Drying of lumber

Description A tray or compartment dryer is an enclosed, insulated housing in which solids are placed upon tiers of trays in the case of particulate solids or stacked in piles or upon shelves in the case of large objects. Heat transfer may be direct from gas to sohds by circulation of large volumes of hot gas or indirect by use of heated shelves, radiator coils, or refractory wmls inside the housing. In indirect-heat units, excepting vacuum-shelf equipment, circulation of a small quantity of gas is usually necessary to sweep moisture vapor from the compartment and prevent gas saturation and condensation. Compartment units are employed for the heating and drying of lumber, ceramics, sheet materms (supported on poles), painted and metal objects, and all forms of particulate solids. 

Keey, Drying of Loose and Particulate Materials. Hemisphere, New York, 1992. Keey, Langrish, and Walker, Kiln Drying of Lumber, Springer-Verlag, Heidelberg, 2000. 

Barnes D, Admiraal L, Pike RL and Mathur VNP (1976) Continuous system for the drying of lumber with microwave energy. Forest Products Journal, 26(5) 31 -42 Barnes D (1988) Parallam a new wood product - invention and development to the pilot scale stage. In Timber a material for the future. The Marcus Wallenberg Foundation Symposium Proceedings. Falun, Sweden, 4 5-24 Barnes HM, WUhams LH and Morrell JJ (1989) Borates as wood preserving compounds the status of research in the United States. International Research Group on Wood Preservation, Document No IRG/WP/3542... 

Richardson BA (1993) Wood Preservation (2 edit). E FN SPON, London Richardson SD (1978) Appropriate operational scale in forest industries. Proceedings 8 World Forestry Conference, FAO, Rome Document FID 1E21-18 Rietz RC and Page RH (1971) Air drying of lumber a guide to industry practice. USDA, Forest Service, Agriculture Handbook No. 402... 

The rapid drying of lumber is also made use of in the furniture industry, in which precut furniture parts may be dried in minutes rather than days or weeks and the shrinkage is well controlled. Dielectrics are also used to dry the glue. Golf clubs are also dried in this manner [10,11]. 

Rosen has given pilot-scale data on pressure steam drying of lumber for 27-mm-thick, green, yellow poplar, and red oak [10]. He also made a technoeconomic study based on a number of plausible assumptions. Essentially, he showed that the capital cost of the steam dryer was about the same as that of a conventional kiln, although the drying times were reduced. 

FIN Rosen, RE Bodkin, KD Gaddis, Pressure steam drying of lumber. Forest Products Journal 33 17-23, 1983. 

These ideas can now be applied to the drying of lumber boards, which is assumed to be stress-free at the beginning. At the beginning of drying (constant drying-rate period),... 

Source Keey, R.B. et al.. The Kiln-Drying of Lumber, Springer, Berlin, Germany, 2000. 

FIGURE 40.45 A vertical cross section through a single-tracked, box kiln. (Adapted from Keey, R.B. et al., The Kiln-Drying of Lumber, Springer, Berlin, Germany, 2000.)... 

Solar drying of lumber has attractions in remote locations with favorable climates because of the free nature of the energy source. Imrd (1995) has classified solar-heated dryers into three main groups ... 

Ressel, J.B., 1994. State-of-the-art report on vacuum drying of lumber, in Proceedings of the Fourth lUFRO International Wood Drying Conference, Rotorua, New Zealand, pp. 255-262. 

The transfer of energy in the form of heat occurs in many chemical and other types of processes. Heat transfer often occurs in combination with other unit operations, such as drying of lumber or foods, alcohol distillation, burning of fuel, and evaporation. The heat transfer occurs because of a temperature difference driving force and heat flows from the high- to the low-temperature region. 

Several additional sources or methods can be considered as possibilities for naval stores production. These include by-products from solvent drying of lumber, conifer foliage extractives from logging slash, and induced lightwood. 

An unusual microwave application was in the drying of lumber for the manufacture of baseball bats from wood from the tanoak tree. This wood normally takes up to 2 years to dry. A microwave system at 2450 MHz heated the wood for 4 h, after which it was allowed to dry for another 2 weeks at ambient conditions. This was done on precut billets, which were later shaped into the bats, but is no longer used [17]. 

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