Dairy Evaporator and Dryer Data

Milk from cows is stored refrigerated at roughly 12% milk solids plus water. To produce shelf stable powdered milk it is dried to roughly 3% moisture (97% solids) normally in two stages evaporation and spray drying. Evaporation is commonly TVR (thermal vapor recompression) where steam is exchanged indirectly with milk fed to an evaporator effect, which produces a higher solids milk liquor and evaporated vapor, which is used to further exchange heat with another effects liquor to increase milk solids effect-by-effect with this reuse of vapor from previous effects. At the final effect evaporated milk at a high solids concentration is achieved (monitored by density) and the final effect vapor. To maximize the utilization of steam that final effect's vapor is condensed to a target stable vacuum pressure with cooling water. All of the condensate from steam and various effect's utilized vapor along with the final condenser are sent to treatment plant prior to discharge or reuse.

The evaporated milk concentrate is fed to a tall-form spray dryer via a high pressure pump, required to both pump the concentrate to the top of a very high tower dryer, but also through a dryer feed nozzle designed to generate small droplets more easily contacted with air for drying (e.g. the high pressure is needed to push through a nozzle that can produce smaller droplets increasing the surface area for drying). In addition normally ambient air is heated to a high temperature and blown into the dryer from the side to circulate those droplets maximizing their time to dry into powder by having them swirl around the dryer internal circumference before dropping to the bottom cone at the bottom of the tower. Air is exhausted from the other side of the dryer in a smaller continuous slip-stream (e.g. air blown in must be in balance with exhausted air). By drying water included with our droplets the air temperature cools (evaporative cooling) and the exhaust air humidity increases.

A second set of dairy dryer and evaporator data is provided for independent exploration if you have completed the primary lab covering features on two gas turbines.