The matching between oil and catalyst in a downward pointed feed injection scheme was investigated in a large scale model cold riser. Two new parameters were introduced as relative concentration of feed jets and that of catalyst particles

which an oil/catalyst matching index was calculated from the concentration distributions of feed jets and catalyst particles. Experimental results showed that the downward pointed feed injection quickly covered the whole cross section of the riser and significantly shortened the mixing height of oil and catalysts such that the feed oil and the catalyst particles could contact rapidly and uniformly. According to axial distributions of the oil/catalyst matching index

the feed segment under the proposed new scheme of feed injection were divided into three regions

i.e. the initial contact region

the gas-solid diffusion region and the recovery region. A better matching between oil and catalyst could be obtained through a lower nozzle setting angle α

a higher prelift gas velocity Ur and a moderate jet gas velocity Uj. The optimal operating condition was Ur=4.1 m·s-1

Uj=64.2 m·s-1 and α=30°. Furthermore

the simulation of axial distribution of the average oil/catalysts matching index were performed by combination with experimental data

which could certainly provide some guidance for the design of downward pointed feed injection scheme.