GB701231A - Improvements in or relating to contacting gases with powdered solids - Google Patents

Abstract

<PICT:0701231/III/1> In a process for contacting gases and solids wherein finely divided solids are continously circulated between separate contacting zones in each of which the solids are maintained as a dense fluidized bed having a dilute phase thereabove, the amount of fines, e.g. below 40 microns lost from the system is compensated by jetting a gas into a dense phase region of the system to break up larger particles to fines thereby maintaining a more smooth operation. The process is particularly applicable to hydrocarbon conversion wherein there is a conversion zone and regeneration zone and catalyst such as silica-alumina or silica-magnesia of 1 to 100 microns size is employed. In Fig. 1, oil to be cracked is introduced through line 1, preferably through a plurality of spaced points, into a transfer line 2 where it meets hot regenerated catalyst and steam from regenerator 12. The mixture of oil vapours, steam and catalyst pass to a reactor 5 and cracked vapours are withdrawn at 7 the catalyst is withdrawn through pipe 11 to regenerator 12 after stripping and is regenerated by steam, and air from pipe 13. The catalyst is discharged into a stand-pipe 3 and thence through valve 17 to a conduit 18 where jets of inert gas such as steam are introduced from pipes 19 of velocities from 500 to 3000 f.p.s. to grind the particles by mutual attrition. The jets may be located at other dense phase regions such as the dense phase beds in the contacting vessels.