Nowadays, air pollution is a serious social problem caused by the remarkable progress of industries, rapid increase of automobile and concentration of population. Air pollution must be solved through some kinds of means. Under such circumstance, Electrostatic Precipitator (E. P.) is valuable to prevent from air pollution. In spite of high reputation of E. P., they entail several problem, such as:
(1) The limited applications caused by the electrical resistivity of dusts.
(2) The large scale of plants.
(3) The expensive equipment costs.
If E. P. will be accomplished a more compact design and a more high efficiency, it must possibily grows almighty precipitator. However, collecting efficiency of E. P. may be influenced significantly with electrical resistivity of dusts. Then we observed some phenomena on the collecting electrode through T. V. camera with a microscope, and confirmed three points enumerated hereunder;
(1) Re-entrainment of low resistivity dust, like carbon black.
(2) The irregular flow of the surface dust of moderate resistivity.
(3) The strange behavior of high resistivity dusts, such as sulfur and glass beads.
So we made up some compact trial models with an original scraper to remove the dust deposit. The first point is the compact design of the E. P. This achieved by the short distance of 16mm between the corona wire and flat plate collecting electrode, and by using fine corona wires of 0.15mm in diameter. In order to simplify the test, we used the voltage of positive direct current of 10kV from selen rectifire, so the electric field strength and current density are high, as compared with an industrial E. P. and two-stage air cleaner. Another point is scraping. The capacity of the E. P. depends considerably upon the adhesiveness in the dust layer on the collecting electrode and its removing system. We selected a method to scrape directly along the surface of the electrode, even in the case when carbon black and sulfur were collected on the electrode in thin layer. Scraping is primitive and intricate method but reliable for such unmanegeable dust. We put talc, sulfur dust and the carbon black exhausted from Diesel engine to the test. The results of the tests were rather satisfactory. We have dawn of hope for the application of E. P. to the Diesel engine.