JPS6317157B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adjusting the moisture content of a paper sheet in the press section of a paper machine, in which a temperature difference is formed partially in the width direction of the felt in the press stage to increase the moisture content of the paper sheet. The purpose of this invention is to reduce the variation in moisture content in the width direction and to obtain a paper sheet of stable quality with little variation in paper sheet thickness.

To dehydrate paper sheets that are currently wet-processed in the press section of paper machines, the paper sheets that have been made are placed on felt and pressed between upper and lower press rolls to remove moisture from the paper sheets. However, the compressed felt has extremely low porosity, so that the water dewatered in the press becomes a high-velocity flow in the nip and is removed through the roll surface or inside the roll.

It is known that the viscous resistance of water at the nip greatly affects dewatering performance, and the higher the temperature, the lower the viscosity.
For this reason, conventional steamboxes have been proposed that inject steam directly onto the sheet or the sheet and felt, but since they use steam, they are not desirable in terms of energy conservation, and because a separate steambox is used, running costs increase. There are drawbacks.

In addition, we use winding rolls as products such as newspapers, etc.
For continuous printing, uniformity of paper thickness is considered to be an important factor. Therefore, in order to make the paper thickness uniform, if you make strong adjustments to specific parts,
This is not preferable because it may cause problems such as partial elongation or breakage of the paper sheet, and for this reason, it is preferable to adjust small quantities using a plurality of adjustment parts.

As described in the claims of the present invention, the temperature difference in the width direction of the felt is achieved by partially spraying hot water and cold water in the width direction of the felt in the press part of a paper machine. It was possible to achieve uniformity of water content in the width direction of the paper sheet laminated on the felt and pressed, and also to make the thickness of the paper sheet uniform in the press part.

1 and 2 show one embodiment of the present invention, and the present invention will now be described based on these drawings. Felt 1 of the 3rd press part
The dehydrated paper sheet 2 is sucked by the vacuum roll 3 of the fourth press part as shown by the arrow in FIG. 1 and peeled off from the press roll 4 of the third press part. It is placed on the felt 5, and while it is laminated on the felt 5, it is pressed by a press roll 7 via a vacuum roll 6 and sent to a drying section (not shown).

The felt 5 of the fourth press part is attached to guide rolls 8, 9, 10, 1 in the form of an endless belt.
1 and 12 and vacuum rolls 3 and 6, and between two felt suction boxes (hereinafter referred to as FSB) between guide rolls 10 and 11.
) 13, 13, and two shower devices 14, 14 are installed between the two FSBs 13, 13.

The shower devices 14, 14 each have a plurality of shower nozzles for showering the felt 5 running on the upper surface of the pipes 15, 15 installed at right angles to the running direction of the felt 5 (arrow direction in FIG. 2). 16 are attached, one of the shower devices 14 is adapted to shower hot water and the other shower device 14 is adapted to shower cold water.

Further, 92 shower nozzles 16 are installed on the pipe 15 at intervals of 100 mm, and the shape is flat in the shape of a caudal fin, but the shower nozzle 16 is not limited to this. The spacing, shape, etc. of 16 depends on the type of paper sheet,
An appropriate selection can be made taking into consideration the paper making conditions, etc.

The paper sheet 2 pressed by the press roll 7 shown in FIG. 1 is placed before the reel part (not shown).
The water content in the width direction of the paper sheet 2 is measured, and if there is variation in the water cooling content of the paper sheet 2 in the width direction, the paper sheet 2 is
The felt 5 is peeled off and transferred by the guide rolls 8, 9, and 10, and hot water is showered onto the portion of the felt 5 corresponding to the portion of the paper sheet 2 having a high moisture content in the width direction. The valve of the shower nozzle 16 at the corresponding position of the device 14 is opened to shower hot water, while the portion of the felt 5 corresponding to the low moisture content portion of the paper sheet 2 is opened by the shower device 14 which showers cold water. Open the shower nozzle 16 at the corresponding position to shower cold water.

In this case, the hot water and cold water to be showered are each 70℃.
and a temperature of 20° C., and showering with a water pressure of 2 Kg/cm ² G. The hot water used in the kettle can be the hot water of around 70°C discharged from paper mills, which is particularly advantageous for energy saving measures. However, it goes without saying that the temperature and water pressure are not limited to these and can be appropriately selected and used.

As mentioned above, the felt 5 is showered with hot water and cold water, and the excess water adhering to the surface of the felt 5 is removed by the FSB, and most of the water is retained within the pores of the felt 5 and is transferred to the press roll 7 Moving. That is, the felt 5 has a local temperature difference in the width direction of about 70°C in the area where hot water is showered and about 20°C in the area where cold water is showered, and then reaches the press roll 7. .

As mentioned above, when the paper sheet 2 laminated on the felt 5 having a temperature difference in the width direction is pressed by the press roll 7, a strong dehydration effect is activated in the area where the hot water is showered, and therefore, The areas that had a high moisture content have a low moisture content, while the areas that have been showered with cold water have a weak dehydration effect and are pressed with a relatively high moisture content, so the paper sheet 2 after being pressed by the press roll 7 The variation in moisture content in the width direction of the reel part, which was conventionally 4% when measured in the reel part, has been reduced to 2%, and can be made more uniform.

Furthermore, as mentioned above, when the felt 5 has a local temperature difference in the width direction, the compressed paper thickness does not recover at room temperature in the part of the paper sheet 2 that is stacked against the part holding hot water. In addition, the paper thickness can be reduced because the calender roll is heated in the next drying process, and on the other hand, the area holding the cold water is compressed more than the area holding the hot water. Because paper thickness recovery is greater,
The thickness of the pressed paper sheet 2 in the width direction is also made uniform, and therefore the thickness of the paper sheet can be partially adjusted.

In FIGS. 1 and 2, hot water and cold water are sprayed onto the felt 5 of the fourth press part of the paper machine, but the present invention does not necessarily spray the felt 5 of the fourth press part It does not have to be, but it is preferable that it is the last part of the press part of the paper machine.Furthermore, if the present invention is implemented in a plurality of press parts, there is an advantage that the thickness of the paper sheet can be partially adjusted.

Furthermore, according to the present invention, the machine speed immediately after the press felt is replaced can be greatly increased compared to the conventional method.
That is, when a new felt is installed as described above, the new felt has high elasticity and has a significant internal porosity, so the moisture content of the felt increases, causing problems such as rewetting of the paper sheet. Therefore, the moisture content of the paper sheet is high on average and also tends to vary.

As mentioned above, if the paper sheet has a high moisture content when pressed using new felt, the next drying process will take time, and if the moisture content varies in the width direction, the quality of the paper sheet will deteriorate. As a result, the paper machine speed had to be initially reduced to 900 mm/min to reduce the strength of the paper sheet.

However, if the felt is pressed with a temperature difference in the width direction as in the present invention, the variation in moisture in the width direction of the paper sheet can be made uniform, the quality of the paper sheet is made uniform, and the wet paper strength is also stabilized. Even when replacing with a new felt, the machine can be operated at a speed of 1000 mm/min, improving efficiency.

As described above, the present invention uses a simple method of partially spraying hot water and cold water in the width direction of the felt in the press part of a paper machine to create a temperature difference in the width direction of the felt. The moisture content in the width direction of the paper sheet can be made uniform with less variation, and the thickness of the paper sheet can be partially adjusted to be uniform in the width direction of the paper sheet.

Furthermore, since the present invention can utilize hot water discharged from a paper mill, it is possible to effectively utilize waste heat, which is preferable from an energy-saving measure.
Furthermore, since the device is simple, there is also the advantage that running costs can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a side view of a main part of a device for implementing the present invention, and FIG. 2 is a plan view of a main part of a shower device. :3rd press part, :4th press part, 1, 5: felt, 2: paper sheet, 3, 6:
Vacuum roll, 4: Press roll of the third press part, 8, 9, 10, 11, 12: Guide roll,
7: Press roll of the fourth press part, 13: Felt suction box, 14: Shower device, 15: Shower device pipe, 16: Shower nozzle.

Claims (1)

[Claims] 1. By spraying hot water and cold water partially on the felt in the press part of the paper machine in the width direction of the felt, a temperature difference is formed partially in the width direction of the felt, and the felt is heated. A method for adjusting the moisture content of paper sheets, which comprises adjusting the moisture content in the width direction of paper sheets that are stacked and pressed.