Modeling and Simulation of an Oxygen-Blown Bubbling Fluidized Bed Gasifier using the Computational Particle-Fluid Dynamics (CPFD) Approach

Abstract

Fluidized beds are conventional components of many industrial processes, such as coal gasification for energy generation and syngas production. Numerical simulations help to properly design and understand the complex multiphase flows occurring in these reactors. Two modeling approaches are usually adopted to simulate multiphase flows: the two fluids Eulerian-Eulerian model and the continuous/discrete Eulerian-Lagrangian model. Since fluidized beds account for an extremely large number of particles, tracking each of them could not assure to get results within a reasonable computational time. The Computational Particle-Fluid Dynamics (CPFD) approach, which belongs to the Eulerian-Lagrangian models class, groups together particles with similar key parameters (e.g. composition, size) into computational units (parcels). Parcel collisions are modeled by an isotropic solid stress function, depending on solid volume fraction. In this paper, the bubbling fluidized bed (BFB) upstream gasifier of the EU research infrastructure ZECOMIX (Zero Emissions of Carbon with Mixed technologies) has been simulated using a CPFD approach via Barracuda ® software. The effect of different fluidizing agent injection strategies on bed bubbling and mixing, for non-reacting cases, has been studied. The numerical results for a reacting case have been compared to the available experimental data, gathered during the coal gasification campaign. The model has proved to be very useful in the choice of the more efficient injection configuration that assures a more effective contact of the gas with the solid bed and a good bubbling fluidization regime, together with a satisfactory prediction of the outlet gas composition. The numerical approach has turned out to be robust and time-saving and allowed to dramatically reduce the computational cost with respect the classical two fluids Eulerian-Eulerian models.

Numerical Study on Combustion Characteristics of Biogas Cocombustion in a 300MW Coal-Fired Boiler Furnace

“…The increased ξ value corresponds to an elevated flow rate of the injected biogas, resulting in a lower local excess air coefficient near the biogas nozzles. This limits the air available for coke burning, thereby reducing unburned coke reaching the SOFA region. , Consequently, the NO emission concentration decreases with the increased cocombustion ratio ξ across all types of biogases. The fact that the NO emission is inversely proportional to the cocombustion ratio is consistent with the findings of Yang’s work. , …”

CPFD Simulation of Gas-Solid Flow in Dense Phase Zone of Pant-Leg Fluidized Bed with Secondary Air

“…The results supported that the two-dimensional CPFD model could effectively predict the flow pattern of particles near the feed zone. Nardo et al (2018) found that CPFD model could assure a more effective contact of gas with solid bed and a good bubbling fluidization mechanism, and the prediction of the outlet gas composition was satisfactory. Raheem et al (2019) conducted experimental and CPFD numerical research on CFB combustor under cold flow conditions.…”

Effects of Inlet Types and Lengths on the Flow Field of Cyclone Separators

“…The gas-liquid two-phase flow behaviors are extremely complex in a cyclone separator. The structural size plays an important role on the flow field and the separation performance of the cyclone (Gao et al 2020;Nardo et al 2018). Computational Fluid Dynamics (CFD) is an effective technique to explore the complex flow field in a cyclone, and predict the droplet behavior and performance.…”