How it works
A decanter centrifuge is a horizontal rotating bowl with a co-rotating screw conveyor (scroll) turning at a slightly different speed. Slurry is fed into the bowl, where the centrifugal field — many times gravity — drives the denser solid particles outward to the bowl wall, where they accumulate as a liquid-saturated sediment. The clarified liquid forms a rotating annular pond and flows toward the overflow weir, while the screw, turning at a small differential speed relative to the bowl, scrapes the sediment along the wall toward the conical end and lifts it out of the pond, where it drains further before discharge.
Two things therefore happen at once and interact: sedimentation of particles out of the flowing slurry, set by bowl speed, particle size, and density difference; and sediment build-up and transport, where the cake compacts (a compressible, hindered-settling material) and is conveyed out. Capture of fine particles depends on the centrifugal force and the residence time in the pond; cake dryness depends on how long the sediment is worked and compacted before it leaves. This is an inherently dynamic, transient process — the cake builds up over time toward a steady state.
The model
The decanter centrifuge is a dynamic model that splits the machine into two coupled zones — a sedimentation zone and a sediment zone — and solves the unsteady mass and volume balances, so it captures transient cake build-up and the approach to steady state, not just a static split.
In the sedimentation zone, a series of well-mixed compartments applies a time-dependent grade efficiency — derived from bowl speed, particle size and density difference, liquid viscosity, and geometry — to settle solids out of the flowing slurry. In the sediment zone, the settled material builds up as a compressible, liquid-saturated cake (with a hindered-settling function and a gel-point transition) and is transported toward discharge by the screw at its differential speed. Solid and liquid phases and a PSD are required.
Key parameters
- Bowl (angular) speedSets the centrifugal force, hence capture and centrate clarity.
- Screw differential speed & pitchSet conveying rate and cake residence, hence cake dryness.
- Weir radius (pond depth)Trades clarification residence against drying-beach length.
- Cake / hindered-settling parametersCompressibility and gel point of the sediment cake.
Equipment this model can represent
Any continuous centrifugal dewatering duty producing a dry cake and a clarified centrate.
Counter-current decanters
Slurry and sediment move in opposite directions (the classic configuration this model represents).
Co-current decanters
Feed and sediment move the same way, gentler on flocs.
High-G / fine-bowl decanters
Long, slender bowls at high speed for fine-particle clarification.
Three-phase (tricanter) decanters
Separate two liquids plus solids simultaneously.
Typical engineering studies
What teams investigate with the decanter model.
Centrate & cake prediction
Predict centrate clarity and cake solids for a given decanter setting and feed, including the transient.
Speed & pond-depth studies
Study bowl speed, differential speed, pond depth, and feed flow against clarity and cake dryness.
Dynamic upsets
Feed-solids upsets, startup, and the approach to steady cake build-up.
Calibration & scale-up
Calibrate the cake/settling parameters to measured performance, then scale up or transfer to new feeds.
Flowsheet coupling
Couple to upstream thickening and downstream cake-handling units in one flowsheet.
Existing application example
Industrial zeolite production
End-to-end catalyst process with synthesis, decanter washing/concentration, spray drying, and two-stage rotary-kiln calcination. Dyssol connected surrogate synthesis models with dynamic downstream units in one flowsheet.
Technical FAQ
How does a decanter centrifuge separate solids from liquid?
A rotating bowl drives denser solids to the wall as a sediment while clarified liquid overflows a weir, and a screw turning at a small differential speed conveys the cake out of the pond. DyssolPro models exactly this with coupled sedimentation and sediment-transport zones, resolved over time.
Why is my decanter centrifuge producing wet solids?
Wet cake means too little compaction or residence in the sediment zone — often too high a feed rate or too low a differential speed. DyssolPro models the compressible, liquid-saturated cake build-up, so you can predict cake solids and tune differential speed and flow to dry it.
How can I improve clarification efficiency in a decanter?
Clarity improves with higher bowl speed, lower throughput, and a deeper pond for more residence. In DyssolPro these are model parameters, so you study centrate clarity against bowl speed, flow, and weir radius to find the right setting.
What causes high solids carryover in the centrate?
Fine particles that don’t settle within the pond residence escape with the centrate. DyssolPro’s size-resolved grade efficiency shows which fines escape, so you can study how more bowl speed or less flow captures them.
How do bowl speed and differential speed affect separation?
Bowl speed sets the centrifugal force (and thus capture and clarity); differential speed sets conveying rate and cake residence (and thus dryness). DyssolPro takes both as parameters and models their distinct effects, so you can balance clarity against cake dryness explicitly.
How can I reduce polymer consumption in centrifuge operation?
Polymer flocculates fines into larger, faster-settling aggregates — a chemistry the model doesn’t simulate. DyssolPro represents its effect through a coarser effective feed PSD, so you can study how much aggregation is actually needed for target capture and aim for the minimum dose.
What parameters influence cake dryness in a decanter centrifuge?
Cake dryness is governed by residence and compaction in the sediment zone — differential speed, feed flow, and the compressibility of the solids. DyssolPro’s dynamic sediment-zone model predicts cake solids as a function of those settings.
How do I size a decanter centrifuge for slurry treatment?
Sizing balances throughput against required clarity and cake dryness. In DyssolPro you run the model at the feed conditions and check centrate and cake; the mechanical bowl sizing is a separate calculation the simulation feeds with the required duty.
What causes vibration in a decanter centrifuge?
Vibration is mechanical — imbalance from uneven cake or wear — and is not represented in the model. DyssolPro addresses the process side (how cake builds up and discharges); the vibration diagnosis stays with the machine.
How can I optimize decanter operation for changing feed solids?
Because the model is dynamic, DyssolPro lets you impose feed-concentration transients and watch the cake and centrate respond, so you can find settings (speed, differential speed, flow) that stay robust across the expected feed range.
Why does my decanter cake quality change during operation?
Cake quality evolves as the sediment builds up toward steady state and with feed variation. DyssolPro is a transient model, so it shows that cake build-up over time and helps you tell a normal approach-to-steady-state from a genuine upset.
How do I reduce wear in a decanter centrifuge?
Wear is driven by abrasive solids at high speed — a mechanical effect outside the model. DyssolPro doesn’t compute wear, but by helping you meet the duty at the lowest adequate bowl speed and load it supports the process choices that reduce it.
How does feed particle size affect decanter performance?
Finer feed is harder to capture and tends to escape in the centrate. DyssolPro resolves the PSD and computes a size-dependent grade efficiency, so you see directly how feed fineness shifts clarity and recovery.
How can I improve solids recovery in a decanter?
Recovery improves with more centrifugal force and residence — higher bowl speed, lower flow. In DyssolPro you study recovery against those settings and the feed PSD to find the operating point that captures the required fraction.
What causes foaming in centrifuge operation?
Foaming is a physico-chemical surface effect (surfactants, air entrainment) that the model doesn’t represent. DyssolPro covers the sedimentation and dewatering performance, not the gas–liquid foaming behavior.
How do I optimize pond depth in a decanter centrifuge?
A deeper pond gives more clarification residence but a shorter drying beach, trading clarity against cake dryness. DyssolPro takes the weir radius (pond depth) as a parameter, so you can study that trade-off and pick the depth that meets both targets.
What is the effect of feed flow rate on cake dryness?
Higher feed flow shortens residence, giving a wetter cake and poorer clarity. DyssolPro lets you vary the feed flow and read cake solids and centrate clarity off the dynamic model to set the throughput.
How can I reduce torque overload in a decanter?
Torque overload comes from too much cake load on the screw — an operational/mechanical limit. DyssolPro models the cake build-up that drives torque (so you can avoid the conditions that overload it) but doesn’t compute the torque value itself.
How do I troubleshoot poor liquid clarity after centrifugation?
Poor clarity means fines are escaping the pond. In DyssolPro you study which size classes leave in the centrate against bowl speed and flow, which localizes whether the cause is insufficient force, too much throughput, or a finer feed.
How can I model sedimentation and transport in a decanter centrifuge?
This is exactly the unit: a dynamic model with a sedimentation zone (time-dependent, size-resolved capture) coupled to a sediment zone (compressible cake build-up and screw transport), giving centrate clarity and cake solids over time inside the flowsheet.