Small and micro liquid nitrogen machine

Small and micro liquid nitrogen machine is a low-temperature equipment specifically designed for on-site and small-scale production of liquid nitrogen. It is widely used in university laboratories, research institutions, biological sample banks, medical clinics, food processing workshops, and electronic research and development.

　　Small and micro liquid nitrogen machineIt is a low-temperature equipment specifically designed for on-site and small-scale production of liquid nitrogen, widely used in university laboratories, research institutions, biological sample banks, medical clinics, food processing workshops, and electronic research and development scenarios. Compared with large industrial air separation units, small liquid nitrogen machines have the advantages of compact structure, easy operation, moderate energy consumption, and low maintenance costs. They are particularly suitable for users who do not have a large demand for liquid nitrogen but require stable supply and high purity.

1、 Basic working principle

　　Small and micro liquid nitrogen machineEssentially, it is a miniature air separation and liquefaction system that operates based on the fundamental physical principles of low-temperature distillation and gas liquefaction. The entire process can be divided into the following five main steps:

Air intake and compression: Environmental air enters the equipment through the intake port and is pressurized to 5-8 bar by the built-in oil-free or micro oil air compressor. The use of oil-free compression can avoid oil vapor pollution in subsequent systems, which is crucial for high-purity liquid nitrogen.

Air purification treatment: Compressed air is sequentially passed through multi-stage filters (including water separators, precision filters, activated carbon adsorbers) and molecular sieve drying towers to remove impurities such as moisture, carbon dioxide, oil mist, and dust. This step is the key to preventing icing and blockage in the low-temperature range.

Pre cooling and heat exchange: The purified high-pressure air enters the main heat exchanger (usually a plate fin or coiled tube type) and undergoes counter current heat exchange with the low-temperature nitrogen gas flowing back, gradually reducing the temperature to nearly -190 ℃.

Low temperature separation and liquefaction: Air that has been deeply cooled enters the distillation tower (or cold box), and utilizes the difference in boiling points between nitrogen (boiling point -195.8 ℃) and oxygen (boiling point -183 ℃) to achieve efficient separation inside the tower. The nitrogen rich gas is enriched at the top of the tower and further cooled and liquefied through a throttle valve or expander.

Liquid nitrogen collection and storage: The generated liquid nitrogen flows into an internal or external Dewar vessel (typically 50-200 liters capacity), from which users can directly access it. Unliquefied nitrogen gas is discharged as reflux gas after participating in heat exchange, achieving energy recovery.

The entire process is usually based on an improved Linde cycle or a Claude cycle with a turbine expander, and some models also integrate variable frequency control to adapt to different load requirements.

2、 Core components

Air compression system: Silent oil-free piston or screw compressors are commonly used to ensure clean gas and low noise.

Purification unit: includes dual tower molecular sieves (alternate regeneration) and high-efficiency filter groups to ensure the quality of air entering the cold box.

Cold Box: Integrated with core low-temperature components such as heat exchangers, distillation towers, and throttling valves, the entire system is insulated with vacuum insulation or filled with pearl sand insulation.

Control system: Based on PLC or embedded microprocessor, it has functions such as automatic start stop, fault alarm, liquid level monitoring, remote communication (such as Wi Fi/4G), etc.

Liquid storage system: Equipped with a small vacuum insulated storage tank or standard Dewar flask interface, making it easy for users to access flexibly.

Safety protection device: including pressure relief valve, oxygen concentration monitoring, overheating protection, leakage protection, etc., to ensure safe operation.

3、 Technical characteristics and performance indicators

Capacity range: The typical daily output is 10-100 liters of liquid nitrogen, and some high-performance models can reach up to 150 liters per day.

Nitrogen purity: usually ≥ 99.995% (i.e. 4.5N), suitable for most scientific research and medical purposes; Some models can reach 99.999% (5N).

Energy consumption level: The unit energy consumption of the model is about 0.7-1.2kWh/L, significantly better than early products.

Floor area: The overall size of the machine is mostly between 0.5-1.5m ², and it can be placed in a corner of the laboratory or next to a fume hood.

Noise control: The operating noise is generally below 60dB (A), suitable for indoor use.

High degree of automation: supports unmanned continuous operation, and some devices have a "one click start" function.

4、 Typical application scenarios

Life science research: used for cryopreservation of cell lines, stem cells, tissue sections, DNA/RNA samples, etc., to avoid loss of precious samples due to liquid nitrogen supply interruption.

Medical and Assisted Reproduction: In IVF centers, sperm banks, and dermatology cryotherapy, small liquid nitrogen machines provide a stable and clean source of liquid nitrogen.

University teaching experiments: Low temperature demonstration experiments (such as superconductivity and embrittlement testing) in physics, chemistry, materials and other courses can produce liquid nitrogen on site, improving teaching safety and convenience.

Small scale food processing: such as hand frozen ice cream, low-temperature grinding of spices, and preservation of small batches of seafood, without relying on external delivery.

Electronic and Optical Research and Development: Used for cooling infrared detectors, temperature control of lasers, semiconductor testing, and other applications that require temporary low-temperature environments.

Application in the wild or remote areas: In areas without liquid nitrogen supply networks (such as high-altitude scientific research stations and island clinics), small liquid nitrogen machines become key support equipment.