The Circulating Balls Heat Exchanger (CIBEX)

Abstract

The CIBEX heat exchanger consists of a gas cooling section (gas generator) and an air heating section (air preheater) coupled with a stream of solid particles. The stream of particles falls through a hot gas stream, picking up heat and cooling the gas, then through the airstream, heating the latter. The cooled particles are then returned to the top of the device and the heating/cooling cycle repeated. The paper describes the two-phase equations of motion for the flow of the spherical particles through the fluid. The solid phase is treated as a pseudo-gas by using concentrations instead of density. The equations are then non-dimensionalized and solved by numerical integration. The solution gives temperature and velocity profiles for the two phases for parametric variations in the solid loading and the fluid flux rate. The solution is applied for the design of a heat exchanger for a hypothetical 2500 tons/day coal gasification plant. The dimensions of the CIBEX heat exchanger are much smaller than those of a comparable conventional heat exchanger.