To cut CO₂ emissions from manufacturing as far as possible, the BMW Group strives constantly to integrate innovations and the latest technologies into production. The newly developed electric purification system opens up a host of opportunities.

When car bodies are painted and dried, gaseous and vaporous substances are produced. To prevent paint shop solvents from harming the environment, this exhaust is purified by burning the substances off before releasing the air via a chimney. This is done by passing the contaminated air through a bed of ceramic media, where solvent residues are burned off. For this to happen, the air has to be heated up to very high temperatures in a short space of time – which could previously only be done with natural gas.

But instead of natural gas, the BMW Group is now purifying exhaust from its first paint shops electrically. A new procedure called eRTO can generate sufficient heat purely with electricity. The system can reach temperatures of up to 1,000 degrees Celsius, which are what’s needed for the thermal purification of exhaust from paint booths and drying areas.

Thanks to the eRTO system, thermal oxidation can now be carried out entirely without fossil fuels. Instead, electricity from renewable sources is used. The eRTO system is installed between the painting booth, drying process and chimney. Thermal energy is recovered by a flat, two-metre-deep ceramic bed where temperatures reach up to 1,000° Celsius and which serves as a recuperator. Electrical heating rods heat the surrounding ceramics, and because most of the heat is retained, with only small amounts escaping, a connected load of just a few hundred kilowatts is sufficient to run the system. With that, another gas-free process has been introduced in production, cutting CO2 emissions significantly.

Michele Melchiorre, Head of Production System, Planning, Tool Shop, Plant Construction at the BMW Group: “For other energy-intensive paint shop processes, such as vehicle drying and water heating, solutions already exist for working without natural gas. So, electric exhaust purification is the final steppingstone for the BMW Group to run its paint shops on regenerative energy in the future.”

The eRTO system was initially function-tested in ongoing paint shop operations at BMW Group Plant Regensburg. It is being further validated at BMW Brilliance Plant Lydia in China, where an eRTO system is used to purify exhaust from the drying system for car bonnets. The first European BMW Group facility to use the technology in series paint shop operations is Plant Dingolfing, where the first of four paint lines has already been converted for electric exhaust purification. The new plant in Debrecen will purify paint shop exhaust only by eRTO.