Gas path system of LPCVD (Low Pressure Chemical Vapor Deposition) reaction chamber

Abstract

The utility model discloses an LPCVD (low pressure chemical vapor deposition) reaction chamber gas path system which comprises a gas inlet assembly connected with a furnace mouth gas inlet flange and a gas supply assembly connected with a furnace tail gas extraction flange, the gas inlet assembly adopts an embedded spraying structure, and the gas supply assembly adopts a stepped layered structure, so that gas in a furnace tube of an LPCVD reaction chamber is uniformly distributed, and the gas supply efficiency is improved. And local concentration of gas in the furnace tube is avoided. The air inlet device has the advantages of compact structure, convenience in operation, high air inlet uniformity, benefit for improving the process stability of equipment and the like, solves the problems of short service life of an air path system and low film forming yield of the equipment caused by easiness in blockage of an air inlet pipeline in the prior art, and meets the diversified process requirements of customers.

Description

Technical Field

[0001] The utility model belongs to the technical field of LPCVD reaction equipment, and in particular relates to a gas path system for an LPCVD reaction chamber. Background Art

[0002] Tubular LPCVD equipment is a key technical equipment for the preparation of Topcon solar cells. It can not only integrate the three processes of tunneling oxide layer, Poly layer and Poly doping to realize the preparation of Topcon structure through one device, but also reduce the metal recombination on the back of the battery and improve the conversion efficiency. It has a wide range of applications in the field of photovoltaic industry equipment.

[0003] The reaction chamber is the core component of the LPCVD equipment. It is the place where the three process reactions of tunneling oxide layer, Poly layer and Poly doping occur. The gas path system inside the reaction chamber directly determines the film quality of the three processes of preparing tunneling oxide layer, Poly layer and Poly doping in the reaction chamber. It is a key component system in the reaction chamber. For a long time, the tubular LPCVD equipment in the photovoltaic field has been used to prepare SiOx film structures by vertically feeding N from the bottom of the furnace. 2 , O 2 , Si H enters horizontally from the bottom of the furnace tail 4 structure, which is often replaced by Si H 4 The products of thermal decomposition in the pipeline cause local blockage of the pipeline, affecting the process effect of the equipment and causing defects such as poor film formation. Utility Model Content

[0004] In order to improve the service life of the gas path system of the reaction chamber of the tubular LPCVD equipment, improve the film forming yield of the equipment, and meet the diversified process requirements of customers, the utility model provides a LPCVD reaction chamber gas path system with a compact structure, convenient operation, high air intake uniformity, and conducive to improving the process stability of the equipment. To achieve the above purpose, the utility model can adopt the following technical solutions:

[0005] A LPCVD reaction chamber gas circuit system includes an air intake assembly connected to a furnace inlet flange and an air supply assembly connected to a furnace tail exhaust flange. The air intake assembly adopts an embedded spray structure and the air supply assembly adopts a stepped layered structure to achieve uniform distribution of gas in the furnace tube of the LPCVD reaction chamber and avoid local concentration of gas in the furnace tube.

[0006] As a further improvement of the present invention, the air intake assembly includes an embedded spray pipe and a mixed air intake pipe. An arc groove is provided on the inner side of the middle part of the furnace mouth air intake flange. The embedded spray pipe is nested in the arc groove. The embedded spray pipe is used to input phosphine gas and silane gas; the mixed air intake pipe is arranged at the bottom of the furnace mouth air intake flange, and the mixed air intake pipe is used to input a mixed gas of nitrogen and oxygen.

[0007] As a further improvement of the utility model, the air intake assembly also includes an air supply joint, which is arranged on the furnace mouth air intake flange and is used to supplement the gas required for the reaction or to balance the air pressure of the inner and outer quartz tubes of the double quartz tube reaction structure.

[0008] As a further improvement of the present utility model, a phosphine air inlet joint and a silane air inlet joint are provided on the furnace mouth air inlet flange; the embedded spray pipe comprises an arc-shaped air inlet pipe and a gas mixing chamber, the arc-shaped air inlet pipe is evenly provided with spray holes, a sealing plate is welded at one end of the arc-shaped air inlet pipe, and the other end of the arc-shaped air inlet pipe is inserted into the gas mixing chamber and welded internally to form a whole with the gas mixing chamber; two air inlet nozzles are welded at the lower part of the gas mixing chamber, and the two air inlet nozzles are respectively in contact with the phosphine air inlet joint and the silane air inlet joint through sealing rings to form a sealed air inlet structure.

[0009] As a further improvement of the utility model, the phosphine air inlet joint and the silane air inlet joint are horizontally welded to the side of the furnace mouth air inlet flange; the arc-shaped air inlet pipe adopts a 270° arc structure, and small spray holes are evenly opened on the arc-shaped air inlet pipe at intervals of 12°.

[0010] As a further improvement of the utility model, a ferrule joint is provided on the inner side of the bottom of the furnace mouth air inlet flange, and a nitrogen and oxygen mixed air inlet joint is provided on the outer side of the bottom of the furnace mouth air inlet flange. The mixed air inlet pipe is connected to the nitrogen and oxygen mixed air inlet joint through the ferrule joint to realize the transportation of nitrogen and oxygen mixed gas.

[0011] As a further improvement of the utility model, the mixing air intake pipe extends from the furnace mouth of the reaction chamber to the furnace tail, and the mixing air intake pipe is evenly provided with spray ports with an angle of 120° along the length direction.

[0012] As a further improvement of the present invention, a uniform flow insulation plate group is fixed on the inner side of the furnace tail exhaust flange; the air supply assembly includes a long air supply pipe group and a short air supply pipe group, the long air supply pipe group is installed at the top and the upper middle part of the furnace tail exhaust flange, and the short air supply pipe group is installed at the bottom and the lower middle part of the furnace tail exhaust flange.

[0013] As a further improvement of the present invention, the length of the long gas supply pipe group exceeds the middle of the reaction chamber; the long gas supply pipe group includes long gas supply pipe one and long gas supply pipe two, the long gas supply pipe one adopts a single-tube structure, and the long gas supply pipe two adopts a pipeline structure divided into two, the long gas supply pipe one is arranged at the top of the furnace tail exhaust flange, and the long gas supply pipe two is arranged in the middle and upper part of the furnace tail exhaust flange.

[0014] As a further improvement of the present invention, the length of the short air supply pipe group is shorter than the middle part of the reaction chamber; the short air supply pipe group includes short air supply pipe one and short air supply pipe two, and the short air supply pipe one and short air supply pipe two both adopt a pipeline structure divided into two, short air supply pipe one is arranged at the middle and lower part of the furnace tail exhaust flange, and short air supply pipe two is arranged at the bottom of the furnace tail exhaust flange.

[0015] Compared with the prior art, the advantages of the utility model are:

[0016] The utility model discloses an LPCVD reaction chamber gas path system, which comprises an air intake component connected to the furnace mouth air intake flange and an air supply component connected to the furnace tail exhaust flange to form the main structure of the air path system, thus avoiding occupying the quartz boat inlet and outlet space, and having the characteristics of compact structure and convenient assembly and disassembly; further, the air intake component adopts an embedded spray structure to expand the diffusion range of the gas in the reaction chamber, and the air supply component adopts a stepped layered structure to realize the replenishment of the silane required for the coating of the quartz boats in front and behind the reaction chamber, thus avoiding the blockage of the silane air inlet at a certain place due to the thermal decomposition of silane, resulting in insufficient gas uniformity, thereby affecting the film forming quality of the silicon wafers in the front and rear boats, thus achieving uniform gas distribution in the furnace tube of the LPCVD reaction chamber, and avoiding local concentration of gas in the furnace tube, which is beneficial to prolonging the service life of the gas path system of the reaction chamber of the tubular LPCVD equipment, improving the film forming yield of the equipment, and meeting the diversified process requirements of customers. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structural principle of the gas circuit system of the LPCVD reaction chamber in a specific embodiment of the utility model;

[0018] Figure 2 This is a schematic diagram of the structural principle of the air intake assembly in a specific embodiment of the utility model;

[0019] Figure 3 A schematic diagram of the structural principle of the air intake assembly from another perspective in a specific embodiment of the utility model;

[0020] Figure 4 This is a schematic diagram of the partial structural principle of the air intake assembly in a specific embodiment of the utility model;

[0021] Figure 5 This is a schematic diagram of the structural principle of the air replenishing component in a specific embodiment of the utility model;

[0022] Figure 6 It is a schematic diagram of the structural principle of the air replenishing component from another perspective in a specific embodiment of the utility model;

[0023] Legend: 1. Air intake assembly; 2. Air supply assembly; 11. Furnace inlet flange; 12. Embedded spray pipe; 13. Mixed air intake pipe; 14. Air supply connector; 111. Phosphine air intake connector; 112. Silane air intake connector; 113. Nitrogen-oxygen mixed air intake connector; 114. Compression fitting; 121. Curved air intake pipe; 122. Gas mixing chamber; 123. Sealing ring; 21. Furnace tail exhaust flange; 22. Long air supply pipe group; 23. Short air supply pipe group; 24. Uniform flow insulation board group; 221. Long air supply pipe one; 222. Long air supply pipe two; 231. Short air supply pipe one; 232. Short air supply pipe two. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0025] In the description of the present invention, it should be understood that the terms "side", "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation to the present invention.

[0026] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present utility model, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0027] Example

[0028] like Figures 1 to 6 As shown, the LPCVD reaction chamber gas path system of the utility model includes an air intake component 1 connected to the furnace mouth air intake flange 11, and an air supply component 2 connected to the furnace tail exhaust flange 21. The air intake component 1 adopts an embedded spray structure, and the air supply component 2 adopts a stepped layered structure to achieve uniform distribution of gas in the furnace tube of the LPCVD reaction chamber and avoid local concentration of gas in the furnace tube.

[0029] In this embodiment, the main structure of the gas path system is formed by the gas intake component 1 connected to the furnace mouth gas intake flange 11, and the gas replenishment component 2 connected to the furnace tail exhaust flange 21, so as to avoid occupying the quartz boat inlet and exit space, and has the characteristics of compact structure and convenient disassembly and assembly; further, the gas intake component 1 adopts an embedded spray structure to expand the diffusion range of the gas in the reaction chamber, and the gas replenishment component 2 adopts a stepped layered structure, which can realize the replenishment of the silane required for the coating of the quartz boats in front and behind the reaction chamber, and avoids the blockage of the silane gas inlet at a certain place due to the thermal decomposition of silane, resulting in insufficient gas uniformity, which affects the film forming quality of the silicon wafers in the front and rear boats, and realizes the uniform distribution of gas in the furnace tube of the LPCVD reaction chamber, and avoids the local concentration of gas in the furnace tube, which is beneficial to prolong the service life of the gas path system of the reaction chamber of the tubular LPCVD equipment, improves the film forming yield of the equipment, and meets the diversified process requirements of customers.

[0030] like Figure 2 As shown, the air intake assembly 1 includes an embedded spray pipe 12 and a mixed air intake pipe 13. The inner circle of the furnace inlet flange 11 is an arc structure of more than 180°. An arc groove is provided on the inner side of the middle of the furnace inlet flange 11. The embedded spray pipe 12 is nested in the arc groove. The embedded spray pipe 12 is used to input phosphine gas and silane gas. Specifically, the embedded spray pipe 12 is embedded in the furnace inlet flange 11, and it is kept within the inner circle of the furnace inlet flange 11 to avoid occupying the quartz boat inlet and exit space. The two sides of the embedded spray pipe 12 are fixed to the furnace inlet flange 11 by screws. The mixed air intake pipe 13 is arranged at the bottom of the furnace inlet flange 11. The mixed air intake pipe 13 is used to input a mixed gas of nitrogen and oxygen.

[0031] Furthermore, the gas inlet assembly 1 also includes a gas supply joint 14, which is a VCR joint. The gas supply joint 14 is welded at the upper side of the furnace inlet flange 11, and is used to supply the gas required for the reaction or to balance the gas pressure of the inner and outer quartz tubes in the double quartz tube reaction structure.

[0032] like Figure 3 and Figure 4As shown, a phosphine inlet joint 111 and a silane inlet joint 112 are provided on the furnace inlet flange 11, and both the phosphine inlet joint 111 and the silane inlet joint 112 use VCR joints to connect the corresponding special gas pipelines. The embedded spray pipe 12 includes an arc-shaped inlet pipe 121 and a gas mixing chamber 122, and spray holes are evenly opened on the arc-shaped inlet pipe 121. A sealing plate is welded at one end of the arc-shaped inlet pipe 121, and the other end of the arc-shaped inlet pipe 121 is inserted into the gas mixing chamber 122 for internal welding to form an integral body with the gas mixing chamber 122. Two cylindrical inlet nozzles are welded at the lower part of the gas mixing chamber 122, and the two inlet nozzles are respectively in contact with the phosphine inlet joint 111 and the silane inlet joint 112 through a sealing ring 123 to form a sealed inlet structure.

[0033] Furthermore, the phosphine inlet joint 111 and the silane inlet joint 112 are both welded to the side of the furnace inlet flange 11 in the horizontal direction to ensure that the special gas pipeline is horizontally connected for easy disassembly and assembly. The arc-shaped inlet pipe 121 adopts a 270° arc structure, and spray holes are evenly opened at intervals of 12° on the arc-shaped inlet pipe 121. Silane and phosphine are mixed in the gas mixing chamber 122, and then evenly sprayed into the reaction chamber through the 270° arc-shaped inlet pipe 121, so as to realize the mixed intake of silane and phosphine in the reaction chamber.

[0034] In this embodiment, a stainless steel ferrule joint 114 is provided on the inner side of the bottom of the furnace mouth air inlet flange 11, and a nitrogen-oxygen mixed air inlet joint 113 with horizontal, vertical, and front-to-back directions is welded to the bottom of the furnace mouth air inlet flange 11. The mixed air inlet pipe 13 is connected to the nitrogen-oxygen mixed air inlet joint 113 through the ferrule joint 114. After nitrogen and oxygen are mixed, they are introduced into the reaction chamber from the bottom of the furnace mouth air inlet flange 11.

[0035] Furthermore, the mixed air inlet pipe 13 extends from the furnace mouth of the reaction chamber to the furnace tail, and the mixed air inlet pipe 13 is evenly provided with spray ports at an angle of 120° along the length direction. The spray ports on the mixed air inlet pipe 13 evenly extend from the furnace mouth of the reaction chamber to the furnace tail, so as to achieve uniform intake of nitrogen and oxygen in the entire reaction chamber, thereby ensuring uniform film formation on the surface of the silicon wafer.

[0036] like Figure 5 and Figure 6As shown, a uniform flow heat insulation board group 24 is fixed to the inner side of the furnace tail exhaust flange 21. The uniform flow heat insulation board group 24 is fixed to the inner side of the furnace tail exhaust flange 21 by screws to ensure uniform distribution of gas in the furnace tube to avoid local concentration of gas in the furnace tube. The furnace tail gas supply adopts a layered gas supply structure with two gradients. The gas supply component 2 includes a long gas supply pipe group 22 and a short gas supply pipe group 23. The long gas supply pipe group 22 is installed at the top and the upper middle part of the furnace tail exhaust flange 21, and the short gas supply pipe group 23 is installed at the bottom and the lower middle part of the furnace tail exhaust flange 21. In this embodiment, the gas supply component 2 is located at the tail end of the reaction chamber. Seven flange-type gas supply interfaces are evenly welded in the circumferential direction of the furnace tail exhaust flange 21, which are connected to the long gas supply pipe group 22 and the short gas supply pipe group 23 through a quick-release clamp to realize the tail end gas supply of the reaction chamber.

[0037] In this embodiment, the length of the long gas supply pipe group 22 exceeds the middle of the reaction chamber, and the silane required for the quartz boat coating behind the reaction chamber can be supplemented. The long gas supply pipe group 22 includes a long gas supply pipe 1 221 and a long gas supply pipe 222. The long gas supply pipe 1 221 adopts a single-tube structure, and the long gas supply pipe 222 adopts a pipeline structure divided into two. The long gas supply pipe 1 221 is arranged at the top of the furnace tail exhaust flange 21, and the long gas supply pipe 222 is arranged at the upper middle part of the furnace tail exhaust flange 21.

[0038] In this embodiment, the length of the short gas supply pipe group 23 is shorter than the middle of the reaction chamber, and the silane required for coating of the quartz boat in front of the reaction chamber can be supplemented to avoid the blockage of a certain silane inlet caused by thermal decomposition of silane, resulting in insufficient gas uniformity and affecting the film quality of silicon wafers in the front and rear boats. The short gas supply pipe group 23 includes a short gas supply pipe 1 231 and a short gas supply pipe 2 232. Both the short gas supply pipe 1 231 and the short gas supply pipe 2 232 adopt a pipeline structure divided into two. The short gas supply pipe 1 231 is arranged at the middle and lower part of the exhaust flange 21 at the furnace tail, and the short gas supply pipe 2 232 is arranged at the bottom of the exhaust flange 21 at the furnace tail.

[0039] In this embodiment, the long gas supply pipe 221 is connected to the single gas supply special gas connecting pipe at the top of the furnace tail exhaust flange 21 through a VCR joint, and the long gas supply pipe 222, as well as the short gas supply pipe 231 of the silane short supply and the outside of the bottom short gas supply pipe 2 232 are all connected to the VCR joint one divided into two special gas connecting pipes to realize gas delivery from the gas source to the tail of the reaction chamber.

[0040] The working principle of the gas circuit system in this implementation is:

[0041] Silane (SiH) required for the reaction of coating on the surface of silicon wafer 4 ), phosphine (PH 3 ), nitrogen (N 2 ) and oxygen (O 2) The gas source is connected to the furnace mouth and furnace tail air intake interface of the reaction chamber through a special gas pipeline. Nitrogen and oxygen are mixed in the special gas pipeline outside the reaction chamber and enter through the nitrogen and oxygen mixed air intake joint 113 at the bottom of the furnace mouth air intake flange 11, and then sprayed evenly inside the reaction chamber through the bottom mixed air intake pipe 13; silane and phosphine are mixed in the gas mixing chamber 122 of the embedded spray pipe 12 through the special gas pipeline, and then silane and phosphine are evenly inhaled at the furnace mouth through the spray holes on the arc-shaped air intake pipe 121. Since the thermal decomposition products of silane are easy to cause blockage in the air intake pipe and affect the film quality, the long air supply pipe group 22 and the short air supply pipe group 23 on the air supply component 2 are used at the tail end of the reaction chamber to realize the gradient supplement of silane gas in the front and rear quartz boats in the reaction chamber to ensure the process stability of the equipment.

[0042] Although the utility model is disclosed as above with preferred embodiments, it is not intended to limit the utility model. Any technician familiar with the art can use the above disclosed methods and technical contents to make many possible changes and modifications to the technical solution of the utility model without departing from the spirit and technical solution of the utility model, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the utility model without departing from the content of the technical solution of the utility model still falls within the scope of protection of the technical solution of the utility model.

Claims

1. A LPCVD reaction chamber gas path system, characterized in that: The invention comprises an air intake component (1) connected to a furnace inlet air intake flange (11), and an air supply component (2) connected to a furnace tail exhaust flange (21), wherein the air intake component (1) adopts an embedded spray structure, and the air supply component (2) adopts a stepped layered structure, so as to achieve uniform distribution of gas in the furnace tube of the LPCVD reaction chamber and avoid local concentration of gas in the furnace tube.

2. The LPCVD reaction chamber gas path system according to claim 1, characterized in that: The air intake assembly (1) comprises an embedded spray pipe (12) and a mixed air intake pipe (13); an arc-shaped groove is provided on the inner side of the middle of the furnace inlet flange (11); the embedded spray pipe (12) is nested in the arc-shaped groove; the embedded spray pipe (12) is used to input phosphine gas and silane gas; the mixed air intake pipe (13) is arranged at the bottom of the furnace inlet flange (11); the mixed air intake pipe (13) is used to input a mixed gas of nitrogen and oxygen.

3. The LPCVD reaction chamber gas path system according to claim 2, characterized in that: The gas inlet assembly (1) further comprises a gas supply joint (14), wherein the gas supply joint (14) is arranged on the furnace inlet flange (11), and the gas supply joint (14) is used to supply gas required for the reaction or to balance the gas pressure of the inner and outer quartz tubes of the double quartz tube reaction structure.

4. The LPCVD reaction chamber gas path system according to claim 3, characterized in that: The furnace inlet flange (11) is provided with a phosphine inlet joint (111) and a silane inlet joint (112); the embedded spray pipe (12) comprises an arc-shaped inlet pipe (121) and a gas mixing chamber (122); the arc-shaped inlet pipe (121) is evenly provided with spray holes; a sealing plate is welded to one end of the arc-shaped inlet pipe (121); the other end of the arc-shaped inlet pipe (121) is inserted into the gas mixing chamber (122) for internal welding, and is integrated with the gas mixing chamber (122); two inlet nozzles are welded to the lower part of the gas mixing chamber (122); the two inlet nozzles are respectively in contact with the phosphine inlet joint (111) and the silane inlet joint (112) through sealing rings (123) to form a sealed inlet structure.

5. The LPCVD reaction chamber gas path system according to claim 4, characterized in that: The phosphine air inlet joint (111) and the silane air inlet joint (112) are welded to the side of the furnace inlet flange (11) in the horizontal direction; the arc-shaped air inlet pipe (121) adopts a 270° arc structure, and small spray holes are evenly opened on the arc-shaped air inlet pipe (121) at intervals of 12°.

6. The LPCVD reaction chamber gas path system according to claim 3, characterized in that: A ferrule joint (114) is provided on the inner side of the bottom of the furnace inlet flange (11), a nitrogen-oxygen mixed inlet joint (113) is provided on the outer side of the bottom of the furnace inlet flange (11), and the mixed inlet pipe (13) is connected to the nitrogen-oxygen mixed inlet joint (113) via the ferrule joint (114) to realize the transportation of nitrogen and oxygen mixed gas.

7. The LPCVD reaction chamber gas path system according to claim 6, characterized in that: The mixing air inlet pipe (13) extends from the furnace opening of the reaction chamber to the furnace tail, and the mixing air inlet pipe (13) is evenly provided with spray openings with an angle of 120 degrees along the length direction.

8. The LPCVD reaction chamber gas path system according to any one of claims 1 to 7, characterized in that: A uniform flow insulation board group (24) is fixed on the inner side of the furnace tail exhaust flange (21); the air supply component (2) comprises a long air supply pipe group (22) and a short air supply pipe group (23), wherein the long air supply pipe group (22) is installed at the top and the upper middle part of the furnace tail exhaust flange (21), and the short air supply pipe group (23) is installed at the bottom and the lower middle part of the furnace tail exhaust flange (21).

9. The LPCVD reaction chamber gas path system according to claim 8, characterized in that: The length of the long gas supply pipe group (22) exceeds the middle of the reaction chamber; the long gas supply pipe group (22) comprises a long gas supply pipe 1 (221) and a long gas supply pipe 2 (222); the long gas supply pipe 1 (221) adopts a single-pipe structure, and the long gas supply pipe 2 (222) adopts a pipeline structure divided into two; the long gas supply pipe 1 (221) is arranged at the top of the furnace tail exhaust flange (21), and the long gas supply pipe 2 (222) is arranged at the middle and upper part of the furnace tail exhaust flange (21).

10. The LPCVD reaction chamber gas path system according to claim 8, characterized in that: The length of the short air supply pipe group (23) is shorter than the middle of the reaction chamber; the short air supply pipe group (23) comprises a short air supply pipe 1 (231) and a short air supply pipe 2 (232); the short air supply pipe 1 (231) and the short air supply pipe 2 (232) both adopt a pipeline structure divided into two parts; the short air supply pipe 1 (231) is arranged at the middle and lower part of the furnace tail exhaust flange (21), and the short air supply pipe 2 (232) is arranged at the bottom of the furnace tail exhaust flange (21).

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