Activated Carbon Dosage in CIL Plants: A Practical Operating Guide

By the YELI Technical Team · Updated August 2026 · 7 min read

In a carbon-in-leach (CIL) plant, the carbon concentration in the tanks is not a "set it and forget it" number. It drifts down through attrition, elution losses and regeneration — and when it drifts, gold recovery drifts with it. This guide covers how to set the dosage, how to keep it in range, and what to monitor so the carbon — and the gold — stay where they belong.

1. Setting the Initial Charge

The starting point is the target carbon concentration, typically 10–25 g of carbon per litre of slurry. Higher concentrations give faster gold pickup but cost more in inventory and can increase screen loading and carbon abrasion. Most CIL circuits are designed around 15–20 g/L.

Initial charge = total slurry volume × target concentration. For a 4 × 800 m³ tank train at 15 g/L, that is about 48 tonnes of carbon to load the circuit for the first time.

Two practical points at startup: charge the carbon gradually (a full dump at once can flood the screens), and confirm the actual concentration by sampling each tank after charging — volumes and densities on site rarely match the design exactly.

2. The Daily Dosage Routine

Once the circuit is running, carbon is lost every day in small amounts — through screen overflow, elution losses, kiln attrition and carbon-in-fines. The operating routine should be:

• Sample carbon concentration per tank, daily or shiftly. A simple displacement or volume measurement tells you if the inventory is holding.
• Log make-up carbon added — weight and date. This gives you the consumption trend that drives your purchasing.
• Watch the leach profile. If gold in the last tank's tail solution climbs, concentration may have dropped below the design point.

Make-up is usually added in small daily or weekly doses rather than big monthly dumps — steady-state inventory management beats feast-and-famine.

3. Regeneration and Its Cost

Carbon is stripped and regenerated on a cycle (often weekly to monthly, depending on loading). Each regeneration pass restores activity but costs a little carbon to attrition. The two levers are:

• Regeneration frequency — regenerate before activity collapses, not after recovery has already dropped.
• Carbon quality — a harder carbon (≥98%) survives more regeneration cycles, so your inventory lasts longer and make-up demand falls.

Track "cycles survived" for your carbon. Coconut shell GAC typically withstands many more kiln cycles than softer coal-based grades — another reason gold plants standardize on it.

4. What the Numbers Should Look Like

Healthy CIL operations typically see 5–15% monthly make-up of total in-circuit inventory, and specific consumption of roughly 50–300 g of make-up carbon per tonne of ore milled — with the lower end achievable on hard, well-managed circuits. If your consumption is above the range, check carbon hardness, screen efficiency and regeneration temperature before blaming the ore.

Carbon dosage is not an expense to minimize — it is a variable to control. The plant that holds its concentration steady recovers more gold with less total carbon than the plant that swings between over- and under-dosed.

5. Monitoring Checklist for Plant Managers

• ☐ Carbon concentration per tank, daily
• ☐ Make-up weight and date logged
• ☐ Tail solution gold trend (early warning of under-dosing)
• ☐ Screen efficiency — fines and oversize both cost money
• ☐ COA of every delivered lot — verify hardness and iodine match the spec you designed around

FAQ: Activated Carbon Dosage in CIL Plants