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

• A pre-lifting scheme with two strands of catalysts inlets for FCC is proposed.
• Heat exchange uniformity β is used to quantify the mixing of cold-hot particles.
• The mixing of cold-hot particles zone can be well described by using β.
• The cold-hot particles have mixed completely and fiercely in the pre-lifting zone.

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.

A pre-lifting scheme with two strands of catalyst inlets is proposed. Heat exchange uniformity β is used to quantify the mixing of cold–hot particles. The heat exchange uniformity is uniform and close to 0 at 1.3 m, illustrating that cold–hot particle has mixed completely and fiercely in the proposed pre-lifting scheme.Figure optionsDownload as PowerPoint slide