Liquid oxygen is a light-blue fluid with strong paramagnetic qualities. This substance is one of the four states of aggregation of oxygen, and is used in aerospace and chemical industry, as well as in submarines.
The first notable gas liquefaction success belongs to Michael Faraday, in 1845. At that time there remained six gases which could not be liquefied, oxygen one of them. In 1877 in France and Switzerland two scientists, Louis Paul Cailletet and Raoul-Pierre Pictet obtained several drops of liquid oxygen, using different methods, however. For the first time, a measurable amount of liquid oxygen was produced in Poland by professors Zygmunt Florenty Wróblewski and Karol Stanislaw Olszewski in 1883.
Special systems produce liquid oxygen. The substance is not heated to the ambient temperature, but is output in liquid state. Cold is used to liquefy oxygen, cover the loss of cold to the environment and the approach.
Large gaseous oxygen production units use most energy to separate the air, only 10-15% of the energy is used for cooling. Liquid oxygen production systems are different in that most energy (up to 65%) is used for cooling, and the rest is used for separation of air. This is why such systems are only as efficient as their refrigeration cycle.
The equipment for liquid oxygen production is usually designed for one or two pressure process. In the former case, one stream of air is supplied to separation section from the compressor to facilitate separation of air and refrigeration. In a two pressure system part of the air is compressed to 0.6 MN/m2, while the other part is compressed to an even higher pressure.