THE ADVANTAGES OF CO-FIRING PEAT AND WOOD IN IMPROVING BOILER OPERATION AND PERFORMANCE

摘要

Wood fuels differ from peat in many properties; moisture content, heating value, energy density, particle size, ash content and ash quality etc. One of the most important differences between wood fuels and peat is ash behaviour during combustion. Easily soluble alkalines are released during combustion into gas phase and cause risk for boiler bed material agglomeration, fouling of heat transfer surfaces and superheater corrosion. Fouling inhibits heat transfer and reduces boiler efficiency, additionally; chlorine rich deposits induce hot corrosion of heat transfer surfaces. VTT's studies show that with co-firing peat with wood a great deal of benefits is achieved in controlling emissions and harmful forming of deposition. Depending on the boiler type, it is recommended to combust 10 - 20 % of peat with wood fuels in order to reduce above mentioned operational problems. If wood fuels consist mainly of new tree growth, like logging residue, it is favourable to use even higher share of peat, 30 - 40 %, as co-firing fuel.