Fuel characteristics of sewage sludge using thermal treatment

Pretreatment of sewage sludge under inert condition can produce enhanced solid fuel qualities. In this study, sewage sludge was torrefied in a horizontal tubular reactor at temperatures ranging from 200 to 450 °C. Improved fuel characteristics with reduced oxidized compounds which become more like coal were depicted by the CHO index and Van Krevelen diagram. The CHO index based on molecular C, H, and O data obtained for 450 °C was − 0.65. Statistical Grindability Index (SGI) gradually decreased with the lowest value for 450 °C while the fuel ratio increased with increase in torrefaction temperature. The spontaneous combustion of sewage sludge was analyzed and the average spontaneous combustion temperature of 211.4 °C was obtained.