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Hydrometallurgy

Leach Tank Residence Time Calculator

In a hydrometallurgical leach circuit, hydraulic residence time is the average time slurry spends in the leach tanks — the total online working volume divided by the slurry volumetric flow. This calculator builds the installed working volume from the number of tanks and the working volume per tank, applies an optional availability / online tank factor, divides by the slurry flow to get the nominal residence time, and applies an optional design margin. It is a preliminary hydraulic estimate only: it does not predict leach recovery or reaction kinetics.

TypeInteractive engineering calculator

Calculator

m³/h

combined solids + liquid flow

tanks

whole number ≥ 1

m³

operating volume, not total

%

0–100% (optional, default 100)

%

optional contingency above nominal

Result
Installed working volume1800 m³
Effective online volume1800 m³
Nominal residence time7.2 h
Residence time with margin7.92 h
  • !Hydraulic residence time only — it does not predict leach recovery. Confirm against metallurgical testwork.

Formulas

Installed working volume
V_installed = N_tanks × V_working
Effective online volume
V_online = V_installed × online% / 100
Nominal residence time
τ = V_online / Q_slurry
Residence time with margin
τ_margin = τ × (1 + margin% / 100)

Diagram

Leach tank train — τ = V_online / Q_slurryslurryT1T2T3T4τ = (N × V_working × online%) / Q_slurryhydraulic time only — not recovery

Worked example

A leach train is six agitated tanks, each 300 m³ working volume, fed with slurry at 250 m³/h. Online factor 100%, design margin 10%. Estimate the residence time.

  1. 01Installed working volume: V = 6 × 300 = 1800 m³
  2. 02Online volume: 1800 × 100 / 100 = 1800 m³
  3. 03Nominal residence time: τ = 1800 / 250 = 7.2 h
  4. 04With 10% margin: 7.2 × 1.10 = 7.92 h
Result

Installed volume 1800 m³, online volume 1800 m³, nominal residence time 7.2 h, residence time with margin 7.92 h.

FAQ

Should I use slurry flow or solution flow for Q?
Use the slurry volumetric flow — the combined solids plus liquid flow that passes through the tanks. Using the liquid flow alone understates the volume moving through and overstates the residence time.
Does enough residence time guarantee recovery?
No. Residence time gives the reaction time, but recovery depends on the leach kinetics, slurry density and percent solids, temperature, reagent concentrations, grind, and mixing. Residence time is a sizing input; recovery comes from testwork.
What does the online factor do?
It reduces the installed working volume to the volume actually in service, accounting for tanks taken offline for maintenance or availability. At 100% the full installed volume is online.
Why apply a design margin?
A margin adds contingency above the nominal residence time for flow variability, future throughput, and uncertainty in the kinetics. It is a preliminary allowance, not a substitute for residence-time-distribution work.

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