Spray Drying Process for Dairy Powders and Infant/Baby Formulas

The production of dry dairy powders and infant/baby formulas requires extremely sanitary design of the equipment. The system provided must handle a wide variety of difficult flowing and temperature-sensitive ingredients, including vitamins, nutrient additives and even probiotics. In addition, dependent upon the type of process and the processing environment, the equipment must be able to be cleaned by either dry or wet cleaning methods. Coperion pneumatic conveying systems and material handling components are utilized for the transfer of the raw ingredients as well as the final blended/spray dried product prior to packaging. The pneumatic conveying systems include both positive pressure and vacuum, dilute and dense phase.

Powdered infant formula is generally manufactured via dry blending or wet blending with subsequent spray drying. In the spray drying process the pasteurized and homogenized liquid is atomized in the spray dryer chamber. Water is evaporated and then dry powder deposits on the spray dryer bottom, where it is discharged with a sanitary Coperion rotary valve to a fluidized bed. There the product is typically dried further, cooled, sifted and then pneumatically conveyed to storage silos or packaging lines. The outlet air from the spray drying chamber still carries product (fines) which is normally ducted into cyclones and bag filters. From there the product is discharged with sanitary Coperion rotary valves into the fines return line. The fines can either be transported with pneumatic conveying to the fluidized bed or back to the top of the spray dryer for agglomeration purposes. The actual conveying path is selected by the sanitary Coperion WYK diverter valve. Moisture and warm temperatures are conducive to bacterial growth, therefore wet cleaning is normally applied in this process while dry cleaning is often typical in the process after the fluid bed dryer.

The wet cleaning process can require extensive resources. Time and costs can be saved if the washing process can be automated (clean-in-place or CIP). For the past years Coperion has been delivering special components that can be cleaned in the process without need for dismantling. This also reduces the risk of external contamination in the process. Coperion rotary valves are designed such that the rotor stays in the housing and discharges the washing liquids by rotating. Retention-free design including special CIP-gaskets at the inlet and outlet as well at the sideplates assure that no product or liquid remains anywhere. Tests at authorized institutes (EHEDG) have proven that the components are absolutely clean. As an added benefit for food safety, Coperion rotary valves can also be equipped with the innovative Rotorcheck design option, which can detect metal to metal contact between the rotating blades and valve housing, as a function of electrical resistance between the rotating vanes and housing.

The stainless steel WYK diverter valve was specifically designed on the basis of the guidelines of the EHEDG for CIP cleaning of the fines return line or other powder conveying pipes. The conical rotor is switched between conveying tubes via actuator while the diverter is operated in conveying mode. During CIP cleaning the rotor is extracted slightly by a second actuator which allows the cleaning liquid to reach all areas of the inside while the diverter is still closed to the outside. The diverter valve, often installed at positions with limited access, does not need to be opened during or after CIP and yet is thoroughly clean afterwards, which saves time and costs. Today, the WYK is in operation in many dairy and infant formula plants and has become a standard wherever highest hygienic requirements must be fulfilled.