This document provides a summary of the design of a natural gas to olefins plant. It describes the process of taking a feedstock of ethane and propane from North Dakota, cracking it in a furnace cracker to produce ethylene, propylene, and other products, quenching and dehydrating the products, and fractionating them into final products. It discusses the economics of the project, noting the capital cost estimate and projected profitability. It outlines future work to further optimize the design and processing.

1. Natural Gas to Olefins
By
The Crackers
December 6th
, 2012
CHE 4070 – Senior Design 1
Final Report
Salman Almutawa
Mohammed Alzain
Scott Chase
Travis Wells

2. Table of Contents
ManagementSummary
-Brief processdescription
-Economics
-Assumptions
-Recommendations
ProjectDefinition
-Assumptions
-Material balance
-Businessopportunity
-Issues
-Future work
ProcessDescription
-Feed
-Cracker
-Reactions
-Quench
-Dehydration
-Fractionation
Economics
-Capital
-Sensitivities
References
Appendices

3. Management Summary
Overthe last three monthswe have workedonthe design,economics,andfeasibilityof buildingan
olefinsplantthatwill utilize NorthDakotanatural gasliquids(NGLs) asa feedstock. The objective isto
designaplantthat will have a 1.5 billionpoundperyearproductioncapacity. Thisreportcontainsthe
lastthree monthsof work summarizedbysectiontodate.
Processdescription
Thisplantwill use NorthDakotaethane andpropane as a feedstockina 75/25 mass percentmix
respectively. Uponenteringthe plant,the feedisdilutedwith500°F steamand sentthrougha furnace
cracker. Thiscracker will notuse a catalystdue to the productionof heavyundesirablebyproductsand
produce ethylene,propylene,methane,andhydrogenasitsmainproducts. Afterthe cracker,the
productswill be sentthrougha quenchtowerforcoolingandto stop the reaction. The quenchsystem
will completelysaturate the productstreamwithwater,thereforerequiringadehydrationsystem.
The dehydrationsystemforthe plantwill use athree phase separatortoremove mostof the waterand
a molecularsieve (akamole sieve) systemtoremove the smallerremainingportionof water. After
dehydration,the productsare sentthroughanextensivefractionationsystemthatwill separatethe
variouscomponents. The final productsof the fractionationsystemare ethane,propane, ethylene,
propylene,hydrogen,methane,andC4+ heavybyproducts. Ethyleneandpropylene will be the main
productssold,hydrogencanalsobe soldif a consumerisnearbythat can use it,methane can be burned
withinthe planttoreduce utilitycosts,andthe heavybyproductcanbe soldas condensate orgasoline
additives. The ethane andpropane will be recycledbacktothe cracker forconversionintoolefins.
Economics
Currentlywe knowourcapital cost is50%-75% lowerthanwhatit shouldactuallybe. Thisisdue to an
incomplete design,estimations,andlackof heatintegration. The sectionlaterinthe reportgoesfurther
indetail aboutthe economicassumptionsandcostingestimates. Ourcapital cost to date is $421.24
Milliondollars. With thiscapital cost,the NPV0is$19,371.92 millionwithanIRRof 58.7% on a twenty
yearperiod. Because of the lowcapital cost and highIRR,sensitivitieswereruntoverifythe economics
of the project. Atthree timesthe capital costwhichis $1.262 billion dollars,ourNPV0is $18,837.68
million,IRRis36.6% and paybackperiodis 3.62 yearsat full capacityproduction. The highIRR can be
attributedtothe lowcost of the feedstockandthatethylenesellsfordouble whatethanecosts.
Assumptions
The firstand largestassumptionwe have made isthatwe can deliverourproductbyrailcar once it has
beenproduced. Ideally,the locationof the plantwouldbe inanareawhere there ismore industry
presentandcloserto potential customersorlargermeansof shipping. KinderMorgancurrentlyhasa
pipelinethatrunsfromCanada, throughNorth Dakota,and endsaroundChicago. Unfortunatelythe
flowof thispipelinewill be reversedinthe nearfuture toaccommodate the heavyoil sandsinCanada
[1].

4. Some of the otherassumptionswe have made include:
-Feedis75/25 mass percentmix of ethane/propane
-Crackerproductsare basedoff of table 6 inthe appendix
-We have a customerfor the hydrogenbyproduct
-We have customersthat will purchase the olefinproducts
-Many of the heatexchangerswere modeledasheatersorcoolers,whichincreasesutilitycost
-Aspen+simulationsare reasonablyaccurate andvalid
Recommendations
We recommendthatthisprojectkeepsmovingtowardafinal productbasedoff of the sensitivities,IRR,
and paybackperiod. We are usinga proventechnologythatwill have littlesurprisesandalow
maintenance costsbecause there will be noexpensive catalysttoreplace. The largestissue withmoving
forwardfromwhere we are now isplacingthe plantinNorth Dakota. This isan isolatedregionwithno
majorpetrochemical plantsnearby. Thisleavesalarge shippingcosttous andmakesit harderto sell
useful byproducts.
As thisprojectproceedsintothe comingmonths,we willbeginworkon:
-Findinganewlocationforthe plant
-Furtherandmore detailedeconomicreview
-Heatintegrationtosave onutilitycosts
-Optimizationof unitoperations
-Designarefrigerationsystem

5. Project Definition
Recentadvancesindrillingtechnologyhave openedmanyoil andnatural gasreservesthatwere
previouslythoughtinaccessible oreconomicallyunfeasible. NorthDakotahas seenalarge growth inthe
productionof natural gas overthe last decade significantlyincreasingthe amountof Natural GasLiquids
(NGLs) available onthe market. Withthisincrease of potentialfeedstocks,we have takenonthe
projectof designingaplantthat will convertthe NGLsto olefinsforfurtheruse inthe petrochemical
industry.
Our goalsfor designingthisplantare:
 Successfullydesignaplantthatwill convertNGLsto olefinswitha1.5 billionlb/yr
capacitywithethylene andpropylenebeingthe primaryproductsusingNorthDakota
feedstocks.
 Place the plantinNorth Dakotaand sendproductsout by railroad.
 Use ethane andpropane as a feedstockfromthe NorthDakotareserves.
 Designthe plantto produce highpurity(99.8%) ethylene andpropylene for
petrochemical usessuchaspolymerizationforplastics.
Thisplantwill use the traditional approachtomanufacturingolefinsbyasteamcrackingreactor, a
quenchsystem, dehydration, andanextensivefractionationsystem.
Material Balance
(lb/hr) Ethane Propane Ethylene Propylene Methane H2 Heavies
Feed 180000 60000 - - - - -
Main
Products - - 166561 21624 - - -
By-
products - - - - 24937 19563 7315
Recycle 125489 31335 - - - - -
Table 1 – Material balance fromAspen+simulation
Cracker DehydrationQuench
FractionationProducts

6. BusinessOpportunity
Ethylene iscurrentlythe largestproducedpetrochemical inthe world. Withthe openingof these new
gas reserves,producingethylenefromethane ischeapandeasy. Ethylene isan importantprecursorfor
manyproducts including plastics,polymers,ethylene glycol,andethylenedichloride. Propyleneisalsoa
largelyusedproductandisalso an importantprecursorformanyproducts [2].
Manufacturingethyleneandpropylene from ethane andpropane canbe veryprofitable whenthe
marketconditionsare good. Currentlythe price forethane is $0.22 per poundandthe price for
ethylene is$0.55 perpound [3]. Thisgivesusa profitmarginof $0.33 perpound,whichisclose to what
we will alsosee forthe propane topropylene marginof $.0.235 perpound [4].
The byproductsfromthe plantare also profitable if aconsumerisfoundfor them. Hydrogengaswill be
producedat a rate of 19563lb/hr and can be soldforup to $1.40 perpound. The methane producedwill
be usedto helpcut downonour utilitycost. Also,sellingthe heavybyproductsasgasoline additives
couldalsoturn a small profit.
Issues
The largestissue nowisthe locationof the plant. The locationinNorthDakota waschosenso an ample
feedstockwasavailable. However,thisleavesushavingtoshipoutthe product. One possible
alternative locationwouldbynearConway,Kansas. Currently,OneOKisbuildingaNGL pipeline from
NorthDakota to Wyomingwhere iswill tie intotheircurrent OverlandPassPipeline(OPPL) andendin
Conway. Atthis time itisunknownhowConwayshipstheirfractionatedproductsorwhere theygo.
Researchisstill goingonto findan alternativelocation. Withourlocationbeingso remote itisdifficult
to findconsumersthatmayuse ourbyproducts. If no one is foundtouse the hydrogenitwill be usedto
heatthe furnaces. The same scenarioappliestoourheavybyproducts.
Issueswiththe plantare constantlychanging. Rightnow we have notworkedon anyheat integrationso
our utilitycostsare veryhighand a refrigerationsystemhasnotyetbeendeveloped. The dehydration
systemchangesslightlywitheachmodificationtothe plant. The currentmodel we are workingwith
differsgreatlyfromthe model thisreportisbasedoff of. Ourcurrentmodel requiresthe use of a
molecularsieve system, where the versionusedforthisreportdoesnot. A molecularsievesystemwas
pricedintothe capital because itwill be usedinfuture simulations.
Future Work
We still have alotof work for thisprojectfornextsemester. First,we willbe researchinganew location
possibilityforourplantthatwill allowustomake a profitfromour byproductsandreduce shipping
costs onour mainproducts. Optimally,thiswouldeitherbe inthe gulf coast regionoraroundChicago
and the Great Lakesregion. Basedonhow we will be movingourproducts,we will be modifyingour
plantto make the appropriate changestoour products. If anotherplantisclose bythat can use our
productsas vapor,we can save moneyoncompressionandliquefyingourproducts.
The nextbigstepwill be workingonthe heatexchangernetworkandoptimizingourplant. All of the
towersneedtobe thoroughlygone throughandsizedproperly. There will alsobe manyheat

7. exchangersandmanyoptionsof howto setup the heatexchangernetworkthatneedtobe researched.
As we continue tomodifythe design,we will alsobe updatingoureconomicinformation alongwith
keepingtrackof currentfeedandproduct prices. The lastpart of our worknextsemesterwill be looking
intoenvironmental issuesandregulations. We wantour plantto meetall EPA regulationsanddonot
wantto modifyourequipmentafterinstallation.

8. Process Description
Feed
The feedforthe plant will consistof amixture of ethane andpropane fromNorthDakota. This mixture
will be a 75/25 mass percentmix of ethane andpropane respectivelythatwill be diluteddownbysteam
uponenteringthe plant. The steamservestwopurposes. First,itpreheatsthe reactantsbeforethe
cracker to cut downon the cracker dutyand increase yield. Second,itdilutesthe reactantstreamto
allowforbetterconversionintoethylene andpropylene. Ethane and propane thatwasunconvertedis
recycledbackintothe cracker by streamsH104-O and H103-O respectively(see figure 1).
Cracker
The cracker technologychosenwill be afurnace withtube bundlesinside whichthe feedwill flow
through. Due to the extremelyfastreactiontime of 0.2-0.5seconds [5],the feedwill have averyhigh
velocityasittravelsthroughthe cracker. The furnace cracker, R101, was chosenovercatalyst
technologies due tothe lowercapital costs,proveneffectiveness,andlessundesirable byproducts. The
catalystsresearchedhada 5% increase inyieldof productsanda lowerreactiontemperature [6],but
alsohad an increase inundesirable byproducts.
Figure 1 – Feed,cracker,andquenchtower
Reactions
The main reactiontakingplace inside the crackeristhe conversionof analkane intoanalkene. Equation
1 belowshowsthe basicreactionforthe feedalkane.
𝐶 𝑛 𝐻2𝑛+2
𝐻𝑒𝑎𝑡
→ 𝐶 𝑛 𝐻2𝑛 + 𝐻2 Eqn 1
The reactionin equation1takesplace inan environmentvoidof oxygentoreduce byproductsandthe
riskof combustion. The actual kineticsbehindequation1is extremelycomplex. Equations2-4below
summarize the basicmechanismforethane beingconvertedtoethylene [7].

9. 𝐶𝐻3 𝐶𝐻3 → 2𝐶𝐻3 • Eqn 2
𝐶𝐻3 • + 𝐶𝐻3 𝐶𝐻3 → 𝐶𝐻4 + 𝐶𝐻3 𝐶𝐻2 • Eqn 3
𝐶𝐻3 𝐶𝐻2 • → 𝐶𝐻2 = 𝐶𝐻2 + 𝐻 • Eqn 4
Equation2 showshowthe heatfromthe furnace causestwofree radicalstoform fromethane. In
equation 3,these radicalsthenreactwithanotherethane moleculetoformmethane molecule andan
ethane radical. Inequation 4 the ethane radical decomposes intoanethyleneandhydrogenradical.
Thisis the basicform of howethane iscracked. Many otherside reactionsoccurduringthisprocess
givingrise tobyproductsandin some casescoke [7].
QuenchTower
An extremely large quenchsystemisrequiredtocool the productsafterthe cracker to stopthe reaction.
Leftuncooled,the productswill continue toreactand polymerize intoheavierbyproducts. The quench
systemwill be alarge towerinwhichcool water will enter the topandflow downtrayspast the vapor
productswhichenterat the bottomand rise to the top. Thiscounter-flow coolingprocesswill
effectivelycool ourproductstreamfrom1292°F downto 204°F. Anoil quenchsystemwasavoideddue
to the lowamountof heavybyproductsproducedbyourcracker and the increasedcapital cost.
Dehydration
The water quenchsystemwill cool downourproductstream butwill alsocompletelysaturate itwith
watervapor. Thiswaterhas to be removedbefore enteringthe cryogenicfractionationsystemwhere it
wouldfreeze andclogthe towers. The firstandmainpart of the dehydrationsystemisa three phase
separator(D101) whichremoves99.9%of the waterinthe streamreducingthe watercontentto80ppb.
Due to our large flowrate,the concentrationof waterneedstobe below 100ppb to avoidfreezingin
the towers. Currentlywe achieve thiswiththe simulationthatthe reportisbasedoff of. However,later
modelsdonotget below100ppbfrom the three phase separatoralone. The secondpartof the
dehydrationsystemwill achievethis. Byusingmolecularsieve,the productstreamcanbe almost
completelydehydratedandreadyforfractionation. The molecularsievesystemwill have fourbeds
(S101) that can be run in parallel. Onlytwoof the fourbedswill actuallybe usedatone time,while the
othertwo will be regeneratingthe molecularsieve tobe usedagain.

10. Figure 2 – Dehydrationsystem
Fractionation
The fractionationsystembeginsinthe middle of the dehydrationsystem (seefigure2above). Afterthe
maintowerremovesmostof the water,the liquidproductsare fedtoa depropanizer (T101) which
performsthe splitbetweenC3moleculesandC4 molecules. The vapor C1-C3 phase thentravels
throughthe molecularsieve andgoesthroughacompressor (C101) whichbringsthe pressure from
15psia to 900psia (see figure 3). Thislarge pressure increase causes alarge temperature increase,which
isloweredthroughaseriesof heatexchangers (H102).
The vapor and liquidfractionsare separatedinaflashdrum(D104) and each fractionisthentakesa
large pressure dropwhichwill alsodropthe temperature. The vaporisexpandedthroughanexpander
(C102) whichwe can utilize the expansionenergyforcompressionlateron. The liquidportionis
decreasedinpressure byavalve (V101) so it isthe same pressure as the vaporstream. Bothstreams
are thenfedtothe demethanizer(T103in figure 3).
The demethanizersplitshydrogenandmethane fromthe C2and C3 moleculesata frigidtemperatureof
-208°F. Currently,the towerconsistsof 40 theoretical trays,akettle reboiler,andapartial condenser.
The vapor streamis sentto a H2 splitterwhichwillseparate the methane fromthe hydrogen,andthe
liquidstreamgoestothe deethanizerforfurtherfractionation.

11. Figure 3 – Compression,expansionanddemethanizer
The H2 splitter(T104 figure 4 below) iswhatwill be usedtoseparate the methane fromthe hydrogen.
Thistowerconsistsof 12 trays and onlya condenser. A reboilerisnotrequireddue tothe low
temperature of -226°F to liquefymethane. The liquidmethane will be ranthroughheatexchangersand
eventuallyburnedtoproduce steamandolefins. The vaporhydrogenstreamisat96% mole purity and
can be soldif a customerisfound. If not,thissectionmaybe removedfromthe final plans.
Figure 4 – H2 splitter
The final portionof the fractionationsystemisrepresentedinfigure 5below. T105 is the deethanizer
whichseparatesthe C2 moleculesfromthe C3molecules. The C2 streamisthensentto the C2 splitter
(T106), whichseparatesunconvertedethane fromthe productethylene. Ethane isrecycledbacktothe
cracker and the final ethylene productisshippedoutforuse. The C3 streamfromthe deethanizeris
sentto the C3 splitter(T107),whichperformsthe verydifficultsplitof propane andpropylene. Inorder
for T107 to performthissplit,isrequires125 theoretical traysandisabout198.5 feettall. Again,
propane isrecycledandpropylene isshippedoutforuse.

12. Figure 5 – Deethanizer,C2splitter,andC3 splitter
Economics
Capital
Our currentcapital estimate isprobablyabout50%-75% lessthan whatit will actuallybe. Due tothe
constantchangesin the processas we continue todesignandresearchit,costsfluctuate frequently.
Many assumptionswere made while doingthe capital costof the plant. Below isalistof what
assumptionswere made tobase the capital costfrom:
-Pumpshave notbeen sized,soapump cost of 10% wasaddedin
-Notall the heat exchangerswere abletobe sizeddue tothe lack of a refrigerationsystem
-Towershave notbeen fully optimized
-Plantisbasedoff of one furnace cracker, whichwill change nextsemester
-Only one quenchtowerinthe design,will change nextsemester
-Noheatintegrationyetsoutilitycostsare veryhigh
-OSBLis about10% of the ISBL cost
The overall capital costat this pointis$421.24 milliondollars. Thisisall the pricedequipmentdelivered
and installed. Fordetailsof equipment costsee file 5inthe appendix.

13. Equipment Millions of Dollars
Pumps $4.93
Compressor $18.52
Furnace/ Crackers $21.93
Heat Exchangers $3.28
Vessels $0.54
Catalyst $0.00
Towers & Trays $5.25
TOTAL ISBL FOB $54.17
Delivery $5.45
Equipment Installation $323.03
Installed ISBL $380.82
Installed OSBL $38.08
Table 2 – Capital cost summary
Basedon the capital cost fromabove,table 3 below illustratesthe NPV,IRRandpayback periodforthis
project.
NPV0 $19,371.92
NPV20 $4,494.75
IRR 58.7%
PBP (approx.) (yrs.) 1.4
MARR 12%
Table 3 – NPV,IRR,and paybackperiod (Millionsof dollars)
Sensitivities
We knowthatour current capital cost fromabove islow for a few reasons. Mainly,we have notpriced
all the equipmentandwe are notfar enoughintothe projectto have designedall the equipment. For
thisreason,we ran twosensitivityanalysesbased ontwice andthree timesthe fixedcapital coststated
above. Table 4 and 5 belowshowhowdoublingandtriplingthe capitol costaffectsthe NPV andIRR.
NPV0 $15,283.52
NPV20 $3,336.98
IRR 39.8%
PBP (approx) (yrs) 2.8
MARR 12%
Table 4 – NPV and IRR basedondouble capital cost (Millionsof dollars)

14. NPV0 $18,837.68
NPV20 $3,967.39
IRR 36.6%
PBP (approx) (yrs) 3.3
MARR 12%
Table 5 – NPV and IRR basedontriple capital cost (Millionsof dollars)
Basedoff of the sensitivities,capital costdoesaffectthe IRRand NPV,butnotas drastic as expected.
Thisis believedtobe due tothe current low price of natural gas and feedstock. Thisisalso supported
by the fact that manyothercompaniesare buildingolefins plantsorhave nearfuture plansof doingso
[8].

15. References
[1] "ProductsPipelines - Mid-continentoperations,"KinderMorgan,2012. [Online].Available:
http://www.kindermorgan.com/business/products_pipelines/cochin_open_season.cfm.[Accessed
20 11 2012].
[2] "FlintHillsResources,"ChemicalsandBiofuelsProductions,[Online].Available:
http://www.fhr.com/about/default.aspx.[Accessed03 11 2012].
[3] D. Lippe,"US,Canada flushwithpropane atwinter'send;marketstoadjust," TheOil & gasjournal,
p. 116, 5 11 2012.
[4] J. Fahey, Heating costson the rise this winter, Telegraph- Herald,2012.
[5] O. W. K.S. L. Kneil,Ethylene- Keystoneto the Petrochemical Industry,New York:Marcel Dekker
Inc.,1980.
[6] N.K. Ibrahim,"Scribd,"[Online].Available:http://www.scribd.com/doc/56377886/24/Comparison-
between-thermal-and-catalytic-cracking.pdf.[Accessed12 9 2012].
[7] R. M. Rioux,"The PennsylvaniaState University,"[Online].Available:
http://www.research.psu.edu/events/expired-events/naturalgas/presentations/Rioux.pdf.
[Accessed04 9 2012].
[8] S. Jenkins,"Shalegasushersinethylene feedshifts:growthinNorthAmericanethane crackinghas
widereffectsforthe CPI,while somecompanieslooktoharnessmethane forethylene," Chemical
Engineering, p.17, October2012.
[9] A. LIQUIDE, "Gas Encyclopaedia,"AIRLIQUIDE,2009. [Online].Available:
http://encyclopedia.airliquide.com/encyclopedia.asp?GasID=41&LanguageID=11&CountryID=17.
[10] "EPA,"1994. [Online].Available:http://www.epa.gov/chemfact/s_toluen.txt.
[11] "OEHHA,"2007. [Online].Available:http://oehha.ca.gov/air/chronic_rels/pdf/71432.pdf.
[12] ChemicalBook, 2008.[Online].Available:
http://www.chemicalbook.com/ProductChemicalPropertiesCB5678167_EN.htm.

16. Appendix
Flowsheet– see embeddedAspen+simulation. The detailedFlowsheethasbeenbrokenupinthe
earlierportionof the report.
File 1 – Aspen+simulationwhichreportwasbasedfrom
Material Balance
Belowisan embeddedExcel file containingthe detailedmaterialbalance reportfromAspen+.
Detailed Material
Balance.xlsx
File 2 – Detailedmaterial balance
Physical Properties
The file belowcontainsresearchedphysical propertiesforthe keycomponentsinthe olefinsplant.
physical
properties.docx
File 3 – Physical Properties

17. Table 6 belowshowsthe masspercentconversionforour thermal cracker. For thisproject,we usedthe
60% ethane columnandthe 75% propane column.
Table 6 – Cracker conversionsinmasspercent
Economics
The Excel file belowcontainsall oursizingdataandcosts,cash flow,sensitivities,andeconomics.
4070-project-cracker
s.xlsx
File 4 – DetailedEconomics
File 5 below containsthe detailedequipmentlistandcosts.
Detailed
Equipment.xlsx
File 5 – Detailedequipmentlistandcosts