Abstract: The standpipe-slide valve system is the key component of the downstream flow of the catalyst particles cycle in FCC unit.The complexity of conveying catalyst operation in standpipe lies in the diversity of catalyst flow patterns in standpipe.The calculation method of standpipe-slide valve system in commercial FCC unit and pressure drop equation was introduced. On a 1.0Mt /a FCC unit, the flow direction, catalyst density and velocity distribution of gas and catalyst particles in the standpipe were analyzed by measuring the axial pressure distribution of the standpipe and recording the processing parameters in different operating conditions. According to the flow characteristics of the gas and catalyst particles, the standpipe was divided into three sections, namely, the negative differential pressure degassing section, the negative differential pressure holding gas section and the positive differential pressure gas leakage section. The reasons causing the formation of half pipe flow and effect of gas leakage from slide valve on standpipe pressure distribution were summarized.The results provided theoretical support for the design and operating adjustment of the standpipe-valve system in FCC unit.

Key words: catalytic cracking, standpipe, pressure loss, half pipe flow, gas leakage