---
title: "Waste-heat boiler (WHB)"
description: "A waste-heat boiler (WHB) is a tube-bundle steam generator that recovers heat from a process gas stream — typically Claus SRU exhaust, sulphuric-acid plant SO₃ converter outlet, BOF off-gas, or similar process-side energy source — to generate steam for site use. Distinct from a heat-recovery steam generator (HRSG), which serves gas-turbine exhaust."
canonical_url: "https://sylio.co/glossary/waste-heat-boiler"
last_updated: "2026-06-28T02:29:41.060Z"
---

A **waste-heat boiler (WHB)** is a tube-bundle steam generator that recovers heat from a process gas stream — typically [Claus SRU](/glossary/claus-unit-sulphur-recovery-unit) exhaust, sulphuric-acid plant SO₃ converter outlet, [BOF](/glossary/basic-oxygen-furnace) off-gas, or similar process-side energy source — to generate steam for site use. Distinct from a [heat-recovery steam generator (HRSG)](/glossary/heat-recovery-steam-generator), which serves gas-turbine exhaust.

## Fouling characteristics

The fouling pattern depends on the source process:

- **Claus SRU WHB** — sulphur and ammonium-salt deposits on the tube sheet and economiser
- **Sulphuric-acid plant WHB** — sulphate and sulphuric-acid mist below the dew point
- **BOF WHB** — fine iron-oxide dust
- **Metallurgical off-gas WHB** — variable, depends on metal being processed

## Sonic-horn duty

[Sonic horns](/glossary/sonic-horn) on WHB economiser sections and downstream dust hoppers are common where the process side produces particulate-laden gas. Particularly valuable on SRU WHBs where ammonium-salt deposits consolidate quickly and resist conventional cleaning.

## Related terms

- [Claus unit / sulphur recovery unit (SRU)](/glossary/claus-unit-sulphur-recovery-unit)
- [Heat Recovery Steam Generator (HRSG)](/glossary/heat-recovery-steam-generator)
- [Economiser](/glossary/economiser)
- [Sonic horn](/glossary/sonic-horn)