Chemical Engineering July 2022 - 36

lighted here.
Plate heat exchanger. An important
field test was carried out on PHEs
manufactured from three materials.
These were exposed to seawater
with a North Sea salinity of 3.3-3.6%
(see Figure 3). Testing was carried
out at 45, 50, 60 and 70°C with 2
parts per million (ppm) continuous
chlorination over three months.
The first sample was S31254,
a 6% molybdenum and nitrogenalloyed
austenitic stainless steel
with extremely high resistance to
both uniform and localized corrosion.
It was developed especially
for oil-and-gas offshore platforms
and the pulp-and-paper industry,
yet at 45°C it showed crevice corrosion.
The nickel alloy C-276 suffered
shallow crevice corrosion and
transpassive corrosion. In contrast,
S32654 was resistant to crevice
corrosion at 70°C.
Condenser tubing. The first installation
of S32654 took place in the
1990s, when close to 94,000 m of
tubes (O.D. 24 × 0.7 × 7.815 mm)
were used to replace titanium condenser
tubes at Forsmark 1 and 2
nuclear power plants in Sweden.
This was followed by 56,000 m
of tubing at Ringhals, Sweden and
58,000 m at TVO in Finland. In total
these installations included more
than 200 km of 654 SMO condenser
tubes.
Pharmaceutical plant. Vent systems
in pharmaceutical plants can
be exposed to very aggressive
gases, such as hydrogen chloride.
S32654 was installed in the pilot
plant of a Swedish pharmaceuticals
company.
A variety of active substances have
been tested in this plant including
chloride-containing solutions with
pH values ranging from 0 to 14, with
successful results.
Fluegas desulfurization. S32654
has good potential for fluegas desulfurization
plant. For example, in
2017, Babcock Noells
specified
it for plates in absorption towers.
It can also be used for the scrubber
inlets of marine exhaust gas.
As the entry point for hot exhaust
gas, this is a particularly demanding
application.
Traditionally, Alloy 31 has been
36
the material of choice for this type
of project. It is an iron-nickelchromium-molybdenum
alloy with
added nitrogen. This fills the gap
between special alloyed austenitic
stainless steels and nickel alloys.
However, S32654 has a higher
mechanical strength than Alloy 31.
If the design of the inlet enables
this higher strength to be utilized
then it could offer weight savings
between 15 to 25%. Furthermore,
the lower nickel content of S32654
also makes it cost-effective and
more stable in price.
Waste incineration. Fluegas from
municipal waste incineration plants
can contain hydrogen chloride and
hydrogen fluoride due to the presence
of plastics, such as polyvinylchloride
(PVC) and polytetrafluoroethylene
(PTFE) in the garbage.
In 1995, a scrubber made of
S32654 was installed at a municipal-waste
incineration plant in Zeebrugge,
Belgium. Service conditions
in the most aggressive area included
exposure to 35,000 ppm of chlorides
at pH 0.5 and a temperature
of 80°C. The first inspection was
made at a shutdown after almost 15
months of continuous service. The
scrubber was found to be in excellent
condition.
Solvent recovery. When recovering
solvents from emitting air in
certain processes, solvent molecules
are trapped in active carbon
filters. After being saturated, the
filters are back-flushed with steam
at 100-120°C and the steam condensate
solvent mixture is later
cooled and separated.
Chlorides or hydrochloric acid in
the process can cause corrosion
of filter housings made of stainless
steel. Severe corrosion on 316L has
been reported after very short periods
of service when the solvent was
methylene chloride.
The first industrial application of
S32654 for this process was for two
active carbon filters at a facility in
Plymouth, England in 1992.
Pulp bleaching. Bleaching of pulp
in the paper industry exposes the
equipment to strongly oxidizing
and chloride-containing solutions,
sometimes at low pH levels. Comparing
the material options, conventional
stainless-steel grades are
susceptible to pitting and crevice
corrosion in bleaching processes
based on chlorine/chlorine dioxide,
but are resistant to bleaching based
on peroxide. Titanium is resistant to
chlorine/chlorine dioxide, but can
be susceptible to uniform corrosion
in peroxide solutions. Nickel-based
alloys are resistant to peroxide but
can suffer transpassive uniform corrosion
in chlorine dioxide solutions.
Being an iron-based alloy, S32654
is resistant to uniform corrosion in
peroxide and to transpassive corrosion
in chlorine dioxide. It also has
very high resistance to pitting and
crevice corrosion. This combination
makes it an ideal material for bleach
plant components.
One example where 32654 has
been used is a nozzle in a D-stage
bleach tower at a Swedish pulp
plant, replacing 316L, which lasted
only 4 weeks. The environment contains
3,000 ppm of chlorine dioxide,
the pH is 3-3.5 and the temperature
is 70°C. It has also been used for
D-stage filter washers in plants in
Canada, the U.S. and Indonesia. n
Edited by Gerald Ondrey
Authors
Rodrigo Signorelli is a technical
manager at Outokumpu, Americas
(Rua Bandeira Paulista 600,
An 7 Cj 71, 04532-001, Itaim
Bibi - São Paulo, Brazil; Phone:
+55-1124-951-924; Email:
sales.brazil@outokumpu.com).
Signorelli is a materials engineer
with a wealth of experience in applying
stainless steel in industrial
markets. He provides technical advice and support to
customers across the world and has played a key role
in launching new stainless-steel grades in his career.
He holds an MBA degree from Fundacao de Administracao
and a degree in materials engineering from
Universidade de Sao Paulo.
Jan Li is a technical manager at
Outokumpu, Asia (No. 288, Chenfeng
Road, Yushan Town, Kunshan,
Jiangsu Province, 215300
China; Phone: +86-512-50120358;
Email:
sales.china@
outokumpu.com). Based in Beijing,
Li has is a qualified metallurgist
with a masters degree in the
strength and fracture of welded
structures. He has worked with Outokumpu for over 20
years and has extensive experience in the marketing
development and sales of stainless steels, welding
consumables and industrial equipment. Li holds master's
and bachelor's degrees from Tianjin University.
He is also a certified senior welding engineer from the
Metallurgy Ministry of China.
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