Abstract: In view of high and unstable frequency of back flushing of filter of diesel/kerosene hydrocracking unit, filterability of differernt fraction of processed crude oil was tested, and blockage of feedstock filter of diesel/kerosene hudrocracking unit was gathered, then treated and analysised. The results show that, the floccule in diesel/kerosene fraction clogs the filter, and it is difficult to clear away through back flushing. The floccule contains massive ferric ion and phosphate ion, some of inorganic ions, for example,calcium ion,potassium ion,and aluminium ion. Furthermore, it also contains amide group.These substances come from phosphorus-containing fungicides chelated ferrous sulfide in the emulsified oil, which is mixed in processed A crude oil. By taking a series of measures,such as,using cautiously of phosphorus-containing fungicides while emulsion breaking of emulsified oil,prolonging properly storage period of A crude oil mixed with emulsified oil in the petroleum tank,and discharging off separated water,increasing filter elements for enlargement of filter area,high-pressure water cleaning combination with ultrasonic cleaning of clogged filter elements,the frequency of back flushing of filter of diesel/kerosene hydrocracking unit was reduced to 24 h per time.

Key words: floccule, diesel/kerosene fraction, hydrogen cracking, fliter, blockage