PURPOSE: To prevent the degradation in dust collection efficiency owing to fluctuations in dust concn., etc., in the stage of collecting dust in waste gases with an electrostatic dust precipitator by controlling the discharge electric current of electric discharge electrodes finely.
CONSTITUTION: In the stage of removing dust from waste gases of combustion contg. dust with an electrostatic dust precipitator, the degradation in dust collection efficiency in accordance with the change in conditions such as kinds, temps., concns., velocities of flow or the like of dust is prevented. To this end, many electric discharge electrodes for corona discharge for charging the dust electrostatically are segmented to plural groups, and three kinds of voltages; the voltage wherein pulse voltages or AC voltages are superposed on DC voltage, DC voltage and non-impression are selectively impressed upon the electrodes of the respective groups according to respective waste gas conditions. Electric discharge current is finely controlled by changing the crest value, pulse width and repetitive frequencies of the pulse voltages, or the crest value of AC and the impression and quiescent times of AC, whereby the degradation in dust collection efficiency is prevented.
MIYASHITA TAKAO
YOSHIOKA YOSHIO
