Wood pyrolysis liquids upgrading

Chen, N.Y. Walsh, D.E. Koenig, L.R. "Fluidized bed upgrading of wood pyrolysis liquids and related compounds." In This Volume. 

Fluidized-Bed Upgrading of Wood Pyrolysis Liquids and Related Compounds... 

CHEN ET AL. FluuUzed-Bed Upgrading cf Wood Pyrolysis Liquids... 

Figure 2 shows the products obtained in a scheme in which direct upgrading of the wood pyrolysis liquids over ZSM-5 occurs in parallel with upgrading of methanol obtained from synthesis gas derived from gasification of the pyrolysis char. In Figure 3, the methanol is mixed with the pyrolysis liquids prior to co-processing over ZSM-5. Approximately 40 lbs. of methanol per 100 lbs. of dry wood feed is potentially available from the char and pyrolysis gas products. 

The overall conclusion is that pyrolysis liquid may be produced and fired at the same cost level as pellets from wood. At present though, development work on pyrolysis liquid has to secure an acceptable and even quality of the upgraded wood fuel as far as that of pellets. 

Laboratory (4) and Process Development Unit (5,6) studies originally conducted at the Universite de Sherbrooke, and now conducted jointly with the private industry at Universite Laval, province of Quebec, have led to the conclusion that thermal decomposition under reduced pressure is an attractive approach for the conversion of biomass into chemicals and fuels products. The process uses a multiple-hearth furnace for wood pyrolysis. This approach is characterized by a low pressure and a short residence time of the vapor products in the rciactor. When compared with conventional, atmospheric pressure carbonization, vacuum pyrolysis has the potential to significantly enhance the yields of organic liquid products with respect to solid and gaseous products. The pyrolysis oils (biooils) obtained from this process can be deoxygenated into transportation fuels upon further upgrading (7). Specialty as well as commodity (Pakdel, H. Roy, C. Biomass, in press) chemicals can also be extracted from the pyrolysis oil product. 

Stated differently, without char gasification, only about 6% of the carbon in the wood could be upgraded to hydrocarbon products even if all the oxygenates produced by pyrolysis were recycled to extinction. Parallel upgrading of methanol derived from char gasification can increase this value to approximately 36%, i.e., about 6% from the pyrolysis liquids and 30% from methanol. Methanol co-processing boosts the percent of wood carbon transformed into... 

The oil fractions collected on the six hearthes of a wood vacuum pyrolysis process demonstration unit have been upgraded to hydrocarbons in the C5-C10 range on a ZSM-5 catalyst. The use of a precoker at reaction temperature has been demonstrated and C5-Ci 0 hydrocarbons yields of the order of 30 wt% of oil fed, have been reached. GC/FTIR analyses of the heavier liquids collected after the precoker indicate that the acids in the oils play a dominant role in the gas phase reactions occurring in the precoker. 

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