Improving Productivity and Energy Efficiency in Copper Electrowinning Plants
This paper presents strategies to improve energy efficiency and productivity in copper electrowinning (EW) plants. Plant modeling is based on updated technical data and specific measurements obtained in a tankhouse during a complete production cycle (four to five continuous days). The industrial EW plant site examined produces 180 000 ton/year with an operating current density of 300 A/m2 and a current dispersion of 8.5%. Proposals are based on the use of Optibar intercell bars and the reduction of distance between electrodes. Due to these changes, an improvement of +4.3% in energy efficiency combined with an increase of +3.4% in production can be accomplished. The productivity improvement projected for the plant is U.S.$ 10 million/year.
Parametric study of copper electrowinning using a pulsed‐bed electrode reactor
BACKGROUND 
The pulsed bed electrode (PBE) has been used successfully for copper electrodeposition from highly concentrated acidic electrolytes. Advantages of this electrode include high space-time yield (Y) and simple operation and maintenance. In this work, the effects of operational conditions were investigated in an attempt to achieve current efficiencies (CE) higher than 76.7%, which was the maximum value obtained in a previous study. 
 
RESULTS 
The results showed that use of a high current density and low acid concentration provided the best operational conditions for maximizing CE and Y, and minimizing the energy consumption (EC). Nonetheless, the highest current density was limited to 3000 A cm-2 and the lowest acid concentration was limited to 110 g L-1, due to limitations such as metal dissolution, dendrite growth, and short circuiting. The highest CE achieved was 77.7%, using 2838 A m-2. According to a statistical model, the maximum CE value that could be achieved is 82.4%, with application of 3000 A cm-2. This suggests that further improvement of CE would lead to values of EC lower than those found in electrowinning plants. 
 
CONCLUSIONS 
Electrowinning using a pulsed-bed electrode is an excellent method for copper production, but additional improvements are required to increase CE. © 2014 Society of Chemical Industry
Sequential connection and phase control of a high-current rectifier optimized for copper electrowinning applications
This paper proposes an optimized sequential control technique for copper electrowinning high-current rectifiers. The converter comprises two series-connected six-pulse double-wye rectifiers, a step-down transformer, and a tuned input filter. The six-pulse rectifiers are fed from delta and polygon primary windings with different turns ratio and phase shifted by 5/spl deg/. Under the proposed control scheme, one rectifier is kept at nominal output voltage, and the other one is phase controlled to control the load's current. The proposed strategy greatly improves the rectifier's performance, reducing its reactive power maximum demand by 62% compared to conventional rectifiers and, therefore, reduces the input filters power rating also by 62%. This is accomplished while keeping the input power factor above 0.95 throughout the whole operating range. Further, the converter's reactive power consumption presents a low varying characteristic, allowing it to use a fixed filter, even when operating from a power system not capable of withstanding large reactive power variations. Finally, it presents a harmonic current distortion comparable to conventional 12-pulse high-current rectifiers. This paper presents the design and optimization procedure of the rectifying system. A 2.5 kVA laboratory prototype was used to validate the converter model, later employed in evaluating the converter operating in a 10.5 MVA copper electrowinning facility. The results obtained confirm the advantages of the proposed converter and its control strategy.