Since the provincial governments have made their regulations for clean air a lot more stringent, upgrades for exhaust-air purification systems in Chinese factories have become a key topic for almost all OEMs. This is why, two years ago, Dürr started a project to offer advice to customers, jointly develop customized solutions, and support them in the approval processes. More than sixty Ecopure® TARs have been ordered in the last two years alone. They are being installed in new facilities as well as during modernizations of existing paint shops in China.
The milestone model will be installed by a team of Chinese and German Dürr employees to upgrade an existing paint shop at SAIC Volkswagen. It will be used for the purification of exhaust air from spray booths. Usually the painting process generates particularly large volumes of exhaust air, which only contain low amounts of contaminants. For this reason, a continuous adsorption process for concentrating the solvent-laden exhaust air (Ecopure®KPR) should additionally be installed between the paint booth and the thermal exhaust-air purification system. The exhaust-air volume flow is thus significantly reduced for the subsequent thermal purification in the Ecopure® TAR.
The resulting increase in the pollutant concentration substantially decreases the gas consumption because the energy contained in the pollutants can be utilized in the oxidation process. The energy requirement for the exhaust-air purification process is therefore considerably lower. Combined with a system that recirculates up to 95 percent of the air, as is the case at SAIC Volkswagen with the EcoDryScrubber – Dürr's technology for dry separation of overspray – it reduces energy consumption by up to 60 percent compared to conventional systems. Unlike many of its competitors, Dürr produces its exhaust-air purification systems, KPR and TAR, in-house to ensure they work in perfect harmony.
Heat recovery
Further Dürr TAR systems are directly connected to the exhaust-air sources at SAIC Volkswagen. Recuperative oxidation systems are ideally suited to cleaning exhaust air from ovens, as the heating energy contained in the purified gases can be directly and almost completely reused in the drying process. As in all thermal processes, the exhaust air is heated by the Ecopure® TAR to such high temperatures that the hydrocarbons are oxidized to produce mainly water vapor and carbon dioxide. The polluted air is first preheated by the hot air in the integrated (recuperative) heat exchanger, which allows a large portion of the combustion heat to be recovered. When the air enters the combustion chamber, the burner heats it further and initiates oxidation of the pollutants, which is completed once they have passed through the chamber.
SAIC Volkswagen and other customers benefit from Dürr's decades of experience in exhaust-air purification and painting technology. "We deliver everything turn-key", says Magnus Morsch, Head of Sales for Exhaust-Air Purification Systems at Dürr's Clean Technology Systems division. Dürr produces the Ecopure® TAR entirely in-house, including burner and gas train. Several times a week, TAR systems leave the Zisterdorf plant as pre-assembled units, ready for their – often long – journeys all over the world. Aside from the automotive industry, they are also used in other sectors such as the coating industry.
