Pyrolysis, biomass

The decomposition of biomass can be classified in different ways and specific 

Fast pyrolysis process of operation around 500°C, low residence times of gas/vapor flow about 4 s. This favors the production of liquid (bio-oil) with high yield, about 75%. Furthermore, gases and vegetable carbon are formed, between 10- to 15%, approximately. 

Intermediate pyrolysis no pretreatment of the feedstock is required, operation process in the same temperature range of the fast pyrolysis, but with greater residence times of flow of gas/vapor, about 10-40 s, producing about 50wt% liquid and more gases and carbon. 

Carbonization operation at lower temperatures, about 400° C, but with much higher residence times of gas/vapor flow, producing little amount of liquid and a lot of 

In the fast pyrolysis processes, the temperature control and residence time are important variables due to the formation of secondary reactions. High heating rates and good heat transfer at the interface between the particles and gases/vapors are necessary for the reaction to occur. The thermal conductivity of the materials is very low, which requires very fine solid particles of about 4 mm. Besides, it is necessary to remove quickly the carbon to avoid and/or minimize cracking, and cooling the vapor to facilitate the formation of bio-oil. 

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Liquefaction. Siace the 1970s attempts have been made to commercialize biomass pyrolysis for combiaed waste disposal—Hquid fuels production. None of these plants were ia use ia 1992 because of operating difficulties and economic factors only one type of biomass Hquefaction process, alcohohc fermentation for ethanol, is used commercially for the production of Hquid fuels. 

A. V. Bridgwater and G. Grassi, eds.. Biomass Pyrolysis Tiquids Upgrading and Utilicyation, Elsevier AppHed Science, New York, 1991, 377 pp. 

This chapter discusses the technology, practices, and emerging technologies of pyrolysis. Focus is given to the key applications of waste processing, and the application of coal and biomass pyrolysis processes for the production of synthetic fuels. 

Table 4.1 Biomass Pyrolysis Product Slate As A Function of Heating Rate, Residence Time, and Temperature...

Biomass pyrolysis in the presence of a catalyst, in situ, is considered as one of the options to overcome the problem characteristics of bio-oil mentioned above. Selective removal, by decarboxylation, of carboxylic acids (formic, acetic acids)... 

Most importantly, biomass pyrolysis will be carried out at remote locations, and in distributed manner. Thus, the catalysts should be cheap and simple to use. Acidic clays, silica aluminas and H-FAU type zeolites are relatively cheap and robust materials, can be mixed easily with heat carriers, and used for pyrolysis. Efficient contact between the solids (catalyst and biomass) to maximize catalytic action is one of the challenges that need to be overcome. 

Van Swaaij, W.P.M., Biomass pyrolysis in a fluidized bed reactor. Part 1 literature review and model simulations. Ind. Eng. Chem. Res., 2005, 44, 8773. 

Gayubo, A.G., Aguayo, A.T., Atutxa, A., Aguado, R., Bilbao, J., Transformation of oxygenate components of biomass pyrolysis oil on a HZSM-5 zeolite. 

Efficient technology could also be developed based on catalytic biomass pyrolysis for the conversion of biomass into clean and renewable liquid bio-oil. This would facilitate its introduction into the energy market as a renewable fuel or as source of high value chemicals. It is possible to produce stable liquid biofuels from biomass flash pyrolysis, in a single stage catalytic process, although further developments are necessary. 

Miller, R. S. and Bellan, J. (1997) A generalized biomass pyrolysis model based on superimposed cellulose, hemicellulose and lignin kinetics. Comb. Sci. and Techn., 126, 97-137. 

The biomass pyrolysis is attractive because sohd biomass and wastes can be readily converted into hquid products. These liquids, as crade bio-oil or slurry of charcoal of water or oil, have advantages in transport, storage, combustion, retrofitting and flexibihty in production and marketing. 

Table 4.7 Fuel properties of diesel, biodiesel and biomass pyrolysis oil...

Antal M.J, Biomass Pyrolysis A Review of the Literature Part I -Carbohydrate Pyrolysis , in Adv. in Solar Energy - an annual review of R D, Vol 1, Ed. Boer K.W. and Duffie J.A., Plenum Press, New York, bill 1(1982)... 

Few of the primary products of biomass pyrolysis are thermally stable at the typical temperatures of the hydrocarbon reformer. Hence there is significant competition between catalytic reforming reactions (Equation 6.3) and thermally induced cracking decomposition (Equation 6.4). 

Table 6.1 lists the stoichiometric yields of hydrogen and percentage yields by weight from steam reforming of some representative model compounds present in biomass pyrolysis oils, and also several biomass and related materials. The table also shows the equilibrium yield of H2, as a percentage of the stoichiometric yield, predicted by thermodynamic calculations at 750 °C and vdth a steam-to-carbon (S/C) ratio of 5 [32]. 

Hydrogen production via biomass pyrolysis involves heating the biomass rapidly to high temperatures in the absence of oxygen. Products like hydrogen, methane, carbon monoxide, carbon dioxide,... 

Pyrolysis is the degradation of macromolecular materials with heat alone in the absence of oxygen [45]. The development of pyrolysis processes for the production of liquids has gained much attention in the last decade because they offer a convenient way to convert low-value woody residues into liquid fuels and value-added products. Biomass pyrolysis is of growing interest as the liquid product can be stored and easily transported [46]. Pyrolysis processes yield a mixture of gas, liquid, and solid products. If pyrolysis is practiced alone, that is, without a subsequent gasification step (see Section 16.4.3), the process conditions are usually chosen to maximize liquid product yields. 

CFBs as reactors, the solids residence time is an important parameter. Previous studies mostly assess operations at moderate values of the solids circulation rates (<100kg/m2s), whereas gas-catalytic reactions and, e.g., biomass pyrolysis require completely different operating conditions. 

Antal, M.J. "Biomass Pyrolysis. A Review of the Literature -Part Is Carbohydrate Pyrolysis" in Advances in Solar Energy, (Eds. K.W. Boer and J.A. Duffie) Vol. 1, (American Solar Energy Society, Boulder, CO) 1983. 

Biomass Pyrolysis for Hydrogen Production Jet Propulsion Laboratory... 

The desired primary liquid products of biomass pyrolysis react readily in secondary cracking reactions, shifting the product yield from liquids to gases. Those cracking reactions are assisted by contact of the volatiles to the remaining solids, which can be reduced significantly by running the fast pyrolysis in a reaction cyclone [79, 80]. A simplified flow sheet of such a laboratory plant for the fast pyrolysis of biomass is shown in Fig. 15.9. 

Di Blasi, C. Modeling chemical and physical processes of wood and biomass pyrolysis. Progress in Energy and Combustion Science, 2008. 34, 47-90. 

The formation of coke is not a problem for UMR since any coke that is formed is burnt off during the air regeneration step. This allows the use of UMR with diesel/logistics fuel and possibly with biomass pyrolysis liquids, though the latter has not yet been demonstrated. 

Coke Formation during the Hydrotreating of Biomass Pyrolysis Oils Influence of Guaiacol Type Compounds... 

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