Flocculants in Thickening & Clarification

How to use this guide

This is a practical decision aid for thickener/clarifier performance and reagent control. It’s written for B2B teams who need alignment across operations, metallurgy/process, maintenance, EHS, and procurement.

Use it to define your target KPI (clarity, underflow density, throughput, water recovery, or reagent cost), then work through selection criteria, make-down/mixing constraints, and the monitoring signals that prevent performance drift. When you share your site constraints, we can propose supply-ready flocculant options (powder or emulsion) with procurement-ready specs, documentation, and logistics.

Where it fits

• Unit operations: pre-thickening, CCD, tailings thickening, clarification/reclaim water, concentrate thickening.
• Primary outcomes: overflow clarity, underflow density, settling rate, water recovery, rake torque stability.
• Interfaces: feedwell hydrodynamics, dilution water quality, make-down units, dosing pumps, polymer aging tanks.
• Constraints: water recycle chemistry, temperature, pH, shear environment, local discharge rules and EHS requirements.

What a flocculant actually does (technical view)

In most mineral circuits, the flocculant is a high molecular weight polymer (commonly based on acrylamide chemistry) that improves solid-liquid separation by:

• Bridging: polymer chains attach to multiple particles and link them into larger aggregates (“flocs”).
• Charge effects: cationic/anionic functionality changes adsorption behavior and floc structure.
• Hydrodynamics: floc size and strength depend heavily on mixing energy and shear at the point of addition.

The same product can perform very differently depending on make-down quality, dilution water, mixing, feedwell conditions, and the fine fraction/mineralogy in the feed.

Commercial reality: why performance drifts

Thickener circuits rarely fail suddenly—they drift. Most sites see reagent spend creep upward while clarity or density slowly worsens. Common drift drivers are: changes in ore blend, recycled water chemistry, uncalibrated dosing, or make-down system issues that reduce effective polymer activity.

• Cost of drift: more flocculant, more downtime, lower water recovery, pumping problems, and higher tailings moisture.
• Best practice: lock in a small set of “leading indicators” (overflow turbidity, bed level, rake torque, underflow % solids) and tie them to dosing and make-down checks.

Key decision factors

• Mineralogy & fines: clay content, ultrafines distribution, and gangue can dominate polymer demand and floc quality.
• pH & ionic strength: affects adsorption, floc structure, and how sensitive performance is to dosing changes.
• Water recycle chemistry: hardness, TDS, residual reagents, and entrained organics can impact hydration and floc behavior.
• Shear environment: pump shear, feedwell turbulence, and pipe velocities can break flocs if addition is poorly located.
• Equipment constraints: make-down capacity, aging tank volume, dilution points, and dosing control range.
• KPI priority: clarify overflow first vs maximize underflow density vs maximize throughput (often trade-offs).

Selection basics: polymer type and format

Charge type (functional group)

• Anionic: common in many mineral thickeners; often effective for negatively charged particle systems when bridging dominates.
• Cationic: frequently used for some sludges and specific mineral systems; can improve capture/clarity where charge interaction matters.
• Non-ionic: niche uses; sometimes selected when charge sensitivity is problematic.

Physical form

• Powder: often economical per active content; requires controlled wetting, hydration, and aging to avoid fisheyes/lumps.
• Emulsion: can be easier/faster to make down; needs proper inversion and controlled dilution to activate the polymer.

Make-down and dilution: where most problems start

The polymer’s effective activity depends on how it is prepared. Two sites can run the same flocculant at the same nominal dose and get different results because one has better make-down and dilution control.

Make-down checklist (what to control)

• Water quality: stable supply; avoid extreme hardness/contamination swings if possible. Use consistent dilution water source.
• Make-down concentration: keep within your unit’s design window. Too concentrated raises viscosity and mixing risk; too dilute can limit dosing range.
• Wetting/inversion: ensure powder is dispersed without fisheyes; ensure emulsion is properly inverted/activated.
• Aging time: allow sufficient maturation before dosing; under-aged polymer often gives cloudy overflow and higher demand.
• Shear protection: avoid high shear pumps where possible; polymer chains can be damaged, reducing floc size and performance.

Practical mixing guidance (process-friendly)

• Powder: add slowly to a well-controlled vortex/wetting zone; prevent clumping; confirm no undissolved “fish eyes.”
• Emulsion: confirm the inversion step; avoid “short-circuiting” where emulsion enters the line without activation.
• Dilution to application: many circuits benefit from a second-stage dilution to improve distribution and reduce local over-dosing.

Application point: feedwell and mixing energy

In thickening, the goal is to distribute polymer onto particles with enough mixing to contact solids, but not so much shear that flocs break immediately.

Common objectives at the point of addition

• Fast adsorption: polymer must contact solids quickly, before short residence times carry it away.
• Uniform distribution: avoid “hot spots” that cause local overdose (slimy flocs, poor clarity, ragging).
• Controlled shear: enough to mix, not enough to destroy floc structure.

Signs your addition point is wrong

• Large flocs form then disappear (shear breakage) → relocate addition or reduce local turbulence.
• Cloudy overflow despite higher dose → poor distribution or under-activated polymer (not only “wrong polymer”).
• Rake torque spikes after dose changes → overdosing or floc structure causing bed compaction/rat-holing.

KPIs: what to measure and how to interpret

Choose 2–4 KPIs and track them consistently. A good control program ties KPIs to dosing, make-down checks, and ore changes.

Typical dose optimization workflow (plant-friendly)

1. Confirm make-down health: correct concentration, adequate aging time, and stable dilution water.
2. Stabilize operating conditions: avoid changing feed rate, dilution, and rake settings during a test window.
3. Step test dosing: incremental changes with enough time for thickener response (avoid chasing noise).
4. Record KPIs: clarity/turbidity, underflow % solids, torque, bed level.
5. Lock in the setpoint: then monitor drift signals and recalibrate when ore/water changes.

Troubleshooting signals

When performance drops, these are common early indicators and what to check first:

1) Cloudy overflow or rising turbidity

• Likely causes: under-activated polymer, poor distribution, ore/fines shift, excessive shear after floc formation.
• First checks: make-down aging time, dilution water changes, addition location, and whether dose changes correlate with clarity.
• Quick actions: verify polymer solution quality (no lumps/poor inversion), increase dilution at application for better distribution, then re-optimize dose.

2) Underflow density drops (wetter tailings)

• Likely causes: bed instability, insufficient floc strength, short residence time, feedwell hydraulic issues.
• First checks: throughput changes, bed level control, torque trends, and whether flocs are breaking in pumps/lines.
• Quick actions: stabilize bed level, confirm shear exposure, then tune dose and dilution.

3) Reagent consumption increases with no KPI improvement

• Likely causes: overdosing, distribution issues, make-down failure, or changed ore/water chemistry driving demand.
• First checks: calibrate dosing pumps/flowmeters, verify make-down concentration, and confirm polymer is “active.”
• Quick actions: restore preparation quality first; only then consider switching grade/charge.

4) Rake torque spikes / bogging risk

• Likely causes: overdosing causing dense/gel-like bed, uneven distribution leading to bed compaction, or solids loading event.
• First checks: dose changes timing vs torque, bed level, feed solids changes, and polymer addition point.
• Quick actions: reduce dose stepwise, stabilize feed, and improve distribution/dilution.

Specification & acceptance checks (procurement-ready)

Flocculants are performance reagents. Procurement quality should cover both product identity and consistency so the plant can hold setpoints without re-tuning every delivery.

What to request from suppliers (minimum)

• Identity: product name/grade, polymer type (charge), physical form (powder/emulsion), manufacturer, batch/lot traceability.
• COA typical items: appearance, active content/solids, viscosity (emulsions), residual monomer spec (if provided), bulk density (powders), pH (as applicable).
• Performance notes: recommended make-down concentration window, aging time, and dilution guidance; any water quality sensitivities.
• Safety: current SDS; handling precautions; spill/slip hazard notes; recommended PPE.
• Packaging: bags, drums, IBC, bulk; liner/closure details; labeling and palletization.
• Logistics: lead time, shelf life, storage temperature window, Incoterms, origin documentation if needed.

Receiving and acceptance checks (site verifiable)

• Packaging integrity: no punctures, moisture ingress (powders), or phase separation/leaks (emulsions).
• Lot traceability: match COA lot number to delivery labels.
• Storage compliance: confirm storage temperature and protect from direct sunlight/freezing as required.
• Trial protocol: define a standard test window and KPIs before switching suppliers/grades.

Handling & storage (operations + EHS)

• Slip hazard: polymer spills can be extremely slippery—treat spills as high risk; use suitable absorbents and barriers.
• Powder protection: keep dry; reseal bags; prevent humidity exposure that causes clumping and poor dissolution.
• Emulsion stability: store within recommended temperature window; avoid freezing/overheating that can destabilize product.
• Housekeeping: keep dosing areas clean to prevent buildup in lines and fittings.
• Make-down hygiene: keep tanks clean; avoid contamination that changes solution behavior over time.

RFQ notes (what to include)

• Circuit: thickener type/size, feedwell design, feed rate (t/h), typical % solids, and temperature.
• Feed description: ore/mineralogy, fines/clays notes, pH and water chemistry (TDS/hardness if known).
• Targets: overflow clarity/turbidity target, underflow density target, throughput constraints, water recovery goals.
• Current reagent: current flocculant type/format and typical consumption (g/t or kg/t and solution concentration).
• Make-down system: powder or emulsion unit, capacity, aging tank volume, and available dilution points.
• Constraints: site restrictions, required documentation, delivery destination and packaging preference.

Educational content only. Always follow site EHS rules and the supplier SDS for safe use. Performance depends on site-specific ore, water chemistry, and equipment; validate with a controlled trial protocol.