destilacion

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Marzo de 2014

OBJETIVO: DISCUTIR LOS CONCEPTOS BÁSICOS DE LA DESTILACIÓN MULTICOMPONENTE Y LOS REQUERIMIENTOS MÍNIMOS PARA EL MODULO DSTWU PARA EL DISEÑO DE COLUMNAS DE SEPARACIÓN PARA MEZCLAS MULTICOMPONENTES POR MÉTODOS CORTOS.

2.3 Destilación Multicomponente (método corto)

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A B C D E F

D E F

A B C

Conceptos básicos.

• En una mezcla multicomponentes, la separación se realiza consideran solo dos de los componentes, con esta consideración se determina el «corte» de la mezcla.

• Se acostumbra ordenar los componentes en orden de volatilidad

• Los componentes claves son los que se encuentran adyacentes al corte propuesto. En este caso los componentes C y D.

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Marzo de 2014

Conceptos básicos. (continuación) • De estos dos, el más volátil se le da el nombre de componente clave ligero (LK) y al menos volátil, componente clave pesado(HK).

• La cantidad esperada de cada uno de ellos en la corriente de destilado o fondos deberá especificarse inicialmente, este valor se expresa como una fracción, a partir de la siguiente expresión:

ó

ó

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Marzo de 2014

DSTW Configuration Sheet

• Especificar: –Razón de reflujo de operación. –Presión en el condensador y en el rehervidor.

–Componentes claves y fracción de separación en la corriente de destilado.

–Tipo de condensador.

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Marzo de 2014

DSTW Worshop (deoctanizadador) –Start with the General with English Units Template –Use the RK‐Aspen Property Method –When finished, save as filename: Actividad15.apw

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Feed P = 30 psia q=1.0 100 lb/hr (equimolar) n‐pentano n‐hexano n‐heptano (LK) n‐octano (HK)

PD = 30 psia PC= 10 psia Rop = 1.2 Rmin

f(LK)= 0.95

f(HK)= 0.95

CORTOFEED

DESTIL

BOTTOMS

Marzo de 2014

DSTW Workshop (debutanizator) • Objetivo: Diseñar una columna debutanizadora, empleado un método corto

• Con las condiciones especificadas para la columna debutanizadora que se muestra en la siguiente pagina, determine el diseño del proceso

• Preguntas : –Numero de etapas totales obtenidas: _______ –Ubicación del plato de la alimentación, con respecto a los fondos:_______

–Valor de la razón de reflujo de operación: _____

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Marzo de 2014

DSTW Workshop debutanizator (cont.)

–Start with the General with English Units Template

–Use the RK‐Aspen Property Method

–When finished, save as filename: Actividad16.apw

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Feed P = 78.4 psia T = 243.13 °F Comp. lbmol/hr iC4 12 n‐C4(LK) 448 i‐C5 (HK) 36 n‐C5 15 C6 23 C7 39.1 C8 272.2 C9 31.0

PD = 70.4 psia PC= 10 psia Rop = 1.2 Rmin

Comp. lbmol/hr n‐C4 (LK) 442

CORTOFEED

DESTIL

BOTTOMS

Comp. lbmol/hr i‐C5 (HK) 23

Marzo de 2014

OBJECTIVE: DISCUSS THE MINIMUM INPUT REQUIRED FOR THE RADFRAC FRACTIONATION MODEL, AND THE USE OF DESIGN SPECIFICATIONS AND STAGE EFFICIENCIES

2.3 RadFrac

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Marzo de 2014

RadFrac: Rigorous Multistage Separation • Vapor‐Liquid or Vapor‐Liquid‐Liquid phase simulation of:

–Ordinary distillation –Absorption, reboiled absorption –Stripping, reboiled stripping –Azeotropic distillation –Reactive distillation

• Configuration options: –Any number of feeds –Any number of side draws –Total liquid draw off and pumparounds –Any number of heaters –Any number of decanters

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Marzo de 2014

RadFrac Flowsheet Connectivity

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Top‐Stage or Condenser Heat Duty

Feeds

Heat (optional)

Pumparound

Bottom Stage or Reboiler Heat Duty

Vapor Distillate

Heat (optional)

Heat (optional)

Liquid Distillate Water Distillate

Reflux

Heat (optional)

Products (optional)

Product

Decanters

Return

Bottoms

Heat (optional)

for stage

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Marzo de 2014

RadFrac Setup Configuration Sheet

• Specify:

–Calculation type

–Number of stages

–Condenser and reboiler configuration

– Two column operating specifications

–Valid phases

–Convergence

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Marzo de 2014

RadFrac Setup Streams Sheet

• Specify: – Feed stage location

– Feed stream convention

ABOVE‐STAGE: • Vapor from feed goes to stage above feed stage

• Liquid goes to feed stage

ON‐STAGE: • Vapor & Liquid from feed go to specified feed stage

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Marzo de 2014

RadFrac Setup Pressure Sheet

• Specify one of: –Column pressure profile

–Top/Bottom pressure

–Section pressure drop

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Marzo de 2014

Methanol‐Water RadFrac Column –Start with the General with Metric Units Template –Use the NRTL‐RK Property Method –When finished, save as filename: Actividad17.apw

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Filename: Actividad05.awp

T = 65 C P = 1 bar Water: 100 kmol/hr Methanol: 100 kmol/hr

RadFrac specifications Total Condenser Kettle Reboiler 9 Stages Reflux Ratio = 1 Distillate to feed ratio = 0.5 Column pressure = 1 bar Feed stage = 6

COLUMN FEED

OVHD

BTMS

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Marzo de 2014

Columna RadFrac para C2/C3/nC4/nC5/nC6 –Start with the General with English Units Template –Use the Soave‐Redlich‐Kwong Property Method –When finished, save as filename: Actividad18.apw

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Feed P = 250 psia T = 213.9 F lbmol/h etano 3.0 propano 20.0 n‐butano 37.0 n‐pentano 35.0 n‐hexano 5.0

P = 250 psia D = 23 lbmol/h Reflujo = 150 lbmol/h Numero de etapas en la columna = 17 Condensador y hervidor parcial Alimentación en la mitad de la columna

Especificación: la pureza del propano en el destilado será de 0.86 fracción molar

COLUMN FEED

OVHD

BTMS

Marzo de 2014

RadFrac Options • To set up an absorber with no condenser or reboiler, set condenser and reboiler to none on the RadFrac Setup Configuration sheet.

• Either Vaporization or Murphree efficiencies on either a stage or component basis can be specified on the RadFrac Efficiencies form.

• Tray and packed column design and rating is possible. • A Second liquid phase may be modeled if the user selects Vapor‐liquid‐liquid as Valid phases.

• Reboiler and condenser heat curves can be generated.

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Marzo de 2014

Plot Wizard • Use Plot Wizard (on the Plot menu) to quickly generate plots of results of a simulation. You can use Plot Wizard for displaying results for the following operations: – Physical property analysis –Data regression analysis – Profiles for all separation models RadFrac, MultiFrac, – PetroFrac and RateFrac

• Click the object of interest in the Data Browser to generate plots for that particular object.

• The wizard guides you in the basic operations for generating a plot. • Click on the Next button to continue. Click on the Finish button to generate a plot with default settings.

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Marzo de 2014

Plot Wizard Demonstration

•Use the plot wizard on the column to create a plot of the liquid phase compositions throughout the column.

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Marzo de 2014

RadFrac DesignSpecs and Vary

•Design specifications can be specified and executed inside the RadFrac block using the DesignSpecs and Vary forms.

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Marzo de 2014

RadFrac DesignSpecs and Vary

• One or more RadFrac inputs can be manipulated to achieve specifications on one or more RadFrac performance parameters.

• The number of specs should, in general, be equal to the number of varies.

• The DesignSpecs and Varys in a RadFrac are solved in a “Middle loop.” If you get an error message saying that the middle loop was not converged, check the DesignSpecs and Varys you have entered.

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Marzo de 2014

RadFrac Convergence Problems

• If a RadFrac column fails to converge, doing one or more of the following could help: 1. Check that physical property issues (choice

ofProperty Method, parameter availability, etc.) are properly addressed.

2. Ensure that column operating conditions are feasible.

3. If the column err/tol is decreasing fairly consistently, increase the maximum iterations on the RadFrac Convergence Basic sheet.

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Marzo de 2014

RadFrac Convergence Problems (Continued)

4. Provide temperature estimates for some stages in the column using the RadFrac Estimates Temperature sheet (useful for absorbers).

5. Provide composition estimates for some stages in the column using the RadFrac Estimates Liquid Composition and Vapor Composition sheet (useful for highly non‐ideal systems).

6. Experiment with different convergence methods on the RadFrac Setup Configuration sheet.

When a column does not converge, it is usually beneficial to Reinitialize after making changes.

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Marzo de 2014

RadFrac Workshop

– Start with the General with English Units Template

– Use the NRTL‐WATER Property Method

• Part A: – Perform a rating calculation of a Methanol tower using the following data.

– When finished, save as filename: Actividad19.apw

Feed: 63.2 wt% Water 36.8 wt% Methanol Total flow = 120,000 lb/hr Pressure 18.3 psia Saturated liquid

Column specification: 38 stage Feed tray = 23 stage 24 Total condenser Top stage pressure = 16.1 psia Pressure drop per stage = 0.1 psi Distillate flowrate = 1245 lbmol/hr Molar reflux ratio = 1.3

COLUMN FEED

OVHD

BTMS

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Marzo de 2014

RadFrac Workshop (Continued) • Part B:

–Set up design specifications within the column so the following two objectives are met: • 99.95 wt% methanol in the distillate • 99.90 wt% water in the bottoms

–To achieve these specifications, you can vary the distillate rate (800‐1700 lbmol/hr) and the reflux ratio (0.8‐2). Make sure stream compositions are reported as mass fractions before running the problem. Note the condenser and reboiler duties: • Condenser Duty :__________________ • Reboiler Duty :____________________


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Marzo de 2014

RadFrac Workshop (Continued) • Part C:

–Perform the same design calculation after specifying a 65% Murphree efficiency for each tray. Assume the condenser and reboiler have stage efficiencies of 90%.

–How do these efficiencies affect the condenser and reboiler duties of the column?


• Part D:

–Perform a tray sizing calculation for the entire column, given that Bubble Cap trays are used.

• When finished, save as filename: Actividad22.apw

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Marzo de 2014

COL-REAC

BUTENOS

DESTIL

BOTTOMS

METANOL

BOMBA

COMP

VALVULE1

VALVULE2

VALVULE3

MEOH1 MEOH2

D1

B1

BUT1

RadFrac ‐ Reactive Distillation Workshop

– Iniciar con la plantilla “General with Metric Units”

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– Utilizar el método de propiedades UNIFAC.

– Al terminar salvar como des_reac.apw

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Marzo de 2014

• Sistema de reacción. ⇄

Isobutene + alcohol metílico ⇄ Metil‐ TerButil‐ ter Con 1‐butene como inerte

• Con la cinética:

3.67 ∗ 1092440

2.67 ∗ 10134454

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Marzo de 2014

•Corrientes de alimentación

– Methanol • Fujo 711.3 kmol/hr de methanol puro

•Temperatura 320 K

•Presión 1 atm.

– Butenos • Fujo 1965.8 kmol/hr

–xIB = 0.36

–xNB = 0.64

•Temperatura 350 K

•Presión 1 atm.

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Marzo de 2014


•Bomba:

– Discharge Pressure = 11.7 atm

•Compresor

–Type: isentropico – Discharge Pressure = 11.7 atm

•Valvulas

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ID Calculation Type Outlet Pressure

VALVULE1 Adiabatic Flash 11.5 atm



Marzo de 2014


• Columna (COL‐REAC)

– Numero de etapas 17

– Condensador total

– Rehervidor tipo Kettle

– Flujo en el fondo 640.8 kmol/hr

– Razón de reflujo 7

– Alimentaciones • Methanol etapa 10

• Butenos etapa 11

– Presión • Domo de la columna 11 atm

• Caída de presión en la columna 0.5 atm

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Marzo de 2014


• Columna (COL‐REAC) – Reaction

• Zona reactiva Plato 4 al 11 • Reacciones R1 • 1000 kg catalyst/stage

– Packing rating • Zona empacada Plato 2 al 16 • Mellapak Sulzer 250 y • Diametro de la columna 6 mt • HETP = 1 mt

– Convergence • 200 iterationes

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destilacion

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