Testing fluidized bed incinerators for energy-efficient operation for the Southtowns Sewage Treatment Agency. Final report

Two methods for improving the energy efficiency of fluidized bed sludge incinerators were evaluated. The first method used paper pulp and polymer as conditioning agents for municipal sludge instead of lime and ferric chloride. Automatic control of the incinerator was the second method evaluated for energy savings. To evaluate the use of paper pulp and polymer as conditioning agents, varying quantities of paper pulp were added to the liquid sludge to determine the optimal sludge-to-paper pulp ratio. The effect of the paper pulp and polymer-conditioned sludge on plant operations also was evaluated. When compared to sludge conditioned with lime and ferric chloride, the paper pulp and polymer-conditioned sludge had similar cake release and feed characteristics, higher BTU values for the dry sludge solids, required less auxiliary fuel for incineration, and generated less ash for disposal. The paper pulp and polymer did not have any appreciable negative effects on the operation of the wastewater treatment plant. It was estimated that processing and incinerating the sludge conditioned with paper pulp and polymer resulted in a cost savings of up to $91.73 per dry ton of activated sludge solids. To evaluate the effect of automatic control, all the incinerator operating parameters including air flow rates, fuel oil feed rates, and sludge feed rates, were automatically monitored and controlled to minimize auxiliary fuel oil use and to keep the incinerator running at optimal conditions. Although effective, the estimated cost savings for automatic control of the incinerator were small