(335g) Applicability of a Uniflow Cyclone As Third Stage Separator in the FCC-Process

Motivation

Actually the Third Stage Separator (TSS) in a FCC-process is constructed as a standard reverse flow cyclone which can be designed by approved calculation models, as for example by using the model of Barth/Muschelknautz. The FCC-process efficiency mainly depends on the cyclone performance i.e. on its separation efficiency and its pressure loss. The conical shape of the lower separation body of a reverse flow cyclone leads to high tangential velocities and therefore to high erosion which strongly affects its life time. A second cyclone type, which is not yet well investigated, is the uniflow cyclone. Its essential advantages compared to the reverse flow cyclone are its compact construction and its easy integration into pipes. A further advantage is its low pressure loss and therefore its low energy consumption.

Experimental

The experimental testing was performed on 4 uniflow cyclone configurations differing from each other regarding the gas outlet tube diameter and the guide vane angle at the cyclone inlet generating the swirl strength. Figure 1 shows the schematic assembly of the multi uniflow cyclone test facility. The operating conditions have been scaled down from a typical FCC-process.

Results

Figure 2 shows the particle size distribution (PSD) and the fractional efficiency (h(d)) of the multi uniflow cyclone configuration D with an underflow of 3 percent of the main gas flow. The usage of an underflow raises the separation efficiency from 94.8 up to approximately 95.5 percent, Figure 1. The PSD of the used FCC-powder shows an amount of 24 percent fines below 20 microns, Figure 2. Fine particles, leaving the cyclone with the pure gas, have a mean diameter of 2 microns. The fractional efficiency of configuration D allows a complete separation of particles greater than 8 microns at a pressure drop of 7.900 Pa (=1,14 psi).