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| Chemical process industries | ||||
| Mineral acids | ||||
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Well adapted stainless steel solutions for each process condition: | |||
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Hydrochloric acid: UR B6, UR B28 or UR B66 superaustenitic stainless steels may be used
for storage or transport of diluted hydrochloric acid at low temperature.
In any case, an inert gas covering is mandatory.Low chromium Nickel base alloys with high moly additions are required for higher concentration and temperature. |
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Sulphuric acid: this acid is used in a lot of industrial
processes including phosphoric acid, titanium dioxide , hydrometallurgy
(Zn, Cu, Ni), textile industry… A large variety of stainless
steels including austenitic 316L, duplexes
UR 45N and UR 52N+,
superaustenitics UR B6, UR B28, UR B66,
and high silicon URS1 may be selected,
depending on acid concentration, temperature and impurities. |
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Nitric acid: depending on the process conditions
(acidity, redox potential, impurities, temperature), INDUSTEEL offers
a whole range of stainless steels which provide excellent performance
in nitric acid media. | ||||
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| Chemical process industries | ||
| Organic acids | ||
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Stainless steels are widely used for manufacturing or handling of carboxylic acids. 316L as well as duplex grades UR 35N or UR 45N are resistant in pure boiling acetic acid. Formic acid is more aggressive : UR 35N may be used in 20% boiling and UR 2N+ in 50% boiling. In boiling 50% acetic + 50% formic acid, UR 47N+ and UR 52N+ are quite resistant. | |
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| Chemical process industries | ||
| Chlorinated hydrocarbons | ||
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Chlorinated hydrocarbons may be more or less aggressive depending on the molecule constitution. | |
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Chlorinated carboxyl acids are the most dangerous;
they are more aggressive than their corresponding acids due to the
inductive effect of Cl- on O-H bond which causes higher
dissociation. For example, super-austenitic grades like UR B26 or UR B66 must be selected
even at low temperature in monochloracetic acid. |
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Other chlorinated organic species: the main detrimental
process is hydrolysis which can form HCl. This process depends on
the chemical structure of the molecule . Most aggressive are Aliphatic
chlorine with Cl- bonded to a saturated atom (CH3-CH2Cl)
. In such media, those which are not able to mix with water are the
most dangerous since low pH may be reached in the water phase; UR B26, UR B28 or UR B66 are to be
selected. Aliphatic chlorine with Cl- bonded to an unsaturated
atom (CH2=CHCl) are few aggressive while Aromatic (cyclic) chlorine
compounds with Cl- atoms bonded to the aromatic ring (Phénylchloride,
Cyclohexyle) are not aggressive at all. |
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| Chemical process industries | |||||
| Fertilizers | |||||
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Urea: for decades, INDUSTEEL has been providing a
range of grades specially adapted for applications in urea processing.
Laboratory and in-plant testing showed that high chromium containing
alloys are the best materials for the more demanding process conditions
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316L Urea grade is the most common grade
used for reactors |
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Strippers are most often designed using UR 25.22.2
material |
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Thanks to their higher mechanical properties and better resistance
to Stress Corrosion Cracking, super-duplex grades like UR 47N+ may be an attractive option for high pressure condensers
and piping. |
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Phosphoric acid: extensive research confirmed by
in-plant testing and field experience showed that high chromium super
duplex UR 52N+ material is much more
resistant than 904L grade in hemi or di-hydrate process. The combination
of high repassivation rate and mechanical characteristics account
for the superior resistance of UR 52N+
to the synergistic effects of erosion by solid particles and corrosion. |
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Erosion-corrosion resistance properties makes UR 52N+ an attractive material for agitators or scrapers, which
offers over two to three times extended service life compared to 904L
alloy. A worldwide reference list for UR52N+ agitators / scrapers, reactors, decanters, desursaturation tanks … may be provided on request |
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Rotating filters may be designed using UR 45N+ or UR 52N+ instead of type 316L or 904L grades to resolve corrosion problems due to high chloride content. |
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The specific properties of the UR 45N
and UR 52N+ grades make these materials
very competitive compared to coated/brick lined carbon steels for
phosphoric acid storage tanks … … in addition UR 52N+ constitutes a reliable material for alternative storage of 54% P2O5 and 98% H2SO4. Designing storage tanks in duplex or superduplex stainless steels leads to: 
Material cost saving
Welding cost saving
Maintenance cost savingYou can order publications about this topic from the Publication Download portal. |
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| Chemical process industries | ||||||
| Pulp & paper | ||||||
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As far back as 1975, INDUSTEEL has been introducing the innovative concept
of duplex grades for the Kraft process which represents more
than 95% of pulp production worldwide. Since this period, stainless
steel use has been drastically growing as a result of the substitution
of carbon steel. A wide range of austenitic and duplex stainless steels are proposed by INDUSTEEL for the different steps of the pulp and paper production. |
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Chip preparation: erosion by wood and stone/ground
residues is the main problem to face. Special wear resistant low alloyed
steels with microcarbides and appropriate heat treament (Creusabro
4800 and Creusabro 8000) are widely
used with success. Nevertheless, if wood is highly polluted by chlorides,
the combination with humidity makes the conditions too aggressive
for carbon steels. In such conditions, the duplex grade UR 35N
which combines a high corrosion resistance to high mechanical characteristics
is an attractive alternative. |
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Kraft delignification: up to now,
UR 45N has been the most common material for batch digesters
and is becoming more and more used for continous digesters. Some evolution
may be anticipated as a result of recent studies . Thus, the molybdenum
free duplex, UR 35N might be used
for the regular Kraft process while high chromium super-duplex UR 47N+ could be necessary for high sulphidity/high temperature
newer Kraft process. |
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Washing – Bleaching: this quite complex operation
involves several steps and each plant operates its own process conditions.
The materials selection must be adapted to service conditions. 6Mo
super-austenitics such as UR B25, UR
B26 or UR B66 are to be used in
chlorine dioxide. In ozone, UR 35N may
be used at very low chloride level while UR 47N+
or UR 52N+ are suitable at high chloride
levels. In hydrogen peroxide, UR 35N is
recommended. In near neutral chlorine dioxide, UR B66 is suitable. For lignine extraction, UR 35N or 316L may be selected. | ||||||
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Tanks: carbon steel is suffering heavy corrosion
especially in white liquor tanks as a result of high causticity and
temperature. The duplex stainless steel UR 35N
has proved to be fully corrosion resistant and exhibits a much lower
life cycle cost. In general, the corrosion resistance of carbon steel is less critical in green liquor clarifiers and black liquor tanks. Nevertheless, periodic maintenance has to be done as a consequence of high velocity and air ingress which forms detrimental thiosulfate. UR 35N solves this problem. | ||||||
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Paper manufacturing: head boxes are a very critical
part of paper machines which require to be easily machined and electropolished
together with a good resistance to localized corrosion. The required
properties may be achieved with special 316L grades like Fastinox 17.12.2 or Fastinox 17.12.3 where
sulphur content and inclusions are closely controlled. In very aggressive conditions, the duplex grade UR 45N may be used. Paper machine frameworks are generally made of carbon steel and must be protected from corrosion by thin 316L colled rolled sheets. This complicated design may be advantageously replaced by solid UR 35N which combines a good corrosion resistance to excellent fatigue properties and high mechanical characteristics. | ||||||
| Some examples of equipments manufactured with INDUSTEEL products: | ||||||
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| Some examples of worldwide references in pulp and paper industry: | ||||||
 You can order publications about this topic from the Publication Download portal. |
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