Fluid Dynamic and Mixing Characteristics of Biomass Particles in Fluidized Beds

Fluid Dynamic and Mixing Characteristics of Biomass Particles in Fluidized Beds

Katia Tannous (University of Campinas, Brazil) and Joana Bratz Lourenço (University of Passo Fundo, Brazil)
DOI: 10.4018/978-1-4666-8711-0.ch003
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Abstract

The study of fluid dynamic and mixing characteristics of biomass particles in fluidized beds is fundamental for comprehension of thermal conversion processes. In this chapter a review of literature showed a large lacks of technical information about the quality of fluidization and representative models concerning binary mixtures (biomass and inert). A case study was presented involving Eucalyptus grandis wood and tucumã endocarp in order to obtain fluid dynamic parameters such as the characteristic fluidization, velocity and porosity, and the bed expansion. These parameters were more significant for mixtures with smaller diameter and mass fraction ratios, and sphericity ratio, due to the facility of beds to fluidize. A map was presented to identify the limits of effective mixtures considering four classes as a function of the complete fluidization Reynolds' and Archimedes' numbers. Empirical correlations have been proposed and showed a good agreement with the experimental work.
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Background

Despite the efforts in developing technologies to convert biomass into energy employing fluidized beds, few authors have attempted to understand the fluidization mechanics of biomass or it mixture with an inert (Cui & Grace, 2007). Generally, it is assumed that the design and operation of equipment involving biomass can be based on the conventional knowledge of fluidization. The use of fluidized beds stands out with numerous advantages such as: high heat transfer, uniform and controllable temperatures, and efficient gas-solid contact. However, for it occur effectively, the ideal operating conditions and choice of materials must be performed carefully (Basu, 2010; Cui & Grace, 2007; Gómez, Mesa-Pérez, & Brossard-Perez, 2008).

As noted in several studies in subsequent years, biomass does not fluidize or fluidize with low quality without the presence of an inert. The fluidized beds operating conditions for mixtures of biomass and inert particles are classified differently of homogeneous particles. This work will present a literature review and recommendations for readers in order to facilitate fluidized bed designs applying heterogeneous particles (binary mixtures) regarding their fluid dynamic behavior patterns.

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