How to Filter Wet Paint In a Dry Filter System

Every second about three freshly painted cars are leaving one of the hundreds of automobile production plants world wide.

Each automobile paint line is producing a large amount of air-borne paint overspray that has to be filtered before leaving the paint booth. The traditional means used to filter the paint droplets out of the air stream is a wet scrubbing system. In a wet scrubbing system the paint- saturated air from the paint booth is passed through a venturi nozzle and mixed with water coming from a spray nozzle. The paint droplets agglomerate with the water droplets to form larger droplets that can be separated from the air by a mist separator. The down side of this wet scrubbing systems is that the air can’t be reused after the scrubbing process because it’s too humid and not clean enough for the paint booth. Due to this, fresh ambient air has to be filtered and heated again for the paint booth. This heating consumes about half of the energy of the whole paint booth.

Clear-Edge-Paint-Booth-Auto-Line-Durr-Systems-500-500

The solution for this problem is a filter system that filters the droplets that doesn’t change the temperature or the humidity of the paint booth air. A conventional disposable filter bag can do this, but then the filter bags have to be replaced in very short cycles. The solution is a self-cleaning filter system that can filter the paint saturated air.

In 2008 a large German supplier for paint both systems started investigating into using a jet pulse dry filter systems for wet paint overspray. To do this it was necessary to capture the wet paint droplets by a dry dust. This was done by adding limestone powder to the contaminated air stream. Filtering using conventional cartridge-type pulse jet filters was not successful due to the high dust concentration and high volume of air.

Clear Edge Filtration developed a special pleated flat filter panel for this application. These flat panels are called Compact Filter Elements, or CFE’s. Clear Edge Filtration in Salzgitter, Germany has produced CFE type filter’s for over 20 years, and had a unique challenge to meet the paint booth application requirements. The CFE for this application had to match the following parameters:

• High filter surface area at a small size to reduce the footprint of the filter
• Extremely high filter efficiency to make it possible to reuse the filtered air for the paint booth
• No Paint-Wetting Impairment Substances (PWIS) on the filter panel
• At least 60,000 cleaning cycles
• Excellent cleanability
• Antistatic filter media to avoid electro static charging of the filters

This new dry filter system for paint booths started a revolution on the paint booth market. More than half of the new automobile paint lines are equipped with modern dry filtration systems. Even existing paint lines are upgraded to dry filter systems because of the large energy savings. A dry paint filter system can save up to 60% of the energy cost compared to the wet scrubbing systems.

Clear Edge continues to be a pioneer with CFE’s and expand their application field. For more information about our paint filtration solutions, check out Compact Filter Elements supplied by Clear Edge, a part of the Industrial Air Business Unit of Process Technologies Division, contactInfo@clear-edge.com

By John Eleftherakis, Managing Director, Industrial Air and Alexander Grothues, Product Manager – Compact Filter Elements

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