The Synthetic Diesel process comprises of 6 main interlinked process steps:
Central process technology is gasification, where the woody biomass is turned into a high calorific gas; e.g. a mixture of H2 and CO. Since this is a process which requires energy, the energy is taken from combustion of biomass, which produces CO2. The mixture of H2 and CO is referred to as synthesis-gas which is the building block units for many chemicals. Here we consider the production of synthetic fuels.
For doing the gasification, proper sizing, drying and thermal pre-treatment is necessary. Some gasification technologies require particles as small as 1/10 of a millimetre.
After the gasification the gas needs to be cleaned because the successive part requires ultra clean gases: All Nitrogen and Sulphur components are washed out; depending on the gasification technology also tar needs to be removed. CO2 is also removed from the gas.
The clean syn-gas H2/CO is now converted into long chain hydrocarbons: Wax in a Fischer Tropsch synthesis. Huge amount of water are also formed which need separation from organic contaminant before released to the environment. These waxes are not suited as fuels and need to be sized down in a chemical process called hydrocracking and destillation. In these two steps we can fine tune the properties of the final fuel. We can make diesel, gasoline or even jet-fuel.