Loop seals in circulating fluidized beds - Review and parametric studies using CPFD simulation

Loop seal is a robust particle recycling technique used in circulating fluidized bed (CFB) reactors. The rate and the location of the loop seal aeration exert a significant impact on the rate of particle circulation (G(s)). The standpipe balances the cumulative pressure drop across the rest of the CFB by adjusting its particle height or gas-particle slip velocity. Higher fraction of the loop seal aeration naturally flows down to riser. Increased pressure drop in the standpipe results in high rate of particle circulation. Computational-particle-fluid-dynamic (CPFD) code is customized for multiphase flow modelling. The inbuilt tool of BC connectors was incorporated to downsize a CFB into a loop seal. The simulation results of G(s) and system pressures for loop seal showed a perfect match with experimentally validated CFB model. A parametric study for the effects of aeration rate, aeration position and length of the horizontal section was performed using the developed CPFD model of the loop seal. G s increased proportionally with the loop seal aeration, reaching an approximate threshold at 0.9 Nm(3)/h and beyond that G s did not improve significantly. Uniform aeration from the loop seal bottom realized the highest particle circulation with a 71% increment. The length of the horizontal section of the loop seal exhibited an inverse relationship on the particle circulation. (C) 2020 Elsevier Ltd. All rights reserved.