ChE 140 - Sulfur and Sulfuric Acid

8/13/2019 ChE 140 - Sulfur and Sulfuric Acid

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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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ChE 140 - Sulfur and Sulfuric Acid