Behaviour of agglomerates formed by liquid injection in fluidized beds

Formation of agglomerates in fluidized beds can cause operating problems, such as excessive stripper shed fouling, which can lead to premature unit shut down. The focus of this study is to reach a better understanding of how agglomerates move through a fluidized bed to improve the Fluid Cokers and minimize the risk of agglomerates reaching regions where they cause problems. Two experimental methods were used: first, a Gum Arabic binder solution was injected into a two-dimensional (2D) fluidized bed under conditions that simulate agglomerate formation in Fluid Cokers, and the mass and density of recovered agglomerates were measured; second, a new 2D radioactive particle tracking (RPT) method was developed to track the motion of model agglomerates. The fluidized bed had a steel wall, resulting in significant and non-uniform radiation absorption. The 2D RPT system was, thus, calibrated by placing the source at 290 locations in the bed, for each fluidization velocity. Since bubble flow patterns greatly affect agglomerate motion and segregation, a tribo-electric method was used to determine bubble flow distribution in the fluidized bed. The RPT and liquid injection methods gave similar vertical distributions of agglomerates. The main results were that increasing the fluidization velocity reduced segregation, and larger agglomerates were more likely to segregate. There was a strong correlation between the bubbles and agglomerates flow patterns: establishing an asymmetric flow pattern by injecting more fluidization gas in one side of the bed greatly reduced agglomerate segregation.

Automated summary

This study focused on understanding how agglomerates move through a fluidized bed to improve Fluid Cokers and minimize operating problems. Experimental methods included injecting a binder solution and developing a new radioactive particle tracking method. Results showed that increasing fluidization velocity reduced segregation and larger agglomerates were more likely to segregate. Establishing an asymmetric flow pattern greatly reduced agglomerate segregation by correlating bubble flow patterns.