278931 Fast Pyrolysis of Biomass with Microwave Heating: A Preliminary Analysis with CFD Modeling
The search for sustainability instigates the investigation for alternative sources of energy, in order to mitigate economic, social and environmental problems. Thus, biomass appears as one important renewable source for the production of food, materials, chemicals, fuels and energy, being essential to develop processes and equipment to convert its resources efficiently.
Several biochemical and thermochemical processes have been investigated for biomass processing, but thermochemical methods have been shown as the easiest to adapt to the existing energy infrastructure.
In this context, fast pyrolysis has emerged as a promising alternative, consisting in the conversion of biomass into a complex mixture of organic compounds and fractions of char and gas [1; 2]. The main product of this process is the bio-oil, which can be used in engines and turbines, or fed into refineries to obtain products with higher added value .
Fluid beds are the most popular configuration used in fast pyrolysis, due to their ease of operation and ready scale-up, allowing to obtain high yields of bio-oil . At laboratory scale, this reactor is conventionally heated by electric resistances, and at larger scales, by burning by-products of pyrolysis.
Recently, an alternative that is being proposed is the microwave heating, which has been proven to be energy efficient and has been widely accepted as an easy to control technology, resulting in a bio-oil with interesting characteristics for a sustainable manufacturing of chemicals and biofuels, it has also shown favorable energy balances for the process [4; 5; 6; 7; 8; 9; 10; 11].
Aiming to understand and develop this process, the software COMSOL Multiphysics® was used for the simulation of thermal behavior in the fluid bed with microwave heating. The results permit to make a preliminary analysis of the thermal behavior of biomass, the distribution of electric field and resistive losses in the oven, and also its influence on the homogeneity of heating and on the bio-oil yield obtained.
 BAHNG, M. K. et al. Current technologies for analysis of biomass thermochemical processing: A review. Analytica Chimica Acta, v. 651, n. 2, p. 117-138, 2009.
 BRIDGWATER, A. V.; PEACOCKE, G. V. C. Fast pyrolysis processes for biomass. Renewable and Sustainable Energy Reviews, v. 4, n. 1, p. 1-73, 2000.
 BRIDGWATER, A. V. An Introduction to Fast Payrolysis of Biomass for Fuel and Chemicals. In: PRESS, C. (Ed.). Fast Pyrolysis of Biomass: A Handbook. Second. Newbury, UK, 2008. cap. 1, p.1-13.
 BUDARIN, V. L. et al. The preparation of high-grade bio-oils through the controlled, low temperature microwave activation of wheat straw. Bioresource Technology, v. 100, n. 23, p. 6064-6068, 2009.
 CHEN, M. et al. The effects of additives on yields and distribution of gasand liquid from pyrolysis of biomass by microwave heating. Hefei, 2008. 513-516 p.
 CLARK, D. E.; SUTTON, W. H. Microwave processing of materials. Annual Review of Materials Science, v. 26, n. 1, p. 299-331, 1996.
 DE LA HOZ, A.; DÍAZ-ORTIZ, Á.; MORENO, A. Microwaves in organic synthesis. Thermal and non-thermal microwave effects. Chemical Society Reviews, v. 34, n. 2, p. 164-178, 2005.
 DOMÍNGUEZ, A. et al. Production of bio-fuels by high temperature pyrolysis of sewage sludge using conventional and microwave heating. Bioresource Technology, v. 97, n. 10, p. 1185-1193, 2006.
 DU, Z. et al. Microwave-assisted pyrolysis of microalgae for biofuel production. Bioresource Technology, v. 102, n. 7, p. 4890-4896, 2011.
 HUANG, Y. F. et al. Total recovery of resources and energy from rice straw using microwave-induced pyrolysis. Bioresource Technology, v. 99, n. 17, p. 8252-8258, 2008.
 LUQUE, R. et al. Microwave-assisted pyrolysis of biomass feedstocks: The way forward? Energy and Environmental Science, v. 5, n. 2, p. 5481-5488, 2012.
The authors thank to CNPq and CAPES for encouraging the development of this work and for financial support.