Coal

Coal is classified as either lignite, sub-bituminous, bituminous or anthracite, where lignite contains the least carbon and anthracite the most.

Lignite - also known as brown coal - is coal with low organic maturity. It is characterised by its high moisture content and low carbon/energy content compared to coals such as anthracite. It is mainly used in power generation.

Sub-bituminous coal is softer than bituminous coal and contains more moisture, making it less economic to transport long distances. Sub-bituminous has typical bed moisture levels of between 10 - 20% and a carbon content of between 71 - 77%.

Bituminous coal is classified as coal which in terms of rank falls between sub-bituminous and semi-anthracite. Volatile matter can vary widely and bituminous coal is typically divided into three sub-groups - low volatile, medium volatile and high volatile. Bituminous coal has the required properties to generate steam electric power. Substantial quantities are used for power and heat applications in manufacturing as well as to make coke.

Thermal/Steam coal describes coals considered particularly suitable for boiler use i.e. for power generation.

Anthracite is the highest quality coal and is characterised by low volatile matter (always less than 10%) and high carbon content - it contains about 90% fixed carbon, more than any other form of coal. Anthracite has a semi-metallic lustre and is capable of burning without smoke (smokeless fuel). It is used in domestic and industrial applications. Anthracite is the least plentiful of all the coals.

Large pellets of anthracite are used mainly for household heating and specialised industries such as glass, chemicals and as a reductant. Fine anthracite/semi-anthracite is used in the steel industry for pulverised coal injection (PCI), for sintering and briquetting and in the ferrometals market as a reductant.

Steel works around the world are increasingly embracing Pulverised Coal Injection (PCI) as a way of lowering operating costs and extending the life of their coke ovens.

PCI is a technique developed by the steel industry and involves the injection of coal directly into the blast furnace. PCI improves operational efficiency and replaces some of the coke used in the blast furnace. Coke is a higher cost fuel produced in coke ovens using more expensive coking coals.

Traditionally, coals for PCI have been typically high volatile content coals. In recent times it has been recognised that some anthracite / low volatile coals which were previously considered of little value were suitable for PCI use and due to their very high carbon and energy content offer distinct financial advantages from :

• a higher replacement ratio of coke than traditional coals.
• being softer and easier to pulverise.