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Contenuto archiviato il 2022-12-27

FLUIDIZED COAL COMBUSTION IN A LARGE LOW COST INDUSTRIAL WATER TUBE BOILER, INTEGRATED WITH A CHP SYSTEM

Obiettivo

To demonstrate the improved thermal efficiency of fluidized coal combustion used with a large, low cost industrial water tube boiler integrated into a combined heat and power system, and to obtain data for the conversion of oil and gas fired boilers to coal and for the production of new fluidized coal fired boilers.
The original programme submitted to the Commission was changed after 2 tube bursts and the need to protect the bed coil became obvious.
Bed start-up from cold to 900 C can be achieved in 25 minutes with temperatures during normal coal firing operations varying either vertically or horizontally by less than 25 C. The insulating sand layer at the bed's base enables bed phase temperatures to be maintained at less than 200 C. Against a design estimate of 80.4% maximum efficiency to steam attained was 81% and slightly above maximum rated output of 103% MCR. At reduced output (31% MCR) firing on 4 beds, efficiency fell to 69.8%, attributable to heat loss in the blow-down system. A reduction in efficiency to steam at low loads is a feature of this boiler type.
Predicted superheat temperature at full load is 440 C with 460 C regularly attained (the turbine's upper tolerance).
The installation has been developed to a point where it constitutes a viable demonstration unit, providing important data and experience which could improve design for potential customers.
Unfortunately, the River Don project officially ceased operation at the end of December 1985, because the site on which the test plant operated (Sheffield Forgemasters Ltd, Sheffield, England), no longer presented sufficient steam load to take steam from the fluidized-bed boiler. Under these circumstances it was decided that further development work at River Don site could not be justified.
The plant was dismantled and removed from site in 1990 at the insistence of the site owner.
The boiler (producing steam at 45.5 Bar, 10.1 Kgs and 440 C) is fired by a coal fluidized bed combustion unit measuring 5.03 m in width. Designed originally for base load operation, the system was modified to provide 6:1 turndown with rapid response to load change; steam output may either be used for power generation via steam turbines or process purposes such as steam hammers. The bed's 6 individually controlled segments were modified to 3 pairs providing a 3:1 turndown on each with +- 50% of the bed's heat release removed by 2 pancake coils. The remainder is taken out in the convection sections (these include an economiser and a superheater section). Coke oven gas is used as stand-by fuel and start-up, and is capable of providing full boiler output. Air supply to the bed sections is by forced draught fan; they are each equipped with a coal feed rotary valve, drop tube and supply system for coke oven gas. Most of the ash is carried out by flue gas and collected by a multi-cell grit arrestor. Periodically, large particles are removed by the cleaning system on each bed. The boiler is controlled by a programmable logic controller: it also ensures safe operation and provides automatic start-up.

Argomento(i)

Invito a presentare proposte

Data not available

Meccanismo di finanziamento

DEM - Demonstration contracts

Coordinatore

BRITISH COAL CORPORATION (RESEARCH ESTABLISHMENT
Contributo UE
Nessun dato
Indirizzo
COAL RESEARCH ESTABLISHMENT STOKE ORCHARD, CHELTENHAM
GL52 4RZ Gloucester
Regno Unito

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Costo totale
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