RU2348872C1 - Method of timer drying - Google Patents

Abstract

FIELD: heating; drying.

SUBSTANCE: invention relates to woodworking industry and may be used for large timber pieces drying. The timber drying method includes transporting and storage operations with trolleys, process operations in two working chambers lasting at an interval at least 30 minutes, drying agent heating, moving and distributing in piles by means of heaters, reversible fans and flow dividers. The next stages of the method include timber softening and moisture distribution around the timber cross section with the use of hot water, steam and damping system. Then, timber is exposed to heating, atmospheric pressure or residual vacuum. The drying agent is removed from the working chamber to vacuum chamber by cyclic vacuum pulses at power corresponding to their volumetric ratio. After that vacuum conditions are intensified in time in the vacuum chamber by means of vacuum pump. The process is controlled by pressure, temperature and moisture. The drying agent is heated and moved along diffuser channels at 2÷2.5 m/sec through at least two lines of heat-release elements. Accordingly, the elements are heated by the liquid high-temperature coolant passing in different directions. At the same time the moisture is balanced between superficial and central layers in cycles (3÷5)-1 presuming sequential increase of hot water or steam volumes when free or bounded moisture within the limits 15÷30% and 25÷50% respectively is removed.

EFFECT: high-quality drying of whole timer and beams.

8 dwg

Description

The invention relates to the construction industry and the woodworking industry, in particular, to fast technologies for drying large-sized woods with equipment cyclically generating powerful vacuum pulses due to volume ratios of the drying and vacuum chambers, followed by deepening the vacuum in the drying chamber with a vacuum pump.

A known method of drying wood in a drying chamber (French patent 2351366, M. CL F26B 3/04, publ. 1990), which consists in repeatedly alternating cycles of blowing wood with heated air using a heater and a fan with the removal of vapors released by vacuum, the duration heating to the duration of evacuation is in the range from three to one to six to one with a duration of evacuation of 45-120 seconds, cooling is carried out in atmospheric conditions.

A known method of drying wood according to the patent (RU 2056602, Mcl F26В 5/04, F26В 3/04), containing a heating drying vacuum chamber connected through a high-speed vacuum valve through a vacuum pipe system with a receiver and a vacuum pump, the volume ratio drying chamber to the volume of the receiver to create a vacuum of the required depth should be at least 1:10.

The author, after conducting an information search, does not know a prototype with a stage-by-stage organization of the technological process of drying large assortments of cross sections of wood (logs, timber) according to the step-by-step task of the volume of the steaming agent.

Thus, the problem to which the claimed invention is directed is to obtain high-quality drying of logs and timber by reducing the difference in the drying process between the moisture of the surface layers and the middle of the log (timber) with a decrease in stress between them.

This task is achieved in that in order to reduce the impact of the above negative process on wood at a drying agent pumping speed of 2 ÷ 2.5 m / s through diffuser channels through two rows of heat-releasing elements, the drying process is organized in stages, each stage of which consists of 3 ÷ 6 cycles in which the moisture leveling of the surface and central layers of the log (timber) is given in (3 ÷ 6) -1 cycles with a sequentially increasing volume of hot water or steam when removing free and bound moisture, respectively within 15–30% and 25–50%.

A sign that with accelerated vacuum-pulse drying, the proposed step-by-step method of equalizing moisture content slows down the drying of the surface layers with respect to the central layers of wood of large cross sections, is new.

Uniform circulation of the drying agent in a chamber isolated from the atmosphere at a speed of 2 ÷ 2.5 m / s through diffuser channels through at least two rows of heat-releasing elements, respectively heated by pumped in different directions by a liquid high-temperature coolant, in combination with uniform selection of the mixture by flow dividers ensure uniform temperature and humidity of the coolant throughout the chamber and maintains uniform conditions throughout the drying process, which is an essential sign and provides izhenie problem posed invention.

The drawings show:

figure 1 - technological scheme of equipment for implementing the proposed method of drying;

figure 2 is a view a in figure 1, a transverse trolley with a trolley with a stack;

figure 3 - section bb in figure 1;

figure 4 is a cross section GG in figure 3;

figure 5 is a cross section DD in figure 4;

figure 6 - diagram of the movement of the coolant;

7 is a vacuum chamber;

in Fig.8 is a control block diagram.

The method of drying wood of large grades on the equipment proposed according to the technological scheme (Fig. 1) generally includes a group of transport and storage operations carried out using trolleys 1 and 2 with stack clamping mechanisms, access roads and cable traction, and the actual thermo -vacuum-pulsed exposure to lumber in two working chambers 3 and 4, carried out with an interval of, for example, 30 minutes, namely, heating and movement of the drying agent at a speed of 2 ÷ 2.5 m / s is carried out by means of a reverse fans 5 through a heater made of at least two 6 and 7 rows of heat-releasing elements, made with the possibility of sealing the inlet-outlet and passage in different directions of the heat-carrying liquid high-temperature coolant with the subsequent symmetric outlet of the flow of the drying agent along a gradually increasing section of the diffuser channels 8 for distributing by stream dividers 9 to each gap formed by rows of gaskets 10, softening and leveling humidity along the cross-section of the wood with hot water or steam by the system Pressure 11 is carried out in a multi-stage way, in each stage of which the moisture content of the surface and central layers is equalized using a flow meter 14 built in front of the water heater 12 and steam generator 13 in (3 ÷ 6) -1 cycles with a sequentially increasing volume of water or steam, followed by exposure during heating, atmospheric pressure or residual vacuum in the range of 15-30% and 25-50%, respectively, when removing free and bound moisture, removing the drying agent (vapor-air mixture) from chambers 3 or 4 through valves 15 and the pipe the wires 16 to the vacuum chamber 17 are carried out by cyclic vacuum pulses with a power corresponding to their volume ratios, followed by the deepening of the vacuum in time in the working chambers 3 or 4 by the vacuum pump 18, and the technological process is controlled by means of pressure, temperature, humidity and the volume of water or steam ACS 19 shown in Fig.8.

A specific example of the proposed method of drying the beam 100 × 150 × 6100 mm initial humidity W = 68%.

Initial data:

- residual humidity W = 18 ÷ 20%.

- control the moisture content of the beam with six moisture meter sensors. Prevent moisture reduction on the surface in relation to the middle below 12 ÷ 16%.

The initial state of the equipment:

- carts with a stack with gaskets 30 mm thick are loaded into chambers 3 and 4;

- chambers 3 and 4 are hermetically sealed;

- stop valves in the closed position;

- the vacuum pump and compressor are in the “off” state.

Turn on the fan 5 and the flow of coolant through the elements 6 and 7. Heat the wood to a temperature of 60 ° C. Fans 5 shut off. The overpressure distributor is turned on and the valves 15 quickly release pressure from the chambers 3 or 4 into the chamber 17, followed by evacuation by the vacuum pump 18 for 5 minutes. A steaming is carried out with hot water t = 90 ° C with the fans turned on. 5. The amount of water is 12 liters per 1 m ^{3 of} timber. Next is the heating. The specific drying mode of the pile of timber with a volume of V = 10 m ^{3 is} shown in the table.

Cycle number Vacuum time, min Wood temperature, ° С Drying agent temperature, ° С Amount of water, liters Exposure min one 10 70 95 - - 2 twenty twenty 3 25 twenty four 35 thirty . . . . 21 twenty 85 one hundred - - 22 thirty twenty 23 40 thirty 24 80 90

Thus, slowing down the drying of the surface layers by a multi-stage wetting method increased the quality of the timber.

results

The total drying time taking into account heating is 42 hours.

Humidity - W = 15 ÷ 18%.

There are no bends and deformation of the beam.

Plast cracks - no.

End cracks - two with a depth of 10-15 mm.

Claims (1)

A method of drying wood, including transport and storage operations using trolleys, technological operations in two working chambers, carried out at intervals of, for example, 30 minutes, heating, moving and distributing the drying agent to the stack using heaters, reversible fans and flow dividers, softening and equalization of moisture over the cross-section of wood with hot water and steam by a humidification system, followed by exposure to heat, atmospheric pressure or a residual vacuum, removing the drying agent from the cycle vacuum pulses with a power corresponding to their volumetric ratios, followed by a vacuum deepening in time in the working chamber by a vacuum pump and process control by means of pressure, temperature and humidity control, characterized in that the heating and drying agent movement at a speed of 2 ÷ 2.5 m / s through the diffuser channels is carried out through at least two rows of heat-releasing elements, respectively heated by passing in different directions of the liquid high-temperature coolant, with equalization in azhnosti between the surface and central layers in a (3 ÷ 6) -1 cycles with sequentially increasing the volume of hot water or steam, respectively, upon removal of free and bound moisture within the 15 ÷ 30 and 25 ÷ 50%.

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