DE4330675A1 - Drying installation - Google Patents

Abstract

An installation for drying workpieces wetted with liquid has a drying chamber (11) with inlet openings (13) and outlet openings (14). Within the drying chamber (11) a workpiece carrier (21, 22, 23, 25, 26, 27, 31, 34, 35, 36) is mounted such that it can swivel and be driven via a drive shaft (41) which axially penetrates the end side of the drying chamber (11). This makes it possible to impart a non-stationary swivelling and rotating movement to the workpiece carrier. The drying air is extracted from the drying chamber (11) by means of a flow machine (51), a negative pressure within the drying chamber (11) of 0.90 to 0.97 bar absolute being set. The drying air is heated by a radiator (55) and within the drying chamber (11) set to a temperature of 20 to 70 DEG C. The non-stationary swivelling and rotating movement, on the one hand, and the extraction of heated drying air, on the other hand, make an extremely efficient drying process possible. The required outlay on energy, based on the drying power, is extremely low compared to conventional dryers because of the low, required electrical connected loads possible herewith. <IMAGE>

Description

The invention relates to a plant for drying with Liquid-wetted workpieces according to the preamble of Claim 1.

Such systems are required to take workpieces under various types of drying with a liquid are wetted. This is, for example Water or to aqueous liquids, which in the context of a Manufacturing or repair step to cleaning or Rinsing purposes are used. After cleaning or Flushing residues remain on the workpieces stick and must be removed.

Various dryers are used to dry workpieces tion process or drying devices used. A There is an overview of the most common dryers for example in the publication by Kröll, "Trockner und Drying process ", Springer-Verlag, Berlin-Heidelberg-New York, 2nd edition (1978). Subchapter 2.3.1  Convection dryer described, of which the present Invention comes out.

Such convection dryers as are commercially available have a tightly closable drying chamber, in which a workpiece carrier is arranged. The workpiece carrier ger is used to hold and hold the liquid wetted workpieces and can therefore be any or but specifically tailored to the workpieces to be dried his. The drying chamber has inlet and outlet openings for the drying air heated by an air heater and by means of a fluid machine through the drying chamber mer is passed through. The heated drying air transfers part of the thermal energy to the workpiece and takes vaporized liquid with it.

The disadvantage of such drying systems is that the energy required is very high in order to Practice acceptable short drying times. This usually only succeeds when temperatures in the air current of about 100 ° C and more can be provided. Yet such drying systems do not always work satisfactorily providing, especially in cases where work pieces with relatively complicated geometry and cavities are drying. Drying is also problematic Bulk goods packed tightly in the drying chamber be introduced. The dry is completely unsatisfactory effect on workpieces, openings or bores very small diameter, for example in the range of a few tenths of a millimeter, in which liquid residues due to capillary action are retained and therefore a complete drying of such workpieces unsuccessful.  

Such systems also have the disadvantage that they not suitable for drying heat sensitive parts are. This can be plastic parts, for example or electrotechnical components that are highly precise are manufactured and therefore for reasons of dimensional accuracy, Dimensional stability or functionality, such as. B. Creep Current resistance, no high temperature stress may be set.

The invention was therefore based on the problem of drying tion system of the type mentioned at the beginning wrap that they no longer have the disadvantages described having. In particular, a gentle, energy-saving should the and environmentally friendly drying process become.

This problem is solved with a system that the Features of claim 1. Advantageous execution forms of the invention are characterized by the features of the Unteran sayings stated.

The invention is based on the idea of taking suitable measures to ensure that they refer to the work the local flow vector of the drying air constantly changes. The current flow velocity experiences a constant change in amount and Direction.

Specifically, the problem mentioned is solved in that one the flow machine viewed in the direction of flow is arranged behind the drying chamber, which the Exhausts drying air. So it has been shown that the Suction mode leads to better results than a comparison bar printing. Surprisingly, this is open  obviously not the reduction in vapor pressure due to the itself due to the vacuum setting relevant, since according to a preferred embodiment is completely sufficient to adjust the suction so that only a pressure in the range in the drying chamber of 0.9 to 0.97 bar absolute is achieved. Even the last one mentioned value of a minimal pressure drop leads to a enormous increase in drying performance, so the effect to improve the flow around the workpieces leads.

At the same time, the workpiece carrier is inside the dryer tion chamber around a substantially horizontal Axis swiveling and driven by a motor. This enables permanent movement of the items to be dried Workpieces with the consequence of a constantly changing, unsteady flow field. This will make the border area between the workpiece and the flow field of the Drying air reaches a turbulent flow state, an extremely effective heat transfer from the dry air to the workpiece and rapid evaporation allows liquid.

The interaction of both measures, namely suction and the movement of the workpieces, leads to a surprise the improvement of the drying result. One can hand used to increase the drying time significantly to reduce and on the other hand significantly reduce the energy requirement thereby lower that the drying air according to a before preferred embodiment only to values in the range between between 20 and 70 ° C must be heated. Opposite one conventional convection dryers are drying times in the system according to the invention only Fractions of the drying time originally required, even  Workpieces with capillary openings or holes can be in completely dry for a short time at low temperatures be net.

Preferred embodiments of the invention are based on optimal design of the drying chamber and the workpiece carrier directed. The cylindrical shape of the Drying chamber allows maximum use of the drying space with the smallest possible surface, which Avoidance of heat loss should be kept as small as possible got to. Additional advantages arise in connection with preferred embodiments of the workpiece carrier in Form of a parts loading unit that is used to hold a Container designed for the workpieces to be dried and is rotatably mounted on rollers on the chamber wall.

A flow course that is favorable for the drying process can be realized if according to a preferred Embodiment of the air flow below the workpiece carrier fed and discharged above the workpiece carrier. Optimal results can be achieved if the outflow openings in the manner of two separate angular sectors are brought so that the drying stream within the Chamber divides.

A number of other measures can be envisaged, to additional with regard to the flow around the workpieces to generate transient flow conditions. A first one Measures catalog aims to prevent the rotation of the Workpiece carrier or the parts loading unit within the drying chamber as irregularly as possible In this way, a reversing rotary movement can be generated at which the angular velocity during the rotational movement is additionally varied. The rotary movement can also be inter  be carried out in the middle. With the help of a programming baren control such variations on simp generate way.

Another variation is the Strö tion machine, for example as a radial compressor can be executed, not with more constant, but with to operate variable speed and thereby a pulsie generating flow. A similar effect can be seen at constant compressor speed even if for example, a throttle in the discharge port of the compressor flap is operated accordingly.

Eventually the airflow experiences within the drying process chamber an additional transient component if the Part loading unit in cross-section the shape of a Rectangle and the resulting radial gap between the outer edges of the parts loading unit and the chamber wall is sealed. This results in inside the drying chamber between the parts unit and the chamber wall four circular arc segments shaped cells resulting from the rotation of the parts depending on the angular position the inflow or outflow openings or opposite these are largely sealed. To the turning center of the parts unit is the air flow through the inside of the inserted bulk material at least partially obstructed, so that the air flow is permanent must take new directions.

Further measures aim to improve energy efficiency tion of the dryer, the drying in the outflow area A heat exchanger is provided for the supply air electricity warmed and thus the energy requirement for the heating  direction reduced. The system can also be almost complete in a multi-walled, fully insulated in relevant areas ten housing must be installed so that the radiation losses can be kept extremely low.

Further details of the system can be found in the following the description of a preferred embodiment of the Plant according to the invention, which is shown schematically in the figures is shown. There are more, with the respective ones Features achievable advantages described in more detail. Show it in a schematic representation

Fig. 1 drying plant in longitudinal section;

Fig. 2 Drying plant according to Fig. 1, section AB,

Fig. 3 partial section of Fig. 2, but with inserted setztem containers and bulk, increased

Fig. 4 drying system according to FIG. 1, section CD.

The drying system has a drying chamber 11 arranged in a housing 81 . The housing 81 is multi-walled in significant areas and is heat and soundproof. The housing 81 accommodates all components of the system, including a switch box 89 . The system is thus designed as an independent component and is configured as a mobile unit due to a stand 88 that can be moved under the stacker and pallet truck. The housing 81 has a flap 82 on the front through which the drying chamber 11 is accessible. The flap 82 is pivotally mounted on a pivot bearing 85 and can be fixed in the open state by means of supports 83 in a horizontal, open position. The supports 83 are designed as an oil damper to ensure a safe opening. The flap 82 also has a roller conveyor 84 , onto which a container loaded with bulk material 111 can be placed and inserted into the interior of the drying chamber 11 .

The drying chamber 11 is cylindrical, that is to say it has a circular cross section, the outer surface being formed by a chamber wall 12 . The drying chamber 11 is arranged horizontally. Inflow openings 13 , which are formed from a multiple arrangement of oval slots, open into the drying chamber 11 from below. The slots are distributed over the entire axial extension of the chamber wall 12 and over brush in cross section viewed an angular sector of about 90 °. In the illustrated embodiment, five rows of oval slots are attached.

Outflow openings 14 are also provided in the chamber wall 12 . These are also designed in the form of rows of oval slots extending axially over the entire length of the chamber wall 13 . The outflow openings 14 are distributed over two angular sectors of approximately 45 to 60 ° and consist of an arrangement of three rows of slots. The two angular sectors having the outflow openings 14 are separated by a further angular sector of approximately 30 to 45 °, which has no openings.

Within the drying chamber 11 , a part loading unit can be pivoted about an axis which runs coaxially with respect to the drying chamber 11 and is driven by a motor 45 . The parts loading unit has, in the manner of a guide frame, axially parallel rails 21 , 22 . Rollers 23 are rotatably mounted on the rails 22 arranged below and thus form roller tracks. The rails 21 arranged opposite one another are designed as angle profiles. Both the rails 21 and the rails 22 are BEFE Stigt on the drive side bracket, which is formed by two spaced and horizontally arranged cross members 25 , 26 and a connecting connec tion beam 27 . A drive shaft 41 , which penetrates the drying chamber 11 coaxially and in a sealed manner, is attached in a rotationally fixed manner to the connecting cross member 27 .

The rails 21 , 22 are fastened to disks 34 , 35 on the loading side, the disks 34 , 35 being axially spaced apart and receiving bearing rollers 36 . There are five rollers 36 distributed on the circumference, which are supported on the chamber wall 12 .

A part loading unit is thus formed, into which a standard container consisting of a container basket 101 and a lid 102 can be inserted. It is a so-called Euro standard container, which has the external dimensions 600 × 400 × 280 mm. The dimensions of the parts loading unit are matched to the container in such a way that it can be pushed between the rails 21 , 22 with relatively little play and is securely held during the pivoting movements provided for the drying process. The container basket 101 and the lid 102 are at least partially perforated. This is necessary in order to ensure good accessibility of the drying air to the material to be dried, for example the bulk material 111 , located inside the container. An optimal permeability is achieved and thus an optimal flow of parts when the container is made of wire goods, for example from a wire mesh, wire mesh, wire mesh or wire laid. The size of the hole or mesh is limited by the size of the individual parts of the bulk material 111 .

The end of the drive shaft 41 carries a chain wheel 42 , on which a roller chain 48 is engaged. The roller chain 48 continues to engage a pinion 47 , which is attached to a transmission 46 of the motor 45 . The drive shaft 41 , which penetrates the end of the drying chamber, is gela there with a spherical plain bearing 43 .

The motor 45 can be operated in a program-controlled manner in a manner not shown here. The control allows rotary movements in both directions of rotation, the speed itself being variably and transiently controllable. This allows a rotating or swiveling movement of the part loading unit in any manner per se. The possibility of realizing a highly transient reciprocating motion contributes to an optimal drying process. The drying effects described at the outset due to permanently changing flow conditions on the bulk material 111 are caused, inter alia, in that the part loading unit, starting from the normal position, is moved back and forth on both sides by a little less than 90 °. The bulk material 111 can then also perform a further inherent movement if, for example, the parts loading unit is briefly stopped at the reversal point of the rotational movement, so that the bulk material 111 begins to flow or trickle and thus the individual parts of the bulk material 111 are continuously circulated.

Likewise, part-specific can be program-controlled consequently rotating movements in only one and also in both directions of rotation, as well as combinations thereof reali together with the swivel movements described above  be settled.

A further improvement in the drying effect can be achieved if the radial gaps between the rails 21 , 22 and the respectively opposite sections of the chamber 12 are kept as small as possible, that is to say are designed to be largely free of play in the range of less than three millimeters. This creates radially largely sealed cells between the outer walls of the container and the chamber wall 12 , which represent a different flow resistance for the drying air as a result of the pivoting movement of the parts loading support, depending on whether they have a connection to the inflow openings 13 or at a particular point in time. Outflow openings 14 or not. This forces the drying air to constantly look for new flow paths.

The disks 31 , 34 , 35 are also designed towards the chamber wall 12 with a gap of less than three millimeters and ensure an axial sealing of the cells.

An improvement in the effect can be achieved if the radial gaps mentioned are completely sealed, for example by Dichtungslei not shown here, which are attached to the outer edges 21 a, 22 a of the rails 21 , 22 and slide against the chamber wall 12 . In order to prevent parts of the air flow from flowing axially past the container, the disks 31 , 34 , 35 on the part loading unit are designed as a sealing disk.

To guide the drying air outside of the Trocknungskam mer 11 , a supply air duct 61 is provided through which the drying air is sucked in from the surroundings. The supply air shaft 61 opens into a preheating room 62 , which contains a Heizregi ster 55 in the form of a matrix-like multiple arrangement of heating elements. Below the heating register 55 , a collecting container 71 for entrained liquid particles, for example dirty water or emulsions, and mechanical particles is attached. The heating register 55 heats the passing drying air to a predetermined value, depending on the temperature in the drying chamber constantly regulated. The temperature value in the drying chamber can be set to any value in the range between 20 and 70 ° C. The supply air flow Z enters behind the Vorwärmraum 62 into a feed chamber 63 which is located immediately below the drying chamber 11 and 13 has connection to the interior drying chamber 11 via the inflow openings. The drying air enters the drying chamber via the inflow openings 13 and experiences a permanent deflection and division as a result of the unsteady movements of the part loading unit. The drying air leaves the drying chamber 11 through the outflow openings 14 and first arrives in two collecting spaces 64 , 65 which open into a common collecting line 66 . In this way, the partial streams forming within the drying chamber 11 are combined to form a collecting stream S. At the end of the manifold 66 , a compressor 51 is installed, which is driven by a drive motor 52 . At the outlet of the compressor 51 , the drying stream is fed to an exhaust duct 67 , from which a small part of the drying stream is released to the environment as exhaust air stream A. The greater part of the drying flow is passed in the form of a partial flow T via a partial flow return line 69 to the preheating chamber 62 and admixed with the supply air flow Z.

One cannot improve the energy balance here Shown heat exchanger are provided, which  Exhaust air flow A removes heat and supplies the supply air Z. Also it is advantageous for various applications Exhaust air flow A, for example via a condensate separator the to dehumidify.

The arrangement of the compressor 51 described has the effect that the drying air is sucked out of the drying chamber 11 . In this way, more favorable flow conditions can be achieved than would be the case if the compressor were arranged in the flow direction in front of the drying chamber 11 . Further transient effects, which further increase the drying effect, can be achieved by a program-controlled speed variation of the compressor 51 . The drying air can be promoted in this way in the manner of a pulsation flow. A similar effect can also be achieved if an adjustable throttle is installed in the flow path, which variably changes the flow resistance in the system and thus also generates a pulsation flow. For example, the outflow openings 14 can alternately be partially or completely closed, which controls the program.

The compressor 51 is designed so that only a relatively low vacuum is set in the drying chamber 11 . An optimal drying effect results when the value of the absolute pressure in the drying chamber is in the range between 0.90 and 0.97 bar.

From the above it follows that the proposed conception an extremely energy-saving and effective Can realize dryer for workpieces. The energy requirement for a relatively slight heating of the drying stream to a maximum of 70 ° C and for the relatively low vacuum, which is required by suction using a compressor  is considerably lower than with conventional convexes tion dryers. In addition, even when complicated Workpiece or part geometries with the shortest drying time full body drying through an overall energy and resource-conserving, low-noise, compact and environmentally friendly flow drying system achievable.

Reference list

11 drying chamber
12 chamber wall
13 inflow opening
14 discharge opening
21 rail
21 a outer edge
22 rail
22 a outer edge
23 roll
25 crossbar
26 crossbar
27 connecting crossbar
31 disc
34 disc
35 disc
36 bearing roller
41 drive shaft
42 sprocket
43 spherical plain bearings
45 engine
46 gearbox
47 sprockets
48 roller chain
51 compressors
52 drive motor
55 heating registers
61 supply air duct
62 preheating room
63 inflow space
64 collecting room
65 collecting room
66 manifold
67 exhaust duct
69 partial flow return line
71 collecting container
81 housing
82 flap
83 support
84 roller conveyor
85 swivel bearings
88 stand camp
89 control box
101 container basket
102 container lid
111 bulk goods
A exhaust air flow
S collective flow
T partial return flow
Z supply air flow

Claims (31)

1. Plant for drying work pieces wetted with liquid, at least consisting of

• a tightly closable drying chamber with at least one inflow and one outflow opening for drying air,
• a workpiece carrier arranged in the drying chamber,
• - an air heater with which the drying air can be heated, and
• - a turbomachine for conveying the drying air,

characterized in that the workpiece carrier ( 21 , 22 , 23 , 25 , 26 , 27 , 31 , 34 , 35 , 36 ) within the drying chamber ( 11 ) pivotable about a substantially horizontal axis and driven by a motor ( 45 ) is stored and the flow machine (51) in the flow direction viewed behind the drying chamber (11) and is thus determined for extraction of the drying air from the drying chamber (11). 2. Plant according to claim 1, characterized in that the drying chamber ( 11 ) is cylindrical. 3. Plant according to claim 1 or 2, characterized in that the inflow openings ( 13 ) and / or the Abströmöff openings ( 14 ) are formed by a multiple arrangement of oval slots in the chamber wall ( 12 ) which axially continuously in the region of the workpiece carrier ( 21 , 22 , 23 , 25 , 26 , 27 , 31 , 34 , 35 , 36 ) are arranged. 4. Plant according to claim 3, characterized in that the inflow openings ( 13 ) below and the outflow openings ( 14 ) above the workpiece carrier ( 21 , 22 , 23 , 25 , 26 , 27 , 31 , 34 , 35 , 36 ) are arranged. 5. Plant according to claim 4, characterized in that the inflow openings ( 13 ) are arranged in an angular sector of about 90 °. 6. Plant according to claim 4 or 5, characterized in that the outflow openings ( 14 ) are arranged in two separate angular sectors each of about 45 ° to 60 ° and between the two angular sectors a further angular sector of about 30 ° to 45 ° without openings remains. 7. Plant according to one of the preceding claims, characterized in that the workpiece carrier ( 21 , 22 , 23 , 25 , 26 , 27 , 31 , 34 , 35 , 36 ) is designed as a parts loading unit, in which an at least partially perforated container ( 101 , 102 ) can be used to hold loose individual parts or bulk material ( 111 ). 8. Plant according to claim 7, characterized in that the parts loading unit in the manner of a guide frame axially parallel rails ( 21 , 22 ) which are arranged above and below or to the side of the insertable container ( 101 , 102 ) between them. 9. Plant according to claim 8, characterized in that the container ( 101 , 102 ) supporting the bottom rails ( 22 ) are designed as roller conveyors. 10. Plant according to claim 8 or 9, characterized in that the rails ( 21 , 22 ) are each fastened on the drive side to a bracket formed by cross members ( 25 , 26 , 27 ). 11. Plant according to claim 10, characterized in that the parts loading unit ( 21 , 22 , 23 , 25 , 26 , 27 , 31 , 34 , 35 , 36 ) on the drive side in the region of the holder ( 25 , 26 , 27 ) has a sealing washer ( 31 ) which is guided radially to close to the chamber wall ( 12 ). 12. Installation according to one of claims 8 to 11, characterized in that the rails ( 21 , 22 ) are each fastened on the loading side to two disks ( 34 , 35 ) which are mounted on the chamber wall ( 12 ) via bearing rollers ( 36 ). are stored. 13. Plant according to one of claims 8 to 12, characterized in that between the outer edge ( 21 a, 22 a) of the rails ( 21 , 22 ) and the chamber wall ( 12 ) resulting radial gap in the range of smaller is three millimeters. 14. Plant according to one of claims 8 to 12, characterized in that the outer edges ( 21 a, 22 a) of the rail NEN ( 21 , 22 ) have sealing strips which lie opposite to the chamber wall ( 12 ) sliding. 15. Plant according to one of claims 7 to 14, characterized in that the container ( 101 , 102 ) is a standard container. 16. Plant according to one of claims 7 to 15, characterized in that the container ( 101 , 102 ) is made of a wire mesh, wire mesh, wire mesh or wire scrim. 17. Plant according to one of claims 7 to 16, characterized in that the parts loading unit ( 21 , 22 , 23 , 25 , 26 , 27 , 31 , 34 , 35 , 36 ) is rotatably connected to a drive shaft ( 41 ) which coaxially and abge seals the chamber wall ( 12 ) penetrates the end face and carries a sprocket ( 42 ) at the end, via which the motor ( 45 ) is coupled with the interposition of a gear ( 46 ) and a roller chain ( 48 ). 18. Plant according to claim 17, characterized in that the drive shaft ( 41 ) is mounted in the end chamber wall with a spherical plain bearing ( 43 ). 19. Plant according to one of the preceding claims, characterized in that the motor ( 45 ) can be operated in a program-controlled manner in both directions of rotation with variable speed. 20. Plant according to one of the preceding claims, characterized in that the drying chamber ( 11 ) by means of an outside of the drying chamber ( 11 ) in the inflow of the drying air arranged heating register ( 55 ) is heated. 21. Plant according to one of the preceding claims, characterized in that the temperature in the drying chamber ( 11 ) can be regulated constantly to a preselectable value in the range between 20 and 70 ° C. 22. Plant according to one of the preceding claims, characterized in that the absolute pressure in the drying chamber ( 11 ) is adjustable to values in the range between 0.90 and 0.97 bar. 23. Plant according to one of the preceding claims, characterized in that the fluid machine ( 51 ) is a radial compressor, the speed of which can be varied in a non-stationary manner under program control. 24. Plant according to one of the preceding claims, characterized in that a partial flow return line ( 69 ) for a partial flow (T) of the exhaust air (A) is present which, viewed in the flow direction, branches behind the turbomachine ( 51 ) at the inlet of an exhaust air shaft ( 67 ) and mün det before the air heater ( 55 ) at the outlet of a supply air duct ( 61 ) in the preheating room ( 62 ). 25. Plant according to one of the preceding claims, characterized characterized in that a device for dehumidifying the Exhaust air (A) (condensate separator) is available. 26. Plant according to one of the preceding claims, characterized characterized in that a heat exchanger on the exhaust side Heating the supply air (Z) is provided. 27. Plant according to one of the preceding claims, characterized in that it is built in relevant areas in a multi-walled, fully insulated housing ( 81 ), the drying chamber ( 11 ) on the loading side via a roller conveyor ( 84 ) having a flap ( 82 ) is accessible. 28. Plant according to one of the preceding claims, characterized characterized in that it is designed as a mobile unit is. 29. Plant according to one of claims 4 to 28, characterized in that the outflow openings ( 14 ) programmge controls alternately completely or partially closable. 30. Plant according to one of claims 12 to 29, characterized in that the disks ( 31 , 34 , 35 ) are designed as sealing disks radially to the chamber wall ( 12 ) completely sealing.