Ablatable casing pipe for underground coal gasification and manufacturing method of ablatable casing pipe
By designing a ablated casing and using a combined structure of base pipe and lined pipe, the deformation and collapse of the casing of the underground gasification injection well of coal is solved, precise ignition and effective combustion of the coal layer are achieved, useful gases are generated, environmental pollution and carbon emissions are reduced, and underground green coal mining is achieved.
Patent Information
- Application Number
- CN202311547905.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-20
- Publication Date
- 2025-05-30
AI Technical Summary
The casing of the existing underground gasification injection wells of coal has deformation of the casing and crushing the pipe body, which cannot achieve accurate ignition and effective backward control of combustion, resulting in the collapse of the gasification channel and the inability to achieve coal control of combustion, resulting in the scrapping of the underground gasification channel and huge economic losses.
Absorbable casing for underground gasification of coal is designed, including a base pipe and a liner pipe. A multiple screen hole is evenly arranged on the surface of the base pipe, and a blockage is provided in the screen hole. The melting point of the liner pipe and the blockage is smaller than the melting point of the base pipe, and can be ablated at a temperature of 600℃-800℃ to realize the ignition device and the coal layer to ensure the stable operation of the wellbore during coal gasification.
The casing has high anti-extrusion strength, avoids wellbore collapse, realizes effective control of ignition and receding combustion of the coal layer, generates useful gases, reduces environmental pollution and carbon emissions, and achieves green underground coal mining.
Smart Images
Figure CN120061706A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of coal resource mining, and particularly relates to an ablative casing for underground coal gasification and a manufacturing method thereof. Background Art
[0002] Carbon emissions are the main cause of global warming. The traditional coal mining process is to physically mine coal from underground and then burn it on the ground, which is the main source of carbon emissions. China is the world's largest coal producer and consumer. In order to achieve the goal of "carbon peak and carbon neutrality", underground coal gasification is the most ideal mining method. Underground coal gasification is an energy conversion technology that efficiently and cleanly utilizes low-quality coal resources. It is a process of controlling the combustion of coal underground to produce combustible gas through thermal and chemical effects on coal. It is a new multidisciplinary technology for the development of clean energy and chemical raw materials that integrates well construction, coal mining, energy conversion and other processes. This technology is used to extract energetic components from coal, while leaving harmful substances such as ash, gangue, and radioactivity underground to reduce ground environmental pollution and transform traditional physical coal mining into chemical coal mining.
[0003] With the development of underground coal gasification technology, directional drilling technology is currently mainly used to form a "U"-shaped underground coal gasification shaft structure, including injection wells and production wells. The injection well (including vertical well section and horizontal well section) and the horizontal well section in the coal seam are used as coal gasification channels. There are multi-channel continuous pipes in the injection well shaft, and the continuous pipes contain gasifiers, combustion agents, coolants, temperature monitoring, signal transmission and igniters. The continuous pipes can control the movement of the coal seam gas injection point position, thereby controlling the coal gasification zone, strengthening the gasification process, and improving the resource recovery rate. The horizontal section of the injection well is the key connecting channel of this technology, the main channel for the implementation of the controlled retraction injection point (CRIP) gasification technology, and the basic part for the formation of the gasification cavity. At present, the horizontal section casing of the existing injection well has problems such as casing deformation and pipe body crushing, which cannot achieve accurate ignition and effective retreat control combustion, and even cause the collapse of the gasification channel. It is impossible to achieve controlled combustion of coal, and even cause the underground gasification channel to be scrapped, causing huge economic losses. Summary of the invention
[0004] In view of the above problems, the object of the present invention is to provide an ablatable casing for underground coal gasification and a manufacturing method thereof. The ablatable casing has a high collapse resistance strength, can solve the risk of collapse of the injection well during underground coal gasification, ensure the safe, reliable and stable operation of the underground coal gasification channel, and can achieve ablation of the casing between 600°C and 800°C, so that the ignition device is connected to the coal seam, realizing effective control of ignition and backward combustion process of the coal seam underground, and enabling coal to generate H 2 , CH 4 , CO, CO 2 and other useful gases. By extracting gas through the production well, it reduces air pollution, carbon emissions and other environmental pollutions generated by physical coal mining to the ground and then carrying out processes such as coal ground combustion and coal-to-hydrogen production, realizes green underground coal mining, and greatly reduces environmental pollution and carbon emissions.
[0005] The technical solution of the present invention is as follows: An ablatable casing for underground coal gasification, including a base pipe, an inner lining pipe is arranged inside the base pipe, a plurality of screen holes are evenly distributed on the surface of the base pipe, plugs are arranged in the screen holes, and the outer end surface of the plugs is flush with the outer surface of the base pipe. The melting points of the inner lining pipe and the plugs are both lower than the melting point of the base pipe. External threads are respectively arranged at the left and right ends of the base pipe, and a coupling is connected to the outside of the external thread at the left end.
[0006] An adhesive layer is arranged between the base pipe and the inner lining pipe. The adhesive used in the adhesive layer has a temperature resistance range ≥ 950°C and a pressure bearing range ≥ 55 MPa. The melting point range of the inner lining pipe and the plugs is 600°C - 800°C.
[0007] The screen holes are arranged in a spiral line along the surface of the base pipe.
[0008] The screen holes are conical holes or pipe column holes, and the aperture range of the screen holes is 8 mm - 20 mm.
[0009] The chemical element components of the base pipe are by weight percentage: C: 0.15 - 0.35%, Si: 0.20 - 0.80%, Mn: 0.75 - 1.55%, Cr: 0.90 - 18.00%, Mo: 0.20 - 0.50%, Ni: 0.25 - 0.45%, Nb: 0.15 - 0.45%, V: 0.05 - 0.15%, Ti ≤ 0.04%, S ≤ 0.002%, P ≤ 0.008%, and the balance is Fe and inevitable impurities.
[0010] The inner liner tube 6 is an aluminum alloy tube, and its chemical element composition by weight percentage is: Si: 0.40 - 2.50%, Fe: 0.20 - 0.45%, Cu: 0.35 - 0.85%, Mn: 0.25 - 0.65%, Mg: 0.70 - 1.45%, Cr: 0.20 - 0.45%, Zn: 0.25 - 0.8%, Ti ≤ 0.20%, harmful impurities ≤ 0.015%, and the rest is Al.
[0011] A manufacturing method of an ablatable casing for underground coal gasification, manufacturing an ablatable casing for underground coal gasification as described above, includes the following steps: S1: Manufacturing the base tube, the specific process is: S11: Using molten iron with chemical element composition by weight percentage: C: 0.15 - 0.35%, Si: 0.20 - 0.80%, Mn: 0.75 - 1.55%, Cr: 0.90 - 18.00%, Mo: 0.20 - 0.50%, Ni: 0.25 - 0.45%, Nb: 0.15 - 0.45%, V: 0.05 - 0.15%, Ti ≤ 0.04%, S ≤ 0.002%, P ≤ 0.008%, after pretreatment, secondary refining, light desulfurization treatment and calcium treatment, controlling harmful elements, the superheat during continuous casting is less than 28°C. After the continuous casting billet is heated at 1100°C - 1320°C, the corresponding ingot is made, and then it is rolled into the required tube blank by skew rolling piercing. After heat treatment, the tube blank of the required steel grade is made; S12: Processing the sieve holes on the tube blank, using mechanical drilling or laser cutting to process sieve holes on the tube blank. The sieve holes are arranged in a spiral pattern on the tube blank, and the sieve hole diameter is designed to be 8mm - 20mm; S2: Manufacturing the inner liner tube, the specific process is: S21: Using aluminum alloy raw materials with chemical element composition by weight percentage: Si: 0.40 - 2.50%, Fe: 0.20 - 0.45%, Cu: 0.35 - 0.85%, Mn: 0.25 - 0.65%, Mg: 0.70 - 1.45%, Cr: 0.20 - 0.45%, Zn: 0.25 - 0.8%, Ti ≤ 0.20%, harmful impurities ≤ 0.015%, and the rest is Al, through a resistance melting furnace, melting at a temperature of 780°C - 990°C. Stirring is required during the melting process, and the stirring speed is controlled at 80 - 220 revolutions per minute. Melting for 2 - 4 hours to ensure the aluminum alloy is fully uniform, and the corresponding bar is prepared; S22: The pre-prepared aluminum alloy bar is heated to 380℃-450℃, and the bar is extruded into a tube blank of corresponding specifications and wall thickness by hot extrusion equipment, and the tube blank is straightened by a straightening machine, and the aluminum alloy tube blank is subjected to a solid solution treatment at a temperature of 530℃±20℃ and an artificial aging treatment at a temperature of 170℃±20℃ for more than 10 hours to complete the manufacture of the liner pipe; S3: After removing rust, oil and other debris from the inner wall of the base pipe blank and the outer wall of the inner liner pipe, an adhesive with a temperature resistance of 950°C and a pressure resistance of 55MPa is evenly coated on the outer wall of the inner liner pipe and the inner wall of the base pipe blank, and the inner liner pipe is inserted into the base pipe blank. The outer diameter of the inner liner pipe is 3mm-6mm smaller than the inner diameter of the base pipe blank to ensure that the inner liner pipe can be inserted into the base pipe blank, and the inner liner pipe is made to yield through a hydraulic composite method or an explosive composite method, so that the inner liner pipe and the base pipe blank are tightly combined; S4: According to the size of the sieve holes, the corresponding plugs are processed. The plugs are made of the same aluminum alloy as the liner pipe. The above-mentioned adhesive is coated on the plugs to seal all the sieve holes on the base pipe and solidify for more than 24 hours to form a pipe body of the ablative composite casing. The pipe body passes relevant tests such as composite force test and water pressure test. After the performance is qualified, the API thread or special thread processing is performed on the pipe end to finally form an ablative casing for underground coal gasification.
[0012] In the step S12, the tube blank is subjected to sieve hole processing, and the distance between the sieve hole and the end of the tube blank is ≥800 mm.
[0013] The technical effects of the present invention are as follows: 1. The mechanical properties of the ablative casing for underground coal gasification of the present invention meet the mechanical property requirements of API 5CT for 80ksi-110ksi steel grade casing products. An inner liner is arranged in the base pipe, and a plurality of sieve holes are evenly arranged on the surface of the base pipe. A plug is arranged in the sieve hole. The melting points of the inner liner and the plug are both lower than the melting point of the base pipe. When in use, during the backward combustion of coal, the inner liner and the plug are ablated at 600°C-800°C, so that the ignition device is connected to the coal layer through the sieve hole, so that the coal is effectively controlled to burn, and it is ensured that the shaft will not collapse during the coal gasification process; 2. After the backward combustion of coal, the ablative casing for underground coal gasification of the present invention generates H2O2 by thermal and chemical action on coal underground. 2 , CH 4 ,CO,CO 2 Useful gases such as coal can be mined by entering the base pipe through multiple sieve holes evenly distributed on the surface of the base pipe. This reduces the air pollution, carbon emissions and other environmental pollution caused by processes such as coal combustion and coal-to-hydrogen production after the physical mining of coal on the ground in the existing technology, realizes green underground coal mining, and greatly reduces environmental pollution and carbon emissions.
[0014] The following is a further description with reference to the accompanying drawings. Brief Description of the Drawings
[0015] Figure 1 The figure is a schematic structural diagram of an ablatable casing for underground coal gasification according to an embodiment of the present invention.
[0016] Reference numerals: 1 - coupling, 2 - external thread, 3 - base pipe, 4 - sieve holes, 5 - plug, 6 - inner lining pipe string, 7 - adhesive layer. Detailed Description of the Embodiment Embodiment 1
[0017] As Figure 1 shown, an ablatable casing for underground coal gasification includes a base pipe 3. An inner lining pipe 6 is provided inside the base pipe 3. A plurality of sieve holes 4 are evenly distributed on the surface of the base pipe 3. A plug 5 is provided in the sieve holes 4. The outer end face of the plug 5 is flush with the outer surface of the base pipe 3. The melting points of the inner lining pipe 6 and the plug 5 are both less than the melting point of the base pipe 3. External threads 2 are respectively provided at the left and right ends of the base pipe 3. A coupling 1 is connected to the outside of the external thread 2 at the left end.
[0018] During the actual use process, in the present invention, an inner lining pipe is provided inside the base pipe, a plurality of sieve holes are evenly distributed on the surface of the base pipe, a plug is provided in the sieve holes, and the melting points of the inner lining pipe and the plug are both less than the melting point of the base pipe. When in use, during the backward combustion process of coal, the inner lining pipe and the plug are ablated at 600°C - 800°C, so that the ignition device is connected to the coal seam through the sieve holes, realizing effective control of coal combustion and ensuring that the shaft will not collapse during the coal gasification process. After the backward combustion of coal, the useful gases such as H 2 , CH 4 , CO, CO 2 produced by the thermal and chemical effects of coal underground enter the base pipe through a plurality of sieve holes evenly distributed on the surface of the base pipe for exploitation, reducing the environmental pollution such as air pollution and carbon emissions generated by the coal physical mining in the prior art to the ground and then the coal ground combustion, coal-to-hydrogen and other processes, realizing green underground coal mining and greatly reducing environmental pollution and carbon emissions. Embodiment 2
[0019] Preferably, on the basis of Embodiment 1, in this embodiment, an adhesive layer 7 is provided between the base pipe 3 and the inner lining pipe 6. The adhesive used for the adhesive layer 7 has a temperature resistance range ≥ 950°C and a pressure bearing range ≥ 55 MPa. The melting point range of the inner lining pipe 6 and the plug 5 is 600°C - 800°C.
[0020] During actual use, an adhesive layer 7 is provided between the base pipe 3 and the inner lining pipe 6 of the present invention. The high-temperature and high-pressure resistant adhesive ensures the bonding force between the base pipe and the inner lining pipe, realizes the tight bonding of the base pipe and the inner lining pipe, prevents the separation of the base pipe and the inner lining pipe due to excessive external pressure, causes the collapse of the inner lining pipe, blocks the coal gasification channel, and reduces the anti-external pressure extrusion strength of the ablatable casing. Example 3
[0021] Preferably, on the basis of Example 1 or Example 2, in this embodiment, the sieve holes 4 are arranged in a spiral shape along the surface of the base pipe 3.
[0022] During actual use, the sieve holes 4 of the present invention are arranged in a spiral shape along the surface of the base pipe 3, ensuring that the sieve hole layout is evenly distributed in the four quadrants of the base pipe, realizing an equal-hole layout of the base pipe on the same cross-section, and ensuring that the strength of the base pipe remains consistent in the axial direction of the entire pipe body. Example 4
[0023] Preferably, on the basis of Example 1 or Example 3, in this embodiment, the sieve holes 4 are conical holes or pipe column holes, and the aperture range of the sieve holes 4 is 8 mm - 20 mm.
[0024] During actual use, the sieve holes 4 of the present invention are conical holes or pipe column holes, and the aperture range of the sieve holes 4 is 8 mm - 20 mm. During the backward combustion process of coal, the inner lining pipe and the blockage are ablated. The ignition device is connected to the coal layer through the sieve holes to realize the effective controlled combustion of coal. After the backward combustion of coal, the useful gases such as H 2 、CH 4 、CO、CO 2 etc. enter the base pipe through the sieve holes for extraction. Example 5
[0025] Preferably, on the basis of Example 1 or Example 4, in this embodiment, the chemical element components of the base pipe 3 are by weight percentage: C: 0.15 - 0.35%, Si: 0.20 - 0.80%, Mn: 0.75 - 1.55%, Cr: 0.90 - 18.00%, Mo: 0.20 - 0.50%, Ni: 0.25 - 0.45%, Nb: 0.15 - 0.45%, V: 0.05 - 0.15%, Ti ≤ 0.04%, S ≤ 0.002%, P ≤ 0.008%, and the balance is Fe and unavoidable impurities.
[0026] During actual use, according to the above weight percentages of the chemical element components of the base pipe 3 of the present invention, its mechanical properties meet the mechanical property requirements of API 5CT for casing products with a steel grade of 80 ksi - 110 ksi, having a relatively high collapse resistance strength, capable of solving the risk of collapse of the injection well during underground coal gasification, and ensuring the safe, reliable and stable operation of the underground coal gasification channel. Example 6
[0027] Preferably, on the basis of Example 1 or Example 5, in this embodiment, the inner lining pipe 6 is an aluminum alloy pipe, and its chemical element components by weight percentage are: Si: 0.40 - 2.50%, Fe: 0.20 - 0.45%, Cu: 0.35 - 0.85%, Mn: 0.25 - 0.65%, Mg: 0.70 - 1.45%, Cr: 0.20 - 0.45%, Zn: 0.25 - 0.8%, Ti ≤ 0.20%, harmful impurities ≤ 0.015%, and the rest is Al.
[0028] During actual use, according to the above weight percentages of the chemical element components of the inner lining pipe 6 of the present invention, in addition to ensuring that the inner lining pipe has relatively high internal pressure resistance and external extrusion resistance, during the backward combustion process of coal, the inner lining pipe is ablated at 600°C - 800°C, enabling the ignition device to communicate with the coal layer through the sieve holes, and realizing the effective controlled combustion of coal. Example 7
[0029] A manufacturing method of an ablatable casing for underground coal gasification, for manufacturing an ablatable casing for underground coal gasification as described above, includes the following steps: S1: Manufacturing the base pipe 3, the specific process is: S11: Using molten iron with chemical element components by weight percentage: C: 0.15 - 0.35%, Si: 0.20 - 0.80%, Mn: 0.75 - 1.55%, Cr: 0.90 - 18.00%, Mo: 0.20 - 0.50%, Ni: 0.25 - 0.45%, Nb: 0.15 - 0.45%, V: 0.05 - 0.15%, Ti ≤ 0.04%, S ≤ 0.002%, P ≤ 0.008%, after pretreatment, secondary refining, light desulfurization treatment and calcium treatment to control harmful elements, with the superheat degree less than 28°C during continuous casting, after the continuous casting billet is heated at 1100°C - 1320°C, the corresponding ingot is made, and then it is rolled into the required tube blank by skew rolling piercing, and the tube blank is made into the tube blank of the required steel grade after heat treatment; S12: Processing the sieve holes 4 on the tube blank, using mechanical drilling or laser cutting to process the sieve holes 4 on the tube blank, the sieve holes 4 are arranged in a spiral manner on the tube blank, and the diameter of the sieve holes 4 is designed to be 8 mm - 20 mm; S2: Manufacturing the inner lining pipe 6, the specific process is: S21: Use aluminum alloy raw materials with chemical element compositions by weight percentage as follows: Si: 0.40 - 2.50%, Fe: 0.20 - 0.45%, Cu: 0.35 - 0.85%, Mn: 0.25 - 0.65%, Mg: 0.70 - 1.45%, Cr: 0.20 - 0.45%, Zn: 0.25 - 0.8%, Ti ≤ 0.20%, harmful impurities ≤ 0.015%, and the rest is Al. Through a resistance melting furnace, melt at a temperature of 780°C - 990°C. During the melting process, stirring is required, and the stirring speed is controlled at 80 - 220 revolutions per minute. Melt for 2 - 4 hours to ensure the aluminum alloy is fully uniform, and prepare the corresponding bars; S22: Heat the pre-prepared aluminum alloy bars to 380°C - 450°C, extrude the bars into tube blanks with corresponding wall thicknesses through a hot extrusion equipment, and straighten the tube blanks through a straightening machine. Perform solution treatment on the aluminum alloy tube blanks at a temperature of 530°C ± 20°C + artificial aging treatment at a temperature of 170°C ± 20°C for more than 10 hours to make its mechanical properties meet the requirements and complete the manufacturing of the inner liner tube 6; S3: After removing rust, oil, and other sundries from the inner wall of the tube blank of the base tube 3 and the outer wall of the inner liner tube 6, evenly coat an adhesive with a heat resistance of 950°C and a pressure resistance of 55 MPa on the outer wall of the inner liner tube 6 and the inner wall of the tube blank of the base tube 3, and insert the inner liner tube 6 into the tube blank of the base tube 3. The outer diameter of the inner liner tube 6 is 3 mm - 6 mm smaller than the inner diameter of the tube blank of the base tube 3 to ensure that the inner liner tube 6 can be inserted into the tube blank of the base tube 3, and through the hydraulic composite method or the explosion composite method, make the inner liner tube 6 reach yield deformation, so that the inner liner tube 6 is tightly combined with the tube blank of the base tube 3; S4: According to the size of the sieve holes 4, process the corresponding plugs 5. The plugs 5 are made of the same aluminum alloy material as the inner liner tube 6, and the above-mentioned adhesive is coated on the plugs 5. Block all the sieve holes 4 on the base tube 3 and cure for more than 24 hours to form the tube body of the ablatable composite casing. Through relevant tests such as the composite force and hydrostatic test of the tube body, after the performance is qualified, perform API thread or special thread processing on the tube ends, and finally form an ablatable casing for underground coal gasification.
[0030] In the step S12, the sieve holes 4 are processed on the tube blank, and the distance between the sieve holes 4 and the end of the tube blank is ≥ 800 mm. The distance between the sieve holes 4 and the end of the tube blank is ≥ 800 mm to ensure that the tube end thread has sufficient connection strength. Example 8
[0031] Adopt the manufacturing method of an ablatable casing for underground coal gasification as described in Example 7 to manufacture an ablatable casing for underground coal gasification as described in Example 1. The size of the ablatable casing for underground coal gasification is Φ139.7 mm, and the specific process is as follows: S1: The chemical element composition of the base pipe of the ablatable casing in this embodiment by weight percentage is: C: 0.18%, Si: 0.45%, Mn: 1.05%, Cr: 12.00%, Mo: 0.30%, Ni: 0.35%, Nb: 0.25%, V: 0.08%, Ti≤0.04%, S≤0.002%, P≤0.008%, and the balance is Fe and inevitable impurities. The molten iron is pretreated, refined outside the furnace, lightly desulfurized and calcium-treated to control the S content of the molten iron entering the furnace to be less than 0.002%. The superheat during continuous casting is 25°C. After the continuous casting billet is heated at 1180°C, the corresponding ingot is made, and then it is rolled into a tube blank with a specification of Φ139.7×9.17mm by skew rolling piercing. After heat treatment of the tube blank, its performance meets the requirements of 80ksi steel grade. The mechanical properties of the tube blank are yield strength: 720MPa, tensile strength: 815MPa, elongation: 20%, and external pressure collapse strength: 72MPa, serving as the required base pipe of the ablatable casing; For the Φ139.7×9.17mm base pipe, mechanical drilling is used to process the sieve holes in a spiral distribution layout. A Φ12mm drill bit is used for sieve hole processing. The sieve holes are evenly distributed in the four quadrants of the base pipe, and no drilling is carried out within 800mm from the pipe end; S2: Manufacture an aluminum alloy tube as the inner lining tube. Its chemical element composition by weight percentage is: Si: 0.80%, Fe: 0.35%, Cu: 0.75%, Mn: 0.30%, Mg: 1.20%, Cr: 0.40%, Zn: 0.35%, Ti≤0.18%, harmful impurities≤0.012%, and the rest is Al. Through a resistance melting furnace, it is melted at 800°C according to the above ratio. During the melting process, the stirring speed is controlled at 120 revolutions per minute, and it is melted for 2.5 hours to ensure the full uniformity of the aluminum alloy composition, and an aluminum alloy bar with a diameter of Φ150mm is prepared; Heat the Φ150mm aluminum alloy bar to 400°C, and extrude the aluminum alloy bar into an aluminum alloy tube blank with a specification of Φ118×8.00mm through a hot extrusion equipment, and straighten the tube blank through a straightening machine. Then, perform a solution treatment on the aluminum alloy tube blank at 525°C + an artificial aging treatment at 180°C for 12 hours to obtain the inner lining tube of the aluminum alloy tube blank; S3: Rust and oil removal treatments are carried out on the inner wall of the Φ139.7×9.17mm sieve hole base pipe and the outer wall of the Φ118×8.00mm inner lining aluminum alloy tube. A kind of adhesive resistant to 950°C and with a pressure bearing of 55MPa is evenly coated on the outer wall of the aluminum alloy tube and the inner wall of the sieve hole base pipe, and the aluminum alloy tube blank is inserted into the sieve hole base pipe, and the aluminum alloy tube and the sieve hole base pipe are tightly combined together through a hydrostatic composite method; S4: Process an aluminum alloy plug of Φ11mm×9.19 according to the sieve hole size of the base pipe Φ12mm. Coat the plug with the above-mentioned adhesive, seal all the sieve holes on the base pipe, cure for 24 hours, and perform special thread processing on the pipe end. Finally, form a Φ139.7mm×(9.17 + 8.00)mm ablatable casing product for underground coal gasification, detect its external pressure collapse resistance performance, and the external pressure collapse strength reaches 85MPa, which is 18% higher than the original base pipe. And conduct a laboratory combustion experiment. When the temperature of this ablatable casing reaches 695°C, the lining pipe material and the sieve hole plugging material are all melted away, realizing the connection between the gasification channel and the coal seam, and meeting the requirements of the underground coal backward combustion process technology. Example 9
[0032] Adopt the manufacturing method of an ablatable casing for underground coal gasification described in Example 7 to manufacture an ablatable casing for underground coal gasification described in Example 1. The size of this ablatable casing for underground coal gasification is Φ177.8mm. The specific process is as follows: S1: The chemical element components contained in the base pipe of the ablatable casing in this example are as follows by weight percentage: C: 0.30%, Si: 0.60%, Mn: 1.25%, Cr: 16.00%, Mo: 0.45%, Ni: 0.25%, Nb: 0.40%, V: 0.10%, Ti≤0.03%, S≤0.002%, P≤0.007%, and the balance is Fe and inevitable impurities. Through hot metal pretreatment, secondary refining, desulfurization treatment and calcium treatment, control harmful elements and control the S content of the hot metal entering the furnace to be lower than 0.002%. During continuous casting, the superheat is controlled at 23°C. After the continuous casting billet is heated at 1260°C, it is made into the corresponding ingot, and then skew rolling piercing is carried out to make a pipe blank of Φ177.8×10.36mm. After heat treatment, the pipe blank meets the requirements of the 110ksi steel grade. The mechanical properties of the pipe blank are: yield strength: 880MPa, tensile strength: 930MPa, elongation: 22%, external pressure collapse strength: 69MPa, which is used as the required base pipe of the ablatable casing. Adopt laser cutting for the Φ177.8×10.36mm base pipe. The sieve hole is designed as Φ18mm, and the sieve hole taper is 20:1. Process the sieve holes on the base pipe according to the layout method of spiral distribution. The sieve hole layout is evenly distributed in the four quadrants of the base pipe, and no drilling is carried out at a distance of 900mm from the pipe end. S2: Use an aluminum alloy tube as the inner liner tube. The chemical element composition by weight percentage is as follows: Si: 1.90%, Fe: 0.40%, Cu: 0.50%, Mn: 0.60%, Mg: 0.95%, Cr: 0.25%, Zn: 0.75%, Ti ≤ 0.20%, harmful impurities ≤ 0.015%, and the rest is Al. Through a resistance melting furnace, melt according to the above ratio at a temperature of 920 °C. During the melting process, control the stirring speed at 100 revolutions per minute and melt for 3 hours to ensure that the aluminum alloy composition is fully uniform, and prepare an aluminum alloy bar with a diameter of Φ180 mm; Heat the Φ180 mm aluminum alloy bar to 400 °C, extrude the aluminum alloy bar into an aluminum alloy tube blank with a specification of Φ153×9.00 mm through a hot extrusion equipment, and straighten the tube blank through a straightening machine. Perform a solution treatment on the aluminum alloy tube blank at a temperature of 550 °C + an artificial aging treatment at a temperature of 170 °C for 10 hours to support the inner liner tube of the aluminum alloy tube blank; S3: Rust and degrease the inner wall of the Φ177.8×10.36 mm sieve hole base tube and the outer wall of the Φ153×9.00 mm inner liner aluminum alloy tube, and evenly coat an adhesive resistant to 950 °C and with a pressure bearing of 55 MPa on the outer wall of the aluminum alloy tube and the inner wall of the sieve hole base tube. Then insert the aluminum alloy tube blank into the sieve hole base tube, and tightly combine the aluminum alloy tube and the sieve hole base tube together through the explosive bonding method; S4: According to the Φ18 mm tapered sieve hole size of the base tube, process a tapered aluminum alloy plug with a size of Φ17 mm×10.36 mm, coat the above-mentioned adhesive on the plug, block all the sieve holes on the base tube, and cure for 28 hours. Then perform special thread processing on the tube ends to finally form a Φ177.8 mm×(10.36 + 9.00) mm ablatable casing product for underground coal gasification. Detect its external pressure collapse resistance performance. The external pressure collapse strength reaches 90 MPa, which is 30% higher than the original base tube. And conduct a laboratory combustion experiment. When the temperature is 720 °C, the inner liner pipe material and the sieve hole plugging material are all melted away, realizing the connection between the gasification channel and the coal seam, and meeting the requirements of the underground coal backward combustion process technology.
[0033] As mentioned above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.
Claims
1. An ablatable casing for underground coal gasification, characterized in that: It includes a base pipe (3), an inner lining pipe (6) is arranged inside the base pipe (3), a plurality of sieve holes (4) are evenly distributed on the surface of the base pipe (3), plugs (5) are arranged in the sieve holes (4), and the outer end surface of the plugs (5) is flush with the outer surface of the base pipe (3). The melting points of the inner lining pipe (6) and the plugs (5) are both lower than the melting point of the base pipe (3). External threads (2) are respectively arranged at the left and right ends of the base pipe (3), and a coupling (1) is connected to the outside of the external thread (2) at the left end.
2. The ablatable casing for underground coal gasification according to claim 1, characterized in that: An adhesive layer (7) is arranged between the base pipe (3) and the inner lining pipe (6). The adhesive used in the adhesive layer (7) has a temperature resistance range ≥ 950 °C and a pressure bearing range ≥ 55 MPa. The melting point range of the inner lining pipe (6) and the plugs (5) is 600 °C - 800 °C.
3. The ablatable casing for underground coal gasification according to claim 1, characterized in that: The sieve holes (4) are arranged in a spiral shape along the surface of the base pipe (3).
4. The ablatable casing for underground coal gasification according to claim 1, characterized in that: The sieve holes (4) are conical holes or pipe column holes, and the aperture range of the sieve holes (4) is 8 mm - 20 mm.
5. The ablatable casing for underground coal gasification according to claim 1, characterized in that: The chemical element composition of the base pipe (3) by weight percentage is: C: 0.15 - 0.35%, Si: 0.20 - 0.80%, Mn: 0.75 - 1.55%, Cr: 0.90 - 18.00%, Mo: 0.20 - 0.50%, Ni: 0.25 - 0.45%, Nb: 0.15 - 0.45%, V: 0.05 - 0.15%, Ti ≤ 0.04%, S ≤ 0.002%, P ≤ 0.008%, and the balance is Fe and unavoidable impurities.
6. The ablatable casing for underground coal gasification according to claim 1, characterized in that: The inner lining pipe (6) is an aluminum alloy pipe, and its chemical element composition by weight percentage is: Si: 0.40 - 2.50%, Fe: 0.20 - 0.45%, Cu: 0.35 - 0.85%, Mn: 0.25 - 0.65%, Mg: 0.70 - 1.45%, Cr: 0.20 - 0.45%, Zn: 0.25 - 0.8%, Ti ≤ 0.20%, harmful impurities ≤ 0.015%, and the rest is Al.
7. A manufacturing method of an ablatable casing for underground coal gasification, manufacturing the ablatable casing for underground coal gasification according to claim 1, characterized in that: It includes the following steps: S1: Manufacturing the base pipe (3), the specific process is: S11: Use molten iron with chemical element components by weight percentage as follows: C: 0.15 - 0.35%, Si: 0.20 - 0.80%, Mn: 0.75 - 1.55%, Cr: 0.90 - 18.00%, Mo: 0.20 - 0.50%, Ni: 0.25 - 0.45%, Nb: 0.15 - 0.45%, V: 0.05 - 0.15%, Ti ≤ 0.04%, S ≤ 0.002%, P ≤ 0.008%. After pretreatment, secondary refining, mild desulfurization treatment and calcium treatment to control harmful elements, the superheat during continuous casting is less than 28°C. After the continuous casting billet is heated at 1100°C - 1320°C, the corresponding ingot is made, and then it is rolled into the required tube blank by skew rolling piercing. After heat treatment, the tube blank of the required steel grade is made; S12: Process the sieve holes (4) on the tube blank. The sieve holes (4) are processed on the tube blank by mechanical drilling or laser cutting. The sieve holes (4) are arranged in a spiral pattern on the tube blank, and the diameter of the sieve holes (4) is designed to be 8mm - 20mm; S2: Manufacture the inner liner tube (6), and the specific process is as follows: S21: Use aluminum alloy raw materials with chemical element components by weight percentage as follows: Si: 0.40 - 2.50%, Fe: 0.20 - 0.45%, Cu: 0.35 - 0.85%, Mn: 0.25 - 0.65%, Mg: 0.70 - 1.45%, Cr: 0.20 - 0.45%, Zn: 0.25 - 0.8%, Ti ≤ 0.20%, harmful impurities ≤ 0.015%, and the rest is Al. Through a resistance melting furnace, melt at a temperature of 780°C - 990°C. During the melting process, stirring is required, and the stirring speed is controlled at 80 - 220 revolutions per minute. Melt for 2 - 4 hours to ensure that the aluminum alloy is fully uniform, and prepare the corresponding bar; S22: Heat the pre-prepared aluminum alloy bar to 380°C - 450°C, extrude the bar into a tube blank with a corresponding wall thickness through a hot extrusion equipment, and straighten the tube blank through a straightening machine. Then, perform a solution treatment on the aluminum alloy tube blank at a temperature of 530°C ± 20°C + an artificial aging treatment at a temperature of 170°C ± 20°C for more than 10 hours to complete the manufacture of the inner liner tube (6); S3: After removing rust, oil and other sundries from the inner wall of the tube blank of the base tube (3) and the outer wall of the inner liner tube (6), evenly coat an adhesive with a temperature resistance of 950°C and a pressure bearing of 55MPa on the outer wall of the inner liner tube (6) and the inner wall of the tube blank of the base tube (3). Then, insert the inner liner tube (6) into the tube blank of the base tube (3). The outer diameter of the inner liner tube (6) is 3mm - 6mm smaller than the inner diameter of the tube blank of the base tube (3) to ensure that the inner liner tube (6) can be inserted into the tube blank of the base tube (3). Then, through the hydraulic composite method or the explosion composite method, make the inner liner tube (6) reach yield deformation, so that the inner liner tube (6) is tightly combined with the tube blank of the base tube (3); S4: According to the size of the sieve holes (4), process the corresponding plugs (5). The plugs (5) are made of the same aluminum alloy material as the inner lining pipe (6). Coat the above-mentioned adhesive on the plugs (5), seal all the sieve holes (4) on the base pipe (3), and cure for more than 24 hours to form the pipe body of the ablatable composite casing. After passing relevant tests such as the composite force and hydrostatic test of the pipe body and being qualified in performance, perform API thread or special thread processing on the pipe ends to finally form the ablatable casing for underground coal gasification.
8. The manufacturing method of an ablatable casing for underground coal gasification according to claim 6, wherein: in step S12, sieve holes (4) are processed on the pipe blank, and the distance between the sieve holes (4) and the end of the pipe blank is ≥ 800 mm.