Taking Advantage of PV Energy in Copper Electrowinning Requires a Trend Reversal: Increasing Inter-Electrodes Spacing

PV energy prices have experimented a dramatic fall. For 9 hours, the highly irradiated desert of Chile produces PV at half the price compared to that generated from fossil fuels. A major challenge for the mining industry is to take advantage of it. However, the design concept for the equipment was to operate with carbon-based energy 24-hour flat-price. Moreover, since electrical energy used to be more expensive, these plants operate with small inter-electrode distances to reduce electrical consumption. They also require oil-heated exchangers to supplement the electrolyte heat required by the process. Now, during the 9 hour low PV price scenario a larger process current should be enough for electrolyte heating. To complement the heat required a solution is remove some electrodes per cell. Results indicate that the heat storage capacity of the electrolyte is enough to keep a semi-constant temperature throughout the day. Moreover, there are various advantages of larger electrode spacing: higher short circuit impedance, lower cathode-currents dispersion and, lower sensitivity to electrode misalignments and contact resistances dispersion. A 3D FEM fed with industrial data predicts the results. A discussion of the positive-negative effects on the copper deposit current efficiency and energy consumption is included. Finally as an example, the paper calculates the inter-electrode distance required to eliminate the oil-heated external exchanger for a copper cathode electro winning plant of 240,000 tons / year.