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Hydrometallurgy

Thickener Feed Dilution Calculator

Thickener and clarifier feeds are often diluted (frequently by feedwell auto-dilution) to the percent solids where the flocculant works best. This calculator estimates the dilution water required to take a feed from an initial wt% solids to a lower target wt% solids, working on a dry-solids basis: the initial and target slurry and liquid mass flows, then the extra water that makes up the difference, in t/h and m³/h. It is a preliminary dilution water mass-balance estimate only. The target feed % solids is an input from testwork or operations, not something this tool optimises. It is NOT a flocculation model, feedwell/auto-dilution design, or thickener sizing tool, and it does not model settling, overflow clarity, underflow density, residence time, or rake torque.

TypeInteractive engineering calculator

Calculator

t/h

dry solids basis

wt%

0–100 wt% solids by mass

wt%

must be lower than initial

kg/m³

dilution water / liquor density

Result
Initial slurry mass flow222.222 t/h
Initial liquid mass flow122.222 t/h
Target slurry mass flow285.714 t/h
Target liquid mass flow185.714 t/h
Dilution water required63.4921 t/h
Dilution water required63.4921 m³/h
  • !Preliminary dilution water mass-balance estimate only — target solids must be lower than the initial solids for dilution.
  • !Does not model thickener settling, flocculation, feedwell mixing, overflow clarity, underflow density, residence time, or rake torque. The target feed % solids is an input from testwork/operations, not optimised here.

Formulas

Initial slurry mass flow
ṁ_slurry,i = ṁ_solids / (initial% / 100)
Initial liquid mass flow
ṁ_liquid,i = ṁ_slurry,i − ṁ_solids
Target slurry mass flow
ṁ_slurry,t = ṁ_solids / (target% / 100)
Target liquid mass flow
ṁ_liquid,t = ṁ_slurry,t − ṁ_solids
Dilution water (mass)
ΔW = ṁ_liquid,t − ṁ_liquid,i
Dilution water (volume)
ΔV = ΔW × 1000 / ρ_liquid

Diagram

Thickener feed dilution — added water drops feed % solids to targetfeed (high %)dilution watertarget %thickenerΔW = solids × (1/Cw,target − 1/Cw,initial)a dilution mass balance — not a flocculation model

Worked example

A thickener feed carries 100 t/h dry solids at 45 wt% solids and must be diluted to 35 wt% solids. Liquid density 1000 kg/m³.

  1. 01Initial slurry mass: 100 / 0.45 = 222.22 t/h
  2. 02Initial liquid mass: 222.22 − 100 = 122.22 t/h
  3. 03Target slurry mass: 100 / 0.35 = 285.71 t/h
  4. 04Target liquid mass: 285.71 − 100 = 185.71 t/h
  5. 05Dilution water: 185.71 − 122.22 = 63.49 t/h
  6. 06As a volume at 1000 kg/m³: 63.49 × 1000 / 1000 = 63.49 m³/h
Result

Initial slurry 222.22 t/h, target slurry 285.71 t/h, dilution water 63.49 t/h (≈ 63.49 m³/h).

FAQ

Does this calculator set the flocculation-optimum feed density?
No. The target feed % solids is an input you supply from settling testwork or operating experience. The calculator only works out the dilution water needed to reach that target on a dry-solids mass balance.
Why must the target be lower than the initial solids?
Dilution adds water, which lowers the percent solids. If the target equalled or exceeded the initial you would be concentrating, not diluting, and the dilution-water figure would be zero or negative.
Is this a thickener or feedwell design tool?
No. It is a preliminary dilution mass balance. Feedwell auto-dilution design, settling, overflow clarity, and underflow density all require testwork and vendor data, which this does not model.
How does this relate to the slurry dilution water calculator?
They share the same dry-solids dilution engine. The feed dilution page is framed for a thickener/clarifier feed (flocculation target, diluted-feed context); the slurry dilution water page is the generic slurry version for any dilution duty.

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