Controlled Drying of Pine Roundwood

In this study, peeled southern pine bolts were dried under controlled conditions, such as are possible in forced air driers or in dry kilns. A compact stacking method was used which minimized the void spaces between bolts and led to high air velocities (600 to 700 feet per minute). Two temperatures (120?F. and 190?F.) were tested without controlling the relative humidity. Two bolt lengths were used (18 inches and 55 inches), with bolt diameters ranging from 4 to 13 inches. Ten of the larger bolts were halved lengthwise to determine the effect of splitting on drying time reduction. Freshly cut bolts, ranging in initial moisture content from 90 to 180 percent, were dried until the mean moisture content for the bolts was reduced to 25 percent for each size class. After drying was completed, two equalization methods were used to restore moisture content uniformity within the bolts: 1) 1-hour cold water soaking; and, 2) steaming for 2 to 5 days. Depending on bolt diameter, bolt length, and temperature, drying time ranged from 3 to 16 days. Halving the bolts lengthwise cut 3 to 4 days off the equivalent roundwood drying time. Bolt length did not influence drying time as much as the temperatures used. In equalizing within-bolt moisture con tent, soaking provided a greater gross bolt moisture pickup, but steaming did a more uniform job of moisture pickup.

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