Kuliah 4-Pyrometallurgy 2014

PYROMETALLURGY -2

1. Termodinamika dan kinetika

2. Preliminary Treatment

3. Smelting Process and Furnace

THERMODYNAMICS AND KINETICS IN EXTRACTIVE METALLURGY

References

1. M. A. Rhamdhani, Appplication of Thermodynamics to Industrial Processes, Workshop materials, Swinburne Univ. of Technology, 2012

2. C. K. Gupta, Chemical Metallurgy: Principles and Practices, Willey-VCH, 2003

3. M. Bahrens, Solid State Kinetics, Lecture materials, Fritz Haber Institute, 2012

Content

Thermodynamics Fundamentals

Definitions and Basics Concepts

Energy, Energy Transfer and general energy analysis

0th law, 1st law, 2nd law and 3 rd law of thermodynamics

Ellingham Diagram

Content

Solid state Kinetics Fundamentals

Basics kinetic

Solid defects

Solid reactivity

Decomposisition reactions, sintering

Solid gas reaction

Solid solid reaction

Solid liquid reaction

Thermodynamics

Thermodynamics Science of energy

Therme: heat and dynamis: power

All activities and processes in nature involve some interaction between energy and matters

(source: Ref [1])

Thermodynamics

Classical thermodynamics: A macroscopics approach to the study of

thermodynamics that does not require a knowledge of the behavior of individual particles

It provides a direct and easy way to the solution of engineering problems

Statistical thermodynamics: A microscopic approach, based on the average

behavior of large groups of individual particles More difficult but potentially better for predicting

behavior of a system.

(source: Ref [1])

Definitions

The theory assume that Universe consist of system and surroundings,i.e.

Universe = System + Surroundings

System: a quantityof matter or a region in space chosen study Surroundings: the region outside the system Boundary: surface that separates the system from its surroundings (can be real or imaginary, fixed or movable)

Surroundings

System

Boundary

(source: Ref [1])

Closed, open, and Isolated Systems

Closed (control mass): No mass enter or leave the system. Energy may cross the boundaries.

Open (control volume): Mass and energy can enter/leave the system.

Isolated: No mass and energy can enter/leave the system.

(source: Ref [1])

Other Definitions

Property any characteristics of a system. Example: pressure P*, temperature T*, volume V and mass m

Thermal: thermal conductivity, thermal expansion

Electrical: electrical conductivity

Physicochemical: viscosity, surface energy, density

Mechanical: modulus of elasticity, strenth

Note: *In thermodynamic calcualtion, always use absolute temperature and pressure

State definition of a system (has certain properties)

Process when property(ies) change thus change of state

(source: Ref [1])

Energy

Various forms: Thermal, Mechanical, Kinetic, Potential, Electrical, Magnetic, Chemical, Nuclear

In SI system in Joule (J) or kJ sometimes express per unit mass (J/g) or unit time

(J/s=watt) Can be classified: Macroscopic Those a system posseses a whole with

respect to some outside reference frame, e.g. PE, KE Microscopic related to the mo;ecular structures and

activities internal energy (U)

(source: Ref [1])

Internal Energy, U

Sensible energy: the internal energy associated with the kinetic energies of the molecules.

Latent energy: the internal energy associated with the phase of a system.

Chemical energy: : the internal energy associated bonds in a molecule.

Nuclear energy: the tremendous amount of energy associated with the strong bonds within the nucleus of atom itself.

Thermal = sensible + latent Internal = sensible + latent + chemical + nuclear (source: Ref [1])

(source: Ref [1])

Variation of free energy and temperature

Standard free energy change is expressed by equation:

G0 = - R T ln K By the corresponding entropy (a measure of degree and enthalphy

change by the relation:

G0 = H0 T S0 ---- y = m x + c Note: Entropy: quantitative measure of the amount of thermal energy not available to do work/ a measure of disorder in closed system Enthalphy: heat content

Ellingham diagram Line 1: -Endothermic reaction with entropy decreasing (G is always positive)

-Line 3: -Exothermic reaction with entropy decreasing (the slope is positive)

-Line 2: -Endothermic reaction with entropy increasing.

-Line 4: -Exothermic reaction with entropy increasing.

Ellingham diagram

Ellingham diagram

Line 1: a typical case of phase transformation of reactant. Line 3: a typical case of phase transformation of product.

Ellingham diagram

KINETIKA DALAM METALURGI EKSTRAKSI

Referensi: Solid State Kinetics Malte Behrens Fritz Haber Institute of the Max Planck Society Department of Inorganic Chemistry [email protected]

HEAT GENERATION SUMBER DAN PEMBANGKIT PANAS

COMBUSTION OF CARBONACEOUS FUELS

Heat is generated during the combustion of carbonaceous fuels by air or oxygen

The quantity of heat generated on complete combustion of a unit weight of fuel calorific value

Heat is transferred to the charge by conduction, convection, radiation

Calorific Value of fuel

Generation of Heat

when carbonaceous fuel is burned by the stoichiometric amount of air, there is always a fraction that escapes combustion due to:

o the design of the reactor

o kinetics of the reaction itself

This represent heat loss

Generation of Heat

Carbonaceous fuels can be solid, liquid, or gaseous.

In metallurgy, gaseous fuels are more preferable than the types. Why??

Easily stored can be obtained free from sulfur leave no solid residue on combustion (ash)

Generation of Heat: coal

Coal, basic raw material which can be converted to a liquid fuel (coal liquefaction) by reaction with hydrogen under pressure, or to a gaseous fuel (coal gasification) by reaction with air and water vapor.

Types of coal: charcoal prepared by the carbonization of wood, and mineral coal that occurs in nature.

Generation of Heat: coal

Sulfur in coal is a problem of special importance because it is a source of pollution when coal is burned, and source of contaminating metals during their production.

Generation of heat: gas

Natural gas is a mixture of hydrocarbons that occurs in nature in underground reservoirs.

CH4 = 50 90% other CnHm

Small amount of N2 and CO2

Variable amount of H2S. It is removed from gaseous fuels by: passing the gases over a bed of heated ferric oxide which reacts forming a mixture of iron sulfides:

Fe2O3 + 3 H2S FeS + FeS2 + 3 H2O

http://www.energy

.alberta.ca/Natura

lGas/723.asp

Generation of heat: electric heating

Achieved by the following method:

Resistance heating based on the resitivity of the medium when an electric current is passed through.

Graphite electrode carrying the current may be used in the following way

Above the solid feed

Immersed in slag layer

Contacted to a solid charge

TUNGKU PELEBURAN METALURGI

Metallurgical Furnace

Hearth Furnace Vertical Furnace Horizontal Furnace Rotary Kilns Retort Furnace Moving Grate Furnace Multiple Hearth Furnace Fluidized bed Furnace Tunnel Furnace Induction Furnace Plasma Furnace

1. Rotary kiln

1. Rotary kiln

Applications:

Roasting and calcining

Iron ore reduction

Ilmenite reduction

2. Multiple hearth furnace

3. Shaft furnace

4. Smelting, melting and refining in bath and flash smelting reactor

www.tms.org

5. Electrothermal reactor

Resistance Furnace

Arc Furnace

Induction furnace

Electron beam furnace

Plasma furnace

Laser beam furnace

6. Electron beam furnace

7. Fused salt electrolytic cell

REFRAKTORI

Refractory

Refractory

Properties:

Refractory

PROCESS: PRELIMINARY, SMELTING, REFINING

Preliminary Treatment

Preliminary Treatment

Thermal Pretreatment

Alkali Fusion

Sulfation of Oxide

Oxidation of Sulfide

Matte Formation

Chlorination

Fluoration

Alkali Fusion

Alkali fusion ini merupakan metode yang melibatkan pemanasan bijih atau konsentrat dengan suatu alkali atau alkali tanah untuk mengkondisikan mineral yang berharga siap untuk dilakukan proses berikutnya. Metode ini biasa digunakan untuk oksida dan batuan silikat dan pada sedikit sulfide

Alkali Fusion

Reagent Melting Point 0C Aplikasi

CaO CaO-Na2CO3*

NaCl Na2CO3

Na2SO4 NaOH

Na2S**

2580 800 801 851

884

318.4

1180

Clays, Spodumene, Zircon Clays, Beryl

Vanadium dari Carnotite Bauxite, Clays, beryl, Chromite,

Wolfarmite Radium dari pitchblende

Beryl, Nb-Ta Ores, pasir zircon Sulfida

Alkali Fusion

Alkali fusion pada bauxite untuk menghasilkan aluminium, digunakan sebelum penemuan Bayer dengan metode pressure leaching. Pada proses ini, bahan baku halus diaduk dengan Na2CO3 dan CaO secara merata dan lalu dipanaskan di rotary kiln pada 1000 0C. dimana aluminium akan menjadi sodium aluminat.

2 Al(OH)3 + Na2CO3 2 NaAlO2 + CO2 + 3 H2O Ketika CaO bereaksi dengan SiO2 dalam batuan maka akan

membentuk dikalsium silicate yang tidak larut air. 2 CaO + SiO2 Ca2SiO4

Alkali Fusion

Mineral Fe dan Ti juga akan menyisakan senyawa yang tidak larut juga. Proses ini juga bisa digunakan untuk mengekstrak aluminium dari clays, seperti kaolinite, Al2(Si2O5)(OH)4, dan nepheline syenite, (Na,K)(Al,Si)2O4. Reaksi dengan kaolinite bisa dilihat pada persamaan dibawah ini.

Al2(Si2O5)(OH)4 + Na2CO3 + 4 CaO 2 Na2AlO2 + 2 CaSiO4 + CO2 + 2 H2O

Outline

Reduction of Nonferrous Oxides

Reduction of Halides

Reduction of Sulfides

Conversion of Sulfides

Reduction of Nonferrous Oxides

Introduction

Nonferrous Oxides reduced by carbon on an industrial scales are those of lead, zinc, and tin and to minor extent are those of copper, antimony, arsenic, nickel, and magnesium.

Nonferrous oxides reduced by hydrogen are

those of molybdenum and tungsten. while those reduced by metals are the oxides of

magnesium, boron, and vanadium (metallothermic reactions).

Oxides Reduced by Carbon

Lead Oxide

Lead sulfide the major lead ore is usually oxidized to oxide which is then reduced by coal to metallic lead in a blast furnace.

Rx: PbO + CO Pb + CO2 CO2 + C 2CO

Oxides Reduced by Carbon Lead Oxide

To prevent unwanted reaction (ex: Cu), enough sulfur is maintained in the charge so that copper can be separated as a matte.

Oxides Reduced by Carbon Lead Oxide

Oxides Reduced by Carbon Zinc Oxide

Zinc Oxide

Zinc Oxide is obtained by the oxidation of ZnS concentrate. Low grade zinc oxide and carbonate ores occur in nature


An important feature of the reduction of ZnO is the fact that the reduction temperature is above the boiling point of zinc which is 906 C. Zinc is thus obtained in the vapor phase from which it must be condensed.

Zinc vapor is very susceptible to oxidation by water vapor or CO2 arising from the reduction reaction.


Reduction is conducted by a variety of methods: product 97% Zn and is always followed by refining.

Oxides Reduced by Hydrogen

The most important nonferrous oxides reduced by hydrogen on an industrial scales are MoO3 and WO3. Both are volatile at high temperature.

The Three Steps of the Pidgeon Process (magnesium oxide)

1. Calcination of Dolomite,

CaMg(CO3)2 = CaO + MgO + 2CO2

2. Ferrosilicon Alloy Production ,

Fe2O3 + 4SiO2 + 11C = 2(Fe)Si2 + 11CO

3. Silicothermic Reduction of MgO by Ferrosilicon,

2MgO + 2CaO + (Fe)Si = 2Mg(g) + Ca2SiO4(s) + Fe

Oxides Reduced by Metals

Reduction of Halides

Introduction

Metals produced by the reduction of their halides are usually the reactive metals that cannot easily be prepared by the reduction of their oxide.

Halide of these metals may be reduced by hydrogen or by metals.

Reduction of Sulfides

Reaksi konversi

Transformasi sulfida logam menjadi logam oleh udara atau oksigen.

Mekanisme: 2 MS + 3/2 O2 MO + SO2 (exotermik)

2 MO + MS 3 M + SO2 (endothermik)

----------------------------------------------

MS + O2 M + SO2 (exothermik)

Tembaga: 2 Cu2S + 3 O2 2 Cu2O + 2 SO2 H = -184 kcal

2 Cu2O + Cu2S 6 Cu + SO2 H = + 28 kcal

Cu2S + O2 2 Cu + SO2 H = - 52 kcal

Syarat terjadi reaksi konversi

Sulfida dapat dipanaskan hingga temp tertentu pada laju pemanasan yang memadai tanpa volatisasi.

Oksida yang terbentuk harus bisa melarut dalam leburan sulfida sehingga interaksi sulfida-oksida terjadi dengan cepat.

Logam yang terbentuk tidak boleh larut dalam leburan sulfida-oksida sehingga membentuk lapisan terpisah dan mendorong reaksi ke kanan.

Diagram fasa Cu Cu2S

Smelting

Ada 2 jenis peleburan:

Reduction smelting menghasilkan logam cair tak murni dan terak cair hasil reaksi logam oksida dan reduktor;

Matte smelting campuran cairan logam sulfida dan terak.

Jenis dapur:

Reverberatory/oxygen reverberatory furnace

Electric furnace

Flash smelting

Continous smelting

Blast furnace/low shaft blast furnace

Reverberatory smelting

- Reverberatory smelting are used for the matte smelting of fine flotation concentrate,

Where a relatively quiet operation is desired that will not blow too much of the fine

feed material out of furnace

Outokompu Flash smelting

Blast furnace

Reverberatory type of flash smelting furnace (Inco)

Continous matte smelting and converting furnace (mitsubishi process)

Smelting Electric furnace (nickel)

Stationary furnace

Cylindrical rotary furnace

Comparison of smelting process

Converting

Stationary smelting-converting

Top blown Rotary converter (Hoboken siphon converter)

Cylindrical rotating smelting-converting

REFINING

Slow cooling refining

Dross refining

Electro refining

Electrolytic cell

Documents

Kuliah 4-Pyrometallurgy 2014