(56b) How Fccu Trickle Valves Affect Catalyst Losses

HOW FCCU TRICKLE VALVES AFFECT CATALYST LOSSES

High or abnormal catalyst losses from Fluid Catalytic Cracking Unit (FCCU) cyclone systems are sometimes attributed to plugged diplegs, often believed to be caused by one or more malfunctioning trickle valves. Sometimes, units are shut down and catalyst unloaded to ?clear? a plugged dipleg. This paper will look at the fundamental forces that affect the opening and closing of a trickle valve for both positive and negative pressure cyclones. These forces are caused by the trickle valve design, weight of the flapper or counterweight, and catalyst level in dipleg. The opening and closing forces will be compared for the various types of valves that are widely used on FCCU's. The features of various trickle valve configurations will also be discussed, including the advantages and disadvantages for various applications as well as measures taken to improve their performance, including their erosion resistance.