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Feedstock
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The main feedstock for sulphuric acid production
is sulphur dioxide, from several different sources:
- Sulphur mining (now the least significant
source)
- Recovery of sulphur from oil and gas
- Recovery of sulphur dioxide from metal smelting
and ore roasting, or flue gas emissions in power stations
- Recycling spent (used) sulphuric acid
Sulphur is mined as the element in volcanic
areas or above salt domes in buried sedimentary strata associated
with natural gas and crude oil deposits. The sulphur can be mined
directly or extracted using the Frasch Process, and used to produce
sulphur dioxide. (for more
details of this see the section on sulphur mining)
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Metal Ores
The metal ores Galena (lead) and Sphalerite
(zinc) are both sulphides and are usually found together. They
are mined in several countries including China, Australia, and
parts of North and South America. A considerable amount of sulphur
dioxide is produced when they are roasted to convert them into
the oxide.
In the past, the sulphur dioxide was vented to the atmosphere,
contributing to air pollution, but today the sulphur dioxide is
recovered from the emission gases. See the section on sulphur
recovery from oil for more detail.
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Acid Recycling
Acid recycling takes place in two ways.
A significant volume of sulphuric acid is now recovered, cleaned
and re-used on site using plant designed by a specialist company.
If it is too contaminated for this, it may be processed to produce
sulphur dioxide.
Acid recovery and concentration systems, remove impurities (often
volatile organic compounds) and concentrate the purified acid.
For more information on
this, click here.
The SATCO process generates sulphur dioxide from spent acid, and
this can then be used directly in the manufacture of more sulphuric
acid. Click here for more information.
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Sulphur is recovered from
oil and natural gas and now accounts for about 70% of all sulphur
used. It is present in both crude oil and natural gas as hydrogen
sulphide, H2S, or as alkyl sulphides. These have to be removed
before further use to meet increasingly strict sulphur emission
targets. Hydrogen sulphide is also highly toxic and strongly corrosive
to equipment used, and will poison catalysts used, for example,
in ammonia production.For
more details of this see the section on sulphur
recovery from oil.
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Feedstock Shift
The proportions of sulphur dioxide from metal
smelting, flue gas recovery, recovery from oil/gas and acid recycling
are growing in response to increasingly strict controls on permitted
sulphur dioxide emission levels to protect air quality. This is
at the expense of direct mining and pyrites roasting. |
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