Distributions of solids holdup and particle velocity in the FCC riser with downward pointed feed injection scheme

A downward pointed feed injection scheme in which the feed jets contact with the catalysts countercurrently is put forward to improve the nonuniform distribution of solids in the feed injection zone of FCC riser. The radial nonuniformity index (RNI) is used to quantify the nonuniformity in radial distributions of catalyst particles in the new and traditional feed injection scheme. Comparison between the two types of schemes is made. Experimental results show that the particles distribute more uniformly in the initial contact region of oil with catalysts in the downward pointed feed injection scheme. The influence region of feed spray above the nozzles shortens considerably. Based on the axial profile of RNI, the proposed scheme is divided into three subzones. The proper operating conditions and setting angle of nozzles are also given. In addition, the correlations for calculating the distributions of solids holdup and particle velocity are established through which an industrial example are predicted.