EP0592973A1 - Apparatus for drying wood or other solid materials - Google Patents

Apparatus for drying wood or other solid materials Download PDF

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Publication number
EP0592973A1
EP0592973A1 EP93116395A EP93116395A EP0592973A1 EP 0592973 A1 EP0592973 A1 EP 0592973A1 EP 93116395 A EP93116395 A EP 93116395A EP 93116395 A EP93116395 A EP 93116395A EP 0592973 A1 EP0592973 A1 EP 0592973A1
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EP
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Prior art keywords
boiler
cooling
cooling air
duct
wall
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EP93116395A
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German (de)
French (fr)
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EP0592973B1 (en
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Reinhard Dipl.-Ing. Brunner
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26DRYING
    • F26BDRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B25/00Details of general application not covered by group F26B21/00 or F26B23/00
    • F26B25/06Chambers, containers, or receptacles
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26DRYING
    • F26BDRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B5/00Drying solid materials or objects by processes not involving the application of heat
    • F26B5/04Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26DRYING
    • F26BDRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B9/00Machines or apparatus for drying solid materials or objects at rest or with only local agitation; Domestic airing cupboards
    • F26B9/06Machines or apparatus for drying solid materials or objects at rest or with only local agitation; Domestic airing cupboards in stationary drums or chambers
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26DRYING
    • F26BDRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B2210/00Drying processes and machines for solid objects characterised by the specific requirements of the drying good
    • F26B2210/16Wood, e.g. lumber, timber

Definitions

  • the invention relates to a device for drying wood or other solids, consisting of a boiler for vacuum operation, in which supports for lumber stacks, a heating device and a circulating device for the drying medium are installed, a condenser and a cooling air duct, the wall of which is through a Part of the outside of the boiler is formed.
  • This device is the subject of EP 0 505 586 A1.
  • This device dries wood at negative pressure and represents a so-called vacuum dryer.
  • This consists of a pressure-resistant, hermetically lockable drying chamber with a connected vacuum pump, has a support for wood piles, is equipped with a heating device and a circulating device for a gaseous drying medium and has inside Boiler on a condenser, which is wholly or partly formed by a part of the chamber inner wall, which is cooled by a cooling air duct located on the outside of the boiler, for which that part of the chamber wall, which acts as a condenser on the inside, forms a boundary surface.
  • the cooling air duct is used to dissipate the heat of condensation, which is the moisture escaping from the wood in the form of water vapor releases during condensation to the condenser cooled to below the dew point.
  • the boiler shown in this document has no boiler insulation in its lower area under the condensation space separated by a partition wall, but fans arranged at the side, which allow cooling air to pass the boiler wall transversely to the axial direction through a channel arranged under the boiler. Since the length of the boiler is usually much greater than its width, a large number of fans must be arranged along an axis-parallel line on the boiler wall for effective cooling, which drive the cooling air along the entire length of the boiler as far as possible along the boiler walls. The purchase and arrangement of such a large number of fans is complex and expensive.
  • the present invention avoids the disadvantages of the prior art. It is the object of the invention to achieve the task of adequate cooling, in particular of the condenser, with little construction effort and with little energy input.
  • the invention consists in that the cooling air duct extends axially parallel over most of the boiler in the longitudinal direction, that the air flow in the cooling air duct runs in the longitudinal direction of the boiler and that the effective duct width is large compared to the duct height is.
  • the channel height cannot be selected close to zero, since otherwise the flow resistance of the channel becomes large without the flow speed increasing further.
  • the amount of air that can be transported per unit of time or the available heat capacity of this amount of air must at least be so high that the amount of heat generated can be absorbed by the boiler wall before temperature compensation is reached.
  • duct heights between 2 cm and 15 cm are to be selected depending on the length and diameter of the drying boiler and the overall cross section of the fans used for cooling.
  • the exact choice of the channel height within the limits mentioned also depends on the type and strength of the dry goods, ie the drying speed most favorable for this good, by means of which the required cooling capacity is predetermined.
  • a duct height is thus chosen which is so small that the air conveyed in the duct reaches a sufficiently high speed and all air sub-volumes come into contact with the boiler wall on its way, but the duct cross section is still large enough that the The amount of air conveyed per unit of time is sufficient to absorb the heat of condensation depending on the drying speed.
  • the cooling duct is widened in its course, preferably at one end, and contains fans for conveying cooling air at this widened point. This ensures that high-performance fans of conventional design can be used to convey the cooling air through the very flat duct.
  • cooling channel protruding beyond the end of the boiler is terminated by a vertical wall, in the openings of which the nozzles of the fans used to convey the cooling air can be simply mounted.
  • the boundary surface missing from the end of the boiler of the channel can be replaced by a cover attached at the top.
  • the production of the cooling channel is simple and very inexpensive if the outer wall of the cooling channel consists of sheet metal or plastic.
  • the outer wall of the cooling channel is thermally insulated or consists of a heat-insulating material. This ensures that the cooling capacity can be reduced to a small value when the fans are at rest, if no or only slight dehumidification is to take place in the current drying phase.
  • an additional condenser with a closed liquid cooling circuit is used in the drying chamber, an additional cooling device can be avoided by installing the flat heat exchanger of this additional condenser in the cooling duct.
  • the cooling duct is connected to a chimney. It is advantageous here if the cooling air duct is led beyond the fan opening to an at least 3 m high chimney, which expediently contains an adjustable air flap inside or at the upper end. When the flap is open, the wind in the chimney creates an air flow through the cooling duct, even when the fans are not running. The strength of this flow can be controlled by the flap position.
  • Another function of the fireplace is to dampen the noise generated by the cooling fans. For this purpose, it may be advantageous to line the inside of the fireplace with sound-absorbing materials. The same purpose is also achieved with a brick fireplace, for example. This makes it possible to operate drying systems in the vicinity of residential areas, since economical drying cannot be interrupted at night or is preferably done at night due to the lower electricity costs.
  • the cooling tasks in vacuum drying also affect the operation of the vacuum pump:
  • a powerful pump first requires pre-cooling in the suction area so that the partial pressure of the condensable vapors can be reduced to a level necessary for the pumping process.
  • the process heat of the pump must be removed so that a favorable operating temperature can be maintained. For larger pumps, this is done using a closed cooling circuit with an external heat exchanger or by direct cooling with mostly expensive fresh water.
  • the suction pipe between the drying boiler and the pump is led through the cooling duct, the pump can be set up in such a way that the pump motor is swept by the pumped air flow, and the heat exchanger of the pump cooling circuit is arranged at a suitable point in the duct.
  • the chimney or the expanded part of the cooling channel is the most suitable location.
  • speed-controlled cooling fans are preferably used. Controlled cooling of two independent systems with only one blower control is possible because normally not both systems are in operation at the same time:
  • the vacuum pump is only switched on for a longer period of time before the drying process begins while the drying chamber is evacuated, if the wood has not yet is heated up and no condensation takes place yet.
  • the pump is only used for a relatively short time if the partial air pressure in the chamber has to be reduced to the setpoint due to leaks or air escaping from the wood.
  • the setpoint for the steam partial pressure is set via the condenser temperature and does not require use of the pump.
  • the boiler 2 provided with a gate 1 is provided with insulation 3 on its upper side.
  • the non-insulated lower part of the boiler has on its outside a cooling channel 4, the width of which is much larger than the height.
  • This cooling channel is formed on the one hand by the lower, non-insulated part of the wall of the boiler 2, on the other hand by an outer wall 5.
  • a carriage 6 with the loading surface 7 is inserted, on which a stack 8 of wood to be dried is loaded.
  • the loading area 7 forms part of the partition, which is continued on both sides of the carriage 6 with the loaded stack of wood 8 through inner walls 9.
  • the condensation space l0 is thus formed by the loading surface 7, the inner walls 8 and the non-insulated part of the wall of the boiler 2.
  • the remaining part of the interior of the boiler is the actual drying room, in which a fan l2 and a heating device l3 are accommodated.
  • the fan 12 produces a circular flow of the desiccant in the drying room.
  • water vapor constantly migrates from the drying space 11 into the condensation space 10 and is deposited here in the form of water on the boiler wall.
  • the kettle stands on feet l4, which rest on foundations (not shown).
  • the cooling air enters the cooling channel 4 close to the gate l.
  • the cooling duct extends beyond the side of the boiler remote from gate 1 and points here a part l5 with an enlarged cross-section.
  • the cooling duct is terminated here by a partition l6 in which openings l7 for fans l8 are arranged. These convey the heated cooling air into the chimney l9, in which the vacuum pump 20 and a heat exchanger 2l of the pump cooling circuit are accommodated.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Molecular Biology (AREA)
  • Drying Of Solid Materials (AREA)

Abstract

The invention relates to an apparatus consisting of a boiler (2) for low-pressure operation, in which supports (7) for sawn timber stacks (8), a heating device (13) and a circulating device (12) for the drying medium are installed, of a condenser and of a cooling air duct (4), one wall of which is formed by a part of the boiler outer side. The aim of the invention is, with low structural outlay and with low energy use, to achieve the aim of adequate cooling, in particular of the condenser. The invention consists in that the cooling air duct (4) extends axially parallel over the major part of the boiler (2) in the longitudinal direction, that the air flow in the cooling air duct (4) runs in the longitudinal direction of the boiler (2) and that the effective duct width is large in relation to the duct height. <IMAGE>

Description

Die Erfindung betrifft eine Vorrichtung zum Trocknen von Holz oder anderen Feststoffen, bestehend aus einem Kessel für Unterdruckbetrieb, in welchem Auflager für Schnittholzstapel, eine Heizvorrichtung und eine Umwälzvorrichtung für das Trocknungsmedium eingebaut sind, aus einem Kondensator und aus einem Kühlluftkanal, dessen eine Wandung durch einen Teil der Kesselaußenseite gebildet ist.The invention relates to a device for drying wood or other solids, consisting of a boiler for vacuum operation, in which supports for lumber stacks, a heating device and a circulating device for the drying medium are installed, a condenser and a cooling air duct, the wall of which is through a Part of the outside of the boiler is formed.

Diese Vorrichtung ist Gegenstand der EP 0 505 586 A1. Diese Vorrichtung trocknet Holz bei Unterdruck und stellt einen sogenannten Vakuumtrockner dar. Dieser besteht aus einer druckfesten, hermetisch abschließbaren Trockenkammer mit angeschlossener Vakuumpumpe, weist ein Auflager für Holzstapel auf, ist mit einer Heizvorrichtung und einer Umwälzvorrichtung für ein gasförmiges Trocknungsmedium ausgestattet und weist im Inneren seines Kessels einen Kondensator auf, der ganz oder teilweise durch einen Teil der Kammerinnenwandung gebildet wird, die von einem außen am Kessel liegenden Kühlluftkanal gekühlt wird, für den derjenige Teil der Kammerwand, der im Inneren als Kondensator fungiert, eine Begrenzungsfläche bildet. Der Kühlluftkanal dient dabei der Abführung der Kondensationswärme, die die aus dem Holz in Form von Wasserdampf austretende Feuchtigkeit bei ihrer Kondensation an den unter den Taupunkt abgekühlten Kondensator abgibt.This device is the subject of EP 0 505 586 A1. This device dries wood at negative pressure and represents a so-called vacuum dryer. This consists of a pressure-resistant, hermetically lockable drying chamber with a connected vacuum pump, has a support for wood piles, is equipped with a heating device and a circulating device for a gaseous drying medium and has inside Boiler on a condenser, which is wholly or partly formed by a part of the chamber inner wall, which is cooled by a cooling air duct located on the outside of the boiler, for which that part of the chamber wall, which acts as a condenser on the inside, forms a boundary surface. The cooling air duct is used to dissipate the heat of condensation, which is the moisture escaping from the wood in the form of water vapor releases during condensation to the condenser cooled to below the dew point.

Der in dieser Druckschrift gezeigte Kessel weist in seinem unteren Bereich unter dem durch eine Trennwand abgetrennten Kondensationsraum keine Kesselisolierung auf, sondern seitlich angeordnete Ventilatoren, die durch einen unter dem Kessel angeordneten Kanal Kühlluft quer zur Achsrichtung an der Kesselwandung vorbeistreichen lassen. Da die Länge des Kessels üblicherweise sehr viel größer ist als dessen Breite, müssen für eine wirkungsvolle Kühlung eine Vielzahl von Gebläsen entlang einer achsparallelen Linie an der Kesselwandung angeordnet werden, die die Kühlluft möglichst längs der gesamten Länge des Kessels an den Kesselwandungen vorbeitreiben. Die Anschaffung und die Anordnung einer solchen Vielzahl von Gebläsen ist aufwendig und teuer.The boiler shown in this document has no boiler insulation in its lower area under the condensation space separated by a partition wall, but fans arranged at the side, which allow cooling air to pass the boiler wall transversely to the axial direction through a channel arranged under the boiler. Since the length of the boiler is usually much greater than its width, a large number of fans must be arranged along an axis-parallel line on the boiler wall for effective cooling, which drive the cooling air along the entire length of the boiler as far as possible along the boiler walls. The purchase and arrangement of such a large number of fans is complex and expensive.

Der Energieaufwand für den Antrieb der Vielzahl von Gebläsen macht sich erheblich im Preis der Holztrocknung bemerkbar. Denn auf der kurzen Strecke, die die Kühlluft an der Kesselwandung bei der bekannten quer zur Achsrichtung verlaufenden Strömung vorbeistreicht, wird nur relativ wenig Wärme pro Kühlluftvolumen abgeleitet.The energy expenditure for driving the large number of fans has a considerable impact on the price of wood drying. Because on the short distance that the cooling air passes the boiler wall in the known cross-axial flow, only relatively little heat is dissipated per cooling air volume.

Diese Nachteile werden durch eine andere Ausführungsform eines Vakuumtrockners, der in der DE-OS 42 08 9l3 beschrieben ist, zum Teil vermieden. Diese Druckschrift zeigt einen Kühlluftkanal, der durch die Kesselaußenwand und das Fundament begrenzt ist, sich in Achsrichtung des Kessels erstreckt und die Kühlluftventilatoren im Kanal unterhalb des Kessels enthält. Hierdurch wird die große Anzahl von Gebläsen vermieden. Diese Ausführungsform hat, insbesondere bei langen Kesseln, den Nachteil hoher Fundamentkosten. Außerdem läßt sich wegen der relativ großen Höhe des Kanals, die größer ist als der Ventilatordurchmesser, die dem Ventilatormotor zugeführte elektrische Energie nicht voll nutzen, da ein wesentlicher Teil der geförderten Kühlluft mit der Kesselwandung nicht in Berührung kommt und deshalb nicht zur Kühlung beiträgt.These disadvantages are partially avoided by another embodiment of a vacuum dryer, which is described in DE-OS 42 08 9l3. This document shows a cooling air duct which is delimited by the outer wall of the boiler and the foundation, extends in the axial direction of the boiler and the cooling air fans in the channel below the boiler. This avoids the large number of fans. This embodiment has the disadvantage of high foundation costs, particularly in the case of long boilers. In addition, because of the relatively large height of the duct, which is larger than the fan diameter, the electrical energy supplied to the fan motor cannot be fully used, since a substantial part of the conveyed cooling air does not come into contact with the boiler wall and therefore does not contribute to cooling.

Aber nicht nur der Kondensator ist zu kühlen, sondern auch andere Aggregate, insbesondere die Vakuumpumpe oder deren Teile. Die Energie für die Kühlung der Vakuumpumpe oder ihrer Teile ist hingegen nicht so hoch, weil die Vakuumpumpe nicht ständig im Betrieb ist, sondern vornehmlich zu Beginn des Trocknungsvorganges eingeschaltet wird. Sie ist dann zu einer Zeit im Betrieb, zu der die Kesselwandung noch nicht gekühlt zu werden braucht.But not only the condenser has to be cooled, but also other units, especially the vacuum pump or its parts. The energy for cooling the vacuum pump or its parts, on the other hand, is not so high because the vacuum pump is not constantly in operation, but is switched on primarily at the beginning of the drying process. It is then in operation at a time when the boiler wall does not need to be cooled yet.

Die vorliegende Erfindung vermeidet die Nachteile des Standes der Technik. Es ist die Aufgabe der Erfindung, mit geringem baulichen Aufwand und mit geringem Energieeinsatz die Aufgabe einer ausreichenden Kühlung, insbesondere des Kondensators, zu erreichen.The present invention avoids the disadvantages of the prior art. It is the object of the invention to achieve the task of adequate cooling, in particular of the condenser, with little construction effort and with little energy input.

Die Erfindung besteht darin, daß der Kühlluftkanal sich achsparallel über den größten Teil des Kessels in Längsrichtung erstreckt, daß die Luftströmung im Kühlluftkanal in Längsrichtung des Kessels verläuft und daß die effektive Kanalbreite groß gegenüber der Kanalhöhe ist.The invention consists in that the cooling air duct extends axially parallel over most of the boiler in the longitudinal direction, that the air flow in the cooling air duct runs in the longitudinal direction of the boiler and that the effective duct width is large compared to the duct height is.

Durch diese Gestaltung ist eine große Wärmetauscherfläche relativ zum Volumen des Kühlkanales erreicht. Je nach Kessellänge genügen ein oder zwei Ventilatoren. Wird bei vorgegebener Kanalbreite die Höhe des Kanals und damit auch sein Querschnitt verkleinert, so erhöht sich bei gleicher Förderleistung der Ventilatoren die Strömungsgeschwindigkeit im Kanal entsprechend. Nun ist aber diejenige Wärmemenge, die bei gegebener Temperaturdifferenz pro Zeit- und Flächeneinheit von einem festen Körper in ein strömendes Medium übertritt (gekennzeichnet durch die Wärmeübergangszahl) in grober Näherung proportional der Strömungsgeschwindigkeit. Es wird somit dadurch, daß die Kanalhöhe klein gegen die effektive Kanalbreite (d.h. die Länge des Kreisbogens des Kanalquerschnitts) gewählt wird, erreicht, daß eine wirksamere Kühlung des Kondensators mit weniger Luft stattfindet. Jedoch kann die Kanalhöhe nicht nahe Null gewählt werden, da sonst der Strömungswiderstand des Kanals groß wird, ohne daß die Strömungsgeschwindigkeit weiter ansteigt. Die pro Zeiteinheit transportierbare Luftmenge bzw. die zur Verfügung stehende Wärmekapazität dieser Luftmenge muß zumindst so hoch sein, daß die anfallende Wärmemenge vor dem Erreichen des Temperaturausgleichs mit der Kesselwand überhaupt aufgenommen werden kann. In der praktischen Ausführung sind je nach Länge und Durchmesser des Trockenkessels sowie je nach Gesamtquerschnitt der zur Kühlung eingesetzten Ventilatoren Kanalhöhen zwischen 2 cm und l5 cm zu wählen. Die genaue Wahl der Kanalhöhe innerhalb der genannten Grenzen hängt außerdem von Art und Stärke des Trockenguts ab, d.h. der für dieses Gut günstigsten Trocknungsgeschwindigkeit, durch welche die erforderliche Kühlleistung vorgegeben ist.With this design, a large heat exchanger area is achieved relative to the volume of the cooling channel. Depending on the boiler length, one or two fans are sufficient. If the height of the channel and thus also its cross-section is reduced for a given channel width, the flow rate in the channel increases accordingly with the same fan output. Now, however, the amount of heat that, at a given temperature difference per unit of time and area, passes from a solid body into a flowing medium (characterized by the heat transfer coefficient) is roughly proportional to the flow velocity. It is thus achieved in that the channel height is small compared to the effective channel width (ie the length of the circular arc of the channel cross section) that more effective cooling of the condenser takes place with less air. However, the channel height cannot be selected close to zero, since otherwise the flow resistance of the channel becomes large without the flow speed increasing further. The amount of air that can be transported per unit of time or the available heat capacity of this amount of air must at least be so high that the amount of heat generated can be absorbed by the boiler wall before temperature compensation is reached. In the practical version, duct heights between 2 cm and 15 cm are to be selected depending on the length and diameter of the drying boiler and the overall cross section of the fans used for cooling. The exact choice of the channel height within the limits mentioned also depends on the type and strength of the dry goods, ie the drying speed most favorable for this good, by means of which the required cooling capacity is predetermined.

Erfindungsgemäß wird somit eine Kanalhöhe gewählt, die so klein ist, daß die im Kanal geförderte Luft eine genügend hohe Geschwindigkeit erreicht und alle Luftteilvolumina mit der Kesselwandung auf dem Lauf ihres Weges in Berührung kommen, wobei der Kanalquerschnitt jedoch immer noch groß genug ist, daß die pro Zeiteinheit geförderte Luftmenge ausreicht, um die je nach Trocknungsgeschwindigkeit anfallende Kondensationswärme aufzunehmen.According to the invention, a duct height is thus chosen which is so small that the air conveyed in the duct reaches a sufficiently high speed and all air sub-volumes come into contact with the boiler wall on its way, but the duct cross section is still large enough that the The amount of air conveyed per unit of time is sufficient to absorb the heat of condensation depending on the drying speed.

Vorteilhaft ist es, wenn der Kühlkanal in seinem Verlauf, vorzugsweise an seinem einen Ende, aufgeweitet ist und an dieser aufgeweiteten Stelle Ventilatoren für die Förderung von Kühlluft enthält. Hierdurch ist erreicht, daß leistungsstarke Gebläse von üblicher Bauform eingesetzt werden können, um die Kühlluft durch den sehr flachen Kanal hindurchzufördern.It is advantageous if the cooling duct is widened in its course, preferably at one end, and contains fans for conveying cooling air at this widened point. This ensures that high-performance fans of conventional design can be used to convey the cooling air through the very flat duct.

Dabei ist es zweckmäßig, wenn der über das Kesselende hinausragende Kühlkanal durch eine senkrechte Wand beendet ist, in deren Öffnungen die Düsen der zur Förderung der Kühlluft dienenden Ventilatoren einfach montiert werden können.It is expedient if the cooling channel protruding beyond the end of the boiler is terminated by a vertical wall, in the openings of which the nozzles of the fans used to convey the cooling air can be simply mounted.

Hier kann man Axial- oder Radialventilatoren zum Einsatz bringen.Here you can use axial or radial fans.

Die jenseits des Kesselendes fehlende Begrenzungsfläche des Kanals kann durch eine oben aufgebrachte Abdeckung ersetzt sein.The boundary surface missing from the end of the boiler of the channel can be replaced by a cover attached at the top.

Die Herstellung des Kühlkanales wird einfach und sehr preiswert, wenn die Außenwand des Kühlkanales aus Blech oder Kunststoff besteht.The production of the cooling channel is simple and very inexpensive if the outer wall of the cooling channel consists of sheet metal or plastic.

Dabei kann es zweckmäßig sein, wenn die Außenwand des Kühlkanales wärmeisoliert ist oder aus einem wärmeisolierenden Material besteht. Hierdurch wird erreicht, daß sich die Kühlleistung bei ruhenden Ventilatoren auf einen kleinen Wert reduzieren läßt, wenn in der laufenden Trocknungsphase keine oder nur geringe Entfeuchtung stattfinden soll.It can be expedient if the outer wall of the cooling channel is thermally insulated or consists of a heat-insulating material. This ensures that the cooling capacity can be reduced to a small value when the fans are at rest, if no or only slight dehumidification is to take place in the current drying phase.

Wenn z.B. für eine rasche Trocknung von Weichhölzern bei hohen Außentemperaturen ein zusätzlicher Kondensator mit geschlossenem Flüssigkeitskühlkreislauf in der Trockenkammer verwendet wird, kann man dadurch, daß der flache Wärmetauscher dieses Zusatzkondensators im Kühlkanal angebracht wird, eine zusätzliche Kühlvorrichtung vermeiden.If e.g. For a quick drying of softwood at high outside temperatures, an additional condenser with a closed liquid cooling circuit is used in the drying chamber, an additional cooling device can be avoided by installing the flat heat exchanger of this additional condenser in the cooling duct.

Um den Strombedarf der Kühlventilatoren zu verringern, ist es zweckmäßig, wenn der Kühlkanal an einen Kamin angeschlossen ist. Hierbei ist es vorteilhaft, wenn der Kühlluftkanal über die Ventilatoröffnung hinaus zu einem mindestens 3 m hohen Kamin geführt ist, der zweckmäßigerweise im Inneren oder am oberen Ende eine einstellbare Luftklappe enthält. Bei geöffneter Klappe entsteht durch den Aufwind im Kamin eine Luftströmung durch den Kühlkanal auch bei stillstehenden Ventilatoren. Die Stärke dieser Strömung kann durch die Klappenstellung gesteuert werden. Eine weitere Funktion des Kamins besteht darin, die starke Geräuschentwicklung der Kühlventilatoren zu dämpfen. Für diesen Zweck kann es vorteilhaft sein, den Kamin im Inneren mit schallschluckenden Materialien auszukleiden. Derselbe Zweck wird z.B. auch mit einem gemauerten Kamin erreicht. Dadurch wird es möglich, Trockenanlagen auch in der Nähe von Wohngebieten zu betreiben, da eine wirtschaftliche Trocknung nachts nicht unterbrochen werden kann bzw. wegen der geringeren Stromkosten bevorzugt nachts erfolgt.In order to reduce the power consumption of the cooling fans, it is useful if the cooling duct is connected to a chimney. It is advantageous here if the cooling air duct is led beyond the fan opening to an at least 3 m high chimney, which expediently contains an adjustable air flap inside or at the upper end. When the flap is open, the wind in the chimney creates an air flow through the cooling duct, even when the fans are not running. The strength of this flow can be controlled by the flap position. Another function of the fireplace is to dampen the noise generated by the cooling fans. For this purpose, it may be advantageous to line the inside of the fireplace with sound-absorbing materials. The same purpose is also achieved with a brick fireplace, for example. This makes it possible to operate drying systems in the vicinity of residential areas, since economical drying cannot be interrupted at night or is preferably done at night due to the lower electricity costs.

Bei besonders langen Kesseln kann es vorteilhaft sein, von beiden Enden des Kühlkanales Kühlluft anzusaugen, im Bereich der Kesselmitte den erweiterten Raum des Kanals anzuordnen und hier auch die verbrauchte Kühlluft herauszulassen, z.B. über einen oder zwei Kamine.In the case of particularly long boilers, it can be advantageous to draw in cooling air from both ends of the cooling duct, to arrange the expanded space of the duct in the middle of the boiler and to let out the used cooling air, e.g. over one or two fireplaces.

Die Kühlaufgaben bei der Vakuumtrocknung betreffen auch den Betrieb der Vakuumpumpe: Eine leistungsstarke Pumpe benötigt zunächst eine Vorkühlung im Ansaugbereich, damit der Partialdruck der kondensierbaren Dämpfe auf ein für den Pumpvorgang erforderliches Maß herabgesetzt werden kann. Zum zweiten muß die Prozeßwärme der Pumpe abgeführt werden, damit eine günstige Betriebstemperatur aufrecht erhalten werden kann. Das geschieht bei größeren Pumpen mit Hilfe eines geschlossenen Kühlkreislaufs mit externem Wärmetauscher oder durch Direktkühlung mit meist teurem Frischwasser. Zum dritten ist es erforderlich, den Elektromotor der Pumpe zu kühlen, um den Verschleiß zu mindern und die Lebensdauer der Pumpe zu verlängern. Es ist daher zweckmäßig, wenn die Vakuumpumpe oder Teile der Vakuumpumpe, vorzugsweise das Ansaugrohr, ein Wärmetauscher und/oder der Motor im Kühlkanal untergebracht sind. Hierdurch läßt sich eine zusätzliche Kühlvorrichtung für die Vakuumpumpe einsparen. Das Ansaugrohr zwischen Trockenkessel und Pumpe wird durch den Kühlkanal geführt, die Pumpe läßt sich derart aufstellen, daß der Pumpenmotor vom geförderten Luftstrom überstrichen wird, und der Wärmetauscher des Pumpenkühlkreislaufs wird an geeigneter Stelle im Kanal angeordnet. Als geeignete Stelle ergibt sich vor allem der Kamin oder der aufgeweitete Teil des Kühlkanals.The cooling tasks in vacuum drying also affect the operation of the vacuum pump: A powerful pump first requires pre-cooling in the suction area so that the partial pressure of the condensable vapors can be reduced to a level necessary for the pumping process. Secondly, the process heat of the pump must be removed so that a favorable operating temperature can be maintained. For larger pumps, this is done using a closed cooling circuit with an external heat exchanger or by direct cooling with mostly expensive fresh water. Thirdly, it is necessary to cool the electric motor of the pump in order to reduce the wear and the service life to extend the pump. It is therefore expedient if the vacuum pump or parts of the vacuum pump, preferably the intake pipe, a heat exchanger and / or the motor are accommodated in the cooling duct. This can save an additional cooling device for the vacuum pump. The suction pipe between the drying boiler and the pump is led through the cooling duct, the pump can be set up in such a way that the pump motor is swept by the pumped air flow, and the heat exchanger of the pump cooling circuit is arranged at a suitable point in the duct. The chimney or the expanded part of the cooling channel is the most suitable location.

Um einerseits die Kühlleistung für den Kondensator und auch für den Pumpenwärmetauscher regeln zu können und um andererseits Kosten für elektrische Energie einzusparen, werden vorzugsweise drehzahlgeregelte Kühlventilatoren verwendet. Eine geregelte Kühlung von zwei unabhängigen Systemen mit nur einer Gebläsesteuerung ist deshalb möglich, weil im Normalfall nicht beide Systeme gleichzeitig im Betrieb sind: Die Vakuumpumpe wird nur vor Beginn der Trocknung während der Evakuierung der Trockenkammer für einen längeren Zeitraum eingeschaltet, wenn das Holz noch nicht aufgeheizt ist und noch keine Kondensation stattfindet. Im weiteren Verlauf der Trocknung kommt die Pumpe nur dann relativ kurzfristig zum Einsatz, wenn der Luftpartialdruck in der Kammer wegen Undichtigkeiten oder wegen aus dem Holz austretender Luft auf den Sollwert abgesenkt werden muß. Die Einstellung des Sollwerts für den Dampfpartialdruck erfolgt über die Kondensatortemperatur und erfordert keinen Einsatz der Pumpe.In order to be able to regulate the cooling capacity for the condenser and also for the pump heat exchanger on the one hand and to save costs for electrical energy on the other hand, speed-controlled cooling fans are preferably used. Controlled cooling of two independent systems with only one blower control is possible because normally not both systems are in operation at the same time: The vacuum pump is only switched on for a longer period of time before the drying process begins while the drying chamber is evacuated, if the wood has not yet is heated up and no condensation takes place yet. In the further course of drying, the pump is only used for a relatively short time if the partial air pressure in the chamber has to be reduced to the setpoint due to leaks or air escaping from the wood. The setpoint for the steam partial pressure is set via the condenser temperature and does not require use of the pump.

Wenn mit relativ hohen Temperaturen getrocknet wird und die längs des Kessels erwärmte Kühlluft nicht mehr zur Kühlung der Pumpe ausreicht, ist der Einsatz von reversierbaren Kühlventilatoren zweckmäßig. Bei Reversierung der Drehrichtung erreicht die angesaugte, kühle Frischluft zunächst die Vakuumpumpe bzw. ihre Teile. Das Ansaugen kann auch durch den Kamin erfolgen. Die Reversierbarkeit hat noch einen zusätzlichen Vorteil: Wenn mit relativ hohem Luftpartialdruck des Trocknungsmediums getrocknet wird, ist die spontane, gleichmäßige Ausbreitung des Wasserdampfs in der Trockenkammer durch Diffusionsvorgänge behindert. Holzstapel, die den kühleren Kondensatorbereichen an der Lufteintrittsseite am nächsten liegen, trocknen dann etwas schneller als die Stapel am wärmeren Ende. Durch Reversierung der Luftrichtung zu geeigneten Zeitabschnitten läßt sich dieser Effekt eleminieren. Es lassen sich aber auch Stapelbereiche an den Enden des Trockenkessels gezielt unterschiedlich trocknen, wenn sie beispielsweise mit unterschiedlichen Anfangsfeuchten in die Kammer eingebracht werden.If drying takes place at relatively high temperatures and the cooling air heated along the boiler is no longer sufficient to cool the pump, the use of reversible cooling fans is advisable. When the direction of rotation is reversed, the drawn-in, cool fresh air first reaches the vacuum pump or its parts. The chimney can also be used for suction. The reversibility has an additional advantage: If drying is carried out with a relatively high air partial pressure of the drying medium, the spontaneous, uniform spread of the water vapor in the drying chamber is impeded by diffusion processes. Wood stacks that are closest to the cooler condenser areas on the air inlet side then dry somewhat faster than the stacks at the warmer end. This effect can be eliminated by reversing the direction of the air at appropriate times. However, stack areas at the ends of the drying kettle can also be specifically dried differently if, for example, they are introduced into the chamber with different initial moisture levels.

Das Wesen der Erfindung ist nachstehend anhand eines in der Zeichnung schematisch dargestellten Ausführungsbeispieles näher erläutert. Es zeigen:

Fig. l
eine Ansicht der Trocknungsvorrichtung,
Fig. 2
einen Schnitt durch den Kessel,
Fig. 3
die Anordnung der Ventilatoren im erweiterten Bereich des Kühlluftkanals.
The essence of the invention is explained below with reference to an embodiment shown schematically in the drawing. Show it:
Fig. L
a view of the drying device,
Fig. 2
a cut through the cauldron,
Fig. 3
the arrangement of the fans in the extended area of the cooling air duct.

Der mit einem Tor 1 versehene Kessel 2 ist an seiner Oberseite mit einer Isolierung 3 versehen. Der nicht isolierte untere Teil des Kessels weist an seiner Außenseite einen Kühlkanal 4 auf, dessen Breite sehr viel größer als dessen Höhe ist. Dieser Kühlkanal wird einerseits durch den unteren, nicht isolierten Teil der Wand des Kessels 2 gebildet, andererseits durch eine Außenwand 5. Im Inneren des Kessels ist ein Wagen 6 mit der Ladefläche 7 eingefahren, auf welcher ein Stapel 8 von zu trocknendem Holz aufgeladen ist. Die Ladefläche 7 bildet einen Teil der Trennwand, die zu beiden Seiten des Wagens 6 mit dem aufgeladenen Holzstapel 8 durch Innenwände 9 fortgesetzt ist. Der Kondensationsraum l0 ist somit durch die Ladefläche 7, die Innenwände 8 und den nicht isolierten Teil der Wand des Kessels 2 gebildet. Der übrige Teil des Innenraums des Kessels ist der eigentliche Trocknungsraum, in welchem ein Ventilator l2 und eine Heizvorrichtung l3 untergebracht sind. Durch den Ventilator l2 wird im Trocknungsraum eine kreisförmige Strömung des Trockenmittels erzeugt. Durch die Spalten zwischen der Ladefläche 7 und den Innenwänden 9 wandert ständig aus dem Trocknungsraum ll Wasserdampf in den Kondensationsraum l0 und wird hier in Form von Wasser an der Kesselwandung niedergeschlagen. Der Kessel steht auf Füßen l4, die auf (nicht dargestellten) Fundamenten ruhen.The boiler 2 provided with a gate 1 is provided with insulation 3 on its upper side. The non-insulated lower part of the boiler has on its outside a cooling channel 4, the width of which is much larger than the height. This cooling channel is formed on the one hand by the lower, non-insulated part of the wall of the boiler 2, on the other hand by an outer wall 5. Inside the boiler, a carriage 6 with the loading surface 7 is inserted, on which a stack 8 of wood to be dried is loaded. The loading area 7 forms part of the partition, which is continued on both sides of the carriage 6 with the loaded stack of wood 8 through inner walls 9. The condensation space l0 is thus formed by the loading surface 7, the inner walls 8 and the non-insulated part of the wall of the boiler 2. The remaining part of the interior of the boiler is the actual drying room, in which a fan l2 and a heating device l3 are accommodated. The fan 12 produces a circular flow of the desiccant in the drying room. Through the gaps between the loading surface 7 and the inner walls 9, water vapor constantly migrates from the drying space 11 into the condensation space 10 and is deposited here in the form of water on the boiler wall. The kettle stands on feet l4, which rest on foundations (not shown).

Die Kühlluft tritt in den Kühlkanal 4 dicht neben dem Tor l ein. Der Kühlkanal ist über die dem Tor l abgelegene Seite des Kessels hinaus geführt und weist hier einen Teil l5 mit erweitertem Querschnitt auf. Der Kühlkanal ist hier durch eine Trennwand l6 beendet, in der Öffnungen l7 für Ventilatoren l8 angeordnet sind. Diese fördern die erwärmte Kühlluft in den Kamin l9, in welchem die Vakuumpumpe 20 und ein Wärmetauscher 2l des Pumpenkühlkreislaufs untergebracht sind.The cooling air enters the cooling channel 4 close to the gate l. The cooling duct extends beyond the side of the boiler remote from gate 1 and points here a part l5 with an enlarged cross-section. The cooling duct is terminated here by a partition l6 in which openings l7 for fans l8 are arranged. These convey the heated cooling air into the chimney l9, in which the vacuum pump 20 and a heat exchanger 2l of the pump cooling circuit are accommodated.

Liste der Bezugszeichen:List of reference numerals:

11
Torgate
22nd
Kesselboiler
33rd
Isolierunginsulation
44th
KühlkanalCooling channel
55
AußenwandOuter wall
66
Wagendare
77
LadeflächeLoading area
88th
HolzstapelWood pile
99
InnenwändeInterior walls
l0l0
KondensationsraumCondensation room
llll
TrocknungsraumDrying room
l2l2
Ventilatorfan
l3l3
HeizvorrichtungHeater
l4l4
FüßeFeet
l5l5
KühlkanalteilCooling duct part
l6l6
Trennwandpartition wall
l7l7
Öffnungopening
l8l8
Ventilatorfan
l9l9
Kaminstack
2020th
VakuumpumpeVacuum pump
2l2l
WärmetauscherHeat exchanger

Claims (10)

Vorrichtung zum Trocknen von Holz oder anderen Feststoffen,
bestehend aus einem Kessel für Unterdruckbetrieb, in welchem Auflager für Schnittholzstapel, eine Heizvorrichtung und eine Umwälzvorrichtung für das Trocknungsmedium eingebaut sind, aus einem Kondensator und aus einem Kühlluftkanal, dessen eine Wandung durch einen Teil der Kesselaußenseite gebildet ist,
dadurch gekennzeichnet,
daß der Kühlluftkanal (4) sich achsparallel über den größten Teil des Kessels (2) in Längsrichtung erstreckt,
daß die Luftströmung im Kühlluftkanal (4) in Längsrichtung des Kessels verläuft,
und daß die effektive Kanal breite groß gegenüber der Kanalhöhe ist.
Device for drying wood or other solids,
consisting of a boiler for vacuum operation, in which supports for lumber stacks, a heating device and a circulating device for the drying medium are installed, a condenser and a cooling air duct, the wall of which is formed by part of the outside of the boiler,
characterized,
that the cooling air duct (4) extends axially parallel over most of the boiler (2) in the longitudinal direction,
that the air flow in the cooling air duct (4) runs in the longitudinal direction of the boiler,
and that the effective channel width is large compared to the channel height.
Vorrichtung nach Anspruch 1.
dadurch gekennzeichnet,
daß der Kühlkanal (4) in seinem Verlauf, vorzugsweise an seinem einen Ende aufgeweitet ist und an dieser aufgeweiteten Stelle (l5) Ventilatoren (l8) für die Förderung von Kühlluft enthält.
Device according to claim 1.
characterized,
that the cooling channel (4) is widened in its course, preferably at one end, and contains fans (l8) for conveying cooling air at this widened point (l5).
Vorrichtung nach Anspruch 1.
dadurch gekennzeichnet,
daß die Außenwand des Kühlkanales (4) aus Blech oder Kunststoff besteht.
Device according to claim 1.
characterized,
that the outer wall of the cooling channel (4) consists of sheet metal or plastic.
Vorrichtung nach Anspruch 1.
dadurch gekennzeichnet,
daß die Außenwand des Kühlkanales (4) wärmeisoliert ist oder aus einem wärmeisolierenden Material besteht.
Device according to claim 1.
characterized,
that the outer wall of the cooling channel (4) is thermally insulated or consists of a thermally insulating material.
Vorrichtung nach Anspruch 1.
dadurch gekennzeichnet,
daß der Kondensationsraum (l0) im Inneren des Kessels (2) befindlich ist und durch den am Kühlkanal (4) anliegenden Teil der Kesselwand gebildet ist.
Device according to claim 1.
characterized,
that the condensation chamber (l0) is located inside the boiler (2) and is formed by the part of the boiler wall which bears against the cooling channel (4).
Vorrichtung nach Anspruch 1.
dadurch gekennzeichnet,
daß ein Kondensator als Zusatzkondensator oder ein diesem zugeordneter Wärmetauscher im Kühlkanal (4) untergebracht ist.
Device according to claim 1.
characterized,
that a condenser as an additional condenser or a heat exchanger assigned to it is accommodated in the cooling channel (4).
Vorrichtung nach Anspruch 1.
dadurch gekennzeichnet,
daß der Kühlkanal (4) an einen Kamin (l9) angeschlossen ist.
Device according to claim 1.
characterized,
that the cooling duct (4) is connected to a chimney (l9).
Vorrichtung nach Anspruch 1.
dadurch gekennzeichnet,
daß der Kamin (l9) mit einer Zugregelklappe ausgerüstet ist.
Device according to claim 1.
characterized,
that the chimney (l9) is equipped with a draft control flap.
Vorrichtung nach Anspruch 1.
dadurch gekennzeichnet,
daß die Vakuumpumpe (20) oder Teile der Vakuumpumpe, vorzugsweise das Ansaugrohr, ein Wärmetauscher (21) und/ oder der Motor, im Kühlkanal (4) untergebracht sind.
Device according to claim 1.
characterized,
that the vacuum pump (20) or parts of the vacuum pump, preferably the suction pipe, a heat exchanger (21) and / or the motor, are housed in the cooling channel (4).
Vorrichtung nach Anspruch 1,
dadurch gekennzeichnet,
daß die die Kühlluft fördernden Ventilatoren (l8) drehzahlgeregelt und/oder reversierbar sind.
Device according to claim 1,
characterized,
that the fans (l8) which promote the cooling air are speed-controlled and / or reversible.
EP93116395A 1992-10-14 1993-10-09 Apparatus for drying wood or other solid materials Expired - Lifetime EP0592973B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4234683A DE4234683A1 (en) 1992-10-14 1992-10-14 Device for drying wood or other solids
DE4234683 1992-10-14

Publications (2)

Publication Number Publication Date
EP0592973A1 true EP0592973A1 (en) 1994-04-20
EP0592973B1 EP0592973B1 (en) 1997-08-20

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US (1) US5425182A (en)
EP (1) EP0592973B1 (en)
AT (1) ATE157157T1 (en)
DE (2) DE4234683A1 (en)
ES (1) ES2108182T3 (en)

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JP3906313B2 (en) * 2004-08-31 2007-04-18 株式会社加来野製作所 Vacuum drying machine and wood drying method using the same
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AT515466B1 (en) 2014-02-26 2016-05-15 Mühlböck Kurt Process for drying bulk material
US10619921B2 (en) 2018-01-29 2020-04-14 Norev Dpk, Llc Dual path kiln and method of operating a dual path kiln to continuously dry lumber
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US5425182A (en) 1995-06-20
ATE157157T1 (en) 1997-09-15
DE59307158D1 (en) 1997-09-25
ES2108182T3 (en) 1997-12-16
EP0592973B1 (en) 1997-08-20
DE4234683A1 (en) 1994-04-21

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