Mixing of cold and hot particles in a pre-lifting scheme with two strands of catalyst inlets for FCC riser

Abstract

The paper presents a pre-lifting scheme for an FCC riser with two strands of catalyst inlets. The solid volume fraction, particle velocity and the mixing of cold and hot particles in the pre-lifting zone are investigated using optical-fiber and a thermal technique in a large cold Plexiglas model. The heat exchange uniformity is used to quantify the mixing of cold and hot particles under different operating conditions. The whole pre-lifting zone is divided into four regions. The flow characteristics are different in each region, indicating that the particles are redistributed in this proposed pre-lifting scheme. The distribution of heat exchange uniformity shows that the mixing extent of cold and hot particles decreases in the following sequence: the riser entrance region>the central tube region>the bottom region. This may be due to the fact that the cold and hot particles have mixed completely and intensely in the proposed pre-lifting scheme. The mixing of cold and hot particles is quite desirable when the mass flux ratio of cold particles to hot particles is 3:2.