RU2558742C2 - Wood heat treatment method - Google Patents

Abstract

FIELD: heating.SUBSTANCE: invention relates to woodworking technology of construction engineering and can be used for drying of wood materials and products. In the method of wood heat treatment in the drying unit consisting of a closed chamber, a fan, a heater, air ducts, moisture collecting and discharge system and regeneration system, a closed chamber is made as separate sections fitted with the identical fans, heaters and air ducts with energy carrier flow switching units, providing its cyclic recirculation, while ensuring gradual decrease of working power of heaters towards the energy carrier movement in the range from 90 to 10% of their rated power depending on number of sections in the unit, ambient air temperature and humidity, and also a grade, volume, configuration, external dimensions, temperature and humidity of the processed wood, and each cycle of operation of separate section consists of the periods the amount of which corresponds to number of sections in the unit, for example for two-section unit such period amounts 7-10 days at the cycle 14-20 days, for seven-section unit such period of work of one separate section amounts 2-3 days at the cycle 14-21 days with alternation of the process of full selection of the exhausted energy carrier from the section with its partial selection amounting 60-80% of supply of the initial energy carrier with simultaneous release of the residue of the exhausted energy carrier in the volume 20-40% into atmosphere.EFFECT: improvement of efficiency, continuity and profitability of the wood heat treatment process.2 cl, 3 dwg

Description

The invention relates to woodworking machinery for the construction industry and can be used to dry materials and wood products.

Known drying installations of periodic and continuous operation, in which the transfer of thermal energy is carried out by convective or contact, radiation and mixed methods using high-frequency electric current; with periodic pressure relief; with the movement of the energy carrier in a once-through, counter-current or combined scheme with recirculation and reverse circulation; spray and gas layer; with drying of building materials of products in a filtering, boiling and vibro-boiling layer; single and multi-section; drum, screw, tunnel and conveyor (Peregudov V.V., Rogovoy M.I. Thermal processes and installations in the technology of building products and parts. - M .: Stroyizdat, 1983. - S.208-232).

At the same time, despite the fact that building materials from wood are used more and more widely in modern construction industry, the creation of fundamentally new technologies for their heat treatment lags significantly behind the general level of technological development and insufficient information has been disclosed in published information sources.

Known conveyor multi-tier dryer, designed for processing plate-shaped products according to RU patent for invention No. 2367868 (F 26 15/12, F26В 21/02, patent patent: LINDAUER DORNIR GESELSHAFT, publ.: September 20, 2009), in the sectional tiers of which the drying circulates energy carrier, and each tier contains its own heat source and several axial fans, made with the possibility of supplying energy to the supply holes above and below the vehicle of the corresponding tier for blowing products and suction of the spent energy carrier, and also mines, regeneration chambers and connecting channels.

However, the known dryer is not well suited for heat treatment of wood, the products of which are also partially produced in the form of plates, is difficult and laborious in the manufacture, assembly, commissioning and maintenance of low performance, unreliability and fragility of its main structural components and elements.

A known method of determining the need for an energy carrier for drying wood according to RU patent for invention No. 2451254 (F26В 3/04, F26В 25/22, patent file .: VALUTEK AB, publ.: 05.20.2012), which consists in placing the wood in a closed drying chamber and drying energy carrier is passed through it, measuring the temperature of the “wet” and “dry” thermometers, as well as their psychrometric difference and controlling the moisture content of the treated wood during the entire process of its heat treatment.

In a known manner, it is possible to control the condition of the wood being processed, however, it does not provide for measures to control the drying process, as well as to save energy and its reuse.

A known drying unit according to RU patent for invention No. 2362100 (F26В 9/06, patented patent: TOU VPO “Military Engineering University, publ.: 07.20.2009), consisting of a closed chamber, fan, air heater, ducts, collection system and moisture removal and regeneration system.

The drying energy carrier in such an installation under the influence of a regeneration system containing a recirculation channel with fins and arcuate pipelines through which a second energy carrier is passed, which is water, should be reused after it has been worked out, and the drying process should be intensified. However, the absence of the release of spent energy in a known installation to the outside plays a negative role, because causes blowing of the dried wood with spent moist air, which leads to its secondary moistening and causes unjustified delay and destabilization of the heat treatment process, accompanied by interruptions and failures in work.

The technical task of the invention is to increase the efficiency, continuity and efficiency of the process of heat treatment of wood, reducing its energy intensity and ensuring low waste. This problem is solved by the fact that in the method of heat treatment of wood in a drying plant consisting of a closed chamber, fan, air heater, air ducts, a system for collecting and removing moisture and a regeneration system, the closed chamber is made in the form of separate sections equipped with fans of the same type, heaters and air ducts with nodes for switching the energy carrier flows, providing for its cyclical recirculation, while providing for a gradual decrease in the operating power of heaters in the direction of energy flow medium in the range from 90 to 10% of their rated power, depending on the number of sections in the installation, the temperature and humidity of the outdoor air, as well as the grade, volume, configuration, external dimensions, temperature and humidity of the treated wood, and each operation cycle of a separate section consists of periods, the number of which corresponds to the number of sections in the installation, for example, for a two-section installation, such a period is 7-10 days with a cycle duration of 14-20 days, for a seven-section installation, such a period of operation is separate The projection is 2-3 days with a cycle duration of 14-21 days with alternating the process of complete selection of spent energy from the section with its partial selection of 60-80% of the input of the original energy, with the simultaneous release of the remaining part of the spent energy in the amount of 20-40% in atmosphere. In addition, loading each batch of processed wood into a separate section as well as unloading from it is carried out for 3-6 hours, and to stabilize the return of spent energy to the heat treatment of wood in plants with more than five sections, the bypass duct is equipped with an additional a fan.

The inventive method is essentially a creative modernization of the known processes of heat treatment of wood, which are widely used in domestic and foreign practice and are implemented mainly in multi-section drying units with a cyclic action, heat transfer using the combined radiation-convection method in a direct-flow circuit with energy recirculation. The practical uses of the invention in real production are described by two examples, the first of which considers the operation of a two-section technological line for cyclical processing of wood, and the second - the work of a seven-section line, on the basis of which it is also possible to consider the features of the functioning of such individual production units as three , four-, five- and six-section units.

The implementation of the proposed method is illustrated in the drawings, in which Fig. 1 shows the operation of a two-section, and in Figs. 2 and 3, a seven-section drying unit, which includes the hermetically sealed sections themselves, combined into a single complex with the help of suction and discharge air ducts, switching units flows of energy carrier, ventilation and heating equipment, and all the elements of such installations that are currently in the process of heat treatment of wood are shown using thickened lines, and those in the process of downtime - thin lines. As already noted, the functioning of all sections is carried out in a cyclic mode with the division of each cycle into periods, the number of which corresponds to the number of sections in the installation in question.

So, for a two-section installation, the operation period of each section is 7-10 days, and the cycle duration is 14-20 days, for a three-section installation, respectively, 5-7 days and 15-21 days, for a four-section installation, 4-5 days and 16-20 days, for a five-section - 3-4 days and 15-20 days, for a six-section - 2.5-3.5 days and 15-21 days, for a seven-section installation, respectively, 2-3 days and 14-21 days. At the same time, the indicated duration of periods and cycles in actual production conditions can be adjusted taking into account the actual temperature and humidity data of the state of the surrounding air environment and the wood being processed, as well as the variety, external dimensions, volume and configuration of the processed products. After completion of the full cycle of operation of each individual section, it is stopped for mechanized unloading of a dried batch of wood and the same load of the next batch, the duration of each of which is taken in the range from 3 to 6 hours

As can be seen from figures 1, 2 and 3, each section of the described installations, namely (C1), (C2), (C3), (C4), (C5), (C6) and (C7), is equipped with located under them fans (B1), (B2), (B3), (B4), (B5), (B6) and (B7) and heaters (K1), (K2), (K3), (K4), (K5), (K6) and (K7) using additional fans (K8) and (K9), air ducts, as well as a moisture collection and removal system, an air distribution device from perforated pipes, an air intake (not shown in the drawings) and an air outlet (shown by an arrow in the upper right corner of individual working sections). The discharge, suction and branches of the bypass (returning the spent energy carrier for reuse) working ducts are also represented in the drawings by thickened lines with an arrow.

Example 1. A two-section drying installation operates as follows. As can be seen from the fragment “a” of Fig. 1, at the beginning the first section (C1) is turned on, pre-loaded with the first batch of processed wood, for which the first period of its 1st cycle begins, for which the first fan is turned on (B1 ) and the first air heater (K1). During this period, 20-40% of the spent part from the fresh source of energy coming from the outside is released to the outside, and the remaining 60-80% of its spent part is sucked off by the second fan (B2) and returns through the lower branch of the bypass duct to the suction pipe of the first fan (B1). The second phase of the installation is shown in fragment "b" of figure 1, where section (C1) operates in the 2nd period of the 1st cycle of its operation, and section (C2) enters the 1st period of its 1st cycle. At the same time, the fan (B1) and the air heater (K1) continue to supply and heat fresh source air entering the section (C1), and the fan (B2) begins to collect the energy spent in it and through the air heater (K2) fill the section (C2), from where its smaller part in the amount of 20-40% of the intake is thrown out, and a large part in the amount of 60-80% by the fan (B3) is pumped through the upper branch of the bypass duct into the suction pipe of the fan (B2). In this phase, the full cycle of the first section (C1) ends, amounting to 7 + 7 = 14 days or 10 + 10 = 20 days, and it is stopped for wood reloading, and the second section continues to work. The third phase of the installation is shown in the fragment "c" of Fig.1. To carry out this phase, section (C1) begins to work in the 1st period of its 2nd cycle, and section (C2) enters the 2nd period of its 1st cycle of work. In this case, the entire energy carrier worked out in section (C2) through the fan (B3), both branches of the bypass duct, the fan (B1) and the air heater (K1) enter the section (C1), from where the energy carrier is completely thrown out after it has been exhausted. At the same time, the fan (B2) begins to draw fresh source air and through the air heater (K2) fill the section (C2). In this phase, the full cycle of the second section (C1) ends, amounting to 7 + 7 = 14 days or 10 + 10 = 20 days, and it is stopped for wood reloading, and the first section continues to operate. The fourth phase of the installation is shown in the fragment "g" of figure 1. To carry out this phase, section (C1) begins to work in the 2nd period of its 2nd cycle, and section (C2) in the 1st period of its 2nd cycle. In this case, fresh source energy is supplied by the fan (B1) through the air heater (K1) to the section (C1), and the energy spent in it by the fan (B2) through the air heater (K2) is discharged to the section (C2), from where it is partially released after working out, and partly with the help of a fan (VZ) along the upper branch of the bypass duct it is returned for reuse to the suction pipe of the fan (B2). In this phase, the 2nd period of the 2nd cycle of the section (C1) ends and it is stopped for wood reloading. The fifth phase of the operation of the installation is illustrated by the fragment "d" of figure 1, which shows that there is a 1st period of the 3rd cycle of operation of the section (C1) and a 2nd period of the 2nd cycle of operation of the section (C2), and this phase of operation installation is identical to the third phase shown in the fragment "in" of Fig.1.

Thus, the fourth phase is a repetition of the second phase, the fifth is a repetition of the third phase, the sixth phase is a repetition of the fourth phase, etc.

In addition, to ensure uniform, stable and economical heat energy production, the heaters (K1) and (K2) alternately switch to reduced power through each cycle, for example, to use 80-60% of their rated power.

Example 2. Consider the process of heat treatment of wood in a seven-section installation, the principle of which can be used for installations with fewer or more sections. The order of sequential inclusion in the work of all sections of the installation from (C1) to (C7) is shown on fragments "a", "b", "c", "d", "e" and "e" of figure 2 and, as a continuation of this drawing, fragments "g", "h", "and", "k", "l", "m" and "n" of Fig.3. So, on the fragment “a”, the initial phase of putting the installation into operation is described, for which its section (C1), previously loaded with the first batch of processed wood, begins to receive the initial energy source coming from the external environment through the fan (B1) and air heater (K1 included for this) ) Thus, the first period of operation of the section (C1) begins, lasting 2-3 days. At this time, 20-40% of the spent energy is released outside, and 60-80% is sucked out by the fan (B2) and through the lower branch of the bypass duct enters the suction pipe of the fan (B1). Next, the next section (C2) is included in the work, the first period of which fully repeats the work of section (C1) in its first period. The section itself (C1) at this time transfers the entire volume of the spent energy carrier formed in its cavity with the help of a fan (B2) into the section (C2). And section (C2) in its first period, as well as in the previous case, discharges 20-40% of the spent energy source to the outside, and 60-80% of its volume with the help of the fan (B3) in the return mode to the suction pipe of the fan (B2) ) As can be seen from fragment “a”, only the air heater (K1) is included in the first period of operation of section (C1), and the air heater (K1) and air heater (K2) from fragment “b”. From the following fragments “c”, “g”, “d”, and “e” of FIG. 2, it follows that sections (C3), (C4), (C5) and (C6) gradually and sequentially begin to be included in the operation, moreover the release of the part of the spent energy carrier and the return of the remaining part for reuse is carried out only within the framework of the uppermost section included in the work of the latter. From the fragment "g" of figure 3 it is seen that the full first cycle of the operation of section (C1), which is (2-3) × 7 = 14-21 days, has ended, and it should be stopped for unloading and reloading of wood, the duration of each such an operation is taken equal to 3-6 hours, and the remaining sections continue to work in this mode of drying. From the same fragment “g” it follows that the installation begins to work in the mode of returning the spent energy from the last section (C7) to the first section (C1), for which all fans (B1) - (B8) plus a fan (B9) are turned on, all air heaters (K1) - (K7) and all branches of the bypass duct, moreover, section (C1) operates in the mode of partial exhaustion of the spent energy carrier (20-40%) into the atmosphere, and section (C2) works in the mode of fresh air source intake with the help of a fan (IN 2). Then, according to fragments “h”, “and”, “k”, “l”, “m”, and “n”, the complete first cycle of the sections (C2), (SZ), (C4), (C5), ( C6) and (C7) and they are also stopped for 3-6 hours to reload the treated wood. From the same fragments, it follows that the role of the first section (C1), performed by it according to the fragment “g” of FIG. 3, sequentially passes to the sections upstream in the direction of energy movement. So, on the fragment “m” it is shown that part of the spent energy carrier is released into the atmosphere by section (C6), and the fan (B7) takes the source of the fresh energy carrier from the atmosphere. The last fragment “n” of FIG. 3 describes the completion of the complete first cycle of operation of the last section (C7), followed by its stopping for wood reloading, during which all other sections continue to work in the drying mode. During this period, the bypass duct is switched off and the fresh source of energy is supplied only to section (C1), all fans except (B9), all air heaters are working, and exhaust energy is released to the outside only through fan (B8).

In example 2, the same as in example 1, the principle of a gradual decrease in the power of heaters in the direction of movement of the energy carrier is used, but already in a larger interval, namely from 90 to 10% of their rated power. In addition, for multi-section (with four and a large number of sections) installations, to ensure their compactness and to save the area of the sections, it is proposed to arrange not parallel lines, but parallel lines in plan, for example, 2,3,4 or more rows.

The most important role in ensuring stable uninterrupted and trouble-free operation of all nodes and elements of the drying unit of the claimed type is played by the energy flow control system, which usually consists of manually operated gate valves located in separate sections of the air ducts. However, the operation of such a system can be automated, for which each slide gate should be equipped with a servomotor using a software control subsystem that includes appropriate time relays and timers.

Claims (2)

1. The method of heat treatment of wood in a drying plant, consisting of a closed chamber, fan, air heater, ducts, a system for collecting and removing moisture and a regeneration system, characterized in that the closed chamber is made in the form of separate sections equipped with the same fans, heaters and air ducts with switching nodes of the energy carrier flows, providing its cyclical recirculation, while providing for a gradual decrease in the operating power of heaters in the direction of energy in the range from 90 to 10% of their rated power, depending on the number of sections in the installation, the temperature and humidity of the outdoor air, as well as the grade, volume, configuration, external dimensions, temperature and humidity of the treated wood, and each operation cycle of a separate section consists of periods the number of which corresponds to the number of sections in the installation, for example, for a two-section installation, such a period is 7-10 days with a cycle duration of 14-20 days, for a seven-section installation, this period of operation of a separate section of it lasts 2–3 days with a cycle duration of 14–21 days, alternating the process of complete selection of the spent energy from the section with its partial selection amounting to 60–80% of the input of the initial energy, with the simultaneous release of the remaining part of the spent energy in the amount of 20–40% the atmosphere. 2. The method according to claim 1, characterized in that the loading of each batch of processed wood in a separate section as well as unloading from it, is carried out for 3-6 hours, and to stabilize the return of spent energy to the process of heat treatment of wood in plants with more than five sections, the bypass duct is equipped with an additional fan.

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