Drying and gas or vapor contact with solids – Process – Gas or vapor pressure is subatmospheric
Patent
1997-12-03
1999-10-26
Bennett, Henry
Drying and gas or vapor contact with solids
Process
Gas or vapor pressure is subatmospheric
34396, F26B 504
Patent
active
059706244
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lumber drying method and an impregnation processing method to have the lumber absorb various agents such as preservative, mothproofingg agent, preservative/mothproofing agent, anti-ant agent, anti-fungus agent, dimensional stabilizer and resin.
2. Related Art
As shown in FIG. 3, lumbers are conventionally dried, for example, by a drying apparatus 1 consisting of a drying chamber 2 to accommodate lumbers 6, a heating boiler 3 to send heated air into the drying chamber 2, heat stirrers 4 installed in the drying chamber 2 and an exhaust pipe 5 to discharge the water vapor generated from the lumbers 6.
The lumbers 6 are, for example, placed on a carriage 7 and accommodated in the drying chamber 2. These lumbers 6 are cedars having an end face of about 105 mm.times.105 mm and a length of 3 to 4 m. The lumbers 6 are piled up on the carriage 7 with inserting a 1 to 2 cm thick spacer 8 between each pair of lumbers. Further, the initial moisture content of the lumber 6 is 50 to 70%.
The drying apparatus 1 maintains the temperature in the drying chamber 2 at 60 to 70.degree. C. with the heated air sent from the heating boiler 3 to dry the lumbers 6. Drying by this apparatus is continued for 15 to 20 days. The final moisture content is 15 to 20%.
According to the conventional lumber drying method as shown in FIG. 3, however, the heated air is discharged to outside via the exhaust 5 together with the water vapor from the lumbers 6, which makes the energy cost expensive.
Another drawback is that variation of the water vapor in the drying chamber 2 prevents uniform drying of the lumbers 6.
Further, the heated air drying may cause crack in lumbers 6 when the temperature is raised.
In addition, long drying time (15 to 20 days) means that the apparatus can be used only once or twice a month.
The lumber is inferior to other materials in its dimensional stability, uniformity, preservability, moth-proof, flame retardancy and strength. To improve such drawbacks of lumber and to add functions, the lumber is made composite with chemicals by impregnation. For example, large wooden products such as telephone poles and railroad ties are impregnated for preservation and moth-proof processing.
On the other hand, under the situation with shortage of lumber resources and lower prices in international competition, improvement of unused wood species and low quality wood, development of high durability technology and wooden product manufacturing by such methods are eagerly awaited.
In particular, it is expected that woods are improved or provided with new functions for higher additional values in the field of building materials, furniture members and art objects.
As a conventional method to improve drawbacks of or add functions to lumbers, the impregnation method to have the lumber absorb the agent has been known.
Impregnation methods include vacuum/pressure injection, compression and pressurizing methods. Vacuum/pressure injection methods are, for example, disclosed in Chapter II "Research on Function Enhancement by High Impregnation of Lumbers" contained in researches about processing of wooden members for higher functions issued by the Small and Medium Enterprise Agency in October 1990, the article titled "Pressurized Injection Conditions and Their Characteristics in Impregnation of Lumbers" in Vol. 28 of the Research Report from Shimane Prefectural Industrial Engineering Center (1991), and "Lumber Storage (1)--Focusing on Processing Technology--" in "Lumber Industry" Vol. 49, No. 7, 1994.
The vacuum/pressure impregnation method repeats pressurizing and vacuuming to impregnate the lumber with the processing agent.
The above article "Pressurized Injection Conditions and Their Characteristics in Impregnation of Lumbers" has made impregnation of lumbers with the injection conditions changed as follows: 1) Temperature, pressurizing force and pressurizing time of the injection system; 2) Combination of processes such as repetition of vacuuming and pres
REFERENCES:
patent: 3986268 (1976-10-01), Koppelman
patent: 4345384 (1982-08-01), Pagnozzi et al.
patent: 4466198 (1984-08-01), Doll
PCT International Search Report, Aug. 26, 1997.
Bennett Henry
Common Facility Co-Operatives Forest Nishikawa
Wilson Pamela A.
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