MechChem Africa January 2018

Endress+Hauser’s Pieter Andjelkovic describes the solvent extraction process and highlights an important aspect: the detection and monitoring of the depth of the organic phase. Endress+Hauser has taken the reliability and accuracy of its guided wave radar and capacitance level, and combined it into a single device for better control of the process and associated better extraction efficiencies. Solvent extraction: extracting more for less

“ C opper is one of the few metals that occur in nature in a di- rectly usablemetallic form, also known as native metals, as op- posed to needing extraction froman ore. This led to very early human use, from8000BC. It was the first metal to be smelted from its ore (5000 BC), the first to be cast into a shape in a mould (4000 BC) and the first metal to be purposefully al-

almost pure copper anodes produced. The pyrometallurgical method uses com- minution (pulverisation), flotation, smelting and conversion to produce anodes. The ce- mented copper that is produced by precipita- tion in the leaching process can be added to the smelting process for further processing to anodes. During this cementation (iron pre- cipitation), copper is producedby running the pregnant leachsolution throughapileof scrap iron or steel. An electromechanical process takes place, and the copper precipitates onto the iron/steel, which in turn dissolves into the solution. It detaches as flakes or powder. The pregnant leachate that is produced from the leaching process will contain the leaching agent, either water or H 2 SO 4 for

oxide ores. Acid cure and acid- ferric cure are used for mixed ores. Some plants use an acid/kerosene mix. The process should remove and recover the copper from the leachate, and remove impurities. “This process

must be controlled, and as we know, whenwemeasure, we can control,” he notes. Ores that have been mined,

loyed with another metal, tin, to cre- ate bronze (3500 BC),”Andjelkovic begins. In the middle ages, the oxidised layer of copper was naturally leached by water, depleting the upper layers of oxi-

crushed and dumped on impervious pads are usually sprinkled or sprayed with the leach- ing solution, in the heap leaching process. Ponding, flooding or trickle systems can be used for dump leaching. The pregnant liquor is then fed to a solvent extraction plant, which can be optimised by various methods. Endress+Hauser suggests that bymeasuring the pH, conductivity and interface levels, the process can be managed and optimised for maximumextraction, andminimumwastage. “The objective of streamlining the solvent extraction process is to produce a rich and concentrated solution to be used further in the electro winning process,” Andjelkovic explains. Level interface with Levelflex FMP55 with Heartbeat Technology™ Most important in the solvent extraction phase (sx) is the detection and monitoring of the depth of the organic phase. The copper is trapped in the top layer. Automation is the

disedore and revealing the rich copper-laden solutions. This promptedminers todig deeper, heap the ore and leach it out. This is known as hydrometallurgical produc- tion; the extracted solvents can be electro-won, and Endress+Hauser’s radar Levelflex FMP55 guided wave sensor with Heartbeat Technology™.

The CM44 Liquiline is a digital multiparameter transmitter for process monitoring and controlling in any application.

A liquid flow diagram of the solvent extraction process.

32 ¦ MechChem Africa • January 2018