FI12433U1 - Arrangement for an air dryer of a fibre web machine - Google Patents

Description

COMPOSITION WITH A FIBER DRYER AIR DRYER

The invention relates to an arrangement with an air dryer of a fiber web machine, in which the air dryer is arranged against a coated fiber web, the fiber web being supported by rollers.

At the end of or after unwinding of a fibrous web, such as paper and especially cardboard, the properties of the fibrous web can be adjusted as desired. Various coatings may be provided on the surface of the fibrous web to impart desired properties to the final product. The coating may be, for example, a paste which is applied or sprayed onto the surface of the fibrous web. After coating, further drying is still required. Thus, separate dryers are used to dry the coating. Instead of the previously used infrared dryers, air dryers are increasingly used in which hot air is blown from the nozzles towards the coated fibrous web. At the same time, air is drawn out of the nozzle gap. Thus, the coated side, and in particular the coating of the fibrous web itself, can be dried.

The air dehumidifier removes some of the air shortly after blowing. However, part of the heated blast escapes to the data center. At the same time, the inlets draw air in the data center, which reduces the efficiency of the air dryer. In other words, energy is lost. In addition, the motion of the fibrous web at the air dryer may be restless, which must be taken into account when positioning the rolls supporting the fibrous web.

The object of the invention is to provide a novel arrangement for the air dryer of a fiber web machine, which can improve the energy efficiency of the air dryer. Characteristic features of the embodiment of the present invention will be apparent from the appended claims. The arrangement according to the invention is simple in structure and easy to fit into a fiber web machine even after retrofitting. Deployment is possible without modifications to existing structures. In addition, the flow of the fibrous web even calms as air flows decrease.

The invention will now be described in detail with reference to the accompanying drawings, in which:

Figure 1a is a schematic drawing of the embodiments of the invention disposed on a fiber web machine,

Figure Ib shows a first embodiment of a controller structure included in an arrangement according to the invention,

Figure 2a shows a guide structure according to the invention fitted between two guide rolls,

Figure 2b shows an assembly of three guide rollers and two guide structures,

Fig. 3a shows another embodiment of a controller structure according to the invention,

Figure 3b shows a modification of the embodiment of Figure 4a,

Figure 3c shows a second modification of the embodiment of Figure 4a,

Figure 4a is a schematic plan view of the embodiment of the invention,

Figure 4b shows a portion of the image arrangement viewed from the machine direction.

Figure 1 shows the final step of manufacturing a fibrous web in which the fibrous web is coated. A fiber web machine is essentially a paper or board machine. The devices shown may be an extension of a fiber web machine or a separate unwinding station. After coating, the coating must be dried. This ensures that the coating adheres to the fibrous web and, on the other hand, avoids adhering the fibrous web to the rolls supporting the fibrous web. Here, there are several air dryers 10 and the coated fibrous web 11 is supported by rollers 12, also called paper guide rolls. After coating, the rolls support the uncoated side of the fibrous web and the coating must be dried before the fibrous web can again be supported on the coated side. When the fiber web is coated, it is already tensile, making the fabrics used in the earlier stages of production unnecessary.

The arrangement of the air dryers 10 is shown in principle in Figure 1a. Here, the fibrous web 11 is guided from the left underneath the machine plane 13 to the coating station 14. The design and operation of the coating station may vary in different applications, but only one surface of the fibrous web, here the upper surface, is coated. After the coating station 14, the fibrous web 11 is supported by rolls 12. The roller is not shown. As shown, the air dryer 10 may be horizontal, upright or inclined. By placing the rollers, the fiber web path is warped, which shortens the machine length of the post-treatment section, while at the same time bringing the air dryers close together. Air dryers are placed as needed, usually one to three per coating station. Thus, there are several, preferably one, arrangements for each air dryer in one production line according to the invention.

In the arrangement, the air dryer is mounted against the coated fibrous web 11, the fibrous web 11 being supported by the rollers 12. More specifically, the air dryer is on the coating side of the fibrous web. In practice, the aim is to dry only the coating. The arrangement according to the invention has a guide structure 15 on the opposite side of the air dryer 10 for recirculating the heated air back to the air dryer 10. The guide structure allows for the recovery of otherwise leaking air leakage and on the other hand reduces airflow from the machine room to the air dryer. Thus recycled, secondary energy can be reused in the production process. At the same time, the control structure insulates to prevent heat leakage into the environment. As a result, the overall efficiency of air drying is further improved. At the same time, the progress of the fibrous web slows down and the moisture profile of the fibrous web remains constant. In other words, the coating dries uniformly across the fiber web machine.

Fig. Ib shows a guide structure 15 according to the invention. The guide structure 15 is a type of trough which is mounted opposite the air dryer. A greater proportion of the air blown through the unidirectional air dryer is recycled by recirculating the air to the process via a baffle plate between the nozzles. The trough-shaped guide structure allows for the recovery and recycling of the amount of air normally lost, which improves the overall efficiency of the fiber web machine.

Figures 2a and 2b show exemplary applications of full-width guide structures 15. The guide structures are disposed between the rolls and extend substantially over the entire width of the fibrous web. Here, a gasket 16 is provided between the guide structure 15 and the roller 12. The gasket prevents airflow from the machine room to the air dryer outlet. On the other hand, the seal prevents hot air from escaping from the air dryer to the data center.

The air temperature in the air dryer is above 100 ° C. Thus, the difference with the data center temperature is considerable. According to the invention, the guide structure 15 includes an insulator. This prevents heat from escaping, while avoiding condensation problems. The dielectric can be implemented in various ways, but preferably the trough has a frame structure to which the dielectric is fitted and finally the frame structure is closed by a surface structure. The full-width guide structure is easily adapted to narrow web forming machines. However, as the width increases, the mass of the guide structure increases. In addition, the air escapes mainly from the edges of the fibrous web. Thus, in the invention, the guide structure 15 comprises two mutually arranged guides 17 and 18, each located at different peripheral regions of the fiber web 11. In other words, the guide structure is in the peripheral region and the middle region of the fibrous web is without the guide structure. In the middle of the fibrous web, air cannot pass through the fibrous web, whereby there is no escape of air there.

In the invention, the projection S of the guide 17 and 18 in the transverse direction of the fibrous web machine is less than half the width L of the fibrous web 11 (Fig. 4a). In this case, the peripheral areas of the fibrous web are covered with the central portion of the fibrous web without a guide. The guide extends over a sufficient distance from the edge. Depending on the application, the distance, i.e. the aforementioned gauge S, is between 500 and 2000 millimeters, but clearly less than the width of the fibrous web. In this case, the guide is easily supported on the structures of the fiber web machine and the structure of the guide can be made light.

Figures 3a-3c show various guides 17, 18 according to the invention, which extend over a portion of the distance starting from the edge of the fibrous web. The guides can be easily supported from the body of the fiber web machine as a protrusion. Fig. 3a shows a guide 17,18 having side walls 19 with the end open. When installing near the roll, the side walls are unnecessary. In this case, the guide can be left without side walls. In addition, the air flow is greatest at the peripheral regions of the fibrous web.

The guide of Fig. 3a can therefore be lightened. In other words, the guide 17, 18 includes a plane 20 opposite to the fibrous web, which is inclined upwardly starting from the edge of the fibrous web 11. This creates a volume in the peripheral areas which decreases across the fiber web machine. At the same time, the guide structure is lightened, which makes it easier to carry. In Figure 3b, the guide 17,18 has side walls 19. If the guide is placed between the rollers, the side walls are unnecessary. Such an embodiment is illustrated in Figures 3c and 4b.

In Figure 3b, a plate 21 is provided as an extension of the level 20, the plate forming a separate pressure zone with the running fibrous web, which keeps the fibrous web away from the sheet. In practice, an air mattress is formed between the fibrous web and the sheet, which passes along the fibrous web. The air mattress prevents the air inside the controller from escaping. Here, the plate 21 is bent downward, which increases stiffness. At the same time, protrusions that may damage the fibrous web are avoided. The plate 21 is also located in the guide 17,18 of Figure 3c.

The control structure according to the invention can reduce the energy required for drying. In addition, the flow of the fiber web remains undisturbed. The guide structure is easy to place on a dry mill machine. Only the speed of the air dryer fan or the temperature of the air dryer heat source such as a burner, steam radiator or electric resistor, or both, are adjusted as necessary. Controller structures reduce airflow from the environment to the air dryer and vice versa. In addition, the controls avoid heavy structures. At the same time, changes to the chassis parts are avoided, whereby the assembly can easily be retrofitted.

Figure 4a shows a top view of an arrangement according to the invention. Here, guides 17 and 18 supported by adjustable brackets 22 on a fiber web machine body 23 are shown. The weight of a full-width guide structure would be about 100 to 300 kilograms per meter, but a single guide typically has a mass of only about 20 to 80 kilograms. Thus, the guide can easily be carried on the frame without any special solutions. The lightweight design also allows easy installation. In addition, the controller can be transported without special arrangements.

Despite the guide structures, the behavior of the fibrous web remains problem-free without the risk of web break. In practice, the air dryer bends the fibrous web toward the air dryer, thereby avoiding hits to the guide. In addition, the air currents generated in the guide structure are small, so that the flow of the fibrous web remains undisturbed. The guide structure can be easily mounted between the rollers while sealing against the rollers. Thus, it is easy for the existing fiber board machines formed by the arrangement.

Claims (6)

PROTECTION REQUIREMENTS 1. Arrangemang i en fiberbanmaskins lufttork, enligt whisk arrangemang lufttorken (10) anordnad mot en bestru-ken fiberbana (11) när fiberbanan (11) stöds av valsar (12), kännetecknat av att vid lufttorken (10) det på fiberbanans (10) 11) motstående sida finns en styrkonstruktion (15) för åter-circulation av uppvärmd luft tillbaka till lufttorken (10). An arrangement with an air dryer of a fiber web machine, wherein the air dryer (10) is arranged against the coated fiber web (11) with the fiber web (11) supported by rollers (12), characterized in that the air dryer (10) (15) to recirculate the heated air back to the air dryer (10). 2. Arrangemang enligt skyddskrav 1, kännetecknat av att det mellan styrkonstruktionen (15) och valsen (12) finns en tätning (16). Arrangement according to Claim 1, characterized in that a seal (16) is provided between the guide structure (15) and the roll (12). 3. Arrangemang enligt skyddskrav 1 eller 2, kännetecknat av att styrkonstruktionen (15) innefattar isolering. Arrangement according to claim 1 or 2, characterized in that the guide structure (15) comprises an insulator. 4. Arrangemang enligt något av skyddskraven 1 - 3, kännetecknat av att styrkonstruktionen (15) innefattar två motstående anordnade styrenheter (17, 18), av voch en är placerad på fiberbanans (11) olika kantområden. Arrangement according to one of Claims 1 to 3, characterized in that the guide structure (15) comprises two oppositely arranged guides (17, 18), each of which is disposed on different edges of the fibrous web (11). 5. Arrangemang enligt skyddskrav 4, kännetecknat av att styrenhetens (17, 18) tecning (S) i fiberbanmaskinens tvärriktning and mind hänften av fiberbanans (11) bredd (L). Arrangement according to Claim 4, characterized in that the guide (17, 18) in the transverse direction of the fiber web machine is less than half the width (L) of the fiber web (11). Arrangement according to one of the claims 4 or 5, characterized in that the guide (17, 18) comprises a plane (20) opposed to the fibrous web (11), which is inclined upwards from the edge of the fibrous web (11). SKYDDSKRAV 6. Arrangemang enligt något av shielddskraven 4 eller 5, kännetecknat av att styrenheten (17, 18) innefattar et mot fiberbanan (11) motstående plan (20), whistling har anordnats snett stigande med början från fiberbanans (11).