OxyChem Caustic Soda Handbook

OxyChemCaustic SodaHandbook 1 of 52

Page

Introduction & Principal Uses . . . . . . . . . . . . . . . .2

Forms of Caustic Soda . . . . . . . . . . . . . . . . . . . . .3

Manufacturing . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Methods of Shipping Caustic Soda . . . . . . . . . . . .5

Safety in Handling Caustic Soda . . . . . . . . . . . . . .6

Unloading and Handling Liquid Caustic Soda . . . .8

Anhydrous Caustic Soda . . . . . . . . . . . . . . . . . .15

Shipments, Handling and Storage of . . . . . . . . .16Caustic Soda Beads

Dissolving Anhydrous Caustic Soda . . . . . . . . . .19

Equipment for Handling Caustic Soda . . . . . . . .20

Technical Data . . . . . . . . . . . . . . . . . . . . . . . . . .23

Dilution Calculations . . . . . . . . . . . . . . . . . . . . . .38

Methods of Analysis . . . . . . . . . . . . . . . . . . . . . .40

THE INFORMATION PRESENTED HEREIN WAS PREPARED BY TECHNICAL PERSONNEL AND IS TRUE AND ACCURATE TO THE BEST OF OURKNOWLEDGE. OXYCHEM DOES NOT MAKE ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, EXPRESS ORIMPLIED, REGARDING PERFORMANCE, STABILITY OR ANY OTHER CHARACTERISTIC. THE INFORMATION CONTAINED HEREIN IS NOT TO BECONSTRUED AS AN EXPRESS WARRANTY CONCERNING THE PERFORMANCE, STABILITY OR ANY OTHER CHARACTERISTIC OF ANY OXYCHEMPRODUCT. THIS INFORMATION IS NOT INTENDED TO BE ALL-INCLUSIVE AS TO MANNER OR CONDITIONS OF USE. HANDLING, STORAGE, DIS-POSAL AND OTHER ACTIVITIES MAY INVOLVE OTHER OR ADDITIONAL LEGAL, SAFETY OR PERFORMANCE CONSIDERATIONS. WHILE OURTECHNICAL PERSONNEL WILL RESPOND TO ANY QUESTIONS REGARDING SAFE HANDLING AND USE PROCEDURES, SAFE HANDLING AND USEREMAINS THE RESPONSIBILITY OF THE CUSTOMER. NO SUGGESTIONS FOR USE ARE INTENDED AS, AND NOTHING HEREIN SHALL BE CON-STRUED AS A RECOMMENDATION TO INFRINGE ANY EXISTING PATENT OR TO VIOLATE ANY FEDERAL, STATE OR LOCAL LAW.

Occidental Chemical Corporation 2000

NaOHNaOH

Caustic SodaHandbook

OxyChemfifiOxyChem is a registered trademark of Occidental Chemical Corporation.

ForewordThis handbook outlines the methods for handling,

storing, preparing and using caustic soda. Itincludes information on the manufacture, physicalproperties and analytical methods for testing caus-tic soda.

Additional information and contacts can be foundat www.oxychem.com

Occidental Chemical CorporationBasic Chemicals GroupOccidental Tower5005 LBJ FreewayDallas, TX 75244

Principal Uses andConsumption ofCaustic Soda

Introduction2 of 52

Caustic soda is most commonlymanufactured by the electrolysis ofsodium chloride brine in either amercury amalgam, membrane ordiaphragm electrolytic cell. The co-products are chlorine and hydro-gen.

The largest users of caustic sodaare the pulp and paper, detergentand chemical industries. Causticsoda is also used in the alumina,oil and gas and textile industries,mostly for its alkalinity value.

OxyChem has played a leadingrole in providing caustic soda tomeet the increasing demands ofindustry. OxyChem plants arestrategically located to convenientlyand economically serve industry.Warehouse stocks of our caustic

soda and other products are main-tained in many principal cities.Distributor stocks are also availablein these and many other cities andform a network of supply for theend users convenience.

Caustic soda is one of the veryfew chemicals finding a very broadrange of applications. Some princi-pal products or processes in whichcaustic soda is used are:

Acid Neutralization Agricultural Chemicals Aluminum Industry Boiler Compounds Cellulose Film Chemicals:

AmmoniaAmyl AminesCresolEthylene AminesFormic AcidGlycerine

Maleic AnhydridePentaerythritolPhenolPropylene OxidePolycarbonatesSalicylic AcidSodium AluminateSodium HydrosulfideSodium HypochloriteSodium PhosphatesStyreneVinyl Chloride Monomer

Detergents Drain Cleaners Drilling Muds Dyestuffs Food Processing Fruit & Vegetable Peeling

Glass-Batch Wetting Ion-Exchange Resin

Regeneration Ore Flotation and Processing Paint Removers Petroleum Refining pH Adjustment Pharmaceuticals Pigments Pulp & Paper Rayon Soap Surfactants Textile Bleaching, Dyeing, and

Mercerizing Vegetable Oil Processing Water Treatment

Forms ofCaustic Soda 3 of 52

Liquid caustic soda is availableas a 50% solution in four grades;diaphragm, rayon, membrane andpurified diaphragm. To be techni-cally correct, only molten causticsoda should be called liquid, butsince the term liquid caustic sodahas historically been used todescribe solutions of caustic soda,it is used in this document inter-changeably with the term solution.

Anhydrous caustic soda is mar-keted in four forms; beads, flakes,compounders and solid castings.These forms have the same chemi-cal composition and differ only inparticle size and shape.

OxyChem packages the anhy-drous forms of caustic soda in:

Solid: 735-lb. drums

Flake: 500-lb. drums100-lb. drums50-lb. bags 1,600-lb. mini bulk bags

Compounders:450-lb. drums

Beads: 500-lb. drums50-lb. bags 2,000-lb. mini bulk bagsBulk trucks and rail cars

Caustic Soda Beads Caustic Soda Compounders

Caustic Soda #4 Flake Caustic Soda #2 Flake

4 of 52

NaCl + H2O = Brine

Brine Treatment

Diaphragm Cell Membrane CellMercury Cell

Decomposers Cell Liquor 12% Caustic Soda 30% Liquid Caustic Soda

Filters

Evaporators Evaporators

Filters

50% LiquidCaustic Soda



ConcentratorConcentrator

DowthermDehydrator

DowthermDehydrator

Flaker Flaker Prilling Tower

Electricity

Chlorine

Water

Hydrogen

Electricity

Hydrogen

Chlorine

Rayon Flake Diaphragm Flakeand Compounders

Diaphragm Beads

RayonCaustic

Soda

Purification PurifiiedCaustic

Soda

MembraneCaustic

Soda

DiaphragmCaustic

Soda

Caustic soda is produced com-mercially by an electrolytic processas shown in the flow diagrambelow. Brine, prepared from sodi-um chloride, is electrolyzed ineither a mercury cell, diaphragmcell or membrane cell. The co-products are chlorine and hydro-gen.

In the mercury cell process, asodium-mercury amalgam isformed in the cell. The amalgam issent to a decomposer where it isreacted with water to form liquidNaOH, hydrogen and free mercury. The free mercury is returned to theelectrolytic cell. The resulting caus-tic soda solution is then inventoriedin storage tanks at a 50% solution.The solution is shipped in tanktrucks, tank cars or barges.

In the membrane process, asolution of approximately 30% instrength is formed. The solution isthen sent to evaporators, whichconcentrate it to a strength of 50%by removing the appropriateamount of water. The resultingcaustic soda solution is inventoriedin storage tanks prior to shipment.

The diaphragm process is verysimilar to the membrane processexcept that a solution of only 10-12% is formed in the cell.Therefore, additional evaporation isrequired to reach the saleable con-centration of 50%.

The anhydrous forms of causticsoda are obtained through furtherconcentration of 50% caustic soda.Solid caustic soda results whenmolten caustic soda, from which allthe water has been evaporated, isallowed to cool and solidify. Flakecaustic soda is made by passingmolten caustic soda over cooledflaking rolls to form flakes of uni-form thickness. The flakes can bemilled and screened into severalcrystalline products with controlledparticle size. The manufacture ofcaustic soda beads involves feed-ing molten liquor into a prillingtower under carefully controlledoperating conditions, producing aspherical bead.

ManufacturingProcess

Diagram 1: Production Flowchart

5 of 52Methods of ShippingLiquid Caustic Soda

Liquid caustic soda is availablefrom OxyChems many plants andterminals in tank truck, tank car,barge and ship quantities. Eachform of transportation has its ownadvantages. The type of serviceselected will depend upon suchfactors as size and location ofstorage, rate of consumption,plant location, freight rates, etc.OxyChems Technical Service Staffis well qualified to survey anyfacility and recommend the mosteconomical form of transportationwhich is best suited for a particularrequirement.Caustic soda, liquid and dry, is reg-ulated by the U.S. Department ofTransportation (DOT) and is classi-fied as a corrosive material.

The DOT identification number is UN I824 for liquid, andUN I823 for anhydrous product.

6 of 52Safety in HandlingCaustic Soda

Caustic soda in any form mustbe respected by everyone whohandles and uses it. Beforestarting to work with it, the usershould be aware of its proper-ties, know what safety precau-tions to follow, and know how toreact in case of contact.Accidental exposure to causticsoda may occur under severalconditions. Potentially haz-ardous situations include han-dling and packaging operations,equipment cleaning and repair,decontamination following spillsand equipment failures.Employees who may be subjectto such exposure must be pro-vided with proper personal pro-tective equipment and trained inits use. Some general guidelinesfollow. Read and understand the latest

Material Safety Data Sheet. Provide eyewash fountains and

safety showers in all areas wherecaustic soda is used or handled.Any caustic soda burn may beserious. DO NOT use any kind ofneutralizing solution, particularlyin the eyes, without direction by aphysician.

Move the patient to a hospitalemergency room immediatelyafter first aid measures areapplied.

FIRST AID MEASURESFor Eyes: If for any reason

caustic soda contacts the eyes,flood the eyes immediately withplenty of clean water. Continueflushing for at least 15 minutes.While flushing, forcibly hold theeyelids apart to ensure rinsing ofthe entire eye surface. Do not useany kind of neutralizing solutionin the eyes.GET MEDICAL ATTENTIONIMMEDIATELY.

For skin: If caustic soda comesin contact with skin or clothing,flush with plenty of clean water forat least 15 minutes. Remove conta-minated clothing and footwear.Thoroughly wash affected clothingand rubber/vinyl footwear. Discardcontaminated leather footwear.GET MEDICAL ATTENTIONIMMEDIATELY.

For inhalation: If a worker isovercome due to the inhalation ofcaustic soda dust, mist or spray,remove them from the contaminat-ed area to fresh air. If breathing isdifficult, have a trained personadminister oxygen. If breathing hasstopped, have a trained personadminister artificial respiration. GET MEDICAL ATTENTIONIMMEDIATELY.

For ingestion: Although it is unlikely in an industrial situation that caustic soda wouldbe ingested, it could be swallowedaccidentally. If that occurs, DONOT induce vomiting. Give largequantities of water. If available,give several glasses of milk. Ifvomiting occurs spontaneously,position individuals head to keepairway clear. NEVER give anythingby mouth to an unconscious person. GET MEDICAL ATTEN-TION IMMEDIATELY.

PROTECTIVE EQUIPMENTOSHA requires employers to

supply suitable protective equip-ment for employees. When han-dling caustic soda, the followingprotective equipment is recom-mended: Wear suitable chemical splash

goggles for eye protection dur-ing the handling of causticsoda in any form. The gogglesshould be close-fitting and pro-vide adequate ventilation to pre-vent fogging, without allowingentry of liquids.

The use of a face shield may beappropriate when splashing canoccur, including loading andunloading operations.

Wear rubber gloves or glovescoated with rubber, syntheticelastomers, PVC, or other plas-tics to protect the hands whilehandling caustic soda. Glovesshould be long enough to comewell above the wrist. Sleevesshould be positioned over theglove wrists.

Caustic soda causes leather todisintegrate quite rapidly. For thisreason, wear rubber boots. Wearthe bottoms of trouser legs out-side the boots. DO NOT tuck in.

Wear chemical resistant clothingfor protection of the body.Impregnated vinyl or rubber suitsare recommended.

Wear hard hats for some protec-tion of the head, face and neck.

If exposures are expected toexceed accepted regulatory limitsor if respiratory discomfort isexperienced use a NIOSHapproved air purifying respiratorwith high efficiency dust and mistfilters.

FACESHIELD

CHEMICALSUIT

RUBBERBOOTS

CHEMICALSPLASH

GOGGLES

RUBBERGLOVES

7 of 52Safety in HandlingCaustic Soda

PROTECTIVE PRACTICES Avoid breathing dust, mist or

spray of caustic soda. Wear proper protective equip-

ment. If warranted, wearapproved respiratory protection.

Keep equipment clean by wash-ing off any accumulation of caus-tic soda.

Weld pipelines where practical.Use flanged joints with gasketsmade of caustic soda resistantmaterial such as rubber, PTFE,or EPDM rubber. If a screwed fit-ting is used, apply Teflon tape tothe threads.

When disconnecting equipmentfor repairs, first verify that thereis no internal pressure on theequipment and that the equip-ment has been drained andwashed.

Provide storage tanks with suit-able overflow pipes. Overflowpipes should be directed near thebottom of the diked area.

Shield the packing glands ofpumps to prevent spraying ofcaustic solutions in the event of aleak.

When releasing air pressure froma pressurized system, take everyprecaution to avoid spurts orsprays of caustic solution.

When making solutions, alwaysadd the caustic soda slowly tothe surface of the water with con-stant agitation. Never add thewater to the caustic soda.Always start with lukewarm water(80 -100F). Never start with hotor cold water. Dangerous boilingor splattering can occur if causticsoda is added too rapidly,allowed to concentrate in onearea or added to hot or cold liq-uids. Care must be taken toavoid these situations.

Exercise extreme care whenbreaking solid caustic soda intosmaller pieces.

In case of a spill or leak, stop theleak as soon as possible. Aftercontainment, collect the spilledmaterial and transfer to a chemi-cal waste area. Remove large liq-uid spills by vacuum truck.Neutralize residue with diluteacid. Flush spill area with waterand follow with a liberal coveringof sodium bicarbonate or otheracceptable drying agent.

HANDLING ANHYDROUSCAUSTIC SODA

Extreme care must be takenwhen adding anhydrous causticsoda to water or any solution. Itshigh heat of solution generateslarge amounts of heat which cancause local boiling or spurting.

When making solutions withanhydrous caustic soda, alwaysadd the caustic soda slowly to thewater surface with constant stirring.Never add the water to the caus-tic soda. Always start with luke-warm water (80 -100F). Neverstart with hot or cold water.Dangerous boiling and/or splatter-ing can occur if caustic soda isadded too rapidly, is not sufficientlyagitated or added to hot or cold liq-uids. Care must be taken to avoidthese situations.

Anhydrous caustic soda will dis-solve freely in a well agitated solu-tion under proper conditions.Without agitation, the anhydrouscaustic soda will fall to the bottomand form a layer of hydrate whichdissolves quite slowly and can lead

to localized boiling and splattering.To operate safely, slowly add the

anhydrous caustic soda to the sur-face of a well-agitated solution. Thepreferred equipment utilizes a pro-peller-type agitator or a circulatingpump with sufficient mixing capaci-ty. Avoid agitation with air, becauseair will cause excessive formationof sodium carbonate.

HANDLING LIQUIDCAUSTIC SODA

In handling caustic soda solu-tions, care must be taken to avoidsolidification which will plugpipelines and equipment. Graph 1(pg. 29) shows the freezing pointsfor solutions of caustic soda at vari-ous concentrations.

Should a caustic soda solutionbecome frozen in process equip-ment or piping, care must be takenwhen thawing the material. Useonly low pressure (10 PSIG orless) steam. Accelerated corrosioncan occur in areas where equip-ment is subjected to extremely hightemperatures.

Unloading and Handling LiquidCaustic Soda in Tank Cars8 of 52

GENERAL INFORMATIONCaustic soda in liquid form

has a markedly corrosive actionon all body tissue. Even dilutesolutions may have a destructiveeffect on tissue after prolongedcontact. Inhalation of concentrat-ed mists can cause damage tothe upper respiratory tract, whileingestion of liquid caustic sodacan cause severe damage to themucous membranes or other tis-sues where contact is made. Inaddition, considerable heat isgenerated when liquid causticsoda is mixed with water whichcan result in boiling or splatter-ing. When diluting, always addcaustic soda to water; never addwater to caustic soda.

It is important that those whohandle caustic soda are aware ofits highly reactive and corrosiveproperties and know what pre-cautions to take. In case of acci-dental exposure, immediatelyflush exposed area with largeamounts of water and seek med-ical attention. For more specificinformation refer to the Safety inHandling Caustic Soda sectionof this handbook and to theMSDS.

PLACEMENT OF THE CAR FORUNLOADING1. After the car is properly spot-

ted, DOT regulations requirethat the hand brake be set andthe wheels blocked before anyconnections are made.

2. Caution signs must be placedat both ends of the car beingunloaded to warn people andswitching crews approachingthe car. DOT regulations statethat caution signs must beplaced on the track or car togive warning to personsapproaching the car from theopen end or ends of siding.Caution signs must be left upuntil the car is unloaded anddisconnected from the dis-charge connections. Signsmust be made of metal or othersuitable material, at least 12x15inches in size, and bear thewords, STOP-TANK CARCONNECTED, or STOP-MENAT WORK.

3. It is recommended that derailattachments be placed at theopen end or ends of siding,approximately one car lengthaway.

4. Before hooking up a car, theresponsible individual shouldfirst locate and test the nearesteyewash and safety shower.Purge water through each toremove rust that may haveaccumulated.

UNLOADING PRECAUTIONS1. Only responsible and well

supervised employees shouldbe entrusted with the unloadingof liquid caustic soda.Unloading operations must bemonitored while the car is con-nected.

2. Since serious burns can resultfrom contact of caustic sodawith the skin and eyes, workersshould be well protected andcautioned to exercise care.Persons hooking up a carshould wear the following per-sonal protective equipment: Hard hat Chemical splash goggles Face shield Rubber, steel-toed boots Rubber gloves or

equivalent Vinyl or rubber jacket and

pants If warranted, wear approvedrespiratory protection

3. A car of caustic soda should beunloaded only when adequatelighting is available throughoutthe entire unloading process.

4. Before starting to unload, makecertain that the tank car is vent-ed and that the storage tank isvented and has sufficientcapacity.

5. No one should enter the carunder any circumstances.

6. If a tank car needs to be movedwhen partially unloaded, DOTregulations require that allunloading lines must be discon-nected and car closures mustbe replaced.

7. A suggested method for sam-pling is to draw intermittentsamples from a 1/2 sampleline, connected to a verticalsection of the unloading line.

Unloading and Handling LiquidCaustic Soda in Tank Cars 9 of 52

The sample line should be fit-ted with a valve and a 1/4 nip-ple.

8. OxyChems liquid caustic sodais shipped in well insulated andspecially lined tank cars.Linings in these tank cars willwithstand temperatures up to225F. To prevent damage tothe linings, neither water norsteam should be added directlyinto the tank cars if the car con-tains a level of caustic.

9. Unloading lines should be cov-ered with suitable insulationand heated just prior to transferof liquid caustic soda to stor-age. The preferred method ofheating is to provide electric orsteam heat tracing around theunloading line, under the insu-lation. An alternate method isto provide tees in the unloadingline so that steam (or hotwater) can be run through theunloading line just prior to itsuse. These precautions willprevent the solidification of liq-uid caustic soda in cold unload-ing lines. Running steamthrough unloading lines willincrease corrosion in unlinedsteel piping systems and ironpickup in the product.

10. If compressed air is used inunloading operations, it isimportant that all fittings beinspected for leaks or otherdefects before unloading.Dome fittings in particularshould be inspected. If leaksare found, unloading operationsshould be suspended until theyare corrected.

HANDLING IN COLD WEATHERSince OxyChem tank cars

are well insulated and liquid causticsoda is loaded hot, it usuallyarrives at its destination in a liquidcondition. However, since 50% liq-uid caustic soda begins to crystal-lize at 54F, in cases of unusualdelays in transit, freezing may takeplace in cold weather. If freezinghas occurred, the following proce-dure should be used.1. Carefully open tank car dome

cover.2. If a layer of caustic soda has

formed over the contents of thecar, this crust should be brokenbefore admitting steam to thejacket around the bottom dis-charge valve. The puncturing ofthe crust permits expansion ofthe liquid as it increases in tem-perature.

3. If no crust is present, determineif crystals have formed on thebottom of the car by probing thebottom with a rubber-cappedrod introduced through thedome opening.

4. If freezing has occurred, con-nect a steam line (10 PSIG orless) to the jacket around thebottom discharge valve.Connect a condensate returnline at the valve jacket steamoutlet. If a condensate returnline is not used, it is advisableto connect a valve at the steamoutlet, which should be openedsufficiently to relieve conden-sate and direct it toward theground or into a sewer. As con-

tents liquefy, the valve may beclosed further to conservesteam.

5. If necessary, steam can be con-nected to the rail car steamcoils. A condensate return line,pressure reducing valve, and/orsteam trap should be used. Donot exceed a steam pressure of10 PSIG.

6. When examination indicatesthat the contents have liquefiedand operation of the valve rodshows that the bottom dis-charge valve is free, the causticsoda is ready for unloading.The unloading temperature of50% caustic soda should beless than 120oF to minimizecorrosion of unlined steelpiping systems and equip-ment.

7. If the above measures do notliquefy the contents on the car,contact your OxyChem repre-sentative.

Placard

Handbrake

Electrical Ground

Warning Signs

2. Manway

19. 4" Insulation

20. 1/8" Steel Shell

7/16" Steel Tank

3. Safety Vent

Bottom Unloading Assembly

10. Steam Coil Inlet & Outlet

18. Outlet Valve Operating Rod

7. 1" Air Connection Valve

5. 2" Unloading Connection

11. Bottom Outlet Valve

12. Steam Chamber

13. Steam Inlet16. Steam Outlet

21. Plug Cock

14. Supplementary Valve

15. Plug in Bottom Outlet

Top Unloading Assembly

6. Protective Housing Cover

8. 2" Eduction Pipe

8. 2" Induction Pipe17. Heating Coils

9. Pipe Guide

19. 4" Insulation 20. 1/8" Steel Shell

7/16" Steel Tank

18. Outlet Valve Operating Rod

Eduction Pipe Assembly

Stuffing Box

1. Stuffing Box Cover

Safety Chain & Toggle

4. Manway Cover Safety Guard

Rail Car DrawingDetails of Caustic Soda Car(DOT 111A100W1)10 of 52

Figure 1

Unloading Liquid Caustic Soda in Tank Cars 11 of 52

Rail cars can be either bottomunloaded (gravity, pump or pressure)or top unloaded (with air pressure).Refer to appropriate unloading proce-dure based on the method to beemployed.

UNLOADING THROUGHBOTTOM DISCHARGE VALVE1. Open the dome cover and deter-

mine if the contents of the carare liquid. If not, see Handlingin Cold Weather. Keep thedome cover at least partiallyopen during the entire unloadingoperation to vent the tank car.

2. Refer to Figure 1. Insure that thebottom outlet valve is closedtightly. The valve rod which oper-ates the bottom discharge valvehas a handle on it which is locat-ed outside the dome of the car.The handle can be reversed andserves as a cap in transit.

3. Remove the pipe plug, then care-fully open the supplementaryvalve to drain any liquid that mayhave seeped past the bottomoutlet valve during transit. If thesupplementary valve cannot beopened, the application of steamfrom a steam lance, directed on

the valve, should free it for open-ing.

4. Attach the unloading line to thebottom of the supplementaryvalve.

5. Check the unloading line to seethat all valves are in the properposition for unloading.

6. Open the bottom outlet valve byturning the valve rod to allowcontents to flow by gravity topump or tank. If the bottom outletvalve does not open upon appli-cation of light pressure, frozencaustic soda is probably presentin the bottom of the car.Application of steam to the heatcoils may be necessary. SeeHandling in Cold Weather.

7. Compressed air can be used toincrease the flow rate of causticsoda to storage or to transfer liq-uid without the use of a pump. Ifcompressed air is to be used,check the rupture disk in thedome to be sure it is intact.Close the dome cover securely.Remove the one-inch air inletplug and connect a flexible airline at this point. The air lineshould have a release valve, oiltrap, pressure relief valve set at

20 PSIG, pressure reducingvalve set at 18 PSIG and a shut-off valve. Apply air pressure tothe car slowly. Note that thepressure relief device (rupturedisk and/or pressure relief valve)in the dome will relieve at a pres-sure between 75 PSIG and 165PSIG, depending on the type ofcar. Refer to the stenciling on theside of the railcar.

8. When the car and unloading lineare empty, shut off air supply andopen the release valve.

9. When the tank car is empty andthe discharge pipe has complete-ly drained, disconnect the airline, if used, close the bottomoutlet valve and supplementaryvalve, and detach the unloadingline at the car.

10. Prepare the car for return.

Steam jacket

UnionPump

2 Steel pipe

Pump inlet valve

Low line drain valveRail carunloading valve

Vent

Tank inlet valve

To process

Drain

TANK CAR

STORAGE TANK

Steam coils

Figure 2: Bottom Unloading

Unloading Liquid Caustic Soda in Tank Cars12 of 52

UNLOADING THROUGHDOME WITH AIR PRESSURE

1. Open the dome cover to deter-mine if the contents of the carare liquid. If not, see Handling inCold Weather.

2. Close the dome cover and fastensecurely, making certain that it isair tight. Check that the rupturedisk in the dome is intact.

3. Check that the product storagetank is vented and has sufficientcapacity.

4. After opening the protectivehousing cover, connect theunloading line to the two-inch topunloading valve. After removingthe protective housing cover, aflexible steel hose connection forthe unloading line is recommend-ed since a car may rise as muchas 2 during unloading.

5. Connect the flexible air supplyline to the one-inch air inletvalve. This line should have arelease valve, oil trap, pressurerelief valve set at 20 PSIG, pres-sure reducing valve set at 18PSIG and a shut-off valve. Notethat the relief device (rupture disk

or pressure relief valve) in thedome will relieve at a pressurebetween 75 and 165 PSIG,depending on the type of car.Refer to the stenciling on theside of the railcar.

6. Apply air pressure slowly untilthere is a normal flow of liquid tothe storage tank. The pressureshould be adjusted and main-tained until the tank car is com-pletely empty. A drop in air pres-sure or the sound of air rushingthrough the unloading line indi-cates that the tank car is empty.

7. Shut off the air supply, open therelease valve, and allow theeduction pipe to drain.

8. When the eduction pipe hasdrained and the tank car is atatmospheric pressure, discon-nect the air supply line at the car.

9. Do not enter the car to make aninspection.

10. Open the dome cover and deter-mine if the car is empty. If empty,disconnect the unloading line atthe car, replace pipe plugs andtightly replace the dome coverand the protective housing cover.

11. Care should be taken not to spill

caustic soda on the car, since itwill cause damage to the car andmay endanger workers handlingthe empty car on its return.

12. Prepare the car for return.

PREPARING EMPTY TANKCARS FOR RETURN1. Make sure the bottom outlet

valve and supplementary valveare closed.

2. Disconnect the unloading lineand replace the bottom outletplug. Do not replace closures onsteam openings.

3. Close dome cover and fastensecurely.

4. Return the empty tank carpromptly in accordance with theshippers instructions. The ship-pers routing directions must befollowed in all instances.

!""

""

##

#""$%#

&'((""

)

)

$

(""*#

Figure 3: Top Unloading

Unloading Liquid Caustic Soda in Tank Trucks 13 of 52

CARRIER RESPONSIBILITIESOxyChem tank truck drivers have

received instructions regardingequipment and delivery proce-dures. If an OxyChem arrangedcarrier, delivering caustic soda toyour plant, fails to adhere to the fol-lowing guidelines, please contactOxyChem so that corrective actioncan be taken.

EquipmentEquipment must meet

Department of Transportation regu-lations, Code of FederalRegulations (CFR), Title 49.

Tank Truck SpecificationTank trucks should meet the

established DOT requirements forhauling liquid caustic soda.

Four DOT CORROSIVE plac-ards must be permanently affixedto the cargo tank.

Unloading EquipmentIf unloading is by gravity to stor-

age or customers unloading pump,no special equipment is needed.

If unloading is by truck-mountedpump, use only an all iron or nickelunit. The pump can be driven by atractor powered take-off or an aux-iliary gasoline engine. Use at leasta 2-inch pump line.

If unloading is by compressedair, the tank vessel must meet theDOT requirements of the CFR, Title49. The line used to supply air tothe tank truck is required to beequipped with: pressure reducingvalve, pressure release valve,pressure gauge, pressure reducingvalve and pressure relief valve.The relief valve should be set at amaximum pressure of 20 PSIG andthe pressure reducing valve shouldbe set at 2 to 3 pounds lower.Whether this equipment is attached permanently to the tank or carriedas an assembled unit to beattached at each unloading, itshould be properly maintained andperiodically tested.

A 40 foot length of air hose isrequired if the customers air sup-ply is used. When compressed airis not available from the customersplant, trucks equipped with pumpsor air compressors can be providedat the customers request.

Unloading LinesUnloading hoses must be con-

structed of material resistant tocaustic soda. Hoses should be atleast 2 inches in diameter and 15to 30 feet in length.

Whether the unloading hose isfitted with a union, pipe flange, or aquick type coupler, the truck drivershould have available matching fit-tings and tools to facilitate a con-nection to a 2-inch or 3-inchthreaded pipe.

TRUCK DRIVER RESPONSIBILITIES

Truck drivers must obtain permis-sion to unload from the properauthorities and observe any specialinstructions from the customer.

Truck drivers must wear the pro-tective equipment required byOxyChem as listed underProtective Equipment, (pg. 6) or bycustomer, whichever is more inclu-sive, and at all times follow safehandling practices. Customersmust not allow truck drivers who donot meet these requirements tounload.

The following unloadingprocedures are recommended: Check the operation of the safety

shower and eyewash fountain.Purge water through each toremove rust that may have accu-mulated.

If a shower and eyewash are notavailable, a water hose connect-ed to a source of water isrequired. If the valve on the lineis not conveniently located nearthe unloading area, leave astream of water flowing duringunloading.

Connect one end of the unload-ing hose to the customers stor-age tank fill line.

During cold weather and if facili-ties are provided, preheat withsteam the fill line, the unloadinghose, and, if needed, the truckoutlet.

Check the unloading line to besure that it is open.

Connect the unloading hose tothe discharge outlet on the tanktruck.

Start the pump or start pressuriz-ing the tank, depending on thetype of equipment used.

Open the valves on the truckdischarge line.

Stand by until the truck cargo iscompletely unloaded.

If compressed air is used,allowthe air to flush out the lines to thestorage tank and then cut off theair supply.

When a pump is used, flush outthe unloading line before discon-necting the hose. If water isavailable, a small quantity canbe added into the truck while thepump is running to flush out theline. Air or water can be used toflush the caustic soda in the lineinto the storage tank or back tothe truck. If no water is availablefor flushing out lines, exercisegreat caution when lines are dis-connected.

Unloading Liquid Caustic Soda in Tank Trucks14 of 52

Close the valve on the storagefill line.

Close all valves on the tanktruck.

In some installations the cus-tomers fill line is fitted with adrain to be used instead of flush-ing the line before the hose isdisconnected.

Disconnect the hose with cautionand discharge any caustic sodaremaining in the hose to a suit-able container.

Unload caustic soda in an areawith adequate safeguards forspill control. No caustic sodashould be spilled, but in theevent a small amount is spilled,hose down the area with water.Clean up all spills and dispose inaccordance with federal, stateand local regulations.

FACILITY EQUIPMENTTypical installations of storage

vessels for receipt of truck ship-ments are similar to those shown inFigures 2 and 3 for rail car deliver-ies.

A storage tank with a minimumcapacity of 1.5 tank cars is recom-mended.

A fill line to the top of the storageis strongly recommended. If a bot-tom fill line is used, the truck drivermust be informed.

A permanent fill line in closeproximity to the tank truck unload-ing area is required.

A 2-inch or larger fill line is rec-ommended.

A 3/4-inch valve connection isrecommended on the fill line foruse in flushing out the line with air,water, or steam. It can be used asa drain.

Cap or close the end of the fillline when not in use.

A source of running water for useduring unloading operations isrequired. A safety shower and eye-wash fountain are recommended.

15 of 52Anhydrous Caustic Soda Dry Bulk Systems

Caustic soda beads have anangle of repose of 30 degrees ascompared to 40 degrees for crys-talline grades of caustic soda. Thismeasure of flowability means fasterunloading times for bulk handlingand easier transfer from storage toprocessing or mixing. In addition,beads dissolve faster than othergrades due to increased surfacearea.

OxyChem has long recognizedthe need for a system to conveyand store large quantities of bulkanhydrous caustic soda. Havingpioneered this concept in 1966 withthe introduction of the source-to-silo system, OxyChem has contin-ually strived to improve bulk han-dling of anhydrous caustic soda.OxyChem utilizes pressure differ-ential self-unloading trucks with aself-contained desiccating system.These trucks eliminate the need forthe customer to install dry aircapacity as is needed for unloadingcars. It also assures that the cus-tomer receives dry, free flowingcaustic soda.

To further satisfy the needs ofour customers, OxyChem manufac-tures caustic soda beads. The par-ticle size of caustic beads matchthose of most granular grades ofsoda ash, silicates and phos-phates. This leads to a more uni-form compound mixture with lesssegregation of the components.Typically, over 80% of the particlesare concentrated between the U.S.No. 20 and U.S. No. 40 screens.The uniform spherical nature of thebead also insures consistent andsuperior flow ability in handling,and storage of the final product.

16 of 52Shipments, Handling and Storage ofCaustic Soda Beads

Caustic soda beads are manufactured at the OxyChemPlant near Houston, Texas. The fin-ished product is stored in desiccat-ed storage bins from which bothrail cars and trucks are loaded forshipment. Caustic soda beads areshipped to customers or terminalsin 100-ton, 15 PSIG, pressure-dif-ferential (P-D), center-flow cars; or20-ton, P-D, self-desiccating trucks.

When a bulk shipment arrives ata customer plant by either car ortruck, the beads are transferredwith dry air by either a blower or aircompressor (depending on the sys-tem installed) through a flexiblehose and a dry receiving line into apre-dried storage bin. The storagebin and receiving lines must bemoisture free and well sealed toprevent agglomeration and stickingof the beads. Dry air (-40F DewPoint) must be used during theentire unloading process. Dewpoints should be checked hourlyduring railcar unloading.

TRUCKSTo receive bulk truck shipments

of caustic soda beads, only a verysimple unloading system isrequired (See Figure 4). Since thetruck is equipped with its own blow-er and desiccator, these need notbe supplied by the customer. Also,since truck unloadings use anopen-loop system (air is exhaustedthrough the filter, not returned tothe compressor), an elaborate dustfilter and return system are notneeded. Basically, all that isrequired is a 4-inch unloading pipe,a storage bin, a simple dust filterand a vent air dryer.

Upon arrival of the truck, thetruck driver makes all the neces-sary hose connections. After this isdone, the air system of the truck isturned on and all of the piping, thestorage bin and the dust filter arepurged with dry air for 3-5 minutes.

Once the system is completelypurged, the unloading is started. Abulk truck unloading takes about 90to 120 minutes. Once completed,the lines are again purged with dryair to make sure no caustic soda isremaining.

RAIL CARSThe differences between unload-

ing from a rail car versus unloadingfrom a truck are: (1) the rail carsare not equipped with a blower,hoses or an air dryer; these mustbe supplied by the customer aspart of their storage system, and(2) because the blower, hoses andair dryer are supplied by the cus-tomer, either a closed-loop oropen-loop system may be used.

Open LoopThe open-loop system used to

unload rail cars is almost identicalin design to the system used tounload bulk trucks (See Fig. 4).After connecting the car to theunloading system, the lines are firstpurged for 3-5 minutes to removeany trace amounts of moisture.After purging the lines, the air isdiverted to the car and the hopperis pressurized. Once the car ispressurized, the unloading can pro-ceed. The unloading time for a railcar varies depending on the type ofcar and the configuration of thereceiving system, but generallyspeaking, 4-8 hours is an averagerange.

Closed-Loop SystemAs the name implies, a closed-

loop system is based on the recircu-lation of dry air. After passingthrough the dust filter, the air isreturned to the compressor. Themajor advantage of a closed-loopversus an open-loop is that once theair has been dried (and assuming noloss due to leaks) the systemrequires very little additional air dry-ing capacity. Otherwise, the proce-dure for unloading a rail car is thesame as an open-loop system.

EQUIPMENTA bulk handling system for caustic

soda beads can be adapted to thesimplest or most sophisticated sys-tem. The OxyChem TechnicalService Department is available tosurvey your complete plant site andto assist you in choosing the bestsystem to fit your individual needs.They will consult and plan with youand even check the installation.

Although the design of individualhandling systems may vary greatly,the following is a general guidelinefor choosing storage and handlingequipment.

17 of 52Shipments, Handling and Storage ofCaustic Soda Beads

1. Storage CapacityThe storage bin or silo capacityshould be a minimum of 1.5 timesthe volume of the bulk vehicle.For truck shipments, the minimumbin size is 1,000 cubic feet. Forrail cars, a minimum of 4,500cubic feet is required. The binshould be fabricated from carbonsteel and should be of weldedconstruction to minimize potentialair leaks. It should have a conebottom with a slope of 55-60degrees. The type of valvearrangement on the bottomdepends on the in-plant transfersystem. In general, a quick-seal-ing valve, such as a knife-gate, orbutterfly, should be used so thatthe bin can be sealed off from therest of the system.

2. Air BlowersFor unloading rail cars, the blowershould be able to develop 10-12PSIG while drawing 600-700 cfmat the inlet. Positive displacementblowers are preferred.

3. Air DryerAir dryers can be fairly simple indesign (a tank containing desic-cant) or very sophisticated (twin-tower automatic system). Thebasic requirements, however, donot change. The dryer must becapable of producing dry air at a-40F dew point temperature at680 cfm and 10 PSIG. It shouldbe able to operate effectively overa wide range of inlet tempera-tures, and should have a mini-mum operating time of 10 hours.

4. Vent DryerA vent dryer is required on allstorage bins. The purpose of thevent dryer is to maintain dry airabove the product while the con-tents of the bin are being dis-charged to the process. In thecase of a closed-looped system,the unloading air dryers can beused as vent dryers. For an open-loop system, a small air dryer isneeded. The type of dryer canvary, but it should be capable ofproducing -40F dewpoint air.

Desiccant Bed

Slip-StreamAir

Butterfly Valves

Loading LineOutletVent to

Bag House

Air Filter

Air Blower

Air Cooler

Air Drier

Quick-ConnectCouplings

Vent Drier

DustCollector

UnloadingLIne

Support Beams

PressureRelief Vent

Air Recycle Line

Hopper(Optional)

HopperScale

(Optional)

To Process To Process

DiverterValves

Flexible BeadUnloading Hose

Fan/BeadDisperser

NaOH Bead Silo

RotaryValve

KnifeGate

Low-LevelIndicator

RotaryValve

KnifeGate

Figure 4: Typical Truck Unloading System for Caustic Soda Beads

Shipments, Handling and Storage ofCaustic Soda Beads18 of 52

5. Dust FilterWhile Caustic soda beads aredustless, some dust will be creat-ed during transport and unloadingdue to abrasion of the particlesagainst the pipe. Whether thesystem is open or closed loop, adust filter is required. It should becapable of removing virtually all ofthe dust from the air stream, but itshould only provide a nominalresistance to flow. If the pressuredrop across the dust filter is toogreat, the back-pressure createdwill slow or potentially stop theunloading. Call OxyChemsTechnical Service for assistancein choosing the right kind of filter.

6. PipingThe transfer piping should be 4-inch steel pipe. The number ofbends should be as few as possi-ble. When necessary, they shouldbe minimum 4-foot radius bendsthat will not restrict the flow ofproduct. In addition, long horizon-tal runs should be avoided, asproduct will tend to drop out of theair stream and lay on the bottomon the pipe. This causes addition-al back pressure.

HANDLING CAUSTIC SODAThe final customer seldom usescaustic soda in the anhydrous form.For utilization in most processes, asolution must be prepared by dis-solving anhydrous caustic in water.For that reason, some knowledge ofthe properties and characteristics ofcaustic soda solutions is essential.The customer usually requires a def-inite weight of caustic soda in agiven solution. To assist in meetingsuch situations, the charts andtables contained in this handbook listpounds of actual caustic soda pergallon of solution. For easy refer-ence, the concentrations of causticsolutions are expressed in several ofthe most common ways in Tables 1and 2. (pgs. 23, 24)

Placard

Hatch Covers

Caustic SodaBeads

Air Filter

Air Blower

Air Cooler

Air Drier

Quick-ConnectCouplings

Flexible Air Inlet Hose

Vent Drier

DustCollector

UnloadingLIne

Support Beams

PressureRelief Vent

Air Recycle Line

Hopper(Optional)

HopperScale

(Optional)

To Process To Process

DiverterValves

Flexible BeadUnloading Hose

Fan/BeadDisperser

NaOH Bead Silo

RotaryValve

KnifeGate

Low-LevelIndicator

RotaryValve

KnifeGate

Slip Stream Air Inlet

Figure 5: Typical Rail Car Unloading System for Caustic Soda Beads

Dissolving AnhydrousCaustic Soda 19 of 52

Considerable heat is generatedwhen solid caustic soda is dis-solved in water. Graph 6 shows thetemperature that results when theindicated solutions are preparedwithout benefit of cooling. In manycases it is necessary to cool solu-tions during the dissolving processin order to avoid excessive temper-atures that can exceed material ofconstruction limitations.

In handling caustic solutions,care must be exercised to avoidsolidification which will plugpipelines and equipment. For thatreason, it is desirable to know atwhat temperature a solution ofknown concentration will freeze.Graph 1 shows that caustic sodasolutions exhibit peculiar freezingcharacteristics, as indicated by thepeaks and valleys of the freezingpoint curve. In addition to this infor-mation, Graph 1 also shows theboiling points for solutions of differ-ent concentrations.

There are several methods formeasuring the concentration of acaustic soda solution, but the onlyreally accurate method is chemicalanalysis. Since this is ratherlengthy and complicated, thestrength of a solution for processuse is usually determined as afunction of the density which isfound by use of a hydrometer.There are three scales for express-ing density of a caustic solution,namely specific gravity, degreesBaum and degrees Twaddell. Nomatter which scale is used, thedensity of the solution will vary witha change in temperature.

DISSOLVING BEADS, FLAKEAND COMPOUNDERS

These three forms of causticsoda will dissolve freely in well agi-tated solutions under the properconditions. It is important toremember that while dry causticsoda dissolves freely, it is a haz-ardous material and should betreated with the utmost care andsafety. Protective equipment, asdescribed in this handbook, shouldbe worn at all times.

For best results, the beads, flakeor compounders should be addedslowly to the surface of a well-agi-tated solution of water. When largequantities of flake caustic soda areplaced in stagnant solutions, theflake material falls to the bottomand forms a layer of hydrate whichdissolves quite slowly. This condi-tion may lead to local overheatingand spurting of the solution. Becertain that most of the causticsoda has dissolved before addingmore. Agitation of the solution by apropeller-type agitator is preferred.A circulating pump may be usedinstead, providing it recirculates thesolution at a high enough capacity.An air lance is not recommendedsince it can cause excessive car-bonate formation. The followingtable lists relative rates of dissolu-tion for each grade.

DISSOLVING RATES OFVARIOUS GRADES OFANHYDROUS CAUSTIC SODA*No. 2 Flake 44 SecondsNo. 4 Flake 41 SecondsCompounders 20 SecondsBeads 15 Seconds

*At 5% concentration, 50F, and con-stant speed agitation with a magneticstirrer.

DANGER!Caustic soda, liquid and anhy-drous, has a very high heat ofsolution. If caustic soda is addedto a solution too rapidly, or if thesolution is not sufficiently agitat-ed, or if added to hot or cold liq-uid, a rapid temperature increasecan result in dangerous boilingand/or spattering which maycause an immediate violenteruption.

20 of 52Equipment For HandlingCaustic Soda

GENERAL CONSIDERATIONSCaustic soda is a corrosive

chemical which is normally handledin either steel, nickel, nickel alloysor certain types of plastic equip-ment. The specific material willdepend on the conditions underwhich the material is being used.Temperature, solution concentra-tion, location and safety considera-tions are all important factors inequipment selection.

MATERIALS OF CONSTRUCTIONThe most common construction

materials for handling and storingcaustic soda solutions are blackiron and mild steel; however, liquidcaustic soda will attack these met-als at elevated temperatures. Theideal storage temperature for caus-tic soda solutions is 80 to 100F. Insteel systems, temperatures above120F will cause accelerated corro-sion and iron contamination of thecaustic (above 120F, cracking canoccur if concentrated caustic isprocessed in steel equipment thathas not been stress relieved.)Where iron contamination or corro-sion is unacceptable, epoxy linedsteel, 316L and 304L stainlesssteels are recommended. 316Land 304L stainless is acceptable to200F. At temperatures above200F, nickel is typically used butMonel, Inconel, or Hastelloycan also be used. Consult with theepoxy supplier about the workingtemperature range of a particularepoxy lining.

Plastics, such as polyethylene,polypropylene, PVC, and CPVC,are chemically suitable with causticsoda. They can be used to preventiron contamination if maximumtemperatures for each material arenot exceeded. The manufacturer ofthe tank, drum, piping or equipmentin question should be contacted to

determine the exact limitations ofthe specific plastic. Aluminum, cop-per, zinc, lead and their alloys(e.g., brass and bronze) are NOTsuitable. Caustic soda readilyattacks these materials.STORAGE TANKS

Tanks can be either vertical orhorizontal. They are usually fabri-cated from at least 1/4-inch steelplate. A 1/8-inch corrosionallowance should be included inthe design. If iron contamination isa problem, tanks can be fabricatedfrom 304L or 316L stainless steel.If the tanks are large, its usuallymore economical to fabricate asteel tank and line it with an epoxycoating. Plastic tanks are usuallyfabricated from polypropylene orFRP (Since caustic can attackglass reinforcement fibers ofimproperly constructed FRP tanks,care must be taken to ensure thatthe FRP tanks are built with theproper reinforcing materials, resins,catalysts, curing procedures andcorrosion barriers).

The product draw-off line shouldbe at least 4 inches above the bot-tom of the tank and the drain con-nection should be at the lowestpoint in the tank. This will facilitatedrainage during periodic cleaningof the tank. Most tanks have a leveltransmitter for measuring liquidlevel.

Where heating is required, anexternal heat exchanger with a cir-culating pump or internal steamheating coils are most commonlyemployed. The preferred materialsfor the coils are nickel, Monel, orInconel. Despite this, stainlesssteel is most commonly usedbecause of cost considerations.(Athigh temperatures, stainless steel

may crack). If it is necessary toinsulate the storage tank, a two-inch layer of polyurethane foam orcellular glass should be adequate.

Proper design of a storage sys-tem will include adequate contain-ment in case of tank failure. Stateand local regulatory authoritiesshould always be consulted duringthe design phase of construction.

TANK CLEANING ANDPASSIVATION

Tank cleaning is dependent onthe product stored in it previously.A tank that previously containedcaustic soda requires scaleremoval, wall thickness testing,rinsing, passivation, floor cleaning,and immediate filling. A tank previ-ously containing another productrequires cleaning with an appropri-ate solvent or soap, as well as theother steps mentioned above.

Scale removal is accomplishedby blasting the walls with an abra-sive such as sand or pecan shells.Abrasives containing high percent-ages of metals are not recom-mended.

The wall thickness of the tankshould be measured to ensure thatthe tank has structural integrity forthe density of the product and theheight of product in the tank.

Passivation requires permeationof the steel tank walls with causticsoda. This is usually accomplishedby spraying the cleaned walls witha hot solution of caustic soda.Temperatures of 100 - 140F andsolutions of 5 - 20% are recom-mended. While this is more of anart than a science, a standard rec-ommendation would be spraying

21of 52Equipment For HandlingCaustic Soda

the walls for 2-4 hours with 10%solution at 140F. The larger thetank the longer it should besprayed to complete the passiva-tion. Utilizing a hotter and strongersolutions will require less time forpassivation. One way to achievethe solution heat necessary is todilute 50% caustic soda to 20%.The heat of dilution will cause thecaustic soda temperature to rise.Additional heat may be necessaryto achieve optimal solution temper-atures. The coating of the tankwalls is best accomplished with anelliptical sprayer. If this type ofsprayer is not available, the spray-ing may be done manually withextreme caution taken to protectthe operator.

After passivation, the tank bottommust be cleaned out as well aspossible. The quality of the initialproduct stored in the tank willdepend greatly upon the extent towhich the tank bottom is cleaned ofscale abrasive compound. If anelliptical sprayer is used for thecleaning, a squeegee will need tobe used to clean the tank bottom. Ifmanual spraying is used for clean-ing, the sprayer can be used topush the scale and abrasive towardthe sump followed up by use of asqueegee.

After cleaning, the tank shouldbe filled with caustic soda as soonas possible. This will prevent thetank walls from losing their passi-vation. If the tank cleaning is notcompletely successful, it may benecessary to filter the initial productfrom the tank to keep it free fromparticulate matter. This wouldrequire a 5-10 micron filter mediahoused in a unit that would beacceptable with the temperature,pressure, and chemical.

PIPING AND VALVESPipelines are usually at least two

inches in diameter and constructedof Schedule 40 black iron or mildsteel with welded or flanged joints.Where disconnects are necessary,flanged joints are preferred to facili-tate maintenance. A safety shieldof wrap-around polypropylene isrecommended for all flanged joints.This will protect against spraying incase a gasket leaks.

Proper pipeline design includesan adequate pitch to permit com-plete draining. Avoid any loops orpockets. Lines should also includewater or air connections for purgingafter use.

Where slight iron contaminationis unacceptable, CPVC, polypropy-lene, polypropylene-lined steel, andTeflon lined steel pipe are suit-able materials. Pay special atten-tion to suitable operating tempera-tures and pressures with thesematerials.

Ductile iron, cast steel, stainlesssteel, Alloy 20, and Teflon-linedquarter-turn plug or ball valves arerecommended for caustic soda ser-vice. Various other types of valvescan also be used; however, keep inmind that less elaborate fittingsprovide better reliability in this ser-vice.

PUMPSCentrifugal pump of stainless

steel or Alloy 20 construction, witheither double mechanical seals or adeep packing gland, is recom-mended. Packing material shouldbe Teflon impregnated, causticresistant fibers, or equivalent. Toavoid seals altogether, magneticallycoupled pumps could be used.

Pump location should receivecareful consideration. For ease ofoperation, keep the suction lines asshort as possible. A recirculatingline will help prevent excess wearon the pump and, in many cases,can assist in controlling flow rates.

METERSCaustic soda solutions can be

metered through standard rotame-ters having non-glass tubes andnickel or stainless steel floats.Magnetic, coriolis or orifice-typemeters are preferred for strong, hotsolutions. They should be made ofcorrosion resistant materials suchas stainless steel, alloy 20, monelor nickel.

Installation of Tanks22 of 52

))"

#

+

)

!,#

"

-),.*

&(

!!

-,.*

./01

&)0

-,.*

&(

!!

./01

&)0

))"

+

)

"

(

#

!,#

-"+

,#&-")

-"+

,#&-")

*NOTE: All tanks should be located within a diked area.

Figure 6: Typical Storage Tank Installation

TechnicalData 23 of 52

Table 1 Density and Caustic Soda Content of Rayon/Membrane GradeCaustic Soda Solutions at 60F

DEGREES TOTAL WT TOTAL WTWT% % SPECIFIC BAUM NaOH NaOH SOLUTION NaOH SOLUTIONNaOH Na2O GRAVITY [AM STD] G/L LB/GAL LB/GAL LB/CU FT LB/CU FT

1.0 0.775 1.0120 1.706 10.118 0.084 8.437 0.631 63.1132.0 1.550 1.0230 3.259 20.457 0.171 8.529 1.277 63.8043.0 2.325 1.0342 4.782 31.019 0.259 8.622 1.935 64.4974.0 3.100 1.0453 6.274 41.803 0.349 8.715 2.608 65.1915.0 3.874 1.0564 7.736 52.811 0.440 8.807 3.295 65.8856.0 4.649 1.0676 9.170 64.042 0.534 8.900 3.995 66.5817.0 5.424 1.0787 10.580 75.496 0.630 8.993 4.710 67.2778.0 6.199 1.0899 11.960 87.174 0.727 9.087 5.438 67.9739.0 6.974 1.1010 13.310 99.076 0.826 9.180 6.181 68.670

10.0 7.748 1.1122 14.630 111.210 0.927 9.273 6.937 69.36711.0 8.523 1.1234 15.930 123.550 1.031 9.366 7.707 70.06312.0 9.298 1.1345 17.200 136.130 1.136 9.459 8.492 70.75913.0 10.080 1.1457 18.440 148.920 1.242 9.552 9.290 71.45514.0 10.850 1.1569 19.660 161.930 1.351 9.645 10.110 72.15015.0 11.630 1.1680 20.850 175.170 1.461 9.738 10.930 72.84516.0 12.400 1.1791 22.030 188.630 1.573 9.830 11.770 73.53917.0 13.180 1.1902 23.170 202.300 1.687 9.923 12.620 74.23118.0 13.950 1.2013 24.300 216.200 1.803 10.020 13.490 74.92219.0 14.730 1.2124 25.400 230.310 1.921 10.110 14.370 75.61220.0 15.500 1.2234 26.480 244.640 2.040 10.200 15.260 76.30021.0 16.280 1.2344 27.530 259.180 2.162 10.300 16.170 76.98722.0 17.050 1.2454 28.570 273.940 2.285 10.390 17.090 77.67223.0 17.830 1.2563 29.590 288.910 2.409 10.480 18.030 78.35524.0 18.600 1.2672 30.580 304.090 2.536 10.570 18.970 79.03525.0 19.370 1.2781 31.550 319.470 2.664 10.660 19.930 79.71326.0 20.150 1.2889 32.510 335.070 2.794 10.750 20.910 80.38927.0 20.920 1.2997 33.440 350.870 2.926 10.840 21.890 81.06228.0 21.700 1.3105 34.350 366.870 3.060 10.930 22.890 81.73129.0 22.470 1.3212 35.250 383.070 3.195 11.020 23.900 82.39830.0 23.250 1.3317 36.120 399.450 3.331 11.110 24.920 83.05731.0 24.020 1.3424 36.980 416.070 3.470 11.200 25.960 83.72232.0 24.800 1.3529 37.830 432.860 3.610 11.280 27.010 84.37933.0 25.570 1.3634 38.650 449.850 3.751 11.370 28.070 85.03334.0 26.350 1.3738 39.450 467.010 3.895 11.460 29.140 85.68135.0 27.120 1.3842 40.240 484.370 4.039 11.540 30.220 86.32736.0 27.900 1.3944 41.020 501.910 4.186 11.630 31.310 86.96837.0 28.670 1.4046 41.770 519.630 4.333 11.720 32.420 87.60538.0 29.450 1.4148 42.510 537.520 4.482 11.800 33.530 88.23739.0 30.220 1.4248 43.230 555.590 4,633 11.880 34.660 88.86440.0 31.000 1.4348 43.940 573.830 4.785 11.970 35.800 89.48741.0 31.770 1.4447 44.640 592.240 4.939 12.050 36.950 90.10542.0 32.550 1.4545 45.310 610.810 5.094 12.130 38.110 90.71743.0 33.320 1.4643 45.980 629.530 5.250 12.210 39.270 91.32444.0 34.100 1.4739 46.630 648.420 5.407 12.290 40.450 91.92645.0 34.870 1.4835 47.260 667.450 5.566 12.370 41.640 92.52246.0 35.650 1.4930 47.880 686.640 5.726 12.450 42.840 93.11347.0 36.420 1.5023 48.480 705.970 5.887 12.530 44.040 93.69748.0 37.200 1.5116 49.080 725.440 6.049 12.610 45.260 94.27549.0 37.970 1.5208 49.650 745.040 6.213 12.680 46.480 94.84750.0 38.740 1.5298 50.220 764.780 6.377 12.760 47.710 95.41251.0 39.520 1.5388 50.770 784.640 6.543 12.830 48.950 95.97152.0 40.290 1.5476 51.310 804.630 6.710 12.910 50.200 96.523

24 of 52TechnicalData

Table 2 Density and Caustic Soda Content of Diaphragm GradeCaustic Soda Solutions at 60F

DEGREES TOTAL WT TOTAL WTWT% % % SPECIFIC BAUM NaOH NaOH SOLUTION SOLUTIONNaOH Na2O NaCl GRAVITY [AM STD] G/L LB/GAL LB/GAL LB/CU FT LB/CU FT

1.0 0.775 0.020 1.0121 1.726 10.120 0.084 8.438 0.631 63.1222.0 1.550 0.040 1.0233 3.300 20.463 0.171 8.532 1.277 63.8233.0 2.325 0.060 1.0346 4.842 31.032 0.259 8.626 1.936 64.5254.0 3.100 0.080 1.0459 6.351 41.827 0.349 8.719 2.610 65.2275.0 3.874 0.100 1.0571 7.829 52.846 0.441 8.813 3.297 65.9306.0 4.649 0.120 1.0684 9.282 64.095 0.535 8.908 3.999 66.6367.0 5.424 0.140 1.0797 10.710 75.568 0.630 9.002 4.714 67.3418.0 6.199 0.160 1.0911 12.100 87.269 0.728 9.096 5.444 68.0479.0 6.974 0.180 1.1024 13.460 99.195 0.827 9.191 6.188 68.75210.0 7.748 0.200 1.1137 14.800 111.350 0.928 9.285 6.946 69.45811.0 8.523 0.220 1.1250 16.110 123.730 1.032 9.379 7.718 70.16412.0 9.298 0.240 1.1363 17.390 136.340 1.137 9.474 8.505 70.87013.0 10.080 0.260 1.1476 18.650 149.170 1.244 9.568 9.305 71.57514.0 10.850 0.280 1.1589 19.880 162.220 1.353 9.662 10.120 72.27915.0 11.630 0.300 1.1702 21.090 175.500 1.464 9.756 10.950 72.98316.0 12.400 0.320 1.1815 22.270 189.000 1.576 9.850 11.790 73.68517.0 13.180 0.340 1.1927 23.430 202.730 1.691 9.944 12.650 74.38718.0 13.950 0.360 1.2040 24.560 216.680 1.807 10.040 13.520 75.08819.0 14.730 0.380 1.2152 25.670 230.840 1.925 10.140 14.400 75.78720.0 15.500 0.400 1.2263 26.760 245.230 2.045 10.230 15.300 76.48521.0 16.280 0.420 1.2375 27.830 259.830 2.167 10.320 16.210 77.18022.0 17.050 0.440 1.2486 28.870 274.650 2.291 10.410 17.140 77.87423.0 17.830 0.460 1.2597 29.900 289.690 2.416 10.510 18.080 78.56624.0 18.600 0.480 1.2708 30.900 304.930 2.543 10.600 19.030 79.25525.0 19.370 0.500 1.2818 31.880 320.400 2.672 10.690 19.990 79.94326.0 20.150 0.520 1.2928 32.840 336.070 2.803 10.780 20.970 80.62827.0 20.920 0.540 1.3037 33.780 351.940 2.935 10.870 21.960 81.31028.0 21.700 0.560 1.3146 34.700 368.020 3.069 10.960 22.960 81.98829.0 22.470 0.580 1.3254 35.600 384.310 3.205 11.050 23.980 82.66530.0 23.250 0.600 1.3362 36.490 400.800 3.342 11.140 25.010 83.33831.0 24.020 0.620 1.3470 37.350 417.490 3.482 11.230 26.050 84.00732.0 24.800 0.640 1.3576 38.200 434.370 3.622 11.320 27.100 84.67333.0 25.570 0.660 1.3683 39.030 451.450 3.765 11.410 28.170 85.33534.0 26.350 0.680 1.3788 39.840 468.720 3.909 11.500 29.240 85.99435.0 27.120 0.700 1.3893 40.630 486.170 4.054 11.590 30.330 86.64836.0 27.900 0.720 1.3997 41.410 503.820 4.201 11.670 31.430 87.29937.0 28.670 0.740 1.4101 42.170 521.640 4.350 11.760 32.540 87.94438.0 29.450 0.760 1.4204 42.920 539.650 4.500 11.850 33.670 88.58639.0 30.220 0.780 1.4306 43.640 557.830 4.652 11.930 34.800 89.22340.0 31.000 0.800 1.4407 44.360 576.190 4.805 12.020 35.950 89.85441.0 31.770 0.820 1.4508 45.050 594.710 4.959 12.100 37.100 90.48142.0 32.550 0.840 1.4607 45.740 613.400 5.115 12.180 38.270 91.10343.0 33.320 0.860 1.4706 46.400 632.260 5.272 12.270 39.440 91.72044.0 34.100 0.880 1.4804 47.060 651.270 5.431 12.350 40.630 92.33045.0 34.870 0.900 1.4901 47.690 670.440 5.591 12.430 41.830 92.93546.0 35.650 0.920 1.4997 48.320 689.760 5.752 12.510 43.030 93.53547.0 36.420 0.940 1.5092 48.930 709.220 5.914 12.590 44.250 94.12948.0 37.200 0.960 1.5187 49.520 728.830 6.078 12.670 45.470 94.71649.0 37.970 0.980 1.5280 50.100 748.580 6.242 12.740 46.700 95.29750.0 38.740 1.000 1.5372 50.670 768.460 6.408 12.820 47.940 95.87251.0 39.520 1.000 1.5506 51.490 790.690 6.594 12.930 49.330 96.71152.0 40.290 1.000 1.5604 52.070 811.250 6.765 13.010 50.610 97.317

TechnicalData

Table 3 Specific Heats of Caustic Soda Solutions in BTUs per PoundPERCENT TEMPERATURE FCAUSTIC 32 40 50 60 80 100 120 140 160 180 200 220 240 260 280 300

0 1.004 1.003 1.001 0.999 0.998 0.997 0.998 0.999 1.000 1.002 1.004 - - - - -

2 0.965 0.967 0.968 0.969 0.972 0.974 0.977 0.978 0.980 0.983 0.986 - - - - -

4 0.936 0.940 0.943 0.946 0.951 0.954 0.957 0.960 0.962 0.965 0.966 - - - - -

6 0.914 0.920 0.924 0.928 0.933 0.938 0.941 0.944 0.946 0.948 0.950 - - - - -

8 0.897 0.902 0.907 0.911 0.918 0.923 0.927 0.930 0.932 0.934 0.936 - - - - -

10 0.882 0.888 0.893 0.897 0.905 0.911 0.916 0.918 0.920 0.922 0.923 - - - - -

12 0.870 0.877 0.883 0.887 0.894 0.901 0.906 0.909 0.911 0.912 0.913 - - - - -

14 0.861 0.868 0.874 0.879 0.886 0.892 0.897 0.901 0.903 0.903 0.904 - - - - -

16 0.853 0.860 0.866 0.871 0.880 0.886 0.891 0.894 0.896 0.897 0.897 - - - - -

18 0.847 0.854 0.860 0.865 0.873 0.880 0.885 0.888 0.890 0.891 0.891 - - - - -

20 0.842 0.848 0.854 0.859 0.868 0.875 0.880 0.884 0.886 0.886 0.887 - - - - -

22 0.837 0.844 0.849 0.854 0.863 0.870 0.876 0.880 0.882 0.882 0.883 - - - - -

24 - 0.839 0.844 0.849 0.858 0.866 0.873 0.877 0.879 0.879 0.880 - - - - -

26 - 0.835 0.840 0.845 0.854 0.863 0.869 0.874 0.875 0.876 0.876 - - - - -

28 - 0.830 0.836 0.841 0.850 0.859 0.866 0.870 0.872 0.872 0.873 - - - - -

30 - 0.826 0.832 0.837 0.846 0.855 0.862 0.866 0.868 0.869 0.869 - - - - -

32 - 0.822 0.828 0.833 0.842 0.850 0.857 0.862 0.863 0.864 0.864 - - - - -

34 - - 0.823 0.828 0.837 0.845 0.852 0.856 0.857 0.858 0.858 - - - - -

36 - - 0.819 0.824 0.832 0.840 0.845 0.849 0.850 0.851 0.851 - - - - -

38 - - 0.816 0.820 0.827 0.833 0.837 0.841 0.842 0.842 0.843 - - - - -

40 - - 0.812 0.815 0.821 0.826 0.829 0.831 0.832 0.832 0.832 - - - - -

42 - - 0.807 0.809 0.813 0.816 0.819 0.819 0.820 0.820 0.820 - - - - -

44 - - - 0.802 0.804 0.806 0.807 0.807 0.807 0.806 0.804 - - - - -

46 - - - 0.793 0.794 0.795 0.794 0.794 0.793 0.791 0.789 - - - - -

48 - - - - 0.783 0.782 0.781 0.780 0.779 0.777 0.776 - - - - -

50 - - - - 0.771 0.769 0.768 0.767 0.765 0.765 0.764 0.763 0.762 0.762 0.761 0.761

52 - - - - 0.759 0.757 0.756 0.754 0.753 0.752 0.751 0.749 0.748 0.747 0.746 0.745

54 - - - - 0.746 0.744 0.741 0.739 0.739 0.738 0.737 0.735 0.733 0.731 0.730 0.728

56 - - - - 0.733 0.730 0.728 0.726 0.724 0.723 0.722 0.721 0.719 0.717 0.715 0.713

58 - - - - - 0.719 0.717 0.715 0.713 0.711 0.709 0.707 0.705 0.703 0.702 0.700

60 - - - - - 0.706 0.705 0.703 0.701 0.699 0.697 0.696 0.693 0.691 0.690 0.688

62 - - - - - - 0.694 0.692 0.690 0.688 0.687 0.685 0.683 0.681 0.679 0.677

64 - - - - - - 0.684 0.682 0.681 0.679 0.677 0.675 0.673 0.671 0.670 0.668

66 - - - - - - 0.675 0.673 0.671 0.669 0.668 0.666 0.664 0.662 0.660 0.658

68 - - - - - - - 0.663 0.662 0.660 0.658 0.656 0.655 0.653 0.651 0.649

70 - - - - - - - 0.655 0.653 0.651 0.649 0.647 0.646 0.644 0.642 0.640

72 - - - - - - - - 0.645 0.643 0.641 0.639 0.637 0.635 0.634 0.632

73 - - - - - - - - - 0.639 0.637 0.635 0.633 0.631 0.630 0.628

74 - - - - - - - - - 0.635 0.633 0.631 0.629 0.628 0.626 0.624

74.5 - - - - - - - - - 0.633 0.631 0.629 0.627 0.626 0.624 0.622

76 - - - - - - - - - 0.628 0.627 0.625 0.623 0.621 0.619 0.617

78 - - - - - - - - - - 0.620 0.618 0.616 0.615 0.613 0.611

25 of 52


Properties of Anhydrous Caustic Soda

Table 4Miscellaneous Properties

Property ValueChemical Formula . . . . . . .NaOHMolecular Weight . . . . . . . .40.00Freezing or meltingpoint . . . . . . . . . . . . . . . . .318C or 604FBoiling point . . . . . . . . . . . .1388C or 2530F at

760 mm Hg pressureSpecific heat . . . . . . . . . . .0.353 cal/gm/C at

20C or 0.353BTU/Ib/F at 68F

Free energy offormation . . . . . . . . . . . . . .-90,762 cal/mol at

25C, 760 mm Hg pressure

Refractive index forlight wavelength of5894 A . . . . . . . . . . . . . . . .N = 1.433 at 320C

N = 1.421 at 420C

Latent heat of fusion . . . . .40.0 cal/gm or 72.0 BTU/lb

Lattice energy . . . . . . . . . .176.2 kg-cal/molEntropy . . . . . . . . . . . . . . .12.43 kg-cal/mol/K

at 25C, 760 mm Hg pressure

Heat of formation . . . . . . . . 101.723 kcal/molNa+1/2O2+

1/2H2 = NaOH

Table 5Specific Gravity of Solid Caustic Soda

Temp.C 20 299.6 320 350 400 450

Specificgravity 2.130 2.08 1.786 1.771 1.746 1.722

Note:The average bulk density of flake Caustic Soda is about 60 pounds per cubic foot. This value varies with the packing conditions and flake characteristics.

Table 6Enthalpy of

Anhydrous Caustic Soda(Above 32F base temperature)

Solid NaOH Molten NaOHTemp.F BTU/lb Temp.F BTU/lb

32 0.00 605.1 356.0650 5.57 650 381.47

100 21.71 700 408.94150 38.82 750 435.59200 56.91 800 461.28250 75.98 850 486.48300 96.01 900 510.70350 117.03 950 534.12400 139.02 1000 556.72450 161.98 1050 578.52500 185.92 1100 599.51550 210.83 1150 619.68600 281.27 1300 675.35

605.1 283.97 1350 692.29

Table 7Viscosity of

Molten Caustic Soda Temp. C . . . . . . . . . . . 350 400 450 500 550Viscosity, centipoise . . . 4.0 2.8 2.2 1.8 1.5

Table 8Vapor Pressure of

Molten Caustic Soda

Temp.C . . . . . . . .1000 1050 1100 1200 1300 1388

Vapor Pressurein mm Hg . . . . . . . . .41 66 103 225 447 760

TechnicalData 27 of 52

Properties of Caustic Soda Solutions

Table 9Coefficient of Expansion of

Caustic Soda Solutions

The coefficient of expansion is the volume changeper unit change in temperature. It may be derivedfrom data on the change of density with tempera-ture according to the following formula:

d = 1.0200 + 0.0105OX - (0.0005+0.0000049X)t

Note: d is the density in g/cc; X is the concen-tration in percent by weight of NaOH; and t is thetemperature in C. The formula is limited to con-centrations from 10% to 70% NaOH and to tem-peratures from 15C to 70C.

Table 10Compressibility of

Caustic Soda Solutions

Moles H2O/Mole NaOH Density B x 10

6

25.01 1.08670 31.2350.09 1.04391 36.15

100.15 1.02114 39.12

Note: The compressibility coefficient B is expressed as compressibilityper cc per megabar at 25C. Data is valid between 100-300 megabars.

Table 11Heat of Solution of Caustic Soda

Heat Liberated % Moles H2O/ BTU/lb. BTU/lb. cal/g

NaOH Mole NaOH NaOH Solution NaOH0.44 500 455.8 2.0 253.20.55 400 456.0 2.5 253.31.10 200 456.6 5.0 253.72.17 100 458.3 9.9 254.64.26 50 462.0 19.7 256.78.16 25 462.6 37.7 257.0

14.14 13.5 470.1 66.5 261.219.80 9 462.2 91.5 256.824.10 7 457.9 110.4 254.430.77 5 419.2 129.0 232.942.55 3 323.5 137.6 179.7

Table 12Heat of Dilution of

Caustic Soda SolutionsWt.% BTU/lb BTU/lbNaOH NaOH Solution

0 0 02 + 1.18 + 0.02364 - 2.04 - 0.08086 - 4.78 - 0.2878 - 7.15 - 0.572

10 - 8.60 - 0.86012 - 9.13 - 1.0914 - 8.65 - 1.2116 - 7.34 - 1.1718 - 4.99 - 0.89720 - 1.50 - 0.30122 + 3.28 + 0.72124 9.47 2.2726 17.14 4.4628 26.43 7.4030 37.34 11.2032 49.97 15.9934 64.05 21.7636 79.63 28.6638 96.50 36.6740 114.2 45.6942 132.8 55.7844 151.7 66.7646 170.7 78.5248 189.7 91.04

Note: Enthalpy of solutions at 68F relative to infinitely dilute solutions.

Table 13

Index of Refraction ofCaustic Soda Solutions

NaOHTemp.C g/L Refractive Index

20C 0 1.333027.88 1.33517

13.12 1.3366035.44 1.3423655.12 1.3471498.48 1.35685

131.52 1.36364

25C 0 1.332517.88 1.33467

13.08 1.3360535.4 1.3417455.04 1.3464498.28 1.35603

131.2 1.36279

30C 0 1.331967.88 1.33411

13.04 1.3355135.36 1.3410854.96 1.3457298.08 1.35530

130.92 1.36204

TechnicalData28 of 52

Table 14

Hydrogen Ion Concentrations ofCaustic Soda Solutions at 25C

NaOH% NaOH Moles/L pH

7.40 2.0 14.03.83 1.0 13.81.96 0.5 13.60.39 0.1 12.90.20 0.05 12.60.04 0.01 12.0

Due to the difficulty of obtaining accurate pH read-ings at values above 12, pH is not a valid methodto determine concentration.


-40

-20

0

20

40

60

80

100

120

140

160

180

200

-40

-4

32

68

104

140

176

212

248

284

320

356

392

0 10 20 30 40 50 60 70 80 90

Percent NaOH by weight

Tem

pera

ture

C

Tem

pera

ture

F

Range of Liquid Caustic Soda

Solidifying Curve

Boiling Point Curve(Atmospheric Pressure)

Solid Caustic Soda

Graph 1Boiling and Solidifying Temperatures of Aqueous Caustic Soda Solutions


1

1.05

1.1

1.15

1.2

1.25

1.3

1.35

1.4

1.45

1.5

1.55

1.6

1.65

1.7

1.75

1.8

0 10 20 30 40 50 60 70 80 90 100

32 50 68 86 104 122 140 158 176 194 212

Temperature F

Spe

cific

Gra

vity

70% by weight NaOH

60%

55%

50%

45%

40%

35%

30%

25%

20%

15%

10%

5%

Temperature C

Graph 2Specific Gravity of Aqueous Caustic Soda Solutions


0.2

1

10

100

10 20 30 40 50 60 70

50 68 86 104 122 140 158

Temperature F

Temperature C

Vis

cosi

ty, C

entip

oise

s

60% by weight NaOH

50%

40%

30%

20%

10%

0%

Graph 3Viscosity of Aqueous Caustic Soda Solutions


10

100

1000

10000

0 50 100 150 200 250

32 122 212 302 392 482

Temperature F

Temperature C

Vap

or P

ress

ure,

mm

Hg

0% NaOH

10% NaOH

20% NaOH

30% NaOH

40% NaOH

50% NaOH

60% NaOH

Graph 4Vapor Pressures of Aqueous Caustic Soda Solutions

33 of 52

50

100

150

200

0 10 20 30 40 50

80F

100F

120F

140F


Res

ultin

g F

inal

Tem

pera

ture

(F

)

TechnicalData

50

100

150

200

250

300

0 10 20 30 40 50 60 70


Res

ultin

g F

inal

Tem

pera

ture

(F

)

60F Dilution Water

80F Dilution Water

100F Dilution Water

Graph 5Approximate Resultant Temperature When Diluting Caustic Soda

Solution

Anhydrous

Note: Graph for use starting with 50% Caustic Soda Solution using 70F water.

Note: Graph for use starting with Anhydrous Caustic Soda.


0

100

200

300

400

500

0 10 20 30 40 50 60 70 80


Rel

ativ

e E

ntha

lpy,

BT

U/lb

of S

olut

ion

400F

380F

360F

340F

320F

300F

280F

260F

240F

220F

200F

180F

160F

140F

120F

100F

80F

Graph 6Relative Enthalpy of Aqueous Caustic Soda Solutions

To approximate the final temperature after diluting a NaOHsolution, start on the bottom axis at the percentage of the origi-nal solution. Proceed up until the temperature of the originalsolution is reached. From that point, draw a line that intersectson the y-axis at the temperature of the water used for dilution.Then find the final diluted percentage on the x-axis and draw avertical line that intersects the second line drawn. The intersec-tion point of those lines represents the resultant temperature.

Example: Diluting 50% NaOH at 120F to 20% using 80F water.* Approximate resultant temperature 143 F


Graph 7Solubility of Sodium Chloride in Aqueous Caustic Soda Solutions


0.32

0.33

0.34

0.35

0.36

0.37

0.38

0.39

0.4

0.41

0.42

0 10 20 30 40 50 60 70 80

30F

50F

70F

90F

100F

130F

170F

190F


The

rmal

Con

duct

ivity

- B

TU

/HR

x S

Q. F

t xF

Graph 8Thermal Conductivity of Aqueous Caustic Soda Solutions


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5

0 5 10 15 20 25 30 35 40 45 50


Spe

cific

Con

duct

ance

, ohm

-1cm

-1

0C

18C

50C

100C

Graph 9Specific Conductance of Aqueous Caustic Soda Solutions

Dilution Calculations38 of 52

HOW TO DILUTE CAUSTIC SODA SOLUTIONS

Sometimes it is necessary to dilute caustic sodabefore it is used, or when the potential for freezingexists. A procedure for calculating the amount ofconcentrated caustic and water required is givenbelow.

DILUTING A SOLUTIONProblem: To dilute 3,000 gallons of 50% NaOH to

a 20% solution. How much water is necessary toaccomplish this task?

Solution: The dilution can be simplified by usingthe following formula:D=V[A(B-C)/C]

Where:A=Specific gravity of strong solutionB=Concentration of strong solution (% NaOH)C=Concentration of desired solution(% NaOH)D=Volume of water to be addedV=Volume of strong solution(The specific gravity of 50% NaOH is 1.5372 takenfrom Table 2)

Therefore:D=3,000((1.5372)(50-20)/20)D=3,000(2.3058)=6,917 gallonsResult: It will take 6,917 gallons of water to dilute3,000 gallons of 50% NaOH to a 20% solution.

VOLUME OF FINAL SOLUTIONIt should be noted that when diluting caustic soda,

volumes are not additive. Therefore, in the previousexample, the final volume of the solution would notbe 6,917 gallons of water + 3,000 gallons of 50%NaOH = 9,917 total gallons. The actual volume willbe slightly less. To calculate the final volume, thewater and caustic soda must be converted to aweight basis, and then divided by the density of thedesired solution.

DILUTION GRAPHGraph 10 can also be used to determine approxi-

mate volumes of 50% NaOH and water necessary toachieve a particular dilution. For example, you wantto produce 3,000 gallons of a 25% NaOH solutionand want to know how much water and 50% NaOHare needed to accomplish this goal.

Using the chart, start on the bottom axis at the3,000 gallon line. Proceed upward until you intersectthe first 25% line on the bottom half of the graph.From the intersection point go to the right and leftaxes to determine the volume and weight of waterneeded. In this case the volume is read at 1,920 gal-lons and the weight at 16,000 pounds.

Then continue upward until you intersect the 25%line at the top of the graph. Again from the intersec-tion point go to the left and right axes to determinethe volume and weight of 50% NaOH needed. In thiscase the volume is read at 1,248 gallons and theweight at 16,000 pounds.

Therefore, it would take 1,248 gallons of 50%NaOH to be added to 1,920 gallons of water to pro-duce 3,000 gallons of a 25% solution.

39 of 52DilutionCalculations

40000

30000

20000

10000

0

4800

3600

2400

1200

0

0 1000 2000 3000 4000 5000

0

10000

20000

30000

40000

0

780

1560

2340

31200 1000 2000 3000 4000 5000

Vol

ume

of 5

0% N

aOH

Req

uire

d (g

allo

ns)

Vol

ume

of W

ater

Req

uire

d (g

allo

ns)

40%

35%

30%

25%

20%

15%

10%

40%

35%

30%

25%

15%

10%

20%

50% Caustic Soda (NaOH)

Water

Wei

ght o

f 50%

NaO

H R

equi

red

(lbs)

Wei

ght o

f Wat

er R

equi

red

(lbs)

Volume of Desired Solution (gallons)

Graph 10Approximate Dilution Chart For 50% Caustic Soda

Methodsof Analysis40 of 52

DETERMINATION OFTHE TOTAL ALKALINITY OF CAUSTIC SODAPURPOSE AND THEORY

The accurate determination ofthe total alkalinity value for causticsoda is necessary for calculatingthe correct billing concentrations ofthis product.

Total alkalinity in caustic sodaproducts is determined by titrationof a sample with a standardizedsolution of 1N hydrochloric acid.Modified methyl orange indicator isused to determine the titration endpoint.

APPARATUS100 ml Buret; Class A

Volumetric, Fisher Scientific Cat #:03-775 or equivalent.

Analytical Balance; capable ofweighing to 0.001 grams.250 ml Erlenmeyer Flasks; widemouth, Fisher Cat#: 10-090B orequivalent.

Magnetic Stirrer; Fisher Cat#:14-493-120S or equivalent.

Magnetic stirring bars; 1 1/2 x5/16 dia. Fisher Cat#: 14-511-64or equivalent.

REAGENTS1N Hydrochloric Acid;

measure 83.0 ml of ACS Reagentgrade concentrated hydrochloricacid into a graduated cylinder andtransfer it to a one liter volumetricflask containing approximately 500ml of deionized water. Dilute to vol-ume with additional water, mix welland store in a tightly closed con-tainer. A prepared solution of 1NHCl can also be purchased (FisherScientific Cat# SA48-20 or equiva-lent). Hydrochloric Acid must bestandardized to 0.0001N beforeuse.

Sodium Carbonate;anhydrous, volumetric grade (EMScience Cat#: 6394-2 or equiva-lent.) Dry at 250C in a platinum orporcelain crucible for 4 hours.Store in a desiccator.

Modified methyl orangeindicator; dissolve 0.14 grams ofmethyl orange (Fisher Cat#: M216-25) and 0.12 grams of XyleneCyanole FF (Fisher Cat#: BP565-10) in deionized water and dilute to100 ml.

Water, Deionized & CarbonDioxide free; boil and cool thedeionized water or purge it withnitrogen for two hours.

SAFETYRefer to the MSDS for the proper

handling procedures for each of thechemicals listed in this procedure.

Caustic soda is a strong base.Hydrochloric acid is a strongacid. These chemicals are corro-sive to body tissue and cancause immediate and severeburns to eyes. Wear propergloves, proper eye protectionand other protective clothingwhen handling these chemicals.

A. STANDARDIZATION OF 1NHYDROCHLORIC ACID1. Weigh 4.2 grams of sodium

carbonate to the nearest0.0001 gram into a weighing dish. Carefully transfer toan Erlenmeyer flask. Add 75ml of deionized water and swirl to dissolve. Add threedrops of the modified methylorange indicator and titrate with the HCl solution to asteel gray color change.

2. The following formula is usedto calculate the normality ofthe HCl.Let:N = Normality of HClW = Weight (g) of Na2CO3usedV = Volume (ml) of HClrequired to endpoint.Milliequivalent weight ofNa2CO3= 0.053N = W/V x 0.053

3. Determine the normality byaveraging the result of atleast three titrations.

B. ANALYSIS1. To a clean, dry Erlenmeyer

flask, accurately weigh to thenearest 0.001 grams an amountof sample as determined in thetable below. Weighing should beperformed as rapidly aspossible. The sample sizes are:50% NaOH..............6 - 7 gAnhydrous NaOH....3 - 4 g

2. Immediately add 50 ml of deion-ized water, making sure thesides of the beaker are washeddown.

3. Add 3 to 4 drops of modifiedmethyl orange indicator andcarefully add the magnetic stir-ring bar.

4. Titrate the sample to a steelgray color with 1N HCl. Samplesshould be titrated as soon aspossible to avoid pick up of car-bon dioxide from the air.

5. Record the volume of acidrequired to reach this color.Estimate the buret reading tothe nearest 0.02 ml.

Methodsof Analysis 41 of 52

C. CALCULATIONSThe following are formulas used

to calculate total alkalinity.Let:W = Weight (g) of sample titratedN = Normality of HClV = Volume (ml) of HCl requiredMilliequivalent wt. of Na2O =0.03099

% Na2O = (V) (N) (0.03099)(100)W

% NaOH = 1.2907 (%Na2O)

EXAMPLE6.530 grams of caustic soda

required the addition of 81.77 ml of1.0011N HCl to reach the modifiedmethyl orange endpoint.

% Na2O = (V) (N) (0.03099)(100)W

% Na2O = (81.77)(1.0011)(3.099)6.530

% Na2O = 38.85%% NaOH = (1.2907) (38.85)% NaOH = 50.14%

QUALITY ASSURANCEWith each batch of samples

being analyzed, at least one of thesamples should be analyzed induplicate. On a regular basis, sam-ples that have been previouslyanalyzed for total alkalinity shouldbe reanalyzed and the results com-pared.

Alkalinity values obtained foreach sample should be comparedwith OxyChem specifications forthat product. Hydrochloric acidshould be restandardized at least monthly.

DETERMINATION OFSODIUM HYDROXIDEIN CAUSTIC SODAPURPOSE AND THEORY

The sodium hydroxide content ofcaustic soda is determined byadding barium chloride to a pre-pared sample and titrating with 1 NHCl to the phenolphthalein endpoint. The results are reported aspercent NaOH on a sample weightbasis.

APPARATUS100 ml Buret; Class A

Volumetric, Fisher Scientific Cat #:03-775 or equivalent.Analytical Balance; capable ofweighing to 0.001 grams.250 ml Erlenmeyer Flasks; widemouth, Fisher Cat#:10-090B orequivalent.Magnetic Stirrer; Fisher Cat#: 14-493-120S or equivalent.Magnetic stirring bars; 1-1/2 x5/16 dia. Fisher Cat#: 14-511-64or equivalent.

REAGENTS1N Hydrochloric Acid; the

preparation of this reagent isdescribed in the method for:Determination of Total Alkalinity.

1% Phenolphthalein Indicator;dissolve one gram of phenolph-thalein (Aldrich Cat#: 10,594-5 orequivalent) in 100 ml of methanol.

10% Barium Chloride; Dissolve120 g of reagent grade BaCl2.2H2O(Fisher Cat#: B34-500) in 880 ml ofdeionized water.

Water, Deionized & CarbonDioxide free; boil and cool thedeionized water or purge it withnitrogen for two hours.

SAFETYRefer to the MSDS for the

proper handling procedures foreach of the chemicals listed inthis procedure. Caustic soda is astrong base. Hydrochloric acidis a strong acid. These chemi-cals are corrosive to body tissueand can cause immediate andsevere burns to eyes. Wearproper gloves, proper eye pro-tection and other protectiveclothing when handling thesechemicals. Barium chloride ishighly toxic. Avoid inhaling bari-um chloride dust.

A. STANDARDIZATION OF 1NHYDROCHLORIC ACID

Standardization procedure isdescribed in the method for:Determination of Total Alkalinity.

B. ANALYSIS1. To a clean, dry Erlenmeyer

flask, accurately weigh to thenearest 0.001 grams an amountof sample described in the tablebelow. Weighing should be per-formed as rapidly as possible.The sample sizes are:50% NaOH................ 6 - 7 gAnhydrous NaOH...... 3 - 4 g

2. Immediately add 100 ml of bari-um chloride solution, makingsure the sides of the beaker arewashed down.

3. Add 3 to 4 drops of phenolph-thalein indicator and carefullyadd the magnetic stirring bar.

4. Titrate the sample with 1N HCluntil the pink color changes towater white. The sample shouldbe titrated as soon as possibleto avoid pick up of carbon diox-ide from the air.

Methodsof Analysis42 of 52

5. Record the volume of acidrequired to reach this color, esti-mating the buret reading to thenearest 0.02 ml.

CALCULATIONSThe following are formulas used

to calculate % NaOH.Let:W = Weight (g) of sample titratedN = Normality of HClV = Volume (ml) of HCl requiredMilliequivalent wt. of NaOH =0.04000

% NaOH = (V) (N) (0.04000) (100)W

EXAMPLE6.467 grams of caustic soda

required the addition of 80.85 ml of1.0020N HCl to reach the phe-nolphthalein endpoint.

% NaOH = (V) (N) (0.04000) (100)W

% NaOH = (80.85) (1.0020)(4.000)6.467

% NaOH = 50.11%

QUALITY ASSURANCEFor each batch of samples being

analyzed, at least one of the sam-ples should be analyzed in dupli-cate. On a regular basis, samplesthat have been previously analyzedfor total alkalinity should be reana-lyzed and the results compared.Alkalinity values obtained for eachsample should be compared withOxyC

OxyChem Caustic Soda Handbook

Documents