Lab-Scale Carbon-in-Leach (CIL) Reactor

A carbon-in-leach reactor runs leaching and carbon adsorption in the same vessel: ore slurry, leachant and activated carbon agitated together, so that gold or silver is adsorbed as soon as it is dissolved rather than after a solid-liquid separation.

Where it fits in the flowsheet

CIL exists to defeat the “preg-robbing” problem. In some ores, the carbonaceous or clay fraction re-adsorbs dissolved gold almost as fast as cyanide liberates it, and a conventional leach followed by separate adsorption loses recovery that cannot be recovered later. Running carbon in the leach vessel keeps the dissolved metal one step ahead of the robbing material. Whether your ore behaves that way is a bench question, and this reactor is the vessel that answers it.

What the tests have to establish

Four things, and they are all scale-dependent. Leach kinetics with carbon present, which differ from kinetics without it because the dissolved metal never accumulates. Carbon loading against time, which tells you the carbon advance rate. The competitive effect between carbon and the ore’s own adsorptive solids, which is the preg-robbing question in its purest form. And carbon attrition, which is a real operating cost that bench tests routinely ignore to their regret.

Reading the configuration

• Agitated reactor with carbon in pulp — the defining feature. Agitation has to suspend both the ore and the carbon without grinding the carbon to fines; this is the central mechanical compromise of any CIL design, and it is why impeller selection matters more here than in a plain leach reactor.
• pH and ORP control — cyanide leaching lives and dies by pH (to prevent HCN formation) and benefits from controlled oxidation. Both need to be held, not monitored.
• Carbon handling — screening or retaining the carbon inside the vessel, and sampling it without losing it. Ask specifically how this is done at bench scale; it is where most lab CIL rigs leak data.
• Materials of construction — the liquor is alkaline and cyanide-bearing, which rules out a good deal of what a normal leach reactor would use. Specify the wetted path against cyanide, not against acid.

Typical duty

Diagnosing preg-robbing ore, comparing CIL against CIP for a specific deposit, establishing carbon loading and advance rate, and generating the recovery curve a feasibility study needs.

What to send us

The ore type and head grade, the preg-robbing indication from preliminary tests, the carbon type and size you intend to use, and the sample volume per test. Cyanide duty also means telling us your safety and ventilation arrangements, because that determines the configuration we can offer.