Effects of Fuel Staging on the NO Emission Reduction during Biomass–Biomass Co-combustion in a Fluidized-Bed Combustor

Abstract

Fuel-staged co-combustion of sunflower shells (as a base fuel) and coconut coir dust/moisturized rice husk (as a secondary fuel) was studied on a 205 kWth fluidized-bed combustor with bottom air injection. During the experiments, the energy fraction of both secondary fuels in the total heat input to the reactor was varied from 0 to 0.22, while the amount of excess air ranged from ∼20% to ∼80% for each co-firing option. Temperature and gas concentrations (O2, CO, CxHy, and NO) were measured along the reactor centerline, as well as at stack, to evaluate the emissions and combustion efficiency of the combustor for the specified operating parameters. The experimental results revealed significant effects of excess air on the combustion and emission characteristics of the reactor, whereas the influence of fuel staging on these characteristics was moderate. An optimization method minimizing “external” costs of the co-firing was used to quantify the optimal energy fractions of the co-fired fuels and optimal amoun...