The matching with Yankee dryer is called gas hood, which can be divided into steam hood and gas hood according to the classification of gas. The steam hood uses fresh steam and recovered secondary steam, and the gas hood uses natural gas as heat source. Generally, under the total dehydration capacity of Yankee dryer and gas hood, Yankee dryer can contribute 50~60%, and gas hood can contribute 40~50%.
Yankee dryer is called the heart of household paper machine, not only because of its large size and high value, but also because of the following reasons:
Carry for providing heat source for dry paper web
It provides support for the transmission of paper web in the drying process.
As a roller, it cooperates with the vacuum roller to provide the hot rolling function.
Provides a carrier for paper web wrinkling.
The specific reason why Yankee dryer is called Yankee dryer is not clear. Some people say that it is to commemorate the name Yankee, but this statement has no solid factual basis.
In the past 200 years, casting dryer has been the absolute mainstream of dryer. Years of practical experience show that casting can effectively improve the properties of materials, such as strength and thermal conductivity. At the same time, in the development process of casting Yankee dryer, the thermal conductivity can be effectively improved by changing the internal structure of Yankee dryer, such as replacing the smooth internal structure with grooves and baffles.
Since about 2000, the steel Yankee dryer has appeared on the market as a concept product. The upgrading of manufacturing method and the improvement of welding technology make it possible for steel Yankee dryer.
As the pioneer of steel Yankee dryer, Italy Toscotec Company has made outstanding contributions to the marketization of steel Yankee dryer with its 40 years of production experience. Headquartered in Lucca, Italy, Toscotec has positioned the development direction of Yankee dryers as steel Yankee dryers since 1960, and started producing steel Yankee dryers from 1999. Since 2000, the company has delivered a steel Yankee dryer with a diameter of 2.5 meters (8 feet) and put it into use. On 20 13, the company began to design the second generation steel Yankee dryer, with a diameter of 22 feet and a width of 5.6 meters. The speed of the paper machine supporting the Yankee dryer is 2000 meters per minute. This Yankee dryer is by far the largest steel Yankee dryer and the fastest steel Yankee dryer with steam as the only heat source.
The steel Yankee dryer has the following advantages:
Safety: For paper mills, safety is the primary factor. Due to the defects of raw materials, the casting Yankee dryer is in danger of explosion. In the production process, if the internal pressure of the billet dryer is too high, the pressure of the vacuum roller is too high, or some safety accidents may lead to the explosion of the billet dryer. The main reason for the explosion of the casting Yankee dryer is that the internal pressure exceeds the limit it can bear. Because steel is a kind of material with higher strength than cast iron, and has a certain ductility, its pressure resistance is higher than that of cast iron, so the pressure resistance of steel Yankee dryer is higher than that of cast Yankee dryer.
At the same time, it also means that under the same pressure, the wall of the steel Yankee dryer can be thinner. This also means that the thermal conductivity of steel Yankee dryer is better than that of cast Yankee dryer. The wall thickness of steel Yankee dryer can be reduced by about 30% compared with that of cast Yankee dryer.
Higher thermal conductivity and lower energy consumption: When the wall thickness of steel Yankee dryer is reduced by 30%, considering the thermal conductivity of cast iron and steel and the drying mode of paper web as Yankee dryer and hood, the actual production experience shows that the steel Yankee dryer can increase the production capacity by about 65,438+05% under the same other parameters. Another advantage of reducing the wall thickness is that the Yankee dryer can use steam with lower pressure to achieve the same drying efficiency.
Of course, increasing the steam consumption in Yankee dryer can reduce the output of gas hood, thus reducing the power consumption of gas hood system. In the case of producing the same paper, the total energy consumption of the paper machine will inevitably decrease, and the degree of reduction depends on the heat source used by the gas hood. According to the production experience, the steel Yankee dryer can reduce the total energy consumption by up to 20%. In addition, the investment cost of steel Yankee dryer is lower than that of casting Yankee dryer, because the weight of steel Yankee dryer is about 25-30% lighter than that of casting Yankee dryer.
Advantages of surface spraying of steel Yankee dryer: Compared with corrugated scraper, the surface of steel Yankee dryer has lower hardness, so the surface of steel Yankee dryer needs to be sprayed with a layer of metal compound, which can also effectively prevent the corrosion of steel Yankee dryer. Spray coating can effectively reduce the frequency of Yankee dryer grinding, and spray coating can better control the thickness of wrinkles, and the obtained paper wrinkles are more balanced and stable.
Compared with the casting Yankee dryer, the steel Yankee dryer has the advantages of safety, energy saving and stable production. The maintenance of steel Yankee dryer is more cost-effective than that of cast Yankee dryer during its life cycle.
In the global scope, Tosoctec is the company with the most patents on steel Yankee dryers and the company that provides the most steel Yankee dryers. Besides Toscotec, steel suppliers in Yankee dryers include Voith, Weimeide, Andritz, PMP, Recard, Acelli, Hergern and many other companies.