Modelling and experimental investigation of the full-loop gas-solid flow in a circulating fluidized bed with six cyclone separators

In the literature, there are few reports on the full-loop gas-solid flow in a circulating fluidized bed (CFB) with large scale and complex cyclone arrangement. In this paper, a new approach based on computational particle fluid dynamic (CPFD) method combined with electrical capacitance tomography (ECT) is used to investigate the hydrodynamic behavior of gas-solid flow in a CFB with six cyclone separators in order to improve the design and performance of a large scale CFB boiler. The full-loop CFB system for the simulation includes the CFB riser, cyclone, standpipe and U-loop. Two types of cyclone arrangement, i.e. axis and point based symmetric arrangement, are used for the CPFD simulation and ECT measurements. To validate the CPFD simulation, ECT is applied to measure the solids concentration in the standpipe with eight electrodes mounted on the outside of the standpipe. Key parameters including pressure, solids recirculation flux and velocity profile along different positions based on the CPFD simulation are analyzed and compared with experimental results. The CPFD simulation shows that the gas-solid flow is non-uniform among the six parallel cyclones. The solids concentration of four cyclones at the corner of the riser is higher than that of the others. The location of cyclone as well as the inlet angle of the cyclone needs to be optimized. The study shows that the presented approach based on CPFD simulation and ECT measurements can be used to optimize the arrangement of cyclone separators in a supercritical pressure circulating fluidized bed system.