Pulp and paper
Chill-and-blow
Also known as chill and blow, C&B, thermal-shock cleaning.
Chill-and-blow is the periodic thermal-shock cleaning campaign performed on kraft recovery-boiler superheaters when in-service cleaning is no longer sufficient. The boiler load is rapidly reduced; the superheater tubes cool quickly; the temperature differential between the cooled tubes and the consolidated deposit cracks the deposit; intense sootblowing then dislodges the cracked deposit.
Why it matters operationally
A chill-and-blow campaign typically interrupts the boiler at full load for several hours and may require a brief mill production cutback. Mills target intervals of 12–18 months between chill-and-blow events; each additional week of run time defers a chill event and improves the mill's bottom line.
Continuous cleaning to extend the interval
Sonic horns and infrasonic cleaners installed on the superheater extend the chill-and-blow interval substantially by preventing deposits from consolidating to the point where chill-and-blow is required. This is the headline operating-cost argument for acoustic-cleaning installation on recovery boilers.
Distinguishing from water wash
Water wash is the more aggressive offline cleaning during a full boiler shutdown, where high-pressure water removes baked-on deposits that even chill-and-blow could not address.
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.
- 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.
- Water wash (recovery boiler)A water wash is the offline cleaning campaign performed during recovery-boiler shutdowns, using high-pressure water to remove deposits that in-service cleaning cannot reach.
- 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.