Question
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Changes in feedstocks processed through hydrotreating and hydrocracking reactors may sometimes lead to lower efficiency, such as thermal maldistribution problems and reduced cycle length. Can you report any recent cases, such as distillate hydrotreaters challenged with meeting T95 diesel specifications, where conversion problems were resolved that can be duplicated with other hydrotreating units facing similar challenges?
Mar-2023
Answers
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Charles Brandl, Honeywell UOP, charles.brandl@honeywell.com
Maintaining feedstock composition and quality is extremely critical in hydroprocessing units (whether hydrocracking or hydrotreating), and refiners try to operate their respective unit close to its design conditions. If the feedstock gets heavier in terms of composition, distillation, or contaminants, the unit’s operating severity needs to be increased to meet the target design conversion and product specifications. This, in turn, may impact product selectivity, catalyst life, and/or unit performance. With careful catalyst selection and utilising new and improved process and equipment solutions, existing assets could be fully utilised to deliver overall unit objectives.
We have seen one hydrocracking unit where a refiner wanted to increase the unit capacity and process higher end-point feed than design. Due to increased feed rate and higher severity, radial spread in one of the beds was >25-40°C and was also seen in subsequent cycles due to catalyst volume, which was not effectively utilised. As a result, the refiner had replaced the previous generation internals with UOP’s latest generation reactor internals, and in close collaboration with UOP during start-up the refiner lowered the radial spread to ≤4°C. Lower radial spread resulted in meeting design conversion at lower WABT, which was pivotal for the refiner and provided additional operational flexibility to achieve higher distillate yields until the end-of-run conditions.
Mar-2023
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