The solution to the poor evenness of the paper machine

The methods of improving the evenness of the paper machine are generally as follows:

1. Reduce the proportion of long fibers:

The ratio of pulp is changed from the original 20%: 80% to 10%: 90%, so that the ratio of medium and long fibers to short fibers is reduced from the original 20%: 80%.

The longer the fibers in the pulp, the more serious the flocculation, reducing the long fiber ratio can effectively improve the uniformity of the paper sheet, and at the same time, it should be ensured that the long fiber ratio does not exceed 0.3% when surfing the Internet.

2. Breeding of long-fiber wood varieties:

The fibers of northern coniferous pine pulp are relatively fine, and spruce, fir, and hemlock can all produce better paper.

The fibers of southern pine coniferous wood pulp are thick and stiff, such as loblolly pine and Douglas fir, which have good tear resistance, but have a great influence on the uniformity of paper.

The wood pulp produced in Canada has a single tree species, long production period and good materials. Therefore, the selection of Canadian wood pulp varieties generally depends on the Canadian wood pulp varieties.

3. Set the deaerator:

The amount of degassing is very important to obtain good uniformity, and the residual air in the net seriously affects the dehydration uniformity and fiber distribution.

For slurry streaming, 0.1% of the air mass is equivalent to 25% of the total fiber volume.

The degassing device is located after the desander and before the pressure screen.

4. Adjust the mass fraction of the mesh slurry:

5. Adjust the landing point of the online slurry:

Change the position of the lower weir plate so that the lower weir plate protrudes from the upper lip plate by 15~20mm.

Therefore, the spray angle is reduced, the point of contact is located at the front edge of the forming plate, the severe dehydration of the breast roller is slowed down, the screen printing weight caused by the large spray angle and high forming pressure is avoided, the retention rate is low, and the slurry channel is easily formed. and other disadvantages.

6. To maintain the necessary vibration of the pulp:

①Increase the slurry level of the head box slurry, so that the pressure increases, the flow rate increases, and the turbulent motion is accelerated.

②Use a good vibrating mesh device.

③Adjust the finish roller.

The installation position of the decorative roller, after the first vacuum box or after the vacuum box, the free mesh surface under the decorative roller should be equal to the diameter of the decorative roller.

The free mesh surface is 1/3 at the front of the roller and 2/3 at the back of the roller. The depth of the pressing layer is adjusted from 4mm to 6mm, and the mass fraction of the slurry in the lower part of the roller of the decoration machine is 2~2.5%.