The use of municipal solid waste as an additional fuel in boilers engineered for other fuels has gained increasing interest because it offers a possibility for utilizing the waste on a smaller scale than in special incinerators for waste combustion. The use of municipal solid waste as an additional fuel; however, is associated with many problems, particularly where conventional boiler constructions are concerned. Fluidized-bed boilers have been regarded as more attractive because they have given positive experiences with many different kinds of fuels.

To find out the degree of pre-treatment required for municipal solid wastes and the characteristics "of fluidized-bed combustion of waste in general, as well as the harmful effects, a series of industrial-scale combustion tests was performed. The experiments were carried out by burning manually sorted municipal wastes as an addition to the fiber waste from a fiber mill. In another series of experiments, pellets manufactured frcm n~nicipal wastes were burned alternately with fiber waste, bark waste, or hard coal.

It was learned frcm these experiments that appropriately pre-treated municipal solid waste can be used as additional fuel in fluidized-bed boilers. Emission studies showed that the burning can be acccmplished so that the highest environmental requirements will be filled. The corrosion studies revealed that no significant corrosion was formed in test material. ever, to avoid corrosion risk on superheater surfaces, the proportion of municipal wastes must not be too high, preferably less than 20%. By using high-alloyed steel as tube material, corrosion risks are insignificant here too.

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