DEPOSITION INVESTIGATION IN STRAW-FIRED BOILERS

Applying annual crops as fuel in power plants may give rise to severe deposition in the boilers. in Denmark, straw is applied as fuel in som e small combined power and district heating boiler plants. Large diffe rences have been observed in the amount of deposition in the furnace c hamber and on superheater tubes when different straw fuel parcels are applied. We have performed 12 experiments at two straw-fired power pla nts with a fuel input of 23 and 31 MW. in all the experiments the boil ers were fed by one type of reasonably uniform straw during an 8 h per iod. Deposition probes simulating superheater coils were inserted near the superheaters and in the boiler chamber. A long range of parameter s was measured, including local temperature, exit flue gas composition , and aerosol particles in the flue gas. Detailed chemical analyses ha ve been performed on the straw, bottom and flue ash, and deposition sa mples. On the basis of the experimental data the transport of the mine rals through the boilers has been followed. For wheat and barley straw s the extent of deposition could be correlated with the content of pot assium in the straws.