External bed type double-fluidized bed system for preventing boiler contamination

Abstract

An external bed type double-fluidized bed system for preventing boiler contamination includes a fluidized bed combustion furnace, a cyclone separator, a coal ash distributor and a fluidized bed pyrolysis furnace. The fluidized bed combustion furnace is connected with the coal ash distributor, the coal ash distributor is connected with the coal ash inlet on a side wall of the fluidized bed combustion furnace through a return feeder with which the coal ash outlet of the fluidized bed pyrolysis furnace is also connected through an external bed, and the return feeder is connected with the fluidized bed combustion furnace. A fuel coal is pyrolyzed in the fluidized bed pyrolysis furnace at a temperature to volatize alkali chlorides into a pyrolysis gas, thereby reducing the content of the alkali chlorides contained in the coal in the fluidized bed combustion furnace and relieving the contamination to a convective heat-absorbing surface.

Claims

1. An external bed type double-fluidized bed system for preventing boiler contamination, comprising a fluidized bed combustion furnace (4), a cyclone separator (5), a coal ash distributor (6) and a fluidized bed pyrolysis furnace (8), wherein an outlet on an upper end of a side wall of the fluidized bed combustion furnace (4) is connected with an inlet of the cyclone separator (5), the cyclone separator (5) separates a high-temperature coal ash from the fluidized bed combustion furnace (4), an outlet on a bottom of the cyclone separator (5) is connected with an inlet of the coal ash distributor (6) to feed the separated high-temperature coal ash into the coal ash distributor (6), a smoke outlet is provided on a top of the cyclone separator (5), a first coal ash outlet and a second coal ash outlet are provided on the coal ash distributor (6), the first coal ash outlet is connected with a coal ash inlet on a side wall of the fluidized bed combustion furnace (4) through a return feeder (13), the second coal ash outlet is connected with a coal ash inlet on a side wall of the fluidized bed pyrolysis furnace (8), a pyrolysis gas outlet is provided on an upper end of a side wall of the fluidized bed pyrolysis furnace (8), a raw coal inlet is provided in a middle or on a lower part of a side wall of the fluidized bed pyrolysis furnace (8), a coke-coal ash mixture outlet is provided on a lower end of a side wall of the fluidized bed pyrolysis furnace (8), the coke-coal ash mixture outlet is connected with the return feeder (13) through an external bed (15) and further connected with the coal ash inlet of the fluidized bed combustion furnace (4) through the return feeder (13), and the smoke outlet on the top of the cyclone separator (5) is connected with a bottom of the fluidized bed pyrolysis furnace (8) through a second blower (12) to feed separated high-temperature smoke into the fluidized bed pyrolysis furnace (8).

2. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 1, further comprising a cleaner (14) and a pyrolysis separator (7), a pyrolysis gas inlet is provided on a side wall of the pyrolysis separator (7), a pyrolysis gas outlet is provided on a top of the pyrolysis separator (7), and a pyrolyzed coal ash outlet is provided on a bottom of the pyrolysis separator (7) for separating the obtained pyrolyzed coal ash; the pyrolysis gas inlet of the pyrolysis separator (7) is connected with the pyrolysis gas outlet on the fluidized bed pyrolysis furnace (8), the pyrolysis gas outlet of the pyrolysis separator (7) is connected with an inlet of the cleaner (14), the pyrolyzed coal ash outlet of the pyrolysis separator (7) is connected with the external bed (15) and further connected with the return feeder (13) through the external bed (15), and the return feeder (13) is connected with the fluidized bed combustion furnace (4).

3. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 1, wherein the smoke outlet of the cyclone separator (5) is connected with a chimney through a draught fan (11).

4. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 3, wherein the coal ash outlet of the fluidized bed pyrolysis furnace (8) is connected with the external bed (15), the external bed (15) is connected with the coal ash inlet on a side wall of the fluidized bed combustion furnace (4) through the same return feeder (13).

5. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 4, wherein the fluidized bed combustion furnace (4) is connected with a first feeder (2) which is provided with a first coal hopper (1).

6. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 4, wherein an outlet of a cleaner (14) is connected with a pyrolysis gas inlet on a side wall of the fluidized bed combustion furnace (4).

7. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 6, wherein the raw coal inlet of the fluidized bed pyrolysis furnace (8) is connected with a second feeder (10) which is provided with a second coal hopper (9).

8. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 7, wherein the working process of the system is as follows: a pyrolyzed semi-coke is combusted with air in the chamber of the fluidized bed combustion furnace (4), the resulting coal ash and smoke enters the cyclone separator (5) to be separated, one part of the separated smoke is fed into the fluidized bed pyrolysis furnace (8) through the second blower (12) while the other part is discharged from the chimney through the draught fan (11); the separated coal ash enters the coal ash distributor (6) to be divided into two parts according to the need of the fluidized bed pyrolysis furnace (8): one part is directly returned to the chamber of the fluidized bed combustion furnace (4) by the return feeder (13) through the first coal ash outlet while the other part enters the fluidized bed pyrolysis furnace (8) through the second coal ash outlet to be mixed with the high-alkalinity coals from the second coal hopper (9) and the second feeder (10) and then pyrolyzed in the fluidized bed pyrolysis furnace (8), the sodium contained in the gas resulting from the pyrolysis is removed using the cleaner (14), then the gas enters the fluidized bed combustion furnace (4) to be combusted; the pyrolyzed hot ash and high-alkalinity semi-coke enters the external bed (15) to be exchanged heat, after the temperature of the hot ash and the high-alkalinity semi-coke is adjusted, the hot ash and the high-alkalinity semi-coke enter the return feeder (13) through the external bed (15) and is then fed into the fluidized bed combustion furnace (4) by smoke to be combusted herein; the slag discharging of the boiler is carried out on the bottom of the fluidized bed combustion furnace (4); most of volatilizable sodium is removed after the high-alkalinity coals are pyrolyzed in the fluidized bed pyrolysis furnace (8), as the sodium content of the high-alkalinity coals is reduced, there is almost no contamination.

9. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 2, wherein the smoke outlet of the cyclone separator (5) is connected with a chimney through a draught fan (11).

10. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 9, wherein the coal ash outlet of the fluidized bed pyrolysis furnace (8) is connected with the external bed (15), the external bed (15) is connected with the coal ash inlet on a side wall of the fluidized bed combustion furnace (4) through the same return feeder (13).

11. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 10, wherein the fluidized bed combustion furnace (4) is connected with a first feeder (2) which is vided with a first coal hopper (1).

12. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 10, wherein an outlet of the cleaner (14) is connected with a pyrolysis gas inlet on a side wall of the fluidized bed combustion furnace (4).

13. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 12, wherein the raw coal inlet of the fluidized bed pyrolysis furnace (8) is connected with a second feeder (10) which is provided with a second coal hopper (9).

14. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 7, wherein the working process of the system is as follows: a pyrolyzed semi-coke is combusted with air in the chamber of the fluidized bed combustion furnace (4), the resulting coal ash and smoke enters the cyclone separator (5) to be separated, one part of the separated smoke is fed into the fluidized bed pyrolysis furnace (8) through the second blower (12) while the other part is discharged from the chimney through the draught fan (11); the separated coal ash enters the coal ash distributor (6) to be divided into two parts according to the need of the fluidized bed pyrolysis furnace (8): one part is directly returned to the chamber of the fluidized bed combustion furnace (4) by the return feeder (13) through the first coal ash outlet while the other part enters the fluidized bed pyrolysis furnace (8) through the second coal ash outlet to be mixed with the high-alkalinity coals from the second coal hopper (9) and the second feeder (10) and then pyrolyzed in the fluidized bed pyrolysis furnace (8), the sodium contained in the gas resulting from the pyrolysis is removed using the cleaner (14), then the gas enters the fluidized bed combustion furnace (4) to be combusted; the pyrolyzed hot ash and high-alkalinity semi-coke enters the external bed (15) to be exchanged heat, after the temperature of the hot ash and the high-alkalinity semi-coke is adjusted, the hot ash and the high-alkalinity semi-coke enter the return feeder (13) through the external bed (15) and is then fed into the fluidized bed combustion furnace (4) by smoke to be combusted herein; the slag discharging of the boiler is carried out on the bottom of the fluidized bed combustion furnace (4); most of volatilizable sodium is removed after the high-alkalinity coals are pyrolyzed in the fluidized bed pyrolysis furnace (8), as the sodium content of the high-alkalinity coals is reduced, there is almost no contamination.

15. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 2, wherein an outlet of the cleaner (14) is connected with a pyrolysis gas inlet on a side wall of the fluidized bed combustion furnace (4).

16. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 15, wherein the raw coal inlet of the fluidized bed pyrolysis furnace (8) is connected with a second feeder (10) which is provided with a second coal hopper (9).

17. The external bed type double-fluidized bed system for preventing boiler contamination according to claim 16, wherein the working process of the system is as follows: a pyrolyzed semi-coke is combusted with air in the chamber of the fluidized bed combustion furnace (4), the resulting coal ash and smoke enters the cyclone separator (5) to be separated, one part of the separated smoke is fed into the fluidized bed pyrolysis furnace (8) through the second blower (12) while the other part is discharged from the chimney through the draught fan (11); the separated coal ash enters the coal ash distributor (6) to be divided into two parts according to the need of the fluidized bed pyrolysis furnace (8): one part is directly returned to the chamber of the fluidized bed combustion furnace (4) by the return feeder (13) through the first coal ash outlet while the other part enters the fluidized bed pyrolysis furnace (8) through the second coal ash outlet to be mixed with the high-alkalinity coals from the second coal hopper (9) and the second feeder (10) and then pyrolyzed in the fluidized bed pyrolysis furnace (8), the sodium contained in the gas resulting from the pyrolysis is removed using the cleaner (14), then the gas enters the fluidized bed combustion furnace (4) to be combusted; the pyrolyzed hot ash and high-alkalinity semi-coke enters the external bed (15) to be exchanged heat, after the temperature of the hot ash and the high-alkalinity semi-coke is adjusted, the hot ash and the high-alkalinity semi-coke enter the return feeder (13) through the external bed (15) and is then fed into the fluidized bed combustion furnace (4) by smoke to be combusted herein; the slag discharging of the boiler is carried out on the bottom of the fluidized bed combustion furnace (4); most of volatilizable sodium is removed after the high-alkalinity coals are pyrolyzed in the fluidized bed pyrolysis furnace (8), as the sodium content of the high-alkalinity coals is reduced, there is almost no contamination.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram illustrating the structure of a system according to the disclosure.

(2) Explanation of reference signs in FIG. 1: 1 first coal hopper; 2 first feeder; 3 first blower; 4 fluidized bed combustion furnace; 5: cyclone separator; 6 coal ash distributor; 7 pyrolysis separator; 8 fluidized bed pyrolysis furnace; 9 second coal hopper; 10 second feeder; 11 draught fan; 12 second blower; 13 return feeder; 14 cleaner; 15 external bed.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) The disclosure is described below in detail with reference to accompanying drawings.

(4) As shown in FIG. 1, an external bed type double-fluidized bed system for preventing boiler contamination comprises: a fluidized bed combustion furnace 4, a cyclone separator 5, a coal ash distributor 6 and a fluidized bed pyrolysis furnace 8, wherein the fluidized bed combustion furnace 4 is connected with a first feeder 2, the outlet on the upper end of a side wall of the fluidized bed combustion furnace 4 is connected with the inlet of the cyclone separator 5, the cyclone separator 5 separates the high-temperature coal ash from the fluidized bed combustion furnace 4, the outlet on the bottom of the cyclone separator 5 is connected with the inlet of the coal ash distributor 6 to feed the separated high-temperature coal ash into the coal ash distributor 6, a smoke outlet is provided on the top of the cyclone separator 5; a first coal ash outlet and a second coal ash outlet are provided on the coal ash distributor 6, the first coal ash outlet is connected with the coal ash inlet on a side wall of the fluidized bed combustion furnace 4 through a return feeder 13, and the second coal ash outlet is connected with the coal ash inlet on a side wall of the fluidized bed pyrolysis furnace 8; a pyrolysis gas outlet is provided on the upper end of a side wall of the fluidized bed pyrolysis furnace 8, a raw coal inlet is provided in the middle or on the lower part of a side wall of the fluidized bed pyrolysis furnace 8; a coke-coal ash mixture outlet is provided on the lower end of a side wall of the fluidized bed pyrolysis furnace 8 and connected with the return feeder 13 through an external bed 15 and then connected with the coal ash inlet on the fluidized bed combustion furnace 4 through the return feeder 13.

(5) The system is further equipped with a cleaner 14 and a pyrolysis separator 7, a pyrolysis gas inlet is provided on the side wall of the pyrolysis separator 7, a pyrolysis gas outlet is provided on the top of the pyrolysis separator 7, and a pyrolyzed coal ash outlet is provided on the bottom of the pyrolysis separator 7 for separating the obtained pyrolyzed coal ash. The pyrolysis gas inlet of the pyrolysis separator 7 is connected with the pyrolysis gas outlet on the fluidized bed pyrolysis furnace 8, the pyrolysis gas outlet of the pyrolysis separator 7 is connected with the inlet of the cleaner 14, the pyrolyzed coal ash outlet of the pyrolysis separator 7 is connected with an external bed 15 and further connected with the return feeder 13 through the external bed 15, and the return feeder 13 is connected with the fluidized bed combustion furnace 4.

(6) The smoke outlet on the top of the cyclone separator 5 is connected with the bottom of the fluidized bed pyrolysis furnace 8 through a second blower 12 to feed the separated high-temperature smoke into the fluidized bed pyrolysis furnace 8.

(7) Further, the smoke outlet of the cyclone separator 5 is connected with a chimney through a draught fan 11.

(8) That is, one part of the smoke from the top of the cyclone separator 5 is fed into the fluidized bed pyrolysis furnace 8 through the second blower 12 while the other part is discharged from a chimney through the draught fan 11.

(9) Further, the coal ash outlet of the fluidized bed pyrolysis furnace 8 is connected with the external bed 15, the external bed 15 is connected with the coal ash inlet on a side wall of the fluidized bed combustion furnace 4 through the same return feeder 13.

(10) The first feeder 2 is provided with a first coal hopper 1.

(11) The outlet of the cleaner 14 is connected with the pyrolysis gas inlet on a side wall of the fluidized bed combustion furnace 4.

(12) The raw coal inlet of the fluidized bed pyrolysis furnace 8 is connected with a second feeder 10 which is provided with a second coal hopper 9.

(13) The working process of the system is as follows:

(14) pyrolyzed semi-coke is combusted with the air from the first blower 3 in the chamber of the fluidized bed combustion furnace 4, the resulting coal ash and smoke enters the cyclone separator 5 to be separated, one part of the separated smoke is fed into the fluidized bed pyrolysis furnace 8 through the second blower 12 while the other part is discharged from the chimney through the draught fan 11; the separated coal ash enters the coal ash distributor 6 to be divided into two parts according to the need of the fluidized bed pyrolysis furnace 8: one part is directly returned to the chamber of the fluidized bed combustion furnace 4 by the return feeder 13 through the first coal ash outlet while the other part enters the fluidized bed pyrolysis furnace 8 through the second coal ash outlet to be mixed with the high-alkalinity coals from the second coal hopper 9 and the second feeder 10 and then pyrolyzed in the fluidized bed pyrolysis furnace 8, the sodium contained in the gas resulting from the pyrolysis is removed using the cleaner 14, then the gas enters the fluidized bed combustion furnace 4 to be combusted; the pyrolyzed hot ash and high-alkalinity semi-coke enters the external bed 15 to be exchanged heat, after the temperature of the hot ash and the high-alkalinity semi-coke is adjusted, the hot ash and the high-alkalinity semi-coke enter the return feeder 13 through the external bed 15 and is then fed into the fluidized bed combustion furnace 4 by smoke to be combusted herein; the slag discharging of the boiler is carried out on the bottom of the fluidized bed combustion furnace 4; most of volatilizable sodium is removed after the high-alkalinity coals are pyrolyzed in the fluidized bed pyrolysis furnace 8, as the sodium content of the high-alkalinity coals is reduced, the content of the active sodium in the smoke resulting from the combustion carried out in the chamber of the fluidized bed combustion furnace 4 is greatly reduced, consequentially, there is almost no contamination caused when the smoke passes the subsequent heat-absorbing surface.

(15) By using a two-bed system to first pyrolyze fire coal in the fluidized bed pyrolysis furnace 8 at a high temperature to volatilize volatilizable alkali chlorides into pyrolysis gas, the disclosure reduces the content of the alkali metals contained in the coal entering the fluidized bed combustion furnace 4 and therefore decreases the alkali metals in combustion-produced smoke, in this way, the disclosure fundamentally eliminates or greatly relieves the contamination to a convective heat-absorbing surface, besides, as the pyrolysis gas is fed into the fluidized bed combustion furnace 4 to be combusted after the sodium in the pyrolysis gas is removed using the cleaner 14, the combustible components contained in the coal is effectively used, thus guaranteeing the combustion efficiency of a boiler. The heat exchange between the heat-absorbing surface of the external bed 15 with pyrolyzed semi-coke and pulverized coal ash not only increases a heat exchange capacity but also adjusts the temperature of a pyrolysis and combustion fluidized bed, thus keeping the system in an optimal working state.

(16) The technical route of the disclosure is that combusted coal ash having a relatively high temperature is continuously separated and collected using the cyclone separator 5 and then fed into the fluidized bed pyrolysis furnace 8 through the coal ash distributor 6 to be uniformly mixed with the pulverized coal fed by the second feeder 10, the pulverized coal entering the furnace is pyrolyzed in the fluidized bed pyrolysis furnace 8 by means of the heat of the coal ash and the gas resulting from the combustion in a fluidized bed combustion furnace 4 so that the alkali metals contained in the pulverized coal volatilizes into the pyrolysis gas at a high temperature, the pyrolysis gas enters a cleaner 14 from the outlet of the pyrolysis separator 7 provided on the top of the fluidized bed pyrolysis furnace 8, after the alkali metals contained in the pyrolysis gas are removed, the pyrolysis gas is fed into the chamber of the fluidized bed combustion furnace 4 to be combusted. After being adjusted in temperature by an external bed 15, the mixture of the coke and coal ash from the outlet of the fluidized bed pyrolysis furnace 8 enters a return feeder 13 through the external bed 15, and the return feeder 13 feeds the mixture into the chamber of the fluidized bed combustion furnace 4 so that the mixture is combusted in the chamber of the fluidized bed combustion furnace 4. As the alkali metals in the coke are greatly decreased, the formation of an initial contamination layer for the adhesion of the alkali metal compounds contained in the smoke resulting from the combustion in the fluidized bed combustion furnace 4 on the pipe wall of a convective heat-absorbing surface at a low temperature is prevented, thus breaking the initial condition for the formation of contamination.