Thermodynamic analysis of Torrefaction process

Abstract

This paper discusses the exergy and energy analysis of torrefaction process for four different residual biomass (wet leaf, rice husk, coconut shell and tree bark). Torrefaction is a thermo-chemical conversion process carried out in an inert atmosphere. The biomass samples are torrified using waste heat from a diesel engine at a temperature of 240ËšC for a duration of an hour. Exergy and Energy efficiencies, and exergy and energy saved are assessed with the help of the actual system data. The exergy saved in the overall system is found to be 0.258 kW, 0.702 kW, 1.812 kW, 2.486 kW for wet leaf, rice husk, coconut shell and tree bark respectively. The most efficient biomass in the torrefaction process is tree bark, yielding an energy efficiency of 58.76% whereas wet leaf is the least efficient biomass. It is found that maximum exergy efficiency is obtained from the reactor if the exhaust from the source is in the range 430-470ËšC.