HISTORY
Coal chemicals were discovered early in the steel-making process as by-products derived from coal-to-coke conversion. In both gas and liquid forms, these chemicals were to become extremely valuable in a great variety of applications.
The coke ovens produced coke for the blast furnace and iron production as well as chemicals such as fertilisers, town gas, coal tar and benzole. Coal tar and benzole were then further processed in a chemical plant.
These aromatic chemicals were converted into useful chemicals such as dyes, wood-protection oils, fuels and solvents.
PROCESS
Coal is converted to coke in the first stage of steel production. This is done by heating coal in a coke oven at approximately 1100 °C for about 20 hours.
The volatile elements that escape during this process are recovered to serve as energy sources or chemical raw materials for further use.
Typical by-products are: ammonium sulphate, sulphur, coke gas, crude benzole and coal tar.
Crude benzole and coal tar are valuable raw materials for chemistry. In coal chemical plants (coal tar refinery and benzole plant), various chemical processes are used to convert and extract new valuable chemicals.
Downstream, other industries rely on these coal chemicals to produce aluminium, carbon black, resins, electrodes and more.
Coal chemicals have unique properties making them essential in many daily life applications: railways infrastructure, construction, health protection and fuel efficiency
Bakelite, based on phenol extracted from coal tar, was the first synthetic polymer ever produced, marking the launch of polymer chemistry, which is still thriving today.
ALUMINIUM
No aluminium without coal tar pitch
Aluminium is extracted from its oxide, alumina, using an electrolytic process. Electric current runs between two carbon electrodes (a positive and negative) in a high-temperature liquid bath of dissolved aluminium oxide.
The process relies on the anodes that are manufactured by mixing petroleum cokes with coal tar pitch, which functions as a binder. The mixture is formed into blocks of the required size and subsequently baked to about 1100°C. During the baking cycle, the coal tar pitch reacts to form graphitic structured coke and becomes electrically conductive.
Coal tar pitch is the only carbon binder that meets the requirements of the aluminium production process.
ca. 70 kilograms of coal tar pitch are needed to produce 1 tonne of aluminium.
CARBON BLACK
Providing added strength, durability to tires and other rubber products
Carbon black is a black powder that is used to increase the strength of products made of rubber, like tires. Adding carbon black extends the life of such products, thereby saving natural resources.
Thanks to extensive carbon black research and development, the latest grades have increasingly high abrasion resistance and low rolling resistance, which in turn increases fuel efficiency and curbs CO2 emissions from cars.
Carbon black is produced by injecting aromatic oils into a high-temperature reactor, where they form agglomerates of structured carbon particles. Coal chemical aromatic oils are excellent raw materials for this process and give the highest carbon black yields. This means less CO2 emissions for each kg of carbon black produced.
Carbon black is also used as a pigment for paints and inks.
Tires, main users of carbon black
Black ink, staying black thanks to Carbon black
Carbon black, the black color pigment for printing
ACTIVATED CARBON
Special contribution to environment and health protection
Coal chemicals are used in the production of activated carbon to adsorb hazardous chemicals from air and water. Activated carbon is a form of carbon that is highly porous and attracts and holds organic chemicals inside its pores.
Activated carbon is widely used in essential environment and health-protection applications such as waste-water treatment, air treatment and respiratory protection.
It is also used in consumer applications such as air purification systems in air-conditioning, fish tank filters and medical devices.
Water in fish tanks is kept pure thanks to activated carbon filters
Industrial activated carbon air purification filter, removing hazardous pollutants
Filter housing containing activated carbon
Modern cars often use activated carbon to prevent exhaust gases polluting the air inside the car through the air conditioning system.
CARBON & GRAPHITE
Adding value to coal chemicals in high-tech applications and green technologies
Coal chemicals have an extremely high carbon content, and their molecular structure makes them ideal materials to be transformed into pure carbon and graphite.
This is particularly useful in applications where metals cannot meet the high-temperature or chemical-resistance requirements. In these specific conditions carbon will resist.
Many compounds containing pure carbon can be found in high-tech applications: high temperature smelting, carbon reinforced disc brakes, electrodes in Li-ion batteries and brushes for electric motors.
Batteries depend on carbon electrodes to function.
Everyday batteries, which contain carbon electrodes.
Batteries in electric cars also depend on carbon components.
Carbon anodes, used in the electrolysis of Bauxite, are essential to produce aluminium.
Modern graphite brakes, providing optimal brake performance.
Different crystals, but still carbon…
Many different applications for the same element: carbon. And as many different processes to convert coal chemicals to carbon. Each process results in a different crystal structure and properties of the carbon components:
- the rigid hexagonal planes of graphene and graphite
- partly graphitic structures of anodes for aluminium
- to the spherical agglomerates for carbon black
PAH : unique heat-polymerisation process
- Liquid to solid conversion, with crystalline structure
- Final structure, after long high-temperature reaction = graphite.
- Intermediate = smaller graphitised patches/crystallites
WOOD PROTECTION
An unmatched wood preservative and antiseptic for over a century
Creosote is a wood-protection substance that extends the service life (to 30 years) of outdoor heavy-duty applications such as railway sleepers and utility poles.
Having proved its value for over 100 years, creosote continues to be the biocide of choice across the globe for these applications. Creosote's ability to prevent rot extends the life of wooden infrastructure, thereby reducing the need to harvest new trees.
Creosote is a mixture of defined coal tar fractions that have biocidal properties.
Various examples of vital rail and transport infrastructure, often in locations difficult to access, supported by wood protection agents based on coal chemicals since the 19th century.
SUPER PLASTICIZERS
Performance enhancers in buildings and construction
Superplasticizers are chemicals used as water reducers. They bring the ‘fast-drying’ quality to materials like fast-drying concrete. They can therefore drastically improve the performance of concrete and mortar.
They are produced by converting naphthalene to poly-naphthalene sulphonate.
They have become indispensable in a number of industries, extending the life of concrete structures, and more durable structures are more sustainable.
Moreover, most of the world’s most iconic modern skyscrapers simply could not have been built without the help of superplasticizers.
Skyscraper which could never have been built without superplasticizers.
RESINS
Essential raw materials for resin production
Resins respond to the high-performance requirements of many automotive, appliance, consumer and industrial applications. They can offer outstanding durability, excellent physical properties and a high-end finished appearance.
Indene is used in indene/coumarone resins, an important component in paints, glues and rubber applications. In these applications, the resins can increase solid content, improve the gloss, increase abrasion resistance, and protect against corrosion.
In addition, naphthalene is converted to phthalic anhydride and polyester resins for use in paints and reinforced polyester applications.
Phenolics are used in the production of phenolic resins, a group of versatile polymers used as hardeners and to preserve material properties.
Resins based on coal chemicals in windmills help produce sustainable energy.
Resins allow the addition of pigment in bitumen, creating better visibility for instance on cycling lanes.
Heavy duty flooring lines are made possible thanks to advanced resins.
Resins are widely used to enhance the properties of paints.
Source: Coal Chemicals Europe
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