Oct-2015

Exploiting excess catalyst activity (TIA)

A refinery in the Asia Pacific region has reported an annual $1.5 million increase in ultra low sulphur diesel (ULSD) margin from leveraging excess catalyst activity.

Diane Chamberlin
Criterion Catalysts & Technologies

Article Summary

The 78-bar, 4000 t/d ULSD unit uses Criterion Catalysts & Technologies’ (Criterion) Ascent catalyst system. The unit has been continuously monitored and optimised, and has run smoothly with a stable catalyst system. However, in a competitive climate with low margins, the refiner is always looking for improvement opportunities and recognised that using industry leading catalysts was just one step in delivering maximum value. Consequently, it took advantage of Criterion’s understanding of the entire catalyst system, including site-specific constraints such as hydrogen availability and feedstock options, to increase its ULSD margin.

A projection of the remaining cycle life based on performance monitoring showed that the unit would not reach end-of-run operating conditions at the scheduled change-out time. The weighted average bed temperature was decreasing by less than 0.5°C/month, which gave the refiner the opportunity to use the excess catalyst activity to its advantage (see Figure 1).

An obvious option was to extend the planned three-year cycle length, thereby deferring the cost of catalyst change-out and regeneration, but analysis demonstrated that the additional operating window could be used to greater effect.

Few handles for leveraging higher margins were available. The unit was already operating at maximum intake and there was little opportunity for upgrading heavier feedstocks while continuing to meet product specifications. The best option was to lower the reactor pressure to reduce the hydrogen consumption.

In mid-2014, the reactor outlet pressure was reduced by 10 bar (see Figure 1). This led to a 8.5% weight-on-feed reduction in hydrogen consumption and a 90 kW cut in recycle gas compressor power. An added bonus was a 0.6% weight-on-feed increase in ULSD yield. This slight yield increase is attributed to lower naphtha production, which is believed to be related to less boiling curve shift (as a result of less aromatic saturation), especially at the front end. Shutdown occurred as planned in May 2015.

The refinery reports a total annual margin benefit of $1.5 million from reduced hydrogen and energy costs, and increased yields (see Table 1). This was achieved at no additional cost. Interestingly, although reducing hydrogen consumption was the primary aim, the related modest yield increase accounts for 60% of the financial gain.

This short case study originally appeared in PTQ's Technology In Action feature - Q4 2015 issue.
For more information: Teresa.Brod@CRI-Criterion.com