Many refiners have continually revamped and debottlenecked their FCC units to increase feed throughput and improve profitability. Most FCC units are running at a significantly higher feed rate than the original design. With higher throughput, in order to maintain catalyst and vapor velocity in the riser and cyclones, the unit pressure and consequently the hydrocarbon partial pressure need to be increased. Current laboratory methods for evaluating FCC catalysts and additives cannot match hydrocarbon partial pressures in commercial FCC units. One reason is available laboratory testing equipment, such as, ACE and MAT, typically operates at atmospheric pressure. The Davison Circulating Riser (DCR), a pilot plant-scale testing unit, is regularly operated under total pressure similar to commercial FCC units [1]. However, due to the small diameter of the DCR riser, a relatively large amount of nitrogen is needed to lift the catalyst, thus decreasing the hydrocarbon partial pressure. Studies documenting the effect of hydrocarbon partial pressure on FCC yields are scarce.
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