FI97995B - Plant for drying solid timber and wood-based products - has material placed in drying camber which is then closed and its air evacuated prior to heat being fed into it - Google Patents

Abstract

The plant is for drying solid timber and wood-based products, and involves the material being placed in a drying chamber (1) which is then closed. The air is evacuated from the chamber, and heat is then fed into it so that moisture is evaporated at the same time as pressure and/or temp. are regulated. Steam is removed during the drying process by being made to condense in a heat exchanger (5), the steam flow between the drying chamber and the heat exchanger being regulated. The condensate in the heat exchanger is conducted away and the heat released with condensation is taken back into the heat exchanger and re-used.

Description

ηιιιιιιιηιιιι F10000979958

(B) (11) NOTICE OF PUBLICATION

UTLAGGHIHGSSKRIFT 97995 - * --- (51) Kv.lk.6 - Int.cl.6 F 268 3/04. 5/04 FINLAND - FINLAND (21) Patent application - Patentansökning 930392 (22) Application date - Ansöknlngsdag 29.01.93 ^ ^ (24) Start date - Lopdag 29.01.93 (41) Has become public - Blivit offentlig 30.07.94

Patent and Registration Office

Patent- och ragisterstyrelsen <">, 3., 2.» (71) Applicant - SSkande 1. Nurmisen Konepaja Ky, Yrittäjäntie 2, 19700 Sysmä, (FI) (72) Inventor - Uppfinnare 1. Oinonen, Reijo, Vehkatie 8 A, 19700 Sysmä, (FI) (74) Agent - Ombudsman: Oy Heininen Ab (54) Title of the invention - Uppfinningens benämning

Method and apparatus for drying wood and wood products Förfarande och anordning för torkning av trä octraserade produkter (56) Reference publications - Anförda pubiikationer EN A 793297 (F 26B 5/04), EN A 841046 (F 26B 21/00), EN C 87691 ( F 26B 3/04) (57) Seals - Sammandrag

Method for removing moisture from a solid Förfarande for avfuktning av massivt batch och wood and wood-based products or counterparts for the production of wood or wood-based products, i refers to a method in which wood or wood-based products are placed in a drying chamber ), (1), after which the drying chamber (1) is closed and the air chamber (l) is cleaned and deaerated, while heat is supplied to the chamber with heat from a liquid chamber in the wood. to remove the tea by steaming and adjusting the genom förängning samt tryeket och / eller by pressing the drying process under pressure and / or peraturen regleras. Angan avlägsnas under temperature. During the drying process, the genome of the steam torkprocessen ur torkkammaren (1) is removed from the drying chamber (1) by sealing the condenser in the heat exchanger (5), leaving the steam in the heat exchanger (5) - Växlaren (5) regleras. the condensate in the heat exchanger (5) is adjusted so that the condensed liquid is discharged in the heat exchanger (5) and the condensed liquid is discharged in the heat exchanger (5) and the steam in the heat exchanger (5) is condensed in the steam condenser (5) och äteranvänds. The heat released by the feedstock is recovered and used for a further account and is still used. The invention also relates to going uppinning.

equipment implementing the system.

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97995

METHOD AND EQUIPMENT FOR DRYING WOOD AND WOOD PRODUCTS -FÖRFARANDE OCH ANORDNING FÖR TORKNING AV TRÄ OCH TRÄBASERADE PRODUKTER

The invention relates to a method for drying wood and wood products according to the preamble of claim 1.

The invention also relates to an apparatus according to claim 7.

10

One such method and apparatus is known, for example, from EN B 87691. A disadvantage of the known methods and apparatus is e.g. their poor suitability for cold climate countries, especially in terms of heat recovery. According to the publication, the solution according to the publication presents a so-called an open system in which a pressure control valve opening and closing at certain pressure values is placed between the drying chamber and the cooler sealing tank, which is used to control the drying process. This system requires large 20 sealing tanks to operate.

It is an object of the present invention to provide a new type of drying method and apparatus in which the pressure, the temperature and the amount of water to be removed are continuously controlled in a continuously closed cycle in order to obtain optimal drying conditions. In addition, the heat recovered from the dryer is used in the method • · · ·. ·. and hardware more efficiently for the benefit of special ·: 1. by means of a condensing heat exchanger.

This object is achieved by a method according to the invention, which is characterized by what is stated in the claims below.

• · • · »··

The method and apparatus of the invention provide 3J5. fast drying with low energy consumption. In addition to heat · '·. Thanks to the recovery system, the heat recovered from the dryer can be better utilized with a special condensing heat exchanger. In the method according to the invention, the control of the process takes place by adjusting the flow of steam and the condensation of steam 40 and, if necessary, the rate and amount of water removal.

2 97995

The solution enables e.g. flexible placement of the heat exchanger in connection with the drying chamber. Low-cost utilization of distillates is also possible.

The following describes in more detail the method and apparatus according to the invention with reference to the drawings, in which

Fig. 1 is a diagram showing a dryer according to the invention, Fig. 2 is a diagram showing another dryer according to the invention,

Figure 3 shows a condensing heat exchanger according to the invention.

The process of the invention is commonly referred to as vacuum drying.

The drying chamber 1 of the vacuum dryer receives the initial and additional heat from the boiler plant (not shown in the figure) via pipes 10. Heating may be carried out by other possible methods,. . such as electricity. A drying chamber according to the invention is disclosed in FI B 87691. The principles of vacuum drying are also explained in the publication. Depending on the stage of the drying process: a significant part of the heat demand of the drying process can be • • ·: 2J5: covers the heat provided by the secondary circuit of the condensed heat exchanger 5 by means of 1 2 V. The water flow directions in the pictures are marked with arrows.

• · • · «• · ·

The drying chamber 1 contains wood to be dried, which is preferably stacked in layers in a stack of wood so that open spaces are formed between the layers of wood 30. The drying chamber is preferably a cylindrical space constructed to be pressure resistant.

• · · III One or more heating elements are arranged in the drying chamber. Tue 11 such as a rib coil or similar. The dimensions of the drying chamber vary depending on the application. In a preferred case, the chamber is about 18 m long and 3.5 m in diameter.

· »· • · 2 • · *. In the initial heating, the temperature of the drying chamber 1 and the batch of timber placed therein (not shown in the figure) is raised to 20-90 ° C, preferably 45-80 ° C. The vacuum pump 3 97995 2 is then started, which sucks the air out of the drying chamber 1. The pressure in the drying chamber is then 0.02 to 0.9 at. In this pressure range, the boiling point of water varies in the temperature range 17.2 to 96.2 ° C, preferably 45 to 80 ° C. It is also possible to first lower the pressure in the drying chamber and then raise the temperature.

The valve TV l.l opens and the boiler circuit circulating water pump P3 starts. In the drying chamber 1, the liquid, such as water, starts to evaporate and the temperature is raised so high that the liquid in the dry wood boils. Convection fans 12 or the like located in the drying chamber circulate this saturated or superheated steam, preferably between the strip-packed timber. By replacing the removed air, preferably with steam, the harmful effect of oxygen in the drying process is prevented. 15 As a result of heating and water evaporating from the wood, the steam pressure in the drying chamber starts to rise. In this case, a vacuum pump 3 is started, which sucks water from the lower part of the heat exchanger 5 (continuous removal), keeping the vacuum in the drying chamber to the desired size defined by the drying program. The steam to be removed from the drying chamber 1. the flow can be adjusted, for example, by controlling the 3 rpm of the pump. The water or other liquid sucked by the vacuum pump 3 causes a 'steam flow' from the drying chamber 1 to the heat exchanger 5, where the steam is condensed into a liquid. The liquid is discharged to a sewer, for example. ··· 25 »: The amount of liquid leaving and, if necessary, the temperature are monitored: with measuring device 4.

• · • · · • · · of the heat exchanger 5 secondary flow is directed primarily to the drying chamber 1. The temperature of the maintenance, in the alternative (the heating of the facility.. ·. Pipelines denoted with the system reference numeral 6) 30, for example, the production facilities for heating • · · '.Il and finally a cooling device 7, for example, cooling radiator \. Rille. Most of the waste heat of the cooling device 7 can also be used for heating production facilities (shown by reference number 3.5. * 8), in which case the heat is only dissipated during the warm season.

y] * The purpose of this secondary circuit is to cool the temperature of the water • circulating in the circuit to such a low level that, when it returns to the heat exchanger 5, it condenses, so that its temperature is below the drying temperature.

4 97 995 The heat exchanger 5 secondary flow is passed along the pipe through the pump P3 into the drying chamber 5 arranged in one or more of the heating element 11, such as a battery. The drying chamber is preferably provided with fans 12, which circulate 5 steam in the drying chamber 1 in order to ensure a rapid and even heating of the timber. From time to time, the direction of air flow can be changed, preferably by changing the direction of rotation of the axial fan 12. This enhances the transfer of moisture to the steam and provides a more even drying result. The motors 10 of the fans 12 are preferably located outside the drying chamber. The blades of the fans are shaped so that they give good efficiency when rotating in both directions. The radiators 11 of the secondary loop is guided to the valve TV 2.2. The TC 2.2 controller controls the TV 2.2 valve. The temperature of the flow 15 of the heating network 6 of the production facilities is measured by a sensor TE 2.2, which is connected to

to the controller TC 2.2. When the temperature is within the desired temperature range, water is directed through valves 2.2 and 2.1 to the heating network 6 of the production facilities. If the temperature is higher than TE

2.2 The setpoint is controlled by the water flow from the valve TV 2.2 to the radiator-20 m 7.

• · • »• * · I .. The return current of the heating network 6 is led to the heat exchanger 5 via the valve TV 3.1 • ·, or if the temperature measured by the measuring element TE 3.1 • · is too high, the valve TV 3.1 directs it to the supply line of the radiator 7 for cooling.

·· · • ·.

Figure 2 shows an alternative solution. Central to this is the alternating operation of the vacuum pumps 2, 3, which enables more versatile control of the drying process.

30,, · The exhaust air vacuum pump 2 draws in air through the condensing heat exchanger 5 0 · lii. The advantage of this is that if • · * becomes during drying. . the need to remove more steam than the water removed by the vacuum pump 3: .j. quantity required, the automatic V switches on the vacuum pump 2.

· · ·

The vacuum pump 2 is preferably more powerful than the vacuum pump; · * * 3. The power of both vacuum pumps can be adjusted, for example, ) also taking into account the drying time. The drying conditions are regulated by a control system called open formulas for drying formulas 11a. Drying formulas refer to the optimization of drying conditions e.g. regarding the quality and drying time of the 5 wood to be dried.

In the solution according to the examples, the process is controlled by a control system, some components of which are shown in the figures below, the controller TC 1.1 controls the control valve TV 1.1 by means of the sensors TE 1.1 and TE 1.2. In a preferred case, the drying program keeps the set temperature in the drying chamber constant. The temperature can be changed, for example, from the control center or by means of a drying program.

15 The TC 2.1 control unit controls the control valve of the TV 2.1 sensor TE

2.1 and the sensor TE 2.2 so as to obtain the desired temperature in the production rooms 6. The TC 2.1 controls the control valve TV 2.2 so that when the temperature of the water passing through the TV 2.1 rises above the set value TE 2.2, the valve TV 2.2 directs the water flow 20 to the cooler 7.

Valve 3.1 directs the constant heat * · h '' water to the return line of the heat exchanger 5. If the water temperature is too high, the valve controls •. to the flow line of its radiator 7 for recirculation through the cooler 7.

• · · • * • ·: V The heat generated by cooling can be used to heat production facilities, especially during the cold season. Otherwise, the heat generated is removed.

30

Figure 3 shows a condensing heat exchanger according to the invention.

Here I moved schematically. The heat exchanger consists of a tank 14, • · * \. inside which the steam of the drying chamber 1 is led from the drying chamber 1 through the steam removal pipe 13 and in which the tank has a pipe coil 3 * 3 15, inside which water circulates and on the outer surface of which the steam .. * * condenses into water. Water drains to the bottom of the tank from where it is removed • • * by means of pump 3 to a drain or the like. The amount of water accumulating in the lower part of the tank • · # · is limited by the electrode controllers Y, E. The controllers give an impulse to the control device V, which controls riUMrrr-'i ..... unt-v- -—---------- - - 6 97995 alternating operation of the vacuum pumps 2, 3 in the case according to Fig. 2. In this case, the water level remains in the desired range YR, AR. The control can also work so that the power of the pump is increased as the water level approaches the upper limit YR and the power decreases as the water level 5 approaches the lower limit AR. The control of the pumps can be relative or stepped.

It will be clear to a person skilled in the art that the invention is not limited to the above-mentioned application examples, but can be varied within the scope of the following claims.

• · • · • · • · • • m • · • · • • • • • • • • • • • • • • • · • · · · .. ·. ... .. ..—— · · = ——...................

Claims (8)

A method for dehumidifying solid wood and wood-based products or the like, in which method the wood or wood-based products are placed in a drying chamber (1), after which the drying chamber (1) is closed and the air is evacuated at the same time as heat is added to the chamber for moisture in the wood to be emit by displacement and the pressure and / or temperature is regulated and the meadow formed during the drying process is removed from the drying chamber by condensing it in a heat exchanger (5) connected to it, characterized in that the pressure in the drying chamber and the meadow flow from the drying chamber (1). ) to the heat exchanger (5) is controlled by extraction of water from the lower part of the heat exchanger (5), and thereby the vacuum is poured at programmed value, that the temperature in the drying chamber (1) is controlled by transferring heat from the secondary circuit of the heat exchanger (5). the heat exchanger (5) exiting the fluid flow is regulated. • · Process according to Claim 1, characterized in that *. * Meadow and / or the outgoing fluid flow is controlled by ** ·. controlling the speed of one or more pumps (2,3). 3. Method according to claims 1 or 2, characterized in that the meadow flow is regulated by damper control. Method according to Claim 2, characterized in that the pumps (2,3) are controlled with rotary operation according to the drying scheme in the *: · control system. 5. Method according to any one of claims 1-4, characterized in that the heat recovered in the heat exchanger (5) in the first • · m · »► · • · rw t '· ΓΜιΒϊίίηϊ V · ιί · ιίι- ~ i imi »i ι · ι · Τι ii * ii 'linii in ι'« i lU Γ.i iWnrr, · -> ^ .... - .. ^ ----- - ... .......... 97995 hand is used in the drying process and secondly for heating production premises or the like. Method according to any of claims 1-5, characterized in that the water in the secondary circuit of the heat exchanger (5) circulates to one or more heating elements (11) in the drying chamber (1) and / or to a heating network (6) or similar to the production premises and / or to a radiator (7) and finally via the return line back to the heat exchanger (5). Apparatus for use in a method according to claim 1, comprising a drying chamber (1), one or more heating elements (11) for raising and maintaining the temperature in the drying chamber (1), one or more tubes for extraction of steam and air from the drying chamber (1), a heat exchanger (5) connected to a meadow drain pipe (13), where the meadow condenses to liquid, and control means for the drying process, characterized in that the meadow is sucked by means of the heat exchanger (5). one or more pumps (2,3), the liquid is removed: from the heat exchanger (5), and the secondary circuit of the heat exchanger (5) is connected to a pipe network in which the water can be ···: *. to flow through the heating element (11) in the drying chamber and / or one or more heat distribution networks (6) and / or via a cooling device (7) so that the secondary circuit is terminated in the heat exchanger (5). . 8. Apparatus according to claim 7, characterized in that the heat exchanger (5) is provided at its lower part with sensors • · · · (Y, E) or the like which transmit control pulses to the 9 * ... control unit (V) which controls the alternate use of the pumps, * · whereby liquid level is poured into the area between the desired Upper • ♦: Y limit (YR) and the desired lower limit (AR). e · • * • · *