Slurry concentration converter

Durand only covers settling slurries. It was fitted to sand, gravel and coarse tailings in water, so it applies to heterogeneous (settling) systems, roughly d₅₀ 0.05–5 mm and C_v up to 20–25 %. Fine tailings, paste backfill and red mud are homogeneous or non-Newtonian — a “deposition velocity” does not exist for them, and a number from this formula would be meaningless.

The result is a floor, not a design value. V_D is the point at which a bed just stops forming; practice keeps 10–30 % above it. Going much higher does not help either — wear and power climb faster than throughput.

Pressure drop is deliberately not calculated here. Durand’s hydraulic-gradient correlation can be tens of percent off on a real line, and a concrete number would mislead pump selection. Use the manufacturer’s curves or dedicated software.

① The solids density must be known and stable. Inferring solids content from density rests entirely on that one constant. Change the mineral, the blend ratio or the concentrate grade and ρ_s changes with it — C_w then drifts systematically while the density reading itself looks perfectly normal. Weight it by the actual blend for mixed feeds, or sample and measure periodically.

② Entrained air pulls every result low. Bubbles are a third phase (ρ≈0.0012) in what the maths treats as two; measured density comes out low and so do C_v and C_w. Aeration basins, pump suction under vacuum and runs after a free fall are the usual offenders. There is no computational fix — only tapping-point placement and pipework design.

③ Everything here is a cross-section average. Solids are not evenly distributed: coarse particles run along the invert and the section carries a concentration gradient. Where the meter sits and which side the sampling port opens can shift the reading noticeably. Horizontal runs are the worst; vertical runs are much better.