Near Infrared Optical Sensing Protocols for Wet End Pulp Slurry Verification
Inline NIR transflectance sensors stabilize wet end pulp slurry consistency within +/- 0.3 percent, cutting fiber giveaway and dryer steam consumption.
Wet End Slurry
Fiber Suspension
Highly diluted mixture of water, pulp fibres, and mineral fillers represents the starting material that is formed into a continuous sheet of paper. This mixture, known as wet end slurry, has a very low fibre concentration to allow the fibres to disperse uniformly on the forming wire. It must be carefully prepared in the stock approach system to ensure consistent sheet properties.
The chemical balance of this mixture determines the efficiency of the paper machine.
Chemistry Regulation
Monitoring the pH and electrical conductivity of the suspension prevents the accumulation of dissolved organic materials. If the chemical additives in the wet end slurry are not balanced, the fibres can clump together or the retention of fillers can drop, leading to poor paper quality. Operators use drainage aids and polymers to stabilize the suspension and improve water release during sheet forming.
Flow Management
Designing the stock piping to maintain a high velocity prevents fibres from settling out of the suspension before it reaches the headbox. Turbulence must be controlled within the wet end slurry to avoid the formation of large flocs that would create a blotchy appearance in the finished paper sheet. When the slurry flows onto the forming wire, the water must drain away rapidly and evenly.
Precise control of the pump speed and dilution water flow maintains a constant flow rate and consistency. This stability is the primary requirement for achieving a uniform sheet weight across the entire width of the machine.