A modification method for coupling solid slag discharge with liquid slag discharge in drum boiler

Abstract

A method for modifying a drum boiler by coupling solid slag removal with liquid slag removal belongs to the technical field of liquid slag removal boilers. The purpose of the present invention is to modify the local structure of an existing solid slag removal boiler to liquid slag removal. In order to solve the serious coking and contamination problems that occur when burning highly coking coals such as Zhundong coal, the present invention, without changing the original boiler combustion and slag removal methods, adds a vertical post-furnace to the exterior of the furnace, replacing a portion of the original boiler's burners. The lower outlet of the vertical post-furnace is connected and communicated with the lower part of the original boiler furnace by welding. The inner wall of the vertical post-furnace combustion chamber is completely covered with refractory castables, raising the temperature in the combustion chamber, melting the ash and achieving liquid slag removal. A swirl burner is used to increase the effect of liquid slag wall rejection. This solution of converting solid slag removal to local liquid slag removal is flexible and convenient. The present invention is mainly used to improve the existing solid slag removal method of drum boilers.

Description

Technical Field

[0001] The invention relates to the technical field of liquid slagging boilers, and in particular to a transformation method for coupling solid slagging with liquid slagging in a drum boiler. Background Art

[0002] my country has abundant reserves of Zhundong coal, which is inexpensive. Converting existing boilers to burn Zhundong coal would significantly reduce coal costs and improve economic efficiency. Zhundong coal has a high alkali metal content and presents serious slagging and fouling issues. Many boilers converted to burning Zhundong coal have experienced varying degrees of slagging and fouling, with frequent damage to the ash hopper water-cooled walls, malfunctions in the slag removal system, and flue blockages, forcing boiler shutdowns in severe cases. Liquid slagging boilers have a high slag capture rate, trapping most low-melting-point alkali metal components in the slag, reducing the ash content in the flue gas, particularly the alkali metal content, and preventing coking and fouling of the furnace and heating surfaces. Liquid slagging is an effective way to address the coking and fouling issues associated with boilers burning highly coking coals. Summary of the Invention

[0003] The purpose of the present invention is to transform the local structure of an existing solid slag discharge boiler into a liquid slag discharge system to solve the serious coking and contamination problems that occur when burning strong coking coals such as Zhundong coal. A method for transforming a drum boiler from solid slag discharge to liquid slag discharge is proposed.

[0004] A method for transforming a drum boiler by coupling solid slag discharge with liquid slag discharge is achieved by the following steps:

[0005] The slag hopper is inserted into the slag discharge port, and the outer wall of the slag hopper is fixed to the inner wall of the slag discharge port, and the slag hopper is fixed to the inner wall of the slag discharge port, and the slag hopper is inserted into the slag discharge port, and the outer wall of the slag hopper is fixed to the inner wall of the slag discharge port, and the slag hopper is inserted into the slag discharge port, and the outer wall of the slag hopper is fixed to the inner wall of the slag discharge port, and the slag catching pipe is set at the outlet end of the combustion chamber, and the outer wall of the slag catching pipe is fixedly connected to the inner wall of the outlet end of the combustion chamber, and the combustion chamber and the slag catching pipe replace one or more layers of burners in the original boiler structure and are connected to the pulverized coal pipeline of the pulverizer;

[0006] Step 2: In step 1, water-cooled membrane tube panels are arranged around the combustion chamber, and a water-cooled membrane tube panel inlet header is installed at the inlet of the water-cooled membrane tube panel, and a water-cooled membrane tube panel outlet header is installed at the outlet of the water-cooled membrane tube panel;

[0007] Step 3: Install an inlet connecting pipe between the water-cooled membrane tube panel inlet header and the original boiler economizer in step 2, and weld one end of the inlet connecting pipe to the water-cooled membrane tube panel inlet header, while welding the other end of the inlet connecting pipe to the water outlet of the original boiler economizer.

[0008] Step 4: Install an outlet connecting pipe between the water-cooled membrane tube panel outlet header in step 2 and the steam drum in the original boiler structure, and weld one end of the outlet connecting pipe to the water-cooled membrane tube panel outlet header and fix it. At the same time, weld the other end of the outlet connecting pipe to the water inlet end of the steam drum and fix it. The original boiler structure is connected to the economizer by replacing the original economizer outlet connecting pipe through the structure consisting of the inlet connecting pipe, the outlet connecting pipe and the vertical post-furnace;

[0009] Step 5: Arrange a downcomer between the steam drum in step 4 and the water-cooled wall in the original boiler structure, weld the water inlet end of the downcomer to the water outlet end of the steam drum, weld the water outlet end of the downcomer to the bottom water inlet end of the water-cooled wall, and connect the top water outlet end of the water-cooled wall to the water inlet end of the steam drum through a pipe;

[0010] Furthermore, the cross section of the combustion chamber in step 1 is rectangular, and the perimeter of the combustion chamber is surrounded by a water-cooled membrane tube panel, which is covered with pins on the fire side and covered with refractory castables;

[0011] Furthermore, in the step 1, the front and rear walls of the lower portion of the combustion chamber are inclined inwardly to form a constriction, and the angle between the inwardly inclined surfaces of the front and rear walls and the vertical direction is between 15° and 40°;

[0012] Furthermore, the slag catching pipes provided at the outlet of the combustion chamber in said step 1 are arranged in a staggered or in-line manner;

[0013] Furthermore, the bottom of the combustion chamber in step 1 is a conical slag hopper, the lowest position of the slag hopper has a slag discharge port, the slag hopper has an inclined bottom, and the angle with the horizontal direction is between 0° and 25°;

[0014] Furthermore, in the step 1, the vertical post-furnace is located behind the original boiler furnace, the outlet of the combustion chamber is tilted upward and connected to the cold ash hopper on the rear wall of the original boiler furnace, and a window is provided on the water-cooled wall at the connection position of the cold ash hopper on the rear wall of the furnace to connect the furnace and the combustion chamber;

[0015] Furthermore, in the step 2, the water-cooled membrane tube panel at the periphery of the combustion chamber adopts a direct current method, the lower part of the water-cooled membrane tube panel is a straight tube panel, and the upper part is a spiral tube panel;

[0016] Furthermore, one or more vertical post-furnaces in step 1 may be arranged along the circumference of the original boiler furnace;

[0017] Furthermore, the vertical post-furnace in step 1 can be replaced by a vertical cyclone furnace, and the combustion chamber of the vertical cyclone furnace is a cylindrical structure;

[0018] Furthermore, the inlet connecting pipe in step 3 and step 4 can be replaced with a downcomer connecting pipe, one end of the downcomer connecting pipe is welded and fixed to the water-cooled membrane tube panel inlet header, and the other end of the downcomer connecting pipe is welded and fixed to the downcomer, and the original economizer outlet connecting pipe in the original boiler structure is used to connect the economizer and the steam drum;

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The invention relates to a modification method for coupling solid slag discharge with liquid slag discharge of a drum boiler. On the basis of not changing the combustion mode and slag discharge mode of the original boiler, a vertical post-furnace is designed to be added outside the furnace to replace a part of the burners of the original boiler. The lower outlet of the vertical post-furnace is connected and communicated with the lower part of the furnace of the original boiler by welding. The inner wall of the combustion chamber of the vertical post-furnace is completely covered with refractory castables, which increases the temperature in the combustion chamber, melts the ash, and realizes liquid slag discharge. A swirl burner is used to increase the wall-swinging effect of the liquid slag. The high-temperature flue gas generated by the combustion in the combustion chamber of the vertical post-furnace enters the furnace of the original boiler after passing through a slag catching pipe and is mixed with the high-temperature flue gas generated by the combustion in the furnace of the original boiler. This scheme of changing from solid slag discharge to local liquid slag discharge is flexible and convenient, and the method is unique and ingenious. After the modification, Zhundong coal with extremely strong coking property or other coal with low ash melting point is burned in the vertical post-furnace. The high slag catching rate of the liquid slag discharge method is utilized to reduce the dust content of the flue gas at the furnace outlet, and prevent slagging and contamination of the furnace and other heating surfaces. Through the coupling of solid slag discharge and liquid slag discharge, the original boiler can burn strong coking coal such as Zhundong coal, reducing fuel costs and improving operating economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the original drum boiler;

[0022] Figure 2 This is a structural diagram of a neutral post-furnace in a drum boiler solid slag removal coupled with liquid slag removal modification method proposed by the present invention;

[0023] Figure 3 The schematic diagram of the boiler layout after the transformation is formed by combining a vertical post-furnace with the original boiler structure using a transformation method of solid slag removal coupled with liquid slag removal proposed by the present invention;

[0024] Figure 4 This is a schematic diagram of a boiler system after being modified using the modification method for coupling solid slag discharge with liquid slag discharge proposed in the present invention (the original boiler structure is connected to the economizer by replacing the original economizer outlet connecting pipe through a structure consisting of an inlet connecting pipe, an outlet connecting pipe and a vertical post-furnace).

[0025] Figure 5 This is a schematic diagram of a boiler system after being modified using the modification method for coupling solid slag discharge with liquid slag discharge of a drum boiler proposed in the present invention (the inlet connecting pipe is replaced with a downcomer connecting pipe to connect the vertical post-furnace to the downcomer, and the original boiler structure is connected to the economizer using the original economizer outlet connecting pipe). DETAILED DESCRIPTION

[0026] Specific implementation method 1: refer to Figures 1 to 5 This embodiment describes a method for modifying a drum boiler by coupling solid slag discharge with liquid slag discharge, and the method is implemented by the following steps:

[0027] Step 1: A liquid slag discharge vertical post-furnace is set outside the original solid slag discharge drum boiler furnace. The vertical post-furnace includes a combustion chamber 1, a swirl burner 2, a slag catching pipe 3, a slag hopper 4 and a slag discharge port 5. The combustion chamber 1 is a J-shaped combustion chamber. The outlet end of the combustion chamber 1 is connected to the lower part of the original solid slag discharge drum boiler furnace. The outlet wall of the combustion chamber 1 is welded to the outer wall of the original solid slag discharge drum boiler furnace. The swirl burner 2 is inverted on the outer top of the combustion chamber 1, and the shell of the swirl burner 2 is connected to the outer wall of the combustion chamber 1. The outer top is fixedly welded, the combustion end of the swirl burner 2 is arranged inside the combustion chamber 1, a slag discharge port 5 is processed at the bottom of the bent pipe section in the combustion chamber 1, the slag inlet end of the slag hopper 4 is inserted into the slag discharge port 5, and the outer wall of the slag inlet end of the slag hopper 4 is welded and fixed to the inner wall of the slag discharge port 5, the slag catching pipe 3 is arranged at the outlet end of the combustion chamber 1, and the outer wall of the slag catching pipe 3 is fixedly connected to the inner wall of the outlet end of the combustion chamber 1, the combustion chamber 1 and the swirl burner 2 replace one or more layers of burners 8 in the original boiler structure and are connected to the pulverized coal pipeline of the pulverizer;

[0028] Step 2: In step 1, water-cooled membrane tube panels are arranged around the perimeter of the combustion chamber 1, and a water-cooled membrane tube panel inlet header 12 is installed at the inlet of the water-cooled membrane tube panel, and a water-cooled membrane tube panel outlet header 13 is installed at the outlet of the water-cooled membrane tube panel;

[0029] Step 3: Install an inlet connecting pipe 11 between the water-cooled membrane tube panel inlet header 12 and the original boiler economizer in step 2, and weld one end of the inlet connecting pipe 11 to the water-cooled membrane tube panel inlet header 12, while welding the other end of the inlet connecting pipe 11 to the water outlet of the original boiler economizer.

[0030] Step 4: Install an outlet connecting pipe 14 between the water-cooled membrane tube panel outlet header 13 in step 2 and the steam drum 6 in the original boiler structure. One end of the outlet connecting pipe 14 is welded and fixed to the water-cooled membrane tube panel outlet header 13. At the same time, the other end of the outlet connecting pipe 14 is welded and fixed to the water inlet end of the steam drum 6. The original boiler structure is connected to the economizer by replacing the original economizer outlet connecting pipe 10 through the structure consisting of the inlet connecting pipe 11, the outlet connecting pipe 14 and the vertical post-furnace.

[0031] Step 5: In step 4, a downcomer 9 is arranged between the steam drum 6 and the water-cooled wall 7 in the original boiler structure. The water inlet end of the downcomer 9 is welded and connected to the water outlet end of the steam drum 6, and the water outlet end of the downcomer 9 is welded and connected to the bottom water inlet end of the water-cooled wall 7. The top water outlet end of the water-cooled wall 7 is connected to the water inlet end of the steam drum 6 through a pipe.

[0032] This specific implementation method, without changing the original boiler's combustion and slagging methods, achieves localized liquid slagging by adding a vertical post-furnace to the exterior of the furnace, replacing a portion of the original boiler's burners. This modification scheme is flexible and convenient, and the method is unique and ingenious. After the modification, the vertical post-furnace burns highly coking Zhundong coal or other coals with low ash melting points. The high slag capture rate of liquid slagging reduces the dust content of the flue gas at the furnace outlet, preventing slagging and contamination of the furnace and other heating surfaces. By coupling solid and liquid slagging, the original boiler can now burn highly coking coals such as Zhundong coal, reducing fuel costs and improving operational economy.

[0033] In this embodiment, the heat load of the combustion chamber 1 in the vertical post-furnace is much higher than that of a normal solid slag discharge boiler, thereby increasing the flue gas temperature in the combustion chamber 1. After the pulverized coal is burned in the combustion chamber 1 of the vertical post-furnace, the ash is converted into molten liquid slag. The high-temperature flue gas generated by the combustion passes through the slag catcher 3 and enters the original boiler furnace, where it mixes with the high-temperature flue gas generated by the combustion in the original boiler furnace. The original boiler furnace is still in solid slag discharge. This modification method realizes local liquid slag discharge on the solid slag discharge boiler, organically combining the liquid slag discharge method and the solid slag discharge method.

[0034] The original solid slag discharge drum boiler in this embodiment adopts a Π-type arrangement or a tower arrangement, a natural circulation or a controlled circulation drum boiler, and the combustion method adopts a tangential combustion or a counter combustion method. The original boiler mainly includes a drum 6, a water-cooled wall 7, a burner 8, a downcomer 9, and an economizer outlet connecting pipe 10. The original boiler economizer outlet connecting pipe 10 connects the economizer and the drum 6. This transformation method changes the connection of the original boiler economizer from the economizer outlet connecting pipe 10 to the drum 6 to be connected to the combustion chamber 1 water-cooled membrane tube panel inlet header 12 by the connecting pipe 11, and connects the combustion chamber 1 water-cooled membrane tube panel outlet header 13 to the drum 6 through the outlet connecting pipe 14. In addition, the cooling water of the combustion chamber 1 can also be taken from the economizer inlet feed water pipe or the feed water heater front pipe and other locations;

[0035] In this embodiment, the vertical post-furnace combustion chamber 1 is J-shaped, and the swirl burner 2 is inverted on the top of the combustion chamber 1 to facilitate the downward flow of flue gas in the combustion chamber 1. This modification method realizes a double-circulation membrane type with direct current and circulation in parallel in the drum boiler water circulation system.

[0036] Specific implementation method 2: refer to Figures 1 to 5 This embodiment differs from the first embodiment in that the combustion chamber 1 in step 1 has a rectangular cross-section and is surrounded by a water-cooled membrane tube panel. These panels are doweled and covered with refractory castable material on the fire side. The remaining steps are the same as those in the first embodiment.

[0037] In this embodiment, the cross-section of the combustion chamber 1 is rectangular, and the periphery of the combustion chamber 1 is surrounded by a water-cooled membrane tube panel. The water-cooled membrane tube panel is covered with pins on the fire side and covered with refractory castables, thereby reducing heat absorption in the combustion chamber 1, further increasing the flue gas temperature in the combustion chamber 1, and forming a stable liquid slag film on the inner wall of the combustion chamber 1.

[0038] Specific implementation method three: refer to Figures 1 to 5 This embodiment differs from the second embodiment in that, in step one, the front and rear walls of the lower portion of the combustion chamber 1 are inclined inward to form a constriction, with the angle between the inwardly inclined surfaces of the front and rear walls and the vertical direction being between 15° and 40°. The remaining steps are the same as those of the second embodiment.

[0039] With such arrangement, the front and rear walls at the lower portion of the combustion chamber 1 are inclined inwardly to form a constriction, which can facilitate better circulation of the flue gas.

[0040] Specific implementation method four: refer to Figures 1 to 5 This embodiment is different from the third embodiment in that the slag catching pipes 3 provided at the outlet of the combustion chamber 1 in step 1 are arranged in a staggered or sequential manner. The other steps are the same as those in the third embodiment.

[0041] In this embodiment, a slag catching pipe 3 is provided at the outlet of the combustion chamber 1 . The slag catching pipe 3 is arranged in a staggered or sequential manner. The number of longitudinal rows of the slag catching pipes is no less than 2 and no more than 6.

[0042] Specific implementation method five: refer to Figures 1 to 5 This embodiment differs from the fourth embodiment in that, in step one of this embodiment, the bottom of the combustion chamber 1 is provided with a conical hopper 4, which has a slag discharge port 5 at its lowest point. The hopper 4 has an inclined bottom, with an angle between 0° and 25° with respect to the horizontal. The remaining steps are the same as those of the fourth embodiment.

[0043] Such arrangement, through the inclined bottom arrangement of the slag hopper 4, can facilitate better slag discharge when the boiler is working.

[0044] Specific implementation method six: refer to Figures 1 to 5 This embodiment differs from Specific Embodiment 5 in that, in step 1, the vertical post-furnace is located behind the original boiler furnace. The outlet of the combustion chamber 1 is tilted upward and connected to the cold ash hopper 7-1 on the rear wall of the original boiler furnace. A window is provided in the water-cooled wall 7 at the connection point of the cold ash hopper 7-1 on the rear wall of the furnace, connecting the furnace and the combustion chamber 1. The remaining steps are the same as those in Specific Embodiment 5.

[0045] In this embodiment, the vertical rear furnace is located behind the original boiler furnace, and the outlet of the J-shaped combustion chamber 1 is tilted upward and connected to the cold ash hopper 7-1 on the rear wall of the original boiler furnace. A window is opened in the water-cooled wall at the connection position of the cold ash hopper 7-1 on the rear wall of the furnace, connecting the furnace and the J-shaped combustion chamber 1. The design of the J-shaped combustion chamber forms a turn of more than 90° at the bottom of the combustion chamber 1, which enhances the separation effect of liquid slag from the flue gas and improves the slag capture rate. In addition, the upward tilt of the outlet is conducive to the reflux of liquid slag, preventing liquid slag from flowing into the original boiler cold ash hopper.

[0046] Specific implementation method seven: refer to Figures 1 to 5 This embodiment differs from Specific Embodiment 6 in that the water-cooled membrane tube panels surrounding the combustion chamber 1 in step 2 of this embodiment employ a direct current method. The lower portion of the water-cooled membrane tube panels are straight, while the upper portion is spiral. The remaining steps are identical to Specific Embodiment 6.

[0047] In this embodiment, the water-cooled membrane tube panels in combustion chamber 1 utilize a direct flow system. After passing through the economizer, the feedwater enters the water-cooled membrane tube panel inlet header 12 of combustion chamber 1 through connecting pipe 11. It then flows through the panels once in a direct flow system, entering steam drum 6 through outlet connecting pipe 14. The water in steam drum 6 circulates through downcomers 9 and water-cooled walls 7 before returning to steam drum 6. This achieves a dual-circulation membrane system with direct flow and reverse flow in the drum boiler water circulation system. The spiral tube panels, which wrap around combustion chamber 1 for more than one turn, effectively reduce heat absorption deviations in the panels, improving wall temperature uniformity and adaptability to variable loads.

[0048] Specific implementation method eight: refer to Figures 1 to 5 This embodiment is different from the seventh embodiment in that one or more vertical post-furnaces in step one of this embodiment can be arranged along the circumference of the original boiler furnace. The other method steps are the same as those in the seventh embodiment.

[0049] In this embodiment, when there are multiple vertical post-furnaces, the multiple vertical post-furnaces can be arranged in any direction around the original boiler furnace, and the names can be renamed according to the arrangement orientation, such as vertical front furnace, vertical side furnace, etc. The water-cooled membrane tube panel of the combustion chamber 1 in each furnace body is a vertical tube panel type or a spiral tube panel type.

[0050] Specific implementation method nine: refer to Figures 1 to 5 This embodiment is different from the eighth embodiment in that the vertical post-furnace in step one of this embodiment can be replaced with a vertical cyclone furnace, and the combustion chamber of the vertical cyclone furnace is a cylindrical structure. The other method steps are the same as the eighth embodiment.

[0051] Specific implementation method ten: refer to Figures 1 to 5 This embodiment differs from the ninth embodiment in that the inlet connecting pipe 11 in steps three and four of this embodiment is replaced with a downcomer connecting pipe 15. One end of the downcomer connecting pipe 15 is welded and fixed to the water-cooled membrane tube panel inlet header 12, while the other end of the downcomer connecting pipe 15 is welded and fixed to the downcomer 9. The economizer outlet connecting pipe 10 in the original boiler structure is used to connect the economizer and the steam drum 6. The remaining steps are the same as those in the ninth embodiment.

[0052] In this embodiment, the water-cooled membrane tube panel of the combustion chamber 1 adopts a natural circulation or controlled circulation mode. The downcomer 9 of the original boiler and the water-cooled membrane tube panel inlet header 12 of the combustion chamber are connected through the downcomer connecting pipe 15. The outlet connecting pipe 14 connects the water-cooled membrane tube panel outlet header 13 and the steam drum 6. The water-cooled membrane tube panel adopts a vertical tube panel structure.

[0053] The present invention has been disclosed as above with reference to preferred embodiments, but this is not intended to limit the present invention. Any technician familiar with the present invention can make slight changes or modifications to equivalent embodiments using the above-disclosed structures and technical contents without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for modifying a drum boiler by coupling solid slag removal with liquid slag removal, characterized by: The method is achieved by the following steps: Step 1: a liquid slag discharge vertical post-furnace is arranged outside the furnace of the original solid slag discharge drum boiler, the vertical post-furnace comprises a combustion chamber (1), a swirl burner (2), a slag catching pipe (3), a slag bucket (4) and a slag discharge port (5), the combustion chamber (1) is a J-shaped combustion chamber, the outlet end of the combustion chamber (1) is connected to the lower part of the furnace of the original solid slag discharge drum boiler, the outlet wall of the combustion chamber (1) is welded to the outer wall of the furnace of the original solid slag discharge drum boiler, the swirl burner (2) is inverted on the outer top of the combustion chamber (1), and the shell of the swirl burner (2) is fixed to the outer top of the combustion chamber (1). Fixed welding, the combustion end of the swirl burner (2) is arranged inside the combustion chamber (1), a slag discharge port (5) is processed at the bottom of the bent pipe section in the combustion chamber (1), the slag inlet end of the slag bucket (4) is inserted into the slag discharge port (5), and the outer wall of the slag inlet end of the slag bucket (4) is welded and fixed to the inner wall of the slag discharge port (5), the slag catching pipe (3) is arranged at the outlet end of the combustion chamber (1), and the outer wall of the slag catching pipe (3) is fixedly connected to the inner wall of the outlet end of the combustion chamber (1), and the combustion chamber (1) and the swirl burner (2) replace one or more layers of burners (8) in the original boiler structure and are connected to the coal mill coal pulverized pipe; The vertical post-furnace is located behind the original boiler furnace, the outlet of the combustion chamber (1) is tilted upward and connected to the cold ash hopper (7-1) on the rear wall of the original boiler furnace, and a window is provided on the water-cooled wall (7) at the connection position of the cold ash hopper (7-1) on the rear wall of the furnace to connect the furnace and the combustion chamber (1); The cross section of the combustion chamber (1) is rectangular, and the periphery of the combustion chamber (1) is surrounded by a water-cooled membrane tube panel, which is covered with pins on the fire side and covered with refractory castables; The front and rear walls of the lower part of the combustion chamber (1) are inclined inwards to form a constriction, and the angle between the inward inclined surfaces of the front and rear walls and the vertical direction is between 15° and 40°; The slag catching pipe (3) provided at the outlet of the combustion chamber (1) is arranged in a staggered or sequential manner; The bottom of the combustion chamber (1) is a conical slag hopper (4), the lowest position of the slag hopper (4) is provided with a slag discharge port (5), and the slag hopper (4) has an inclined bottom, and the angle with the horizontal direction is between 0° and 25°; Step 2: In step 1, a water-cooled membrane tube panel is arranged around the periphery of the combustion chamber (1), and a water-cooled membrane tube panel inlet header (12) is installed at the inlet of the water-cooled membrane tube panel, and a water-cooled membrane tube panel outlet header (13) is installed at the outlet of the water-cooled membrane tube panel; The water-cooled membrane tube panel on the periphery of the combustion chamber (1) adopts a direct current method, the lower part of the water-cooled membrane tube panel is a straight tube panel, and the upper part is a spiral tube panel; Step 3: in step 2, an inlet connecting pipe (11) is provided between the water-cooled membrane tube panel inlet header (12) and the original boiler economizer, and one end of the inlet connecting pipe (11) is welded and connected to the water-cooled membrane tube panel inlet header (12), and at the same time, the other end of the inlet connecting pipe (11) is welded and connected to the water outlet end of the original boiler economizer; Step 4: In step 2, an outlet connecting pipe (14) is provided between the water-cooled membrane tube panel outlet header (13) and the steam drum (6) in the original boiler structure, and one end of the outlet connecting pipe (14) is welded and connected to the water-cooled membrane tube panel outlet header (13), and the other end of the outlet connecting pipe (14) is welded and connected to the water inlet end of the steam drum (6). The original boiler structure is connected to the economizer by replacing the original economizer outlet connecting pipe (10) with the structure composed of the inlet connecting pipe (11), the outlet connecting pipe (14) and the vertical post-furnace; Step 5: In step 4, a downcomer (9) is arranged between the steam drum (6) and the water-cooled wall (7) in the original boiler structure. The water inlet end of the downcomer (9) is connected and fixed to the water outlet end of the steam drum (6) by welding. The water outlet end of the downcomer (9) is connected and fixed to the bottom water inlet end of the water-cooled wall (7) by welding. The top water outlet end of the water-cooled wall (7) is connected and arranged to the water inlet end of the steam drum (6) through a pipeline.

2. The method for transforming a drum boiler by coupling solid slag removal with liquid slag removal according to claim 1, characterized in that: The vertical post-furnace in step 1 can be arranged one or more along the circumference of the original boiler furnace.

3. The method for modifying a drum boiler by coupling solid slag removal with liquid slag removal according to claim 2, characterized in that: The vertical post-furnace in step 1 can be replaced by a vertical cyclone furnace, and the combustion chamber of the vertical cyclone furnace is a cylindrical structure.

4. The method for modifying a drum boiler by coupling solid slag removal with liquid slag removal according to claim 1, characterized in that: The inlet connecting pipe (11) in step 3 and step 4 can be replaced by a downcomer connecting pipe (15), one end of the downcomer connecting pipe (15) is welded and connected to the water-cooled membrane tube panel inlet header (12), and the other end of the downcomer connecting pipe (15) is welded and connected to the downcomer (9), and the original economizer outlet connecting pipe (10) in the original boiler structure is used to connect the economizer and the steam drum (6).

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