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Cyclones and Multicyclones

Cyclones and multicyclones — high-efficiency mechanical separators for coarse and medium dust, with abrasion-rated materials matched to your duty.

Image shows cyclone dust collectors designed and built by Fowlerex Engineering

Cyclone Dust Collector

Cyclones are mechanical centrifugal separators — incoming gas spirals through a tangential inlet, larger particles are thrown outward by centrifugal force and fall to the dust hopper, cleaned gas exits up the vortex finder. No moving parts, no consumables, no compressed air.

  • Removal efficiency 70–95% depending on particle size and design (Stairmand high-efficiency vs standard)
  • Operating range: 5 μm and above on standard, down to ~3 μm on high-efficiency
  • Pressure drop 0.8–2 kPa
  • Temperature up to 400°C (carbon steel), higher with refractory or alloy
  • Abrasion-resistant linings to duty: Ni-Hard, Cr-carbide weld overlay, ceramic tile, AR400/AR500 plate

Typical roles:

  • Pre-separator upstream of a baghouse or WESP — drops the bulk dust load, extends bag life
  • Product recovery in pneumatic conveying — milling, drying, crushing
  • Standalone collector for coarse dust — timber, sawdust, grain, woodchip
  • Spark arrestor on boiler emission systems — drops embers + coarse ash before the filter

Limitation: efficiency falls off below ~5 μm. For sub-μm or sticky/condensable dust, pair the cyclone with a baghouse or WESP.

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Multicyclone dust collector

Multicyclone Dust Collector

Multicyclones — banks of small-diameter cyclones operating in parallel — exploit the fact that smaller cyclones run at higher tangential velocity and capture finer dust. The tubes are banked in pyramidal or rectangular arrays.

  • Removal efficiency 85–95% on 5 μm, useful down to ~2 μm
  • Operating temperature up to 400°C continuous (carbon steel + insulation)
  • Pressure drop 1–1.5 kPa
  • Common in boiler emission control, cement plants, lime kilns, asphalt plants, milling circuits, grinding processes

Delivered projects:

  • NZ Steel Glenbrook (NZ) — multi-cyclone + venturi as a 2-stage system on the iron-melter offgas, 3Cr12 hot abrasive duty, 132 kW fan
  • PT Kaltim Coal (East Kalimantan, Indonesia) — Multicyclone 56-7 for coal-handling dust

Often deployed as a pre-conditioner: drops the worst of the dust before a downstream baghouse or scrubber sees it. Reduces filter loading, extends bag life, removes embers/sparks where the upstream process produces them.

Frequently asked questions

What do cyclones remove?
Coarse-to-medium particulate by centrifugal separation — well suited as pre-separators and for product recovery.
Will a cyclone meet my dust limit?
For fine or sub-micron limits, no — pair it with a baghouse, ESP or WESP; the cyclone drops the bulk load first.
Cyclone vs multicyclone?
Multicyclones use many small-diameter tubes for higher efficiency on finer (but still not sub-micron) dust.
Abrasive dust?
We line the unit to the abrasiveness of your material so it survives the duty.
Why do multicyclones underperform in practice?
Gas maldistribution is the dominant failure mode. The tubes share a common inlet plenum and only perform as a set if each one sees its design share of the gas. Poor plenum design, a badly placed inlet bend or a partly fouled bank sends too much gas through some tubes and too little through others, and measured efficiency then sits well below the single-tube figure. Extra pressure drop does not recover it — the fix is inlet and plenum geometry.
What causes multicyclone tube blockage?
Sticky, hygroscopic or condensing dust bridges small-diameter tubes long before it would trouble a single large cyclone. Insulation, trace heating and keeping the gas comfortably above its dew point matter more on a multicyclone than on any other collector.
Why does air in-leakage at the hopper matter?
Because it lifts collected dust straight back into the outlet. If the vortex extends into the hopper, or air leaks in at the discharge, dust that was already separated re-entrains and leaves with the clean gas. Vortex breakers, correct hopper geometry and a sealed discharge are what prevent it.
What is the trade-off between efficiency and pressure drop?
They move together. Geometry that collects finer dust costs more fan energy for the life of the plant. The economic answer is usually a cyclone doing what it is genuinely good at — dropping the bulk load cheaply and without consumables — ahead of a device that can actually meet the limit, rather than a cyclone pushed to do a filter job.
Can a cyclone be used for product recovery?
Yes, and it is one of the better uses. On spray dryers, mills and pneumatic conveying the collected stream is saleable product rather than waste, so separation efficiency converts directly into yield.
Can a cyclone act as a spark or ember arrestor?
Yes. Ahead of a fabric filter on wood, biomass and other combustible-dust duties a cyclone arrests embers as well as dropping bulk load, which is a specifiable function within the wider fire and explosion-protection strategy rather than a substitute for it.
What wears out first, and can it be relined?
On abrasive minerals the tube inlet vanes and cone tips go first. Replaceable tube inserts and abrasion-resistant liners — ceramic, Ni-hard or chrome-carbide overlay chosen to the material — are what make a long service life achievable, and they are renewable rather than terminal.

Relevant Industries & Applications