Zirconium Extraction - An Improved Plant Practice

摘要

Formation of stable emulsion is one of the many process problems faced in solvent extraction. Presence of fine solid phase in feed, even up to micron level, is considered to be main reason for emulsification. Tributyl phosphate solvent, used in Zr extraction has a tendency to form emulsion, crud formation due to complex formation with silica and zirconium. The mixer settler contractor used (at NFC ) for Zr production required highly clarified feed to avoid emulsion . Formation of emulsion leads to severe loss of solvent and valuable zirconium. However, the production of clarified feed in presence of soluble silica, necessitated a precoat filtration step which is costly, labor intensive and leads to dilution of feed stream. It also generates effluents of both liquid and solid and disposal of solid effluent, in particular; posed a major problem. Hence, a study was conducted to extract Zr from Zr feed slurry (without filtration). containing solid suspension between 6-10% using a specially designed extraction contractor, which has over come the solid sedimentation and emulsion formation . These two major process difficulties have been tackled by keeping solid under continuous movement, with final complete settling at last stage only and emulsion formation was suppressed by keeping high O/A ratio with recycle of solvent at each stage. This paper describes the development and incorporating the unit for regular production with improved efficiency and cost reduction to an appreciable level.