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 โ 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
3
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
โข Conversion: specify the conversion (%) of the limiting reagent as a
function of temperature.
โข Equilibrium: specify the equilibrium constant (K) as a function of
temperature, a constant value or calculated from the Gibbs free energyreaction (DG/R).
โข 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.
โข 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
โข It is assumed that the user has information regarding the conversion ofone of the reactants as a function of temperature.
โข By knowing the conversion and the stoichiometric coefficients, thequantities of the components in the reaction can be calculated.
โข 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:
๐๐ด + ๐๐ต โ ๐๐ถ
๐๐ด = ๐๐ด๐ โ ๐๐ด๐๐๐ด ๐๐ต = ๐๐ต๐ โ๐
๐๐๐ด๐๐๐ด ๐๐ถ = ๐๐ถ๐ +
๐
๐๐๐ด๐๐๐ด
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
โข 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), ฮฝ is thestoichiometric coefficient of component j and n is the number ofcomponents in the reaction.
โข The equilibrium constant can be obtained:
โข Considering it as a constant.
โข Considering it as a function of temperature.
โข Calculating it automatically from the Gibbs free energy at thetemperature of the reaction.
๐พ =
๐=1
๐
๐๐๐๐
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
โข It is defined by the parameters of the equation of Arrhenius (frequencyfactor and activation energy) for both the direct order and for reverseorder.
โข Considering the following kinetic reaction:
โข The reaction rate for the A component can be defined as:
where:
โข The kinetic reactions are used in Plug-Flow Reactors (PFR) and inContinuous-Stirred Tank Reactors (CSTR).
๐๐ด + ๐๐ต โ ๐๐ถ + ๐๐ท
๐น๐ด = ๐น๐ด๐ +
๐
๐๐ด๐๐
๐๐ด = ๐ ๐ด ๐ต โ ๐โฒ[๐ถ][๐ท]
๐ = ๐ด ๐๐ฅ๐(โ๐ธ/๐ ๐) ๐โฒ = ๐ดโฒ ๐๐ฅ๐(โ๐ธโฒ/๐ ๐)
โข FA is the molar flow of the A component.
โข 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
โข It is described the rate of catalytic reactions involving solid catalyst.
โข Considering the following reaction:
โข 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.
๐๐ด + ๐๐ต โ ๐๐ถ
๐ =๐๐ ๐=1๐ ๐๐๐ ๐ถ๐
๐ผ๐ โ๐๐ ๐=1๐๐๐๐ ๐ถ
๐
๐ฝ๐
1 + ๐=1๐ ๐พ๐ ๐=1
๐ ๐ถ๐๐พ๐๐
๐
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
12
Reactions
โข Chemical reactions in DWSIM are managed through the ChemicalReactions Manager and in COCO through Settings โ Reaction packages .
โข 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.
โข In the reaction set configuration window we define the reactionordering.
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
13
Reactors
โข Conversion Reactor
โข Equilibrium Reactor
โข Gibbs Reactor
โข CSTR
โข 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
โข The conversion reaction is a vessel in which conversion reactions areperformed.
โข You can only attach reaction sets that contain conversion reactions.
โข It should be specified the stoichiometry of all reactions and theconversion of the limiting reactant.
โข This reactor calculates the composition of the outlet streams.
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
16
Reactors
Equilibrium Reactor
โข The equilibrium reactor is a vessel which models equilibrium reactions.
โข The outlet streams of the reactor are in a state of the chemical andphysical equilibrium.
โข 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
โข Gibbs reactors can work with equilibrium reactions or without anyreaction information (Gibbs minimization mode).
โข 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
โข The CSTR (Continuous-Stirred Tank Reactor) is a vessel in which Kineticand Heterogeneous catalytic reactions can be performed.
โข The conversion in the reactor depends on the rate expression of thereactions associated with the reaction type.
โข 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.
โข 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
โข The PFR (Plug Flow Reactor, or Tubular Reactor) generally consists of abank of cylindrical pipes or tubes.
โข 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.
โข 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:
๐ = ๐๐น๐ถ๐๐๐ด๐๐ถ๐ต๐ข๐๐ป โ ๐๐ ๐ถ๐๐๐๐ป๐ถ๐ต๐ข๐ด๐๐๐๐๐
๐ ยท๐3
๐๐น = 7 ยท 106 ๐๐ฅ๐โ
71960๐ ๐
๐๐ = 9.467 ยท 106 ๐๐ฅ๐โ
72670๐ ๐
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:
โข Conversion reactor, assuming 10% of methyl acetateโข Gibbs reactor.โข Plug Flow Reactor (PFR), 4 m length and 0.5 m diameter.โข Continuous-Stirred Tank Reactor (CSTR), 2 m3 volume.
A. Carrero , N. Quirante & J. Javaloyes
Introduction to chemical process simulators
23
Ethylene Glycol Production
รxido 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
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