(493a) A Preliminary Study On Uncertainties in CFD Simulations of a Pilot-Scale Circulating Fluidized Bed Riser

In this work, we present a preliminary study on numerical approximation uncertainties in the CFD simulation of a pilot scale 12-inch circulating fluidized bed riser available at NETL. As the first step of a systematic Uncertainty Quantification (UQ) study, we compare the numerical results of CFD simulations with different numerical settings and configurations including grid and temporal resolution, averaging time for mean flow field, boundary conditions (inflow and wall boundary conditions) and operating conditions (gas flow rate and solids circulation rate) carried out by the open-source CFD code-MFIX. Differences between numerical results are analyzed with respect to axial pressure gradient, solids concentration and solids velocity to estimate the numerical approximation uncertainty in the predicted flow hydrodynamics causing by the aforementioned factors. In addition, the experimental data measured through various experimental techniques are used to compare against the CFD results for validation. Through this exercise the primary contributors to one of the most significant source of total uncertainty in numerical simulations, i.e., numerical approximation uncertainty will be identified and the efforts in the future will be directed to reduce these uncertainties.