GB743697A - Method of aerating liquids - Google Patents

Abstract

743,697. Purifying liquids. UNION RHEINISCHE BRAUNKOHLEN KRAFTSTOFF AKT.-GES., KRIEGBAUM, O., and DIEM, A. Aug. 5, 1953 [Sept. 1, 1952], No. 21616/53. Class 46. In a method of de-acidifying and removing iron and manganese compounds from liquids, especially water, in a container, by the action of air bubbles rising through the liquid from porous aerating devices on the bottom or sides of the container, the liquid to be treated flows continuously under no appreciable head through the container in a stream of such depth, freedom from turbulence and flow velocity that the air bubbles introduced into the liquid remain substantially unaltered in size as they rise through the liquid. The air may contain a germicidal and bactericidal gas such as ozone. The surface tension of the liquid may be reduced where necessary by addition of wetting agents, or in. creased to permit foaming by addition of higher alcohols. Liquid flowing in at 2, Fig. 2, across the full width of a tank 1, is constrained to follow a tortuous path to the outlet 3 by a series of baffles 5 and 6 inclined so that air forced in through fritted glass, ceramic or like elements 4 may rise in the form of small bubbles through the liquid without the formation of larger bubbles. The flow path ensures close contact between the liquid and the elements 4; the last element 4a is arranged substantially parallel to the liquid flow. In Fig. 3a, not shown, the tank is covered and the baffles are all vertical, an aerating element being provided near the bottom of the tank between adjacent baffles and also between the end baffles and the tank walls. The liquid thus flows alternately with and against the air current. In Fig. 3b the flow is countercurrent only and in Fig. 3c the liquid flows in zig-zag fashion across the air current. In Fig. 3d, not shown, the baffles are omitted. Where carbon dioxide is being removed the air is preferably freed from carbon dioxide before use. The optimum de-acidification effect is determined by testing the liquid for free carbon dioxide before and after the treatment and then by selecting the porediameter of the aerating elements, the liquid flow velocity, the liquid depth and the gas volume accordingly. Where compounds of iron and manganese are being removed the liquid must be filtered after aeration to remove the precipitates formed. The method is effective to remove combined carbon dioxide, with consequent precipitation of calcium hydroxide, from liquid containing carbonates. Thus water may be partially softened when required for brewing, for example.