DD240331A1 - METHOD AND DEVICE FOR DISCONNECTING AND DRYING FLAECHEN-FORMED MATERIALS WITH LOW MECHANICAL STRENGTH - Google Patents

Abstract

The invention relates to a method and apparatus for drying and separating film webs, particularly in low pressure tobacco film webs formed at low pressure at the dryer inlet. The dryer works on the convection principle, whereby the film web is directed perpendicular to the transport direction of the drying agent and at the same time on Saugkaesten, which are installed below the conveyor belt, is fixed on selbiges. In conjunction with those attached to the top of the conveyor belt cutting edges separating the film takes place by attacking Stroemungskraefte. The drying unit working according to the convection principle allows a multiple increase in the drying speed compared to the previously used radiation dryers and thus provides a significant energy and Investkostensenkung in tobacco film production.

Description

For this 1 page drawing

Field of application of the invention

The drying and separating method and apparatus find use in the manufacture of film webs, particularly in low pressure tobacco sheet formed under pressure, with drying taking place in the dryer area, while the separation takes place only in the initial stage or before.

Characteristic of the known technical solutions

One possibility for the production of tobacco foil is according to the principle of the pressing technology, which in the patents

BRD 1215567 ·.

FRG 1532042 ·

Germany 2055672.

GB 8004414

is described. An important technological step in the production of tobacco foils is the drying and separation of the film web. Due to the low strength of the undried film web, the known solutions work on the principle of radiation drying. The radiant dryer ensures by the absence of the intermediate heat carrier air gentle drying of the film web. Downstream of the radiation dryer is a cutting device which separates the film web into predetermined pieces. The disadvantages of radiation drying for drying pressed tobacco film webs are essentially given by

- the unconditional use of highly refined energy sources, such as gas and electric energy.

- Low specific drying performance, which is for the drying of tobacco sheets, an average of 1 kg of water per hour and m ² drying area. This leads to large and therefore expensive drying systems.

- Increased demands on the fire safety of the system in case of failure of the transport equipment.

The use of convection dryers (jet dryer) for the drying of pressed tobacco film webs is not known, since drying-technically desirable flow velocities to the dry material leads to uncontrolled destruction of the film web. A non-destructive drying of the pressed film web is possible according to the usual convection principle only with extremely low air velocities in the blowing jet, which do not allow economic dryer dimensioning. For this reason, in practice, the drying of pressed tobacco foil webs takes place exclusively according to the principle of radiation drying

 (Presented in the offer catalog for the HEIBOFLAKE system of the company Borgwaldt, Hamburg)

Object of the invention

The aim of the invention is to apply the principle of convection drying for the drying of pressed tobacco film webs with the following effects:

- Achieving high specific drying performance in the drying of pressed tobacco film webs by realizing high air velocities in the blowing jet. This leads to compact drying systems and thus to reducing the specific energy consumption of the system.

Use of any energy carrier for dryer heating and thus better integration of the pressed film plant into the existing operational energy supply systems of cigarette factories. ,

- The usual requirement for unconditional availability of the energy sources gas and electric energy for dryer heating thus eliminated and leads to a significant reduction in energy costs in film production.

- Use of secondary energy sources (eg waste heat from drum dryers, vacuum chamber, air conditioning, humidifier) of cigarette production for dryer heating and thus negligible energy costs in film production.

Use of the flow forces acting on the pressed tobacco foil web during the drying process for separating the film web and thus avoiding the need for maintenance-intensive mechanical cutting devices in the process of producing tobacco sheets.

The essence of the invention _:

The object of the invention is to provide a method and a device which allows the simultaneous intensive drying and separation of the pressed tobacco sheet. According to the invention, this object is achieved in that the launched on an endless net strip film web is fixed by the acting at the web bottom negative pressure in her'Lage and separated in conjunction with the arranged on the net strip cutting edges. The tobacco foil fixed in this position makes it possible to realize high air velocity in the blowing jet of the convection dryer and thus a high effectiveness of the drying while avoiding the uncontrolled destruction of the tobacco foil by the flow forces acting in the drying process. An optimum in the drying of pressed tobacco foil webs is achieved while maintaining the parameters:.

- Air velocity at the nozzle element <22 m / s

- Vacuum in the suction box p _u = 1300Pa ·.

The specific drying performance is a multiple compared to the radiation drying pressed tobacco film webs. The convection dryer according to the invention consists of a plurality of nozzle box connected in series, which are provided on the outlet side with slot or round nozzles (nozzle elements). Underneath the drying units, a mesh tape is passed to receive the tobacco sheet. The mesh tape is equipped according to a given geometry with corresponding cutting edges, preferably sawtooth. Below the upper run of the mesh belt suction boxes are installed, which allow an effective pressure difference between the lower side of the film and the upper side of the film. The required negative pressure on the film web is produced by fans 4 arranged on the suction boxes 5 or by means of a fan which is installed outside the machine and which is connected to the individual suction boxes by a collecting line. In both variants, the extracted air is supplied to the drying unit via distribution devices on the discharge side.

The pressed tobacco sheet produced by a known method is placed on an endless net tape. By acting on the underside of the film web due to negative pressure forces and arranged on the net top cutting edges, the film in predetermined areas, preferably rectangle, separated and held on the net. In the drying device, the film which has been fixed on the net strip is dried by blowing blasts incident perpendicular to the transport direction of the film. It is ensured that the forces acting on the underside of the film forces are always greater than the forces acting upon impact of the blow jet and by flowing the drying air to the film top flow forces. After exiting the drying device, the effect of the negative pressure on the underside of the film is removed and the film is deposited from the net.

embodiment

The invention will be explained in the following embodiment, according to FIG.

The pressed tobacco sheet produced by a known method is deposited on the net 1. After the films have entered the surrounding structures 10 of the dryer, they are fixed in position on the net by negative pressure in the suction box 5, which is generated by the fan 6. In conjunction with the attached on the net top cutting edges 8 a separation of the film takes place. Via nozzle elements 2, the film is blown perpendicular to its conveying direction and dried. The heating and conveying of the air in the individual drying units 11 is realized via fan 4 and heat exchanger 3. Air sucked in by the fan 6 on the underside of the film remains in the drying space and is blown out on the delivery side via distribution devices 7. The expelled moisture in the drying device is sucked by exhaust fan 9. At the openings of the dryer to Netzbandein- and exit the exhaust air is automatically replaced by inflowing supply air. At the dryer outlet, the effect of the negative pressure on the film is dissolved and discharged from the net.

Claims (3)

claims: 1. A method for separating and drying sheet-like materials with low mechanical strength, characterized in that the material to be dried and separated by vacuum fixed on a support member and separated by attached to the support member cutting edges and dried according to the convection principle. 2. A method for separating and drying sheet-like materials with low mechanical strength according to item 1, characterized in that the film web is fixed by static negative pressure in the suction box 5 on the net and subsequently separated by the arranged on the net band top cutting edges separation of the film and after the principle of convection is dried in a slot or round nozzle dryer, wherein the ratio between static vacuum in the suction box and dynamic pressure of the blower blaster is preferably 3.5 ... 4.5. 3. Device for separating and drying sheet-like materials with low _; mechanical strength according to point T, characterized in that under the upper run of the provided with cutting edges on the top net strip • Suction box 5 are arranged, which are individually vacuumed via fan or via a manifold and a fan, the suctioned via the suction boxes air flow through the valve device flows back to the dryer again.