Medium thickness screening system
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Pulp mills profit from precision screening.
Our medium thickness screening systems have been specifically designed for pulp mills, as they require wood chips of relatively uniform size to maintain the optimum function of their digester and the overall yield of the mill. Our screens ensure this uniformity.
The system is based on primary disc thickness screens that pass acceptably thin chips for onward processing, while rejecting and re-processing chips that are too thick in a Bruks’ chip optimizer. Once processed through the optimizer, the wood chips pass directly to the ‘accepts belt’ as they are now equivalent in digesting performance to the smaller chips.
Medium thickness screening systems are free standing on a robust, integral steel frame. All chutes and components are enclosed for environmentally-friendly operations that keep dust emissions to a minimum. The chutes and screens can be connected to an air collection system for dust-tight processing.
Single-line chip processing capacities are available from in rated capacities from 200 to over 1,000 m3/hour.
Unique design features
Our medium thickness screening system has some unique design features including screw screens that are located below the disc screen. These perform the important function of separating wood fines, which are high in bark and grit, and helping to control the quantity of pin chips. Pin chips are problematic in the digester as their thin, needle-like shape can block liquor extraction screens, which can negatively impact pulp mill productivity.
The design and arrangement of screening components ensures the highest possible retention of good fiber under all conditions, while eliminating dirt, grit, and fines.
Coping with the climate
The ability to operate under all conditions is essential for maintaining peak operational performance. Cold weather wood processing can have a negative impact on pulp mill yields.
We cannot change the weather, but we can mitigate some of its effects. When frozen wood is chipped it has a greater tendency to splinter, which increases the production of fines and pin chips. The adjustable and adaptive fines and pin screening method that we use makes Bruks’ medium thickness screening approach a true four-season screening system, significantly reducing the negative impact that pin chips have on the pulp digester during cold weather operations.