---
title: "Lime kiln"
description: "A lime kiln at a kraft pulp mill calcines spent lime mud (CaCO₃) back to burnt lime (CaO) at ~1,200 °C for re-use in the recausticising chemical-recovery cycle. The kiln is a long inclined rotating cylinder, similar in form to a cement rotary kiln but smaller and lower-temperature."
canonical_url: "https://sylio.co/glossary/lime-kiln"
last_updated: "2026-06-28T02:29:36.252Z"
---

A **lime kiln** at a kraft pulp mill calcines spent lime mud (CaCO₃) back to burnt lime (CaO) at ~1,200 °C for re-use in the [recausticising](/glossary/recausticising) chemical-recovery cycle. The kiln is a long inclined rotating cylinder, similar in form to a [cement rotary kiln](/glossary/rotary-kiln) but smaller and lower-temperature.

## Preheater and chain section

Most modern lime kilns have a preheater (often a chain section inside the kiln itself or an external preheater) where incoming damp lime mud is pre-dried by exhaust gas. The chain section accumulates lime-mud build-up — *mud rings* — that progressively narrow the gas path and reduce kiln throughput.

## Lime-kiln ESP

The flue gas exiting the kiln carries entrained lime dust, captured in a downstream [ESP](/glossary/electrostatic-precipitator) before the stack. The ESP hopper handles fine lime, which bridges easily.

## Cleaning

[Sonic horns](/glossary/sonic-horn) are installed at three points on a typical lime-kiln gas-cleaning train:

- **Lime-kiln preheater / chain section** — prevent mud-ring formation
- **Lime-kiln ESP hopper** — prevent fine-lime bridging
- **Stack adjacency** — if vent fouling becomes problematic

## Related terms

- [Recausticising](/glossary/recausticising)
- [Recovery boiler](/glossary/recovery-boiler)
- [Rotary kiln](/glossary/rotary-kiln)
- [Sonic horn](/glossary/sonic-horn)