When a gasometer or gas tank is decommissioned, its contents need to be filtered to avoid groundwater pollution and odour nuisance. A large gas storage tank in the city of Hollerich, Luxembourg, provides an interesting case study of how to do this efficiently and safely.

Case study: decommissioned gasometer in Luxembourg

Until 2012, a gas tank in the city of Hollerich, Luxembourg, was used to store natural gas near atmospheric pressure at ambient temperatures. In the past, such gas holders were used to store natural gas for later use, or for balancing purposes, making sure gas pipes could be operated within a safe range of pressures. The increasing supply of natural gas via pipelines, however, made this gasometer redundant and led to the decision to disconnect it from the gas net in 2012. The methane was removed, and the tank was consequently filled up with water.

THT contamination

In 2015, the first phase of the demolition works commenced, during which the water was discharged from the tank. The water, however, contained the molecule tetrahydrothiophene (THT), which is used in many European countries for natural gas odourisation. The atmosphere inside the gasometer was also polluted with THT. In order to prevent odour nuisance in the vicinity of the tank and groundwater pollution, filtration was required to completely remove all traces of THT.

Carbon water and air filtering

MOBICON^® activated carbon filters with ORGANOSORB^® grade carbon were chosen to treat the residual water and waste water from cleaning the inside of the gasometer. For air filtration, AIRCON^® units and AIRPEL^® activated carbon were in use to guarantee a safe working environment and zero odour emission into the atmosphere. These mobile activated carbon filters were in use for the full duration of the project and were then transported back to DESOTEC. The used-up activated carbon are recycled in a state-of-the-art DESOTEC reactivation installation. Following the cleaning phase in which the air and water from the gasometer are tackled, the actual tank dismantling could begin, after which the area is to be redeveloped for urban housing projects.

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.