Dual-bed system for preventing boiler heating surface from being contaminated

Abstract

A dual-bed system for preventing a boiler heating surface from being contaminated comprises a fluidized bed, a cyclone separator, a coal ash distributor, an ash-coal mixer, a lower pyrolysis bed, a return feeder and a cleaner, wherein the cyclone separator is connected with the upper lateral side of the fluidized bed; the inlet end of the coal ash distributor; the two outlets of the coal ash distributor are respectively connected with the inlet of the return feeder and the inlet of the ash-coal mixer; the outlet of the ash-coal mixer is connected with the inlet of the lower pyrolysis bed; the return feeder close to the lower lateral side of the fluidized bed is connected with the inlet on the lower lateral side of the fluidized bed; and the outlet of the cleaner is connected with the inlet on the lower lateral side of the fluidized bed.

Claims

1. A dual-bed system for preventing a boiler heating surface from being contaminated comprising: a fluidized bed, a cyclone separator, a coal ash distributor, an ash-coal mixer, a lower pyrolysis bed, a return feeder and a cleaner, wherein the cyclone separator is connected with the upper lateral side of the fluidized bed so that the high-temperature coal ash from the fluidized bed enters the cyclone separator, the outlet end of the cyclone separator is connected with the inlet end of the coal ash distributor; the coal ash distributor is provided with two outlets one of which is connected with the inlet of the return feeder and the other one of which is connected with the inlet of the ash-coal mixer; the outlet of the ash-coal mixer is connected with the inlet of the lower pyrolysis bed; the lower pyrolysis bed is provided with two outlets one of which is connected with the inlet of the return feeder and the other one of which is connected with the inlet of the cleaner; the return feeder close to the lower lateral side of the fluidized bed is connected with the inlet on the lower lateral side of the fluidized bed; and the outlet of the cleaner is connected with the inlet on the lower lateral side of the fluidized bed.

2. The system according to claim 1, wherein a heat exchanger is arranged behind the cyclone separator and connected with a draught fan which is connected with a chimney.

3. The system according to claim 1, wherein coal is fed into the ash-coal mixer via a feeder which is connected with the ash-coal mixer, and a coal hopper is arranged above the feeder.

4. The system according to claim 1, wherein the upper end of the fluidized bed extends into the cyclone separator, the high-temperature coal ash of the cyclone separator enters the coal ash distributor to feed part of the high-temperature coal ash into the return feeder and the other part of the high-temperature coal ash into the ash-coal mixer, meanwhile, raw coal is fed into the ash-coal mixer) through a coal hopper and the feeder to be mixed with the high-temperature coal ash in the ash-coal mixer; the mixture of the coal and the coal ash enters the lower pyrolysis bed to be pyrolyzed, the pyrolyzed high-alkalinity semi-coke and coal ash enters the return feeder; and the high-temperature coal ash not passing the lower pyrolysis bed and the pyrolyzed and mixed high-alkalinity semi-coke and coal ash are both fed into the furnace chamber of the boiler of the fluidized bed through the return feeder to be combusted, wherein the pyrolysis gas obtained by the lower pyrolysis bed first passes the cleaner to be sodium-removed and then enters the fluidized bed to be combusted.

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 coal hopper; 2 feeder; 3 blower; 4 fluidized bed; 5: cyclone separator; 6 coal ash distributor; 7 heat exchanger; 8 draught fan; 9 chimney; 10 coal hopper; 11 feeder; 12 ash-coal mixer; 13 cleaner; 14 lower pyrolysis bed; 15 return feeder.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) As shown in FIG. 1, a dual-bed system for preventing a boiler heating surface from being contaminated comprises a fluidized bed 4, a cyclone separator 5, a coal ash distributor 6, an ash-coal mixer 12, a lower pyrolysis bed 14, a return feeder 15 and a cleaner 13. The cyclone separator 5 is connected with the upper lateral side of the fluidized bed 4 so that the high-temperature coal ash from the fluidized bed 4 enters the cyclone separator 5, and the outlet end of the cyclone separator 5 is connected with the inlet end of the coal ash distributor 6 which is provided with two outlets one of which is connected with the inlet of the return feeder 15 and the other one of which is connected with the inlet of the ash-coal mixer 12; the outlet of the ash-coal mixer 12 is connected with the inlet of the lower pyrolysis bed 14; the lower pyrolysis bed 14 is provided with two outlets one of which is connected with the inlet of the return feeder 15 and the other one of which is connected with the inlet of the cleaner 13; the outlet of the external bed is connected with the inlet of the return feeder 15; the return feeder 15 close to the lower lateral side of the fluidized bed 4 is connected with the inlet on the lower lateral side of the fluidized bed 4; and the outlet of the cleaner 13 is connected with the inlet on the lower lateral side of the fluidized bed 4.

(4) A heat exchanger 7 is arranged behind the cyclone separator 5 and connected with a draught fan 8 which is connected with a chimney 9.

(5) Coal is fed into the ash-coal mixer 12 via a feeder 11 which is connected with the ash-coal mixer 12, and the feeder 11 is provided with a coal hopper 10.

(6) The cleaner 13 may be a filter.

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

(8) As shown in FIG. 1, in the initial operation phase of a boiler, a non-local coal may be blended or external ash may be added through the coal hopper 1 and the feeder 2 until the boiler runs normally and generates a given amount of coal ash, then the coal ash generated by the boiler is used to pyrolyze the raw coal from the coal hopper 10 and the feeder 11. The feeding of the coal using the coal hopper 1 and the feeder 2 can be stopped after the lower pyrolysis bed 14 runs normally. When the boiler runs normally, the semi-cake resulting from the pyrolysis is combusted with the air from the blower 3 in the furnace chamber of the fluidized bed 4, and the resulting coal ash and smoke enters the separator 5 to be separated. After the temperature of the separated smoke is reduced by the heat exchanger 7, the smoke is discharged into the air by the draught fan 8 through the chimney 9. The separated coal ash enters the distributor 6 to be divided into two parts according to the need of the lower pyrolysis furnace 14, one part of the coal ash is directly returned to the furnace of the fluidized bed 4 by the return feeder 15 while the other part of the coal ash enters the mixer 12 to be mixed with the high-alkalinity coal from the coal hopper 10 and the feeder 11. The hot ash and the high-alkalinity coal uniformly mixed in the mixer 12 enter the lower pyrolysis bed 14 to be pyrolyzed; after the Na contained in the gas resulting from the pyrolysis is removed by the cleaner 13, the gas enters the fluidized bed 4 to be combusted, and the pyrolyzed hot ash and high-alkalinity semi-cake enters the return feeder 15 to be combusted in the furnace chamber of the fluidized bed 4. The slag discharging of the boiler is carried out on the bottom of the fluidized bed 4. Most of volatilizable sodium is removed after the high-alkalinity coal is pyrolyzed in the lower pyrolysis furnace 14, as the sodium content of high-alkalinity coal is reduced, the content of the active sodium contained in the smoke resulting from the combustion carried out in the furnace chamber of the fluidized bed 4 is greatly reduced, thus there is almost no contamination caused when the smoke passes the subsequent heat-absorbing surface.