Biomass Conversion The Biomass Pyrolysis Spectrum Temperature determines the state-of-matter yielded by pyrolysis: torrefied biomass, bio-oil, biocarbon or gas products. By Gerald Kutney W e use the pyrolysis of biomass every day without realizing it. The roasting and baking of foods are such processes. Common py-rolysis reactors include toasters and bar-becue grills. Caramel is produced by the pyrolysis of sugar, and another popular product is roasted coffee. Pyrolysis is the thermal decomposition of biomass occurring in the absence of oxygen. The products of biomass pyroly-sis (Figure 1 on page 22) include torrefied biomass, biocarbon, bio-oil and producer gas (methane, hydrogen, carbon monox-ide and carbon dioxide). Depending on the thermal environment and the final temperature, pyrolysis will yield mainly biocarbon at low temperatures, less than 450˚C, when the heating rate is relatively slow, and mainly gases at high tempera-tures, greater than 600˚C, with rapid heat-ing rates. At an intermediate temperature, but at higher heating rates, the main prod-uct is bio-oil. The choice of one technology over an-other is often determined by the state-of-matter of the biofuel that is desired. TORREFACTION The mildest pyrolysis process is torrefac-tion. During this reaction oxygen-rich compounds are volatilized from the bio-mass, including non-condensables such as carbon dioxide (80%) and carbon monoxide, and condensables such as wa-ter (60%), acetic acid (25%), methanol, formic acid and furaldehyde. These prod-ucts mainly originate from hemicellulose, which is decomposed in the process. Tor-refied wood is thus mainly composed of cellulose and lignin. Torrefaction reaction rates are highest in straw, followed by hardwoods and softwoods, but the final properties are similar. The various reac-tion rates are attributed to the differing hemicellulose structures found in the dif-ferent types of biomass. The torrefaction reaction begins at 200˚C, but the practical range is 250˚C to 280˚C. In the torrefaction process, temperature is a more important factor than reaction time, which is typically 30 minutes or less. Care must be taken not to go much higher in temperature as car-The Port of Belledune is your trans PORT ation solution to the world! www.portofbelledune.ca Wood pellets, wood chips, and all forms of wood products are handled at the Port of Belledune; not only does the port connect to strategic shipping routes, it is also an intermodal gateway with a rail spur and direct congestion-free access to a highway system spanning North America. Canadian BIOMASS 21
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