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Wood drying (also seasoning lumber or wood seasoning) reduces the moisture content of wood before its use. When the drying is done in a kiln , the product is known as kiln-dried timber or lumber , whereas air drying is the more traditional method.
The Thermo wood process consists of drying, heat treatment and finally cooling/conditioning, and takes up to 72 hours. [4] The Plato process consists of hydrothermolysis, dry curing and conditioning, and can take up to 7 days. The required time depends on wood species, width and initial moisture content. [5]
Further drying of the wood results in strengthening of the wood fibres, [1] and is usually accompanied by shrinkage. Wood is normally dried to a point where it is in equilibrium with the atmospheric moisture content or relative humidity, and since this varies so does the equilibrium moisture content. Laboratory testing has found the average FSP ...
If the wood is placed in an environment at a particular temperature and relative humidity, its moisture content will generally begin to change in time, until it is finally in equilibrium with its surroundings, and the moisture content no longer changes in time. This moisture content is the EMC of the wood for that temperature and relative humidity.
Green wood is considered to have 100% moisture content relative to air-dried or seasoned wood, which is considered to be 20%. Energy density charts for wood fuels tend to use air dried wood as their reference, thus oven dried or 0% moisture content can reflect 103.4% energy content.
Green wood coming straight from the felled tree has far too high a moisture content to be commercially useful and will rot, warp and split. Both hardwoods and softwood must be left to dry out until the moisture content is between 18% and 8%. This can be a long process unless accelerated by use of a kiln.
However, in the 1980s, the development of chemical treatment processes allowed the wood to be more widely used for furniture making and frames. Rubberwood is generally treated soon after sawing by pressurized immersion in boron preservative solution to diffuse the chemicals. Then, the treated timber is kiln-dried to reduce its moisture content ...
Torrefaction is a thermochemical treatment of biomass at 200 to 320 °C (392 to 608 °F). It is carried out under atmospheric pressure and in the absence of oxygen.During the torrefaction process, the water contained in the biomass as well as superfluous volatiles are released, and the biopolymers (cellulose, hemicellulose and lignin) partly decompose, giving off various types of volatiles. [4]