Chapter 4- Material Balances

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Batch process
Products and leftover reactants removed in batches. No mass crosses the system boundaries between the time the feed is charged and the product is removed.
Continuous process
Inputs and Outputs flow continuously through the process
Semi batch process
Neither batch nor continuous,
Steady-State
The values of all variables in a process (T, P, V, N) do NOT change with time
Transient
The values of all variables in a process (T, P, V, N) do change with time
Batch and semi batch processes are usually....?
Transient
Continuous processes may be....?
Either steady state or transient
A balloon is filled with air at a steady rate of 2g/min
Semi batch, transient
A bottle of milk is taken from the refridgerator
Batch, transient
Water is boiled in an open flask
Semi batch transient
Solving material balances single process unit
DOF
1) Choose a basis if not given
2) Total Mass Balance
3) Species balance
4)Energy balance
5) Specifications
6) Stoichiometric relations
Solving material balances multiple process unit
DOF
1) Overall mass balance on the system
2) Total Mass Balance on each process
3) Species balance on each process
4)Energy balance
5) Specifications
6) Stoichiometric relations
Excess
(N feed - N Stoichiometric)/ N Stoichiometric
Fractional conversion
Moles reacted/ moles fed
Extent of Reaction
Amount of limiting reactant reacted
Yield
Moles of desired product formed/ Stoichiometric amount that should have been formed
Selectivity
Moles of desired product formed/moles of undesired product formed
Reactive Process Balance
Use molecular balances instead of species balances
Add independent reactions when doing degrees of freedom
Overall Conversion
(Reactant input to process-Reactant output to process)/ Reactant input to process
Single Pass Conversion
(Reactant input to reactor-Reactant output to reactor)/Reactant input to reactor
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