Biomass Drying for an Integrated Power Plant: Effective Utilization of Waste Heat

Abstract

Unlike fossil fuels, biomass offers potential benefits due to its low cost and presumed zero-carbon emission for power generation. However, raw biomass contains high moisture level that reduces combustion temperature and causes certain operational problems and due to this reason biomass is often dried prior to combustion. Having multiple advantages however, drying biomass is an energy intensive and relatively low efficiency process. Hence, for making drying process more economical, reasonable waste heat from some other industries or processes should be assessed and extracted for drying purpose. Biomass power plant is one of the process industries where the existing waste heat can be utilized for drying the feedstock before combustion for improved operations. In this work, heat integration studies are performed to a 12.5 MW capacity biomass power plant that burns empty fruit bunches (EFB) as fuel. A multi-stage drying process that combines, hot air dryer (HAD), superheated steam dryer (SSD) and flue gas dryer (FGD) is considered. Pinch analysis is used to show the effectiveness of the heat integration of different design options. The result of this study shows that, when compared with a system with no drying, nearly 10 % improvement in overall efficiency is achievable by proper integration of the dryers with the power plant.