Reagent Dosing and Consumption Explained

Definition

Reagent dosing and consumption calculations tie a reagent addition to the material it treats. In hydrometallurgy and mineral processing, a reagent is dosed either per tonne of dry solids (kg/t — for leaching reagents, lime, flocculant) or per unit of solution volume (g/L — for a target solution strength). Consumption is then the rate at which the reagent is used: the dose multiplied by the dry solids throughput (or the solution volume), giving a kg/h rate and a daily kg/day or t/day figure. Make-up strength is a related but distinct idea — how concentrated the prepared reagent solution or slurry is (g/L for cyanide, wt% for milk of lime, g/L for flocculant make-down). The ProcessConvert reagent calculators each do one of these preliminary mass balances; none of them predicts process performance.

Why it matters

Reagent is often one of the largest operating costs and one of the biggest safety and environmental exposures on a hydromet circuit, so getting a defensible first-pass consumption and make-up estimate matters for budgeting, storage sizing, delivery scheduling, and dosing-system design. The recurring trap is confusing a consumption or make-up number with a performance number. A leach reagent dose is an input from testwork — it does not by itself set recovery. A cyanide solution mass balance tells you how much NaCN to dissolve — it is not a safety procedure and says nothing about free-cyanide speciation or pH. A milk-of-lime make-up tells you the lime and water for a target wt% — it does not predict neutralisation or pH. A flocculant make-down tells you the polymer and solution flow — it does not guarantee settling rate or underflow density. Every one of these must be tied to the correct basis (dry solids throughput or solution volume) and then read as a preliminary estimate to be confirmed by testwork, plant data, vendor data, safety review, and qualified engineering review.

Formula

Units involved

• •dose — kg/t (solids basis) or g/t for flocculant
• •C_target, C_solution — g/L (solution concentration)
• •wt% — solids concentration by mass (lime slurry)
• •ṁ_solids — dry solids throughput in t/h
• •ṁ_reagent — consumption rate in kg/h; m_day in kg/day or t/day
• •V — solution volume in m³ or L

Concept diagram

Worked example

Common mistakes

• •Reading a reagent dose as if it set recovery — dose is an input, not a result.
• •Treating a cyanide solution mass balance as a safety, handling, or dosing procedure.
• •Confusing milk-of-lime make-up strength with pH control or neutralisation performance.
• •Reading a flocculant make-down (solution flow) as a thickener performance guarantee.
• •Mixing the basis — applying a per-tonne dose to a solution volume, or g/L to dry solids.

When to use the calculator

Use the leach reagent consumption calculator for kg/t consumption from dry solids throughput; the cyanide solution preparation calculator for the NaCN mass and dilution mass balance of a target solution; the lime slurry preparation calculator for the lime and water in a milk-of-lime make-up; and the flocculant make-down calculator for the polymer and make-down solution flow. Each is a preliminary mass balance — performance comes from testwork, vendor data, and qualified review, not these tools.

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