¡Descarga Tablas de Naoh, características y más Apuntes en PDF de Procesos Químicos solo en Docsity!
OxyChem
Caustic Soda
Handbook 1 of 44
Page
• • Introduction & Principal Uses.................
• • Manufacturing.............................
• • Methods of Shipping Caustic Soda............
• • Safety in Handling Caustic Soda..............
• • Unloading and Handling Liquid Caustic Soda....
• • Equipment for Handling Caustic Soda........
• • Technical Data...........................
• • Dilution Calculations.......................
• • Methods of Analysis.......................
"Important: The information presented herein, while not guaranteed, was prepared by technical personnel and is true and accurate to the best of our knowl- edge. NO WARRANTY OF MERCHANTABILITY OR OF FITNESS FOR A PARTICULAR PURPOSE, OR WARRANTY OR GUARANTY OF ANY OTHER KIND, EXPRESS OR IMPLIED, IS MADE REGARDING PERFORMANCE, SAFETY, SUITABILITY, STABILITY OR OTHERWISE. This information is not intended to be all-inclusive as to the manner and conditions of use, handling, storage, disposal and other factors that may involve other or additional legal, environmental, safety or performance considerations, and OxyChem assumes no liability whatsoever for the use of or reliance upon this information. While our technical personnel will be happy to respond to questions, safe handling and use of the product remains the responsibility of the customer. No sugges- tions for use are intended as, and nothing herein shall be construed as, a recommendation to infringe any existing patents or to violate any Federal, State, local or foreign laws."
Occidental Chemical Corporation 2009
CellBW
N a O HN a O H
Caustic Soda
Handbook
fi (^) OxyChem is a registered trademark of Occidental Chemical Corporation. OxyChemfi
Foreword
This handbook outlines the methods for
handling, storing, preparing and using caustic
soda. It includes information on the manufacture,
physical properties, safety considerations and
analytical methods for testing caustic soda.
Additional information and contacts can be
found at www.oxychem.com
Occidental Chemical Corporation (OxyChem)
Basic Chemicals Group
Occidental Tower
5005 LBJ Freeway
Dallas, TX 75244
Principal Uses and
Consumption of
Caustic Soda
Introduction 2 of 44
Caustic soda (sodium hydroxide
or NaOH) is most commonly manu-
factured by the electrolysis of a
sodium chloride (NaCl) solution.
OxyChem manufactures caustic
soda using either membrane or
diaphragm electrolytic cells.
OxyChem does not use mercury
based electrolytic cells to produce
caustic soda. The co-products
formed from the electrolytic produc-
tion of caustic soda are chlorine
and hydrogen.
The largest users of caustic soda
are the pulp and paper, detergent
and chemical industries. Caustic
soda is also used in the alumina,
oil and gas and textile industries,
mostly for its alkalinity value.
OxyChem has played a leading
role in providing caustic soda to
meet the increasing demands of
industry. OxyChem plants are
strategically located to conveniently
and economically serve industry.
Terminals are used to maintain
stocks of our caustic soda in many
principal cities. Distributor stocks
are also available in these and
many other cities and form a net-
work of supply for the end user’s
convenience.
Liquid caustic soda is available as
a 50% solution in two main grades.
The name of the grades corre-
sponds to the equipment used to
produced the caustic soda; mem-
brane grade and diaphragm grade.
Specification sheets for each grade
can be found on our website at
www.oxychem.com
To be technically correct, only
molten caustic soda should be
called liquid, but since the term liq-
uid caustic soda has historically
been used to describe solutions of
caustic soda, it is used in this doc-
ument interchangeably with the
term solution.
OxyChem produces caustic soda
at the following locations:
- Battleground, TX (Diaphragm)
- Convent, LA (Diaphragm)
- Geismar, LA (Membrane and
Diaphragm)
- Ingleside, TX (Diaphragm)
- Niagara Falls, NY (Diaphragm)
- Taft, LA (Diaphragm)
- Wichita, KS (Membrane and
Diaphragm)
Caustic soda is one of the very
few chemicals utilized in a very
broad range of applications. Some
principal products or processes in
which caustic soda is used are:
- Acid Neutralization
- Agricultural Chemicals
- Aluminum
- Battery Recycling
- Bleach
- Boiler Compounds
- Cellulose Film
- Chemicals:
Ammonia
Amyl Amines
Cresol
Ethylene Amines
Formic Acid
Glycerine
Maleic Anhydride
Pentaerythritol
Phenol
Propylene Oxide
Polycarbonates
Salicylic Acid
Sodium Aluminate
Sodium Hydrosulfide
Sodium Hypochlorite
Sodium Phosphates
Styrene
Vinyl Chloride Monomer
- Cleaning Formulations
- Corn Syrup
- Detergents
- Drain Cleaners
- Dyestuffs
- Ethanol Fermentation
- Food Processing
- Fruit & Vegetable Peeling
- Glass-Batch Wetting
- Ion-Exchange Resin
Regeneration
- Metal Production and Casting
- Ore Flotation and Processing
- Paint Removers
- Petroleum Refining
- pH Adjustment
- Pharmaceuticals
- Pigments
- Pool & Spa chemicals
- Pulp & Paper
- Rayon
- Silicates
- Soap
- Surfactants
- Textile Bleaching, Dyeing, and
Mercerizing
- Vegetable Oil Processing
- Water Treatment
4 of 44
Methods of Shipping
Liquid Caustic Soda
Liquid caustic soda is available
from OxyChem’s many plants and
terminals in tank truck, tank car,
barge and ship quantities. Each
form of transportation has its own
advantages. The type of service
selected will depend upon such
factors as size and location of
storage, rate of consumption,
plant location, freight rates, etc.
Caustic soda, liquid, is regulated by
the U.S. Department of
Transportation (DOT) and is classi-
fied as a corrosive material.
The DOT identification
number is UN I824 for liquid caus-
tic soda.
5 of 44
Safety in Handling
Caustic Soda
Caustic soda in any concentra-
tion must be respected by every-
one who handles and uses it.
Before starting to work with it,
the user should be aware of its
properties, know what safety
precautions to follow, and know
how to react in case of contact.
Accidental exposure to caustic
soda may occur under several
conditions. Potentially haz-
ardous situations include han-
dling and packaging operations,
equipment cleaning and repair,
decontamination following spills
and equipment failures.
Employees who may be subject
to such exposure must be pro-
vided with proper personal pro-
tective equipment and trained in
its use. Some general guidelines
follow.
- Read and understand the latest
Material Safety Data Sheet.
- Provide eyewash fountains and
safety showers in all areas where
caustic soda is used or handled.
Any caustic soda burn may be
serious. DO NOT use any kind of
neutralizing solution, particularly
in the eyes, without direction by a
physician.
- Move the patient to a hospital
emergency room immediately
after first aid measures are
applied.
FIRST AID MEASURES
For Eyes: If for any reason
caustic soda contacts the eyes,
flood the eyes immediately with
plenty of clean water. Continue
flushing for at least 15 minutes.
While flushing, forcibly hold the
eyelids apart to ensure rinsing of
the entire eye surface. Do not use
any kind of neutralizing solution
in the eyes.
GET MEDICAL ATTENTION
IMMEDIATELY.
For skin: If caustic soda comes
in contact with skin or clothing,
flush with plenty of clean water for
at least 15 minutes. Remove conta-
minated clothing and footwear.
Thoroughly wash affected clothing
and rubber/vinyl footwear. Discard
contaminated leather footwear.
GET MEDICAL ATTENTION
IMMEDIATELY.
For inhalation: If a worker is
overcome due to the inhalation of
caustic soda dust, mist or spray,
remove them from the contaminat-
ed area to fresh air. If breathing is
difficult, have a trained person
administer oxygen. If breathing has
stopped, have a trained person
administer artificial respiration.
GET MEDICAL ATTENTION
IMMEDIATELY.
For ingestion: Although it
is unlikely in an industrial
situation that caustic soda would
be ingested, it could be swallowed
accidentally. If that occurs, DO
NOT induce vomiting. Give large
quantities of water. If vomiting
occurs spontaneously, position indi-
vidual’s head to keep airway clear.
NEVER give anything by mouth to
an unconscious
person. GET MEDICAL ATTEN-
TION IMMEDIATELY.
PROTECTIVE EQUIPMENT
OSHA requires employers to
supply suitable protective equip-
ment for employees. When han-
dling caustic soda, the following
protective equipment is recom-
mended:
- Wear suitable chemical splash
goggles for eye protection dur-
ing the handling of caustic
soda in any concentration. The
goggles should be close-fitting
and provide adequate ventilation
to prevent fogging, without allow-
ing entry of liquids.
- The use of a face shield may be
appropriate when splashing can
occur, including loading and
unloading operations.
- Wear rubber gloves or gloves
coated with rubber, synthetic
elastomers, PVC, or other plas-
tics to protect the hands while
handling caustic soda. Gloves
should be long enough to come
well above the wrist. Sleeves
should be positioned over the
glove wrists.
- Caustic soda causes leather to
disintegrate quite rapidly. For this
reason, wear rubber boots. Wear
the bottoms of trouser legs out-
FACE SHIELD
CHEMICAL SUIT
RUBBER BOOTS
CHEMICAL SPLASH GOGGLES
RUBBER GLOVES
7 of 44
Unloading and Handling Liquid
Caustic Soda in Tank Cars
GENERAL INFORMATION
Caustic soda in liquid form
has a markedly corrosive action
on all body tissue. Even dilute
solutions may have a destructive
effect on tissue after prolonged
contact. Inhalation of concentrat-
ed mists can cause damage to
the upper respiratory tract, while
ingestion of liquid caustic soda
can cause severe damage to the
mucous membranes or other tis-
sues where contact is made. In
addition, considerable heat is
generated when liquid caustic
soda is mixed with water which
can result in boiling or splatter-
ing. When diluting, always add
caustic soda to water; never add
water to caustic soda.
It is important that those who
handle caustic soda are aware of
its highly reactive and corrosive
properties and know what pre-
cautions to take. In case of acci-
dental exposure, immediately
flush exposed area with large
amounts of water and seek med-
ical attention. For more specific
information refer to the Safety in
Handling Caustic Soda section
of this handbook and to the
MSDS.
PLACEMENT OF THE CAR FOR
UNLOADING
1. After the car is properly spot-
ted, DOT regulations require
that the hand brake be set and
the wheels blocked before any
connections are made.
2. Caution signs must be placed
at both ends of the car being
unloaded to warn people and
switching crews approaching
the car. DOT regulations state
that caution signs must be
placed on the track or car to
give warning to persons
approaching the car from the
open end or ends of siding.
Caution signs must be left up
until the car is unloaded and
disconnected from the dis-
charge connections. Signs
must be made of metal or other
suitable material, at least 12x
inches in size, and bear the
words, “STOP-TANK CAR
CONNECTED”, or “STOP-MEN
AT WORK.”
3. It is recommended that derail
attachments be placed at the
open end or ends of siding,
approximately one car length
away.
4. Before hooking up a car, the
responsible individual should
first locate and test the nearest
eyewash and safety shower.
Purge water through each to
remove rust that may have
accumulated.
UNLOADING PRECAUTIONS
1. Only responsible and well
supervised employees should
be entrusted with the unloading
of liquid caustic soda.
Unloading operations must be
monitored while the car is con-
nected.
2. Since serious burns can result
from contact of caustic soda
with the skin and eyes, workers
should be well protected and
cautioned to exercise care.
Persons hooking up a car
should 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 approved
respiratory protection
3. A car of caustic soda should be
unloaded only when adequate
lighting is available throughout
the entire unloading process.
4. Before starting to unload, make
certain that the tank car is vent-
ed and that the storage tank is
vented and has sufficient
capacity.
5. No one should enter the car
under any circumstances.
6. If a tank car needs to be moved
when partially unloaded, DOT
regulations require that all
unloading lines must be discon-
nected and car closures must
be replaced.
7. A suggested method for sam-
pling is to draw intermittent
samples from a 1/2” sample
line, connected to a vertical
section of the unloading line.
The sample line should be fitted
with a valve and a 1/4” nipple.
8. OxyChem’s liquid caustic soda
is shipped in well insulated and
specially lined tank cars. Linings
in these tank cars will withstand
temperatures up to 225°F.
Recommended steam pressure
used to heat up a rail car is lim-
ited to 10psig max due to this
fact. To prevent damage to the
linings, neither water nor steam
should be added directly into
the tank cars if the car contains
a level of caustic.
9. Unloading lines should be cov-
ered with suitable insulation and
heated just prior to transfer of
liquid caustic soda to storage.
The preferred method of heat-
ing is to provide electric or
steam heat tracing around the
unloading line, under the insula-
tion. An alternate method is to
provide tees in the unloading
line so that steam (or hot water)
can be run through the unload-
ing line just prior to its use.
Unloading and Handling Liquid
Caustic Soda in Tank Cars
8 of 44
These precautions will prevent
the solidification of liquid caus-
tic soda in cold unloading lines.
Running steam through
unloading lines will increase
corrosion in unlined steel
piping systems and iron
pickup in the product.
10. If compressed air is used in
unloading operations, it is
important that all fittings be
inspected for leaks or other
defects before unloading.
Dome fittings in particular
should be inspected. If leaks
are found, unloading operations
should be suspended until they
are corrected.
11. General purpose caustic rail
car tanks are structurally
designed and constructed for
100 psig, and have a design
burst rating of 500 psig. Per 49
CFR 179 and the AAR
Specifications for Tank Cars, a
pressure relief device is
installed sized for a fire sce-
nario, that is set for 75 to 165
psig. The higher set pressure is
allowed due to the premature
failure of the lower rated relief
devices that occurred during
transport handling, and resulted
in injuries to rail road person-
nel. Even through they are
designed and equipped as
such, these are NOT pressure
rail cars, nor should they be
padded above what OxyChem
and the Chlorine Institute rec-
ommends (20-25 psig).
After a rail car is loaded with
product, it is leak checked at
approx 30 psig to meet the
DOT shipping requirement, and
that test pressure is released
prior to shipping.
Because of inherent shaking
and jarring experienced by the
rail car and contents during the
shipping process, gaskets and
joints can loosen up and cus-
tomers should be cautious of
that possibility. If pressure
unloading, particular areas to
watch are the manway gasket,
the bottom flange gasket (when
bottom unloading), and the top
operator gland area for bottom
outlet valve (if so equipped).
Additionally the top operated
bottom outlet valve reach rods
can in rare instances, come
detached during transit, and
there have been reports that
these rods can be 'pushed up'
from a rail car if unloading
pressures > 30 psig are used.
HANDLING IN COLD WEATHER
Since OxyChem tank cars
are well insulated and liquid caustic
soda is loaded hot, it usually
arrives at its destination in a liquid
condition. However, since 50% liq-
uid caustic soda begins to crystal-
lize at 54°F, in cases of unusual
delays in transit, freezing may take
place in cold weather. If freezing
has 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 the
car, this crust should be broken
before admitting steam to the
jacket around the bottom dis-
charge valve. The puncturing of
the crust permits expansion of
the liquid as it increases in tem-
perature.
3. If no crust is present, determine
if crystals have formed on the
bottom of the car by probing the
bottom with a rubber-capped
rod introduced through the
dome opening.
4. If freezing has occurred, con-
nect a steam line (10 psig or
less) to the jacket around the
bottom discharge valve.
Connect a condensate return
line at the valve jacket steam
outlet. If a condensate return
line is not used, it is advisable
to connect a valve at the steam
outlet, which should be opened
sufficiently to relieve conden-
sate and direct it toward the
ground or into a sewer. As con-
tents liquefy, the valve may be
closed further to conserve
steam.
5. If necessary, steam can be con-
nected to the rail car steam
coils. A condensate return line,
pressure reducing valve, and/or
steam trap should be used. Do
not exceed a steam pressure of
10 psig. Using steam pressure
above 10 psig may damage the
railcar lining.
6. The amount of material that is
frozen in a caustic soda rail car
is dependent upon the outside
temperature, wind chill, and the
time between when the rail car
is loaded and unloaded.
Although it is unlikely, it is pos-
sible for a caustic soda rail car
to be totally frozen. If the caus-
tic soda in a rail car is totally
frozen, it may be necessary to
apply steam to the rail car jack-
et for two days (48 hours) to liq-
uefy all of its contents.
7. When examination indicates
that the contents have liquefied
and operation of the valve rod
shows that the bottom dis-
charge valve is free, the caustic
soda is ready for unloading.
The unloading temperature of
50% caustic soda should be
less than 120 oF to minimize
corrosion of unlined steel
piping systems and equip-
ment.
8. If the above measures do not
liquefy the contents on the car,
contact your OxyChem repre-
sentative.
Unloading Liquid Caustic Soda
in Tank Cars 10 of 44
Rail cars can be either bottom
unloaded (gravity, pump or pressure)
or top unloaded (with air pressure).
Refer to appropriate unloading proce-
dure based on the method to be
employed.
UNLOADING THROUGH
BOTTOM OUTLET VALVE
1. Open the dome cover and deter-
mine if the contents of the car
are liquid. If not, see “Handling
in Cold Weather.” Keep the
dome cover at least partially
open during the entire unloading
operation to vent the tank car.
2. Refer to Figure 1. Insure that the
bottom outlet valve is closed
tightly. The valve rod which oper-
ates the bottom discharge valve
has a handle on it which is locat-
ed outside the dome of the car.
The handle can be reversed and
serves as a cap in transit.
3. Remove the pipe plug, then care-
fully open the supplementary
valve to drain any liquid that may
have seeped past the bottom
outlet valve during transit. If the
supplementary valve cannot be
opened, the application of steam
from a steam lance, directed on
the valve, should free it for open-
ing.
4. Attach the unloading line to the
bottom of the supplementary
valve.
5. Check the unloading line to see
that all valves are in the proper
position for unloading.
6. Open the bottom outlet valve by
turning the valve rod to allow
contents to flow by gravity to
pump or tank. If the bottom outlet
valve does not open upon appli-
cation of light pressure, frozen
caustic soda is probably present
in the bottom of the car.
Application of steam to the heat
coils may be necessary. See
“Handling in Cold Weather.”
7. Compressed air can be used to
increase the flow rate of caustic
soda to storage or to transfer liq-
uid without the use of a pump. If
compressed air is to be used,
check the rupture disk in the
dome to be sure it is intact.
Close the dome cover securely.
Remove the one-inch air inlet
plug and connect a flexible air
line at this point. The air line
should have a release valve, oil
trap, pressure relief valve set at
20 PSIG, pressure reducing
valve set at 18 PSIG and a shut-
off valve. Apply air pressure to
the car slowly. Note that the
pressure relief device (rupture
disk and/or pressure relief valve)
in the dome will relieve at a pres-
sure between 75 PSIG and 165
PSIG, depending on the type of
car. Refer to the stenciling on the
side of the railcar.
8. When the car and unloading line
are empty, shut off air supply and
open the release valve.
9. When the tank car is empty and
the discharge pipe has complete-
ly drained, disconnect the air
line, if used, close the bottom
outlet valve and supplementary
valve, and detach the unloading
line at the car.
10. Prepare the car for return.
Steam jacket
Union Pump
2” Steel pipe
Pump inlet valve
Rail car Low line drain valve unloading valve
Vent
Tank inlet valve
To process
Drain
TANK CAR
STORAGE TANK
Steam coils
Figure 2: Bottom Unloading
11 of 44
Unloading Liquid Caustic Soda
in Tank Cars
UNLOADING THROUGH
DOME WITH AIR PRESSURE
1. Open the dome cover to deter-
mine if the contents of the car
are liquid. If not, see “Handling in
Cold Weather.”
2. Close the dome cover and fasten
securely, making certain that it is
air tight. Check that the rupture
disk in the dome is intact.
3. Check that the product storage
tank is vented and has sufficient
capacity.
4. After opening the protective
housing cover, connect the
unloading line to the two-inch top
unloading valve. After removing
the protective housing cover, a
flexible steel hose connection for
the unloading line is recommend-
ed since a car may rise as much
as 2” during unloading.
5. Connect the flexible air supply
line to the one-inch air inlet
valve. This line should have a
release valve, oil trap, pressure
relief valve set at 20 PSIG, pres-
sure reducing valve set at 18
PSIG and a shut-off valve. Note
that the relief device (rupture disk
or pressure relief valve) in the
dome will relieve at a pressure
between 75 and 165 PSIG,
depending on the type of car.
Refer to the stenciling on the
side of the railcar.
6. Apply air pressure slowly until
there is a normal flow of liquid to
the storage tank. The pressure
should be adjusted and main-
tained until the tank car is com-
pletely empty. A drop in air pres-
sure or the sound of air rushing
through the unloading line indi-
cates that the tank car is empty.
7. Shut off the air supply, open the
release valve, and allow the
eduction pipe to drain.
8. When the eduction pipe has
drained and the tank car is at
atmospheric pressure, discon-
nect the air supply line at the car.
9. Do not enter the car to make an
inspection.
10. Open the dome cover and deter-
mine if the car is empty. If empty,
disconnect the unloading line at
the car, replace pipe plugs and
tightly replace the dome cover
and the protective housing cover.
11. Care should be taken not to spill
caustic soda on the car, since it
will cause damage to the car and
may endanger workers handling
the empty car on its return.
12. Prepare the car for return.
PREPARING EMPTY TANK
CARS FOR RETURN
1. Make sure the bottom outlet
valve and supplementary valve
are closed.
2. Disconnect the unloading line
and replace the bottom outlet
plug. Do not replace closures on
steam openings.
3. Close dome cover and fasten
securely.
4. Return the empty tank car
promptly in accordance with the
shipper’s instructions. The ship-
per’s routing directions must be
followed in all instances.
!
" ##
## $ $
$ ## %& $
' ( )) ##
*
*
%
) ## + $
Figure 3: Top Unloading
13 of 44
Unloading Liquid Caustic Soda
in Tank Trucks
- Close the valve on the storage
fill line.
- Close all valves on the tank
truck.
- In some installations the cus-
tomer’s fill line is fitted with a
drain to be used instead of flush-
ing the line before the hose is
disconnected.
- Disconnect the hose with caution
and discharge any caustic soda
remaining in the hose to a suit-
able container.
- Unload caustic soda in an area
with adequate safeguards for
spill control. No caustic soda
should be spilled, but in the
event a small amount is spilled,
hose down the area with water.
Clean up all spills and dispose in
accordance with federal, state
and local regulations.
FACILITY EQUIPMENT
Typical installations of storage
vessels for receipt of truck ship-
ments are similar to those shown in
Figures 2 and 3 for rail car deliver-
ies.
A storage tank with a minimum
capacity of 1.5 tank cars is recom-
mended.
A fill line to the top of the storage
is strongly recommended. If a bot-
tom fill line is used, the truck driver
must be informed.
A permanent fill line in close
proximity 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 is
recommended on the fill line for
use in flushing out the line with air,
water, or steam. It can be used as
a drain.
Cap or close the end of the fill
line when not in use.
A source of running water for use
during unloading operations is
required. A safety shower and eye-
wash fountain are recommended.
14 of 44
Equipment For Handling
Caustic Soda
GENERAL CONSIDERATIONS
Caustic soda is a corrosive
chemical which is normally handled
in either steel, nickel, nickel alloys
or certain types of plastic equip-
ment. The specific material will
depend on the conditions under
which the material is being used.
Temperature, solution concentra-
tion, location and safety considera-
tions are all important factors in
equipment selection.
MATERIALS OF CONSTRUCTION
The most common construction
materials for handling and storing
caustic soda solutions are black
iron and mild steel; however, liquid
caustic soda will attack these met-
als at elevated temperatures. The
ideal storage temperature for caus-
tic soda solutions is 80 to 100°F. In
steel systems, temperatures above
120°F will cause accelerated corro-
sion and iron contamination of the
caustic (above 120°F, cracking can
occur if concentrated caustic is
processed in steel equipment that
has not been stress relieved.)
Where iron contamination or corro-
sion is unacceptable, epoxy lined
steel, 316L and 304L stainless
steels are recommended. 316L
and 304L stainless is acceptable to
200°F. At temperatures above
200°F, nickel is typically used but
Monel®, Inconel®, or Hastelloy®
can also be used. Consult with the
epoxy supplier about the working
temperature range of a particular
epoxy lining.
Plastics, such as polyethylene,
polypropylene, PVC, and CPVC,
are chemically suitable with caustic
soda. They can be used to prevent
iron contamination if maximum
temperatures for each material are
not exceeded. The manufacturer of
the tank, drum, piping or equipment
in question should be contacted to
determine the exact limitations of
the specific plastic. Aluminum, cop-
per, zinc, lead and their alloys
(e.g., brass and bronze) are NOT
suitable. Caustic soda readily
attacks these materials.
STORAGE TANKS
Tanks can be either vertical or
horizontal. They are usually fabri-
cated from at least 1/4-inch steel
plate. A 1/8-inch corrosion
allowance should be included in
the design. If iron contamination is
a problem, tanks can be fabricated
from 304L or 316L stainless steel.
If the tanks are large, it’s usually
more economical to fabricate a
steel tank and line it with an epoxy
coating. Plastic tanks are usually
fabricated from polypropylene or
FRP (Since caustic can attack
glass reinforcement fibers of
improperly constructed FRP tanks,
care must be taken to ensure that
the FRP tanks are built with the
proper reinforcing materials, resins,
catalysts, curing procedures and
corrosion barriers).
The product draw-off line should
be at least 4 inches above the bot-
tom of the tank and the drain con-
nection should be at the lowest
point in the tank. This will facilitate
drainage during periodic cleaning
of the tank. Most tanks have a level
transmitter for measuring liquid
level.
Where heating is required, an
external heat exchanger with a cir-
culating pump or internal steam
heating coils are most commonly
employed. The preferred materials
for the coils are nickel, Monel®, or
Inconel®. Despite this, stainless
steel is most commonly used
because of cost considerations.(At
high temperatures, stainless steel
may crack). If it is necessary to
insulate the storage tank, a two-
inch layer of polyurethane foam or
cellular glass should be adequate.
Proper design of a storage sys-
tem will include adequate contain-
ment in case of tank failure. State
and local regulatory authorities
should always be consulted during
the design phase of construction.
TANK CLEANING AND
PASSIVATION
Tank cleaning is dependent on
the product stored in it previously.
A tank that previously contained
caustic soda requires scale
removal, wall thickness testing,
rinsing, passivation, floor cleaning,
and immediate filling. A tank previ-
ously containing another product
requires cleaning with an appropri-
ate solvent or soap, as well as the
other steps mentioned above.
Scale removal is accomplished
by 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 tank
should be measured to ensure that
the tank has structural integrity for
the density of the product and the
height of product in the tank.
Passivation requires permeation
of the steel tank walls with caustic
soda. This is usually accomplished
by spraying the cleaned walls with
a hot solution of caustic soda.
Temperatures of 100 - 140°F and
solutions of 5 - 20% are recom-
mended. While this is more of an
art than a science, a standard rec-
16 of 44 Installation of Tanks
#
$
, * " -$
#
. - /+ *
' ) " "
- /+ . / 01
'* 1
. - /+
' " " )
(^) / 01
'* 1
#
, *
#
)
$
" -$
.# ,
-$' .# *
.# ,
-$' .# *
*NOTE: All tanks should be located within a diked area.
Figure 6: Typical Storage Tank Installation
Table 1 Density and Caustic Soda Content of Rayon/Membrane Grade
Caustic Soda Solutions at 60°F
DEGREES TOTAL WT TOTAL WT
WT% % SPECIFIC BAUMÉ NaOH NaOH SOLUTION NaOH SOLUTION
Technical
Data
Table 3 Specific Heats of Caustic Soda Solutions in BTU’s per Pound
PERCENT TEMPERATURE °F CAUSTIC 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. 52 - - - - 0.759 0.757 0.756 0.754 0.753 0.752 0.751 0.749 0.748 0.747 0.746 0. 54 - - - - 0.746 0.744 0.741 0.739 0.739 0.738 0.737 0.735 0.733 0.731 0.730 0. 56 - - - - 0.733 0.730 0.728 0.726 0.724 0.723 0.722 0.721 0.719 0.717 0.715 0. 58 - - - - - 0.719 0.717 0.715 0.713 0.711 0.709 0.707 0.705 0.703 0.702 0. 60 - - - - - 0.706 0.705 0.703 0.701 0.699 0.697 0.696 0.693 0.691 0.690 0. 62 - - - - - - 0.694 0.692 0.690 0.688 0.687 0.685 0.683 0.681 0.679 0. 64 - - - - - - 0.684 0.682 0.681 0.679 0.677 0.675 0.673 0.671 0.670 0. 66 - - - - - - 0.675 0.673 0.671 0.669 0.668 0.666 0.664 0.662 0.660 0. 68 - - - - - - - 0.663 0.662 0.660 0.658 0.656 0.655 0.653 0.651 0. 70 - - - - - - - 0.655 0.653 0.651 0.649 0.647 0.646 0.644 0.642 0. 72 - - - - - - - - 0.645 0.643 0.641 0.639 0.637 0.635 0.634 0. 73 - - - - - - - - - 0.639 0.637 0.635 0.633 0.631 0.630 0. 74 - - - - - - - - - 0.635 0.633 0.631 0.629 0.628 0.626 0. 74.5 - - - - - - - - - 0.633 0.631 0.629 0.627 0.626 0.624 0. 76 - - - - - - - - - 0.628 0.627 0.625 0.623 0.621 0.619 0. 78 - - - - - - - - - - 0.620 0.618 0.616 0.615 0.613 0.
19 of 44
20 of 44
Technical
Data
Properties of Anhydrous
Caustic Soda
Table 4
Miscellaneous Properties
Property Value
Chemical Formula....... .NaOH
Molecular Weight....... .40.
Freezing or melting
point................. .318°C or 604°F
Boiling point........... .1388°C or 2530°F at
760 mm Hg pressure
Specific heat........... .0.353 cal/gm/°C at
20°C or 0.
BTU/Ib/°F at 68°F
Free energy of
formation.............. .-90,762 cal/mol at
25°C, 760 mm Hg
pressure
Refractive index for
light wavelength of
5894 A................ .N = 1.433 at 320°C
N = 1.421 at 420°C
Latent heat of fusion..... .40.0 cal/gm or 72.
BTU/lb
Lattice energy.......... .176.2 kg-cal/mol
Entropy.............. .12.43 kg-cal/mol/°K
at 25°C, 760 mm Hg
pressure
Heat of formation........ 101.723 kcal/mol
Na+ 1 / 2 O 2 +^1 / 2 H 2 = NaOH
Table 5
Specific Gravity of Solid Caustic Soda
Temp.°C 20 299.6 320 350 400 450
Specific
gravity 2.130 2.08 1.786 1.771 1.746 1.
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 6
Enthalpy of Anhydrous Caustic Soda
(Above 32°F base temperature)
Solid NaOH Molten NaOH Temp.°F BTU/lb Temp.°F BTU/lb
32 0.00 605.1 356. 50 5.57 650 381. 100 21.71 700 408. 150 38.82 750 435. 200 56.91 800 461. 250 75.98 850 486. 300 96.01 900 510. 350 117.03 950 534. 400 139.02 1000 556. 450 161.98 1050 578. 500 185.92 1100 599. 550 210.83 1150 619. 600 281.27 1300 675. 605.1 283.97 1350 692.
Table 7
Viscosity of Molten Caustic Soda Temp. °C........... 350 400 450 500 550 Viscosity, centipoise... 4.0 2.8 2.2 1.8 1.
Table 8
Vapor Pressure of Molten Caustic Soda
Temp.°C....... .1000 1050 1100 1200 1300 1388
Vapor Pressure in mm Hg......... .41 66 103 225 447 760
