Thermochemical liquefaction of biomass

Thermochemical Liquefaction. Most of the research done since 1970 on the direct thermochemical liquefaction of biomass has been concentrated on the use of various pyrolytic techniques for the production of liquid fuels and fuel components (96,112,125,166,167). Some of the techniques investigated are entrained-flow pyrolysis, vacuum pyrolysis, rapid and flash pyrolysis, ultrafast pyrolysis in vortex reactors, fluid-bed pyrolysis, low temperature pyrolysis at long reaction times, and updraft fixed-bed pyrolysis. Other research has been done to develop low cost, upgrading methods to convert the complex mixtures formed on pyrolysis of biomass to high quality transportation fuels, and to study liquefaction at high pressures via solvolysis, steam—water treatment, catalytic hydrotreatment, and noncatalytic and catalytic treatment in aqueous systems. 

Thermochemical liquefaction of biomass is basically a simple process whereby it is heated with alkali under pressure at temperatures up to 400 C. This simple procedure converts the biomass to a mixture of gas (2-10%), char (5-40%), and oil (up to 40%), on a weight basis. It is one of several methods available for conversion of biomass to potential liquid fuels, the others being direct heating of dry matter (destructive distillation, pyrolysis) (1), fermentation (or anaerobic digestion) ( ), and gasification (partial oxidation) ( ) followed by liquefaction to methanol. There are variants on all of thesb processes. 

Elliott, D., et al., 1991. Developments in direct thermochemical liquefaction of biomass 1983-1990. Energy Fuels 5 (3), 399-410. 

Various catalysts were examined to increase the products obtained from thermochemical reaction of biomass. Appell and co-workers demonstrated that solid organic materials, including urban refuse, agricultural wastes, wood and bovine manure, can be converted directly to heavy fuel oil in the presence of a catalyst such as sodium carbonate. Since then, a great number of works have been reported on the direct liquefaction of biomass in the presence of suitable catalysts. Recent publication, the addition of Na2C03 greatly increased the reaction rate. Minowa et... 

Pacific Northwest Laboratory (PNL) and Lawrence Berkeley Laboratory (LBL) have been selected to provide program management services to the Biomass Energy Systems Program. PNL is responsible for the technical management of development activities directed toward the thermochemical conversion of biomass feedstocks by direct combustion, gasification and indirect liquefaction via synthesis gas. LBL is responsible for the technical management of development activities on the direct liquefaction of biomass feedstocks. 

Russell, J. A. Molton, P. M. Landsman, S. D. Chemlcal Comparisons of Liquid Fuel Produced by Thermochemical Liquefaction of Various Biomass Materials presented at the 3rd Miami International Conference on Alternative Energy Sources, Miami, Florida, PNL-SA-8602, Pacific Northwest Laboratory Richland, Washington, 1980. 

Davis, H., G. et al. "The Products of Direct Liquefaction of Biomass," in Fundamentals of Thermochemical Biomass Conversion. R. P. Overend, T. A. Milne, and L. K. Mudge, Eds Elsevier Applied Science Publishers, New York, 1985 p 1027. 

Sawayama S, MinowaT,YokoyamaYS. Possibility of renewable energy production and CO2 mitigation by thermochemical liquefaction of microalgae. Biomass Bioenergy 1999 17(1) 33—9. 

Jena, U., et al, 2011. Evaluation of microalgae cultivation using recovered aqueous co-product from thermochemical liquefaction of algal biomass. Bioresource Technology 102 (3), 3380-3387. 

Modell, M., Gasification and liquefaction of forest products in supercritical water. In Fundamentals of Thermochemical Biomass Conversion, Overend, R. P. Milne, T. A., Eds., Elsevier Applied Science Publishers, London, 1985, pp. 95-119. 

Liquefaction. Figure 21 outlines most of the biomass liquefaction methods under development. There are essentially three basic types of biomass liquefaction technologies, ie, fermentation, natural, and thermochemical processes. 

Stevens, D.J. "An overview of biomass thermochemical liquefaction research sponsored by the U.S. Department of Energy. In Production. Analysis and Upgrading of Oils from Biomass. Vorres, K.S., Ed., American Chemical Society, Division of Fuel Chemistry Abstracts, 1987, 32(2). 223. 

E. Chornetr R.P. Overend and co-workers at the Universite de Sherbrooke have been working on a liquefaction process in pressurized solvent for some years. Their approach involves an overall integration of biomass pretreatment, fractionation, acid processing, thermochemical and biochemical treatment. 

Beckman, D., Elliott, D.C., Comparisons of the yields and properties of the oil products from direct thermochemical biomass liquefaction processes, Can. J. Chem. Eng., 1985, 63, 99. 

Biomass pyrolysis though is one of the fint process man developed, is being studied extensively since the last two decades to obtain liquid, gaseous and solid fuels and chemicals. It is well recognised that pyrolysis plays a key role in any of the thermochemical conversion process be it combustion, gasification, liquefaction, production of char or active carbon. In this context, selection of feedstock and optimal utilisation of the products can play a vital role [1], This paper suggests a criteria to select an appropriate biomass or find its relative suitability to the conversion processes. 

The oldest method of using biomass to create energy is direct combustion, which has been used for thousands of years. Other thermochemical techniques which can be used for the production of chemicals from biomass usually involve depolymerisation at elevated temperatures and pressures. Among these are gasification, pyrolysis, liquefaction and acid hydrolysis. 

Catalytica Associates, Inc. is conducting a study to produce a systematic assessment of the role of catalysis in thermochemical conversion via gasification and liquefaction. This study is also examining the potential impact of catalytic concepts under development in other areas, such as coal conversion, and new reactor technology on biomass conversion. 

The data in this paper are drawn from a number of studies performed at Pacific Northwest Laboratory (3,7-9). We have examined biomass pyrolysis tar samples from many types of pyrolytic gasification and liquefaction systems through the U.S. Department of Energy support of domestic biomass thermochemical conversion research and international cooperative efforts. Many of these can be compared directly as a function of temperature since they are all produced at short residence time, approximately one second. Others produced at longer residence time or pressure require discussion separately. 

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