Lowering energy costs and emissions
November 2013 – Bodywork drying has become the most energy-intensive process in automotive painting. It accounts for around one third of the total energy consumption. As part of its Eco+Paintshop concept to reduce consumption, Dürr has developed three innovative oven heating processes.
Ecopure TAR Suntec relies on solar thermal energy to preheat the TAR system, which is used to clean the exhaust air from the oven while generating process heat at the same time. In the Eco+Energy CPS process, ovens are heated with the help of a micro gas turbine, which produces heat and electricity. The third process, Eco+Energy CPS Suntec, combines micro gas turbine technology and solar thermal energy. All three solutions offered by Dürr reduce operating costs and CO2 emissions of paint shops significantly.
Ecopure TAR Suntec is based on the proven TAR technology, which is used for exhaust-air purification and oven heating in many paint shops. Its innovative feature is the combination of TAR technology and solar thermal energy. It is particularly suited to automotive production facilities in sunny locations. This is where the linear concentrating Fresnel collectors, which harness solar energy, come into their own.
The solar heat is initially used to preheat the exhaust air from the oven with the help of a heat exchanger. In a second step, it is fed into the Ecopure TAR Suntec exhaust-air purification system. This considerably reduces the amount of natural gas necessary to heat the combustion chamber to around 720 °C, the temperature required to clean the exhaust air from the oven. Further energy savings result from the fact that the collector modules installed on the roof of the paint shop 'catch' some of the sunlight. This reduces the temperature in the building and thus the requirement for cooling.
Eco+Energy CPS, the second process designed to save energy in oven heating, generates not only heat but also electrical energy. The highly efficient, decentralized combined heat and power technology (CHP) gives the plant operator more autonomy regarding the energy supply as, for example, fewer emergency power generators are required. Eco+Energy CPS relies on Dürr's Compact Power System based on micro gas turbine technology. An RTO exhaust-air purification system can be connected to clean the exhaust air from the oven. This process is suitable for direct or indirect oven heating.
In direct heating, the warm turbine air flows directly into the oven. This highly efficient use of thermal energy is suitable, for example, for predrying in electro-coating applications due the low emissions. In indirect heating, a heat exchanger is placed between turbine and oven. This is less energy-efficient but prevents emissions from the combustion process from entering the oven. Changes in the chemical cross-linking of the recently applied paint can thus be avoided.
Eco+Energy CPS, too, can be combined with solar thermal energy in sunny locations. Thanks to the use of Fresnel collectors, the nominal consumption of primary fuels can be lowered by up to 40 %. Eco+Energy CPS Suntec uses solar energy to preheat the combustion air of the micro gas turbine. All previous approaches for using solar energy to operate micro gas turbines were aimed at completely replacing gas and other fossil fuels. However, this required extremely sophisticated solar technology. Dürr's approach combines solar heat and fossil fuels, and uses solar heat for preheating only, thus allowing the economical use of solar energy even in energy-intensive process such as automotive painting.