Wet End Of Paper Machine
In paper making process, usually there is interferent in the paper machine wet end to influence the paper making, cause paper defects, reduce paper strength, so where is the interferent from and how to deal with it?
Paper Machine Wet End Interferent Type
1. Interferent in the pulping and bleaching process: Sulfate pulping and bleaching processes will decompose lignin and polysaccharides into low molecular weight fragments and dissolve in the slurry, fatty acids and rosin acids are also present in the unthoroughly washed slurry. These substances will produce precipitation, while the impact on the additive is small.
The high molecular weight anionic wood component can be dissolved in the pulping and bleaching of the sulphate pulp and ground wood pulp, which forms a complex mixing system with the cationic additive, adsorbs on the fiber surface and interferes with the effect of the additive.
This situation is particularly severe in the preparation of mechanical pulp: When hemicellulose, lignin, protein, pectin and other substances are present in white water, a significant increase of cationic additives is caused.
2. The material released during the process of defibrination and drainer stock: During the process of defibrination and drainer stock, the dissolution of hemicellulose, lignin, protein, pectin and other substances in the wood in the unbleached pulp is much more than the bleached pulp. In the bleached sulphate pulp suspension, the dissolution is in the range of about 1%~3%.
3. Production water, additives, broken paper and recycled fiber: In addition to the substances mentioned above, there are hydrophobic resins, surface sizing starch, coated compounds, damaged paper and special materials contained in recycled fibers such as thermoplastic rubber particles, plastic particles, printing inks, also will cause precipitation, it is possible that brought in the new filler suspension.
Paper Machine Wet End Interferent Solution
1. When the interferent substance reaches a certain concentration, it is usually neutralized with a charge neutralizing agent. In addition, in paper making process should also strengthen the pulp washing, but also regularly discharged the cycling water, which is running for a period of time.
2. The most important thing to deal with interfering substances is to keep the system clean. For the problem of reuse water, it is not that the more, the better. When the cycles number has led to the accumulation of anionic waste and other ions, the water should be sent to the processing system to process and replenish the new water.