Numerical investigation on fluidization characteristics of binary particles in supercritical water fluidized bed reactor under pulsed conditions

Abstract

The fluidization properties of binary particles in a supercritical water fluidized bed reactor (SCWFBR) are numerically investigated based on coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) simulations. The accuracy and effectiveness of the CFD-DEM model is firstly validated via previously published experimental data. Then, the model is adopted to study the effect of flow velocities and sinusoidal pulse on the mixing of the binary particles. Numerical results show that it is effective to promote mixing of binary particles in SCWFBR by introducing external energy pulses, which cannot be achieved by simply increasing the flow velocities without pulses. Compared to high frequency pulses, low frequency pulses are more effective in promoting mixing. Within the parameters considered here, it is also found that the pulse amplitude is almost positively correlated with the effect on the promotion of particle mixing when it is smaller than the fixed flow velocity. In addition, an efficient and economical method based on Fast Fourier Transform (FFT) on the bed pressure drop is given to determine the optimal pulse frequency, which can prevent the waste of manpower and the physical resources from happening. This study can provide technical guidance to achieve optimal mixing of binary particles in SCWFBR and offer theoretical support for the design and optimization.