Shpylevy L. Automatic Control of the Thickening Process of Rare-Metal Ore suspensions to Improve Quality of Radial Thickener Products.

The thesis addresses a topical scientific issue improving the efficiency of automatic thickening process control of rare-metal ore suspensions and their concentrates in a radial thickener owing to improved control principles and methods, based on establishing laws of thickening flocculated suspensions. Theoretical and experimental research of the thickening process as an object of automatic control allowed to establish an extreme nature of the relationship between the settling velocity of the dispersed phase of flocculated suspension and the specific consumption of flocculant as well as to study the drift of extremum from the suspension pH. It is demonstrated that density of suspension discharged from the thickener cone depends on parameters of the compact sediment and suspension in the compression zone as well as on the ratio of dispersed phase flow rates in the sediment and thickened product. It is proven that it is practical to apply extreme control to the settling conditions of flocculated suspension. A method of extreme control of the settling conditions of the feldspar concentrate from the Mazurovskoye Deposit is developed, which implements the principle of controlling the flocculant consumption by the major disturbance i.e. the pH value of the feed suspension. To control the settling mode of the zirconium concentrate, an extreme system of step type is proposed, where the extremum is traced on a physical analogue of a thickener, which greatly reduces the extremum tracing time. A structural diagram of the control process of thickened product density and the compact sediment height is developed. As opposed to earlier conceptions of the compaction mechanism of the dispersed phase, it is based on the hypothesis of thinning the compact sediment in the discharge cone of a radial thickener and allows for a subprocess of carrying the compact sediment to the discharge cone. An automatic stabilization method of the compact sediment layer height by changing the rotational speed of the thickener frame is proposed. The issue of stabilizing the thickened product density is resolved by adjusting the ratio of mass flow rate of the compact sediment fed to the discharge cone and that of the thickened product discharged from the thickener come. The given ratio is adjusted by density of the thickened product. The flow rate ratio is maintained by changing flow rate of the thickened product. The automatic control system, which implements the proposed control principles and methods, allows to improve the efficiency of automated operation of radial thickeners in case of changed quality of raw materials owing to reduced losses of the concentrate with discharge, lower consumption of flocculant and higher density of the thickened product. The developed methods and algorithms of thickening process automatic control are used in the design of the tantalum-niobium-zirconium ores concentrating plant at the Ilyich Metallurgical Works in Mariupol, which is under construction. The anticipated economic effect of introducing the developments is UAH 194 thousand. Obtained results can be used at other non-ferrous and ferrous metallurgical plants as well as in the chemical and coal industries.