A-Introduction & Thermodynamics 2012

Steady State SeminarIntroductory PresentationJohn Edwards, P&I Design Ltd2012

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CRYOGENIC BATCH REACTOR OPTIMISATION

Engineering advanced

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TYPICAL PROCESSES






PROCESS DEVELOPMENT






DESIGN SEQUENCE






CAUTIONARY STORY

• Modelling requires engineering judgement • Rules of thumb (heuristics) used in initial simulations• Modelling enables the engineer to make mistakes faster • Simulation sometimes will give a result different to intuition > check• Plant problems should be reproducible in simulation• Always verify results with independent calculation>rules of thumb• Some of seminar cases have taken days to develop• Modelling can be frustrating > one incorrect parameter is all it takes






IMPACT OF DESIGN ERRORS






SIMULATION PRINCIPLES

Steady State Steady State

Based on direct substitution of variable each iteration and speed up principles

Models plant behaviour using continuous, time interval based, steady state estimates

Requires least effort to set up and calibrate the flowsheet

Ideal for economic analysis and process optimization

DynamicDynamic

Based on real time or speed up dynamics Real plant and equipment performance, retention times and control systems

Requires more information and more difficult to set up

Ideal for troubleshooting, control loop tuning and real time study






SIMULATION PRINCIPLES


Process Unit / Total PlantProcess Unit / Total Plant

Continuous Steady State – Varying Throughput Continuous Steady State – Varying Throughput

Batch – Cycle Time, Volume ScaleBatch – Cycle Time, Volume Scale

Dynamic simulation is series of steady state cases

Continuous Dynamic – Start up, Shutdown, Feed Change , Composition ChangeContinuous Dynamic – Start up, Shutdown, Feed Change , Composition Change

Feeds Recycles ProductsFeeds Recycles Products

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SIMULATION SUITECHEMCAD SOFTWARE


CHEMCAD SIMULATION SOFTWARE

FLASHFLASHPhysical Physical

PropertiesPropertiesDatabaseDatabase

CC-BATCHCC-BATCHBatch Distillation

CC-THERMCC-THERMHeat Exchangers

CHEMCADCHEMCADSteady State

CC-DynamicsCC-DynamicsReactors-ColumnsReactors-Columns

Relief-PipingRelief-Piping

SAFETYNETSAFETYNETRelief-Piping

Dynamics



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CHEMCAD PROCESS SIMULATOR

Graphical Representation of ProcessUnit Operation Symbols contain Math modelsStream Connections with P-T-x CompositionMass & Energy Balances with RecycleEquipment Sizing





CHEMCAD INTERFACES

Microsoft Word Microsoft WordPad Microsoft Excel OPC-OLE for process control VBA/VSTA






CHEMCAD REPORT FORMATS


Reporting in Excel allows for data manipulation





CHEMCAD EQUIPMENT SIZING

Pipe networks Pump sizing Ventilation systems Relief devices Packed & plate towers Orifice plates, restriction orifice plates Control valves Shell and tube & plate heat exchangers Air cooled heat exchangers Plate heat exchangers Pipe in pipe heat exchanger Tank Sizing






REALITY IN SIMULATION






INTRODUCTORY SESSION OBJECTIVES

• Steady state simulation principles • Modelling procedure • Draw flowsheets• Manipulate text and lines• Specify units• Specify components• Plot component properties• User component for aqueous mixtures• Introduce CHEMCAD sizing features• Introduce Data Map facility


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SIMULATION SUITECHEMCAD SOFTWARE

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MODELLING PROCEDURE

Select Convergence

Set Engineering Units

DrawFlowsheet

Select Thermodynamics

Run Wizard Specify T & P

Adjust K Set Local K

Adjust HSet Local H

Specify Feed Streams

Specify UnitOps

Run Simulation

Equipment Sizing

Analyze Results

TPxy-UnitOp Plots

Sizing Reports

Final PFD Report

Consider Data Maps

GUI Presentation

Set Global Phase SLV

Sensitivity Analyses

Optimise

Component PPD Plots

Controllers & Convergence

Select Components

Data Map & Execution Rule

Consider Electrolytes







CASE 2.01 TUTORIAL FLOWSHEET

SAVE!!!






SPECIFY ENGINEERING UNITS






UNIT CONVERTER

Select cellF6 SelectsUnit Converter

F7 SelectsCalculator

Enter data in your units Press enter to calculate then press OK






CONVERGENCE

DIRECT SUBSTITUTIONValue replaced after each iteration

WEGSTEIN ACCELERATIONValue replaced after three iterations-speed up frequency 3

DOMINANT EIGEN VALUEValue replaced after four iterations-speed up frequency 4

CALCULATION STEPS / ITERATIONS Default set at forty

CONVERGENCE PARAMETERSValue change on subsequent iterationTolerance 0.001 equivalent 10-3 absolute value






SELECT COMPONENTS

Double clickor

select






RUN THERMODYNAMIC WIZARD

Enter service fluids

Use for guidance only

MUST verify against plant data





THERMODYNAMIC WIZARD DECISION TREE

COMP

SYSTEM

PRESS

K=PSRK

H=MIXH

SYSTEM

K=VAP

H=SRK

K=VAP

H=LATE

SINGLE

CHEMICAL OTHER

MULTI

CHEM<13BAR OTHER

CH

EM

>13

BA

R

<7BAR

HE

AV

Y H

C

>7BAR

AMINEK=AMINE H=AMINE

SOUR K=SOUR H=SRK

POLYMERK=UPLM H=LATE

HCL/NH3K=PPAQ H=SRK

HTSL

K=ESSO

90 to 200C

H=LK

K=GS

(P<200BAR)

H=LK

Data>50%

NRTL,Wilson

UNIQUACData<50%

UNIFAC

H=LATE (all)

TEMP

K=PR

H=PR

<70

C

K=SRK

H=SRK

>70C

SPECIAL METHODS







SPECIFY THERMODYNAMICS

Use V/L/L/Sfor extraction& azeotropes

Check whenElectrolytes






SPECIFY FEED STREAM






SPECIFY UNITOPS

Heat Exchanger 1 > Stream 2 > Vapor Fraction 1Heat Exchanger 2 > Stream 3 > -10 deg CPipe 5 > D = 200 mm L =50mFlash 3 > Mode 0 Inlet T&PValve 6 > Outlet Pressure 9 baraTower 4 > Stages 12 with Feed Stage 1 > Top Pressure 8.6 bara

> Column DP 0.34 bar > Bottom mf propane 0.01






CASE 2.02 TUTORIAL DATA

OBJECTIVE: MINIMIZE TOLUENE & BENZENE DISCHARGE TO ATMOSPHERE

SERVICESCOOLING WATER AT 85 deg F & 50 psiaGLYCOL AT -60 deg F

STRATEGY CONSIDER COOLING, COMPRESSION & RECYCLE






CASE 12.01 VOC MINIMIZATION STUDY






THERMODYNAMIC SESSION OBJECTIVES

THERMODYNAMICS• Introduce Thermodynamic Wizard• Review K Model facilities• Review L Model facilities• Physical Property Library • Physical Property Plot facility• User components• User component for aqueous mixtures• Introduce CHEMCAD sizing features• Introduce Data Map facility






THERMODYNAMICS - ENTHALPY






THERMODYNAMICS - PHASES





THERMODYNAMIC WIZARD DECISION TREE

COMP

SYSTEM

PRESS

K=PSRK

H=MIXH

SYSTEM

K=VAP

H=SRK

K=VAP

H=LATE

SINGLE

CHEMICAL OTHER

MULTI

CHEM<13BAR OTHER

CH

EM

>13

BA

R

<7BAR

HE

AV

Y H

C

>7BAR

AMINEK=AMINE H=AMINE

SOUR K=SOUR H=SRK

POLYMERK=UPLM H=LATE

HCL/NH3K=PPAQ H=SRK

HTSL

K=ESSO

90 to 200C

H=LK

K=GS

(P<200BAR)

H=LK

Data>50%

NRTL,Wilson

UNIQUACData<50%

UNIFAC

H=LATE (all)

TEMP

K=PR

H=PR

<70

C

K=SRK

H=SRK

>70C

SPECIAL METHODS







THERMODYNAMIC MODEL SELECTION

PHASE

SYSTEM

IDEAL

IDEAL VAP PRESS

GAS EQUATION

BIP MODEL

BIP MODEL

LLE BIPS

NRTL (5 PAR)

UNIQUAC (2 PAR)

UNIFAC(INCREM)

SYSTEM

PENG ROBINSON

GRAYSON STEED

BENEDICT

WEBB RUBIN

GAS EQUATION

SOAVE REDLICH

KWONG(SRK)

GAS

VAP ONLY NAT GAS

LIQUID

LIQUID

LLEH

YD

RO

CA

RB

ON

AZ

EO

TR

OP

E

NO

VL

E

YES

NRTL (5 PAR)

UNIQUAC (2 PAR)

UNIFAC(INCREM)

H=LATENT HEAT

H=LATENT HEAT H=LATENT HEAT

H=LATENT HEATH=LEE KESSLER

H=LEE KESSLER

IDEAL

VAPOR PRESSURE






THERMO MODEL SELECTION
























THERMODYNAMICS BUBBLE POINT & DEW POINT






LIBRARY EQUATIONS IN CHEMCAD






PHYSICAL PROPERTY DATA PLOTS

Heat Transfer Fluids Liquid Specific Heats

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

-50 0 50 100 150

Operating Temperature (degC)

Liq

uid

Sp

ecif

ic H

eat

(kJ/k

g-K

)

Dowtherm A

Dowtherm J

Dowtherm Q

Syltherm XLT

50% EtGlycol

Water

Therminol 55

Therminol 59

Therminol LT

Transcal LT






PHYSICAL PROPERTY DATA PLOTS

Heat Transfer Fluids Liquid Viscosities

0.1

1

10

100

-100 -50 0 50 100 150

Operating Temperature (degC)

Liq

uid

Vis

co

sit

y (

cP

)

Dowtherm A

Dowtherm J

Dowtherm Q

Syltherm XLT

50% EtGlycol

Water

Therminol 55

Therminol 59

Therminol LT

Transcal LT












TPxy & ACTIVITY COEFFICIENT PLOTS






xy RELATIVE VOLATILITY

xy Diagram System Benzene Toluene NRTL at constant pressure

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Benzene Liquid (x mole fraction)

Ben

zen

e V

pao

ur

(y m

ole

fra

ctio

n)

760 mm Hg Relative Volatility = 1.0 25 mm Hg

Increasing α






CASE 4.01 FLASH FUNDAMENTALS


SET EXECUTION RULES





CASE 4.01 FLASH FUNDAMENTALS






RESIDUE CURVE MAPS

Low boiling nodeHigh boiling nodeSaddleDistillation boundaryResidue curves


CEiP9-p339





CHEMCAD RESIDUE CURVE MAPPING






AZEOTROPE FINDERS


Documents

A-Introduction & Thermodynamics 2012