56 Tons HMGOLD™ Carbon to Ghana: CIP Mesh Size Upgrade
A gold mine in Ghana's Ashanti region had been running 6×12 mesh activated carbon in their CIP circuit for three years. Gold recovery was acceptable — 94.5% — but they were losing carbon at the interstage screens faster than they could account for. Screen blinding, carbon passing through slots, and frequent screen replacements were eating into their operating budget.
They switched to 8×16 mesh HMGOLD™ 7000 in Q1 2026. Fifty-six tons. This is what changed and why the mesh size decision matters more than most operators realize.
CIP vs CIL: Why Mesh Size Requirements Differ
| Parameter | CIL (Carbon-in-Leach) | CIP (Carbon-in-Pulp) |
|---|---|---|
| Carbon residence | In leach tanks with agitation | In adsorption tanks, counter-current flow |
| Slurry abrasion | High (grinding media present) | Moderate (no grinding media) |
| Screen slot size | 0.8–1.0 mm typical | 0.6–0.8 mm typical |
| Standard carbon size | 6×12 mesh | 6×12 or 8×16 mesh |
| Carbon transfer | Pumped between leach tanks | Pumped counter-current to slurry flow |
| Key carbon requirement | Maximum hardness (resist grinding) | Good kinetics + screen compatibility |
The core difference: CIL tanks contain both leaching reagent and grinding media — carbon takes a beating, so you want the biggest, hardest particles possible (6×12). CIP tanks separate leaching from adsorption — there's no grinding media, so you can use smaller carbon particles without catastrophic attrition.
Why smaller matters in CIP: Smaller carbon particles have more surface area per unit mass. More surface area = faster gold adsorption kinetics = higher gold loading per cycle = fewer carbon transfers needed.
The Problem with 6×12 in This CIP Circuit
This Ghana mine's CIP circuit used 0.7 mm interstage screens. On paper, 6×12 mesh (smallest particle = 1.7 mm) should have no trouble staying behind those screens. In reality:
| Issue | What happened | Root cause |
|---|---|---|
| Screen blinding | Screens clogged
every 72–96 hours |
Oversized carbon trapped
fine ore particles against the screen surface |
| Carbon passing | 0.3% carbon loss
per transfer stage |
Breakage of larger
6×12 particles created sub-1.7mm fragments that passed through slots |
| Slow kinetics | Required 5 adsorption stages to
reach 94.5% recovery |
Large particles = lower
surface-to-volume ratio = slower gold uptake |
| Screen replacement | Every 6 weeks | Pressure differential
from blinding stressed screen panels |
The mine was spending $18,000/month on screen maintenance alone — plus the hidden cost of gold lost with passing carbon.
Why 8×16 Mesh Solved It
8×16 mesh carbon particles range from 1.0 to 2.4 mm. That's smaller than 6×12 (1.7–3.4 mm) but still well above the 0.7 mm screen slot size.
| Metric | Before (6×12) | After (8×16 HMGOLD™ 7000) | Change |
|---|---|---|---|
| Gold recovery | 94.5% | 96.8% | +2.3 points |
| Adsorption stages needed | 5 | 4 (same tanks,
one taken offline for maintenance) |
-1 stage |
| Carbon loss
per cycle |
0.3% | 0.15% | -50% |
| Screen cleaning frequency | Every 72–96
hours |
Every 168+ hours | -55% fewer cleanings |
| Screen
replacement interval |
6 weeks | 14 weeks | +133% longer life |
| Carbon loading
(g Au/kg C) |
3,200 | 4,100 | +28% |
| Screen
maintenance cost |
$18,000/month | $7,500/month | -58% |
The math on 2.3% recovery improvement: On a mine producing 3,000 oz/month, 2.3% additional recovery = ~69 oz/month × $2,300/oz = $158,700/month in additional gold revenue. Against a carbon cost of roughly $85,000 for 56 tons. Payback: under 20 days.
Specification: HMGOLD™ 7000 (8×16 Mesh)
| Parameter | Value |
|---|---|
| Mesh size | 8×16 (US standard) |
| Particle size range | 1.0–2.4 mm |
| Iodine number | ≥1100 mg/g |
| Hardness (ball-pan) | ≥98% |
| Attrition (Wenman test) | ≤2% |
| Ash content | <3% |
| Moisture | ≤5% |
| Bulk density | 0.48–0.52 g/cm³ |
| Gold adsorption rate (K value) | ≥3.2 mg Au/g C/hr |
| Equilibrium loading | ≥30 mg Au/g C |
| Raw material | 100% coconut shell |
HMGOLD™ series full specifications →
When to Use 6×12 vs 8×16: Decision Framework
| Your situation | Recommended mesh | Reason |
|---|---|---|
| CIL circuit (carbon in leach
tanks with ball mill discharge) |
6×12 | Maximum particle size =
maximum survival in abrasive environment |
| CIP circuit with
≥0.8 mm screen slots |
8×16 | Better kinetics, less
screen blinding, acceptable attrition |
| CIP circuit with
0.5–0.6 mm screen slots |
6×12 | Safety margin — 8×16
fines might pass through |
| CIC columns
(carbon in column) |
6×12 or 5×10 | Column flow dynamics
need larger particles for permeability |
| Heap leach
with carbon columns |
6×12 | Dirty solution = need
robustness over kinetics |
Rule of thumb: If your screen slot size is ≥0.7 mm and you're running CIP (not CIL), test 8×16 mesh. The kinetics improvement alone typically justifies the switch. If you're running CIL with SAG/ball mill discharge in the same tanks, stay with 6×12 — the abrasion environment is too harsh for smaller particles.
Shipment Details
| Item | Detail |
|---|---|
| Product | HMGOLD™ 7000 (8×16 mesh) |
| Quantity | 56 tons |
| Destination | Ashanti Region, Ghana |
| Port | Tema |
| Lead time | 35 days (order to port arrival) |
| Application | CIP gold recovery |
| Previous carbon | 6×12 mesh (competitor brand) |
FAQ
Is 8×16 mesh carbon weaker than 6×12?
Not inherently. Hardness is a property of the carbon material itself, not the particle size. HMGOLD™ 7000 in 8×16 mesh has the same ≥99% ball-pan hardness as the 6×12 version — same raw material, same activation process, just screened to a different size fraction. What changes is abrasion behavior: smaller particles have more surface area exposed to mechanical forces per unit mass, so they experience slightly higher proportional wear in highly abrasive environments (CIL). In CIP conditions (moderate agitation, no grinding media), 8×16 attrition is negligible.
How do I test whether 8×16 will work in my circuit?
Run a parallel basket test: load 5–10 kg of 8×16 mesh carbon in a screen basket within one of your existing CIP tanks. After 7 days, measure carbon loss (dry weight before vs after), gold loading, and check for screen passing. Compare against your current 6×12 performance. If carbon loss is <0.5% per cycle and gold loading is higher, scale up. Most mines see results within the first cycle (5–7 days).
Does switching mesh size require changing my screens?
Usually no. If you're going from 6×12 to 8×16, your existing screens (designed for 6×12) have slot sizes that will retain 8×16 particles with even more margin. The smallest 8×16 particle (1.0 mm) is still larger than typical CIP screen slots (0.6–0.8 mm). You might actually find screen blinding decreases because the smaller carbon particles create a less aggressive bridging pattern against the screen face.
What about carbon-in-column (CIC) — can I use 8×16 there?
Not recommended. CIC columns need good permeability for pregnant solution to flow through the carbon bed. Smaller particles create higher pressure drop and increase channeling risk. For CIC, stick with 6×12 or even 5×10 mesh for optimal flow characteristics. The exception: very small-scale CIC with low flow rates, where the
htmlpressure drop from 8×16 is manageable.
What's the price difference between 6×12 and 8×16?
Minimal — typically 3–5% higher for 8×16 because the yield of that size fraction from raw activated carbon is slightly lower than 6×12. On HMGOLD™ 7000, the difference is approximately $30–50/ton. Negligible compared to the operational savings from better kinetics, less screen maintenance, and higher gold recovery.
Need HMGOLD™ 8×16 mesh samples for CIP testing? Free 2kg sample, COA included. WhatsApp: +86 181-3792-7803 | Request quote →
