Give you a brief introduction: what types of headboxes are there in paper machines?

Main types of papermaking headbox

According to the working principle, it can be divided into three categories: open type, air cushion type and hydraulic type (full flow type). In addition, Tik Tok Encyclopedia, a variety of full flow air cushion combined type and multi-layer headbox, is derived.

1. Open headbox (open type)

Principle: The upper part of the box is ventilated with air, and the spraying speed is controlled by the static pressure head generated by the height of the pulp level. It is equipped with double homogenizing rollers for rectification, and has overflow grooves to discharge floating bubbles and floating pulp.

Speed: ≤250m/min, low speed, mostly old paper machines.

Advantages: simple structure, low cost and convenient maintenance.

Disadvantages: the speed can not be high, and the box is tall when the pulp level is high, which is easy to bring in bubbles; The banner is fine-tuned by the lip plate.

Application: small paper machine, corrugated base paper, low-grade cultural paper, toilet paper rotary screen/fourdrinier.

2. Air cushion headbox (closed weir pool)

Principle: the box is sealed, and a compressed air cushion is formed above the slurry; The pulp level is basically unchanged, and the spraying pressure is adjusted by the air cushion pressure; Equipped with homogenizer roller/step diffuser, with overflow defoaming.

Vehicle speed: 200‑600m/min, medium-speed mainstream, and some can reach 800m/min.

Advantages: wide adjustment range, high box height, good defoaming effect and stable operation.

Disadvantages: the rotation of homogenizing roller brings pulse, and the fiber is easy to agglomerate at high speed; The old model relies on lip bolt to adjust the banner quantity.

Application: cultural paper, writing paper, wrapping paper, medium-speed fourdrinier paper machine, and a large number of reforming machines are in use in China.

3. Hydraulic headbox (full flow, modern mainstream)

Principle: the box is completely filled with slurry, without free liquid level and air cushion; Depending on the pressure of the slurry pump, the slurry jet head is provided; Cancel the rotation of homogenizing roller, and use turbulence generator, step diffuser and deflector to produce micro-turbulent dispersed fibers.

Subdivision:

1) Ordinary hydraulic headbox: fine-tune the banner by lip plate;

2) Dilution water hydraulic headbox: The modern mainstream, the dilution water valve adjusts the local pulp concentration to control the banner ration, and the paper quality is better without hard lip-breaking.

Speed: 300‑2000m/min, suitable for fourdrinier, nipper and crescent tissue paper machine.

Advantages: no rotating parts, no bubbles, good turbulence quality and good fiber dispersion; Diluted water banner has high quantitative accuracy.

Disadvantages: sensitive to pulp feeding pulse, pulse attenuator is needed in the preamble; High cost, high requirements for pumps and control systems.

Application: High-speed culture paper, coated base paper, white board paper, high-grade box board paper, tissue paper, and paper machine.

4. Full-flow air cushion combined type (transitional type)

Full-flow main body, adding small air cushion surge chamber, taking into account hydraulic headbox+air cushion to eliminate pulsation, is mostly used in reconstruction projects, but now there are few new ones.

5. Multilayer headbox

It belongs to a special form of hydraulic headbox, which is divided into 23 layers of independent pulp feeding, and the pulp of each layer can be mixed in different proportions to produce linerboard, white board with gray background and multi-layer box board paper, so as to realize the composite networking of different pulp types.