JPS5853268B2 - How to dry wood - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for drying wood by heating, and more particularly to a method for drying wood by rapid drying without causing cracks on the surface of the wood.

Since raw wood contains 30-100% water, it cannot be used unless it is dried to a moisture content of 15-10.

This is because if wood that has not been sufficiently dried is used as it is, the wood will shrink as it dries after use, causing cracks, warping, and peeling at bonded areas.

The easiest way to dry wood is to simply stack the wood in a well-ventilated condition, but drying to a moisture content of about 15% with this method depends on the type of wood. This generally takes several years, and no matter how much drying is done with this method, an equilibrium state is reached at a moisture content of 15, and it is impossible to dry the rice below this level.

One way to dry wood in a relatively short period of time is to expose the wood to hot air or steam, but the biggest drawback of this method is that if you raise the heating temperature to dry quickly, the wood surface will overdry and shrink. However, cracks occur on the surface, making it impossible to raise the temperature and making it extremely difficult to adjust temperature and humidity.
It was impossible to dry wood in such a short period of time.

For example, in the case of karaki, it takes several days to about a week to dry a piece of wood with a moisture content of 30 degrees by applying steam to 15 tons.

When the temperature of the steam was raised to speed up the drying time, numerous cracks appeared on the surface of the wood, significantly reducing the commercial value of the wood.

Also, since it takes several days to a week to dry, the rotation of the dryer,
That is, the processing capacity per day is reduced, and the dryer becomes extremely large, requires a large installation space, and is extremely expensive.

If the amount of wood used is small, the large capacity of the dryer may not be such a problem, but most factories that use wood use a significantly large amount of wood, so the Drying foreign wood at once required an enormous amount of volume.

Therefore, even factories that use a relatively small amount of wood, such as Buddhist altar manufacturing factories, do not actually use dryers, and wood is left to dry every year.

However, in this case, it was necessary to stock up on wood for several years, which was extremely uneconomical, requiring an extremely large material storage area and an estimated 100,000 yen of financial resources, even for a manufacturing factory of an ordinary scale.

The inventor of the present invention looked for ways to dry wood quickly without causing cracks, and as a result of closely observing the state in which cracks occur on the surface of wood due to hot air drying, the inventor found that when hot air is applied to wood, only the surface of the wood is damaged. It was found that it dries rapidly and shrinks, resulting in cracks on the surface.

The shrinkage rate at this time differs slightly depending on the type of wood, but in general, for every 1 decrease in moisture content, the shrinkage rate is 1 in the tangential direction of the annual rings.
For example, the surface has a moisture content of 10% compared to the center.
When it dried, the surface shrank several times, causing cracks in the radial direction of the annual rings.

Therefore, with this method, it was necessary to gradually heat the entire wood over time, rather than drying only the surface, which significantly extended the drying time.

In addition, when heating wood with hot air, it is not possible to blow the hot air evenly over the entire surface of the wood, and the temperature rises faster in areas that are often hit by the hot air than other areas, and even if the same piece of wood is used, the back and front of the wood may be different. The heating state becomes uneven, causing temperature differences,
This resulted in frequent warping and cracking of the wood.

As a result of further experiments and research, the inventor of the present invention found that the wood was first soaked in boiling water and then heated, then taken out of the boiling water and heated again with hot air, steam, high frequency, etc. before being cooled. We succeeded in drying it on time.

Therefore, an important object of the present invention is to provide a method for drying wood that can rapidly dry wood without causing surface cracks.

Another important object of the present invention is to provide a method for drying wood that allows oil removal at the same time as drying.

Hereinafter, embodiments of the present invention will be described based on the drawings. First, as shown in FIG. 1, a predetermined amount of wood 1 is stored in a container 2 for heating boiling water, and then filled with water. Heat water to a specified temperature and leave it for a certain period of time as shown.

Thereafter, as shown in FIG. 3, the wood 1 is taken out from the container 2 or the water is removed from the container 2, and when the wood 1 is in a heated state without being cooled, hot air, heated steam, smoke or high frequency The wood 1 is further dried by heating.

The temperature of the hot water used to heat the wood is preferably 100°C because it can shorten the heating time, but it is not necessarily 100°C.
Even if it is not 00°C, it is sufficiently effective at 60°C to 100°C.

Also, the time for soaking wood in boiling water varies considerably depending on the type of wood and the temperature of the boiling water, but according to the experiments of the present invention, for heavy Chinese wood with a lot of oil, the optimum time is 3 to 5 hours in boiling water at 90°C. Ta.

However, even if the wood was soaked in boiling water for a longer period of time, there was no problem with the wood cracking or warping.

When wood from which hot water has been removed is reheated with hot air, the appropriate temperature of the hot air is 70°C to 80°C, and preferably the temperature of the hot air is lower than the temperature of the wood taken out of the hot water to prevent cracking. .

In addition, in the case of karaki heated with hot air for 3 to 5 hours, the moisture content could be dried to 6 to 9 in about 5 hours.

In the present invention, as a method of heating the wood taken out from the hot water, a method of applying hot air, heated steam or smoke to the wood, or a method of heating the wood with high frequency is used.

If there is too much difference between the drying atmosphere temperature and the temperature of the wood, drying will cause cracks in the wood and a reduction in the drying speed, so it is necessary to dry the wood after it is removed from the boiling water while it is still in the heated state without being cooled. be.

In the present invention, after the wood is heated with hot water, the hot water is removed and the wood is reheated and dried using hot air, heated steam, smoke, or high frequency waves. This allows for rapid drying to the ideal moisture content in a short period of time.

It is not possible to fully explain why wood can be dried quickly without cracking if it is soaked in hot water before hot air drying, but according to actual experiments conducted by the present inventor, A difficult, dense piece of wood with a moisture content of 30φ was dried to a grade of 6 to 9 in a total of 9 hours, with 4 hours of heating time in hot water and 5 hours of drying time with hot air.

By the way, the temperature of the hot water at this time was 90℃, and the temperature of the hot air was 7.
The temperature was 5°C.

The reason why wood can be dried quickly on the order of hours is that the entire wood is uniformly and rapidly heated by boiling water, and also because soaking in boiling water makes even hard wood pliable enough to be bent by hand. My guess is that when the wood is heated with hot air after being taken out of the oven, it shrinks and dries without cracking due to the flexibility of the wood.

In addition, heating the wood with boiling water causes the oil content to flow out, which has the effect of shortening the drying time, and this, combined with the above, allows the wood to reach its ideal state in a short time of less than 10 hours. It can be dried.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 are schematic sectional views showing one embodiment of the present invention. 1...wood, 2...container, 3...
... Heater, 4... Heater.

Claims (1)

[Claims] 1. A method for heating and drying wood, which is characterized by soaking the wood in hot water in advance and heating it, and then heating the wood again with hot air, heated steam, smoke, or high frequency waves before the hot water is removed and the wood is cooled.