Question

Week 4 Process 1: Consider the process below: Water in Combustor Steam Generator Gas In Gas Out Combustor exit Steam Out A methane (CH) and air mixture is burnt in the combustor then the heat is recovered to produce steam. The CHa/air mixture comes in at 25°C and contains 10 kg/h of CH4 and 500 kg/h of air (assume 79% Nitrogen (N2) and 21 % Oxygen (O2)). The final outlet gas leaves at 100 °C. The combustion reaction follows the following chemical reaction: CH4 +202 CO2 + 2H20 The heat of reaction is - 802000 J/mol of CHA reacted at 25 °C. The water enters the steam generator at 20 °C and leaves at 400 °C. Other useful information: Molecular masses (g/mol): N2 = 28, O2 = 32, CH4 = 16, H20 = 18, CO2 = 44 pecific heats (J/kgK): N2 = 1040, O2 = 935, CH4 = 2440, CO2 = 920, H20 = 1890 (gas) = 4200 (liquid) Heat of vaporisation (J/kg) = 2257000 Use a reference temperature of 25 °C. 1. Complete the table below for the gas in stream. Compound Mass flow (kg/h) Mole flow (kmol/h) N2 02 CH4 Total 2. What is the average specific heat for the gas stream? 2020/7/30 18:25

Answer 1

Oriven eaction: scog+ 2H₂O CH4 + 202 Heout of reaction (OH) = -8,02,000 J mol Mass flowrate of CH4 = 10 kg れて 10 kg hЛ ni 16(kmah.kg 0.625 kmal Mass flowrate of alf=500kg [79%. N2 her 21702 Ne rate= 395 kg 395kg hr 28 kg kmol 14.10 kmol O2 rate = 105 kg 2 105 kg na 32109 kmol 3.28 Ic mol z

(2) we have: Attrar (crhaug AT = 100°C-25°C - - 802000 J AT • 75C0295 [-57 mol = 10,693 J 10.69 kJ - (Clang molle molk 3) Enthaby of gous in stream: AH = -74,590 J/mol. 4) Limiting reagent Methane. Because the amount of air or on will always be in excess of the reaction :