The increase in the speed of the paper machine means that the paper web must be dried quickly in the dryer section, which imposes higher requirements on the dryer section of the paper machine.
Compared with the dryer section of the old paper machine, the dryer section of modern high-speed paper machines has made many improvements both in technology and equipment.
No matter what improvements are made, the drying part generally must meet the following performance requirements:
After the wet paper leaves the press section, it is stably adsorbed to the dryer net. Through the combination of the paper web stabilizer and the vacuum roller in the whole dryer section, the transfer of the paper web is completed safely and reliably, which greatly reduces the loss of the paper web in the dryer section. End breaks caused by instability, fluttering, and running of the fold, thereby improving the running performance of the paper machine.
High evaporation rate
Due to the equipment characteristics of the drying section, the wet paper sheet can effectively obtain heat from the surface of the dryer, and remove or emit the water vapor evaporated from the paper sheet. In this process, the energy source is well controlled.
Control paper shrinkage
In the initial drying stage of the paper web, due to the increase in the temperature of the paper web, the strength of the wet paper sheet decreases, and the elongation of the paper web increases. When the paper web is stretched, its longitudinal direction will be stretched and the transverse direction will shrink.
However, modern high-speed paper machines reduce the force required when the paper web is peeled from the surface of the dryer through the paper web stabilizer, thereby reducing the longitudinal elongation and lateral contraction of the paper web.
Because the dryer group is short, the elongation of the paper web in the wet end can be compensated by adjusting the speed difference, thus preventing the paper from running out of folding.
The paper web is tightly attached to the dryer net in the entire dryer section, which also prevents the paper sheet from shrinking and deformation, but the paper web stress generated in this way will cause the paper web to tear, cause breakage, and affect the normal production of the paper machine .
The solution is to ease the shrinkage of the paper web by adjusting the speed difference between the dryer groups.
Prevent paper curl
Single-sided drying paper webs are easy to curl, which is caused by uneven moisture distribution between the front and back sides of the paper web in the dryer section, and the paper web curls toward the side that is finally dried.
This problem can be controlled by adjusting the humidity distribution on both sides of the paper web, which can be treated either in the front drying process or in the later process.
Of course, if you want to increase the speed, it is obviously not enough to improve the dryer section.
As a system, the paper machine must be reasonably optimized in all aspects in order to exert the best performance of the paper machine.
Post time: Sep-23-2020