Torrefaction

Torrefaction of biomass, e.g., wood or grain, is a mild form of pyrolysis at temperatures typically between 200 and 320 °C. Torrefaction changes biomass properties to provide a better fuel quality for combustion and gasification applications. Torrefaction produces a relatively dry product, which reduces or eliminates its potential for organic decomposition. Torrefaction combined with densification creates an energy-dense fuel carrier of 20 to 21 GJ/ton lower heating value (LHV). Torrefaction causes the material to undergo Maillard reactions. Torrefied biomass can be used as an energy carrier or as a feedstock used in the production of bio-based fuels and chemicals. Biomass can be an important energy source. However, there exists a large diversity of potential biomass sources, each with its own unique characteristics. To create efficient biomass-to-energy chains, torrefaction of biomass, combined with densification (pelletisation or briquetting), is a promising step towards overcoming the logistical challenges in developing large-scale sustainable energy solutions, by making it easier to transport and store. Pellets or briquettes have higher density, contain less moisture, and are more stable in storage than the biomass they are derived from.

Torrefaction of biomass, e.g., wood or grain, is a mild form of pyrolysis at temperatures typically between 200 and 320 °C. Torrefaction changes biomass properties to provide a better fuel quality for combustion and gasification applications. Torrefaction produces a relatively dry product, which reduces or eliminates its potential for organic decomposition. Torrefaction combined with densification creates an energy-dense fuel carrier of 20 to 21 GJ/ton lower heating value (LHV). Torrefaction causes the material to undergo Maillard reactions. Torrefied biomass can be used as an energy carrier or as a feedstock used in the production of bio-based fuels and chemicals. Biomass can be an important energy source. However, there exists a large diversity of potential biomass sources, each with its own unique characteristics. To create efficient biomass-to-energy chains, torrefaction of biomass, combined with densification (pelletisation or briquetting), is a promising step towards overcoming the logistical challenges in developing large-scale sustainable energy solutions, by making it easier to transport and store. Pellets or briquettes have higher density, contain less moisture, and are more stable in storage than the biomass they are derived from. ===Higher energy density=== An energy density of 18–20 GJ/m 3 – compared to the 19–24 GJ/m 3 heat content of natural anthracite coal – can be achieved when combined with densification (pelletizing or briquetting) compared to values of 10–11 GJ/m 3 for raw biomass, driving a 40–50% reduction in transportation costs. Importantly, pelletizing or briquetting primarily increases energy density. Torrefaction alone typically decreases energy density, though it makes the material easier to make into pellets or briquettes. ===More homogeneous composition=== Torrefied biomass can be produced from a wide variety of raw biomass feedstocks that yield similar product properties. Most woody and herbaceous biomass consists of three main polymeric structures: cellulose, hemicellulose and lignin. Together these are called lignocellulose. Torrefaction primarily drives moisture and oxygen-rich and hydrogen-rich functional groups from these structures, producing similar char-like structures in all three cases. Therefore, most biomass fuels, regardless of origin, produce torrefied products with similar properties with the exception of ash properties, which largely reflect the original fuel ash content and composition. ===Hydrophobic behavior=== Torrefied biomass has hydrophobic properties, i.e., repels water, and when combined with densification make bulk storage in open air feasible. ===Elimination of biological activity=== All biological activity is stopped, reducing the risk of fire and stopping biological decomposition like rotting. ===Improved grindability=== Torrefaction of biomass leads to improved grindability of biomass. This leads to more efficient co-firing in existing coal-fired power stations or entrained-flow gasification for the production of chemicals and transportation fuels. ==See also== Pyrolysis Thermally modified wood Carbonization (contains a detailed description of the inferior combustion qualities of biomass compared to coal, and the positive effects of torrefaction.) ==Further reading== "Torrefied Wood Powder to Propane"; Zwart, R.W.R.; "Torrefaction Quality Control based on logistic & end-user requirements", ECN report, ECN-L–11-107 Verhoeff, F.; Adell, A.; Boersma, A.R.; Pels, J.R.; Lensselink, J.; Kiel, J.H.A.; Schukken, H.; "TorTech: Torrefaction as key Technology for the production of (solid) fuels from biomass and waste", ECN report, ECN-E–11-039 Bergman, P.C.A.; Kiel, J.H.A., 2005, "Torrefaction for biomass upgrading", ECN report, ECN-RX–05-180 Bergman, P.C.A.; Boersma, A.R.; Zwart, R.W.R.; Kiel, J.H.A., 2005, "Development of torrefaction for biomass co-firing in existing coal-fired power stations", ECN report, ECN-C–05-013 Bergman, P.C.A., 2005, "Combined torrefaction and pelletisation – the TOP process", ECN Report, ECN-C–05-073 Bergman, P.C.A.; Boersma, A.R.; Kiel, J.H.A.; Prins, M.J.; Ptasinski, K.J.; Janssen, F.G.G.J., 2005, "Torrefied biomass for entrained-flow gasification of biomass", ECN Report, ECN-C–05-026. Benchmarking the torrefaction process and product performance: Insights from the SteamBioAfrica project in Namibia

Text derived from https://en.wikipedia.org/w/index.php?oldid=1323585107 under CC BY-SA 4.0; modifications have been made.