Gas injection end structure of gas injection pipe for underground coal gasification

Abstract

The invention belongs to the technical field of energy equipment, and discloses a gas injection end structure of a gas injection pipe for underground coal gasification, the gas injection end structure comprises a gasifying agent injection header pipe and at least two gasifying agent injection branch pipes movably connected with the gasifying agent injection header pipe, the tail end distance of the gasifying agent injection branch pipes is variable, and the multiple injection branch pipes are elastically connected through elastic components. And the tail ends of all the injection branch pipes are restrained together by detachable restraining pieces. The gas injection end can enter an underground coal bed gasification area through a narrow drill hole and a gasification channel along with the continuous pipe, the restraining piece is removed under the external effect, the tail ends of the multiple injection branch pipes are unfolded, and a gasification agent is dispersed to the gasification area. The end structure of the injection pipe is improved, so that the injected gasifying agent can be more dispersed, can be in contact with the gasified coal surface as soon as possible and covers a larger coal bed gasification surface, and then the coal gasification amount of a single drilling well is increased.

Description

Technical Field

[0001] This application belongs to, but is not limited to, the field of energy equipment technology, and particularly relates to the gas injection end structure of a gas injection pipe for underground coal gasification. Background Technology

[0002] Underground coal gasification, especially shaftless underground coal gasification, involves injecting a gasifying agent into an underground coal seam through a borehole, causing a combustion and gasification reaction. The resulting coal gas is then transported to the surface through the borehole for collection and utilization. The diameter of the smallest section of the borehole determines the maximum diameter of the equipment entering the coal seam, particularly in continuous tube reverse injection gasification (CRIP), which in turn affects the amount of gasifying agent injected, the amount of coal gasified per borehole, and the coal gas production. Typically, the diameter of the smallest section of the borehole does not exceed 200 mm.

[0003] In continuous tube retraction gasification technology, the diameter of the injection pipe is smaller than the diameter of the finest borehole section. Typically, the injection pipe has only one gasifying agent outlet at its front end, or the front end is designed as a perforated tube structure to disperse the gasifying agent. Compared to an injection pipe with only one gasifying agent outlet, an injection pipe with a perforated tube structure at the front end can improve the dispersion of the gasifying agent, thereby increasing the coal gasification rate per borehole. However, the increase is relatively low because as the coal seam near the gasification channel near the injection pipe front end gasifies, the combustion air zone gradually expands. The injection pipe front end moves further away from the coal seam, and the dispersed gasifying agent diffuses laterally while also flowing rapidly axially towards the outlet channel. Moving the injection pipe front end once eventually forms an oval or pear-shaped gasification zone (also called a combustion air zone). Moving the injection pipe front end periodically creates a series of gasification zones. The radial expansion width of the gasification zone depends on various factors such as gasification pressure, temperature, and gasifying agent composition. The most crucial factor is whether the gasifying agent can quickly reach the radial coal surface of the gasification channel and react with it. Summary of the Invention

[0004] To address the problems existing in the prior art, this application provides a gas injection end structure for a gas injection pipe used in underground coal gasification.

[0005] This application is implemented as follows: a gas injection end structure for a gas injection pipe used in underground coal gasification, the structure comprising:

[0006] The system includes a gasifying agent injection main pipe and at least two variable-distance gasifying agent injection branch pipes movably connected to the main pipe. Each branch pipe has a movable end connected to the main pipe and a terminal end connected to it. The movable ends of the two branch pipes are connected by an elastic component, located on the side of the branch pipe closest to the main pipe wall. The side of each branch pipe's movable end corresponding to the elastic component connection is hinged to the main pipe. The terminals of each branch pipe are restrained together by releasable constraints. This injection end, along with the continuous pipe, can enter the underground coal seam gasification zone through narrow boreholes and gasification channels. Under external pressure, the constraints are released, and the terminals of each branch pipe move away from each other (i.e., expand), dispersing the gasifying agent into the gasification zone. This allows the gasifying agent to contact the coal surface as quickly as possible, covering a larger coal seam cross-section and thus gasifying a greater amount of coal.

[0007] Furthermore, one end of the injection manifold is provided with two ear-shaped structures that are parallel to each other and parallel to the wall of the injection manifold. Each injection branch pipe has two ear-shaped structures at its movable end. One ear-shaped structure is used for hinged connection with the injection manifold, called the hinge ear, and its ear surface is perpendicular to the central axis of the injection branch pipe. The other ear-shaped structure is used for elastic connection, called the spring-loaded ear, and its ear surface is an extension cut from the wall of the injection branch pipe. Each injection branch pipe is connected to the ear-shaped structures of the injection manifold via the hinge structure. The spring-loaded ears of two injection branch pipes are connected by an elastic component to adjust the distance between the ends of the injection branch pipes. Preferably, when there are an even number of injection tubes, the spring-loaded lugs of two symmetrically distributed injection tubes are connected by an elastic component; when there are an odd number of injection tubes, one of them is selected, and the remaining ones are symmetrically and elastically connected according to the even number of tubes. Then, the selected tube is elastically connected to one of the injection tubes that is nearly symmetrically distributed (e.g., injection tube A). (At this time, the spring-loaded lug of injection tube A is connected to the spring-loaded lugs of the other two injection tubes) so as to achieve maximum distance between the ends of different injection tubes.

[0008] Furthermore, the ends of the injection sub-pipes are equipped with constraint members to bind the ends of each injection sub-pipe together, reducing the occupied space volume, so that it can be sent into the underground gasification zone through narrow boreholes. At this time, the elastic components connecting the injection sub-pipes are in a tensioned or stretched state. After reaching the gasification zone, the constraint can be released under external forces (e.g., gasifying agent pressure, temperature, mechanical force, etc.), the elastic components contract, and the injection sub-pipes rotate around the hinge structure as an axis, realizing the unfolded state of the ends of different injection sub-pipes.

[0009] Furthermore, the restraint can be a rope that can melt at a certain temperature, or multiple connected plugs (which can be ejected from the injection pipe under a certain pressure, or the perforated plug can be vaporized as the temperature rises), or a casing that can be decomposed as the underground coal seam is gasified, such as a PVC casing.

[0010] Furthermore, the injection pipes can be multiple, each with a cross-section approximately fan-shaped, with a sector angle of 360 / n degrees (where n is the number of injection pipes). This maximizes space utilization. Preferably, there are two injection pipes. In this case, the cross-section of the injection pipe is approximately semi-circular, the structure is relatively simple, and it is easy to fix. More importantly, when dispersing the gasifying agent into the combustion zone of underground coal gasification, it is optimal to distribute the gas to the lower part of the coal seam at the edge of the combustion zone, thus gasifying more coal.

[0011] Furthermore, after the end of the injection branch tube is extended, the central axis of the injection main tube and the injection branch tube forms a certain angle α (0°<α≤60°), preferably 30°~45°.

[0012] Furthermore, the equivalent diameter (outer diameter) of the multiple injection branch pipes is less than or equal to the equivalent outer diameter of the injection main pipe, and the length of the injection branch pipes is greater than or equal to 3 times the equivalent outer diameter of the injection main pipe, preferably 5 to 10 times. This allows for uniform dispersion of the gasifying agent, good continuity of the combustion air zone, and also takes into account the connection strength between the main pipe and the branch pipes and the driving ability of the elastic components on the injection branch pipes.

[0013] Furthermore, the injection manifold is provided with multiple gas distribution holes along its length, which makes the gasifying agent dispersed in the injection manifold more dispersed and react with the coal seam as soon as possible.

[0014] Furthermore, the connection between the main injection pipe and the branch injection pipe can be equipped with a seal to reduce the leakage of gasifying agent from the gap between them, allowing more gasifying agent to flow along the branch injection pipe and be distributed to the coal seam at the edge of the combustion zone; the seal is preferably made of pressure-resistant and high-temperature resistant flexible rubber material. For example, when there are two branch injection pipes, the seal is a Y-shaped rubber tube, with the main pipe of the rubber tube (i.e., the lower part of the Y) fixed inside the main injection pipe, and the branch pipes of the rubber tube (i.e., the upper part of the Y) fixed in the two branch injection pipes respectively.

[0015] Based on the above technical solutions and the technical problems they solve, the advantages and positive effects of the technical solution to be protected in this application are as follows:

[0016] First, in order to facilitate the rapid arrival of the gasifying agent at the radial coal surface of the gasification channel and its reaction, this application improves the end structure of the injection pipe so that the injected gasifying agent can be more dispersed, contact the gasified coal surface as soon as possible, cover a larger coal seam gasification surface, and thus increase the amount of coal gasified in a single well.

[0017] The equivalent diameter (outer diameter) of the multiple injection sub-pipes is less than or equal to the equivalent outer diameter of the injection main pipe, and the length of the injection sub-pipes is greater than or equal to 3 times the equivalent outer diameter of the injection main pipe, preferably 5 to 10 times. Theoretically, the longer the length of the injection sub-pipes, the more the gasifying agent can be dispersed to a position further away from the gasification channel after the ends of each injection sub-pipes are extended, which is beneficial to the expansion of the width of the gasification zone (or combustion air zone). However, it is necessary to consider the distribution of gasifying agent along the direction of the injection branch pipe. An excessively long injection branch pipe will cause the gasifying agent to be concentrated near the end of the injection branch pipe, while there will be less gasifying agent at the connection between the injection branch pipe and the injection main pipe, thus forming multiple gasification zones or combustion zones with little overlap, resulting in coal leakage and resource waste. Alternatively, if the injection branch pipe has gas distribution holes along its length, an excessively long injection branch pipe will cause the gasifying agent to be dispersed from the gas distribution holes before reaching the end of the injection branch pipe, and the part of the injection branch pipe near the end will not play a gas distribution role. At the same time, considering the connection strength between the injection branch pipe and the injection main pipe, as well as the driving ability of the elastic components between different injection branch pipes on the injection branch pipe, the length of the injection branch pipe should be greater than or equal to 3 times the equivalent outer diameter of the injection main pipe, preferably 5 to 10 times.

[0018] Secondly, based on pilot-scale experimental data, under identical conditions, the cross-sectional area of ​​the combustion zone in simulated underground coal seam gasification is more than twice that of the injection end with an injection branch pipe and the injection end without an injection branch pipe. In real underground coal seam gasification, with all other process parameters being the same, it is conservatively estimated that the cross-sectional area of ​​the combustion zone obtained by the injection end with an injection branch pipe can reach 1.5 times that of the injection end without an injection branch pipe. Therefore, it is estimated that the amount of coal gasified can reach 1.5 times that of the injection end. The construction cost of the gasification channel within the coal seam alone (the cost of drilling coal seams in wellless underground gasification projects is 4,000-6,000 yuan / meter, and coal seam drilling is usually 100m-200m) can be reduced by more than 33%. There are also labor costs and time costs that can be saved but are difficult to estimate.

[0019] The technical solution of this application, by simply matching appropriate injection pipes, can expand the expected width of the gasification combustion zone laterally through the narrow coal seam gasification channel. Prior to this solution, the width of the lateral expansion of the combustion zone was uncontrollable; it could only be appropriately influenced by increasing the pressure and flow rate of the injected gasifying agent, making it difficult to achieve the desired result. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the gas injection end structure provided in an embodiment of this application;

[0021] Figure 2 This is a schematic diagram of the end of the injection manifold provided in an embodiment of this application;

[0022] Figure 3 This is a schematic diagram of the injection manifold end provided in an embodiment of this application;

[0023] Figure 4 This is a schematic diagram of the connection of the injection manifold provided in an embodiment of this application;

[0024] Figure 5 This is a schematic cross-sectional view of the combustion zone of the prior art provided in the embodiments of this application;

[0025] Figure 6 This is a schematic diagram of the cross-section of the combustion zone provided in an embodiment of this application;

[0026] Figure 7 This is a schematic diagram of a conventional underground gasification combustion zone provided in an embodiment of this application;

[0027] Figure 8 This is a schematic diagram of the underground gasification combustion zone provided in an embodiment of this application;

[0028] Figure 9 This is a schematic diagram of a cross-section of a conventional underground gasification combustion zone provided in an embodiment of this application;

[0029] Figure 10 This is a schematic cross-sectional view of the underground gasification combustion zone provided in an embodiment of this application;

[0030] Figure 11 This is a 19cm*21cm cross-sectional view of the underground gasification combustion zone of a conventional injection pipe provided in an embodiment of this application;

[0031] Figure 12 This is a 40cm*22cm cross-sectional view of the underground gasification combustion zone provided in an embodiment of this application;

[0032] Figure 13 This is a schematic diagram showing the connection between the injection main pipe, injection branch pipes, and sealing element provided in the embodiments of this application;

[0033] Figure 14 This is a cross-sectional schematic diagram of the connection between the injection manifold and the sealing manifold provided in the embodiments of this application;

[0034] In the diagram: 1. Injection main pipe; 2. Injection branch pipe; 3. Hinge; 4. Ear-shaped structure; 5. Elastic component; 6. Seal main pipe; 7. Seal branch pipe; 8. Sleeve pipe; 9. Tensioning ring. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0036] In underground coal gasification projects, existing gas injection pipe structures generally face problems such as limited space, uneven gas distribution, and insufficient coal seam coverage. These problems directly lead to the gasifying agent failing to quickly contact the coal surface, resulting in low gasification reaction efficiency and insufficient coal conversion rate. Especially when the pipeline is sent into the underground combustion zone through narrow boreholes or gasification channels, the traditional rigid pipeline ends lack variable structures, often only achieving localized gas distribution and failing to meet the requirement of large-scale coal seam coverage. Therefore, how to expand the gas injection end and uniformly distribute the gasifying agent within a confined space is a key problem that the industry has long needed to solve.

[0037] The "gas injection end structure" proposed in this application provides a systematic solution to this technical dilemma. By setting a combination of hinges 3 and elastic components 5 between the main injection pipe 1 and multiple injection branch pipes 2, the ends of the injection branch pipes 2 can automatically unfold around the hinges after the constraints are released, exhibiting a scissor-like unfolding effect. The presence of the elastic components 5 allows the ends of each injection branch pipe 2 to open rapidly when the force is released, forming a larger gas distribution range. This structure avoids the fixed shape of rigid pipes and achieves the dual functions of transportation and unfolding under limited drilling conditions.

[0038] In terms of working mechanism, the restraints are responsible for volume compression during transportation and can take the form of fused ropes, integrated plugs, etc. When the injection end reaches the target gasification zone, external temperature, pressure, or the gasifying agent itself can trigger the release of the restraints, causing the elastic components to contract and move the ends of each injection pipe away from each other, achieving the deployment effect. This process requires no additional complex mechanical operations and can be achieved solely based on the coal seam environmental conditions, demonstrating the advantages of structural self-adaptation and coal seam coupling.

[0039] After the end-capsule is extended, each injection branch pipe 2 forms a certain angle with the main pipe according to the design angle (the angle is greater than 0 degrees and less than or equal to 60 degrees, preferably 30 degrees to 45 degrees), which can effectively disperse the gasifying agent to the edge of the combustion zone and the lower coal seam. Compared with the direct-flow gas distribution, this application is beneficial to improving the overall coal gasification rate. This directional gas distribution mode not only improves the utilization rate of the combustion zone, but also reduces coal residue and increases gas production.

[0040] In addition, the injection branch pipe 2 is equipped with gas distribution holes along its length, and pressure-resistant and high-temperature-resistant rubber seals (such as Y-type rubber tubes) are used to seal the joint between the main injection pipe and the injection branch pipe, further ensuring the efficient transfer and dispersion of the gasifying agent. The sealing structure significantly reduces gap leakage, allowing more gasifying agent to enter the injection branch pipe and ultimately act on the coal seam, improving energy efficiency and coal utilization.

[0041] The significance of this gas injection end structure in industrial applications lies in its ability to address the engineering feasibility of entering through narrow channels while simultaneously achieving efficient and wide-coverage gas distribution within the coal seam combustion zone. Its working principle embodies a four-step cyclic mechanism of "constraint-release-expansion-uniform distribution," relying on the mechanical cooperation between elastic components and hinges to demonstrate high reliability and ease of operation even under extreme underground conditions. This innovative design significantly enhances the efficiency and large-scale application potential of underground coal gasification processes.

[0042] This application provides an injection end structure for an injection pipe used in underground coal gasification. The structure includes: a gasifying agent injection main pipe 1, and at least two gasifying agent injection branch pipes 2 with variable end spacing, movably connected to the gasifying agent injection main pipe. One end of each injection branch pipe 2 connected to the injection main pipe 1 is a movable end, and the other end is a terminal end. The movable ends of the two injection branch pipes 2 are connected by an elastic member 5, the connection point of which is on the side of the injection branch pipe 2 closest to the wall of the injection main pipe 1. The side of each injection branch pipe 2 corresponding to the connection point of the elastic member 5 is connected to the injection main pipe 1 by a hinge 3. The ends of the multiple injection branch pipes 2 are constrained together by a releasable constraint member. This injection end, along with the continuous pipe, can enter the underground coal seam gasification zone through narrow boreholes and gasification channels. Under external action, the constraint member is released, and the ends of the multiple injection branch pipes 2 move away from each other, dispersing the gasifying agent into the gasification zone, quickly contacting the gasified coal surface, allowing the gasifying agent to cover a larger coal seam cross-section, thereby gasifying a greater amount of coal.

[0043] like Figure 2 As shown, one end of the injection main pipe 1 is provided with two ear-shaped structures 4 that are parallel to each other and parallel to the pipe wall of the injection main pipe 1. The movable end of the injection branch pipe 2 is provided with two ear-shaped structures 4. One ear-shaped structure 4 can be used for hinge, called the hinge ear, and the ear surface of the hinge ear is perpendicular to the central axis of the injection branch pipe 2. The other ear-shaped structure is used for elastic connection, called the spring connecting ear, and the ear surface of the spring connecting ear is cut from the extension of the pipe wall of the injection branch pipe 2. Each injection branch pipe 2 is hinged to the ear-shaped structure of the injection main pipe through the hinge structure. The spring connecting ears of the injection branch pipe 2 are connected by an elastic component 5, and the distance between the ends of the injection branch pipe 2 can be adjusted by the extension and retraction of the elastic component 5.

[0044] like Figure 3 As shown, there can be multiple injection pipes 2, each with a cross-section approximately fan-shaped, with a sector angle of 360 / n degrees (where n is the number of injection pipes 2). This maximizes space utilization. Preferably, there are two injection pipes 2, with a cross-section approximately semi-circular. This structure is relatively simple and easy to fix. More importantly, when dispersing the gasifying agent into the combustion chamber of underground coal gasification, it is best to distribute the gas to the lower part of the edge of the combustion chamber, thus gasifying more coal.

[0045] After the ends of each injection branch pipe 2 are extended, the central axis of the injection main pipe 1 and the injection branch pipe 2 form a certain angle α (0°<α≤60°), preferably 30°~45°. Within this angle range, the coal gasification effect is optimal.

[0046] The injection pipe 2 has air distribution holes along its length to increase the dispersion efficiency of the gasifying agent.

[0047] A seal can be installed at the connection between the main injection pipe 1 and the branch injection pipe 2 to reduce the leakage of gasifying agent from the gap between them, so that more gasifying agent can flow along the branch injection pipe and be distributed to the coal seam at the edge of the combustion zone. The seal is preferably made of pressure-resistant and high-temperature resistant flexible rubber material, such as Y-type rubber pipe. The main pipe of the rubber pipe is fixed inside the main injection pipe 1, and the branch pipes of the rubber pipe are respectively fixed in the branch injection pipe 2.

[0048] A constraint member is installed at the end of injection manifold 2 to bind the ends of multiple injection manifold 2 together, reducing the occupied space volume, so that it can be sent into the underground gasification zone through narrow boreholes. At this time, the elastic component connecting the injection manifold is in a tensioned or stretched state. After reaching the gasification zone, the constraint can be released under external forces, such as gasifying agent pressure, temperature, mechanical force, etc., the elastic component contracts, and the injection manifold 2 rotates around the hinge structure, realizing the unfolding of the ends of different injection manifold 2.

[0049] The restraint can be a rope that can melt at a certain temperature, or multiple connected plugs that can be ejected from the injection pipe 2 under a certain pressure, or a perforated plug that is vaporized as the temperature rises.

[0050] The method (steps) for using this application are as follows:

[0051] 1. Connect the main injection pipe 1 and the branch injection pipes 2 of the gas injection end described in this application. Different branch injection pipes 2 are connected together by elastic components, and each branch injection pipe 2 is connected to the main injection pipe by a hinge structure.

[0052] 2. Connect one end of the injection main pipe 1 to the continuous pipe for conveying the gasifying agent.

[0053] 3. All the ends of the injection pipes 2 are constrained together by the constraint members. At this time, the elastic component is in a tensioned (stretched) state.

[0054] 4. The gas injection end follows the continuous pipe through the narrow borehole and coal seam gasification channel, and is sent to the predetermined location of the underground coal seam to be gasified.

[0055] 5. After ignition, the gasifying agent and coal undergo a combustion-gasification reaction. The restraint is released under high temperature and high pressure. The elastic component 5 contracts, causing each injection pipe 2 to rotate around the hinge structure. The ends of each injection pipe 2 are slightly expanded.

[0056] 6. As coal seam gasification proceeds, the gasification channel where the gas injection end is located gradually widens, and the end of injection branch pipe 2 is fully expanded, dispersing the gasifying agent towards the edge of the gasification zone to achieve the best effect.

[0057] 7. After gasification for a period of time, the continuous pipe is withdrawn. Due to the narrowing of the gasification channel, the channel walls force the ends of each injection branch pipe 2 to move closer to each other (i.e., injection branch pipe 2 is retracted), and the elastic component is once again in a tensioned (stretched) state. In this way, one deployment and retraction of injection branch pipe 2 is completed. After reaching the new position, injection branch pipe 2 continues to inject gasifying agent to gasify the coal seam.

[0058] 8. As coal seam gasification proceeds, the gasification channel where the gas injection end is located gradually widens, and multiple injection pipes 2 can gradually expand to disperse the gasifying agent to the edge of the gasification zone.

[0059] Repeat steps 6-8 above until the expected underground coal seam is completely gasified.

[0060] Example 1

[0061] like Figures 1-4 As shown, a gas injection end structure for an underground coal gasification gasification pipe includes a main injection pipe 1, with two ear-shaped structures 4 extending along the pipe wall at its end. Two branch injection pipes 2 each have two ear-shaped structures 4 at their movable ends. One ear-shaped structure is connected to the ear-shaped structure of the main injection pipe via a hinge 3, and the other ear-shaped structure is connected to the adjacent branch injection pipe via an elastic component 5. During transportation, the ends of the two branch injection pipes 2 are fixed together by restraints to maintain a folded state.

[0062] like Figure 4 As shown in the attached figure, during use, the injection end enters the coal seam gasification zone along with the continuous pipe. Under high temperature or pressure, the restraints are released, and the elastic components contract, causing each injection branch pipe 2 to unfold around the hinge 3. After the ends of each injection branch pipe 2 unfold, the gasifying agent is injected into the combustion air zone through each injection branch pipe 2, thereby expanding the gas distribution range and achieving rapid coverage of the coal seam cross-section. The combustion air zone morphology obtained by underground coal seam gasification using the injection end structure designed in this application is shown in the attached figure. Figure 6 , Figure 8 , Figure 10 ) and conventional gas injection end structure ( Figure 5 , Figure 7 , Figure 9 Compared to the previous method, the width of the combustion zone and the degree of gasification of the underlying coal seam are significantly increased.

[0063] Example 2

[0064] An injection pipe for underground coal gasification has two injection branch pipes 2 with approximately semi-circular cross-sections below its main injection pipe 1. The two injection branch pipes are kept parallel and converging under the action of a restraining element, allowing them to enter the combustion zone of the coal seam through a narrow borehole. Upon reaching the target location, the restraining element is released under external force, and the ends of the injection branch pipes 2 unfold under the action of an elastic component, forming a fan-shaped distribution.

[0065] After each injection pipe 2 is deployed, the injection direction corresponds to the lower edge of the combustion zone, allowing the gasifying agent to flow directly to the lower edge of the coal seam, preferentially gasifying the bottom coal, such as... Figure 8 As shown, in underground coal gasification using conventional gas injection structures, the coal in the lower areas is difficult to contact the gasifying agent, which can easily lead to coal loss and under-mining, resulting in resource waste. This design improves the overall coal gasification efficiency and increases the coal seam utilization rate.

[0066] Example 3

[0067] In another embodiment, after the injection branch pipe 2 is deployed, it forms an angle with the axis of the injection main pipe 1. The angle is controlled within the range of 30 to 45 degrees to ensure that the injection branch pipe 2 can disperse the vaporizing agent after deployment without causing mutual interference between the branch pipes. The range of the angle can be controlled by selecting elastic components of different specifications. For example, if a spring is selected as the elastic component, the angle after the injection branch pipe is deployed can be controlled by selecting springs of different lengths. The longer the spring is stretched, the larger the angle after the injection branch pipe 2 is deployed (i.e., after the spring is contracted), and vice versa.

[0068] In actual operation, after the two injection pipes 2 are deployed, they inject gasifying agent in different directions, covering a larger area of ​​the coal seam cross-section in the combustion zone. Compared with the traditional straight gas distribution, this angled gas distribution method can reduce dead zones and improve coal mining efficiency and gas production.

[0069] Example 4

[0070] Multiple air distribution holes are evenly distributed along the length of injection branch pipe 2. The diameter of the air distribution holes is controlled within a reasonable range to ensure that the vaporizing agent can be evenly discharged during the delivery process of injection branch pipe 2. The distribution of air distribution holes gradually increases from near the end of injection main pipe 1 to the end of injection branch pipe 2, forming a gradient arrangement.

[0071] During the gasification process, the gasifying agent is not only injected from the end of injection pipe 2, but also released step by step along the gas distribution holes, creating a multi-point gas distribution pattern in the coal seam combustion zone. This method increases the contact area between the gasifying agent and the coal surface, improves the coal reaction rate, and reduces the risk of uneven local temperature.

[0072] Example 5

[0073] like Figure 13 , Figure 14 As shown, a high-temperature and high-pressure resistant flexible rubber seal is installed at the connection between the injection main pipe 1 and the injection branch pipes 2. The flexible rubber seal includes a main sealing pipe 6 and multiple branch sealing pipes 7 at one end of the main pipe and connected to it. Multiple holes or inwardly extending sleeves are provided on the main sealing pipe 6 near the connection of the branch sealing pipes 7, allowing the elastic components 5 of the injection branch pipes 2 to pass through and enter the interior of the main sealing pipe 6. During connection, the main sealing pipe 6 is placed inside the injection main pipe 1, and the branch sealing pipes 7 are respectively placed in the multiple injection branch pipes 2.

[0074] The elastic component 5 of the injection branch pipe 2 passes through a small hole or sleeve 8 on the sealing main pipe 6 and enters the interior of the sealing main pipe 6, where it is then connected by the elastic component 5. The small hole or sleeve 8 on the sealing main pipe 6 and the elastic component 5 of the injection branch pipe 2 can be tightly fitted together or made tightly fitted together by fasteners. For example, a tensioning ring 9 is provided in the sealing branch pipe 7 and the sealing main pipe 6 so that the pipe wall of the sealing element is tightly fitted to the pipe wall of the injection pipe.

[0075] This seal can withstand the high temperature and high pressure environment of the coal seam while maintaining good sealing performance. Any suitable material can be selected for the seal, and its shape can be adjusted according to the number of injection manifolds.

[0076] During operation, as the gasifying agent flows from injection main pipe 1 to injection branch pipe 2, the seals effectively prevent leakage at the joint, allowing more gasifying agent to enter injection branch pipe 2 and flow into the coal seam combustion zone. By reducing leakage, the utilization efficiency of the gasifying agent is improved, and the overall uniformity of coal seam gasification is enhanced.

[0077] Example 6

[0078] In one specific application, a high-temperature fusible rope is used as a restraint at the end of the injection pipe 2 to tightly bind the ends of the two injection pipes 2. After the gas injection end enters the coal seam gasification zone, the high-temperature environment of the coal seam causes the rope to automatically melt and break. The injection pipe 2 then rapidly unfolds under the action of the elastic component, forming a gas distribution structure.

[0079] In another approach, the constraint component is a single plug embedded in the two injection ports. Under the pressure of the gasifying agent, the single plug is pushed out and discharged with the gas flow, or the perforated plug is gradually gasified and decomposed in the high-temperature environment of the coal seam. This structure can automatically release the constraint under specific conditions without manual intervention, realizing the automatic deployment of the gas injection end structure.

[0080] In another approach, the restraints utilize fusible sleeves, such as PVB sleeves. These sleeves can be a single sleeve or multiple sleeves connected together. If it's a single sleeve, all ends of injection sub-pipes 2 can be covered by the sleeve. If it's multiple sleeves connected together, the sleeves can be designed according to the number of injection sub-pipes, ensuring that each sleeve covers the end of one injection sub-pipe 2. During later use, the sleeves gradually decompose and gasify under the high-temperature environment of the coal seam, releasing the restraints on the ends of the injection sub-pipes 2.

[0081] Example 7

[0082] In a pilot-scale coal underground gasification furnace, 80cm*80cm*80cm coal blocks were pieced together to form a 80cm*80cm*640cm coal layer. Each coal block had a 2cm diameter hole drilled in its lower part, connecting to form a simulated gasification channel within the coal layer. The area around and above the coal layer was compacted with loess. A conventional gasifying agent injection pipe (15mm inner diameter) was lowered into the gasification channel for gasification. When the total effective component content of the coal gas decreased by 10%, the gasifying agent injection pipe was withdrawn a certain distance (20cm). The total effective component content of the coal gas gradually increased, stabilized for a period, and then began to decrease again. When the decrease reached 10%, the gasifying agent injection pipe was withdrawn a certain distance (20cm) again. This withdrawal was repeated at least 5 times. Nitrogen gas was then injected for fire extinguishing, cooling, and depressurization. The experimental furnace was opened, the loess layer was peeled off, and the width of the conventional underground gasification combustion zone cross-section was measured to be 19cm and the height to be 21cm (e.g., ...). Figure 11 (As shown).

[0083] In the comparative experiment, the gasifying agent injection pipe was replaced with an injection pipe having two injection branches (the main pipe inner diameter was 15 mm, and the length of each of the two injection branches was 5 cm). All other devices, operating parameters, and operating procedures were the same as in the above experiment. The width of the cross-section of the underground gasification combustion zone in this application was obtained to be 40 cm and the height to be 22 cm (e.g., Figure 12 (As shown).

[0084] Figure 11 and Figure 12 The comparison shows the difference in cross-sectional area of ​​the actual underground gasification goaf zone between conventional injection pipes and the gas injection end structure of this application. The cross-sectional area of ​​the goaf zone formed by a conventional injection pipe is approximately 19cm × 21cm, while the cross-sectional area of ​​the goaf zone under the action of the gas injection end structure of this application can reach 40cm × 22cm, with an area approximately 2.2 times that of the underground gasification goaf zone of a conventional injection pipe, significantly expanding the cross-sectional area of ​​the goaf zone. This result indicates that this application can achieve a longer-distance dispersed supply of gasifying agent within the coal seam, thereby effectively expanding the goaf zone, improving coal resource utilization, and avoiding missed mining and resource waste.

[0085] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in this application, and within the spirit and principles of this application, should be included within the scope of protection of this application.

Claims

1. A gas injection end structure for a gas injection pipe used in underground coal gasification, characterized in that, It includes a vaporizing agent injection main pipe and at least two injection branch pipes movably connected to the end of the injection main pipe; One end of the injection branch pipe is connected to the injection main pipe, which is a movable end, and the other end is a terminal end. The movable ends of the two injection branch pipes are connected by an elastic component. The connection part of the elastic component is on the side of the injection branch pipe close to the wall of the injection main pipe. The side of the movable end of each injection branch pipe corresponding to the connection part of the elastic component is connected to the injection main pipe by a hinge. The ends of the injection pipes are fixed together by a constraint member. After the constraint member is released under external force, the ends of the injection pipes can be separated from each other.

2. The gas injection end structure according to claim 1, characterized in that: The injection manifold has two ear-shaped structures extending along the pipe wall at its end; each injection branch has two ear-shaped structures at its movable end, one of which is used to connect to the injection manifold hinge, and the other is used to connect to the elastic component.

3. The gas injection end structure according to claim 1, characterized in that, The restraint is a component that can be released under certain temperature or pressure conditions. The restraint is a fusible rope, a plug that can be ejected under pressure, or a casing that can be decomposed during coal seam gasification.

4. The gas injection end structure according to claim 1, characterized in that, The cross-section of the injection branch pipe is fan-shaped, and the angle of the fan is equal to 360 degrees divided by the number of branch pipes. When the number of branch pipes is 2, the cross-section of the injection branch pipe is approximately semi-circular.

5. The gas injection end structure according to claim 4, characterized in that, When the ends of the injection branch pipes are separated from each other, the injection branch pipes form an angle with the central axis of the injection main pipe, and the angle is greater than 0 degrees and less than or equal to 60 degrees.

6. The gas injection end structure according to claim 5, characterized in that, The included angle is between 30 and 45 degrees.

7. The gas injection end structure according to claim 1, characterized in that, The length of the injection branch pipe is greater than or equal to three times the equivalent outer diameter of the injection main pipe.

8. The gas injection end structure according to claim 1, characterized in that, The injection pipe has multiple gas distribution holes along its length to expand the coal seam contact area during the dispersion of the gasifying agent.

9. The gas injection end structure according to claim 1, characterized in that, The connection between the main injection pipe and the branch injection pipe is equipped with a seal. The seal is used to reduce the leakage of the gasifying agent in the connection gap, so that more gasifying agent can flow along the branch injection pipe.

10. The gas injection end structure according to claim 9, characterized in that, The sealing element is a pressure-resistant and high-temperature resistant flexible rubber tube structure. The main pipe end of the rubber tube is fixed inside the injection main pipe, and the branch pipe ends are respectively fixed inside each injection sub-pipe.

Images