Design methods for fluidised bed gasifiers: comparison of three approaches

摘要

An effort is made here to develop a systematic design method for fluidised bed gasifiers. Three design approaches are considered: equilibrium approach, residence time approach and kinetic model approach. The equilibrium approach, which only predicts the gas composition, has two models: simple stoichiometric model and more comprehensive model. The latter gives better prediction of maximum achievable gas yield for a given set of feedstock and operating conditions. The residence time approach is primarily based on experimentally derived char gasification time and provides a good option for sizing of a gasifier, especially for carbonaceous fuels. The kinetic model, which is generally used for simulation of an existing gasifier, has been used here for the design considering the rate of reactions and effect of geometry and bed hydrodynamics on the gasifier performance. Because of its complexity, the kinetic model is most difficult to implement for initial design of a gasifier. More than three design approaches have been used to theoretically design a gasifier. Design results are compared with those predicted and obtained from experiments.