Browsing by Author "Draganova K."

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    Analytical study of the Waelz clinker dissolution in NH3 - (NH4)2SO4 system
    (2014-02-25) Draganova K.; Stefanova V.; Iliev P.; Lucheva B.
    In the NH3-(NH4)2SO4 system a thermodynamical analysis of dissolution process of the Waelz clinker, which is a waste product of zinc production, has been carried out. The analytical study has been executed by the help of a professional program HSC Chemistry Ver. 7.1 using both modules ``Reaction Equation`` and ``Eh - pH Diagrams``. The NH3-Fe-S-H2O, NH3-Cu-S-H2O and NH3-Ag-S-H2O systems describing the dissolution of iron, copper and silver compounds (oxides and sulfides) of Waelz clinker in an ammonia medium in the presence of ammonium salt (NH4)2SO4 have been investigated at various temperatures and pressures. The influence of temperature (25 and 110°C), pressure (atmospheric and 0.4 MPa) and the consumption of the reagents on the substance composition of the solutions has been defined on the basis of the calculated and constructed Eh - pH diagrams.
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    Recovery of copper and silver from Waelz clinker wasted from zinc production
    (2014-02-25) Lucheva B.; Iliev P.; Draganova K.; Stefanova V.
    Waelz clinker is a waste material from the processing of zinc-lead cake into Waelz furnace in Bulgarian metallurgical plant KCM Ltd, Plovdiv, which contains valuable components such as copper silver, iron and carbon. Previously the clinker was treated by sulfuric acid solution in order to remove iron. The residue which contains 3,8 % copper, 250 g t-1 Ag and 26 % C is an object of this experimental work. The purpose of the work is to investigate the silver and copper recovery from this residue using H2SO4-HNO3 solutions. The influence of dissolution time, temperature and concentration of nitric acid at constant sulfuric acid concentration on the silver and copper recovery degree were investigated. The maximum silver recovery degree - 95 % is achieved at the following conditions: process duration - 1 h; temperature - 90°C; sulfuric acid concentration - 1M; nitric acid concentration - 1M; pulp density - 10 %. At these conditions the copper is practically completely recovered. The remaining insoluble residue contains 0,02 % Cu and 22 g t-1Ag. A technological scheme for two stage processing of Waelz clinker is developed.