Types of Cryogenic Gases

Cryogenic technology is the process of producing gas and liquid products by using low temperature refinement so as to disunite air components and receive the required product. The cryogenic process is considered as the most cost effective separation process. Cryogenic technology is widely preferred for producing high purity products at high production rates.

Each cryogenic gas has its own specific properties. However all cryogenic gases can be classified into one of three groups:

• Flammable Gases
• Liquid Oxygen
• Inert Gases

Flammable Gases
Flammable gases are those gas which burn in air. The flammable gas usually fall in the following statistics: Boiling point at 20 °C (68 °F) or less, ignitable at 101.3 kPa (14.7 psi) when in a mixture of 13% or less by volume with air. The most common examples of flammable gas can be classified in to two groups:

• High pressure cylinders: Hydrogen, Carbon monoxide, Methane, Natural gas
• Liquefied or dissolved gases under pressure: LPG, Acetylene

Liquid Oxygen
Comprising 20.8% by volume, oxygen is the second largest component of the atmosphere. Used primarily in the aerospace, submarine and gas industry, liquid oxygen (LOX) is the liquid form of oxygen, which is pale blue in color and extremely cold. Liquid oxygen has a boiling point of -297.3°F (-183.0°C). Liquid oxygen is non inflammable but being a strong oxidizer many non-combustible materials can burn in the presence of liquid oxygen. Because there is the need of difference in temperature between the product and the surrounding environment even in the winter, keeping liquid oxygen insulated from the encompassing heat is essential. Hence, liquid oxygen requires special equipment for handling and storage. Some popular storage systems are a cryogenic storage tank, a pressure control system, vaporizers, and all piping necessary for the vaporization, fill, and supply functions.

Inert gases
Inert gases are those type of gases that are non reactive under normal circumstances. They do not react chemically. Because of this property of inert gases, they are used to prevent undesirable chemical reactions from taking place. They are also non flammable and non toxic. They are found basically in the atmosphere and are extracted by cooling air to a very cold temperature. There are different types of inert gases like nitrogen, helium, neon, argon and krypton. Argon is supposed to be the most prevalent of all inert gases while xenon is the rare inert gas. Helium and neon are considered to be the true elemental inert gases because they do not form any true chemical compounds. Carbon dioxide and nitrogen, though not inert in the true sense, also fall into the category of inert gases.

The following table displays some statistics regarding the various inert gases:

Name	Atomic number	Boiling pt. (degree C)	Maximum available pressure (PSI)	Amt. in atmosphere
Helium	2	-268.9	6,000	5.2 PPM
Neon	10	-246.07	6,000	18.2 PPM
Argon	18	-185.88	6,000	7600 PPM
Krypton	36	-156.6	1,350	1.1 PPM

A quick recap The main types of cryogenic gas are:
Helium Neon Argon Krypton Xenon Hydrogen	Carbon monoxide Methane Natural gas LPG Acetylene Liquid oxygen