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Permeate Drying – the Process, Application, Dahmes Advantage

Updated: Mar 27


When it comes to dairy processing, handling of whey or milk permeate streams play a vital role in the viability of a plant. Understanding the process of permeate drying is crucial for companies aiming to optimize efficiency and quality in their production. Dahmes is at the forefront of improving this technology, offering cutting-edge solutions tailored to meet the unique needs of each client.

Permeate Drying Systems

The Basics: What is Permeate?

Permeate is derived from Whey produced in cheese processing or UF Skim Milk. The Whey or UF Skim Milk can be further processed with membrane filtration to create Whey Protein Concentrate (WPC) or Milk Protein Concentrate (MPC), and the byproduct of those processes is called Permeate - it is all the milk minerals that permeates the membranes. These products can also be referred to as Whey Permeate or De-Proteinized Whey (DPW), or Milk Permeate, which comes from MPC. Permeates are comprised mostly of lactose and minerals, making it a valuable resource for further processing into feed or food ingredients.

How to Process Permeate

First Steps: Concentrating the Liquid

Following separation with UltraFiltration (UF) to extract WPC or MPC, the Permeate is processed through a Reverse Osmosis (RO) skid to increase the solids to 25-30% of the mass, with the rest being water. The permeate then goes to an evaporator, which begins with a calcium precipitation process, and then concentrates the permeate to approximately 62% or higher solids.

Creating Product Stability: The Crystallization Process

Following evaporation, the lactose is in an uncrystallized, amorphous form. Amorphous lactose can not be effectively dried because it is hygroscopic and will always re-absorb water in the drying and packaging process. Thus, the product must be crystallized to create a stable molecular form that will be a stable free flowing powder. The first step of crystallization is to flash cool the product. This is a crucial step to build a small crystal that is ideal for permeate drying. From there, it enters a series of crystallization tanks for 6-12 hours, where the permeate is cooled and agitated to facilitate the further creation of small crystals.

Dahmes Equipment: Revolutionizing the Drying Process

Following crystallization, the product is fed to the spray dryer with a High Pressure Pump that forces the product through high-pressure nozzles to transform the liquid into small droplets. As the product is atomized, the surface area per mass is greatly increased to efficiently interact with the hot air, and in the case of permeate drying, create enough surface are on the small lactose crystals to carry the remaining minerals through the drying process.

At this point in the drying process, the permeate powder still contains Lactose Beta crystals, which are prone to sticking in the system. This can lead to unwanted shutdowns due to clogged ductwork or cyclones. Dahmes' Ductless Dryer contains an integrated baghouse, eliminating product entrained ductwork and cyclones to create the optimal permeate drying solution.

Final Crystallization: Alpha Crystals and Beyond

When lactose is crystallized out of solution, they can form into either Alpha or Beta crystals. The Alpha crystals are very stable and when dried are not hygroscopic. Beta crystals, on the other hand, are very hygroscopic and if not converted to Alpha crystals will cause the powder to turn to a rock in powder bins or after packaging. In the presence of enough moisture, the Beta crystals will undergo mutarotation into an Alpha crystals, which are not hygroscopic and will not turn into a rock when in a storage bin or packaged into a bag. To facilitate the conversion process, Dahmes provides a crystallization belt after the dryer to convert all remaining Beta crystals into Alpha crystals.

Final Drying & Cooling: The Fluid Bed

The last step in the drying process is to fluid bed dry the remaining product to 96% solids, and cool the powder down prior to storage in a powder bin or packaging. The fluid bed is similar to an air hockey table with a perforated screen that fluidizes the powder. The fluid bed is split into a well-mix zone, a heating zone, and cooling zone, and ensures uniform drying and prevents clumping prior to sending the powder to classification and packaging.

The Dahmes Advantage: Permeate Drying and Beyond

In the competitive landscape of dairy processing, efficiency and quality are paramount. At Dahmes, we pride ourselves as a leader in permeate drying solutions, offering unparalleled expertise and cutting-edge technology. When you work with us, your company can optimize their production processes, maximize product quality, and stay ahead of the curve in today's dynamic market.


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