RU2226661C1 - Method for wood drying - Google Patents

Abstract

FIELD: drying procedure, applicable in production of lumbers, in furniture, wood-working industries and in other branches. SUBSTANCE: the distance between rows in the pile and the flow of drying agent are formed by layers of perforated plates and by inclined walls, the wood is seasoned in a chamber for 6 to 18 hours at a temperature within 120 to 200 C, at a uniform static pressure on the pile within 10 to 15 kgf/sq.cm until the water content attains maximum 8 per cent. EFFECT: enhanced efficiency of lumber drying, enhanced resistance of the processed wood to various physical, chemical and biological effects, changing of natural color of lumber in the process of drying. 5 dwg

Description

The invention relates to a drying technique and can be used in the production of lumber, in the furniture, woodworking industry and in other areas.

A known method of drying wood by forced circulation of a drying agent heated by a heater, sent along a stack of lumber.

Due to the friction of the drying agent on the lateral surfaces of the circulation channel and distribution into the inter-row space of the stack, the speed of the drying agent decreases along the length of the stack.

One way to compensate for speed losses is to install along the stack at the injection site of the drying agent a perforated partition 1/4 ... 1/3 of the length of the stack.

The presence of such a partition limits the flow of the drying agent to the stack. On the one hand, this leads to a decrease in the air velocity in the front of the stack due to an increase in the aerodynamic drag of this part of the circulation circuit and, on the other hand, to an increase in speed in the rear of the stack as a result of a decrease in the consumption of the drying agent in the front of the circulation channel. Biley P.V. Chamber drying technology for hardwood lumber. Lviv LLTI. 1991, p. 79.

Another way to increase the uniform distribution of the drying agent is to use a chamber with a variable cross-sectional length decreasing towards the end door.

Lumber is stacked in a chamber of trapezoidal section, a drying agent is forcibly fed along the walls of the chamber and partially into the inter-row space of the stack. A stack of lumber in the chamber is treated with a drying agent heated by a heater. The circulation of the drying agent along the contour formed by the circulation channel and the inter-row space of the stack is created by the fan along the walls.

To ensure uniform drying, the chamber is made tapering to the end door, and a perforated partition is installed along the stack with the size of the perforation increasing in the direction of circulation. Patent of the Russian Federation No. 2022221, IPC F 26 V 9/06, 1994 (Prototype).

The disadvantage of the prototype is that the main stream of the drying agent circulates along the walls of the chamber and only a small part of it enters the inter-row space, which increases the drying time and leads to its unevenness.

This invention eliminates the disadvantages of the analogue and prototype.

The technical result of the invention is to increase the drying efficiency of lumber, increase the stability of treated wood in relation to various physical, chemical and biological influences, change the own color of the lumber in the drying process.

The technical result is achieved in that in the method of drying wood, which consists in stacking lumber in a chamber of a trapezoidal section, forcing the drying agent into the inter-row space of the stack, regulating the flow of the drying agent with a perforated partition, the inter-row space in the stack and the flow of the drying agent are formed by layers of perforated plates and inclined walls, withstand wood in the chamber for 6-18 hours at a temperature of 120 ° -200 ° C, with uniform static pressure on a stack within 10-15 kg / cm ² until a moisture content of not more than 8% is reached.

The invention is illustrated in figures 1-5.

Figure 1 schematically shows a section of a chamber for drying lumber, where 1 is a chamber body, 2 are hydraulic cylinders, 3 is a beam transmitting force, 4 is heating elements (heating elements), 5 is a group of axial fans, 6 is a press plate, 7 is sawn timber to be dried, 8 - package plates, 9 - package rails. The arrows indicate the direction of circulation of the drying agent.

Figure 2 schematically shows a top view of the plate of the package in section, where 10 is a metal module, 11 ’and 11’ ’are the elements of the lock connection, 12 are the perforation holes.

Figure 3 presents the metal module 10, where 11 ’and 11’ ’are the elements of the lock connection, 12 are the perforation holes.

Figure 4 schematically shows parallel-welded plates (side view), where 8 - plate package, 13 - profiled metal sheets.

Figure 5 presents the curves of the characteristics of the drying process of wood on the example of wood from birch. The curves are given for different initial temperatures in the housing 1 of the drying chamber. The ordinate axis shows the temperature scale in degrees Celsius, and the abscissa axis shows time in minutes.

The flow of the drying agent does not circulate along the walls and around the stack, as in the prototype and analogue, but across the stack through the perforation holes 12 in the plates 8 of the package. In the drying process, humidity is constantly monitored, when the required humidity is reached, the process is completed.

Drying of lumber is as follows.

Lumber sawn into boards of the same thickness are laid in a package consisting of perforated metal plates 8 (Fig. 1).

The plates 8 of the package are formed of individual metal modules 10 connected in series by the locking elements 11 ’and 11’ ’(Figs. 2, 3). The perforation holes 12 of the plates 8 in the Assembly represent a series of channels (Fig.2, 3), through which the drying agent (air) freely passes. Channels for the flow of the drying agent are formed by perforation holes 12, inclined side walls of the housing 1, a group of axial fans 5, evenly located in the ceiling of the housing 1 along one of the walls, and a group of air-water heaters 4.

The cross section of the housing is a trapezoid, the smaller base of which is located on the floor of the housing 1.

You can connect the plate 8 and in pairs (figure 4) by welding with profiled sheets of metal 13, and thereby soften the drying modes of wood. The distance between the plates 8 with a parallel, spaced in height arrangement of plates 8 connected by profiled sheets of metal 13, exceeds the size of the holes 12 perforation. When forming a package of such boards 8 and lumber 7 during the drying process, various modes for groups of lumber in a single cycle are possible.

For laying lumber 7 and excavating dried lumber 7, the package is equipped with a mechanism for pulling plates 8 of the pantograph type with a hydraulic or other mechanical drive.

A folded package of plates 8 and lumber 7 is rolled into the housing 1 of the chamber along the rails 9.

The camera body 1 is a sealed steel container with two gates for loading and unloading packages, assembled on a rigid steel frame. The walls, floor and ceiling of the chamber are thermo and vapor insulated with several layers of mineral wool and aluminum foil. The inner lining of the chamber is made of stainless steel or other composite thermo, steam and chemical resistant material.

In the ceiling part of the chamber there is a valve for releasing steam at overpressure (not shown in the figures). By adjusting the valve to different pressures, you can control the drying process.

In a sealed enclosure 1 at high pressure in accordance with the combined gas law of Klaiperon-Mendeleev, you can create high temperature.

Hydraulic cylinders 2 are independently located on the steel frame of the housing 1, which transmit force through the beam 3 to the press plate 6, creating a uniformly distributed pressure in the bag up to 10-15 kg / cm ² .

The air in the housing 1 of the chamber is heated by a block of electric water-air heaters or combined using external air heating units (based on optimal local energy sources) to 140-200 ° С. At the same time, it is mixed with the help of a group of axial fans 5, reflected from the inclined walls of the housing 1 and passing through the channels inside the plates 8, creating a uniform heating of the timber 7 in the bag. Due to the rapid heating of wood throughout the entire volume of the package to temperatures of 120-160 ° C, it passes into a plastic state, in which internal stresses from its transverse drying decrease, while the pressure artificially created inside the package due to hydraulic cylinders 2 compacts the wood and compensates for stresses from shrinkage. Excess moisture leaves the chamber due to overpressure through a steam valve located in the ceiling.

The design of the chamber allows it to achieve an additional effect of wood processing, in which the wood is heat treated with temperatures from 180 ° C to 230 ° C. At these temperatures, the chemical properties of wood (plasticization) change: its resistance to various physical, chemical and biological influences significantly increases, and, in addition, the material itself changes color.

When the required humidity of about 8% is reached, the process is completed, and the bag of lumber 7 and boards 8 is rolled out through the second gate, the next packet is rolled into the first gate.

Fresh wood is dried in a chamber at a temperature of about 120 ° C, as shown in Fig. 5 using birch as an example. The duration of the process, depending on the initial moisture and thickness of the board and until the required humidity of 8% is reached, can be from 6 to 18 hours. In particular, for pine: 6-8 hours, for oak 14-18 hours.

In the chamber shown as an illustration, the second stage is also possible. At this stage, the temperature can reach up to 230 ° C, depending on which end product the user wants to receive. As a raw material, you can use pre-dried wood. Processing at maximum temperature also lasts several hours. At temperatures above 200 ° C, many rocks are intensively processed. In this case, only thermal energy, steam and fresh water are used. As a result of processing, the wood darkens evenly throughout the volume, swelling and shrinkage sharply decrease (by 40-60%), and the process of reproduction of rotting bacteria stops. The wood that has undergone such processing can be used for the production of parquet, furniture, exterior decoration of houses, as well as for window and door frames.

Claims (1)

The method of drying wood, which consists in stacking lumber in a chamber of a trapezoidal section, forcing the drying agent into the inter-row space of the stack, regulating the flow of the drying agent with a perforated partition, characterized in that the inter-row space in the stack and the flow of the drying agent are formed by layers of perforated plates and inclined walls, withstand wood in the chamber for 6-18 hours at a temperature of 120-200 ° C, with uniform static pressure on the stack in the range of 10-15 kg / cm ² , until moisture reaches not more than 8%.

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