Natural gas of the following composition by volume: methane - 89%, nitrogen - 7%,ethane - 1.5%, hydrogen sulphide - 1%, propane - 1.5% is burnt in a boiler with 40%excess air and used to generate steam. All the hydrogen sulphide oxidises to sulphur dioxide. Write all relevant chemical equations. (b)Calculate the composition of the exhaust gas on a wet basis. Planning permission requires SO2 emission to be less than 65 ppm. The proposal is to add a de sulphurisation unit before the boiler. The manufacturer guarantees92% efficiency of the desulphurisation unit and a capacity of 500 kg sulphur removed. Calculate the flue gas composition on a wet basis after desulphurisationand show that SO2 is within the limit required.(i)[8 marks] (ii)Calculate the time the desulphurisation unit can be on-line before its capacity is used up if the flow rate of natural gas is 3000 m³/h at 0°C and 1[2 marks] atm.