FI58173C - SAETT OCH ANORDNING FOER ATT TORKA FUKTIGT MATERIAL FOERETRAEDESVIS EN FUKTIG MATERIALBANA - Google Patents

Description

\ · ΪΜΪΓ * \ Γβΐ tt1> ANNOUNCEMENT rn.n, fSTk lBJ UTLÄGGNINGSSKRIFT 5 ö 1 7 3 C Patent granted 10 12 1000 (^) Patent meddelat ^ ¥ ^ (51) Kv.! K? /Lnt.a.3 D 21 F 5/00 FINLAND — FINLAND (fl) 2183/70 (OT) 1-Uk »mliptlv» —Am5knlnnd «f 07-08.70 (23) AtkupUvt — GlMghctfdtg 07.08.70 (41) Tullut] utklMk *) - Bltvtt offwitllg 1? .02.71

Patent ·] · registry office (44) NlhttvUriptnon et al. -

Patent and trade repositories AmMcait utl * | d oeh utUkrtftan publfcarad 29.08.80 (32) (33) (31) Pn * «« y • tuolk.ui-Bnirt prlorltat 13.08.69

Sweden-Sverige (SE) 1129 ^ / 69 (71) AB Inventing, Bergsgatan U, Säffle, Sweden-Sverige (SE) (72) Hans Ivar Wallsten, Säffle, Sweden-Sverige (SE) (Jk) Berggren Oy Ab (5) * 0 Method and apparatus for drying a wet material, in particular a wet web - Sätt och anordning för att torka fuktigt material, företrädesvis en fuktig materialbana

The invention relates to the drying of webs, for example paper, cellulose, other fibers, cardboard, textiles and the like. Thanks to the invention, a very efficient and fast drying, i.e. the departure of water or the like, is achieved, so that the drying rate is made quite higher than when other types of dryers are used. If the invention is used, for example, in the production of paper on a paper machine, then the speed of the paper machine is made even higher or the drying section of the paper machine is made rather shorter than usual and less space-consuming.

The following are some examples of the application of the invention in the manufacture of paper and cellulose, but the invention is by no means limited thereto.

As is known, paper or board is made so that the wet fibrous web first passes through the press section of the machine, where water is pressed from the web as far as possible in terms of quality. The moist paper web then passes through a drying section, 58173, the main parts of which are warm rotating rollers, usually heated by pressurized superheated steam. The rollers are usually in two top rows. The paper web passes through the drying section so that it alternates with the lower roll, the upper roll. The paper web is regularly pressed against the surface of the rotating roll with a drying felt or drying wire. The paper web is thus dried in the drying section alternately on different sides.

As is known, the drying section may be a single large heated roll on the surface of which the wet paper web leaving the pressing section comes into contact.

When the roll has rotated most of its rotation, the paper web is dry, taking it off the surface of the roll.

It is easy to see that the disadvantage of said drying method is that - the water expelled by evaporating from the paper web must leave the side of the paper which is away from the warm surface of the roll. This is explained by the fact that the water vapor formed cannot penetrate through the uniform surface of the roll. In addition, when continuous hot rollers are used for drying and the drying is alternating, the disadvantage is that the vapor film formed on the surface of the web away from the warm roll hits the next roll and thus makes it difficult to transfer heat from the roll surface to the paper web.

Various methods have been proposed to improve the drying efficiency.

Thus, the web can be dried, for example, by replacing the drying rollers with perforated drums over which the web passes. The heat then comes from outside as hot air, for example. The steam formed ~ is sucked from the drums under vacuum.

According to another method, the wet web is dried using hollow rolls having a porous shell with a plurality of grooves extending from the outer surface to the inner surface. From the source of dry heat inside the rollers, heat is conducted from the inside outwards through its porous material to the moist web, whereby the water vapor generated by the heat is transferred in the opposite direction through the cavities of the roll wall to the roll cavity. When the indoor air of the rollers is kept dry using a suitable heat source (e.g. electricity, dry gas or oil), the steam penetrating the rollers is prevented from condensing and is then discharged from the rollers. In one case, full-bodied roll casings, such as perforated stainless steel, are used to achieve a similar effect.

However, the latter method has some drawbacks. For example, the choice of heat source type has its limits. Thus, superheated steam cannot be used. This is due to the humidity and overpressure inside the roll. The overpressure would result in water vapor leaking away and the vapor from the wet web being prevented from penetrating through the porous jacket from the outside to the inside. In addition, it would be problematic to make the porous jacket strong enough to withstand the pressure of superheated water vapor acting from the inside. In addition, the implementation that there are holes in the solid jacket has the disadvantage that such holes, which for practical reasons must be large, tend to leave marks on the web, in addition to which the holes tend to become blocked due to easily settling particles.

It has now surprisingly been found that the above-mentioned drawbacks can be avoided by means of the present invention, the features of which are apparent from the appended claims.

The invention will be explained in connection with the drawing. Figure 1 is a cross-section of a drying roll according to an embodiment of the invention, and Figure 2 is a longitudinal section. Figures 3, 4 and 5 show on a larger scale parts of the device according to Figure 1. Figure 6 shows on a larger scale a special implementation. Figures 7-10 show on a larger scale w a part of a drying roll according to different embodiments, illustrating the input of heat, the removal of steam and the enhancement of the contact pressure between the web and the drying surface. Figures 11 and 12 show cross-sections of drying cylinders according to still other embodiments according to the invention.

According to Figure 1, the dryer includes a support roll or jacket 1 which is suitably heated, for example by introducing superheated steam into its cavity. The roller has ends, shaft pins on which the roller rotates, as well as steam inlet equipment and steam and condensate outlet equipment. A novelty of the invention is that there is a second jacket 2 around a uniform jacket 1 of thermally conductive material, for example cast iron, which is heated by the heat due to the jacket 1. The web 3 to be dried is against the outer sheath 2. The outer sheath is a low-porosity material capable of conducting steam, namely sintered material, for example sintered iron or metal, the outer surface of which is so flat that no marks remain on the surface of the paper web and that the fibers of the paper web do not adhere to the cavities. The requirements for the smoothness of the surface of the sheath 2 and at the same time the porosity and strength of the sheath are met by the use of a suitable sintered material. To maintain these properties, the surface can be cured.

Due to the properties of the jacket 2, the steam generated when the paper web 3 heats up can also escape through the porous layer, as illustrated in Figure 3. In this figure, the two main paths the volatile vapor tends to go to ^ minimum flow resistance for you. The porous layer 2 is illustrated by circles, although its structure is not so regular. In the embodiment according to Fig. 1, the steam penetrating the porous layer 2 enters the axial slots 4 in the roll, which are much larger than the fine pores of the layer 2.

In this way, the steam passes towards one or both ends or ends of the roll so that the flow resistance is as small as possible. When the heat enters all or part of the porous layer 2, the steam does not condense as it passes through this layer. According to Figures 1, 2 and 4, the slots 4 are parallel troughs of the uniform jacket 1. The salts can, of course, be reserved for the porous layer 2, Fig. 8.

The heat can be conducted to dry the web 3 in many different ways. Some ways appear in Figures 7-10. According to Figure 7, heat comes from both the outside and the inside according to the arrows E, respectively. From the outside, heat ~ can, of course, come from radiation and / or conduction. This heat input can be achieved by infrared radiation, combustible gas, heated air or gas. Inside the heat source may be, for example, the superheated water vapor, combustible gas, hot oil or other fluid. The steam outlet slots 4 are in this case in a uniform inner jacket. For example, a heating medium, such as superheated water vapor, may both enter and exit through the shaft or pins on which the roll rotates.

According to Figure 8, the heat comes only from the inside. The heat source is, for example, superheated water vapor. The vapor removal slots 4 are in the porous material 2.

5 58173

According to Fig. 9, the web 3 is pressed against the porous layer 2 by a porous substance 5, for example a drying hood or wire, whereby heat transfer is enhanced. Heat may come from either the outside or the inside, or both. The vapor escapes through both substance 5 and substance 2. The vapor removal slots 4 are partly in the porous material 2 and partly in a uniform inner jacket.

According to Fig. 10, there is a sealing means 6 on the outside (for example a steel strip) which presses the web 3 against the porous layer 2. The heat input can, of course, be arranged in different ways. In this case, the steam only goes towards the porous layer. This implementation is different in mind, because in some cases the paper can be made very uniform and very smooth in surface.

According to Fig. 11, the paper web 3 rotates a dryer similar to Fig. 1, but is pressed against the porous layer 2 of the device according to layer 5 of Fig. 9 or layer 6 of Fig. 10.

As mentioned, for example, the paper web is dried by pressing the wet web against the surface of a single roll. According to the invention, a porous outer jacket and steam removal slots can also be provided for such a roll. Such a dryer according to Fig. 12 has a converging roll 7, from which the paper web 3 goes to a porous layer 2 with steam removal slots. Heat may come according to moles E both from the inside through the jacket 1 and from the outside. A release scraper 8 can be provided for the dried web and the take-up roll 9-Heat can, of course, be applied from the outside to that part of the porous surface of the drying roll which is not covered by the paper web. This also applies to the implementations according to Figures 1 and 11.

The porous material used is preferably a sintered metal, the metal of which is, for example, copper, a copper alloy, for example brass or iron, steel or an iron or steel alloy. It is essential for the invention that the porosity is so sufficient that the steam is well permeable, that the strength is sufficient and that the outer surface is so smooth that no marks remain on the paper web. In addition, it is important that the surface is so flat that no pieces of fiber, etc. are placed on it. To keep the porous surface clean, a scraper, such as man-made fiber, is suitable. A material suitable for the size of the granules must be used to make the sintered metal. In practice, the so-called granule size has proved to be suitable. For 10% bronze, a maximum of 6 58173 is 75 / U and an average of about 40. This is only an example, since, depending on the other conditions of manufacture of the sintered material, coarser or finer granularity may in fact be used.

In order to meet both the requirements for surface uniformity and strength and the low resistance to flow of the formed steam, the porous material may consist of layers with different properties.

Thus, it is appropriate to make the surface layer of the porous material such that it has an abundance of fine pores and that its surface is smooth, while the inner layer or layers are of a rather coarser sintered material to minimize the vapor flow resistance. _

The different layers can be pressed together before sintering. Depending on the circumstances, the outer shell may be chromium plated or otherwise coated so that the surface hardness is appropriate. The circles of different sizes in Figure 5 are intended to illustrate the different layers of sintered material.

In this way, in some cases the resistance to the flow towards the ends of the roll is made so small that no special steam removal soles are required, especially for short drying rolls. In order to achieve a good drying efficiency, it has also proved advantageous that at least the ducts in the outer layer of the porous material are very fine. Indeed, it has been shown that in some temperature ranges the fine pores absorb water as a liquid by the capillary action, which then evaporates in the deeper porous material.

The steam flowing through the sintered material and / or from the steam removal sol can, of course, be collected from the ends of the roll and may be used for heating air used on the drying side of a paper machine, etc.

As mentioned, evaporation is faster when the device according to the invention is used than when the paper web is conventionally dried. The webs of the paper types tested in the comparison, which contained 40% dry matter, were dried so that the dry matter content became 95%. The shortening of the drying times is shown in the table. The outdoor temperature was 120 ° C in all cases.

Claims (5)

7 58173 Type Drying time sec. When Time shortened warm response surface was * uniform porous Kraft paper, 80 g 6.5 3.7 43 Fluting, 127 g 20.5 15.5 24 Writing paper, 70 g 5.7 3.5 39 Sack paper, 90 g 9.7 5.6 42 A method for drying a moist substance, in particular a wet web, characterized in that heat is conducted from a heat source through a homogeneous barrier layer (1) to one side of a porous thermally conductive layer (2) having pores to remove steam, the moist substance (3) settling against the opposite side of the porous layer (2) and removing the steam formed by the water contained in the moist substance (3) through the porous layer (2) and then in the substantially porous layer (2) and / or on the surface facing the porous layer (2) of the barrier layer (1) through the channels (4) at a distance from the contact surface of the porous layer (2) and the moist material (3). Apparatus for applying a method according to claim 1 for drying a wet material, in particular a wet web, characterized by a porous thermally conductive layer (2) for the wet material (3), supported on the side away from the wet material (3) by a homogeneous barrier layer O), adapted to heat the porous layer (2) to co-operate with the heat source, and to dissipate steam from the channels arranged in the porous layer (2) and / or the surface facing the porous layer (2) of the barrier layer (1) at a distance from the porous layer (2) and the contact surface of the moist substance. Device for drying a wet web of material according to claim 2, characterized in that the porous thermally conductive layer (2) and the barrier layer (1) below it are arranged as a rotating casing of a bearing-drying cylinder. Device according to claim 2, characterized in that the porous thermally conductive layer (2) is made by sintering and that its surface facing the moist material (3) is formed by a fine sintering agent, preferably a thermally conductive metal material, to form a smooth surface. Device according to Claim 4, characterized in that the inner part of the porous thermally conductive layer (2) consists of a coarser sintering agent in order to reduce the steam flow resistance.