Title:
Review and Compilation of Existing and New Experimental Data on Torrefaction Gas Composition
Author(s):
Pommer, L., Olofsson, I., Borén, E., Nordwaeger, M., Nordin, A.
Document(s):
Paper
Abstract:
Torrefaction is an emerging and promising thermal pre-treatment method, which improves a range of properties of the biomass. Depending on process conditions, up to 40 % of the energy in the biomass is volatilized to a gaseous product. Possible uses of the gas comprise combustion for use of energy for drying and torrefaction, extraction of higher value-added “green” products or reformation to liquid fuels or bulk chemicals. Changing biomass and operation conditions of the torrefaction process substantially alters both the amount of gas volatilized and its composition. A literature review on torrefaction gas composition was performed and the results (15 studies) were compiled together with our own experimental data (7 studies). The latter stem from successful sampling of torrefaction gas on-line and in gas-phase at 300°C from both lab- and in pilot-scale torrefaction work. At increasing torrefaction conditions, the yields of permanent gases and condensables increased. The fraction of carbon monoxide increased and carbon dioxide decreased when torrefaction severity increased. Components deriving from carbohydrate (cellulose, hemicellulose) decomposition were observed at relatively low temperatures (>240°C), for example methanol at the lower temperature range and furfural and hydroxypropanone at somewhat higher temperatures. Components related to lignin decomposition (guaiacol, p-creosol, p-ethylguaiacol etc.) were mainly observed at torrefaction temperatures of 300°C and above. Dihydroconiferyl alcohol was extensively formed during torrefaction with long residence times. The different lignin constituents of hard and soft wood species resulted in raw material specific speciation of the condensable fraction. Syringyl derived components and furfural were for example present in higher concentrations for broadleaved trees, while coniferylaldehyde were present in higher concentrations for conifers. Torrefaction conditions could be optimized for the production of maximum levels of selected decomposition products from carbohydrates and lignin for increasing the economic value of the pretreatment system via extractable “green” chemicals.
Keywords:
biomass, product gas, tar, thermochemical conversion, gas analysis, green chemistry
Topic:
R&D on Processes for Solid, Liquid and Gaseous Fuels from Biomass
Subtopic:
Advanced solid biofuels
Event:
21st European Biomass Conference and Exhibition
Session:
3EO.2.3
Pages:
1413 - 1418
ISBN:
978-88-89407-53-0
Paper DOI:
10.5071/21stEUBCE2013-3EO.2.3
Price:
FREE
