Aust Conserv

One kind of clean coal preparation is coal washing which helps in removing unwanted minerals by mixing crushed coal with liquid and allowing impurities to separate and settle. There are other systems which control the coal burn to reduce emissions of sulfur dioxide and nitrogen oxides. Since carbon-dioxide is released into the atmosphere and contributes to global warming it has become a major international concern. This has led the researchers in discovering a more efficient and economical means of carbon capture. The three various types of carbon capture are:

1. Flue-gas separation - This process removes CO₂ with a solvent, and separates CO₂ with steam and makes this steam into a concentrated stream. This is commercially viable which results in offsetting of price.
2. Oxy-fuel combustion - This second process burns the fuel into pure or high quality oxygen and in-turn creates flue gas which consists of CO₂ and water.
3. Pre-combustion capture - This third technology removes the CO₂ before it is burned as a part of a gasification process.

There are other technologies for obtaining clean coal such as ocean storage which is still in its infancy. This involves injecting liquid CO₂ into waters of 500 to 3000 meters deep and to find out where it dissolves under pressure. However, this technology would slightly decrease the pH level and potentially harm the marine habitat. To avoid creating environmental problems, all forms of CO₂ storage require careful preparation and monitoring.

When it comes to nuclear power plants, it only acts as an alternative because they do not produce greenhouse gas emissions. Coal power plants burn coal to produce steam and heat water. This steam converts turbines and generates electricity. Electricity is generated in the same way by the nuclear power plants except that they use uranium, instead of coal thus avoiding byproducts of burning coal. Thus, it is unusual to consider nuclear power as "clean coal technology" because it avoids the use of coal altogether.

Therefore, the major technological challenge is burning coal to clean coal, without adding to global carbon dioxide. The clean coal technology field is proceeding towards the direction of coal gasification. The second stage is to produce concentrated and pressurized carbon dioxide steam followed by its separation and geological storage. This clean coal technology has the potential to provide to what may be called as "zero emission."

The coal industry and its counterparts are spending a lot to promote the nation with clean coal, but until now clean coal is more an advertising myth rather than practical. Despite the various definitions for clean coal, there is not a single grasp on what clean coal really is or what it could be.