Coal Mining – Types Of Coal

Coal is made of old organic matter that rocks have compressed over millions of years. The rank, or quality, of coal is determined by pressure, temperature, and time to form. With each rank, the percentage of volatiles and moisture drops and the percentage of carbon increases.

Although there is a universal acceptance of which type of coal fits into which broad range, there is no fixed or precise lowest or highest figure for any range. The categorisation figures can and do overlap. Furthermore, countries tend to give their own names and definitions to the different types of coal.

TYPES OF COAL

Peat

Peat is the “forgotten fossil fuel” used for domestic and commercial heating in northern Europe, Scandinavia, Indonesia and Finland. Formed over millions of years from decaying vegetation, peat is the first step in the natural coal process.

Used: Used as an absorbent for fuel and oil spills on land and water.

Lignite

Also called brown coal, lignite is formed from compressed peat. It is the lowest grade and highly volatile with the lowest concentration of carbon. Lignite is brownish-black in colour, dull and crumbly with a low heating value and high moisture content.

Used: Mainly used in electricity generation and some briquettes.

Sub-Bituminous

Also called black lignite, sub-bituminous coal is dark brown to black in colour and rather dull. It has a low-to-moderate heating value.

Used: Power generation and industrial uses like chemicals and pharmaceuticals, in the manufacture of carbon fibre – which is used in solid and light-weight products, like tennis rackets and up-market bicycles, and cement manufacture. Also used to make briquettes and coke and fire the kilns that bake bricks, blocks, and building materials.

Bituminous

Bituminous is a dense, sedimentary rock with a high heating value. Formed from compressed lignite, bituminous is positioned in the ranking between sub-bituminous and anthracite.

It is dark brown to black in colour. At first sight, it appears smooth and shiny, but look closely and you will see it has thin, altering shiny and dull layers.

Bituminous coal is divided into two types.

  1. Thermal (Steam Coal); and
  2. Mettallurgical (coking coal)
Anthracite

Often called ‘Green carbon’, anthracite is a natural, smokeless fuel with the highest heating value and a long burning time.

Used: Primarily used in the metallurgy processes industry. A small percentage is used for specialised industrial uses that require smokeless fuels. Residential and commercial heating and water treatment. Manufacture of iron and steel. The pharmaceutical industry and chemical processes.

Coal Trading
COALDRY, CARBON CONTENT MOISTURE CONTENT BEFORE DRYING DRY, VOLATILE CONTENTHEAT CONTENT (MJ/KG)
Sub-Bituminous Coal70-7618-3842-5318-23
Peat<607563-6915
Lignite65-7035-5553-6317-18
Bituminous coal76-868-1814-4623-33
Anthracite86-927-103-14 32-33