The 4 Types of Coal and Their Uses

Coal and Related Carbon Resources / Exploration, Production, Coal Ash, & Rare Earths

Date posted: 02/19/17

Coal originally began to form during the Carboniferous period, which took place between 360 and 290 million years ago. Put simply, plant matter accumulated in swamps and peat bogs, and after being buried and exposed to high heat and pressure, largely due to the shifting of tectonic plates, it was transformed into coal. The quality of coal is largely determined by: 1. The type of vegetation the coal originated from. 2. The coal depth of burial. 3. Temperatures and pressures at that depth. 4. How long it took the coal to form. All of these factors contribute to the degree of transformation of the original plant material to carbon, and it is carbon content that determines a coal rank. Essentially, higher-carbon content is associated with coal that has spent a longer time forming, while lower carbon content is a characteristic of younger coal (lignite). The four main coal types, arranged from lowest to highest carbon content, as well as explanations of what they are used for ... Lignite is the youngest form of coal. It is soft and ranges in color from black to shades of brown. As a result, it is sometimes called brown coal. Lignite is mainly used for power generation and accounts for 17% of the world coal reserves. After millions of years, continued pressure and temperature convert lignite into sub-bituminous coal. It burns more cleanly than lignite due to its lower sulfur and ash content. Sub-bituminous coal has applications in power generation and also in industrial processes. This type of coal is 30% of the total coal reserves. Bituminous coal is harder and blacker than lignite and sub-bituminous coal, and can be divided into two types ... thermal and metallurgical. Together, they make up 52% of the total coal reserves. Thermal coal is mostly used for power generation, cement manufacturing and other industrial purposes, while metallurgical coal is used for manufacturing iron and steel, etc. Anthracite, a mature coal (1%), was once used for home heating.