Circulating fluidized bed boiler steam-water path system using coal with strong contamination property as fuel

Abstract

The utility model discloses a steam-water path system of a circulating fluidized bed boiler, which takes coal with stronger contamination property as fuel, and solves the problem of how to design the steam-water path system of the fluidized bed boiler so as to reasonably arrange the heating surface of the boiler. A high-temperature platen superheater (8) and a medium-temperature platen superheater (9) are respectively arranged in the hearth (1), a low-temperature platen superheater (10) is arranged in the rear flue (3), and a low-temperature economizer (11) and a high-temperature economizer (12) are respectively arranged in the tail flue (4); the main water supply pipe (13) sequentially passes through the high-temperature coal economizer and the low-temperature coal economizer and then is communicated with the coal economizer water supply header (14); a saturated steam outlet pipe (15) is connected with the input end of the low-temperature platen superheater, the output end of the low-temperature platen superheater is communicated with the input end of the medium-temperature platen superheater through a low-temperature superheater outlet header (16), and the input end of the medium-temperature platen superheater is communicated with the input end of the high-temperature platen superheater (8).

Description

Technical Field

[0001] The utility model relates to a circulating fluidized bed boiler, in particular to a steam-water system of a circulating fluidized bed boiler using coal with strong fouling property as fuel. Background Art

[0002] The content of alkali metals sodium and potassium in some steam coals is much higher than that of other steam coals. The melting points of alkali metal compounds are usually within 800 °C, but the melting points of complex alkali metal sulfates are between 890 - 1210 °C. In a pulverized coal boiler, the flue gas temperature in the high-temperature zone of the furnace is usually above 1400 °C. This means that all alkali metals and their compounds in the steam coal with a high content of alkali metals sodium and potassium will sublime or melt in the boiler furnace and cause fouling on the heating surfaces of the boiler. How to design the steam-water system of a fluidized bed boiler to control the combustion temperature of the fluidized bed boiler between 850 - 870 °C, avoid the melting point of complex alkali metal sulfates to the greatest extent, and thus greatly reduce the risk of flue gas fouling on the heating surfaces of the boiler has become a problem faced by boiler manufacturing enterprises. Summary of the Invention

[0003] The utility model provides a steam-water system of a circulating fluidized bed boiler using coal with strong fouling property as fuel, and solves the technical problem of how to design the steam-water system of a fluidized bed boiler to achieve a reasonable layout of the boiler heating surfaces and reduce the fouling of flue gas on the heating surfaces of the boiler.

[0004] The utility model solves the above technical problems through the following technical solutions:

[0005] A steam-water system of a circulating fluidized bed boiler using coal with strong fouling property as fuel includes a furnace, a cyclone separator, a rear flue, a tail flue and a steam drum. The cyclone separator is connected to the rear flue through a separator flue gas outlet, and the rear flue is connected to the tail flue through a connecting flue. A main water supply pipe, a saturated steam extraction pipe, a first centralized downcomer and a second centralized downcomer are respectively arranged on the steam drum. A high-temperature platen superheater and a medium-temperature platen superheater are respectively arranged in the furnace, a low-temperature superheater is arranged in the rear flue, and a high-temperature economizer and a low-temperature economizer are respectively arranged in the tail flue. The boiler feed water passes through the economizer feed water header, the low-temperature economizer and the high-temperature economizer in sequence, and then enters the steam drum through the main water supply pipe. The saturated steam extraction pipe is connected to the input end of the low-temperature superheater, i.e., the low-temperature superheater inlet header. The output end of the low-temperature superheater passes through the low-temperature superheater outlet header, and is connected to the input end of the medium-temperature platen superheater after passing through a primary desuperheater in the middle. The output end of the medium-temperature platen superheater is connected to the input end of the high-temperature platen superheater after passing through a secondary desuperheater in the middle. A steam collecting header is connected to the output end of the high-temperature platen superheater.

[0006] At the lower end of the downcomer in the first set, a first furnace distributed downcomer group, a second furnace distributed downcomer group, and a third furnace distributed downcomer group are connected in parallel; at the other end of the first furnace distributed downcomer group, a lower header of the front furnace membrane wall is connected, a front furnace membrane wall is connected to the lower header of the front furnace membrane wall, the other end of the front furnace membrane wall is connected to an upper header of the front and rear furnace membrane walls, a first furnace steam guide pipe group is arranged on the upper header of the front and rear furnace membrane walls, and the first furnace steam guide pipe group is connected to the steam drum; at the other end of the second furnace distributed downcomer group, a lower header of the side furnace membrane wall is connected, a side furnace membrane wall is connected to the lower header of the side furnace membrane wall, the other end of the side furnace membrane wall is connected to an upper header of the side furnace membrane wall, a second furnace steam guide pipe group is arranged on the upper header of the side furnace membrane wall, and the other end of the second furnace steam guide pipe group is connected to the steam drum; at the other end of the third furnace distributed downcomer group, it is connected to a lower header of the rear furnace membrane wall, a rear furnace membrane wall is connected to the lower header of the rear furnace membrane wall, and the other end of the rear furnace membrane wall is connected to an upper header of the front and rear furnace membrane walls.

[0007] At the lower end of the downcomer in the second set, a first flue distributed downcomer group, a second flue distributed downcomer group, and a third flue distributed downcomer group are connected in parallel; at the other end of the first flue distributed downcomer group, a lower header of the front flue membrane wall is connected, a front flue membrane wall is connected to the lower header of the front flue membrane wall, the other end of the front flue membrane wall is connected to an upper header of the front flue membrane wall, a first flue steam guide pipe group is arranged on the upper header of the front flue membrane wall, and the first flue steam guide pipe group is connected to the steam drum; at the other end of the second flue distributed downcomer group, a lower header of the side flue membrane wall is connected, a side flue membrane wall is connected to the lower header of the side flue membrane wall, the other end of the side flue membrane wall is connected to an upper header of the side flue membrane wall, a second flue steam guide pipe group is arranged on the upper header of the side flue membrane wall, and the other end of the second flue steam guide pipe group is connected to the steam drum; at the other end of the third flue distributed downcomer group, it is connected to a lower header of the rear flue membrane wall, a rear flue membrane wall is connected to the lower header of the rear flue membrane wall, and the other end of the rear flue membrane wall is connected to an upper header of the rear flue membrane wall; at the other end of the fourth flue distributed downcomer group, it is connected to a lower header of the middle partition wall flue membrane wall, a middle partition wall flue membrane wall is connected to the lower header of the middle partition wall flue membrane wall, and the other end of the middle partition wall flue membrane wall is divided into two parts, half of which is connected to an upper header of the front flue membrane wall and half of which is connected to an upper header of the rear flue membrane wall.

[0008] In the rear flue, a convection tube bundle is arranged. The input end of the convection tube bundle is connected to the downcomer in the second set, and the output end of the convection tube bundle is connected to the steam drum through a convection tube bundle steam guide pipe.

[0009] The boiler of the utility model adopts a low-temperature combustion mode, and there is no problem of fouling on the heating surface in the furnace; the feed water of the boiler is heated by a low-temperature economizer and a high-temperature economizer and then enters the drum through the main feed water pipe. The boiler water in the drum enters the lower headers of the membrane walls in the furnace and the rear flue, the membrane wall tubes, the convection tube bundles, and the upper headers of the membrane walls through their respective centralized downcomers and distributed dispersion pipes, and then enters the drum through the outlet pipes; a steam-water separation device is provided in the drum, and the saturated steam is led from the steam connection pipe at the top of the drum to the low-temperature superheater in the rear flue, through the inlet header of the low-temperature superheater, the low-temperature superheater, the outlet header of the low-temperature superheater, the first-stage spray desuperheater, the medium-temperature screen, the second-stage spray desuperheater, the high-temperature screen, and the steam collecting header, and finally the qualified superheated steam is led out. Brief Description of the Drawings

[0010] Figure 1 is a schematic diagram of the overall structure of the utility model;

[0011] Figure 2 is a schematic diagram of the structure of the steam-water pipeline of the utility model. Detailed Embodiment

[0012] The following is a detailed description of the utility model with reference to the drawings:

[0013] A steam-water path system of a circulating fluidized bed boiler using highly contaminated coal as fuel, comprising a furnace 1, a cyclone separator 2, a rear flue 3, a tail flue 4 and a drum 5. The cyclone separator 2 is connected to the rear flue 3 through a separator flue gas outlet 6, and the rear flue 3 is connected to the tail flue 4 through a connecting flue 7. A main water supply pipe 13, a saturated steam extraction pipe 15, a first centralized downcomer 18 and a second centralized downcomer 19 are respectively arranged on the drum 5. A high-temperature platen superheater 8 and a medium-temperature platen superheater 9 are respectively arranged in the furnace 1, a low-temperature superheater 10 is arranged in the rear flue 3, and a low-temperature economizer 11 and a high-temperature economizer 12 are respectively arranged in the tail flue 4. The boiler feed water passes through a feed water header of the economizer 14, the low-temperature economizer 11 and the high-temperature economizer 12 in sequence, and then enters the drum 5 through the main water supply pipe 13. The saturated steam extraction pipe 15 is connected to the input end of the low-temperature superheater 10, i.e., the low-temperature superheater inlet header 52. The output end of the low-temperature superheater 10 is connected to the medium-temperature platen superheater 9 through a low-temperature superheater outlet header 16 and a primary desuperheater in the middle. The output end of the medium-temperature platen superheater 9 is connected to the input end of the high-temperature platen superheater 8 through a secondary desuperheater in the middle. A steam collecting header 17 is connected to the output end of the high-temperature platen superheater 8. The high-temperature platen superheater 8 and the medium-temperature platen superheater 9 are arranged in the furnace, and the low-temperature superheater 10 is arranged in the rising flue of the rear flue. The advantages are that the heat transfer surface of the superheater is arranged in countercurrent as a whole, the heat transfer temperature difference is high, the system is simple, and the boiler cost is low. The temperature of the working medium at the outlet of the last heating surface in the furnace is controlled, and the temperature of the working medium is basically stable under various loads, not affected by desuperheating by spraying water, the wall temperature fluctuation is small, the platen will not deform, and the operation is safe. It is beneficial to reasonably distribute the radiant heat absorption and convective heat absorption of the boiler under various loads, so that the wall temperature of each stage of superheater is stable under load changes.

[0014] In the first episode, at the lower end of the downcomer 18, the first furnace distributed downcomer group 20, the second furnace distributed downcomer group 21, and the third furnace distributed downcomer group 22 are connected in parallel; at the other end of the first furnace distributed downcomer group 20, the lower header 23 of the front furnace membrane wall is connected, on the lower header 23 of the front furnace membrane wall, the front furnace membrane wall 24 is connected, the other end of the front furnace membrane wall 24 is connected and communicated with the upper header 25 of the front and rear furnace membrane walls, on the upper header 25 of the front and rear furnace membrane walls, the first furnace steam guide pipe group 26 is arranged, and the first furnace steam guide pipe group 26 is connected and communicated with the drum 5; at the other end of the second furnace distributed downcomer group 21, the lower header 27 of the side furnace membrane wall is connected, on the lower header 27 of the side furnace membrane wall, the side furnace membrane wall 28 is connected, the other end of the side furnace membrane wall 28 is connected and communicated with the upper header 29 of the side furnace membrane wall, on the upper header 29 of the side furnace membrane wall, the second furnace steam guide pipe group 30 is arranged, and the other end of the second furnace steam guide pipe group 30 is connected and communicated with the drum 5; the other end of the third furnace distributed downcomer 22 is connected and communicated with the lower header 31 of the rear furnace membrane wall, on the lower header 31 of the rear furnace membrane wall, the rear furnace membrane wall 32 is connected, and the other end of the rear furnace membrane wall 32 is connected and communicated with the upper header 25 of the front and rear furnace membrane walls.

[0015] In the second episode, at the lower end of the downcomer 19, the first flue distributed downcomer group 33, the second flue distributed downcomer group 34, and the third flue distributed downcomer group 35 are connected in parallel; at the other end of the first flue distributed downcomer group 33, the lower header 36 of the front flue membrane wall is connected, on the lower header 36 of the front flue membrane wall, the front flue membrane wall 37 is connected, the other end of the front flue membrane wall 37 is connected and communicated with the upper header 38 of the front flue membrane wall, on the upper header 38 of the front flue membrane wall, the first flue steam guide pipe group 39 is arranged, and the first flue steam guide pipe group 39 is connected and communicated with the drum 5; at the other end of the second flue distributed downcomer group 34, the lower header 40 of the side flue membrane wall is connected, on the lower header 40 of the side flue membrane wall, the side flue membrane wall 41 is connected, the other end of the side flue membrane wall 41 is connected and communicated with the upper header 42 of the side flue membrane wall, on the upper header 42 of the side flue membrane wall, the second flue steam guide pipe group 43 is arranged, and the other end of the second flue steam guide pipe group 43 is connected and communicated with the drum 5; the other end of the third flue distributed downcomer group 35 is connected and communicated with the lower header 44 of the rear flue membrane wall, on the lower header 44 of the rear flue membrane wall, the rear flue membrane wall 45 is connected, and the other end of the rear flue membrane wall 45 is connected and communicated with the upper header 48 of the rear flue membrane wall; the other end of the fourth flue distributed downcomer group 49 is connected and communicated with the lower header 50 of the flue middle partition wall membrane wall, on the lower header 50 of the flue middle partition wall membrane wall, the flue middle partition wall membrane wall 51 is connected, and the other end of the flue middle partition wall membrane wall 51 is divided into two parts, half of which is connected and communicated with the upper header 38 of the front flue membrane wall, and half of which is connected and communicated with the upper header 48 of the rear flue membrane wall.

[0016] A convection tube bundle 46 is arranged in the rear flue 3. The input end of the convection tube bundle 46 is communicated with the second centralized downcomer 19, and the output end of the convection tube bundle 46 is communicated with the drum 5 through a convection tube bundle steam guide pipe 47; both the furnace and the flue are composed of a fully sealed membrane water wall welded by tubes and flat steels on all four sides. The fluidization velocity of the furnace is designed to be 3.6 - 4.2 m / s at BMCR load to ensure sufficient residence time of the fuel in the furnace and guarantee full combustion; the cross-sectional dimension of the furnace is in a rectangular structure; the tubes at the lower part of the front and rear membrane water walls in the dense phase area contract at a certain angle with the vertical line, and the bottom is a water-cooled air distribution plate. The water-cooled air chamber is composed of a half-rear membrane water wall tube bent forward and the membrane water walls on both sides below the air distribution plate; the lower water-cooled bed of the furnace is relatively small, and the contraction ratio is controlled at 45%, that is, the depth of the water-cooled bed is 45% of the upper cross-section of the furnace; the height of the lower dense phase area is 9 - 11 meters, and dense pins are welded and wear-resistant plastic refractory is coated.

Claims

1. A steam-water system for a circulating fluidized bed boiler using highly contaminating coal as fuel, comprising a furnace (1), a cyclone separator (2), a rear flue (3), a tail flue (4) and a boiler drum (5), wherein the cyclone separator (2) is connected to the rear flue (3) via a separator smoke outlet (6), the rear flue (3) is connected to the tail flue (4) via a connecting flue (7), and a main water supply pipe (13), a saturated steam outlet pipe (15), a first centralized downcomer (18) and a second centralized downcomer (19) are respectively provided on the boiler drum (5), characterized in that: A high-temperature screen superheater (8) and a medium-temperature screen superheater (9) are respectively arranged in the furnace (1), a low-temperature superheater (10) is arranged in the rear flue (3), and a low-temperature economizer (11) and a high-temperature economizer (12) are respectively arranged in the tail flue (4); a main water supply pipe (13) passes through the high-temperature economizer (12) and the low-temperature economizer (11) in sequence and is then connected to an economizer feed water header (14); a saturated steam outlet pipe (15) is connected to the low-temperature economizer (11) and the saturated steam outlet pipe (15). The low-temperature superheater inlet header (52) of the heat exchanger (10) is connected together, the output end of the low-temperature superheater (10) is connected to the input end of the medium-temperature screen superheater (9) through the low-temperature superheater outlet header (16) and the first-stage water spray desuperheater, the output end of the medium-temperature screen superheater (9) is connected to the input end of the high-temperature screen superheater (8) through the second-stage water spray desuperheater, and the output end of the high-temperature screen superheater (8) is connected to the steam collecting header (17).

2. The steam-water system of a circulating fluidized bed boiler using highly contaminating coal as fuel according to claim 1, characterized in that: A first furnace dispersed downpipe group (20), a second furnace dispersed downpipe group (21) and a third furnace dispersed downpipe group (22) are connected in parallel at the lower end of the first concentrated downpipe (18); the other end of the first furnace dispersed downpipe group (20) is connected to a furnace front membrane wall lower header (23); the furnace front membrane wall (24) is connected to the furnace front membrane wall lower header (23); the other end of the furnace front membrane wall (24) is connected to a furnace front and rear membrane wall upper header (25); a furnace first steam guide pipe group (26) is provided on the furnace front and rear membrane wall upper header (25); the furnace first steam guide pipe group (26) is connected to the boiler drum (5); the other end of the second furnace dispersed downpipe group (21) is connected to the furnace front membrane wall lower header (23); the furnace front membrane wall (24) is connected to the furnace front and rear membrane wall upper header (25); the furnace front and rear membrane wall upper header (25) is connected to the furnace front and rear membrane wall upper header (25); the furnace front steam guide pipe group (26) is connected to the boiler drum (5); the other end of the second furnace dispersed downpipe group (21) is connected to the furnace front membrane wall lower header (23); the furnace front membrane wall (24) is connected to the furnace front membrane wall upper header (25); the furnace front membrane wall upper header (25 ... steam guide pipe group (26) is connected to the boiler drum (5); the other end of the second furnace dispersed downpipe group (21) is A furnace side membrane wall lower header (27) is connected to the furnace side membrane wall lower header (27), a furnace side membrane wall (28) is connected to the furnace side membrane wall lower header (27), the other end of the furnace side membrane wall (28) is connected to the furnace side membrane wall upper header (29), a furnace second steam guide pipe group (30) is arranged on the furnace side membrane wall upper header (29), the other end of the furnace second steam guide pipe group (30) is connected to the boiler drum (5); the other end of the furnace third dispersed downcomer group (22) is connected to the furnace rear membrane wall lower header (31), the furnace rear membrane wall (32) is connected to the furnace rear membrane wall lower header (31), the other end of the furnace rear membrane wall (32) is connected to the furnace front and rear membrane wall upper headers (25).

3. The steam-water system of a circulating fluidized bed boiler using highly contaminating coal as fuel according to claim 2, characterized in that: A first flue dispersed downpipe group (33), a second flue dispersed downpipe group (34) and a third flue dispersed downpipe group (35) are connected in parallel at the lower end of the second concentrated downpipe (19); the other end of the first flue dispersed downpipe group (33) is connected to a flue front membrane wall lower header (36); a flue front membrane wall (37) is connected to the flue front membrane wall lower header (36); the other end of the flue front membrane wall (37) is connected to a flue front membrane wall upper header (38); a flue first steam guide pipe group (39) is provided on the flue front membrane wall upper header (38); the first steam guide pipe group (39) is connected to the boiler drum (5); the other end of the second flue dispersed downpipe group (34) is connected to the flue front membrane wall lower header (36); A flue side membrane wall lower header (40) is provided, a flue side membrane wall (41) is connected to the flue side membrane wall lower header (40), the other end of the flue side membrane wall (41) is communicated with a flue side membrane wall upper header (42), a flue second steam guide pipe group (43) is provided on the flue side membrane wall upper header (42), the other end of the second steam guide pipe group (43) is communicated with a boiler drum (5); the other end of the flue third dispersed downcomer group (35) is communicated with a flue rear membrane wall lower header (44), a flue rear membrane wall (45) is connected to the flue rear membrane wall lower header (44), the other end of the flue rear membrane wall (45) is communicated with a flue rear membrane wall upper header (48).

4. The steam-water system of a circulating fluidized bed boiler using highly contaminating coal as fuel according to claim 3, characterized in that: A convection tube bundle (46) is arranged in the rear flue (3); an input end of the convection tube bundle (46) is connected to the second centralized downcomer (19); and an output end of the convection tube bundle (46) is connected to the boiler drum (5) via a convection tube bundle steam guide pipe (47).

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