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

- výroba plášťů zemních kabelů- radiation shields - bullets and shot- lead-acid batteries- alloys: PbSb, solder - PbSn,antifriction

alloy - PbSnSb- compounds: carbonate, oxides

Usage

only in compounds

Occurance

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

only in compounds

Occurance

- selective&collective (PbZn) concentrate: 40-70% Pb- other source(40%): waste batteries etc.

galena - PbS cerussite - PbCO3 anglesite– PbSO4

Pb is produced mainly by pyro. way

Production

- Reduction smelting: 90%- ISP: 5 %- Others: 5%

Production of PbRoasting:removal of S, conversion of sulphide into oxide

Sintering: coarsening agllomerate

Reduction smelting

Purification of lead bullion

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

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

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

Reduction smelting in lead blast furnace

- charge: coke, air, sinter, CaO

Main reactionsPbO + 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

Reduction smelting in lead blast furnace

Reduction smelting in lead blast furnace

Reduction smelting in lead blast furnace

Construction of the furnace

continuous taping, the principle of connected vessels

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 gasCO, CO2, SO2, vapor, N2, dust (3-50 g/m3, 40-80% Pb, toxic)

Refining of lead bullion

- removal of dross and Cu- removal of As, Sn, Sb,- removal (recovery) of noble metals- removal of Bi

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

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%)

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

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

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     

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

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

Refining of lead bullion