Reduction in Fuel Consumption in Biomass-Fired Power Plant Using Hybrid Drying System

Abstract

Fuels used in biomass power plants usually have high moisture contents. Two methods of fuel drying that have been proposed are steam drying and flue gas drying. Steam drying requires extracted steam as its energy source, whereas flue gas drying requires flue gas leaving the boiler as its energy source. Previous works have mostly been concerned with the integration of either dryer in a power plant. There have been a few investigations on the integration of both dryers. This paper proposes a novel hybrid drying system that uses a steam dryer to dry a portion of the fuel. Exhaust vapor from the steam dryer is then used for the heating of combustion air, which increases the flue gas temperature. The higher flue gas temperature increases the potential of the flue gas dryer, which is used to dry another portion of the fuel. It is shown that the hybrid drying system is capable of reducing fuel consumption to 7.76% in a 50 MW power plant. Furthermore, the integration of hybrid drying is shown to be economically justified because the simple payback period is 4.28 years.