Prediction of gas emissions in an internally circulating fluidized bed combustor for treatment of industrial solid wastes

Abstract

Simulations of an ICFB waste combustor are reported with a mathematical model that includes reaction kinetics related to carbon, nitrogen, hydrogen, oxygen and sulphur content of industrial waste. The model assumes formation of volatile and char during the thermal treatment of wastes, followed by a series of homogeneous and heterogeneous reactions catalyzed by bed material such as char and ash+sand. The trends of model predictions are in qualitative agreement with experimental observations from thermal treatment of spent foundry sand in a 20kW ICFB pilot unit. According to the kinetics and experimental data, bed materials are strongly responsible for low level emissions of nitrogen oxides and sulphur dioxide. The validated model allows a comprehensive simulation analysis to be performed by varying some operating parameters such as waste feedrate, aeration rate, solid circulation and reacting zones. The study reveals that for a proper combustor operation, a balance has to be made between combustion efficiency, lower carbon monoxide and nitrogen oxides emission, as well as sulphur dioxide capture.