Introducing an efficient capped fluidized bed and quantifying its flow and heat transfer performance

Abstract

Fluid-solid particle beds have a very wide range of industrial applications but there are few publications relating to a general method to quantify solid particle bed performance for a comparative efficiency study. The conventional approach of characterizing bed efficiency involves bubble sizes, bubble frequency, byproduct quantity for bed reactors, and pressure drop for minimum fluidization. However, different solid particle beds have different states with varying flow rates, which makes the comparative study more difficult to achieve. In this work, a common approach to measure solid particle bed efficiency in terms of heat transfer is presented. The two cases considered here are 1) When work is done by the particles such as in a catalytic reactor, and 2) When work is done on the particles such as in cooling/drying of particles. In addition to the packed bed and fluidized bed, a solid particle bed called a capped fluidized bed is introduced. The Eulerian–Lagrangian method, also known as CFD-DEM simulation, is adopted for this analysis. Numerical simulations show potentially significant advantages of capped beds over packed and fluidized beds under certain fluidization states. Capped fluidized bed pressure drop is comparatively lower than that for a packed bed and similar to a fluidized bed, which allows it to operate at a wider range of flow states. Current fluidized bed performance is limited by the entrainment and possible loss of particles at high flow rates. However, the capped fluidized bed restricts the particles from leaving the bed and thus permits higher flow rate operation. Further experimental research is required to more completely characterize this type of solid particle bed.