Dried sludge reburning blended with calcium magnesium acetate addition in a fluidized bed combustor.

Abstract

The combustion and pollutant emission characteristics of the dried sludge in a fluidized bed combustor (FBC) were studied. The sludge reburning technology was employed for the first time in FBC. A scheme for using the dried sludge reburning blended with calcium magnesium acetate (CMA) to reduce pollutants simultaneously was also proposed, and the effect of the CMA addition was investigated. Results showed that fluidized bed reburning technology can be used to effectively treat the sewage sludge with lower calorific values. As the secondary fuel mass percentage increases, the unburned carbon content in fly ash and the CO emission increase, resulting in lower combustion efficiency. However, the de-NO ratio increases from 37.1% to 53.7%, and the de-SO2 ratio only increased from 1.6% to 7.6% as the secondary fuel mass percentage increase from 10% of 25%. For dried sludge blended with CMA, the minimum emissions of SO2 and NO significantly decrease to 254\xa0mg/Nm3 and 70.9\xa0mg/Nm3 at Ca/S ratio of 2, respectively. Results of main gaseous pollutant emissions from the sludge combustion in an FBC using different pollutant removal methods were compared under well-defined conditions. Fuel reburning blended with CMA addition has the smallest SO2 and NO emissions.