The Effect of Seasonal Variation in Wood Moisture Content on Chip Size and Kraft Pulping

摘要

Wood moisture cycles naturally though the year as transpiration takes place.In North America,we see moisture content of wood drop rapidly as the trees break dormancy in the spring.Transpirational activities in the trees are at a peak at this time of the year.As we enter summer and fall,transpirational activities decrease and wood moisture increases until it climbs back to a maximum in the winter months.When the moisture content of the wood is high,the wood will be weaker.Thus,less cleaving force is required to shear the chips off as a chipper knife passes through the log.This means that when wood moisture is higher,thinner chips will be formed.The opposite will be true when the wood is drier,i.e.thicker chips will be produced.In order to provide the pulp mill with a constant distribution of chip thicknesses all year round,adjustments must be made to the chipper.Chipper adjustment options are discussed.