Liquefaction, direct 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. 

It was concluded from this assessment that the most promising process for gasoline production by direct liquefaction of biomass is atmospheric flash pyrolysis. The high-pressure process may have the same future potential, but the uncertainties are much greater. 

Davis, H. G. (1983). Direct Liquefaction of Biomass Final Report and Summary of Effort 1977-1983, LBL-16243. Lawrence Berkeley Laboratory, University of California, Berkeley. 

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... 

For the conversion of biomass resources into useful chemicals and bio-ener, three major process types, direct combustion, gasification and liquefaction, are effective. Among them, liquefaction for liquid transpiration fuels is, in particular, important because it is difficult to replace them with other energy forms. Thus, a study of the liquefaction of biomass is of interest. ... 

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. 

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. C. "Process Development for Direct Liquefaction of Biomass," Fuels from Biomass and Wastes Ann Arbor Science Publishers Ann Arbor, MI, 1981 pp. 435-450. 

In the early 1970 s, in response to the world oil crisis, studies on the direct thermal liquefaction of biomass were initiated. These studies could be classified into those on water-based processes and those on non-water-based processes. The focus in this chapter is on the water-based processes and, in particular, on a process which uses no catalysts or reducing gases. It should be noted that actual biomass used for commercial liquefaction would certainly contain significant moisture, and water is expected as a product of the liquefaction. Despite this, the water-based and non-water-based processes are significantly different. 

Variations in Product Due to Feedstock. While process-related differences in product composition have been evident, extensive study of the effect of feedstock on product composition has never been undertaken. Some limited comparative tests can be gleaned from the literature however, most process research in direct liquefaction of biomass has been performed with woods of various species. Table I provides some of the results available in the literature for non-woody feedstocks. Significant differences in heteroatom content are evident, but only limited chemical analysis is available in most cases. 

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. 

In addition to pyrolysis and gasification, there are processes in which high-viscosity liquids which are nonsoluble in water are obtained from solid biomass by liquefaction (i.e., the direct biomass to liquid (BTL) process).This conversion can be accomplished at... 

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

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. 

Over the past two decades, considerable interest has been directed toward the conversion of cellulosic biomass (such materials as wood wastes, bagasse, and straw) into useful products, notably fuels. Several procedures, including fermentation, gasification, liquefaction, and pyrolysis, have been commercially applied to carbohydrates with various degrees of success. In order to use the polysaccharides present in lignocel-lulosic materials as a substrate in fermentation processes, pretreatments are necessary, such as with steam (under slightly acid conditions) or... 

Liquid fuels have a high energy density, and the widest applicability of all fuel forms, but a low efficiency of conversion from biomass. It is therefore necessary to compare liquefaction with the more efficient processes of direct burning and gasification as alternative modes of use of the biomass. 

The potential of biomass to substitute for petroleum is examined in terms of resource availability and cost, conversion technology, and conversion and end-use costs. The most energy-efficient and least costly mode of utilization of wood is direct burning, followed by gasification, and, last, liquefaction. 

The development of new syngas-based processes is one of the objectives for the near future, despite the current low price of oil. Syngas can be produced from various carbonaceous sources, including coal, heavy residue, biomass and gas, the latter being the most economical and abundant feedstock. Chemical valorization of natural or associated gas is a priority objective, since liquefaction of remote gas via alcohol synthesis permits convenient shipping to markets not directly connected to the gas source by pipeline. 

Directly liquefying biomass (liquefaction) by, for example, high temperature pyrolysis or high pressure liquefaction. 

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