage is ignited to burn the coal layer on the bottom surface of the front end of the furnace; During the combustion process, the stress-sensing optical fiber in contact with the furnace monitors stress data in real time. When the optical fiber that could detect stress can no longer detect stress, it means that the area has collapsed downward and no longer supports the optical fiber. When all the optical fibers at the bottom of the detection cage suddenly fail to detect stress, it means that the coal seam below has collapsed after being fully burned, and the detection cage is suspended from the gasification pipe. S3: Rotate the detection cage so that the first gas outlet faces the side of the front end of the furnace, and the side wall of the detection cage contacts the side wall of the furnace, and ignites and burns; during the combustion process, the stress sensing optical fiber in contact with the side wall of the furnace monitors the stress data in real time. When the optical fiber that can detect stress can no longer detect stress, it means that the place has collapsed downward and is no longer in contact with the optical fiber; when all stress sensing optical fibers suddenly fail to detect stress, it means that the coal layer on the side wall has collapsed after being fully burned and has fallen to the bottom of the furnace; S4: The second gas outlet faces the other side of the front end of the furnace, and the other side wall of the detection cage contacts the other side wall of the furnace, and ignites and burns; during the combustion process, the stress sensing optical fiber in contact with the side wall of the furnace monitors the stress data in real time. When the optical fiber that can detect stress can no longer detect stress, it means that the place has collapsed downward and is no longer in contact with the optical fiber; when all stress sensing optical fibers suddenly fail to detect stress, it means that the coal layer on the other side wall has collapsed after being fully burned and has fallen to the bottom of the furnace; S5: Rotate the detection cage so that the first gas outlet or the second gas outlet faces the top wall of the front end of the furnace, and the top of the detection cage contacts the top wall of the furnace, and ignites and burns; during the combustion process, the stress sensing optical fiber in contact with the top wall of the furnace monitors the stress data in real time. When the stress detected by the optical fiber at a certain place suddenly increases, it means that the place has collapsed downward; when the optical fiber at the top of the detection cage detects a sudden increase in stress at the same time, it means that the coal layer on the top wall has collapsed after being fully burned and falls on the detection cage. The detection cage rotates, and the coal slag falls to the bottom of the furnace; The detection cage is extended toward the interior of the furnace, and segmented combustion and gasification are performed according to the operations of the above steps S1-S5, with each segment being the length of the detection cage, until the rear end of the furnace.

2. The method for fully burning an underground coal gasification furnace and monitoring the deformation of the furnace inner wall according to claim 1, characterized in that: The gasification pipe includes a vertical part and a horizontal part. The front end of the horizontal part is connected to the bottom of the vertical part, and the tail end of the horizontal part is connected to the outlet pipe through a rotating motor. The front end of the outlet pipe is connected to the rotating shaft of the rotating motor. The tail end of the outlet pipe is divided into two branches to form two outlets. Each outlet is provided with a valve to control whether the outlet is exhausted.

3. The method for fully burning an underground coal gasification furnace and monitoring the deformation of the furnace inner wall according to claim 1, characterized in that: The detection cage is cylindrical in shape as a whole, with its central axis horizontal, and the air outlet pipe coincides with the central axis; the detection cage is divided into a front cage, a middle cage and a rear cage along the central axis, the diameters of the front cage and the rear cage are the same and larger than the diameter of the middle cage, and the middle cage is formed by the detection cage being concave inward; Two outwardly protruding conical combustion corners are arranged on the side wall of the middle cage, which are used to accommodate the air outlets respectively. The two combustion corners are symmetrically arranged with the central axis of the detection cage as the center, and the top ends of the two combustion corners point in opposite directions.

4. The method for fully burning an underground coal gasifier and monitoring the deformation of the furnace inner wall according to claim 3, characterized in that: A plurality of support rods 1 are arranged on the outside of the air outlet pipe to support the inner side of the front cage, and the plurality of support rods 1 are evenly distributed along the length direction and circumference direction of the air outlet pipe; A central rod is connected to the tail end of the air outlet pipe and the root position where the two air outlets meet. The central rod coincides with the central axis. Several support rods 2 are provided on the outside of the central rod to support the inner side of the rear cage. Several support rods 2 are evenly distributed along the length and circumference of the central rod, so that the air outlet pipe drives the detection cage to rotate through support rods 1 and 2.

5. The method for fully burning an underground coal gasification furnace and monitoring the deformation of the furnace inner wall according to claim 4, characterized in that: A position adjustment part is provided at the tail of the horizontal part of the gasification tube, and the position adjustment part includes five adjustable position gears of upper, lower, left, right and center. The central position gear corresponds to the horizontal part of the gasification tube, and the four position gears of upper, lower, left and right are located around the central position gear. The rotating motor is movably connected to the position adjustment part through a control block, and the control block drives the rotating motor to move along the position adjustment part to realize switching among the five position gears of upper, lower, left, right and center, so that the side walls of the detection cage can contact the top wall, bottom surface, left inner wall and right inner wall of the furnace respectively.

6. The method for fully burning an underground coal gasification furnace and monitoring the deformation of the furnace inner wall according to claim 5, characterized in that: In step S2, the detection cage is rotated by a rotary motor so that the line between the two combustion angles is a vertical line and the two air outlets are arranged up and down; the control block drives the rotary motor to switch from the original central position gear to the lower position gear so that the bottom surface of the detection cage contacts the bottom surface of the furnace at this time; The stress on the stress-sensing optical fiber that can contact the bottom of the furnace is greater than zero, and the data obtained by the detection is transmitted to the data processing device on the ground to record and analyze the data.

7. The method for fully burning an underground coal gasification furnace and monitoring the deformation of the furnace inner wall according to claim 6, characterized in that: After the stress on the stress-sensing optical fiber is stabilized, the valve of the first gas outlet is opened to release the gasifying agent, and the corresponding igniter is opened at the same time to ignite the coal layer at the bottom of the furnace; The stress-sensing optical fiber at the bottom of the front cage and the rear cage continuously monitors stress changes. As the coal seam at the bottom burns, the stress continues to change, reflecting the slight deformation of the coal seam during combustion. If the stress at a certain point of the optical fiber increases, it means that the coal seam at this point is expanding or displacing; if the stress at a certain point of the optical fiber decreases, it means that the coal seam at this point is shrinking. As the combustion continues, when the optical fiber at a certain place on the bottom of the detection cage continues to detect no stress, it means that the place has collapsed downward; when all the optical fibers at the bottom of the detection cage detect no stress, it means that the coal seam at the bottom of the furnace of the detection cage has collapsed after full combustion, and the detection cage is supported by the horizontal part of the gasification pipe, and the detection cage is reset to the central position.

8. The method for fully burning an underground coal gasifier and monitoring the deformation of the furnace inner wall according to claim 1, characterized in that: The tail end of the underground gasifier is connected to another vertical shaft, and the two vertical shafts are parallel to each other; the detector is connected to a rod, and before the gasifier starts gasification, the rod moves the detector along the bottom of another vertical shaft to the position corresponding to the tail end of the furnace, and then detects the shape of the inner wall of the furnace in sections and batches towards the front end of the furnace.

9. The method for fully burning an underground coal gasification furnace and monitoring the deformation of the furnace inner wall according to claim 8, characterized in that: The detector includes a main rod and a plurality of detection parts, the detection parts include an arc-shaped detection piece and a retractable support rod, the plurality of support rods are evenly arranged along the circumference of the main rod, one end of the support rod is connected to the main rod, and the other end is connected to the inner side of the detection piece, so as to push the detection piece to the inner wall of the furnace; The detection piece is made of stress-sensitive optical fibers that are staggered horizontally and vertically. Two adjacent optical fibers are in contact with each other but do not squeeze each other. The curvature of each detection piece is the same, and the width of the detection piece is the length direction of the furnace.

10. The method for fully burning an underground coal gasification furnace and monitoring the deformation of the furnace inner wall according to claim 9, characterized in that: The method for the detector to monitor the unburned furnace inner wall is: (1) The horizontal rod extends the detector into the rear end of the furnace and stops at the first detection section. The length of the detection section is equal to the width of the detection piece. The main rod coincides with the central axis of the furnace. Several support rods are extended in sequence, so that the outer sides of several detection pieces contact the inner wall of the furnace in sequence. The detection pieces form a circle and monitor the deformation of a circle of the inner wall of the furnace in real time. (2) At the beginning, the stress detected by 85-90% of the optical fibers of each detection piece is greater than zero, indicating that most of the optical fibers have contacted the inner wall of the furnace. The position where the detection value is zero is the original depression of the inner wall of the furnace. The greater the stress detected, the more the inner wall of the furnace protrudes toward the detection piece, compressing the flexible detection piece, and recording the detection data at the beginning; (3) The support rod is shortened, so that the detection values ​​of all detection pieces return to zero, the detection pieces are separated from the inner wall of the furnace, and the horizontal rod continues to send the detector into the furnace for detection of the next detection section.

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