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The conditions of the freeze dryer drying stage

Freeze drier in the sublimation drying time length and the thickness of the product varieties and repackaging and provide heat for sublimation, in product variety and repackaging thickness is set, if you want to shorten the time, ensure the quality, the accelerating heat transfer must begin. Freeze drying machine of the shelf is the source of products for heat, pressure and the casing is the product get heat environmental conditions.

for a long time, the lack of interaction between enterprises, always thought freeze-drying box, the lower the pressure, the better, in fact not the case. Low pressure is advantageous to the product inside the sublimation of ice, of course, but if the pressure is too low, is adverse to the heat transfer, the product is not easy to get heat sublimation rate reduce instead. When the pressure is too high, the product inside the sublimation of ice speed slow down, the product will reduce heat absorption, so the product of the temperature rise, when the temperature is higher than the eutectic point, product melting freeze-dried failure will occur.

so what kind of pressure is more appropriate, experience has shown that the pressure of freeze-drying box in 10 ~ 30 pa, to facilitate heat transfer, and sublimation. But the pressure will be strictly controlled within the range, can't do without a good freeze drier. In desorption stage, the products within the frozen ice no longer exists, thus it can be to set the product temperature rise quickly to the highest temperature, is helpful to reduce the residual moisture content of the products already so, also can shorten the desorption drying time. Theoretically, once finished products within the frozen ice sublimation, dry products entered the understanding stage, but in practice, how to define the product of two drying process, it is hard to grasp. In addition, when to rapidly improve product temperature, to minimum the influence of glass bottle, should also be taken into consideration. After many experiments to explore, we basically identified, under normal circumstances, the product to arrive at 0 ℃ has entered the stage of understanding dry absorption; In 0 ℃

above even temperature rising rapidly, the impact on the glass bottle is also relatively small. To ensure the product quality, the lyophilization in the whole freeze-drying process operation is coming to an end before the pressure test is necessary. Specific method is: close freeze-drying box and condenser, the valve between the observed pressure, freeze-drying box if freeze-dried pressure has no obvious rise in the oven, drying has been basically completed, freeze-drying can be ended; If the increased pressure and water escape, still need to continue dry, until the test again, the pressure has no obvious rise. Generally within 30 to 60 seconds after closing valves, pressure rise no more than 3 ~ 8 pa, moisture content of the product is usually about 0. Between 4% ~ 2%. Before the products out of the box, the temperature in the cabinet is the best reply to room temperature, which can avoid the products out of the box after moisture absorption cooling, on the other hand will not cause large fluctuations to room temperature.

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