Use of quillaja saponins (Quillaja saponaria Molina) to control acid mist in copper electrowinning processes -: Part 2:: Pilot plant and industrial scale evaluation

This work describes the use of Mistop (R), a novel surfactant of natural origin that contains primarily triterpenoid saponins (active ingredient), to control acid mist in copper electrowinning (EW). Previous laboratory tests indicated that Mistop (R) has no negative effects on cathode quality, current efficiency, and overall solvent extraction (SX) process conditions (e.g. phase disengagement time, extraction/stripping kinetics, maximum charge/discharge, etc.). In this work Mistop (R) was tested at pilot plant, semi-industrial and industrial scale. The work was performed in the facilities of Radomiro Tomic (RT), which produces approximately 900 tons copper/day. Pilot plant tests were performed during 6 months with product dosages in the electrolyte entering the EW cells within 0 and 32 ppm. The tests indicated that total acid aerosols could be significantly decreased at Mistop (R) dosages within 6 and 8 ppm in the electrolyte entering the EW cells. At these dosages no operational problems in the SX/EW process were encountered. The semi-industrial tests indicated that with 6 ppm of Mistop (R) in the electrolyte entering the EW system, acid mist aerosols decreased significantly with no negative impact on EW operational parameters (e.g. cathode quality, current efficiency). Industrial scale implementation showed that the addition of 8-9 ppm of Mistop (R) to the total electrolyte inventory (24,000 in 3) every 24 h, decreased total acid mist aerosols in the tankhouse below present Chilean environmental regulatory requirements (e.g. 0.58 mg/m(3)). Under the operational conditions tested (e.g. electrolyte average temperature 45 degrees C, average current density 280 A/m(2)) the specific product consumption was approximately 0.21 kg Mistop (R)/ton copper cathodes, resulting in Mistop (R) usage costs significantly lower than that of alternative chemical surfactants. (c) 2005 Elsevier B.V All rights reserved.