Schedule modification of drying rate to decrease the drying time of juvenile tectona grandis l. Wood

The authors investigated modifying schedules to increase the drying rate (DR) and reduce the total drying time for Tectona grandis L. wood from juvenile plantations. The initial MC ranged from 92% to 115%. A conventional teak schedule was used as the basis for developing two faster drying schedules and for comparison. The modifications resulted in a reduction in drying time from 125 to 105 h, a 16% energy savings with less than 1% MC variation in dried lumber; however, this change caused a slight decrease in wood quality. The relationship between the DR, the lumber’s MC, and drying time was modeled. As expected, the dry-bulb temperature and wet-bulb depression had the greatest influence on DR; however, an inflection point was found in the relationship between DR and MC at a 40% MC for all three drying schedules. The inflection point indicates when diffusion becomes the primary driving force of moisture movement, thereby limiting the DR, and indicating when the kiln conditions should be accelerated to minimize the total drying time. DR_hour should remain more than 0.5%/h (high value for tropical species) for the first 72 h (3 da), until the lumber reaches 40% MC and then be lowered to 0.5%/h until drying is completed.