Fouling and Its Mitigation in PC Boilers Co-Firing Forestry and Agricultural Biomass

Abstract

This paper presents a study of the fouling properties of solid fuels based on analyses of ashes from hard coal, forestry biomass, and agricultural biomass, ash deposits collected directly from the boiler surfaces, and ash deposits collected from a deposition probe. All samples were collected in the area of the steam superheater/reheater of a OP 380 pulverized-coal boiler co-firing forestry and agricultural biomass. In addition, the study concerns mitigation of unwanted fouling through application of a silica-based fireside additive. An analysis was carried out to obtain the following information: physical and chemical properties of ash produced during co-firing of a biomass mixture (50 wt.% forestry/50 wt.% agricultural biomass) and coal in order to determine its propensity for fouling and slagging without the use of a fireside additive; slagging/fouling indices during co-firing of a biomass mixture (50 wt.% forestry/50 wt.% agricultural biomass) and coal with the use of a fireside additive; and slagging/fouling indices during co-firing of pure agricultural biomass (sunflower husk) and coal with the use of a fireside additive. The mass flow of co-fired biomass fuel supplied to the boiler during reference measurements and mass flow when the additive was fed were the same and amounted to 33 wt.% of the total fuel mass flow. Finally, the effectiveness of fouling mitigation is determined by comparing the results of the deposition rate obtained with the use of a deposition probe for all three cases of co-firing.