A CFD simulation was performed to evaluate the performance of a novel multiregime gas–solid fluidized riser reactor that was designed to maximize the propylene yield from the catalytic cracking process. Simulation results of the industrial-scale riser reactor show the coexistence of different regimes in the reactor. Also, both the outlet product compositions and the reaction rate vectors indicate that the cracking reactions mainly take place in the feed injection section. The product quality and distribution demonstrate the superiority of this novel process technology. The results of the CFD simulations are in good agreement with the test run results of a real industrial FCC reactor.
in Wiley Online Library (wileyonlinelibrary.com)Particle characteristics are important factors affecting gas fluidization. In this work, the effects of both particle size and shape on fluidization in different flow regimes are studied using the combined computational fluid dynamic-discrete element method approach. The results are first analyzed in terms of flow patterns and fluidization parameters such as pressure drop, minimum fluidization, and bubbling velocities. The results show that with particle size decreasing, agglomerates can be formed for fine ellipsoidal particles. In particular, "chain phenomenon," a special agglomerate phenomenon exists in expanded and fluidized beds for fine prolate particles, which is caused by the van der Waals force. The minimum fluidization velocity increases exponentially with the increase of particle size, and for a given size, it shows a "W" shape with aspect ratio. A correlation is established to describe the dependence of minimum fluidization velocity on particle size and shape. Ellipsoids have much higher minimum bubbling velocities and fluidization index than spheres. V C 2015 American Institute of Chemical Engineers AIChE J, 62: 62-77, 2016
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