GB904137A - Improvements in or relating to electrostatic precipitators - Google Patents

Abstract

904,137. Electrostatic precipitators. PENNEY, G. W. Dec. 30, 1958 [Jan. 8, 1958]; No. 41997/58. Class 39 (1). A large number of precipitator plates are held parallel to the gas stream by a plurality of spacerstrips extending parallel to the gas flow and at regular lateral spacing. The plates may be of any shape which permits a reasonably uniform spacing between adjacent plates to be maintained, in particular they may be flat, cylindrical or spiral. The plates may be flexible or rigid and the spacing must be of between 0.015 and 0.08 inch. The flexibility and closeness of the plates gives rise to possible shorting. The effects of this may be localized by associating a 10<SP>8</SP> ohm resistance comprising a semi-conductive covering on a wire with each adjacent pair of positively charged metal plates. If the plates are of the flexible type such as tricresyl phosphate coated paper then the filtering system may be split into two halves, 7, 7<SP>1</SP>; 8, 8<SP>1</SP>, Fig. 1. In this case the incoming gas stream is ionized in chamber 1 by corona set up between wires 5 and grounded electrode 6a-6d. This ionized gas passes into the collector chamber 2 where it is fed through precipitators 7, 8 which in one form have 229 plates, every 38th plate being good conductor such as metal foil, or foil-coated paper, connected as shown to +13kv. or earth. The remaining plates need only be semi-conducting. The spacer strips must be semi-conducting if the electrodes are mainly semi-conducting, and if metallic electrodes are used the spacers must be insulating. A preferred form is metal electrode 0.005-0.006 inch thick for plates P1, P39, etc.; paper at 0.003 inch thick for plates P2-P38, P40-P76, &c., and cardboard spacer strips. After being joined together using shellac, the whole assembly is then soaked in tricresyl phosphate. The cleaned gas passes out through a blower used to generate an air velocity of about 300 feet per minute. Due to the close spacing of the plates the collector-unit need only be 2-3 inches long in the direction of their flow. Many details of leakage currents and powers, and desired field gradients are given by way of illustration. Short-circuiting in the paper collector does not have any serious effect due to the high resistivity of the plates and spacers since the potential gradient is only adversely affected in the vicinity of the short. When cleansing of this collector is necessary it is preferred that they should be discarded and new ones put in in their place. In the case of a metal-plated collector the plates may be oil-washed, vacuum-cleaned, tapped, or cleaned by other known methods. The preferred potential in this form are + 300V. and 0, all the odd-numbered plates being at earth potential. Specification 475,443 is referred to.