STUDY OF EFFECTS OF TEMPERATURE AND RESIDENCE TIME ON CALORIFIC VALUE OF TORREFIED BIOMASS

Abstract

In developing counties, biomass is a major source of residential energy. In the past, biomass in its unprocessed form was used for cooking and heating. Commercial purpose has been limited due to low heating value of biomass. Many attempts, regarding improvement of energy density have been made in recent times for biomass technology. Due to which process such as pyrolysis are invented for achieving increased efficiency and calorific value of unprocessed biomass by removing water content and volatile organic compounds from unprocessed raw biofuel. Torrefaction is a biomass energy densification process where unprocessed biomass is heated (200 o C – 300 o C) removing water content and volatile organic compounds (VOCs) from them and making them denser in energy. Torrefaction is a relatively new subject where many researches have been done to examine its potential in biofuel energy densification and biofuel development. This paper presents a work of unprocessed biomass torrefaction process performed on Institute of Engineering Biomass Laboratory. The goal of the research was to study effect of residence time and temperature on torrefaction process along with its mass yield (ratio of torrefied mass to initial mass) on dry and ash free basis. For the process, mixed sawdust was used as biomass which was subjected to temperatures 210°C, 240°C and 270°C at 15, 30 and 45 minutes residence times, in inert atmosphere of nitrogen to produce torrefied biomass. Results from the research showed calorific value increase with increasing both temperature and residence time, effect of temperature being more prominent. Highest calorific value was found to be 5454 cal/g at 270 0 C and 15 minutes residence time. The biofuel thus obtained can be further briquetted to increase energy density.