Abstract: The main reason for the increase in pressure drop in the fixed bed reactor of three units(A,B,C) was analyzed.The analysis results of the spent catalyst from unit A showed that the deposition of Fe, Ca, and C in the catalyst bed layer led to a decrease in the porosity of the catalyst bed layer, and the pressure drop in the first reactor was increased. The analysis results of the spent catalyst from the seventh RUN of the series I of unit B indicated that the deposition of Fe and C in the catalyst bed led to a decrease in the porosity of the catalyst bed, and the pressure drop in the first reactor was increased. The expansion rate of the catalyst bed in up-flow reactor of the series I of unit C was relatively high in the second RUN, and the top catalyst particles would collide with the Johnson net or outlet collector on the upper part of the catalyst bed, resulting in an increase in pressure drop of the internal components and an increase in pressure drop of the reactor. The dust or finely ground catalyst generated by the friction of the catalyst in the up-flow reactor entered the second reactor, reducing the porosity of the catalyst bed and increasing the pressure drop in the second reactor. Corresponding measures were proposed to delay the increase in pressure drop for different reactors based on their main causes.

Key words: fixed bed, residue hydrotreating, trickle bed reactor, up-flow reactor, pressure drop