Executive SummaryPyrolysis is one of a number of possible paths for converting biomass to higher value products. As such, this technology can play a role in a biorefinery model to expand the suite of product options available from biomass. The intent of this report is to provide the reader with a broad perspective of pyrolysis technology as it relates to converting biomass substrates to a liquid "bio oil" product, and a detailed technical and economic assessment of a fast pyrolysis plant producing 16 tonne/day of bio-oil.The international research community has developed a considerable body of knowledge on the topic over the last twenty-five years. The first part of this report attempts to synthesize much of this information into the relevant issues that are important to advancing pyrolysis technology to commercialization. The most relevant topics fall under the following categories: 1) Technical requirements for converting biomass to high yields of liquid bio-oil 2) Reactor designs capable of meeting technical requirements 3) Bio-oil stability issues and recent findings that address the problem 4) Product specifications and standards that need to be established 5) Applications for using bio-oil in existing or modified end use devices 6) Environmental, safety, and health issues For the bio-oil plant technical and economic analysis, the process is based on fast pyrolysis, which is composed of five major processing areas: feed handling and drying, pyrolysis, char combustion, product recovery, and steam generation. An ASPEN model was developed to simulate the operation of the bio-oil production plant. Based on a 550 tonne/day biomass (wood chips, 50% by mass water content) feed, the cost of the bio-oil for a fully equity financed plant and 10% internal rate of return is $7.62/GJ on a lower heating value (LHV) basis.

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.

An NREL-designed vortex reactor fast pyrolysis process development unit (PDU) has been used to investigate hot gas filtration of biomass pyrolysis vapors. Most of the experimental work employed a conventional baghouse type of filter that used NEXTEL™ ceramic cloth filter bags as the filter medium.A series of experimental runs demonstrated that hot gas filtered biocrude oils having less than 10 ppm of total alkali could be reproducibly made. Removal of the char cake from the filter elements proved to be a difficult problem. The char appears to become progressively more sintered to itself and the filter as a function of the cumulative biomass processed. Controlled oxidation does remove this dense char from the filters, but leaves residual ash on the filter cloth fibers. This ash may in turn cause subsequent biomass pyrolysis vapors that pass through the filter to produce additional char (coke) in the interstices of the filter cloth. Data are presented that suggest this char formation may contribute to a more rapid rise in the rate of filter blinding as measured by the increase in recovered filter pressure drop.

The primary pyrolysis vapors generated by the fast pyrolysis of biomass at atmospheric pressures consist initially of low-molecular-weight compounds, but which polymerize upon condensation.Prior to condensation, these primary vapors have been found to be very reactive with ZSM-5 catalyst to produce methyl benzenes boiling in the gasoline range. This gasoline is predicted to have very high blending octane numbers. By-products are coke, carbon oxides, water, naphthalenes, ethylene, propylene, and some phenols. The effect of different by-products on the theoretical gasoline yield is examined.Preliminary results, generated with a reactor having a fixed bed of 100 g of catalyst, are examined for the continuous feeding of never-condensed primary vapors and compared to feeding methanol in the same reactor.The conversion of primary pyrolysis vapors made from biomass is a relatively new research and development area which is showing early promise. The extent to which the product slate can be manipulated by process variables will impact heavily on the viability of this process. The conversion of biomass materials to high octane gasoline has been actively pursued for many years.Historically, methanol was made in very low yields by the destructive distillation of hardwoods.More recently, the manufacture of methanol has been by the reaction of synthesis gas over catalysts at high pressures.In theory, any carbon source can be used for this catalytic generation of methanol, but in practice, biomass has not been advantageous relative to coal or natural gas. Other approaches to making liquid fuel from biomass have involved the fermentation of biomass to ethanol in a rather slow process.The conversion of biomass to alcohols is technically feasible, but the utilization of the alcohols as transportation fuels will require modifications to the

The NREL Fast Ablative Pyrolysis Technology was employed to generate oils from various biomass feedstocks. The oil yield from wood (64 percent) was higher than from herbaceous species (51 percent). Biomass oils have potential to be used as fuel though their properties are different from those of petroleum derived oils. They are multicomponent mixtures containing various groups of organic compounds such as sugars, aldehydes, acids, and phenolics. The density of the oils is about 1.2 g/ml and the pH is in the range 2.5–3.7. The viscosity of 20–80 cP (at 45°C) corresponds to that of No. 6 fuel oil. The high heating value for the biomass oils is in the range of 22.5–24.4 MJ/kg on a water-free basis. Considering the highest oil yields, it corresponds to approximately 65 percent of the wood heating value transferred to the oil.