Documentation:CHBE Exam Wiki/Final Exam 2016W/Question 3

From UBC Wiki
Jump to navigation Jump to search
CHBE 241
Exam resources wiki
Example alt text
Chemical and Biological Engineering
Welcome to the CHBE Exam Resources Wiki!

This wiki is intended to host past exams

with fully worked-out hints and solutions
Past Exams
Final Exam 2016W
Midterm Exam 1 2016W
Midterm Exam 2 2016W
Problem Sets
Module 1 - Process Basics
Module 2 - Reactors
Module 3 - Separations 1
Module 4 - Separations 2
Module 5 - Non-reactive Energy Balances
Module 6 - Reactive Energy Balances

A furnace is used in a plant to heat a stream of 1 tonne per hour of pure H2O. The H2O enters as a mixture of water (liquid) and steam (vapour) at 5 bar to produce superheated steam at 300°C and 5 bar. The heat to do this is provided by the complete combustion of 1 kmol/h propane (C3H8) with 100% excess air at 1 atm. The air consists of 79 mol% nitrogen (N2) and 21 mol% oxygen (O2) and enters the furnace with the propane at 200°C. The fractional conversion of propane is 1.00 and the combustion products leave the furnace at 400°C. The heat of propane combustion forming gaseous water is -2220 kJ/(mol C3H8) at 400 °C. The steam and combustion streams are not in direct contact, but energy is transferred between the two streams and you can assume the furnace to be adiabatic with negligible energy contributions from shaft work, kinetic energy, or potential energy.

Compound Cp[J/mol K]
C3H8 68
N2 29
H2O 33.5
O2 29
CO2 36

Note : enthalpy and internal energy values below are in kJ/kg and volumes are in m3/kg CHBE 241 FE 2016 Q3 Steamtable

Question 3a [5 points]

Write out the equation for the combustion reaction. What is the molar flow of oxygen and nitrogen into the process?

Question 3b [10 points]

What are the molar fractions of all species in the gas exiting the furnace?

Question 3c [15 points]

What is the amount of energy transferred due to the combustion reaction in kJ/h?

Question 3d [10 points]

What are the weight fractions of water and steam in the entering pure H2O?

Script error: The function "navbox" does not exist.