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CT: Pyrolysis is the thermal decomposition of biomass occurring in the absence of oxygen. It is the fundamental chemical reaction that is the precursor of both the combustion and gasification processes and occurs naturally in the first two seconds. The products of biomass pyrolysis include biochar, bio-oil and gases including methane, hydrogen, carbon monoxide, and carbon dioxide.
Depending on the thermal environment and the final temperature, pyrolysis will yield mainly biochar at low temperatures, less than 450 0C, when the heating rate is quite slow, and mainly gases at high temperatures, greater than 800 0C, with rapid heating rates. At an intermediate temperature and under relatively high heating rates, the main product is bio-oil.
Pyrolysis can be performed at relatively small scale and at remote locations which enhance energy density of the biomass resource and reduce transport and handling costs. Pyrolysis offers a flexible and attractive way of converting solid biomass into an easily stored and transported liquid, which can be successfully used for the production of heat, power and chemicals.
S: http://www.bioenergyconsult.com/tag/flash-pyrolysis/ (last access: 27 February 2015)
N: 1. Pyrolysis, from the Greek pyro (fire) and lysis (dissolution), is the thermo-chemical decomposition of a substance in the absence of oxygen. Pyrolysis of rocks, kerogens, and asphaltenes form the basis of many laboratory procedures including Rock-Eval pyrolysis, pyrolysis/gas chromatography, and hydrous or anhydrous pyrolysis.
2. When the primary products of the oxygen-deficient decomposition are non-condensible fuel or synthesis gases, the process is known as gasification.
3. The distinction between pyrolysis and incineration is that in a pyrolysis unit the organic material or carbon is not fully oxidised and the residue still has a heating value.
4. pyrolysis: term standardized by ISO.
5. Why is pyrolysis getting interesting now?
There are several ways to make use of the energy contained in the biomass from old direct burning to gasification, pyrolysis. The selection of the most profitable technique to recover the energy from a particular type biomass is and most important step towards a profitable investment.
Direct Combustion is the old way of using biomass. The biomass is completely transformed into heat, but the efficiency is just about 10 percent. The gasification pushes to the maximum level the cracking of biomass by completely transforming it into a combustible gas before burning it. The charcoal production, the slow pyrolysis of wood at temperature 500 °C is a process that charcoal makers have exploited for thousands years. Charcoal is a smokeless fuel which is still used for heating purposes. It first technological use can be dated back to the iron age when charcoal was used in ore melting to produce iron. Production of wood vapor was usually related to the smocking which is one of the oldest food preservation method, probably applied since the development of cooking with fire. These vapors, which contain nature preservatives like formaldehyde and alcohol, were used as feedstocks. The main attraction is small and very simple plants could be made at a very low investment cost. The disadvantage is rather low energy yield and the air pollution.
The biomass pyrolysis is attractive because solid biomass and wastes which are very difficult and costly to manage. can be readily converted into liquid products. These liquids, as crude bio-oil or slurry of charcoal of water or oil, have advantages in transport, storage, combustion, retrofitting and flexibility in production and marketing.
6. Cultural interrelation: Teka HPE 735 Pyrolytic Oven.
S: 1 to 4. TERMIUM PLUS. 5. FAO – http://www.fao.org/docrep/t4470e/t4470e0a.htm (last access: 27 February 2015). 6. https://www.youtube.com/watch?v=LPidk_QuU0c (last access: 27 February 2015).
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