Progress in the Production of Hot-Gas Filtered Biocrude Oil at NREL

Progress in the production of hot-gas filtered biocrude oils from a dry hybrid poplar feedstock in the NREL vortex ablative pyrolysis reactor is discussed. In particular, adjusting the pyrolysis severity in the vortex reactor and the cracking severity in the char baghouse resulted in increased oil yields of very low-ash and low-alkali biocrude oils. The viscosity of these oils meets therequirements for American Society for Testing and Materials (ASTM) #4 fuel oils. Increasing the water content to 30% decreased the viscosity by half, but not enough to meet the viscosity requirement for ASTM #2 fuel oil. Viscosity contours for water and methanol dilution are shown. The addition of water or methanol or both to make a more consistent product may be advantageous. Aging studies ofthis low-alkali oil showed a slower increase in viscosity with time equal to one-third the rate of a biocrude oil with higher alkali contents. It appears that removal of the char fines results in a more stable oil. In fact, after 24 hours at 90 degrees C, the viscosity of this low-ash biocrude oil was lower than that seen previously for the unaged sample of higher ash oil. It is concluded thatthe removal of char fines to produce a premium biocrude oil will be even more important than was previously supposed.