FI115541B - Cooling - Google Patents

Description

115541 COOLING Technical background

The invention relates to the manufacture of paper and relates to the cooling of a heated paper web. The invention can be used to cool paper, for example, after a drying unit or by a coating machine.

In paper making, the temperature of the paper web rises easily after drying to above 100 ° C, and when it reaches the next station or roll, the temperature may still be above 70 ° C. Such a web is generally intended to be cooled before, for example, being taken to a coating station or a winding roll. Especially wood-free paper grades and board are used to cool the web during the coating process. Cooling is done by cooling cylinders, cooling floats or long free thrusts in the basement of the machine.

GENERAL DESCRIPTION OF THE INVENTION A cooling method according to claim 1 has now been invented. Some preferred embodiments of the invention are set forth in the other claims.

According to the invention, the paper web is cooled by a wire against the paper. A wire is best a felt wire. For example, the wire may be cooled by blowing a cooling gas, such as air cooler than the wire. In this case, cool replacement air is also brought to the * 20! Gas is best blown onto the surface facing the paper of the wire. Each side of the paper may have its own cooling; '' wire. Cooling can be performed in particular in the drive roll group.

»· •; ; The invention can be implemented with relatively small and simple devices. When using duo, *, paviras, there is no condensation problem as with metal cooling cylinders, for example. Blowing against the wire is not a sensitive blowing force. and thus does not increase susceptibility to breakage.

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When using blowing, the air can be brought in from the basement of the machine or from outside the building. The air supply system is best equipped with a filter, blower *

Iin, duct and nozzles for air supply to the wire. The air is led to the surface of the par-30 barrier against the paper. Blowing is best performed as close as possible to the contact between the wire and the paper in the direction of the paper inlet. This allows the wire to warm up as little as possible prior to contact. Blowing the air itself is best accomplished with the most effective nozzles available.

The invention is particularly suited for use with a coating machine for cooling paper to or from a coating station. The track can also be cooled between two coating stations. If the coating unit already has a wire drawing roll assembly already in place, the invention can also be implemented with relatively simple attachments to an old machine.

10 Drawings

The accompanying drawings relate to a detailed description of the invention. In them - Figure 1 shows a drawing machine roll assembly of a paper machine to which wire cooling units are connected - Figure 2 shows the nozzle surface of the air blowing box of the cooling unit of Figure 1.

Detailed Description of an Embodiment of the Invention

A draw roll group is generally meant a group supported by 1 to 3 rolls of wire, which is intended to provide a traceable web support. The drive roller assembly provides a traction force equal to that of the track. The group is followed, if necessary, by each station, such as:.: Coating station and drying station.

Fig. 1 schematically shows a group of draw rolls having three rolls 1-3 through which the paper web 4 passes. Above the web passes through wire rollers 5 to 9: wire 10 which presses against the web on the upper rolls 1 and 3.

3 115541 lazy to observe. For example, the flow resistance caused by the filter can be monitored, which is proportional to the filter fouling.

For example, outdoor air can be used as cooling air. The air can first be rough filtered.

5 The width of the blow box 11 in the transverse direction of the wire 10 corresponds to the width of the wire (e.g., about 5-12 m). For example, the length in the direction of the wire passage may be 0.5-1.5 m.

The air blowing speed can be, for example, 20-100 m / s and the air temperature, for example, 0-40 ° C. The cooling effect is based in part on the cooling effect of the cool wire and partly on the introduction of cool replacement air over the entire wire assembly (draw roll group). The total cooling effect may be, for example, 5-15 ° C, such as about 10 ° C, depending on the inlet temperature of the web and, of course, also the cooling air temperature.

Cooling can be used, for example, to the coating station or to the web to be rolled onto the winding 15.

Claims (10)

Method for cooling the paper web during papermaking, characterized in that the paper web is transported with support on the machine cloth (10), which is cooled. 5 The method of claim 1, wherein the paper web is transported on a rotating machine cloth (10). The method of claim 1 or 2, wherein the paper web is transported in a draw roll group (1-3, 5-10). A method according to any of claims 1-3, wherein the machine cloth (10) is cooled by blowing cooling gas against it, such as air colder than the machine cloth. The method of claim 4, wherein the gas is biased on the side of the machine cloth (10) which lands against the paper. The method of claim 4 or 5, wherein the gas is blown at a speed of 20-100 m / s. 15 A process according to any of claims 4-6, wherein the temperature of the gas is 0-40 ° C. A method according to any one of claims 1-7 for cooling a paper web (10) to be fed to or retrieved from the coating station or to be rolled. ...: 20 9. Plant for cooling the paper web during papermaking, characterized · ·. characterized in that it comprises a machine cloth (10) for transporting the paper web and a plant (11) for blowing cooling air against the machine cloth. : 10. Plant according to claim 9, which is placed in the paper web's draw roller group (1-3, 5-10).