Densefluidized

Densefluidized is a term used in the study of fluidized beds to describe a dense fluidized state in which the solid phase forms a high holdup suspension in a carrier phase. In this regime, the bed contains a substantial fraction of solids, resulting in lower porosity and stronger interparticle interactions than in conventional, more dilute fluidization. Dense-fluidized beds often occur at superficial gas velocities near or above the minimum fluidization velocity, where the bed expands but material is not yet fully entrained, and they can also arise in liquid-solid systems at high solids loading.

Hydrodynamics in the dense-fluidized regime are dominated by particle-particle and particle-fluid interactions. The suspension can exhibit non-Newtonian or shear-thickening behavior, with a significant frictional pressure drop and reduced bubble formation compared with more dilute, bubbling fluidization. Modeling approaches frequently use two-fluid (Euler-Euler) frameworks or coupled Euler-Lagrange methods, with constitutive relations that depend on the solids fraction and particle properties. Practical design and operation must account for potential issues such as channeling, wall effects, and defluidization, especially during scale-up or changes in particle size distribution.

Applications of dense-fluidized beds include high-heat-transfer and high-solid-loading processes such as certain high-temperature gasification and catalytic reactions, drying, and coating where close solid contact enhances performance. While offering efficient heat and mass transfer, these systems can present challenges in stability, control, and uniformity at larger scales.

See also: fluidized bed, bubbling fluidized bed, dense phase conveying, two-fluid model, Kunii-Levenspiel fluidization theory.