Flow Regime Characterization and Mixing Optimization in Rotary Drum Blenders for Fortified Rice Production

ABSTRACT

Large‐scale micronutrient fortification of staple foods is a crucial public health intervention for addressing micronutrient malnutrition in population. Governments across the world are increasingly turning toward rice fortification as an affordable and widespread solution to this global health challenge. The micronutrients are infused into the fortified rice kernel, which is blended into the normal milled rice, to make the fortified rice. The aim of this study was to evaluate and optimize particle mixing dynamics to ensure uniform blending in a rotary drum blender used for fortified rice production. A single‐fluid level‐set computational fluid dynamics model with granular rheology was used to simulate the dense granular fortified rice flow within a horizontal drum. An advection–diffusion‐segregation (ADS) scalar transport model was coupled one‐way with the flow field to predict segregation index evolution during blending. The combined effect of rotational speed (2–20 rpm), filling degree (5%–40%) and size ratio (0.0028–0.0042) on flow behavior (dynamic angle of repose, active‐layer thickness, and Froude number) of the grains and FRK segregation index (SI). The results showed that flow transitioned from rolling to cascading as rotational speed increased. The ADS model showed that filling degree was a key factor for segregation control. Optimization results indicated that a rotational speed of 9.93 rpm, a filling degree of 21.45%, and a size ratio of 0.0028 provided the lowest predicted segregation tendency (segregation index of 0.016). The results demonstrate that controlled operation within the rolling regime is critical for achieving uniform mixing in fortified rice production.