Hydrodynamics and Particle Mixing Characteristics of a Ternary Mixture in a Gas-Solid Fluidized Bed

Abstract

Gas-Solid Fluidized Beds are widely used in current industrial practices for their high efficiency in producing products of very high standards. The study of bed dynamics has become an important concern for the design of fluidized beds. Various parameters like pressure, temperature, gas velocity, mean residence time and solids composition affect the bed behavior. In this view, an experimental study was carried out to determine the influence of gas flow rate, mixing time, solids composition and bed height on mixing/segregation behaviour of the bed of particles. Since fluidized beds involving more than two solids are more frequently encountered in current industrial practices, the experiments were conducted using three solid sand particles of average sizes 231 μm, 335 μm, and 510 μm. Various mixing patterns were observed for different mixing times (10, 20 and 30 minutes), different gas flow rates (7.5, 12.5, 17.5, 22.5 and 27.5 LPM), and different solids ratio. Good mixing occurred at an optimum mixing time of 30 minutes and gas flow rates of 17.5 LPM and 22.5 LPM at all solids ratio. The components exhibited relatively better mixing at intermediate bed heights.

Investigation of single particle devolatilization in fluidized bed reactors by X-ray imaging techniques

“…This phenomenon is even more evident for over-bed fuel feeding systems, which are the most commonly used industrially [24]. This has undesirable effects on the chemical reactions in the reactor, as the fuel does not take advantage of the bed-to-fuel transfer phenomena, which are essential for high product yields and quality [25,26]. The same issue is also experienced in other rector configurations, such as circulating fluidized beds, especially in dense regions that form in the bottom section of the riser [24].…”

Axial Segregation Behaviour of a Reacting Biomass Particle in Fluidized Bed Reactors: Experimental Results and Model Validation

“…Moreover, the great amount of volatile matter released by the feedstock particles within the bed evolve in the form of so-called endogenous bubbles, which further enhance the segregation of the feedstock [14][15][16][17][18]. As a consequence of segregation, both solid and gas phases cannot take advantage of the enhanced bed-to-fuel transfer phenomena intrinsic of the fluidized-bed technology, which are essential for high product yield and quality [19,20]. All these aspects are essential to the design of industrial fluidized-bed units and relevant to all thermochemical conversion processes, since the evolution of volatiles is common to pyrolysis, gasification and combustion operations.…”