Cutter shredder

Size reduction uses either hammer mills or blade cutters (shredders). Hammer mills are likely to break glass into finer sizes maldng it hard to separate. Better results may be obtained in a flowsheet where size reduction follows separation (Savage, Seminar on the Apphcation... 

There are basically two types of tire shredding equipment in conunercial use, the solid cutter shredder and the replaceable cutter tire shredder [18,19]. Both of these machines shear a whole tire to produce a chip with a fixed size in one dimension, but to control the oth chip dimension, additicmal passes through the chipper may be required. 

Figure 6.5. Schematic of solid cutter shredder shearing blades...

The CST treats nonprocess waste and dunnage to a 5X decontamination level. Shredded wood pallets, spent activated carbon from the HVAC beds, and shredded plastic from DPE suits are fed to the CST. Wood and DPE suit material are size-reduced by a process that has two four-shaft shredders, one for wood and one for DPE suit material. The shredder for wood has a cutting chamber 44 inches wide by 40 inches long. The shafts and cutters reverse upon amperage overload to minimize januning. A similar but smaller shredder is used to size-reduce DPE suit material. 

After debaling, the material passes through initial size reduction units to separation and selection operations. Most size reduction tasks can be performed by the following machines shredder, cutter or guillotine, screw shredder, and granulator. 

The material is fed manually in a trough or on an open conveyor to the guillotine. The latter operates as opposed to the shredder, on a stroke principle. A cutter, usually hydraulically operated, is lowered from above to cut the material in slices of the desired thickness. The complete cutting process including the material feed is best operated a programmed control. 

Fibrous nature. Materials of a fibrous nature are a special case and must be comminuted in shredders or cutters which are based on the hammer mill design. 

The two main disadvantages of the solid cuttm shredder are that it was not specifically designed for tires and thus tends to tear the tire rather than shear or cut it. and sectmdly the sharpness of the cutter edge tends to deteriorate rapidly. This can be overcome with the use of harder steels however they are more costly. 

The second type of tire chipper is the replaceable cutter tire shredder. This is a low-speed shear shredder specifically designed for tires. The principle cutting feature is shown in Hgure 6.6. Note the addition of star-shaped feed rolls that force the individual tires, one at a tinK, into the cutting zone. As the tires are fed into the cutting zone, the cutters engage them with a true shearing action. 

Figure 6.6. Schematic of replaceable cutter tire shredder system...

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