Cooling device and method for isolated and sealed exhaust pipe of underground coal gasification furnace

Abstract

The present invention provides a cooling device and method for the isolated and sealed exhaust pipeline of an underground coal gasification furnace, including an annular heat exchanger, an inlet and return water pipeline, a water supply and return device, and a monitoring and control system. A plurality of the annular heat exchangers are arranged in the isolated and sealed exhaust borehole, and a plurality of the annular heat exchangers are nested on the outside of the exhaust pipeline. The water inlet and the water return port of the annular heat exchanger are respectively connected to the water supply and return device, and the water supply and return device is connected to the monitoring and control system. The present invention can achieve heat absorption and cooling in the isolated and sealed exhaust pipeline, absorb the heat continuously transferred by the exhaust pipeline, monitor the temperature value of the coal body in the isolated and sealed and around the borehole through the set temperature sensor, reasonably optimize the inlet and return water flow of the cooling device, control the temperature of the material in the isolated and sealed and the temperature of the surrounding coal body within a reasonable range, prevent the high-temperature degradation, cracking, and sealing failure of the isolated and sealed materials, and prevent the surrounding coal body from being overheated and pyrolyzed to produce harmful gases.

Description

Technical Field

[0001] The invention relates to the technical field of underground coal gasification, and in particular to a cooling device and method for an isolated and sealed exhaust pipe of an underground coal gasification furnace. Background Art

[0002] Underground coal gasification is a process of controlled combustion of coal underground to produce combustible gas through thermal and chemical effects on coal. Underground gasification technology only extracts the energy components in coal, changes physical coal mining into chemical coal mining, realizes the integration of the three major processes of well construction, coal mining, and ground gasification, and eliminates the huge coal mining, transportation, washing, gasification and other processes and equipment. Therefore, it has the advantages of good safety, low investment, high efficiency, and low pollution, and is known as the second generation of coal mining methods. Underground coal gasification technology can not only recover coal resources abandoned by mines, but also be used to mine thin coal seams, deep coal seams, "three-down" compressed coal, and high-sulfur, high-ash, and high-gas coal seams that are difficult for underground workers to mine or have poor mining economics and safety. The coal gas produced by underground gasification can be used as fuel gas for direct civilian use and power generation, or as raw gas for extracting pure hydrogen, synthetic oil, dimethyl ether, ammonia, and methanol.

[0003] The coal gasification furnace gasification process is as follows: There are oxidation zone, reduction zone and dry distillation zone in the coal underground gasification furnace. In the oxidation zone, the coal oxygen reacts to generate CO 2 The temperature of the gasifier reaches 1000-1200℃, and the reduction reaction of carbon dioxide and carbon and the decomposition reaction of water vapor occur in the reduction zone, absorbing heat and cooling down. The generated coal gas enters the downstream distillation and drying zone. At this time, the temperature of the coal gas is still as high as 200-500℃. After that, the high-temperature coal gas enters the gas transmission pipeline located at the upper end of the underground gasification furnace, and is transported to the ground pipeline network and users through the gas transmission pipe laid in the underground tunnel and the ground exhaust drilling pipeline.

[0004] The gas transmission pipeline at the upper end of the underground gasifier is generally arranged in the exhaust borehole. In order to maintain the airtightness of the underground coal gasifier and prevent the gas from leaking into the underground tunnel space through the exhaust borehole, it is necessary to build an isolation seal in the exhaust borehole of the underground gasifier, fill the interior with high-temperature resistant materials, and prevent gas leakage. However, since the gas temperature in the gas transmission pipeline is as high as 200-500℃, long-term high-temperature heat transfer will cause heat to be continuously transferred outward along the radial direction of the pipeline, causing the isolation seal of the exhaust borehole and the temperature of the coal body around the borehole to rise, which will cause the isolation seal material to deteriorate at high temperature, crack, and fail to seal, resulting in gas leakage. At the same time, it will also cause the gas temperature around the borehole to rise to the pyrolysis temperature threshold, and the coal will pyrolyze into CO and H 2 S and other toxic and harmful gases pose a hidden danger to underground production safety. Summary of the invention

[0005] The object of the present invention is to provide a cooling device and method for an isolated and sealed exhaust pipe of an underground coal gasification furnace, which can achieve heat absorption and cooling in the isolated and sealed exhaust pipe, absorb the heat continuously transferred by the exhaust pipe, monitor the temperature value of the coal body in the isolated and sealed area and around the borehole through the set temperature sensor, reasonably optimize the inlet and return water flow of the cooling device, control the material temperature in the isolated and sealed area and the temperature of the surrounding coal body within a reasonable range, prevent the isolated and sealed material from high-temperature degradation, cracking, and sealing failure, and prevent the surrounding coal body from being overheated and pyrolyzed to produce harmful gases.

[0006] According to one purpose of the present invention, the present invention provides a cooling device in an isolated and sealed exhaust pipeline of an underground coal gasification furnace, including an annular heat exchanger, an inlet and return water pipeline, a supply and return water device and a monitoring and control system, a plurality of the annular heat exchangers are arranged in the isolated and sealed exhaust drilling hole, and a plurality of the annular heat exchangers are nested on the outside of the exhaust pipeline, the water inlet and return water outlet of the annular heat exchanger are respectively connected to the supply and return water device, and the supply and return water device is connected to the monitoring and control system.

[0007] Furthermore, it also includes a temperature monitoring device, which is connected to the monitoring and control system. The temperature monitoring device includes a first temperature sensor arranged on the outer wall of the exhaust pipeline, a second temperature sensor arranged on the outer wall side of the annular heat exchanger, a third temperature sensor arranged at the interface between the exhaust borehole and the coal wall, and a water temperature sensor arranged in the inlet and return water pipes.

[0008] Furthermore, a flow monitoring device is provided in the water inlet pipeline or the water return pipeline, and the flow monitoring device is connected to the monitoring and control system.

[0009] Furthermore, the water supply and return device includes an inlet pipe, a return pipe, a water pump and a cooling water tank. The inlet pipe or the return pipe is respectively connected to the water inlet or return port of the annular heat exchanger, the other end of the inlet pipe is connected to the water pump, the water pump is connected to the cooling water tank, the other end of the return pipe is connected to the cooling water tank, and a control valve is provided on the inlet pipe.

[0010] Furthermore, the annular heat exchanger is a multi-stage annular heat exchanger, which includes multiple water inlet tanks and return water tanks. The multiple water inlet tanks are connected in sequence, and the multiple return water tanks are connected in sequence. The water inlet tank and the return water tank at the front end are connected together by a U-shaped connecting pipe, and the water inlet tank or the return water tank at the rear end is respectively connected to the water inlet pipeline or the return water pipeline.

[0011] Furthermore, the annular heat exchanger is uniformly nested on the outside of the exhaust pipe through a circular ring reinforcement steel plate.

[0012] Furthermore, a support block is provided between the circular reinforcement steel plate and the exhaust drilling hole for isolation and sealing.

[0013] Furthermore, a plurality of baffles are arranged alternately up and down inside the water inlet tank and the water return tank.

[0014] According to another object of the present invention, the present invention provides a cooling device and method for an isolated and sealed exhaust pipeline of an underground coal gasification furnace, comprising the following steps:

[0015] Step 1: Determine the size parameters of the annular heat exchanger

[0016] The gas exhaust pipeline in the underground coal gasifier is laid in the exhaust borehole at one end of the underground gasifier. The length and inner diameter parameters of the required annular heat exchanger are determined according to the length and outer diameter of the exhaust pipeline.

[0017] Step 2, Annular Heat Exchanger Installation

[0018] The high temperature resistant plugging material is filled between the exhaust drilling hole and the exhaust pipeline, and the maximum resistant temperature is above 1300℃. The annular heat exchanger is installed and nested in the high temperature resistant plugging material outside the exhaust pipeline and between the exhaust drilling hole;

[0019] The annular heat exchanger is embedded in sections on the exhaust pipe in the exhaust drilling insulation and airtightness, and multiple sections of annular heat exchangers are embedded in the exhaust pipe in sequence;

[0020] Step 3: Assemble the water supply and return piping system

[0021] After the annular heat exchanger is installed, the water inlet pipe is connected to the water inlet pipe of the annular heat exchanger, the water return pipe is connected to the water return pipe of the annular heat exchanger, and the water inlet pipe and the water return pipe are connected to the water pump, the control valve and the cooling water tank respectively;

[0022] Step 4, Installation of temperature and flow sensors

[0023] The temperature sensors are installed on the outer wall of the exhaust pipe, the outer wall of the annular heat exchanger, the interface between the exhaust borehole and the coal wall, and the water inlet and return pipes; the flow sensors are installed in the water inlet and return pipes;

[0024] Step 5: Connectivity and sealing inspection

[0025] Before filling the exhaust borehole with high temperature resistant plugging material, test the whole system to detect the overall fluidity and sealing, monitor the flow of the water inlet pipe and the flow of the water return pipe. If the flow of the two is equal at the same temperature, there is no water leakage in the whole cooling system. Increase the water flow, the whole cooling system runs stably, the sensor monitoring is normal, and the valves and control software are running normally, then the whole system runs well.

[0026] Step 6: Run and monitor

[0027] During the normal gas production operation of the underground gasifier, the temperature sensor returns the temperature values ​​of each temperature measuring point to the monitoring and control system as the basis for the monitoring and control system to make decisions;

[0028] Step 7: Temperature and flow control

[0029] When it is monitored that the outer wall temperature of the annular heat exchanger reaches 150°C, or the interface temperature of the exhaust borehole and the coal wall reaches 40°C, or the return pipe temperature reaches 80°C, the operating frequency of the water pump is increased through frequency conversion control to increase the flow rate of the water inlet pipe; the cooling capacity of the cooling water tank is increased, and the water temperature in the cooling water tank and the water temperature of the water inlet pipe are reduced.

[0030] Furthermore, in step 6, the entire control system plots the temperature value of each temperature measurement point in real time, and the main records and data analysis are as follows:

[0031] (1) The temperature of the outer wall of the exhaust pipe reflects the temperature of the high-temperature gas in the pipe, which is between 200 and 500°C. Heat is continuously transferred from the outer wall of the exhaust pipe to the isolated and sealed interior;

[0032] (2) The temperature monitored on the outer wall of the annular heat exchanger reflects the temperature of the high-temperature resistant plugging material. The maximum temperature value of this point is controlled not to exceed 150°C;

[0033] (3) The temperature at the interface between the exhaust borehole and the coal wall reflects the heat of the high-temperature coal gas. The heat is transferred through the exhaust pipe → high-temperature resistant plugging material → - annular heat exchanger → high-temperature resistant plugging material, and finally to the temperature of the adjacent coal body. When the coal body temperature reaches 50-70°C, that is, the self-heating temperature range, significant spontaneous combustion and oxidation characteristics will occur, and small molecular gases CO and H will be volatilized. 2 Therefore, the maximum temperature at this point should not exceed 40℃;

[0034] (4) The water temperature in the water inlet pipe should be within the range of 30°C;

[0035] (5) The water temperature in the return pipe shall not exceed 80°C.

[0036] The beneficial results of the present invention are:

[0037] The technical solution of the present invention can achieve heat absorption and cooling in the isolated and sealed exhaust pipeline, absorb the heat continuously transferred by the exhaust pipeline, monitor the temperature value of the coal body in the isolated and sealed and around the borehole through the set temperature sensor, reasonably optimize the inlet and return water flow of the cooling device, control the temperature of the material in the isolated and sealed and the temperature of the surrounding coal body within a reasonable range, prevent the high-temperature deterioration, cracking, and sealing failure of the isolated and sealed materials, and prevent the surrounding coal body from being too hot and pyrolyzing to produce harmful gases. The annular heat exchanger provided by the present invention is directly nested outside the high-temperature coal gas exhaust pipeline, which is easy to install, and directly cools down the high-temperature resistant plugging material in the isolated and sealed exhaust borehole, with good heat exchange and temperature control effects; and the power system is frequency-controlled to achieve the regulation of the water inlet flow and ensure the cooling effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 It is a schematic diagram of the structure of the cooling device of an embodiment of the present invention in an isolated and sealed exhaust drilling hole;

[0040] Figure 2 It is another structural schematic diagram of the cooling device of the embodiment of the present invention in the isolation and sealing of the exhaust drilling hole;

[0041] Figure 3 Embodiment of the present invention Figure 2 Middle AA cross-section;

[0042] Figure 4 Embodiment of the present invention Figure 2 Middle BB cross-section;

[0043] Figure 5 is a schematic structural diagram of a cooling device according to an embodiment of the present invention;

[0044] Figure 6 is another structural schematic diagram of the cooling device according to an embodiment of the present invention;

[0045] Figure 7 Embodiment of the present invention Figure 2 Schematic diagram of the local structure at A in the middle;

[0046] In the figure, 1. coal seam; 2. isolation and sealing; 3. exhaust pipeline; 4. annular heat exchanger; 5. support block; 6. third temperature sensor; 7. second temperature sensor; 8. first temperature sensor; 9. water inlet pipeline; 10. return pipeline; 11. cooling water tank; 12. water pump; 13. valve; 14. flow sensor; 15. circular reinforcement steel plate; 16. pressure gauge; 17. monitoring and control system; 18. water inlet tank; 19. return tank; 20. rubber sealing ring; 21. U-shaped connecting pipe; 22. baffle. DETAILED DESCRIPTION

[0047] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0049] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] Example 1

[0051] like Figure 1-Figure 7 As shown,

[0052] A cooling device in an isolated and sealed exhaust pipe of an underground coal gasification furnace is provided. A heat-absorbing and cooling device is installed in an isolated and sealed 2 outside an exhaust pipe 3 arranged in a coal seam 1. Cooling water is provided by a power system. The temperature of each position point is monitored by a temperature sensor. The temperature value of each temperature point is controlled by the cooling water inlet flow rate. The power system adjusts the inlet flow rate by frequency conversion. The control system controls the temperature, flow rate, motor frequency, electric regulating valve, etc. Finally, the purpose of controlling the temperature of each temperature point within a reasonable range is achieved.

[0053] A cooling device in an isolated and sealed exhaust pipeline of an underground coal gasification furnace mainly comprises an annular heat exchanger 4, an inlet and return water pipeline and a valve 13, a water pump 12, a cooling water tank 11, and a monitoring and control system 17.

[0054] The annular heat exchanger 4 is a multi-stage annular heat exchanger installed inside the exhaust drilling isolation enclosure 2 and nested outside the exhaust pipeline 3. Each section is composed of a plurality of heat exchange boxes 4-1 evenly distributed on the circular reinforcement steel plate 15, and the boxes used for water inlet and the boxes used for water return are arranged at intervals.

[0055] The annular heat exchanger 4 includes a plurality of water inlet boxes 18 and a water return box 19, wherein the plurality of water inlet boxes 18 are connected in sequence, and the plurality of water return boxes 19 are connected in sequence. Each of the water inlet boxes 18 and the water return box 19 is a rectangular parallelepiped with openings at both ends. The openings at both ends are connecting devices, which can realize the connection of two adjacent sections of the water inlet boxes 18 and the water return boxes 19 with threads or flanges. A rubber sealing ring 20 is provided at the connection to ensure the connection quality and prevent leakage. The water inlet pipe and the water return pipe of the annular heat exchanger 4 at the front end are connected together by a U-shaped connecting pipe 21 to realize the return of the water inlet to the water return pipe of the heat exchanger.

[0056] Baffles 22 are arranged in an alternating manner inside the water inlet box 18 and the water return box 19 to increase the flow area and heat exchange time of water inside the heat exchange box. During the construction stage, the annular heat exchanger 4 is nested outside the exhaust pipe 3 in the exhaust drilling isolation enclosure 2, and its position is fixed by the support block 5.

[0057] The water inlet and return pipelines and valves mainly include a water inlet pipeline 9 connected to the annular heat exchanger 4, a water return pipeline 10 and a control valve 13 on the pipelines.

[0058] The water pump 12 is a water pump with a coal safety mark that provides power for the inlet and return water. The water pump can be frequency-controlled to adjust the inlet flow. The cooling water tank 11 is a high-temperature return water cooling water tank that reduces the water temperature through natural heat dissipation or air cooling, and is also a water storage tank for the water inlet pipe.

[0059] The monitoring and control system 17 refers to the monitoring of temperature, flow, and pressure such as the temperature inside the isolated and sealed area, the temperature of the adjacent coal body, the inlet and return water temperature, the inlet and return water flow rate, and the inlet and return water pressure, as well as the frequency conversion control of the water pump and the control of the electric regulating valve, so as to achieve the purpose of controlling the maximum temperature inside the isolated and sealed area and the maximum temperature of the adjacent coal body.

[0060] A method for cooling an isolated and sealed exhaust pipe of an underground coal gasification furnace comprises the following steps:

[0061] Step 1: Determine the size parameters of the annular heat exchanger

[0062] The coal gas exhaust pipeline 3 in the underground coal gasifier is arranged in the exhaust borehole at one end of the underground gasifier. According to the length and outer diameter of the exhaust pipeline 3, the required length and inner diameter parameters of the annular heat exchanger 4 are determined, and the size parameters of the annular heat exchanger 4 are determined.

[0063] Step 2, Annular Heat Exchanger Installation

[0064] The high temperature resistant plugging material (isolation and sealing 2) is filled between the exhaust borehole and the exhaust pipeline 3, and the maximum tolerable temperature can reach above 1300°C. The material has strong bonding force at room temperature and high temperature. The annular heat exchanger 4 provided by the present invention is installed and nested in the high temperature resistant plugging material (isolation and sealing 2) outside the exhaust pipeline 3 and between the exhaust borehole. The annular heat exchanger 4 is segmented and nested on the exhaust pipeline 3 in the heat-insulated and sealed 2 of the exhaust borehole. Due to the space limitation of the underground tunnel, the annular heat exchanger 4 can be processed into multiple sections, and the length of each section meets the size requirements of the underground tunnel space transportation; the multiple sections of the annular heat exchanger 4 are nested in the exhaust pipeline 3 in sequence, and the water inlet pipe and the water return pipe of the two adjacent sections of the annular heat exchanger 4 are respectively connected in series. The connection method can be flange or threaded connection, and the connection quality is guaranteed without leakage.

[0065] Step 3: Assemble the water inlet and return pipes, valves, water pumps, cooling water tanks and other systems

[0066] After the annular heat exchanger 4 is installed, the water inlet pipe 9 is connected to the water inlet pipe of the annular heat exchanger 4, the water return pipe 10 is connected to the water return pipe of the annular heat exchanger 4, and then the water pump 12, the electric regulating valve 13, and the cooling water tank 11 are connected. The water inlet pipe 9 and the water return pipe 10 are also provided with a pressure gauge 16 for monitoring the pressure in the pipe.

[0067] Step 4, Installation of temperature and flow sensors

[0068] Temperature sensors are mainly installed in the following locations:

[0069] A first temperature sensor 8 is arranged on the outer wall of the exhaust pipe 3, a second temperature sensor 7 is arranged on the outer wall side of the annular heat exchanger 4, a third temperature sensor 6 is arranged at the interface between the exhaust borehole and the coal wall, and a water temperature sensor is arranged in the inlet and return pipes. The flow sensor 14 monitors the flow at the following positions: the inlet pipe flow and the return pipe flow.

[0070] Step 5: Connectivity and sealing inspection

[0071] Before filling the exhaust borehole with high temperature resistant plugging material (isolation and sealing 2), test run the cooling device and the entire system to detect the overall fluidity and sealing. Monitor the flow of the water inlet pipe 9 and the flow of the return pipe 10. If the flow rates of the two are equal at the same temperature, there is no water leakage in the entire cooling system. Increase the water flow, the entire cooling system operates stably, the sensor monitoring is normal, and the valves and control software are operating normally, then the overall system is operating well.

[0072] Step 6: Run and monitor

[0073] During the normal gas production operation of the underground gasifier, the cooling system proposed by the present invention starts to work. The temperature sensor returns the temperature value of each temperature measuring point to the control system 17 as the basis for the decision of the control system 17. The entire control system 17 plots the temperature value of each temperature measuring point in real time, and the main records and data analysis are as follows:

[0074] (1) The temperature of the outer wall of the exhaust pipe 3 basically reflects the temperature of the high-temperature gas in the pipe, which is generally between 200 and 500°C. Heat is continuously transferred from the outer wall of the exhaust pipe 3 to the isolated and sealed 2;

[0075] (2) The temperature monitored on the outer wall of the annular heat exchanger 4 reflects the temperature of the high temperature resistant plugging material 2. In order to maintain a good sealing effect, the maximum temperature value of this point is controlled not to exceed 150°C;

[0076] (3) The temperature at the interface between the exhaust borehole 3 and the coal wall 1 reflects the heat of the high-temperature coal gas, which is transferred through the exhaust pipe 3 → high-temperature resistant plugging material → - annular heat exchanger 4 → high-temperature resistant plugging material (isolation and sealing 2) and finally to the temperature of the adjacent coal body 1. Since the temperature of the coal body 1 reaches 50-70°C, i.e., the self-heating temperature range, significant spontaneous combustion and oxidation characteristics will occur, and small molecular gases CO and H will be volatilized. 2 Therefore, the maximum temperature at this point should not exceed 40℃.

[0077] (4) The water temperature in the water inlet pipe 9 is generally within the range of room temperature to 30°C.

[0078] (5) The water temperature in the return pipe 10 is generally not more than 80°C.

[0079] Step 7: Temperature and flow control measures

[0080] When the outer wall temperature of the annular heat exchanger 4 reaches 150°C, or the interface temperature of the exhaust borehole 3 and the coal wall 1 reaches 40°C, or the temperature of the return water pipeline 10 reaches 80°C, the following measures should be taken:

[0081] (1) By frequency conversion control, the operating frequency of the water pump 12 is increased to increase the flow rate of the water inlet pipeline 9;

[0082] (2) Increase the cooling capacity of the cooling water tank 11 and reduce the water temperature in the water tank and the water inlet pipe.

[0083] Therefore, in summary, the cooling device and method for the isolated and sealed exhaust pipe of the underground coal gasification furnace proposed in the present invention can realize the heat exchange removal of the heat transferred from the high-temperature coal gas in the exhaust pipe to the high-temperature resistant plugging material, control the maximum temperature of the high-temperature resistant plugging material, the return water temperature of the heat exchanger and the maximum temperature of the adjacent coal body. It can prevent the high-temperature resistant plugging material in the isolated and sealed environment from high-temperature deterioration, cracking, and plugging failure, and prevent the surrounding coal body from being overheated and pyrolyzed to produce harmful gases.

[0084] The present invention provides a cooling device and method in an isolated and sealed exhaust pipe of an underground coal gasification furnace. The heat absorption cooling device in the isolated and sealed exhaust pipe provides cooling water through a power system, monitors the temperature of each position point through a temperature sensor, controls the temperature value of each temperature point through the cooling water inlet flow rate, and the power system adjusts the inlet flow rate through frequency conversion. The control system controls the temperature, flow rate, motor frequency, electric regulating valve, etc. Finally, the purpose of controlling the temperature of each temperature point within a reasonable range is achieved.

[0085] The present invention is suitable for an annular heat exchanger installed in an isolated and sealed exhaust borehole of an underground coal gasification furnace and can be nested outside a high-temperature exhaust pipeline. The device is composed of a plurality of rectangular heat exchange boxes, and the boxes used for water inlet and the boxes used for water return are arranged at intervals, and all heat exchange boxes are combined together by annular reinforced steel plates. The annular heat exchanger can be combined in series to increase the total heat exchange length; the openings at both ends are connecting devices, which can realize the connection of two adjacent annular heat exchangers with threads or flanges, and there are rubber sealing rings at the connection to ensure the connection quality and prevent leakage; the annular heat exchanger water inlet pipe and the water return pipe at the front end are connected together by a U-shaped connecting pipe to realize the return of the water inlet to the heat exchanger return pipe. Baffles are arranged in an upper and lower staggered manner inside each heat exchange box to increase the flow area and heat exchange time of water inside the heat exchange box.

[0086] The present invention aims at the heat exchange demand of the exhaust pipeline in the exhaust borehole of the underground coal gasification furnace, and proposes an annular heat exchanger nested outside the exhaust pipeline, and multiple annular heat exchangers can be combined in series, and the overall heat exchange length can be adjusted. The annular heat exchanger provided by the present invention is directly set in the high-temperature resistant plugging material in the exhaust borehole, and effectively absorbs heat and cools the high-temperature resistant plugging material to prevent high-temperature degradation, cracking, and plugging failure of the high-temperature resistant plugging material, which causes gas leakage in the underground gasification furnace. The present invention also considers the temperature protection of the coal body near the exhaust borehole. By absorbing heat and cooling the temperature of the high-temperature resistant plugging material in the exhaust borehole, the purpose of controlling the maximum temperature of the coal body near the exhaust borehole is achieved, and the temperature of the coal body near the gas is prevented from being too high and pyrolyzed to produce harmful gases. The cooling device and method can realize frequency conversion, and can automatically adjust the inlet and return water flow and temperature of the heat exchange system, so as to achieve the dual purposes of energy saving and temperature control.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cooling device for an isolated and sealed exhaust pipe of an underground coal gasification furnace, characterized in that: It includes an annular heat exchanger, an inlet and return water pipeline, a water supply and return device and a monitoring and control system. A plurality of the annular heat exchangers are arranged in an isolated and sealed exhaust borehole, and a plurality of the annular heat exchangers are nested outside the exhaust pipeline. The water inlet and the water return port of the annular heat exchanger are respectively connected to the water supply and return device, and the water supply and return device is connected to the monitoring and control system; It also includes a temperature monitoring device, which is connected to the monitoring and control system, and includes a first temperature sensor arranged on the outer wall of the exhaust pipeline, a second temperature sensor arranged on the outer wall side of the annular heat exchanger, a third temperature sensor arranged at the interface between the exhaust borehole and the coal wall, and a water temperature sensor arranged in the inlet and return water pipes; The water supply and return device comprises a water inlet pipeline, a water return pipeline, a water pump and a cooling water tank. The water inlet pipeline or the water return pipeline is respectively connected to the water inlet or the water return port of the annular heat exchanger, the other end of the water inlet pipeline is connected to the water pump, the water pump is connected to the cooling water tank, the other end of the water return pipeline is connected to the cooling water tank, and a control valve is provided on the water inlet pipeline; The annular heat exchanger is a multi-stage annular heat exchanger, which includes multiple water inlet tanks and return water tanks. The multiple water inlet tanks are connected in sequence, and the multiple return water tanks are connected in sequence. The water inlet tank and the return water tank at the front end are connected together through a U-shaped connecting pipe, and the water inlet tank or the return water tank at the rear end is respectively connected to the water inlet pipeline or the return water pipeline.

2. The cooling device for isolating and sealing the exhaust pipe of an underground coal gasification furnace according to claim 1, characterized in that: A flow monitoring device is provided in the water inlet pipeline or the water return pipeline, and the flow monitoring device is connected to the monitoring and control system.

3. The cooling device for isolating and sealing the exhaust pipe of an underground coal gasification furnace according to claim 1, characterized in that: The annular heat exchanger is uniformly nested on the outside of the exhaust pipe through a circular ring reinforcement steel plate.

4. The cooling device for isolating and sealing the exhaust pipe of an underground coal gasification furnace according to claim 3, characterized in that: A support block is provided between the circular reinforcement steel plate and the exhaust drilling hole for isolation and sealing.

5. The cooling device for isolating and sealing the exhaust pipeline of an underground coal gasification furnace according to claim 1, characterized in that: A plurality of baffles are arranged in an up-and-down staggered manner inside the water inlet box and the water return box.

6. A method for using a cooling device in an isolated and sealed exhaust pipeline of an underground coal gasification furnace, characterized in that: The following steps are involved: Step 1: Determine the size parameters of the annular heat exchanger The gas exhaust pipeline in the underground coal gasifier is laid in the exhaust borehole at one end of the underground gasifier. The length and inner diameter parameters of the required annular heat exchanger are determined according to the length and outer diameter of the exhaust pipeline. Step 2: Annular heat exchanger installation The high temperature resistant plugging material is filled between the exhaust drilling hole and the exhaust pipeline, and the maximum resistant temperature is above 1300℃. The annular heat exchanger is installed and nested in the high temperature resistant plugging material outside the exhaust pipeline and between the exhaust drilling hole; The annular heat exchanger is embedded in sections on the exhaust pipe in the exhaust drilling insulation and airtightness, and multiple sections of annular heat exchangers are embedded in the exhaust pipe in sequence; Step 3: Assemble the water supply and return piping system After the annular heat exchanger is installed, the water inlet pipe is connected to the water inlet pipe of the annular heat exchanger, the water return pipe is connected to the water return pipe of the annular heat exchanger, and the water inlet pipe and the water return pipe are connected to the water pump, the control valve and the cooling water tank respectively; Step 4, Installation of temperature and flow sensors The temperature sensors are installed on the outer wall of the exhaust pipe, the outer wall of the annular heat exchanger, the interface between the exhaust borehole and the coal wall, and the water inlet pipe and the water return pipe respectively; the flow sensors are installed in the water inlet pipe and the water return pipe; Step 5: Connectivity and sealing inspection Before filling the exhaust borehole with high temperature resistant plugging material, test the whole system to detect the overall fluidity and sealing, monitor the flow of the water inlet pipe and the flow of the water return pipe. If the flow of the two is equal at the same temperature, there is no water leakage in the whole cooling system. Increase the water flow, the whole cooling system runs stably, the sensor monitoring is normal, and the valves and control software are running normally, then the whole system runs well. Step 6: Run and monitor During the normal gas production operation of the underground gasifier, the temperature sensor returns the temperature values ​​of each temperature measuring point to the monitoring and control system as the basis for the monitoring and control system to make decisions; Step 7: Temperature and flow control When it is monitored that the outer wall temperature of the annular heat exchanger reaches 150°C, or the interface temperature of the exhaust borehole and the coal wall reaches 40°C, or the return pipe temperature reaches 80°C, the operating frequency of the water pump is increased through frequency conversion control to increase the flow rate of the water inlet pipe; the cooling capacity of the cooling water tank is increased, and the water temperature in the cooling water tank and the water temperature of the water inlet pipe are reduced.

7. The method for using the cooling device in the isolated and sealed exhaust pipeline of an underground coal gasification furnace according to claim 6, characterized in that: In step 6, the entire control system plots the temperature values ​​of each temperature measurement point in real time. The main records and data analysis are as follows: (1) The temperature of the outer wall of the exhaust pipe reflects the temperature of the high-temperature gas in the pipe, which is between 200 and 500°C. Heat is continuously transferred from the outer wall of the exhaust pipe to the isolated and sealed interior; (2) The temperature monitored on the outer wall of the annular heat exchanger reflects the temperature of the high-temperature resistant plugging material. The maximum temperature value of this point is controlled not to exceed 150°C; (3) The temperature at the interface between the exhaust borehole and the coal wall reflects the heat of the high-temperature coal gas, which is transferred through the exhaust pipe → high-temperature resistant plugging material → - annular heat exchanger → high-temperature resistant plugging material, and finally to the temperature of the adjacent coal body. Since the coal body temperature reaches 50~70℃, i.e., the self-heating temperature range, significant spontaneous combustion and oxidation characteristics will occur, and harmful gas products will be volatilized. Therefore, the maximum temperature at this point should not exceed 40℃; (4) The water temperature in the water inlet pipe should be within the range of 30°C; (5) The water temperature in the return pipe shall not exceed 80°C.

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