the process of heating and dewatering wood between hot plates under certain pressure conditions is called hot pressing drying. hot-press drying method was first used for veneer drying. in the mid-century, denmark, the united states and other countries began to use it to dry sawn timber. thereafter, people have been trying to solve the problems of warping and cracking in the drying of low-grade hardwood, small-diameter wood and fast-growing wood by hot-pressing drying method, and some achievements have been achieved.
pressure drying is still in the research stage, and it is not widely used in industrial production. hot-press drying heats wood by contact conduction. because of the high heating temperature of heating plate, close contact with the dried wood and large heat transfer capacity, the interior of wood can quickly reach high temperature, which makes the steam pressure increase rapidly, and promotes the movement of moisture inside the wood to the exterior. some wood with good air permeability can be dried quickly in hours or even tens of minutes.
due to the effect of pressure, the shrinkage of the thickness of the dried wood will be greater than its normal shrinkage, which will increase its density, surface hardness and dimensional stability. the change of wood compression rate is related to the main factors such as hot pressing temperature, pressure, time, wood species, density, texture direction (diameter, chord surface), moisture content and so on. the results show that high hot pressing temperature and pressure can increase wood compression rate, which is beneficial to increase wood density, surface hardness and dimensional stability, and improve wood performance. however, excessive hot-pressing temperature and pressure will not only bring about greater volume loss, but also deepen the color of wood and cause more serious surface hardening and cracking. therefore, in the process of hot-pressing drying, it is necessary to select appropriate hot-pressing drying process according to the characteristics of wood itself and the requirements of its use in order to achieve a better drying effect. fruit.
the above is the basic principles of wood drying equipment. i hope you will understand. our company's main products include rotary drum dryer (hong gan), belt dryer, spray dryer, fluidized bed dryer and so on. for more information, please login: www.baoyangganzao.com
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