Experimental Study Of A Novel Diameter-Changing Riser

With the growing demand on the production of propylene, conventional fluid catalytic cracking (FCC) riser reactors can not fit the multifunctional purpose for the integration of refinery and petrochemical processes. In order to solve this problem, China University of Petroleum developed the two-stage riser fluid catalytic cracking technology for maximizing production of propylene (TMP). The riser of this technology is equipped with an enlarged section at its bottom and multi-injection locations. It is of important academic and engineering value to study the dynamics of gas-solid flow in risers for designing, scaling-up and optimizing risers. The gas-solid flow patterns are different between the novel riser and conventional risers for the reason of the enlarged section and the stratified injection structure, so these conclusions gotten from conventional risers can not applied to the novel riser, and then it is interesting to find effects of the enlarged section and hydrodynamic features of gas-solid flow in the novel riser.The experiment setup is composed of an enlarged section at its bottom and an equal diameter section at its top. The total height of the riser is 8.3m, the diameter of the upper part is 50mm, and the height and diameter of the enlarged section are flexible to be changed. Experiments were carried out using FCC catalyst and air. A calibration of the fiber optic solids concentration probe was carried out. Axial distributions of pressure gradients as well as radial distributions of local solids concentration and particle velocities were studied. Comparison of the dynamics of gas-solid flow was made between the novel riser and a conventional riser. Effects of riser structures on hydrodynamic features of gas-solid flow in the riser were intensively investigated as well. At last, effects of the shape of coil-type inlet were studied on eliminating the bias phenomenon of FCC particles.The experimental results showed that a novel riser with D/d=2, H/D=5, h/H=3/5 is best for the distribution of particles. Compared with the conventional riser, the concentration of FCC particles in the bottom of the novel diameter-changing riser is about 10 times higher. At a certain Ug, the total pressure of the riser is linear to the Gs in either one of these two risers. For the novel riser, larger diameter and height in the changing section can increase the concentration of FCC particles, but if the scale is too large, it would be not conducive to the stability of device operation. Locating the nozzle inlet at the upper section of the expanding section, and appropriately increasing the input air at the bottom of the riser would be benefit for improving its operational flexibility. Increasing Ug or decreasing Gs will lead to more uniform distribution of particles in the riser, but they have different influence on radial particles distribution at different axial heights. Compared with A-type and C-type, B-type is the best coil-type structure for eliminating the bias phenomenon of FCC particles.