Liquid Injection into Fluidized Beds

Authors: Snider, D. ^a, O’Rourke, P. ^b, and Zhao, P. ^a
a CPFD Software
^b CPFD d’OR Software, LLC

Source: Zhao, P.; O’Rourke, P. J.; Snider, D. Liquid Injection into Fluidized Beds; AIChE: New Orleans, LA, 2008; p 8

Abstract: We have developed a unified model for collisional exchange of mass, momentum, and energy between particles in gas/liquid/solid fluidized beds. In a fluidized bed, collisions between liquid spray droplets and bed particles, and between the wet bed particles themselves, are the mechanisms whereby the liquid spreads over the particles’ surfaces. In addition to spreading of the liquid jet-drops over solid particles, collisional mass transfer results in mixing of liquid and energy from particle to particle. The mixing process moves towards local uniformity of liquid chemical composition and liquid temperature in the particle bed. Collisional momentum transfer results in the damping of relative motion between particles, which, in turn, reduces the collision frequency. The new collisional model extends the equations of the Multiphase Particle-in-Cell (MP-PIC) method [1-3] by including collision terms on the right-hand side of the transport equation for the single-particle distribution function. The collision terms are the same as in the BGK model for collisions in the Boltzmann equation of gas dynamics [4] where collisions are represented by a simple relaxation term on the right-hand side of the Boltzmann equation. The numerical integration of the collision terms is included within the computational particle fluid dynamic (CPFD) commercial Barracuda computational software. This paper focuses on the application of this unified collision model to a liquid jet sprayed into an isothermal fluidized bed. The characteristics of the jet penetration and mixing is compared with data from Ariyapadi, et al [5]. The experiments measured liquid jet penetration into gas/solid fluidized beds using an x-ray imaging technique. Both experiment and calculation show that a single number representing jet penetration is difficult to define. The dynamic behavior of interaction between liquid jet and the fluidized bed, and the liquid mass and momentum transfer are presented and discussed.