At the end of this module, you will be able to:
- Describe the effects of refining on wood fibers
- Identify safety hazards and safety guidelines associated with refiners
- State the objectives of refining
- Identify the different refiner types
- Identify and describe the key components of a refiner
- Describe the operation of refiners
- List the typical control strategies
- Identify the effects of refining on sheet properties
- Explain the effects of over-refining
The following key questions are answered in this module:
What is the purpose of paper and board machine refining?
The main purpose of most paper and board machine refining is to improve certain sheet properties, including strength and density-related properties.
What happens to the 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.
Why 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.
Why do broke fibers and recycled fibers not respond as well to refining?
Broke and recycled fibers have already been refined and contain some shorter fibers, which don't respond as well to refining. Also, they have been previously dried, so don't absorb water as readily, making them more difficult to refine.
Below is a transcript of the video sample provided for this module:
All paper and board machine refiners are hydraulic machines with high-speed rotating elements. They are similar to centrifugal pumps in that fluid friction and centrifugal forces have a considerable influence on their operation. Each refiner consists of one or more sets of rotating or rotor plates opposite one or more sets of stationary or stator plates. These plates are positioned very close together. As stick-stock is pumped between the plates. Bars and the plate surfaces treat the surface of the fibers, in order to expose greater amounts of surface area suitable for bonding. Besides fibers selection and pulping method, refining offers the best opportunity for paper makers to enhance the quality of the end product.
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