The effects of torrefaction pre-treatment on the quality of pyrolysis oil
Biomass fast pyrolysis has gathered interest in producing high yield liquids as it is a promising a hydrocarbon biofuel which can be easily transported, burnt directly in existing diesel power plants, stored as liquid fuels and has the lowest cost among liquid biofuels. But, the bio-oils also have unfavorable properties with respect to fossil oil such as low heating value, high oxygen content, and high water content. One of the pre-treatments to overcome those unfavorable bio-oil properties is via the torrefaction process of the biomass (wood) feedstock.
The main goals of this thesis are observing the effects of torrefaction treatment prior to the fast pyrolysis process on bio-oil quality through experiments in a lab-scale bubbling fluidized bed pyrolyzer, and also observing the technoeconomic aspects of torrefaction-fluidized bed pyrolysis in a large scale of 20 ton wood feedstock/hour, with a designed plant site in Indonesia. The large scale torrefaction-fluidized bed pyrolysis plant is simulated in the Unisim flowsheeter, by applying the National Renewable Energy Laboratory (NREL) USA method in calculating its technoeconomic aspects.
The results of this thesis are as follows and will be further detailed during the MSc presentation:
1. Torrefaction pre-treatment on wood feedstock can increase the bio-oil quality by lowering oxygen and water content and also increasing the heating value. But, on the other side, the yield of bio-oil decreases.
2. The large scale torrefaction-fluidized bed pyrolysis plant with a capacity of 20 ton dry wood/h requires an investment of US$ 70 million, and annual operational costs of US$15 million by locating it in Indonesia.
3. The cost of bio-oil which is needed for the plant to be deemed viable have been calculated and will be presented in US$/GJ LHV of bio-oil, as well as the Global Warming Potential (GWP), presented in kg CO2 eq/m3 of bio-oil.