Technical terms of freeze drying machine
January 12, 2023
Vacuum freeze drying is also called sublimation drying. The principle is to freeze the material so that the water it contains turns into ice, and then sublimate the ice in a vacuum to dry it.
Vacuum degree: the degree of gas dilution under vacuum is usually expressed by “high vacuum” and “low vacuum”. High vacuum means “good”, while low vacuum means “poor”.
Pressure or intensity of pressure: The force of gas molecules acting on the unit area of the container wall, expressed by “P”.
Ultimate vacuum: The vacuum vessel is stabilized at a certain vacuum degree after being fully pumped, which is called ultimate vacuum. Generally, the vacuum container must undergo 12 hours of gas refining, and then 12 hours of vacuum pumping. Measure every 10 minutes in the last hour, and take the average of 10 times as the ultimate vacuum.
Pumping rate: At a certain pressure and temperature, the gas pumped from the pump inlet in a unit time is called pumping rate, or pumping rate for short. Namely, Sp=Q/(P - P0).
Sublimation surface: The surface on which free moisture sublimates in the state of solid polymerization. It is not only the surface of the ice core, but also the interface between the ice core and the shell of the drying material in the advanced drying process.
Rate of freezing: Within a given time interval, the thickness change of the frozen material divided by the time interval.
Free water: It refers to water that exists in solution in free form and can flow freely
Bound water: Water adsorbed in the lattice gap of solid substances in molecular form or bound to some polar groups in the form of hydrogen bonds.
Sublimation: Vaporization phenomenon that some solids directly turn into gas without passing through liquid state
Supercooling: The phenomenon that liquid materials remain liquid below the theoretical crystallization temperature.
Subcooling: Difference between theoretical crystallization temperature (Tm) and actual crystallization temperature of liquid materials.
Freezing point: The temperature at which crystals begin to precipitate when the solution cools.
Eutectic point: During the freezing process, some components of the mixed solution composed of several substances crystallize and precipitate at the beginning, making the concentration of the remaining solution change. When a certain temperature or temperature range is reached, its liquid and the components in the formed solid are identical, and the solution is called eutectic solution. The temperature or temperature region at this time is called the eutectic point or eutectic region of the solution. Also known as full curing temperature.
Co-melting point: In the process of heating and melting, when the solid mixed solution reaches a certain temperature T, the liquid begins to appear in the solid. This temperature is called the solution co-melting point, or the initial melting temperature.
Freeze-drying curve: In the freeze-drying process, the temperature of the product and the plate layer, the temperature of the condenser and the vacuum degree correspond to the time.
Disintegration: During sublimation, some dried products will lose rigidity and become sticky when the temperature reaches a certain value, the phenomenon similar to collapse is called disintegration.
Disintegration temperature: Temperature at which the product disintegrates during sublimation.
Reciprocating vacuum pump: A mechanical vacuum pump that uses the reciprocating motion of the piston to pump air.
Roots vacuum pump: Mechanical vacuum pump with a pair of synchronous high-speed rotating sole-shaped rotors, which can not be pumped separately. The front stage needs to be equipped with oil seal, water ring and other vacuum pumps that can directly exhaust the atmosphere.
Cold trap: A device placed between a vacuum container and a pump for absorbing gas or capturing steam
Gas ballast valve: A small hole is opened in the compression chamber of the oil-sealed mechanical vacuum pump, and a regulating valve is installed. When the valve is opened and the air intake is adjusted, the rotor turns to a certain position, and the air is mixed into the compression chamber through this hole to reduce the compression ratio, so that most of the steam will not condense and will be discharged from the pump together with the mixed gas. The valve that plays this role is called gas ballast valve.
Outgassing rate: It refers to the rate at which gas is naturally released from the material placed in the vacuum system.
Permeability: It refers to the rate at which gases outside the vacuum system enter the vacuum system through materials.
Main pump: In the vacuum system, the vacuum pump used to obtain the required vacuum degree to meet the specific process requirements, such as the oil diffusion pump in the vacuum coating machine is the main pump.
Backing pump: A vacuum pump used to maintain the backing pressure of a vacuum pump lower than its critical backing pressure.
Roughing pump: A vacuum pump that starts pumping at atmospheric pressure and pumps the system pressure to another vacuum pump to start working. For example, the slide valve pump in the vacuum coating machine is the roughing pump.
Maintenance pump:In the vacuum system, the air volume is very small, and the backing pump cannot be used effectively. For this reason, an auxiliary pump with small capacity is configured to maintain the operation of the main pump, which is called maintenance pump. A small rotary vane pump is equipped at the outlet of the diffusion pump, which is the maintenance pump.
WHO: World Health Oraganization
FDA: the food and Drug Administration
CIP Cleaning in place: The system or equipment shall be cleaned without any movement in the original installation position.
SIP Sterilization in place: Steam sterilization of the system or equipment without any movement in the original installation position.
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