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The performance of hydroprocessing reactors is determined not only by the catalyst loaded but also by the design of their internals. Shell Global Solutions’ internals technology distributes gas and liquid uniformly, minimises thermal instabilities and maximises reactor catalyst inventory and catalyst utilisation. This is critical for applications with more-stringent product specifications, such as ultra-low-sulphur diesel production as well as for the safety and reliability in high reactive feed applications such as C4/C5 and Pygas hydrogenation in petrochemical plants.

Our anti-fouling trays reduce pressure drop build-up and maximise unit run length. Increased efficiency and technologies to counteract fouling are particularly important when operators are processing increasingly difficult feedstocks.

About the technology

Reactor internals - Figure 1

Figure 1: HD tray technology applies customised nozzles that use the gas flow momentum to disperse the liquid as a mist. This differentiates Shell Global Solutions’ technology from conventional downcomers or bubble caps because the nozzles fully and uniformly wet the entire catalyst surface and make efficient use of the top part of the catalyst bed.

Shell Global Solutions’ reactor internals have continuously advanced through the use of the organisation’s pressurised testing facilities and advanced computer simulations, and experience from Shell Group (“Shell”) and non-Shell refineries and petrochemical plants. The technology is applied to grass-roots units and for replacing lower-performing trays in revamps. To date, our reactor internals have over 20 years of operational experience and have been designed for over 300 applications, most of which have been for customers outside Shell.

Key characteristics and advantages include:

  • a minimum pressure drop;
  • full integration and a lower height, thus a smaller space requirement;
  • no top inert material being required;
  • a robust performance over a wide operating window, including a high tolerance to tray tilt; and
  • a boltless, weldless and ergonomic design that facilitates fast installation, easy maintenance and a shorter turnaround period.

In addition, we provide a total solution for customers through a dedicated design and a range of support services that can include thermocouple advice, complete project management, tray delivery, and on-site installation advice.

Process description

Reactor internals - Figure 2

Figure 2: Advanced computational flow dynamics techniques are used to validate the UFQ design and to optimise quenching and mixing between catalyst beds for maximum elimination of temperature differences.

Shell Global Solutions’ reactor internals can produce 30–50% activity gains through improved catalyst utilisation and extra volume for loading catalyst.

TheThe Shell Global Solutions reactor internals system includes:

  • HD (high-dispersion) trays for highly uniform vapour–liquid distribution and excellent thermal distribution;
  • filter trays to prevent foulants from entering the catalyst beds;
  • UFQ (ultra flat quench) interbed internals for uniform process and quench mixing at the interbeds;
  • catalyst support grids; and
  • compact bottom baskets to help maximise the catalyst volume in the bottom domes.

Performance data

Reactor internals - Diagram 3

Figure 3: The radial temperature differences at the bed outlets before and after retrofitting an HD tray above the top bed.

HD trays can help to utilise nearly 100% of the catalyst inventory, and offer high flexibility of feed rate: typically +50% to –70% for liquid and gas. The installation of such a tray can be achieved in as little as four hours. For a hydrocracker fully equipped with Shell Global Solutions’ internals, the reduction in turnaround length is typically 1–3 days.

UFQ trays help to reduce the radial temperature gradient, typically by a factor of 3–5 compared with a conventional mixer. For a particular residue conversion unit project, a quench load equivalent to 30°C resulted in a radial temperature maldistribution below the UFQ of between 1 and 1.5°C.

Shell Global Solutions’ top-bed filters remove foulants yet take up virtually no space; hence, there is no reduction in catalyst bed volume.

Proof point

Operations at a hydrocracking unit were being hampered by liquid–vapour maldistribution in Bed 1. This resulted in major thermal maldistribution that was transferred to Bed 2 owing to the poor performance of a non-Shell interbed internal. When the original bubble cap distribution tray at the top of Bed 1 was replaced with an HD tray, the radial thermal maldistribution in both beds was virtually eliminated. The average radial temperature difference at the bottom of Bed 1 dropped from 10.6 to 1.6°C, and from 8.0 to 2.4°C at the bottom of Bed 2.

Business value

By using HD trays, refiners may be able to double their cycle lengths. These increased cycle lengths are made possible by slower catalyst deactivation; the lower inlet temperatures required to produce high-specification products; and improved thermal distribution. Anti-fouling trays can help to increase cycle length by up to 200%.