Recovery Boiler

Proven FT-NIR application for recovery boiler and smelt dissolving tank optimization


Recovery Boiler

Recovery Boiler Challenges
Optimization of the recovery boiler in a Kraft mill has been an ongoing challenge for the pulp industry due to the lack of an online sensor for measuring the concentration of key green liquor parameters, such as TTA, for control. Traditional online techniques (i.e., density, conductivity, differential pressure, and bubble tubes) only infer key measurements and suffer from drifting due to probe scaling. Online titrators have not yet been applied to raw green liquor measurements, as the presence of solids reduces the accuracy of volume metering.

FITNIR Solution
FITNIR Analyzers provides more reliable, accurate, and true concentrations of unclarified and clarified green liquor chemical compositions in the recovery boiler and smelt dissolving tank. Our analyzers enable superior TTA control, operation at the highest TTA target, as well as measurements of deadload content all necessary for optimal efficiency.

Properties Measured

FITNIR’s Recovery Boiler analyzer application measures Unclarified and Clarified Green Liquor:

  • Total Titratable Alkali (TTA)
  • Effective Alkali (EA)
  • Active Alkali (AA)
  • Sodium Sulfate (Na2SO4)

  • Sodium Sulfide (Na2S)
  • Sodium Thiosulfate (Na2S2O3)
  • Sodium Carbonate (Na2CO3)
  • Reduction Efficiency (RE)


^ Click on Diagram to Enlarge

Key Benefits

  • $0.5 – $1.2M savings/year
  • 6 – 12 months ROI
  • Reduced TTA (and carbonate, EA, sulphide) variability



  • Maximized TTA target while providing true TTA target
  • Reduced deadload content (sulphate)
  • Fewer lab tests required


Project Highlights

Clearwater Paper, Lewiston Mill

Lewiston, ID


Weyerhaeuser, Grande Prairie Mill

Grande Prairie, AB, Canada

FITNIR Benchtop

Zellstoff Celgar

Castlegar, BC, Canada


Paper Excellence, Skookumchuck Pulp Inc.

Skookumchuck, BC, Canada


Mill in Eastern Canada

Eastern Canada


Get in Touch

Contact FITNIR Analyzers Inc. and we can work together to optimize your recovery boiler operations.


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