First concentrate, then purify
Nuremberg, March 2015 – “How can we purify exhaust air without using a lot of energy?” – This is the question LTB was asking themselves when they were competing for a contract from an automotive component supplier. Since then, the complete system has been operating successfully for a year, and it is saving the customer a bundle. The system incorporates the RoCoSorb and ROXITHERM units.
The automotive component supplier based near Nuremberg (Germany) uses two separate coating processes in the production of its interior trim components. A solvent-based base and filler varnish are applied to the plastic components first, followed by a protective UV coating. The exhaust air from the coating process contains both solvents and particles of UV varnish which become sticky once they come in contact with UV light. As the volume of exhaust air is very high and the concentration of solvents is too low to support the combustion process that occurs in a regenerative thermal oxidizer (RTO), as the process would consume a great deal of energy.
Two coating process – a single purification stage
To make the purification of the exhaust air as energy-efficient as possible, the so-called “RoCoSorb Rotor concentrator” was brought into play. “Its main component is a large rotor coated by the mineral zeolite. The solvent-laden air flows through the rotating rotor, with the solvents settling in the pores in the mineral coating. The result: “clean air,” explains Thomas Scheiring, who is responsible for distribution and sales of exhaust air purification equipment in the field of industrial coating at LTB.
To ensure that the solvent particles do not remain on the rotor, a small section of the rotor is continuously exposed to hot air flowing in the opposite direction. The hot air dissolves the volatile organic compounds and carries them along to the RTO ROXITHERM, where the concentrated flow of exhaust air is purified.
Thanks to the upstream process stage – called concentration – the volume of air entering the ROXITHERM unit is 25 times smaller than the original volume while carrying the same amount of solvent. This means that only a small amount of natural gas needs to be added to improve combustion.
Track record after one year
During the customer’s normal operation, the volume of exhaust air generated is about 33,500 cubic meters per hour. “The combination of the two LTB systems or the exhaust air purification saves the customer a total of 65% in electricity, gas and compressed air – which translates into straight cash,” Thomas Scheiring points out.
Whether in single or three-shift operation, the systems easily adapts to the varying volumes ranging from 5,000 to 33,500 cubic meters and purifies the exhaust air reliably. It goes without saying that the legal emission limits are complied with.
What is of particular importance for the reliable operation of the installed LTB technology: the special design of the systems ensures that the rotor does not sustain damage as a result of the sticky UV paint particles and stays in perfect operational condition.
LTB (Luft- und Thermotechnik Bayreuth), based in Goldkronach, has been a member of the Dürr Group since 2013.