At the end of this module, you will be able to:
- Identify safety hazards and safety guidelines associated with refiners
- Differentiate between low consistency and high consistency refining
- Identify and describe the equipment used in high consistency refiner systems
- Describe the design and operation of high consistency refiners
- Identify the sheet properties affected by high consistency refining
The following key questions are answered in this module:
How does high consistency refining differ from low consistency refining?
Low consistency refining increases the fibers' surface area available for bonding and several sheet strength properties. However, it reduces freeness and drainage. High consistency refining creates microcompressed and curly fibers, which improve sheet stretch and porosity, as well as some strength properties, like tear. It also reduces freeness and drainage, but to a lesser degree.
On what paper or board grades is high consistency refining used?
High consistency refining is well-suited to the production of kraft sack papers and other similar grades which must withstand high levels of strain during use.
At what consistency is high consistency refining performed?
High consistency refining is performed above 20% consistency, and consistencies between 30 and 40% are quite common.
How is 30 to 40% consistency stock transported to the high consistency refiners?
Screw conveyors are typically used to move high consistency stock from the presses to the refiners.
What happens to the filtrate that is removed from the stock by the presses that are positioned ahead of high consistency refiners?
This filtrate can be used to redilute the stock after it has been refined, before it is metered back into the papermaking process.
Below is a transcript of the video sample provided for this module:
High consistency refiners are typically disc type refiners, which utilize one rotating disc or rotor and one stationary disc or stator. The process sides of the discs are fitted with metal refining plates which are covered with a variety of raised bars. A screw type or ribbon type feeder delivers a constant flow of high consistency stock into the center of the space between the two discs. Refining takes place as the stock travels outward between the bars of opposite discs as the rotor rotates. The rotor is driven by a large motor and a smaller motor is used to adjust the gap between the plates. This adjustment is called opening and closing the plates.
Use the additional resources and links below to learn more about this topic: