Industrial gases are a group of manufactured gases that are marketed for different uses. They are mainly used in industrial processes, such as steelmaking, medical applications, fertilizers, semiconductors, etc. The most widely used industrial gases and production are Oxygen, Nitrogen, Hydrogen and inert gases such as Argon.
 
How are industrial gases produced?
Industrial gases can be both organic and inorganic and are obtained from the air by a separation process or produced by chemical synthesis. They can take different forms as tablets, in liquid, or solid state.
 
These gases are produced from the fractionation of air. The cryogenic, non-polluting method for the production of these gases was devised more than 100 years ago by Carl von Linde. Once the interferences of water vapor, particles and carbon dioxide have been eliminated, the air is compressed and cooled at very low temperatures, liquefied and separated by fractional distillation into oxygen, nitrogen, argon and other noble gases.
 
Nowadays other physical methods are also used to separate and purify the air components:

• Separation: through membranes.
• Absorption: several components of the air are retained by specific materials, while the rest flows, without any obstruction.

 
Acetylene
Acetylene is produced from calcium carbide. It is also obtained as a by-product from the petrochemical industry; thus, contributing to the protection of the environment.
 
Hydrogen
Hydrogen can be obtained by means of reforming, from steam and natural gas or other light hydrocarbons. In the refineries and in the electrolysis of chlorine chemistry, hydrogen-rich gases are also generated, from which hydrogen can be obtained.
 
Liquid hydrogen
Hydrogen liquefies at -253ºC and is transported in liquid form in large containers in order to reduce transportation costs.
 
Carbon dioxide
Carbon dioxide can be obtained from natural underground deposits. In Répcelak (Hungary), the largest natural source of carbon dioxide in Europe, more than 100,000 t of CO2 are obtained annually.
 
Where are industrial gases used?
They are mainly used in industrial processes, such as steelmaking, medical applications, fertilizers, semiconductors, etc. The use of these gases in the industry is of great importance. In the food industries they are used to store and preserve food for long periods of time. In the chemical industries they are part of numerous processes of obtaining and transforming.
 
In metallurgy the use of industrial gases is indispensable. Oxygen plays a preponderant role in the manufacture and refining of steels. The use of inert Argon atmospheres is intensive in steel processes. The thermal treatment of steels and non-ferrous alloys requires the use of controlled atmospheres of hydrogen and nitrogen to achieve optimal results.
 
Elements and pieces made of new generation materials such as polymers and composites depend to a great extent of their manufacture, the presence of controlled and / or inert atmospheres as well as a good part of the technologies based on the use of lasers and of superconductors.
 
Inert and blanketing
It is a protection technique that, in general, has no direct relationship with the manufacturing processes, but rather with the safety of the facilities and the quality of the products. These products can be in solid state (blocks, grains), liquid (liquefied gases or liquid or melted products) or gaseous (gases or vaporized solvents).
 
The application examples are very varied:

• For the protection of tanks, reactors or centrifuges where hazardous, malodorous products are stored, etc.
• Overpressure of nitrogen in regulation and control equipment that prevents the access of corrosive vapours to the interior.
• To protect synthetic fibres at the exit of the extruder.
• For the transportation of chemical products produced under a nitrogen atmosphere, etc.

Purges
As in the previous case, working with sensitive products makes it necessary in many moments of the process to perform purges that guarantee the essential conditions of the product: safety, economy and quality. They are mainly distinguished, according to the characteristics of the containers to be purged in three different ways:
 

1. Purge by displacement. The simplest case is by sweeping a pipeline. The nitrogen is injected at one end, producing a mobile front.
2. Purge by dilution. It is carried out in intermediate enclosures with gas inlet and outlet points separated from each other. The volume of gas to be used corresponds to the volume of the enclosure, depending on the desired initial and final levels of the gas to be purged.
3. Purge by compression-expansion cycles. It is used when the geometry of the enclosure and the location of the entrances and exits does not allow a sweep. The calculation of the necessary cycles depends on the pressures that can be obtained in the tank.

Recovery of VOCs
Industrial gases are used in many operations in which it is required to dilute a product in a solvent (paints, inks, resins, etc.). In addition to the environmental requirements, which regulate the emission of these compounds, with increasing restrictions due to the high cost and price of these solvents, it is increasingly interesting to recover them from emissions into the atmosphere through a simple and reliable process: using the refrigerating power of liquid nitrogen which allows the liquefying and subsequent recovery of the solvent in inert atmospheres, without the possibility of explosive mixtures being formed. This way you can reach the required level, emitting the rest to the atmosphere without problems of environmental contamination.
 
In the recovery phase we take advantage of the power of liquid nitrogen, which provides us:

• The latent heat of vaporisation and the sensible heat of the nitrogen gas to condense and separate the solvent.
• The chemical inertness of vaporised nitrogen during the drying of the product, which eliminates the problems inherent in the flammability limits of solvent vapours.

With this technique there are savings on the volume of treatment gas, since the presence of nitrogen allows to work with higher solvent contents, decreasing the investments in the drying circuit.
 
Regulation of temperature and reactions
Many chemical and physicochemical operations in liquid phase must be carried out at a certain temperature, and controlled. When these operations are accompanied by a spontaneous production of heat (exothermic reaction), the maintenance of the required temperature requires putting into play some cooling device. Liquid nitrogen is a means of storing large amounts of frigories and capable of releasing them in a wide range of temperatures. The refrigerating capacity of liquid nitrogen makes it possible to meet exceptional demands that conventional facilities are unable to meet. Its use allows:

• A modest investment.
• A reliable team with high performance and great simplicity.
• A procedure of great flexibility.
• Easy adaptation to existing facilities.
• Improvement of reaction performance.

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