Progress in the production of hot-gas filtered biocrude oil at NREL

Abstract

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 the requirements for American Society for Testing and Materials (ASTM) #4 fuel oils. Increasing the water content to 3 0% 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 of this 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 o 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 that the removal of char fines to produce a premium biocrude oil will be even more important than was previously supposed.

A review of the chemical and physical mechanisms of the storage stability of fast pyrolysis bio-oils

“…Table 2 shows that the chlorine content of the hot-gas-filtered hardwood bio-oils varied considerably, from 0.3 to 2 equivalents of chlorine per equivalent of potassium, sodium, and calcium (Diebold et al 1996;Scahill et al 1997). The chlorine content of switchgrass oils did not change significantly during filtration of the bio-oil and was in the range of 1200 ppm to 1600 ppm; the metal ion content decreased (Agblevor et al 1994).…”

“…Water contents as high as 30 wt % and methanol contents as high as 10 wt % were investigated and found to reduce the viscosity of the mixtures (methanol was slightly more effective). The viscosity at 25ºC was lowered from 76 cP with 20 wt % water and to 12 cP with 30% water and 10% methanol (Diebold et al 1996).…”

Combustion Properties of Biomass Flash Pyrolysis Oils: Final Project Report

“…2, are iypically 50% higher than those for heavy fuel oil (No. 6) (Diebold et al, 1996;Annual Energy Review 1997). This trend is fi.m%eraccentuated in Europe, where light fuel oil typically costs twice as much as heavy fuel oil (Diebold et al, 1996;Gust, this report).…”

“…6) (Diebold et al, 1996;Annual Energy Review 1997). This trend is fi.m%eraccentuated in Europe, where light fuel oil typically costs twice as much as heavy fuel oil (Diebold et al, 1996;Gust, this report). In terms of electrical power production, the most efficient use of a liquid fuel is in fu-ing a gas turbine, normally using a No.…”

“…This property of biomass oils probably poses the most severe technical barrier to substantial commercial use of this fiel, Research has been conducted on hydrotreating bio-oils or cracking with a zeolite catalyst to remove the oxygen functionalities of the oil, but the process efficiency is poor and substantial technical barriers remain (Bridgwater and Cottam, 1992;Maggi and EllioK 1997;Elliott and Neuenschwander, 1997;Conti et al, 1997). The most promising approach to reducing the rate of aging of the oils is to use simple fbel additives, such as water or methanol (Diebold et al, 1996;Maggi and Elliott, 1997). Methanol addition at the 10'%Ievel has been shown to decrease the rate of aging by about a factor of 20 .…”