The form and function of the headbox of a paper machine

The headbox is a key part of the paper machine. The function of the headbox is to change the paper material pumped by the square pump from the pipe flow into a uniform, rectangular slurry flow with the same width as the paper machine, and the longitudinal flow velocity is uniform.

Since the uniformity and uniformity of paper depend on the uniform distribution of fibers and fillers, the design and operation of the flow box system is very important for a successful papermaking system.

The main functions and requirements of Headbox are:

1) Evenly distributed paper material in the horizontal direction: The paper material on the Internet is required to form a paper material flow with a rectangular cross-sectional shape along the banner of the paper machine, and the distribution of speed and turbulence at each point is uniform. The paper flow on the Internet must be a stable paper flow, without disturbance, cross flow and large eddy currents.

2) Effectively disperse fibers and prevent flocculation: The paper material that is required to go online must be a uniformly dispersed fiber suspension.

3) Provide the necessary control for the width of the banner, the landing point and the shotcrete angle, and the shotcrete speed.

4) The flow channel is smooth, there is no phenomenon of hanging slurry, and easy to clean.

5) It can effectively control the fiber orientation.

6) Stability that is not affected by temperature, pressure and normal operation

There are three basic forms of the headbox:

(1) Hydraulic headbox

(2) Air-cushioned headbox

(3) Open headbox

Both open and air-cushioned headboxes are equipped with homogenizing rollers, which are used for paper machines above medium and low speeds, and are suitable for large speed and flow rate changes. The use of hydraulic headboxes on Fourdrinier paper machines is increasing, and the speeds are basically above 300m/min, and they are often used in paper-clamping machines.

With the continuous improvement of paper machine speed and the requirements for paper product quality, in order to adapt to the development of paper machine, the hydraulic flow box has more automation and quality adjustment functions. Thus, the dilution water banner control flow box appears, and the side flow control is increased.