In the process of producing corrugated cardboard, temperature has a great influence on the quality of corrugated cardboard. By controlling the temperature, both the moisture content of the corrugated base paper can be adjusted, and the curing time of the paste can be controlled, so as to achieve the purpose of controlling the adhesion speed and firmness of the corrugated paper. Therefore, temperature control is a very important part in the production process of corrugated paper, so sloppy.
In order to effectively control the temperature, heaters and drying boards are installed in many places on the Corrugated Cardboard Production Line. Under normal circumstances, the curing temperature of the corrugated paper production line with a speed above 100m / min should be 160 ℃ ～ 180 ℃. If the steam heating method is adopted, the pressure of the saturated water vapor of the boiler should reach 0.9MPa-1.4MPa. The corrugated paper production line has a greater impact on the moisture content of corrugated board equipment is mainly single-sided unit and drying unit. According to different situations, these parts should be adjusted at any time to facilitate the smooth production.
1. Temperature control of single-sided unit
According to the analysis of the tension in the corrugated cardboard forming process, when corrugated, the moisture content of the base paper entering the single-sided machine is preferably 9% to 12%. According to this principle, it is necessary to make full use of the preheating roller on the single-sided machine and the preheating machine and spray device before and after the single-sided machine to adjust the moisture content of the base paper.
If the moisture content of the base paper is too high, after the temperature of the preheating roller reaches the requirements, the movable paper guide roller of the preheating roller can be appropriately adjusted to increase the preheating angle of the base paper and the preheating area, so that it can be to a certain extent. It plays a role in reducing the moisture content of the base paper. If the preheating area of the preheating roller is adjusted to the maximum and the moisture content of the base paper is still too high, it should be solved by reducing the vehicle speed.
When the moisture content of the base paper is too high, the temperature of the preheating roller adjusted in advance may be lowered, and the preheating requirement may not be reached. At this time, the steam supply pressure of the boiler should be properly increased under the conditions permitting, so as to achieve the purpose of increasing the temperature of the preheating roller.
If the moisture content of the base paper is too low, the movable paper guide roller should be adjusted accordingly to reduce the preheating area. At the same time, the preheating roller and the spray device on the single-sided machine are used to spray the base paper to increase the moisture content of the base paper and make it meet the standard requirements. In addition, properly increasing the speed of the vehicle to reduce the contact time between the base paper and the preheating roller in disguise can also solve the problem of low water content to a certain extent.
The moisture content and temperature of the base paper should be measured at any time with a moisture meter, thermometer or pressure gauge, and adjusted according to the measurement results. Some materials mention some "soil" methods, such as observing the single-sided corrugated cardboard on the flyover Conveyor Belt. If the shape is positive ∞, it can be considered that the moisture of the base paper is adjusted better and the moisture content is more appropriate; When the thermometer is used, spit saliva on the preheater. If the saliva can bounce on the preheater, it means that the temperature has exceeded 150 ° C and can be produced. However, for the purpose of scientifically managing production and ensuring product quality, these local methods are appropriate. As a formal enterprise, we should still reduce the influence of human factors, follow scientific and accurate data, and manage production.
2. Temperature control of the dryer
The temperature of the dryer directly affects the moisture content of the final corrugated board. The heating plates of the dryer are generally three groups, each group is composed of four, five and six heating plates. Each group of heating plates of a steam-heated dryer is equipped with a pressure regulating valve, which is used to adjust the pressure of steam entering the heating plate, thereby changing the temperature of the heating plate and ensuring the production of high-quality corrugated cardboard. Among them, need to pay attention to the following details.
Before entering the dryer, the moisture content of the single-sided corrugated cardboard stored on the flyover is different, so the moisture content will change. In addition, after using the paste on the single-sided machine for a period of time, the moisture content will also change, which in turn will cause the moisture content of the single-sided corrugated cardboard to change. Therefore, before final compounding, the single-sided corrugated cardboard needs to be preheated a second time. This preheating process also needs to be properly adjusted according to the moisture content, that is, by adjusting the movable paper guide roller to change the preheating area, the purpose of adjusting the moisture content of corrugated cardboard is achieved.
The purpose of drying is to ensure the solidification of the paste and adjust the moisture content of the corrugated cardboard at the same time. Therefore, the pressure reducing valve should be adjusted at any time according to the moisture content of the single-sided corrugated cardboard, so that the dryer reaches the appropriate temperature, not only to ensure the curing of the paste, but also to ensure that the final molded corrugated cardboard has a moderate moisture content. In addition, the length of the dryer cooling section also has a certain effect on the moisture content of the cardboard. When the cooling section is too short, the moisture cannot be volatilized in time. At this time, the local air supply needs to be increased to achieve the purpose of drying.
If the conventional temperature adjustment can not reach the ideal situation, you can try to use the method of changing the speed to adjust. That is, when the water content is too high, the vehicle speed is slowed, and when the water content is too low, the vehicle speed is increased.
When the dryer is working, it can't be stopped unless it is a last resort. If the front single-sided machine needs to replace the paper roll, the speed of the sports car can be faster before the roll is changed, and a part of the single-sided cardboard is accumulated on the flyover. After receiving the paper change notification, the dryer can run at a reduced speed. If the dryer is shut down, the moisture of the cardboard on the dryer will be completely evaporated, causing all the cardboard to be scrapped.
3. The influence of the hydrophobic device on the temperature
In addition to the pressure of the steam supplied by the boiler, the drainage device of the steam piping system is also very important for the temperature of the corrugated board production line. This is because the base paper and single-sided paperboard will take away a lot of heat when passing through the preheaters, thereby condensing part of the saturated steam into liquid water. This part of the condensate must be discharged in time, otherwise it will affect the heating effect of the preheater.
In daily work, if the preheating roller using the rotary head is low or the temperature difference between the two ends is more than 5 ° C, it means that the suction pipe is damaged or the installation position is wrong, and it must be disassembled for maintenance. In general, the flow index of the trap should be 2 to 3 times that of the condensate. If the amount of trap is not enough, the trap should be replaced. In addition, in daily operation and production, you should develop good habits, check the drain outlet of the trap every week, and find that the blockage should be cleaned in time.
During the start-up of the corrugated paper production line, the above parts should be inspected and adjusted at any time. Only in this way can we guarantee the production of qualified products.
