Abstract
Replacing of fossil fuels to biomass, including partial replacement (achieved with co-firing of coal and biomass) is one of the priority problems of modern power producing. In addition to the energy aspects, this is important in terms of reducing harmful man-made impact of fuel and energy sector on the ecological situation. This report presents the results of researches carried out at the Joint Institute for High Temperatures of the Russian Academy of Sciences (JIHT RAS) to develop optimal directions to replace coal in power plants by biomass (wood chips, pellets, torrefied fuel). In JIHT RAS the new scheme of industrial torrefaction technology is proposed. Economic preferences of this scheme are provided by heating of the feedstock by exhaust gases from gas piston power plant. In this case the cogeneration scheme is implemented. The implementation of the scheme demanded working out of operating parameters of the power plant at the stoichiometric ratio of fuel- air mixture. The oxygen content in exhaust gases in this case does not exceed 0.2 % by volume. JIHT RAS technology allows for the main heat engineering parameters of pellets to bring them to coal as much as possible. The torrefaction temperature is determined not only by a variety of properties of raw material, but also by required properties of the final product. Torrefaction advantages are high fuel heating value, high bulk density, low humidity, no tendency to rot and decay, the minimum fire and explosion hazard. Torrefied fuel can almost completely replace coal without major rework of the existing fuel systems. Under the same conditions untreated chips and pellets can replace only 8 – 15 % of the coal.
