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Production of Pb

Production of Pb. - bluish-white color when freshly cut - 11,34g/cm 3 , melting point 327°C (10,69g/cm 3 ) - boiling point 1740°C (vaporizes at 550°C) - bad heat and electrical conductor - very soft, highly malleable. Usage. - výroba plášťů zemních kabelů

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Production of Pb

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  1. Production of Pb - bluish-white color when freshly cut - 11,34g/cm3, melting point 327°C (10,69g/cm3) - boiling point 1740°C (vaporizes at 550°C) - bad heat and electrical conductor - very soft, highly malleable

  2. Usage - výroba plášťů zemních kabelů - radiation shields - bullets and shot - lead-acid batteries - alloys: PbSb, solder - PbSn,antifriction alloy - PbSnSb- compounds: carbonate, oxides

  3. Occurance only in compounds galena - PbS cerussite - PbCO3 anglesite– PbSO4 - galena is the most important and widely used - the main impurities: Cu, Zn, Sb, Fe, As, Sn, Ag, Bi a big amount of gangue

  4. Occurance only in compounds galena - PbS cerussite - PbCO3 anglesite– PbSO4 - selective&collective (PbZn) concentrate: 40-70% Pb - other source(40%): waste batteries etc.

  5. Production Pb is produced mainly by pyro. way - Reduction smelting: 90% - ISP: 5 % - Others: 5%

  6. Production of Pb Roasting:removal of S, conversion of sulphide into oxide Sintering: coarsening agllomerate Reduction smelting Purification of lead bullion

  7. Roasting and sintering - Done together on a (Dwight-Lloyd)sintering machine - providing Pb content under 2%(mixing raw concentrate with returned agglomerate) - partial removal of Sn and Sb as As2O3 a Sb2O3

  8. Reduction smelting in lead blast furnace Obtain as much as possible lead bullion Dissolve as much as possible noble metals in Pb Move all gangue and Zn into slag Separate Cu off Pb in form of matte

  9. Reduction smelting in lead blast furnace 1. zone: under 400°C, drying and warming of charge .2. zone (reduction): 400-900°C, removal of water, decomposition of carbonate & sulfate, reduction of oxides, sulfidization of Cu3. zone (melting): above 900°C, streaming down liquid Pb to crucible, dissolution of Au, Ag, Cu, As, Sb, Sn etc. into lead bullion

  10. Reduction smelting in lead blast furnace - charge: coke, air, sinter, CaO PbO + CO = Pb + CO2PbO.SiO2 + CaO = PbO + CaO.SiO2PbO.Fe2O3 = PbO + Fe2O3PbSO4 = PbO + SO3PbS +2PbO = 3Pb + SO2PbSO4 + 4 CO = PbS + 4 CO2PbSO4 + Pb = 2PbO + SO2PbSO4 + SiO2 = PbO.SiO2 + SO3 Main reactions

  11. Reduction smelting in lead blast furnace

  12. Reduction smelting in lead blast furnace continuous taping, the principle of connected vessels Construction of the furnace

  13. Products of reduction smelting - lead bullion90-96% Pb, 0,2-2,5% Cu, 0,5-5% Sb, 0,1-0,8% As, 0,1-1,5% Sn, 0,06-0,5% Ag - slag25 - 32% SiO2, 34 - 40% FeO, 10 - 16% CaO, 5 - 8% Al2O3 + MgO, Pb, ZnO ( 30%) - BF gas CO, CO2, SO2, vapor, N2, dust (3-50 g/m3, 40-80% Pb, toxic)

  14. Refining of lead bullion - removal of dross and Cu- removal of As, Sn, Sb,- removal (recovery) of noble metals- removal of Bi

  15. Refining of lead bullion removal of dross: - stirring at 500°C - physical impurities ascending to the surface of lead melt (difference in specific gravity) - withdrawing as dross

  16. Refining of lead bullion removal of Cu: - limited dissolution of Cu v Pb at low temp., higher affinity of Cu to S than that of Pb - 1. step: lowering or increasing temperature of the melt just above of melting point of Pb - 2. step (350°C): adding elemental S to form Cu2S (under 0,002%)

  17. Refining of lead bullion removal of Sn, As, a Sb - higher affinity with oxygen, comparing to Pb - oxidation with air or with sodium nitrate - oxidation with air: 500°C to remove Sn, 700°C-800°C to remove As, Sb

  18. Refining of lead bullion removal of Sn, As, a Sb - oxidation with sodium nitrate (Harris’ refining) + fused sodium hydroxide, 500°C + oxides As, Sb, Sn have acidic character, reaction with oxides of alkli metals to form arsenate, antimonate (V), stannate

  19. Refining of lead bullion removal of Sn, As, a Sb - oxidation with sodium nitrate (Harris refining) 2NaNO3 = Na2O +2.5 O2 + N2 2As + 2.5 O2 =AsO5 Sn + O2 = SnO2 2Sb + 2.5 O2 = Sb2O5 As2O5 + 3Na2O = 2Na3AsO4 Sb2O5 + 3Na2O = 2Na3SbO4 SnO2 + Na2O = Na2SnO3

  20. Refining of lead bullion recovery of noble metals (Parkes’ method) - de-silvering lead by adding metal Zn to form inter- metallic compound (higher melting point, lower specific gravity) - 500C, stirring, cooling almost to consolidation, formation of foam containing noble metals (Ag, Au..) - removal of Zn by vacuum

  21. Refining of lead bullion removal of Bi atd1.) Kroll-Betterr’s method (under1%Bi) - adding Pb-Ca (3- 4% Ca) and Mg metal - slow cooling from 400°C to 360°C, foam forming atd2.) electrolytic refining (Bi >1%) - electrolyte : PbSiF6 + H2SiF6 (fluorosilicate and fluorosilic acid) - Pb cathodes - Bi and noble metals report into do anode slugde

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