tice Fixed Carbon or FC derived by subtracting from 100 the value of moisture

Tice fixed carbon or fc derived by subtracting from

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tice Fixed Carbon or FC derived by subtracting from 100 the value of moisture, volatile matter and ash. Proximate Analysis Proximate analysis indicates the percentage by weight of the Fixed Carbon, Volatiles, Ash, and Moisture Content in coal. The amounts of fixed carbon and volatile combustible matter directly 1. Fuels and Combustion 7 Bureau of Energy Efficiency TABLE 1.4 GCV FOR VARIOUS COALS Parameter Lignite Indian Coal Indonesian Coal South African Coal (Dry Basis) GCV (kCal/kg) 4,500* 4,000 5,500 6,000 * GCV of lignite on ‘ as received basis ’ is 2500 – 3000
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contribute to the heating value of coal. Fixed carbon acts as a 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 grate, combustion volume, pollution control equipment and ash handling systems of a furnace. A typical proximate analysis of various coal is given in the Table 1.5. Significance of Various Parameters in Proximate Analysis (a) Fixed carbon: Fixed carbon is the solid fuel left in the furnace after volatile matter is distilled off. It consists mostly of carbon but also contains some hydrogen, oxygen, sulphur and nitrogen not driven off with the gases. Fixed carbon gives a rough estimate of heating value of coal. (b) Volatile Matter: Volatile matters are the methane, hydrocarbons, hydrogen and carbon monoxide, and incom- bustible gases like carbon dioxide and nitrogen found in coal. Thus the volatile matter is an index of the gaseous fuels present. Typical range of volatile matter is 20 to 35%. Volatile Matter Proportionately increases flame length, and helps in easier ignition of coal. Sets minimum limit on the furnace height and volume. Influences secondary air requirement and distribution aspects. Influences secondary oil support (c) Ash Content: Ash is an impurity that will not burn. Typical range is 5 to 40% Ash Reduces handling and burning capacity. Increases handling costs. Affects combustion efficiency and boiler efficiency Causes clinkering and slagging. (d) Moisture Content: Moisture in coal must be transported, handled and stored. Since it replaces combustible matter, it decreases the heat content per kg of coal. Typical range is 0.5 to 10% 1. Fuels and Combustion 8 Bureau of Energy Efficiency Parameter Indian Coal Indonesian Coal South African Coal Moisture 5.98 9.43 8.5 Ash 38.63 13.99 17 Volatile matter 20.70 29.79 23.28 Fixed Carbon 34.69 46.79 51.22 TABLE 1.5 TYPICAL PROXIMATE ANALYSIS OF VARIOUS COALS (IN PERCENTAGE)
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Moisture Increases heat loss, due to evaporation and superheating of vapour Helps, to a limit, in binding fines. Aids radiation heat transfer. (e) Sulphur Content: Typical range is 0.5 to 0.8% normally. Sulphur Affects clinkering and slagging tendencies Corrodes chimney and other equipment such as air heaters and economisers Limits exit flue gas temperature.
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  • Spring '17
  • Jerome Ramos

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