Forest waste torrefaction

Abstract

Torrefaction is a process of thermal conversion of biomass. The properties of the torrefaction product, bio-coal, are comparable with brown coal. Therefore, this type of solid biofuel is a promising substitute for fossil coal. At present, there are several plants producing bio-coal with the torrefaction technology. However, there are many aspects of the technology and ways of implementation still under research. One of the least studied areas of torrefaction is steam torrefaction. In this work, the efficiency of the steam torrefaction unit was evaluated. The facility contains a dryer and a reactor. The heat source for the processes is saturated steam from an intermediate turbine of 500 MW turbine unit. The mathematical model was constructed and analyzed. The results showed that the percentage of heat energy use was 11% on average, and the fuel consumption ratio was 1.3. In other words, this configuration is ineffective. 90% of the energy is consumed in the drying process. This process should be carried out by another energy source. A suitable option is the flue gas from a boiler.