3) Describe of properties, technology of production and analysis of Argon.

Argon - chemical element VIII of group of the periodic table of Mendeleyev, atomic weight of argon makes 39,948, atomic number 18. Argon is noble gas, also gases of this group are called rare gases. Argon has no color, a smell and taste. Argon the lightest gas in the subgroup. At a temperature of 0 °C and pressure of 101,3 kPa argon has density of 1,784 g/dm3.

Receiving argon. Argon is extracted from the atmosphere of air, this source is inexhaustible. Since argon does not enter chemical reactions that it after use comes back to the atmosphere. Generally argon is received in parallel when receiving oxygen and nitrogen from air. Argon - gaseous clear is delivered in accordance with GOST three grades: the highest, the first and second. Content of argon is respectively equal: 99,99%; 99,98%; 99,95%. As impurity serve oxygen, nitrogen and moisture.

Content of argon in air is quite considerable therefore it is got as by-product, when receiving oxygen and nitrogen from air by method of the low-temperature rectification in express devices.

Argon on a volatility is intermediate between nitrogen and oxygen - principal components of air. The specific behavior of argon is also explained by it at rectification of fluid air. Final division of fluid air into nitrogen and oxygen is made in a column of low pressure of the airdividing device. Distillate of this column is gaseous nitrogen, and the lower product - gaseous or fluid oxygen.

In an upper of a column of low pressure argon acts as tyazheloletuchy (in comparison with nitrogen) a component, and in the bottom - easily volatile (in comparison with oxygen). Existence in a column of low pressure of zones of the increased concentration of argon in both sections of a column - concentration (above input of liquid from the bottom of the column of high pressure) and distant-pasture is explained by it (below input). Distribution of argon on rectifying plates of low pressure is strongly influenced by the third component accompanying it - oxygen. Content of argon in a zone of the increased concentration of the top shell of column increases in process of decrease of content of oxygen in distillate at invariable composition of productional oxygen (it can be reached increase in number of plates in a column). Schematically process of extraction of argon is described as follows. In the beginning air is purified of dust and compresses before a liquefaction. Fluid air is exposed to rectification for the purpose of its division into constituents. Turning out аргоно - nitrogen-oxygen mix (crude argon) then is purified of oxygen and nitrogen. Division of air and passing extraction of argon from it in the commercial scale is carried out by liquefaction and rectification at a low temperature. Fluid oxygen under pressure of 101 kPa boils at a temperature of-182,9 °C, and fluid nitrogen - at a temperature of-195,8 °C. Therefore vapors of fluid air when boiling are enriched with the easily boiling nitrogen which boiling point is nearly 13 °C lower, than at oxygen. At the same time there is an enrichment of the boiling liquid oxygen. Thanks to it, in a rectifying dividing column where fluid air continuously boils and its couples are condensed, it is possible to receive at the same time oxygen (in the bottom) and nitrogen - (in an upper). Majority of fluid argon which boiling point of-185,3 °C, accumulates in the mid-range of a column from where in mix with oxygen and nitrogen it is taken away (so-called argonny fraction) in the express argonny column mounted together with the airdistributing device. Here the argonny fraction (containing 8-12% of argon, 0,2-0,3% of nitrogen, the rest - oxygen) is exposed to padding rectification and is enriched with argon to 85-95% (other 15-5% blends nitrogen and oxygen). This product is called crude argon, from it at the subsequent stages of cleaning receive clear argon.

1 - airdividing device

2 – argonny column

3 – recooler

Accession of an argonny column to the device of double rectification of air

Crude argon can be purified of oxygen in several ways. One of them is based on catalytic oxidation of Hydrogenium which is contained in crude argon at a temperature of 400-500 °C. Owing to a toga that at this way resultants of reaction mix up with the purified argon, it is necessary that they easily separated from it. Only the electrolytic Hydrogenium, free of the impurity polluting argon is applied to this purpose. As at this way of cleaning the content of oxygen should not be more than 2-2,5%, gas cycling for a dilution of crude argon by scrubbed gas, free of oxygen is provided in the scheme. Gas cycling is carried out by means of the gas blower. The steam received as a result of compound of Hydrogenium with oxygen in the contact device is condensed in the refrigerator and deleted through a moisture eliminator then gas is drained. The received argon mix with nitrogen is exposed to rectification according to the scheme which is similar applied at air rectification. At the same time the pump for fluid argon is used that allows to avoid pollution of clear argon at its compression and filling of cylinders. By means of the compressor mix of argon and nitrogen compresses and through a receiver moves in the block of the adsorption drying where from it moisture oddments are removed. After this via the heat exchanger mix comes to a rectifying column where it is cooled up to the liquefaction temperature with the division products leaving a column - nitrogen and argon. For providing conditions of rectification and completion of losses of cold give fluid nitrogen and vaporous oxygen-nitrogen mix from the main airdividing device to a rectifying column. Clear argon gathers in the bottom of a column, and "waste" nitrogen is taken away in the atmosphere from a column upper via the heat exchanger.

There are also other ways of receiving argon, for example by production of synthetic ammonia. It is received at synthesis of nitrogen-hydrogen mix in columns. Blow-down gas contains 10-19% of argon, and from this gas it also is taken. It is considered that the argon emitted by production of ammonia has lower prime cost. Anyway quality of gas depends on perfection of systems of cleaning and of accuracy of definition of small impurity of nitrogen, oxygen, Hydrogenium and water vapor in argon.