High-Tech Separating Solution for Overspray in Car Paint Coating
E-Scrub Revolutionizes Automobile Painting
At the beginning of the 1990’s, most of our roads were populated by clear and striking colors. This was then followed by silver-grey and black. The most recent trend color has been white, standing for purity and honesty. The latest trend is brown and matt paint. Colors are expected to become brighter in the course of the next few years, according to trend researchers, and the 1970’s retro look might put in reappearance.
Irrespective of the color which is used, all cars have to be painted. And in general, this is carried out in car coating lines of one of the two leading manufacturers of paintwork installations in the world. Eisenmann with headquarters in Böblingen and Holzgerlingen as well as branches around the globe is one of the two leading manufacturers. With E-Scrub, the leading international system provider has now developed a separating process which is revolutionizing the application of car paintwork.
Electrostatic instead of a wall of water
In traditional solutions, cars have been painted by spraying the “overspray” – the paint which is sprayed past the bodywork – and is deposited against a wall of water. This water is subjected to chemical coagulation and disbanding and is treated with filters or decanters in a recycling arrangement. The high energy input is a major handicap of this method. Depending on the paint application process and the form of the vehicle, the overspray accounts for approximately 25 to 35 percent of all the paint. This is a considerable quantity.
With E-Scrub, Eisenmann AG has developed an electrostatic separation system for wet paint application systems as a highly efficient alternative to traditional separation principles. In this way, it is possible to reduce CO2 emissions by lowering the energy requirement. Water consumption also declines by up to 86 percent, and chemical consumption is reduced by approximately 75 percent. However, the main savings are achieved in terms of energy consumption, which is reduced by up to 75 percent. Particulate emissions can also be reduced by a factor of 35.
The process: the electrostatic dry overspray separating system is located below a grid in the spray booth. The separating modules consist of high voltage wires and separating plates, which are coated with a thin film of separating agent. The high voltage wires ionize the air molecules in the surroundings. The paint particles take on this charge as they pass by, and are then attracted by the earthed separating plate. This is where the paint particles are bound and disbonded by the separating agent. The separating agent together with the overspray then flows into a buffer tank.
Centrifugal separation solution for the valuable separating liquid
And this is precisely the point at which the technology of GEA is used. This is because a process of separating the valuable and this separating liquid from the paint particles requires a high tech separating solution. Eisenmann therefore approached GEA and agreed a long-term co-operation for developing the process. Firstly, GEA designed a specially modified decanter with a capacity of one cubic meter per hour for the laboratory-scale and demonstration installation of Eisenmann in Böblingen. Eisenmann was extremely satisfied with the process engineering implementation, the high separating efficiency which was achieved and also the reliable operation
After the installation had been successfully commissioned, the manufacturer received its first major order for using the E-Scrub at a well-known German car maker, in which two decanters were integrated. These decanters reliably ensure that the separating agent remains at a stable level, is recycled and can be sprayed onto the separating plates – for the next car. The dry overspray which is discharged as a solid from the decanter can be disposed of properly. Accordingly, the combination of E-Scrub and the decanters means that, in future, vehicles can be painted in a much more energy-efficient manner and thus in a much more environmentally friendly manner, and at the same time more efficiently – with the brightest colors.
