Vexed for years by pressure-drop issues, one refiner was stuck in a 12-month production cycle. Unable to identify the problem, engineers installed specialized internals to add catalyst above the distribution tray. Suddenly, the fouling rate was doubled, reducing the cycle time to six months.
In the midst of yet another skim, the engineers called Crystaphase.
After an overnight analysis, Crystaphase identified the offending foulant as iron sulfide—a fairly common problem. Scanning Electron Microscopy (SEM) imaging confirmed our suspicion that it was entering the reactor as iron naphthenate, a soluble compound. This allowed the iron to bypass the filtration system before precipitating in the catalyst bed. By inadvertently adding catalyst above the distributor tray, the refiner had created a precipitation problem above the main bed.
Since the skim was already in process, we implemented a stop-gap solution—active filtration in a limited space above the catalyst. This would sustain the unit until its next catalyst change. It ran for another ten months and 12 days—a 66 percent increase in cycle length—which was within three days of what Crystaphase predicted. At this point, we configured an active-filtration solution built specifically around their unique precipitation issue.
With the new configuration, the unit ran for 16 months, shutting down for activity rather than pressure drop. The efficiency of the Crystaphase solution allowed additional space for catalyst, further extending the activity life in the unit. These modifications at the second shutdown resulted in a 20-month cycle—four times longer than its lowest benchmark.
After more than a decade of struggle, this unit was clear of pressure drop issues, making better use of the catalyst, and performing to its full potential.
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