Effect of Raceway Shape and Size on Gas and Fines Flow Behavior in a Packed Bed.

The multiphase flow of gas and fines in a packed bed proves to be an adequate representation that can reproduce various phenomena observed in complex packed bed reactors, such as iron-making blast furnaces, Direct Reduction of Iron shaft furnaces, and coal gasifier. However, most research neglect vital characteristics of these reactors, such as lateral inflow, presence of tuyere protrusion, and the raceway's shape and size, leading to a significant incongruence with the reactor being modeled. The present work incorporates these features into a 2D numerical study of a gas–fines–solid system with validation through experimental studies. The mathematical modeling considers the gas and fines as an Eulerian–Eulerian system with the constant voidage model for the solid phase representing the packing particles. Well-established theoretical relations and correlations are used to determine the inter-phase forces and fines accumulation regions. Particular emphasis is placed on the accurate representation of the raceway formed at the tuyere exit, and three approaches are considered, viz., its absence, a correlation-based prediction, and an iso-stress-based model. The effect of various parameters such as gas inlet velocity, packing particle material, packing particle size, fines flux through the tuyere opening, and fines size is simulated and analyzed in detail with a marked interest in the raceway shape and size and accumulation profiles of the fines which are important parameters in the overall flow characterization. An insight into the physics based on the interaction forces between the phases, which is difficult to obtain experimentally, is offered to explain the change in the shape and size of the raceway and accumulation profile observed as the parameters mentioned above are varied. The results indicate an accurate mathematical model which demonstrates excellent predictive capabilities of the raceway and fines accumulation characteristics. [ABSTRACT FROM AUTHOR]