Industrial Gravity Thickener & Clarifier Sizing Calculator
Perform industrial process sizing for gravity thickeners and clarifiers using Coe-Clevenger and Talmage-Fitch settling methods. Calculate Unit Area (UA), basin diameter, solids loading flux, hydraulic rise rate (SOR), rake drive torque, and water recovery.
1. Slurry Feed & Settling Parameters
2. Basin Geometry, Hydraulics & Rake Drive
Engineering Principles & Continuous Thickener Derivations
Gravity thickeners rely on hindered settling and compressive consolidation to concentrate mineral slurries and reclaim process water for closed-loop plant recycling.
1. Coe & Clevenger / Talmage-Fitch Unit Area
From sedimentation continuity, the required thickener Unit Area (UA) accounts for the limiting solids settling flux:
Where (C_i) and (C_{uf}) are solids volume fractions and (v_i) is initial settling velocity. Total required settling area (A = dot{M}_s cdot UA). Basin diameter is (D = sqrt{4 A / pi}).
2. Slurry Volumetric Balance & Water Recovery
The total feed volumetric flow (Q_{feed}) and underflow volumetric flow (Q_{uf}) are calculated from component mass balances:
3. AGMA Rake Drive Torque Sizing
Rake drive running torque (T) is scaled quadratically with tank diameter in feet ((D_{ft} = D_m imes 3.28084)):
Rake tip speed is limited to (v_{rake} approx 10 ext{ to }15, ext{m/min}) to prevent shear re-suspension.
5 Fatal Engineering Traps & Industrial Operating Hazards
1. Rake Stalling & Center Drive Pinion Shearing
Allowing thickener inventory to build up past maximum compression height creates an immovable high-yield-stress sludge bed. Without an automated hydraulic rake lift mechanism, drive torque spikes to 150% of rating within minutes, snapping drive gear pinion teeth or twisting the main center shaft.
2. Feedwell Polymer Shear Degradation
High-molecular-weight polyacrylamide flocculant consists of delicate ultra-long polymer chains. Dosing polymer into high-velocity turbulent feed pipes (>1.5 m/s) violently shears the chains in half. Flocculation efficiency drops by 80%, requiring 4x flocculant dosing and causing severe un-flocculated fines carryover into the overflow.
3. Underflow Bed "Doughnut" Island Formation
Operating with slow rake rotation or excessive underflow pump throttling allows dense paste to compact into an immovable ring ("doughnut") surrounding the center cone. The rotating rake blades ride over the top of the island without clearing it, eventually overloading rake arms and halting bed transport.
4. Thermal Density Plunge & Launder Scouring
Introducing feed slurry that is significantly colder (or denser) than the tank liquor creates a downward density current. The heavy stream plunges down the centerwell, scours across the compacted bed surface, and shoots upward along the perimeter wall, dumping clouds of slime directly over the overflow weirs.
5. Clay Slime Viscosity Choking in CCD Circuits
In counter-current decantation (CCD) gold/copper leach circuits, processing ores with high smectite or illite clay content creates high non-Newtonian yield stress in the thickener underflow. Underflow paste cannot flow into the center discharge cone, causing pump cavitation and requiring costly chemical viscosity modifiers.