filling combined with a booster compressor. The compressed gas hydrogen dispenser will have a vent stack line to the atmosphere.
Inert gas purging systems, which can be initiated automatically or manually will be an important ancillary part of the filling station. Inert gas purging systems may be used during start up and shutdown and in emergency situations.
Future hydrogen filling stations, including the production unit, may be fully automated and can be unattended. For demonstration stations, such as in the CUTE project, operation personnel will be located at a certain distance from the station or at the station. Remote monitoring will be carried out, and shut down to failsafe conditions may be carried out automatically or by emergency buttons at the filling station area or from a remote location.
Results General observations
Very sparse technical input was available at the time of analyses. This was due to confidentiality aspects related to accident statistics and technical input. In addition the concepts were not finally designed and there is still some way to go until technical information is ready for some of the production units.
Purification units downstream the production unit, such as PSA (pressure swing absorption) units, were not analysed.
Identified risk of production units
The results from the RRR analyses were very dependent on the participants. A better basis for comparison of different concepts may have been achieved if all participants had been present at all analyses. This was not possible to achieve due to practical reasons. The risk results below can therefore not be used as a basis for comparison between production/supply concepts, but as a listing of potential hazards for the different concepts.
For all concepts the risk of releases of flammable gases inside confined areas should be addressed. Separation of units to prevent backflow from downstream units, gas and/or fire detection coupled to automatic shutdown and fast depressurisation and purging with inert gas will reduce the risk. Prevention of backflow inside a production enclosure/container from the high pressure sections in case of a hydrogen leak is a critical aspect; back flow must be prevented.
Identified hazards for the different production concepts are included in tables below.
Table 1 Results from risk assessment of production concept 1: Hydrogen production by ammonia
splitting. Process unit
Ammonia storage including filling of storage tank from truck
Rupture/large leak in ammonia filling hose, resulting in toxic heavy gas cloud exposing the surroundings. Risk for persons around the installation.
Suggested risk reducing measures
Atmospheric refrigerated liquefied ammonia implies less risk than pressurized ammonia, transportation of refrigerated ammonia should be considered
Cordoned-off area during ammonia