Analisis de Reacto Con Chemcad

7/23/2019 Analisis de Reacto Con Chemcad

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Reactor

Analysis


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Types of Reactors


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Stoichiometric Reactor Module


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Stoichiometric Reactors (1)


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Equilibrium Reactors


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Gibbs Reactor


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RGibbs Module


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Equilibrium Reactor


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REquil Module

E ilib i R t C l l ti


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Equilibrium Reactor Calculations


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Results of Equilibrium Calculations (1)


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Results of Equilibrium Calaulations (2)


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Comments on Equilibrium Reactors


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Kinetic Reactors


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RPLUG Module


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PFTR Reactors (1)


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PFTR Reactor (2)


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CSTR Reactors


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RCSTR Module


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CSTR (1)


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CSTR (2)


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ChemCAD

Reactor Simulation


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ChemCAD Reactors

Types of Reactors

General Considerations and Phase Key

Stoichiometric Reactor

Equilibrium Reactor

Kinetic ReactorGibbs Reactor


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Types of Reactor


Kinetic Reactor

Equilibrium Reactor

Gibbs Reactor

ChemCAD Reactors


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ChemCAD Reactors

General Considerations

Heat of reaction calculated or specified

Reactor thermal mode:

- Adiabatic

- Isothermal

- Heat Load

- Fixed Temp. profile

- Utility StreamPhase Consideration



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General

One Reaction Only

Conversion must be specified

Heat of reaction calculated or specified

Typical Uses

Early of "Budget" process analysis

Component switching - Changing propertiesComplete reactions or known conditions


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Workshop Reactor1 : Stoichiometric Reactor

Benzene + 3 H2 ---> CyclohexaneAdiabatic

Conversion of 1 mole of benzene to cyclohexaneusing excess of hydrogen

Change reactor type to isothermal at 600 F.Note cooling load required

Highly exothermic reactions will usually require

quenching, cooling or multiple reactors.

Cyclohexane is normally produced in multiple reactorswith intercooling.


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Kinetic Reactor

Reactor Type

CSTR

Plug Flow

Calc Mode

Volume specified

Conversion specified

Phase

Liquid (Default)

Vapor

Mixed phase, reaction occurs in the liquid phase

Mixed phase, reaction occurs in the vapor phase

Ki ti R t


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Kinetic Reactor

= = = +=

nrx

j

n

k

Ceekj

n

k

akjRTEjiji

j

bk

RT

j

j kj

j

kkj

CeANr1 1

)**

1

)/( )/(1(*)(***

(kinetic term) * (driving forces)Rate of reaction =

(resistence terms)

ri = Rate of formation for component I, mole/volume-timei = Subscript for componentik = Subscript for reactant kj = Subscript for reactionjNi = Stoichiometric coefficient for component iA = Frequency factor (Arrhenius parameter)

E = Activation energyR = Universal gas constantT = Absolute temperatureCk = Concentration of reactant k, mole/volume or the partial pressure of reactant kakj = Exponential factor for reactant k in reactionjn = Number of reactantsnrx = Number of reaction

kj = Absorption frequency factor for componentkk = Absorption energy factor for componentki = Power factor for absorption sites term for reaction,j = Product of all reaction concentration terms = Sum of absorption factor for each reactantbkj = Exponential factor for reactant k in reactionj


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Workshop Reactor2: Kinetic Reactor

Adiabatic kinetic reaction of a lbmole each of acetic acid and ethanol, fed at it's bubble

point to a 1 liter reactor. Kinetics of the forward and reverse reactions are considered.Mixed phase, reaction occurs in the liquid phase.

Acetic Acid + Ethanol Ethyl Acetate + H2O

r1=K1[AA][EtOH]=k10e-E1/RT[AA][EtOH] Concentration flag : moles/volume

r2=K2[EA][H2O]=k20e-E2/RT[EA][H2O] Time Unit : Min.

k10=29000, E1=7150 Volume Unit : Liters

k20=7130, E2=7150 Activation Energy : Cal

Simulate this reactor Molar Flow Unit : Gm-mole

This reaction is endothermic.

Change reactor type to isothermal at 100 C. The conversion decreases. Why?


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Equilibrium Reactor

TBAK

i

yiyy

i

xixx

eq

RRR

PPP/

....

....ln)ln(

)()()(

)()()(

2

2

1

1

2

2

1

1

+==

Where,

Pi : Parial pressure or mole fraction of product component i

Ri : Parial pressure or mole fraction of reactant component i

Xi

: Power coefficient of the product component i

generally equal to stoichiometric coefficient

Yi : Power coefficient of the reactant component i

generally equal to stoichiometric coefficient

A,B : Arrhenius coefficients

T : temperature, absolute degrees


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Equilibrium Reactor

Equilibrium Reactor Type

General equilibrium reactor

Shift reactor

Methanation reactor

Specify calculation mode

Conversion specified

Approach temperature. ( T = Treactor+ DT)

Approach fractional conversion(eq).

W k h R 3 E ilib i R


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Workshop Reactor3: Equilibrium Reactor

1/2 N2 + 3/2 H2 ---> NH3 Fractional conversion of 1 mole of N2 to ammonia using excess of H2

Adiabatic, P=200 atm, T=1450 R, H2/N2 = 3:1 ( mole ratio) in feed.

Equilibrium data developed from figure, next pageThe equation: ln (Keq) = A + B/T

from figure Keq = 0.003 @ 1452.3 R

Keq = 0.002 @ 1533.75 R

A= -13.444

B = 11088.52

Simulate this reactor

Equilibrium Constant Estimation


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Equilibrium Constant Estimation



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Change reactor type to isotherml at 1534 R and approach fraction of1.0. rerun ( at 200 atm) and check the Keq against the attached data.

Conclusion1. Keq and its correction constants(A and B) are dependent on the

stoichiometric equation.

The stoichiometric coefficients used in the data input must be

consistent with those used to derive the A and B coefficients of

the Keq equation.

2. ChemCAD uses the mole fractions or partial pressures to define

Keq.

The thermodynamically correct form for Keq uses activities,

which are unimportant for liquids. For gases it means that the

Keq equation must be known or correlated at the reactor

pressure.


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GIBBS R t


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GIBBS Reactor

Based on free energy minimization

Similar form to equilibrium reactor

Species derived from component list; inerts may be defined

User components need thermo, atom data

Approach temperature allowed


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Workshop Reactor4 : GIBBS Reactor

Adiabatic equilibrium conversion of 1 mole of nitrogen to ammonia using an excess of

hydrogen. Conversion is based on free energy minimization.

P=200 atm

Simulate this reactor

Change reactor type to isothermal at 1534 R.Rerun and check results against equilibrium reactor results.

The Gibbs reactor is particularly useful where no experimental data

exists on equilibrium or kinetics.


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Analisis de Reacto Con Chemcad

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