Chemical Processing in High-Pressure Aqueous Environments. 7. Process Development for Catalytic Gasification of Wet Biomass Feedstocks

Abstract

Through the use of a metal catalyst, gasification of wet biomass can be accomplished with high levels of carbon conversion to gas at relatively low temperature (350 °C). In a pressurized-water environment (20 MPa), near-total conversion of the organic structure of biomass to gases has been achieved in the presence of a ruthenium metal catalyst. The process is essentially steam reforming, as there is no added oxidizer or reagent other than water. In addition, the gas produced is a medium heating value gas due to the synthesis of high levels of methane, as dictated by thermodynamic equilibrium. While good gas production was demonstrated, biomass trace components caused some processing difficulties in the fixed catalyst bed tubular reactor system used for the catalytic gasification process. Results are described for tests using both bench-scale and scaled-up reactor systems.

Catalytic gasification of dry and wet biomass

“…If coke is formed on the surface of the catalysts, the high H 2 O concentration helps in keeping it clean via gasification. In accordance with that it was found that coke formation on the catalyst surface is a minor problem [8].…”

“…The difference with respect to the product between 350 and 600 8C is its composition: at low temperature the gas contains nearly only CH 4 and CO 2 (see ref. [8] and Fig. 5B) whereas at higher temperature it is a mixture of CH 4 , H 2 and CO 2 .…”

“…A ruthenium catalyst (3 wt% Ru on rutile TiO 2 , d p $ 70-100 mm) was used which was supplied by Pacific Northwest National Laboratory. This catalyst was selected for its proven high activity at 350 8C [8]. Recently, cheaper Ni-based catalysts have been proposed for this purpose [9].…”

“…350 8C while producing a methane rich gas [50,51,8,52]. In an extensive research program that started in the eighties of the last century tests were carried out at laboratory and pilot scale focusing on both catalyst and process development.…”

Supercritical Water Gasification of Biomass and Organic Wastes

“…Sulfur also exists in some waste biomass and it has an influence on supercritical water gasification. Elliott et al claimed that the presence of sulfur lowered the activities of ruthenium catalysts in subcritical water at 623 K (Elliott et al, 2004). Osada et al studied the effect of sulfur on SCWG of lignin at 673K with the catalysis of supported ruthenium (Osada et al, 2007a).…”