Discrepancies in High Yield Pulp Mass Balance Calculations across Multi Ply Board Mills
High yield pulp mass balances fail when mills exclude white water solubles and moisture variation, exposing buyers to chain of custody audit liabilities.
Microwave Consistency
Electromagnetic Slurry Analysis
Automated control systems in paper mills require non-contact measurements of the concentration of fibres suspended in water. The method known as microwave consistency utilizes the speed of high frequency radio waves through the pulp slurry to calculate this density. This provides a real-time output unaffected by mineral fillers.
Measurement Technology Principle
Sensors based on this technology measure the phase shift and amplitude change of a microwave signal as it travels across a pipe containing pulp. Because water has a much higher dielectric constant than wood fibre, the transit time of the signal changes proportionally with the fibre concentration. The calculated microwave consistency is then transmitted to the dilution control valves to adjust stock flow.
Unlike shear force transmitters, this electromagnetic method does not require mechanical contact with the stock, which eliminates the risk of fiber dragging or sensor fouling.
Industrial Application Range
Processing recycled pulp streams and mixed furnishes require durable measurement methods where mechanical sensors fail. In recycled paper mills, the presence of plastic contaminants or stickies does not interfere with the microwave consistency readings. This stability allows the mill to maintain uniform stock dilution and consistent sheet weight even when processing low grade waste paper.
The technology requires professional installation to avoid reflections from metal pipe walls, but once calibrated it provides reliable feedback for the primary stock preparation systems.