|ICESP X CONFERENCE PAPER ABSTRACTS 3B SERIES
Held in Cairns,
Conference on Electrostatic Precipitation (ICESP)
is the official conference of the International Society for Electrostatic
Several experimental and theoretical works pointed out that ionic wind that producessecondary flow inside the ESP channel distorts the carrier gas velocity distribution and particle trajectories and hence influences on the precipitation process.
For valid description of the effect of the ionic wind a complex model is necessary that takesinto consideration the interaction between the gas flow and the corona discharge. However, traditional ESP models approach this problem usually in a simplified way. One group of the models determines the gas velocity distribution in the ESP channel first and considers it as being constant during the further calculations. Another group of the models is focusing only on the corona induced secondary flow itself, ignoring the operational conditions including the effect of the turbulent gas flow and particle space charges.
To handle the difficulty of the interaction between the gas flow and the ionic wind caused bythe corona discharge, a new development of our ESP model has been carried out. With help of the new model complex analysis of ionic wind became possible for different operational conditions. Further development of the present state is needed for examination of parameters that are influenced by the ionic wind induced secondary flow. Coupled electric field, fluid dynamic and also particle transport simulation is under continuous development with the aim of determining the role of the ionic wind in particle transport modelling. Based on the calculated preliminary results already valuable conclusions can be drawn on the effect of the ionic wind in ESP modelling for the single wire sectional model.
WEIXUE WANG, RUINIAN LI, FENG CAO, AIMIN FANG, SHUJIANCHEN AND AIFANG PEI
In this paper the newest results in industrial ESPs for collecting high resistivity dusts aresummed up as follows:
(1) The negative resistance zone in the V-A characteristics when back corona occurs is not ainevitable result due to back corona, but due to the characteristics of the energization to the ESP. With modern techniques is able to stop the appearance of the negative resistance zone by accurate recognition of back corona signals, tracking and controlling them.
(2) Three joint hazards due to electrostatic attractions, electrostatic repulsions and back corona discharges may exist when ESPs are used to collect high resistivity dusts, leading to a far lower precipitation efficiency than that for common dusts.
(3) For collection of high resistivity dusts with
ESPs. If accurate recognition of back coronas, tracking
and controlling them to increase effective voltage and corona current
as a means to increase dust partic
le charging can be realized then the structure design of the ESPs and
the mode of the energisation would
not obey the formula jpd=Es.
On the contrary if ESPs with narrow
gaps, strong corona cathode wires and the electric field strength same
as that in wide gaps ESPs are
adopted collection of high resistivity dust can be remarkably
G. BACCHIEGA, I. GALLIMBERTI1, V. ARRONDEL, N. CARAMAN AND M. HAMLIL
The back-corona discharge is formed by a series of micro-discharges in the air spacesbetween the partcles of the dust layer deposited on the collecting plates. It starts when the particle resistivity is quite high: it changes the voltage-current characteristics of the electrostatic precipitator and significantly lowers its efficiency.
In the present work, the variation of the voltage-current characteristics, depending onresistivity and particle layer thickness, has been successfully reproduced by a simple electrical circuit model of the dust layer, including a back-corona current generator and the voltage drop across the particle layer.
The model also includes an estimation of the variation of the captation efficiency: as backcoronalowers the ion space charge, the computation of the back-corona current allows to evaluate the variation of the particle charging rate and therefore of their migration velocity.
Last updated: May 10, 2009.
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