<< Chapter < Page Chapter >> Page >
  1. Preliminary treatment. In general, there is an initial treatment of the ores to make them suitable for the extraction of the metals. This usually involves crushing or grinding the ore, concentrating the metal-bearing components, and sometimes treating these substances chemically to convert them into compounds that are easier to reduce to the metal.
  2. Smelting. The next step is the extraction of the metal in the molten state, a process called smelting, which includes reduction of the metallic compound to the metal. Impurities may be removed by the addition of a compound that forms a slag—a substance with a low melting point that can be readily separated from the molten metal.
  3. Refining. The final step in the recovery of a metal is refining the metal. Low boiling metals such as zinc and mercury can be refined by distillation. When fused on an inclined table, low melting metals like tin flow away from higher-melting impurities. Electrolysis is another common method for refining metals.

Isolation of iron

The early application of iron to the manufacture of tools and weapons was possible because of the wide distribution of iron ores and the ease with which iron compounds in the ores could be reduced by carbon. For a long time, charcoal was the form of carbon used in the reduction process. The production and use of iron became much more widespread about 1620, when coke was introduced as the reducing agent. Coke is a form of carbon formed by heating coal in the absence of air to remove impurities.

The first step in the metallurgy of iron is usually roasting the ore (heating the ore in air) to remove water, decomposing carbonates into oxides, and converting sulfides into oxides. The oxides are then reduced in a blast furnace that is 80–100 feet high and about 25 feet in diameter ( [link] ) in which the roasted ore, coke, and limestone (impure CaCO 3 ) are introduced continuously into the top. Molten iron and slag are withdrawn at the bottom. The entire stock in a furnace may weigh several hundred tons.

A diagram of a blast furnace is shown. The furnace has a cylindrical shape that is oriented vertically. A pipe at the lower left side of the figure is shaded yellow and is labeled “Slag.” It connects to an interior chamber. Situated at a level just below this piping on the right side of the figure is another pipe that is shaded orange. It opens at the lower right side of the figure. The orange-shaded substance at the bottom of the chamber that matches the contents of the pipe to its right is labeled “Molten iron.” The pipe has an arrow exiting to the right pointing to the label “Outlet.” Just above the slag and molten iron regions is narrower tubing on both the left and right sides of the chamber which lead slightly up and out from the central chamber to small oval shapes. These shapes are labeled, “Preheated air.” The region just above the points of entry of these two pipes or tubes into the chamber is a white region in which small rust-colored chunks of material appear suspended. This region tapers slightly to the bottom of the furnace. The region above has an orange background in which small rust-colored chunks are similarly suspended. This region fills nearly half of the interior of the furnace. Above this region is a grey shaded region. At the very top of the furnace, black line segments indicate directed openings through which small rust-colored chunks of material appear to be entering the furnace from the top. This material is labeled, “Roasted ore, coke, limestone.” Exiting the grey shaded interior region to the right is a pipe. An arrow points right exiting the pipe pointing to the label “C O, C O subscript 2, N subscript 2.” At the right side of the figure, furnace heights are labeled in order of increasing height between the outlet pipes, followed by temperatures and associated chemical reactions. Just above the pipe labeled, “Outlet,” no chemical equation appears right of, “5 f t, 1510 degrees C.” To the right of, “15 f t, 1300 degrees C,” is the equation, “C plus O subscript 2 right pointing arrow C O subscript 2.” To the right of, “25 f t, 1125 degrees C,” are the two equations, “C a O plus S i O subscript 2 right pointing arrow C a S i O subscript 3” and “C plus C O subscript 2 right pointing arrow 2 C O.” To the right of, “35 f t, 945 degrees C,” are the two equations, “C a C O subscript 3 right pointing arrow C a O plus C O subscript 2,” and, “C plus C O subscript 2 right pointing arrow 2 C O.” To the right of, “45 f t, 865 degrees C,” is the equation, “C plus C O subscript 2 right pointing arrow 2 C O.” To the right of, “55 f t, 525 degrees C,” is the equation “F e O plus C O right pointing arrow F e plus C O subscript 2.” To the right of, “65 f t, 410 degrees C,” is the equation, “F e subscript 3 O subscript 4 plus C O right pointing arrow 3 F e O plus C O subscript 2.” To the right of “75 f t, 230 degrees C,” is the equation, “3 F e subscript 2 O subscript 3 plus C O right pointing arrow 2 F e subscript 3 O subscript 4 plus C O subscript 2.”
Within a blast furnace, different reactions occur in different temperature zones. Carbon monoxide is generated in the hotter bottom regions and rises upward to reduce the iron oxides to pure iron through a series of reactions that take place in the upper regions.

Near the bottom of a furnace are nozzles through which preheated air is blown into the furnace. As soon as the air enters, the coke in the region of the nozzles is oxidized to carbon dioxide with the liberation of a great deal of heat. The hot carbon dioxide passes upward through the overlying layer of white-hot coke, where it is reduced to carbon monoxide:

CO 2 ( g ) + C ( s ) 2CO ( g )

The carbon monoxide serves as the reducing agent in the upper regions of the furnace. The individual reactions are indicated in [link] .

The iron oxides are reduced in the upper region of the furnace. In the middle region, limestone (calcium carbonate) decomposes, and the resulting calcium oxide combines with silica and silicates in the ore to form slag. The slag is mostly calcium silicate and contains most of the commercially unimportant components of the ore:

Questions & Answers

who are the alchemist?
Victor Reply
alchemy science of transmutation. typically it is aim at tranforming lead to or other base metals to gold and the creation of the philosophers stone which in reality isn't a stone it's something priceless something we all need for coming times. don't be fooled
read Corinthians 5 verses 50 to the end of the chapter then read revelations chapter 2 verse 17
The word "Alchemy" comes from the forgotten name for Ancient Egypt, Khemmet. Khem was the name for the Egyptian Empire, but the actual land of Egypt was called Khemmet because the "T" on the end of a word denoted a physical location on Earth and not just an idea.
What's the mass number of carbon
Charlie Reply
first Faraday's law
mass number of carbon is 12.
wat d atomic number of oxygen
atomic number of oxygen is 8
which quantum number divides shell into orbitals?
Tomiwa Reply
what is atom
Desmond Reply
an atom is a smallest indivisible part of an element
an atom is the smallest part of an element that takes part in a chemical reaction
wat is neutralization
Dubem Reply
when any acid reacts with base to decrease it's acidity or vice-versa to form salt and solvent.. which is called neutralization
explain buffer
buffer is a solution which resists changes in pH when acid or alkali added to it..
hello, who is online
buffer is the solution which resist the change in pH by addition of small amount of acid or alkali to it
neutralisation is the process of mixing of a acid and a base to form water and corresponding salt
how to solve equation on this
Princewill Reply
what are the elent of ionic and covalent bonding
what is gases
Wesike Reply
Its one of the fundamental sate of matter alone side with liquid, solid and plasma
What is chemical bonding
To my own definitions. It's a unit of measurement to express the amount of a chemical substance.
Ozoaniehe Reply
What is mole
It's the unit of measurements used to express the amount of chemical substance.
What is pressure
Stellamaris Reply
force over area
force applied per unit area
force applied per unit area
Why does carbonic acid don't react with metals
Aditya Reply
Why does carbonic acid don't react with metal
Some metals will react depending on their Standard Electrode Potential. Carbonic acid is a very weak acid (i.e. a low hydrogen ion concentration) so the rate of reaction is very low.
sample of carbon-12 has a mass of 6.00g. How many atoms of carbon-12 are in the sample
Emokiniovo Reply
a sample of carbon-12 has a mass of 6.00g. How many atoms of carbon-12 are in the sample
Sharmin Reply
an object of weight 10N immersed in a liquid displaces a quantity of d liquid.if d liquid displaced weights 6N.determine d up thrust of the object
ugonna Reply
how human discover earth is not flat
Jason Reply
We don't fall off. If set off in any direction in a straight line and keep going. You'll end up back where you started.
earth is spherical
Also, every other planet is spherical as that is the most energy efficient shape. gravity pulls equally on all areas. Sphere.

Get the best Chemistry course in your pocket!

Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Chemistry' conversation and receive update notifications?