Electrostatic precipitators are high efficiency gas
cleaning devices widely used in industry for removing
particulates from process gases. A major factor affecting
their performance is particle migration, which is governed
by the complex interaction of electrical and hydrodynamic
phenomena. A fuller understanding of these fundamental
mechanisms is therefore essential to the development of
realistic mathematical models.
The work described in this thesis concentrates on the fluid-particle interactions in a wire-plate-system. A pilot-scale rig was built using actual components from an
industrial precipitator, allowing realistic conditions to be
simulated in the laboratory.
Hot-wire anemometry and laser-Doppler photon
correlation techniques were employed to study the time-averaged velocity field. Several designs of wall strengthener were considered, and in each case the effect on the surrounding flow field was investigated using helium bubble visualisation. The turbulent nature of the fluid was
characterised by local dispersion coefficient values and fluctuating velocity components.
Alumina test dust in the size range 1-10 pm was used in the precipitator under a variety of operating conditions, and a technique was established for extracting representative dust samples. The samples allowed simultaneous measurement of concentration and size
distribution, from which concentration profile development and collection efficiency information was obtained. Two alternative numerical models of the precipitator were developed, both incorporating the results from the fluid flow field experimentation. The first approach was
based on the finite difference solution of the convective-diffusion equation, using appropriate boundary conditions. In the second approach, the transport of dust down the precipitator duct was simulated by the step-wise progression
of a series of vertical line-sources, whose motion was governed by electrical migration and lateral diffusive spread. The validity of the models was tested by comparison of the predicted concentration profiles with corresponding
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.