Purpose of MixingPowder HandlingWhich mixer do I choose?Mixing MechanismsPowder mixing: technologiesTumbler Mixers (Diffusive)Convective MixersFluidized MixersCombinations of convective & diffusiveVertical axis or horizontal axisBatch or ContinuousMixer Selection - A Step-wise ApproachSegregation can happen in all process steps and equipmentProcessing Of PowdersGranulationSpray DryingExtrusionHigh Shear GranulationLow Shear GranulationProcess model for Savoury mixingCombination of high and low shearMixing – key parameter & challenges
Processing Foundation Module 2: Powder mixing & Granulation Powder Processing & Mixing Raw Material Storage Processing & Mixing Intermediate/ Finished Product Storage Filling & Packing Powder Transport • Scales of Scrutiny • Mixing Mechanisms • Choice of Mixer • Granulation Mechanisms • Choice of Granulator • Spray Drying The purpose of a mixing operation is that the process as a whole leads to an internal structure of acceptable quality. Thus the feeding of material to the mixer, the behaviour of the mixer itself plus that of the equipment downstream of the mixer need to be understood. Purpose of Mixing • Question 1: What is the mixer meant to do? •Answer: Produce a good mix. •Question 2: So what do you mean by “good”? Purpose of Mixing Ideal Mixing Even Ingredient Distribution Even dosing into pack Reproducible Product Why Mixing? Degrees of Mixing Ideal Mix Good Random Mix M = 1 M = 1 M = 0.125 M = Mixing Index CT = Concentration in Top 1/4 of bed Poor Random Mix Concentration Average CT M = Powder Handling Scales of Scrutiny • Must be appropriate for the system • In most cases is the anticipated minimum dosage size • No benefit in trying to achieve good mixing below this • minimum scale of scrutiny Powder Handling Scales of Scrutiny Ideal Mix Sample size = 4 Sample 1: 50%w, 50%b Sample 2: 50%w, 50%b Sample size = 4 Sample 1: 75%w, 25%b Sample 2: 25%w, 75%b Good Random Mix Powder Handling Scales of Scrutiny Ideal Mix Good Mix Sample size = 100 50% black 50% white Sample size = 100 50% black 50% white Powder Handling Unit Operations – Module 2 Which mixer do I choose? . scrutiny Powder Handling Scales of Scrutiny Ideal Mix Sample size = 4 Sample 1: 50%w, 50%b Sample 2: 50%w, 50%b Sample size = 4 Sample 1: 75%w, 25 %b Sample 2: . Processing Foundation Module 2: Powder mixing & Granulation Powder Processing & Mixing Raw Material Storage Processing