No more odour nuisance at Scandinavian biogas plant

Electricity generation in an environmentally friendly way is certainly to be welcomed, but is sometimes accompanied by annoying side effects. For example, odour nuisance may occur during the production of biogas. A Scandinavian biogas plant operator solved that problem accurately and resolutely through a collaboration with Desotec. Two high capacity mobile activated carbon filters ensure that the surrounding area no longer suffers from odours caused by H₂S.

The Scandinavian company specialises in the construction and operation of biogas plants. This company recently built a brand-new unit for an important industrial customer that ferments no less than 300,000 tons of industrial/biological waste per year. This results in an annual production of 8 million m³ biogas, or 1,000 m³ per hour. The biogas is then upgraded to produce natural gas quality biomethane. After injection into the grid, the plant supplies energy to 5,000 families. Production started at the end of 2018.

Upgrading the biogas to biomethane is done by means of the ‘amine scrubber’ technology. This entails an ‘offgas’ stream of 2,000 m³/hour, which is blown out into the ambient air. This stream also contains 2,000 ppm H₂S (hydrogen sulphide), which caused an odour problem. The contractor and co-owner of the biogas unit quickly went looking for the right solution to tackle that problem correctly. After unsuccessfully testing a number of alternatives, they turned to Desotec. The company’s managers remembered Desotec from a first exploratory meeting that had taken place two years ago.

After their approval of our offer, we quickly took up the challenge by installing two AIRCON^® HC-XL activated carbon filters on-site within a week. These mobile filters are very suitable for vigourously treating significant flows with a high level of contamination. After an analysis of the offgas stream they were filled with impregnated activated carbon of the AIRPEL^® ULTRA DS-6 type, which seemed to be the best solution for optimal purification of the residual flow.

The filters have been operating for several weeks now and are showing very good results. Measurements at the filter outlet do not even detect H₂S (0 ppm) anymore. The customer is thus very satisfied with the functioning of this solution. Desotec also ensures a good follow-up of the situation: once the filters are saturated, they are immediately replaced, without compromising the productivity at the biogas plant.

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.