CH1019 Chemical Process Technology

Lecture2

Chapter1Chlor-AlkaliIndustries

BalasubramanianSAssistantProfessor(OG)DepartmentofChemicalEngineering

Chapter1 CHLORALKALIINDUSTRIES

ProductsofChlor-AlkaliIndustries

SodiumChloride

SodiumAsh

Sodiumbi-carbonate

ChlorineandCausKcSoda

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2

Overview of topics

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5

Chapter1 CHLORALKALIINDUSTRIES

ProductsofChlor-AlkaliIndustries

SodiumChloride

SodiumAsh

Sodiumbi-carbonate

ChlorineandCausKcSoda

1

2

Overview of topics

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4

5

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TheChlor-alkaliindustriesrepresentsthreemajorindustrial

chemicals

1.  Sodaash2.  CausKcSoda3.  Chlorine

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Apartfromthesecompoundsthecommonsalt(NaCl),Sodium

chloridesisthebasicrawmaterialforgreatmanycompounds

suchas

1.  Sodiumhydroxide

2.  Sodiumsulfate

3.  Hydrochloricacid

4.  SodiumchlorateandSodiumchlorite

Thesalt(NaCl)isusedintheregeneraKonofsodiumzeolite

watersoWeners

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ManufactureofNaCl

Saltisobtainedinthreedifferentways,namely,

1.  SolarevaporaKonofseawater2.  Miningofsaltrock

3.  Fromwellbrines(andpurificaKonusingvacuumpansystems)

-PurityofsaltobtainedfromsolarevaporaKon=99.0%

-Purityofsaltfromrocksalt =99.5%

-Thesaltobtainedthroughwell =98.0%pure

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ManufactureofNaClusingVacuumpansystems

-  Saltbrineisobtainedbypumpingwaterintoasaltdepositandbringingthebrinetothe

surface.

-  Twoconcentricpipesareusedwithwaterbeingforceddownthecenterpipeandbrine

returningtothesurfacethroughtheannularspacebetweenthetwopipes.

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ManufactureofNaClusingVacuumpansystems

-  ThevacuumpanemployingmulKpleeffectevaporatorsisthemostcommonmethodof

producingbrinefromwellsasshowninabovefigure.

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S.No. Process Equipment UnitOpera6on UnitProcess Objec6ve

01 ConKnuous ConcentricPipes

Drilling - DrillandobtainthebrinesoluKon

02 Batch Vacuumpanevaporator

EvaporaKon - ConcentraKonofsaltfrombrinesoluKonunderreducedatmosphericpressure

03 Batch Receiver

Storage - TostoretheconcentratedbrinesoluKon

04 ConKnuous Washer Washing/Cleaning

- Towashandpurifythebrine

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S.No. Process Equipment UnitOpera6on UnitProcess Objec6ve

05 ConKnuous Rotaryfilter/Drier

FiltraKon/Drying - SeparaKonofsolidsaltcakeandliquidbrinesoluKon.Drythesaltcakebypassingthehotair

06 ConKnuous Scale Weighing - Toweighthesaltobtainedfromtherotaryfilter

07 ConKnuous Helicalconveyor

SolidtransportaKon

- Toconveythesalt(NaCl)andpackthesalttomarket

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ManufactureofSodaAsh(SodiumCarbonate–(Na2CO3)

ClassificaKonofprocessesinthemanufactureofSodaAsh

1.  LeBlancProcess2.  SolvayProcess

3.  Naturalsodafromdeposits

4.  Dualprocess

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History-ManufactureofSodaAsh(SodiumCarbonate–(Na2CO3)

1.  LeBlancProcess

-  Thisprocesswasdiscoveredin1773andwasuseduniversally

formanyyearsintheworld.

-  Saltcake(sodiumsulfate)reactswithlimestonetogivesoda

ashandatroublesomeproductgypsum(calciumsulfate).

-  Theprocessisnolongerused.

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History-ManufactureofSodaAsh(SodiumCarbonate–(Na2CO3)

2.Solvayprocess

-  In1864,ErnestSolvay,aBelgiumchemist,inventedsoda

process(orAmmonia–Sodaprocess)

-  TheSolvaymethodhascompletelyreplacedandtheLeBlanc

methodby1985.

-  ThismethodissKllverypopularWorldwide.

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History-ManufactureofSodaAsh(SodiumCarbonate–(Na2CO3)

3.Naturalprocess

-  InU.S.largedepositsofnaturalTronaorefacilitatesthe

manufactureofsodaashfromit.

-  TheoreTronaalsocalledassodiumsequicarbonate.HeaKng

thisoregivessodaash.

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History-ManufactureofSodaAsh(SodiumCarbonate–(Na2CO3)

3.Dualprocess

-  ItisalsocalledmodifiedSolvayprocess.

-  TheprincipalmodificaKonistherecoveryofNH4Clas

coproductratherthanliberaKonofcombinedammoniafor

cycle.

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References

1.  DrydenC.E,OutlinesofChemicaltechnology–forthe21stCentury,3rdediKon,East-WestPress(2004)

2.  AusKnG.T,Shreve’sChemicalProcessIndustries,5thediKon,McGrawHillInternaKonalediKons(1984)