Abstract:
Suspended fly-ash particles in industrial emission gasses have a major
degrading effect on the whole environment. Electrostatic precipitation is one
of the oldest and most effective gas-cleaning processes used today.
Electrostatic precipitators use electrostatic forces to clean the flue gas of ash
particles. Stricter emission control laws force industries (like SASOL) to
improve their electrostatic precipitators.
This study consists of a comprehensive literature survey and the development
of a numerical fluid flow model. The proper flow of the gas through an
electrostatic precipitator is one of the most important factors to ensure high
collection efficiencies. The gas flow must be distributed over the whole flow
domain in order to utilize the entire collecting area. The three-dimensional
numerical model only considers the fluid dynamics of a precipitator. The finite
volume method together with the SIMPLE algorithm is used to solve the fluid
dynamic equations.
The computer resources available are not sufficient to simulate the full detail
of the structures inside a full-scale precipitator. Thus the precipitator flow
domain was simplified by making certain assumptions and approximations.
The distribution plates in the precipitator inlet ensure good gas distribution
through the entire precipitator. Porous baffles are used to approximate the
distribution plates and the electrical fields are approximated by porous
mediums.
The effect of the distribution plates and the electrical fields on the gas flow
through the precipitator was investigated. The results have shown that the
gas flow was expanded over the whole flow domain and the maximum
velocity inside the precipitator was significantly reduced because of the effect
of the distribution plates. The simulated gas flow velocity profiles are in
relative good agreement with measured velocity profiles. The methodology
followed in this study can be used to predict gas flow patterns inside a
precipitator but further research is necessary.
