On-site sampling at industrial fluid catalytic cracking (FCC) plants was performed using a specially designed sampling apparatus. Catalyst and hydrocarbon samples were analyzed. Light hydrocarbons with high volatility are directly entrained out of the stripper by steam, but the high chemical reactivity of hydrocarbons plays a key role in improving the stripping efficiency. The reduction of the amount of soft coke over the catalyst clearly minimizes coke yield, thereby yielding the maximum amount of desirable products. About 23—25 wt % of the products recovered from industrial strippers were investigated. Comparative lab-scale experiments on physical and chemical stripping were also carried out; In the presence of a regenerated catalyst, chemical stripping produces a higher yield of desirable products and less coke at a shorter stripping time. However, the ratio of regenerated catalyst-to-spent catalyst should be optimized to obtain a satisfactory result for an excessive amount of regenerated catalyst leading to hydrocarbon overcracking, which, is not beneficial to the decrease in coke yield.
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