Case Study

Achieving a first in the USA for CAROL's robotic technology

CAROL robotic catalyst removal

Our robotic catalyst removal technology was used at an operating plant for the first time in the United States to remove built-up catalyst remotely, with vessel temperatures exceeding 50°C.

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.

Our solution

CAROL was used to unload the residual catalyst material (post dumping) in the gas shift reactor vessel and was operated in temperatures not suitable for human entry. The robot successfully removed the catalyst until a hot spot caused the plastic prototype screws to melt. The prototype screws were designed to withstand temperatures of 50°C.

Hot catalyst beds are not uncommon and workers will on occasions experience their boots getting hot, at which point they must get to the ladder before the soles of their shoes melt.

CAROL robot inside the vessel


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.

Aerial view of refinery