Removal of nitrotoluene from storage tank gases during venting

The pursuit of ‘customer delight’ is also an absolute must in the chemical sector. At the request of one of its major customers, a specialist in the storage of chemicals invested in an activated carbon filter to reduce or even completely eliminate nitrotoluene emissions.

An international company that has always focused on the storage of chemicals does so mainly for producers in the chemical industry. One of those chemical products is the highly toxic and hazardous nitrotoluene. In the past, the French branch of this company used gas scrubbers to tackle the exhaust concentration of this substance. However, one important customer felt that this system was not sufficient and, for safety reasons, asked the supplier to invest in a more efficient solution.

Experience with Desotec services at a site in Antwerp

After internal consultation with Belgian colleagues, the responsible parties in France learned about the possibilities of activated carbon filtration. The Belgian branch of the company had excellent experiences with the Desotec solutions and, after a visit to the site in Antwerp, the French stakeholders were also convinced.

The challenge was to select the right solution for a nitrotoluene storage tank under nitrogen atmosphere. Due to temperature differences in the tank, the internal volume may vary and it is necessary to let the tank 'breathe'. To release the pressure, the activated carbon filter only needs to treat a very low flow rate. The selected Aircon 2000 C filter has also proven its added value during storage tank filling and during the venting of the vehicles. This type of filter is very efficient in treating very low flow rates (maximum of 650 m³/h) and has been specially developed for the treatment of venting gases from storage tanks.

Because the venting gases only occur occasionally, a continuous measurement of carbon monoxide takes place at the activated carbon filter outlet. If CO is actually detected, the Inertibox is activated and the magnetic valves close automatically. The filter is flushed with nitrogen to create an inert atmosphere again.

Coconut carbon crucial to meeting limit values

The Aircon 2000 C filter is filled with coconut-based activated carbon. The micro porosity of the coconut carbon allows to adsorb this molecule more strongly. This leads to a much slower and broader desorption peak when using the carbon. Selecting the right carbon type is essential as the emission limit values for nitrotoluene are close to the zero tolerance limit.

For the customer, this application is a pilot project in which the activated carbon filter completely replaces the gas scrubber. If the results are positive, the company will also opt for Desotec mobile filters for the treatment of other air flows with toxic substance contamination.