According to GB/T483-87, the proximate analysis of coal is a test to determine the air dried coal samples moisture content (including inherent moisture), volatile matter, ash, and fixed carbon. There are a total of 5 symbols that represent these 4 parameters.
Mt - moisture content
VM - volatile matter
Aad - ash
FC - fixed carbon
Mt: The moisture content of the coal is tested by heating the weighed sample at 103 to 105 degrees Celsius until a constant weight is obtained. The moisture content, as it is normally expressed, is the difference in the weight of the sample between the “air dried” and “oven dried” weights expressed as a decimal fraction, and calculated to two decimal places - e.g., 0.14, 0.25, 1.06.
VM: After the sample has been heated to a constant weight and the moisture content determined, the sample should be cooled in a desiccator and weighed again on an accurate balance. The residual weight is expressed in percent of the original weight of the air dried sample and is called the volatile matter.
Aad: The ash of a coal sample is determined by ignition of the sample at a temperature of 950° to 1000° Celsius for a period of 1 to 2 hours. After complete combustion, the residue is collected and weighed. The ash content is then expressed as a percentage of the original weight of the air dried sample.
FC: The fixed carbon content of a coal sample should be determined by subtracting the individual percentage of moisture, volatile matter, and ash from the original weight of the air dried sample. The result is then expressed as a percentage of the original weight and reported as the fixed carbon content.
By using these 5 symbols, the proximate analysis of a coal sample can be determined by analyzing the value of each symbol. The total proximate analysis can then be reported as Mt, VM, Aad and FC.
