|
Main functions and requirements of broke handling
The main demands for paper and board production are the cleanliness of the end product and the runability of the machine. Therefore the stock fed into the machine is cleaned in several positions before it enters the headbox. The impurities cause web breaks on the machine, clog wires and felts, impair the quality of the end product and cause problems in coating. In addition, coarse impurities wear the machine parts.
The impurities in stock originate either from raw material or manufacturing process. The most common impurities in raw material are bark, shives and resin. The process produces slime and stock accumulations loosen from tank surfaces, piping and equipment. Different amounts of material outside the manufacturing process enter the process with broke; the most detrimental is plastic. Furthermore, material loosened from the manufacturing equipment may occasionally enter the process, as e.g. wire and felt hairs, rust and pieces of seals.
The main task of a broke handling system is to handle the broke generated by the machine and the finishing into a suitable raw material for reuse in paper and board manufacture. The target is that the broke does not cause any problems with paper machine run ability or paper quality. The rejected amount of fiber and filler from the broke system will be minimized.
Main sub-processes
- Pulping
- Storage
- Thickening
- Screening
- Deflaking
- Broke dosing
|
