Vacuum truck off-gas treatment during a tank cleaning process

Initial situation:

During a high-pressure cleaning inside a tank, a contamination of approx. 500 ppm benzene was expected based on sample measurements.
To ensure safe operation, the exhaust air generated during this process should be collected with a vacuum truck and treated afterwards.
Since a vacuum truck can’t clean its polluted exhaust air, BROCKHAUS ENVIRONMENT was asked on short notice to clean the off-gas of the vacuum truck.





The high-pressure cleaning took approx. 15 hours, within this period a volume flow of approx. 16.000 m³ was conveyed and subsequently treated.
The Ø benzene concentration was approx. 521 ppm, which corresponds to an approximate amount of 27 kg pure benzene in 16.000 m³ exhaust air.*1
521 ppm benzene exceed the EU occupational exposure limit approximately 530 times (limit = 3.25 mg/m³).*2
Legal issues aside, the affected employees would have been exposed to a significant amount of benzene.
The long-term effects of a benzene exposure and the associated high probability of cancer are well known.
In conclusion, it can be said that the use of SARA ensured compliance with the German TA-Luft and, in particular, the protection of the people on site.

*1 521 ppm benzene | 1.013,25 mbar | 15 °C ≈ 1.721,10 mg/m³ benzene
1.721,10 mg/m³ x 16.000 m³ = 27.537.600 mg ≈ 27 kg benzene

*2 521 ppm benzene | 1.013,25 mbar | 15 °C ≈ 1.721,10 mg/m³ benzene
1.721,10 mg/m³ / 3,25 mg/m³ ≈ 530


DOWNLOAD Case study


Evaluation protocols BROCKHAUS SARA:

The constant intervals in the 1st evaluation protocol result from the predetermined cycles of the sensors.
During the process of fresh air purging and sample gas aspiration, the previously measured values are frozen.

Within the period when there is no volume flow, the remaining gas within the line is measured.


Hydrocarbon concentration in ppm entrance:

Hydrocarbon concentration in ppm exit:

Volume flow in m³/h:

Cumulative volume flow in m³: