Freeze Dryer

Freeze drying, also known as lyophilization or sublimation, they are synonymous. Freeze drying is a low temperature dehydrate process that typically used to preserve perishable materials, to extend shelf life, or make the material more convenient for storage or transport. Freeze drying works by freezing the material, then reducing the surround to allow the frozen water(ice) to sublimate.

Freeze dryer and lyophilizer are synonymous names for the same equipment. A freeze dryer executes a water removal process typically used to preserve perishable materials, to extend shelf life or make the material more convenient for transport. Freeze dryers work by freezing the material, then reducing the pressure and adding heat to allow the frozen water in the material to sublimate.

pilot freeze dryer
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Laboratory Freeze Dryer


Lab equipment freeze dryer is the watery element in advance to freeze, then lifted its moisture content under the vacuum state and obtain a technical method of dry goods, freeze-dried article easy to long-term preservation, after adding water can be recovered to form and maintain the original form of biochemical characteristics. For heat-sensitive substances such as antibiotics, vaccines, blood products, enzyme, hormone and other biological products, the freeze-drying technology can display its superiority, more suitable for laboratory the freeze-drying experiment and a small amount of production of the sample.
freeze dryer is divided into four kinds: normal type, gland type, manifold type, manifold pressure cap type, with the function of precool.

Pharmaceutical Freeze Dryer

Pharmaceutical Freeze Dryer removes water from plants and organic compounds while they are in a frozen state. This locks in the freshness of herbs and plants. Their appearance, nutritional content, and potency remain the same as when they were fresh.Freeze drying completely removes water in about 24 hours. No other preservation method comes close to removing water this quickly.

Pilot Freeze Dryer

pilot freeze dryer

The freeze-drying machine is a technical method in which the aqueous article is previously frozen and then the water is sublimated in a vacuum state to obtain a dry product. The freeze-dried article is easy to store for a long period of time, and the water can be restored to the pre-freeze form Keep the original biochemical characteristics, suitable for laboratory samples of freeze-drying experiments and a small amount of production.

Freeze dryer is composed of a refrigeration system, a vacuum system, a heating system, and an electrical instrumentation control system. The main components of in-situ freeze dryer are drying box, condenser, refrigeration unit, vacuum pump, heating / cooling device, etc. Freeze dryer’s working principle is to freeze the articles to be dried below the triple point temperature, and then sublimate the solid water (ice) in the articles directly into water vapor under vacuum conditions, remove them from the articles, and make the articles dry.

Food Freeze Dryer


Vacuum freeze drying is the use of physical sublimation principle, in a high vacuum environment, the frozen food in the water (ice) without melting, directly sublimation from ice to steam, so vacuum freeze drying is also known as freeze sublimation drying.

Vacuum freeze drying is the use of physical sublimation principle, in a high vacuum environment, the frozen food in the water (ice) without melting, directly sublimation from ice to steam, so vacuum freeze drying is also known as freeze sublimation drying.Freeze dryer is use Imported compressor, stable and reliable performance;Widely used in food, biological products, chemical, Chinese medicine, health products and other fields.

The Principles of Freeze drying

Freeze -drying is carried out using the principle of sublimation drying technique , the material to be dried is frozen rapidly at low temperature , and then under the appropriate vacuum , so that the sublimation of frozen water molecules directly into a steam escape process. Frozen the product was dried to obtain a lyophilisate called (lyophilizer), the process is called lyophilized (lyophilization).

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Always in substance before drying at low temperature ( frozen ) , and ice crystals evenly distributed in the material , the sublimation process does not occur due to dehydration concentrated phenomenon , avoiding the side effects produced by vapor bubble oxidation. Dry material was dry porous sponge , is essentially the same volume , highly soluble in water and restitution. Prevention of dry matter in the physicochemical and biological variability maximum extent .

Freeze-drying machine is from the refrigeration system, vacuum system , heating system, electrical instrumentation control system components. The main part of the oven , a condenser , refrigeration units , pumps, heating / cooling devices . Its working principle is to be freeze -dried items to the triple point temperature, and then the articles under vacuum solid water ( ice ) sublimate directly into water vapor , are excluded from the article, the article dry. After the materials are processed before being sent to the freezing of frozen positions , and then into a dry warehouse sublimation dehydration , after the post-processing plant packaging. Vacuum sublimation drying warehouse system established low pressure conditions, the heating system to provide the latent heat of sublimation materials , refrigeration systems to provide the required amount of cold and dry ice condenser chamber . The device uses highly efficient radiant heating , the material is heated evenly ; efficient use of water-cooled trap to catch , and to achieve rapid defrost ; adopt efficient vacuum unit , and to achieve oil-water separator ; centralized refrigeration system using parallel , multi-channel on-demand cooling, working conditions stable , favorable energy efficiency ; using artificial intelligence control , high control accuracy , easy to operate.

What steps are involved in freeze drying? 

All required preparatory steps to be done to the product should be done before freezing. Steps such as placing the product in specific shapes for freezing, adjusting concentration or addition of cryoprotectants, etc.
1)Freezing Phase
Freeze Dryer Termperature and PressureFreeze dryers use various methods to freeze the product. Freezing can be done in a freezer, a chilled bath (shell freezer), or on a shelf in the freeze dryer. The freeze dryer cools the material below its triple point to ensure that sublimation, rather than melting, will occur. This preserves the material’s physical form.
A freeze dryer most easily freeze dries large ice crystals, which can be produced by slow freezing or annealing. However, with biological materials, when crystals are too large they may break the cell walls, and that leads to less-than-ideal freeze drying results. To prevent this, the freezing is done rapidly. For materials that tend to precipitate, annealing can be used. This process involves fast freezing, then raising the product temperature to allow the crystals to grow.
2)Primary Drying (Sublimation) Phase
A freeze dryer’s second phase is primary drying (sublimation), in which the pressure is lowered and heat is added to the material in order for the water to sublimate. The freeze dryer’s vacuum speeds sublimation. The freeze dryer’s cold condenser provides a surface for the water vapor to adhere and solidify. The condenser also protects the vacuum pump from the water vapor. About 95% of the water in the material is removed in this phase. Primary drying can be a slow process. Too much heat can alter the structure of the material.
3)Secondary Drying (Adsorption) Phase
A freeze dryer’s final phase is secondary drying (adsorption), during which the ionically-bound water molecules are removed. By raising the temperature higher than in the primary drying phase, the bonds are broken between the material and the water molecules. Freeze dried materials retain a porous structure. After the freeze dryer completes its process, the vacuum can be broken with an inert gas before the material is sealed. Most materials can be dried to 1-5% residual moisture.

Problems To Avoid While Using a Freeze Dryer

  • Heating the product too high in temperature can cause melt-back or product collapse
  • Condenser overload caused by too much vapor hitting the condenser.
    • Too much vapor creation
    • Too much surface area
    • Too small a condenser area
    • Insufficient refrigeration
  • Vapor choking – the vapor is produced at a rate faster than it can get through the vapor port, the port between the product chamber and the condenser, creating an increase in chamber pressure.

Applications of freeze drying

Freeze-drying causes less damage to the substance than other dehydration methods using higher temperatures. Nutrient factors that are sensitive to heat are lost less in the process as compared to the processes incorporating heat treatment for drying purposes.Freeze-drying does not usually cause shrinkage or toughening of the material being dried. In addition, flavours, smells, and nutritional content generally remain unchanged, making the process popular for preserving food. However, water is not the only chemical capable of sublimation, and the loss of other volatile compounds such as acetic acid (vinegar) and alcohols can yield undesirable results.

Freeze-dried products can be rehydrated (reconstituted) much more quickly and easily because the process leaves microscopic pores. The pores are created by the ice crystals that sublimate, leaving gaps or pores in their place. This is especially important when it comes to pharmaceutical uses. Freeze-drying can also be used to increase the shelf life of some pharmaceuticals for many years.

Pharmaceuticals and biotechnology

Pharmaceutical companies often use freeze-drying to increase the shelf life of the products, such as live virus vaccines, biologics and other injectables. By removing the water from the material and sealing the material in a glass vial, the material can be easily stored, shipped, and later reconstituted to its original form for injection. Another example from the pharmaceutical industry is the use of freeze drying to produce tablets or wafers, the advantage of which is less excipient as well as a rapidly absorbed and easily administered dosage form.

Freeze-dried pharmaceutical products are produced as lyophilized powders for reconstitution in vials and more recently in prefilled syringes for self-administration by a patient.

Examples of lyophilized biological products include many vaccines such as live measles virus vaccine, typhoid vaccine, and meningococcal polysaccharide vaccine groups A and C combined. Other freeze-dried biological products include antihemophilic factor VIII, interferon alfa, anti-blood clot medicine streptokinase, and wasp venom allergenic extract.

Many bio-pharmaceutical products based on therapeutic proteins such as monoclonal antibodies require lyophilization for stability. Examples of lyophilized biopharmaceuticals include blockbuster drugs such as etanercept (Enbrel by Amgen), infliximab (Remicade by Janssen Biotech), rituximab, and trastuzumab (Herceptin by Genentech).

Freeze-drying is also used in manufacturing of raw materials for pharmaceutical products. Active Pharmaceutical Product Ingredients (APIs) are lyophilized to achieve chemical stability under room temperature storage. Bulk lyophilization of APIs is typically conducted using trays instead of glass vials.

Dry powders of probiotics are often produced by bulk freeze-drying of live microorganisms such as lactic acid bacteria and bifidobacteria.

Freeze drying of food

The primary purpose of freeze drying within the food industry is to extend the shelf-life of the food while maintaining the quality.Freeze-drying is known to result in the highest quality of foods amongst all drying techniques because structural integrity is maintained along with preservation of flavors.Because freeze drying is expensive, it is used mainly with high-value products.Examples of high-value freeze-dried products are seasonal fruits and vegetables because of their limited availability, coffee, and foods used for military rations, astronauts/cosmonauts, and/or hikers

Technological industry

In chemical synthesis, products are often freeze-dried to make them more stable, or easier to dissolve in water for subsequent use.

In bioseparations, freeze-drying can be used also as a late-stage purification procedure, because it can effectively remove solvents. Furthermore, it is capable of concentrating substances with low molecular weights that are too small to be removed by a filtration membrane. Freeze-drying is a relatively expensive process. The equipment is about three times as expensive as the equipment used for other separation processes, and the high energy demands lead to high energy costs. Furthermore, freeze-drying also has a long process time, because the addition of too much heat to the material can cause melting or structural deformations. Therefore, freeze-drying is often reserved for materials that are heat-sensitive, such as proteins, enzymes, microorganisms, and blood plasma. The low operating temperature of the process leads to minimal damage of these heat-sensitive products.

In nanotechnology, freeze-drying is used for nanotube purification[19] to avoid aggregation due to capillary forces during regular thermal vaporization drying.

Other uses

Organizations such as the Document Conservation Laboratory at the United States National Archives and Records Administration (NARA) have done studies on freeze-drying as a recovery method of water-damaged books and documents. While recovery is possible, restoration quality depends on the material of the documents. If a document is made of a variety of materials, which have different absorption properties, expansion will occur at a non-uniform rate, which could lead to deformations. Water can also cause mold to grow or make inks bleed. In these cases, freeze-drying may not be an effective restoration method.

In bacteriology freeze-drying is used to conserve special strains.

In high-altitude environments, the low temperatures and pressures can sometimes produce natural mummies by a process of freeze-drying.

Advanced ceramics processes sometimes use freeze-drying to create a formable powder from a sprayed slurry mist. Freeze-drying creates softer particles with a more homogeneous chemical composition than traditional hot spray drying, but it is also more expensive.

A new form of burial which previously freeze-dries the body with liquid nitrogen has been developed by the Swedish company Promessa Organic AB, which puts it forward as an environmentally friendly alternative to traditional casket and cremation burials.

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