Torrefaction and combustion of pellets made of a mixture of coal sludge and straw

The purpose of this paper is to investigate the preconditions required for the development of a novel technology for simultaneous combustion of coal waste, and biomass. This technology integrates pellet production from a coal and biomass mixture and torrefaction of the produced pellets in low oxygen environment in a temperature range between 230 and 270 °C. The results indicate that the torrefied pellets have 17% higher calorific value and 1.55 times lower hygroscopicity limit when compared to the untreated pellets. Thus, the major advantages of the torrefied pellets produced from a mixture of coal and biomass refer to outdoor storage and the increase of boiler's combustion efficiency by 5%.