What is the typical fluctuation in bed temperature for each wax oil hydrogenation unit?

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Hello, colleagues! Regarding the wax oil hydrocracking unit, our company’s wax oil hydrocracking facility utilizes hydrocracking technology developed by Shell Global Solutions, with catalysts supplied by Criterion Catalysts & Technologies. The normal conversion rate is over 85%; however, after the catalysts were replaced and regenerated during the maintenance in 2014, significant temperature fluctuations occurred in the reaction bed, with amplitudes reaching up to 5–8 degrees. To prevent the bed from experiencing excessive temperature rise, it is necessary to reduce the conversion rate, which results in a large amount of hydrogenation tail oil being recycled (of course, 20–30 T/h of hydrogenation tail oil is still sent out, rather than full recycling). I would like to know about the operating conditions of the paraffin oil hydrogenation units at various sister companies, whether similar issues have occurred, and if so, what the reasons are and how they were resolved. Or assess the danger of this situation and determine what the likelihood of a \"temperature spike\" is It’s just for discussion and exchange; everyone is free to share their opinions.