For many centuries, mining has been a key part of economic, environmental and workplace health and safety debates. Mining products like gold, diamonds, iron, nickel and coal are part of our everyday lives, whether we’re aware of it or not.
Without doubt, one of the oldest mining products used by humans is coal. The history of mining this product is fascinating, and the advances made to its processing techniques are incredible.
Coal is a fossil fuel made of hydrogen, sulphur, oxygen and carbon. It can be classified as lignite, sub-bituminous, bituminous or anthracite, depending on its carbon content.
Coal was a crucial source of energy during Europe’s Industrial Revolution in the 18th century. In Canada, the first coal mine was opened in New Brunswick, in 1720. Until the 18th century, Native people and early settlers were the first to use and sell coal. Shortly thereafter, it became the main source of energy for trains, steam boats, industrial machines and residential lighting and heating in major Canadian cities. At the time, it was the only fuel that burned hot enough to create steam.
The end of World War II marked the beginning of the decline of coal production in Canada. Canada dropped from 17 million tons per year in 1949 to less than 10 million. What do you think caused this decline? The arrival of oil! In 2015, in Canada, coal production accounted for no less than 39% of the world’s electricity production.
Two types of mines are used to mine coal: underground and surface. Until the 19th century, coal mining was extremely difficult. Most mines were underground at that time. Long tunnels were dug to allow miners to extract rocks, which were then brought to the surface using conveyors or small carts. As miners broke rocks with picks and shovels, water was pumped away from the tunnels using horses, chains and buckets. The coal was then cleaned in water mixed with magnetite particles. This mixture caused the elements to separate naturally.
As you may have guessed, underground coal mining was extremely dangerous for miners at the time. Floods, accidents, tunnel collapses and methane pocket explosions caused many deaths each year. In fact, did you know that gas leaks were one of the leading causes of mining deaths? Miners would bring canaries with them to detect and prevent gas leaks. When the bird stopped chirping and moving, it was a sign of a gas leak, which carried a high risk of explosion.
Surface mines were much safer and cheaper, and provided better working conditions. Underground mining was more common, but surface mining was more profitable.
What’s more, we’re lucky to live in a time where the health and safety of miners and mineral processers is a much greater concern. The technology is much better, too! Instead of horses, picks and shovels, modern companies can take advantage of innovative mineral processing products.
Coal processing has made significant advancements. Handpicking involved large numbers of people removing stone and shale from a slow-moving conveyor belt, with the discards being thrown into a chute. The whole process was physically demanding and technically inefficient. As the size of coal plants increased, this method became less effective and more powerful techniques were developed. Today, we use trough washers that use a strong flow of water to carry mined coal down a steep chute. Dense Medium Separation (DMS), which uses the different densities of shale and coal to separate them, makes this process more accurate and easier to handle. It also improves the quality of the coal recovered.
Today, the most efficient method is “float-and-sink separation,” which uses DMS cyclones to perform Dense Medium Separation. This method increases productivity and separation. Using cyclones with accurate cut-point separation allows different densities of coal to be separated—something that would be impossible to do by hand. DMS uses magnetite as a separation medium to improve the accuracy of cut-point separation. The magnetite is then recovered from the coal using magnetic separation.
Coal fines (coal less than 0.5 mm in size) are washed using spiral concentrators. The products and discards are separated using adjustable blades that are positioned at different points in the water stream, separating products of the desired quality. They are then collected in pipes and run to either a product or discard washer, respectively. Some facilities also have two-stage spirals, where the product is further treated in a second set of spirals. Spirals are made of polyurethane-coated fibreglass.