Solar pond technology for large-scale heat processing in a Chilean mine. http://dx.doi.org/10.1063/1.4757627

Abstract

Copper mining is the largest industrial activity in Northern Chile, a region that
relies mostly on imported energy resources thus making the mining sector
vulnerable to the rising cost of fuel oil and electricity. The extraction of copper is
mostly accomplished by hydrometallurgy, a three-step low energy process
consisting of heap leaching, concentration by solvent extraction, and metal
recovery by electro-winning. Since the content of copper in its ore tends to degrade
as the mining operation proceeds, higher leaching temperatures would be needed
along with increasing energy requirements. In order to address this demand and
considering that the region has one of the highest levels of solar radiation and clear
skies, the authors assessed the solar pond technology for rising the temperature of
the leaching stream. The working principle of such technology is presented, as well
as its mathematical formulation, restrictions, and assumptions, aiming to simulate
the performance of a solar pond and to size a suitable setup. The results indicate
that this technology can provide sufficient heat to raise the temperature to a range
of 50 to 70 °C throughout the year with an annual gross thermal supply of
626GWh. In order to minimize the loss of water and salt from the pond, a closed
salt cycle is suggested. Savings of up to 59 000 tons of diesel oil per year and the
avoidance of 164 000 tons of CO2 per year could be achieved with a solar pond
effective area of 1.43 km2 reaching an average efficiency of 19.4%. Thus, solar
pond technology is suitable for attaining the goal of increasing the leaching
temperature while diminishing fuel costs and greenhouse emissions.