Glossary
Pulp and paper
Fume (recovery boiler)
Also known as sodium fume, recovery boiler fume.
Fume in recovery-boiler vocabulary refers to the very fine sub-micron sodium-sulphate particulate that forms by vapour-phase condensation in the upper furnace as gas cools from the combustion zone. Distinct from larger carry-over particles, fume is too fine to settle by gravity and remains entrained until captured by the downstream ESP.
Where fume deposits
Fume's small particle size means it follows gas streamlines closely but still deposits where flow eddies allow contact with cooler surfaces:
- Superheater and generating-bank tubes — alongside larger carry-over particles
- Economiser tubes — fume-rich bottoming deposits
- ESP collecting plates — fine cake build-up
Cleaning
Sonic horns on the recovery-boiler convective pass and ESP address both fume and coarser carry-over deposits in the same firing pattern.
Related terms
Related terms
- Recovery boilerA recovery boiler burns kraft black liquor to generate steam, electrical power and recovered pulping chemicals. Iconic application for sonic horns on superheater cleaning.
- Carry-over (recovery boiler)Carry-over is the entrained molten smelt droplets and ash particles carried upward in recovery-boiler flue gas. The dominant fouling agent on superheater and generating-bank tubes.
- SuperheaterA superheater is a tube bank that raises steam temperature beyond the saturation point using flue-gas heat. Sticky alkali ash and slag deposits are the dominant fouling concerns.
- Electrostatic precipitatorAn ESP removes particulate from flue gas by charging dust and collecting it on plate electrodes. Sonic horns are widely used to dislodge ash from plates and to keep hoppers from bridging.