The speed of paper machines has been the focus of most papermakers and paper machine manufacturers. Increasing the speed of a vehicle since it was a paper machine has always been a major technical issue.
At present, under the circumstance of increasing the width potential of the paper machine, it is of great significance to increase the speed of the paper machine and solve the technical problems encountered in increasing the speed of the paper machine.
At the end of the 19th century, the maximum speed of the Fourdrin Paper Machine was only 152m/min. At the beginning of the 20th century, technologies such as a vacuum roll, a vacuum press, a high-pressure headbox, and a paper threading lead were invented, and the speed of the paper machine reached 400m/min in the 20's. Since then, there have been high-speed, closed, uniform, homogeneous headboxes, new formers and dewatering elements, vacuum threading, high-strength, compound presses, high-efficiency drying-through steam dryers, and dry-side ventilation systems. Controllable high roller, new paper net, wet blanket,
Dry blankets and high-performance washing devices, thyristor sub-division drive systems, new detection instruments and control systems and other technologies have enabled the speed of the Fourdrin Paper Machine to reach the 70s.
900m/min. Afterwards, hydraulic headboxes, gap formers, high-strength presses, single-cylinder single-cylinder arrangements for drying, soft calendering, new reelers, high-speed rewinders, more complete QCS and DCS control systems, and Closed threading technology, etc., made the speed of the paper machine reach 1500m/min in 1986 and reached in 1995.
1700m/min, now reaching 2000m/min. At the beginning of the 21st century, the speed of paper machines used to produce newsprint, LWC, SC and other paper grades is expected to reach 2,500 m/min.
The goal of the papermakers in the 21st century is to achieve a paper speed of 3000m/min.
It should be noted that Valmet, Voith Sulzer and Beloit have done a great deal of work and achieved good results in increasing the speed of paper machines.
Key technologies to further increase the speed of paper machines When the speed of paper machines has reached 1500 to 1800 m/min, the speed of vehicles has been further increased to 2,000 to 2,500 m/min, and many technical keys have to be resolved. However, there are mainly the following key technologies: Be solved first.
Increasing the dryness of the wet paper sheet in the press section Currently, the paper feed from the forming section to the press section has been completely resolved, while at higher speeds, the part that affects the breakage of the paper sheet and the stability of the operation are mainly in the press section.
Paper sheet transfer between the press section and the dryer section and the initial position of the dryer section. Increasing the sheet dryness at the press section and the press section is to increase the strength of the wet paper sheet and to increase the ability of the wet paper sheet to be pulled at high vehicle speeds. When the compound press is used, the wet paper sheet released from the center roll is improved. The ability to resist centrifugal force, at the same time, can also enhance the stability of wet paper sheet operation.
Reducing the stress of the wet paper sheet during transfer Increasing the dryness of the wet paper sheet It is necessary to increase the traction resistance of the paper sheet. However, it is not enough to rely on improving the dryness of the sheet to run at higher speeds.
As shown in FIG. 1 , when a center roll press is used, as the speed of the paper machine increases, the centrifugal force of the wet paper sheet discharged from the center roll is also greater. Speed ​​at
Above 1800m/min, the wet paper strength value is already close to the centrifugal force, which means that the paper sheet may break at any time, which limits the further increase of the paper machine speed.
How to reduce the wet paper sheet stress? Abolish open-feed, use closed-feed, full-width wet sheet support operation is very necessary, the specific approach is:
• Vacuum suction transfer from the forming section to the press section. Closing the tails. • Using blankets to support and support the wet paper sheet. • Applying the felt vacuum box and vacuum roller to adsorb the wet paper sheet and the vacuum conveying wet paper sheet • Pressing part to the dryer section. The vacuum roller sucks closed transfer paper. The press section uses a single-carpet single-cylinder arrangement and applies a dry blanket vacuum roller to achieve a closed draw in the dryer section. 1.3 Improves the stability of the wet paper sheet and prevents paper breaks, chatter, flutter, and wrinkling of the sheet. 1.4 Application Specialized felts Rewetting phenomenon on wet paper sheets is reduced to a minimum. The speed limit of the center roll press has been used for a long period of time. The center roll press technology has been used for a long time. Such presses have limited the speed of the paper machine to further increase. The speed limit factors are:
· Open Traction Sheets · Center Roller Wet Sheet Scraping and Stripping · Press Section Leading to Paper Causes Multiple Breaks · After the last press nip, both sides of the sheet are large · The high load of the vacuum roll · Compound three nip presses The design problem Therefore, the center roll press technology can only make the paper machine speed reach 1500 ~ 1700m/min, and further increase the speed is limited.

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