Thermal conversion of biomass

Nikolai DeMartini, Atte Aho, Mikko Hupa, and Dmitry Yu. Murzin 

This work was part of the activities at the Abo Akademi University Process Chemistry Centre within the Finnish Centre of Excelence Programme (2000-2011) by the Academy of Finland. 

Thermal conversion involves the use of elevated temperature with or without the presence of oxygen to break down the structure of the feedstock. It includes torrefac-tion, pyrolysis, gasification, and combustion. Thermal conversion of biomass can also be carried out in a solvent (e.g. as in hydrothermal processing) [1], but in this chapter, only torrefaction fast pyrolysis gasification with air, oxygen, or steam and combustion in air will be considered. 

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U.S. capacity for producing biofuels manufactured by biological or thermal conversion of biomass must be dramatically increased to approach the potential contributions based on biomass availabiUty. For example, an incremental EJ per year of methane requires about 210 times the biological methane production capacity that now exists, and an incremental EJ per year of fuel ethanol requires about 14 times existing ethanol fermentation plant capacity. 

Stassen, H.E.M., Prins, W., Van Swaaij, W.P.M., Thermal conversion of biomass into secondary products the case of... 

The first case covers for example flue-gas treatment, which requires the filtration of fly-ash and the reduction of NOx, or gasification processes, where particulates and high-boiling tars have to be removed. An example of the second case is that of combustion processes, where incomplete combustion leads to the emission of carbonaceous particulates. The most relevant topic in this category is the reduction of diesel particulate emissions ( diesel soot ) by catalytic filtration. A more exotic example is the reaction cyclone for the thermal conversion of biomass, which also combines chemical reactions and separation in one apparatus, though its separation mechanism is not filtration. 

Figure 2.3.2 Possible routes for thermal conversion of biomass. Temperature is given in °C.

Knowledge of the effects of various independent parameters such as biomass feedstock type and composition, reaction temperature and pressure, residence time, and catalysts on reaction rates, product selectivities, and product yields has led to development of advanced biomass pyrolysis processes. The accumulation of considerable experimental data on these parameters has resulted in advanced pyrolysis methods for the direct thermal conversion of biomass to liquid fuels and various chemicals in higher yields than those obtained by the traditional long-residence-time pyrolysis methods. Thermal conversion processes have also been developed for producing high yields of charcoals from biomass. 

The Netherlands Energy Research Foundation (ECN) is the leading institute for renewable energy research in the Netherlands. One of the ECN priority research areas is biomass, in which the unit Biomass focuses on the thermal-conversion of biomass and residues (B R) to generate electricity and heat, liquid and gaseous fuels, and fine chemicals [14], ECN Biomass develops and operates installations for thermal conver-... 

Grpnii M. (1996) A theoretical and experimental study of the thermal conversion of biomass. PhD thesis, NTNU, Trondheim. 

Thermal conversion of biomass/waste streams in oses demands on the fuel quality. The basic physical properties of the biomass and waste streams, such as moisture content, ash content and melting temperature, particle size (distribution), density and calorific value are irrqioitant properties, which determine the design specifications of a new installation to a large extent, The fact that biomass and waste Streams are usually til defined, leads to a significant spread in physical and chemical data. 

Thermal conversion of biomass was perfomied in a Pilot Demonstiation Unit (PDU) scale fluidised bed reactor with a throughput of 5 kg biomass/h and in a laboratory fluidised bed reactor 1 g/batch. Therefore the Hamburg Fluidised Bed Process" ( Hamburger Wirbelschichtverfahren ) had to be modified and empirically optimised for biomass feedstock. 

Liquid fuels producible by thermal conversion of biomass include fuel oil, pyrolysis oils, methanol (discussed under chemicals production), and others. This section discusses the production of fuel oils and pyrolysis oils from wood. 

Kohan, S.M., and Dickenson, R.L., "Production of Liquid Fuels and Chemicals by Thermal Conversion of Biomass Feedstocks," paper 78f to be presented at the 72nd AIChE Annual Meeting,... 

Bioresource Technology. 1979- Amsterdam Elsevier (0960-8524). Online ScienceDirect. Topics include biofuels production, modeling and economics bioprocesses and bioproducts biocatalysis and fermentations biomass and feedstocks utilization and thermal conversion of biomass combustion, pyrolysis, gasification, catalysis. 

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