Polyvinyl alcohol (PVA) drying
Polyvinyl acetate is polymerized to form polyvinyl acetate, which can then be saponified to produce various forms of polyvinyl alcohol, including flocculent, flake, granular, and powdery types. These products have different levels of alcohol solubility, such as 99.9% and 88%. Polyvinyl alcohol solutions are known for their excellent film-forming and emulsifying properties. It is widely used in the production of synthetic fibers, plastics, adhesives, coatings, and new building materials, with applications spanning across the chemical industry, textiles, papermaking, tanning, and construction.
During the manufacturing process, the final polyvinyl alcohol precipitate obtained after saponification must undergo pressing and drying to become the final product. However, polyvinyl alcohol is highly viscous and gel-like, making it challenging to dry. The surface water evaporates much faster than the internal moisture can migrate to the surface, making moisture migration the limiting factor in the drying process. Additionally, the heat required for this material is relatively low, leading to a very slow drying rate. As a result, direct hot-air drying is often unsuitable for such materials.
Currently, most manufacturers use vacuum rake dryers for polyvinyl alcohol drying. However, these dryers only utilize the jacket as the heat transfer surface, and the material typically does not fill the entire cylinder. This results in only about 60% of the jacket area being effectively used, leading to large equipment sizes that occupy significant space and increase civil engineering costs. Moreover, the movement of materials in vacuum rake dryers often fails to maintain a strict first-in, first-out flow, creating dead zones and stagnant areas that may lead to overheating, degradation, and discoloration of the material over time.
Hollow blade dryers represent an advanced alternative to vacuum rake dryers. While vacuum rake dryers can handle a wide range of materials, hollow blade dryers are also capable of processing similar materials. The key improvements include: transitioning from batch to continuous operation, increasing the efficiency of heat transfer surfaces, reducing equipment size, ensuring full contact between the heat transfer surface and the material for more uniform heating, shortening processing time, and minimizing thermal degradation. The material flow path has been redesigned to allow a spiral motion at the micro level and piston-like flow at the macro level. Additionally, the equipment is easier to clean when switching between different materials.
Due to these advantages, Sanmenxia Pakide Drying Engineering Co., Ltd. was selected by a polyvinyl alcohol manufacturer in Shanxi Province to provide a large-scale hollow blade dryer for the drying process, demonstrating the company’s technical expertise and reliability in the field.
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