Development Of A Chemical Kinetic Model For A Biosolids Fluidized-Bed Gasifier

Gasification has become a viable option for treating biosolids in an effort to decrease the land-disposal of sewage sludge. A model was developed to predict the syngas composition and rate from a bubbling fluidized-bed sewage sludge gasifier based on biosolids composition and input rate, air input rate, and other operating parameters. A kinetic reaction mechanism was chosen for gas-phase and char oxidation and reduction reactions, while an instantaneous and complete drying and devolatilization mechanism was developed to represent the initial steps of gasification. The model agreed well with data from three detailed studies on biosolids gasification reported in the literature. The model can be used by gasification facility operators to better predict the effects of a new feedstock. The expected syngas quality and energy recovery values may be useful for determining whether or not auxiliary fuel will be needed to maintain gasifier bed temperatures. By estimating the concentrations of trace gases, combustion modeling can predict the flue gases from a coupled gasifier/thermal oxidizer operation, and aid in the design of necessary air pollution control devices. This is an abstract of a paper presented at the 106th AWMA Annual Conference and Exhibition (Chicago, IL 6/25-28/2013)