Oxygen, nitrogen and argon are recovered from the air by separation. The cryogenic method for accomplishing this was developed by Carl von Linde more than 100 years ago. The air is compressed, freed of vapour, dust and carbon dioxide and is refrigerated to extremely low temperatures. It is compressed to a liquid and separated by distillation into oxygen, nitrogen, argon and other noble gases.

Today, other physical methods are also used to separate and purify air components:


  Separation: by means of membranes.
  Adsorption: various components of air are adsorbed onto a special material while others flow through without obstruction.

Our air separation units are constructed in-house by the Linde Engineering and Contracting Division and are operated by us.
Acetylene
Acetylene is produced conventionally from calcium carbide at numerous locations close to customers. One contribution to environmental protection: the acetylene is a by-product of the petrochemical industry. In Germany, we cover most of our customer requirements with a dedicated plant for dispensing petrochemical acetylene.

Hydrogen
Hydrogen may be obtained by means of a steam-reformer from steam, natural gas or other light hydrocarbons. Refineries and electrolytic processes employed in chlorine chemistry also generate hydrogen-rich gases from which the hydrogen can be recovered. All these methods are used by us, e.g., in Leuna, Buna, and Bitterfeld in Germany, and the Milazzo refinery in Sicily.

Liquid hydrogen
Liquid hydrogen is manufactured in our Ingolstadt plant, Germany's sole industrial plant for hydrogen liquefaction. The hydrogen is liquefied at -253°C and is transported in its liquid state, reducing transport costs.

Gas mixtures
Gas mixtures are either mixed continuously on site from pure gases or supplied premixed in cylinders. Our shielding gases for the metal-processing industry and for the food-processing industry are examples of different gas mixtures.

Helium
Helium is recovered most cost-effectively from natural gas. Long-term contracts guarantee access to sources in the USA, Europe and North Africa.

Carbon dioxide
Carbon dioxide can be recovered from natural, subterranean gas deposits. At Repcelak (Hungary) - the biggest natural carbon dioxide source in Europe - we recover more than 100,000 t CO2 every year. In addition, at other locations, we use carbon dioxide generated in the chemical industry and purify it to the quality required for the food-processing sector.