EP1317647B1 - Double-shell dryer - Google Patents

Abstract

The invention relates to a device and method for the drying of damp products, in particular, pasta. According to the invention, the product to be dried in a dryer, is placed in an inner chamber and humid warm air is circulated around the product, in order to ensure a gentle drying thereof. Dry hot air flows in an outer chamber, enclosing the inner chamber, which prevents condensation of water forming in the outer chamber. The inner shell has essentially no heat insulation as the external shell has a conventional heat insulation from the outside air. The dryer construction with a double shell prevents damp from entering the insulation material of the insulating layer through the inner shell and thus forming heat bridges, despite incomplete sealing of the inner chamber.

Description

The present invention relates to an apparatus and a method for Drying of moist products, in particular pasta, according to the preamble of claim 1 or according to claim 6. When drying moist products, e.g. Wood, pasta, etc., it is particularly important during drying that the Drying process takes place in a controlled atmosphere with a suitable "climate". That means the temperature, the moisture content and the type of drying gas (usually air) must lie in certain areas, hence the produce be dried without damage, i. to a certain target moisture content to be brought.

DE 118 204 describes a drying oven for patent leather, in which the drying Leather is hung in a dry box. The doors of the double-walled But dry boxes are only designed as a simple wall between the inner and the outer wall of the double - walled drying cabinet is heated air in the Countercurrent to the gases introduced inside the drying cabinet passed. As the outer and inner wall of the double-walled drying cabinet are formed identically, heat is both inside the Drying cabinet passed as well as delivered to its external environment. Therefore is the double-walled drying cabinet walled in such a way that between the outer Wall of the double-walled drying oven and the wall another cavity through which the hot combustion gases are passed, which in the Heating the passed through the double wall of the oven Hot air is created. Such a drying oven on the one hand has a bad thermal efficiency, because a lot of heat over the heated masonry in the Environment is discharged and thus for the warming of the interior of the Drying cabinet through flowing dry gases is not available. Because the Doors of the drying cabinet have no insulation and directly with the Atmosphere air is with a strong during drying is, during drying with a strong tendency to condensation to count on the inside of the doors.

DE 40 19 741 describes a drying station for moist materials, in particular for use in papermaking. The drying station consists of one, the material to be dried receiving housing made of a thermally insulating Wall, wherein in the housing interior, a thermally heated, gaseous Introduced drying medium and led out as exhaust gas. The housing wall is so traversed by a heat medium that on the inside of the housing a wall temperature exists, the dew point and underruns the interior of the steam-enriched drying medium prevented. Because the drying station only in its wall area and its ceiling area equipped with the housing wall through which a heat medium flows, Here too, similar to the drying oven of the previous paragraph, one goes lost considerable amount of heat above the ground. Again, there is an increased Tendency to condensation on the ground.

EP 0177 774 discloses a drying device for sheet materials. she contains a drying chamber through which passed the sheet material to be dried and brought into contact with flowing dry gas. Moreover is arranged around the drying chamber, a jacket whose inner walls together with limit the outer walls of the drying chamber a gap. The dry gas is heated in a heater and then flows through the drying chamber passing through, with at least a portion of its heat to the dry gas in the space emits. Through the gap flows cold dry gas, causing the Exterior walls of the jacket remain relatively cool. Thus, there are no waiting times when the device is to be taken apart for cleaning. Special arrangements for the heat insulation of the jacket are not made.

When drying certain products such as wood or pasta in particular it is important that the product is not too fast with too dry air and too hot air is dried, as otherwise on the surface of the product due to shrinkage Cracks that may extend through the entire product. In the Drying of such products therefore requires the heated air usually also moisture be added so that the relative humidity during drying is sufficient is high, causing a too steep moisture gradient from innermost to surface of the product to prevent the mentioned cracking.

To save energy, such dryers are by Verschalungselemente thermally insulated. Due to the process-related high temperature and the high relative humidity in the dryer with temperatures of typically 90 ° C and Relative humidities of 80 to 90% inside the dryer line are the result Today's dryer construction for condensation on the insides of the Shuttering elements, unless you have 100% steam tightness. To one To prevent the ingress of moisture into the insulation material and the To obtain thermal insulation effect, it is necessary to the insulation boarding steam-proof. This results in a high effort in the sealing of the Dryer interior opposite the surrounding The atmosphere. However, until now it can not be avoided that the condensate Leaves the dryer in some places.

The invention is therefore based on the object, the ingress of moisture in To prevent the insulation material of the dryer wall / dryer cover to a wetting of the insulating material and to prevent leakage of the dryer.

This object is achieved by the device according to claim 1 and the method according to Claim 6 solved.

Between the inner shell and the outer shell of the dryer can thus a Hot air flow can be circulated with low relative humidity, preventing any condensation in the space between the inner shell and the outer shell of the dryer in derogation. In other words, by means of this "double hull" the insulation of the Vapor barrier spatially separated, with the interspace with the hot dry Air forms the actual vapor barrier. A previously very expensive Vapor barrier of completely vapor-tight sheet metal directly on the insulating material is therefore not necessary.

In a particularly preferred embodiment, the inner shell, preferably Made of sheet metal, a small heat insulation on, while the outer Case has a high thermal insulation of a conventional insulation material. In Connection with the dry hot air in the space of this double hull is characterized ensures that moisture leaking through leaks on the inner shell neither on the outside of the inner shell, nor on the inside of the outer shell can lead to condensation of water.

Conveniently, the outer shell is spaced far enough from the inner shell, that of the gap formed by the two shells of such a double-hull dryer or "drier in the house" is walkable.

The outer shell may also be partially or completely made of an inflatable compliant Material exist that becomes self-supporting by inflation.

In carrying out the inventive method, it is essential that the inner envelope around flowing hot air has a "climate", its temperature, humidity and pressure are such that in the double hull no condensation can take place.

In particular, the second gas, i. the dry hot air is sufficiently high Temperature and low enough humidity have their dew point below the temperature of the ambient air is. This will cause the condensation on the inside the outer shell prevents even if this bad or even not insulated against the outside air.

It is particularly advantageous to dry the hot air of the space in the double hull to give a slight overpressure. In this way, the leakage current directed from the outside inwards and any discharge of moist hot air from the prevented inner space.

In order to avoid any condensation in the space between the double hull, should during the drying process for pasta and at a common outside temperature of 25 ° C and 50% relative humidity, the dry hot air in the space, e.g. have a temperature of about 110 ° C and a relative humidity of about 2%.

Fig. 1

ist eine schematische Darstellung des erfindungsgemässen Doppelhüllen-Konzeptes; und

Fig. 2

ist eine schematische Darstellung der gesamten erfindungsgemässen Anlage zur Durchführung des erfindungsgemässen Verfahrens.

Further advantages, features and applications of the invention will become apparent from the following description of a non-limiting aufzufassenden embodiment with reference to the drawings.

Fig. 1

is a schematic representation of the inventive double-hull concept; and

Fig. 2

is a schematic representation of the entire inventive system for carrying out the inventive method.

Fig. 1 is a schematic representation of the inventive double-hull concept for a pasta dryer. The drying area consists of an inner Chamber 1, which is surrounded by an inner shell 2. Via an input channel 6 to be dried pasta and not too dry air (e.g. 90 ° C, relative humidity about 80%) supplied. Be via an output channel the dried pasta and the "moist warm" drying air dissipated. This Part of the inventive dryer works like a conventional pasta dryer.

Unlike the conventional dryer, however, is limited by the inner shell inner chamber 1 surrounded by an outer chamber 3, in turn of the outer shell 4 is limited. Through this chamber 3 is very dry and passed hot air. The shell is preferably made of sheet steel. Between the inner Chamber 1 and the outer chamber 3 is made by the good heat conducting Steel sheet therefore only a very small thermal insulation, but forms a Vapor barrier. The outer shell 4, however, is provided with an insulation 5.

In contrast to previous dryers, in which the steel sheet 2 directly on the Insulation 5 is applied, there is a spatial in the inventive dryer Separation between steel sheet 2 and insulation 5. This through the outer chamber. 3 formed gap with its "dry hot" air prevents condensation on the outside of the inner shell 2 and on the inside of the outer Case 4. This avoids that the insulation 5 is soaked and thermal bridges form.

This dry-hot climate in the double hull 3 between inner shell 2 and outer Case 4 is produced by heating ambient air by means of a heater 8. The ambient air can also be supplied to a part of the circulating air before or after the heating become. It is essential that by heating dry air with very low relative humidity is generated.

Typical operating conditions are e.g. about 90 ° C and about 80% relative humidity for the warm and humid air in the drying chamber 1. In the outer chamber 3 e.g. To maintain a dew point of dry hot air of 25 ° C, the relative Humidity at a temperature of 110 ° C at 2%. When using circulating air (Assumption: 25 ° C, 50% relative humidity), this air can also reach 220 ° C are heated, then the relative humidity is 0.1%. By mixing Fresh air from the environment can then produce a dry stream of hot air 110 ° C and 2% relative humidity can be achieved. Fig. 1 shows a line section 12, which extends from the heater 8 to a fresh air supply line 11. The exhaust air from the double hull 3 is discharged via a line 14, while the circulating air of a line 13 is returned to the heater 8. The initially mentioned steam supply in the humid air of the inner chamber 1 is not shown in Fig. 1.

Fig. 2 shows a system for carrying out the inventive method. While in Fig. 1 only through the outer chamber 3 extending "dry hot" air circulation is shown schematically, Fig. 2 shows both this "dry hot" air circulation as well as the "humid" air circulation through the chamber 1, and indeed each with a heat exchanger 16 or 20 and in each case a radial fan 17th or 21. The heat exchangers 16, 20 each provide the necessary heating in the Air chamber, while the radial fan 17, 21 respectively for the circulation of air in provide each cycle.

In the inner circulation of the moist warm air (about 90 ° C, about 80% relative humidity) If necessary steam is introduced by means of a steam injection 22. The pressure the air in the inner circuit can with the help of the aperture 23 and / or throttle 24th be set.

In the external cycle of dry hot air (110 ° C, 2% relative humidity) is only heated to get very dry and hot air. Again, the Pressure of the air using the throttle valve 18 and / or the diaphragm 19 can be adjusted.

It is preferable to set the pressure of the "warm, moist" air in the inner circuit a slightly lower value than the pressure of the "dry" air in the outside Circulation. In this way, by possibly existing leaks in the inner Case 2 no more humid air through leakage in the space 3 of the Double hull arrive; the leakage current is reversed, so to speak. However, one is strives to control the mass flow of the leakage air (Kg / hr) both from inside to outside to keep it as minimal as possible from the outside to the inside.

As shown schematically in Fig. 2, both in the inner chamber 1 and in the outer chamber 2 sensors for detecting the climate parameters of the respective Air provided. For the warm and humid air in the inner circulation and the dry heat Air in the outer circuit, these are the humidity φi or φa, the temperature Ti or Ta and the pressure Pi or Pa.

Of course, the respective actual values of the climate parameters with their desired target values are compared, depending on the actual-target deviation over a corresponding actuator, a heat exchanger and / or a throttle valve and / or an orifice and / or the steam injection 22 to actuate, whereby the corresponding parameters temperature (Ti, Ta), pressure (Pi, Pa) and humidity (φi, φa) are regulated.

For homogenization of the "warm, moist" air in the inner chamber 1 is a recirculation system 15 provided. The inner shell 1 defined by the inner shell 2 stands on two sockets 9, 10. This ensures an almost complete flow around the chamber 1 through the dry hot air.

The space of the double hull is preferably designed so spacious that he is walkable. This is important for cleaning, maintenance and repair work. One Minimum distance of about 0.5 m between inner shell 2 and outer shell 4 should to be available. Preferably, the outer shell 4 as a "house" with door and interior lighting educated.

The dryer according to the invention is particularly advantageous because it hardly consumes more energy needed as a conventional dryer. Due to the spatial separation of vapor barrier (Inner shell 2) and heat barrier or heat insulation (outer shell 4) is at low leakage current from chamber 1 to chamber 2 or vice versa without appreciable Extra effort an excellent tightness of the dryer without big Sealing effort achieved.

Claims (10)

1. A device for drying moist products, in particular pasta products, with an inner chamber (1) enveloped by an inner shell (2) for holding the products to be dried, and an outer shell (4) enveloping the inner shell (2) and spaced apart from it in such a way as to delineate an outer chamber (3) between the inner shell (2) and outer shell (4), wherein the inner shell (2) has a high thermal insulation, and wherein the inner chamber (1) can carry a stream of a first gas or gas mixture with a first atmosphere, and the outer chamber (3) can carry a stream of a second gas or gas mixture with a second atmosphere, characterized in that

   a) the outer chamber (3) envelops the inner chamber (1) essentially completely, and

   b) the interior of outer shell (4) is provided with an insulation (5) comprised of insulating material.
2. The device according to claim 1, characterized in that the inner shell (2) consists of sheet metal, in particular sheet steel, while the outer shell (4) has a layer of sheet metal, in particular sheet steel, as well as an insulation layer (5).
3. The device according to one of the preceding claims, characterized in that the outer shell (4) has a door, and the gap (3) formed by the outer chamber can e traversed between the inner shell (2) and outer shell (4).
4. The device according to claim 3, characterized in that at least portions of the outer shell (4) consist of a flexible material.
5. The device according to claim 4, characterized in that at least the portions of the outer shell (4) is made self-supporting by inflatable, flexible chambers.
6. A method for drying moist products, in particular pasta products, with a device according to one of claims 1 to 5, wherein the products to be dried in the inner chamber are exposed to a stream of a first gas or gas mixture with a first atmosphere (Ti, ϕi, Pi), which absorbs and dissipates water vapor escaping from the products, and the inner chamber is exposed to a stream of a second gas or gas mixture flowing through the outer chamber, whose atmosphere (Ta, ϕa, Pa) and flow rate are such that no condensation takes place in the outer chamber.
7. The method according to claim 6, characterized in that the second gas or gas mixture contains so little moisture and is so hot that its dew point lies under the temperature of the ambient air.
8. The method according to claim 6, characterized in that the pressure (Pa) of the second gas or gas mixture is slightly higher than the pressure (Pi) of the first gas or gas mixture).
9. The method according to claim 6 or 8, in particular for drying pasta products, characterized in that the first gas streaming through the inner chamber is air with a temperature of 70 to 110 °C and a relative atmospheric humidity of 70 to 90 %, while the second gas streaming through the outer chamber is air with a temperature of at least 110 °C and a relative atmospheric humidity of 1 to 5 %.
10. Method according to claim 9, characterized in that the first gas is air with a temperature of 80 to 100 °C, preferably about 90 °C, and a relative atmospheric humidity of 75 to 85 %, preferably about 80 %, and the second gas is air with a temperature of 110 to 120 °C, preferably about 110°C, and a relative atmospheric humidity of 1 to 3%, preferably about 2%.

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