Introduction of paper machine headbox

The headbox is a key component of a modern paper machine and a key hub connecting the two parts of "conveying" and "forming". It is also one of the fastest growing parts of modern paper machines, especially new and modern high-speed paper machines, with a speed of several kilometers per minute and a width of more than ten meters. On this high-speed wide paper machine, it takes only a fraction of a second to tens of seconds from the headbox to eject the pulp to the setting.

　　In such a short period of time, it is difficult or even impossible to produce a paper sheet with a uniform basis weight and a good uniformity by relying on the net part alone. It must be ensured that the paper material that is hit from the headbox along the full width of the paper machine is stable and uniform, to ensure that the fibers are fully dispersed, and the pulp flow needs to have high-strength and micro-turbulent characteristics to prevent the fibers from re-flocculation during the spraying process, and according to process requirements Provide and maintain a stable proportional relationship between shotcrete speed and wire speed.

　　The traditional open headbox is far from meeting the production requirements of the new paper machine. Although the overall structure of the headbox has not changed much in the past few decades, the device has been adjusted more finely. A more uniform and stable pulp flow can be formed across the entire width of the paper, almost free from the interference of the transverse and longitudinal speeds.

Some key improvements of modern headboxes are: first, install a pulse attenuator in the front or inside of the headbox; secondly, install a conical header in the headbox to generate uniform pressure and flow along the transverse direction of the paper web , According to the horizontal positioning and moisture distribution control the overall adjustment of the layout, thereby improving the quality of various papers.

　　The headbox and the sandwich former are representative of the paper industry level in the past two to three decades. This headbox can decouple and control the fiber distribution and lateral quantitative fluctuations of the paper sheet. In the past, it was achieved by controlling the pressure on the online slurry and adjusting the shape of the weir, which would change the flow pattern of the pulp, destroy the non-directional distribution of fibers, and affect the quality of paper.