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Industry Standards and Best Practices
Refining is one of the critical process steps in engineering the structure of tissue as it has a major influence on fiber quality. Refining mechanically alters the fibers by brushing, hydrating, and cutting them. These actions increase the flexibility and total surface area of the fibers. The result is more area available for bonding which directly affects sheet strength, formation, and many other properties. This course will describe refining actions as they relate to disc refiners. Other refiner types will have very similar actions and results.
Double disc refiners contain a double-sided disc that rotates between two stationary discs.
Refining increases strength, but over-refining can have a negative impact on desirable tissue attributes, such as bulk, absorbency, and softness.
External fibrillation is the delamination of the fiber surfaces. This increases the total surface area available for bonding.
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.
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