Electrostatic precipitators for the containment of toxic aerosols

The electrostatic precipitation of airborne dust particles within an enclosed volume through which there is no net air flow, and which fully encloses the source of particles, is examined. A simple theoretical analysis, based on the classical models of particle charging, yields hypotheses describing what might be expected for field charging and diffusion charging respectively as the predominant charging mechanism. These hypotheses were tested in experiments using an idealised cylindrical condenser system with flax dust as the test aerosol, and observing the rate of decay of particle concentration after removal of the dust source and energising the condenser. The results suggest that, although neither charging mechanism predominates over most of the range of conditions tested, each is the main contributor in the contrasting extremes of particle size and corona current. For particle collection, it appears that turbulent mixing (associated with the electric wind of the corona discharge) plays an important role.

The concept of electrostatic precipitation under zero net flow conditions provides possible practical applications in the containment of toxic industrial aerosols which might otherwise be released into the workplace environment. Some pilot studies relating to the textile industries, carried out both in the laboratory and in a factory, have confirmed the potential for achieving effective containment in practical situations.