Aluminum production

Aluminum production

Multiple Select

Which is true for aluminum? (structure)

• BCC

• 1 unpaired electron

• covalent bonding

• atomic lattice

• ionic bonding

Multiple Select

Which is true for aluminum oxide? (structure)

• solid

• red

• covalent bonding

• atomic lattice

• ionic bonding

Poll

Which is the first step?

• alkaline dissolution

• calcination

• crushing & milling

• crystalisation & filtration

• mining

Mining bauxite

its ore, bauxite (colour from an impurity) is

often dug out of the ground in open-cast mines. The ore contains hydrated aluminium oxide: reffered as Al₂O₃·xH₂O – or sometimes Al(OH)₃ - Al₂O₃ mixture or AlO(OH).

Poll

What is next?

• alkaline dissolution

• calcination

• crushing & milling

• crystalisation

• filtration

Preparatory steps - physically

• crushing

• milling

Separation from impurities

• hot concentrated soda lye 

• conversion of oxide into sodium tetrahydroxo aluminate (Na[Al(OH)₄])

• Al₂O₃ + H₂O + NaOH = Na[Al(OH)₄]

• Al(OH)₃ + NaOH = Na[Al(OH)₄]

• AlO(OH) + NaOH + H₂O = Na[Al(OH)₄]

Multiple Choice

Name the process

• alkaline dissolution

• calcination

• crushing & milling

• crystalisation

• filtration

Poll

What is next?

• calcination

• crystalisation

• filtration

• smelting

Separation from impurities

• removal of impurities

• red mud

• 
  

RED MUD

• a mixture of solid and metallic oxides 

• red colour arises from iron oxides (up to 60w%)

• pH= 10-13

• silica, unleached residual alumina, and titanium oxide.

Multiple Choice

Name the process

• alkaline dissolution

• calcination

• crushing & milling

• crystalisation

• filtration

Separation from impurities

• extreme dilution

• against equlibrium system of Na[Al(OH)₄]

• Na[Al(OH)₄] -> Al(OH)₃ + NaOH

• precipitation

Multiple Choice

Name the process

• alkaline dissolution

• calcination

• crushing & milling

• crystalisation

• filtration

Getting alumina

• alumina (timföld) Al₂O₃

• purification of Al₂O₃ .x H₂O into Al₂O₃

• ready for electrolysis?

• The melting point of alumina Al₂O₃ is 2050°C. 

Multiple Choice

which lattice structure does it imply?

• atomic

• ionic

• metallic

• molecular

Smelting - preparatory steps

• Cryolite is added (Na₃AlF₆) to decrease the melting point below 1000°C.

• 1886 Charles Martin Hall and Héroult

• In 1888, Hall opened the first large-scale aluminium production plant in Pittsburgh (later became the Alcoa ).

• Hall–Héroult process

• Al₂O₃→   Al +    O₂

Important aluminium alloys

• Silumin: 12% Si content. → casting alloy (öntvényezés)

• Duraluminium alloy: 3.5-4.5% Cu, 0.5% Mg, 0-0.5% Mn. Extreme strength

• „Hydronalium” Al-Mg alloy. Corrosion resistant

• „Aldrey” alloys, for electric conductivity, corrosion resistance2.8-4.5% Cu, 0.9-1.6% Mg, 0.5-1.2% Mn, 0.2-0.7% Si.

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