Bietigheim-Bissingen, April 26, 2022 – In order to meet the challenge of air pollution control for an innovative manufacturing process for aerosol cans, the mechanical engineering company Mall + Herlan commissioned the specialist Dürr to build an RTO system type Oxi.X RA. This cleans the exhaust air efficiently and economically and prevents permanent deposits thanks to Dürr’s special baking process.
Manufacturers of metal packaging for personal care, household, food and pharmaceutical products around the world use systems from Mall + Herlan. The German engineering company, one of the international technology leaders in this segment, is now taking a familiar step. In order to demonstrate the benefits of a new and innovative manufacturing process to its customers, Mall + Herlan, together with its sister company xtracan, suddenly decided to switch to manufacturing metal packaging itself.
VOCs escape down the line
The air pollution challenges for the innovative manufacturing process of one-piece steel aerosol cans are significant: Polluted exhaust air is emitted from nearly 30 sources at widely varying temperatures. In a three-step process, the spray cans are painted or printed from the inside and the outside. Unlike paper or plastic packaging, metal does not provide an absorbent substrate. Paint colors therefore contain up to 70% solvent. During the baking and drying process at temperatures up to 300 degrees Celsius, volatile organic compounds (VOCs) contained in paints and varnishes are released. In addition to the three furnaces, the three coating stations, the storage tower and various transport routes are significant emission sources in the manufacture of aerosol cans.
Stoving for reliable removal of deposits (self-cleaning)
As part of the manufacturing process, there is also a risk of condensation of critical pollutants, giving rise to solids that can severely clog pipes and the air pollution control system. To clean the exhaust air efficiently and above all economically, a powerful regenerative thermal oxidation (RTO) with thermal efficiency of up to 97% and purification rates close to 100% is used. With an oxidation temperature of up to 850 degrees Celsius, this process even eliminates odor emissions. The Oxi.X The RA system type, with over 100 references in this industry segment, also has an all-ceramic internal structure and a special firing process.
Heat exchanger as heat store
The Oxi.X RA RTO from Mall + Herlan is sized for a maximum treatment capacity of 11,000 m³/h and pollutant loads of 1 to 2 g/m3. During normal operation, which equates to the 1.3 to 1.6 g/m3 range, the highly efficient heat exchanger reduces operating costs to an absolute minimum through largely autothermal operation. What does it mean? The burner can be completely extinguished 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 excess energy in phases with high solvent concentrations. In the following 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 using this special “thermal buffer” principle with fluctuating solvent concentrations to “smooth out” the resulting fluctuating energy inputs.
Environmental protection meets economy
For Mall + Herlan, the Oxi.X RA RTO has proven to be the best solution both economically and ecologically. Regenerative thermal oxidation is not only an innovative and reliable means of ensuring that no official limit values are exceeded, but the resulting high oxidation temperatures and extremely high degrees of purification mean that there is no need to determine or complexly check the smell according to the new “Technical Instructions on Air Quality Control 2021”.