11

CONVERTING STONECONVERTING STONEINTOINTO

METALMETAL

EXTRUCTIVE METALLURGYEXTRUCTIVE METALLURGY

METAL CYCLEMETAL CYCLE

Ore Ore

Metal MetalMetalMetal

ArtifatcsArtifatcs

ProductionProduction

SmeltingSmelting CorrosionCorrosion

OXIDATION POTENTIAL OF SOMEOXIDATION POTENTIAL OF SOMEMETALSMETALS

EO (volts)Au Au+3 + 3e- -1.50Ag Ag+ + e- -0.80Cu Cu+2 + 2e- -0.34Pb Pb+2 + 2e- 0.13Sn Sn+2 + 2e- 0.14Fe Fe+2 + 2e- 0.44Ni Ni+2 + 2e- 0.25Zn Zn+2 + 2e- 0.76Al Al+3 + 3e- 1.66Mg Mg+2 + 2e- 2.37

STABILITY OF METALSTABILITY OF METALOXIDESOXIDES

OXIDEOXIDE ΔΔG(kJ)G(kJ)

AuAu22OO33 +163.2+163.2

AgAg22OO -10.8 -10.8

CuCu22OO -146.4-146.4

FeOFeO -244.4-244.4

SnOSnO -257.3-257.3

22

SPONTANEOUS REDUCTION OFSPONTANEOUS REDUCTION OFSILVER (AgSILVER (Ag++) by COPPER METAL) by COPPER METAL PRODUCTION OF COPPERPRODUCTION OF COPPER

BY PRECIPITATION WITHBY PRECIPITATION WITHMETALLIC IRONMETALLIC IRON

““HELVA MINESHELVA MINES””

GÜMÜGÜMÜŞŞHANEHANE

REDUCTION OF CuO BY Fe METALREDUCTION OF CuO BY Fe METALIs it possible??Is it possible??

CuCu+2 +2 CuCu (Metal) (Metal) EEoo = +0.34 volts= +0.34 volts

Fe (Metal) Fe (Metal) FeFe+2+2 EEoo = +0.44 volts= +0.44 volts

CuCu+2+2 + Fe + Fe Cu Cu + Fe+ Fe+2+2 EEoo = +0.78 volts= +0.78 volts

HELVA MINE

33

Color of water after precipitationColor of water after precipitation

Yellow-orange color is FeO (Rust)Yellow-orange color is FeO (Rust)

44

CuCu+2+2 + 2e + 2e-- Cu CuFe FeFe Fe+2+2 + 2e + 2e--

CuCu+2+2 + Fe + Fe Fe Fe+2+2 + Cu + Cu

The blue-Green color is dueThe blue-Green color is dueto the dissolved Cuto the dissolved Cu+2+2 ions in ions inwater. It is water. It is leaceh leaceh from thefrom the spoils by acidic water.spoils by acidic water.

55

REDUCTION OF METAL OXIDESREDUCTION OF METAL OXIDESBY CARBON MONOXIDEBY CARBON MONOXIDE

1.1. Reduction of metal ore with COReduction of metal ore with COMO + CO M + COMO + CO M + CO22

2.2. Conversion of COConversion of CO22 back to CO back to COC + COC + CO22 2CO 2CO

COMBUSTION OF CARBONCOMBUSTION OF CARBON

2C + O2C + O22 2CO 2CO22

COCO22 C + O C + O22

______________________________________________________C + COC + CO22 2CO 2CO

At 710 At 710 ooC, DG = DH - TDS = 0C, DG = DH - TDS = 0T>710 T>710 ooC, Equilibrium shifts to rightC, Equilibrium shifts to rightT<710 T<710 ooC, Equilibrium shifts to leftC, Equilibrium shifts to left

ELLINGHAM DIAGRAM FORZn, Ni, Mg, Mn, and Al

ELLINGHAM DIAGRAM FORAg, Hg, Sn, Cu, Pb and Fe

66

ELLINGHAM DIAGRAMELLINGHAM DIAGRAM

1.1. Lower the position of the metal oxide greater isLower the position of the metal oxide greater isthe affinity for oxygen.the affinity for oxygen.

2.2. Free energy (Free energy (DDG) of most elements decrease byG) of most elements decrease byincreasing temperature.increasing temperature.

3.3. The slope of carbon line is opposite of othersThe slope of carbon line is opposite of others

4.4. Any metal oxide with line above that of carbonAny metal oxide with line above that of carboncan be reduced by carbon at proper temperature.can be reduced by carbon at proper temperature.

5.5. More stable metal oxides at the lower sectionMore stable metal oxides at the lower sectioncannot be reduced by carbon (Al, Ca, Mn)cannot be reduced by carbon (Al, Ca, Mn)

http://www.jfe-21st-cf.or.jp/chapter_2/2b_1/htmlhttp://www.jfe-21st-cf.or.jp/chapter_2/2b_1/html

EVIDENCE FOR ANCIENTEVIDENCE FOR ANCIENTSMELTINGSMELTING

•• Generally carried out near minesGenerally carried out near mines

•• Remains of slags are mostly visibleRemains of slags are mostly visible

•• Other smelting tools such as bellows,Other smelting tools such as bellows,tuyers, molds, prills may be found.tuyers, molds, prills may be found.

•• Possible furnace structures may bePossible furnace structures may beexistingexisting

MERZMERZİİFON BAKIRÇAY SLAGSFON BAKIRÇAY SLAGS GÜMÜGÜMÜŞŞHANE KARADAHANE KARADAĞĞ

77

GÜMÜŞHACI KÖY SLAG HEAP REQUIREMENTS FOR SMELTINGREQUIREMENTS FOR SMELTING

•• A furnace that can reach high enoughA furnace that can reach high enoughtemperaturestemperatures

•• Fuel to supply the heat neededFuel to supply the heat needed

•• Bellows to reach temperatures over 1000Bellows to reach temperatures over 100000CC

•• Generation of reducing gas (CO) that canGeneration of reducing gas (CO) that canreduce the metal oxide to metalreduce the metal oxide to metal

•• Fluxing agents to reduce the melting pointFluxing agents to reduce the melting pointof rocks and mineralsof rocks and minerals

SMELTING FURNACESSMELTING FURNACES

•• Bowl or crucible processBowl or crucible process•• Shaft furnace processShaft furnace process•• Reverberatory furnaceReverberatory furnace

process (not used inprocess (not used inantiquity)antiquity)

BOWL FUENACE

88

SMELTINGSMELTINGCRUCIBLESCRUCIBLES

SMELTINGSMELTINGCASSITERITECASSITERITEIN A CRUCIBLEIN A CRUCIBLE

Metalik kalay tanecikleri

ANCIENT SHAFT FURNACEANCIENT SHAFT FURNACE

BOWLFURNACE

99

CRUCIBLE SMELTINGCRUCIBLE SMELTINGANCIENT BOWL FURNACE

FURNACEFURNACEWHERE SLAGWHERE SLAG

CAN BECAN BETAPPEDTAPPED

SHAFT FURNACESHAFT FURNACE

1010

SHAFTSHAFTFURNACEFURNACE

SMELTINGSMELTINGFURNACEFURNACE

WITHWITHTAPPINGTAPPING

From From AgricolaAgricola

FUELS FOR SMELTINGFUELS FOR SMELTING

1.1. Wood: Used extensively in antiquityWood: Used extensively in antiquity2.2. Charcoal: Made by removal of volatileCharcoal: Made by removal of volatile

components of wood under reducingcomponents of wood under reducingatmosphere. Extensively and efficientlyatmosphere. Extensively and efficientlyused in smelting.used in smelting.

3.3. Coal: Volatile constituents spoiled theCoal: Volatile constituents spoiled thesmelting processsmelting process

4.4. Coke: Made by the distillation of coal inCoke: Made by the distillation of coal inthe absence of air. Best fuel for thethe absence of air. Best fuel for theproduction of iron in blast furnace.production of iron in blast furnace.

CHARCOAL MAKING

1111

CHARCOAL REQUIREMENT FORCHARCOAL REQUIREMENT FORSMELTINGSMELTING

•• Charcoal to copper ratio for smelting oxideCharcoal to copper ratio for smelting oxideores is between 1:30.ores is between 1:30.

•• To prepare 5 Kg of copper one needs 150To prepare 5 Kg of copper one needs 150Kg of charcoal.Kg of charcoal.

•• Over 1000 Kg of fresh wood would beOver 1000 Kg of fresh wood would beneeded to prepare 150 Kg of charcoal.needed to prepare 150 Kg of charcoal.

•• This will take almost 5 man days of laborThis will take almost 5 man days of labor

1212

AIR SUPPLY TO REACH HIGHTEMPERATURES

BLOW PIPESBLOW PIPES

TUYERS FOR BLOW PIPESTUYERS FOR BLOW PIPESUSE OF BLOW PIPES IN ANCIENTUSE OF BLOW PIPES IN ANCIENT

SMELTING FURNACESSMELTING FURNACES

Human lungs canHuman lungs canproduce produce intermitent intermitent flowflowof 40 l/min and 10-20of 40 l/min and 10-20l/min on continuousl/min on continuous

basis. This can heat abasis. This can heat asmall area over 1000small area over 1000 o oC.C.

1313

WHAT TEMPERATURE CAN BEWHAT TEMPERATURE CAN BEATTAINED BY HUMAN BREATH?ATTAINED BY HUMAN BREATH?

•• GIVEN: 70 Kg person who can sustain anGIVEN: 70 Kg person who can sustain anaverage expelled breath volume of 75average expelled breath volume of 75liter/min. (0.075 mliter/min. (0.075 m33/min)/min)

•• PURPOSE: To maintain a temperature ofPURPOSE: To maintain a temperature of12001200ooC, in a furnace with 25 cm internalC, in a furnace with 25 cm internaldiameter (0.049 mdiameter (0.049 m22))

•• REQUIREMENT: 3 mREQUIREMENT: 3 m33/m/m22 min of air. min of air.

BREATH COMPOSITIONBREATH COMPOSITION

75.875.86.06.05.25.213.013.0DeepDeep

74.874.86.06.03.83.815.415.4QuiteQuite

% N% N22

% H% H22OO

(Vapor)(Vapor)% CO% CO22% O% O22

BreathingBreathing

EffortEffort

BLOWPIPE GENERATION OF HEATBLOWPIPE GENERATION OF HEAT

Needed air flow rate = (0.049 m2)(3 m3/m2 min) = 0.147 m3/min

Heat generated/min = (0.147 m3/min)(2 MJ/m3) = 0.29 MJ/min

Average human breath generate approximately 1.3 MJ/min

0.29 MJ/min

Flow rate of air needed = = 0.22 m3/min

1.3 MJ/m3

Number of persons needed = 0.22 m3/min/0.073 m3/min person

= 3 Persons

Thus to maintain a furnace of 25 cm internal diameter at 1200oC,

Three persons are needed by using blowpipe

GENERATION OF HEAT USING AGENERATION OF HEAT USING ABELLOWBELLOW

•• Muscular mechanic power output of a 75 KgMuscular mechanic power output of a 75 Kgperson is 170 watts.person is 170 watts.

•• Human power can generate 18 watts of gasHuman power can generate 18 watts of gasflow with a 15 % efficient bellow.flow with a 15 % efficient bellow.

•• 18 watts can generate an air flow rate of18 watts can generate an air flow rate of3.6 m3.6 m33/min, which is equivalent to 7.1 MJ/min./min, which is equivalent to 7.1 MJ/min.

•• Thus one person can generate 73 times moreThus one person can generate 73 times moreheat by using a bellow compared to blowpipe.heat by using a bellow compared to blowpipe.

1414

BAG BELLOWBAG BELLOWTUYERS FORTUYERS FOR

BELLOWSBELLOWS

OPERATION OF POT BELLOWOPERATION OF POT BELLOWWITH A TUYERWITH A TUYER

OPERATION OF TUYEROPERATION OF TUYER

1515

OPERATION OF POT BELLOWOPERATION OF POT BELLOW

AcemhöyükAcemhöyük, , AksarayAksaray. Dated to 1900 BC. Dated to 1900 BC

POT POT BELLOWS

KültepeKültepe, , KayseriKayseri. Dated to 1900 BC. Dated to 1900 BC

POT BELOWPOT BELOWFROMFROM

DIFFERENTDIFFERENTARCHAEOL-ARCHAEOL-

OGICALOGICALSITESSITES

1616

PISTONBELLOW

1717

BELLOW (FROM AGRICOLA)BELLOW (FROM AGRICOLA)

GENERATION OF HEAT USING AGENERATION OF HEAT USING ABELLOWBELLOW

•• Muscular mechanic power output of a 75 KgMuscular mechanic power output of a 75 Kgperson is 170 watts.person is 170 watts.

•• Human power can generate 18 watts of gasHuman power can generate 18 watts of gasflow with a 15 % efficient bellow.flow with a 15 % efficient bellow.

•• 18 watts can generate an air flow rate of18 watts can generate an air flow rate of3.6 m3.6 m33/min, which is equivalent to 7.1 MJ/min./min, which is equivalent to 7.1 MJ/min.

•• Thus one person can generate 73 times moreThus one person can generate 73 times moreheat by using a bellow compared to blowpipe.heat by using a bellow compared to blowpipe.

FLUXES USED IN SMELTINGFLUXES USED IN SMELTINGFluxes are materials added to smelting furnace to reduce the Fluxes are materials added to smelting furnace to reduce the melting point of the charge. During smelting, fluxing agents melting point of the charge. During smelting, fluxing agents Combine with the unwanted infusible siliceous materials toCombine with the unwanted infusible siliceous materials toForm a fusible mass called slag Form a fusible mass called slag Components of slags:Components of slags:•• Basic Oxides such as CaO, MnO, MgO, FeO, ZnO, PbO, Basic Oxides such as CaO, MnO, MgO, FeO, ZnO, PbO, N N22O, KO, K22O which provide oxygen ions when dissolved in O which provide oxygen ions when dissolved in a slag. a slag.

MO M MO M+2+2 + O + O-2-2

•• Acidic Oxides such as SiO Acidic Oxides such as SiO22 that absorbs oxygen ions provided that absorbs oxygen ions provided by the basic oxides. by the basic oxides.

SiO SiO22 + 2O + 2O-2-2 SiO SiO44-4-4

1818

FLUX COMPOSITIONFLUX COMPOSITION

A proper balance of iron oxides (basic) and silicates A proper balance of iron oxides (basic) and silicates (acidic) during copper smelting can produce a fluid (acidic) during copper smelting can produce a fluid slag known as Fayalite (Feslag known as Fayalite (Fe22SiOSiO44).).

nnMOMO - 3(n - 3(nAlAl22OO33) + n) + nPP22OO55

Basicity of SlagBasicity of Slag = = 2n2nSiOSiO22

Copper matte smelting produce slag that contains Copper matte smelting produce slag that contains about 50% FeO and 38% SiOabout 50% FeO and 38% SiO22 which gives a basicity which gives a basicity value of 0.48. value of 0.48.

COMPOSITIONOF SLAGS

FeOFeOSiOSiO22

(CaAl(CaAl22SiSi22OO88))

TYPES OF SLAGSTYPES OF SLAGS

•• FAYALITHIC SLAG (Formed in bloomeryFAYALITHIC SLAG (Formed in bloomeryfurnace where wrought iron is produced)furnace where wrought iron is produced)

•• GLASSY SLAG (Formed in blast furnacesGLASSY SLAG (Formed in blast furnaceswhere cast iron is produced)where cast iron is produced)

•• FINARY SLAG (Formed in fineries whereFINARY SLAG (Formed in fineries wherecast iron is converted into wrought iron)cast iron is converted into wrought iron)

1919

ANALYSIS OF SLAGANALYSIS OF SLAG

•• Elemental composition is determined byElemental composition is determined byAAS, ICPE, Neutron activationAAS, ICPE, Neutron activation

•• Mineralogical analysis is determined byMineralogical analysis is determined byXRD, XRD, petrological petrological microscopemicroscope

•• Microstructure is determined by opticalMicrostructure is determined by opticalmicroscopy, SEMmicroscopy, SEM

FAYALITHIC SLAGFAYALITHIC SLAG (Iron slag) (Iron slag)

Gen. Comp.FeO: 60.5SiO2: 22.0CaO: 3.75

Al2O3: 5.86

WüstiteFeO : 67.1%SiO2 : 1.79%CaO: 0.34%Al2O3: 1.28%

FayaliteFeO : 43.9%SiO2 : 18.4%CaO: 1.75%Al2O3: 0.87%

AnorthiteFeO : 12.6%SiO2 : 22.1%CaO: 4.54%Al2O3: 10.3%

IMPURITIES IN COPPER ORESIMPURITIES IN COPPER ORES

•• Most copper ores contain certain amount ofMost copper ores contain certain amount ofimpurities such as As, Sb, Bi, Pb, Ag, Au, Ni, Coimpurities such as As, Sb, Bi, Pb, Ag, Au, Ni, Coand Zn.and Zn.

•• Trace elements from fuel, fluxes furnace liningTrace elements from fuel, fluxes furnace liningmay also enter the metal during smelting.may also enter the metal during smelting.

•• Iron is the major impurity since it is added as aIron is the major impurity since it is added as afluxing agent, copper obtained from low gradefluxing agent, copper obtained from low gradeores may have 2-10 % Fe.ores may have 2-10 % Fe.

•• These elements will partition between the metalThese elements will partition between the metaland the slag depending on the smelting conditions.and the slag depending on the smelting conditions.

2020

The impurities in copper oresThe impurities in copper orespartition between the metal and slagpartition between the metal and slag

SLAGSLAG METALMETAL BOTHBOTH Fe Fe CoCo Zn Zn Mn Mn NiNi As* As*

PbPb Sb* Sb*AgAgAuAu

* Volatile elements. * Volatile elements.

OTHER SOURCES OF MINOR ANDOTHER SOURCES OF MINOR ANDTRACE ELEMENTS IN COPPERTRACE ELEMENTS IN COPPER

•• Deliberate additions to form alloys at metalDeliberate additions to form alloys at metalworking centers (As, Sn, Sb, Pb, Zn)working centers (As, Sn, Sb, Pb, Zn)

•• Trace elements from fuel, fluxes and oreTrace elements from fuel, fluxes and orewhich enter the metal during smelting. Fe iswhich enter the metal during smelting. Fe isespecially diagnostic)especially diagnostic)