Greenwood: Copper Extraction and Smelter Slag EarthCache
Greenwood: Copper Extraction and Smelter Slag
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Difficulty:
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Terrain:
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Size: 
(large)
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Greenwood is the Smallest City in Canada and was a booming mining
town in the late 1800's after the discovery of rich lodes of
copper-gold ore by prospectors in 1891.
Greenwood's smelter plant opened in 1901, processing copper- gold
ore from the nearby Motherlode Mine, and mines in Nelson and
Rossland. The smelter's 121 foot brick smoke stack is one of the
few surviving in the province, surrounded by mounds of black slag
that once glowed red hot.
To log this earthcache, you are going to have to e-mail me the
answers to the following questions and post the optional photo.
Information for the questions can be found on the cache page, and
at the Earth Cache location.
1) What is the approximate height of the slag pile across the road
in front of you?
2) What colour is the Greenwood smelter slag?
3) When was ore first found in Greenwood? (check the information
board at the coordinates)
4) What 3 elements poured from the furnaces of the Greenwood
Smelter? (check the information board at the coordinates)
5) What do you think the bell shaped objects on top of the slag
pile were for? (See cache page)
6) During what stage of copper extraction is copper recycling
performed? (See cache page)
7) Also, you can take a photo of yourself with the slag pile in the
background and submit it when you log the Earth Cache if you want
to share your adventure with others.
Copper Extraction
Most copper ores contain only a small percentage of copper metal
bound up within valuable ore minerals, with the remainder of the
ore being unwanted rock. A key objective in the metallurgical
treatment of any ore is the separation of ore minerals from within
the rock.
The first stage of the process is where the rock particles are
reduced in size thereafter followed by a process of physical
removal of the ore minerals from the rock, which includes roasting
and smelting.
Roasting:
In the roaster, the copper concentrate is heated to approximately
590 °C to produce covellite and sulfur dioxide gas. The reaction
which takes place is:
2CuFeS2(s) (copper concentrate) + 3O2(g)
--> 2FeO(s) + 2CuS(s) (covellite) + 2SO2(g) (sulphur
dioxide)
Smelting:
The covellite is then mixed with silica and coke (fuel, not the
soft drink) and smelted at 1200 °C to form a liquid. This
temperature allows reactions to occur rapidly, and allows the
byproducts and slag to melt, so they can be tapped out of the
furnace. In copper recycling, this is the stage where scrap copper
is introduced.
Several chemical reactions occur, for example iron oxides and
sulfides are converted to slag. The reactions for this are:
FeO(s) (iron oxide) + SiO2 (s) (silica) -->
FeO.SiO2 (l) (slag)
In another reaction the iron sulfide is converted to slag:
2FeS(l) (iron sulfide) + 3O2 + 2SiO2 (l)
--> 2FeO.SiO2(l) (slag) +
2SO2(g)
The slag is then discarded or reprocessed to recover any remaining
copper. When in full production, the smelter's three blast furnaces
were capable of treating 2,600 tons of ore per day.
As the final step in the smelting process, a small steam engine
pushed 4 or 5 cone shaped cars out to the slag heap where the
molten residue was dumped. Each slagpot held 25 tons of slag.
An interesting tidbit of information is that Greenwood has been
working with a California-based scientific company to develop a way
to extract the remaining metals from the slag. The remarkable thing
about this process is that once all the metals are gone, the
remaining minerals are perfect for making solar panels.
Sources:
http://www.vancouverisland.com/regions/towns/?townID=3405
http://en.wikipedia.org/wiki/Copper_extraction_techniques
http://en.wikipedia.org/wiki/Copper_sulfide
http://boundarysentinel.com/news/slag-solar-new-technology-will-change-face-greenwood
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