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Gas Fuels @ Www.07 Met.Tk
 

Gas Fuels @ Www.07 Met.Tk

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    Gas Fuels @ Www.07 Met.Tk Gas Fuels @ Www.07 Met.Tk Presentation Transcript

    • GAS FUELS
      ))) 07MET.TK (((
      All About Metallurgical & Materials Engineering
      Download This & More Stuff @ WWW.07MET.TK
    • Producer Gas
      Producer gas is also called town gas, specifically means a fuel gas made from coke, anthracite or other carbonaceous material.
      Air is passed over the red-hot carbonaceous fuel and carbon monoxide is produced. The reaction is exothermic and proceeds as follows:
      2C + O2 -> 2CO
      The nitrogen in the air remains unchanged and dilutes the gas, giving it a very low calorific value.
    • Water Gas
      Water gas contains carbon monoxide and hydrogen. It is a useful product but requires careful handling because of the risk of carbon monoxide poisoning. The gas is made by passing steam over red-hot coke:
      C + H2O -> CO + H2
      The reaction is endothermic so the coke must be continually re-heated to keep the reaction going.
      45 per cent each of carbon monoxide and hydrogen, with small amounts of nitrogen, oxygen, and carbon dioxide.
      Water gas had a lower calorific value than coal gas.
    • Blast Furnace Gas
      The waste gases from blast furnaces contain over 30 per cent of carbon monoxide and about 63 per cent of nitrogen. These gases are largely employed near the furnaces for heating purposes.
      Natural gas is odorless and before it is distributed to end-users, it is odorized by adding thiols. WHY?
    • Hydrogen & C2H2
      Hydrogen has a clean flame and is good for use in welding.
      It can be used at a higher pressure than acetylene and is therefore useful for underwater welding and cutting.
      It is a good type of flame to use when heating large amounts of material.
      The flame temperature is high, about 2,000 °C
      Acetylene when combined with oxygen burns at a temperature of 3200 °C to 3500 °C (5800 °F to 6300 °F), highest among commonly used gaseous fuels.
      As a fuel acetylene's primary disadvantage, in comparison to other fuels, is high cost.
    • Calculating AFR
      CH4 + 2O2 -> CO2 + 2H2 O
      If we look up the atomic weights of the atoms that make up methane and oxygen, we get the following numbers:
      Carbon (C): 12,01
      Oxygen (O): 16
      Hydrogen (H): 1,008
      So 1 molecule of methane has a molecular weight of: 1 * 12,01 + 4 * 1,008 = 16,042
      One oxygen molecule weighs: 2 * 16 = 32.
    • Calculating AFR
      The oxygen-fuel mass ratio is then: 2 * 32 / 1 * 16,042 = 64 / 16,042 = . 
      So we need 3,99 kg of oxygen for every 1 kg of fuel.
      Since 23,2 mass-percent of air is actually oxygen, we need : 3,99 * 100/23,2 = 17,2 kg air for every 1 kg of methane.
      So the stoichiometric air-fuel ratio of methane is 17.2.
    • Common Values of AFR
      Gasoline: 14.7
      Natural gas: 17.2
      Propane: 15.5
      Ethanol: 9
      Methanol: 6.4
      Hydrogen: 34
      Diesel: 14.6
    • Mixtures-Rich or lean?
      Stoichiometric is the scientific term that indicates the ideal ratio of air and fuel for complete combustion (meaning no gasoline or oxygen is left in the combustion chamber). That stoichiometric air/fuel ratio is 14.7:1.
      When the ratio gets lower than that, the mixture is rich, meaning there’s a greater proportion of fuel.
      When the ratio gets higher, you have a lean mixture and a greater proportion of oxygen.
    • Stoichiometric Mixture
      stoichiometric is the scientific term that indicates the ideal ratio of air and fuel for complete combustion (meaning no gasoline or oxygen is left in the combustion chamber). That stoichiometric air/fuel ratio is 14.7:1.
      When the ratio gets lower than that, the mixture is rich, meaning there’s a greater proportion of fuel.
      Rich mixture = low fuel efficiency.
      When the ratio gets higher, you have a lean mixture and a greater proportion of oxygen.
    • Flames
      The neutral flame is produced when the ratio of oxygen to acetylene, in the mixture leaving the torch, is almost exactly one-to-one.
      The carburizing flame , as its name implies, is created when the proportion of acetylene in the mixture is higher than that required to produce the neutral flame.
      The oxidizing flame results from burning a mixture which contains more oxygen than required for a neutral flame. It will oxidize or ”burn” some of the metal being welded.
    • Heat Exchangers
    • ))) 07MET.TK (((
      All About Metallurgical & Materials Engineering
      Download This & More Stuff @ WWW.07MET.TK