Question

Fuel is burned in a boiler to produce saturated steam at 10.0 bar absolute pressure from saturated liquid water at 10.0 bar absolute pressure. This H20 flows through tubes that run through the boiler, Energy released by combustion is transferred as heat through the walls of the tubes to convert the liquid water to steam at 10.0 bar. The fuel consists of 37 mol% ethane and 63 mol% acetylene, and is fed in the vapor phase at 50 °C and 10 atm absolute pressure. Air is also fed at 50 °C and 1.0 atm absolute pressure. The combustion takes place in the boiler at 400 "Cand 1.0 atm absolute pressure. The fuel is completely converted to CO2 and H20. a. For a basis of 100 mol fuel and 1600 mol air fed, how much saturated steam at 10.0 bar can be produced? b. What is the dew point temperature of the combustion gases exiting the boiler?

Answer 1

's s a Assumptions- complete combustion take place. There is no heat loss from boiles to sorrounding. ③ All gases behave as on ideal gas Steady state condition exits exist. Properties - Enthalby of saturated Liquid water at loban = 763.25 enthalpy of saturated steen at loban=2777.8 kJ kJ/kg Heat of combustion of ethane (AHCE) = 1561 kJ/mol Heat of combustion of acetylene (AHC, A) = 1300kJ/mol All these broperties were not mentioned in question, so I used these values from google. Analysis - Felel bed to the combustion chamber = loomoly Full - 37.10 ethane = 37moly of ethane 630% acetylene = 63 moles of acetylene mole of air bed to the combustion chamber= boomoly Balanced chemical reaction equations, 1 For ethane + 702 2002 + 3H2O mi se 21 1 37 moles (37X7 moly 2x37 moly 3x37 moly 129.5 moles Tu moly Ill moles For acetylene H2O GH2 + 502 2CO2 + 63 moley 2x63 moley (63 moly 126 moes w loon Cho L 3 x 63 moley 157.5 moles Tz soc = 63 moles Boiles C₂H2 CHE (unreacted) 21600 - [129. Stis} = 1313 omoly CO₂ 2744126=200 Moler H₂Oz 111+63 = 174 moles T400°c Steam 737 moly 02 1600 moley water

specific heat capacity a at Tauouoc and latim specific heat capacity table component specific heat capacity at I= soc and latm C2 H₂ 45.4 J/mol-k 55.31 mol-k 29.50 / mol-k C2H6 32.98 J/molok 37.683 (mork 48.4 Il molti CO2 Enthalby table with serkect to Trefoc. component specific enthalby in specific enthalpy Feed Stream at soc in product stream at CH₂ cp (T-Treb) 245.4x50 400°c = (2270 /mol C₂ HG 55.3 1xso - 2765.5 Ilono 29.5oxso 2 1475 Il mole 32.98 xyoo = (13192 IlmoD प H₂O 37.08 xyoo (4832 Jlnil Now CO2 u814 xyoo - 19360J/mol applying the energy balance across boiler, -d + (Total enthalby) in - (Total Enthalby out + Energy Crenerated Where x = Energy given to the water Total enthalbay) in = Elmoles of eth component) enthalpy of ithecowboy = (63x2270 + 37x2765.57 opent is oox4 75 due to ran

2457834 Joule = 2457.834 kJoule Total Enthalpylout = [1313 * 13192] +(114x14832] + (200 * 1936] = 23773864]= 23773.8 kJ due to ethane Energy generated due to rxh = 3781561 + 6x 1300 Jue to acetylene = 139657KJ Now putting all the values in energy balanced equation, - x + 2457.834 - 23773.8 +139657=0 e = 118341 kJ Energy absorbed by leg of liquid to get converted into lleg of saturated steam=(2777.8 - 763125) kJ - 2014.55 kJ Q Total steam produced = 118341 2014.55 2014.55 Total Steam produced = 58,743kg Product gas stream O2 = 1313 moles CO₂ = 200 moly H₂O = 174 moly moles fraction of H₂O in product gas stream= 174 1313 +2oot174 = 0.103 Partial pressure of H₂O in product gas stream= 0.103x latim 20.103 atm dew point Temprature of combustion gases exiting the boiles Toew saturation Temprature of water cornesponding to allo3 atm saturation premne. чт°C