RU2282802C2 - Method for electrically heating drying drum with multilayered cylindrical body, for instance in sizing machine - Google Patents

Abstract

FIELD: drying solid materials or objects, particularly elongated materials, by processes involving the application of heat, for instance in textile, paper-making and polymeric film production industries.

SUBSTANCE: method involves forming three-layered drum body, wherein the core layer is made as electric heater; connecting electric heaters with electric circuit through voltage (power) regulator.

EFFECT: reduced power inputs and improved controllability.

3 dwg

Description

The present invention relates to a technology for drying lengthy materials: wet textile fabric, weaving after sizing, paper; fabrics, as well as for heating film materials touching or covering rotating cylindrical surfaces, and for drying textiles.

1. The prior art

Known methods of heating the drying drums by continuously supplying superheated steam to their internal cavity while draining the condensate [1, 2, 3, 4]. The disadvantages of these methods are the difficulty of obtaining and transporting steam, the complexity of the system of removal and disposal of condensate, the need to use a large amount of water suitable for drinking, and its processing.

Known methods of heating the drying drums by using the combustion products of various natural gases as heat carriers, including burning gas mixtures inside the drum [5, 6, 7, 8, 9, 10].

Compared to steam heating, the combustion products of gaseous fuels provide a higher drum heating temperature. The disadvantages of these methods are fire hazard, the complexity of the communications for the supply of combustible gases or hot mixtures after combustion, the environmental hazards of both the combustion products themselves and the condensate. In addition, a large air flow rate and a complex design of nozzles and nozzles inside the drums are necessary for combustion.

A known method of heating the drying drums with an integrated rotating transformer [11]. A transformer with a length equal to the length of the drum, for example three-phase, is placed inside the drum. In this case, the shells from the ends of the drum serve as the active load of the transformer. The transformer, heating, heats the cylindrical shell of the drum.

The disadvantages of this method are low efficiency and high power consumption; the need for complex and cumbersome electrical insulation of all drum parts; high complexity of the design, its installation and assembly, high material consumption.

Known methods of heating the drying drums from the inside by high-frequency currents by placing cylindrical solid or composite inductors with a gap relative to the inner wall of the drum inside the drum on a fixed axis [12, 13, 14, 15]. The most significant disadvantages of these methods are: high implementation complexity, requiring high-frequency generators, protective shields, etc .; low efficiency; the inability to use lightweight non-ferrous metals or plastics in the manufacture of the drum, in which eddy currents are not induced; high energy intensity of heating and the inability to adjust the temperature.

A known method of contact electric heating of a cylindrical wall from the inside [16, 17]. In this method, a bulk electrode is heated by a pair of electrodes, placed between them, which, in turn, heats it by contact with the shell of the drum. The implementation of this method is the simplest. The disadvantages include high energy intensity. This is due to the fact that the powder is poured down and can be located only in the lower part of the drum, and the heat of the drum wall should be delivered to the contact zone of the dried material with the cylindrical wall of the drum. The cylindrical wall blown outside by air is continuously cooled, so the powder will be hot and not at all in the drying zone of the web.

In fact, the heating method [18] is similar, where a linear electric heater inside the drum heats the water poured into the lower part of the drum. The disadvantages of this method are the inability to ensure sufficient heating of the cylindrical wall of the drum and small functionality.

When boiling water, steam rising from the water, in contact with the inner cylindrical surface, condenses and flows down, cooling the boiling water. The boiling point of water is known: 100-105 ° С, and its condensate cooling occurs cyclically: water boils → steam settles on the inner wall → collects in drops → condensate drains → water cools, stops boiling → boils again, etc. Its average temperature does not exceed 90 ° C, while according to the technical conditions for drying it should not be lower than 110 ° C.

Limited functionality is due to the fact that heating is carried out only in the lower part of the drum. The material to be dried on the dryer covers the drum both from below and from above and from the sides [1, 2]

Due to constant contact with heated water and steam, expensive anticorrosive materials, such as stainless steel, are used to make the drum.

From the source [20, pp. 310-311] there are known devices for increasing the inductance of conductors: inductors (solenoids).

In these devices, a wire of metals with low resistivity is wound in the form of a cylindrical spiral onto a dielectric rod with a gap between the turns in one layer [20, Fig. 19-7] or in several layers [20, Fig. 19-6]. When connected to an electric network, they create a large magnetic flux and simultaneously heat up.

Due to the low resistivity for sufficient heating of the solenoid, it must be very long, i.e. material intensive.

A current collector is known from the source [11, FIG. 2], for example, a three-phase one connecting an electric heater rotating together with a drum (in the form of a three-phase transformer) with a fixed electrical wiring of the electric network.

The disadvantages of transformer heating are noted above, and the current collector itself is not a drum heating element.

2. The closest technical solution (prototype) found from the package of information studies is a method of electric heating of a drying drum, in which the outer cylindrical wall of the drum is heated by heating a fluid located between the outer and inner wall of the drum, by means of electrodes interacting with the liquid placed also between the walls and connected to a source of electricity [21].

In this method, in a double-walled drum with hermetically connected and coaxial cylindrical walls, the gap between the walls is continuously filled with liquid, heated with electrodes in this gap, thereby heating the outer (working) wall of the drum, which interacts with the material to be dried.

The advantages of the prototype compared with analogues is a more evenly distributed on the surface of the drum heating of the outer wall.

3. Reasons that hinder the receipt of technical results.

3.1. Great constructive and technological complexity. This complexity is due to the structural and technological complexity of manufacturing a multilayer cylindrical hermetic container; the need to control and adjust the pressure when heating the liquid to prevent its boiling; the difficulty of installing hermetic electric heaters between the cylinder walls.

3.2. The high energy intensity of the method, due to the need for energy consumption for heating the fluid between the walls. Since the liquid is as close as possible to the outer diameter of the cylinder, its circumferential length and, consequently, the volume are maximal. To heat the liquid to operating temperature, respectively, and more energy is required.

3.3. Specific requirements for drum construction material. Due to constant contact with hot liquid and fumes, these should be anti-corrosion alloys or compounds. This makes the implementation of the method even more expensive.

4. Signs of the prototype, coinciding with the claimed technical solution.

A multilayer cylindrical body, in which one of the intermediate layers is first heated by contacting electric heaters, and then the outer layer is heated by heat transfer from the intermediate layer to the outer one.

5. The task of the invention is to obtain the following technical results.

5.1. Constructive and technological simplification of heating.

5.2. Reducing the energy intensity of heating the outer surface of the drum

6. These technical results are in the inventive method for electrically heating a drying drum with a multilayer cylindrical body and electrodes, in which one of the intermediate layers is first heated by contacting the electrodes connected to the electric network, and then the outer layer is heated by heat transfer from the intermediate layer to the outer are achieved in that the drum is made three-layer with hard layers, the middle layer is formed from an electrically conductive thin and flat tape with a large specific electric resistance, placing it in the form of a uniform cylindrical spiral on the inner layer of the housing and tightly squeezing it with the outer one, while the outer and inner layers of the housing are either electrically conductive or the tape is electrically insulated, and the outer layer is electrically conductive, in addition, the outer layer is thinner than the inner and more heat-conducting, and the pitch between the turns of the tape is set less than its width, in addition, the tape is connected to the electrical network by the ends.

7. The essence of the invention is illustrated by drawings, where Fig. 1 shows schematically a part of a section of a drying machine similar to sizing SB 11/180-K-ZM-2, manufactured in 1992; figure 2 schematically shows a longitudinal section of a drying drum with a current collector made in three layers; figure 3 schematically shows a three-layer cylindrical body with an electrically insulated spiral tape.

Design diagrams explaining the implementation of the method include a section (Fig. 1) of drying drums 1 and 2 (on a sizing machine 11 of them) installed by axles 3 in fixed bearings 4 with the possibility of rotation in bearings (not indicated). The drums are equipped with a kinematic transmission, for example a chain drive (sprockets 5 and chains 6), which is likewise kinematically connected to a drive motor (not shown). Drums 1 and 2 are identical. Their difference is that the drums 1 are covered by the dried material 7 from above, and the drums 2 from the bottom.

The drying drum 1 (2) includes a three-layer cylindrical body, a coaxial pin 3 (figure 2), the inner layer 8 of which is made non-conductive (eg, polypropylene) and rigid; the middle layer 9 is made of an electrically conductive tape with a large resistivity (for example, of nichrome foil), tightly wound with a uniform pitch on the inner layer 8, and the outer layer 10 is tightly mounted on the layer 9, made non-conductive (for example, polypropylene) with the possibility of interaction with dried material 7, the thickness of the inner layer 8 is greater than the thickness of the outer layer 10. The layers 8, 9, 10 of the cylindrical body of the drum 1 (2) are rigidly connected along the edges, left and right, with disks 11 equipped with coaxial trunnions 3. In the trunnion 3, of the kinematic sprocket 5, a through axial hole 12 is made, and a pulley 13 of dielectric material (for example, of getinaks) with two insulated conductive streams 14. Each of the streams 14 is connected by electric wires 15 to the end of the conductive tape 9.

Coaxial to the pulley 13, still, with the possibility of movement and subsequent fixation, a current collector 15 is placed, spring-loaded current collector brushes 16 of which are mounted for sliding along current streams 14 and are spring-loaded to them 17. Current collector 15 is made of thermoplastic dielectric material (e.g., polypropylene). An electrical wiring 18 is mounted in the case of the current collector 15, the ends of which are electrically connected on the one side through the springs 17 to the brushes 16 and, on the other hand, are taken out of the current collector 15 and connected to the output of the voltage regulator 19 (or electric power, for example, to the output of a single-phase LATR), whose output is connected to the mains (~ U). The brushes 16 are made, for example, of a copper-graphite alloy, and the streams 14, for example, of copper foil, which is firmly attached to the streams, for example, glued. Fasteners are not indicated in the drawings.

The three-layer cylindrical body of the drum 1 (2) also contains an internal electrically conductive layer 8A (Fig. 3) made of a durable material (for example, steel), the outside of which is densely wound along a helical line with a uniform pitch t, the electrically conductive tape 9, insulated externally along the entire length by insulation 9A (e.g., glass, asbestos, or mica mastics). The tape 9 with insulation 9A forms the middle layer, and the outer, electrically conductive layer 10A tightly compresses the tape 9 with insulation 9A. The tape is made, for example, of nichrome, its width is b, and its thickness is h, with h <t <b, and the thickness of the outer layer 10A is less than the inner 8A.

The device, the diagrams of which are presented in figures 1-3, implements the inventive method in the following way.

At the input of the regulator 19 (Fig. 2), an electric voltage is supplied, for example, from a 220 V network, which is supplied from the output of the regulator 19 via wiring 18 through springs 17 and brushes 16 to the current conducting streams 14 of the pulley 13. From the current conducting streams 14, electric wires 15 voltage falls on the opposite ends of the conductive tape 9, which, closing the electrical circuit, heats up. Heat through the contact of the tape 9 with the inner layer 8 and the outer layer 10 is transferred to these layers by heat transfer between the layers. Since the outer layer 10 is thinner than the inner 8, the first heats up (warms up) faster.

After warming the outer layer 10 to a predetermined temperature, the drive of a drying, for example, sizing, machine (not shown) is turned on. An electric motor (not shown) by means of a kinematic transmission 5, 6 (Fig. 1) rotates the drums 1 (2), and the dried material 7, pressing and covering the outer and heated layers, moves from one drum to another, heating and gradually drying due to evaporation moisture.

Due to the tight fit to layers 8 and 10 and the small gap between the turns, the tape, for example, from nichrome foil (layer 9) almost does not come into contact with air and can be heated to a temperature only limited by the melting temperature of the outer layer 10 (for polypropylene it is 250 ° C )

Uniform winding of the tape 9 with a pitch between the turns, smaller than the width of the tape, provides uniform and uniform heating and heating of the outer layer over its entire cylindrical surface.

When the outer layer 10 is set by the material 7, heat is transferred to the material 7, the layer 10 is cooled from the outside, and heat is supplied from the inside. The process of heat removal by material 7 from layer 10 with continuous movement of material 7 occurs continuously. Therefore, the heat transfer from layer 9 to layer 10 is continuous. The inner layer 8, when heated, is a heat accumulator. Heat is removed from it only by the air surrounding it from the inside.

In the inventive method for heating the drum 1 (2), three layers of its cylindrical body, one of which is an electric heater, do not require tightness, supply and removal of a heat carrier, maintenance and installation of a multi-electrode electrical network, as well as expensive stainless steels.

Thereby, the first technical result of the task of the invention is achieved: constructive and technological simplification of heating.

Placing an electric heater as an intermediate layer between the outer and inner layers of the cylindrical body and performing this intermediate (middle) layer from a spiral wound on the inner layer from the conductive tape allows the outer layer to be contacted by tightly fitting the outer layer to the tape. It is not required to heat any intermediate media, either liquid or gaseous. When contact heating of the outer layer, the hydrodynamic resistance of heat transfer is minimal; significantly less electricity is needed for contact heating compared to others known from analogues and prototypes.

Thus, due to contact heating of the outer layer, a second technical result of the task of the invention is achieved: reducing the energy intensity of heating the outer surface of the drum.

However, non-conductive materials are generally non-conductive. Therefore, the heating of the outer layer 10 of the cylindrical body (figure 2) is carried out by slowly increasing the voltage at the ends of the tape 9 by the regulator 19, which increases the heating time of the outer surface of the drum.

This disadvantage is eliminated by the fact that the outer layer is made electrically conductive, for example steel or from aluminum-containing alloys, and the tape 9 is covered with electrical insulation 9A along the entire length before being wound on the inner layer 8A. The inner layer 8A is metallic (electrically conductive) or non-metallic (dielectric)

The metal outer layer 10A (FIG. 3) is thermally conductive, the heating of the outer layer 10A is faster, the energy consumption for heating the outer surface of the drum is further reduced. The reliability of the work on heating the outer surface also increases, since there is no heat accumulation between the outer and inner layers.

Since the inner layer 8A is thicker than the outer 10, it has great rigidity in the metal version, which prevents thermal (thermal) deformations of the cylindrical body of the drum 1 (2).

Having a small mass, the outer layer 9, 9 A (a tape of nichrome foil 30-50 microns thick) heats up almost instantly, reducing the heating time and reducing the energy consumption of heating the outer surface of the drum.

The inner layer 8 or 8A is thicker than the outer, has a larger mass and is a good heat accumulator, keeping the temperature of the entire cylindrical surface of the drum 1 (2) uniform and constant along the entire length of its generatrix.

The accumulation of thermal energy in the mass of the inner layer can significantly reduce the energy consumption for drying the material 7. The contact of the material 7 with the drum 1 (2) covers about half (figure 1) of the circumference of the drum. When the material 7 moves together with the outer layer 9, 9A (Fig. 4), the tape 9 should receive only that part of the thermal energy that the material 7 absorbs. Having come out of their contact with the material 7, the outer layer 9 (9A) is cooled by the surrounding air. These heat losses on the trajectory until they come into contact with material 7 are made up for by the inner layer 8 (8A), in which heat energy accumulated on the opposite trajectory.

Information sources.

1. Technical description and instructions for installation and commissioning of the machine ШБ 11/180-К-3М-2. Ed. Vichugmash Plant, Vichuga, Ivanovo Region, 1992

2. Patent of Russia No. 2037588, cl. D 06 B 21/00, publ. 06/19/95.

3. US patent No. 4949475, CL. F 26 B 13/16, 08.21.1990.

4. UK patent No. 1238757, CL F 26 B 13/14.

5. Copyright certificate of the USSR No. 1605085, class. F 26 B 13/06, publ. 1991 year

6. USSR author's certificate No. 579689, cl. F 26 B, publ. 1979 year

7. US patent No. 4683015, CL. F 26 B 3/24, 1987.

8. Copyright certificate of the USSR No. 118224, cl. F 26 B, 1972

9. Patent of Russia No. 2027131, cl. F 26 B 13/14, publ. 01/20/95.

10. Patent of Russia No. 2137996, class. F 26 B 13/14.

11. USSR author's certificate No. 90517, cl. F 26 B 13/14 (claimed 08/20/1948, publ. 1959).

12. Copyright certificate of the USSR No. 220744, cl. D 21 F 5/02, 1952

13. British patent No. 2227823A, CL. F 26 B 13/14.

14. USSR copyright certificate No. 731234, cl. F 26 B 13/18, publ. 04/30/80.

15. Patent of Russia No. 2177129, cl. F 26 B 13/18, publ. 12/20/2001.

16. Copyright certificate of the USSR No. 514177, cl. F 16 B 13/18, publ. 05/15/76.

17. Germany patent No. 1226287, NKI 39a ³ 7/14, 1966

18. USSR copyright certificate No. 596795, cl. F 26 B 13/18, publ. 03/05/78.

19. J. Orir Physics, M., Ed. Mir, 1981, vol. 2 p. 417.

20. J. Orir Physics, M., Ed. Mir, 1981, vol. 1 p. 271.

21. The magazine "Textile Month", October, 1995, "Elictrically Heated Roll", firm DELTA p. CORP.

Claims (1)

A method of electrically heating a drying drum with a multilayer cylindrical body, for example, for a sizing machine, in which one of the intermediate layers is first heated by interacting with electrodes connected to the electric network, and then the outer layer is heated by heat transfer from the intermediate layer to the outer one, characterized in that the drum is performed three-layer with hard layers, turning the middle layer into an electric heater, forming it from an electrically conductive thin and flat tape with a large electrical resistivity, placing it in the form of a uniform cylindrical spiral on the inner layer of the housing and tightly compressing it with the outer one, while the outer and inner layers of the housing are either electrically conductive or the tape is electrically insulated, and the inner and outer layers are electrically conductive, in addition, the outer layer is more heat-conducting, and the pitch between the turns of the tape is set less than its width, and the tape is connected to the electrical network by the ends.

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