Bio-oil is produced by a thermal process in which biomass is heated without the presence of oxygen. In this process which is known as pyrolysis the biomass is decomposed into smaller oxygen containing molecules, which results in three main products: liquid bio-oil, biochar and a small amount of syn gasses. In theory bio-oil can be produced on a basis of any biomass eventhough wood are the most frequently processed.
For converting straw into bio-oil we have chosen the world best available pyrolysis bio oil technology: RTP (Rapid Thermal Processing) which have been developed by Envergent Technologies (a joint venture of UOP, a Honewell company, and Ensyn Corp). Comprehensive preliminary conversion tests and studies have been conducted on RTP units producing bio-oil on straw from danish grown winther wheat to demonstate the technical feasibility of this project.
The RTP is a two stage fast thermal process whereby biomass is introduced into a vessel and rapidly heated to around 500 C by a tornado of hot sand and then rapidly cooled within seconds. The specific temparature and the rapidly cooling of the pyrolysis vapor ensure a high bio-oil yield on the behalf of lower syn gas and biochar yields.
The second stage in the RTP imply a partly combustion of the biochar by-product to supply the thermal energy for the pyrolysis. This is done by reheating the sand in the second stage char combustor and thereby recycling the hot sand to the pyrolysis process. This makes the whole process independent of external thermal energy. In fact the processing of straw in the RTP are expected to produce a surplus of thermal energy to suplly the local district heat system, to produce a small amount of syn gases which will produce electricty on a biogas engine and a to produce a high quality bio ash product with a high content of biochar.