Other Clean Coal Operation Techniques
A variety of other clean coal techniques are under investigation. Some of them are:
Coal washing: When the coal arrives at a power plant, it contains minerals that have to be removed before the process of burning takes place. First, the coal has to be ground into small pieces and then exclude/separate the unwanted material through gravity separation. A method involves the use of barrels that contain fluid. The coal floats and the rest of the material sinks into the bottom. The pulverization of coal follows, and then it is ready to be used for power production.
Gasification: Plants that use gasification techniques have high efficiencies and low emissions, but there are yet to be proven in a large commercial scale. In this technique coal reacts with oxygen and produces syngas. The syngas is cooled and cleaned, and then burned inside a combustor. The heat generates steam that eventually powers steam turbines. A well-known method of gasification is the Integrated Gasification Combined Cycle or IGCC.
Removal of SO2 and NOx pollutants: The burning of coal results in the emission of sulphur dioxide and nitrogen oxides. Several methods are used to remove these pollutants, for instance : Sulphur dioxide - Flue gas desulphurization (FGD) systems use limestone and water, a mixture that reacts with the SO2 of the flue gas to form gypsum, a very popular material used in the construction industry.
Nitrogen oxides - The specially designed low NOx burners prevent the formation of the gas by reducing the amount of oxygen available in the hottest part of the coal combustion chamber.