L.2 - Mass Balance Flashcards
What does the law of conservation of mass state?
mass can neither be produced or destroyed
Give an example where mass balance is ued:
to track pollutants from one place to another
Define Control Volume:
region within which material/mass is analyzed
What is order of reaction used for?
to determine the relationship between rate and concentration
What is Reactor Analysis?
uses mass balance to analyze the pollutant concentration in a control volume modelled as a chemical reactor
What are different types of reactor analysis?
1) Batch Reactor (CMBR)
2) CSTR/CMFR
3) Plug Flow Reactor (PFR)
What are the differences between reactor types?
1) CMBR: nothing enters or leaves
2) CSTR: flow enters and leaves Co enters, Cinside=Cout
3) PFR: flow enters and leaves, each segment acts like a separate CMBR
What does it mean if a system is in steady state?
1) concentration does not vary with time
2) inputs/outputs are constant
3) no sudden changes in conditions
How do you choose between CMFR and PFR?
depends if the system is completely mixed or flows downstream without mixing
Talk about Step Function Response:
1) concentration varies with time
2) short-time response
3) occurs after system is turned on/off or smth added/removed
4) steady state following or preceding
Why is PFR sometimes preferred over CMFR or CMBR?
because in PFR as the rate of the reaction is increased the concentration of reactant increases, increasing efficiency (more conversion in less time, less residence time)
What assumptions are made for PFR?
1) Molecular uniformity
2) Steady state
3) Elementary reactions
4) Constant physical properties
