Overview
Pulp & paper is a heritage industry for density / consistency measurement. From wood preparation, digesting, washing, bleaching to the paper machine, pulp consistency drives fibre dispersion, chemical efficiency and machine stability. Three regimes coexist — LC (1-6%), MC (10-15%) and HC (>20%) — each demanding its own measurement principle. Kraft mills also monitor black-liquor density at evaporator inlets, white-liquor caustic concentration in recovery, and green-liquor concentration.
Process challenges
- Fibres clog and wrap around intrusive sensors
- Black liquor is hot (>100°C), alkaline and scale-prone — demands rugged wetted parts
- Dilution water on the paper machine must respond in milliseconds to hold basis weight
- Cs-137 gauge retirement is accelerating under tightening environmental rules
Recommended solutions
| Measurement point | Principle | Models |
|---|---|---|
| LC pulp (1-6%) | Microwave / ultrasonic sound velocity | PS7600 / PS7020 |
| MC pulp (10-15%) | Ultrasonic acoustic impedance | PS7000 |
| Black liquor (evaporator inlet) | Ultrasonic + T/P compensation | PS7000 |
| White liquor caustic concentration | Ultrasonic sound velocity | PS7020 |
| Digester caustic feed | Ultrasonic / differential pressure | PS7000 / PS7300 |