Rotary Vane Vacuum Pump for High Speed Paper Machine
Vacuum presses are mostly used in medium and high-speed paper machines, and the equipment used is rotary vane vacuum pumps.
The upper pressing roller of the vacuum press is a stone roller, and the lower pressing roller is a vacuum pressing roller.
The structure of the vacuum pressure roll is basically the same as that of the vacuum couch roll. The roll shell is made of bronze or stainless steel. The thickness of the roll shell is determined by the required stiffness and strength. Other working parameters of the paper machine such as speed and vacuum degree remain unchanged. The thicker the roll shell, the smaller the dewatering capacity.
During high-speed paper making, after the moisture of the felt and wet paper is sucked out, it passes through the holes on the rollers, and turns into the vacuum suction area before it reaches the vacuum chamber, and is then thrown into the white water tray by the centrifugal force of the rollers.
The function of the vacuum chamber is only to suck the air in the eye holes of the shell. The thicker the roller shell, the more volume of the sucked air.
Our rotary vane vacuum pump is beneficial to improve the efficiency of press dewatering.
The roller shell of the vacuum pressing roller is covered with rubber with a thickness of 30-40 mm. The benefits of lagging are uniform pressure distribution, reduced felt wear and increased press line pressure.
Production practice shows that the smaller the axial and circumferential center distances of the holes on the vacuum pressure roller and the larger the number of holes, can significantly improve the dehydration effect of the vacuum pressure roller, thereby effectively eliminating the embossing phenomenon and prolonging the service life of the felt.
The hole diameter of the vacuum roller should be properly selected, which not only ensures that the roller has a sufficient dewatering capacity, but also considers that the opening will affect the strength of the roller and leave "shadow marks" on the paper. The hole diameter of the vacuum roller is generally about 4mm.
What is the dehydration mechanism of the rotary vane vacuum pump for vacuum pressing?
The wet paper sheet first enters the pre-dehydration area composed of the vacuum suction chamber. Under the action of the suction force of the rotary vane vacuum pump, the air vertically passes through the wet paper sheet and the felt enters the vacuum chamber, and takes part of the moisture away.
The wet paper sheet enters the mixed dewatering area composed of vacuum suction and positive pressure area from the pre-dehydration area. The blanket enters the vacuum chamber and is discharged.
After the wet paper sheet passes through the positive pressure zone, due to the gradual weakening of the pressure, the capillary pores of the felt and the wet paper sheet will gradually open, and instead, the water that is not discharged will be sucked back.
Vacuum dehydration is suitable for materials with small particle size, which are not easy to precipitate, and the thickness of the filter material can reach more than 3mm.
This article mainly introduces the application of rotary vane vacuum pump in high-speed paper machine. Vacuum pump has the function of vacuum pressing in high-speed paper machine. The dryness of the paper sheet is relatively uniform, and the broken ends are less during pressing, which has a cleaning effect on the felt and prolongs the service life of the felt.
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