Observations on the combustion of torrefied biomass

Abstract

This thesis examines observations on the combustion of different types of torrefied biomass. The targeted biomass types were waste crop, herbaceous, and woody; they included Corn straw, DDGS, Rice husk, Miscanthus, Bagasse, and Beechwood. Combustion of renewable biomass is of technological interest because it is considered to be nearly carbon-neutral. Furthermore, torrefaction of biomass improves the raw biomass properties and makes more "coal-like".Torrefied biomass has lower volatile matter content, higher fixed carbon content and higher energy content than raw biomass. It is also having low moisture content and it is less biodegradable. In this work, all biomass samples were torrefied at T= 275 °C for half an hour in nitrogen. Thereafter, torrefied biomass was size classified by sieving to obtain size cuts of (75-90) µm, (180-212) µm, (180-212) µm, (212-300) µm, (300-350) µm, (350-500) µm. The experimental setup that was used in this investigation consisted of an electrically-heated drop-tube furnace, operated at wall temperature 1400 K. A three-color pyrometer was interfaced with the furnace and a high-speed high-resolution camera, to record the entire luminous particle combustion profiles of individual particles.As identification of the maximum biomass particle size for combustion in an existing boiler is important, this work observed the time-temperature profiles of the aforementioned particle size and contrasted them to those of typically-used coal particles. It was forward that torrefied biomass particles in the size range of 212−300 μm burned in similar times as those of 75-90 μm coal.