Extending capabilities

Refiners everywhere face the challenges of producing fuels that meet increasingly stringent specifications while still remaining competitive. The hydrocracking process can generate added value by converting low-value feedstocks into high-value products. As refiners search for low-investment options to produce clean fuels and help improve operating margins, the hydrocracker can be a valuable asset.

However, hydrocrackers that were state-of-the-art designs 20 to 30 years ago in an environment of relatively low crude oil prices may not be as profitable as recently designed units. For example, uniform gas–liquid flow distribution in the reactor is essential for good catalyst utilisation, but in many older hydrocrackers this technology is less advanced than in newer units.

North Atlantic Refining Ltd, Newfoundland, Canada, faces similar challenges to the rest of the industry. The refinery has a 37,000-barrels-a-day hydrocracker, and, over the years, the need to extend its cycle length and improve the product quality has become evident. With better catalysts and an increased focus on operational issues, the refinery extended the cycle length from nine months in the early 1990s to around three years in the mid 2000s. However, the refinery was experiencing issues with:

• high deactivation rates due to feed contaminants;
• high-pressure drop caused by upstream unit upsets;
• loss of temperature control in the highpressure separator during periods of high ambient temperature; and
• high radial temperature profiles in each of the catalyst beds.
  

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