Pulp and paper
Water wash (recovery boiler)
Also known as recovery boiler water wash, water washing, hydroblasting (recovery).
A water wash on a recovery boiler is the offline cleaning campaign performed during a full boiler shutdown, using high-pressure water lances to remove consolidated deposits from superheater, generating-bank and economiser tubes that in-service sonic horns and chill-and-blow could not remove.
Frequency
Mills target intervals of 18–36 months between water-wash campaigns, depending on:
- Boiler design and age
- Black-liquor solids loading
- Effectiveness of continuous cleaning (sonic horns, IK sootblowers)
- BLRBAC inspection programme
Cost of a water wash
A water-wash campaign typically takes 5–10 days of full boiler shutdown — multi-million-dollar lost production — plus the labour and consumables of the cleaning itself. Every additional month between water-washes is therefore worth substantial money to the mill operator.
How sonic horns extend the water-wash interval
Continuous sonic-horn cleaning during operation prevents the deepest, hardest deposits from forming. Plants commonly report water-wash interval extension from 18 months to 24+ months after retrofitting horns to a previously sootblower-only recovery boiler.
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.
- Chill-and-blowChill-and-blow is the thermal-shock cleaning campaign on a recovery-boiler superheater. The boiler is rapidly cooled to crack deposits; intense sootblowing then dislodges them.
- 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.
- Sonic hornA sonic horn is a pneumatically-driven low-frequency sound emitter (typically 60–400 Hz at 140–180 dB SPL) used to dislodge particulate fouling from boilers, ESPs, baghouses and process vessels.