Co-Firing of Oil Palm Empty Fruit Bunch and Kernel Shell in a Fluidized-Bed Combustor: Optimization of Operating Variables

Abstract

Palm kernel shell and empty fruit bunch (as secondary fuel) were co-fired in a fluidized-bed combustor using alumina sand as bed material to prevent bed agglomeration. During the experiments, the fuels were injected into the reactor at different levels ensuring constant heat input, while the energy fraction of secondary fuel (EF2) was ranged from 0 to 0.25 with excess air (EA) of 20–80%. The study revealed significant effects of EF2 and EA on the CO, CxHy, and NO emissions, as well as on the combustion efficiency of the combustor. Cost-based optimization aimed at minimizing “external” costs of the biomass–biomass co-combustion was applied to determine the optimal values of EF2 and EA. Under optimal operating conditions, the combustor can be operated with high (about 99%) combustion efficiency at minimum emission costs, while reducing the NO emission roughly by 35% compared to firing pure palm kernel shell.