FI59832C - TORKPARTI I EN PAPPERSMASKIN - Google Patents

Description

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Patents · and registrars .... .......... . ., .., .... . (44) Date of publication and date of publication. - Λ. rt.

Patent · och registerstyrelsen Anaökan uttafd och utljkrtft.n publkarad 30.06.81 (32) (33) (31) Requested request — Begird priorities (71) (72) Matti Kankaanpää, Kaskenkaatajantie 12 N, 02100 Espoo 10,

Suomi-Finland (FT) (7 * 0 Forssen & Salomaa Oy (5 * 0 Paper machine drying section - Torkparti i ai pappersmaskin (62) Divided by application 2761/71 (advertisement 5 ^ 163) 'Avdelad frän ansökan 276l / 71 (utläggningsskrift 5 ^ 163)

The invention relates to a drying section of a paper machine having two, preferably horizontal, overlapping rows of cylinders through which a drying wire, preferably a non-wettable plastic wire, and a paper web supported by it pass through a zigzag web, and in which the drying section by means of heated drying cylinders as contact drying.

In a conventional drying section of a paper machine, water from the web is evaporated by means of heated drying cylinders, in cooperation with which there are usually drying blankets or wires which facilitate the removal of water.

The drying cylinders are generally arranged in two or more superimposed horizontal rows, whereby when the paper web travels from one lower row cylinder to the other, i.e. the distance from the lower row cylinder to the upper row cylinder and vice versa without air drying. In these so-called open exports included in the drying section, paper web breaks often occur mainly because the paper web from the press section of the paper machine is still quite weak in strength, e.g. due to the fact that the dryness of the paper web from the press section is usually in the range of 30-42%. . It is, of course, clear that the strength of the paper web increases all the time as it passes through the drying section, so that losses of production time or 2,59832 machine downtime due to open paper breaks in open exports are significantly more likely at the beginning of the drying section.

Since, in practice, the choice of paper machine speed is a certain production process optimization task, the paper machine speed must be kept as high as possible, however, it must be taken into account that increasing the speed increases stress on the paper web. In practice, certain grades of paper have been improved in production terms by using a larger amount of raw material with better strength properties than usual, which, however, is often less favorable in other respects. Thus, for example, in the production of pulp-containing paper grades, it is necessary to increase the amount of cellulose in proportion to the less expensive and other cheaper pulp in terms of its other properties.

The disadvantages caused by the said open exports of the drying section have become more and more significant recently, as the constructive speed and working width of paper machines have been constantly increasing.

The nearest object of the invention has been to eliminate, at least to a significant extent, the disadvantages caused by the open exports of the drying section and thus to have a positive effect on the paper web breakage subsidies and the operating economy of the entire machine.

In order to achieve the set objects, the invention is mainly characterized in that the paper web from the press section of the paper machine is arranged at the beginning of the drying section without open export to be attached to the drying wire when dried on a drying wire.

Within the scope of the invention, it is possible to pass the paper web through the entire drying section without any open export in the drying section, i.e. the paper web passes through the drying section as a closed export. Within the scope of the invention, it is also possible that the paper web travels in the drying section only part of the way as a closed export, i. supported by the wire, or that successive cycles are provided in which the paper web is continuously supported by the drying wire. However, for the practical application of the invention, it is important that the invention is used, especially at the beginning of the drying section, so that the paper web has time to achieve at least a certain dryness, preferably at least 50-60% dryness, before the paper web is open for export.

3,59832

The invention will now be described in more detail with reference to the accompanying diagram of the schematic drawing, which shows an application example of the structure of the drying section of a paper machine according to the invention.

According to the figure, the paper web 9 coming from the press section of the paper machine is tied by means of a suction roll I to a drying wire 5, in which a non-hydrogenated plastic wire or a similar wire is preferably used. The adhesion of the paper web to the wire 5 is enhanced by means of a suction box 2, after which the paper web passes between the conventional drying cylinder 3a and the wire 5 in a compressed manner. The wire 5 winds through two rows of cylinders, the conventional cylinders 3a, 3b, 3c, etc. of the lower row being conventional heated drying cylinders and the upper row of cylinders 10a, 10b, etc. being air-permeable cylinders. In order to keep the paper web well pressed against the wire 5, a high-performance heat-drying hood 7 is arranged above the cylinders I0a, 10b, etc. and a suction chamber 8 below it, due to which the drying air flows through the paper web 9

Within the scope of the invention, it is not necessary to use both blower cabinets and suction chambers, because only with the existence of one can air flow through the paper web. The difference, of course, in practice is that this is the most appropriate procedure in most cases, as it maximizes the drying efficiency using advantageous structures. The flow-through Interit 10 can be replaced by conventional drying cylinders 3.

The invention is in no way narrowly limited to the application examples presented above, but various details of the structure of the drying section of the paper machine according to the invention can be modified and altered in many different ways without departing from the scope of the invention.

Claims (4)

4,55832 Patent claims A dry + usable part of a paper machine comprising two, preferably horizontal, overlapping rows of cylinders through which a drying wire (5), preferably a non-hydrogenated plastic wire, and a paper web (9) supported by it pass a zigzag path, and in which the drying part the paper web (9) coming from the press section of the paper machine on the second cylinder row is dried by contact drying with heated drying cylinders (3), characterized in that the paper web (9) coming from the press section of the paper machine is arranged ) by means of suction devices (2) and that after said suction devices (2) for at least a substantial part of the entire length of the drying section the paper web (9) is adapted to be kept attached to said drying wire (5). Drying section according to Claim I, characterized in that the paper web (9) is adapted to be fastened to the drying wire (5) by the pressure difference across the paper web (9) at least at all points where the paper web (9) does not pass through the drying wire (5). and compressed between the cylinder (3) of the drying section. Drying section according to Claim 1 or 2, characterized in that air-permeable cylinders (10) are used in the second row of cylinders of the drying section, in connection with which devices (7, 10) for maintaining said pressure difference are arranged to act. Drying section according to Claim 1, 2 or 3, characterized in that the paper web (9) is guided in a closed export supported by the drying wire (5) at least until the paper web (9) reaches a dryness of $ 50-60 before it is subject to open exports.