CONRAD™ Freeze Dryer

To many producers of food and beverage products, freeze drying is attractive as it is a gentle process preserving the product's original shape, color, taste, and nutrients. The CONRAD™ Freeze Dryer makes this happen at a large scale.

The CONRAD™ freeze drying plant is designed for high-volume continuous processing of products such as coffee and tea, fruit and vegetables, meat and seafood as well as prepared meals. The CONRAD™ Freeze Dryer is the heart of most freeze-dried instant coffee factories where is renowned not only for delivering superior products but also for its robust operation.

The drying process

The CONRAD™ process is fully automated and requires only minimal staff for continuous operation. All movement and process parameters are carefully controlled, monitored and logged.

The product is prepared, frozen and loaded onto the CONRAD™ trays to pass through the Freeze Dryer. Everything is weighed to ensure the correct volume on each tray for perfect freeze drying. The trays are loaded into the dryer through an efficient airlock system to an inlet elevator inside the CONRAD™ chamber. When the elevator has a full stack of product trays, the entire stack is pushed into the first drying zone. More stacks follow and in turn pushed through the various subsequent drying zones of the dryer - each adjusted to provide the drying characteristics required. When the trays arrive at the dryer exit elevator they are unloaded, again through an airlock, and the product is emptied from the trays.

The vapor from the freeze drying process is collected on in the special condensers. In order to ensure a continuous process, all CONRAD™ Freeze Dryers are equipped with a Continuous De-Icing (CDI) System enabling automatic de-icing of the condensers without any loss of operating vacuum.

The CONRAD™ Freeze Dryers is equipped with an internal vapor condenser with built-in de-icing system unique to GEA. Compared with external condenser systems, it not only saves space, it is more reliable, does not cause product loss and it uses less energy and thus ensures the best overall equipment efficiency.

Design details

The cabinet: A long cylindrical chamber designed to operate under vacuum. At the front-end (inside the cabinet) there is an elevator for stacking the trays with the frozen product. Each tray enters into the cabinet through a uniquely designed airlock system allowing the trays to enter without breaking the vacuum, which would otherwise have a negative impact on the sublimation process. When the elevator has a full stack, the entire stack will be pushed forward into the first drying zone, where the temperature on the heating plates is adjusted in accordance with the type, composition and water content of the product to be processed.
More stacks are filled, and in turn pushed through the various and subsequent drying zones of the cabinet. The conditions in each zone are adjusted to provide the optimal drying characteristics. When the trays on the stack arrive at the dryer exit, an elevator will unload the trays and, once again, they will pass through an airlock when discharged. The dried product is emptied from the trays and conveyed to the packing room.

Heating plates: Are made of anodized aluminium and placed inside the cabinet in order to provide energy for the freeze drying process. Hot water is circulated through the system to secure an efficient heat transfer to the product. This takes place by radiation. The water temperature can be regulated during the freeze drying process to achieve optimal evaporation laps and avoid overheating of the products. By correct loading into the cabinet, the product trays will be placed between the heating plates for optimal heat transfer. Direct contact between product trays and heating plates must be avoided as the heat can damage the product.

Vapor condensers: Installed in the cabinet in order to condense the sublimated water vapor for Continuous De-icing (CDI). When one of the vapor condensers needs de-icing (typically after one hour), the section is sealed off while the other takes over the condensation function. To melt the accumulated ice, 25 ̊ C water vapor (vacuum steam) will be led into the room.

The water vapor will now condense on the cold icy surface of the condenser and thus melt the ice. In order to restore the de-iced condenser to operating condition, any remaining vapor in the condenser chamber must be condensed by cooling it down until the appropriate operating temperature and vacuum conditions have been reached. A direct switch over when the next de-icing cycle is needed can now be performed without any loss of operating vacuum.

Cold store: The empty trays are conveyed back for refilling with frozen products via an externally combined elevator and convey system.