CAROL (Catalyst Removal Amphirol) was used to remove catalyst remotely from a dehydration vessel, avoiding the need for worker confined space entry under inert conditions.

The challenge

The dehydration vessels at the LNG plant, which remove water from gas before it is liquefied, have previously been unloaded using a water flood method. The catalyst is deactivated using water after which workers enter the vessel equipped with breathing apparatus and manipulate the end of a vacuum to remove the material. Other vessels at the plant must be unloaded under inert conditions – a nitrogen environment. Our client was seeking to minimize confined space entry, particularly under inert conditions.

The dehydration vessels at this LNG Plant also provided some unique challenges for the robotic catalyst removal technology. The manway was off-center, which meant the robot needed to travel a long distance to the outer edge of the 4.1-meter diameter vessel. The top ceramic balls were on a steel mesh screen, and there were moisture probes located towards the bottom of the vessel, which the robot needed to navigate around.

Benefits

CAROL remotely removed more than 95 per cent of the catalyst from the vessel including the ceramic support material at the top of the bed. Inert conditions were maintained throughout and the requirement for confined space worker entry in the oxygen deficient atmosphere was eliminated.

The successful trial of CAROL has demonstrated that our robotic catalyst removal provides an alternative to inert confined space entry during catalyst unloading. It also provides an alternative to water flooding and the associated disposal of the potentially contaminated water. Lessons learned from the trial have been implemented in the revised procedures and design.