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oai:digital.lib.washington.edu:1773/235552025-01-07T20:55:25Zcom_1773_4888col_1773_4940

Schwartz, Daniel T Faires, Kenneth B. 2013-07-25T17:53:30Z 2013-07-25T17:53:30Z 2013-07-25 2013 Faires_washington_0250E_11862.pdf http://hdl.handle.net/1773/23555 Thesis (Ph.D.)--University of Washington, 2013 Described is a laboratory-scale continuous-feed supercritical water gasification (SCWG) system. The system is operated using real-world Ponderosa Pine sawmill residues at high biomass loadings, short mean residence times (2-5 sec), and 27.7 MPa pressures. Each run with the SCWG system typically processed several 100 g of biomass/water slurry mixture. We evaluated the effect of operating temperatures (from 700K to 900K) and biomass feedstock loadings (5% to 15% by weight in water) on solids conversion and gaseous product composition. Biomass-to-gasified product conversion efficiencies ranged from 89% to 99%, by mass. Gaseous products were primarily composed of CO2, H2, CH4, and CO, generally in that order of prevalence. The highest hydrogen yield, 43% mole percent, was achieved at 900k with a 5% biomass loading. In general, low biomass loadings corresponded to higher H2:CO2 ratios, but never did we observe stoichiometries that could be explained purely by steam reforming or steam reforming plus water gas shift chemistries. Methanation & Hydrogenation chemistry also occurred, but the mole fraction of CH4 never exceeded 10%. We hypothesize that the real-world biomass samples used here intrinsically include gas-bubbles in the slurry, enabling partial or complete oxidation to occur along with the more conventional SCWG chemistries. As a result, the observed syngas composition was shown to depend more on biomass loading than on processing temperature. In-situ Raman testing was also evaluated as a possible means of monitoring SCWG real time. Biomass (lignin, cellulose, and hemicellulose) were all detected along with variations in concentration. Additionally effluent composition was verified to not contain intermediary compounds. application/pdf en_US Copyright is held by the individual authors. biofuel; biomass; gasification; supercritical Mechanical engineering Chemical engineering mechanical engineering Gasification of in-Forest Biomass Residues Thesis No embargo open.access