It is well known that the liquid nitrogen is being used as the refrigerant for cryogenic physics and chemistry, precooling of helium gas to liquefy, heat shield in liquid helium container, cold trap in high vacuum system, precooling of superconducting magnet, experiment of cryogenic power transmission, and low temperature adsorption to purify the gases. Moreover, in space development, liquid nitrogen is used to cool the fuel tanks of the rocket and for all kinds of low temperature environmental testing. But it can be seen that they are special usage in limited research field.
On the other hand, the large scale production of oxygen by the recent remarkable demand in iron and steel making industry has brought the lowering of the gas cost. This trend is promoting extensive utilization of liquid nitrogen not only in special research field but also in ordinary industrial field.
This paper describes many useful methods of liquid nitrogen use in industry such as food, construction, rubber, metals fabrication, crushing, biology and medicine.
In the future, it is supposed that a large amount of liquid nitrogen will be consumed for disposing of waste materials in a point of view to prevent environmental pollution and to reclaim them.
