Thermal Analysis of Solid Biofuel from the Gasification of Wood Waste

Solid biofuel samples are obtained from pine timber in a shaft system by partial gasification with reverse air flow. The structure, chemical composition, and thermal properties of the biofuel are analyzed. The carbonizate is practically pure carbon with low ash content (up to 3.7%). Its gross calorific value is 8310 kcal/kg; that is significantly higher than the value for the wood (4690 kcal/kg). Special attention is paid to the transformation of the wood’s mineral component and to the composition and morphology of the mineral inclusions formed on heat treatment. The mineral particles are probably forced onto the surface of the carbonizate pieces when the volatile components evaporate; they retain the shape of the veins in which they are formed. The calcium is mainly in the form of calcite and anhydrate, with some apatite. Magnesium, potassium, and manganese from the wood’s organic matrix are converted mainly to sulfates. Magnesium is also partially bound in rhodochrosite. Combustion of the biofuel has little environmental impact, on account of its low content of ash and the ash composition.