Gas composition from Biomass Torrefaction

1. Gas composition from Biomass Torrefaction Linda Pommer1, Lorenz Gerber2, Susanne Wiklund Lindström1, Ingemar Olofsson1, Anders Nordin1 1: Energy Technology and Thermal Process Chemistry, Umeå University, Sweden 2: Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Sweden Background Biomass is a widespread source of renewable energy, and has the potential to play a significant role in the energy conversion decreasing the fossil fuel dependency. However, a number of fuel characteristic properties could be significantly improved. Torrefaction + pyrolysis-GC/MS Raw pulverized biomass samples were torrefied in a Py-GC/MS. Two different heating rates were used; (1) heating of the biomass to 300 ºC during 10 min, and (2) heating to 300 ºC during 5 s. Results The composition of the products gas were determined using both Py-GC/MS and MBMS. The compounds present at the highest concentrations are presented in the table below. Varying energy content of torrefaction gas Identification of main- and separating compounds in the torrefaction gas Figure 2. Weighs selected for analysis of separating compounds between hardwood and softwood. Identification of compounds in the product gas separating hardwood from softwood Mass numbers selected from PLS-DA consisted mainly of compounds derived from lignin. Compounds correlated to hardwood were products derived from S-lignin and for softwood from G-lignin. • The knowledge of the composition of volatiles produced in the temperature range of torrefaction is a topic of interest for • Producing “green chemicals” • Energy process- and exergy optimization • Process behavior and operation • Raw material adaption process • Process control Figure 1. PLS-DA separation of hardwood (Pine and Spruce) and softwood (Birch). Energy content of the product gas Compounds in the product gas were tentatively identified and quantified. The results are preliminary and indicate a higher HHV (Higher Heating Value) for the product gas during torrefaction of Birch. Differences in the contri-bution to the HHV from of specific compounds could be attributable to dissimilarities of softwood and hardwood. Objective The objective with the present work was therefore to determine the composition and the energy content of the product gas from torrefaction utilizing different biomasses. Multivariate analysis All responses from MBMS measurements of the different samples were used for both PCA and PLS-DA. In the PLS-DA presented below the data was centered and UV scaled for identification of to components correlated to coniferous or deciduous wood independent on concentrations. Torrefaction + MBMS analysis Figure 3. Higher heating value of wet torrefaction product gas. Chips from Birch, Pine and Spruce were torrefied at 270-320 ºC. Initially the wood chips were pre-dried in 105ºC over night before it was intro-duced into a heated alumina reactor tube. The size of the wood chips torrefied were 20 x 7 x 3 mm. The wood chips were immersed down through the reactor to stages for initial drying (100ºC) and torre-faction (275-315 ºC). The biomass was exposed to torrefaction condi-tions for 20-50 min. The produced gases were continuously sampled by a molecular beam mass spectro-meter (MBMS). Zone 1 Zone 2 Figure 4. Relative contribution to higher heating value in torrefaction product gas. * Suggestion of compounds based on fragmentation and base peaks from the literature. Energy Technology and Thermal Process Chemistry Umeå University SE-901 87 Umeå, Sweden Phone: +46 (0)70-239 26 91 E-Post: linda.pommer@chem.umu.se linda.pommer@chem.umu.se lorenz.gerber@genfys.slu.se susanne.wiklundlindstrom@chem.umu.se anders.nordin@chem.umu.se