Post on 17-Oct-2019
INTRODUCTION TO CHEMICAL PROCESS SIMULATORS
A. Carrero, N. Quirante, J. Javaloyes
October 2016
DWSIM Chemical Process Simulator
A. Carrero , N. Quirante & J. Javaloyes
Introduction to Chemical Process Simulators
2
Contents
Monday, October 3rd 2016
Introduction to Sequential – Modular Steady State ProcessSimulators
Get used to working with DWSIM and COCO
Monday, October 10th 2016
Simulation of Chemical Reactors
Monday, October 17th 2016
Simulation of Distillation Columns
Monday, October 24th 2016
Case studies
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
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Tips to introduce inlet data in DWSIM
1. Introduce the composition and accept the changes
2. Introduce the rest of the inlet information by pressing Enter after writing each data
PressureTemperatureMass o molar flow
3. Review the thermodynamic model
4. Review the units
For any simulator!
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
4
Reactions
• Conversion: specify the conversion (%) of the limiting reagent as a
function of temperature.
• Equilibrium: specify the equilibrium constant (K) as a function of
temperature, a constant value or calculated from the Gibbs free energyreaction (DG/R).
• Kinetic: specify the frequency factor (A) and the activation energy (E)
for the direct reaction (optionally for the reverse reaction), including theorders of reaction of each component.
• Heterogeneous catalytic: specify the kinetic terms of the kinetic
reaction as well as the activation energy, frequency factor, andcomponent exponent terms of the adsorption kinetics.
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
5
Conversion Reaction
• It is assumed that the user has information regarding the conversion ofone of the reactants as a function of temperature.
• By knowing the conversion and the stoichiometric coefficients, thequantities of the components in the reaction can be calculated.
• Considering the following reaction:
where a, b and c are the stoichiometric coefficients of reactants andproduct, respectively. A is the limiting reactant and B is in excess. Theamount of each component at the end of the reaction can be calculatedfrom the following stoichiometric relationships:
𝑎𝐴 + 𝑏𝐵 → 𝑐𝐶
𝑁𝐴 = 𝑁𝐴𝑜 − 𝑁𝐴𝑜𝑋𝐴 𝑁𝐵 = 𝑁𝐵𝑜 −𝑏
𝑎𝑁𝐴𝑜𝑋𝐴 𝑁𝐶 = 𝑁𝐶𝑜 +
𝑐
𝑎𝑁𝐴𝑜𝑋𝐴
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
6
Conversion Reaction
DWSIM COCO
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
7
Equilibrium Reaction
• The quantity of each component at the equilibrium is related toequilibrium constant by the following relationship:
where K is the equilibrium constant, q is the basis of components (partialpressure in the vapor phase or activity in the liquid phase), ν is thestoichiometric coefficient of component j and n is the number ofcomponents in the reaction.
• The equilibrium constant can be obtained:
• Considering it as a constant.
• Considering it as a function of temperature.
• Calculating it automatically from the Gibbs free energy at thetemperature of the reaction.
𝐾 =
𝑗=1
𝑛
𝑞𝑗𝜐𝑗
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
8
Equilibrium Reaction
DWSIM COCO
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
9
Kinetic Reaction
• It is defined by the parameters of the equation of Arrhenius (frequencyfactor and activation energy) for both the direct order and for reverseorder.
• Considering the following kinetic reaction:
• The reaction rate for the A component can be defined as:
where:
• The kinetic reactions are used in Plug-Flow Reactors (PFR) and inContinuous-Stirred Tank Reactors (CSTR).
𝑎𝐴 + 𝑏𝐵 → 𝑐𝐶 + 𝑑𝐷
𝐹𝐴 = 𝐹𝐴𝑜 +
𝑉
𝑟𝐴𝑑𝑉
𝑟𝐴 = 𝑘 𝐴 𝐵 − 𝑘′[𝐶][𝐷]
𝑘 = 𝐴 𝑒𝑥𝑝(−𝐸/𝑅𝑇) 𝑘′ = 𝐴′ 𝑒𝑥𝑝(−𝐸′/𝑅𝑇)
• FA is the molar flow of the A component.
• V is the reactor volume.
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
10
Kinetic Reaction
DWSIM COCO
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
11
Heterogeneous Catalytic Reaction
• It is described the rate of catalytic reactions involving solid catalyst.
• Considering the following reaction:
• Depending on the reaction mechanism, the reaction rate expression canbe generally written as:
where kf and kr are the rate constants of the forward and reverse kineticrate expressions, K is the absorption rate constant, and M is the number ofabsorbed reactants and products plus absorbed inert species.
𝑎𝐴 + 𝑏𝐵 → 𝑐𝐶
𝑟 =𝑘𝑓 𝑖=1𝑅𝑒𝑎𝑐 𝐶𝑖
𝛼𝑖 −𝑘𝑟 𝑗=1𝑃𝑟𝑜𝑑 𝐶
𝑗
𝛽𝑗
1 + 𝑘=1𝑀 𝐾𝑘 𝑔=1
𝑀 𝐶𝑔𝛾𝑘𝑔
𝑛
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
12
Reactions
• Chemical reactions in DWSIM are managed through the ChemicalReactions Manager and in COCO through Settings – Reaction packages .
• The user can define various reactions which are grouped in ReactionSets. This reaction sets list all chemical reaction, and the user mustactivate only those we wants to become available for one or morereactors.
• In the reaction set configuration window we define the reactionordering.
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
13
Reactors
• Conversion Reactor
• Equilibrium Reactor
• Gibbs Reactor
• CSTR
• PFR
DWSIM COCO
CONVERSION
GIBBS REACTOR
EQUILIBRIUM
CSTR
PFR
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
14
Reactors
Reaction type Reactor type
Conversion Conversion
Equilibrium Equilibrium, Gibbs
Kinetic PFR, CSTR
Heterogeneous catalytic PFR, CSTR
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
15
Reactors
Conversion Reactor
• The conversion reaction is a vessel in which conversion reactions areperformed.
• You can only attach reaction sets that contain conversion reactions.
• It should be specified the stoichiometry of all reactions and theconversion of the limiting reactant.
• This reactor calculates the composition of the outlet streams.
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
16
Reactors
Equilibrium Reactor
• The equilibrium reactor is a vessel which models equilibrium reactions.
• The outlet streams of the reactor are in a state of the chemical andphysical equilibrium.
• The reaction set can contain an unlimited number of equilibriumreactions, which are simultaneously or sequentially solved.
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
17
Reactors
Gibbs Reactor
• Gibbs reactors can work with equilibrium reactions or without anyreaction information (Gibbs minimization mode).
• In this case, it will respect the element mass balance and try to find astate where the Gibbs free energy will be at a minimum.
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
18
Reactors
CSTR
• The CSTR (Continuous-Stirred Tank Reactor) is a vessel in which Kineticand Heterogeneous catalytic reactions can be performed.
• The conversion in the reactor depends on the rate expression of thereactions associated with the reaction type.
• The inlet stream is assumed to be perfectly (and instantaneously) mixedwith the material already in the reactor, so that the outlet streamcomposition is identical to that of the reactor contents.
• To simulate the CSTR we need to know the volume of the reactor.
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
19
Reactors
PFR
• The PFR (Plug Flow Reactor, or Tubular Reactor) generally consists of abank of cylindrical pipes or tubes.
• The flow field is modeled as plug flow, implying that the stream isradially isotropic (without mass or energy gradients). This also impliesthat axial mixing is negligible.
• To simulate the PFR we need to know the volume and the length of thereactor.
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
20
Butyl Acetate Production
The following system is used to produce Butyl-acetate from Methyl acetate and Methanol.
MeAC BuOH MeOH BuAc
Use Peng-Robinson (PR) thermodynamic package
MeAc Feed150 kmol/hT = 305 KP = 15 atm
BuOH Feed100 kmol/hT = 305 KP = 15 atm
R inP = 5 atm
R outT = 305 KP = 5 atm
ReactorDP = 0 atmLiquid phase reaction
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
21
Butyl Acetate Production
The following system is used to produce Butyl-acetate from Methyl acetate and Methanol.
MeAC BuOH MeOH BuAc
Use Peng-Robinson (PR) thermodynamic package
The reaction follows the next kinetic law:
𝑟 = 𝑘𝐹𝐶𝑀𝑒𝐴𝑐𝐶𝐵𝑢𝑂𝐻 − 𝑘𝑅𝐶𝑀𝑒𝑂𝐻𝐶𝐵𝑢𝐴𝑐𝑘𝑚𝑜𝑙
𝑠·𝑚3
𝑘𝐹 = 7 · 106 𝑒𝑥𝑝−
71960𝑅𝑇
𝑘𝑅 = 9.467 · 106 𝑒𝑥𝑝−
72670𝑅𝑇
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
22
Butyl Acetate Production
The following system is used to produce Butyl-acetate from Methyl acetate and Methanol.
MeAC BuOH MeOH BuAc
Use Peng-Robinson (PR) thermodynamic package
Molar flow and composition of the reactor outlet stream, for different types of reactors:
• Conversion reactor, assuming 10% of methyl acetate• Gibbs reactor.• Plug Flow Reactor (PFR), 4 m length and 0.5 m diameter.• Continuous-Stirred Tank Reactor (CSTR), 2 m3 volume.
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
23
Ethylene Glycol Production
Óxido de etileno
Agua
Reciclado
monoetilenglicol
Dietilenglicol
Trietilenglicol
Pesados
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
24
Ethylene Glycol Production
Simulate with COFE (COCO) a reactor to produce ethylene glycol considering that we know the conversion for each reaction.
Reactions:
Use Peng-Robinson (PR) thermodynamic package
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
25
Ethylene Glycol ProductionParametric study varying length of the PFR
Kinetics in COCO
R1 = exp(13.62-8220/T)/60/1000*C(Water)*C("Ethylene oxide")R2 = exp(15.57-8700/T)/60/1000*C("Monoethylene glycol")*C("Ethylene oxide")R3 = exp(16.06-8900/T)/60/1000*C("Diethylene glycol")*C("Ethylene oxide")
Kinetics
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
26
Ethylene Glycol ProductionParametric study varying length of the PFR
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Length of PFR / m
0
0.05
0.1
0.15
0.2
0.25
0.3
Mole
fra
ctio
n
Mole f raction Ethy lene oxide stream 2
Mole f raction Ethy lene gly col stream 2
Mole f raction Diethy lene gly col stream 2
Mole f raction Triethy lene gly col stream 2