Torrefaction is a thermo-chemical treatment used for upgrading biomass into a high-quality solid fuel often referred to as “biocoal.” In general, the process is similar to that used in roasting coffee beans, only on a much larger scale and in a continuous process. The goal of torrefaction is to achieve a high-quality fuel without the problems associated with conventional biomass.
During torrefaction, biomass is heated over a period of time to a temperature typically ranging from 240-300°C. This heating process is carried out in a reactor under atmospheric pressure in the absence of oxygen. In a more or less self-sustaining process, the reactor is heated by the combustion of gases (torgas) released during the torrefaction process itself. The heat generated by combustion of the torgas is used for both torrefaction and drying of the biomass.
During torrefaction, biomass properties are chemically altered. The biomass loses relatively more oxygen and hydrogen compared to carbon and, as a result, the energy value of the remaining product increases. A typical result from biomass torrefaction is that 70% of the dry mass is retained as a solid product containing 90% of the initial energy content.
Torrefied biomass has properties similar to coal and, as a result, is an excellent source of clean, renewable energy for the production of heat and electricity. Torrefied biomass can be used as a full or partial (co-fire) substitute for coal. Torrefaction is also being investigated as a value-added step in the production of cellulosic ethanol.
ATS TorreCat™ Technology brings significant technological advances to the torrefaction process.