Chemical Engineering October 2012 - 41

TABLE 11. SPECIFIC EQUIPMENT, PIPING, VALVES AND PROTECTIVE
CLOTHING GUIDELINES
Equipment HNO3
Tanks
For acid grades lower than 95 wt.%, tanks should be designed for slight pressure and vacuum,
with fumes collected at a disposal system and sent to a scrubber. Vent piping should
be designed taking into consideration possible corrosion from contact with moisture
Pumps
Piping and Fittings
Valves
Protective
Clothing
Wetted
parts should be made of 304L stainless steel for concentrations lower than 95
wt.%; for higher concentrations, they should be made of titanium (with a water content
higher than 1.34% to prevent spontaneous combustion), silicon iron or 3003 aluminum
alloy [11]
Piping made of 304L stainless steel is frequently used for HNO3 up to 95 wt.%, and of aluminum
for higher concentrations. Carbon steel (CS) piping with TFE, FEP or glass linings (up to
certain temperatures) can also be used for all grades. [11]
Butterfly valves: 316 SS, Alloy 20 and Hastelloy C are good stem and disk materials for nitric
acid at various concentrations. Seats made of Viton can handle various concentrations up to
70%; for low concentrations at low temperatures, Neoprene, Hypalon and EPT have also been
used
Neoprene or natural rubber latex gloves are acceptable for handling nitric acid.
TABLE 12. SPECIFIC EQUIPMENT, PIPING, VALVES AND PROTECTIVE
CLOTHING GUIDELINES
Equipment
Tanks
HF
Anhydrous and 70 wt.% HF up to 66°C, or HF between 60 to 70 wt.% up to 38°C, can be
stored in carbon steel (CS) tanks, since the metal is passivated with an iron fluoride film
when the fluid is in contact with the metal. Hydrogen corrosion may occur in steel tanks.
Other grades of HF can be stored in tanks made of CS with natural rubber lining, polyethylene
or unplasticized PVC [11]
Pumps
Diaphragm pumps with TFE or polychlorotrifluoroethylene (CTFE) diaphragms can handle
anhydrous, 70 wt.% and electronic-grade HF.
Centrifugal pump materials depend on grade: Ni-Cu alloy of Alloy 20 is used for anhydrous
HF, Vinylidene chloride (VC)-lined steel for 70 wt.% and electronic-grade HF, and Pentonlined
steel or solid Penton for electronic grade HF [11]
Piping and fittings
Valves
Protective
Clothing
Anhydrous
and 70% wt HF can be transported in seamless CS piping. The rating and schedule
should be selected according to the operating pressure and corrosion allowance, with
Sch 80 and Sch 160 commonly used for both grades, respectively. CS with VC, TFE and FEP
lining is also used, depending on fluid temperature.
Electronic-grade HF can be transported in unplasticized PVC pipe
Butterfly valves: Hastelloy C is the best material for the stem and disk, with Alloy 20 also
exhibiting fair results. Common seat materials include: PVF, Hypalon and Viton; for pure
(100%) HF, only PVF or Viton should be considered
Neoprene and natural rubber gloves are excellent for handling hydrofluoric acid in all concentrations,
glove change is necessary before 8 hours
TABLE 13. SPECIFIC EQUIPMENT, PIPING, VALVES AND PROTECTIVE
CLOTHING GUIDELINES
Equipment
Tanks
HCl
Outdoor tanks are preferred for storing hydrochloric acid; some common measures of protection
when tank is placed indoors are coating the floor with asphalt or another corrosion
resistant material to prevent several damages in case of leaks or spills. The tank must be
provided with a vent so acid fumes do not accumulate in the tank and a drainage system so
maintenance can be performed periodically. Vents should be routed to a scrubber
Pumps
Piping and fittings
Valves
Protective
clothing
Pumps
similar to those used for H2SO4 and H3PO4 can be used.
Centrifugal pumps lined with, or constructed of TFE, PVDF of Derakane are commonly used.
Mechanical seals of carbon and ceramic faces with TFE or fluoroelastomer secondary seals,
and Hastelloy C metal parts, are also recommended [11]
CS piping with TFE, PVDF, Derakane or polypropylene lining is frequently used for HCl.
PVC or FRP piping have also been used, depending on fluid pressure
Butterfly Valves: common stem and disc materials include: lead or Hastelloy C. Common seat
materials include: PVF, Neoprene, Hypalon and Viton
For concentrations up to 40% neoprene and fluoroelastomer gloves are recommended for
handling hydrochloric acid. For concentrated acid, butyl gloves are suitable
which can compromise the safety and
toxicity levels allowed, therefore storage
tanks need proper venting that
shall be directed to a safe location
and treatment facility.
Operators handling hydrochloric
acid must wear protective equipment
and it is advisable for them to take a
shower and gargle with sodium bicarbonate
after manipulating the acid in
order to avoid teeth corrosion in other
activities performed by the operator.
Undesirable reactions can take
place between hydrochloric acid and
Authors
Alberto Baumeister is the
CEO and co-owner of the
Ecotek group of companies,
which is located in the City
of Knowledge, Panama (Calle
60, PH Obarrio 60, Piso 15,
Ofc. 15-A, Obarrio, Panamá,
Rep. De. Panamá; Phone:
+507-203-8490; Fax: +507203-8491;
Email: abaumeister@ecotekgrp.com).
He has
experience as coordinator and
senior process consultant in engineering projects
for the chemical, petrochemical, refining, oil and
gas industries. He has a Master's Diploma in
water treatment management from Universidad
de León (Spain, 2011), a specialization in management
for engineers at Instituto de Estudios
Superiores de Administración (Venezuela, 1990),
and a degree in chemical engineering from Universidad
Metropolitana (1987), graduating first
of his class. He has been a professor of the Chemical
Engineering School at Universidad Metropolitana
between 1995 and 2007 and has written
several technical publications for international
associations.
Sebastiano Giardinella
is the vice president and coowner
of the Ecotek group of
companies (same address as
above; Email: sgiardeinella@
ecotekgrp.com). He has experience
as process leader,
and in project planning and
control, in engineering projects
for the chemical, petrochemical,
refining, oil and gas
industries. He is a certified
project management professional (PMP), has
Master's Degree in project management from
Universidad Latina de Panamá (Panama, 2009),
and a degree in chemical engineering from
Universidad Simón Bolívar (Venezuela, 2006),
graduating summa cum laude; and is currently
a student of the M.Sc. in renewable energy development
at Heriot-Watt University (Scotland).
He is also professor of project management at
Universidad Latina de Panamá, and has written
technical publications for Chemical Engineering
magazine, international associations and academic
institutions.
Mayhell Coronado is a process
engineer of the Ecotek
group of companies (same
address as above; email:
mcoronado@ecotekgrp.com).
She has experience in the development
of conceptual and
basic engineering projects for
the oil and gas, and chemical
industries, as well as in support
to company management.
She has a degree in chemical
engineering from Universidad Metropolitana
(Venezuela), where she taught thermodynamics,
transport phenomena and general chemistry as
professor assistant, and has published a work on
the effects of microbial contamination in diesel
fuel used for thermal power generation.
CHEMICAL ENGINEERING WWW.CHE.COM OCTOBER 2012 33
the following compounds: chromate,
permanganate and sulfate. Such reactions
generate chlorine gas as a
result. A subsequent reaction occurs
with metal peroxide forming its corresponding
chloride.
When storing hydrochloric acid,
proper ventilation has to be ensured
in order to maintain the acid concentration
in air below the permitted
limit of exposure.
■
Edited by Gerald Ondrey

http://WWW.CHE.COM

Chemical Engineering October 2012

Table of Contents for the Digital Edition of Chemical Engineering October 2012