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Homework Help: Desulfurization, Removing ammonia problem

  1. Feb 24, 2012 #1
    1. The problem statement, all variables and given/known data
    A West Virginia coal burned in a steam generator has the following mass analysis: carbon 75.0%, oxygen 6.7%, hydrogen 5.0%, water 2.5%, sulfur 2.3%, nitrogen 1.5%, ash 7.0%.

    How much limestone, CaCO3, in kg/day is needed to remove 96% of the SO2 produced from combustion of the coal, using wet scrubbing flue-gas desulfurization, if the boiler fired using this coal produces combustion heat at a rate of 150 kW? Assume complete combustion of the coal’s carbon, hydrogen and sulfur content to CO2, H2O, and SO2 respectively.

    How much ammonia, NH3, in kg/day is needed to remove 85% of the nitrogen oxides produced from combustion of the coal, using selective catalytic reduction, if 20% of the nitrogen content of the coal is converted into equal molar amounts of NO and NO2 during combustion? Assume that oxidation of the nitrogen content of the coal does not contribute to its heating value.

    you may assume that the coal is burned with 25% excess air and that the water produced from the coal combustion exits with the flue gas as a vapor; i.e. use the lower heating value of the coal in your scaling analysis. This will give you an upper bound on the rates at which the acid gases are produced in the combustion stack gas, and corresponding upper bounds on the rates at which limestone and ammonia must be supplied to the FGD and SCR units to remove these compounds from the flue gas to the specified treatment levels.

    2. Relevant equations


    3. The attempt at a solution

    I wrote the reaction equation and balanced it and ended up with this:

    6.244 C+2.48 H2+0.0717 S+ 0.2093 O2 + 0.053 N2+ 7.5557 O2+ 0.1387 H2O --->6.244 CO2+ 2.6187 H2O+ 0.0717 SO2 + 32.8591 N2

    I am not sure what to do next.

  2. jcsd
  3. Feb 25, 2012 #2
    I was able to find the LHV of the coal in KJ/kmol. Now how can I use this value to find the kg of the coal in another word the LHV in KJ/kg without knowing the molecular mass of the coal?
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