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Hardwood lumber kiln drying schedules typically keep the dry bulb temperature below 80 °C (176 °F). Difficult-to-dry species might not exceed 60 °C (140 °F). Dehumidification kilns are very similar to conventional kilns in basic construction.
Modern high-temperature, high-air-velocity conventional kilns can typically dry 25-millimetre-thick (1 in) green wood in 10 hours down to a moisture content of 18%. However, 25-mm-thick green red oak requires about 28 days to dry down to a moisture content of 8%.
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]
Wood in this process must have a moisture content at 12% or lower which can be attained through simple drying processes. The wood is then placed in a high nitrogen atmosphere with no more than 2% oxygen content. [8] The Perdure Process is relatively similar to retification but holds the wood at a lower temperature. [9]
These processes autoclave the treated wood, subjecting it to pressure and heat, along with nitrogen or water vapour to control drying in a staged treatment process ranging from 24 to 48 hours at temperatures of 180 °C to 230 °C depending on timber species. These processes increase the durability, dimensional stability and hardness of the ...
If wood is heated away from air, first the moisture is driven off. Until this is complete, the wood temperature remains at about 100–110 °C. When the wood is dry its temperature rises, and at about 270 °C, it begins to spontaneously decompose. This is the well known exothermic reaction which takes place in charcoal burning. At this stage ...
(Reuters) - The Washington Post said on Tuesday it would lay off about 4% of its workforce or less than 100 employees in a bid to cut costs, as the storied newspaper grapples with growing losses.
During the drying process, the water concentration decreases to approximately 3%. Then clinkers are fired at temperatures between 1,100 and 1,300 °C (2,010 and 2,370 °F) in a tunnel kiln (earlier in ring kilns), in contrast to the 800 to 1,200 °C (1,470 to 2,190 °F) temperature range seen with normal bricks.