Abstract
Two modeling approaches, the scaling-law and CFD (Computational Fluid Dynamics) approaches, are presented in this paper. To save on experimental cost of the pilot plant, the scaling-law approach as a low-computational-cost method was adopted and a small scale column operating under ambient temperature and pressure was built. A series of laboratory tests and computer simulations were carried out to evaluate the hydrodynamic characteristics of a pilot fluidized-bed biomass gasifier. In the small scale column solids were fluidized. The pressure and other hydrodynamic properties were monitored for the validation of the scaling-law application. In addition to the scaling-law modeling method, the CFD approach was presented to simulate the gas-particle system in the small column. 2D CFD models were developed to simulate the hydrodynamic regime. The simulation results were validated with the experimental data from the small column. It was proved that the CFD model was able to accurately predict the hydrodynamics of the small column. The outcomes of this research present both the scaling law with the lower computational cost and the CFD modeling as a more robust method to suit various needs for the design of fluidized-bed gasifiers.
Highlights
Fluidized bed reactors are widely used in various industries; their hydrodynamic behavior, crucial, has not been very well understood [1]
Measurements of all necessary parameters are challenging for fluidized bed gasifiers working at high temperatures; it is useful if a model column working at ambient condition generates information required for the gasifier
The densities included 950, 1130, 1350, 1800, and 2200 kg/m3 and the. For both large 2.38, and small columns were measured between the bottom diameters included
Summary
Fluidized bed reactors are widely used in various industries; their hydrodynamic behavior, crucial, has not been very well understood [1]. Scaling laws have been used to construct a small scale model which produces identical hydrodynamic behavior as the large scale fluidized bed system [6–8] For this purpose, scaling methods were developed based on different approaches. Using Buckingham’s Pi-theory and incorporating dominant forces in a fluidized bed system including drag, inertia, viscous and gravity forces, other scaling laws have been developed These scaling laws are based on the concept that generally the ratio of different forces in the two scales should be equal if hydrodynamics are going to be equivalent. Compared to the CFD modeling method, the scaling-law approach is a low-computational-cost method. The calculations can be done quickly and don’t require CFD software and high-performance computation facilities This method is proved to be useful for the scale-up of fluidized-bed gasifier and can provide valuable information for the early stage of fluidized-bed gasifiers such as the conceptual design and preliminary design. Who can afford the cost, the CFD modeling approach as a robust method can be a better choice, because
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