---
title: "Preheater cyclone"
description: "A preheater cyclone is one cyclone stage of a cement preheater tower. A 5-stage tower has 5 cyclones in series, numbered from the top (stage 1, lowest temperature) to the bottom (stage 5, hottest, just above the kiln inlet)."
canonical_url: "https://sylio.co/glossary/preheater-cyclone"
last_updated: "2026-06-28T02:29:27.504Z"
---

A **preheater cyclone** is one cyclone stage of a [cement preheater tower](/glossary/preheater-tower). A 5-stage tower has 5 cyclones in series, numbered from the top (stage 1, lowest temperature) to the bottom (stage 5, hottest, just above the [kiln inlet](/glossary/kiln-inlet-riser-duct)).

## Stage-by-stage fouling profile

<table>
<thead>
  <tr>
    <th>
      Stage
    </th>
    
    <th>
      Approximate gas temperature
    </th>
    
    <th>
      Fouling intensity
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      Stage 1 (top)
    </td>
    
    <td>
      300–350 °C
    </td>
    
    <td>
      Low
    </td>
  </tr>
  
  <tr>
    <td>
      Stage 2
    </td>
    
    <td>
      500–550 °C
    </td>
    
    <td>
      Low
    </td>
  </tr>
  
  <tr>
    <td>
      Stage 3
    </td>
    
    <td>
      600–650 °C
    </td>
    
    <td>
      Moderate
    </td>
  </tr>
  
  <tr>
    <td>
      Stage 4
    </td>
    
    <td>
      700–750 °C
    </td>
    
    <td>
      High
    </td>
  </tr>
  
  <tr>
    <td>
      Stage 5 (bottom)
    </td>
    
    <td>
      800–900 °C
    </td>
    
    <td>
      Highest — chloride/alkali condensation peak
    </td>
  </tr>
</tbody>
</table>

Stage 4 and stage 5 cyclones are the dominant fouling problem in any cement-plant preheater. They sit in the temperature window where alkali sulphates and chlorides condense most aggressively, and they hold the [calciner](/glossary/calciner) gas-temperature profile that determines downstream meal preheat efficiency.

## Cleaning

A typical cement-preheater [sonic-horn](/glossary/sonic-horn) installation places multiple horns on stage 4 and stage 5 cyclones, with additional horns on the [kiln-inlet riser duct](/glossary/kiln-inlet-riser-duct) and the [tertiary air duct](/glossary/tertiary-air-duct). The continuous acoustic field prevents the cohesive coatings that cause cyclone pluggage.

## Related terms

- [Preheater tower](/glossary/preheater-tower)
- [Cyclone separator](/glossary/cyclone-separator)
- [Build-up / coating / accretion](/glossary/build-up-coating-accretion)
- [Sonic horn](/glossary/sonic-horn)