Torrefaction of biomass
A thermo-chemical treatment
Torrefaction is a thermo-chemical treatment of biomass under the absence of oxygen. Typical process temperatures range from 250 to 300° C. During the process the remaining water in the biomass evaporates. Additionally, the hemicellulose content of the biomass is reduced. The steam together with the decomposed hemicellulose forms a gas consisting of H2O, CO, CO2, and various organic acids. The gas mass flow is typically 20% of the bone dry input material, while the energy content is only 10%. The final product is the remaining dry solid material with brown to black color. Compared to untreated biomass, torrefied material has different material properties:
- Higher energy density
- Better grindability
- Better hydrophobic properties
After torrefaction, the biomass can be densified with pelleting or briquetting equipment to increase the energy content per unit of volume.
Torrefied biomass is an excellent fuel, especially for co-firing in coal-fired power plants.
The Accelerated Carbonized Biomass (ACB) process is a biomass torrefaction process developed by the Austrian ACB consortium. ANDRITZ has the exclusive rights for commercialization.