Patent GB-1441018-A (GB)
Title: Treatment of a flotation concentrate containing two or more different minerals
IPC: B03D1/08
Filed: 1973-09-24
Abstract: 1441018 Froth flotation BOLIDEN AB 24 Sept 1973 [26 Sept 1972] 44706/73 Heading B2H A method of treating an ore flotation concentrate containing particles of at least two different minerals capable of being separated by a further flotation process comprises: adding to an aqueous suspension of the concentrate, prior to the further flotation process, a reagent which on at least one of the minerals nullifies the effect of one or more collectors used in a previous flotation process; filtering the aqueous suspension after the reagent has been added to it and/or during the addition of the reagent to it so that unwanted reaction products and unreacted reagent are separated from the modified concentrate and so that the concentrate is maintained in contact with the reagent for an average time not exceeding 30 minutes; slurrying the modified concentrate in water to form a pulp; subjecting the pulp to a mechanochemical treatment step to form fresh surfaces on the particles in the presence of one or more reagents which, in the further flotation process will depress the mineral or minerals on which the collection effect has been nullified; and subjecting the pulp to the further flotation process. The method is applicable to the treatment of flotation concentrates containing two or more sulphides and/or oxides of zinc, copper, lead, arsenic, iron, nickel, cobalt, molybdenum, gold, silver, antimony, bismuth, mercury, cadmium and tin and also to concentrates containing apatite, ironglance, fluorspar and bartye. The concentrates may have been obtained by one or more flotation processes. In the plant illustrated in Fig. 1, an ore is passed through a crusher 1 and the crushed ore is concentrated in a flotation apparatus 2, the desired minerals being rendered hydrophobic with collectors to yield a concentrate containing at least two valuable minerals slurried in water. The concentrate slurry is treated, if necessary, in a thickener 3 to obtain a pulp of the required density. The pulp is passed to a container 4, and then to a filter 6. Where the concentrate to be treated is obtained from a different plant, it is first passed through a wet scrubber and a mixer before passing to the thickener 3, the container 4 and the filter 6. The nullifying reagent may be added to the pulp in the conduit through which it passes to the filter, to the pulp bath of the filter and/or to the filter surface itself. The cake discharged from the filter is slurried in water to form a pulp which is introduced into a mill 8 for grinding the pulp particles, e.g. 'by using grinding bodies which produce ions when subjected to wear, the ions by means of a mechanochemical reaction promoting in a subsequent flotation step, depression of at least one of the minerals affected by the nullifying reagent. From the mill 8 the pulp is directed to a flotation apparatus 9 in which one or more minerals are floated off under the influence of remaining or added collectors and one or more minerals are depressed. The filtrate discharged from the filter 6 through a conduit 7 contains reactive products and non-consumed reagent and may be utilized in one other process step integrated with the mineral treatment process. Alternatively, the reagent may be recovered from the filtrate. Another plant for carrying out the method is described. Examples of grinding bodies used in the mechanochemical treatment of the pulp particles include: iron balls for generating ferro- and ferric-ions with cyanide or SO 2  additions for depressing zinc mineral; zinc balls with cyanide SO 2  additions for depressing zinc mineral; brass balls or iron pyrite pellets with activation of zinc blends and simultaneous depression of lead mineral; limestone or dolomite bodies for elevating the pH; bauxite bodies for floe formation; and sintered iron oxide bodies for removing surplus sulphides. To amplify the mechanochemical reaction, additives in the form of powdered iron, zinc, brass, iron pyrite, limestone, bauxite and iron oxide may be added. Collectors used include potassium amyl xanthate and sodium isopropyl xanthate. Nullifying reagents mentioned are sodium sulphide, sodium dichlorate and sulphuric acid.