Treating air emissions at a chemical park in France

Chemical companies are under increasing pressure to curb their emissions, facing the threat of closure if they cannot comply with stringent pollution controls. Activated carbon is a highly effective and reliable treatment for air purification in many circumstances, enabling plants to continue production with confidence.

The problem

A company provides utilities and industrial services at a chemical park in France. It operates an incinerator for the chemical companies on the park. The incinerator contains refractory stones which must be replaced every two to three years.

During these maintenance periods, which last one to two months, a speciality chemical company at the park must instead flare off its waste gas. However, this does not remove all pollutants.

The chemical company came under pressure from the local environmental authority to prove it was abiding by its emissions limits: VOCs up to 110 mg/m³, tert-butyl mercaptan (TBM) up to 20 mg/m³, and hydrogen sulphide (H₂S) up to just 5 mg/m³.

The authority has the power to close down the factory if conditions are not met, so the industrial services company sought a back-up solution.

The solution

DESOTEC installed an HC-XL filter, capable of treating the flow rate of 100 m³/h to 200 m³/h.

It is tall enough to use two layers of different carbon types to treat the H₂S and the non-sulphurous compounds. Had there been more H₂S, we would have installed two filters to treat these contaminants separately, although in this case it was unnecessary.

The client also chose to fit safety equipment designed by DESOTEC: an INERTI-BOX and an HC-BOX. This system uses a CO sensor to detect if hotspots are forming in the filter bed; automatically close the valves supplying oxygen to the filter; and douse it with nitrogen.

There is always a very slim chance of hotspots when H₂S is present, as the filter requires oxygen to function properly. Although the risk here is very low, the client took a safety-conscious approach.

The results

The system was installed in autumn. For the first month, the client measured emissions at the outlet every two days, and detected zero pollution.

This enabled the chemical company to demonstrate to the environmental authorities that it is complying with its permit, lifting the threat of closure.

The first filter lasted six months before it needed to be exchanged.

Both the client and the chemical company remain very satisfied. They have been pleasantly surprised by the effectiveness of activated carbon.

Initially, it was envisaged that the filter would be used only during the incinerator downtime. However, the client is now considering it as a permanent solution due to the incinerator’s reliability issues, which have on occasion forced the chemical company to pause production.

The client is pleased with how quickly the filter was installed. Alternative fixed technology might require extensive engineering and building, quickly taking a few months, but DESOTEC's filter was installed within two weeks.

It is also a very simple solution: within an hour of installation, there was zero pollution.

There are also few capex costs. Alternative solutions could cost millions of euros, yet might not prove effective. DESOTEC filters are supplied on a rental basis, so can be removed if necessary.

DESOTEC handles all waste carbon, transporting it safely in closed filter units. At our facilities in Belgium, we analyse samples to determine how to store and treat it. All molecules that were adsorbed during operation are desorbed inside DESOTEC's furnaces, and most carbon is then reactivated for reuse. The contaminants are destroyed in accordance with national and European legislation. The entire installation and its emissions are under continuous online monitoring, and only harmless water vapour exists the chimney.