Providing a complete filtration system for odour removal

While DESOTEC filters are usually supplied on a ‘plug-and-play’ basis, our projects team can also provide all-in solutions to meet major clients’ filtration requirements. Our team has the engineering, mechanical and electrical expertise to design and install a complete system to remove VOCs, odours or other contaminants, acting as a one-stop shop for clients looking to comply with emissions limits.

The problem

Our client is a German company making roofing materials from bitumen, which emits odorous Volatile Organic Compounds (VOCs).

As the factory is located today near residential office areas, it needs to reduce this odour nuisance, meet strict emissions limits, and avoid complaints from neighbours.

After a pilot test, the client decided to replace its underperforming water scrubbers with two AIRCON V-XL filters. These would treat a flow rate of up to 40 000 m3/h from several different production lines and emission points across the factory.

The factory varies its production to meet demand throughout the year, increasing hours in spring and summer. Therefore, they wanted production to continue during the exchange of the filters. This is an increasingly common request from cost-conscious companies, even though filter exchange takes just about thirty minutes.

The client contacted DESOTEC not only to supply the activated carbon filters, but also to design and install a complete system including all mechanical, engineering and electrical components.

The solution

DESOTEC designed the system to meet the client’s specifications and German safety and emissions standards. It took four to six weeks to build on site, and has the following main features.

  1. It is a valve system based on a lead-lag configuration. The first filter adsorbs the VOCs until the carbon is saturated, with a second filter in place as polishing step. The valve system is used to divert emissions to the second filter while the first is exchanged by DESOTEC’s truck with the replacement filter. Once the new filter with fresh carbon is put in place, it takes on the role of polishing filter. When this second filter is saturated, emissions are rerouted back to the first filter while the second is exchanged.
    This is cost-effective, as it enables clients to use filters until they are fully saturated and avoid any downtime while filters are exchanged. The valves could also be used to bypass the filters altogether in the event of a problem.
  2. There are two fans, placed in parallel, which can automatically adjust their speed depending on how many production lines are running to improve energy and cost efficiency. Only one fan is in operation at a time, with the second as a back-up in case of a fault in the first.
  3. The fans are contained in noise boxes, with a limit of 75 dB at one metre’s distance. As the fans are near the factory entrance, the client wants to keep noise levels low.
  4. The system includes an INERTI-BOX to detect hotspots. These hotspots could occur when a high concentration of VOCs is adsorbed by the carbon, causing the filter bed to glow. This is a safety feature developed by DESOTEC that incorporates a carbon monoxide (CO) sensor. If CO is detected, the valves to the related filter will automatically close, and the filter will be filled with nitrogen to displace the oxygen and prevent fire. After a cooling down period, the filter can be put in operation again.
  5. It has a VOC monitoring system, so the client can see when a filter is becoming saturated and arrange for it to be exchanged. This enables the client to comply with emissions limits at all times, rather than wait for an external monitoring company to visit and then potentially have to exchange the filter as a matter of urgency.
  6. As well as the mechanical and engineering scopes, DESOTEC designed and installed the full electrical scope according to the client’s specifications. This allows control of the system from either the dedicated electrical cabin, or from the plant’s main control room.

Despite all these features and associated work such as ducting, the final installation is very compact.

The results

The complete filtration system is now working efficiently, removing odours from the factory to the satisfaction of those living nearby.

DESOTEC has been a one-stop shop for the client, completing work that might otherwise have required several different contractors. This makes planning the installation simpler, and avoids costly delays.

DESOTEC also has specialist knowledge on optimising activated carbon filtration systems that other contractors may lack. For example, our teams can potentially improve both safety and efficiency by placing fans correctly in relation to the filters, and installing the INERTI-BOX to eliminate hotspots.