Chemical Reaction Engineering Flashcards
What is a chemical reaction?
A process where one or more substances are converted to one or more different substances.
There is a change in CHEMICAL IDENTITY
Define Conversion
Conversion is used to measure the progress of a reaction
n. reacted / n. fed
Define Yield
Yield shows how much of a reactant was transformed into a desired product
Define Selectivity
Selectivity shows the fraction of a desired product in all products
Define Chemical Equilibrium
Chemical Equilibrium is the state of a system where all reactants and products are present with NO TENDENCY FOR FURTHER CHANGE in conc. over time
What is Gibbs free energy equation used for
To calculate composition of reaction mixture at eq. under chosen react. cond.
Define Steady State
Steady state is where there are NO CHANGES IN TIME in composition of reaction mixture and conditions.
Define Rate of reaction
Rate of reaction gives quantitative info about the process and changes in reaction conditions.
Define Space/Residence time
Space/Residence time is the time needed to PROCESS ONE REACTOR VOLUME OF FLUID @ set inlet conditions
What is the Space/Residence time equation
Volume of reactor / volumetric flow rate of fluid
Define Space velocity
Space velocity is the ratio of the volumetric flow rate and reactor volume
What is the Space velocity equation
SV = 1/residence time = volumetric flow rate/ volume of reactor
What is the rate of reaction equation?
-rA = moles of A consumed / (vol)(time)
How to find instantaneous rate of reaction
It is an infinitely small interval of time, expressed as limit or DERATIVE EXPRESSION
rA = -(ΔCA/Δt) --> rA = -lim(ΔCA/Δt) --> rA = - dCA / dt
Define Rate Law
Rate Law describes relationship of reaction rate & reactant conc. in an eq.
-rA = k (CA)^m (CB)^n
Factors affection RoR
- Temperature
- Reaction Order
- Conc.
- (Pressure)
- (Catalyst)
What is the Arrhenius Equation
k= Ae^(-Ea / RT)
lnk = (-Ea/R) (1/T) + lnA
y = m x c
What do Conc/Time graphs look like
(google)
What do Rate/Conc graphs look liek
(google)
How to determine k from 1st/2nd order reactions
1st Order: ln(Co/C) / time graph, m = k
2nd Order: 1/C / time graph, m = k
What is a Batch Reactor and conditions
1-10,000L vessels
With controlled temp/pres/vol @ UNSTEADY state
Batch Reactor Advantages
- HIGH CONVERSIONS
- Batch reactor jacket changes heating/cooling
- Versatile, (consecutive production of products)
- Produces small amount of products in TESTING PHASE
Batch Reactor Disadvantages
- HIGH COST of LABOUR
- Hard MAINTAINANCE
- Lots of time CLEANING
Batch Reactor Application
- LIQUID PHASE reaction @ high temp w/ biological materials
- chem/pharma/food industry:
- fermentation
- sewage treatment
- photobioreactors
What is a Semi-Batch Reactor and conditions
- Reactant added CONTINUOUSLY to another reactant
- optimal for GAS & LIQ. reactions, no bubble formation (unlike batch)
What is a Tubular / Plug Flow Reactor and conditions
- reactants flow continuously @ STEADY STATE
What affects diameter size in PFR
- construction/pumping cost
- desired residence time
- heat transfer needs
LOW DIAMETER = HIGH RoR
What is a Continuous Flow Reactor and conditions
- CONTINUOUS feed of reactants and withdrawal of products
- for HGIH QUANTITIES of products
- must run for months
Define Parabolic Flow Rate
- LOWER flowrate (velocity) than turbulent
- LAMINAR flow
- Re > 2100
- no eddies & no mixing
Define Flat Flow Rate
- HIGHER flowrate (velocity) than laminar
- TURBLUENT / plug flow
- Re > 2100
- RANDOM eddies & mixing
Tubular Reactor Applications
- Hydrogenation
- Hydrocracking
- Polymerization
- Reforming
- Catalytic Converters
Tubular Reactor Advantages
- Either small / large scale
- HIGH CONVERSION
- NO RADIAL VARIATION in CONC
- GOOD HEAT TRANSFER
- LOW OPERATING COST
Tubular Reactor Disadvantages
- undesired THERMAL GRADIENTS
- CHANNELLING may occur
- Shutdown & cleaning could be EXPENSIVE
What is a Continuous Stirred Tank Reactor and conditions
- Has constant volume and stirring
- OPEN system & STEADY STATE
- in series
CSTR Application
- Homogenous liq-phase flow reactions
-pharma / biological processes (fermentation)
CSTR Advantages
- easy to maintain temp
- LOW UPFRONT cost
- HIGH HEAT CAPACITY
- accessible interior
CSTR Disadvantages
- LOW CONVERSION
- (small reactor)
