“Wherever you find highly carbonaceous material, you find froth,” says Nico Mautsa, Kemira’s technical sales representative for Kemira’s mining chemistry business. “This particular customer, a copper and cobalt hydroxide producer, had up to 30% froth in its leaching tanks.”
Because of the issue, the plant wasn’t achieving its designated throughput (about 1,300 tonnes per hour). The facility faced significant financial losses as a result.
It was a very dangerous situation. Operators could not be in the area because it was slippery. No one could tell where it was safe to walk.
But the problem didn’t stop at the leaching tank. Froth was also overflowing into the bunded area surrounding the tanks, where it would thicken and crust over, causing operational and maintenance issues. “It was a very dangerous situation. Operators could not be in the area because it was slippery, and it was hard to judge if they were about to step on the ground or crust. No one could tell where it was safe to walk,” Nico explains.
The foam from the leach tanks would form stable crust on the downstream thickeners surface which would gradually chip off and carry solids into downstream solvent extraction (SX) processes, leading to more total suspended solids in the solvent extraction process. This increased maintenance in the difficult to access SX area.
“When SX settling tanks fill with solids, they must be cleaned. But that’s not a simple process because there are large quantities of flammable liquids. Operators must avoid using equipment with internal combustion, and therefore must take extreme measures and use specialized equipment to clean the area,” explains Nico.
Finding a defoamer to fight the froth
Nico went to site and analyzed the situation so that he could help the plant find a solution. “First we had to understand the composition of the froth and its minerals,” he explains. After his assessment, Nico tested various chemistries to kill the froth. Ultimately, he proposed KemFoamXTM 9980, a defoamer for high acid systems that associates with solids, which can then be pumped to a storage facility.
Ruan Pretorius, another Kemira mining chemistry expert on the project, explains, “KemFoamXTM 9980 is designed to work in an acid system, but we had never used it at a copper facility. Nico tested it, and it worked perfectly leaving downstream processes unaffected.”
He further explains, “Anything added upstream must not reduce extraction efficiency downstream, so mining companies want to be very cautious to make sure that chemicals are compatible.”
Fortunately, the downstream areas were unaffected. This is because KemFoamXTM 9980 associates with the solids in the slurry and is then pumped out to the tailings storage facility. Nico and Ruan found that any residual KemFoamXTM 9980 loses up to 80% efficacy after 24 hours in the acidic system. As a result, there were no complications downstream for the customer.
After identifying KemFoamXTM 9980, the next steps were to find the right dosing method and dosing point. Nico recommended adding the product to raffinate to help it disperse throughout the slurry. He also identified three potential application points: the leaching tank, the thickener, and the acid mills. “The dosing point was subject to the customer’s needs. In this case, the leaching tank was chosen as the ideal spot,” Nico says.
KemFoamXTM 9980 put a stop to the froth ─ and the financial losses. Moreover, the bunded area was clean.