Article pubs.acs.org/EF
Pyrolysis of Woody Residue Feedstocks: Upgrading of Bio-oils from Mountain-Pine-Beetle-Killed Trees and Hog Fuel Alan H. Zacher,*,† Douglas C. Elliott,† Mariefel V. Olarte,† Daniel M. Santosa,† Fernando Preto,‡ and Kristiina Iisa§ †
Pacific Northwest National Laboratory, Richland, Washington 99352, United States CanmetENERGY, Natural Resources Canada, Ottawa, Ontario K1A 1M1, Canada § National Renewable Energy Laboratory, Golden, Colorado 80401, United States ‡
ABSTRACT: Liquid transportation fuel blendstocks were produced by pyrolysis and catalytic upgrading of woody residue biomass. Mountain-pine-beetle-killed (MPBK) wood and hog fuel from a saw mill were pyrolyzed in a 1 kg/h fluidized bed reactor and, subsequently, upgraded to hydrocarbons in a continuous fixed bed hydrotreater. Upgrading was performed by catalytic hydrotreatment in a two-stage bed at 170 and 405 °C with a per bed liquid hourly space velocity between 0.17 and 0.19. The overall yields from biomass to upgraded fuel were similar for both feeds (24−25%), despite the differences in bio-oil (intermediate) mass yield. The pyrolysis bio-oil mass yield was 61% from MPBK wood, and subsequent upgrading of the bio-oil gave an average mass yield of 41% to liquid fuel blend stocks. Hydrogen was consumed at an average of 0.042 g/g of bio-oil fed, with a final oxygen content in the product fuel ranging from 0.3 to 1.6% over the course of the test. Comparatively, for hog fuel, the pyrolysis bio-oil mass yield was lower at 54% because of inorganics in the biomass, but subsequent upgrading of that bio-oil had an average mass yield of 45% to liquid fuel, resulting in a similar final mass yield to fuel compared to the cleaner MPBK wood. Hydrogen consumption for the hog fuel upgrading averaged 0.041 g/g of bio-oil fed, and the final oxygen content of the product fuel ranged from 0.09 to 2.4% over the run. While it was confirmed that inorganic-laden biomass yields less bio-oil, this work demonstrated that the resultant bio-oil can be upgraded to hydrocarbons at a higher yield than bio-oil from clean wood. Thus, the final hydrocarbon yield from clean or residue biomass pyrolysis/upgrading was similar.
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feedstock cost comprised over 25% of the final minimum fuel selling price.16 Clean, debarked wood gives the highest bio-oil yields, but the use of woody residues may offer a competitive option, in particular, for pioneer plants and aid in the adaptation of pyrolysis technology.17 The total potential availability of biomass for biofuel and bioproduct production in the U.S. has been estimated at over 1 billion dry tons/year.18 Forest biomass and wood wastes potentially available at a cost of
