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Natural gas of the following composition by volume: 85% methane, 14.5% nitrogen, 0.5%hydrogen sulphide, is burnt in a boiler with 50% excess air and used to generate steam.All the hydrogen

sulphide oxidises to sulphur dioxide. Write all relevant chemical equations and calculate the composition of the fluegas.[10 marks] Planning permission requires SO2 emission to be less than 50 ppm. The proposalis to add a desulphurisation unit before the boiler. The manufacturer guaranteesthis to be 90% efficient for an effective capacity of 600 kg sulphur removed. Calculate the flue gas composition after desulphurisation and show that theSO2 is below 50 parts per million (ppm).(i)[7 marks] (ii)Calculate the time the desulphurisation unit can be on-line before itscapacity is used up if the flow rate of natural gas is 2000 m3/h at 0°C and 1[3 marks]atm.

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