Rotary Concentrators

Rotary Concentrators are auxiliary units that can be placed prior to catalytic or thermal oxidizer air pollution technologies to reduce overall system size and operating costs.

  • Box-shaped gray machinery (concentratror) on a cement platform outside of an industrial plant. An oxidizer system is behind and to the left of the concentrator.
    Concentrator unit outside of an industrial plant.
  • Box-shaped gray machinery (concentratror) on a cement platform outside of an industrial plant. An oxidizer system is behind and to the left of the concentrator.

What is a Rotary Concentrator for Air Pollution Control?

When treating large airflows with low concentrations of VOCs (below 1000 ppm), a rotary concentrator wheel acts as an auxiliary unit that may be installed prior to thermal and catalytic oxidization systems. By taking the same mass of pollutants and concentrating it into a smaller stream, concentrators effectively reduce the overall size and operating cost of the air pollution control equipment needed. 

How Does a Rotary Concentrator Work?

Typically 5-14 feet in diameter and shaped like a wheel, the concentrator sits vertically and turns as process air is brought in. The zeolite is an adsorbent that covers the wheel and collects the VOCs from the incoming waste stream. As the zeolite reaches a certain concentration of VOCs adsorbed, one section of the wheel remains dedicated to desorption, using higher temperatures to strip the VOCs from the resorption sections of the wheel.

By collecting the VOCs onto 90% of the wheel and releasing 10% using heated air, the concentrated VOCs can be released to the oxidizer in a controlled manner.

Utilizing zeolite as the adsorbent allows VOCs to be captured at temperatures up to 120°F, and subsequently released from the concentrator at higher temperatures (approx. 360°F). The desorption air (5-10% of the process air volume) is sent to the oxidizer for treatment. This reduces the flow rate of process air coming through the oxidizer, shrinking the overall system size.

A 20,000 cfm stream containing 500 ppm of VOCs is easily concentrated into a 2,000 cfm stream containing 5,000 ppm of VOCs, which can be treated with much smaller air pollution control equipment.

Removal efficiencies vary based on VOC composition. If high destruction efficiency is needed, multiple wheels may be required upstream of the oxidizer.

Key Features of Rotary Concentrators

  • Zeolite Composition: Its hydrophobic properties mean moisture in the air will not impact performance (humidity).
  • Lower Maintenance: A Regenerative Thermal Oxidizer (RTO) has many internal moving parts, whereas a Concentrator followed by a CatOx or straight Thermal Oxidizer will require less ongoing maintenance.
    • The concentrator unit is self-cleaning, ensuring VOCs do not build up on the wheel and affect overall performance during its life.
  • Economical: Besides the operating cost savings of treating a much smaller exhaust stream, the capital investment of a combined unit concentrator and smaller oxidizer may be less than that of an oxidizer that treats the total flow.
  • Support Sustainable Operations: By desorbing with the use of electric heaters or by heat recovery from the downstream air pollution control equipment, a concentrator helps ensure no additional NOx is created.

Common Industry Applications

Frequently Asked Questions

Concentrators are susceptible to particulates but can include a filter box to treat PM before reaching the concentrator (Filtration of 95% at 1 micron).

It is not recommended to treat above 120°F as high temperatures can damage the concentrator wheel.

Exhaust streams with relative humidity up to 90% are acceptable for a concentrator.

Activated carbon could be used as well but it is not used as often due to it being granular and can’t easily be put into a wheel that is rotating, it would have to be in beds. Zeolite is more robust than activated carbon.

The wheel should be replaced after about 10 years of continuous operation.

A concentrator can handle most VOCs. Before we design an APC system for your process, our engineering team will review your waste stream composition to confirm that a concentrator will be the most effective solution for your needs.

Need to Treat a Large Air Stream?

If the stream contains less than 1,000ppm of VOCs, a rotary concentrator may be effective for your process and can reduce the overall size of your air treatment equipment. Our engineering team will review your process specifications and determine if a concentrator/oxidizer combination system would make economical and practical sense for your application.

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