Introduction
Liquor consistency suffers when there are undetected changes in the lignin content in black liquor. Lignin content is a measure of digester performance and also critically impacts the viscosity and thermal properties of the liquor, with severe implications for evaporator and boiler operations. Mills typically measure lignin content values from isolated liquor tests, sometimes using an external lab. There may be hours or even days between samples being taken and numbers determined.
Impact
Evaporator and recovery boiler optimizations are made using these numbers but without real-time data, money is lost when lignin content changes and operator corrections are not updated. Many mills simply lack the data to make process control decisions on this today.
Lignin content varies significantly for multiple reasons including green liquor inconsistency, process conditions, and distribution of digester residence times, and will vary even more when wood species change.
Measuring Dissolved Lignin
The solution to this challenge is Keit’s revolutionary IRmadillo process analyzer. Recent laboratory tests within Keit have shown that the IRmadillo FT-IR analyzer can add dissolved lignin to the growing list of materials it can simultaneously monitor in real-time in pulp mill processes.
The plot below shows the calibration curve obtained plotting measured values against those predicted by the IRmadillo based on offline lab measurements.
Figure 1: The correlation between measured and IRmadillo predictions of dissolved lignin content in weak black liquor. RMSECV = 1.51 g/L
A single IRmadillo analyzer can also simultaneously and accurately monitor a wide range of additional chemicals and properties, often at the mg/kg or ppm level:
- Total Dissolved Solids
- REA
- Crude Tall Oil
- Carbonate
- Oxalate
- Thiosulfate
- Sulfate
- Sodium
- Density
Conclusion
Real-time analysis with IRmadillo affords a step change in efficiency, through control of black liquor properties and efficient and optimal operation of digesters, evaporators, and recovery boilers. Revolutionize your mill’s operations with savings and efficiency increases from up-to-the-minute insights into your processes.
