As nitrogen is an abundant gas in the atmosphere, liquid nitrogen is frequently used as a cryogenic refrigerant. The widespread availability of nitrogen means that large quantities can be easily obtained and utilised. It is a critical element of modern human life, used in many applications across society, and in science in particular. In this article we discuss how liquid nitrogen generators work and their key characteristics. [1]
What is a Liquid Nitrogen Generator?
Liquid nitrogen generators consist of a nitrogen gas generator that divides and extracts nitrogen gas from the oxygen molecules in the air. The generator has a cryocooler that is used for turning the nitrogen gas into a liquid by reducing its temperature to below its evaporation point of approx. -195.8 °C (-320 °F) and a vacuum-heat insulated vessel that stores the liquid nitrogen. [2]
How Does a Liquid Nitrogen Generator Work?
Cryoplants typically comprise a pre-treatment, a cryogenic, and a compressor/expander section. During pre-treatment, freezable components which may damage cryogenic equipment — such as water and carbon dioxide — are removed by absorption. Other impurities (such as mercury) may also be removed by catalysis.
In a cryoplant’s liquid nitrogen generator, atmospheric air is pressurized by a compressor and fed into a buffer tank. From the buffer tank, this air is channelled towards a set of filters behind the cryoplant to remove impurities. Any remaining moisture is eliminated by an internal air dryer unit.
This treated air is further channelled towards a Pressure Swing Adsorption (PSA) module. Within this module, a carbon molecular sieve adsorbs oxygen and carbon monoxide molecules in an adsorption bed. Once this bed is saturated, the flow is switched to a second adsorption bed during which time the first bed is purged. Thus, by constantly switching the flow between these two adsorption beds, pure nitrogen gas is obtained and fed into a cryocooler located in a cryogenic storage vessel. [3]
Nuclear Magnetic Resonance (NMR) Spectroscopy
NMR is a critical aspect of molecular structure investigation. It is often used to gain insight into the interaction between molecules in samples such as biological systems. Because NMR signal is dependent on maintaining a steady temperature, liquid nitrogen is often used to facilitate this.
Using an in-house liquid nitrogen generator provides a range of benefits to NMR spectroscopists. The use of a liquid nitrogen generator decreases the safety hazards involved in storage of liquid nitrogen, minimizes operational costs, increases convenience, and lessens the environmental impact of supply. [4]
Liquid Nitrogen Generators for X-Ray Diffraction
In X-Ray diffraction, crystals must be cryo-cooled to increase their data capacity and quality. This process requires liquid nitrogen generators produce a cryogenic N2 stream, allowing crystals to cool throughout their exposure to X-Rays and for rapid cooling and storing of crystals.
Liquid Nitrogen Generators for IVF Clinics
In IVF clinics, embryologists store sperm, eggs, and embryos for fertilization treatments. These tissues are stored in liquid nitrogen at -1960C in vacuum tanks that are constantly monitored. With such precious stock, a reliable supply is key.
Sample Storage
Liquid nitrogen generators make it possible to cryopreserve valuable biological samples stably and securely. Cryopreservation minimizes the threat of microbial contamination or cross contamination with other tissue or cell samples that may be present.
Cold Traps
Liquid nitrogen generators are often used in cold traps that use the cold thimble design. The cold thimble contains liquid nitrogen at -187°C which leads to molecules rapidly condensing in the vapor phase, causing a trapping effect.
Liquid Nitrogen Generators Offer More User-Safety
Using an in-house liquid nitrogen generator enhances safety because the gas is present only in small amounts and at low pressure. The liquified gas is ported directly to the users NMR spectrometer, or to small storage receptacles for simple relocation to the users work site. Conversely, the large high-pressure tanks used for storage of supply deliveries have extremely high pressures and are more prone to leaks or potential explosions.
A More Convenient Option
An in-house liquid nitrogen generator can provide liquid nitrogen for chemists’ investigations 24 hours a day, without requiring user interaction. If a gas tank is used instead, it must be monitored and replaced frequently which can take up valuable manpower and time. Using a liquid nitrogen generator offers a convenient and reliable supply with no loss or contamination frequently experienced through delivered supplies.
CNP Liquid Nitrogen Generators
Asynt stocks a range of Cryogenic Nitrogen Plant Liquid Nitrogen Generators which can generate between 10 to 840 litres per day. They provide purity of more than 99% and an operating outlet pressure of 2 bar. All units come with an 8″ HMI display for easy operation.
Medium Scale Liquid Nitrogen Generators
These generators supplied by Asynt offer easy installation, efficient production, low noise levels, and easy liquid nitrogen dispensing. They have a high production capacity, fast start-up time, and relatively low noise levels.
Large Scale Liquid Nitrogen Generators
These generators are for processes that require large scale liquid nitrogen generation. These instruments can produce up to 3,000 litres of liquid nitrogen per day and can be manufactured to meet your precise requirements.
Asynt offers servicing and maintenance of their liquid nitrogen generators, increasing the length of service and enhances their overall sustainability. This maintenance also increases the reliability and performance of the generators.
On-Demand Liquid Nitrogen Generators
To access liquid nitrogen, organizations traditionally relied on tanker deliveries or expensive storage facilities. By installing Asynt on-site liquid nitrogen generators, organizations avoid the need for transportation or storage, reduce costs, reduce their carbon footprint, and eliminate evaporation or contamination problems. Furthermore, insulated dispensing lines reduce wastage of liquid nitrogen during operation.
Servicing and Maintenance
Asynt offer full servicing and maintenance for your liquid nitrogen generator to give users reliable performance and increase the lifetime of your apparatus.
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[1] Introduction Of Liquid Nitrogen Generator | Vacuum Magazine. (2022). Retrieved 16 March 2022, from https://www.ulvac.co.jp/wiki/en/liquid_nitrogen_generator/
[2] Introduction Of Liquid Nitrogen Generator | Vacuum Magazine. (2022). Retrieved 16 March 2022, from https://www.ulvac.co.jp/wiki/en/liquid_nitrogen_generator/
[3] Cryogenic Plant | Thermopedia. (2022). Retrieved 16 March 2022, from https://www.thermopedia.com/content/677/
[4] NMR Spectroscopy Principles, Interpreting an NMR Spectrum and Common Problems. (2022). Retrieved 16 March 2022, from https://www.technologynetworks.com/analysis/articles/nmr-spectroscopy-principles-interpreting-an-nmr-spectrum-and-common-problems-355891
