A worthy headbox of dual-pressure zone thickener

 The double-pressure zone thickener is mainly used for the washing and concentration of the slurry in the waste paper deinking and reducing treatment system. The machine is mainly composed of active rollers, driven rollers, and endlessly woven filters and flow boxes running around two rollers. , Discharge screw conveyor and other components. The slurry passes through the headbox, which is dewatered by the squeezing action between the filter screen and the active roller in the nip between the filter screen and the active roller. The active roller is engraved with deep grooves, which can obtain a high nip pressure, so that the slurry is concentrated on the inner surface of the mesh into a form of slurry strips. These strips are kept on the filter screen. When the slurry enters the filter In the nip between the net and the movable roller, it will be further dehydrated and then separated from the net surface, falling onto the roller surface and being scraped off and discharged by the scraper. The concentration of the slurry discharged by the machine is constant, and the discharged slurry will be transported away by a screw conveyor, and the removed white water containing ink particles and fillers will be discharged from the bottom of the white water tray.

The double-nip thickener is favored by users because of its good performance, but with the continuous expansion of the wide screen of the filter screen, major problems have become more and more serious; one is the thickness of the slurry layer on the entire web is inconsistent, and the slurry concentration is uneven; the other is The filter is easy to run off, causing the filter to tear. But this will bring great economic losses to the enterprise.

For the problems of the double-pressure thickener, the reasons are as follows:

1. At first, I suspected that the quality of the filter was not good enough; after consulting with the manufacturer of the filter, it was required to strictly follow the technical requirements of the filter. After many experiments, it was proved that the tearing of the filter was not caused by the quality of the filter itself.

2. The sensitivity of the deviation adjustment mechanism is not enough, and the deviation signal cannot be transmitted in time, which will cause the movement of the deviation adjustment motor to lag. By replacing several sets of new control modules, the test is carried out quickly, the deviation adjustment signal is transmitted in time, and the deviation adjustment mechanism moves quickly. The tearing of the filter has little to do with this item.

3. If the machining error of the worm and connecting rod of the two worm gear boxes is too large, the transmission will not be in place and the deviation can not be corrected. Through machining a higher precision worm and connecting rod, the phenomenon of deviation of the filter screen will also occur.

4. If the coaxiality of the two transmission rollers processing fails to meet the requirements or the installation axes of the two rollers are not parallel, vibration will occur, which will cause the filter screen to jump and cause deviation. Re-adjusting the installation accuracy of the two rollers, the effect is still not satisfactory.

It may also be the problem of the headbox. The function of the headbox (1) is that the slurry that is sprayed is evenly distributed along the horizontal direction of the active roller; it effectively disperses the fibers and improves the uniformity of the slurry layer; the spraying is stable. If the pulp output from the headbox is not uniform, the pulp concentration will be uneven, and the filter screen will run off and cause tearing. Therefore, improving the design of the headbox structure is a key issue to solve the problem of the dual-pressure thickener.

After the improvement of the headbox, there are mainly several aspects:

1. In order to ensure that the pressure of the slurry flowing through each section along the way is the same, the sizing main pipe is designed into a square cone pipe with a smaller and smaller cross-sectional area.

2. In order to facilitate the hole arrangement and keep the direction of the slurry flow at the end of the main pipe unchanged, a rectangular tapered pipe of equal width will be used, and the "height ratio" at the entrance is 1:2~3.

3. The main pipe should facilitate the incoming slurry to change the direction of slurry flow. A transition pipe is set between the main pipe and the slurry inlet pipe, and the circular slurry inlet pipe is gradually changed into a rectangular main pipe. The final wall of the slurry inlet pipe and the square cone pipe should be on a horizontal line.

4. Equipped with a return pipe. The function of setting backflow is mainly to ensure the stability of the slurry flow pressure in the branch pipe and the uniform distribution of the slurry. At the same time, there is no dead corner at the end of the cone pipe to prevent the slurry clusters from gathering, expel air bubbles, and play a cleaning role.

5. The main pipe is made of stainless steel, and the inner wall is processed smoothly, without grout or rust. In order to ensure that the main pipe is not deformed, reinforcing ribs are arranged on both sides of the outer wall of the main pipe to make the main pipe have sufficient rigidity.

6. Ensure that the center of gravity of the headbox is on a straight line, which is more conducive to the stability of the headbox.

After the improved design of the headbox, the thickness of the slurry layer on the entire web is uniform, the slurry concentration is basically stable, the service life of the filter is greatly improved, the maintenance cycle of the equipment is reduced, the cost is correspondingly reduced, and the production efficiency of the enterprise is improved.

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