The drying module is designed for continuous operation by utilizing intermediate vacuum chambers functioning as air-locks, cascading individual temperature-controlled vibratory shelves, and a dual ice condenser setup.
Following uniform droplet generation and freezing, the frozen product particles are transferred from the freezing chamber to the drying chamber, shown in Figure 1, through an intermediate chamber. The intermediate chamber, utilizing a dedicated vacuum pump and silicone jacket cooling, allows for transfer between the freezing column, at atmospheric pressure and the drying chamber, under vacuum without impeding continuous operation. The freeze dryer chamber is a pressure vessel that houses the product shelves. Continuous operation dictates controlled movement that allows sufficient resident time for drying. However, it is imperative that the transport be gentle on the product. Thus, here the product is moved at a controlled rate through a cascading shelf stack while drying, using vibratory agitation for transport. A system of vibratory drives is mounted from the outside of the vessel through vacuum seals into the chamber and is mounted to each pair of shelves. The system is used to vibrate the shelves at set frequency and amplitude, to move the product through the drying chamber in a controlled manner, as shown in Figure 2.
Figure 1: Drying chamber with cascading shelves
Figure 2: Product transfer between shelves
In traditional approach to freeze dryers, the product is placed in vials or bulk containments directly onto the shelf. It has been identified that poor thermal contact between the shelf and the containment is the rate limiting resistance to heat transfer in traditional freeze drying. In this technology, the product is in direct contact with the temperature controlled shelves. The drying chamber contents are both agitated and heated to promote rapid sublimation and prevent agglomeration. Each shelf is designed with a serpentine path of channels through which a heat transfer fluid is passed for temperature regulation. Heat exchangers, in series, through which heat transfer fluid is circulated by a pump for each shelf allow for individual shelf temperature control. The pressure control necessary for the freeze drying process is created by using a vacuum pump group mounted on the machine frame.
A second intermediate chamber is utilized downstream of the drying chamber for product discharge. Like the upper intermediate chamber, the lower intermediate chamber can be aerated and pumped down for vacuum as needed to transfer product between the low operating pressure in the drying chamber and at or near atmospheric pressure conditions maintained in the product canister. In traditional freeze dryers, a single ice condenser is defrosted and drained before it can be used again, a process which requires down time. Lynfinity features a dual ice condenser setup allowing continuous operation with condenser change-over during drying, where a condenser can be defrosted, while the other condenser is in use.
Finally, the system is designed for sterile application using clean-in-place/sterilize-in-place technology utilizing nozzles and drainage principles in line with requirements from traditional freeze-dryers currently in production for several decades.