Why is the forming part of the paper machine not working well? Do you have such a question?
To pursue greater economic benefits and better product quality, it is important to understand the causes that affect the formation of paper machines forming part.
Now let’s learn some tips to improve the forming setup of the paper machine forming.
Common problems to be considered in improving web forming：
If the dewatering capacity of the forming fabric allows: reduce the concentration of the headbox;
If other aspects of page quality permit: Change the paper to shorter fibers (for coated base paper or double adhesive paper, use more hardwood; For ground wood pulp paper, reduce the freeness of ground wood pulp, or increase the amount of groundwood pulp); Increase beating if appropriate.
What can be done to improve the setting of the forming wire?
- Correctly set the distance between the front roller and the wiper blade so that there is no large water flow between them.
- Make sure all wiper blades and forming mesh are properly positioned so that no water passes through the wiper blades to form a stream of water.
- Confirm that all dewatering elements are aligned (the tip of the chopping board must be in correct contact with the forming wire; all chopping boards must have the same wear); all rollers rotate freely
- Check the homogenizer roller
How to improve the dehydration capacity of dewatering elements?
- Move the vacuum box toward the vacuum roller and add more dehydration components
- Add board or preferably wet absorb vacuum box
- Install a vacuum box with a low friction coefficient (this allows the forming wire to run more tightly on the breast roller, and allows the front part of the wire to fully exert its dehydration effect in addition to dehydration in the vacuum box)
- If the stability of the slurry on the forming net allows, the angle of the chopping board can be increased and the vacuum degree of the wet vacuum box can be increased
- Reduce initial dehydration to prevent mesh sticking
If a shaking device is used and the shaking speed does not meet the effective requirements:
a) Increase the shaking energy (the effectiveness of shaking is basically proportional to the square of the vibration order and the amplitude; the limitations of the mechanical structure of the forming part must be considered)
b) If the structure of the forming section is suitable for low-speed paper machines, you can use cross bars to extend the vibration further behind the wire and achieve good results.
What does it mean to paste the wire?
Pasted mesh means that there are patches of holes on the mesh surface that are blocked and cannot filter water. The paste surface has a great impact on the formation and dehydration of paper sheets and even normal papermaking. When the web is pasted, the paper material around the pasted web will be filtered and shaped first after the paper material is put on the web. The thickness of the pulp layer will become thinner, and the paper material at the pasted web will flow to the surroundings, and the pasted surface will become a thin pulp area or no area. The pulp area will eventually become a curtain or hole in the finished paper.
What are the common types of web paste?
The common types of paste mesh include star-shaped white dots that are widely distributed on the mesh surface, and each small white dot blocks 1 to 4 meshes. There are also strips with a length of about 20~30 mm and a width of about a few holes. At the back of the forming mesh joint, the star-shaped white dots are pasted into horizontal strips of a certain width and density.
- A mixture of fine fibers and non-fibrous qualities. If calcium carbonate is used as filler, the mixture of yellow viscous matter and fine fibers of calcium carbonate can cause the phenomenon of network paste. The temperature is high in summer. If you use rosin rubber with too high freeness, it is easy for the rubber to agglomerate and paste the network.
- Resin blocks. If wood pulp with a high resin content is used, the resin blocks will stick to the net.
- Asphalt blocks, white wax spots, plastic spots, oil stains, rubber blocks, paint spots, etc. mainly appear in paper machines that use waste paper pulp containing these impurities as raw materials.
There are three main types of substances that block meshes:
Wire blocking not only affects the quality of the paper, but also has a great impact on production. Often, the machine has to be shut down for processing.In the most serious cases, the material used to paste the wire cannot be processed cleanly at all, and it has to be replaced.
Processing methods when pasting the web:
- Treatment of smeared webs caused by non-resin obstacles
a) When web sticking occurs, the vacuum degree of the vacuum suction box should not be too high. It is best to be lower than normal. If lowering the total vacuum degree will cause the moisture content of the wet paper to be too high and affect normal papermaking, you can also lower the vacuum degree of the first and second vacuum boxes only. degree of vacuum;
b) Appropriate tensioning of the forming mesh is often effective in eliminating pits on the mesh, mesh smear at folds and mesh joints;
c) Strengthen net washing during the return journey of the forming net, especially the swing high-pressure cleaning water system must be normal and the pressure must reach 20~25kg/cm2;
d) When it is found that the net is stuck, the foam in the front box should be removed in time, because the foam often contains a high content of alcohol-benzene extract, and the foam will often cause the net to be stuck after the paper material is put online.
In addition, when the temperature is high in summer, measures such as appropriately reducing the degree of freeness of rosin rubber, reasonably controlling the dissolution and addition process of calcium carbonate, and preventing the formation of yellow sticky matter will help solve the problem of network paste.
- Netting caused by resin obstruction
a) Reasonably control the resin content of pulp, which is the most basic measure;
b) Reasonably control the pH value and use alum to control resin obstruction;
c) Strengthen cleaning work, and regularly wash pipes, beaters, pulp tanks and various pulp tanks to prevent too much resin from accumulating, which will fall off and mix into the paper stock, which will cause smear on the paper machine;
d) Use resin dispersants and fixatives to disperse and remove resin.
When the web is stuck, steam is generally used to clean it. Asphalt, rubber blocks, oil stains, and paint can be cleaned with organic solvents (such as gasoline or kerosene).
Under normal circumstances, do not use acid to treat the forming mesh, because the mesh wires will become sluggish after being corroded by acid, and it is easy to catch fibers, which will make the mesh more sticky.
