---
title: "BFB boiler (bubbling fluidised bed)"
description: "A bubbling fluidised-bed (BFB) boiler burns fuel in a bed of inert solids fluidised by an upward gas flow slow enough that the bed surface bubbles like boiling water but particles do not entrain into the flue gas. Compared with CFB, BFB uses lower fluidisation velocity, no external cyclone, and a simpler bed-management regime."
canonical_url: "https://sylio.co/glossary/bfb-boiler"
last_updated: "2026-06-28T02:29:25.881Z"
---

A **bubbling fluidised-bed (BFB) boiler** burns fuel in a bed of inert solids fluidised by an upward gas flow slow enough that the bed surface bubbles like boiling water but particles do not entrain into the flue gas. Compared with [CFB](/glossary/cfb-boiler), BFB uses lower fluidisation velocity, no external cyclone, and a simpler bed-management regime.

## Where BFB is used

- Wet biomass and forest residues
- Sewage-sludge incineration
- [Hog-fuel](/glossary/hog-fuel-boiler-bark-boiler) and bark boilers at pulp mills
- Small-to-mid capacity district-heating and process-steam duty
- High-moisture, low-calorific fuels generally

## Fouling

The fouling pattern resembles a CFB but with less cyclone deposition. The convective pass, [economiser](/glossary/economiser) and [air heater](/glossary/air-heater) accumulate fine ash; the [waterwall](/glossary/waterwall) above the bed can experience alkali-rich slagging on agricultural-residue and straw fuels. [Sonic horns](/glossary/sonic-horn) on the convective pass and air-heater cold end are the typical cleaning fit.

## Related terms

- [Boiler](/glossary/boiler)
- [CFB boiler](/glossary/cfb-boiler)
- [Hog-fuel boiler / bark boiler](/glossary/hog-fuel-boiler-bark-boiler)