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  • I would like to know which are de main strategies (related to WABT of the beds) for operating an hydrocracker unit in order to minimize the catalyst deactivation and extend as much as possible the catalyst life. The unit has three beds: the first one with pretreating catalysts, the second one half preatrating half hydrocracking catalysts and the last one with 2/3 of hydrocracking catalyst and the other 1/3 with isodewaxing catalyst. There are 2 quenches between bed 1 & 2 and bed 2 & 3.

    Jan-2025

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  • Marcio Wagner da Silva, Petrobras, marciows@petrobras.com.br

    The catalyst lifecycle in a hydrocracker relies on some variables like the desired conversion, feedstock quality, LHSV, hydrogen partial pressure, and the catalyst temperature. It's important to know the feed characteristics, especially related to the concentration of polynuclear aromatics (PNA and HPNA) which are the most severe coke precursors on the catalysts which severely reduces the catalyst lifecycle. Regarding the WABT (Weighted Average Bed Temperature), this variable determines the level of contaminants (like sulfur and nitrogen) removal and it's important to reach a balance between the conversion and catalyst lifecycle. According to the literature the temperature rise in the reactor should be controlled under the following limits: 1 - For noble metal catalysts the temperature rise is limited to 17 oC; 2 - For high-activity base metals (focus on naphtha production) the temperature rise is limited to 14 oC; 3 - For catalysts with low zeolite content catalysts (focus on middle distillate production) the temperature rise is limited in 22 oC; 4 - For amorphous catalysts, the temperature rise in the bed is limited to 28 oC; 5 - The maximum bed temperature rise of 28 oC is recommended for the pretreating catalyst bed. These limits are medium values that can vary according to the catalyst supplier and if the main goal is optimizing the lifecycle of the catalysts the operation conditions should allow equal catalyst bed temperatures.

    Jan-2025


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