LT4152B - Combining method for drying and circulation drier - Google Patents

Abstract

This combined timber drying method and the air circulation drying chamber may be used in furniture manufacturing to industrially dry the sorts of timber that are prone to deform and crack.In order to improve the quality of the dried timber, reduce the drying period, and power consumption, the stack of timber is dried by a whirling flow of drying air, whose direction of helical movement and is repeatedly reversed, and whose pace is alternated contra-proportionally by high frequency electric field voltage alterations in each drying stage depending on stack mass changes. In the circulation dryer, ventilators (10, 11, 12, 13) with heaters (14) make up the drying medium flow helical movement direction and pace adjustment mechanism, which consists of panels (18), swinging around rigid axes (15), whose attack angle a is controlled by a gear (17), a high potential electrode (19) installed in a trolley (20) and which, using lifting equipment (24), can make contact with high frequency electric field generator (22), while low potential electrodes (5, 6) are equipped with louver-type drying medium distribution openings (34). Further, each chamber is equipped with an air intake aperture and outlet for exhaust air expelled into the atmosphere (31, 37).

Description

The combined drying method can be used in the wood processing industry, furniture manufacturing, construction companies for the industrial drying of sawn and round timber and blanks.

A known method of drying wood, which involves drying in several stages of the technological mode with individual drying medium (DT) parameters in each of them, when in the 1st - pre-conditioning - the temperature is raised to the optimum level and the surface moisture is reduced; finishes when the relative DT humidity DT reaches the values set in the technological mode, and in the third stage stabilizes the wood moisture parameters [RU Pat. No. 2023963, TPK ⁵ F26B 3 / 04,1994],

The disadvantage of this method is that the wood is additionally moisturized with hot steam before and after the stabilization stage, which requires additional energy costs.

It is also known to circulate DTs with fixed size parameters in separate dryer sections, thereby realizing drying at different stages of the technological mode [U.S. Pat. No. 5197201, TPK ⁵ F26B 5/04; 21/06],

The disadvantage of the described method - the necessity to transport the product to be dried from one section to another - dictates the complexity of the dryer, furthermore, it is difficult to remove moisture inside a separate wooden beam, which prolongs drying time and increases energy costs.

A simpler drying method is known using convection heat generated by generating a high frequency electric field (ADEL) directed by the DT stream into the drying cavity with the ability to combine flow movement and irradiation during the ADEL drying process at various time intervals [DE Pat. No. 4231897, TPK ⁵ F26B 15/18; 3/347; H05B6 / 64,1995],

The disadvantage of this method is the uncontrolled circulation and recirculation of DT, which reduces the drying intensity and drying quality, and furthermore, electric drying can occur during drying of the product with extremely high initial humidity.

The short-term solution is to dry the sawn timber by stacking the logs on a trolley, heating it with adjacent heaters, and feeding the DT in a transverse, reversible pulse flow motion. [SU al. 1615500, TPK ⁵ F26B 3/04; 9 / 06,1990].

-2LT4152 B

The disadvantage of this method is that the fan-fed DT makes it difficult to get into the lower area of the log stack and into the space separating them, and does not solve moisture removal from the inner layers of wood, which prolongs the drying process and does not guarantee its quality.

The aim of the proposed solution is to improve the quality of dried wood prone to deformation and decomposition, to reduce energy consumption per unit of evaporated water mass and to shorten the cycle time.

The solution to this problem is to produce the following technical results:

Drying of wood, especially solid species - ash, oak, etc. - is a serious problem requiring proper technological regime to avoid stress between wood layers causing deformation and cracking of the workpiece. This is avoided by using a combination method of drying and combining the targeted circulation of DT with irradiation ADEL, ensuring uniform drying conditions throughout the stack. This reduces cycle time because the process is continuous and energy consumption per unit mass of water evaporated. This method can also be used for drying agricultural products, textile raw materials and so on.

According to the proposed solution, logs are stacked on a trolley with slots for DT circulation and dried over time in three steps, moving from one another to a controlled parameter change of temperature, relative humidity, as follows: Stage I - Preparation - removes external wood moisture reversing the direction of the circulating DT flow by a maximum step;

In stage II, during the intensive drying stage, irradiation is initiated to displace the ADEL water molecules from the inner layers of the wood and the step of reversing the DT direction of circulation is uniformly reduced;

In stage III, during the parameter stabilization stage, it retains to a defined moisture content of the wood using DT recirculation and ADEL irradiation.

The following essential features determine the essence of the invention and its novelty at the technical level:

- drying the wood in a stacking stack with a vortex flow of DT, which reverses the direction of the pitch of the helical movement and changes the size of the step in each drying step inversely proportional to the intensity of the ADEL irradiation;

- transitions from one stage of the technological mode to another according to the additionally controlled change of the stack mass;

- The stack is dried by weighing, for example, by lifting it hydraulically, and the weight loss is determined by the change in pressure in the hydraulic system.

-3 The drying method is explained by the following graphs:

FIG. 1 - controlled drying parameters and their curves with respect to time t: stack mass M, relative humidity φ, temperature T °; for heat energy input DT preparation Ε | «, ι. and Eadelic epilepsy of irradiation energy.

FIG. 2 - Variation of the direction and magnitude of the DT motion of the vortex flow of the vortex flow i

in the three stages of the technological mode, the dependence on the ADEL voltage at the drying stage Uadel - in the preparatory stage - the stack mass Mi and DT have the highest relative humidity <pi, so U _A del = 0. This is done not only for energy saving reasons, but also to prevent electric breakage between electrodes if the wood has high initial humidity. The DT flow, which passes through the stack space by vortex movement, removes surface moisture by transferring it to the atmosphere by reversing the DT flow at maximum pitch S by changing the helical motion pitch S, which provides uniform drying conditions across the stack volume.

II - The intensive drying stage starts when the weight Mi of the stack is reduced eg ΔΜ = 18%, i.e. the size necessary and sufficient to remove surface moisture. Starts displacement of water molecules from the inner wood layers by ADEL, while T ° remains constant. The helical motion pitch S of the DT stream is uniformly reduced inversely in proportion to the increment of Uadel, while reducing the heat input for DT preparation as the amount of cold air is drawn from the atmosphere.

When the mass of the stack decreases, for example by another 26%, it enters the ΠΙ-parameter stabilization step: T ° and Uadel constant, DT flow step S is close to zero - recirculation occurs, heat is used only to maintain the T ° parameter, Eadel also decreases as the wood dries.

The drying process is completed when the relative humidity reaches a set value of φ ₂ and ΔΜχΟ.

The circulating dryer can be used in the woodworking industry, furniture manufacturing, construction companies for the industrial drying of sawn and round timber and billets.

Known for drying sawn timber, consisting of two chambers separated by a baffle, each containing a stack of wood stacked on a trolley, and fans with calorifiers mounted above the chambers. Drying is performed by periodically disconnecting one or another chamber's heaters, thereby changing the drying modes [SU

al. 1672172, TPK ⁵ F26B 9 / 06,1991],

The drawback of the known device is that the heat factor has a high inertia, so changing the drying mode cannot be efficient, and in addition, heat drying alone removes the internal moisture of the logs poorly.

Also known is a vacuum drying chamber having a high potential electrode placed on a trolley 5 in the middle of a stack of wood connected to an ADEL generator and compressed by plates having a low potential electrode application [SU al. 1682738, TPK ⁵ F26B 3/34, 9 / 06,1991],

The disadvantage of this drying chamber is that in the absence of directional circulation of DT, the drying requires high energy consumption and, in the case of wood with a high initial moisture content, electrical breakdown can occur between the condenser panels.

The nearest solution is a circulation dryer with two separate sections for stacked timber, above which is a fan with heaters. Dries wood by reversing the flow of DT flow inside the dryer as the flow passes from one chamber to another on its way to the intermediate zone, is reheated there, and the flow movement is controlled by valves [U.S. Pat. No. 5226244, TPK ⁵ F26B 21/06].

The disadvantage of this dryer is that not all of the DT passes through the valves, which reduces drying efficiency, increases energy consumption, and, by using DT circulation alone, makes it difficult to remove internal moisture.

The aim of the proposed solution is to improve the quality of dried wood prone to deformation and decomposition, to reduce energy consumption per unit of evaporated water mass and to shorten the cycle time.

The solution of the problem gives the following results:

- a combined drying method is implemented using the targeted circulation of DT and the effect of ADEL on solid species - ash, oak, etc. drying of logs;

- reducing energy consumption per unit mass of evaporated water;

- Improves the quality of dried wood by preventing deformation and cracking;

- shortening the drying time by a continuous process.

For this purpose, a circulating dryer with two separate partition chambers with air intake and exhaust vents, stackers for drying stacks, fans above the chambers for the preparation of DT and its flow directional control mechanism, additionally equipped with: ADEL generator, high and low potential electrodes, bogie lift mechanisms, and the DT flow control mechanism is made as a flow shape and direction control unit.

The following essential features determine the essence of the invention and its novelty in the state of the art:

- the fans with calorifiers are arranged so that the DT flow, through the shape and direction control unit, has access to the chamber's high pressure zone at an adjustable angle and from the low pressure zone to the adjacent fan thrust zone, giving the flow a vortex motion the longitudinal axis;

The DT flow shape and direction control unit consists of fixed axes and rotatable flow path plates with a common flexible link actuator that can adjust the direction and size of the helical flow pitch of the flow by varying the angle of attack;

- the high potential electrode is mounted in the bogie, has a permeable DT design and has the ability to contact the ADEL generator network via a bogie platform lift mechanism such as a hydraulic one;

- the low-potential electrodes have DT flow distribution openings, such as blinds, and their asymmetric arrangement in the chamber forms high and low pressure zones;

- the hydraulic lift mechanism of the trolley platform has the function of a device for controlling the weight loss of the stack due to the pressure change system;

- each chamber has two equal openings at the opposite ends of the stack length for air intake and exhaust.

The construction of the circulation dryer is illustrated graphically:

FIG. 3 - Dryer cross section: wood stack on the left in the start state, right on the drying stage.

FIG. 4 is a schematic diagram of the fan arrangement, DT flow shape and direction control unit, and flow direction of flow.

The housing 1 (Fig. 3) has two identical chambers 3 and 4 separated by a baffle 2, with fixed low-potential electrodes 5 and 6 forming in the chambers 3, 4 high-pressure zones 7 and 8 with openings in the DT preparation zone 9 with located there in one row with fans 10,11, 12, 13 (fig. 4) and heat sinks 14, and thereto a DT flow shape and direction control unit consisting of panels 16 with flexible connections 16 actuated by actuators 17 The high potential electrode 19 has a permeable DT flow structure such as a net and mounted in a carriage 20 whose platform 21 can be raised to contact the electrode 19 with the ADEL generator 22 network 23 lifting mechanism 24, e.g., a hydraulic stacker 25 in its system. a mass M change control device 26, and a high pressure zone 7 equipped with DT relative humidity (p and temperature T ⁴¹ control sensors 27, 28, plus 25 of the stack located at

-6LT4152 B between electrodes 5 and 19, or 6 and 19 stacked such that its width b with height h forms a ratio b: h = 1: (2.5 + 3).

The dryer operates as follows: a stack 25 having slots 29 for DT circulation, a workable lifting mechanism 24 together with platform 21 to electrode 19 contact with ADEL generator 22 network 23, leaving process slots 29 to overlay 30 separating chambers 3 and 4 from DT preparation zones 9. In this position, stack 25 is locked by a mechanism 24 known in the hydraulics such that device 26 shows a change in mass 25 of stack 25.

In the drying stage I-jc, air from the atmosphere enters chamber 3 through opening 31 by the draft of fan 10 and, after passing through heat sink 14, becomes DT flow 32 which is directed by a screen 33 33 of rotated attack angle a to high pressure zone 7 at the same angle. Passing through electrode 5 louvre-type DT distribution openings 34, the dry stream 32, passing through stacking gaps 29, absorbs moisture there and enters low pressure zone 8 where, when in contact with the outer wall 35, part of the moisture condenses and passes through filter 36 , and the stream 32 enters the thrust zone of the fan 11 in the adjacent row, gaining speed again, being heated in the coil and entering the zone 7 at an angle of attack set by the plates 18. Similarly, the flow 32 enters the following fans 12, 13, which takes the form of a vortex motion and exits through the opening 37 to the atmosphere, removing moisture that cannot condense. As the actuator 17 rotates the plates 18 at an angle 2a, the helical direction of flow of the flow 32 is reversed and air from the atmosphere enters the thrust zone of the fan 13 from the opening 37 and passes through the slit 25 ). By periodically rotating the positions of the panels 18 at an angle 2a, the motion of the stream 32 is reversed, providing uniform drying conditions over the entire length and volume of the stack 25.

The drying step a-a is started when the devices 26, 27, 28 show changes in the stack mass 25, the relative humidity φ, and the temperature T ° of the set value. Since, at stage I, the surface moisture of the stack 25 has already been removed, there is no risk of electric shock, generator 22 is activated, electrodes 5, 6, 19 start to act as capacitor plates and the ADEL effect pushes water molecules from the inner wood layers to the surface. reversed flow 32 direction of movement, but the angle of attack of 2a size gradually reduced in inverse proportion to increasing ADEL voltage U _A, say nothing about phase flow 32 in the chamber passes the longer path to the reduction of the screw movement step S stream 32 from one fan to an adjacent falls off immediately, but only

-7LT4152 B made several revolutions of rotation, the number of which depends on the size of the angle 18 adjustable by the plates 18. This allows the DT to rotate longer in the chamber, reducing the amount of cold air in the chamber, and reducing heat consumption for DT heating.

In stage III, the stack 25 is kept in a constant technological mode: the angle of attack α of the panels 18 is kept close to 0, the flow 32 of the stream is close to circular, cold air enters the chamber minimally as wood dries, conduction between condenser panels The process is completed when the mass M of the stack reaches M2 and the relative humidity of DT reaches ψ2.

The proposed solutions are supported by experimental inputs:

The wood stack, with dimensions 1.5 x (0.5 + 0.5) x6 m, has an initial weight Mi = 3546 kg and a dried stack up to 8% relative humidity M2 = 2333 kg. Then the mass of evaporated water Mv = Mi - M2 = 1213 kg.

The energy consumption per kilogram of evaporated water is calculated as follows:

Drying time ti - 5h;

in separate stages: you - 24h;

tm - 6h;

Total 35h.

Energy consumption ΣΕ = ΣΕι + ΣΕ „+ ΣΕιπ, where ΣΕι, ΣΕ„, ΣΕ ,,, - sum of the energy costs in the individual drying stages:

SEi = (E _A del + E vcnt. + Ekal.) 'T [, where Eadel is the energy input for the irradiation ADEL;

Evcm. - fan power, E _ven t. ⁼ 4 kW.

Ecai. - power used by the heat generator to heat the coils.

Once values are set,

ΣΕι = (0 + 4 + 6) · 5 = 50 kWh,

ΣΕ ,, = (16 + 4 + 8) -24 = 672 kWh,

ΣΕι „= (14 + 4 + 4) · 6 = 132 kWh, then ΣE = 854kWh and energy consumption per kilogram of evaporated water

M _v 1213

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The positive effect that creates a combined drying method and the use of a circulating dryer consists of the following factors:

- the vortex flow of DT shifts the entire mass of air contained in the dryer, which makes the drying process more efficient since intensive convection occurs in each unit volume of dryer;

- reverses the direction of the vortex movement of the vortex flow throughout the drying process, which provides uniform drying conditions across all sections of the stack, which improves the quality of dried wood;

- By changing the size of the vortex flow pitch of the vortex flow, it is possible to adjust the composition of DT 10 by reducing the amount of cold air in it, which reduces energy consumption;

- fixing the high potential electrode in the trolley with the possibility of contact with the ADEL generator network thanks to the lift mechanism not only prevents electric breakage but also allows additional control of the stack mass change during drying, and with the trolley set - with and without the electrode drying options - ADEL irradiation alone or convective alone for other materials, including bulk. This expands the capacity of the circulation dryer.

Claims (8)

DEFINITION OF INVENTION 1. Combined drying method, whereby logs are stacked on a trolley to a stack with a space for circulating drying medium, irradiated with a high frequency electric field, combined with directionally circulating streams, changing drying regimes according to changes in controlled parameters during the preparation, intensive drying and stabilization stages For example, that the wood is dried by a vortex flow in a stacking stack, which is continuously reversed in the pitch of the screw movement and the step size is changed by moving from one drying stage to another depending on the additionally controlled change of the stack mass. 2. The drying method of claim 1, wherein the step size of the DT flow helical motion is maintained inversely proportional to the amount of field voltage at each drying step. 3. Drying method according to claim 1, characterized in that the change in mass of the stack is controlled by weighing during drying, e.g. 4. Circulation dryer with two separate bulkhead chambers stacked on wood for carts, overhead chamber mounted fans with heat sinks, air intake and exhaust vents, drying media flow control mechanism, high frequency electric field generator, high and low potential electrodes characterized in that the vortex flow fans are arranged in a row parallel to each other and perpendicular to the longitudinal axis of the stack, and the flow control mechanism consists of rotatable flow path plates mounted on fixed axes and having a common flexible drive which can change at each drying stage angle of attack, which determines the direction and magnitude of the flow helical motion pitch, and the high potential electrode mounted on the trolley has the potential to contact the ADEL generator network and the low potential lo electrodes are mounted in the chamber asymmetrically, creating high and low pressure areas. 5. Dryer according to claim 4, characterized in that the high potential electrode has a permeable flow structure and the contact with the generator network is made possible by the lifting mechanism of the trolley platform, e.g. 6. Dryer according to claim 5, characterized in that the hydraulic lifting mechanism, by means of a pressure change system, can continuously control the loss of weight of the stack. -10LT4152 B 7. Dryer according to claim 4, characterized in that the low-potential electrodes have flow distribution openings, e.g. 8. Dryer according to claim 4, characterized in that each chamber has two equal, located at opposite ends of the stack length for air intake and exhaust. 5 atmospheric openings.