What’s a Freeze Dryer? How does a Freeze Dryer work?

Freeze dryer machines are made to create all the necessary conditions that sublimation needs, to process vacuum freeze drying processes. Which can pre-freeze the raw products below its freezing point, and later create vacuum environment to allow frozen water in raw product sublimate directly from solid phase to gas phase. By this, water in raw product success removed and dehydrated.

In in pharmaceutical industry, freeze drying equipment also calls lyophilizer. They are synonymous, there are no differences between.

There are many methods to group the freeze dryers. Generally, there are 2 methods that people use a lot: By application and by production capacity.

Base on application field, they can be divided into Pharmaceutical lyophilizers, Food freeze dryers and General-purpose freeze dryers.

• Pharmaceutical lyophilizers. As its name, mainly to freeze dry pharmaceuticals, especially injectable formulations. Like human or veterinary vaccines, penicillin etc. The main difference between pharmaceutical dryers and others is the vials capping device installed, to enable the vials close after drying finish.
• Food freeze dryers. Fit all kinds of edible products drying, for example, fruit, vegetables, prepared meals, seafood, meat, herbs etc. Some pet food also is freeze dried.
• General purpose freeze dryers, also called tray freeze dryers or shelf freeze dryers. Mainly use to freeze dry products in biological, chemical and dairy industry. Very similar to food freeze dryers, but request extreme system performance and temperature efficiency.

Base on production capacity, they can be divided into lab scale, pilot production scale and production scale.

• Lab scale. Aim to preserve lab samples or small volume trial. Proof the lyophilization possibility and accumulate experimental data. A lab freeze dryer can be either small benchtop unit or a floor type with freestanding body. Capacity less than 10kgs per load.
• Pilot production scale. Capacity less than 50kgs. Aim to check lyophilized products quality and lyophilization process optimize. Prepare for later commercial mass production.
• Production scale. Large machines or plants, that use for commercial and industrial mass production. The final product will directly sell to market, help manufacturers earn revenue.

As mentioned, freeze drying machines works by freezing the material, and then reduce its surrounding pressure to allow the frozen water in the material to sublime directly from solid phase to gas. So, a freeze dryer must have the following functions and accessories of:

• Drying chamber. A pressure vessel that can create vacuum environment.
  Shelves. Installed in drying chamber, main function is load material trays.
• Condenser. Collect vapors that come from raw material.
• Vacuum system. Vacuumize the drying chamber and condenser, and maintain their pressure during whole freeze drying.
• Compressor system. Continuous and stable provide cooling energy to condenser, enable vapor condensing on condenser coils.
• Control system. To control sub-systems, parts and valves working.
• Shelf heating system. Heat the shelves and plates, enable frozen material get extra energy, to speed up the freeze drying.