The headbox is a key part of the paper machine. The function of the headbox is to convert the paper stock pumped by the square pump into a uniform, rectangular pulp flow with a width equal to that of a paper machine, and its longitudinal flow velocity is uniform.
Because the uniformity and uniformity of paper depends on the uniform distribution of fibers and fillers, the design and operation of a headbox system is very important for a successful papermaking system.
The main functions and requirements of the flow box are:
1) Uniform horizontal distribution of paper stock: The paper stock required to be on the Internet forms a paper stock stream with a rectangular cross-section along the banner of the paper machine, and the speed and turbulence distribution at each point is uniform. The paper flow on the Internet must be a stable paper flow without disturbance, cross flow and large eddies.
2) Effectively disperse fibers and prevent flocculation: The paper materials required to be on the Internet must be a uniformly dispersed fiber suspension.
3) Provide necessary control for banner weight, landing point, shot angle and shot speed.
4) The flow channel is smooth, there is no slurry hanging, and it is easy to clean.
5) Can effectively control fiber orientation.
6) Stability not affected by temperature, pressure and normal operation
There are three basic forms of headbox:
(1) Open headbox
(2) Air cushion headbox
(3) Hydraulic headbox
Both open and air-cushioned headboxes are equipped with homogenizing rollers, which are used in paper machines with medium and low speeds and above, to adapt to a wide range of speed and flow changes. Hydraulic headboxes are increasingly used on Fourdrinier paper machines, and their speeds are basically above 300m / min, and they are often used in folder paper machines.
With the continuous improvement of the paper machine speed and the requirements for the quality of paper products, in order to adapt to the development of the paper machine, the hydraulic flow box has more automation and quality adjustment functions. This results in a dilution water banner to control the flow box and adds side flow control.