Patent GB-688547-A (GB)
Title: Method and apparatus for continuously removing substances from solutions by causing foaming in such solutions
IPC: B03D1/26
Filed: 1950-02-01
Abstract: 688,547. Purifying liquids. KODAK, Ltd. (Kodak Pathe, and Abribat, M. M. B.). April 30, 1951 IFeb. 1, 1950], No. 2606/50. Class 46 In a method of continuously removing one or more substances from a solution thereof by foaming the foam is produced above a pool of the solution, liquid is allowed to drain from the foam and back into the pool, the drained foam containing the substance or substances to be removed is taken off, the solution from which foam is to be produced flows continuously into one part of the pool, and the solution from which foam has been produced flows continuously out of another part of the pool and may then be subjected to further foaming in the same manner. A suitable amount of solution is introduced from a reservoir 9, Fig. 1, into a tube 1 through a valve 8 which is thereupon closed. A gas, e.g. air, is then passed through a diaphragm 2 from a valve 3 at constant pressure to form a foam. The line of demarcation between the liquid pool and the foam gradually falls to a level such as 12; it is maintained there by appropriate adjustment of the valve 8 and a valve 11 on a liquid outlet tube 10. Thenceforward if the concentration Co of the liquid in the reservoir 9 remains constant those in the pool and the foam, Ci and Cm respectively, will also remain constant; the inequality Cm> Co> Ci holds. The augmentation of concentration produced by foaming, i.e. Cm-Co, increases with the length of the column of foam, the quantity discharged from an elbow 5 decreasing at the same time. The concentration Cm may exceed the solubility so that the foam contains a solid phase. A succession of foaming columns is preferably provided having connections between the receptacles of successive columns whereby liquid which has been subjected to foaming in one receptacle is fed to the next, the columns being of successively decreasing cross-section and/or the receptacles being of successively increasing volume. Such a succession is shown in Fig. 4. In Fig. 2 (not shown) three columns of identical size and uniform cross-section are arranged at the same level, while in Fig. 3 (not shown) four such columns are arranged in descending order from the first to the last. Fig. 5 shows a series parallel arrangement having transverse pipes 17 with valves 18 to equalize the deliveries from the different parts of the installation. Pumps may be installed in the pipe lines of any of the circuits. There may be introduced into the solutions being treated in the different columns substances for varying the pH or salt concentration, surface active, precipitating or coagulating agents, coloured reagents or diluents. The foaming may be carried out at different temperatures in different columns. Some columns may be heated or cooled, or the foam or the liquid alone may be heated or cooled. As the concentration of substance being removed by foaming is less in each successive column to which liquid is fed, it is necessary to augment the gas supply to the later columns and even to modify the delivery of gas so as to obtain suitable foaming and drainage despite the decreased concentration of substance to be removed by foaming. The method may be used in the treatment of sugar and starch. Specification 535,099 is referred to.