---
title: "Claus unit / sulphur recovery unit (SRU)"
description: "A Claus unit — also called a sulphur recovery unit (SRU) — recovers elemental sulphur from H₂S-bearing acid gas in a refinery or gas-processing plant. The Claus process partially combusts H₂S to SO₂, then catalytically reacts the remainder of the H₂S with SO₂ to form liquid sulphur in two or three downstream converter stages."
canonical_url: "https://sylio.co/glossary/claus-unit-sulphur-recovery-unit"
last_updated: "2026-06-28T02:29:40.037Z"
---

A **Claus unit** — also called a **sulphur recovery unit (SRU)** — recovers elemental sulphur from H₂S-bearing acid gas in a refinery or gas-processing plant. The Claus process partially combusts H₂S to SO₂, then catalytically reacts the remainder of the H₂S with SO₂ to form liquid sulphur in two or three downstream converter stages.

## Cleaning targets

- **Waste-heat boiler (WHB)** downstream of the Claus reaction furnace — high-temperature economiser surfaces foul with ammonium-salt and sulphur deposits
- **Sulphur condenser tubes** — periodic external cleaning during outages
- **Acid-gas line dust traps** — particulate from upstream

## Sonic-horn duty

[Sonic horns](/glossary/sonic-horn) on the SRU [waste-heat boiler](/glossary/waste-heat-boiler) economiser keep ammonium-salt and sulphur deposits from consolidating between scheduled maintenance windows. The high-value, continuous-operation nature of SRUs makes the avoidance of unplanned shutdowns particularly valuable.

## Related terms

- [Reformer furnace](/glossary/reformer-furnace)
- [Waste-heat boiler](/glossary/waste-heat-boiler)
- [Sonic horn](/glossary/sonic-horn)