What is a VOC Rotary Concentrator?
A VOC Rotary Concentrator is an air pollution control technology used in applications with a combination of high volume of air with low concentration of solvents or VOCs (volatile organic compound). Practically speaking, it is a front-end, pre-conditioning unit placed upstream of a thermal oxidizer or regenerative thermal oxidizer (RTO). By concentrating the VOCs from a large airstream into a small airstream, it allows the use of a smaller thermal oxidizer (or RTO).
The VOC destruction/ removal efficiency (DRE) of a Rotary VOC Concentrator is from 90-97% and is dependent on several factors:
- Type and concentration of VOC
- Process exhaust temperature
The main benefit of using rotary VOC concentrators is reduced fuel and electric consumption compared to an oxidizer only. Processes with a large airflow, light VOC concentrations (<500 ppmv), and temperatures below 100F are ideal applications for a VOC concentrator.
Processes that are well suited for VOC rotary concentrators include:
- Fiberglass gel coating
- Automotive paint processes
- Beer / beverage can production
- Composite fabrication
- LCD panel production
- Semiconductor Fabrication
- Steel furniture paint booths
- Wood furniture surface finishing
How does a VOC rotary concentrator work?
VOC Rotary Concentrators absorb VOCs from a high volume airstream, and release the VOCs to a low volume airstream, that then gets treated in a thermal oxidizer. VOC Rotary Concentrators utilize a honeycomb wheel coated with adsorbent material (typically zeolite) to capture VOCs. This wheel is divided into three sectors: adsorption, desorption and cooling.
The adsorption section is approximately 80% of the rotor’s face area. Process air passes thru the absorption section (1), VOCs are absorbed on the zeolite, and the cleaned air is passed through to atmosphere (2).
The desorption section is where the concentrated VOCs are removed from the zeolite media. Here a smaller, warm airstream is passed over the rotor to strip (desorb) the VOCs from the zeolite (3). This desorption flow is only 7-10% of the original process exhaust flow. This smaller flow, now carrying nearly all of the absorbed VOCs, is then directed to a thermal oxidizer (4) for destruction of the VOC. The desorption section makes up about 8% of the rotor’s face area.
Common Process Example
Incoming airstream: 50,000 scfm of spray booth emissions; 300 ppmv MEK & MIBK
Desorption airstream: 5,000 scfm of air with 2910-3000 ppmv MEK & MIBK
A VOC Concentrator coupled with a 5,000 scfm RTO, can be utilized rather than a 50,000 scfm RTO
In the cooling section, rotor exhaust (or fresh) air is passed over the Zeolite wheel to cool it (5). This air is then mixed with hot air from the RTO or oxidizer, and routed to the desorption section (3). Once this rotor section is cooled, it is ready to return to the adsorption sector to absorb VOCs again. The cooling sector makes up about 8% of the rotor’s face area.