Presentation on Chemistry Prepared By :- Pushpa (Applied Science Deptt. Gpes Meham)

Metallurgy The process of extraction of metals from their ores is called metallurgy.

Production of metals Mining of ores. Crushing and Grinding of ores. Pulverisation of ores. Concentration and Beneficiation of ore. Extration of metal from concentrated ore. Refining of metal.

Mining Five main types of mining: Open cast mining Underground mining Open pit mining Dredging Solution mining

Ore concentration Also called ore dressing, the aim is to increase the amount of metal in each tonne of ore. The ore is crushed then ground and concentrated, the following methods may be used: Gravity concentration Flotation Magnetic separation Amalgamation

Gravity concentration Some ores are heavier than the waste. The ore is shaken by a jolting box, or similar, while wet. Particles will separate into layers depending on weight, the metal may be removed as a layer.

Gravity Concentration

Flotation The fine particles of ore are swirled around in large tanks with air blown in and flotation agents added. The particles attach to the bubbles and float to the surface where the froth is skimmed off.

Magnetic seperation In the seperation of ores that have magnetic properties, the ore is ground and passed over a rotating drum. The drum has a magnet inside it which holds the magnetic ore particles as the waste falls outside the screen. The ore held on the drum can be released or scraped off.

Magnetic seperation http://www.youtube.com/watch?v=XZjPr8WZtas

Metal extraction The process of extracting metals from concentrates: Pyrometallurgy – furnace heat is used with a reducing agent (iron uses coke) and a flux to produce metal and slag waste. Hydrometallurgy – leaching dissolves ore in a solvent and then electrolysis is used to separate the metal.

Thermo-electrometallurgy Thermo-electrometallurgy. Aluminium can be extracted from salt or mineral mixtures by electrolysis. It uses a lot of electricity making it an expensive process. Blister copper is refined by electrolysis.

Extration Of Iron The extraction of Iron is a reductive process whereby oxygen is removed from the iron oxide by carbon monoxide. The process occurs within a Steel blast furnace lined with refractive(fire) bricks at temperatures from 800C upto 1900C. The Chamber is kept hot by jets of hot air at over 800C, giving it the name “Blast” furnace.

Starting Materials 2. Lime(CaCO3) Haematite ore 3. Coke

Extraction of Iron: Step1 Burning of Lime Iron ore, limestone(CaCO3) and coke are delivered to the top of the blast furnace, where the temperature is around 800C. The lime stone burns at 800C yielding calcium oxide(CaO) and Carbon Dioxide(CO2). CaCO3 CaO + CO2 The Calcium oxide causes impurities which are present with the ore to fall as a precipitate near to the bottom producing a layer of “slag”.

Extraction of Iron: Step 2 Production of Carbon Monoxide The carbon Dioxide yielded from the Burning of Lime passes over the coke. Coke is a coal like substance produced from the heating of Tar and Petrochemicals without heat and contains a high percentage of carbon. The Carbon atoms of coke remove a single oxygen from each molecule of CO2 producing carbon monoxide. CO2 + C 2 CO

Extraction of Iron: Step 3 Reduction of Iron The Carbon monoxide yielded from the reaction of Carbon dioxide and lime removes the oxygen from Iron oxide. Each Carbon monoxide molecule is capable of binding a single oxygen so 3 are used to completely remove all oxygen from the iron oxide. Fe2O3 + 3 CO -> 2Fe(s) + 3 CO2 The molten iron sinks to the bottom lowest level of the furnace, where it can be tapped off. The iron produced by this process is called pig iron and is 95% pure.

Extraction of Iron: overview Production of iron from it’s ore uses Carbon monoxide to reduce Iron oxide to iron atoms. 1.Lime burns CaCO3 -> CaO + CO2 2. CO2 reduced by coke to CO CO2 + C -> 2 CO 3. Iron oxide reduced by CO. Fe2O3 + 3CO -> 2Fe + 3CO2 Removes impurities : slag production

Extraction of Aluminium Aluminium is extracted using electrolysis because it is too reactive to be extracted using carbon.

Raw materials Bauxite :- ore containing hydrated aluminium oxide ,i.e Al2O3.2H2O. The ore is dissolved in cryolite ,i,e molten sodium aluminium fluoride (Na3AlF6) to lower the melting point approximately up to 900 degree celsius. Carbon electrodes.

The electrolysis cell Carbon anode Molten aluminium oxide Oxygen bubbles cathode Molten aluminium Steel case Temperature 900 C

Reactions in the cell At the cathode Al3+ + 3e-  Al At the anode 2O2-  O2 + 4e- The oxygen formed reacts with the carbon anodes to form carbon dioxide. Carbon anodes have to be replaced periodically because they get dissolved during the cell reaction.

OCCURRENCE OF COPPER Copper pyrite or chalcopyrite i.e CuFeS2 Chalocite (Cu 2 S) or copper glance. Malachite green [CuCO3.Cu(OH )2 Azurite blue [2CuCO3.Cu(OH)2]. Bornite (3Cu2S.Fe2S3) or peacock ore. Melaconite (CuO) etc.

STEPS INVOLVED IN EXTRACTION CONCENTRATION ROASTING SMELTING BESSEMERIZATION REFINING

CONCENTRATION OF ORE FROTH FLOATATION PROCESS

ROASTING The following reaction takes place. 2CuFeS2 + O2 è Cu2S + 2FeS + SO2 S + O2 è SO2 4As + 3O2 è 2As2O3 4Sb + 3O2 è 2Sb2O3    Cuprous sulphide and ferrous sulphide are further oxidized into their oxides. 2Cu2S + 3O2 è 2Cu2O + 2SO2 2FeS + 3O2 è 2FeO + 2SO2

SMELTING The roasted ore is mixed with coke and silica (sand) SiO2 and is introduced in to a blast furnace. The hot    air is blasted and FeO is converted in to ferrous silicate (FeSiO3). FeO + SiO2 è FeSiO3 Cu2O + FeS è Cu2S + FeO    FeSiO3 (slag) floats over the molten matte of copper

BESSEMERIZATION  Copper metal is extracted from molten matte through bessemerization. The matte is introduced in to Bessemer converter which uphold by tuyers. The air is blown through the molten matte. Blast of air converts Cu2S partly into Cu2O which reacts with remaining Cu2S to give molten copper.

BESSEMERIZATION 2Cu2S + 3O2 è 2Cu2O + 2SO2 2Cu2O + Cu2Sè 6Cu + SO2

REFINING OF COPPER Cu è Cu+2 + 2e- (at the anode) Cu+2 +2e-è Cu (at the cathode) This electrically refined copper is 100% pure

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