Fast pyrolysis is a high temperature process in which biomass is rapidly heated in the absence of oxygen. As the biomass thermally decomposes, it is converted mostly into vapours and some charcoal. Cooling and condensation forms a dark brown liquid, which has a heating value about half that of conventional fuel oil.
The essential features of a fast pyrolysis process are: very high heating and heat transfer rates, which usually require a finely ground biomass feed; and rapid heating up to 500°C and then rapid cooling of the pyrolysis vapours to give the main product – bio-oil. Bio-oil is not oil in the conventional sense; rather, it is a multi-component mixture of alcohols, acids, aldehydes, phenols, etc. Some of these components are very valuable chemicals that, if they can be separated/extracted, will generate substantial economic benefits. Bio-oil is water-soluble and can contain significant amounts of water when it is created. It is also pungent, corrosive, and polymerizes readily, which creates special requirements for its handling and conversion.
Canadian “fast pyrolysis” companies are poised to take advantage of a biorefinery approach to biomass utilization. All have experience with the direct utilization of pyrolysis oil for energy. Even so, commercial production is still in its infancy. Pyrolysis oil does, however, have a significant advantage over some other biomass-based fuels in that, once produced, it can easily be stored and/or transported. Hence, good economies of scale can be utilized in the extraction of value-added products and even in the conversion to energy by transporting the liquid to a central processing plant.
We have developed a burner/nozzle system for firing bio-oils and successfully demonstrated firing up to 100 litres/minute for potential application in kilns and boilers (see our facilities section for more information). We work closely with industry to demonstrate a portable pyrolysis unit that can be used at remote sites to process forestry residues into pyrolysis oil. This higher energy-density material could then be more economically transported to a central biorefinery location for the extraction of value-added chemicals and for energy conversion.
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