---
title: "Superheater"
description: "A superheater is a tube bank in a boiler's convective pass that raises the steam temperature beyond its saturation point using residual heat from the flue gas. Most utility boilers have at least two superheater stages: a primary superheater (cooler gas) and a secondary or finishing superheater (closest to the furnace, hottest gas)."
canonical_url: "https://sylio.co/glossary/superheater"
last_updated: "2026-06-28T02:29:26.509Z"
---

A **superheater** is a tube bank in a boiler's [convective pass](/glossary/convective-pass-backpass) that raises the steam temperature beyond its saturation point using residual heat from the flue gas. Most utility boilers have at least two superheater stages: a primary superheater (cooler gas) and a secondary or finishing superheater (closest to the furnace, hottest gas).

## Fouling

- **Slagging** on the finishing superheater — semi-molten ash from the [furnace](/glossary/furnace) deposits on the hottest tubes
- **Bonded ash** on the primary superheater — drier deposits that sinter under sustained temperature
- **Sodium / potassium-rich deposits** on [biomass](/glossary/waste-to-energy), [WtE](/glossary/waste-to-energy) and [recovery boilers](/glossary/recovery-boiler) — sticky, low-melting, aggressive

## Cleaning

Steam [sootblowers](/glossary/steam-sootblower) and [sonic horns](/glossary/sonic-horn) work together:

- Sootblowers attack hard slag on the finishing superheater
- Sonic horns ([60–125 Hz](/glossary/low-frequency-acoustic-cleaner)) keep dry ash from consolidating on the primary superheater and convective superheater
- [Infrasonic cleaners](/glossary/infrasonic-cleaner) below 30 Hz are used on deep [recovery-boiler](/glossary/recovery-boiler) superheater cavities

The combination extends the interval between major water-washes and reduces steam-attemperation requirements that mask deteriorating heat transfer.

## Related terms

- [Boiler](/glossary/boiler)
- [Convective pass / backpass](/glossary/convective-pass-backpass)
- [Reheater](/glossary/reheater)
- [Slagging](/glossary/slagging)
- [Sonic horn](/glossary/sonic-horn)
- [Sonic sootblower](/glossary/sonic-sootblower)