The hottest nipcoflex calendering technology impro

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Nipcoflex calendering technology improves the output and quality of packaging paperboard

the global production of box paperboard currently totals about 42million tons/year, with an annual growth rate of about 2%~2.5% in Europe and the United States, and the production in Asia currently totals about 1000. Customized products are more suitable for today's emerging new demand of 10000 tons/year, with an annual growth rate of 8%~10%. The production of carton board in China increased by about 20% last year, about 3.5 million tons/year

it can be seen from these growth rate data that the investment in new equipment in China will obviously rise, while the production demand in Europe is mainly met through equipment restructuring or equipment optimization

design concept of traditional box paperboard production equipment

in Europe, box paperboard is mainly produced by multi-layer long paper machine with Yankee dryer, as shown in Figure 1. Before coating, hard roller calendering technology is used to ensure accurate caliper control under low pressure. According to the requirements of smoothness and gloss of the final product, consider whether it is necessary to carry out soft calendering after double and multiple coating

in the past 15 years, no new paperboard production equipment has been installed in Europe. In addition to nipcoflex slide printing machine technology, it has successfully increased the output of paperboard by 10% - 15%

In the past 15 years, the production capacity of Asia has been significantly improved. The main difference between European and Asian carton board production equipment is calendering technology, as shown in Figure 2. In order to simplify the operation, the cardboard production equipment used in Asia does not use Yankee dryer, but usually pretreates the cardboard for boxes on a heated hard calender. All kinds of cardboard boxes need to be treated by soft roller calendering technology after coating

the difference between these design concepts in Europe and Asia will essentially be reflected in the quality of the final product. In Europe, machines with Yankee dryers are used. The smoothness per unit volume of cardboard produced by them is extremely high, which cannot be achieved by hard or soft roller calendering. In other words, the smoothness of Asian box paperboard is only equivalent to that of European paperboard with smaller loose thickness, because its smoothness is achieved through stronger calendering pressure and thicker coating, which will have a negative impact on the loose thickness of paperboard

yankee dryer

as shown in Figure 3, Yankee dryer is a steam preheated cast iron drum with a diameter of 7000mm, and its installation accounts for 60% of the total length of drying components. Cardboard with high surface humidity is embossed with Yankee dryer. Ideally, the humidity of the paperboard entering the printing machine should be between 63% and 67%, so that the web paper can adhere to the drum and complete the drying and flattening treatment at the same time. In addition, the steam pressure and operating speed must be adjusted so that the paperboard can leave the drum immediately before the doctor blade arrives and smoothly transfer to the next drying part

under the action of appropriate pressure and long residence time exerted by Yankee roller, the paperboard surface is softened, and at the same time, with the help of smooth roller surface, the paperboard is flattened under appropriate pressure

yankee dryer has many shortcomings, especially reflected in the production capacity:

1 Because the dryness degree in the production process is defined very accurately, the steam pressure of Yankee dryer must increase with the increase of operation speed, or choose to install a larger drum

the pre drying part of the nkee dryer must be heated unevenly to ensure that the available drying capacity is not completely used up. With the increase of production, a longer preheating process is needed to ensure that the back of the paperboard can also be fully dried. Another limitation is the need to correct the flatness, because the preheating part mainly dries the back of the paperboard, while the surface of the paperboard is dried through the Yankee dryer

3. When the production volume increases, the current drying volume on the Yankee dryer deviates from the ideal value, and the smoothness of the paperboard will be damaged, which can only be compensated by sacrificing the loose thickness of the paperboard in the future

these problems can be replaced by using a three-layer drying group, reinstalling the Yankee dryer, or using a larger drying group. According to the amount of output to be increased, three methods can be considered at the same time

however, each solution is both expensive and time-consuming. Of course, it cannot simplify the operation of carton equipment during high-speed transportation

to sum up, Yankee dryer can guarantee the quality of cartons, but there are deficiencies in the ease of operation and efficiency of the equipment, especially when the output increases

this is why Voith developed nipcoflex ± 1% calendering technology with an accuracy of 20% of the starting value of each range. By using slide printing technology, the basic limitations of Yankee dryer can be solved, while ensuring product quality

nipcoflex calendering unit

the design of nipcoflex calendering unit is based on the basic principles and basic elements of nipcoflex printing machine, and has been proved on more than 300 voith paper, paperboard and cotton paper printing machines in the past 20 years

by loading the printing press on the circumference of the hot backup roll, the residence time can be extended and the load of the production line can be reduced. The same as using Yankee dryer, it also uses humidity and temperature gradient to achieve the best value

a special advantage of nipcoflex calendering unit is that it will not be affected by the acceleration of operation speed, because the circumference of calendering roller can be adjusted to ensure the required residence time

Figure 4 shows the arrangement diagram of a typical nipcoflex calendering unit. Nipcoflex roller with soft surface and rigid sliding rolling are both located under the rolled cardboard, and above the cardboard is a heated flexitherm roller with metal surface

nipcoflex calendering unit is applicable to pre calendering or post calendering after coating. The operating parameters of its box paperboard are as follows

compared with Yankee dryer, nipcoflex calendering unit is installed at the end of drying components and used for pre calendering before coating production line. After a large number of experiments and the first installation on the BM3 paperboard machine of Storaenso baienfurt company, it is confirmed that nipcoflex calendering unit is superior to Yankee dryer in terms of product quality

from the comparative test in Figure 5, we can see the typical paperboard parameters that can be pre calendered on Yankee dryer and nipcoflex calender. For unprocessed and processed paperboard, the micro smoothness (PPS s S-10) of paperboard obtained by nipcoflex calender is no less than that obtained by Yankee dryer, and the loose thickness of paperboard increases by 4% even when the operating speed is increased by 40%

these advantages of nipcoflex calendering unit can meet the needs of greater production

the paperboard obtained by calendering with nipcoflex calender rather than soft calender and then coating is similar to the paperboard after pre calendering

Another advantage of nipcoflex calendering technology is consistent pressure distribution, which ensures more consistent gloss and micro smoothness. This also improves the printability (gravure or offset) of the cardboard on the whole, which is higher than that of the cardboard produced by the equipment with Yankee dryer

apply nipcoflex calendering unit to the new machine design concept

How can we make full use of nipcoflex calendering unit to pre calender paperboard, so as to improve the output of Yankee drying equipment

the potential of nipcoflex calendering unit is most obvious on the carton machine with Yankee dryer, which has double-layer pre drying and post drying units, and operates with maximum capacity. From the following examples, we can estimate the potential of output increase for each possible application. For ease of comparison, the entire length of the equipment is the same as that of the current drying components

option 1.1

this is the simplest option, that is, install nipcoflex calender at the end of the post drying part, and operate the Yankee dryer as an ordinary drying drum, as shown in Figure 6. As the top and bottom layers of paperboard are uniformly heated, the production capacity is increased

in addition to making some modifications to the steam and condensation system in the traditional design concept, there is no need to make other changes in the drying part

option 1.2

is different from option 1.1. In this option, we can remove the Yankee dryer and replace it with another double-layer drying unit. The effective drying space is increased and the corresponding drying capacity is increased. A greater advantage of this solution is that it also simplifies the process of paper conveying

option 2.1

another way to increase production capacity is to replace the double-layer drying unit with the three-layer drying unit, as shown in Figure 7. It maximizes the length of the plant and can expand the drying length by 50%. This concept can be applied to machines with operating speeds up to 800m/min

in order to effectively use the three-layer drying unit to improve production capacity, it is usually necessary to replace the Yankee drying drum with a larger one. Voith recently successfully implemented this method on aanekoski's Bm1 cardboard machine

in many cases, using nipcoflex calender is more convenient and affordable, which also avoids uneven heating of the pre drying part and improves the drying capacity of the equipment. This has also been affirmed in the BM3 machine of Storaenso baienfurt

however, the three-layer dryer is more difficult to operate than the traditional dryer, especially when the cardboard is broken, and it takes longer to install the dryer

option 2.2

in the three-layer drying part, the drying drum can be used to replace the Yankee dryer, which can significantly improve the drying capacity of the equipment

option 3

the capacity improvement potential of option 3 is mainly theoretically introduced, because the size of Yankee dryer is restricted by manufacturing capacity, and the product quality can not reach the ideal value in all cases

figure 8 summarizes the proportion of the special material capacity of ultra-high activity polyethylene composites that can be increased by options 1 and 2 at the running speed of 500m/min for the paperboard with a basic gram weight of 250gsm. It can be seen from the figure that the nipcoflex calender has the following potential for increasing production capacity:

-- the production capacity of the double-layer drying part using Yankee dryer increases to 0%

-- the production capacity of the double-layer drying part using Yankee roller and nipcoflex calender unit (option 1.1) increases to 5%

-- using nipcoflex calender unit, At the same time, replace with another double-layer drying part. At this time, 1 must be repaired in time. The capacity of Yankee dryer (option 1.2) is increased to 10%-15%

-- the capacity of three-layer drying part using Yankee dryer (option 3) is increased to 35%

-- the capacity of three-layer drying part using Yankee dryer and nipcoflex calender (option 2.1) is increased to 40%

-- nipcoflex calender is used, At the same time, another three-layer drying part is used to replace the Yankee dryer (option 2.2), and the capacity is increased to 60%-65%

using nipcoflex calender can not only significantly improve the drying capacity, but also improve the quality of products. Nipcoflex calender can improve the smoothness and loose thickness of paperboard when it is used for pre calendering. Plus

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