ROTOR-INDUCED CLEANERS. Rotor-induced cleaners use a motor, which is mounted on the cleaner and connected to a rotor, to mechanically create a vortex. Stock from the pulper is pumped to the cleaner's inlet. Centrifugal force is then induced--not only by the shape of the cleaner but also by the rotor. The rotor allows the cleaner to operate efficiently at various inlet consistencies and at different throughput rates. Contaminants are collected in a reject chamber at the base of the cleaner and are discharged automatically at predetermined intervals.

VARIABLES THAT AFFECT HIGH-DENSITY CLEANERS.

The following six equipment design features and operating variables affect separation efficiency and the operational life of high-density cleaners:

• Feed consistency
• Cleaner diameter
• Pressure drop
• Internal orifice size
• Reject collection chamber and automatic reject system.

Materials of construction
While high-density cleaning is being performed, all variables should be continually monitored to ensure smooth operation of the equipment.

Feed consistency
The most important variable affecting separation of high-reject material is the consistency of the feed pulp. Feed-pulp consistency has a direct effect on the viscosity of the rotating slurry in the cleaner. High viscosity is detrimental to the cleaner's ability to strip heavy reject material from the fibrous pulp. Cleaning efficiency has a direct relationship to feed consistency. Cleaning efficiency is best at lower feed consistencies and deteriorates at higher consistencies. Generally, feed consistencies vary from 2.5 to as high as 5 %, depending on the application. Cleaners in typical wastepaper applications are fed at consistencies in the 3.5% area range, since this is the consistency generally discharged from the pulper detrashing unit or dump chest.

Under these conditions, an appropriately sized, well-designed cleaner can remove metal particles the size of small paper staples, small pieces of pipe scale, bits of broken glass, and other extraneous high-specific-gravity material. At consistencies as low as 0.5 to 1.0%, cleaners can remove high-specific-gravity particles as fine as 200 mesh, which is approximately the size of beach sand. At consistencies in the 4.0% area, even smaller-diameter cleaners will only be able to remove heavy reject particles coarser than 3 mm. Some cleaners have been installed for feed consistencies as high as 5 %, but these were only used to protect downstream equipments by removing large heavy reject material such as nuts or bolts etc.