Fluidized bed waste incinerators: Design, operational and environmental issues

The paper starts by reviewing the increasing production of waste and the growing importance of its thermal treatment, which aims at volume reduction of the waste, at the destruction, capture, and concentration of hazardous substances, and at the recovery of energy (WtE).Incineration is a generally applied thermal treatment technique, whereas pyrolysis and gasification are still under development. Within the incineration techniques, bubbling, rotating and circulating fluidized beds have found specific and growing applications. As technical information on fluidized bed waste incinerators is spread throughout literature, the present review paper collates the relevant literature and critically examines the parameters that govern the design and operation of these incinerators.Secondly, the design strategy of a fluidised bed incinerator is outlined, which involves considerations of hydrodynamic (velocities, mixing), thermal (heat balances) and kinetic (reaction rate and burnout) nature. Application of the design equations and recommendations will facilitate the sizing of an appropriate fluidized bed incinerator.Since during waste incineration pollutants are formed, the origin and fate of the pollutants and their abatement are reviewed.Finally, special attention is given to the specific de-fluidization problems often encountered during fluidized bed combustor operation, mainly because of agglomeration and sintering. The mechanisms of agglomeration and sintering are discussed, and possible remedies are given. Additionally, important issues of equipment erosion and uniform feeding of the waste into the fluidized bed reactor are considered.