Find out the industrial gas uses in one hour
The diverse physical and chemical properties of industrial gases means their uses, or gases applications, are legion and the industrial gases companies are constantly seeking to develop new applications in order to expand the market place. For this sales development effort to be successful requires a good understanding on the part of the gas supplier of the industrial and medical processes which utilise the gases.
The major gas companies employ specialists in particular fields of application, supported by an ability to design and supply specialised equipment for effective use of the gas in the customer’s processes. The marketing effort is often organised around particular “market sectors” or industry groupings to capitalise on the specialist knowledge. Typical market sector groups encompass:
- Food & Beverages
- Chemicals & Petroleum
These market sectors may utilise a variety of gases and there are many applications outside these particular groupings which are still of importance. The diverse chemical and physical properties of the air gases, as well as the other industrial gases, lead to a multitude of uses, which have been continuously expanded and developed by the major gases companies in collaboration with their customers.
It is no exaggeration to say that without the industrial gases both industry and medicine would have been unable to develop to their current extent. Industrial gases are an essential part of the industrial and economic infrastructure of modern life. Volume growth is generally reckoned to run at 1.5-2.0 times the national GDP growth regardless of the current development stage of an economy, so there is no sign of their importance or growth being in decline.
As the air gases are so important in industry and their manufacture mostly depends on air separation technologies, we shall begin with a review of the gaseous components of air and their boiling points at normal barometric pressure, together with an indication of whether the cryogenic air separation unit (ASU) can be employed:
GASEOUS COMPOSITION OF AIR
|Volume parts per million
|Boiling point oC
Common “impurities” found in air are water vapour, methane, carbon monoxide, sulphur dioxide, nitrous oxide, ozone, nitrogen dioxide, radon and nitric oxide. In addition there can be dust, pollen and local “pollutants” from industrial and chemical processes, vehicle exhausts, etc.
It will be seen that the main constituents of air are nitrogen (78%), oxygen (21%) and to a lesser extent argon (0.9%). The other constituents are minute in comparison. Nonetheless, special steps have to be taken in the cryogenic production process to remove the impurities and CO2 from the air before liquefaction.
It will be seen from the above table that the three major constituents, nitrogen, oxygen and argon have boiling points, which are quite similar. This is convenient for the cryogenic process (fractional distillation of air) where these three products are usually co-produced in the ASU. Normally, the other constituents of air are vented in a waste product stream, although in small measure they remain as impurities in the main product. Occasionally, where the plant size is sufficient to make the process economic, the rare gases – neon, krypton, xenon are also distilled from the air in “specialised” side columns operating in the appropriate temperature range. Given their very low boiling points close to absolute zero (-273 OC) and small concentrations, helium and hydrogen are not recovered from air but obtained by other means. CO2 is removed as an impurity prior to air separation in an ASU and is manufactured by different and more economic processes.
In the early years of the industrial gases business, oxygen was the main product along with acetylene. Although this is still the case in developed markets, generally speaking the volume of nitrogen sold is now well in excess of oxygen. There are three key properties of nitrogen from which its main uses arise:
- as a gas it is inert (un-reactive) under normal conditions;
- as a liquid (LN or LIN for short) it is very cold (-196OC);
- as either a gas or in liquid from it is non-toxic
It is impossible to list every single application of nitrogen (this would take a whole book and the list is growing all the time), but market sectors and the major applications which rely on the inert or non-toxic characteristics of nitrogen and/or the cryogenic properties of the liquefied gas include (but are not limited to):
Food and Beverage
Food preservation (controlled atmospheres for packaging or MAP – modified atmosphere packaging), storage/blanketing of fresh produce and beverages in warehouses, storage silos, liquid tanks, cellars, etc. and transport of fresh foods and beverages under conditions of controlled atmosphere (composition and temperature) for national and international distribution. These techniques provide a means of keeping food fresh in the best possible condition throughout the food chain from the point of harvesting to point of consumption in the home, thus increasing shelf life of the food products.
Food freezing and chilling rely on both the non-toxic and cold properties of liquid nitrogen. In many countries, food freezing/chilling is the largest single application for liquid nitrogen. Although carbon dioxide and mechanical refrigeration methods can be employed, liquid nitrogen has advantages in speed of freezing (and therefore in quality and productivity measures). Food freezing/chilling can be performed at the initial food preparation stage, or at the food processing stage through to the distribution chain of the food (in-transit refrigeration).
Freeze grinding is a relatively minor use but it can also be employed in spice grinding to improve the quality of the spices.
- Primary Metal Production
In steel-making nitrogen, which is relatively inert, can be used for ladle stirring, reduced oxygen atmospheres in pouring stages and stainless steel production.
- Secondary Metal Production
In controlled atmospheres for annealing (toughening by heat treatment), galvanising, hardening and tempering. In powder technologies such as atomising, brazing, and thermal spraying. Liquid nitrogen is used in the shrink fitting of metals.
Substantial quantities of gaseous nitrogen, mixed with about 5% hydrogen, are used in float glass manufacture to create an oxygen free reducing atmosphere where the molten glass floats on the tin.
Chemicals & Petroleum
The inert properties of nitrogen are crucial for safe operations in many chemical and petroleum plant processes and these industries represent a very substantial market for nitrogen. The uses mainly fall under the headings of inerting/blanketing, purging, sparging, pressure transfer of products and pressure testing. In addition it can be used in chemical synthesis, for cooling to control chemical reactions and for adding to natural gas to control the calorific value of towns’ gas supplies. Liquid nitrogen can be employed in solvent recovery and recycling of chemicals. It is also used in enhanced oil recovery to force oil from difficult or nearly exhausted wells.
The electronics industry is a major consumer of nitrogen, particularly in the manufacture of microchips (where special gases are also important) and the production of high quality circuit boards. Other such applications classified under electronics are light bulb manufacture, fibre optics etc.
It can be used for cooling purposes in concrete mixing, soil freezing, blow moulding of plastic and glass containers and blown plastic film. As a liquid it is also used in cryosurgery, cryogenic storage of organs and biotechnology. Another liquid application is fog dispersal. Nitrogen is also used as an assist gas in laser cutting and for light bulbs (mixed with argon). It is used as a fire suppressant in mine fires and for filling aircraft tyres.
In the oil industry nitrogen can be used for the purging and cleaning of pipelines and also in enhanced oil recovery.
Oxygen is a very reactive gas and features in a variety of chemical (oxidation) processes. It also possesses two remarkable properties – it supports combustion and is essential to life. Oxygen was the foundation stone of industrial gases as it has been used in welding and medicine since the turn of the century. Today, chemical processes, combustion and environmental applications have expanded the market enormously:
Chemicals and Petroleum
Oxygen is used as either an effective substitute for air or an enriching agent to air in the production of several commodity chemicals and petrochemicals (vinyl chloride, vinyl acetate, propylene oxide and ethylene oxide to name a few). It can also be used in the de-bottlenecking of refinery fluidised catalytic cracking units by oxygen enrichment and Claus sulphur recovery plants.
Other major uses include the use in primary or secondary reforming operations and partial oxidation processes which are commonly used in the production of ammonia, methanol and hydrogen.
Oxygen can also be used in the production of inorganic products such as Titanium Dioxide, Carbon Black and Nitric Acid etc.
These are usually consumed in tonnage volumes, which require large ASU production supplies.
Primary Metal Production
The steel industry is the largest user of oxygen world-wide. Processes which originally utilised air have been vastly improved by using oxygen in the reaction and new oxygen based processes have been invented. As a result the tonnage of oxygen used per tonne of steel produced has steadily (and sometimes dramatically) risen through the decades.
In integrated steel plants oxygen is used for enrichment in blast furnaces and in BOS (basic oxygen steel-making) converters to produce the molten steel. New technologies in blast furnace operation, such as oxy-coal injection (to avoid expensive and polluting coke ovens) increase the oxygen requirement. The Corex process which is an innovative large scale steel-making process consumes almost one tonne of oxygen per tonne of steel and utilises the largest cryogenic air separation units which can be built.
On a smaller scale, electric arc furnaces (EAF) require oxygen (enriched air) to be introduced into the furnace. This requirement can be met by a pipeline supply, onsite supply from an oxygen generator (cryogenic) or oxygen PSA plants or vaporised liquid oxygen, depending on the volume of demand.
Oxygen is widely used in oxy-fuel burners in the smelting of ores (Copper, Nickel and Zinc) and in specialist applications such as gold recovery from tailings where it reduces cyanide usage and increases the leaching rate.
Secondary Metal Fabrication
Oxygen is used in secondary metal fabrication in enhanced furnace heating technologies in which it increases furnace temperatures whilst reducing fuel usage.
Other Combustion Processes
Oxygen is widely used in other furnace enrichment and oxy-fuel burning applications where it improves fuel economics, heat transfer rates and reduces unwanted Nitrous Oxides (NOX) emissions. Besides steelworks it is used in glass furnaces, cupolas and ceramics and brick-making. Oxygen is used in fluidised combustion processes, particularly coal gasification for combined heat and power plants or the production of synthetic fuels. It is also used in incinerators for solid waste disposal.
Welding and cutting operations are traditional users of oxygen. It is used in oxyacetylene welding, oxy-cutting, brazing, flame hardening, re-heating and moulding. The users are in shipbuilding, engineering industries, building, assembly, metal fabrication, ship-breaking and scrap yards.
Oxygen is used in water purification processes. This includes the oxygenation of rivers, the treatment of sewage, and the purification of drinking water (ozone is generated from oxygen). It is also used in the treatment of industrial effluents.
Oxygen is vital to healthcare and hospitals are the main users. They pipe supplies (usually from liquid storage) or use cylinder supplies for operating theatres, emergency wards, intensive care units and to supply individual beds. Oxygen therapy is also used in the home, supplied in cylinders or from oxygen concentrators (smallscale PSA units). Oxygen is also used in the breeding and transport of fish.
Oxygen is used for de-lignification in the paper pulp industry. Another use is to speed up fermentation processes in brewing and pharmaceuticals. It is also used in liquid from as a rocket propellant.
Although less than one per cent of the atmosphere, this gas is of increasing importance as it is absolutely inert (more so than nitrogen). While for most metallurgical applications nitrogen is sufficiently inert, argon is the choice when extreme conditions (higher temperatures etc.) are used.
Primary Metal Production
One of argon’s main uses is in the steel and stainless steel industry where it is used to stir molten metal (in ladles) and “eject” traces of carbon and nitrogen (to prevent nitrides formation). In stainless steel, a licensed process is that of argon oxygen decarburisation (AOD) which was invented by Union Carbide (now Praxair).
Argon is also used in some other, rarer metal production and in some Aluminium smelting operations.
Welding Shielding Gases
Argon is a common component of welding gases and gas mixtures for TIG and MIG welding (and more recently laser welding) where it is used as a shielding gas to prevent oxidation of the weld. These welding gas mixtures are generally used in the more developed industrialised countries where welding techniques are more advanced.
The gas is also commonly used to fill household light bulbs (its inertness prolongs filament life) and fluorescent tubes. In electronics it is used for cleaning silicon chips, producing fibre optics and in some lasers.
Argon is also widely used as a carrier gas in research and laboratory operations, again due to its inert nature.
The Noble (or Rare) Gases – Nenon, Krypton, Xenon
Between them, these gases represent less than two thousandths of one per cent of air. However, they are worth separating in large ASUs because each has its own unique applications. Due to their rarity and cost they from part of the Special Gases portfolio.
The main uses of neon are in (“neon”) lighting, display signs and electronic tubes. It is also used with helium in continuous lasers. Krypton is also used in eximer lasers, particularly in surgery. Krypton is used as a barrier gas in double glazing and in energy saving light bulbs (together with argon). Xenon is used in special lighting applications such as flash-lighting, high performance automobile headlights, lighthouses and xerography. It is also present in some eximer lasers. A new application is in ion engines for deep space propulsion. In the field of medicine it can be used as an anaesthetic and in medical imaging.
Carbon Dioxide (CO2) is soluble in water, 0.9 volumes of the gas dissolving in 1 volume of water at 200C to produce a mildly acidic solution. Like a number of other gases, the relatively inert qualities of CO2 under normal conditions, makes it useful for suppressing combustion or oxidation. Another importance characteristic of CO2 is its bacteriostatic nature (does not support life and respiration of aerobic microbes and beings).
Being non-toxic it can also be used in food applications. CO2 in its liquid from, besides being a good source of cold (-780C), has a unique character in that whilst it is kept under pressure will remain a liquid but when the pressure is released (when expanded rapidly) it solidifies. This property allows solid carbon dioxide to be produced as snow, in pellets or blocks as “dry ice”. Dry ice possesses the useful property that it does not melt as a liquid but turns into gas (sublimes) without leaving any residue.
A major use of CO2 is in the manufacture of carbonated beverages where, when dissolved under a pressure of 2-5 atmospheres, it causes effervescence (fizz). Hence all the carbonated drinks produced by companies such as Coca Cola, Pepsi etc. and the carbonated mineral water, use carbon dioxide to generate the “fizz”.
CO2 is also used in the production of beer (both alcoholic and non-alcoholic) where it is used in various stages of the beer processes, from carbonation, bottling and barrelling as well as mass transfer of liquids.
In most developing countries, the use of CO2 in these applications usually accounts from between 50 and 75% of the total demand for the gas.
The CO2 is also used in the dispensing of soft drinks and beers in pubs and fast food chains.
Food Processing and Transportation
Liquid CO2 is much used as a refrigerant in food freezing and chilling, especially where the use of LIN is too extreme in temperature or too volatile (high boil off rate). Dry ice and CO2 snow is used in food preservation. In gaseous from it can be used in protective atmospheres for the transport and storage of food or as an inert gas for purging of pipelines.
A relatively new application includes in-transit refrigeration where additional cold is required above that provided by mechanical refrigeration units or instead of these units. Other food related applications includes MAP of food (like nitrogen).
CO2 is used in smaller chemical processes and in the manufacture of pharmaceutical products and sweeteners. In the chemicals industry it is used in the Solvay process to manufacture soda ash. It is also used to correct syngas ratios in carbon chemistry and in the production of urea from Ammonia.
Waste Water Treatment
CO2 can be used in two main forms of waste water treatment, firstly for reducing the pH value of the water in high alkaline conditions and secondly to remove minerals and heavy metals.
Another large use of CO2 is in the horticulture business in those countries with slightly lower light levels (all year round) in order to stimulate growth and increase crop yield in green house grown produce.
CO2 is the gas used in gas cooled nuclear reactors, particularly in the UK.
- Foaming of plastics and rubber usually rely on CO2.
- As a liquid it is also used as a cooling agent in many non-food industries such as metal casting.
- CO2 is used for fire fighting
- Use as an anaesthetic gas in cattle slaughter
Hydrogen (H2) is the simplest chemical element and forms 75% of the mass of the universe but less than 1% of the mass of the earth. It is highly reactive and combines readily with oxygen (explosively if not controlled) and many non-metals. It also combines with some metals to from hydrides. It is commonly used as a reducing agent.
The reducing properties of hydrogen are used to remove oxygen during high-temperature processes such as metal treatment or float glass production. The reactive/reducing properties of hydrogen are utilised to a great extent in intermediate processes in the chemicals/petrochemicals and refinery industries where it is usually produced on-site. Hydrogen is also used to hydrogenate unsaturated fats and oils to thicken them and reduces oxidation. This process finds applications in the manufacture of margarine and edible oils as well as shampoos, lubricants, household cleaners and a variety of industrial products. Hydrogen is a key gas in microchip manufacture where it is used in atmospheres for growing crystals, etching, annealing and bonding. Hydrogen is used in welding mixtures and cutting applications. Waste hydrogen is often burnt as a fuel gas. A dramatic use for liquid hydrogen, along with liquid oxygen, is for rocket propulsion.
Helium is one of the noble gases and is the second most abundant element in the universe after hydrogen but only minute amounts are present in air. It occurs on earth mainly in the presence of natural gas in which it has resulted from radioactive decay. Helium is very inert and has a uniquely low boiling point within a few degrees of absolute zero (-268.90C).
Its inertness makes it ideal for helium based shielding gases in welding applications (stainless steel, aluminium, copper alloys). It is also used as an inerting medium in the manufacture of optical fibres. As a small molecule it is also highly “leaky” and is used for leak detection in vessels and pipe-work. It can be used for heat transfer in nuclear reactors because it remains chemically inert and non-radioactive. Being so light and inert it is used for balloons. Helium is used in breathing gas mixtures by divers, where it replaces the nitrogen. Another medical use is in breathing mixtures to relieve respiratory difficulties. The very low temperature of liquid helium is utilised in super conducting magnets which are used in medical MRI scanners and specialised research apparatus.
This is an explosive gas which in the presence of the right amount of oxygen burns with a brilliant flame at a temperature of about 30000C. Hence the oxy-acetylene blowtorch is widely used in welding and cutting metals with high melting points and this forms almost the sole use for the gas. For chemical synthesis it has been replaced by ethylene and its use for lighting has been superseded by high performance lamps using the noble gases. For cutting operations where the highest temperature and speed are not necessary it has lost market share to cheaper LPG and consequently, acetylene is usually in low or even negative growth.
The principal use of nitrous oxide is as an anaesthetic in medicine. When inhaled in pure from, it is asphyxiating, but in high concentrations (80% plus) with oxygen it induces rapid but rather shallow anaesthesia (which is insufficient for major surgery). The gas is useful for analgesia and sedation and as a background anaesthetic in conjunction with more potent additives for major surgery. It is still the most widely used anaesthetic gas. Non-medical uses are much smaller and include aerosol propellants, leak testing, food packaging, refrigeration and spectroscopy.
The noble gases – helium, neon, krypton and xenon are usually marketed as “special gases” as are ultra-high purity oxygen and nitrogen. However, there are many other special gases sold in cylinders, which are either simple chemical compounds or more often are mixtures of gases. Many are complex and formulated to the highest level of purity. Some are made specifically for a single customer. The major industrial gases companies market up to 20 000 special gases and mixtures, with very high values per cylinder.