Factors Affecting Sawmill Residue Chip Quality, 1991 Pulping Conference Proceedings

A study was conducted to determine the effects of residue type, chipper speed, knife angle, and wood temperature on loblolly pine sawmill residue chip quality. A 152-cm, six-knife horizontal infeed, top-discharge chipper restored to factory specification was used as the test machine. Chips were recovered after being blown 4m vertically through a cyclone settler onto the screen pack with the top screen blinded. Oversize chips were not re-chipped. Material types included cants as controls, slabs, edgings, and trim blocks. Chipper rim speeds included the manufacturer’s recommended 4,164 meters per minute along with 3,330 meters per minute and 2,498 meters per minute achieved by the drift-down method. Knife angles included 30,31,32, and 33 0 straight grinds. Wood temperatures ranged from ambient temperatures of over 21°C through chilled (approximately t 2 O C) and frozen (-4 O C). The chip distributions from chipping slabs and edgings were not significantly different from those of the cants. Less than 50 percent of the weight of trim blocks was returned as acceptable chips in most trials. Reducing chipper speed resulted in a major reduction in pin chips and fines. Knife angles had less effect on chip size distributions than any of the other variables tested. The percentage of pin chips and fines was greater for chilled and frozen wood than for wood at ambient summer temperature.