Effect of Novel Swirling Perforated Distributor on Fluid Dynamic Characteristics of Circulating Fluidized Bed Riser

The present work is associated with Circulating Fluidized Bed (CFB) technology, related to the energy sector. The applications of CFB technology span across wide range of areas i.e. boiler, gasifier, combustor, dryer, etc. In the present paper, CFD simulations using ANSYS-Fluent 14.5 were performed to study the effect of novel swirling perforated distributor on fluid dynamics characteristics like pressure drop along the riser and distributor, suspension density variations along the riser of the Circulating Fluidized Bed (CFB). The simulation results were also used to compare qualitatively and quantitatively the dead-zone formations in the four corners of riser just above the distributor plate for swirl and normal distributor plates. The riser alongwith distributor was modeled using Pro-E 5.0, and it was meshed in ICEM CFD 14.5. Post processing simulations were performed using Fluent 14.5. 3D CFD simulations were performed on the CFB riser of cross section 0.15 m × 0.15 m and height 2.85 m. RNG k-ε model was used for turbulence modeling. Eulerian model with Syamlal-O’Brien phase interaction scheme was used to simulate the two phase flow (air + sand mixture flow). RNG k-ε model was used for turbulence modeling of the flow inside the riser. The RNG turbulence model has a calculation for effective viscosity. Modeling and simulations were performed for normal perforated distributor plate and results obtained were compared with available experimental data. In this way, after validation of computational results, further CFD simulations were performed for novel geometry of swirl distributor plate. It is observed that suspension density (particles’ concentration) was more in the middle and upper region of the riser in case of swirl distributor plate. However, pressure drop across the distributor plate increased in the case of novel swirl distributor plate. The objective of significant reduction in the dead-zone formation just above the normal distributor plate was achieved through novel swirl distributor, which in-turn is expected to increase particles’ participation in combustion which takes place in oxygen rich middle portion of CFB riser and subsequently increases heat transfer rate in the CFB riser.