Impurities, fines, gums, scales and inorganic matter that can be carried over with the feed are very often responsible for unsustainable pressure drop issues in the first bed of hydroprocessing reactors. The contamination level is sometimes so high that even the most efficient grading system is not sufficient to limit the pressure drop increase.
Consequently, a skimming of the first bed in the middle of the cycle is needed, causing production and profitability loss for the refiner.
