Phosphorous Transformation during Coal and Sewage Sludge Co-Combustion

Abstract

Sewage sludge (SS) contained considerable phosphorous resource and SS incineration technology had become an important method to reuse SS. To alleviate the difficulty of SS mono-combustion caused by its low heating value, high-rank fuels should be introduced. Effects of SS and coal co-combustion on phosphorus fixation rate in ash were studied through drop tube furnace. It was concluded that rising temperature increased the fixation rate of phosphorus in SS ash. Due to the obvious high calcium content in Xiaolongtan coal (XLT), the co-combustion of SS and XLT effectively increased the fixation rate of phosphorus in ash and phosphorous capture by solid minerals was improved by temperature increase. In the meanwhile, more XLT introduced more calcium into the combustion system, which captured more phosphorous in ash. Whereas, there were just a small quantity of calcic and magnesian minerals in Xiheishan coal (XHS) and as a result, higher temperature accelerated phosphorous emission. The fixation rate of phosphorus during co-combustion of SS and XHS was not significantly affected by the different proportions of XHS. Finally, the co-combustion of 70 % XLT and 30 % SS effectively fixed phosphorus at 1000 °C, where the fixation rate in ash was risen dramatically to as high as 93.29 %.