Views: 2 Author: Site Editor Publish Time: 2021-11-11 Origin: Site
The basic composition of the dryer section of a paper machine. Today with the highly developed science and technology, the final drying of general paper and paperboard is still done by heating and drying with dryers. This is because dryer drying has an ironing effect in addition to the above-mentioned effects. Improve the quality of finished paper. Although in recent years new technologies have been developed such as hot air impingement drying, through-drying, rib drying cylinders, grooved drying cylinders, spoiler bars, infrared adjustment of banner moisture, vacuum contact drying, press drying, and superheated steam drying. The new technology is used as an auxiliary measure to strengthen or improve the drying efficiency of the dryer.
The drying section of paper machine drying cylinder is mainly composed of drying cylinder, blanket cylinder, cold cylinder, blanket guide roller, scraper, paper guiding rope, canvas corrector and tensioner, steam hood or hot air hood, frame and transmission device, etc. . For the production of tissue paper, the drying section of a low-speed paper machine can be composed of one or two drying cylinders. The single drying cylinder is a large drying cylinder with a diameter of 3m or more. In double-cylinder drying, the first drying cylinder is equipped with a hot air hood. With supporting rollers, no canvas, the second drying cylinder uses pressure rollers and sail blankets to promote the other side of the paper sheet to adhere to the cylinder surface to improve smoothness. Multi-dryer dryer sections are used in paper machines that produce general paper and cardboard. Traditionally, the arrangement of the dryers is in a double-row arrangement, as shown in Figure 6-1. The upper and lower drying cylinders are equipped with sail blankets (or dry nets), and the sail blankets lead the paper web to run around the drying cylinder and press the paper web against the surface of the drying cylinder.
According to the shrinkage of different paper types during the drying process, the drying cylinder of the drying section can be divided into 2-4 groups for general paper types, and the number of sail blankets is matched accordingly. Each group of dryers has one upper and lower sail blanket. Each sail blanket is provided with a corresponding guide blanket roller, a correction roller and a tension roller. In order to reduce the moisture content in the sail blanket, a blanket dryer is provided. On medium and low-speed paper machine, each sail blanket is usually equipped with one dryer blanket; on high-speed paper machines, each sail blanket is equipped with two blankets, one of which is installed so that the blanket can be dried after bypassing half of the drying cylinders in this group.
In the past ten years, dry nets with good air permeability have been used to replace sail blankets in paper machine dryers that produce newsprint, offset book paper, paper bag paper and cardboard. The use of dry net can not only improve the drying efficiency, but also does not use the dry net dryer, which can save steam consumption.
There are usually 1-2 cold cylinders at the end of the drying device. Flowing cooling water is passed into the cold cylinder to cool the paper web before entering the calender, condense water vapor on the surface of the paper web, increase the water content and plasticity, and improve the calendering effect. Between the last drying cylinder and the calender in the drying section, a spring roll is generally installed (the bearing shell is surrounded by a spring supported roll). It can adapt to the change of the paper web tension and produce corresponding displacement to reduce the tension fluctuation of the paper web and reduce the breakage of the paper web.
In recent years, the paper machine's speed has reached as high as 1800m/min. For these high-speed paper machines, if the traditional double-layer dryer arrangement and upper and lower sail blankets are used, the paper sheet will vibrate in the dryer section and cause paper breaks. Affecting the normal papermaking of the paper machine, in order to solve this problem, a single-layer dryer with a vacuum roller arrangement and a single-sail blanket configuration of the dryer section has been developed to solve this problem.