In 2003, CLG developed a newer class of reactor internals for fixed-bed hydroprocessing reactors. The newer, patented technology called ISOMIX® allows both new and retrofitted reactors to successfully employ new high-activity catalysts with low risk of reactor temperature maldistribution or hot spots often associated with high-activity catalysts. ISOMIX® internals use a uniquely designed mixing box to provide complete mixing, quenching and equilibration between catalyst beds, correcting any catalyst bed temperature and concentration maldistribution, with low pressure drop while using minimal reactor volume.

The second key component of the ISOMIX® internals design is flow nozzles. These high-efficiency spray nozzles provide a more uniform distribution of gas and liquid to the catalyst surface and a greater contacting efficiency. Also, with a good gas-liquid spray, the bed depth needed to achieve uniform and complete wetting is reduced, further improving catalyst usage. The overall result is greater catalyst utilization. The nozzles also give greater tolerance to distributor trays that can be become somewhat out of level.

Nozzles as constructed

There are many installations worldwide that use ISOMIX® internals. Some are in full operation, while others are being built and installed. Chevron’s own and customer-licensed units are getting excellent performance achieving uniform temperatures through catalyst beds and greater utilization of catalyst. In some retrofit applications, activity advantage as high as 10°C was reported.

ISOMIX® internals were included in CLG’s standard EDP packages for all hydroprocessing reactors until the advent of our latest technology innovation in 2011. Since its inception in 2003, ISOMIX® internals were designed for 20 retrofit applications and 40 grass roots applications. These projects are in various stages of design, fabrication, installation and startup. In one retrofit application, the refiner achieved a 10°C activity advantage after installation of ISOMIX® internals. This activity advantage can translate into equivalent capacity increase or in extended catalyst life (approximately one extra year was estimated in this case). The temperature distribution improved significantly, as the following graph from an operating unit shows.

Reactor Bed 3 Top/Middle/Bottom dT




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