Effects of Interparticle Forces on Fluidization Characteristics in Liquid-Containing and High-Temperature Fluidized Beds

Abstract

Interparticle forces exert a critical effect on particle fluidization characteristics in gas–solid fluidized beds. Glass and steel fluidized beds are specially designed to study the effects of liquid and high temperature, two key parameters in the condensed-mode operation of industrial polymerization reactors, on particle fluidization characteristics mainly from two aspects: interparticle forces and minimum fluidization velocity. Variations in interparticle forces are reflected in the peak values and gas velocity ranges of the “hump” in the ΔP–ug curve. This is because an increase in liquid content or bed temperature enhances the compaction of fixed-bed particles and makes complete fluidization of the particles difficult to achieve. Moreover, the increase of the minimum fluidization velocity can be ascribed to the delay of particle fluidization caused by the growth of interparticle cohesive forces due to the increase in liquid content and temperature. Three types of methods, namely, pressure drop measurements, accelerometry, and visual observation, are compared, and accelerometry was found to be superior to the pressure drop method for measuring umf in a liquid-containing fluidized-bed reactor. In addition, the reversibility of agglomeration and its implications for industrial operation are discussed. This work aims at further understanding wet and high-temperature gas–solid fluidized beds, especially the condensed-mode operation of polyethylene fluidized-bed reactors.