Recently interest has been shown in drying timber at very high temperatures (close
to or above 100°C, using superheated steam). These high temperature timber drying
systems are therefore operating at temperatures much higher than used in conventional
timber drying kilns This can be especially attractive when drying timber species
which are very prone to distortion on drying, and consequently dried timber of high
quality can be produced. High temperature timber drying kilns can dry suitable species
up to twice as rapidly as can conventional “Heat and Vent” type kilns. It is however,
vital that very high humidities are retained throughout the high temperature stage
of the drying process otherwise the timber will be seriously damaged -
(For an introductory understanding of the factors determining the removal of water from wood, and how these factors can be controlled to successfully dry timber without reducing the quality of the timber see: Factors Controlling the Drying of Wood).
The intention is to use the high temperatures to rapidly remove the water from the wood and also, importantly, plasticise the material – so that rather than distorting in response to the drying stresses generated, the material “flows” in the manner of a heated plastic. The high operating temperatures and high humidities used in these high temperature timber drying kilns must be rapidly produced to reduce the chances of the timber being dried rapidly before plasticisation temperatures are attained. For similar reasons good air circulation must be ensured and the sizes of timber stacks dried in these high temperature kilns are necessarily smaller than used in conventional drying kilns. In addition, accurate monitoring and control of the drying conditions within high temperature timber drying kilns is vital.
The most popular high temperature timber drying kilns are designed to operate at less than 100°C, since the construction of this type is cheaper than those designed to operate at greater than 100°C which require expensive, pressurised containers.
HOME
Reasons to Dry Timber: An Introduction to Timber Drying
Timber Drying -
Factors controlling the Drying of Wood
The Structures of Softwoods and Hardwoods and their effect on Wood Drying
An Introduction to the Air Seasoning of Timber
Layout of a Timber Drying Yard
Design of Stacks in the Timber Drying Yard
Types of Kiln Drying Equipment
Benefits of Kiln Dried Timber production compared to Air Seasoning Timber
Using a Dehumidifier to Dry Wood
High Temperature Timber Drying
Avoiding Case Hardening by Monitoring the Drying of Timber. Also Collapse & Staining of Timber