Two-stage-type electrostatic precipitator re-entrainment phenomena under diesel flue gases

One of the applications of the electrostatic precipitator (ESP) is the clea ning of air to increase the visibility index in highway tunnels. Particles floating in air in highway tunnels are mainly carbon. Collection efficiency of a large particle diameter in an ESP often decreases when the ESP collec ts carbon particles which have low electric resistance. Collection efficien cy often becomes negative in an experimental ESP, The negative collection e fficiency means that the particle concentration flowing downstream is great er than that upstream in the ESP, This phenomenon is explained as the re-en trainment of particles. In this paper, experiments were carried out to inve stigate the cause of the decrease in efficiency of particle collection of t he ESP, The time characteristic of the collection efficiency and the distri bution of particle size on the collection electrodes were studied. Experime ntal results showed that the decrease in the collection efficiency was caus ed by re-entrainment of particles during the ESP operation. The effect of g as-flow velocity on the collection efficiency of the ESP was also investiga ted to study the cause of re-entrainment phenomena. The result showed that the re-entrainment phenomena depended on the gas-how velocity.