Laboratory liquid nitrogen preparation machine

1、 Working principle

Laboratory liquid nitrogen preparation machineThe basic workflow includes five stages: air compression, air purification, cooling, separation, and liquefaction

Air compression: The ambient air is first drawn into an air compressor and undergoes multi-stage compression to increase the pressure (usually 5-10 bar), providing the power foundation for subsequent processing.

Air purification: Compressed air contains impurities such as moisture, oil, carbon dioxide, and dust. It needs to be deeply purified through multi-stage filters (such as pre filters, activated carbon filters, molecular sieves, etc.) to prevent impurities from freezing and blocking the system at low temperatures.

Cooling and heat exchange: The purified high-pressure air enters the heat exchanger and undergoes heat exchange with the low-temperature nitrogen gas flowing back, gradually cooling down to near the liquefaction temperature (about -196 ℃).

Air separation: Utilizing the different boiling points of various components in the air (mainly nitrogen 78%, oxygen 21%, argon about 1%), separation is achieved in a low-temperature distillation tower. The boiling point of nitrogen (-195.8 ℃) is lower than that of oxygen (-183 ℃), so during the distillation process, nitrogen evaporates first and accumulates at the top of the tower, while oxygen accumulates at the bottom of the tower.

Liquefaction and storage: The separated high-purity nitrogen is further cooled and liquefied, and stored in low-temperature Dewar tanks or storage tanks for user use.

The entire process is usually based on low-temperature refrigeration cycle theories such as Lind cycle or Claude cycle, and some models also incorporate expander technology to improve energy efficiency.

2、 Main types

According to different production capacity, structure, and application scenarios, liquid nitrogen preparation machines can be divided into the following categories:

Small laboratory type: The daily output is usually between 10-100 liters, compact in size, suitable for use in universities, research institutes, or small medical institutions, and can be directly placed in the laboratory.

Medium sized industrial type: with a daily output of 100-1000 liters, suitable for small and medium-sized food processing plants, electronic manufacturing plants, or biological sample banks, often equipped with automatic control systems and remote monitoring functions.

Large scale centralized gas supply type: With a daily production capacity of thousands or even tens of thousands of liters, it is commonly used in large chemical plants, steel enterprises, or liquid nitrogen distribution centers. It is usually integrated with an air separation unit (ASU) and has the ability to operate continuously and stably.

In addition, according to the cooling method, it can also be divided into:

Throttle expansion type: simple structure, low cost, but low efficiency;

Turboexpander type: using gas expansion to do work for refrigeration, with high efficiency, suitable for large and medium-sized equipment.

3、 Key technologies

Efficient molecular sieve adsorption technology: used for deep removal of water vapor and carbon dioxide, ensuring that the system does not freeze or block at low temperatures.

Low temperature distillation tower design: using regular packing or high-efficiency trays to improve separation efficiency and product purity (usually up to 99.999% or more).

Intelligent control system: integrating PLC or DCS system to achieve fully automatic start stop, fault diagnosis, energy consumption optimization, and remote operation and maintenance.

Insulation and cooling technology: using vacuum multi-layer insulation (MLI) or pearl sand filling methods to minimize liquid nitrogen evaporation losses.

Energy saving optimization algorithm: Reduce unit liquid nitrogen energy consumption through frequency conversion control, load regulation, and residual cooling recovery.

4、 Application scenarios

Medical and biological fields: used for cryopreservation of cells, tissues, and vaccines; Cryotherapy during surgery also relies on liquid nitrogen.

Food industry: Frozen foods (such as seafood, meat, fruits and vegetables), frozen ground spices, and inert gas replacement in food packaging all require a large amount of liquid nitrogen.

Electronic and semiconductor manufacturing: In processes such as chip manufacturing and LED packaging, liquid nitrogen provides an ultra-low temperature environment or serves as a protective atmosphere.

Research and education: Superconducting experiments, low-temperature physics research, material testing, etc. cannot do without liquid nitrogen as a cooling medium.

Industrial maintenance: used for cold shrink assembly of pipelines, cold treatment of metal parts to improve hardness, and emergency leak sealing.