CO2 Laser Incised Teak and Mahogany Lumber Dried by Microwave and Steam Injection

摘要

The aim of this study was to investigate the application of microwave and steam injection drying on CO2 laser incised teak (Tectona grandis) and mahogany (Swietenia mahagoni) lumber. The specimens were teak and mahogany lumber with dimensions of 60 by 120 by 600 mm. Three incising densities, 0, 1,250, and 2,500 holes per m(2), were applied to the drying specimens. The drying process was carried out by a combination of microwave and steam injection drying. Microwave irradiation had a power of 3 kW at a frequency of 2.45 GHz, while steam injection drying was done by injecting superheated steam at 105 degrees C to 110 degrees C through a perforated plate at 110 degrees C to 120 degrees C. Drying rate, moisture content (MC) distribution, and checks were observed to evaluate the quality of the drying process. The results indicate that microwave heating and steam injection drying could successfully dry incised teak and mahogany lumber. The highest drying rate was achieved in the specimens with an incising density of 2,500 holes per m(2). Interestingly, reducing the MC of teak from 46 to 20 percent required only 20 hours, while lowering the MC of mahogany from 60 to 20 percent took only 24 hours, without the formation of surface and internal checks. Laser incising, microwave heating, and the setting temperature of steam injection drying contributed considerably in creating a more uniform moisture distribution in teak and mahogany lumber, which significantly reduced surface and internal check formation.