Abstract
Wet-biomass such as sewage-sludge is very large resources of renewable energy and carbon material. However, since such wet-biomass contains much moisture, it is necessary to be dried before energy utilization as fuel. Therefore, we have developed a carbonization process combined with drying by fermentation. This process consists of two steps; drying by aerobic fermentation without additional energy to vaporize the moisture, and carbonizing by heat generated from burning of only volatile-matter derived from the sludge. In this paper, we focus on the drying step. In drying step, wet-sludge received was immediately mixed with wood-chips of about 2 times by volume to make a heap for fermentation. The temperature in the heap increased rapidly up-to ca.80 °C for several days, then decreased gradually. The moisture of the sludge decreased gradually with temperature from ca.80wt% to below 30 wt% for 40 ～60 days. During fermentation, the heap was re-built every 7～10 days. The dried sludge was fed to carbonization step after removing the wood-chips by sieving. We discussed the changes of the sludge properties by drying, and the effects of the heap size and air-flow-rate blown into the heap on the changes of temperature and moisture during fermentation.
