Packed bed reactors with counter-current, gas-liquid flows have been considered to be applicable in CO2 capture systems for post-combustion processing from fossil-fueled power production units. However, the hydrodynamics within the packing used in these reactors under counter-current flow has not been assessed to provide insight into design and operational parameters that may impact reactor and reaction efficiencies. Hence, experimental testing of a laboratory-scale spherical ball, packed bed with two-phase flow was accomplished and then a meso-scale 3D CFD model was developed to numerically simulate the conditions and outcomes of the experimental tests. Also, the hydrodynamics of two-phase flow in a packed bed with structured packing were simulated using a meso-scale, 3D CFD model and then validated using empirical models. The CFD model successfully characterized the hydrodynamics inside the packing, with a focus on parameters such as the wetted surface areas, gas-liquid interactions, liquid distributions, pressure drops, liquid holdups, film thicknesses and flow regimes. The simulation results clearly demonstrated the development of and changes in liquid distributions, wetted areas and film thicknesses under various gas and liquid flow rates. Gas and liquid interactions were observed to occur at the interface of the gas and liquid through liquid entrainment and droplet formation, and it became more dominant as the Reynolds numbers increased. Liquid film thicknesses in the structured packing were much thinner than in the spherical ball packing, and increased with increasing liquid flow rates. Gas flow rates had no significant effect on film thicknesses. Film flow and trickle flow regimes were found in both the spherical ball and structured packing. A macro-scale, porous model was also developed which was less computationally intensive than the meso-scale, 3D CFD model. The macro-scale model was used to study the spherical ball packing and to modify its closure equations. It was found that the Ergun equation, typically used in the porous model, was not suitable for multi-phase flow. Hence, it was modified by replacing porosity with the actual pore volume within the liquid phase; this modification successfully accounted for liquid holdup which was predicted via a proposed equation.

The multi zone fluidized bed reactor instantaneously creates several chemical/physical environments in a single reactor vessel. Effective solid circulation across zones can be achieved by tuning the reactor geometries, solid properties, and operating conditions. However, there is limited research for this innovative reactor concept beyond the laboratory scale, among which a better understanding of the complex fluid dynamics, dominating the solid circulation in different zones, is a basis. This work aims to propose a new method to capture the fluid dynamics of a pilot MZFBR by laboratory measurements with validation from theoretical analysis and simulation. Toward this goal, we first performed particle characterizations, and fluidization testing experiments in a laboratory scale fluidized bed reactor and a pilot scale multi zone fluidized bed reactor at ambient conditions to study the development of fluidization regimes. Then we compared the minimum fluidization velocity with argon and air between the experimental measurements and theoretical calculation results and proposed a modified Ergun equation, which better fits our system. Finally, we conducted computational particle fluid dynamics simulations for the pilot multi zone fluidized bed reactor with the Ergun equation and our modified equation and compared the results against previous experimental observations. Simulations display that the prediction of pressure drop in the pilot scale multi zone fluidized bed reactor with the proposed Ergun equation is similar to that of the original equation, with a relative deviation of around 3%. However, the modified equation captured the bubbling fluidization behavior as the experiment, while the Ergun equation predicted a smooth fluidization without any bubbles. The better agreements validated both our workflow of estimating the fluidization behavior in a pilot multi zone fluidized bed reactor from laboratory measurements and the simulation strategy.