Chemical Characterization of Coal PDF

Chemical characterization of Coal Proximate and ultimate analysis  Analysis of coal  Proximate analysis:  It involves analysis of Fixed Carbon, Volatiles, Ash, and Moisture Content in coal expressed in Wt%.  The amounts of fixed carbon and volatile matter directly co...

Chemical characterization of Coal Proximate and ultimate analysis  Analysis of coal  Proximate analysis:  It involves analysis of Fixed Carbon, Volatiles, Ash, and Moisture Content in coal expressed in Wt%.  The amounts of fixed carbon and volatile matter directly contribute to the heating value of coal.  Fixed carbon acts as the main heat generator during burning.  High volatile matter content indicates easy ignition of fuel.  The ash content is important in the design of the furnace, combustion volume, pollution control equipment and ash handling systems of a furnace.  Proximate analysis Measurement of Moisture A sample of powdered raw coal of size 200-micron is put in an uncovered crucible and it is placed in the oven kept at 108±2 oC along with the lid. Then the sample is cooled to room temperature and weighed again. The loss in weight represents moisture.  Proximate analysis Measurement of Volatile Matter: Fresh sample of crushed coal is weighed, placed in a covered crucible, and heated in a furnace at 900 ± 15 0C. The sample is cooled and weighed. Loss of weight represents moisture and volatile matter. The remainder is coke (fixed carbon and ash).  Proximate analysis  Measurement of Carbon and Ash:  The cover from the crucible used in the last test is removed and the crucible is heated over the Bunsen burner until all the carbon is burnt.  The residue is weighed, which is the incombustible ash. The difference in weight from the previous weighing is the fixed carbon.  In actual practice Fixed Carbon or FC derived by subtracting from 100 the value of moisture, volatile matter and ash.  Rank-wise avg. proximate analytical values Volatile Ranks of Coal Fixed Carbon Moisture Matter Lignite 29 26 46 Subbituminous 42 34 23 Low-rank/volatile bituminous 47 41 12 Medium-rank/volatile bituminous 54 41 5 High-rank/volatile bituminous 65 32 3 Semianthracite 86 12 3 Anthracite 96 1.2 3  Analysis of coal Ultimate analysis: – (wt%):  Involves analysis of the various elemental chemical constituents such as Carbon, Hydrogen, Oxygen, Sulphur, etc.  It is useful in determining the quantity of air required for combustion and the volume and composition of the combustion gases.  This information is required for the calculation of flame temperature  Coal Types (based on their source material) Humic Coal: Those developed from terrestrial plant debris that was exposed to atmosphere and passed through peat stage Higher plant kingdom is the source Sapropelic coal: Developed from plankton, algae, terrestrial plant in aerobic or laccustrine condition. E.g. bog head coal, canal coals