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 Pulp & Paper
Krebs supplies pulp cleaners for the pulp and paper industry to remove dense contaminants from paper pulp. These units fall into two basic categories: continuous rejects cleaners that are usually installed in multiple stages to remove fine sand from paper pulp and intermittent rejects cleaners that are designed to collect larger reject material and to discharge it intermittently to minimize fiber loss.
The basis for both types of pulp cleaners is the Krebs Cyclone. Continuous rejects cleaners are hydrocyclones with conventional apexes that may be connected to a rejects header or rejects trough if multiple cleaners are being operated in parallel. Intermittent rejects cleaners are hydrocyclones with a grit pot and isolation valves added. Intermittent rejects cleaners discharge the contents of the grit pot periodically without shutting down the cleaner.
The applications for centrifugal cleaners in the pulp and paper industry can be divided into two major categories: chemical (or virgin) pulp cleaning and recycled fiber cleaning.
Chemical Pulp
Softwood and hardwood species are chemically digested to produce paper pulp. This is mostly Kraft (sulfate) pulp and intermittent rejects cleaners can be used to protect secondary knotters from rocks and gravel or they may be installed in various positions to protect screening equipment. Continuous rejects cleaners in 2 or 3 stages are sometimes used for fine sand removal in the screen room.
Recycled Fiber
Many new recycling paper mills have been built because of an increased emphasis on environmental protection and recycling. Feed stocks to these mills can vary from old corrugated cardboard (OCC), old newsprint (ONP), mixed office waste (MOW), ledger paper (LED) to magazines or computer paper. The debris contained in these feed stocks include baling wire, packing bands, box staples, paper staples, broken glass, gravel and sand. These contaminants may represent a significant amount of the feed. Krebs intermittent rejects cleaners are used after the pulper to remove these contaminants prior to screening which greatly increases the wear life of the screen baskets. This is a demanding application and it requires a heavy duty cleaner and valves.
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