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Freeze dryer

The freeze dryer is based on vacuum freeze drying technology and is widely used in the fields of medicine, biological products, food blood products, and active substances.

Fundamental of Freeze Dry System

The basic principle of vacuum freeze dry system is based on the three-state change of water. Water has solid, liquid and gaseous states, and the three states can be converted to each other and can coexist. When water is at the triple point (temperature of 0.01℃ and water vapor pressure of 610.5Pa), water, ice, and water vapor can coexist and balance each other.

In the high vacuum state, the sublimation principle is used to make the water in the pre-frozen materials directly sublimate into the ice state to be removed without the melting of ice, so as to achieve the purpose of freeze drying.

Freeze-dried products are sponge-like, no shrinkage, excellent rehydration, and very little moisture. After corresponding packaging, they can be stored and transported at room temperature for a long time.

The Structure of Vacuum Freeze Drying Machine

The vacuum freeze dryer consists of a drying box, a refrigeration system, vacuum system, a media heat exchange cycle system, an automatic control system, a pneumatic system, and an in-place cleaning and disinfection system.

freeze dryer diagram

Structure of freeze dryer  

Vacuum Drying Oven

The industrial vacuum drying oven is a vacuum-sealed low-pressure container. The materials are all made of stainless steel, which can withstand positive and negative pressures and meet the requirements of steam sterilization from the heat sterilizer. In order to meet the sealing requirements, high-temperature and low-temperature resistant silicone rubber is used, and the insulation layer is made of closed-cell elastic thermal insulation materials.

The electric drying oven is mainly composed of a box body, a shelf and a door. The box body is equipped with a pressure gauge, a temperature-measuring resistor, a gas release valve, a gas permeation valve, a safety valve, and a spray inlet connector.

Media Heat Exchange Circulation System

The energy required for cooling and heating of the food is driven by the circulating pump and transmitted to the shelf through the heat exchange medium, and then to the food.

The source for food cooling is provided by the refrigeration system of the dryer dehydrator, and the heating source for food is provided by the heating tank. The switch between cooling and heating is completed by controlling the electromagnetic valve switch of the cold source and the heat source.

When the temperature rises, the steam enters the heating tank to heat the medium. At the same time, the pneumatic three-way regulating valve is used to adjust the mixing ratio of the heat medium from the heating tank and the return heat medium of the shelf, and control the opening and closing of the cooling water solenoid valve of the plate heat exchanger to control the shelf temperature.

Automatic Control System

The system has functions such as freeze-drying curve setting, vacuum pump test and control, media temperature, food temperature water trap temperature control, dry state detection, in-place cleaning and sterilization, automatic protection and alarm functions.

Pneumatic System

Controlling pneumatic valves.

In-place Cleaning and Disinfection System

Used for cleaning and steam sterilization of dry box water traps.

Types of Freeze Dryers

By Structure

bell-jar type freeze-drying machine & in-situ freeze-drying machine

Bell-type Freeze Dryer

This type of industrial vacuum dryer requires manual operation to transfer the material from the pre-freezing chamber to the vacuum freeze-dry chamber when the material is transferred to the drying process at the end of the pre-freezing.

The bell jar type is most used as a lab freeze dryer. Compared with the production vacuum freeze dryer machine for sale, their structure is simpler and the cost is low.

The freeze-drying room uses a transparent glass cover to facilitate the observation of the freeze-drying of the materials.

In-situ Freeze Dryer

The freeze drying chamber and the cold trap are two independent chambers. The shelf in the freeze-drying chamber has a refrigeration function. After the materials are placed in the freeze-drying chamber, the pre-freezing and drying process of the materials does not require manual operation.

The production process of this type of freeze vacuum drying equipment is complicated and the manufacturing cost is high. However, the in-situ freeze dryer is the development direction of the freeze dryer and is an ideal choice for exploring the freeze drying process. It is especially suitable for freeze-drying of medicines, biological products and other special products.

By Function

Ordinary shelf type freeze dryer & multi-manifold type freeze dryer

Ordinary Shelf Type

The materials are packed in bulk trays. This freeze dryer is suitable for Chinese herbal medicine, and powder materials.

Type with capping device: suitable for drying cillin bottled materials. When preparing for freeze-drying, divide the materials into cillin bottles as needed, and freeze-dry the cap after the cap is closed. After drying, the capping mechanism is operated to press the cap tightly, which can avoid secondary pollution, re-absorb moisture, and is easy to store for a long time.

Multi-manifold Type

The use of this lyophilizer needs to connect the flask outside the drying room to dry the material spin-frozen on the inner wall of the bottle. At this time, the flask is connected to the manifold outside the drying box as a container, and the materials in the flask are heated to room temperature. Through the multi-manifold switch device, the flask can be removed or installed at any time as needed without stopping the machine.

The freeze dry machine with pre-freezing function, and the pre-freezing and drying of the materials in the freeze-drying process are all completed on the freeze drying machine. The freeze dryer is highly efficient and saves the cost of low-temperature refrigerators.

Vacuum Freeze Drying Machine

 Vacuum freeze dryer for food SED-DG series

How Does Freeze Dryer Work?

The process steps of freeze drying equipment include three stages: pre-freezing, sublimation and re-freezing. The use of industrial dryer machine can reasonably shorten the freeze-drying cycle of production and has obvious economic value.

Freezing of Products

There are two ways to pre-freeze drugs in the lyophilizer for sale: one is to cool the product and the drying box at the same time; the other is to wait for the shelf of the drying oven to cool down to about 40 ℃ and then put the products into the dryer. The former is equivalent to slow freezing, while the latter is between quick freezing and slow freezing. Therefore, the latter is often used to give consideration to both freeze-drying efficiency and product quality.

Conditions and Speed of Sublimation

Ice can begin to sublime when the saturated vapor pressure at a certain temperature is greater than the water vapor pressure of the environment; the suction and capture of water vapor by the condenser, which is lower than the product temperature, is a necessary condition for maintaining sublimation.

The temperature of the product and condensation is usually 25°C and 50°C. The saturated vapor pressure of ice at this temperature is 63.3Pa and 1.1Pa, respectively, so a considerable pressure difference is generated between the sublimation surface and the condensation surface. At this time, the partial pressure of the non-condensable gas in the system can be ignored, and the pressure difference will cause the water vapor sublimated from the product to reach the surface of the condenser at a certain flow rate and form frost.

Sublimation Freeze Drying process

In the first stage of heating (mass sublimation stage), the product temperature is lower than its eutectic point by a range.

In the large-scale sublimation process, although the temperature of the shelf and the product is very different, because the plate temperature, condenser temperature and vacuum temperature are basically unchanged, the sublimation heat absorption is relatively stable, and the product temperature is relatively constant.

The presence of ice crystals can no longer be seen with the naked eye, indicating that more than 90% of the water has been removed at this time, and the process of substantial sublimation has basically ended. 

In order to ensure that a large amount of sublimation of the whole box of products is completed, the plate temperature still needs to be maintained for a stage before the second stage of heating.

What is a Freeze Dryer Used For?

Biological Products, medicines: such as the preservation of antibiotics, antitoxins, supplies and vaccines.

Biological Tissues and Biological Specimens: such as dry preservation of skin, bones, aorta, heart valves and other marginal tissues used for animal xenotransplantation or allogeneic transplantation; production of various animal and plant specimens.

Nutritional products, especially high-level nutritional products and Chinese herbal medicines: such as royal jelly, honey, pollen, Chinese herbal preparations, etc., the use of freeze dryers is increasing.

Microorganisms and Algae: such as long-term preservation of various bacteria, yeasts, enzymes, protozoa, microalgae, etc.

Drying Machine for Food: such as coffee, tea, meat, fish and eggs, seaweed, fruits, vegetables, seasonings, tofu, convenience foods, etc.

1 application of SED-DG Series Food Vacuum Freeze Drying Machine.jpg

What are the Advantages of Freeze Drying?

The freeze drying method is basically carried out below 0°C, that is, the product is carried out in a frozen state, and generally does not exceed 60°C during drying.

Under vacuum conditions, when the water vapor is directly sublimated, the drug remains in the frozen ice shelf, forming a sponge-like loose porous structure, so its volume is almost unchanged after drying.

Advantages of Freeze Drying Process

1. Many heat-sensitive substances will not be denatured or inactivated.

2. During the freeze-drying process, the growth of microorganisms and the action of enzymes cannot proceed, so the original properties can be maintained.

3. Because the product is dried in a frozen state, the volume of the product is almost unchanged, and the original structure is maintained without concentration.

4. Since the drying process is carried out under vacuum, there is very little oxygen, so some easily oxidized substances are protected.

5. The drying process can remove 95%~99% of moisture, so that the product can be stored for a long time without deterioration.

6. Because the material is in a frozen state and the temperature is very low, the temperature of the heat source for heating is not high, and the normal temperature or low temperature heater can meet the requirements.

Where to Get a Freeze Dryer?

SED Pharma has rich experience in sales of best dryer machine for Labs (such as laboratory spray dryer) or manufacturers in pharmaceutical, food, chemical industry. We also have our own factory that can provide you with complete after-sales service. Welcome to consult! 

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