The challenge

Catalyst from the gas shift reactor was removed in the first instance using a dump nozzle, located at the bottom of the catalyst bed. While this allowed for the catalyst to be gravity dumped from the vessel, not all the catalyst was removed, and this remaining catalyst can be up to 40 per cent of the total vessel volume.

Workers are typically required to enter the vessel to vacuum the remaining material, while remaining aware of the built-up catalyst around the vessel walls and the associated risk of being buried. Purging of the vessel with nitrogen is required to prevent the catalyst from self-heating. If there is insufficient nitrogen, then the catalyst bed heat up and pockets of catalyst (hot spots) can reach up to 200°C. The vessel temperature needs to be lower than 40°C for human entry meaning a consequence of the hot conditions is significant time delays.

Benefits

The use of CAROL demonstrated that robotic catalyst removal technology can be used effectively in combination with gravity dumping to minimize the time spent by workers inside confined spaces during catalyst unloading. The vessel temperatures following the catalyst dumping operation were still too high for human entry, however the use of CAROL allowed for the job to continue.

We have also developed a set of 3D-printed nylon screws that are able to withstand catalyst temperatures of up to 82°C. Aluminium screws are in production that will withstand temperatures higher still.

Advisian Digital’s development of CAROL responds to the increasingly stringent requirements to reduce human risk in inert confined space entry.