Independent circulation pipeline evaporator

Abstract

The utility model 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 particularly relates to an independent circulation pipeline evaporator. BACKGROUND

[0002] With the comprehensive implementation of the garbage classification policy, the combustible substances and non-combustible substances in household garbage can be effectively separated, so that the composition of the garbage entering the incineration link is more pure, and the heat value of the garbage entering the furnace is greatly improved. In addition, the garbage incineration disposal industry in China has gradually become mature and saturated, and garbage incineration projects are generally in the predicament of 'not being able to eat enough', and the problem of overcapacity has become an inevitable trend. Therefore, mixed burning of industrial garbage and other high-calorific-value waste has become a new development direction for many garbage incineration projects. In the face of these changes, the first problem is the problem of over-temperature of the boiler. Frequent over-temperature of the heating surface tube system not only accelerates the thermal aging of the tube material, but also may cause high-temperature corrosion, pipe explosion, and other serious consequences such as unplanned shutdown, which seriously threatens the safe operation of the garbage incineration facility. In addition, the rapid combustion of high-calorific-value waste is often accompanied by the formation of a large amount of molten ash, i.e., the intensification of coking. Coking in the high-temperature superheater not only easily blocks the flue gas passage, but also reduces the heat exchange efficiency, shortens the continuous operation time, and directly affects the processing efficiency and continuity of garbage incineration. On the other hand, for traditional horizontal garbage incineration boilers, the heating surfaces such as the evaporator, the superheater, and the coal economizer are arranged in the horizontal flue. Due to the limited expansion space and support structure of the horizontal flue, the possibility of expansion of the heating surfaces in this area is relatively small, and the construction difficulty is relatively large.

[0003] In summary, in order to solve the problems of over-temperature and high-temperature corrosion of the superheater, 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

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

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows: an independent circulation pipeline evaporator, comprising:

[0006] An uptake pipe connected to a steam drum;

[0007] A first evaporation screen connected to the uptake pipe through a first uptake communication pipe, the first evaporation screen comprising a plurality of first tube pieces, and the plurality of first tube pieces being arranged in parallel in two flues;

[0008] Each of the first tube pieces is arranged in an arch shape in the vertical direction to increase the heating area of each of the first tube pieces, and a steam sootblower can penetrate each of the first tube pieces and perform coking and ash removal on each of the first tube pieces.

[0009] a first down communication pipe connected between the first evaporation screen and a down pipe connected to a bottom of the steam pocket, for transporting water in the steam pocket to the first down communication pipe and then to the first evaporation screen.

[0010] Preferably, the first tube sheet comprises:

[0011] a first steam header connected to the first up communication pipe;

[0012] a first evaporation tube bundle composed of a plurality of first evaporation tubes, each of the plurality of first evaporation tubes being arranged in an arch shape in a vertical direction, and a first T-shaped limiting support plate being arranged between two adjacent first evaporation tubes, the first T-shaped limiting support plate being used to ensure that a flue gas flow channel is reserved between the first evaporation tubes to increase a heating area of the first evaporation tubes, and upper ends of the plurality of first evaporation tubes being connected to the first steam header;

[0013] a first water header connected to lower ends of the plurality of first evaporation tubes, for distributing water in the first water header to the first evaporation tubes, the first water header being connected to the first down communication pipe.

[0014] Preferably, the first T-shaped limiting support plate comprises:

[0015] a first connecting piece welded to the first evaporation tube, and the first connecting piece being provided with a sliding groove and a receiving cavity;

[0016] a first T-shaped sliding block welded to another adjacent first evaporation tube, the first T-shaped sliding block being slidingly connected to the sliding groove;

[0017] an expansion gap being formed between the first T-shaped sliding block and a tube wall, the expansion gap being used to protect the first T-shaped limiting support plate from being damaged due to deformation of the first evaporation tube caused by thermal expansion or contraction as the air temperature rises or falls.

[0018] Preferably, a plurality of U-shaped supports are arranged in a vertical direction in the second flue, the U-shaped supports being used to support the first tube sheet in the vertical direction.

[0019] Preferably, the U-shaped support comprises:

[0020] a support plate, the number of which is two, both of the support plates being fixedly connected to the water-cooled wall;

[0021] a supporting plate fixedly connected to the two support plates, the supporting plate being provided with an arc-shaped groove, the arc-shaped groove being used to support the first tube sheet.

[0022] Preferably, the transverse part of the first evaporator tube is obliquely arranged, and the oblique angle is less than 20°, which can avoid dead angle, accumulation, reduce tube wear, and help the uniformity and stability of the medium flow in the tube, so as to improve the heat exchange efficiency and operation safety.

[0023] Preferably, a plurality of the first tube pieces are arranged in the two flues at equal intervals, and the interval is greater than 500 mm, which facilitates the erection of a scaffold and the replacement of the tube during maintenance, and the large interval design will not cause dust accumulation, coking, and flue blockage.

[0024] Preferably, the application further comprises:

[0025] A second evaporation screen is connected to the rising pipe through a second rising communication pipe, and the second evaporation screen comprises a plurality of second tube pieces arranged in three flues at equal intervals.

[0026] Each of the second tube pieces is arranged in an arch shape in the vertical direction to increase the heating area of each of the second tube pieces, and a steam soot blower can penetrate each of the second tube pieces to clean the coking and dust of each of the second tube pieces.

[0027] A second descending communication pipe is connected between the second evaporation screen and a descending pipe connected to the bottom of the steam drum, for transporting water in the steam drum to the second descending communication pipe and then to the second evaporation screen.

[0028] Preferably, the second tube piece comprises:

[0029] A second steam header is connected to the second rising communication pipe.

[0030] A second evaporator tube bundle is composed of a plurality of second evaporator tubes, each of which is arranged in an arch shape in the vertical direction, and a second T-shaped limiting support plate is arranged between two adjacent second evaporator tubes, which is used to ensure that the second evaporator tubes retain a flue gas flow channel 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.

[0031] A second water header is connected to the lower ends of the plurality of second evaporator tubes, for distributing water in the second water header to the second evaporator tubes, and the second water header is connected to the second descending communication pipe.

[0032] Preferably, a plurality of U-shaped supports are arranged in the vertical direction in the three flues, which are used to support the second tube pieces in the vertical direction.

[0033] The independent circulating pipeline evaporator provided by the application has the following advantages:

[0034] 1、The application has compact structure, high space utilization rate, convenient access of the descending pipe and the ascending pipe, segmented hoisting of the evaporator pipe bundle from the two side walls, reduced installation and maintenance complexity, convenient modification construction during overhaul and shutdown, and greatly shortened shutdown period;

[0035] 2、The bow-shaped multi-pipe ring structure of the first evaporator pipe bundle and the second evaporator pipe bundle is beneficial to steam blowing arrangement, avoids the problem that the middle tube grid in the traditional partition wall water-cooled wall cannot be cleaned, improves the phenomenon of ash deposition and coking, and improves the evaporator heat exchange efficiency;

[0036] 3、The heat exchange area can be flexibly adjusted according to the overheating condition of the heating surface, so as to ensure sufficient flue gas temperature control effect, improve the boiler heat load, and increase the boiler evaporation capacity;

[0037] 4、The application adopts a first steam header connected to the first ascending communication pipe, a first evaporator pipe bundle composed of a plurality of first evaporator pipes, the plurality of first evaporator pipes are arranged in an arch shape in the vertical direction, and a first T-shaped limiting support plate is arranged between adjacent two first evaporator pipes, the first T-shaped limiting support plate is used to ensure that a flue gas flow channel is reserved between the pipes of the first evaporator pipe to increase the heating area of the first evaporator pipe, the upper ends of the plurality of first evaporator pipes are connected to the first steam header, a first water header is connected to the lower ends of the plurality of first evaporator pipes and is used to distribute water in the first water header to the first evaporator pipes, the first water header and the first descending communication pipe are connected to an independent circulating pipeline, water circulation is clear, and the possibility of cross contamination of raw water flow in the original water cooling system is avoided;

[0038] 5、Each pipe sheet transverse pipe bundle is provided with a small-angle inclination, which can avoid dead angles, accumulation, reduce pipe wear, and also help the uniformity and stability of the medium flow in the pipe, so as to improve the heat exchange efficiency and operation safety;

[0039] 6、The weight of the evaporator is transmitted to the water-cooled wall through the U-shaped support at the elbow, without the need to additionally add a hanging device;

[0040] 7、The first steam header, the first water header, the second steam header, and the second water header are located outside the boiler, which is convenient for draining and gas release;

[0041] 8、The transverse spacing between adjacent pipe sheets is greater than 500 mm, which is convenient for scaffold erection and replacement of the tube grid during maintenance; at the same time, the large spacing pitch design will not cause ash deposition, coking, and flue blockage, and is suitable for high-ash waste incineration projects such as sludge and industrial waste blending. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0043] Figure 1 A structural schematic diagram of an independent circulating pipeline evaporator provided by the embodiments of the present application is shown in the figure.

[0044] Figure 2 A top view structural schematic diagram of a boiler flue provided by the embodiments of the present application is shown in the figure.

[0045] Figure 3 A top view structural schematic diagram of the connection between the first rising communication pipe and the first rising communication branch pipe provided by the embodiments of the present application is shown in the figure.

[0046] Figure 4 A structural schematic diagram of a first evaporator pipe provided by the embodiments of the present application is shown in the figure.

[0047] Figure 5 A three-dimensional structural schematic diagram of a first T-shaped limiting support plate provided by the embodiments of the present application is shown in the figure.

[0048] Figure 6 A sectional view structural schematic diagram of a first T-shaped limiting support plate provided by the embodiments of the present application is shown in the figure.

[0049] Figure 7 A U-shaped support structure schematic diagram provided by the embodiments of the present application is shown in the figure.

[0050] In the figure, various reference signs are as follows:

[0051] 1, steam drum; 2, rising pipe; 3, first rising communication pipe; 301, first rising communication branch pipe; 4, second rising communication pipe; 5, first steam header; 6, second steam header; 7, first evaporator pipe bundle; 701, first evaporator pipe; 702, horizontal part; 703, vertical part; 8, first T-shaped limiting support plate; 801, first connecting piece; 802, first T-shaped sliding block; 803, expansion gap; 9, U-shaped support; 901, support plate; 902, supporting plate; 903, flat steel; 904, water-cooled wall pipe; 10, furnace; 11, double flue; 12, triple flue; 13, second evaporator pipe bundle; 14, steam sootblower; 15, water-cooled wall; 16, first descending communication pipe; 17, first water header; 18, second descending communication pipe; 19, second water header; 20, interval. DETAILED DESCRIPTION

[0052] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0053] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0054] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0055] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0056] Please refer to the following: Figures 1 to 4 The present application will now describe an independent circulation pipeline evaporator provided in the embodiments of this application.

[0057] An independent circulation pipeline evaporator includes a riser pipe 2, a first evaporation screen, a first rising connecting pipe 3, and a first descending connecting pipe 16.

[0058] Specifically, the riser pipe is connected to the steam drum 1, which can contain the generated steam and release it into the system when needed, ensuring a stable steam supply. The steam drum 1 is equipped with a steam-water separator. The internal pressure of the steam drum 1 can be controlled by adjusting the inlet and outlet steam flow rates, which helps to maintain stable pressure within the system. The first evaporation screen is connected to the riser pipe 2 via the first riser connecting pipe 3. The first evaporation screen includes multiple first tube segments, which are arranged in parallel with equal spacing 20 in the second flue 11. The spacing 20 is greater than 500mm, which facilitates scaffolding erection and tube replacement during maintenance. At the same time, the large spacing 20 design prevents ash accumulation, coking, and flue blockage, making it suitable for incineration projects involving co-firing sludge, industrial waste, and other high-ash waste. Each of the first tube segments is arranged in an arc shape in the vertical direction to increase the heating area of ​​each first tube segment. At the same time, the steam soot blower 14 can penetrate each first tube segment and clean the slag and ash from each first tube segment. It should be noted that each first tube segment is connected to the first rising connecting pipe 3 through the first rising connecting branch pipe 301. The first descending connecting pipe 16 is connected between the first evaporation screen and the descending pipe. The descending pipe is connected to the bottom of the steam drum 1 and is used to transport 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 multiple first descending connecting branch pipes, and each first descending connecting branch pipe is connected to one first tube segment.

[0059] Specifically, the first tube segment includes: a first steam header 5, which is connected to the first rising connecting pipe 3; and a first evaporator tube bundle 7, which is composed of multiple first evaporator tubes 701. These multiple first evaporator tubes 701 are arranged in an arc shape in the vertical direction, and a first T-shaped limiting support plate 8 is provided between adjacent first evaporator tubes 701. The first T-shaped limiting support plate 8 is used to ensure that flue gas flow channels are maintained between the tubes of the first evaporator tubes 701 to increase the heating area of ​​the first evaporator tubes 701. The upper ends of the multiple first evaporator tubes 701 are all connected to the first steam header 5. Specifically, the first T-shaped limiting support plate 8 includes: a first connector 801, which is welded... The first evaporator tube 701 and the first connector 801 are provided with a sliding groove and a receiving cavity; a 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 sliding 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 to protect the first T-shaped limiting support plate 8 from damage when the first evaporator tube 701 deforms due to thermal expansion and contraction as the temperature rises or falls; a first water collector 17 is connected to the lower end of multiple first evaporator tubes 701 and is used to distribute the water in the first water collector 17 to the first evaporator tubes 701, and the first water collector 17 is connected to the first descending connecting pipe 16.

[0060] In a preferred embodiment, a plurality of U-shaped supports 9 are vertically arranged within the second flue 11. These U-shaped supports 9 are used to support the first tube segment vertically. Specifically, each U-shaped support 9 includes: a support plate 901, wherein there are two support plates 901, both of which are fixedly connected by welding to a flat steel 903 between water-cooled wall tubes 904 on the water-cooled wall 15; and a support plate 902, which is fixedly connected to the two support plates 901. The support plate 902 has an arc-shaped groove for supporting the first tube segment.

[0061] In a preferred embodiment, the first evaporator tube 701 has a vertical portion 703 and a horizontal portion 702. The horizontal portion 702 is inclined and the inclination angle is less than 20°. The inclined arrangement of the horizontal portion 702 can avoid dead corners and accumulation, reduce pipe wear, and also help to improve the uniformity and stability of the medium flow inside the tube, thereby achieving the purpose of improving heat exchange efficiency and operational safety.

[0062] Furthermore, the independent circulation pipeline evaporator also includes a second evaporation screen, which is connected to the riser pipe 2 via a second rising connecting pipe 4. The second evaporation screen includes multiple second tube segments, which are arranged in parallel at equal intervals 20 on the three flues 12. The interval 20 is greater than 500mm, which facilitates the erection of scaffolding and replacement of tube screens during maintenance. At the same time, the large interval 20 design will not accumulate ash, coke, or block the flue, making it suitable for high-ash waste incineration projects such as co-firing sludge and industrial waste. Each of the second tube segments is arranged in an arc 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 penetrate each second tube segment and clean the coke and ash from each second tube segment. It should be noted that each second tube segment is connected to the second rising connecting pipe 4 through the second rising connecting branch pipe. The second descending connecting pipe 18 is connected between the second evaporation screen and the descending pipe. The descending pipe is connected to the bottom of the steam drum 1 and is used to transport 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 multiple second descending connecting branch pipes, and each second descending connecting branch pipe is connected to one second tube segment.

[0063] Specifically, the second tube segment includes: a second steam header 6, connected to the second rising connecting pipe 4; and a second evaporator tube bundle 13, composed of multiple second evaporator tubes arranged in an arc shape in the vertical direction, with a second T-shaped limiting support plate between adjacent second evaporator tubes. The second T-shaped limiting support plate is used to ensure that flue gas flow channels are maintained between the tubes of the second evaporator tubes to increase the heating area of ​​the second evaporator tubes. The second evaporator tube is connected to the second steam header 6. It has a vertical section and a horizontal section, with the horizontal section inclined at an angle of less than 20°. This inclined arrangement avoids dead angles and accumulation, reduces pipe wear, and contributes to the uniformity and stability of the medium flow within the tube, thereby improving heat exchange efficiency and operational safety. A second water header 19 is connected to the lower end of multiple second evaporator tubes and is used to distribute water from the second water header 19 to the second evaporator tubes. The second water header 19 is connected to the second downcomer pipe 18. The specific structure of the second T-shaped limiting support plate is the same as that of the first T-shaped limiting support plate 8, and will not be described in detail here. Multiple U-shaped supports 9 are also vertically arranged within the three flues 12, supporting the second tube segments in the vertical direction. It should be noted that the first water header 17 and the second water header 19 are located on the outside of the lower part of the water-cooled ash hopper of the second flue 11 and the third flue 12, respectively. The first steam header 5 and the second steam header 6 are located above the water-cooled wall tube 904 on the top of the boiler. 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 to facilitate drainage and venting.

[0064] Principle: Water in steam drum 1 is distributed to the first downcomer pipe 16 through the downcomer pipe under the internal pressure of steam drum 1. It is then distributed to each of the first evaporator tubes 701 through the first water header 17. The water in the first evaporator tubes 701 is vaporized into water vapor after heat exchange in the second flue 11. It is then collected through the first steam header 5 and then through the first rising pipe 3 and rising pipe 2 before returning to steam drum 1, thus achieving circulation within the second flue 11. Water in steam drum 1 is also distributed to the second downcomer pipe 18 through the downcomer pipe under the internal pressure of steam drum 1. It is then distributed to each of the second evaporator tubes through the second water header 19. The water in the second evaporator tubes is vaporized into water vapor after heat exchange in the third flue 12. It is then collected through the second steam header 6 and then through the second rising pipe 4 and rising pipe 2 before returning to steam drum 1, thus achieving circulation within the third flue 12.

[0065] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A standalone circulation line evaporator characterized in that, The utility model relates to a steam generator, which comprises: a riser pipe connected to a steam drum; a first evaporation screen connected to the riser pipe through a first riser communication pipe, the first evaporation screen comprising a plurality of first tube pieces arranged in parallel in two flues; each of the first tube pieces is arranged in an arch shape in the vertical direction to increase the heating area of each of the first tube pieces, while a steam soot blower can pass through and clean each of the first tube pieces; a first downcomer communication pipe connected between the first evaporation screen and a downcomer pipe connected to the bottom of the steam drum, for conveying water in the steam drum to the first downcomer communication pipe and then to the first evaporation screen.

2. A self-contained circuit piped evaporator as claimed in claim 1, characterized in that The first tube piece comprises: a first steam header connected to the first riser communication pipe; a first evaporator tube bundle composed of a plurality of first evaporator tubes, each of the first evaporator tubes being arranged in an arch shape in the vertical direction, and a first T-shaped limiting support plate being arranged between two adjacent first evaporator tubes, the first T-shaped limiting support plate being used to ensure that a flue gas flow channel is reserved between the first evaporator tubes to increase the heating area of the first evaporator tubes, and the upper ends of the first evaporator tubes being connected to the first steam header; a first water header connected to the lower ends of the first evaporator tubes, for distributing water in the first water header to the first evaporator tubes, the first water header being connected to the first downcomer communication pipe.

3. A self-contained circuit piped evaporator as claimed in claim 2, characterized in that The first T-shaped limiting support plate comprises: a first connecting piece welded to the first evaporator tube, and the first connecting piece being provided with a sliding groove and a receiving cavity; a first T-shaped sliding block welded to another adjacent first evaporator tube, the first T-shaped sliding block being slidably connected to the sliding groove; an expansion gap being formed between the first T-shaped sliding block and the tube wall, the expansion gap being used to protect the first T-shaped limiting support plate from being damaged due to the deformation of the first evaporator tube caused by thermal expansion or contraction as the air temperature rises or falls.

4. A self-contained circuit piped evaporator as claimed in claim 3, characterized in that: A plurality of U-shaped supports are arranged in the vertical direction in the two flues, the U-shaped supports being used to support the first tube pieces in the vertical direction.

5. A self-contained circuit piped evaporator as set forth in claim 4, characterized in that: The U-shaped support comprises: two support plates fixedly connected to the water-cooled walls; a supporting plate fixedly connected to the two support plates, the supporting plate being provided with an arc-shaped groove for supporting the first tube pieces.

6. A self-contained circuit piped evaporator as set forth in claim 5, characterized in that: The transverse part of the first evaporator tube is arranged at an inclination, and the inclination angle is less than 20°, which can avoid dead angles and accumulation, reduce pipeline wear, and help the uniformity and stability of the flow of the medium in the tube, thereby improving the heat exchange efficiency and operational safety.

7. A self-contained recirculating line evaporator as claimed in claim 6, characterized in that: The plurality of first tube pieces are arranged in parallel at equal intervals in the two flues, and the interval is greater than 500 mm, which facilitates the erection of a scaffold and the replacement of the tube during maintenance, and the large interval design does not cause soot accumulation, coking, and flue blockage.

8. A self-contained circuit line evaporator as claimed in claim 1 or 7, characterized in that The utility model further comprises: a second evaporation screen connected to the riser pipe through a second riser communication pipe, the second evaporation screen comprising a plurality of second tube pieces arranged in parallel at equal intervals in three flues. Each of the second tube pieces is arranged in an arch shape in the vertical direction to increase the heating area of each of the second tube pieces, while a steam sootblower can pass through and clean each of the second tube pieces; A second down communication pipe is connected between the second evaporation screen and a down pipe connected to the bottom of the steam pocket, for transporting water in the steam pocket to the second down communication pipe and then to the second evaporation screen.

9. A self-contained circuit piped evaporator as claimed in claim 8, characterized in that: The second tube piece comprises: A second steam header connected to the second up communication pipe; A second evaporation tube bundle composed of a plurality of second evaporation tubes, each of the second evaporation tubes being arranged in an arch shape in the vertical direction, and a second T-shaped limiting support plate being arranged between two adjacent second evaporation tubes, for ensuring that a flue gas flow channel is reserved between the second evaporation tubes to increase the heating area of the second evaporation tubes, and the upper ends of the second evaporation tubes being connected to the second steam header; A second water header connected to the lower ends of the second evaporation tubes, for distributing water in the second water header to the second evaporation tubes, the second water header being connected to the second down communication pipe.

10. A self-contained circuit piped evaporator as claimed in claim 9, characterized in that: A plurality of U-shaped supports are arranged in the vertical direction in the three flues, for supporting the second tube pieces in the vertical direction.

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