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The Model Validation Purpose, Particulate Solid Research, And National Energy Technology Laboratory ( Netl )

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For model validation purpose, Particulate Solid Research Inc. (PSRI) and National Energy Technology Laboratory (NETL) organized the modeling competitions in the form of third Challenge Problem []. By providing the geometry of a circulating bed and operating parameters for different conditions, the organizers asked modelers to predict the hydrodynamic characteristics without prior knowledge of test results. In third Challenge Problem, the CFD models did better than their performance in first and second challenge problems organized by PSRI. One of the issues in model mismatch was the high computational time required to reach the steady state of the fluid bed process. Other mismatch was partly due to modeling only the riser section rather …show more content…

The cycle repeats thus creating a continuous circulation of solid around the loop.
The miniCFB was made out of clear acrylic pieces. Operators can clearly see the dynamics of gas-particle mixing throughout the riser. They can visually record the height of moving solids or bed height in the standpipe. The particles swirl indicating rotational dynamics inside the cyclone is clearly visible during gas solid separation. Researchers may take image of gas-solid interactions at any section of the rig, be it at the interface of the L-valve and riser entrance or at the riser exit and crossover. For instance, a high-speed particle image velocimetry (PIV) using a shadowing technique counted accurate number of falling particles in the lean region of standpipe. The shadowing method gives improved depth of focus enhancing accurate measurement of solid circulation rate at steady state.
The solid circulation rate connects the dynamics of a CFB riser and its return loop. The parameter strongly affects heat and mass transfer between particles and gas, and between particles and particles. It greatly influences the mixing and reaction times, residence time distribution, performance and hydrodynamics of the overall system. The full loop simulation of the DEM model produces the solid circulation rate as the output rather than requiring it as an input. Later case arises when CFD models simulate only a riser portion of the CFB. The precise model of a full

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