A-Z of industries

ChemiCAL AND PharmaCeutiCAL IndustrY

Hydrogen is used in the manufacture of a wide range of chemical and pharmaceutical products. Applications include:

• The production of aldehydes and ketones from carbon monoxide and hydrogen
• The production of high-density polyethylenes and polypropylenes
• The production of alcohols from aldehydes and ketones by reducing hydrogen in the presence of a catalyst
• The production of chlorinated hydrocarbons through the reaction of hydrogen with chlorine
• The production of synthetic natural gas

Hydrogen is also used in

• Methanol synthesis
• Sorbitol production (sugar substitutes)
• Hydrogenation of coal (coal liquefaction) or coke to make petrol, fuel oil, toluenes, xylenes and benzenes
• Naphthalene production
• and the manufacture of many medicines

Further information can be found at www.airproducts.co.uk/refining

EleCtrICAL industrY

• Hydrogen is used in hard soldering for the manufacture of vacuum tubes, lamps, ceramic-metal compounds and other electronic equipment. In view of the high temperatures, the metals concerned are very reactive and oxidise easily. Hydrogen is used to prevent oxidation.
• Oxygen-hydrogen mixtures are used as a fuel gas in the production and sealing of glass tubes. The carbon-free flame cannot be achieved with any other fuel gas.

Semiconductor industry

In the Semiconductor Industry, hydrogen is used

• as a transport gas for diffusion processes
• as a reaction gas with O₂ to generate water vapour for wet oxidation
• as an atmosphere for growing epitaxial layers on silicon wafers
• as fuel for oxy-H₂ torches to facilitate the deposition or strengthening of quartz rods.

In view of the stringent purity requirements, the hydrogen is delivered in liquid form.

POWER STATIONS

HydrOGENATION OF OILS AND GREASES

Metal processing – ferrous metals

To achieve specific properties, irons and steels are heat-treated in protective atmosphere furnaces. Hydrogen plays an important role in these processes. The following characteristics can be achieved through thermal treatment:

• Increased ductility
• Higher yield point
• Improved metal cutting properties
• Transformation of the grain structure
• Modification of the surface chemical composition (carburising, nitiriding)
• Modification of the magnetic properties
• Modification of the electrical properties

Hydrogen is also used in the following applications:

• Stress relief annealing
• Hardening
• Recrystallisation and soft annealing of cold-formed material
• Bright annealing

An exact product specification can be achieved in a protective atmosphere furnace. The main variables to be controlled are the composition of the protective atmosphere and the temperature of the material being treated. For most applications a nitrogen-hydrogen mixture is suitable for the protective atmosphere (i.e. a reducing atmosphere to prevent oxidation). The ratio of hydrogen to nitrogen in an N₂H₂ protective atmosphere is 3 – 30% hydrogen to 97 – 70% nitrogen, depending on the type of material and the desired product specification. However, in some applications (e.g. heat treatment of stainless steels) the hydrogen content can be considerably higher – as much as 100%.

Metal processing – NON-ferrous metals

• A reducing N₂H₂ atmosphere is used for annealing and heat treatment. The mixing ratio of hydrogen to nitrogen varies depending on the application. The mixing ratios mentioned above for iron and steel also apply to non-ferrous metals. Applications include, for example, annealing of copper and copper alloys.
• Processes for producing tungsten, molybdenum and magnesium require hydrogen to reduce oxides and prevent oxidation. A reducing atmosphere consisting almost entirely of hydrogen is used in the sintering of tungsten oxides. Molybdenum is made from concentrated molybdenite. This is roasted to form molybdenum trioxide, which is then reduced in a furnace at 1,000°C with hydrogen. The powder thereby obtained is extruded under pressure into rods and sintered in a reducing hydrogen atmosphere. The sintered rods can then be forged, rolled or drawn.
• Hydrogen is used in the production of magnesium by electrolysis. Hydrogen binds the oxygen and the chlorine, which would otherwise combine with the molten magnesium.
• Hydrogen is also used in the manufacture of moulded parts and tools by powder metallurgy. Applications include, for example, sintering of different metals and metal compounds and sinter-HIP, or pressure-assisted sintering.

WELDING AND CUTTING

The following processes are carried out using hydrogen:

• Plasma cutting and welding
• Soldering and welding in a protective atmosphere. A nitrogen-hydrogen mixture is used as a forming gas for welds where the underside of the seam needs to be protected from the effects of oxygen.
• TIG-welding of high-alloy austenitic materials. In this case an argon-hydrogen mixture is used. The weld seam stays bright and temper colours are reduced.

GlaSs / QuarTz

• In float glass manufacturing, hydrogen is used in combination with nitrogen to create a reductive atmosphere over the tin bath.
• In the glass industry hydrogen is sometimes used as a fuel gas in combination with oxygen for the melting and cutting of quartz. The advantages of hydrogen over other fuel gases are, above all, the carbon-free flame (avoiding inclusions) and the reduction of crystal formation in quartzes.

PETROLEUM industrY

In oil refineries, hydrogen has the following applications:

• In hydrotreating or hydrofining, hydrogen is used to desulphurise crude oil fractions. It is also used in catalytic reforming, where light hydrocarbons are converted into middle fractions.
• In hydrocracking, hydrogen is taken up by long molecules which are broken up into the middle fractions needed for petrol production.