Assessment of the Effect of Dairy Powder Properties on Lean-Phase Pneumatic Transport: A CFD-DEM Modelling Approach

The design of pneumatic transport for dairy powders depends on multiple parameters: several of them are associated with powder characteristics - such as powder type (e.g., fat-filled milk powders or skim milk powders­), particle size distribution, bulk density, flowability. et cetera - with operating variables - such as solids loading, operating pressure, velocity, and pressure drop - and with the lay-out of the transport line. Essentially, the dynamics of the pneumatic conveying system is dominated by the dynamics of the fluid-particle interaction, the particle-particle interactions and the particle-wall interactions which all are affected by the above system parameters.

In this study, a multi-scale CFD-DEM model was developed and validated with data from a 50 mm diameter pneumatic transport rig based on conveying of cohesive fat-filled milk powder fines. The impact of conveying parameters and the properties of the powder fines on pressure drop and blockage boundary in the rig was analyzed. Pressure drop and local particle volume fractios were measured with the aid of a differential pressure gauge and an optical fibre probe respectively.

The multi-scale model is achieved by dynamically coupling computational fluid dynamics (CFD) for modelling the fluid flow field, and discrete element method (DEM) for modelling the behaviour of the powder particles, referred to as CFD-DEM. The validated CFD-DEM model shows a reasonable accuracy in predicting the system pressure drop and particle volume fraction. The validated model can be used to solve pneumatic transport problems associated with highly cohesive dairy powders.