2015 Volume 94 Issue 12 Pages 1422-1427
A carbonization process combined with drying by fermentation has been developed to utilize effectively wet-biomass such as sewage-sludge. This process consists of two steps; drying by aerobic fermentation and carbonizing without fossil fuel for heating. In this paper, we focus on the carbonization step because we reported the drying step in the previous paper. We designed and constructed a carbonization plant to treat 1.0 t/h dried-sludge of lower 30wt% moisture. It consists of a rotary kiln heated externally and a combustor burning only volatile-matter from the sludge during stable operation of the plant. At a start of the plant operation, A-fuel is burned in the combustor to heat the kiln up to over 400 °C. Then the dried sewage-sludge of ca.30 wt% moisture is gradually fed into the kiln. These operations provided that the stable carbonization condition without A-fuel was temperature of 410 - 430 °C at the sludge feeding rate of 1.0 t/h. Under this condition, char yield was ca.50wt%, and its heating value and carbon content were ca.3,500 kcal/kg and 35 - 38 wt%, respectively. At present, the plant is continuously operated for around 3 weeks at once without fossil fuels except at start up.
