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How to avoid a large number of bubbles in the paper machine production process
Date: 2020-07-17 Views: 17 views

 In the process of papermaking, if there are bubbles, it will cause paper defects, such as holes, transparent points, color difference and other problems, affecting the dewatering performance of paper in the mesh part, affecting the normal operation and efficiency of equipment.

How do bubbles form

Air is found mainly in waterfalls and eddies and is often present in mud preparation systems.

The areas that generally cause falls are:

The outlet of the pipe to the slurry pond does not enter below the liquid level of the slurry pond

The potential difference between the weir plate or the flowmeter and its downstream equipment is too large or the downstream liquid level cannot be controlled;

The control valve is too high to fill the downstream pipe with slurry.

How to avoid a large number of bubbles in the paper machine production process

By degassing, foam causes can be completely eliminated, which is conducive to reducing paste and paste, and may eliminate the spray of flow tank.

And the paper layer after degassing is tight and smooth, which improves the heat conduction of the dryer.

In addition, the paper copied with air free paper has good tightness, uniformity, moisture strength and smoothness.

How to avoid a large number of bubbles in the paper machine production process

Degassing before paper making: Proper slurry transport facilitates separation of slurry from air and then discharge in proper place. For example, high air in a closed pipe system can be discharged from there through a continuous drain to a white pool. The most effective method of venting is to use an open surface, such as a high level box, slurry tank, or white water tank, which is particularly effective for low speed paper machines.

Generally, there is no need to add degelling device for low speed paper making machine and medium speed paper making machine of common varieties. It can meet the quality requirements of production varieties only through reasonable selection of equipment and correct configuration of piping to remove part of free gas mixed with slurry.

Degassing of white water: The degassing of white water in the white water runner and the white water trough is achieved through the following aspects:

(1) As the flow path into the mixing tank is long and has many elbows, the flow time of concentrated white water should be increased to try to make the bubbles in concentrated white water float on the surface of concentrated white water and reduce the bubble content in concentrated white water

(2) Add a spray device on the flow passage to make the bubbles on the liquid surface break quickly and the bubbles below the liquid surface rise to the surface;

(3) Add formatting devices in the flow path to increase the turbulence level of concentrated white water in the flow path and enhance the chances of small bubbles in concentrated white water floating on the surface of the white water

(4) Adding lattice structure to the top of the mixing tank can reduce the impact caused by the flowing of concentrated white water into the mixing tank and destroy the bubbles on the surface of white water

(5) With the mixing tank column body and the return line open, as long as the whitewater and overflow slurry have enough residence time in the column body, the gas mixed with whitewater and overflow slurry can be discharged well.

Coupled with the reasonable design of the pipe and the reasonable arrangement of the valve, can effectively prevent the air into the short flow system, avoid the pulp pump caused by the vaporization phenomenon, eliminate the foam on the uniformity and appearance of the paper.

For high - speed paper machine white water, sometimes also using mechanical degassed, degassed white water and degassed pulp mixed.

Degassing of paper after mixing of white water and pulp: Generally speaking, degassing of paper is done after mixing of white water and pulp. Although the white water runner and the white water tank are used to remove part of the free air, the air content in the pulp still cannot meet the requirements of production and quality.0.03?~?The air content of 0.2% has great influence on the dewatering and paper forming characteristics of mesh.

In the medium high speed machine, white water and slurry in the open liquid level retention time has not reached the time of bubble rise and rupture, so in order to further remove the slurry air, medium high speed machine usually also need to be set in a slurry pump after the installation of bubble removal system.

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