Effect of co-firing on the properties of submicron aerosols from biomass combustion

As part of a more general study on particle formation process (and, specifically, the submicron fraction of the particle size distribution) in biomass combustion, the effect of combining biomass with other sulfur-enriched fuels (such as coal and coke) on particulate emissions has been investigated. Pulverized orujillo (an olive oil production process residue) combustion, alone, resulted in an important submicron particle mode composed of, essentially, potassium chloride (KCl) and potassium sulfate (K2SO4) in almost the same mass proportion. Differently, experiments in which pure gases (sulfur dioxide, SO2) and other sulfur-containing fuels (coal and coke) were added to the orujillo combustion lead to a total disappearance of chlorine in those particles. Orujillo was responsible for the key element (i.e., potassium) in the fine particles emitted in co-combustion of the fuel blends; coal and coke served only as "sulfur sources" in this process. These results are interpreted in the framework of the fine particle formation model in biomass combustion, and give a basic support to previous field and laboratory measurements on deposit formation and corrosion in biofired boilers. Chlorides being associated to boiler corrosion and molten deposit formation at relatively low wall temperatures, the present results show that cofiring of biomass with other traditional fuels (even in small amounts) can be a feasible way to appreciably attenuate such adverse effects in industrial boilers. (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.