Torrefaction of biomass: Influence of operating conditions on products

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(1)Torrefaction of biomass: influence of operating conditions on products J-M. Commandré, P. Rousset, L. Van De Steene, F. Broust CIRAD, UPR42 Biomasse Energie, TA 10/16, 73 Rue J-F. Breton, 34398 Montpellier Cedex 5, France E-mail: jean-michel.commandre@cirad.fr. Introduction - Context Gasification of biomass in Entrained Flow Reactor (EFR) produces a clean, tar and methane-free syngas thank to the high temperature reaction. This thermo-chemical conversion is one of the most promising technologies to produce synfuels or H2. But : short residence time (≈1 s) requires a fine grinding of biomass, which is energy costly Interest of our work : Biomass torrefaction = pre-treatment process allowing to reduce grinding energy consumption Objectives of this study : Characterization of the influence of operating conditions on the products of torrefaction Composition of torrefied wood. Experimental results Effect of residence time and reactor temperature 45% 40%. Wood mass loss (%). 35% 30% 25% 20% 15% 10%. 240°C 260°C 280°C. 5%. When torrefaction temperature increases : → Hemicellulose content → Lignin and Cellulose contents. 0% 0. 10. 20. 30. 40. 50. 60. Residence time (min). N2 or CO2. Effect of nature of atmosphere (N2/CO2). Lower calorific value of torrefied wood. 35% 25000. 25%. 20%. 15%. 26mm i.d.. 550mm. 10%. x y=. 5%. Low calorific value (J/g dry basis). Mass loss under CO2 (%). 30% 20000. 15000. 10000. 5000. 0% 0%. 5%. 10%. 15%. 20%. 25%. 30%. 35%. 0. M. Mass loss under N2 (%). 0. 50. 100. 150. 200. 250. 300. Temperature (°C). Effect of natural moisture. N2 or CO2. 40%. Heating value yield 120%. 35% 100% Heating value yield (%). Wood mass loss (%). 30% 25% 20% 15%. Mass balance (260°C). 10%. 80%. 60%. 40%. Bois sec. 5% 0% 200. Condensable volatiles 12,8%. Bois non sec. 220. 240. 260. 280. 20%. 300. 0% 160. Temperature (°C). 180. 200. Water (condensed) 11,9% Torrefied wood 69,9%. Condensable volatiles Acetic acid 19,0% Furfural 4,8% Others 1,8%. N.Q. 74,5%. 220. 240. 260. 280. Temperature (°C). Noncondensable volatiles 6,6%. Non-condensable volatiles. Propanoic acid 0,3% Butanoic acid 0,1%. H2 0,00%. CO2 85,99%. Furanmethanol 0,5%. Others 0,19%. Guaiacol 0,2% HydroxyAcetone 0,6%. CO 13,82%. CH4 0,10% C2H4 0,03% C2H2 0,00% C2H6 0,05%. Conclusions - No influence of nature of the atmosphere and of natural moisture of wood (on dry basis) on wood mass loss - When torrefaction temperature : Hemicellulose content ; Lignin and Cellulose contents - Heating value yield is ≈100% until 240°C, then decreases at higher temperat ure - Wood mass loss is mainly due to the release of condensable volatiles ; water, acids and furfural are major species - Gas amounts are small ; gases are mainly constituted of CO2 and CO. 300.

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