چكيده به لاتين
Abstract:
The aim of this project is concentration and purification of pregnant liquor derived from Mehdi Abad non-sulfide zinc deposit leaching process. At first, series of experiments with purpose of finding the optimum conditions for iron removal as a major contaminant ion in the electrowinning process and minimizing iron concentration and keeping zinc concentration at the maximum level was done by response surface method and using Central Composite Designs (CCD). Interpretation of results showed that the optimum condition is 150g/lit, 500rpm and 90 minutes for lime concentration, rotating speed and time; respectively. At this situation, concentration of iron in the leach liquor reaches down to 100ppm.
At the extraction stage McCabe-Tiele Diagram for D2EHPA solvent diluted in Industrial Kerosene at 30% v/v without adjustment of pH was plotted. With the aid of operation line, it has identified that 3 stages extraction with organic to aqueous ratio of 1:1 whit the same solvent, which mentioned above, a zinc concentration of 2g/lit in the scrub solution can be reach. Semi-continues solvent extraction experiments verified this prediction and led to a zinc recovery of 92%. In order to determine suitable scrub solution, different experiments was designed and a solution containing 18g/lit sulfuric acid and 6g/lit zinc, was selected. At the next step, McCabe-Tiele Diagram for stripping stage was plotted. This diagram demonstrated that for zinc stripping of the organic phase to less than 50ppm, two continuous stage by a solution containing 40g/lit zinc and 180g/lit sulfuric acid, with organic to aqueous ratio of 2:1 is needed. This condition was investigated at semi continuous stripping experiments and the obtained results verified McCabe-Tiele prediction. In order to design the solvent extraction circuit, a conceptual flowsheet considered, also, details of electrowinning and heap leaching units formed the basis of designing and mass balance for inflows and outflows was measured.
At the next stage, designing of precipitation tanks; extraction, scrubbing and stripping mixer-settlers by considering solution flow of 930m3/h that derived from heap leaching stage and data, obtained from industrial and research literatures was done.
Keywords: Zinc solvent extraction, Iron removal, Flowsheet design, Equipments design, MehdiAbad
