Frövi, Sweden

Locations: Frövi, Sweden
Plant information: Packaging board manufacturing, Kraft process
Capacity: 1200 tons DS/day
Boiler manufacturer: Kvaerner/Metso
Boiler type: Black liquor recovery boiler
Dust: Sodium sulfate, pH 10.5-11.5
Installation year/s: 2007
Infrasound generator: APX2000
Cleaning area: Duct between generating bank and economizer

Dust accumulations and resultant plugging of the duct between the generating bank and the economizer constituted a bottleneck in the process and limited the production rate of the boiler. The duct was kept clean by a combination of four steam soot blowers, online water washing with manually operated spray nozzles in the duct, and offline water washing using the soot blowers. The soot blowers were regularly operated as part of the overall boiler soot-blowing program. In addition, every other day the duct was water washed while the boiler continued operating. During scheduled outages every sixth week, the duct was water washed more thoroughly.

Water washing corroded the duct, requiring replacement of damaged sections. A complete replacement of the duct was made in 2003. Despite the cleaning efforts outlined above, the differential pressure across the duct would increase uncontrollably and the washing process would only temporarily reduce the differential pressure. As a result, ID fans would typically operate at or near their maximum capacity.

Results with infrasound cleaning:

  • All plugging and fouling issues have been eliminated
  • Water washing has been completely eliminated with attendant elimination of water consumption, man-hours for cleaning, and corrosion of ductwork.
  • Two steam soot blowers have been shut down. The other two are at reduced operating levels
  • Duct differential pressure is low and stable
  • ID fan speed is low and stable
  • Pulp production records have been achieved
  • The consensus of operating personnel is that the overall boiler operation has significantly improved
  • The return on investment has been less than six months