Method of separating mists from gases and vapours

Gases and vapours other than those treated in the parent Specification are freed from mist by passage through filters at a higher speed than corresponds to the break point in the logarithmically plotted pressure drop-speed diagram. In an example a horizontal filter 10 mm. thick, of solid particles with a porosity of 55 per cent and a mean capillary diameter of 100 microns is saturated with sulphuric acid and gas containing 20 gm. sulphuric acid per cubic metre is passed through at increasing amounts per hour. The break point is found to be about 37 cubic metres per hour and at 50 the limit of visibility of mist in the outgoing gas is reached, i.e. 100 mgm. per cubic metre. A pressure loss of at least 200-250 mm. water column is necessary to effect 96 per cent separation. With larger pored filters the material may be sprinkled with the same or different liquid, or liquid may be sprayed into the mist and separated with it. By spraying with 1 litre of water per cubic metre of gas in one example the pressure loss of the filter is increased from 100 to 300 mm. water column and the separation from 80 to 98 per cent. Porous ceramic or fritted materials, fritted glass bodies, fabrics, felted fibres, &c., may be used and liquid forced through the pores and collected may be redistributed over the inlet side of the filter which may be operated at elevated temperature. Application of the process to sulphuric acid and concentration plants is referred to.