Independent circulation pipeline evaporator

Abstract

The invention provides an independent circulation pipeline evaporator which comprises an ascending pipe connected to a steam pocket; the first evaporation screen is communicated with the ascending pipe through a first ascending communicating pipe, the first evaporation screen comprises a plurality of first pipe pieces, and the first pipe pieces are arranged on two flues in parallel; each first duct piece is arranged in a bow shape in the vertical direction, so that the heating area of each first duct piece is increased, and meanwhile, a steam soot blower can penetrate through each first duct piece and carry out decoking and soot cleaning on each first duct piece; the first descending communicating pipe is connected between the first evaporation screen and a descending pipe, and the descending pipe is connected to the bottom of the steam pocket and used for conveying water in the steam pocket to the first descending communicating pipe and then conveying the water to the first evaporation screen. The problems of overtemperature and high-temperature corrosion of the superheater mentioned in the background technology are solved.

Description

Technical Field

[0001] The present application belongs to the technical field of boilers, and more specifically, to an independent circulation pipeline evaporator. Background Art

[0002] With the comprehensive implementation of the garbage classification policy, the combustible and non-combustible substances in domestic garbage can be effectively separated, making the garbage entering the incineration link purer and the calorific value of the garbage entering the furnace greatly increased. In addition, my country's garbage incineration disposal industry has gradually matured and saturated, and garbage incineration projects are generally in a dilemma of "not being able to eat enough", and the problem of overcapacity has become an inevitable trend. Therefore, the incineration of high calorific value wastes such as industrial waste has become a new development direction for many garbage incineration projects. In the face of this series of changes, the first problem to be affected is the boiler overheating. Frequent overheating of the heating surface pipe system not only accelerates the thermal aging of the pipe, but also may cause serious consequences such as high-temperature corrosion, pipe burst, and unplanned shutdown, which seriously threatens the safe operation of garbage incineration facilities. In addition, the rapid combustion of high calorific value waste is often accompanied by the formation of a large amount of molten ash, that is, the intensification of coking. The coking of high-temperature superheaters not only easily blocks the flue gas channel, but also reduces the heat exchange efficiency and shortens the continuous operation time, which directly affects the treatment efficiency and continuity of garbage incineration. On the other hand, for traditional horizontal waste incineration boilers, the evaporator, superheater, economizer and other heating surfaces are usually arranged in the horizontal flue. Due to the limited expansion space and supporting structure of the horizontal flue, the possibility of expanding the heating surface in this area is relatively small, and the construction difficulty is relatively large.

[0003] In summary, in order to solve the problems of superheater overheating and high-temperature corrosion and to improve the thermal efficiency of the boiler as much as possible, it is necessary to develop an independent circulation pipeline evaporator with a simple structure, a large heat exchange area, and a clear water circulation network. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide an independent circulation pipeline evaporator to solve the problems of superheater overheating and high-temperature corrosion mentioned in the background technology.

[0005] To achieve the above purpose, the technical solution adopted in this application is: an independent circulation pipeline evaporator, comprising: Riser, connected to the steam drum; A first evaporation screen is connected to the riser through a first riser connecting pipe, wherein the first evaporation screen comprises a plurality of first tube sheets, and the plurality of first tube sheets are arranged in parallel in the second flue; Each of the first tube segments is arranged in a bow shape in the vertical direction to increase the heating area of ​​each of the first tube segments, and a steam soot blower can penetrate each of the first tube segments and perform decoking and deashing on each of the first tube segments; The first descending connecting pipe is connected between the first evaporation screen and the descending pipe, and the descending pipe is connected to the bottom of the drum, and is used for conveying water in the drum to the first descending connecting pipe and then to the first evaporation screen.

[0006] Preferably, the first pipe segment comprises: a first steam header connected to the first ascending connecting pipe; A first evaporator tube bundle is composed of a plurality of first evaporator tubes, the plurality of first evaporator tubes are arranged in a bow shape in the vertical direction, and a first T-shaped limiting support plate is arranged between two adjacent first evaporator tubes, the first T-shaped limiting support plate is used to ensure that a flue gas flow channel is retained between the tubes of the first evaporator tubes to increase the heating area of ​​the first evaporator tubes, and the upper ends of the plurality of first evaporator tubes are connected to the first steam header; The first water header is connected to the lower ends of the plurality of first evaporator tubes and is used to distribute the water in the first water header to the first evaporator tubes. The first water header is connected to the first descending connecting pipe.

[0007] Preferably, the first T-shaped limiting support plate comprises: A first connecting piece is welded to the first evaporator tube, and the first connecting piece is provided with a slide groove and a receiving cavity; a first T-shaped slider, welded to another adjacent first evaporator tube, wherein the first T-shaped slider is slidably connected to the slide groove; An expansion gap is formed between the first T-shaped slider and the tube wall. The expansion gap is used to prevent the first evaporator tube from deforming due to thermal expansion and contraction as the temperature rises or drops, thereby protecting the first T-shaped limiting support plate from damage.

[0008] Preferably, a plurality of U-shaped supports are arranged in the vertical direction in the second flue, and the U-shaped supports are used to support the first pipe sheet in the vertical direction.

[0009] Preferably, the U-shaped support comprises: Support plates, the number of which is two, and the two support plates are fixedly connected to the water-cooled wall; A support plate is fixedly connected to the two support plates, and the support plate is provided with an arc-shaped groove, and the arc-shaped groove is used to support the first pipe segment.

[0010] Preferably, the transverse portion of the first evaporator tube is inclined, and the inclination angle is less than 20°. The inclined transverse portion can avoid dead corners and accumulation, reduce pipeline wear, and also contribute to the uniformity and stability of the medium flow in the tube, thereby achieving the purpose of improving heat exchange efficiency and operating safety.

[0011] Preferably, a plurality of the first pipe segments are arranged in parallel at equal intervals in the two flues, and the intervals are greater than 500 mm, which is convenient for scaffolding construction and replacement of pipe panels during maintenance. At the same time, the large-interval design will not cause dust accumulation, coking, or clogging of the flue.

[0012] Preferably, it also includes: A second evaporation screen is connected to the rising tube through a second rising connecting tube, the second evaporation screen comprises a plurality of second tube sheets, and the plurality of second tube sheets are arranged in parallel at equal intervals in the three flues; Each second tube segment is arranged in a bow shape in the vertical direction to increase the heating area of ​​each second tube segment, and a steam soot blower can penetrate each second tube segment and perform decoking and deashing on each second tube segment; The second descending connecting pipe is connected between the second evaporation screen and the descending pipe, and the descending pipe is connected to the bottom of the drum, and is used for conveying the water in the drum to the second descending connecting pipe and then to the second evaporation screen.

[0013] Preferably, the second pipe segment comprises: a second steam header connected to the second ascending connecting pipe; A second evaporator tube bundle is composed of a plurality of second evaporator tubes, the plurality of second evaporator tubes are arranged in a bow shape in the vertical direction, and a second T-shaped limiting support plate is arranged between two adjacent second evaporator tubes, the second T-shaped limiting support plate is used to ensure that a flue gas flow channel is retained between the tubes of the second evaporator tubes to increase the heating area of ​​the second evaporator tubes, and the upper ends of the plurality of second evaporator tubes are connected to the second steam header; The second water header is connected to the lower ends of the plurality of second evaporator tubes and is used to distribute the water in the second water header to the second evaporator tubes. The second water header is connected to the second descending connecting pipe.

[0014] Preferably, a plurality of U-shaped supports are also provided in the vertical direction in the three flues, and the U-shaped supports are used to support the second pipe segments in the vertical direction.

[0015] The beneficial effects of an independent circulation pipeline evaporator provided by the present application are: 1. The present invention has a compact structure, high space utilization, convenient access to downcomers and upcomers, and the evaporator tube bundle can be hoisted in sections from the two side walls, which reduces the complexity of installation and maintenance, facilitates renovation and construction during overhaul and decommissioning, and can greatly shorten the decommissioning period; 2. The bow-shaped multi-tube ring structure of the first evaporator tube bundle and the second evaporator tube bundle is conducive to the steam soot blowing arrangement, avoiding the problem that the middle tube layer of the traditional partition wall water-cooled wall cannot be cleaned, improving the soot accumulation and coking phenomenon, and improving the heat exchange efficiency of the evaporator; 3. The heat exchange area can be flexibly adjusted according to the over-temperature of the heating surface to ensure sufficient smoke temperature control effect, increase the boiler heat load and increase the boiler evaporation capacity; 4. The present invention adopts a first steam header connected to the first ascending connecting pipe; a first evaporator tube bundle is composed of a plurality of first evaporator tubes, the plurality of first evaporator tubes are arranged in a bow shape in the vertical direction, and a first T-shaped limit support plate is arranged between two adjacent first evaporator tubes, the first T-shaped limit support plate is used to ensure that the flue gas flow channel is retained between the tubes of the first evaporator tubes to increase the heating area of ​​the first evaporator tubes, and the upper ends of the plurality of first evaporator tubes are connected to the first steam header; a first water header is connected to the lower ends of the plurality of first evaporator tubes, and is used to distribute the water in the first water header to the first evaporator tubes. The first water header is connected to the first descending connecting pipe with an independent circulation pipeline design, and the water circulation is clear, avoiding the possibility of chaotic cross-contamination of the water flow of the original water cooling system; 5. Each tube segment has a small inclination in the transverse tube bundle, which can avoid dead corners and accumulation, reduce pipe wear, and also help the uniformity and stability of the medium flow in the pipe, thereby achieving the purpose of improving heat exchange efficiency and operation safety; 6. The weight of the evaporator of the present invention is transferred to the water-cooled wall through the U-shaped support at the bend, without the need for additional hanging devices; 7. The first steam header, the first water header, the second steam header, and the second water header are located outside the boiler to facilitate drainage and venting; 8. The horizontal spacing between adjacent pipe segments is greater than 500mm, which is convenient for scaffolding construction and replacement of pipe panels during maintenance; at the same time, the large spacing pitch design will not accumulate dust, coke, or block the flue, and is suitable for high-ash waste incineration projects such as sludge and industrial waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0017] Figure 1 A schematic diagram of the structure of an independent circulation pipeline evaporator provided in an embodiment of the present application; Figure 2 A schematic diagram of the top view of the boiler flue provided in an embodiment of the present application; Figure 3 A schematic diagram of a top view of the connection structure between the first ascending connecting pipe and the first ascending connecting branch pipe provided in an embodiment of the present application; Figure 4 A schematic diagram of the first evaporator tube structure provided in an embodiment of the present application; Figure 5 A schematic diagram of the three-dimensional structure of a first T-shaped limiting support plate provided in an embodiment of the present application; Figure 6 A schematic diagram of a cross-sectional structure of a first T-shaped limiting support plate provided in an embodiment of the present application; Figure 7 This is a schematic diagram of the U-shaped support structure provided in an embodiment of the present application.

[0018] Among them, the reference numerals in the figure are: 1. Steam drum; 2. Rising pipe; 3. First rising connecting pipe; 301. First rising connecting branch pipe; 4. Second rising connecting pipe; 5. First steam header; 6. Second steam header; 7. First evaporator tube bundle; 701. First evaporator tube; 702. Horizontal part; 703. Vertical part; 8. First T-type limit support plate; 801. First connecting piece; 802. First T-type slider; 803. Expansion gap; 9. U-shaped support; 901. Support plate; 902. Support plate; 903. Flat steel; 904. Water-cooled wall tube; 10. Furnace; 11. Second flue; 12. Third flue; 13. Second evaporator tube bundle; 14. Steam soot blower; 15. Water-cooled wall; 16. First descending connecting pipe; 17. First water header; 18. Second descending connecting pipe; 19. Second water header; 20. Spacing. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0020] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0021] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0022] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0023] Please also read Figures 1 to 4 Now, an independent circulation pipeline evaporator provided in an embodiment of the present application is described.

[0024] An independent circulation pipeline evaporator comprises a rising pipe 2, a first evaporation screen, a first rising connecting pipe 3, and a first descending connecting pipe 16.

[0025] Specifically, the riser is connected to the drum 1, which can contain the generated steam and release it into the system when needed to ensure a stable steam supply. The drum 1 is equipped with a steam-water separation device; the internal pressure of the drum 1 can be controlled by adjusting the flow of water inlet and steam outlet, which helps to maintain the pressure in the system stable. The first evaporation screen is connected to the riser 2 through the first riser connecting pipe 3. The first evaporation screen includes a plurality of first tube segments, and the plurality of first tube segments are arranged in parallel with equal spacing 20 in the second flue 11, and the plurality of first tube segments are arranged in parallel with equal spacing 20 in the second flue 11, and the spacing 20 is greater than 500mm, which is convenient for scaffolding construction and replacement of pipe panels during maintenance. At the same time, the large spacing 20 design will not accumulate dust, coke, or block the flue, and is suitable for high-ash waste incineration projects such as sludge and industrial waste. Each of the first tube segments is arranged in a bow shape in the vertical direction to increase the heating area of ​​each of the first tube segments. At the same time, the steam soot blower 14 can pass through each of the first tube segments and clean coke and ash for each of the first tube segments. It should be noted that each of the first tube segments is connected to the first rising connecting pipe 3 through the first rising connecting branch 301; the first descending connecting pipe 16 is connected between the first evaporation screen and the downcomer, and the downcomer is connected to the bottom of the steam drum 1, and is used to transport the water in the steam drum 1 to the first descending connecting pipe 16 and then to the first evaporation screen. The first descending connecting pipe 16 has a plurality of first descending connecting branches, and each first descending connecting branch is connected to a corresponding first tube segment.

[0026] Specifically, the first tube sheet includes: a first steam header 5, which is connected to the first rising connecting pipe 3; a first evaporator tube bundle 7, which is composed of a plurality of first evaporator tubes 701, and the plurality of first evaporator tubes 701 are arranged in a bow shape in the vertical direction, and a first T-shaped limiting support plate 8 is arranged between two adjacent first evaporator tubes 701, and the first T-shaped limiting support plate 8 is used to ensure that the flue gas flow channel is retained between the tubes of the first evaporator tubes 701 to increase the heating area of ​​the first evaporator tubes 701, and the upper ends of the plurality of first evaporator tubes 701 are connected to the first steam header 5. Specifically, the first T-shaped limiting support plate 8 includes: a first connector 801, and the first connector 801 is welded The first evaporator tube 701 is provided with a slide groove and a receiving cavity in the first connecting member 801; the first T-shaped slider is welded to another adjacent first evaporator tube 701, and the first T-shaped slider 802 is slidably connected to the slide groove; an expansion gap 803 is formed between the first T-shaped slider 802 and the tube wall, and the expansion gap 803 is used for the first evaporator tube 701 to deform due to thermal expansion and contraction as the temperature rises or drops, thereby protecting the first T-shaped limit support plate 8 from damage; a first water header 17 is connected to the lower ends of multiple first evaporator tubes 701, and is used to distribute the water in the first water header 17 to the first evaporator tube 701, and the first water header 17 is connected to the first descending connecting pipe 16.

[0027] As a preferred embodiment, a plurality of U-shaped supports 9 are arranged in the vertical direction in the second flue 11, and the U-shaped supports 9 are used to support the first tube segment in the vertical direction. Specifically, the U-shaped supports 9 include: a support plate 901, the number of the support plates 901 is two, and the two support plates 901 are fixedly connected to the flat steel 903 between the water-cooled wall tubes 904 on the water-cooled wall 15 by welding; a support plate 902, the support plate 902 is fixedly connected to the two support plates 901, and the support plate 902 is provided with an arc groove, and the arc groove is used to support the first tube segment.

[0028] As a preferred embodiment, the first evaporator tube 701 has a vertical portion 703 and a transverse portion 702. The transverse portion 702 is inclined and the inclination angle is less than 20°. The inclined arrangement of the transverse portion 702 can avoid dead corners and accumulation, reduce pipeline wear, and also contribute to the uniformity and stability of the flow of the medium in the tube, thereby achieving the purpose of improving heat exchange efficiency and operating safety.

[0029] Furthermore, the independent circulation pipeline evaporator also includes: a second evaporation screen, the second evaporation screen is connected to the riser 2 through a second rising connecting pipe 4, the second evaporation screen includes a plurality of second tube segments, and the plurality of second tube segments are arranged in parallel at equal intervals 20 in the three flues 12, and the interval 20 is greater than 500 mm, which is convenient for scaffolding construction and replacement of pipe panels during maintenance. At the same time, the large interval 20 design will not accumulate dust, coke, or block the flue, and is suitable for high-ash waste incineration projects such as co-burning sludge and industrial waste. Each second tube segment is arranged in a bow shape in the vertical direction to increase the heating area of ​​each second tube segment. At the same time, the steam soot blower 14 can pass through each second tube segment and clean the coke and ash of each second tube segment. It should be noted that each second tube segment is connected to the second rising connecting pipe 4 through a second rising connecting branch pipe; the second descending connecting pipe 18 is connected between the second evaporation screen and the downcomer, and the downcomer is connected to the bottom of the steam drum 1, which is used to transport the water in the steam drum 1 to the second descending connecting pipe 18 and then to the second evaporation screen. The second descending connecting pipe 18 has a plurality of second descending connecting branches, and each second descending connecting branch is connected to a corresponding second tube segment.

[0030] Specifically, the second pipe sheet includes: a second steam header 6, the second steam header 6 is connected to the second rising connecting pipe 4; a second evaporator tube bundle 13, the second evaporator tube bundle 13 is composed of a plurality of second evaporator tubes, the plurality of second evaporator tubes are arranged in a bow shape in the vertical direction, and a second T-shaped limiting support plate is arranged between two adjacent second evaporator tubes, the second T-shaped limiting support plate is used to ensure that the flue gas flow channel is retained between the tubes of the second evaporator tubes to increase the heating area of ​​the second evaporator tubes, and the plurality of second evaporator tubes are arranged on the upper The end is connected to the second steam header 6, and the second evaporator tube has a vertical portion and a transverse portion. The transverse portion is inclined, and the inclination angle is less than 20°. The inclined setting of the transverse portion can avoid dead corners and accumulation, reduce pipeline wear, and also contribute to the uniformity and stability of the flow of the medium in the tube, thereby achieving the purpose of improving heat exchange efficiency and operational safety; the second water header 19 is connected to the lower ends of multiple second evaporator tubes, and is used to distribute the water in the second water header 19 to the second evaporator tube. The second water header 19 is connected to the second descending connecting pipe 18. The specific structure of the second T-type limit support plate is the same as that of the first T-type limit support plate 8, which will not be repeated here. And a plurality of U-shaped supports 9 are also arranged in the vertical direction in the three flues 12, and the U-shaped supports 9 are used to support the second tube sheet in the vertical direction. It should be noted that the first water header 17 and the second water header 19 are respectively located on the outside of the water-cooled ash hopper at the lower part of the second flue 11 and the third flue 12, and the first steam header 5 and the second steam header 6 are located above the furnace top water-cooled wall tube 904. The first steam header 5, the first water header 17, the second steam header 6, and the second water header 19 are all located on the outside of the boiler for easy drainage and venting.

[0031] Principle: The water in the drum 1 is distributed to the first descending connecting pipe 16 through the downcomer under the internal pressure of the drum 1, and then distributed to each first evaporator tube 701 through the first water header 17. The water in the first evaporator tube 701 is vaporized to form water vapor after heat exchange in the second flue 11, and then gathered through the first steam header 5, and then gathered to the drum 1 through the first ascending connecting pipe 3 and the ascending pipe 2, so as to realize circulation in the second flue 11; the water in the drum 1 is distributed to the second descending connecting pipe 18 through the downcomer under the internal pressure of the drum 1, and then distributed to each second evaporator tube through the second water header 19. The water in the second evaporator tube is vaporized to form water vapor after heat exchange in the third flue 12, and then gathered through the second steam header 6, and then gathered to the drum 1 through the second ascending connecting pipe 4 and the ascending pipe 2, so as to realize circulation in the third flue 12.

[0032] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. An independent circulation pipeline evaporator, characterized in that: include: Riser, connected to the steam drum; A first evaporation screen is connected to the riser through a first riser connecting pipe, wherein the first evaporation screen comprises a plurality of first tube sheets, and the plurality of first tube sheets are arranged in parallel in the second flue; Each of the first tube segments is arranged in a bow shape in the vertical direction to increase the heating area of ​​each of the first tube segments, and a steam soot blower can penetrate each of the first tube segments and perform decoking and deashing on each of the first tube segments; The first descending connecting pipe is connected between the first evaporation screen and the descending pipe, and the descending pipe is connected to the bottom of the drum, and is used for conveying water in the drum to the first descending connecting pipe and then to the first evaporation screen.

2. An independent circulation pipeline evaporator according to claim 1, characterized in that: The first pipe segment comprises: a first steam header connected to the first ascending connecting pipe; A first evaporator tube bundle is composed of a plurality of first evaporator tubes, the plurality of first evaporator tubes are arranged in a bow shape in the vertical direction, and a first T-shaped limiting support plate is arranged between two adjacent first evaporator tubes, the first T-shaped limiting support plate is used to ensure that a flue gas flow channel is retained between the tubes of the first evaporator tubes to increase the heating area of ​​the first evaporator tubes, and the upper ends of the plurality of first evaporator tubes are connected to the first steam header; The first water header is connected to the lower ends of the plurality of first evaporator tubes and is used to distribute the water in the first water header to the first evaporator tubes. The first water header is connected to the first descending connecting pipe.

3. An independent circulation pipeline evaporator as claimed in claim 2, characterized in that: The first T-shaped limiting support plate comprises: A first connecting piece is welded to the first evaporator tube, and the first connecting piece is provided with a slide groove and a receiving cavity; a first T-shaped slider, welded to another adjacent first evaporator tube, wherein the first T-shaped slider is slidably connected to the slide groove; An expansion gap is formed between the first T-shaped slider and the tube wall. The expansion gap is used to prevent the first evaporator tube from deforming due to thermal expansion and contraction as the temperature rises or drops, thereby protecting the first T-shaped limiting support plate from damage.

4. The independent circulation pipeline evaporator according to claim 3, characterized in that: A plurality of U-shaped supports are arranged in the vertical direction in the second flue, and the U-shaped supports are used to support the first pipe segment in the vertical direction.

5. The independent circulation pipeline evaporator according to claim 4, characterized in that: The U-shaped support comprises: Support plates, the number of which is two, and the two support plates are fixedly connected to the water-cooled wall; A support plate is fixedly connected to the two support plates, and the support plate is provided with an arc-shaped groove, and the arc-shaped groove is used to support the first pipe segment.

6. The independent circulation pipeline evaporator according to claim 5, characterized in that: The transverse portion of the first evaporator tube is tilted, and the tilt angle is less than 20°. The tilted transverse portion can avoid dead corners and accumulation, reduce pipeline wear, and also contribute to the uniformity and stability of the medium flow in the tube, thereby achieving the purpose of improving heat exchange efficiency and operating safety.

7. An independent circulation pipeline evaporator according to claim 6, characterized in that: The plurality of first pipe segments are arranged in parallel in the two flues at equal intervals, and the intervals are greater than 500 mm, which is convenient for scaffolding erection and replacement of pipe panels during maintenance. At the same time, the large-interval design will not cause dust accumulation, coking, or clogging of the flue.

8. An independent circulation pipeline evaporator according to claim 1 or 7, characterized in that: Also includes: A second evaporation screen is connected to the rising tube through a second rising connecting tube, the second evaporation screen comprises a plurality of second tube sheets, and the plurality of second tube sheets are arranged in parallel at equal intervals in the three flues; Each second tube segment is arranged in a bow shape in the vertical direction to increase the heating area of ​​each second tube segment, and a steam soot blower can penetrate each second tube segment and perform decoking and deashing on each second tube segment; The second descending connecting pipe is connected between the second evaporation screen and the descending pipe, and the descending pipe is connected to the bottom of the drum, and is used for conveying the water in the drum to the second descending connecting pipe and then to the second evaporation screen.

9. An independent circulation pipeline evaporator as claimed in claim 8, characterized in that: The second pipe segment comprises: a second steam header connected to the second ascending connecting pipe; A second evaporator tube bundle is composed of a plurality of second evaporator tubes, the plurality of second evaporator tubes are arranged in a bow shape in the vertical direction, and a second T-shaped limiting support plate is arranged between two adjacent second evaporator tubes, the second T-shaped limiting support plate is used to ensure that a flue gas flow channel is retained between the tubes of the second evaporator tubes to increase the heating area of ​​the second evaporator tubes, and the upper ends of the plurality of second evaporator tubes are connected to the second steam header; The second water header is connected to the lower ends of the plurality of second evaporator tubes and is used to distribute the water in the second water header to the second evaporator tubes. The second water header is connected to the second descending connecting pipe.

10. An independent circulation pipeline evaporator according to claim 9, characterized in that: A plurality of U-shaped supports are also arranged in the vertical direction in the three flues, and the U-shaped supports are used to support the second pipe segments in the vertical direction.

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