Торрефикация — ресурсосберегающее направление термохимической переработки биомассы

Abstract

Significant scales in which biomass accumulates have prompted specialists to search ways of efficiently using its energy potential at the background of the crisis of non-renewable energy sources. One of such ways is torrefaction – thermochemical pyrolysis of biomass by subjecting it to slow heating and holding at a temperature of 200–300°C to obtain a solid carbon-containing product. Investigations carried out in the biomass torrefaction field are reviewed and analyzed. Biomass properties and various ways of processing it for use as power-generating fuel are considered. The properties of non-torrefied and torrefied pellets are compared. The latter, in comparison with the source ones, feature an increased heating value, low hygroscopicity, sufficient bulk density, and good grindability. The main torrefaction technologies and types of torrefaction reactors are considered. A mathematical model of a wood waste torrefaction plant was developed in the Aspen Plus software environment. The study results have revealed the effect the specific heat admission to the torrefaction reactor and the initial moisture content in the material have on the process operating parameters: the mass fraction of carbon transferred into solid torrefaction products and the pyrolysis gas specific yield, composition, heating value, and temperature. The possibility to arrange autonomous heating of the reactor using the chemical heat of pyrolysis gas has been shown. The reactor heating requires 44% of the gas waste from the torrefaction process; the other 56% can be used as an energy source in related technologies. The obtained results can be used in studying and designing the reactor and torrefaction plant.