GB1391695A - Treatment of gases - Google Patents

Abstract

1391695 Electrostatic separators ENVIRONMENTAL ELEMENTS CORP 28 March 1972 14578/72 Heading B2J An aqueous solution of ammonium sulphate or bisulphate is injected into a particleladen gas stream to condition it and thereby improve the electrostatic collection characteristics of the entrained particles. As shown, the solution is fed from a tank 24 by way of a pump 29, a valve 28 and a meter 30 to injection nozzles 31 in a duct 18 through which flue gas from a coal-fired boiler (10) Fig. 1 (not shown) passes on its way to an electrostatic precipitator 12, the duct 18 being downstream of a preheater 14 in which the gas gives up some of its heat to ambient air supplied to the boiler. The solution may contain from 5% to 50% by weight of the conditioner, the preferred range being 10% to 20%. The rate of injection is such that the conditioned gas contains at least 31.2 lb of conditioner per million cu. ft. of gas. The gas stream is exposed to the conditioner, before the entrained particles are collected, for no less than 0.25 seconds, with the temperature preferably being no less than 240‹F and no more than 800‹F. It is stated that the conditioning controls the resistivity of the entrained particles to within about 10<SP>6</SP> to 10<SP>10</SP> ohm-centimeters, whether or not the particles have a normally high or normally - low resistivity characteristic, whereby the collecting efficiency of the precipitator is improved.