High Density Pulp Cleaners

Shibli Engineers company 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 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. Features and Benefits  APPLICATIONS 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 : With increased emphasis on environmental protection and recycling, many new recycled paper mills have been built. 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 includes baling wire, packing bands, box staples, paper staples, broken glass, gravel, and sand. These contaminants may represent a significant amount of the feed. After the pulper, Krebs intermittent rejects cleaners are used to remove these
		Working High-density cleaning, which takes place after pulping, is the second step in a deinking system. High-density cleaners are specifically designed to remove high-and medium-specific-gravity contaminants from stock slurries with consistencies that usually range between 2.5 and 5%. Contaminants such as rocks, nuts, bolts, nails, paper clips, junk metal, high density particals and other heavy debris are trapped by the cleaner and retained in a rejects chamber. The chamber is then dumped through a valve, which is controlled by a sequence timer, into a dumpster or sediment separator. Using a high-density cleaner to remove contaminants that have passed through the pulper extraction plates or screening drums protects the downstream equipment from damage. These cleaners are fabricated from many types of material; however, stainless steel is most commonly used for the body. Some cleaners are designed with replaceable internal liners, which are made of various materials including epoxy or ceramics, to maximize cleaning efficiency and to prolong wear life by combating conditions where abrasion, corrosion, or high temperature exists. These cleaners are also designed with replaceable internal orifices to provide operating flexibility in the field. They also incorporate heavy-duty reject collection chambers and automatic reject discharge systems designed to operate under high pressure and to withstand the increased abrasion caused by today's contaminated recycled paper. High-density cleaners are available in sizes ranging from 6 to 16 in. in diameter, with capacities ranging from 35 to 2,000 lpm. This capacity range corresponds to a pressure drop from 6 to 30 psi across the cleaner. High-density cleaners can be categorized as either free vortex or rotor-induced, depending on the means used to create a vortex. FREE VORTEX CLEANERS. In a free vortex cleaner, wastepaper from the pulper is pumped under pressure into the inlet chamber, and the tangential entry design of the cleaner inlet allows it to convert the kinetic energy of the pulp slurry into a rotating mass within the cleaner . As the slurry rotates inside the cleaner, shear planes are caused by acceleration of the pulp slurry as it travels from the outside diameter of the cleaner radially inward toward the axis of rotation, where it is then diverted upward through the vortex finder out of the top of the cleaner. These shear planes tend to strip high-density particles from the pulp fiber. In addition to the shear planes, the rotational motion results in extremely high centrifugal forces that push high-specific-gravity particles to the outside of the cleaner wall where they migrate down into the heavy reject collection chamber. Rejects are then discharged intermittently by an automatic discharge system.