homework 01

CBEN 472 Spring 2015 ‐1‐ January 9, 2015 Homework #1 (Rev B) 1. Fossil fuels are made up molecules that are primarily carbon & hydrogen with some additional sulfur, oxygen, & other minor constituents. Consider a model molecule for a fossil fuel to have a molecular formula of C n H m S x N y O z . Balance the combustion equation (i.e., find expressions for , , , ,& in terms only of the variables n , m , x , y ,& z ): n m 2 2 2 2 2 CHSNO+ O CO + HO SO NO x y z . How much CO 2 is produced (in units of mass CO 2 per mass fuel) from burning this molecule (in terms of the variables n , m , x , y ,& z ). 2. Illinois no. 6 coal has a mass distribution of elements as shown in the following table. Using the “daf” column (i.e., dry and ash free) & neglecting the amount of chlorine: What are the appropriate values of m , x , y ,& z if we arbitrarily set 100 n . How much CO 2 is produced from burning this coal (in units of kg CO 2 per kg fuel)? 3. Using values from the spreadsheet "GPSAData_13ed.xlsx”: How much CO 2 is produced from burning propane (in units of kg CO 2 per kg propane)? What are the HHV & LHV values for propane (in units of kJ/kg, ideal gas basis)? How much CO 2 is produced from burning propane (in units of kg CO 2 per kJ propane ideal gas LHV basis)? 4. Consider the complete combustion of methane with air (21/70 molar ratio of O 2 /N 2 ,N 2 as an inert). When using a stoichiometric amount of oxygen how much air is needed (in terms of moles air per mole methane)? What is the molar composition of the product gas? When using 20% excess oxygen how much air is needed (in terms of moles air per mole methane)? What is the molar composition of the product gas?

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CBEN472Spring2015 1 January9,2015

Homework#1(RevB)

1. Fossilfuelsaremadeupmoleculesthatareprimarilycarbon&hydrogenwithsomeadditionalsulfur,oxygen,&otherminorconstituents.ConsideramodelmoleculeforafossilfueltohaveamolecularformulaofCnHmSxNyOz.Balancethecombustionequation(i.e.,findexpressionsfor , , , ,& intermsonlyofthevariablesn ,m , x , y ,& z ):

n m 2 2 2 2 2C H S N O + O CO + H O SO NOx y z .HowmuchCO2isproduced(inunitsofmassCO2permassfuel)fromburningthismolecule(intermsofthevariablesn ,m , x , y ,& z ).

2. Illinois no. 6 coal has a mass distribution of elements asshowninthefollowingtable.Usingthedafcolumn(i.e.,dryandashfree)&neglectingtheamountofchlorine:

Whataretheappropriatevaluesofm , x , y ,& z ifwearbitrarilyset 100n .

HowmuchCO2isproducedfromburningthiscoal(inunitsofkgCO2perkgfuel)?

3. Usingvaluesfromthespreadsheet"GPSAData_13ed.xlsx:

HowmuchCO2isproducedfromburningpropane(inunitsofkgCO2perkgpropane)? WhataretheHHV&LHVvaluesforpropane(inunitsofkJ/kg,idealgasbasis)? HowmuchCO2isproducedfromburningpropane(inunitsofkgCO2perkJpropaneideal

gasLHVbasis)?

4. Considerthecompletecombustionofmethanewithair(21/70molarratioofO2/N2,N2asaninert).

Whenusingastoichiometricamountofoxygenhowmuchairisneeded(intermsofmolesairpermolemethane)?Whatisthemolarcompositionoftheproductgas?

Whenusing20%excessoxygenhowmuchairisneeded(intermsofmolesairpermolemethane)?Whatisthemolarcompositionoftheproductgas?