JPH0127355B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves sequentially putting incoming raw material wood into a pressure vessel type dryer and taking out a certain amount as drying material at short intervals. This relates to a wood dryer that was developed with the aim of eliminating the unreasonableness that was required.

In the lumber industry, only thin wood such as rotary veneer or sliced veneer is dried while moving the wood to be dried; thick wood such as sawn wood is dried while being moved. It was not possible to move the wood to be dried from the beginning to the end of drying the sawn timber products.

In the steel industry, the quality of the raw materials is the same, so a production method can be used in which large quantities are poured, but in the timber industry, since the wood is a natural material, grains exist, and the dried raw materials are inspected one by one at the entrance of the wood processing factory. The situation is such that we have to remove the wood. Therefore, even if dried wood is sent little by little to the starting point of the processing factory line, with the current drying method, it is not possible to dry the wood while moving it, so the number of drying days is Considering the production volume, it was necessary to increase the size of the drying equipment. If the wood to be dried can be dried while moving and the dried wood can be produced in proportion to the production volume of the processing factory, then the inconvenience of having to build a large-scale facility to start a wood processing factory will be eliminated. Furthermore, considering that wood is a special material whose release status of contained water changes as its moisture content decreases, the present application provides a system that allows various drying methods to be used simultaneously in one dryer, This is the world's first proposal that allows for drying by sequentially moving materials to be dried to locations where a drying method appropriate to the reduced moisture content of the materials can be used.

In the past, unlike the present invention, loading wood was carried out without taking measures to move the loaded wood sequentially according to the drying level to a place where there is a gas flow according to the drying level as in the present invention. Many construction methods have been proposed in which the wood is heated by steam injection, heated by a hot air stream, and then depressurized repeatedly, without moving the wood from beginning to end. There were some prototypes made, but due to the following reasons, the quality of the dried wood deteriorated significantly, and all of them disappeared without being put into practical use.

When drying wood, it is common knowledge that if the wood being dried is not given a uniform heating distribution and uniform air speed and air volume, a large amount of cracks and distortions will occur in the drying quality. . And in the wood,
The presence of resin that inhibits the release of contained water and the presence of contained water within the cell cavities that are difficult to release exist in all types of wood, and it is difficult to release the water without correcting the situation. It is common knowledge that if the vacuum drying method, which is a rapid drying method, is used, a large number of defects such as cracks and distortions are likely to appear, and the quality of the wood will deteriorate significantly.

To be able to perform vacuum drying, the dryer must be cylindrical. Even if steam is injected into a cylindrical dryer to heat the wood without creating a pressurized state of 100℃, there will be areas where the steam will hit and areas where it will not, and the temperature will vary depending on the location of the loaded wood. Not only is there unevenness, but individual pieces of wood also have temperature unevenness on the side opposite to the direction of the steam injection. If a cylindrical dryer is used as a pressure vessel and steam is pressurized, the temperature distribution around the loaded wood will be uniform, but by placing the wood under pressure, Due to the pressure, the water contained in the wood is forced into the center of the wood, and since there is no place for the contained water to cause convection, a low-temperature water mass is created, and the thickness of the wood remains unchanged no matter how long it is heated. Unevenness in temperature distribution occurs in the horizontal direction. If vacuum drying is performed under reduced pressure with this temperature unevenness in the thickness direction, the moisture gradient will increase, causing a large amount of cracking and distortion. Also, even if hot air is sent into a cylindrical dryer or a fan is installed inside the container,
When the wind passes through the stacked timbers, since the wall surface is circular, only the circumference of the stacked timbers rotates, causing only the outer periphery of the stacked timbers to overdry. After that, if the pressure was reduced and vacuum drying was carried out, the unevenness of the moisture content distribution would further increase, resulting in severe damage such as cracks and distortion. Furthermore, with these methods, the resin within the wood cannot be removed uniformly, and the water contained within the cell cavities cannot be easily dispersed.
If a drying method such as vacuum drying that rapidly reduces the moisture content is used, it has the drawback of increasing the occurrence of cracks and distortions. The present invention has developed a method that solves all of the above-mentioned problems, completely prevents loss due to cracking and distortion, and sequentially extracts high-quality dried material in a short period of time.

In explaining the present invention, the explanation will begin with reference to a configuration diagram. Inside the pressure vessel...
The saturated steam that passes through the pressure reducing valve 6 from the boiler 4 is sent to the saturated steam injection pipes 10, 11, 12, 13,
14, 15, to enable more injection. The section uses this saturated steam as its only heating source.
Saturated steam from the boiler 4 is passed through a pressure reducing valve 6 and then turned into superheated steam (hereinafter superheated steam will be referred to as super steam) in a heating furnace 5 through super steam injection pipes 16, 17, 18, 19. , section, , , , to be able to inject. The heat source of the section is saturated steam and super steam. Saturated steam from the boiler is passed through the pressure reducing valve 7 and air from the blower 8 is introduced into the heating furnace 5 to form a mixture of super steam and air.
This allows the sprayer to be sprayed more in the section. The section uses saturated steam and a mixed gas as its heat source. Attach the super steam suction pipes 20, 21, 22, 23 to the opposite side of the wall where the super steam injection pipe is attached to the section,
The pressurized super steam that has passed through the wood to be dried is sucked out from the pressure vessel, passes through the super steam concentration pipe 24, and is injected from the super steam release pipe 25 attached to the heat preservation warehouse 9 to be converted into saturated steam and released. A mixed gas suction pipe is installed on the opposite side of the wall where the mixed gas injection pipe is installed in the section, and the pressurized mixed gas that has passed between the pieces of wood to be dried is sucked out from the pressure vessel, and the mixed gas discharge pipe attached to the inside of the warming chamber 9 is connected to the mixed gas suction pipe. It is injected from 28 and dispersed. The trolley is shaped like a trolley 3 with a width of about 50 cm that almost reaches the ceiling of the pressure vessel, attached to the front and rear of the trolley 2 carrying the wood to be dried. Drain water accumulated in the pressure vessel is discharged to the outside from the drain pipe 29.

Each Toro shown in Figure 1 will be explained. The untreated wood taken out of the thermal storage is in the section. Sectional wood is wood that has undergone the sectioning process. Section wood is wood that has completed the process of making a section. Sectional wood is wood that has undergone the sectioning process. Below, items that have completed each process are moved to the next section. The section is pressurized and heated under the fluctuating pressure of saturated steam (pressure fluctuation under pressurized conditions, the same applies to subsequent fluctuations of pressure), and then depressurizes (pressure drops below atmospheric pressure, the same applies to subsequent pressure reductions). It is a process. The section is the location of the process where the temperature is raised with saturated steam, then pressurized and heated with fluctuating pressure of super steam, and then depressurized.The section is where the temperature is raised with saturated steam, and then the super steam is mixed with air. This is the place where the pressure is reduced after the gas is heated under fluctuating pressure.

Next, an example of the method of operating a pressure vessel of the present application will be described. Let us assume that a trolley loaded with lumber that has gone through its respective processes moves into each section, and all the sections are filled up.

First, saturated steam is injected into the pressure vessel from each saturated steam injection pipe, and the drain pipe 29 is opened to prevent a pressurized state, and the temperature of the entire inside of the vessel is lowered.
Make sure the temperature is 100℃. Thereafter, the drain pipe is opened less frequently, and while drain water and part of the saturated steam are released, saturated steam is continued to be injected until the entire system reaches a predetermined pressure higher than atmospheric pressure. When the pressure inside the pressure vessel reaches a predetermined pressure, the saturated steam injection pipes 11, 1
2, 13, 14, 15 are closed, and saturated steam is injected only at 10, and the super steam injection pipes 16, 17, 1 are
Injection of super steam is started from 8 and 19, and the super steam is discharged through the stacked timbers from super steam suction pipes 20, 21, 22, and 23 on the opposite side to the super steam waste gas concentration pipe outside the pressure vessel. let me,
Further, a mixed gas of super steam and air is injected from the mixed gas injection pipe 26, passes through the stacked timbers, and is discharged from the mixed gas suction pipe 27 on the opposite side to the outside of the pressure vessel. The valves attached to the drain pipe 27, the valves attached to the super steam waste gas concentration pipe, and the valves connected to the mixed gas suction pipe are controlled respectively to make the discharge amount smaller than the injection amount of each gas, and the injection of each gas is performed. If you can repeat injecting each gas at the same time and stopping the injection at the same time while keeping the release amount the same even when stopped, the pressure will fluctuate frequently within a predetermined pressure range with the entire inside of the pressure vessel being at the same pressurized pressure. Be able to do it. After pressurizing and heating each gas at varying pressure for a predetermined number of hours, the injection of each gas is stopped simultaneously,
Release each gas from inside the container, reduce the pressure inside the container for a predetermined time, and when the decompression time is over, fill the container with air to bring it to normal pressure, open the front and rear doors, and insert the section to the outside from the exit side. Load the untreated wood in the thermal storage compartment 9, put the Toro in the section on the entrance side, move the Toro one section at a time from the section, close the front and rear doors, and repeat the above process. I'll give it back.

Next, the numerical values required for commonly performed operations are listed. The pressure when stopping the injection of saturated steam after the section is 1Kg/cm ² (gauge pressure, the same applies hereafter), and the range of the predetermined pressure for heating with variable pressure is 1Kg/cm ² to 0.8Kg/cm ² . The temperature of super steam is approximately 120℃, which is the temperature of 1Kg/cm ² saturated steam.
Requires a higher temperature of 20℃ or more. Better results can be obtained if the temperature of the gas mixture of super steam and air is lower than the temperature of super steam. The time for performing the variable pressure heating requires a time equal to or longer than a fraction of 1.5 times the thickness of the treated wood expressed in mm. In other words, if the wood is 40 mm thick, it will take more than 60 minutes. This time is extended to include the situation in which the moisture content decreases up to the section. One unit of time in which fluctuating pressure is repeated is 40
Between seconds and 120 seconds, depending on the tree species. The depressurization time is between 30 and 40 minutes.

In this operation, special attention must be paid to the pressure (approx. 2 kg/cm ² The above is desirable), and be careful to keep the valves connected to each injection pipe and discharge pipe open, and the super steam and mixed gas are colorless during pressurization, and when the pressure disappears. However, immediately after being released into the atmosphere, it is colorless and dangerous, so it is safer to release it into a heat insulating chamber where it will not be pressurized.

Next, we will explain the efficacy of each section. Since each section is heated with pressurized gas, the entire circumference of the wood can be heated to the same temperature regardless of how it is stacked. , it is pushed into the center of each piece of wood, and due to the specific heat, there is a disadvantage that a phenomenon occurs that prevents the temperature at the center of the wood from increasing. In order to eliminate this drawback, each section
By varying the pressure of the heated gas, when the applied pressure decreases, the contained water that was pushed into the center of the wood by the applied pressure is pulled back toward the surface layer, and the water is moved to the center of the wood. Eliminates the phenomenon of condensation of contained water. Due to the variable pressure pressure heating using only saturated steam in the section, the high temperature drain water generated on the wood surface mixes with the low temperature water contained from the beginning. , the temperature of the contained water will be the same as the saturated steam temperature. Although it was stated above that this predetermined time may be extended depending on the situation after sectioning, extending the time will only slightly increase the amount of water contained in the wood. Because it is attached, it has no effect on the big picture. After that, in the process of releasing saturated steam and depressurizing, all the water contained in the wood was boiled at the same time, the resin that was blocking the movement of water was removed, and some of the water was released into all cell cavities. A condition is created in which the wood has hollow parts, which facilitates the subsequent movement of the contained water. In the area where the super steam is used to pressurize and heat the area from the section to the section, the pressure is slightly higher in the area surrounded by the wall of the pressure vessel where the super steam injection pipe is located and the stacked wood. The part surrounded by the wall of the pressure vessel with the super steam extraction pipe and the stacked timbers is
Because the pressure is slightly lower than elsewhere, super steam flows between stacked timbers under almost the same conditions. The temperature of super steam is 20 degrees higher than that of saturated steam.
Because the temperature is higher than ℃, it is heated at a temperature higher than the boiling point of the pressurized pressure, and unlike heating saturated steam, it is not possible to reduce the water content during pressurization.
The contained water is constantly boiling, and the water content decreases even during pressurization. Furthermore, due to the wood's sectional process, which makes it easy for the water content to move, and the pressure heating caused by the fluctuating pressure of the super steam, the water content in the center of the wood can easily move to the surface layer and boil. It's getting easier to vent. After a predetermined period of pressurized heating due to the fluctuating pressure of super steam, the injection of super steam is stopped,
By releasing super steam and reducing pressure,
Boiling of the water contained in the center of the wood is also promoted and the occurrence of moisture gradient is corrected. Immediately after moving on to the next section, pressurized heating using saturated steam is first performed to prevent a significant drop in moisture content on the wood surface and prevent damage to the treated wood.
The reason why we installed four sections for super steam treatment is that the moisture content of the wood decreases just by applying pressure and heating under the fluctuating pressure of super steam. This does not necessarily mean that four sections are necessary as in this embodiment. In the last section of this example, the section for performing pressurized heating by fluctuating pressure of a gas mixture of super steam and air was provided because the moisture content reduction due to pressurizing heating due to the fluctuating pressure of super steam is not balanced. When the moisture content decreases to the moisture content level, it can be said that it is super steam, so when the moisture content decreases to near the equilibrium moisture content, the speed of moisture content decrease is extremely slow, so the amount of steam is small. This is because pressure heating using fluctuating gas pressure is required.

In this example, three types of gas were injected simultaneously, but the reason why the three types of gas did not mix in the pressure vessel was that each section had a hole in each section, so there was a gap between each piece of wood. It is partitioned by the presence of a 1m area where no gas flows, and the injection pressure of the three types of gas into the pressure vessel is the same.
The pressure in each section fluctuates at the same pressurization pressure, and each section has a corresponding injection pipe and drain pipe/steam absorption pipe that discharges into a space that is not pressurized. This is because the pressurized gas in each section flows toward the pipes connected to the outside of each section, and does not flow into the absorption pipes of other sections through the small gaps created. be.

As explained above based on the embodiments, the present invention allows wood to be dried to move sequentially through a pressure vessel capable of heating with saturated steam and reducing pressure, and adjusts the drying level of the wood to be dried as it moves. , it is characterized by being able to simultaneously pressurize by fluctuating pressure under pressurized conditions with two or more gases with different properties, and depressurize below atmospheric pressure, so it is optimal depending on the drying level at the time. It is possible to perform pressurization by fluctuating pressure under pressurized conditions and depressurization below atmospheric pressure using a suitable gas, and wood, which until now required a long period of time, can be put into the dryer of the present invention as soon as it arrives. As long as you keep going, high-quality dried wood with no cracks or distortion will come out every 2 hours, reducing the amount of inventory to 1.
It was a huge benefit to the industry, which was having trouble securing land due to dry conditions, lack of inventory, interest rates, and dry land.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a state in which Toro is contained in a pressure vessel. FIG. 2 is a configuration diagram for implementing the present invention. 1... Pressure vessel, 2... Toro, 4... Boiler, 5... Heating furnace, 6, 7... Pressure reducing valve, 8... Blower, 10, 11, 12, 13, 14, 15...
Saturated steam injection pipe, 16, 17, 18, 19...Super steam injection pipe, 20, 21, 22, 23...
Super steam suction pipe, 26...Mixed gas injection pipe,
27...Mixed gas discharge pipe.

Claims (1)

[Claims] 1. A pressure vessel without bulkheads containing a trolley loaded with wood to be dried that can be moved sequentially.
It has an injection pipe that can inject saturated steam on the inlet side, superheated steam in the middle, and a mixture of superheated steam and heated air on the outlet side, and each gas is injected through the stacked timbers to the other side. After performing pressurization and heating by repeating small-scale pressurization and depressurization using each gas, each gas is released from the inside of the container, and the inside of the container is depressurized. After that, air is pumped in to create a normal pressure, and the trolley loaded with the wood is moved forward one section to simultaneously pressurize and depressurize with gases with different properties depending on the dryness level of the wood. A wood dryer characterized by having: