A modification method for coupling solid slag discharge with liquid slag discharge in a once-through boiler
By designing a liquid slag discharge vertical furnace outside the direct current boiler, the coupling of solid and liquid slag discharge is achieved, which solves the slagging and contamination problems when the boiler burns Zhundong coal, and improves the operating stability and economy of the boiler.
Patent Information
- Application Number
- CN202210954998.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-08-10
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2042-08-10
AI Technical Summary
Existing boilers have serious slagging and fouling problems when burning Zhundong coal, which causes damage to the water-cooled wall of the ash hopper and failure of the slagging system, affecting the stability and economy of boiler operation.
A liquid slag discharge vertical furnace is designed outside the direct current boiler, including a combustion chamber, a swirl burner and a slag hopper. The slag is melted into liquid by the swirl burner and discharged toward the inner wall by the centrifugal effect of the swirl, where it is mixed with the original boiler flue gas to achieve coupling of solid and liquid slag discharge. The high slag capture rate of liquid slag discharge is utilized to reduce the alkali metal content and dust content in the flue gas.
It can effectively prevent coking and fouling of furnace and heating surface, reduce fuel cost, improve the economic efficiency of boiler operation, and is suitable for burning coal with strong coking property such as Zhundong coal.
Smart Images
Figure CN115654480B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of liquid slag discharge boilers, and in particular to a method for transforming solid slag discharge coupled with liquid slag discharge in a once-through boiler. Background Art
[0002] my country has abundant reserves of Zhundong coal and it is cheap. If existing boilers can be converted to burn Zhundong coal, the cost of coal burning will be greatly reduced and the economy will be improved. Zhundong coal has a high alkali metal content and has serious slagging and fouling problems. After many boilers were converted to burn Zhundong coal, slagging and fouling occurred to varying degrees. The cold ash hopper water-cooled wall was frequently damaged, and the slag removal system failed to operate and the flue was blocked. In serious cases, the boiler was forced to shut down. Patent document CN112944331A relates to a liquid slagging conversion method for a solid slagging coal-fired boiler. The liquid slagging conversion is achieved by lowering the overall position of the burner, reducing the distance between the primary air nozzles of the four-corner cut-circle burner or the distance between the centers of each swirl burner, and setting a tapered furnace arch above the burner area. This document is completely converted to liquid slagging. Summary of the Invention
[0003] To overcome the shortcomings of existing technologies, this invention provides a method for modifying a once-through boiler by coupling solid-state slag removal with liquid slag removal. This method, based on a solid-state slag removal once-through boiler, partially converts it to liquid slag removal, solving the severe coking and fouling problems that occur when burning highly coking coals such as Zhundong coal.
[0004] A method for modifying a once-through boiler by coupling solid slag discharge with liquid slag discharge comprises the following steps:
[0005] A liquid slag discharge vertical furnace is designed outside the original once-through boiler furnace. The liquid slag discharge vertical furnace includes a combustion chamber, a swirl burner, a slag catcher pipe and a slag hopper. The swirl burner is inverted at the top of the combustion chamber, and the slag hopper is located at the bottom of the combustion chamber.
[0006] The outlet of the vertical furnace is connected to the lower part of the original once-through boiler furnace. A part of the pulverized coal is burned in the combustion chamber of the vertical furnace. The ash slag formed is a melted liquid slag. Under the centrifugal action of the swirl burner, the liquid slag is thrown to the inner wall and discharged through the slag hopper.
[0007] The high-temperature flue gas generated by combustion in the vertical furnace enters the furnace of the original direct current boiler through the slag catching pipe and mixes with the high-temperature flue gas generated by combustion in the furnace of the original direct current boiler. The furnace of the original direct current boiler is still solid slag discharge, and local liquid slag discharge is realized on the solid slag discharge boiler, and liquid slag discharge and solid slag discharge are coupled.
[0008] The beneficial effects of the present invention compared to the prior art are:
[0009] The present invention overcomes the shortcomings of the prior art. On the basis of not changing the combustion mode and slag discharge mode of the original boiler, a vertical furnace (rear-mounted, front-mounted or side-mounted) is added to the outside of the furnace to replace a part of the burners of the original boiler. The lower outlet of the vertical furnace is connected and communicated with the lower part of the original boiler furnace by welding. The inner wall of the combustion chamber of the vertical furnace is completely covered with refractory castables, which increases the temperature in the combustion chamber, melts the ash, and realizes liquid slag discharge, while the furnace of the original boiler is still solid slag discharge. Through the coupling of solid slag discharge and liquid slag discharge, the original boiler can burn strong coking coal such as Zhundong coal on the basis of burning the original fuel. After the transformation, Zhundong coal with extremely strong coking property or other coal with low ash melting point is burned in the vertical furnace. The high slag capture rate of the liquid slag discharge method is utilized to reduce the content of alkali metal substances, reduce the dust content of the flue gas at the furnace outlet, prevent the furnace and other heating surfaces from coking and contamination, reduce fuel costs, and improve operating economy.
[0010] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments: BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 This is a schematic diagram of the original once-through boiler;
[0012] Figure 2 It is a schematic diagram of the vertical post-furnace of the present invention;
[0013] Figure 3 Schematic diagram of boiler layout after transformation of the solid slag discharge coupled with liquid slag discharge method of a once-through boiler according to the present invention;
[0014] Figure 4 This is a schematic diagram of a boiler system after the transformation method of the present invention for coupling solid slag discharge with liquid slag discharge for a once-through boiler. DETAILED DESCRIPTION
[0015] The following embodiments of the technical solution of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only examples and are not intended to limit the scope of protection of the present invention.
[0016] It should be noted that, unless otherwise specified, the technical or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.
[0017] A method for modifying a once-through boiler by coupling solid slag discharge with liquid slag discharge in this embodiment includes the following steps:
[0018] A liquid slag discharge vertical furnace is designed outside the original once-through boiler furnace. The liquid slag discharge vertical furnace includes a combustion chamber 1, a swirl burner 2, a slag catching pipe 3 and a slag hopper 4. The swirl burner 2 is inverted on the top of the combustion chamber 1, and the slag hopper 4 is located at the bottom of the combustion chamber 1.
[0019] The outlet of the vertical furnace is connected to the lower part of the original once-through boiler furnace. A portion of the pulverized coal is burned in the combustion chamber 1 of the vertical furnace. The ash formed is a melted liquid slag. Under the centrifugal action of the swirl burner 2, the liquid slag is thrown toward the inner wall and discharged through the slag hopper 4.
[0020] The high-temperature flue gas generated by combustion in the vertical furnace enters the furnace of the original direct current boiler through the slag-catching pipe 3, and is mixed with the high-temperature flue gas generated by combustion in the furnace of the original direct current boiler. The furnace of the original direct current boiler is still solid slag discharge, and local liquid slag discharge is achieved on the solid slag discharge boiler. The liquid slag discharge and the solid slag discharge are coupled, so that the original direct current boiler can burn Zhundong coal with strong coking properties or coal with a low ash melting point on the basis of burning the original fuel.
[0021] The present embodiment does not change the original direct current boiler combustion mode and slag discharge mode, but adds a matching vertical furnace (rear furnace, front furnace or side furnace) to the outside of the furnace to replace part of the burners of the original direct current boiler. The lower outlet of the vertical furnace is connected and communicated with the lower part of the original direct current boiler furnace (the connection can be made by welding). A swirl burner is used to increase the liquid slag wall throwing effect, which is convenient for forming a stable liquid slag film and facilitating slag discharge. The high-temperature flue gas generated by the combustion in the combustion chamber of the vertical furnace passes through the slag catching pipe and enters the original boiler furnace, where it is mixed with the high-temperature flue gas generated by the combustion in the original boiler furnace. This solution of changing from solid slag discharge to local liquid slag discharge is flexible and convenient, and the method is unique and ingenious. After the transformation, the vertical rear furnace is burned with highly coking Zhundong coal or other coal with a low ash melting point. The high slag capture rate of the liquid slag discharge method is used to reduce the dust content of the flue gas at the furnace outlet, and prevent slagging and contamination of the furnace and other heated 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.
[0022] As a possible implementation, Figure 2-Figure 4 As shown, the combustion chamber 1 is J-shaped. The J-shaped combustion chamber design forms a bend exceeding 90° at the bottom of the combustion chamber 1, enhancing the separation of liquid slag from flue gas and improving the slag capture rate. Flue gas flows downward within the combustion chamber 1 , which has a rectangular cross-section. The combustion chamber 1 is surrounded by a water-cooled membrane tube panel. This water-cooled membrane tube panel is covered with refractory castables on the fire side, reducing heat absorption within the combustion chamber 1 and further increasing the flue gas temperature within the combustion chamber 1 , forming a stable liquid slag film on the inner wall of the combustion chamber 1 . The entire inner wall of the combustion chamber is covered with refractory castables, raising the temperature within the combustion chamber, melting the ash, and achieving liquid slag discharge.
[0023] Optionally, the original once-through boiler adopts a Π-type arrangement or a tower arrangement, and the combustion method adopts a tangential combustion or a counter-combustion method, such as Figure 1As shown, the original once-through boiler includes a start-up separator 6, a water-cooled wall 7, a burner 8, a water-cooled wall lower header 9 and an economizer outlet connecting pipe 10; the modification method described in this embodiment also includes the connection modification of the economizer and the water-cooled membrane tube panel, such as Figure 1 and Figure 4 Specifically, the connection between the economizer outlet connecting pipe 10 of the original once-through boiler and the water-cooled wall lower header 9 is replaced by the economizer outlet connecting pipe 10 being connected to the water-cooled membrane tube panel inlet header 12 of the combustion chamber 1. The water-cooled membrane tube panel outlet header 13 of the combustion chamber 1 is then connected to the water-cooled wall lower header 9 of the original once-through boiler via the outlet connecting pipe 14. Furthermore, the cooling water for the combustion chamber 1 can also be taken from the economizer inlet feedwater pipe or the feedwater heater upstream pipe.
[0024] Furthermore, if Figure 4 As shown, the water-cooled membrane tube panels of combustion chamber 1 utilize a once-through process. After passing through the economizer, the feedwater enters the water-cooled membrane tube panel inlet header 12 of combustion chamber 1 through economizer outlet connecting pipe 10. It then flows through the water-cooled membrane tube panels once through a once-through process, entering the waterwall lower header 9 through outlet connecting pipe 14. The water in the waterwall lower header 9 then flows through the waterwall 7 of the existing once-through boiler and enters the startup separator 6. This modification method achieves a dual-chamber series combustion, dual-throughflow water circulation system.
[0025] As a possible embodiment, the front and rear walls of the lower portion of the combustion chamber 1 are inclined inward to form a constriction, and the angle between the inward inclined surfaces of the front and rear walls and the vertical direction ranges from 15° to 40°. The constriction is conducive to the discharge of liquid slag.
[0026] Optionally, the slag hopper 4 is a conical slag hopper with a slag discharge port 5 at the lowest position of the slag hopper 4. The bottom of the slag hopper 4 is inclined, and the angle between the bottom inclined surface and the horizontal direction ranges from 0° to 25°. Such an arrangement facilitates the discharge of liquid slag.
[0027] like Figure 4 As shown, the plurality of slag catching pipes 3 are arranged in staggered rows or in series. Optionally, the number of longitudinal rows of slag catching pipes 3 is not less than 2 and not more than 6.
[0028] As a possible implementation, Figure 3-Figure 4 As shown, the vertical furnace is arranged at the rear of the original direct current boiler chamber, as shown in FIG. Figure 2 and Figure 3As shown, the outlet of combustion chamber 1 is tilted upward and connected to the cold ash hopper 7-1 on the furnace rear wall of the original once-through boiler. A window is opened in the water-cooled wall at the connection point of the cold ash hopper 7-1 on the furnace rear wall, connecting the furnace and combustion chamber 1. The J-shaped combustion chamber design forms a bend of more than 90 degrees at the bottom of combustion chamber 1, which enhances the separation of liquid slag from the flue gas and improves the slag capture rate. The upward tilt of the outlet also facilitates the backflow of liquid slag, preventing it from flowing into the original boiler's cold ash hopper.
[0029] Furthermore, the system eliminates one or more layers of burners 8 from the original boiler and instead connects the pulverized coal pipes from the pulverizer to the swirl burners 2 in the combustion chamber 1. The water-cooled membrane tube panels in the combustion chamber 1 are straight at the bottom and spiral at the top. The spiral panels surround the combustion chamber 1 in more than one circle, effectively reducing heat absorption deviations and improving wall temperature uniformity and load adaptability.
[0030] As an implementation method, the number of combustion chambers 1 is one or more, which can be arranged in any direction around the original boiler furnace, such as a vertical rear furnace, a vertical front furnace or a vertical side furnace, etc. The water-cooled membrane tube panel of the combustion chamber 1 is a vertical tube panel type or a spiral tube panel type.
[0031] Based on the transformation method of the above embodiment, the vertical post-furnace can be changed into a vertical cyclone furnace, and in this case the combustion chamber 1 is a cylindrical structure.
[0032] The present invention has been disclosed above with reference to preferred embodiments, but this is not intended to limit the present invention. Any person skilled in the art who, without departing from the scope of the technical solution of the present invention, can make slight changes or modifications to the above-disclosed structures and technical contents to produce equivalent embodiments with equivalent changes, all of which still fall within the scope of the technical solution of the present invention.
Claims
1. A method for transforming a once-through boiler by coupling solid slag discharge with liquid slag discharge, characterized by: The following steps are involved: A liquid slag discharge vertical furnace is designed outside the furnace of an original direct current boiler, the liquid slag discharge vertical furnace comprising a combustion chamber (1), a swirl burner (2), a slag catching pipe (3) and a slag hopper (4), the swirl burner (2) being inverted on the top of the combustion chamber (1), and the slag hopper (4) being located at the bottom of the combustion chamber (1); the periphery of the combustion chamber (1) is surrounded by a water-cooled membrane tube panel, the water-cooled membrane tube panel being covered with refractory castables on the fire side, the lower portion of the water-cooled membrane tube panel of the combustion chamber (1) being a straight tube panel, and the upper portion being a spiral tube panel; The economizer and the water-cooled membrane tube panel connection are modified. The economizer outlet connecting pipe (10) of the original direct current boiler is connected to the water-cooled wall lower header (9) instead of being connected to the water-cooled membrane tube panel inlet header (12) of the combustion chamber (1). The water-cooled membrane tube panel outlet header (13) of the combustion chamber (1) is connected to the water-cooled wall lower header (9) of the original direct current boiler through the outlet connecting pipe (14). The outlet of the vertical furnace is connected and communicated with the lower part of the furnace of the original direct current boiler. A part of the pulverized coal is burned in the combustion chamber (1) of the vertical furnace to form ash. The liquid slag is centrifugally thrown toward the inner wall of the swirl burner (2) and discharged through the slag hopper (4). After the feed water passes through the economizer, it enters the water-cooled membrane tube panel inlet header (12) of the combustion chamber (1) through the economizer outlet connecting pipe (10), flows through the water-cooled membrane tube panel of the combustion chamber (1) in a direct current manner, and enters the water-cooled wall lower header (9) through the outlet connecting pipe (14). The water in the water-cooled wall lower header (9) enters the start-up separator (6) through the water-cooled wall (7) of the original direct current boiler, thereby realizing a double-chamber combustion series double direct current water circulation system membrane type; The high-temperature flue gas generated by combustion in the vertical furnace enters the furnace of the original direct current boiler through the slag catching pipe (3) and is mixed with the high-temperature flue gas generated by combustion in the furnace of the original direct current boiler. The furnace of the original direct current boiler is still solid slag discharge, and local liquid slag discharge is achieved on the solid slag discharge boiler. The liquid slag discharge and the solid slag discharge are coupled, so that the original direct current boiler can burn Zhundong coal with strong coking properties or coal with low ash melting point on the basis of burning the original fuel.
2. The method for transforming a once-through boiler by coupling solid slag discharge with liquid slag discharge according to claim 1, characterized in that: The combustion chamber (1) is J-shaped, smoke flows downward in the combustion chamber (1), and the cross section of the combustion chamber (1) is rectangular.
3. The method for transforming a once-through boiler by coupling solid slag discharge with liquid slag discharge according to claim 1, characterized in that: The original direct current boiler adopts a Π-type arrangement or a tower-type arrangement, and the combustion method adopts a tangential combustion or a counter-combustion method.
4. The method for transforming a once-through boiler by coupling solid slag discharge with liquid slag discharge according to claim 1, characterized in that: 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 in the range of 15°-40°.
5. The method for transforming a once-through boiler by coupling solid slag discharge with liquid slag discharge according to claim 1, characterized in that: The slag bucket (4) is a conical slag bucket, and a slag discharge port (5) is provided at the lowest position of the slag bucket (4). The bottom of the slag bucket (4) is inclined, and the angle between the bottom inclined surface and the horizontal direction ranges from 0° to 25°.
6. The method for transforming a once-through boiler by coupling solid slag discharge with liquid slag discharge according to claim 1, characterized in that: The plurality of slag catching pipes (3) are arranged in a staggered or sequential manner.
7. The method for transforming a once-through boiler by coupling solid slag discharge with liquid slag discharge according to claim 2, characterized in that: The vertical furnace is rear-mounted and arranged behind the original direct current boiler chamber. 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 furnace of the original direct current boiler. 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 to connect the furnace and the combustion chamber (1).
8. The method for transforming a once-through boiler by coupling solid slag discharge with liquid slag discharge according to claim 3, characterized in that: The invention also includes removing one or more layers of burners (8) of the original boiler and replacing the coal mill pulverized coal pipeline connected to the one or more layers of burners (8) with a pipeline connected to the swirl burner (2) of the combustion chamber (1).