CFD-DEM Coupling Simulation and Cross-Scale Correlation Analysis of a Liquid-Containing Gas–Solid Spouted Fluidized Bed Reactor

Abstract

The effect of liquid addition on the gas–solid flow characteristics in a spouted fluidized bed reactor is investigated from multiple scales using a coupled computational fluid dynamics-discrete element method. First, to address the problem that most studies only consider capillary force, this work proposes a liquid bridge model that includes both the capillary force and viscous force. Then, the microscopic mechanism of liquid action is investigated for multiscale analysis. The microscale study reveals that the increase of liquid content and viscosity will lead to the increase of the liquid bridge strength between particles, that is, the increase of liquid content leads to the increase of the liquid bridge capillary force, while the increase of the liquid viscosity leads to the increase of the viscous force and a decrease in the capillary force, which also causes a reversal of the dominant interparticle forces of the particles. Additionally, the number of liquid bridges and contact points between particles increases due to the increase in liquid content, while both decrease when the liquid viscosity increases. The mesoscopic-scale study finds that more liquid content brings about more large agglomerates and fewer agglomerates. When μ < 50 mPa·s, higher viscosity increases large agglomerates and decreases small agglomerates. When μ > 50 mPa·s, the reverse applies. The macroscale study demonstrates that growing liquid content and viscosity causes a reduction in the bed expansion ratio and the bubble phase volume. With a multiscale analysis of liquid action mechanisms from a microscopic perspective, this work can provide an important reference for the research on liquid-containing systems.

Multiscale Turbulence Characteristics of Gas–Liquid Pressure Fluctuations in an Industrial Quatro Static Mixer

“…Different flow patterns could influence the contact area, mass transfer, and chemical reaction rate of the gas–liquid two-phase, and so on. − As a result, flow pattern identification is of great significance for deeply understanding the comprehensive characteristics of gas–liquid two-phase flow. In recent years, comprehensive research on the pressure fluctuation characteristics of the gas–liquid two-phase in a variety of reactors such as a bubble column, , fluidized bed, − stirred tank, , and static mixer − has been conducted by many scholars. Letzel et al characterized the chaotic characteristics of the fluid in the bubble column by PFS, and the fluid transition from a uniform flow state to a nonuniform flow state could be found quantitatively.…”