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PRO/II APPLICATION BRIEFS

GAS PROCESSING REFINING PETROCHEMICAL CHEMICAL SOLIDS

TechnicalAssistance

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South America SIMSCI Latinoamerica C.A. 58-2-959-8033 58-2-993-2717

Centro Banaven (Cubo Negro)Torre A, PH A-2Av. La Estancia, ChuaoCaracas, 1060, Venezuela

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Table of ContentsPRO/II APPLICATION BRIEFS

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

INDEX OF FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . IF-1

GAS PROCESSING

PHASE ENVELOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G1-1

DEETHANIZER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G2-1

REFRIGERATION LOOP . . . . . . . . . . . . . . . . . . . . . . . . . . . G3-1

COMPRESSOR TRAIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . G4-1

EXPANDER PLANT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G5-1

THREE STAGE LETDOWN . . . . . . . . . . . . . . . . . . . . . . . . . . G6-1GAS DEHYDRATION USING TEG . . . . . . . . . . . . . . . . . . . . . . G7-1

AMINE SWEETENING PLANT . . . . . . . . . . . . . . . . . . . . . . . . G8-1

REFINING

CRUDE HEATING CURVE . . . . . . . . . . . . . . . . . . . . . . . . . . R1-1

DE-IC4 TOWER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R2-1

CRUDE OIL DISTILLATION . . . . . . . . . . . . . . . . . . . . . . . . . . R3-1

VACUUM COLUMN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R4-1

FCC MAIN FRACTIONATOR . . . . . . . . . . . . . . . . . . . . . . . . . R5-1

SOUR WATER STRIPPER . . . . . . . . . . . . . . . . . . . . . . . . . . R6-1STABILIZER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R7-1

NAPHTHA SPLITTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R8-1

PETROCHEMICAL

C3 SPLITTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P1-1

AROMATICS SEPARATION . . . . . . . . . . . . . . . . . . . . . . . . . P2-1

ETHYLENE FRACTIONATOR . . . . . . . . . . . . . . . . . . . . . . . . P3-1

CYCLOHEXANE PLANT . . . . . . . . . . . . . . . . . . . . . . . . . . . P4-1

NAPHTHALENE RECOVERY . . . . . . . . . . . . . . . . . . . . . . . . . P5-1

MTBE SEPARATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P6-1

PROPYLENE CHLORINATION . . . . . . . . . . . . . . . . . . . . . . . . P7-1

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CHEMICAL

DRYER COLUMN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C1-1

AMMONIA-ACETONE-WATER SEPARATION . . . . . . . . . . . . . . . C2-1

MEK-WATER-TOLUENE . . . . . . . . . . . . . . . . . . . . . . . . . . . C3-1

AZEOTROPIC SEPARATION . . . . . . . . . . . . . . . . . . . . . . . . C4-1

PHENOL EXTRACTION . . . . . . . . . . . . . . . . . . . . . . . . . . . C5-1

DECANT COLUMN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C6-1

SHIFT AND METHANATOR REACTORS . . . . . . . . . . . . . . . . . . C7-1

ADVANCED

CASCADE REFRIGERATION . . . . . . . . . . . . . . . . . . . . . . . . A1-1

PHENOL DISTILLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-1

HDS REACTOR SECTION . . . . . . . . . . . . . . . . . . . . . . . . . . A3-1TURBO-EXPANDER GAS PLANT OPTIMIZATION . . . . . . . . . . . . . A4-1

SULFURIC ACID ALKYLATION . . . . . . . . . . . . . . . . . . . . . . . A5-1

AMMONIA SYNTHESIS . . . . . . . . . . . . . . . . . . . . . . . . . . . A6-1

SOLIDS

P-XYLENE CRYSTALLIZATION . . . . . . . . . . . . . . . . . . . . . . . S1-1

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Refinery . . . . . . . . . . . . . . . . . . . . . . . . R3, R4, R5Simple . . . . . . . . . . . . . . . . . . . . . . . . . P2, P5

LIQUID SIDE DRAW . . . . . . . . . . . . . . . . . . . . C2, R3, R4, R5, R8

MULTI-FEED . . . . . . . . . . . . . . . . . . . . . . . . A4, C4, R3, R4, R5, R8

NO REBOILER . . . . . . . . . . . . . . . . . . . . . . . G7, G8, P3, R3, R4, R5

PSEUDO STREAMS . . . . . . . . . . . . . . . . . . . . R4

PUMPAROUNDS . . . . . . . . . . . . . . . . . . . . . . P3, R3, R4, R5

SIDE HEATERS/COOLERS . . . . . . . . . . . . . . . . . P3, R3, R4, R5

SIDE STRIPPERS . . . . . . . . . . . . . . . . . . . . . . R3, R5, R8Steam stripped . . . . . . . . . . . . . . . . . . . . P3, R3, R5, R6Reboiled . . . . . . . . . . . . . . . . . . . . . . . . R8

SPECIFICATIONSComponent purity/recovery . . . . . . . . . . . . . . A2, C1, C3, C5, G2, G8, P1, P2, P5,

. . . . . . . . . . . . . . . . . . . . . . . . . . . . P6, R6, R8Component ratio . . . . . . . . . . . . . . . . . . . C6, G5Distillation point . . . . . . . . . . . . . . . . . . . . R3, R5Overflash/runback to feed zone . . . . . . . . . . . . R3, R4Product molal rate . . . . . . . . . . . . . . . . . . A4, C2, R7Product volume rate . . . . . . . . . . . . . . . . . P3, R4, R5Product weight rate . . . . . . . . . . . . . . . . . . A2, C4Reflux (external) . . . . . . . . . . . . . . . . . . . A2, C2, C3, C4, C5, C6, G8, P6Reflux (internal) . . . . . . . . . . . . . . . . . . . . R4RVP . . . . . . . . . . . . . . . . . . . . . . . . . . R7Tray temperatures . . . . . . . . . . . . . . . . . . . A5, G7, P3, R4

SPECIFICATION VARIABLESFeed . . . . . . . . . . . . . . . . . . . . . . . . . . G8, P3, R3, R4, R5, R6, R8Heater/cooler . . . . . . . . . . . . . . . . . . . . . A2, A5, C1, C2, C3, C4, C5, C6, G2, G5,

. . . . . . . . . . . . . . . . . . . . . . . . . . . . G7, G8, P1, P2, P5, P6, R3, R5, R7, R8Side draw rate . . . . . . . . . . . . . . . . . . . . . P2, R4

THERMOSIPHON REBOILER . . . . . . . . . . . . . . . G2, R5

TRAY SIZING/RATING . . . . . . . . . . . . . . . . . . . C1, C4, G2, R5

VAPOR SIDE DRAW . . . . . . . . . . . . . . . . . . . . P2

WATER DECANTING . . . . . . . . . . . . . . . . . . . . P3, R3, R5

Application Brief

IF-2 INDEX OF FEATURES PRO/II APPLICATION BRIEFSAugust 1995


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COMPONENT PROPERTIES INPUTCRITICAL PROPERTIES . . . . . . . . . . . . . . . . . A2, A5

LATENT HEAT . . . . . . . . . . . . . . . . . . . . . . . A2

LIQUID ENTHALPY . . . . . . . . . . . . . . . . . . . . A2

LIQUID DENSITY . . . . . . . . . . . . . . . . . . . . . A2

MOLECULAR WEIGHT . . . . . . . . . . . . . . . . . . A2

NORMAL BOILING POINT . . . . . . . . . . . . . . . . . A2

SPECIFIC GRAVITY . . . . . . . . . . . . . . . . . . . . A2

VAPOR PRESSURE . . . . . . . . . . . . . . . . . . . . A2

COMPRESSORSAFTERCOOLER . . . . . . . . . . . . . . . . . . . . . . G4GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . A1, A3, A5, A6, G6, P4, P7

LINKED TO EXPANDER . . . . . . . . . . . . . . . . . . A4, G5MANUFACTURERS PERFORMANCE CURVES . . . . . G3

CONTROLLERS . . . . . . . . . . . . . . . . . . . . . . A1, A3, A5, A6, G3, G6, P3, P4, S1

DIMENSIONAL UNITSENGLISH . . . . . . . . . . . . . . . . . . . . . . . . . . A1, A3, A4, A5, A6, C3, C4, C5, C6, C7,

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G1, G2, G3, G5, G6, G7,G8, P3, P4,

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P6, R3, R5, R6, R7, R8

METRIC . . . . . . . . . . . . . . . . . . . . . . . . . . A2, C1, P5, R4SI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C2, G4, P2

ENTHALPY OPTIONSLEE-KESLER . . . . . . . . . . . . . . . . . . . . . . . . P5

IDEAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2, C1,C2, C4

EXPANDER . . . . . . . . . . . . . . . . . . . . . . . . . . A4, G5

FLASHESADIABATIC . . . . . . . . . . . . . . . . . . . . . . . . . A1, A4, A6, G3, G4, G5, G6, G7, P4

DECANT WATER . . . . . . . . . . . . . . . . . . . . . . G6ISOTHERMAL . . . . . . . . . . . . . . . . . . . . . . . A1, A2, A3, A5, A6, G6, G7, R5

DEFINED SPECIFICATION . . . . . . . . . . . . . . . . G8, R3, R4

Application Brief

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FUGACITY OPTIONSIDEAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2, C1

SOAVE-REDLICH-KWONG . . . . . . . . . . . . . . . . . P6

HEAT EXCHANGERATTACHED . . . . . . . . . . . . . . . . . . . . . . . . . A4CONFIGURATION . . . . . . . . . . . . . . . . . . . . . . P4

PROCESS/PROCESS . . . . . . . . . . . . . . . . . . . A1, A3, A4, A5, A6, G5, G7, G8, P4, S1

PROCESS/UTILITY . . . . . . . . . . . . . . . . . . . . . A4, A5, C5, G6, G8, P4, S1

SINGLE SIDED . . . . . . . . . . . . . . . . . . . . . . . A5, G3, G5, G7, P7

SPECIFICATIONApproach . . . . . . . . . . . . . . . . . . . . . . . A1, A5, G5Duty . . . . . . . . . . . . . . . . . . . . . . . . . . G3Liquid fraction . . . . . . . . . . . . . . . . . . . . . A1, A5, G3Temperature . . . . . . . . . . . . . . . . . . . . . . A3, A4, A5, A6, G3, G5, G6, G8, P4, P7

HEATING/COOLING CURVESFEED VAPORIZATION . . . . . . . . . . . . . . . . . . . R1

INTERACTIVE . . . . . . . . . . . . . . . . . . . . . . . . G3, P2

K-VALUESALCOHOL . . . . . . . . . . . . . . . . . . . . . . . . . . C3, C6AMINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . G8

BRAUN K10 . . . . . . . . . . . . . . . . . . . . . . . . . R3, R4, R5

CHAO-SEADER/GRAYSON-STREED . . . . . . . . . . . A3, P2, P4, P5, R7

GLYCOL . . . . . . . . . . . . . . . . . . . . . . . . . . . G7

NRTL . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2, C1, C2, C5

PENG-ROBINSON . . . . . . . . . . . . . . . . . . . . . A1, G3, G5, P1, P3Interaction parameter . . . . . . . . . . . . . . . . . P1

POYNTING . . . . . . . . . . . . . . . . . . . . . . . . . A2, C1, P6

SOAVE-REDLICH-KWONG . . . . . . . . . . . . . . . . . A5, A6, C7, G1, G2, G4, G6, R8

UNIFAC . . . . . . . . . . . . . . . . . . . . . . . . . . . C5, P6

VAN LAAR . . . . . . . . . . . . . . . . . . . . . . . . . . C4

SOUR . . . . . . . . . . . . . . . . . . . . . . . . . . . . R6

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LIQUID DENSITY OPTIONSAPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A1, C7

IDEAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2, C6, G7

LEE-KESLER . . . . . . . . . . . . . . . . . . . . . . . . G3, G2, G4, G5, P5

COSTALD . . . . . . . . . . . . . . . . . . . . . . . . . . P3, P7

MIXER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A1, A3, G3, G8, P4, P7, R4

OPTIMIZER . . . . . . . . . . . . . . . . . . . . . . . . . . A4, R7

OUTPUT OPTIONSASTM/TBP CURVES . . . . . . . . . . . . . . . . . . . . P3, R1, R3, R4, R5LIQUID VOLUME . . . . . . . . . . . . . . . . . . . . . . A5, G5

MULTIPLE OUTPUTS . . . . . . . . . . . . . . . . . . . C7, G5

PARTIAL . . . . . . . . . . . . . . . . . . . . . . . . . . G4, R8

STREAM COMPONENT FRACTION/PERCENT . . . . . A2, A3, C1, C2, C3, C4, P1, P2, P6, R8, S1

STREAM SUMMARY . . . . . . . . . . . . . . . . . . . . R3, R4, R5, R6

PETROLEUM FRACTION INPUT . . . . . . . . A3, G4, G6, P3, P5

PHASE ENVELOPE . . . . . . . . . . . . . . . . . . . G1

PUMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A4, C5, G7, G8, P4, S1

REACTORSCONVERSION . . . . . . . . . . . . . . . . . . . . . . . A3, A5, P4

CSTR . . . . . . . . . . . . . . . . . . . . . . . . . . . . P7

EQUILIBRIUM . . . . . . . . . . . . . . . . . . . . . . . A6METHANATOR . . . . . . . . . . . . . . . . . . . . . . . C7

SHIFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . C7

RECYCLEACCELERATION . . . . . . . . . . . . . . . . . . . . . . A3, A6, G8, P4, P7, S1

CLOSED LOOP . . . . . . . . . . . . . . . . . . . . . . A1, A5, G3GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . A2, A4, G4, G6

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PURGED . . . . . . . . . . . . . . . . . . . . . . . . . . A3, P4THERMAL . . . . . . . . . . . . . . . . . . . . . . . . . . A1, G5

TOLERANCE . . . . . . . . . . . . . . . . . . . . . . . . P4

REFERENCE STREAMS . . . . . . . . . . . . . . . A1, G5, G8, P4

SEQUENCING . . . . . . . . . . . . . . . . . . . . . . . . A4, G5, P4

SHORTCUT DISTILLATIONFENSKE MULTIPRODUCT . . . . . . . . . . . . . . . . . R3

ONE FEED, TWO PRODUCT . . . . . . . . . . . . . . . . P1, P5, P7

SOLIDSCENTRIFUGE . . . . . . . . . . . . . . . . . . . . . . . . S1

CRYSTALLIZER . . . . . . . . . . . . . . . . . . . . . . . S1

DISSOLVER . . . . . . . . . . . . . . . . . . . . . . . . . S1

MELTER . . . . . . . . . . . . . . . . . . . . . . . . . . . S1

SPLITTER . . . . . . . . . . . . . . . . . . . . . . . . . . . A1, A3, A4, A6, C5, G6, G8, P4, P7

STREAM CALCULATOR . . . . . . . . . . . . . . . A3, A6, C7, G7, G8, P4, P7

STREAM INPUTASTM CURVE . . . . . . . . . . . . . . . . . . . . . . . . R1, R4, R5LIGHTENDS . . . . . . . . . . . . . . . . . . . . . . . . . R1, R3

LIQUID FRACTION . . . . . . . . . . . . . . . . . . . . . G2

TBP CURVE . . . . . . . . . . . . . . . . . . . . . . . . . R3, R5

THERMODYNAMIC PROPERTIES INPUTSOAVE-REDLICH-KWONG . . . . . . . . . . . . . . . . . A6

TRANSPORT PROPERTIESAPI LIQUID VISCOSITY . . . . . . . . . . . . . . . . . . R3, R5PETROLEUM . . . . . . . . . . . . . . . . . . . . . . . . A4, R1, R3, R4, R5

PURE/LIBRARY . . . . . . . . . . . . . . . . . . . . . . . C2, C5, C7, G2

SIMSCI LIQUID VISCOSITY . . . . . . . . . . . . . . . . R4

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VALVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2, A4, A5, C5, G3, G5

VAPOR PRESSURE SPECIFICATIONSRVP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R7

TVP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G6

VLE REGRESSION . . . . . . . . . . . . . . . . . . . C1, P1

VLLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C3, C6

WATERDECANTATION IN COLUMN CONDENSER . . . . . . . R3, R5WATER TRAP TRAYS . . . . . . . . . . . . . . . . . . . P3

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Amine Sweetening Plant

Deethanizer

Refrigeration Loop

Compressor Train

Expander Plant

Three Stage Letdown

Gas Dehydration using TEG

G3

G2

G7

G6

G5

G4

G8

Phase Envelope G1

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PHASE ENVELOPEA high pressure natural gas stream is being transported through a pipeline. Youneed to establish whether liquid will dropout during a cold winter, and, if so, whatyou must do to prevent it.

The first step is to determine the conditions under which liquid will appear. Theeasiest way to do this is to produce a phase envelope for the gas mixture andexamine the boundary of the two phase region.

Process Data Table G1.1 shows the composition of the gas stream. No additional data arerequired to solve this problem.

Table G1.1GAS STREAM COMPOSITION

Component mole % Component mole %

Nitrogen 1.40 N-butane 0.44

Methane 94.30 N-pentane 0.37

Ethane 2.60 N-hexane 0.21

Propane 0.68

Methodsand Data

The phase envelope will solve using either Soave-Redlich-Kwong (SRK) or Peng-Robinson (PR) for the equilibrium and enthalpy calculations. This example usesSRK.

SimulationModel

Phase envelopes may be generated for any flow sheet stream whether it is a definedfeed stream or the product from a unit operation. The phase envelope is a functiononly of the stream composition.

All you need to specify to generate the complete envelope is the stream label. Noinitial estimates are required. The critical point, cricondentherm and cricondenbar,will all be calculated.

Input Data The phase envelope is generated by the first EVALUATE statement. The otherstatements produce lines of constant liquid fraction which are superimposed on theenvelope.

The temperature and pressure of the stream must be entered on the PROPstatement, but they are not used in the calculation.

G1 P H A

S E

E N V E L

OP E

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Input Data File:

TITLE PROBLEM=G1,PROJECT=APPBRIEFS,& USER=SIMSCI,DAT E=SEPT 90

COMPONENT DATA

LIBID 1,N2/2,C1/3,C2/4 ,C3/5,NC4/6,NC5/7,NC6

THERMODYNAMIC DATA

METHOD SYSTEM=SRK

STREAM DATA

PROP STREAM=1,TEMP=1,PRESS=1,&

COMP=1.4/94.3/2.6/0.68/0.44/0.37/0.21

UNIT OPERATION

PHASE UID=PHS1

EVALUATE STREAM=1

EVALUATE STREAM=1,LFRACT=0.05

EVALUATE STREAM=1,LFRACT=0.01

Results The maximum dew point temperature occurs at the cricondentherm which is 28.2F at a pressure of 600 psia.

Figure G1.1

Phase Envelope Plot

G 1 P H A S E

E N V E L O P E

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Conclusions If temperatures below 28 F are possible, condensation could occur in parts of thepipeline which are exposed to the atmosphere.

You will need to study the specific pipeline further to establish whether heaters arerequired or if insulation will be sufficient. Alternatively, you might consider removingmore of the heavier components in the gas treatment before the gas enters thepipeline.

Output The phase envelope information is most easily interpreted when presented ingraphical form. The phase envelope plot shows the type of output produced fromthe PC graphics option.

The plot shows the envelope with the lines of constant liquid fraction at 1% and 5%superimposed on it. If you could accept up to 1% liquid in your line, there would beno problem unless the temperature fell below -19 F.

The tabular temperature and pressure points for the phase envelope are printed,and the critical point is identified. Similar tables are available for the lines of constantliquid fraction.

G1 P H A

S E

E N V E L

OP E

PRO/II APPLICATION BRIEFS PHASE ENVELOPE G1-3February 1991


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P HASE E NVELOPE TABULAR O UTPUT UNIT 1, PHS1

SET 1, STREAM 1

F PSIA CRICONDENTHERM 28.20 599.6 CRICONDENBAR -27.98 1324.5 CRITICAL POINT -96.06 847.7 MAX. TEMP AND PRES 28.20 1324.5

TEMP PRES TEMP PRES F PSIA F PSIA ---------------- ---------------- ---------------- ---------------- 1 DEW PT 4.33 147.0 41 MAX PRES -27.98 1324.5 2 DEW PT 6.92 177.1 42 DEW PT -41.73 1292.7 3 DEW PT 9.51 207.3 43 DEW PT -51.21 1260.9

4 DEW PT 12.11 237.5 44 DEW PT -56.09 1229.1 5 DEW PT 14.70 267.7 45 DEW PT -60.96 1197.3 6 DEW PT 17.29 297.9 46 DEW PT -65.84 1165.5 7 DEW PT 19.88 328.0 47 DEW PT -70.09 1133.7 8 DEW PT 22.48 358.2 48 DEW PT -73.34 1102.0 9 DEW PT 24.29 388.4 49 DEW PT -76.59 1070.2 10 DEW PT 24.85 418.6 50 DEW PT -79.84 1038.4 11 DEW PT 25.41 448.7 51 DEW PT -83.01 1006.6 12 DEW PT 25.97 478.9 52 DEW PT -85.70 974.8 13 DEW PT 26.52 509.1 53 DEW PT -88.40 943.0 14 DEW PT 27.08 539.3 54 DEW PT -91.06 911.2 15 DEW PT 27.64 569.5 55 DEW PT -93.55 879.5 16 MAX TEMP 28.20 599.6 56 CRITICAL -96.06 847.7 17 DEW PT 27.67 628.6 57 BBL PT -98.98 815.8 18 DEW PT 27.14 657.6 58 BBL PT -102.03 784.0 19 DEW PT 26.61 686.6 59 BBL PT -105.17 752.1 20 DEW PT 26.07 715.6 60 BBL PT -108.38 720.2 21 DEW PT 25.54 744.6 61 BBL PT -111.63 688.4 22 DEW PT 25.01 773.6 62 BBL PT -115.00 656.5 23 DEW PT 24.48 802.6 63 BBL PT -118.37 624.7 24 DEW PT 23.94 831.6 64 BBL PT -121.91 592.8 25 DEW PT 23.41 860.6 65 BBL PT -125.50 561.0 26 DEW PT 22.48 889.6 66 BBL PT -129.19 529.1 27 DEW PT 20.60 918.6 67 BBL PT -133.21 497.3 28 DEW PT 18.73 947.6 68 BBL PT -137.22 465.4 29 DEW PT 16.85 976.6 69 BBL PT -141.24 433.5 30 DEW PT 14.97 1005.5 70 BBL PT -145.77 401.7 31 DEW PT 13.10 1034.5 71 BBL PT -150.79 369.8 32 DEW PT 11.22 1063.5 72 BBL PT -155.81 338.0 33 DEW PT 9.35 1092.5 73 BBL PT -160.83 306.1 34 DEW PT 7.47 1121.5 74 BBL PT -165.85 274.3 35 DEW PT 5.59 1150.5 75 BBL PT -172.23 242.4 36 DEW PT 3.72 1179.5 76 BBL PT -179.30 210.6 37 DEW PT 1.14 1208.5 77 BBL PT -186.36 178.7 38 DEW PT -5.25 1237.5 78 BBL PT -194.08 146.8 39 DEW PT -11.64 1266.5 79 BBL PT -204.72 115.0 40 DEW PT -18.03 1295.5 80 BBL PT -215.36 83.1

G 1 P H A S E

E N V E L O P E

G1-4 PHASE ENVELOPE PRO/II APPLICATION BRIEFSFebruary 1991


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DEETHANIZERYou have to design a deethanizer to remove C2 and lighter components from a lighthydrocarbon gas stream. 99% of the propane in the feed must be recovered in thebottom product. The bottoms purity is defined by an ethane to propane ratio of0.025.

There is a design trade-off between capital and operating costs. Capital costdepends on the number of stages, which determines the height, and on the diameterof the column. Operating costs depend on condenser and reboiler loadings.

In order to develop a relationship between capital and operating costs, a number ofruns with different column heights (stages) is required. This example calculates thediameter of a 20 theoretical tray column operating at 82% of flood, with an 18-inchsieve tray spacing. The diameters of the sections above and below the feed aredetermined separately.

Process Data The flow sheet is shown in Figure G2.1.

Figure G2.1

Deethanizer Column

G2 D E E T H A N I Z E R

PRO/II APPLICATION BRIEFS DEETHANIZER G2-1February 1991


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Table G2.1 shows the composition of the feed stream.

Table G2.1GAS STREAM COMPOSITION



Methane 44.59 I-pentane 1.68

Ethane 19.83 N-pentane 1.16

Propane 19.09 N-hexane 2.96

I-butane 4.16 N-heptane 1.90

Total flow (lb moles/hr) 900.00

The known process conditions are shown in Table G2.2.

Table G2.2Process Conditions

Stream Pressure(psig)

ThermalConditions

1 (feed) 440 30 mole % vaporized

2 (condenser) 425 dew point

3 (bottoms) 440 bubble point

Methodsand Data

Soave-Redlich-Kwong has been chosen to calculate equilibrium, enthalpy, andvapor density. Lee-Kesler is used for liquid density. The tray sizing calculationrequires transport properties which are generated by component blending.

SimulationModel

The deethanizer is modeled as a conventional distillation column with 20 theoreticalstages including the condenser. A thermosiphon reboiler is required; this is simu-lated by a pump-around heater on the bottom tray, with a return stream vapor fractionof 0.35. The feed is flashed at the feed tray pressure, the vapor rising under tray 9and the liquid dropping onto tray 10.

G 2 D E E T H A N I Z E R

G2-2 DEETHANIZER PRO/II APPLICATION BRIEFSFebruary 1991


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Input Data Standard English units have been chosen except that the pressure units have beenchanged to psig and liquid volume units to US gallons.

The liquid fraction of the feed is entered, and the temperature at the feed pressurewill be calculated.

The SEPARATE keyword on the FEED statement sends the vapor to the tray above.Without it, the vapor portion of a mixed phase feed would enter below the feed tray.The tray sizing calculations are invoked by the TSIZE statements. The size of eachtray is determined, and each section is then rated at its largest tray diameter.

The propane recovery is defined by a 1% molar loss in the overhead. The ethane/pro-pane ratio in the bottoms, 0.025, is the ratio of the component molar flow rates. Thecondenser and reboiler duties are varied in order to meet the specifications.

Input Data File:

TITLE PROBLEM=G2,PROJECT=APPBRIEFS,USER=SIMSCI,DATE=SEPT 90

DIMENSION PRES=PSIG,LIQVOL=GAL

COMPONENT DATA

LIBID 1,N2/2,C1/3,C2/4,C3/5,IC4/6,NC4/&

7,IC5/8,NC5/9,NC6/10,NC7

THERMODYNAMIC DATA

METHOD SYSTEM=SRK,DENSITY(L)=LK,TRANSPORT=PURE

STREAM DATA

PROP STREAM=1,LFRACT=0.7,PRESS=440,RATE=900,&

COMP=0.03/44.59/19.83/19.09/4.16/&

4.60/1.68/1.16/2.96/1.90

NAME 1,FEED/2,OVERHEAD/3,BOTTOMS

UNIT OPERATIONS DATA

COLUMN UID=D101,NAME=DEETHANIZER

PARA TRAY=20 FEED 1,10,SEPARATE

PROD OVHD=2,540,BTMS=3

COND TYPE=PARTIAL,PRES=425

PSPEC TOP=430,DPCOL=10

HEAT 1,1/2,20

ESTI MODEL=CONVENTIONAL,RRATIO=0.4

SPEC STREAM=3,COMP=3,RATE,RATIO,COMP=4,VALUE=0.025

SPEC STREAM=2,COMP=4,RATE,RATIO,STREAM=1,VALUE=0.01

PA FROM=20,TO=20,LFRACTION=0.65

VARY HEAT=1,2

TSIZE SECTIONS=2,9,SIEVE,SPACING=18,FF=82,DMIN=18

TSIZE SECTIONS=10,20,SIEVE,SPACING=18,FF=82,DMIN=18

END




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Results The capital cost of the column depends on its height and diameter. The height is afunction of the number of trays. The diameters for 20 theoretical stages are 30inches above the feed and 54 inches below it.

Conclusions This simulation shows the diameter and duties for one specific column height. Thecolumn cost is obtained from the height and diameter. The column duties determinethe capital costs of the condenser and reboiler, as well as representing the majoroperating costs. You will need to run cases at other column heights to determinethe capital/operating cost relationship.

Output The column summary output shows the details of the temperatures, pressures,duties and flow rates in the column.

The tray sizing results show the calculated diameter for each tray. Where thecalculated diameter is not sufficient to accomodate the tray free area plus thedowncomer area, a warning is printed and the diameter is increased until therestriction has been overcome.

The largest tray diameter in each section is used to rate the whole section, 30 inchesin the top and 54 inches in the bottom of the column. The flooding factor anddowncomer backup are printed for each tray.

Finally, part of the stream printout is presented with a summary of the feed andproduct streams.




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DEETHANIZER C OLUMN O UTPUTCOLUMN SUMMARY

-------------------- NET FLOW RATES --------------------- HEATER TRAY TEMP PRESSURE LIQUID VAPOR FEED PRODUCT DUTIES DEG F PSIG LB-MOL/HR MM BTU/HR ------------ ------------- ---------------- ---------------- ---------------- ----------------- ----------------- ------------------------ 1 -36.6 425.00 314.3 577.5V -1.4598 2 -8.0 430.00 312.3 891.9 3 1.1 430.56 293.0 889.8 4 8.2 431.11 270.0 870.5 5 15.4 431.67 250.9 847.5 6 21.9 432.22 237.9 828.5 7 26.9 432.78 228.9 815.4 8 30.7 433.33 219.4 806.4 9 34.5 433.89 203.7 796.9 272.6V 10 70.6 434.44 1045.5 508.5 627.4L

11 112.8 435.00 1216.8 723.0 12 135.2 435.56 1313.5 894.3 13 150.7 436.11 1380.8 991.0 14 162.7 436.67 1438.0 1058.4 15 172.4 437.22 1487.2 1115.5 16 180.4 437.78 1524.6 1164.7 17 187.7 438.33 1541.7 1202.1 18 195.8 438.89 1517.4 1219.2 19 208.4 439.44 1399.9 1194.9 20 234.9 440.00 1077.4 322.5L 5.4219

FEED AND PRODUCT STREAMS

TYPE STREAM PHASE FROM TO LIQUID FLOW RATES HEAT RATES TRAY TRAY FRACTION LB-MOL/HR MM BTU/HR ------------- ------------ ------------ -------- -------- ---------------- ------------------------ ------------------------

FEED 1 MIXED 10 0.6971 900.00 -1.3611 PRODUCT 2 VAPOR 1 577.51 0.1573 PRODUCT 3 LIQUID 20 322.49 2.4438

OVERALL MASS BALANCE, (FEEDS - PRODUCTS) 3.8436E-04 OVERALL HEAT BALANCE, (H(IN) - H(OUT) ) -1.1936E-04

PUMPAROUNDS

TRAY TEMP, DEG F LIQUID FRACTION ------------------------ RATES ------------------------- FROM TO FROM TO FROM TO LB-MOL/HR M LB/HR STD GAL/HR -------- -------- ------------- ------------- ------------- ------------- -------------------- -------------------- -------------------- 20 20 234.9 249.9 1.0000 0.6500 2772.58 155.309 33007.07 SPECIFICATIONS

PARAMETER TRAY COMP SPECIFICATION SPECIFIED CALCULATED TYPE NO NO TYPE VALUE VALUE ----------------- -------- ------------ ------------------------- -------------------- -------------------- STRM 3 20 3 MOL RATIO 2.500E-02 2.501E-02 STRM 2 1 4 MOL RATIO 1.000E-02 9.966E-03




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TRAY S IZING C ALCULATION OUTPUTTRAY SIZING MECHANICAL DATA

SECTION TRAY TRAY TRAY SPACING SYSTEM TRAY MIN DIAMETER NUMBERS PASSES IN FACTOR TYPE IN ------------- ----------------- ------------ ------------------------ ------------ --------- ------------------------ 1 2 - 9 N/A 18.00 1.00 SIEVE 18.00 2 10 - 20 N/A 18.00 1.00 SIEVE 18.00

TRAY SIZING RESULTS

TRAY VAPOR LIQUID VLOAD ---- DESIGN ---- NEXT SMALLER NEXT LARGER NP CFS HOTGPM CFS DIA, IN FF DIA, IN FF DIA, IN FF -------- --------- ------------ --------- ------------- -------- ------------- -------- ------------- -------- ---- 2 2.071 42.6 0.714 25.1 82.0 24. 91.5 30. 53.5 1

3 2.078 40.9 0.706 24.8 82.0 24. 88.8 30. 52.3 1 4 2.076 38.6 0.691 24.3 82.0 24. 84.9 30. 50.4 1 5 2.074 36.7 0.679 27.0 62.0 24. 81.9 30. 48.9 1 MECHANICAL RESTRICTION ON TRAY 5, FOR FF = 82.0, CALCD. DIA = 24.0 6 2.073 35.5 0.671 26.8 61.9 24. 80.0 30. 48.0 1 MECHANICAL RESTRICTION ON TRAY 6, FOR FF = 82.0, CALCD. DIA = 23.8 7 2.073 34.7 0.666 29.6 48.7 24. 78.7 30. 47.3 1 MECHANICAL RESTRICTION ON TRAY 7, FOR FF = 82.0, CALCD. DIA = 23.6 8 2.076 33.7 0.660 29.4 48.6 24. 77.3 30. 46.6 1 MECHANICAL RESTRICTION ON TRAY 8, FOR FF = 82.0, CALCD. DIA = 23.4 9 2.037 31.8 0.643 29.0 48.4 24. 74.1 30. 44.9 1 MECHANICAL RESTRICTION ON TRAY 9, FOR FF = 82.0, CALCD. DIA = 23.0 10 1.961 179.7 0.715 37.2 63.2 36. 69.6 42. 46.2 1 MECHANICAL RESTRICTION ON TRAY 10, FOR FF = 82.0, CALCD. DIA = 34.2 11 2.401 229.9 0.960 40.0 82.0 36. 121.7 42. 70.4 1 12 2.647 263.4 1.118 43.5 82.0 42. 92.1 48. 61.8 1 13 2.812 289.5 1.236 46.1 82.0 42. 114.0 48. 72.6 1 14 2.947 312.6 1.339 48.3 82.0 48. 83.6 54. 60.3 1 15 3.062 333.2 1.429 50.2 82.0 48. 94.9 54. 66.8 1 16 3.155 350.3 1.503 51.8 82.0 48. 105.6 54. 72.6 1 17 3.217 362.3 1.555 52.9 82.0 48. 114.1 54. 77.0 1 18 3.226 365.0 1.566 53.1 82.0 48. 116.1 54. 78.0 1 19 3.107 347.3 1.486 51.5 82.0 48. 103.6 54. 71.6 1** WARNING ** DESIGN DIAMETER INCLUDES MECHANICAL RESTRICTION ALLOWANCES




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TRAY RATING C ALCULATION O UTPUT

TRAY SELECTION FOR TRAY RATING

SIEVE HOLE AREA 12.00 PERCENT OF ACTIVE AREA SIEVE HOLE DIAMETER 0.5 IN

DESIGN NUMBER --------- DOWNCOMER WIDTHS ------------- SECTION TRAY DIAMETER NP OF VALVES SIDE CENTER OFF-CENTER NUMBER IN OR CAPS IN IN IN ------------- ------------ ---------------- ---- ----------------- ------------ ------------- -------------------- 1 2 30. 1 N/A 4.112 N/A N/A 2 18 54. 1 N/A 15.289 N/A N/A

TRAY RATING AT SELECTED DESIGN TRAYS

PRES DOWNCOMER TRAY VAPOR LIQUID VLOAD DIAM FF NP DROP GPM/LWI BACKUP, IN CFS HOTGPM CFS IN PSI GPM/IN CLEAR LIQD -------- --------- ------------ --------- -------- -------- ---- ------------ ------------- -------------------- 2 2.071 42.6 0.714 30. 53.5 1 0.039 2.1 5.51 3 2.078 40.9 0.706 30. 52.7 1 0.040 2.0 5.46 4 2.076 38.6 0.691 30. 51.4 1 0.040 1.9 5.37 5 2.074 36.7 0.679 30. 50.3 1 0.040 1.8 5.30 6 2.073 35.5 0.671 30. 49.6 1 0.040 1.7 5.26 7 2.073 34.7 0.666 30. 49.1 1 0.040 1.7 5.23 8 2.076 33.7 0.660 30. 48.6 1 0.040 1.6 5.19 9 2.037 31.8 0.643 30. 47.2 1 0.040 1.5 5.11 10 1.961 179.7 0.715 54. 34.9 1 0.043 3.7 6.05 11 2.401 229.9 0.960 54. 46.7 1 0.043 4.7 6.67 12 2.647 263.4 1.118 54. 54.5 1 0.045 5.4 7.15 13 2.812 289.5 1.236 54. 60.6 1 0.046 6.0 7.53

14 2.947 312.6 1.339 54. 65.9 1 0.047 6.4 7.88 15 3.062 333.2 1.429 54. 70.7 1 0.047 6.8 8.21 16 3.155 350.3 1.503 54. 74.6 1 0.048 7.2 8.49 17 3.217 362.3 1.555 54. 77.4 1 0.049 7.4 8.69 18 3.226 365.0 1.566 54. 78.0 1 0.049 7.5 8.74 19 3.107 347.3 1.486 54. 73.9 1 0.048 7.1 8.44




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S TREAM COMPONENT F LOW RATE OUTPUT

STREAM ID 1 2 3 NAME FEED OVERHEAD BOTTOMS PHASE MIXED VAPOR LIQUID FLUID RATES, LB-MOL/HR 1 N2 0.2700 0.2700 1.5463E-10 2 C1 401.3100 401.3098 4.8525E-04 3 C2 178.4700 174.2154 4.2543 4 C3 171.8100 1.7123 170.0974 5 IC4 37.4400 7.7944E-05 37.4398 6 NC4 41.4000 3.1072E-06 41.3999 7 IC5 15.1200 1.8147E-10 15.1200 8 NC5 10.4400 9.3386E-12 10.4400 9 NC6 26.6400 3.7012E-16 26.6400 10 NC7 17.1000 5.9000E-16 17.1000

TOTAL RATE, LB-MOL/HR 899.9999 577.5077 322.4919

TEMPERATURE, F -29.8002 -36.5693 234.8548PRESSURE, PSIG 440.0000 425.0000 440.0000ENTHALPY, MM BTU/HR -1.3611 0.1573 2.4438MOLECULAR WEIGHT 33.1385 20.3633 56.0159MOLE FRAC VAPOR 0.3000 1.0000 0.0000MOLE FRAC LIQUID 0.7000 0.0000 1.0000




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REFRIGERATION LOOPA refrigeration loop was originally designed to take advantage of a low temperaturestream from another process, to help condense the refrigerant. Now it is proposedthat some or all of this stream will be used elsewhere in the plant. You mustdetermine the effect on the refrigeration loop of losing this auxiliary cooling duty.

Process Data The process flow sheet is shown in Figure G3.1. The loop is closed and operateswith a fixed quantity of refrigerant. The liquid refrigerant flashes through the valve,V1, and some of the vapor produced is condensed in the cooler H2. The proposedmodifications will reduce or eliminate this duty.

The two phases in the stream leaving the cooler are separated in the flash, F1, andthe liquid portion is vaporized to provide the required refrigerant duty. The two vapor

streams are then combined, recompressed, and condensed.

The refrigerant composition is shown in Table G3.1.

Table G3.1REFRIGERANT COMPOSITION

Component lb moles/hr Component lb moles/hrEthane 1.04 i-Butane 1.68

Propane 96.94 n-Butane 0.34

Figure G3.1

Refrigeration Loop Flow Sheet

G 3 R E F R I G

L O OP

PRO/II APPLICATION BRIEFS REFRIGERATION LOOP G3-1February 1991


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Because the process changes will change the flow rate through the existingcompressor, performance curves supplied by the manufacturer are used in the

calculations. The curves are shown in Figure G3.2.

Methodsand Data

The Peng-Robinson equation of state has been selected for calculating equilibriumK-values, enthalpies, and entropies. Liquid densities are calculated using theLee-Kesler correlation. This combination gives accurate results for this type of lighthydrocarbon system.

SimulationModel

The independent variable in this simulation is the flow rate of the refrigerant. Thisflow rate is estimated in the Stream Data Catagory based on the latent heat ofpropane, and a feedback controller is used to calculate it as shown in Figure G3.3.The vaporizer exit stream is set to its dew point, and the controller varies the rate ofstream 1 in order to meet the required refrigerant duty.

Figure G3.2

Compressor Performance Curves

G 3 R E F R I G

L O O P

G3-2 REFRIGERATION LOOP PRO/II APPLICATION BRIEFSFebruary 1991


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We want to study the effect of reducing the duty of H2. Although multiple casescould be executed, in this example, the interactive facility is used to change the dutyand observe its effect on the other important parameters. This facility uses aquestion and answer procedure, and allows any specification in the flow sheet tobe changed and any parameter to be inspected during the program execution. Theinteractive facility may be invoked via the Graphics User Interface on the PC, or via

the PRO/II driver on mainframe computers.The existing base case is simulated. Then the duty of H2 is reduced in steps untilthe program indicates that the combination of required process conditions isimpossible. The refrigerant flow rate, the compressor work, and the cooling in H1are inspected at each step.

Input Data English units default, and U.S. gallons are specified for liquid volume on the DIMENSION statement.

The defined stream 1 flow rate of 20,000 moles/hr is an estimate, and this is variedby the controller to meet the duty specification on exchanger, H3. An absolutetolerance of 0.5 MM BTU is specified on this duty.

The H3 specification of a zero liquid fraction sets the outlet condition to its dew point.

The compressor performance curves for actual head and adiabatic efficiency are

input as tabular values against actual inlet flow rate.

Figure G3.3

Simulation Flow Sheet

G 3 R E F R I G

L O OP



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Input Data File:

TITLE PROBLEM=G3,PROJE CT=APPBRIEFS,USER=SIMSCI,DATE=SEPT 90 DIMEN LIQV=GAL

COMPONENT DATA

LIBID 1,ETHANE/2,PROPANE/3,IBUTANE/4,BUTANE

THERMODYNAMIC DATA

METHODS SYSTEM=PR,DENSITY(L)=LK

STREAM DATA

PROP STREAM=1,TEMP=140,PRES=315,RATE=20000,&

COMP=1,1.04/2,96.94/3,1.68/4,0.34

NAME 1,PROPANE

UNIT OPERATIONS

VALVE UID=V1,NAME=VALVE

FEED 1

PROD V=2

OPER PRES=88

HX UID=H2,NAME=COOLER

HOT FEED=2,L=3,DP=5

OPER DUTY=12.5

FLASH UID=F1,NAME=SEPARATOR

FEED 3

PROD V=4,L=5

ADIA

HX UID=H3,NAME=VAPORIZER

COLD FEED=5,V=6,DP=9

OPER CLFRACT=0

CONTROL UID=CON1,NAME=CONTROL

SPEC HX=H3,DUTY,VAL UE=82.74,ATOL=0.5

VARY STREAM=1,RATE CPAR ITER=10

MIXER UID=M1,NAME=SURGE

FEED 4,6

PROD M=7

OPER PRES=65

COMPRESS UID=C1,NAME=COMPRESSOR

FEED 7

PROD V=8

HEAD ACTUAL=912000, 38000/1018000,37000/1237000,35300 /&

1356000,33100/1427000,27250

EFFI ADIA=912000,69 /1018000,71 /1237000,72 /&

1356000,73 /1427000,71

HX UID=H1,NAME=COOLER

HOT FEED=8,V=1,DP=8

OPER HTEMP=140

END

G 3 R E F R I G

L O O P



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Interactive The interactive procedure pauses for commands after the input check. The RUNcommand is entered to execute the program and solve the flow sheet. The relevantportions of the output are then examined using the VIEW command. This is shownbelow for the initial case. The user entries are underlined. An entry of HELP to anyquestion gives a list of the possible replies. The HELP facility may be turned onpermenantly with the SET MENU command.

The command parts may be entered singularly, as when requesting the streamoutput, or they may be entered together, as shown for the compressor and cooleroutput.

It is not necessary to wait for the execution to finish to inspect or change data. Theexecution may be interrupted at any time by pressing the interrupt key (Esc onIBM PCs and compatibles, Break on Prime, ^C on VAX). Items may then beexamined or altered, and the execution continued.

ENTER COMMAND (HELP)

} VIEW

STREAM OR UNIT (/ TO ABORT COMMAND)

VI } STREAM

ENTER STREAM ID OR #NUMBER (HELP - / TO ABORT COMMAND)

VI ST } 1

STREAM 1, 1, PROPANE

TOTAL VAPOR LIQUID

-------------------- -------------------- ----------------

TEMPERATURE, F 140.00PRESSURE, PSIA 313.82

RATE, LB-MOL/HR 16687.8300 0.0000 16687.8300

FRACTION 0.0000 1.0000

ENTHALPY, BTU/LB/MOL 3314.0750 0.0000 3314.0750

CP, BTU/LB-MOL-F 0.0000 39.2404

Z FROM FUGACITIES 0.6680 0.0815

Z FROM ENTHALPY 0.7425 0.0815

COMP 1, ETHANE 173.5535 0.0000 173.5535

2, PROPANE 16177.1890 0.0000 16177.1800

3, IBUTANE 280.3556 0.0000 280.3556

4, NBUTANE 56.7386 0.0000 56.7386

G 3 R E F R I G

L O OP



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} VIEW UNIT C1

UNIT 7, C1, COMPRESSOR

TYPE COMPRESSOR

FEEDS 7

PRODUCTS 8

OUTLET TEMPERATURE, F 183.65

OUTLET PRESSURE, PSIA 321.82

PRESSURE INCREASE, PSI 256.82

ACTUAL WORK, HP 13121.76

HEAD, FT 35184.28

ADIABATIC EFFICIENCY 72.00

POLYTROPIC EFFICIENCY 76.82

AFTER-COOLER TOUT, F MISSING

AFTER-COOLER DP, PSI (ACDP) 0.00

AFTER-COOLER DUTY, MM BTU/HR MISSING


} VIEW UNIT H1

UNIT 8, H1, COOLER

TYPE HEAT EXCHANGER

FEEDS - HOT SIDE 8PRODUCTS - HOT SIDE 1

HOT OUTLET TEMPERATURE, F

(HTEM) 140.00

COLD OUTLET TEMPERATURE, F MISSING

HOT PRESSURE DROP, PSI (HDP) 8.00

COLD PRESSURE DROP, PSI (CDP) 0.00

HOT LIQUID FRACTION 1.0000

COLD LIQUID FRACTION MISSING

DUTY , MM BTU/HR 98.78

U, BTU/HR-FT2-F MISSING

AREA, FT2 MISSING

FT 1.00

LMTD, F 621.24

ZONE-WEIGHTED LMTD, F MISSING

G 3 R E F R I G

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When the refrigerant flow rate exceeds 18000 lb mole/hr, both the efficiency andhead fall with increasing flow rate. When this happens, the feed pressure to the

valve, V1, is reduced, and so the expansion produces less cooling. This, in turn,leads to less liquid for the vaporizer. The controller then increases the refrigerantflow rate, which again reduces the amount of liquid, and it is not possible to supplythe specified refrigeration duty.

Conclusions The refrigerant loop can only operate as currently configured if the cooling duty inexchanger H2 exceeds 12.2 MM Btu/hr. If the duty is to be reduced farther, the flowsheet will require other modifications.

The interactive feature is extremely useful in this type of study, as the user canintervene when impossible process conditions occur. When low H2 duties areentered, the compressor calculation fails, and the execution is interrupted. The dutyis then changed and the calculation continues until a solution is possible.

This simulation shows the importance of considering the real performance charac-

teristics of process equipment. If the compressor were specified with only a definedexit pressure, the problem with increased flow rate might not have been detecteduntil a later, and more costly, stage.

Output The stream output is shown for the case with the cooler duty at 12.5 MM Btu/hr. G 3 R E F R I G

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S TREAM OUTPUT

STREAM ID 1 2 3 4 NAME PROPANE PHASE LIQUID MIXED MIXED VAPOR FLUID RATES, LB-MOL/HR 1 ETHANE 186.3393 186.3394 186.3394 121.7109 2 PROPANE 17368.9922 17368.9922 17368.9922 5869.7583 3 IBUTANE 301.0101 301.0100 301.0100 50.4964 4 BUTANE 60.9187 60.9187 60.9187 7.4506

TOTAL RATE, LB-MOL/HR 17917.2598 17917.2598 17917.2598 6049.4155

TEMPERATURE, F 140.0000 47.4142 43.5651 43.5654PRESSURE, PSIA 311.6193 88.0000 83.0000 83.0000ENTHALPY, MM BTU/HR 59.4047 59.4057 46.9135 43.6858MOLECULAR WEIGHT 44.2345 44.2345 44.2345 43.9492MOLE FRAC VAPOR 0.0000 0.4257 0.3376 1.0000MOLE FRAC LIQUID 1.0000 0.5743 0.6624 0.0000

STREAM ID 5 6 7 8 NAME PHASE LIQUID VAPOR VAPOR VAPOR FLUID RATES, LB-MOL/HR 1 ETHANE 64.6284 64.6284 186.3393 186.3393 2 PROPANE 11499.2334 11499.2334 17368.9922 17368.9922 3 IBUTANE 250.5137 250.5137 301.0101 301.0101 4 BUTANE 53.4681 53.4681 60.9187 60.9187

TOTAL RATE, LB-MOL/HR 11867.8438 11867.8438 17917.2598 17917.2598

TEMPERATURE, F 43.5654 39.3252 37.7888 181.8029PRESSURE, PSIA 83.0000 74.0000 65.0000 319.6193ENTHALPY, MM BTU/HR 3.2371 85.9822 129.6680 164.7797MOLECULAR WEIGHT 44.3799 44.3799 44.2345 44.2345MOLE FRAC VAPOR 0.0000 1.0000 1.0000 1.0000MOLE FRAC LIQUID 1.0000 0.0000 0.0000 0.0000

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COMPRESSOR TRAINA plant has been designed to compress a gas stream from 450 kPa to 6200 kPa,in three stages, for transportation by a pipeline. To select the compressors, youhave to calculate the required work for each stage. You also need the cooler dutiesand recycle rates in each stage for utility calculations.

The compressed gas is to be cooled to 60 C after each stage, to condense theheavier components. In order to maximize the gas product rate, the liquid from eachstage is recycled back to the previous stage.

Process Data The flow sheet is shown in Figure G4.1. Each stage consists of a compressor,aftercooler, and separator drum. Table G4.1 lists the specified operating conditionsfor the compressors.

Table G4.1COMPRESSOR DATA

Compressor Pressure (kPa) Adiabatic Efficiency (%)Stage 1 1100 78Stage 2 2600 75Stage 3 6200 72

Figure G4.1

Compressor Train Flow Sheet

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The feed details are shown in Table G4.2

Table G4.2FEED STREAM INFORMATION

Component kg moles/hr Component kg moles/hr

Nitrogen 181 I-pentane 953

CO2 1920 N-pentane 1633

Methane 14515 Hexane 1542

Ethane 9072 BP 135 11975

Propane 7260 BP 260 9072

I-butane 770 BP 500 9072

N-butane 2810

Pressure (kPa) 450

Temperature (C) 45

Methodsand Data

The Soave-Redlich-Kwong (SRK) equation of state is used to calculate equilibriumK-values, enthalpies, and vapor densities. Binary interaction parameters are builtinto the program in order to model accurately the non-ideal behavior of N 2 and CO 2with the hydrocarbons.

The SRK method has been found to predict liquid densities which may be 10-20%low. For this reason, the LK method has been selected as the most suitable for lighthydrocarbon, high methane mixtures.

The heavy end of the gas stream is characterized as three petroleum fractions. Theproperties of the fractions are listed in Table G4.3.

Table G4.3PETROLEUM FRACTION PROPERTIES

Fraction Molecular wt. Sp. Grav. NBP (C)BP 135 120 0.757 135BP 260 200 0.836 260

BP 500 500 0.950 500

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SimulationModel

The compressors are modeled with fixed outlet pressures and efficiencies. ThePRO/II compressor model has a built-in aftercooler and flash separator drum.

The separators for stages 1 and 2 are modeled as separate adiabatic flash drums,in order to mix the compressor product with the recycled liquid.

No estimates are required for the rate and composition of the three recycle streams.

Input Data SI units are used in this simulation with the temperatures in Celsius rather than thedefault of Kelvin. The three petroleum fractions are characterized by molecularweight, specific gravity, and boiling point. XDEN=SPGR indicates that specificgravity is entered rather than density, the default for SI units.

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Input Data File:

TITLE PROBLEM=G4,PROJECT=APPBRIEFS,USER=SIMSCI,DATE=SEPT 90 DIMENSION SI,TEMP=C,XDEN=SPGR

PRINT STREAM=PART

COMPONENT DATA

LIBID 1,NITROGEN/2,CO2 /3,METHANE /4,ETHANE / &

5,PROPANE /6,IBUTANE /7,BUTANE /8,IPENTANE/ &

9,PENTANE /10,HEXANE

PETRO 11,BP135,120,0.757,135/12,BP260,200,0.836,260/ &

13,BP500,500,0.95,500

THERMODYNAMIC DATA

METHODS SYSTEM=SRK,DENSIT Y(L)=LK

STREAM DATA

PROP STREAM=100,TEMP=45,PRES=450,&

COMP=1,181/2,1920/3,14515/4,9072/5,7260/6,770/7,2810/&

8,953/9,1633/10,1542/11,11975/12,9072/13,9072

NAME 100,INLET GAS/10,COMPR VAPOR /11,CONDENSATE

UNIT OPERATIONS

FLASH UID=F1,NAME=FEED FLASH

FEED 100,5

PROD V=2,L=11

ADIA

COMPRESS UID=C1,NAME=STAGE 1

FEED 2

PROD V=3

OPER EFF=78,PRES=1100

COOLER TEMP=60

FLASH UID=F2,NAME=STAGE 1 SEP

FEED 3,8 PROD V=4,L=5

ADIA


FEED 4

PROD V=6


COOLER TEMP=60

FLASH UID=F3,NAME=STAGE 2 SEP

FEED 6,9

PROD V=7,L=8

ADIA


FEED 7

PROD V=10,L=9


COOLER TEMP=60

END


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Results The recycles converged after 8 iterations. The work, duty, and recycle rates aresummarized in Table G4.4.

Table G4.4COMPRESSOR RESULTS

Compressor Work (kW) Duty (GJ/hr) Recycle (kmol/hr)Stage 1 27801 -81.9 111.8Stage 2 28048 -120.1 518.0Stage 3 27782 -164.8 973.0

Conclusions The work required for all the compressors is similar, and it may be possible to useidentical machines for each. The duty required to cool the vapor and the amount ofliquid to be recycled increase as the pressure difference increases across eachstage. The total cooling requirement is 366.8 GJ/hr.

Output The flash summary shows the details of the feed flash and first two letdown stages.

Details of the third stage are shown on the output from compressor C3.

The PRINT statement specifies that only part of the stream printout is required. Thisprints the component flow rates, temperatures, and pressures, but omits theproperty output. The final output lists the details of the feed and product streams.

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FLASH S UMMARY

FLASH ID F1 F2 F3 NAME FEED FLASH STAGE 1 SEP STAGE 2 SEP

FEEDS 100 3 6 5 8 9

PRODUCTS VAPOR 2 4 7 LIQUID 11 5 8

TEMPERATURE, C 45.000 55.736 57.107PRESSURE, KPA 450.000 1100.000 2600.000PRESSURE DROP, KPA 0.000 0.000 0.000MOLE FRAC VAPOR 0.44700 0.99653 0.98433MOLE FRAC LIQUID 0.55300 0.00347 0.01567DUTY, M*KJ/HR 0.00000 0.00000 0.00000FLASH TYPE ADIABATIC-P ADIABATIC-P ADIABATIC-P


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OUTPUT FOR S TAGE 3 C OMPRESSOR

UNIT 6, C3, STAGE 3

FEEDS 7 PRODUCTS LIQUID 9 VAPOR 10

OPERATING CONDITIONS

INLET ISENTROPIC OUTLET --------------------- --------------------- --------------------- TEMPERATURE, C 57.11 110.76 122.19

PRESSURE, KPA 2600.00 6200.00 6200.00 ENTHALPY, M*KJ/HR 334.2003 406.2101 434.2138 ENTROPY, KJ/KG-MOL-C 209.4579 209.4579 211.6669 CP, KJ/KG-MOL-C 63.5285 75.1511 CV, KJ/KG-MOL-C 48.6656 56.5508 CP/(CP-R) 1.1506 1.1244 CP/CV 1.3054 1.3289 MOLE PERCENT VAPOR 100.0000 100.0000 100.0000 MOLE PERCENT LIQUID 0.0000 0.0000 0.0000 ACT VAP RATE, M3/SEC 8.3816 ADIABATIC EFF, PERCENT 72.0000 POLYTROPIC EFF, PERCENT 74.6812 ISENTROPIC COEFFICIENT, K 1.2019 POLYTROPIC COEFFICIENT, N 1.2902 HEAD, M ADIABATIC 7566.30 POLYTROPIC 7848.06 ACTUAL 10508.75 WORK, KW THEORETICAL 20002.73 POLYTROPIC 20747.60 ACTUAL 27781.56 AFTERCOOLER DUTY, M*KJ/HR -164.79 TEMPERATURE, C 60.00 PRESSURE, KPA 6200.00

NOTE: POLYTROPIC AND ISENTROPIC COEFFICIENTS ARECALCULATED FROM HEAD EQUATION.

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FEED AND P RODUCT S TREAM O UTPUT

1STREAM ID 10 11 100 NAME COMPR VAPOR CONDENSATE INLET GAS PHASE VAPOR LIQUID MIXED FLUID RATES, KG-MOL/HR 1 NITROGEN 179.5963 1.3944 181.0000 2 CO2 1812.2617 107.5004 1920.0001 3 METHANE 14113.3457 400.3724 14515.0010 4 ETHANE 8001.8335 1068.5183 9072.0000 5 PROPANE 5124.0815 2133.8696 7260.0000 6 IBUTANE 397.2075 372.5232 770.0000 7 BUTANE 1220.0641 1588.9044 2810.0000 8 IPENTANE 235.6160 716.9981 953.0000 9 PENTANE 332.7747 1299.5493 1633.0000 10 HEXANE 121.2520 1419.9563 1542.0000 11 BP135 28.3821 11946.9199 11975.0020 12 BP260 7.2584E-07 9072.0410 9072.0000 13 BP500 9.0082E-16 9072.0400 9072.0000

TOTAL RATE, KG-MOL/HR 31566.4160 39200.5898 70775.0000

TEMPERATURE, C 60.0000 44.9995 45.0000PRESSURE, KPA 6200.0000 450.0000 450.0000ENTHALPY, M*KJ/HR 263.1534 134.0240 462.9854MOLECULAR WEIGHT 29.3555 211.8170 130.4179MOLE FRAC VAPOR 1.0000 0.0000 0.4475MOLE FRAC LIQUID 0.0000 1.0000 0.5525


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EXPANDER PLANTThe demethanizer in an expander plant removes methane from a production gasstream, to maintain a methane/ethane volumetric ratio of 0.015 in the column liquidproduct. A new feed gas stream with a different composition is being brought onstream, and you must ensure that the same purity specification can be maintained,and that the new reboiler duty does not exceed the capacity of the unit.

You also need to know what pressure recovery is possible on the methane streamleaving the plant.

Process Data The flow sheet is shown in Figure G5.1 and the new feed composition is in TableG5.1.

Figure G5.1

Expander Plant Flow Sheet

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Table G5.1FEED STREAM INFORMATION



Methane 73.05 I-pentane 0.69

Ethane 7.68 N-pentane 0.82

Propane 5.69 Hexane 0.42

I-butane 0.99 Heptane 0.31

Flow rate (scfd) 24.4x106

Temperature (F) 120.0

Pressure (psig) 588.0

The expander lets the pressure down to 125 psig, which is the working pressure ofthe demethanizer column. 90% of the expander work is utilized by the compressor.The expander efficiency is 80% and the compressor efficiency is 75%.

Methodsand Data

Peng-Robinson is chosen for K-value and enthalpy calculations. It is applicable tolight hydrocarbon systems, and PRO/II includes binary interaction constants topredict accurate N 2 /hydrocarbon equilibria. The Lee-Kesler method, specified forliquid density, works well for hydrocarbon components lighter than about C 10 .

SimulationModel

The flow sheet shown in Figure G5.1 is thermally coupled in the gas-gas exchangerE1. However, you can often eliminate thermal couples and significantly reduce thecomputation time, simply by re-ordering the calculation.

The purpose of the chiller is to ensure that the temperature of the flash separatorD1 is constant, and so you know all the process conditions of stream 3. If you startthe calculation at D1, then E1 and E2 can be calculated after the column, and noiteration is required.

The procedure for this is simple:

1) reference stream 3 to feed stream 100 in the STREAM data section2) use a SEQUENCE statement to start the calculations with unit D13) give the product stream from unit E2 a dummy stream label 3X. Streams 3 and 3X are identical.

The demethanizer is modeled as a conventional distillation column with 10 theoreti-cal stages, including the reboiler. The reboiler duty is varied to achieve the specifiedmethane/ethane ratio in the bottom product.

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Input Data The problem input data are supplied in standard English units, except that thepressures are in psig rather than psia. The results, however, are required in SI unitsso an OUTDIMENSION statement is used to obtain both English and SI output. Thestream output is requested in both molar and liquid volume units.

The SEQUENCE statement lists the UIDs of the units, in the order in which they willbe calculated. Any units which are not specified on this statement are not calcu-lated.

No solution method is defined for the demethanizer column, and so the defaultInside-Out (IO) method will be used. The column has no condenser and stream 7is fed to tray 1.

The DEFINE statement in the compressor specifies that 90% of the work producedby the expander is used.

Input Data File:

TITLE PROBLEM=G5,PROJECT=APPBRIEFS,USER=SIMSCI,DATE=SEPT 90

DIMEN PRES=PSIG

OUTD SI,ADD,PRES=BAR

SEQU D1,V1,X1,T1,E1,E2 ,C1

PRINT RATE=M,LV

COMPONENT DATA

LIBID 1,NITROGEN/2,ME THANE /3,ETHANE /4,PROPANE / &

5,IBUTANE /6,BUTANE /7,IPENTANE/8,PENTANE / &

9,HEXANE /10,HEPTANE

THERMODYNAMIC DATA

METHOD SYSTEM=PR,DENSITY(L)=LK

STREAM DATA

PROP STREAM=100,TEMP=120,PRES=588,PHASE=V,RATE(G)=1.0167E+6,&

COMP=1,7.91/2,73.05/3,7.68/4,5.69/5,0.99/6,2.44/&

7,0.69/8,0.82/9,0.42/10,0.31

PROP STREAM=3,REFS=100,TEMP=-84,PRES=573

NAME 100,INLET GAS/11,GAS PRODUCT/9,LIQUID PROD

UNIT OPERATIONS

HX UID=E1,NAME=GAS- GAS EX

HOT FEED=100,V=2,DP=10

COLD FEED=8,V=10,DP=5

OPER HICO=10

HX UID=E2,NAME=CHILLER

HOT FEED=2,V=3X,DP=5

OPER HTEMP=-84

FLASH UID=D1,NAME=SEPARATOR

FEED 3 PROD V=4,L=5

ADIA

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Results The demethanizer column solves with a reboiler duty of 2.5 GJ/hr. The expanderproduces 287 kW of work, and 258 kW are used by the compressor. The compres-sor feed is at 9.29 bar, and the outlet pressure is 12.07 bar. The expander dropsthe pressure from 40.5 bar to 9.6 bar.

Conclusions The demethanizer column can meet the purity specification with the new feed streamas long as the required 2.5 GJ/hr is available for the reboiler. The compressorrecovers 2.78 bar from the expansion of the column feed vapor stream through 30.9bar.

Output The demethanizer output is in SI units and shows the required duty as well as thecolumn temperatures and internal flow rates. The expander and compressoroutputs show the isentropic and theoretical calculation results, as well as the actualperformance.

The heat exchanger results are shown in the input (English) units.

The stream component flow rates showing the feed and product streams arepresented in both the molar and liquid volume units.

VALVE UID=V1,NAME=LIQ VALVE

FEED 5

PROD V=6 OPER PRES=125

EXPANDER UID=X1,NAME=EXPANDER

FEED 4

PROD M=7


COLUMN UID=T1, NAME=DEMETHANIZ ER

PARAM TRAY=10

FEED 7,1/6,3

PROD OVHD=8,500, BTMS=9

HEAT 1,10

VARY HEAT=1

PSPEC TOP=125

ESTI MODEL=CONV

SPEC STREAM=9,RATE( V),COMP=2,RATIO, COMP=3,VALUE=0.015

COMPRESS UID=C1,NAME=COMPRESSOR

FEED 10

PROD V=11

OPER EFF=75

DEFINE WORK AS EXPANDER=X1, WORK MULTIPLIED BY 0.9

END

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EXPANDER AND COMPRESSOR O UTPUT UNIT 3, X1, EXPANDER

FEEDS 4 PRODUCTS MIXED 7


INLET ISENTROPIC OUTLET --------------------- --------------------- --------------------- TEMPERATURE, K 208.71 154.98 158.37 PRESSURE, BAR 40.52 9.63 9.63 ENTHALPY, M*KJ/HR -3.1092 -4.4020 -4.1434 ENTROPY, KJ/KG-K 164.3970 164.3988 166.4469 MOLE PERCENT VAPOR 100.0000 91.3830 93.7988 MOLE PERCENT LIQUID 0.0000 8.6170 6.2012 ACT VAP RATE, M3/SEC 0.0684

ADIABATIC EFF, PERCENT 80.00 WORK, KW THEORETICAL 359.09 ACTUAL 287.27

UNIT 7, C1, COMPRESSOR

FEEDS 10 PRODUCTS VAPOR 11


INLET ISENTROPIC OUTLET --------------------- --------------------- --------------------- TEMPERATURE, K 316.48 336.28 342.42 PRESSURE, BAR 9.29 12.07 12.07 ENTHALPY, M*KJ/HR 1.0304 1.7279 1.9604 ENTROPY, KJ/KG-MOL-K 194.6615 194.6616 195.3494 CP, KJ/KG-MOL-K 37.0346 38.1747 CV, KJ/KG-MOL-K 28.0197 29.1108 CP/(CP-R) 1.2895 1.2784 CP/CV 1.3217 1.3114 MOLE PERCENT VAPOR 100.0000 100.0000 100.0000 MOLE PERCENT LIQUID 0.0000 0.0000 0.0000 ACT VAP RATE, M3/SEC 0.7720 ADIABATIC EFF, PERCENT 75.0000 POLYTROPIC EFF, PERCENT 75.7832 ISENTROPIC COEFFICIENT, K 1.3025 POLYTROPIC COEFFICIENT, N 1.4418 HEAD, M ADIABATIC 4102.30 POLYTROPIC 4145.14 ACTUAL 5469.74 WORK, KW THEORETICAL 193.75 POLYTROPIC 195.77 ACTUAL 258.33

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HEAT E XCHANGER O UTPUT

UNIT 5, E1, GAS-GAS EX


DUTY, MM BTU/HR 5.283 LMTD, F 58.254

F FACTOR (FT) 1.000MTD, F 58.254U*A, BTU/HR-F 90681.305

HOT SIDE CONDITIONS INLET OUTLET --------------------- --------------------- FEED 100

MIXED PRODUCT 2 VAPOR, LB-MOL/HR 2679.187 2375.275 M LB/HR 60.307 46.742 CP, BTU/LB-F 0.546 0.569 LIQUID, LB-MOL/HR 303.912 M LB/HR 13.565 CP, BTU/LB-F 0.571 TOTAL, LB-MOL/HR 2679.187 2679.187 M LB/HR 60.307 60.307 CONDENSATION, LB-MOL/HR 303.912 TEMPERATURE, F 120.000 7.421 PRESSURE, PSIG 588.000 578.000

COLD SIDE CONDITIONS INLET OUTLET --------------------- --------------------- FEED 8

VAPOR PRODUCT 10 VAPOR, LB-MOL/HR 2196.011 2196.011 M LB/HR 38.210 38.210 CP, BTU/LB-F 0.515 0.508 TOTAL, LB-MOL/HR 2196.011 2196.011 M LB/HR 38.210 38.210 CONDENSATION, LB-MOL/HR 0.000 TEMPERATURE, F -170.170 110.000 PRESSURE, PSIG 125.000 120.000

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FEED AND P RODUCT STREAM OUTPUT(Molar)

STREAM ID 9 10 11 100 NAME LIQUID PROD GAS PRODUCT INLET GAS PHASE LIQUID VAPOR VAPOR VAPOR FLUID RATES, KG-MOL/HR 1 NITROGEN 1.2340E-08 96.1271 96.1271 96.1269 2 METHANE 1.8788 885.8679 885.8679 887.7458 3 ETHANE 79.4449 13.8866 13.8866 93.3318 4 PROPANE 68.9393 0.2085 0.2085 69.1482 5 IBUTANE 12.0292 0.0018 0.0018 12.0311 6 BUTANE 29.6510 0.0011 0.0011 29.6523 7 IPENTANE 8.3852 1.3505E-05 1.3505E-05 8.3853 8 PENTANE 9.9651 5.4456E-06 5.4456E-06 9.9651 9 HEXANE 5.1041 4.5556E-08 4.5556E-08 5.1041 10 HEPTANE 3.7673 4.6990E-10 4.6990E-10 3.7673

TOTAL RATE, KG-MOL/HR 219.1648 996.0930 996.0930 1215.2578

TEMPERATURE, K 269.1954 316.4834 342.4180 322.0389PRESSURE, BAR 9.6317 9.2870 12.0703 41.5544ENTHALPY, M*KJ/HR -0.1479 1.0304 1.9604 4.6986MOLECULAR WEIGHT 45.7329 17.3997 17.3997 22.5095MOLE FRAC VAPOR 0.0000 1.0000 1.0000 1.0000MOLE FRAC LIQUID 1.0000 0.0000 0.0000 0.0000

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FEED AND PRODUCT STREAM OUTPUT(Volume)

STREAM ID 9 10 11 100 NAME LIQUID PROD GAS PRODUCT INLET GAS PHASE LIQUID VAPOR VAPOR VAPOR FLUID RATES, M3/HR 1 NITROGEN 4.2817E-10 3.3355 3.3355 3.3355 2 METHANE 0.1006 47.4200 47.4200 47.5205 3 ETHANE 6.7095 1.1728 1.1728 7.8823 4 PROPANE 5.9937 0.0181 0.0181 6.0119 5 IBUTANE 1.2429 1.8979E-04 1.8979E-04 1.2431 6 BUTANE 2.9520 1.1440E-04 1.1440E-04 2.9521 7 IPENTANE 0.9725 1.5663E-06 1.5663E-06 0.9725

8 PENTANE 1.1406 6.2328E-07 6.2328E-07 1.1406 9 HEXANE 0.6631 5.9183E-09 5.9183E-09 0.6631 10 HEPTANE 0.5491 6.8488E-11 6.8488E-11 0.5491

TOTAL RATE, M3/HR 20.3239 51.9468 51.9468 72.2707

TEMPERATURE, K 269.1954 316.4834 342.4180 322.0389PRESSURE, BAR 9.6317 9.2870 12.0703 41.5544ENTHALPY, M*KJ/HR -0.1479 1.0304 1.9604 4.6986MOLECULAR WEIGHT 45.7329 17.3997 17.3997 22.5095MOLE FRAC VAPOR 0.0000 1.0000 1.0000 1.0000MOLE FRAC LIQUID 1.0000 0.0000 0.0000 0.0000

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THREE STAGE LETDOWNThe dissolved gases in crude oil from a well are released as the pressure drops andmust be removed in order to avoid storage and transportation difficulties. Tominimize oil loss,it is removed in several stages, recompressing vapor and recyclingliquid which drops out.

You must simulate the three-stage letdown process to determine how much gas willbe produced and calculate the crude oil flow rate for transportation. The true vaporpressure (TVP) of the oil product must not exceed 14.7 psia, to ensure that no vaporflashes off.

Cooling water for the compressor aftercoolers is available at 70 F and is allowed torise 30 F. You must determine how much cooling water is required.

Process Data The flow sheet for the three stage process is shown in Figure G6.1. The feedconsists of water, pure hydrocarbons, and petroleum fractions as shown in TableG6.1.

Figure G6.1

Three Stage Letdown Flow Sheet

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Table G6.2PETROLEUM FRACTION PROPERTIES

Fraction Molecular Wt. API Grav. NBP (F)Cut11 91 64 180

Cut12 100 61 210

Cut13 120 55 280

Cut14 150 48 370

Cut15 200 40 495

Cut16 245 35 590

Cut17 300 30 687

Cut18 360 26 770

Cut19 430 22 865

SimulationModel

The TVP specification is the vapor pressure of the liquid at a defined temperature.The most widely used temperature is 100 F and this is the default in PRO/II. Differenttemperatures may be defined with the TVPBASIS entry on the CALC statement inGeneral Data.

The pressure of the final letdown stage (VAL2) is varied using a controller to meetthe TVP specification on the liquid product. The initial pressure defined for VAL2 isa first estimate.

The calculation requires recycle and controller loops. Computation time is reducedby modeling the compressors as isothermal flashes within the loops. After the

recycle and controller have solved, the compressors and aftercoolers are rigorouslymodeled to determine horsepowers and duties. No initial estimates are required forthe recycles.

In order to calculate the cooling water requirements, separate heat exchangermodels are used instead of the built-in compressor aftercoolers.

Input Data No dimensional units are defined for this simulation, so they default to the standardset of English units.

The free water is decanted from the first stage flash, and 60% is removed by thesplitter unit. The remainder of the water is fed to the second stage.

The controller specifies that the TVP of the oil must be 14.7 with an absolutetolerance of 0.1. The variable is defined as the pressure of unit VAL2. Theconvergence of the controller is handled automatically.

The flashes C1+ and C2+ replace the compressors and aftercoolers during recycletrials. A stream may feed more than one unit operation, and so the feeds to C1+and C2+ are also fed to the rigorous compressor models. The products from theaftercoolers do not feed other units ,and so the program only calculates thecompressors and aftercoolers after the recycle has converged.

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The cooling water required in the aftercoolers is calculated when WATER isspecified with the UTILITY statement. The inlet and outlet water temperatures are

supplied, and the quantity is calculated from the heat balance.Input Data File:

TITLE PROBLEM=G6,PROJECT=APPBRIEFS,USER=SIMSCI,DATE=SEPT 90 DIME LIQVOL=BBLCOMPONENT DATA LIBID 1,WATER/2,CO2/3,N2/4,C1/5,C2/6,C3/& 7,IC4/8,NC4/9,IC5/10,NC5 PETRO 11,CUT11, 91,64,180/12,CUT12,100,61,210/ & 13,CUT13,120,55,280/14,CUT14,150,48,370/ & 15,CUT15,200,40,495/16,CUT16,245,35,590/ & 17,CUT17,300,30,687/18,CUT18,360,26,770/ & 19,CUT19,430,22,865THERMODYNAMIC DATA METHODS SYSTEM=SRKSTREAM DATA PROP STREAM=100,TEMP=150,PRES=1000,& COMP=1,3000/2,35/3,30/4,890/5,300/6,520/7,105/8,283/& 9,100/10,133/11,165/12,303/13,560/14,930/15,300/& 16,300/17,300/18,280/19,260 NAME 100,OIL FEED/105,OIL PRODUCT/110,GAS PRODUCTUNIT OPERATIONSFLASH UID=D-1,NAME=STAGE 1 FEED 100 PROD V=20,L=2,W=W1 ISO TEMP=200,PRES=300SPLITTER UID=SPL1,NAME=WATER SPLIT FEED W1 PROD M=SW1,M=SW2 OPER PRES=300 SPEC STREAM=SW1,RATE,RATIO,REFFEED,VALUE=0.4FLASH UID=VAL1,NAME=STAGE 2

FEED 2,SW1 PROD V=21,L=3,W=W2 ADIA PRES=100FLASH UID=VAL2,NAME=STAGE 3 FEED 3,10,9,11 PROD V=22,L=105,W=W3 ADIA PRES=16.7HX UID=HX-1 HOT FEED=22,V=24,L=11,W=W5,DP=3 SPEC HOT,TEMP=120 UTILITY WATER,TIN=70,TEMP=100

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Results The gas product dry flow rate is 715,789 ft 3 /hr, and the oil production is 2498 bbl/hr.The final stage pressure which gives the required oil TVP is 35.7 psia.

The cooling water required by stages 1 and 2 is 83,124 and 112,554 lb/hr respec-tively (simulation output not shown here).

Conclusions This simulation has provided all the necessary information. The model could nowbe used to investigate if different letdown and/or compressor conditions couldimprove the oil product rate.

Output The flash drum summary shows the conditions in each letdown and compressionstage. The full details of the second stage compressor and aftercooler appear onthe compressor and heat exchanger output. The aftercooler details show the coolingwater requirement.

A portion of the stream property output showing the feed and product streams ispresented.

FLASH UID=C1+,NAME=1ST COMPRESSOR FEED 24,21

PROD V=27,L=10 ISO TEMP=120,PRES= 97FLASH UID=C2+,NAME=2ND COMPRESSOR FEED 27,20 PROD V=110,L=9 ISO TEMP=120,PRES=297CONTROL UID=CON1,NAME=TVP CONTROL SPEC STREAM=105,TVP,VALUE=14.7,ATOL=0.1 VARY FLASH=VAL2,PRESCOMPRESS UID=COM1 FEED 24 PROD V=25 OPER EFF=70,PRES=100HX UID=HX-2,NAME=COM1 COOLER HOT FEED=25,21,V=27A,L=10A,DP=3 OPER HTEMP=120 UTILITY WATER,TIN=70,TEMP=100COMPRESS UID=COM2 FEED 27 PROD V=28 OPER EFF=70,PRES=300HX UID=HX-3,NAME=COM2 COOLER HOT FEED=28,20,V=110A,L=9A,DP=3 OPER HTEMP=120 UTILITY WATER,TIN=70,TEMP=100END

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FLASH S UMMARY

FLASH ID D-1 VAL1 VAL2 C1+ NAME STAGE 1 STAGE 2 STAGE 3 1ST COMPRESS

FEEDS 100 2 3 24 SW1 10 21 9 11

PRODUCTS VAPOR 20 21 22 27 LIQUID 2 3 105 10 WATER W1 W2 W3

TEMPERATURE, F 200.000 192.986 178.680 120.000PRESSURE, PSIA 300.000 100.000 35.739 97.000

PRESSURE DROP, PSI 700.000 200.000 -3.000 -64.261MOLE FRAC VAPOR 0.12747 0.10070 0.12468 0.89502MOLE FRAC TOTAL LIQUID 0.87253 0.89930 0.87532 0.10498MOLE FRAC H/C LIQUID 0.54115 0.71095 0.87312 0.04236MOLE FRAC FREE WATER 0.33139 0.18835 0.00220 0.06261DUTY, MM BTU/HR 25.17655 0.00000 0.00000 -2.52528FLASH TYPE ISOTHERMAL ADIABATIC-P ADIABATIC-P ISOTHERMAL

FLASH ID C2+ NAME 2ND COMPRESS

FEEDS 27 20

PRODUCTS VAPOR 110 LIQUID 9

TEMPERATURE, F 120.000PRESSURE, PSIA 297.000PRESSURE DROP, PSI -200.000MOLE FRAC VAPOR 0.91846MOLE FRAC TOTAL LIQUID 0.08154MOLE FRAC H/C LIQUID 0.05822MOLE FRAC FREE WATER 0.02332DUTY, MM BTU/HR -3.47833FLASH TYPE ISOTHERMAL


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S TAGE 2 C OMPRESSOR UNIT 11, COM2

FEEDS 27

PRODUCTS VAPOR 28


INLET ISENTROPIC OUTLET --------------------- --------------------- --------------------- TEMPERATURE, F 120.00 209.16 234.87 PRESSURE, PSIA 97.00 300.00 300.00 ENTHALPY, MM BTU/HR 6.8129 8.0100 8.5230 ENTROPY, BTU/LB-MOL-F 55.7960 55.7961 56.5927

CP, BTU/LB-MOL-F 17.9093 21.3113 CV, BTU/LB-MOL-F 15.3146 17.9144 CP/(CP-R) 1.1247 1.1028 CP/CV 1.1694 1.1896 MOLE PERCENT VAPOR 100.0000 100.0000 100.0000 MOLE PERCENT LIQUID 0.0000 0.0000 0.0000 MOLE PERCENT H/C LIQUID 0.0000 0.0000 0.0000 MOLE PERCENT WATER 0.0000 0.0000 0.0000 ACT VAP RATE, M FT3/MIN 0.9457 ADIABATIC EFF, PERCENT 70.0000 POLYTROPIC EFF, PERCENT 72.7132 ISENTROPIC COEFFICIENT, K 1.1511 POLYTROPIC COEFFICIENT, N 1.2203 HEAD, FT ADIABATIC 25141.32 POLYTROPIC 26115.78 ACTUAL 35916.16 WORK, HP THEORETICAL 470.46 POLYTROPIC 488.69 ACTUAL 672.08

NOTE: POLYTROPIC AND ISENTROPIC COEFFICIENTS ARE CALCULATED FROM HEAD EQUATION. G

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S TREAM P ROPERTIES O UTPUT

STREAM ID 28 100 105 110 NAME OIL FEED OIL PRODUCT GAS PRODUCT PHASE WET VAPOR WET LIQUID WET LIQUID WET VAPOR --------- TOTAL STREAM ---------RATE, LB-MOL/HR 944.442 8793.999 3932.193 1896.986 M LB/HR 37.038 830.134 718.323 58.389TEMPERATURE, F 234.871 150.000 178.680 120.000PRESSURE, PSIA 300.000 1000.000 35.739 297.000MOLECULAR WEIGHT 39.217 94.398 182.677 30.780ENTHALPY, MM BTU/HR 8.523 29.855 29.259 8.558 BTU/LB 230.114 35.964 40.733 146.561MOLE FRACTION LIQUID 0.00000 1.00000 1.00000 0.00000MOLE FRACTION FREE WATER 0.00000 0.33870 0.00000 0.00000

--------- TOTAL VAPOR ------------RATE, LB-MOL/HR 944.442 N/A N/A 1896.986 M LB/HR 37.038 N/A N/A 58.389 M FT3/HR 20.872 N/A N/A 35.127STD VAP RATE(1), M FT3/HR 358.397 N/A N/A 719.870MOLECULAR WEIGHT 39.217 N/A N/A 30.780ENTHALPY, BTU/LB 230.114 N/A N/A 146.561CP, BTU/LB-F 0.543 N/A N/A 0.503DENSITY, LB/M FT3 1774.529 N/A N/A 1662.237

--------- TOTAL LIQUID ---------RATE, LB-MOL/HR N/A 8793.999 3932.193 N/A M LB/HR N/A 830.134 718.323 N/A BBL/HR N/A 3182.665 2647.934 N/A GAL/MIN N/A 2227.858 1853.548 N/A

STD LIQ RATE, BBL/HR N/A 3037.827 2498.861 N/AMOLECULAR WEIGHT N/A 94.398 182.677 N/AENTHALPY, BTU/LB N/A 35.964 40.733 N/ACP, BTU/LB-F N/A 0.549 0.522 N/ADENSITY, LB/BBL N/A 260.830 271.277 N/A

(1) STD VAPOR VOLUME IS 379.48 FT3/LB-MOLE (60 F AND 14.696 PSIA) G

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S TREAM P ROPERTIES O UTPUT (Cont)

STREAM ID 28 100 105 110 NAME OIL FEED OIL PRODUCT GAS PRODUCT PHASE WET VAPOR WET LIQUID WET LIQUID WET VAPOR ------------ DRY STREAM ------------RATE, LB-MOL/HR 928.047 5794.000 3907.521 1886.231 M LB/HR 36.743 776.089 717.878 58.196STD LIQ RATE, BBL/HR 217.641 2883.415 2497.591 385.751MOLECULAR WEIGHT 39.592 133.947 183.717 30.853MOLE FRACTION LIQUID 0.0000 1.0000 1.0000 0.0000REDUCED TEMP (KAYS RULE) 1.1716 0.6359 0.5413 1.1548 PRES (KAYS RULE) 0.4782 2.2613 0.1044 0.4574ACENTRIC FACTOR 0.1238 0.3662 0.5022 0.0844WATSON K (UOPK) 15.094 12.296 12.000 15.956

STD LIQ DENSITY, LB/BBL 168.824 269.156 287.429 150.863 SPECIFIC GRAVITY 0.4821 0.7687 0.8208 0.4308 API GRAVITY 161.989 52.586 40.883 196.928

------------ DRY VAPOR -------------RATE, LB-MOL/HR 928.047 N/A N/A 1886.231 M LB/HR 36.743 N/A N/A 58.196 M FT3/HR 20.467 N/A N/A 34.902STD VAP RATE(1), M FT3/HR 352.176 N/A N/A 715.789SPECIFIC GRAVITY (AIR=1.0) 1.367 N/A N/A 1.065MOLECULAR WEIGHT 39.592 N/A N/A 30.853Z (FROM K) 0.8876 N/A N/A 0.8834CP, BTU/LB-F 0.543 N/A N/A 0.505DENSITY, LB/M FT3 1795.257 N/A N/A 1667.374

------------ DRY LIQUID ------------RATE, LB-MOL/HR N/A 5794.000 3907.521 N/A M LB/HR N/A 776.089 717.878 N/A BBL/HR N/A 3025.374 2646.628 N/A GAL/MIN N/A 2117.755 1852.634 N/ASTD LIQ RATE, BBL/HR N/A 2883.415 2497.591 N/ASPECIFIC GRAVITY (H2O=1.0) N/A 0.7687 0.8208 N/AMOLECULAR WEIGHT N/A 133.947 183.717 N/AZ (FROM K) N/A 0.5399 0.0245 N/ACP, BTU/LB-F N/A 0.518 0.522 N/ADENSITY, LB/BBL N/A 256.527 271.243 N/A

(1) STD VAPOR VOLUME IS 379.48 FT3/LB-MOLE (60 F AND 14.696 PSIA)


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GAS DEHYDRATIONUSING TEGGas dehydration is being performed by an existing TEG plant currently in operation.You wish to model the operation of this plant based on recent plant test data in orderto estimate annual TEG vaporization losses.

Process Data The process flowsheet for the TEG dehydration system is shown in Figure G7.1. Thefeed to this system is 39 MMSCFD of wet gas (21.5 pounds of water per MMSCF ofwet gas) at 80 F and 720 psig.

This feed stream is synthesized by mixing the hydrocarbon gas on a dry basis (stream1G) with water (stream 1W) to yield the actual wet gas feed (stream 1"). TheStream Data specifications consist of the composition and thermal condition of thetwo feed streams (streams 1G" and 1W) and the recycle stream (stream 3"):

Table G7.1Feed Stream Information

Stream IDStream Name

1GGas Mix

1WWater Mix

3Lean TEG

StreamComponents

MolePercent lb/day

WeightPercent

1 CO2 1.365 0.00 0.0002 H2S 1.700 0.00 0.0003 C1 88.140 0.00 0.0004 C2 6.410 0.00 0.0005 C3 1.710 0.00 0.0006 IC4 0.181 0.00 0.0007 NC4 0.239 0.00 0.0008 IC5 0.069 0.00 0.0009 NC5 0.071 0.00 0.00010 NC6 0.054 0.00 0.00011 NC7 0.061 0.00 0.00012 H2O 0.000 838.50 1.400

13 TEG 0.000 0.00 98.600Input Units

Stream RateSCFD

39.0E+6lb/day838.50

gal/hr600.000

Temperature (F)Pressure (psig)

80720

80720

130720

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Methodsand Data The system keyword GLYCOL is used to select equilibrium and enthalpy data for the

dehydration calculations. This is a special data package provided in PRO/II specifi-cally for glycol dehydration systems. The data in this package have been fitted overa range of typical temperatures and pressures for TEG dehydration systems.

The GLYCOL package is based on TEG solutions which are typically used indehydration operations (98+ percent TEG by weight). Note that ideal flowingdensities are selected for the TEG solutions.

SimulationModel

The TEG plant process flowsheet is shown in Figure G7.1. The corresponding PRO/IIsimulation flow diagram is shown in Figure G7.2.

Figure G7.1TEG Plant Flowsheet

Figure G7.2Simulation Flowsheet for TEG Process

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The standard convergence criteria have been modified to ensure that the tracerecycle component (water) will be tested for closure. Convergence of the recycle

stream (lean TEG, stream 3") is enhanced by specifying the recycle stream tem-perature (see Cooler" heat exchanger specification). This is good simulation prac-tice and also corresponds well to actual operations.

The actual feed stream is synthesized as mentioned above by isothermal mixing ofthe water and natural gas portions of the feed stream in a flash module.

The Stream Data Category also includes specifications to:

Speed convergence by utilizing the reference stream feature to relate heatexchanger inlet and outlet streams.

Establish a user-defined output format. Name the principal process streams.A contactor model using three theoretical trays or equilibrium stages is used to match

actual plant data accurately.The regenerator is modeled by feeding the warm, rich glycol to tray one. If it is desiredto furnish a condenser, the reflux rate should be specified and the condenser dutycalculated. The reboiler temperature is specified, which sets the lean TEG concen-tration.

The Inside/Out (I/O) method is used for both the contactor and the regenerator.

Regenerators in which stripping gas is injected may also be modeled. Externalstripping columns may be modeled with two or three equilibrium stages.

A Stream Calculator utility module is used to create the make-up TEG stream. TEGlosses in the plant outlet streams (treated gas----stream 2", flash gas----stream 7",and water vapor----stream 11") are summed to determine the required TEG make-up.

Input Data The standard stream summary is suppressed (Note 1) and a user-defined outputformat is used to generate special reports instead (Note 2). Note the tightening ofthe trace component tolerance for the recycle streams (Note 3) and the use of theStream Calculator utility module (Note 4) as discussed above.

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Input Data FileTITLE PROJECT=APPBRIEF,PROBLEM=G7, & USER=SIMSCI,DATE=01/30/92 DESC GAS DEHYDRATION USING TEG DIMEN ENGLISH PRINT STREAM=COMP,INPUT=NONE $NOTE 1 DBASE DATA=PC1,IDATA=3,SDATA=G7AMC TOLER STREAM=0.01,,0.0005 $NOTE 3

COMPONENT DATA LIBID 1,CO2/2,HYSULFID/3,METHANE/4,ETHANE/ & 5,PROPANE/6,IBUTANE/7,BUTANE/8,IPENTANE/ & 9,PENTANE/10,HEXANE/11,HEPTANE/12,H2O/ & 13,TEG

THERMODYNAMIC DATA

METHOD KVALUE(VLE)=SRKM,ENTH(V)=SRKM,ENTH(L)=SRKM, & ENTR(V)=SRKM,ENTR(L)=SRKM,DENS(V)=SRKM, & DENS(L)=IDEA,SET=SET01,DEFAULT KVALUE(VLE) BANK=GLYCOL,SIMSCI

STREAM DATA PROP STREAM=1G,TEMP=80,PRES=720,PHASE=M, & RATE(GV,FT3/DAY)=39.0e+006, & COMP(M)=1,1.365/2,1.7/3,88.14/4,6.41/ & 5,1.711/6,0.181/7,0.239/8,0.069/ & 9,0.071/10,0.054/11,0.061,NORMALIZE PROP STREAM=1W,TEMP=80,PRES=720,PHASE=M, & COMP(WT,LB/DAY)=12,838.5 PROP STREAM=3,TEMP=130,PRES=720,PHASE=M, & RATE(LV)=600, & COMP(WT)=12,1.4/13,98.6,NORMALIZE

PROP STREAM=6,REFS=4,TEMP=170,PRES=50 PROP STREAM=10,REFS=8,TEMP=240,PRES=40 NAME 1G,GAS MIX/1W,WATER MIX/3,LEAN TEG/ & 6,FLASH FEED/10,RICH TO REG/8,FLASH LIQUID/ & 11,OFF GAS/15,MAKEUP TEG/2,DRY GAS/ & 4,RICH TEG/7,FLASH GAS/12,HOT LEAN/ & 1,WET GAS

OUTPUT FORMAT=1,STRM=1,3,2,4, & $NOTE 2 DESC=CONTACTOR STREAMS OUTPUT FORMAT=1,STRM=10,11,12, & DESC=REGENERATOR STREAMS OUTPUT FORMAT=1,STRM=6,7,8, & DESC=FLASH TANK STREAMS FORMAT IDNO=1,NAME,PHASE,TEMP,PRES,CRATE, & RATE,LINE,CRATE(WT),RATE(WT),LINE,VAPOR, &

RATE(GV,FT3/DAY),MW,DENSITY(LB/FT3), & LIQUID,RATE(LV,GAL/MIN),SPGR, & DENSITY(LB/FT3)

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PUMP UID=9,NAME=GLYCOL PUMP FEED 14,15 PROD L=16 OPER PRESS=730

HX UID=10,NAME=COOLER HOT FEED=16,L=3,DP=10 OPER HTEMP=130 CONFIG TPASS=1,SPASS=1END

Results The recycle loop converged in three iterations. The regenerator duty is 0.63 MMBtu/hr, the glycol pump hydraulic horsepower is 4.6 hp and the duties for theLean-Rich 1", Lean-Rich 2", and Cooler heat exchangers are 0.25 MM Btu/hr,0.32 MM Btu/hr, and 0.38 MM Btu/hr respectively. The make-up TEG flowrate is0.014 Lbmole/hr.

Conclusions The natural gas stream is dehydrated from a water content of 21.5 pounds of waterper MMSCF of gas to 2.8 pounds of water per MMSCF of gas with a 10 gpm leanTEG flowrate to the contactor. Annual TEG vaporization losses will be approximately1900 gallons per year based on a 97% operating factor (excluding losses due toentrainment or upsets in column operation).

Output Partial results are shown below for the simulation input given

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