Dust removal from hot and compressed gas streams by fibrous- and granular-bed filters: a state of the art review. [101 references

Abstract

Achieving acceptable filtration efficiency of gas-entrained solid particles has been an important industrial problem. A high dust collection efficiency is essential for many industrial operations either to avoid the possibility of a serious health hazard or to recover valuable solid materials which would otherwise be lost. There is renewed interest in using fibrous and fluidized-bed filters to remove dust from the hot combustion gases from a pressurized fluidized-bed combustor. Such gases may be used to drive a turbine system for power generation. The literature available on the use of fixed-bed and fluidized-bed filters is reviewed to assess our present ability to design efficient and reliable filtration units for hot, compressed gases. The basic mechanisms for solids collection from gas streams are: gravity settling, direct interception, inertial impaction, Brownian diffusion, and thermal separation. The guiding principles of these mechanisms and the characteristic parameters which control the collection of particles are summarized. Calculation procedures are enumerated for estimating total or overall collection efficiency of a single filter unit (cylinder or sphere) and that of a filter consisting of an assembly of individual filter units. Most investigations were at room temperature and 1-atm pressure, and the probable effect of these two variables (temperaturemore » and pressure) on the solids collection efficiency has been analyzed theoretically. The use of fluidized beds in series and containing bed material which can be electrically charged appears to be promising for flue-gas cleaning. It is possible to develop an efficient filter that will match a specific requirement for a given system. Much theoretical and experimental research and development work will be needed for successful understanding and operation of efficient filter systems.« less