Question

Consider the combustion chamber boundary (C), using natural gas and air entering and an exhaust gas leaving. Which of the following balances can be applied to this system boundary, giving a reason for each answer? 7. [10 marks] A. Sum of all masses in sum of all masses out B. Sum of all moles in sum of all moles out C. Total moles of each species in total moles of each species out Total mass of each species in total mass of each species out Total moles of each element in total moles of each element out 8. Consider the combustion chamber C: 1 kg of natural gas is burnt with 10% excess air (containing 1.5 mol% moisture) to generate heat as it is an exothermic reaction Combustion reactions can have multiple side reactions and often there are many reason for not going to completion, or forming the products expected Assuming you do not know what reactions are taking place inside the combustion chamber, and assuming you do not know if all reactions have gone to completion, perform a Degree of Freedom analysis for the following possible combinations of exhaust gas: i. Only CO2, H20, O2 and N2 are in the exhaust i Only CO, CO2, H2O, O2 and N2 are in the exhaust Only CO, CO2, H2, H20, 02 and N2 are in the exhaust v Only CH4, CO, CO2, H20, 02 and N2 are in the exhaust You do NOT have to write or solve any equations, but simply use the element balance to state clearly Nu and NE (and what they are), and therefore calculate No for each [12 marks] case

Answer 1

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