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Principles of Chemical Engineering > Chemical Reaction Engineering > Flashcards

Chemical Reaction Engineering Flashcards

1
Q

What is a chemical reaction?

A

A process where one or more substances are converted to one or more different substances.
There is a change in CHEMICAL IDENTITY

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2
Q

Define Conversion

A

Conversion is used to measure the progress of a reaction
n. reacted / n. fed

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3
Q

Define Yield

A

Yield shows how much of a reactant was transformed into a desired product

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4
Q

Define Selectivity

A

Selectivity shows the fraction of a desired product in all products

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5
Q

Define Chemical Equilibrium

A

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

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6
Q

What is Gibbs free energy equation used for

A

To calculate composition of reaction mixture at eq. under chosen react. cond.

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7
Q

Define Steady State

A

Steady state is where there are NO CHANGES IN TIME in composition of reaction mixture and conditions.

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8
Q

Define Rate of reaction

A

Rate of reaction gives quantitative info about the process and changes in reaction conditions.

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9
Q

Define Space/Residence time

A

Space/Residence time is the time needed to PROCESS ONE REACTOR VOLUME OF FLUID @ set inlet conditions

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10
Q

What is the Space/Residence time equation

A

Volume of reactor / volumetric flow rate of fluid

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11
Q

Define Space velocity

A

Space velocity is the ratio of the volumetric flow rate and reactor volume

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12
Q

What is the Space velocity equation

A

SV = 1/residence time = volumetric flow rate/ volume of reactor

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13
Q

What is the rate of reaction equation?

A

-rA = moles of A consumed / (vol)(time)

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14
Q

How to find instantaneous rate of reaction

A

It is an infinitely small interval of time, expressed as limit or DERATIVE EXPRESSION

 rA = -(ΔCA/Δt)  --> rA = -lim(ΔCA/Δt) --> rA = - dCA / dt
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15
Q

Define Rate Law

A

Rate Law describes relationship of reaction rate & reactant conc. in an eq.

-rA = k (CA)^m (CB)^n

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16
Q

Factors affection RoR

A
  • Temperature
  • Reaction Order
  • Conc.
  • (Pressure)
  • (Catalyst)
17
Q

What is the Arrhenius Equation

A

k= Ae^(-Ea / RT)

lnk = (-Ea/R) (1/T) + lnA
y = m x c

18
Q

What do Conc/Time graphs look like

A

(google)

19
Q

What do Rate/Conc graphs look liek

A

(google)

20
Q

How to determine k from 1st/2nd order reactions

A

1st Order: ln(Co/C) / time graph, m = k
2nd Order: 1/C / time graph, m = k

21
Q

What is a Batch Reactor and conditions

A

1-10,000L vessels
With controlled temp/pres/vol @ UNSTEADY state

22
Q

Batch Reactor Advantages

A
  • HIGH CONVERSIONS
  • Batch reactor jacket changes heating/cooling
  • Versatile, (consecutive production of products)
  • Produces small amount of products in TESTING PHASE
23
Q

Batch Reactor Disadvantages

A
  • HIGH COST of LABOUR
  • Hard MAINTAINANCE
  • Lots of time CLEANING
24
Q

Batch Reactor Application

A
  • LIQUID PHASE reaction @ high temp w/ biological materials
  • chem/pharma/food industry:
    • fermentation
    • sewage treatment
    • photobioreactors
25
Q

What is a Semi-Batch Reactor and conditions

A
  • Reactant added CONTINUOUSLY to another reactant
  • optimal for GAS & LIQ. reactions, no bubble formation (unlike batch)
26
Q

What is a Tubular / Plug Flow Reactor and conditions

A
  • reactants flow continuously @ STEADY STATE
27
Q

What affects diameter size in PFR

A
  • construction/pumping cost
  • desired residence time
  • heat transfer needs

LOW DIAMETER = HIGH RoR

28
Q

What is a Continuous Flow Reactor and conditions

A
  • CONTINUOUS feed of reactants and withdrawal of products
  • for HGIH QUANTITIES of products
  • must run for months
29
Q

Define Parabolic Flow Rate

A
  • LOWER flowrate (velocity) than turbulent
  • LAMINAR flow
  • Re > 2100
  • no eddies & no mixing
30
Q

Define Flat Flow Rate

A
  • HIGHER flowrate (velocity) than laminar
  • TURBLUENT / plug flow
  • Re > 2100
  • RANDOM eddies & mixing
31
Q

Tubular Reactor Applications

A
  • Hydrogenation
  • Hydrocracking
  • Polymerization
  • Reforming
  • Catalytic Converters
32
Q

Tubular Reactor Advantages

A
  • Either small / large scale
  • HIGH CONVERSION
  • NO RADIAL VARIATION in CONC
  • GOOD HEAT TRANSFER
  • LOW OPERATING COST
33
Q

Tubular Reactor Disadvantages

A
  • undesired THERMAL GRADIENTS
  • CHANNELLING may occur
  • Shutdown & cleaning could be EXPENSIVE
34
Q

What is a Continuous Stirred Tank Reactor and conditions

A
  • Has constant volume and stirring
  • OPEN system & STEADY STATE
  • in series
35
Q

CSTR Application

A
  • Homogenous liq-phase flow reactions

-pharma / biological processes (fermentation)

36
Q

CSTR Advantages

A
  • easy to maintain temp
  • LOW UPFRONT cost
  • HIGH HEAT CAPACITY
  • accessible interior
37
Q

CSTR Disadvantages

A
  • LOW CONVERSION
    • (small reactor)

Principles of Chemical Engineering (3 decks)

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