Determination of Sulphur in Coal
Sulphur (S) is an essential element for living organisms and is found in many different forms in natural substances. In coal, sulphur is generally present as a combination of organic and inorganic compounds. The amount of sulphur in coal is an important measure in determining the emitted sulphur dioxide by-product produced during combustion of the coal. Therefore, correct determination of sulphur in coal is essential for pollution control, as well as for determining the commercial value of the coal.
The most common method used to determine sulphur in coal is by proximate analysis. Proximate analysis is a physical process which allows the determination of moisture, ash, volatile matter, and fixed carbon in coal. Sulphur content can be determined by subtracting the percentage of the volatile matter, ash, and fixed carbon from 100%; this remaining value is the sulphur content. However, this method only gives an approximate sulphur content, ranging from 0.5 to 4.5 weight %.
A more accurate way to determine sulphur in coal is through elemental analysis. This includes an acid digestion method or a Fourier Transform Infrared Spectroscopy (FTIR). The acid digestion method is the most widely used elemental analysis method and involves treating the furnace with a combination of acids, such as hydrochloric acid and nitric acid, to create a lower-sulphur product. This acid solution is then analyzed by an inductively coupled argon plasma spectrometer, which measures the amount of sulphur in the solution.
The FTIR method is faster and more accurate than the acid digestion method and involves passing an infrared beam through the coal sample. The electrons in the molecules absorb the beam and emit their own unique infrared radiation at different frequencies. By measuring these frequencies, it can be determined how much sulphur is present in the coal sample.
The determination of sulphur in coal is important for several reasons. As mentioned previously, it helps determine the amount of sulphur dioxide produced by the combustion of coal, therefore it helps determine the environmental impacts of burning coal. It can also help determine the energy content of the coal, because the higher the level of sulphur, the lower the energy content of the coal. In addition, the higher level of sulphur present in coal can affect how it is transported and stored, as well as the cost of shipping and storing the coal.
In conclusion, it is important to accurately measure the amount of sulphur in coal. The most common method of determination is through proximate analysis, which gives an approximate sulphur content of 0.5 to 4.5 weight %. More accurate methods include acid digestion and FTIR analysis, which measure sulphur in parts per million or parts per billion. These methods are important for assessing the environmental impact of burning coal, as well as for determining the energy content and storage requirements of the coal.
