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Afluidized bed combustion system having an output of 35 MW at 80% efficiency when using a coal of heating value 26 MJ/kg with a sulphur content of 3.6% requires a particular limestone to be fed to it at a calcium-sulphur molar ratio of 3.0 so as to limit emissions of SO2 adequately. The limestone used contains 85% CaCO3. The required flow rate of limestone will be (a) 2405 kg/h (b) 2805 kg/h (c) 3205 kg/h (d) 3605 kg/h |
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Answer» (a) 2405 kg/h Output = 35 MW Heat input = \(\cfrac{35}{0.8}\) MW Mass of fuel = \(\cfrac{35\times10^6}{0.8\times26\times10^6}\) = 1.682 kg/sec Mass of sulphur = 0.036 × 1.682 = 0.06057 kg/sec Moles of sulphur = \(\cfrac{0.06057}{32}\) = 0.001893 Moles of CaCO3 = 3 × 0.001893 = 0.005679 kmoles/sec = 20.44 kmoles/hr Mass = 20.44 × 100 = 2044 kg/hr Mass of CaCO3 = \(\cfrac{2044}{0.85}\) = 2405 kg/hr |
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