Introduction

It is a modern tendency in the chemical industry to continuously protect and improve the environment. Some companies apply more stringent measurements than needed to comply with the local environmental legislation. Styrene emissions can occur in the case of coating jobs. In situations like these, activated carbon filters to reduce styrene emissions (resulting from the paint coating) can provide a necessary means to comply to emission legislations. DESOTEC’s range of mobile adsorption filters are often used when temporary solutions are needed.

Reduce styrene emissions with a AIRCON^® HC mobile activated carbon filter

Cars and metal parts are usually painted in paint shops that are mostly equipped with an activated carbon filter to reduce the VOC emissions. When a 350m³ storage tank needs to be recoated for maintenance it is not possible to transport the tank to a maintenance shop. Due to the temporary nature of such an operation, mobile VOC removal filters offer a cost effective solution.

At one of DESOTEC’s customer’s sites, a 350m³ storage tank needed to be recoated with a vinylester resin based coating. During the spray coating and forced venting during the drying process, styrene solvents are temporarily released into the atmosphere. These were the calculated operating conditions:

• Storage tank volume: 350 m³
• Forced venting air flow rate: 3,500m³/h
• Air changes: 10 per hour
• Temperature: Ambient
• Type of impurities: Styrene
• Concentration of impurities: 100-200mg/m³ but variable

• Treatment objective: Odour threshold of < 1 ppm

The customer wanted to coat the storage tank with three layers, thus inducing a styrene emission of 150kg per layer or a total of 450 kg styrene to be removed. Since after applying each different coating layer there is a drying step of ca. 1 week, the concentrations were expected to be fluctuating. DESOTEC proposed a longer superficial contact time for possible desorption effects and an AIRCON^® HC with fan was installed, filled with AIRPEL^® 10 in order to significantly reduce styrene emission values.

The stack of the fan outlet was put on purpose on man height in order to ensure that the odour threshold was not exceeded. After successful use of the temporary odour control system, the AIRCON^® HC with used AIRPEL^® 10 was returned to DESOTEC for spent activated carbon recycling by thermal reactivation.

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At DESOTEC’s facilities, all used carbon is analysed so the right measures can be taken for handling and removing the saturated carbon out of the mobile filters. All molecules that were adsorbed on the activated carbon at the customers’ site, are desorbed inside DESOTEC’s reactivation furnaces. These contaminants are then fully destroyed, in accordance with National and European legislation, by an incineration and neutralisation setup. The entire installation and it's emissions are under continuous on-line monitoring, which guarantees that only harmless water vapour is seen exiting the chimney.