Pilot freeze dryers are common in daily life. Air freeze-drying technology, referred to as freeze-drying, is also known as sublimation air drying. Freeze-drying is a specific method of pre-freezing water-containing materials and then subliming them in a vacuum state to obtain air-dried objects. The original biological and chemical properties of the freeze-dried objects are basically unchanged, and they are easy to be stored for a long time. After being soaked in water, they can be restored to the form before freeze-drying, and their original biochemical properties can be maintained. Therefore, freeze-drying technology is widely used in various fields such as industrial chemistry and medical equipment. However, many people are not very clear about how to use it specifically, and they are not very aware of the precautions. Next, let us learn more about the pilot freeze dryer. First of all, let's take a look at how it works and get ready to work.
Before use, place the object to be air-dried in a low-temperature refrigerator or liquid nitrogen to make the object freeze solid, and then freeze-drying can be performed. The main engine and the vacuum pump are connected with each other by a vacuum tube, and standard clamps are used at the connection. The clamp contains a sealing rubber ring. Before connecting, apply an appropriate amount of vacuum grease on the rubber ring, and then clamp it with the clamp. There is a power socket for the vacuum pump on the right-side panel of the main unit, and the power cord of the vacuum pump is connected well. Check the vacuum pump to confirm that the vacuum pump oil has been filled, and it cannot be run without oil. The oil level should not be less than the centerline of the oil mirror. The "o" type sealing rubber ring above the cold trap of the main unit should be kept clean. When using it for the first time, a thin layer of vacuum grease can be applied. The plexiglass cover is placed on the rubber ring and rotated a few times, which is conducive to sealing.
The main methods of pressure control of the pilot freeze dryer are: ① the control method of the septum valve; ② the control method of the water vapor condenser; ③ the control method of the small butterfly valve; ④ the aeration method.
1. Metoda kontrole ventila septuma
Odnosi se na svrhu kontrole tlaka podešavanjem-površine poprečnog presjeka prolaza između kutije za sušenje i kondenzatora vodene pare pilot-liofilizirajućeg sušača kako bi se povećao parcijalni tlak vodene pare u kutiju za sušenje.
2. Metoda upravljanja kondenzatorom vodene pare
Odnosi se na način rada u svrhu kontrole tlaka povećanjem površinske temperature kondenzatora vodene pare kako bi se smanjio njegov kondenzacijski kapacitet, što rezultira povećanjem parcijalnog tlaka vodene pare u kutiji za sušenje.
3. Metoda upravljanja malim leptir ventilom
Svrha regulacije tlaka u kutiji postiže se povremenim otvaranjem ili zatvaranjem ventila između kondenzatora vodene pare i vakuumske pumpe. Metoda upravljanja malim leptir ventilom kontrolira otvaranje i zatvaranje ventila signalom koji se šalje iz upravljačkog sustava. Kada je tlak veći od zadane vrijednosti (to jest, stupanj vakuuma je prenizak), ventil se otvara; kada je tlak niži od zadane vrijednosti (to jest, stupanj vakuuma je prenizak) visok), zatvorite ventil. Međutim, ako je temperatura kondenzatora u ovom trenutku vrlo niska, temperatura police proizvoda također je vrlo niska. Zbog usporavanja brzine sublimacije parcijalni tlak vodene pare nastavlja opadati. U ovom trenutku, tlak u pilot-sušilici zamrzavanjem je niži od zadane vrijednosti. Međutim, budući da ova metoda ne može povećati unutarnji tlak, ne može se postići svrha podešavanja tlaka.
4. Metoda aeracije
Metoda rada uvođenja sterilnog zraka ili dušika u kutiju za sušenje kontroliranjem unosa zraka kroz mikro-kontrolni ventil. Ova metoda se obično koristi u stvarnoj proizvodnji, ali ima i određene nedostatke:
①Since the introduction of mostly non-condensable gas (air or nitrogen), the existence of this gas reduces the effective condensation area of the condenser, which makes the condenser prone to ice blockage, and the introduction of nitrogen will also increase the cost.
②Because the gas is introduced from the outside, the cleanliness of the gas directly determines the quality of the product, which is easy to cause pollution and cause the product to have hidden dangers in quality and safety.
③With the alternation of air aeration and high vacuum, the products with a lighter texture and less filling volume are constantly reciprocating up and down. During this process, the friction between the product and the bottle wall makes the formed product into powder. And being taken away not only affects the loading and content of the product but also affects the appearance of the product.
④Due to the direct introduction of gas from the filling room, the normal fumigation and disinfection work in the clean area cannot be carried out, and there are two identical ones that cannot be accelerated, thus hindering the production progress. Although the above methods can achieve the purpose of pressure control, they all have various disadvantages. The degree of vacuum is directly determined by the vacuum pump, so it is recommended to start with the vacuum pump, study the variable frequency vacuum pump, and then automatically control the switch and running speed of the pump through the indoor pressure, so as to fundamentally solve the problem of pressure control. At the same time, due to the power of the vacuum pump being Smaller, it can also save energy.
