The Role Of The Drying Department In Paper Machine

The drying section is responsible for removing moisture from wet paper after the pressing section, and also plays three roles: improving paper strength, increasing paper smoothness, and completing paper sizing.

The influence of paper quality during drying

(1) Shrinkage of paper pages

There are three different forms of moisture in the wet paper sheet entering the drying section, namely free capillary water and bound water. During drying, the first to be removed is the free ions between fibers, followed by capillary water in the fiber micropores, and finally the bound water in the fiber cell wall.

When drying, the flexibility and plastic strength of the paper change, and shrinkage occurs.

(2) The Influence of Paper Shrinkage on Paper Properties during Drying

Due to the longitudinal elongation of the paper during drying, the extensibility of the finished paper decreases, the bursting resistance decreases, and the folding resistance begins to increase. However, as the moisture content of the paper decreases, the fiber plasticity decreases, so it turns to decrease after reaching the highest point.

Drying not only affects the mechanical strength of paper, but also other properties such as tightness, absorbency, breathability, smoothness, and sizing.

The rapid heating and high-temperature enhanced drying will increase the softness, porosity, absorbency, and breathability of the paper, while reducing its tightness, transparency, and mechanical strength. On the contrary, low-temperature drying with slow heating results in the opposite.