Analysis on the Function of Papermaking Machinery

1. Headbox The headbox is a key part of a modern paper machine. It is a key hub connecting the two parts of “flow delivery” and “formation”. It is also one of the fastest growing components on modern paper machines, especially new modern high speed paper. The machine, with a speed of a few kilometers per minute and a width of more than ten meters, is only a fraction of a second to a few tenths of a second from the headbox on the high-speed wide-format paper machine.
In such a short period of time, it is required that the quantitative value of the paper sheets be the same along the entire width of the paper sheets, and the well-formed paper sheets should be copied out. It is difficult to achieve the net parts alone, and even impossible, and the flow must be required. The full width of the paper material discharged from the box along the paper machine is strictly consistent and uniform. The fibers are well-distributed, and the pulp flow has the characteristics of high strength and small turbulence, so as to prevent the fiber from re-slurrying during the spraying process, and according to the process Requirement to provide and maintain a stable relationship between spray speed and speed.
The traditional split type headbox is far from meeting the production requirements for the new type of paper machine. Although the headbox has not changed greatly in the overall structure in the past decade, the regulating devices have become more sophisticated. A more uniform and stable paper stream can be formed across the width of the web, with no or little perturbation of lateral and longitudinal velocities.
Some of the key improvements in modern headboxes are: first, a pulse attenuator in front of or in the headbox; and second, a conical head in order to create evenly distributed pressure and flow in the cross-web direction. , And according to the horizontal positioning and moisture distribution to control the full width of the lip adjustment, thereby improving the quality of a variety of paper.
Headstream headboxes and Bel Beie screen formers are representative of the level of the paper industry in the last two decades. ConceptIV-MHTM headbox can realize the control of fiber sheet distribution and quantitative fluctuations of the paper sheet. In the past, the flow rate of the ejected pulp, the non-directional distribution of fibers, and the quantitative fluctuation of the paper sheet in both vertical and horizontal directions were adjusted. All of this is achieved by controlling the pressure of the Internet paste and adjusting the shape of the gills. This will change the flow state of the paste material, destroy the non-directional distribution of the fibers, and affect the quality of the paper sheet.
The ConceptIV-MHTM headbox patented technology adds dilution water to adjust the concentration profile above the headbox rinsing. The dilution water is flushed along a series of pipes (evenly distributed in the machine's transverse direction) perpendicular to the direction of the pulp flow. Into the nearest fabric pipeline, to achieve the purpose of regulating the horizontal fluctuations of the sheet.
Through a series of experiments, the smaller the center distance of these pipes in the paper machine becomes, the higher the adjustment of quantitative fluctuations can be, and the adjustment ability can increase by 25% for every half of the center distance. Experiments show that when the center distance of these dilution pipes is 35mm, the result of the control can be quite satisfactory. Both the flow state and the quantitative distribution of the fibers can be well controlled, but this technique requires a very high level of automation.
2. Forming Department Since the 1950s, the paper industry has conducted systematic research on the forming mechanism and new forming methods of the clamp type, resulting in the emergence of various forms of the wire forming machine. Because the inserter is dehydrated on both sides, the dewatering rate can be increased by about 4 times compared with the traditional one-sided dehydration, and another advantage of the former is closed forming. The suspension does not exist in the exposed air in the former. Free surface. Because the dewatering capacity of the inserter meets the requirements of high-speed paper machines, and its excellent paper-making performance, it gradually occupies a dominant position on high-speed paper.
3. Pressing 1% of the moisture in the press section can save 4% energy consumption in the dryer section. This importance of the press section makes the research on the press section a breakthrough in recent decades. . Pressing is very important for the smoothness of paper, surface printing performance, two-sidedness, water absorption, tightness and stiffness. After the nip, a 4th press is almost a standard configuration for a new type of paper machine. Adding a 4th press can increase the dryness of the web by 2-3%. Not only can save energy, but also it is very beneficial to improve the quality of the sheet, it can improve the fatal weakness of the 3 nip press, that is, the Z direction of the paper sheet distribution and surface smoothness.
Reducing the difference between two sides of a sheet of paper significantly improves the tightness and smoothness of the sheet. In the press method, shoe press is a relatively new press technology, its wide nip, good dewatering ability, and can adjust its pressure curve in the direction of the paper running, by adjusting its pressure in the pressure side The rise is slower, and the pressure on the pressure side decreases rapidly, the dewatering ability is good and the paper sheet is not easy to get wet, and the dryness of the paper sheet entering the drying section can be improved.
Using this press technology not only can further increase the running speed of the paper machine, but also can reduce the number of dryer cylinders and reduce the length and operating costs of the paper machine. This technology reuses the vacuum closure system to make the machine run optimally.