Matters needing attention in the production of special paper by paper machine

- Nov 09, 2020-

With the successful development of the domestic inclined wire paper machine, the quality of special paper is improved and the variety is developed. The domestic oblique wire former has gradually developed from the initial single-layer forming to three-layer simultaneous forming (and has all intellectual property rights) and oblique round net compound forming. Especially the successful development and application of multi-layer inclined wire forming provides conditions for the development of many products. Paper machines are gradually becoming one of the main models for specialty paper production.
The working principle of the domestic multi-layer oblique net former: the multi-layer oblique net former is layered and sizing in the square tapered tube spreader, and the unique rectification and layering technology is adopted to realize the layered forming of the fiber in the forming area. Two-layer or three-layer sizing.
During the production of inclined wire mesh, on-site adjustments should be made to the production quality and process parameters of normal operation.
Internet concentration
The online concentration must first ensure the quality of the copy, especially long fibers. Under the premise of quantitative determination, the online concentration is the main parameter that determines the amount of online slurry. The adjustment when the online concentration is low will cause a large change in the sizing amount. For example, if the slurry concentration is adjusted from 0.03% to 0.02%, the sizing amount will increase by 50%. .
Pulp-to-net speed difference ratio
The difference in web speed is an important factor that affects the forming quality and the anisotropy of the paper performance (fiber direction arrangement). It is a process parameter that often needs to be adjusted in the operation of the inclined wire. Generally, the fixed wire speed is controlled by the adjustment of the pulp speed. Note the following:
(1) The pulp speed is not allowed to be higher than the network speed. Fourdrinier wire forming allows pulp-to-net speed ratio>1, but not in inclined wire forming. It will cause the initially formed pulp layer deposited on the net to be washed and destroyed by the pulp flow, forming a wave-shaped pulp block on the wet paper sheet. Practice confirmed.
(2) The pulp-to-net speed ratio should be adjusted according to the aspect ratio required by the finished paper, and the corresponding law of MD/CD and pulp-to-net speed ratio should be established through feedback and summary of quality data.
(3) Production practice has proved that on the premise that the forming quality meets the requirements, a larger pulp-to-net speed difference can be used to extend the dewatering time.
Dehydration pressure difference
The dewatering pressure difference is a dynamic parameter to ensure the dewatering of the inclined net. It is to complete the whole process of stable and uniform dewatering under a constant dewatering pressure difference to ensure the good bulk and air permeability of the paper. The dehydration pressure difference is mainly determined by the dehydration resistance. Through the vacuum degree adjustment of the dehydration box, it is recommended to choose a low vacuum degree as much as possible under the premise of ensuring the dehydration capacity to reduce the wear of the forming screen and the power consumption of the screen drive roller.
Dehydration control and dehydration curve
The speed of dehydration directly affects the forming of the inclined wire. If the dehydration is too fast, it is easy to cause excessive loss of fine fibers in the initial deposition layer of the slurry, which will aggravate the two-sided difference and the possibility of pinholes; while the dehydration is too slow, delaying the forming process-waterline position After moving, the dehydration speed depends on the selection and distribution of the dehydration volume of each partition of the dehydration box.

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