When Is Wet Mineral Agglomeration Truly Scaled Up? A Critical Review from Bench Tumbling Tests to Industrial Drums and Granulators

Wet mineral agglomeration is routinely described as “scaled up” when a larger drum, disc, or granulator reproduces an acceptable mean granule size, or when laboratory conditions are converted through geometric or Froude-number similarity. That interpretation is too narrow for mineral systems in which feed particle-size distribution, fines content, mineralogy, pore structure, wetting kinetics, binder delivery, collision mechanics, breakage, and downstream bed hydrodynamics are strongly coupled. This structured critical review evaluates scale transfer from bench tumbling tests to pilot and industrial granulators, with emphasis on iron-ore sinter granulation and ore agglomeration for heap leaching. The evidence base comprises 83 sources: 78 contemporary publications from 2020–2026 and five foundational wet-granulation studies retained to anchor mechanistic scale-up concepts. Sources were retrospectively coded by primary evidence family and inferential role rather than treated as interchangeable evidence. The review shows that matching Froude number may preserve selected flow features while failing to preserve particle-to-equipment resolution, mixing and segregation kinetics, residence-time distributions, spray coverage, collision-force distributions, or specific power. Meaningful correspondence is nevertheless possible when feed state, moisture and binder delivery, filling, residence time, product structure, and downstream response are constrained together. True scale transfer is therefore formulated as a non-compensatory multivariable equivalence problem rather than an equipment-sizing exercise. The proposed AGG-SUVF (Agglomeration Scale-Up Validation Framework) uses six gates covering feed equivalence, wetting and binder distribution, kinematic/dynamic similarity, product-state equivalence, downstream functional equivalence, and uncertainty/robustness. It distinguishes insufficient evidence from demonstrated failure and separates conditionally transferable, functionally validated, and robustly scaled processes. The resulting framework defines the minimum evidence needed to make falsifiable scale-up claims while keeping industrial feasibility—throughput, energy, operability, and control authority—as a separate engineering requirement.