Reducing VOC and BTEX emissions for a major Spanish thermosolar company

Generating renewable energy is a top priority for those striving for a more sustainable society. Thermosolar systems, of which compound parabolic concentrators (CPCs) are the most developed, are among the technologies that have proven their value in this area. As this case study from Spain demonstrates, DESOTEC’s sustainable mobile filters purify the emissions generated by CPCs, ensuring green energy solutions to meet the needs of generations to come.

The problem

Compound parabolic concentrators (CPCs) use cylindrical parabolic solar collectors to harvest the rays of the sun. A synthetic organic fluid runs through these collectors, which is crucial for heat transfer. This fluid is a mixture of biphenyl and diphenyl ether, and can quickly reach temperatures up to 400°C.

A negative consequence of this high temperature is the formation of volatile organic compounds (VOCs) including: benzene, toluene, ethylbenzene and xylene (BTEX); naphthalene; diphenyl ether; and biphenyl. To maintain good air quality, it’s crucial to prevent these substances from entering the atmosphere.

This issue may be partially avoided by using an expansion vessel and different separation processes. Even so, emissions still contain VOCs that require treatment.

DESOTEC has the simple and sustainable answer: mobile activated carbon filtration solutions that reduce VOCs to acceptable levels.

The solution

DESOTEC has been working with this Spanish customer since the end of 2020. We installed two Aircon 2000 activated carbon filters, capable of handling the variable flow rates of between 50 and 2 000 m³/ h.

The filters are placed in a lead-lag configuration. The emissions are passed over the first filter, with the activated carbon adsorbing the VOCs. The second filter acts as a back-up, ensuring that any molecules that break through are also removed.

The lead-lag configuration optimizes activated carbon consumption and allows a swift and easy exchange of the filters with no production downtime. This customer exchanges both filters in a matter minutes approximately once a month.

The results

The client is happy with DESOTEC’s solution, and is renewing its contract with us for a third year.

Activated carbon is a simple and adaptable technology, capable of treating fluctuating flow rates and concentrations. Therefore, our solutions are well suited to the variable conditions common to thermosolar systems, which depend on the season and level of solar radiation.

We also provide mobile water treatments for thermosolar customers who experience an issue with heat transfer fluids (HTF) ending up in rainwater.

All our filters are mobile, allowing them to be quickly installed. Once the carbon is saturated, the entire filter unit is transported safely away from customers’ sites to DESOTEC’s facilities. There, the adsorbed molecules are destroyed in our furnaces in accordance with national and European legislation, and the carbon is reactivated wherever possible. Only harmless water vapour is seen exiting the chimney. This circular system reduces costs and boosts sustainability, helping to build a greener future for everyone.