Transcript refining ores ppt

Historical Availability of Metals
 Before 1800’s, only 10 were in use:
Cu, Sn, Fe, Pb, Au, Ag, Zn, Hg, Bi, Pt
 They were either found uncombined
Or
 Extracted by heating with Carbon
 More metals in use today than 200 years ago.
Why?
Abundance; need for metals with new
properties; ease of extraction
Extracting Metals from Ores
 Mineral: a pure crystalline compound found
in the Earth’s crust (aluminium oxide)
 Ores: a compound or mixture from which it
is economic (or profitable) to extract desired
substances (ie. Metals)
 Eg. Bauxite (aluminium oxide) is an ore but aluminium
silicates is not (not economic)
Extracting Metals from Ores
 5 tonnes bauxite mined produces one tonne Aluminium
 Bauxite is crushed to obtain alumina mineral (Al2O3 –
aluminium oxide)
Bauxite ore, a source of Al, is
the most abundant element
found in the earth's crust
Uses of Aluminium
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•
•
•
kitchen utensils
cans & foil
aircraft & rockets
Window & door frames
60% less conductive than Copper but
used for high voltage transmission lines
• Properties: light weight (low density); good tensile strength,
high resistance to corrosion
Digging for Bauxite
 Digging up the bauxite
The size of the scoop
Bauxite Reserves:
1985 1990 1993 2006 -
21 billion tons
21.8 billion tons
23 billion tons
25 billion tons
Rate of use in 2006: 177 million tons per year
How long will reserves last? 141 years
Extracting Metals from Ores
 Strong electric current pass through the molten alumina
(mobile ions of Al3+ and O2-) separating it into
Aluminium metal & Oxygen gas
 To keep it molten and to perform electrolysis, electricity
is a major cost
 Most smelters have their own electrical power plant
Energy Consumption
Electricity consumption by the aluminium
industry in the USA alone is equal to the
consumption of all of New York City
Alcoa Aluminum
smelter in Texas
requires 36 million
pounds of coal to fuel
operations
per day
Australia is the world’s leading producer of bauxite.
In 2010, it produced 71.5 million tons
Aluminium Industry
16,700 Employees
50 Years of Industry in
Australia
 5 Bauxite mines
 7 Alumina refineries
 6 Aluminium smelters
 12 Extrusion mills (19 presses)
 2 Rolled product plants
It a significant contributor the econonmy:
$5,055,402,000 in 2011
Factors Affecting Price
 Abundance & location of ores
 Cost of extracting the metal from the ore
 Cost of transportation (eg. to smelter)
 World-wide demand
Metal
Price/tonne
Al
$ 2 150
Cu
$ 3 250
Au
$ 17 000 000
Zn
$ 1 360
Pb
$ 1 070
Recycling
 it can be recycled indefinitely – 2/3 of the aluminum
ever produced since 1886 is still in use
 This does not change the fact that between 1990 and
2000, 7.1 million tons of aluminum cans (only cans!)
were wasted – enough to reproduce the world’s
commercial air fleet 25 times
 At an average scrap value of $.58/lb, this represents
$8.236 billion in lost revenue – just in cans!
Energy Expenditure
Metal
from natural ores
(MJ)
from recycled material
(MJ)
Aluminium
200
7
Copper
70
4
Mild steel
40
8
Recycling Steps
 1. collect used Al products from homes, etc.
 2. transport to central processing plant
 3. separate the cans
 4. Re-smelt the metal into ingots and transport them to
product manufacturers
Australians currently recycle more than 2 billion aluminium
cans each year. But 900 million aluminium cans are thrown
away every year ($15 million dollars in the landfill)
Benefits of Recycling
 Less energy: requires 5% of the energy needed
 No waste: 1 tonne recycled Al = 1 tonne new Al
 Less rubish
 Conserve Natural Resources: ores are non-renewable
Australians consumed more than 3
billion aluminium cans in 2002. Of
these, 47% were soft drink cans and
53% where alcoholic beverage cans.