While freezing, low conditions of temperature (- 50☌) and atmospheric pressure are maintained in the chamber.įreezing is done at a high rate of 1-3 Kelvin/min facilitating the formation of large ice crystals with large holes. In case the quantity is more, it can be evaporated by using vacuum tray dryers. The quantity of the material to be dried (solution) should be optimum to facilitate complete freezing. Initially, the solution is frozen in cold shelves (1-3) Kelvin/min with solutions) in a mixture of acetone and solid CO 2. Distance between the drying chamber and the condenser must be in such a way that, it equals the mean free path travelled by the vapour molecules. Both the ends of the condenser are connected by the vacuum pump (along with the steam ejector). Internally it consist of a coiled pipe surrounded by a mixture of acetone and dry ice (solid CO 2), in order to maintain the temperature lower than the frozen material. It is present in between the drying chamber and the condenser, and is provided with an inlet for steam (steam jet). A vacuum pipe is connected to the chamber by means of an opening present at the conical top of the chamber. A door is attached for the entry and removal of materials from the chamber. The compression apparatus is placed at the bottom (to carry out the mechanism of compression). Thermally heated trays are installed horizontally in the centre with the help of a holder. It is made of stainless steel which has a conical top and a flat bottom.
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