introduction to chemical process simulators · a. carrero , n. quirante & j. javaloyes...

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


Simulation of Distillation Columns


Case studies


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!



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.



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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



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Conversion Reaction

DWSIM COCO



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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



8

Equilibrium Reaction

DWSIM COCO



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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.



10

Kinetic Reaction

DWSIM COCO



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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



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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.



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Reactors

• Conversion Reactor

• Equilibrium Reactor

• Gibbs Reactor

• CSTR

• PFR

DWSIM COCO

CONVERSION

GIBBS REACTOR

EQUILIBRIUM

CSTR

PFR



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Reactors

Reaction type Reactor type

Conversion Conversion

Equilibrium Equilibrium, Gibbs

Kinetic PFR, CSTR

Heterogeneous catalytic PFR, CSTR



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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.



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.



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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.



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.



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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.



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



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MeAC BuOH MeOH BuAc


The reaction follows the next kinetic law:

𝑟 = 𝑘𝐹𝐶𝑀𝑒𝐴𝑐𝐶𝐵𝑢𝑂𝐻 − 𝑘𝑅𝐶𝑀𝑒𝑂𝐻𝐶𝐵𝑢𝐴𝑐𝑘𝑚𝑜𝑙

𝑠·𝑚3

𝑘𝐹 = 7 · 106 𝑒𝑥𝑝−

71960𝑅𝑇

𝑘𝑅 = 9.467 · 106 𝑒𝑥𝑝−

72670𝑅𝑇



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MeAC BuOH MeOH BuAc


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.



23

Ethylene Glycol Production

Óxido de etileno

Agua

Reciclado

monoetilenglicol

Dietilenglicol

Trietilenglicol

Pesados



24

Ethylene Glycol Production

Simulate with COFE (COCO) a reactor to produce ethylene glycol considering that we know the conversion for each reaction.

Reactions:




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



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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

introduction to chemical process simulators · a. carrero , n. quirante & j. javaloyes...

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