Keeping pollutants out of the can

A wide range of products that we use in everyday life, whether deodorant, soft drinks, spray paint, or even oven cleaner, come in metal tins. But how many of us ever give a thought to how these packaging are manufactured? Mechanical engineering companies like Mall + Herlan play a big part in making sure that hygiene and cleaning products are safely packaged before they make their way into our homes. And how is clean air ensured during the manufacturing process? With environmental technology from Dürr.

As part of the manufacturing process, there is also a risk of the condensation of critical pollutants, giving rise to solids that can severely clog pipes and the air pollution control system. Dürr started by analyzing and separating the numerous sources in an air recording model. On average, the exhaust air temperature is 80 to 90 degrees Celsius. When the various exhaust air sources are mixed, the very hot air from the ovens is cooled down significantly. During this process, so-called “high boilers” in the air (i.e. organic compounds like resin with high boiling temperatures) condense. This can lead to critical deposits in the pipes and clogging of the ceramic heat exchanger bodies in the long run. “To purify the exhaust air effectively and, above all, economically, we recommended powerful regenerative thermal oxidation (RTO) with a thermal efficiency of up to 97 percent and purification rates approaching 100 percent,” explains Dietmar Decker, Senior Sales Manager Surface Treatment in Dürr’s Environmental Technology division. “With an oxidation temperature of up to 850 degrees Celsius, this process even eliminates odor emissions.”

For the implementation of the optimum air pollution control system, Dürr was able to draw on its extensive product portfolio with eight different RTO designs. “The reason we picked the Oxi.X RA system type with over 100 references in this special industry segment was the fully ceramic internal structure and the special bake-out process,” adds Dietmar Decker.

The Oxi.X RA RTO from Mall + Herlan is rated for a maximum treatment capacity of 11,000 m³/h and pollution loads of 1 to 2 g/m3. In normal operation, which is equivalent to the range from 1.3 to 1.6 g/m3, the highly efficient heat exchanger reduces the operating costs to the absolute minimum through largely autothermal operation. What does this mean? The burner can be switched off completely, and no additional primary energy is needed to operate the air pollution control system. This is possible because the heat exchanger simultaneously acts as a heat accumulator by storing the excess energy in phases with high solvent concentrations. In subsequent phases with low pollutant concentrations, the excessive temperature level – i.e. the stored excess energy – is slowly lowered again and made available. This also saves natural gas. Dürr is increasingly employing this special principle of “thermal buffering” with fluctuating solvent concentrations to “smooth” the resulting fluctuating energy entries, making it an extremely interesting alternative to upstream concentration smoothers. This is a major plus because these adsorptive smoothers are not only extremely expensive, but also cannot be used in applications in which the exhaust gas temperatures are on the higher side and there is a risk of contamination.