Combustion Characteristics of Sewage Sludge in a Fluidized Bed

Combustion experiments of Shidongkou sewage sludge from China were carried out by using a small lab-scale fluidized bed, and the effects of moisture content and feed rate of sewage sludge and the transfer of heavy metals were analyzed. Studied sewage sludge with a moisture content of no more than 40% can stably burn in the fluidized bed without any auxiliary fuel input. Enhancing the bed temperature of the dense phase, strengthening the gas-solid mixing of dense phase, and increasing the feed rate of sludge are very necessary for the ignition of sludge with higher moisture content; however, higher feed rate will give rise to an increase of both the incomplete combustion heat loss and the physical absorbing heat amount of new sludge into the fluidized bed, reducing the bed temperature. Gaseous pollutants from the fluidized bed were discussed under different experimental conditions. At last, it was presented that heavy metals except Zn within sewage sludge are mostly concentrated in bottom ashes and bag filter ashes.