Key Questions
The following key questions are answered in this module:
What is the purpose of refining?
The primary objective of refining is to develop sheet strength.
What happens to fibers during refining?
The fiber cell walls are delaminated, allowing them to absorb more water and increasing their flexibility. External fibrillation of the fiber surfaces increases the surface area available for bonding, and some fiber cutting and creation of fines takes place.
What is it important to keep the flow rate through a refiner steady?
Flow rate determines the amount of time the fibers are available for treatment in the refiner. Low flow can lead to fiber cutting, fiber channeling in the plate grooves, and poor strength development. High flow can cause plugging and poor fiber development.
What happens if fibers are over-refined?
Over-refining causes fiber cutting, fines generation, and poor strength, with negatively affects runnability, drainage, drying demands, and production rate.
How is refining controlled?
Control strategies include power control, net specific energy control, and freeness control.