(36c) Agglomeration in the Spray Zone of a Spray Drier

Instant milk powders have been produced by the dairy industry to give an agglomerated powder with improved dispersibility and flowability compared to standard powders. Agglomeration occurs initially at the top of the spray drier where recycled fines are contacted with milk concentrate droplets. Successful agglomeration depends on particle collision and adhesion followed by evaporative drying to form inter-particle bridges. The process of agglomeration is complex and can be broken down into many micro steps including droplet formation, coating, coalescence and drying. It is difficult to isolate each of these individual steps and still apply it to the industrial situation. A fines curtain and spray device have been designed to vary the relevant physical properties and operating parameters that affect the agglomeration process. This system was contained within a small scale NIRO spray drier to ensure scalability to the industrial process. The effect of concentrated milk and fine powder properties on agglomeration is discussed. Results on the work currently being completed will be presented showing the affects of the ratio of fines to spray on the properties of the agglomerates produced.