Gas-cleaning equipment (wet-dust and mist eliminators, as well as drop and spray eliminators) in which a gas flow contains drops of liquid are classed as wet precipitators.The disperse composition of suspended particles directly at the inlet to, and outlet from gas-cleaning equipment is usually determined experimentally using an impactor [ 1 ]. The most accurate results may be obtained when samples are removed by the internal-filtration method, i.e., when the impactor is introduced directly inside the gas conduit.The operation of wet precipitators is characterized by a series of phenomena that complicate disperse analysis of the suspended particles contained in the gas flow. The simultaneous existence of solid and liquid suspended particles, and also condensation of water vapor as samples are removed from the saturated gas, and spray carryover at the outlet from the apparatus are therefore possible in the gases being cleaned. The NIIOGAZ has developed methods of dispersion analysis, which make it possible to overcome these difficulties.In cases when the gas flow proceeding into the gas-cleaning equipment is a mist (aerosol) containing exclusively suspended liquid particles (drop diameter dp), the dispersivity of the drops is determined using an impactor designed by the NIFKhI (Model 12) [1], the operating principles of which are the same as those for other similar devices. An AFA type of filter is installed at the outlet from the instrument to determine the quantitative fraction of the finest particles. Figure 1 shows results of the disperse analysis of a sulfuric-acid mist, which was conducted with the use of the NIFKhl impactor by the external-filtration method at the inlet to, and outlet from a wet electrostatic precipitator installed for the production of sulfuric acid by the Cherepovets open joint-stock company Ammofos. The impactor was thermostatically controlled (its heating was called for to eliminate condensation of water from the vapor). The acid content on the plates of impactor was determined by a chemical method (titration).During wet dust collection, samples of saturated gas containing solid suspended particles are also taken by electrically heating the elements of the impactor; this ensures that the temperature of the gas in the device will be maintained 5-10 ~ above the dew point. Figure 2 shows a schematic diagram of the device employed to determine the disperse composition of dust during the wet cleaning of gas.When there is no carryover of drops, however, the impactor is introduced into the gas conduit when the moisture content of the gas is high, mounted with the tip of the gas sampler in the path of the gas, and heated for no less than 30 min to the temperature of the gas flow, after which it is turned toward the dust-laden gas flow and gas samples are taken for disperse analysis. During the experiment, possible condensation of water vapor is monitored continuously. For this purpose, a glass tube is usually installed between the impactor and cooler-condenser; the absence of condensate on the ...

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