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Breault, Greggory

Publications and source records attributed to Breault, Greggory.

Validation and optimization of batch and continuous particle separation processes

Recent advances in simulation capabilities coupled with advanced manufacturing can be leveraged to create highly efficient compact reactors with low emissions, low cost, high reliability, and high flexibility for energy conversion. This type of reactor is especially important for conversion of bio-mass, a storable, renewable and fast-growing energy source, considering the distributed nature of raw material and cost of biomass collection and transportation. To achieve this goal, it is critical to developing new process technologies that are significantly more efficient than traditional processes for which the added manufacture provides a fast way of realization and evaluation. Based upon the flagship MFiX multiphase computational fluid dynamic software suite, NETL has developed an Optimization Toolset to facilitate the CFD simulation based reactor design and optimization, and process intensification. This technical report presents the recent development and application of the Optimization Toolset and the framework for process optimization of particle separation in batch and continuous processes. In these processes, a fluidized bed reactor under proper operating condition was used to separate particles of different physical properties. MFiX-DEM simulations were conducted for a batch system to simulate the process covering a wide range of superficial gas velocities from which the optimal operational parameter can be determined through analyzing the system response. After successful demonstration of the framework, a continuous system for particle separation was designed based on CFD simulations. Similar optimization exercises were conducted for the continuous particle separation considering multiple operating parameters. The design was then fabricated in the laboratory through 3D printing for testing. The particle separation performance was carefully measured through high-speed video for particle tracking. Quantitative comparison between numerical results and experimental measurements were conducted for confirmation and validation.

30 DIRECT ENERGY CONVERSION↗

Numerical Simulation and Experimental Study of the Gas–Solid Flow Behavior Inside a Full-Loop Circulating Fluidized Bed: Evaluation of Different Drag Models

Both experimental and computational studies of the fluidization of high-density polyethylene (HDPE) particles in a small-scale full-loop circulating fluidized bed (CFB) are conducted. Experimental measurements of pressure drop are taken at various locations along the bed. The solids circulation rate is measured with an advanced particle image velocimetry (PIV) technique. Bed height of the quasi-static region in the standpipe is also measured. Comparative numerical simulations are performed with a computational fluid dynamics solver utilizing a discrete element method (CFD-DEM). Here, this paper examines the effect of different drag laws used in the CFD simulations through a detailed and direct comparison with experimental data from a small-scale, full-loop circulating fluidized bed. The Hill–Koch–Ladd drag correlation was shown to have good agreement with respect to system component pressure drop and inventory height in the standpipe.

42 ENGINEERING↗

Experimental study and discrete element method simulation of Geldart Group A particles in a small-scale fluidized bed

Geldart Group A particles are of great importance in various chemical processes because of advantages such as ease of fluidization, large surface area, and many other unique properties. It is very challenging to model the fluidization behavior of such particles as widely reported in the literature. In this study, a pseudo-2D experimental column with a width of 5 cm, a height of 45 cm, and a depth of 0.32 cm was developed for detailed measurements of fluidized bed hydrodynamics of fine particles to facilitate the validation of computational fluid dynamic (CFD) modeling. The hydrodynamics of sieved FCC particles (Sauter mean diameter of 148 µm and density of 1300 kg/m3) and NETL-32D sorbents (Sauter mean diameter of 100 µm and density of 480 kg/m3) were investigated mainly through the visualization by a high-speed camera. Numerical simulations were then conducted by using NETL’s open source code MFIX-DEM. Both qualitative and quantitative information including bed expansion, bubble characteristics, and solid movement were compared between the numerical simulations and the experimental measurement. Furthermore, the cohesive van der Waals force was incorporated in the MFIX-DEM simulations and its influences on the flow hydrodynamics were studied.

42 ENGINEERING↗

Investigation of CO 2 capture using solid sorbents in a fluidized bed reactor: Cold flow hydrodynamics

Both experimental tests and numerical simulations were conducted to investigate the fluidization behavior of a solid CO 2 sorbent with a mean diameter of 100 μm and density of about 480 kg/m, which belongs to Geldart's Group A powder. A carefully designed fluidized bed facility was used to perform a series of experimental tests to study the flow hydrodynamics. Numerical simulations using the two-fluid model indicated that the grid resolution has a significant impact on the bed expansion and bubbling flow behavior. Due to the limited computational resource, no good grid independent results were achieved using the standard models as far as the bed expansion is concerned. In addition, all simulations tended to under-predict the bubble size substantially. Effects of various model settings including both numerical and physical parameters have been investigated with no significant improvement observed. The latest filtered sub-grid drag model was then tested in the numerical simulations. Compared to the standard drag model, the filtered drag model with two markers not only predicted reasonable bed expansion but also yielded realistic bubbling behavior. As a result, a grid sensitivity study was conducted for the filtered sub-grid model and its applicability and limitation were discussed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗