Liquid-nitrogen freeze drying machine and control method thereof

Abstract

The invention discloses a liquid-nitrogen freeze drying machine and a control method thereof. The liquid-nitrogen freeze drying machine comprises a freeze drying box and a cold trap, wherein a plate layer is arranged in the freeze drying box, the plate layer is connected with a circulation pump, a liquid-nitrogen heat exchanger and an electric heater, and a coil pipe is arranged in the cold trap, wherein the freeze drying box and the cold trap are connected through a middle separation valve, the liquid-nitrogen heat exchanger is connected with a first electromagnetic valve and a first opening degree regulation valve, the coil pipe is connected with a second electromagnetic valve and a second opening degree regulation valve, and the first electromagnetic valve and the second electromagnetic valve are directly connected with a liquid-nitrogen tank. The liquid-nitrogen freeze drying machine and the control method thereof provided by the invention improve the freeze temperature range and the precision, and improve the heat exchange efficiency.

Description

technical field [0001] The invention relates to a freeze dryer and a control method thereof, in particular to a liquid nitrogen freeze dryer and a control method thereof. Background technique [0002] Vacuum freeze dryer (referred to as freeze dryer) is mainly composed of eight systems: freezing, circulation, vacuum, electrical, hydraulic, pneumatic, water ring, and SIP / CIP. The freezing system is the most important system of the freeze dryer, also known as The heart of the freeze dryer. [0003] At present, the freeze dryer is mainly based on the compressor refrigeration system, and a small amount of liquid nitrogen freeze dryer is also produced, but the utilization efficiency of liquid nitrogen is not high, and the limit temperature is not low, and the cold trap of the freeze dryer is mainly produced indirectly. The Chinese patent number is 200610008269.x, the application date is 2006.02.20, and the patent titled as freeze dryer discloses a freeze dryer, such as figure 1...

AI Technical Summary

Problems solved by technology

[0005] 1) The compressor is a moving part, and the probability of failure during operation is relatively high, especially the longer the use time, the greater the probability of failure, thereby increasing the maintenance cost of the system; 2) The freeze dryer mainly uses two-machine compression Machine refrigeration, the normal evaporation temperature of this refrigeration method should be ≥ -65°C, while the minimum evaporation temperature of the freeze dryer is -75~-80°C, and it runs for a long time, which makes the operation of the compressor extremely unstable and the probability of failure is even higher. 3) Due to the characteristics of freon refrigerants at low temperatures, especially after ≤-50 ℃, the cooling efficiency of the unit is greatly reduced; in addition, if freon refrigerants are used, if they leak into the environment, they will cause damage to the environment and destroy the ozone layer, causing global Warming, and the noise of the compressor is loud when it is running, which also pollutes the environment; 4) Using compressor refrigeration, the temperature of the cold trap of the freeze dryer cannot be controlled, and the reproducibility of the freeze-drying process is limited; 5) Due to the development of the freeze-drying process , the use of organic solvents is increasing. To realize the freezing of organic solvents requires extremely low temperatures. Conventional compressor refrigeration is difficult to achieve this temperature. For example, alcohol needs to be below -121°C to freeze into ice

[0006] The liquid nitrogen freeze dryer currently in use uses liquid nitrogen instead of Freon refrigerant, and still indirectly controls the cold trap of the freeze dryer through heat transfer oil, so that the limit temperature of the cold trap is limited by the limit temperature of the heat transfer oil, which is currently suitable for freeze dryers There is very little heat transfer oil in high and low temperature environments, and generally the low temperature can only reach -80°C

In addition, the indirect refrigeration through heat transfer oil makes the heat intrusion large, and the effective utilization of cooling capacity is low

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