A device and method for monitoring and controlling multi-directional heat flow in backward underground gasification

Abstract

The present invention discloses a device and method for monitoring and controlling multi-directional heat flow of retreat-type underground gasification, the device comprising a coiled pipe and two heat flow meters; a circular foil is provided at the center of the front end of the heat flow meter, a heat sink is provided inside the heat flow meter, a cooling water channel is opened in the middle of the heat sink, the heat sink and the protective shell body of the heat flow meter are thermally insulated, two copper wires connected to a signal processor and a temperature measuring thermocouple connected to the circular foil are provided in the heat flow meter, the other ends of the two copper wires are respectively connected to the heat sink and the circular foil; the present invention integrates a heat flow meter suitable for continuous measurement in a high-temperature environment on the coiled pipe, can collect the axial and radial heat flux density and temperature of the coiled pipe at the underground gasification injection point in real time, grasp the expansion of the combustion zone, comprehensively judge the coal seam combustion state in combination with the gas composition of the gas gathering well, and guide the retreat of the gas injection point.

Description

Technical Field

[0001] The present invention relates to the technical field of underground coal gasification, and in particular to a device and method for monitoring and controlling multi-directional heat flow in a backward underground gasification. Background Art

[0002] Underground coal gasification technology allows for controlled combustion of in-situ coal, converting it into combustible gas through thermal and chemical reactions. An underground gasifier typically consists of an inlet well, a gasification channel, an outlet well, and auxiliary monitoring wells. The gasifier is injected through the inlet well and undergoes complex thermochemical reactions with the coal seam in the gasification channel. The generated coal gas is then transported to the surface along the gasification channel and outlet well. The underground gasifier transforms traditional physical coal mining into chemical gas extraction, offering advantages such as low gas production costs, high safety, and good environmental benefits. This technology has broad application prospects in the mining and utilization of residual coal, such as low-quality (high sulfur, high ash), steeply inclined, thin coal seams, deep coal seams, and those that are uneconomical and unminable using conventional technology.

[0003] The controlled-retreat injection point (CRIP) gasification process consists of a gasifier constructed by drilling long horizontal and vertical boreholes in the coal seam. Using ground-based, controllable, mobile, multi-media integrated injection equipment and detection equipment, precise control of the fire zone and regulation of gasification parameters within the long horizontal boreholes in the coal seam are achieved. When the gasification cavity expands to the point where it can no longer maintain chemical reaction conditions, causing a decline in gas quality, a gasification cycle is considered complete. The injection point is then withdrawn, and a new gasification process is initiated in a new coal seam. This process intensifies the gasification process and effectively improves coal resource utilization. Existing technologies generally employ continuous retreat of the injection pipe or intermittent retreat of the injection pipe based on the temperature of the injection pipe nozzle and the gas composition of the gas collection well. However, temperature measurement is subject to error and cannot reflect the overall temperature of the gasification reaction zone. Furthermore, gas collection has a certain lag, making it impossible to accurately and accurately reflect coal seam combustion at the underground gasification surface in real time to guide the retreat of the injection point. Summary of the Invention

[0004] In view of the above-mentioned technical deficiencies, the purpose of the present invention is to provide a backward underground gasification multi-directional heat flow monitoring and control device, which can improve the movement efficiency of the backward gas injection point and achieve more efficient and precise controllable combustion.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The present invention provides a backward underground gasification multi-directional heat flow monitoring and control device, comprising a continuous tube provided with an inner tube, a combustion head connected to the inner tube provided at the front end of the continuous tube, and two heat flow meters provided on the end face and side wall of the front end;

[0007] The heat flow meter comprises a protective shell fixed on the coiled tube, a heat sink arranged coaxially therewith is disposed in the protective shell, and both the front and rear ends of the protective shell are provided with a heat insulating base for supporting and fixing the heat sink;

[0008] A bell mouth is provided at the center of the front end of the heat sink and a round foil is pressed and fixed by the heat insulation base on the same side. The front end of the protective shell is provided with an opening adapted to the round foil.

[0009] The heat sink has a central cavity connected to the bell mouth, and a No. 1 copper wire connected to the circular foil and a temperature measuring thermocouple are arranged in the central cavity; a No. 2 copper wire is connected to the rear end of the heat sink, and the No. 1 copper wire, the No. 2 copper wire, and the temperature measuring thermocouple extend out of the protective shell and into the signal line protection tube, wherein the No. 1 copper wire and the No. 2 copper wire are connected to the signal processing end;

[0010] The heat sink is further provided with an annular groove as a cooling water channel, and the continuous pipe is provided with a cooling water inlet pipe and a cooling water outlet pipe communicating with the annular groove; the signal processing end and the temperature measuring thermocouple are electrically connected to the ground control center.

[0011] Preferably, the surface of the circular foil is blackened by 2 mm and the material is constantan.

[0012] Preferably, the thermal insulation base is tightly connected to the heat sink by ultrasonic welding, the front end of the thermal insulation base covers the circumference of the circular foil and fixes the circular foil by physical compression, and the thermal insulation base is made of quartz material.

[0013] Preferably, the heat sink is made of red copper, and the central cavity is encapsulated with insulating and shock-resistant materials to ensure the stability of the overall structure and the stability of the No. 1 copper wire, No. 2 copper wire, and temperature measuring thermocouple.

[0014] Preferably, the protective shell is made of carbon steel and the surface is coated with 4-8mm high temperature resistant heat insulation coating.

[0015] Preferably, the protective shell includes a connector fixed to the coiled tubing, the connector fixing the protective shell body on the end face away from the coiled tubing, the signal line protection tube is arranged inside the coiled tubing and fixed thereto, and the connector is provided with through holes for passing through No. 1 copper wire, No. 2 copper wire, and a temperature measuring thermocouple, and reserved holes for passing through a cooling water inlet pipe and a cooling water outlet pipe.

[0016] Preferably, the signal processing end calculates the heat flux density value on the circular foil based on the temperature data measured by the No. 1 copper wire and the No. 2 copper wire, according to the temperature difference between the two and a calibrated heat flux density algorithm, and transmits its data signal to the ground control center.

[0017] The present invention also provides a method for using a backward underground gasification multi-directional heat flow monitoring and control device, specifically:

[0018] Two sets of heat flow meters are used to obtain real-time heat flux and temperature data in the axial and radial directions of the coiled tube. The axial and radial temperatures of the coiled tube are defined as T1 and T2, and the heat flux is defined as Q1 and Q2. M = Q1:Q2, and the value of λ is in the range of 1-2.

[0019] The calorific value of gas is determined by performing real-time online analysis of the gas components collected from the gas gathering wells, visualizing the trend of the calorific value. When the calorific value of the gas drops sharply or reaches a critical value, it is considered that ash deposition has caused a decline in gas quality, and the gasification cycle is considered complete, and the gas injection point is withdrawn.

[0020] The temperature criterion is that a decrease in the reaction zone temperature will lead to unstable synthesis gas production and low output quality. Therefore, when the measured temperatures T1 and T2 are both lower than the theoretically derived critical value T0, the gasification parameters are adjusted to increase the reaction zone temperature, or the gasification cycle is considered to be over and the gas injection point is withdrawn.

[0021] The first heat flow criterion is to visualize the real-time monitored Q1 and Q2 data to form a trend chart, reflecting the expansion of the front and upper combustion zones. To ensure the controllability of the combustion zone, the gasification parameters are adjusted in a timely manner to keep Q1 and Q2 within the theoretical range.

[0022] The second heat flow criterion is: in the early stage of gasification, the coal seam above the coiled tube burner begins to heat up and burn. With continued gas injection, the coal seam combustion zone mainly expands above and behind the gas injection point, and slightly expands forward. According to the two sets of heat flow meters, the radial heat flux Q2 gradually increases, while the axial heat flux Q1 slows down. Therefore, the ratio M of Q1 and Q2 is used to determine the expansion of the combustion zone. The specific criteria are as follows:

[0023] (3) When M>1, it indicates that the combustion-free zone has not yet expanded significantly, and combustion and gasification still occur on the surface of the coal seam above the gas injection point. This stage is considered to be in the initial stage.

[0024] (4) When λ>M>1, it means that the fuel-gap zone has partially expanded upward, but has not yet developed backward to cover the radial heat flux meter. This stage is considered to be in the development stage.

[0025] When M>λ, it indicates that the combustion void zone has expanded upward and backward to a large extent, and the front end of the coiled tubing has been covered by the combustion void zone. To prevent the combustion and gasification reactions on the wall of the combustion void zone from damaging the gas injection ignition device, and to prevent the combustion void zone from expanding upward and exposing the roof surrounding rock, which will reduce the gas production quality, this is considered to be the end of a gasification cycle, and the gas injection point is withdrawn.

[0026] The beneficial effects of the present invention are:

[0027] 1. Compact structure, integrating temperature measuring thermocouple and heat flow meter on the coiled tubing, improving the mobility of detection equipment and realizing real-time monitoring of gas injection points;

[0028] 2. Optimize the structure of the heat flow meter to make it suitable for the high-temperature working environment of underground gasification;

[0029] 3. Two sets of heat flux meters, one in the axial direction and the other in the radial direction, are set up to judge the expansion of the combustion zone by the relationship between the heat flux densities in the two directions. When the combustion zone develops upward to a certain extent, the gas injection point is withdrawn in time to achieve precise and controllable combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 A schematic structural diagram of a heat flow meter provided in an embodiment of the present invention;

[0032] Figure 2 A schematic diagram of the installation position of a heat flow meter on a coiled tubing according to an embodiment of the present invention;

[0033] Figure 3 A schematic diagram of the initial period of expansion and change of the combustion-cavity zone provided by an embodiment of the present invention;

[0034] Figure 4 A schematic diagram of the expansion and change development period of the combustion-empty zone provided in an embodiment of the present invention;

[0035] Figure 5 A schematic diagram of the final phase of the expansion and change of the combustion-empty zone provided in an embodiment of the present invention;

[0036] Figure 6 This is a schematic diagram of the situation when the combustion zone retreats to the gas injection point and secondary ignition is provided in an embodiment of the present invention.

[0037] Description of reference numerals:

[0038] 1. Round foil; 2. Insulation base; 3. Protective shell; 4. Heat sink; 5. Central cavity; 6a. No. 1 copper wire; 6b. No. 2 copper wire; 7. Temperature measuring thermocouple; 8. Connector; 9. Signal line protection tube; 10a. Cooling water inlet pipe; 10b. Cooling water outlet pipe; 11. Signal processing end; 12. Continuous tube; 13. Inner tube; 14. Burner head. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] like Figures 1 to 2 As shown, a backward underground gasification multi-directional heat flow monitoring and control device,

[0041] The continuous tube 12 includes an inner tube 13, a combustion head 14 communicating with the inner tube 13 is provided at the front end of the continuous tube 12, and two heat flow meters are provided on the end face and side wall of the front end;

[0042] The heat flow meter comprises a protective shell 3 fixed on the continuous tube 12, a heat sink 4 arranged coaxially therewith is disposed in the protective shell 3, and a heat insulating base 2 for supporting and fixing the heat sink 4 is disposed at both the front and rear ends of the protective shell 3;

[0043] The front center of the heat sink 4 is provided with a trumpet mouth and a round foil 1 is pressed and fixed by the heat insulation base 2 on the same side. The front end of the protective shell 3 is provided with an opening adapted to the round foil 1; the surface of the round foil 1 is 2mm blackened and the material is constantan.

[0044] The thermal insulation base 2 and the heat sink 4 are tightly connected by ultrasonic welding. The front end of the thermal insulation base 2 covers the circumference of the circular foil 1 and fixes the circular foil 1 by physical compression. The thermal insulation base is made of quartz material.

[0045] The heat sink 4 has a central cavity 5 in the center thereof, which is connected to the bell mouth. A No. 1 copper wire 6a connected to the circular foil 1 and a temperature measuring thermocouple 7 are arranged in the central cavity 5. A No. 2 copper wire 6b is connected to the rear end of the heat sink 4. The No. 1 copper wire 6a, the No. 2 copper wire 6b, and the temperature measuring thermocouple 7 extend out of the protective shell 3 and into the signal line protection tube 9. The No. 1 copper wire 6a and the No. 2 copper wire 6b are connected to the signal processing terminal 11.

[0046] The heat sink 4 is further provided with an annular groove as a cooling water channel, and the continuous pipe 12 is provided with a cooling water inlet pipe 10a and a cooling water outlet pipe 10b communicating with the annular groove; the signal processing end 11 and the temperature measuring thermocouple 7 are electrically connected to the ground control center.

[0047] The heat sink 4 is made of copper, and the central cavity 5 is encapsulated with insulating and shock-resistant materials to ensure the stability of the overall structure and the stability of the No. 1 copper wire 6a, No. 2 copper wire 6b, and the temperature measuring thermocouple 7.

[0048] The protective shell 3 is made of carbon steel and coated with a 4-8mm thick layer of high-temperature resistant, heat-insulating coating. The protective shell 3 includes a connector 8 secured to the coiled tubing 12. The connector 8 secures the main body of the protective shell to the end face facing away from the coiled tubing 12. The signal line protection tube 9 is positioned within the coiled tubing 12 and secured thereto. The connector 8 includes through-holes for the No. 1 and No. 2 copper wires 6a and 6b, as well as for the temperature-measuring thermocouple 7, and pre-reserved holes for the cooling water inlet and outlet pipes 10a and 10b.

[0049] The signal processing end 11 calculates the heat flux density value on the circular foil 1 according to the temperature data measured by the No. 1 copper wire 6a and the No. 2 copper wire 6b, according to the temperature difference between the two and the calibrated heat flux density algorithm, and transmits its data signal to the ground control center.

[0050] Combine Figure 3-Figure 6 The embodiment of the present invention further provides a method for using a backward underground gasification multi-directional heat flow monitoring and control device, specifically:

[0051] Two sets of heat flow meters are used to obtain real-time heat flux and temperature data in the axial and radial directions of the coiled tube 12. The axial and radial temperatures of the coiled tube 12 are defined as T1 and T2, and the heat flux is defined as Q1 and Q2. M = Q1:Q2, and the value of λ is in the range of 1-2.

[0052] The calorific value of gas is determined by performing real-time online analysis of the gas components collected from the gas gathering wells, visualizing the trend of the calorific value. When the calorific value of the gas drops sharply or reaches a critical value, it is considered that ash deposition has caused a decline in gas quality, and the gasification cycle is considered complete, and the gas injection point is withdrawn.

[0053] The temperature criterion is that a decrease in the reaction zone temperature will lead to unstable synthesis gas production and low output quality. Therefore, when the measured temperatures T1 and T2 are both lower than the theoretically derived critical value T0, the gasification parameters are adjusted to increase the reaction zone temperature, or the gasification cycle is considered to be over and the gas injection point is withdrawn.

[0054] The first heat flow criterion is to visualize the real-time monitored Q1 and Q2 data to form a trend chart, reflecting the expansion of the front and upper combustion zones. To ensure the controllability of the combustion zone, the gasification parameters are adjusted in a timely manner to keep Q1 and Q2 within the theoretical range.

[0055] The second heat flow criterion is: in the initial stage of gasification, the coal seam above the coiled tube burner 14 begins to heat up and burn. With continued gas injection, the coal seam combustion zone mainly expands above and behind the gas injection point, and slightly expands forward. According to the two sets of heat flow meters, the radial heat flux Q2 gradually increases, while the axial heat flux Q1 slows down. Therefore, the ratio M of Q1 and Q2 is used to determine the expansion of the combustion zone. The specific criterion is as follows:

[0056] (5) When M>1, it indicates that the combustion zone has not yet expanded significantly, and combustion and gasification still occur on the surface of the coal seam above the gas injection point. This stage is considered to be in the initial stage.

[0057] (6) When λ>M>1, it means that the fuel-gap area has partially expanded upward, but the fuel-gap area has not yet developed backward to cover the radial heat flux meter. This stage is considered to be in the development stage.

[0058] When M>λ, it indicates that the combustion void zone has expanded significantly upward and backward, and the front end of the coiled tubing 12 is covered by the combustion void zone. To prevent the combustion and gasification reactions on the wall of the combustion void zone from damaging the gas injection ignition device, and to prevent the combustion void zone from expanding upward and exposing the roof surrounding rock, which would reduce the gas production quality, a gasification cycle is considered to have ended, and the gas injection point is withdrawn.

[0059] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A multi-directional heat flow monitoring and control device for a backward underground gasification system, characterized by: The invention comprises a continuous tube (12) provided with an inner tube (13), wherein a combustion head (14) communicating with the inner tube (13) is provided at the front end of the continuous tube (12), and two heat flow meters are provided on the end face and side wall of the front end; The heat flow meter comprises a protective shell (3) fixed on a continuous tube (12), a heat sink (4) coaxially arranged therewith is provided in the protective shell (3), and a heat insulating base (2) for supporting and fixing the heat sink (4) is provided at both the front and rear ends of the protective shell (3); The front center of the heat sink (4) is provided with a bell mouth and a circular foil (1) is pressed and fixed by the heat insulation base (2) on the same side, and the front end of the protective shell (3) is provided with an opening adapted to the circular foil (1); The heat sink (4) has a central cavity (5) in the center thereof connected to the bell mouth, and a No. 1 copper wire (6a) connected to the circular foil (1) and a temperature measuring thermocouple (7) are arranged in the central cavity (5); a No. 2 copper wire (6b) is connected to the rear end of the heat sink (4); the No. 1 copper wire (6a), the No. 2 copper wire (6b), and the temperature measuring thermocouple (7) extend out of the protective shell (3) and into the signal line protection tube (9), wherein the No. 1 copper wire (6a) and the No. 2 copper wire (6b) are connected to the signal processing end (11); The heat sink (4) is further provided with an annular hollow groove as a cooling water channel, and the continuous pipe (12) is provided with a cooling water inlet pipe (10a) and a cooling water outlet pipe (10b) communicating with the annular hollow groove; the signal processing end (11) and the temperature measuring thermocouple (7) are electrically connected to a ground control center.

2. The device for monitoring and controlling multi-directional heat flow in a backward underground gasification system according to claim 1, characterized in that: The surface of the circular foil (1) is blackened by 2 mm and is made of constantan.

3. The device for monitoring and controlling multi-directional heat flow in a backward underground gasification system according to claim 1, characterized in that: The heat insulating base (2) and the heat sink (4) are tightly connected by ultrasonic welding. The front end of the heat insulating base (2) covers the circumference of the circular foil (1) and fixes the circular foil (1) by physical compression. The heat insulating base is made of quartz material.

4. The device for monitoring and controlling multi-directional heat flow in a backward underground gasification system according to claim 1, characterized in that: The heat sink (4) is made of copper, and the central cavity (5) is encapsulated with insulating and anti-vibration materials to ensure the stability of the overall structure and the stability of the No. 1 copper wire (6a), the No. 2 copper wire (6b), and the temperature measuring thermocouple (7).

5. The device for monitoring and controlling multi-directional heat flow in a backward underground gasification system according to claim 1, characterized in that: The material of the protective shell (3) is carbon steel, and the surface is coated with 4-8mm high temperature resistant heat insulation coating.

6. The device for monitoring and controlling multi-directional heat flow in a backward underground gasification system according to claim 1, characterized in that: The protective shell (3) includes a connecting piece (8) fixed to the continuous tube (12), the connecting piece (8) fixing the protective shell body on the end face away from the continuous tube (12), the signal line protection tube (9) is arranged in the continuous tube (12) and fixed thereto, and the connecting piece (8) is provided with a through hole for passing through a No. 1 copper wire (6a), a No. 2 copper wire (6b), and a temperature measuring thermocouple (7), and a reserved hole for passing through a cooling water inlet pipe (10a) and a cooling water outlet pipe (10b).

7. The backward underground gasification multi-directional heat flow monitoring and control device according to claim 1 is characterized in that: The signal processing end (11) calculates the heat flux density value on the circular foil (1) based on the temperature data measured by the No. 1 copper wire (6a) and the No. 2 copper wire (6b), the temperature difference between the two, and a calibrated heat flux density algorithm, and transmits the data signal to the ground control center.

8. A method for using the backward underground gasification multi-directional heat flow monitoring and control device according to claim 1, characterized in that: Specifically: Two sets of heat flux meters are used to obtain the heat flux density and temperature data in the axial and radial directions of the coiled tube (12) in real time, and the axial and radial temperatures of the coiled tube (12) are defined as T1 and T2, the heat flux density as Q1 and Q2, M=Q1:Q2, and the value range of λ is 1-2; The calorific value of gas is determined by performing real-time online analysis of the gas components collected from the gas gathering wells, visualizing the trend of the calorific value. When the calorific value of the gas drops sharply or reaches a critical value, it is considered that ash deposition has caused a decline in gas quality, and the gasification cycle is considered complete, and the gas injection point is withdrawn. The temperature criterion is that a decrease in the reaction zone temperature will lead to unstable synthesis gas production and low output quality. Therefore, when the measured temperatures T1 and T2 are both lower than the theoretically derived critical value T0, the gasification parameters are adjusted to increase the reaction zone temperature, or the gasification cycle is considered to be over and the gas injection point is withdrawn. The first heat flow criterion is to visualize the real-time monitored Q1 and Q2 data to form a trend chart, reflecting the expansion of the front and upper combustion zones. To ensure the controllability of the combustion zone, the gasification parameters are adjusted in a timely manner to keep Q1 and Q2 within the theoretical range. The second heat flow criterion is: in the early stage of gasification, the coal seam above the continuous tube burner (14) begins to heat up and burn. With the continuous gas injection, the coal seam combustion zone mainly expands above and behind the gas injection point, and slightly expands forward. According to the two sets of heat flow meters arranged, the radial heat flux Q2 gradually increases, while the axial heat flux Q1 slows down. Therefore, the ratio M of Q1 and Q2 is used to judge the expansion of the combustion zone. The specific criterion is as follows: (1) When M>1, it indicates that the combustion zone has not yet expanded significantly, and combustion and gasification still occur on the surface of the coal seam above the gas injection point. This stage is considered to be in the initial stage. (2) When λ>M>1, it means that the fuel-gap zone has partially expanded upward, but has not yet developed backward to cover the radial heat flux meter. This stage is considered to be in the development stage. When M>λ, it indicates that the combustion void zone has greatly expanded upward and backward, and the front end of the coiled tube (12) has been covered by the combustion void zone. In order to avoid the combustion and gasification reaction of the combustion void zone wall surface causing damage to the gas injection ignition device, and to avoid the combustion void zone expanding upward to expose the roof surrounding rock and reduce the gas production quality, it is considered that a gasification cycle is completed and the gas injection point is withdrawn.

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