Wall superheater and wall method for supercritical CFB boiler

Abstract

Wall superheater and wall method for supercritical CFB boiler. The number of tubes in the side wall and the middle partition wall is limited, resulting in relatively high flow resistance in the two downward processes and a relatively high total resistance of the entire wall superheater system. The composition of the present invention includes: front wall superheater (1), rear wall superheater (2), side wall superheater (3), middle partition wall superheater (4), superheater suspension pipe (5), suspension pipe upper header (6), side wall upper header (7), wall lower header (8), front and rear wall upper headers (9) and middle partition wall lower header (10); the superheater suspension pipes are arranged in four rows in the tail flue: the two rows of suspension pipes close to the front and rear wall superheaters are connected in parallel with the side wall to form a set of downward circuits in the wall superheater system; the two rows of suspension pipes close to the middle partition wall superheater are connected in parallel with the middle partition wall superheater to form another set of downward circuits in the wall superheater system. The present invention is used for the wall superheater of a supercritical CFB boiler.

Description

Technical Field:

[0002] The present invention relates to a water wall superheater for a supercritical CFB boiler and a water wall method. Background Art:

[0004] With the increase of the steam pressure of the boiler, the economic efficiency of the power plant will be significantly improved. When the boiler is upgraded from ultra-high pressure parameters to subcritical parameters, the economic efficiency of the power plant will increase by about 1.7%; when upgraded from subcritical parameters to supercritical parameters, the economic efficiency of the power plant will increase by about 1.8%. Therefore, high parameters and large scale have become an important development direction of circulating fluidized bed boilers, and a 350MW supercritical circulating fluidized bed boiler scheme has been formed. With the further application of the 350MW supercritical circulating fluidized bed boiler scheme in different units, there is room for further optimization of some systems and layout methods in the 350MW supercritical circulating fluidized bed boiler scheme.

[0005] At present, the technology of 300MW subcritical CFB boilers has been very mature and has been widely applied at home and abroad. The water wall process at the tail is as follows: superheated steam enters the upper header of the side water wall through a connecting pipe, descends through the side water wall to the lower header of the water wall, then ascends through the front and rear water wall superheaters to the upper headers of the front and rear water walls, and finally descends through the intermediate partition wall to enter the lower header of the intermediate partition wall and then is introduced into the inlet header of the low-temperature superheater through a connecting pipe; in the two descending processes, due to the limited number of tubes in the side water wall and the intermediate partition wall, the resistance of the two descending processes is relatively high, resulting in a relatively high total resistance of the entire water wall superheater system. Summary of the Invention:

[0007] The purpose of the present invention is to provide a water wall superheater for a supercritical CFB boiler and a water wall method that reduce the resistance of the water wall superheater system.

[0008] The above purpose is achieved by the following technical solutions:

[0009] A water wall superheater for a supercritical CFB boiler, the water wall superheater for a supercritical CFB boiler includes a front water wall superheater, a rear water wall superheater, a side water wall superheater, a middle partition wall superheater, superheater suspension pipes, a suspension pipe upper header, a side water wall upper header, a water wall lower header, front and rear water wall upper headers, and a middle partition wall lower header;

[0010] The superheater suspension pipes are arranged in four rows in the tail flue: two rows of suspension pipes close to the front and rear water wall superheaters are connected in parallel with the side water wall to form a set of downward circuits in the water wall superheater system; two rows of suspension pipes close to the middle partition wall superheater are connected in parallel with the middle partition wall superheater to form another set of downward circuits in the water wall superheater system; the front and rear water wall superheaters form a set of upward circuits.

[0011] The membrane wall superheater for a supercritical CFB boiler. After the two groups of the downcomer circuits and one group of the riser circuit are connected in series through headers, they finally form a membrane wall superheater system.

[0012] A membrane wall method for the membrane wall superheater of a supercritical CFB boiler. The method includes the following steps: The superheated steam led out from the steam-cooled separator first enters the upper header of the hanging pipes located at the top of the tail flue and the upper header of the side membrane wall. At the same time, it descends through the side membrane wall and the two-way hanging pipes close to the front and rear membrane walls to the lower header of the membrane wall, then ascends through the front and rear membrane wall superheaters to the upper headers of the front and rear membrane walls. Finally, it descends through the intermediate partition wall and the two rows of hanging pipes close to the intermediate partition wall and enters the lower header of the intermediate partition wall, leading the superheater into the low-temperature superheater, completing all the processes of the superheater in the membrane wall superheater.

[0013] Beneficial effects:

[0014] 1. For the present invention, the cross-sectional area of each group of the downcomer circuits increases and the mass flow rate decreases, finally achieving the purpose of reducing the resistance of the membrane wall superheater system. At the same time, the working medium at the outlet of the economizer is directly led away through the outlet header of the economizer without being reheated by the hanging pipes, making it easier to control the water temperature at the outlet of the economizer and making the water circulation system of the boiler more stable.

[0015] 2. The present invention solves the problems of relatively high resistance in the traditional membrane wall superheater system and difficult control of the water temperature at the outlet of the economizer, and can be used for the membrane wall superheater of a 350MW supercritical circulating fluidized bed boiler.

[0016] 3. The present invention successfully reduces the resistance of the membrane wall superheater system and realizes the controllability of the water temperature at the outlet of the economizer. Description of the drawings:

[0018] Attached Figure 1 is a schematic structural diagram of the present invention;

[0019] Attached Figure 2 is the front view of Attached Figure 1 ;

[0020] Attached Figure 3 is the middle view of Attached Figure 1 ;

[0021] Attached Figure 4 is the top view of Attached Figure 1 ;

[0022] Attached Figure 5 is the system flow chart of the present invention;

[0023] In the figure: 1. Front wall superheater; 2. Rear wall superheater; 3. Side wall superheater; 4. Intermediate partition wall superheater; 5. Superheater suspension pipe; 6. Upper header of suspension pipe; 7. Upper header of side wall; 8. Lower header of wall; 9. Upper headers of front and rear walls; 10. Lower header of intermediate partition wall. Detailed implementation method:

[0025] Embodiment 1:

[0026] A wall superheater for a supercritical CFB boiler, the wall superheater for a supercritical CFB boiler includes a front wall superheater 1, a rear wall superheater 2, a side wall superheater 3, an intermediate partition wall superheater 4, a superheater suspension pipe 5, an upper header of suspension pipe 6, an upper header of side wall 7, a lower header of wall 8, upper headers of front and rear walls 9, and a lower header of intermediate partition wall 10;

[0027] The superheater suspension pipes are arranged in four rows in the tail flue: The two rows of suspension pipes close to the front and rear wall superheaters are connected in parallel with the side wall to form a group of downward circuits in the wall superheater system; The two rows of suspension pipes close to the intermediate partition wall superheater are connected in parallel with the intermediate partition wall superheater to form another group of downward circuits in the wall superheater system; The front and rear wall superheaters form a group of upward circuits.

[0028] Embodiment 2:

[0029] According to the wall superheater for a supercritical CFB boiler described in Embodiment 1, the two groups of downward circuits and a group of upward circuits are connected in series through headers and finally form a wall superheater system.

[0030] Embodiment 3:

[0031] A wall method for a wall superheater of a supercritical CFB boiler, the method includes the following steps: The superheated steam led out from the steam-cooled separator first enters the upper header of suspension pipe and the upper header of side wall located at the top of the tail flue, and at the same time passes through the side wall and two-way suspension pipes close to the front and rear walls and descends to the lower header of wall, then ascends through the front and rear wall superheaters to the upper headers of front and rear walls (upper header of intermediate partition wall), and finally, descends through the intermediate partition wall and two rows of suspension pipes close to the intermediate partition wall and enters the lower header of intermediate partition wall (inlet of low-temperature superheater), introducing the superheater into the low-temperature superheater, and completing all processes of the superheater in the wall superheater.

[0032] The boiler applicable to this invention is a supercritical circulating fluidized bed boiler with supercritical parameters, once-through intermediate reheat natural circulation steam drum boiler, balanced draft, tightly enclosed layout, solid slag removal, and all-steel frame suspension structure.

Claims

1. A water wall superheater for a supercritical CFB boiler, characterized in that: The wall - enclosed superheater for a supercritical CFB boiler includes a front wall - enclosed superheater, a rear wall - enclosed superheater, side wall - enclosed superheaters, a middle partition wall superheater, superheater suspension tubes, a suspension tube upper header, side wall - enclosed upper headers, a wall - enclosed lower header, front and rear wall - enclosed upper headers, and a middle partition wall lower header; The superheater suspension tubes are arranged in four rows in the tail flue: the two rows of suspension tubes close to the front and rear wall - enclosed superheaters are connected in parallel with the side wall - enclosed superheaters to form a group of downward circuits in the wall - enclosed superheater system; the two rows of suspension tubes close to the middle partition wall superheater are connected in parallel with the middle partition wall superheater to form another group of downward circuits in the wall - enclosed superheater system; the front and rear wall - enclosed superheaters form a group of upward circuits; The two groups of downward circuits and a group of upward circuits are connected in series through headers and finally form the wall - enclosed superheater system; The wall - enclosing method of the wall - enclosed superheater for a supercritical CFB boiler includes the following steps: the superheated steam led out from the steam - cooled separator first enters the suspension tube upper header and the side wall - enclosed upper header located at the top of the tail flue, and at the same time, it descends through the side wall - enclosed superheater and the two - way suspension tubes close to the front and rear wall - enclosed superheaters to the wall - enclosed lower header, then ascends through the front and rear wall - enclosed superheaters to the front and rear wall - enclosed upper headers, and finally, it descends through the middle partition wall and the two rows of suspension tubes close to the middle partition wall and enters the middle partition wall lower header, leading the superheater to the low - temperature superheater, completing all the processes of the superheater in the wall - enclosed superheater. The cross - sectional area of each group of downward circuits increases and the mass flow rate decreases, finally achieving the purpose of reducing the resistance of the wall - enclosed superheater system. At the same time, the working medium at the outlet of the economizer is directly led away through the economizer outlet header without passing through the secondary heating of the suspension tubes.

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