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S ULFUR AND
S ULFURIC ACID by Marialie M. Enecio
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SULFUR
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WHAT IS SULFUR ?
nonmetallic element (about 0.06% of the earth'scrust 20 km deep) in a pure crystalline form
also called brimstone, it oxidizes and isresponsible for the characteristic smell of manyvolcanoes
used in a number of applications including themanufacture of gunpowder, insecticides, and
prescription drugs
it is also part of the vulcanization process forrubber
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HISTORY said to have been used by caveman to cleanse his
blood
used by Egyptians, Greeks and Romans asfumigant
used by Chinese inventors as main ingredient ofgunpowder
in 1900, sulfur deposits of the Texas and Louisianaprovide a new source of high-purity (99.5%)elemental sulfur and the golden age of U.S. sulfurindustry
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HISTORY
U.S. expertise allowed a considerable developmentof sulfur mining in Mexico just after World War II
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HOW IS IT PRODUCED ?
Sulfur from the Frasch Process
Sulfur from the Claus Process
Sulfur from Pyrites
Recovered Sulfur from Fuel Gases
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FRASCH PROCESS
invented by Herman Frasch in 1891 process for extracting sulfur from sulfur-
bearing calcite deposits
three concentric pipes are lowered down abore-hole to the ore where superheated waterat 165C is pumped down the outermost pipeand compressed hot air is blown down the
innermost pipe which forces a frothy mixture ofmolten sulfur up the middle pipe
very pure sulfur is produced
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CLAUS SULFUR RECOVERY PROCESS
2H 2S + SO 2 ==> 3S + 2H 2O
H2S is separated from the host gas streamusing alkanolamines
it is then fed to the Claus unit, where it is convertedin two steps:
Thermal Step. The H 2S is partially oxidizedwith air. This is done in a reaction furnace athigh temperatures (1000-1400 deg C). Sulfuris formed, but some H 2S remains unreacted,
and some SO 2 is made.
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Catalytic Step. The remaining H 2S is reactedwith the SO 2 at lower temperatures (about200-350 deg C) over a catalyst to make more
sulfur.
This residual quantity, together with other trace sulfur
compounds, is usually dealt with in a tail gas unitwhich can give overall sulfur recoveries of about99.8%, which is very impressive indeed.
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S ULFUR FROM PYRITES
Pyrites is the term given to a variety of sulfide ores.
The salt dome deposits and sulfur recovered frompetroleum and natural gas are much more economical
sources. Pyrites are obtained either as run-of-mine or
beneficiated ore from straight pyrite deposits orrecovered as by-product flotation concentrates duringthe refining of iron ore.
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RECOVERED SULFUR FROM FUEL GASES
Removal of hydrogen sulfide during purification of sournatural gas, coke-oven gas and from petroleumrefinery by dissolving it in potassium carbonatesolution or ethanolamine
H2S is converted to sulfur via modified Claus process:
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Other sources include coke-oven gas and syntheticcrude oils from tar sands or shale oils.
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FURTHER DEVELOPMENT IN INDUSTRY
Waste sulfur can be transformed into a lightweightplastic that may improve batteries for electric cars.The new plastic has other potential uses, includingoptical uses.
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S ULFURIC ACID
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WHAT IS SULFURIC ACID ?-an oily, colorless liquid with no odor
-a key component in batteries, wastewater treatment, oreproduction, and fertilizer creation
-65% of all fertilizers available on the market today arecreated from a combination of this acid and otherchemicals
-created from inorganic materials through a process thatutilizes a special type of chemical reaction
-more than 40 million tons are produced annually in theUnited States alone
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HISTORY It was prepared by Johann Van Helmont ( c.1600 ) bydestructive distillation of green vitriol (ferrous sulfate)and by burning sulfur
A process for its synthesis by burning sulfur with
saltpeter (potassium nitrate) was first used by JohannGlauber in the 17th century and developedcommercially by Joshua Ward in England ( c.1740 ).
It was soon taken over by the lead chamber process,invented by John Roebuck in 1746 and since, improvedby many others
The contact process was originally developed ( c.1830 )
by Peregrine Phillips in England
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HOW IS IT PRODUCED ?
Lead Chamber Process
Contact Process
Wet Sulfuric Acid Process
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LEAD C HAMBER P ROCESS
In the original lead chamber process, sulfur andpotassium nitrate are ignited in a room lined with lead foilwhich was a batch process and resulted in theconsumption of potassium nitrate.
In 1835, Joseph Gay-Lussac invented a process forrecovering the nitrogen in nitrogen monoxide andrecycling it to replace the saltpeter as a source of
nitrogen.
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In this process, SO 2 is oxidized to SO 3 by the oxides ofnitrogen and the SO 3 thus formed is dissolved in steamto form H 2SO 4.
SO 2 + NO 2 > SO 3 + NO ; 2 NO + O 2 > 2 NO 2 SO 3 + H 2O > H 2SO 4
The classic lead chamber process consists of 3 stages;Glover tower, lead chambers and Guy-Lussac Tower.
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CONTACT P ROCESS
In the contact process, SO 2 obtained by burning of S oriron pyrities is catalytically oxidized to SO 3 in presenceof finely divided Pt or V 2O 5 as catalyst.
S + O 2
> SO 2 or4FeS 2 + 11 O 2 > 2 Fe 2O 3 + 8 SO 2
V2O 5 or Pt (673-732 K)
2SO 2 + O 2 2SO 3.
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WET SULFURIC ACID PROCESS Combustion - H2S is mixed with 02 (hot air) to
form sulphur dioxide (S02)
Oxidation - sulfur dioxide is combed with oxygen(oxidised) in order to form sulphur trioxide
Hydration - sulfur trioxide (S03) is mixed withwater (H20) to form sulphuric acid in gas form
Condensation - with the use of water cooling,the acid is condensed from gas form to liquidform
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FURTHER DEVELOPMENT IN INDUSTRY
Some examples of recent sulfuric acid-related patentssummarised in the report include:The use of ruthenium catalysts for the final bed of acontact sulfuric acid plant.
The use of certain metals for constructing heat recoveryequipment for use in the acid-making circuit of a sulfuricacid plant.Claimed improvements in the materials of constructionin handling the acid.
Claimed improvements in dealing with spent acid.Removing organic impurities from sulfuric acid withliquid or supercritical carbon dioxide.Process for manufacturing sulfuric acid from a gascontaining sulfur dioxide and steam.
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