Biofuels Production by Torrefaction Process Supplied with Different Biomasses

Solid fuel production from different biomass sources become a very challenging area. The paper presents the torrefaction process, mild pyrolysis, where biomass material is converted into solid fuel with higher heating value. The material is processed in inert atmosphere or in the atmosphere with very low oxygen concertation. The study is done for three varied materials, oak wood, mixed wood and dehydrated, granulated sewage sludge. The influence of the temperature is examined, and the optimal temperature is determined. Furthermore, the optimal operation time for each material is evaluated. The experiments were done without flue gases integration. The results show that from energy point of view the optimal operation time for oak and mixed wood is around 1.2 h at 260°C. The torrefaction of sewage sludge is energetically unjustified.