methane is the largest component of natural gas generally properties of methane

Methane is the largest component of natural gas

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methane is the largest component of natural gas, generally properties of methane are used when comparing the properties of natural gas to other fuels. Natural gas is a high calorific value fuel requiring no storage facilities. It mixes with air readily and does not produce smoke or soot. It has no sulphur content. It is lighter than air and disperses into air easily in case of leak. A typical comparison of carbon contents in oil, coal and gas is given in the table 1.13.
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1.5 Properties of Agro Residues The use of locally available agro residues is on the rise. This includes rice husk, coconut shells, groundnut shells, Coffee husk, Wheat stalk etc. The properties of a few of them are given in the table 1.14 and 1.15. 1. Fuels and Combustion 14 Bureau of Energy Efficiency TABLE 1.14 PROXIMATE ANALYSIS OF TYPICAL AGRO RESIDUES Deoiled Bran Paddy Husk Saw Dust Coconut Shell Moisture 7.11 10.79 37.98 13.95 Ash 18.46 16.73 1.63 3.52 Volatile Matter 59.81 56.46 81.22 61.91 Fixed Carbon 14.62 16.02 17.15 20.62 TABLE 1.15 ULTIMATE ANALYSIS OF TYPICAL AGRO RESIDUES Deoiled Bran Paddy Husk Saw Dust Coconut Shell Moisture 7.11 10.79 37.98 13.95 Mineral Matter 19.77 16.73 1.63 3.52 Carbon 36.59 33.95 48.55 44.95 Hydrogen 4.15 5.01 6.99 4.99 Nitrogen 0.82 0.91 0.80 0.56 Sulphur 0.54 0.09 0.10 0.08 Oxygen 31.02 32.52 41.93 31.94 GCV (kCal/kg) 3151 3568 4801 4565 Fuel Oil Coal Natural Gas Carbon 84 41.11 74 Hydrogen 12 2.76 25 Sulphur 3 0.41 - Oxygen 1 9.89 Trace Nitrogen Trace 1.22 0.75 Ash Trace 38.63 - Water Trace 5.98 - TABLE 1.13 COMPARISON OF CHEMICAL COMPOSITION OF VARIOUS FUELS
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1.6 Combustion Principle of Combustion Combustion refers to the rapid oxidation of fuel accompanied by the production of heat, or heat and light. Complete combustion of a fuel is possible only in the presence of an adequate supply of oxygen. Oxygen (O 2 ) is one of the most common elements on earth making up 20.9% of our air. Rapid fuel oxidation results in large amounts of heat. Solid or liquid fuels must be changed to a gas before they will burn. Usually heat is required to change liquids or solids into gases. Fuel gases will burn in their normal state if enough air is present. Most of the 79% of air (that is not oxygen) is nitrogen, with traces of other elements. Nitrogen is considered to be a temperature reducing dilutant that must be present to obtain the oxygen required for combustion. Nitrogen reduces combustion efficiency by absorbing heat from the combustion of fuels and diluting the flue gases. This reduces the heat available for transfer through the heat exchange surfaces. It also increases the volume of combustion by-products, which then have to travel through the heat exchanger and up the stack faster to allow the introduction of additional fuel air mixture. This nitrogen also can combine with oxygen (particularly at high flame temperatures) to produce oxides of nitrogen (NO x ), which are toxic pollutants. Carbon, hydrogen and sulphur in the fuel combine with oxygen in the air to form carbon dioxide, water vapour and sulphur dioxide, releasing 8084 kCals, 28922 kCals & 2224 kCals of heat respectively. Under certain conditions, Carbon may also combine with Oxygen to form Carbon Monoxide, which results in the release of a smaller quantity of heat (2430 kCals/kg of
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  • Spring '17
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