Abstract
A bubbling-fluidized bed furnace has been used conventionally to incinerate sewage sludge. In recent years, for sludge treatment, especially for incineration, measures are required to deal with changes and fluctuations in sludge properties due to : 1. High-calorie sewage sludge, 2. Centralized collection and treatment of sewage sludge, and 3. Mixed incineration of screenings. To cope with the above, the Fast Fluidized Bed Incinerator (circulating-fluidized bed incinerator), is expected to be applied effectively in a wide range for sewage sludge incineration. The operating conditions and facts obtained from an actual 90-ton sewage sludge/day plant using a fast-fluidized bed furnace are described in this report. A circulating-fluidized furnace system with a circulating loop equipped without a seal structure has been established. An self-standing structure has been developed to prevent vibrations, which has been an issue with conventional circulating-fluidized furnaces. Accordingly, moisture-load fluctuations (76∿83%) has been dealt with sufficiently. Moisture and calorie fluctuations due to mixed combustion of screenings have been absorbed sufficiently as well.
