MODELING OF AGGLOMERATION IN A FLUIDIZED BED A. Rehmat, C. Huang,* R. Carty Institute of Gas Technology Chicago, Illinois 60616 H. Hariri, H. Arastoopour Illinois Institute of Technology Chicago, Illinois 60616 ABSTRACT A fluidized bed containing a central jet was operated with low-temperature melting materials to obtain the rate of agglomeration as well as to measure the temperature distribution within the fluidized bed. The rate of agglomeration was obtained as a function of operating parameters such as temperature and velocity. The agglomeration rate defined, as the rate of change in the number of particles of a particular size, was determined from the particle population balance using the experimental data. The agglomeration model developed to predict the agglomeration rate constant based on the temperature distribution in the fluidized bed and the rate of entrainment of particles into the jet yielded values for the rate constants similar to the experimental values. INTRODUCTION Fluidized-bed systems have been used in many coal conversion and other chemical processes. The fluidized beds are sometimes operated under agglomerating conditions to maximize coal utilization. The operating conditions in such cases are chosen to prevent the onset of sinters and defluidization (1,2,3,4). Under suitable operating conditions, ash agglomeration provides a very effective means of ash removal from a coal gasifier (5). A distinguishing feature of an ash-agglomerating coal gasifier is a region where the temperature of the ash particles is high enough to make the surfaces sticky so that when they collide with each other, they adhere to each other to produce agglomerates. The rate of the formation of these agglomerates depends upon several factors such as the oxidant distribution within the bed, the overall fluidization velocity, and the ash properties. The oxidant distribution primarily influence the formation of the localized zone of high temperature within the fluidized bed, whereas the velocity influences the rate of particle collision as well as the particle entrainment within this zone. Based on these factors, a mathematical model for agglomeration has been developed to predict the rate of agglomeration in a fluidized bed containing a central jet. These rates are then compared with those obtained from the actual experiments. EXPERIMENTAL APPARATUS AND PROCEDURE The apparatus consists of a 15.2-cm-ID glass fluidized-bed column, a metal section positioned beneath the glass column for temperature measurement end sampling, a gas distributor, a jet and fluidizing air heating system, temperature controlling and temperature measurement devices, and flow regulation and measurement systems (Figure 1). In the experiment, the jet and the fluidizing air temperatures *Dr. Huang is currently at Nalco Chemical, Naperville, Illinois. ___.I__- 176