RU2156934C1 - Wood drying plant - Google Patents

Abstract

FIELD: lumber drying equipment; wood- working industry. SUBSTANCE: plant includes cylindrical hermetic housing, drying chamber, calorifiers, fan and vacuum pump. Drying chamber is formed by lateral and upper partitions fitted in housing at spaced relation. Lateral partitions are perforated; they form segment clearances where calorifiers are arranged. Fan is communicated with drying chamber through segment clearances and perforated lateral partitions. Upper partition is vertically movable; hermetic reservoir made from elastic material is located in clearance between partition and housing. EFFECT: improved quality of boards due to identical conditions of drying process of lumber located in different rows of stack. 2 dwg

Description

 The invention relates to equipment for drying lumber and can be used in the woodworking industry.

 Known drying chamber for drying lumber in stacks, containing a housing in the cavity of which is located a circulation channel with a fan and air heater. The chamber is equipped with a perforated partition installed in the circulation channel along the stack, and the dimensions of the perforation of the partition are increased in the direction of circulation of the agent flow. On the side walls of the casing rotary shutters are fixed, limiting the longitudinal size of the circulation circuit / see, for example, US Pat. RF N 2022221, MKI F 26 B 19/06, 1994 /.

 The disadvantage of the drying chamber is the low quality of lumber, due to the development of the volume-stress state inside the wood during convective drying, which occurs as a result of the uneven distribution of moisture content and temperature over the material cross section.

 There is also an installation for drying wood, including a horizontally sealed sealed container with a lid, a heating device with angular profile elements located along the container, a fan for circulating hot air and a vacuum pump, the intake pipe of which is connected to the internal cavity of the container, and the outlet pipe with atmosphere / see, for example, application N 93015429 RF, MKI F 26 B 19/00, dated 24.03.93. Publ. B.I. N 18, 1995 /.

 The disadvantages of the known installation are the uneven drying of lumber and the low quality of wood in the upper row of the stack.

 These shortcomings are caused by the organization of the coolant circulation during the period of warming up of the stack and the intensive drying of the upper rows of boards, leading to cracking and warping of the latter.

 The closest in technical essence and the achieved result to the invention is a wood drying installation comprising a sealed cylindrical body with a lid in communication with a vacuum source, a drying chamber placed inside the body with a gap and formed by side and upper partitions, the last of which is made with the possibility of vertical movement and connected to the housing by springs, and a heating element / see, for example, Pat. RF N 2022215, MKI F 26 B 19/06, 1994 /.

 The disadvantage of this installation is the low quality of lumber due to non-identical conditions of the drying process in rows of stack boards of various heights.

 As a result of the intense heat supply to the lumber during the drying process, the moisture content of the outer layers decreases faster than the inner layers due to the diffusion mechanism of moisture transfer. As a result of the uneven distribution of moisture content over the cross-section of the material, leading to the appearance and development of internal stresses, deformation (warping) of lumber occurs. The inner rows of stacked boards are under load from the top, which eliminates warping of lumber. The upper layers, deprived of a sufficient compensating counteraction to internal stresses, change their shape.

 The aim of the invention is to improve the quality of drying of lumber.

 This goal is achieved by the fact that in the installation for drying wood containing a sealed cylindrical body with a lid in communication with a vacuum source, a drying chamber placed inside the body with a gap and formed by side and upper partitions, the last of which is made with the possibility of vertical movement and connected to case by springs, and a heat exchanger according to the invention, the latter is located along the case behind side partitions made perforated with a variable size of perforations and along their length and established with the formation of closed segment gaps for the coolant supplied by a fan placed in the drying chamber inside the casing, communicating with each other through segment gaps, and a tight container made of elastic material is placed in the gap between the upper partition and the casing.

 Comparative analysis with the prototype allows us to conclude that the claimed technical solution is distinguished by the following features: a heat exchanger is located along the body behind the side partitions made perforated with a variable perforation size along their length and installed with the formation of closed segmented gaps for the coolant supplied by a fan placed in the drying chamber inside the housing, communicated to each other through segmented gaps, and in the gap between the upper partition and the core a sealed container made of elastic material is placed by the pus.

 This ensures identical conditions for the drying of lumber that make up the stack.

 The invention is illustrated by drawings. In FIG. 1 shows a longitudinal section of a wood drying plant (top view); in FIG. 2 - cross section of the installation.

 The installation contains a sealed cylindrical housing 1 with a cover 2, a drying chamber 3, heaters 4, a fan 5, a vacuum pump 6.

 The drying chamber 3 is formed by side 7 and upper 8 partitions installed in the housing 1 with gaps. The side walls 7 are perforated and form closed segment gaps 9. In the segment gaps 9 along the housing 1 are placed heaters 4.

 The fan 5 is in communication with the drying chamber 3 through segmented gaps 9 and perforated side walls 7.

 The upper partition 8 is vertically movable and connected to the housing 1 by springs 10. In the gap 11 formed by the upper movable partition 8 and the housing 1, a sealed container 12 is made of an elastic material, for example rubber.

 The internal cavity of the housing 1 is in communication with the vacuum pump 6 through the pipe 13, and with the atmosphere of the crane 14.

 Inside the drying chamber 3, a stack of lumber 16 is placed on the trolley 15.

 Installation works as follows. The stack of lumber 16 on the trolley 15 is placed in the drying chamber 3, after which the housing 1 is sealed with a cover 2. Turn on the vacuum pump 6, communicated through the pipe 13 with a sealed housing 1, and reduce the pressure above the stack of lumber 16. Due to the pressure difference the internal space of the housing 1 and the sealed container 12, the latter expands, moving the upper partition 8 towards the stack 16, and squeezes the upper row of boards. The pressure exerted by the upper partition 8 on the upper row of boards counteracts the internal stresses that occur in the wood during drying, and retains the original shape of the lumber. In the process of evacuation of the housing 1, the accumulated thermal energy of the wood is consumed in the evaporation of moisture. As moisture is removed, the material cools, thereby reducing the rate of evaporation of the liquid.

 To increase the drying speed, the housing 1 is depressurized with a valve 14 (when equalizing the pressure at the time of depressurization, the springs 10 return the upper partition 8 to their original position) and turn on the fan 5. The air passing through the heaters 4 heats up and flows into the drying chamber 3. Due to the variable perforation size side partitions 7 creates a uniform inlet and outlet of the coolant along the length of the drying chamber 3, which when it moves in the gaps formed by the gaskets across the stack 16 provides identical conditions for all boards in the process of heating.

 Heating of lumber is carried out in a closed volume with a mixture of air with vapor of an evaporated liquid and is accompanied by wetting of the surface of the boards and redistribution of moisture content over the cross section.

Heating is stopped when the surface temperature of the lumber reaches 40-60 ^o C.

 After the heating process by the valve 14, the housing 1 is sealed and the evacuation process is carried out again. Evacuation and convective heating alternate until the moisture content of the lumber reaches a predetermined final value (6-8%).

 The advantages of the proposed installation is illustrated by the following specific example of its implementation.

Overall dimensions of installation, mm:
length - 8000
width - 3100
height - 3000
Case diameter, mm - 2200
Diameter of perforation, mm - 10-53
Fan - МЦ N 12
Fan motor power, kW - 7.7
Vacuum pump - VVN 1-25M1
Power of the electric motor of the vacuum pump, kW - 35
Stack dimensions, mm - 4200x1000x1000
The developed drying unit was accepted for implementation at the Kazan factory of musical instruments for drying valuable wood species.

 Thus, the use of the proposed installation can improve the quality of lumber subjected to drying in stacks, by ensuring identical process conditions.

Claims (1)

 A wood drying apparatus comprising a cylindrical body with a lid in communication with a vacuum source, a drying chamber located inside the body with a gap and formed by side and upper partitions, the last of which is made with the possibility of vertical movement and connected to the body by springs, and a heat exchange device, characterized the fact that the latter is located along the body behind the side partitions made perforated with a variable size of perforation along their length and installed with the formation of Deputy segmented gaps for the coolant supplied by a fan located in the drying chamber inside the housing, communicated to each other through segmented gaps, and in the gap between the upper partition and the housing there is a sealed container made of elastic material.

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