RU2338137C2 - Vacuum-convective timber-drying device - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: application: in woodworking industry. Vacuum-convective timber-drying device contains drying chamber, which consists of sealed casing with heat insulation, track of drying agent, heater, fan, facilities for control of technological process parameters and vacuum pump, additionally contains the second drying chamber coupled with the first one, at that both chambers are embraced with lining, connected with pipeline between each other and with vacuum pump through vacuum valves with electromechanical drives. Casing of every chamber has equilateral rectangular profile and consists from three identical sections made of, for instance, glass-fibre anisotropic press-material with arched closure of walls and flanged tight connection of sections that form through air-tight drying chamber with electric heating panel-radiators, which are fixed in vertical walls of sections, closed on both sides with sealed covers. Every section of both drying chambers contains heat-exchanging device that consists of angular screening profile, bottom surface of pile trolley and axial suction fan from external electric drive, which is installed in window cross-section in the center of vertical wall.

EFFECT: intensification of drying process, reduction of power inputs, provision of high quality of drying.

3 cl, 1 dwg

Description

The invention relates to techniques for drying wood materials using reduced pressure and can be used in the woodworking industry for accelerated vacuum drying of lumber.

A known design of a vacuum drying chamber, comprising a housing in the form of a horizontally oriented cylinder with internal panels for condensate drain and an end cover mounted on a swing arm with the ability to open and close the chamber, rail tracks for installing a cart with a stack of wood, a vacuum station, means for connecting temperature sensors and humidity of wood associated with the control panel, as well as fixed inside the camera on its sides of the device connecting a flat heater by the elements of zone heating timber. In this case, the panels for condensate drainage are made in the form of fiberglass sheets, obliquely placed in the upper part of the chamber on both sides of the vertical plane of symmetry of the casing with the formation of a gap for steam to enter the upper part of the chamber, the devices for connecting the heating elements and sensors are made in the form of two boxes with panels of electrical connectors connected to a current source and to a control panel equipped with at least first and second temperature controllers for controlling heating elements in personal zones stack [Patent RU 2215954 C1, MPK ⁷ F26b 5/04, 9/06. Vacuum drying chamber [Text] / S.V. Milovanov, V.E. Ivashkevich, S.M. Uetsky; No. 2002106367/06; declared 03/13/2002; publ. 11/10/2003; 7 p.].

A drying unit containing a sealed cylindrical body with thermal insulation, a drying agent path with its distribution means and a condenser, fan and air heater placed in it along the stream, a vacuum pump, a condensate drain pipe connected to the bottom of the case, and an external inlet pipe were selected as a prototype air with shutoff valves. In this case, the condenser is made in the form of the bottom of the casing, the external air inlet pipe is connected to the bottom of the casing and a regenerative heat exchanger is placed in the area of its connection [Patent RU 2137995 C1, MKI ³ 6 F26B 9/06, 5/04. Dryer [Text] / G.N. Kochnev, V.P. Makshantsev, V.N. Oslonovich, A.V. Tetelmin; No. 98115333/06; declared 07/27/98; publ. 09/20/99; 5 s.].

A disadvantage of the known installations is the reduced loading volume of a rectangular stack in a cylindrical chamber, the low efficiency of concentrated type heaters that do not provide an even distribution of heat in the volume of the entire stack, as well as the overly complicated drying procedure. Practical studies conducted by the authors with industrial installations have shown that the use of cylindrical vacuum convection chambers is ineffective in terms of reducing the ability to control process parameters in a very rarefied volume with reduced loading efficiency, which in real industrial conditions does not ultimately lead to an increase in quality and reduced drying time. To ensure the highest intensity and quality of the vacuum-convection drying process as a whole, it is necessary to strive to maximize the use of the useful volume of the chamber, create a uniform distribution of the rarefied drying agent inside the device, and also use the drying equipment as efficiently as possible.

The invention solves the problem of ensuring high quality of the dried material, intensifying the drying process and reducing the energy consumption for drying.

This is achieved by the fact that the vacuum-convection forest drying unit containing a drying chamber, consisting of a sealed enclosure with thermal insulation, a drying agent path, a heater, a fan, means for controlling process parameters and a vacuum pump, according to the invention further comprises a second drying chamber associated with the first moreover, both chambers are covered by a lining, connected by a pipe to each other and to a vacuum pump through vacuum valves with electromechanical actuators. The body of each chamber has an equilateral rectangular profile and consists of three identical sections, made, for example, of fiberglass anisotropic press material with an arcuate closure of the walls and flange-tight connection of the sections forming a passage drying chamber with electric heating panels-radiators mounted on the vertical walls of the sections, sealed on both sides by sealed covers. Each section of both drying chambers contains a heat exchanger consisting of an angular shielding profile, the bottom surface of the stacking trolley and an axial suction fan from an external electric drive installed in the window alignment in the center of the vertical wall. The condensate collector in each chamber of the unit is made in the form of unheated space on the side of the bottom surface of the chamber body with a connected vacuum valve for draining condensate, bounded from above by the bases of sections with a system of oval drainage holes.

The drawing shows a diagram of the unit.

The unit consists of the following main units. Each chamber of the unit contains a housing 1 of an equilateral rectangular profile, consisting of a corrosion-resistant fiberglass press material that provides the necessary strength for long-term operation in a thermo-humid environment. The housing consists of three identical sections with an arcuate closure of the walls, with flanged sealed sections. The formed passage drying chambers are closed on both sides by hermetic covers with the possibility of rolling in and out on both sides of the lumber stacks 2. The role of the heaters in the chamber sections is performed by the system of electric heating panels-radiators 3, mounted on the vertical walls of the sections connected to a 50-Hz three-phase industrial network with voltage 380 V: one section - one phase. The maximum power consumption is 50 kW. The use of a composite heating casing for the entire length creates the best conditions for removal and uniform distribution of heat in the volume of the stack, as well as increased structural rigidity.

The drying agent is circulated using axial suction fans 4 from external electric drives installed in each section in the window alignment in the center of the vertical wall. The path of the drying agent in the chambers is formed in the form of a gap of a width of about 200 mm between the inner surfaces of the shielding corner profile 5 together with the surface of the under-platform platform 6 mounted on the roller tables 7. The circulation of the drying agent is transverse. Each chamber is equipped with an inlet pipe 8 with a shutter 9 for the influx of fresh air. The unit provides a system of vacuum valves 10-14, interconnected and a vacuum pump 15 through pipelines 16.

The condensate collector 17 — the unheated space between the bottom of the chamber body and the base of the sections — communicates with the vapor-air rarefied medium of the drying chamber through oval drainage holes in the base of the sections.

The use of rectangular chambers with an arcuate closure of the walls ensures maximum filling of the chamber volume with a stack of lumber and better conditions for heat removal from the walls of the heater due to the formation of a laminar transverse flow of the drying agent. A high degree of filling the chamber volume allows the most efficient use of the internal moisture of evaporation and eliminates the use of special humidifiers.

Drying is carried out by heating-vacuum cycles in an amount that reduces the moisture content of the material to the required level. The cameras are equipped with a bimetallic psychrometer to control the parameters of the vapor-air mixture. The unit is equipped with a computer with software that controls the drying process and the procedure for opening and closing valves. The course of the drying process is controlled by the operator-technologist.

The operation of the valves is shown in the table.

Valve Operation No. p / p Chamber A Camera B one 2 3 one Stack heating, fans 4a are included Evacuation, the vacuum pump is turned on, valves 11b, 14 are open 2 Steam-air heat exchange between chambers A and B, valve 10 is open 3 Evacuation, pump on, valve 11a open, stack drying, all valves closed Steam-air mixture supply, valve 13b is open, stack heating, fans 4b are on four Steam-air heat exchange between chambers A and B, valve 10 is open 5 Supply of vapor-air mixture, valve 13a is open, condensate drain, valve 12a is open, stack heating, fans 4a are on Evacuation, the vacuum pump is turned on, valve 11b is open, drying of the stack, all valves are closed 6 Steam-air heat exchange between chambers A and B, valve 10 is open 7 Evacuation, the vacuum pump is turned on, valve 11a is open, drying of the stack, all valves are closed Steam-air mixture supply, valve 13b is open, condensate drain, valve 12b is open, stack heating, fans 4b are on 8 Vacuum discharge, valves 13a, 14 are open, condensate drain, valve 12a is open Evacuation, the vacuum pump is turned on, valves 11b, 14 are open, drying of the stack, all valves are closed 9 Cooling, rolling out stacks, rolling up stacks Vacuum discharge, valves 13b, 14 open, condensate drain, valve 12b open 10 Stack heating, fans 4a are included Cooling, rolling out stacks, rolling up stacks

The aggregation of two vacuum drying devices allows heating the stacks in mismatched periods of time, using heat and vacuum residual from the previous cycle, and, thus, reducing energy costs by at least 1.5 times. In addition, it becomes possible to simultaneously dry materials with different initial physical and mechanical parameters: initial and final moisture, cross-sectional dimensions, rock, quality category for matching or antiphase drying steps.

Thus, the connection between the two vacuum drying chambers between each other and with the vacuum pump through controlled vacuum valves, forming a two-chamber forest-drying unit with steam-air heat exchange, is new.

The invention allows in an industrial environment, without the use of complicated modes and devices to reduce the drying time of wood, increase its quality, reduce energy costs.

Claims (3)

1. A vacuum-convective forest drying unit containing a drying chamber, consisting of a sealed enclosure with thermal insulation, a drying agent path, a heater, a fan, means for controlling process parameters and a vacuum pump, characterized in that it further comprises a second drying chamber associated with the first, moreover, the housing of each chamber has an equilateral rectangular profile and consists of three identical sections, made, for example, of fiberglass anisotropic press material with an arc a clear closure of the walls and a flanged hermetic connection of the sections forming a through airtight drying chamber with electric heating panels-radiators mounted on the vertical walls of the sections, closed on both sides by hermetic covers, both chambers are lined, connected by a pipe to each other and to the vacuum pump through vacuum valves with electromechanical drives. 2. The unit according to claim 1, characterized in that each section of both drying chambers contains a heat exchanger consisting of an angular shielding profile, the bottom surface of the stacking trolley and an axial suction fan operating from an external electric drive installed in the window alignment in the center of the vertical wall. 3. The unit according to claim 1, characterized in that the condensate collector in each chamber of the unit is made in the form of unheated space on the side of the bottom surface of the chamber body with a connected vacuum valve for draining the condensate, bounded from above by the bases of the sections with a system of oval drainage holes.