When Sadaf was consistently having difficulty reaching the design capacity of its MTBE plant in Jubail, the company decided to implement a Performance Improvement Project.

The objectives of the project were two-fold - firstly to improve the circulation of catalyst through the MTBE dehydrogenation unit using a new technology developed by Shell, and secondly to improve gas and solids separation, which involved the replacement of the cyclones in the reactor of the unit.

The 700,000 tonnes per year (tpy) MTBE unit started production in 1997 but had consistently had trouble reaching much more than 60 per cent of its design capacity.

A team was set up to define and develop corrective action plans to address the mechanical reliability and integrity of the reactor and regeneration components of the unit, as well as process improvement.

Using a Sadaf model involving simulation, mathematical models, plant behaviour and run data, along with evaluations of safety and operability, the circulation of the catalyst and the separation of gas and solids in the reactor overhead stream were identified as potential factors affecting the reliability and production capacity of the unit.

A total of 24 individual projects were, according to the company, identified to remove flaws and enable the plant to reach full capacity.

A major initial objective was to improve the circulation of the catalyst, said one project official. It was discovered that the reduced circulation was a result of erosion and catalyst problems, so, adopting Shell technology and design, transfer lines were modified.

This action improved catalyst circulation dramatically, improved production and reduced the associated erosion problems.

The second major objective was the improvement of the separation of gas and solids, achieved by the modification and replacement of the cyclone system within the reactor.

The MTBE reactor is 54m high and the cyclones are suspended from a dome at the top of the reactor.