اسید سولفوریک

Sandvik SX – Sulphuric Acid Steel
An austenitic stainless steel developed by Sandvik in the early 70’s
Introduced by EDMESTON in 1984
UNS S 32615, ASME Code Case 2029-3
Chemical Composition:
Cr 16.5 - 19.5 % C 0.07 %
Mo 0.3 - 1.5 % Si 4.8 – 6.0 %
Ni 19.0 – 22.0 % Mn 2.0 %
Cu 1.5 – 2.5 %

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Introduction
Sulphuric acid is a chemical that is used in numerous industrial
processes as well as in the leaching of many metals from their
ores. It is produced from sulphur dioxide, which may be
generated by burning sulphur, it may be a by-product of a
metallurgical smelting process, or it may be produced by thermal
decomposition (regeneration) of spent acid. The sulphur dioxide
is reacted with oxygen over a catalyst at ~420° to 625°C to form
sulphur trioxide. The latter gas then reacts with water in the
absorbing towers to form sulphuric acid. This process is
exothermic and the acid can reach temperatures as high as 180°
to 200°C. Most of this energy is recovered by a range of means to
minimise energy consumption. Usually the acid is then cooled
from around 100°C to close to ambient for storage.
Materials
Traditionally materials such as acid-brick lined steel were used for
vessels, and ductile irons, such as Mondi® or low alloy austenitic
stainless steels such as 316 for piping, within a limited
temperature and acid concentration range. However, the
development of modern, high alloy stainless steels, with improved
resistance to hot concentrated acid has changed the materials
selection options. Table 1 shows the composition of some
stainless steels that are used with sulphuric acid. 304 and 316 are
the common austenitic grades that are widely used by the
chemical and process industry. Alloy 310 is a high chromium,
nickel austenitic alloy that has superior acid corrosion resistance
compared with 304 and 316