Drying and gas or vapor contact with solids – Apparatus – With means to treat gas or vapor
Patent
1989-02-07
1990-12-18
Bennet, Henry A.
Drying and gas or vapor contact with solids
Apparatus
With means to treat gas or vapor
34 138, F26B 300
Patent
active
049776860
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for processing rough timber wherein the wood, such as sawn wood prepared for seasoning is dried in a kiln, at a temperature of between 40.degree. C. and 100.degree. C., to a moisture content of not more than 30%.
BACKGROUND OF THE INVENTION
The primary products of timber industry, such as various kinds of sawn timber, veneer, and wood waste, that are produced for further use, usually have a moisture content above the saturation limit of the fiber. In this state timber is not suitable for further processing or shaping, therefore the moisture content has to be reduced by natural or artificial drying to under the saturation limit of the fiber to the air-dry (12-18%) or the room-dry (6-12%) state. The rapid increase in industrial use of wood products and the need for producing components of room-dry state made it essential to accelerate the slow natural drying process that usually lasts for at least 2 to 5 years, by the use of various artificial drying methods.
The acceleration of the natural drying processes (temperature, wind, humidity) has not led in an unchanged form to a good result, therefore various methods have been developed to remove the moisture from the wood as quickly and carefully as possible. Nearly all these methods are based on modifications of the properties and parameters (temperature, speed of air current, pressure, humidity) of the surrounding air, except for high frequency drying in which drift of the moisture begins from the inside.
Known artificial drying methods include: suitable for reaching the required degree of humidity by changing various parameters of time and space. Quick drying of "dry" timber, which is quick compared with natural drying, usually involves three main phases: adjusted to the required level, but achieved value (usually in the order of 1-5%), splitting, of butt or pith, etc.) because of the accelerated reduction of moisture content, until processing when further bending and warping take place, and balance in the moisture content of the wood, and other changes in the humidity (e.g. moistening) have the result that the artificially dried material changes its shape and dimension to a larger extent than naturally dried material.
DESCRIPTION OF THE INVENTION
The object of the present invention is to eliminate the aforementioned deficiencies and to provide a drying method for timber with reduced deformation, and changes in shape and dimensions, and holding the remaining stresses and the duration of the drying to an acceptable minimum.
During the development of the method of the invention we relied on the known methods and combined them with chemical processes that have had significant effects but have not been used before. Therefore any drying technique (convection, condensation, or vacuum drying) can be used subject to the following considerations.
Accordingly the present invention is a timber processing method which comprises drying substantially unseasoned timber while spraying it at least once with a mixture of a mineral acid and an aqueous solution of an alkali earth metal salt, whereby the pectin of the wood fiber which normally blocks the evaporation moisture from therebetween will become loosened to permit evaporation of the water content of the wood, and said alkali earth metal is incorporated in the wood fiber.
By the process of the present invention the stiffened state of the pectin in the molecular structure of the timber material is loosened at the critical moment. This enables the internal moisture to reach the surface and to evaporate without problems and then the acidic alkali earth solution promotes the incorporation of the alkali earth metal into the fibers of the natural material.
Suitably nitric acid is mixed with a solution in distilled water of an alkali earth metal salt, and this mixture is sprayed at least once into the drying kiln. The spray loosens the pectin of the fiber that otherwise blocks the evaporation of the moisture, while the alkali earth metal is built into the fi
REFERENCES:
patent: 1855666 (1932-04-01), Curtin
patent: 2500954 (1950-03-01), Loughborough
Balint Laszlo
Erdosi Gyorgy
Osvath Peter
Bennet Henry A.
Top-Coop Idegenforgalmi es Vendeglatoipari Kisszovetkezet
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