Investigations in the field of fluidization, carried out at London University College

Abstract

The main trend in investigations carried out at London University College is an elucidation of the mechanism of the operation of chemical reactors with a fluidized bed. The work involved in these investigations consisted of a detailed study of the corresponding physical processes to permit the development of an adequate model of a reactor. Verification of the model by a study of the chemical reactions taking place in a reactor with a fluidized bed is one of the most important stages of the work. The investigations were limited to the case of fluidization by gases. The nature of isolated unperturbed bubbles has been rather thoroughly studied, which makes it possible to construct a simple model [1, 2] which with subsequent refinenment, can become considerably more complicated. The necesary information with respect to two essential elements of this model is lacking. In the first place, heat transfer between the gas in a cloud, surrounded by bubbles, and the gas in the adjacent parts of the fluidized bed has been little studied. In the second place, for actual cases there is no acceptable method for calculating the mean size of the bubbles, their particle-size distribution, the change in their dimensions with height, as a function of the determining parameters such as the velocity of the gas, the particle size, and the construction of the gas-distributing device. Over the course of the last five years, a group of associates^* carried out investigations aimed at obtaining this information, as well as at testing models, and at analyzing of the process of stratification of the solid phase. A review of the latest results is given below.