Pyrolysis oil

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Pyrolysis oil is under investigation as substitute for petroleum. It is extracted by destructive distillation from dried biomass in a reactor at temperature of about 500°C with subsequent cooling. Pyrolytic oil is a kind of tar and normally contains too high levels of oxygen to be a hydrocarbon. As such it is distinctly different from similar petroleum products.

1 Process
2 Fuel oil characteristics
3 External links
4 References

[edit] Process

The biomass is split into solid, liquid, and gaseous components under the influence of heat only (anhydrous pyrolysis). The produced charcoal may be used for heating the process or as activated carbon in absorption processes. The gas, consisting of hydrogen (H₂), carbon monoxide (CO), carbon dioxide (CO₂) and methane (CH₄), may be burned but the condensable gases have to be kept gaseous until the combustion. The heating value is 15-22 MJ/m₃, which is much lower than natural gas.

[edit] Fuel oil characteristics

The produced oil is sour with a pH of 1.5-3.8 (2.8) and has an elevated water content 8-20% wt. This leads to corrosion problems especially at higher temperatures. The density is approximately 1.2-1.3 (1.22) kg/l, which is much higher compared to diesel. The oxygen content is 40-50%, mostly from the water content, and no sulfur may be detected normally. The lower heating value is approximately 16-21 (17.5) MJ/kg. The pour point is -12°C to -33°C, no cloud point could be observed until -21°C. The carbon residue is 17-23 % wt (0.13% ash). The flash point is 40-100°C, the pyrolysis oil is not auto-igniting in a diesel engine. The cetane number is only minus 10. The viscosity increases to a maximum in period of 12 months due to polymerization. The pyrolysis oil is not stable reacting with air and degasing. Pyrolysis oil cannot be blended with diesel ^[1].

It may be very attractive, from an economic standpoint, to first recover valuable bio-chemicals from the bio-oil. The remainder of the bio-oil can then be combusted to generate electricity or converted to a syngas from which chemicals and clean fuels can be synthesized ^[2].