CSIR - National Metallurgical Laboratory (Council of Scientific and Industrial Research)

Jamshedpur, Jharkhand

Summer Project Report

On

“Evaluation of Process conditions for Magnesium Production from Dolomite Ore Using CALPHAD Method”

(13th May-2013 to 21th June-2013)

Under the Guidance of:

Mr. Madan Mohanasundaram Scientist

MEF Division NML – Jamshedpur

Submitted by:

Rakesh Kumar Singh MSME Department MANIT- Bhopal

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CERTIFICATE This is to certify that Mr. RAKESH KUMAR SINGH B.Tech. Final Year of Material Science & Metallurgical Engineering, Maulana Azad National Institute of Technology, Bhopal, has done a summer project entitled, “Evaluation of Process conditions for Magnesium Production from Dolomite Ore Using CALPHAD Method” submitted at National Metallurgical Laboratory – Jamshedpur, is a record of an original work done by me under the guidance of Mr. Madan Mohanasundaram, Scientist, Metal Extraction and Forming Division (MEF), NML –Jamshedpur, during the period 13th May-2013 to 21th June-2013 and this summer project work has not been submitted for the award of any other Degree or Diploma / Associate ship / fellowship and similar project if any.

RAKESH KUMAR SINGH Project Guide

Date: - 21th June-2013

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ACKNOWLEDGEMENT First of all I am thankful of my project guide Mr. Madan Mohanasundaram under whose guideline I was able to complete my project. I am whole heartedly thankful to him for giving me his valuable time & attention & for providing me a systematic way for completing my project in time. I would like to express my sincere thanks to Mr. K.L. Hansda (Training Co-Ordinate) at CSIR -National Metallurgical Laboratory, Jamshedpur, India for arranging vocational Industrial project at their esteemed organization. My first experience of Industrial/R&D project has been successfully complete, thanks to the support staff of many friends & colleagues with gratitude. I wish to acknowledge all of them. However, I wish to make special mention of the following.

RAKESH KUMAR SINGH

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ABSTRACT

Extraction of metals is depending upon their ore processing, better route of

processing and freezing the better process condition. So, the purpose of this project

is to analyze the best process condition for extraction process for Magnesium

production by Magnotherm Method using CALPHAD. In this project, the

Dolomite ore along with Ferro-Silicon, Bauxite & Lime for observing the efficient

production of Magnesium. A computational thermodynamic analysis was

completed on a variety of slag compositions and reaction temperatures. All

available thermodynamic and phase diagram data for these systems were collected

and used to determine three key factors: (1) Efficient amount of Magnesium

Vapors (2) Aggressiveness of the slag (3) Fraction of solid in the bulk slag.

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Table of Content

Chapter 1:- Literature Review

1. Introduction of Magnesium

1.1. Thermal Properties…………………………………………………………….8

1.2. Mechanical Properties…………………………………………………………8

2. Magnesium Extraction

2.1. Pidgeon Process……………………………………………………………….9

2.2. Dow Process………………………………………………………………….10

2.3. NML Process………………………………………………………………...10

2.4. Magnotherm Process…………………………………………………………10

2.5. Magnola Process……………………………………………………………..11

3. Thermodynamics

3.1. Zeroth Law…………………………………………………………………..11

3.2. First Law of Thermodynamics……………………………………………….11

3.3. Heat capacity…………………………………………………………………12

3.4. Heat Balanced………………………………………………………………..13

3.5. Mass Balance………………………………………………………………...13

3.6. Second Law of Thermodynamics……………………………………………14

3.7. Gibbs Free Energy…………………………………………………………...14

3.8. Helmholtz Free Energy……………………………………………………....15

3.9. Third Law of Thermodynamics……………………………………………...15

3.10. Gibbs Energy Minimization……………………………………………….…15

4. FactSage

4.1. Info………………………………………………………………………….18

4.2. Databases…………………………………………………………………....18

4.3. Calculate…………………………………………………………………….19

4.4. Manipulate…………………………………………………………………..20

Chapter 2:- Experimental Detail

1. Methodology………………………………………………………………..22

Chapter 3:- Results & Discussions…………………………………....26

Chapter 4:- Conclusions…………………………………………..……..39

Chapter 5:- Future work…………………………………………..…….40

Chapter 6:- References……………………………………………………41

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List of the Figures

Fig No. Figures Page No. 1.1 FactSage Menu 17 2.1 The Main Menu of Mixture Module 23 2.2 The Main Menu of Equilib Module 23 2.3 The Main Menu of Phase Diagram: Last system 25 3.1 Magnesium amount at constant Temperature 28 3.2 Magnesium amount at constant Pressure 29 3.3 Effect of MgO at Binary Phase Diagram 31 3.4 Effect of Al2O3 at Binary Phase Diagram 32 3.5 Effect of SiO2 at Binary Phase Diagram 33 3.6 Effect of CaO at Binary Phase Diagram 34 3.7 Liquidus Projected Ternary Phase Diagram at MgO = 3gm 35 3.8 Liquidus Projected Ternary Phase Diagram at MgO = 4.5gm 36 3.9 Liquidus Projected Ternary Phase Diagram at MgO = 6gm 36 3.10 Liquidus Projected Ternary Phase Diagram at MgO = 8gm 37

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List of Tables

Table No. Table Page No. 1.1 Magnesium Ores 9 3.1 Magnesium Yield at Different ratio of Raw Material 26 3.2 Magnesium Amount at changing amount of Fe-Si 27 3.3 Magnesium Amount at changing amount of Bauxite 27 3.4 Effect of Lime Addition 30 3.5 Feed Requirement 30 3.6 Effect of MgO at the slag 31 3.7 Effect of Al2O3 at the slag 33 3.8 Effect of SiO2 at the slag 34 3.9 Effect of CaO at the slag 37 3.10 Effect of the MgO at the Viscosity of slag 37 3.11 Effect of the Al2O3 at the Viscosity of slag 38 3.12 Effect of the SiO2 at the Viscosity of slag 38 3.13 Effect of the CaO at the Viscosity of slag 38

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Chapter 1:- Literature Review

1. Introduction of Magnesium:

Magnesium is the lightest of all the engineering materials known and has good ductility, better noise and vibration damping characteristics than Aluminium and excellent cast ability. Alloying magnesium with Aluminium, manganese, rare earths, thorium, zinc or zirconium increases the strength to weight ratio making them important materials for applications where weight reduction is important, and where it is imperative to reduce inertial forces. It has good shielding ability for Electromagnetic Interface Frequency & Radio Frequency Interface. [1]Magnesium is placed in Rare earth metal group with Mg��

�� . It has Hexagonal Closed Pack crystal structure & paramagnetic behavior at the room temperature. The density of Mg is 1.738 gm-cm-3 (room temperature) & twining effect occurs across the (1013) planes. Here are some properties of Mg as followings:-

1.1 Thermal Properties:-

The melting point of pure Magnesium under atmospheric pressure is 650±1 oC [1]which is increases with increasing the pressure.

The boiling point of pure Magnesium under atmospheric pressure is 1090 oC[1].

Thermal Expansion of pure Magnesium at the room temperature is 24.8 µm-

m-1-K-1. [1]

The Specific Heat Capacity (Cp) at the room temperature is 1.025 kJ/kg.K. [1]

The latent heat of Fusion & Vaporization (∆L) is 360 to 377 kJ/kg & 5150 to

5400 kJ/kg respectively. [1]

The Heat of combustion (∆H) of pure Magnesium under atmospheric pressure

is 24900 to 25200 kJ/kg. [1]

1.2 Mechanical properties:- The Tensile Strength and Compressive Strength of cast rod (1/2 in.

diameter) of pure Magnesium is 90 MPa and 21 MPa respectively. [1]

The Hardness of the same sample is 16 (HRE) & 30 (HB). [1]

Magnesium has dynamic viscosity of liquid is 1.23 mPa.s at 650 oC and 1.13

mPa.s at 700 oC. [1]

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2. Magnesium Extraction:-

Ores and Minerals of the Magnesium are described below with the fair percentage

of magnesium present:- [2]

Name Composition Molecular Weight Percentage Mg

Magnesite MgCO3 84 29

Dolomite MgCO3-CaCO3 184 13

Brucite Mg(OH)2 58 42

Carnalite MgCl2-KCl-6H2O 278 9

Kieserite MgSO4-H2O 138 17

Serpentino Mg3Si2O7 240 30

Enstatite MgSiO3 100 24

Olivine Mg2SiO4 140 34

Kainite MgSO4-KCl-3H2O 249 10

Out of the above Ores; Magnesite, Dolomite & Brucite easily available in our country.

There are some extraction processes for the magnesium from its ores is following:

2.1 Pidgeon Process:-

The Pidgeon process involved essentially solid – state reactions. During the Pidgeon

Process, the following distinct stages are observed:-

1. The initial reaction takes place between ferrosilicon and CaO to produce a liquid

Ca-Si-Fe alloy, which permeates the briquette and forms a metallic network. This

reaction takes place rapidly at around 1000 oC and is mildly exothermic.

Table: 1.1:- Magnesium Ores

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2. Magnesium vapours are produced at the temperature 1550 oC by the reduction of

MgO by the Ca-Si-Fe alloy. At this stage, the pressure builds up rapidly, slowly

down the rate of reaction. The subsequent reaction rate is governed by the rate at

which magnesium can escape from the briquettes[4].

MgO (c) + Si (c) Mg (g) + SiO (g) ………...(i)

PSiO at 1550 K = 3.26 * 10-1mm Hg

2SiO (g) + 2CaO (c) 2CaO-SiO2 (c) + Si (c) ………...(ii)

PSiO at 1550 K = 8.24*10-3mm Hg

2.2. Dow Process:-

The Dow Process is generally applied for extraction of Magnesium from Sea

water. In this process first we add lime for thickening then mix with 10% HCl.

The final product contaminated with the magnesium oxide by which Mg

production occurs by the Electrolysis process[2].

MgCl2.6H2O = MgO + 2HCl + 5H2O ………...(iii)

In the Electrolysis Process, there is large amount of Flux required in electrolyte

composition for maintain fluidity and increases the density of bath. There are steel

wall of the cell use as the cathode and graphite anode are employed.

2.3. NML Process:-

The raw material for Magnesium Production is Dolomite, Ferro –Silicon (75%-

80%), Fluorspar. Dolomite is calcined in the temperature range 950-1100 oC[2].

The calcined dolomite and the ferrosilicon are first ground and then mixed with

1% fluorspar. Then make briquette of that mix charged in the Tubular retorts and

create vacuum. Magnesium is distilled from the charge and then condensed on a

removable sleeve at the cold end of retorts.

2.4. Magnotherm Process:-

A Magnotherm Process is essentially a ferrosilicon Reduction process similar to the

Pidgeon process, except that it is carried out at a temperature of 1500 oC [2]and the

bath is maintained in a molten state by the addition of alumina to form a molten slag.

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2.5. Magnola Process:-

In this process first take the raw material from the Asbestos mine then make the Pure

Brine by the acid leaching. The filtrate pure brine dry and produce Magnesium Chloride

which contain the oxide of Magnesium. Then by the Electrolysis Process we can able to

produce the Magnesium.

3. Thermodynamics:-

For economical Magnesium production, it is essential to calculate the raw material

requirement for the optimized temperature & pressure. Thermodynamics is required to

proceed in the right direction. Computational Thermochemistry based on the Calphad

method is a modern tool that supplies quantitative data to guide the development or the

optimization of materials processing. It enables the calculation of multicomponent phase

diagrams and the tracking of individual compounds, species or slag during Extraction

process in Furnace/Retort. There are some basic laws of thermodynamics which describe

below:

3.1. Zeroth Law:-

According to Zeroth Law of thermodynamics “Two systems in thermal equilibrium with

a third are in thermal equilibrium with each other”.

3.2. First law of thermodynamics:-

The first law of thermodynamics is nothing but a statement of the law of conservation of

energy means “Energy cannot be created or destroyed, but it can be converted from one

form to another”.

3.2(a) First Law in Terms of Internal Energy:-

The absorption of heat q increases the internal energy dE of the body by the amount ∂q

and performance of work w by the body decreases its internal energy dE by amount ∂w.

dE = ∂q - ∂w …..(1)

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3.2 (b) First Law in terms of Enthalpy:-

The first law of thermodynamics can be expressed in terms of the enthalpy instead of

energy.

dH = ∂q + VdP …..(2)

Where,

“d” indicates a differential element of a state function or state property.

“∂” indicates a differential element of some quantity which is not a state function.

3.3. Heat Capacity:-

The Heat capacity, “C” of a substance is defined as the amount of heat required to raise

its temperature by one degree.

C = ��

�� ……(3)

Heat Capacity at the constant volume is given by

Cv = (��

��)v = (

��

��)v …..{from equation (1) }

Heat Capacity at the constant Pressure is given by

Cp = (��

��)p= [

�(����)

��]p …..{from equation (1) }

Heat Capacity at the constant Pressure is also depending upon the temperature changes of

species which is denoted below in polynomial form:-

Cp (T) = a + bT + cT-2 + dT2 …….. (4)

Where,

a, b, c & d are the arbitrary constant which are stored for every species.

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3.4. Heat Balance:-

Heat balanced is depending upon the first law of thermodynamics. In furnace constant

pressure can be created easily than the constant volume, means at constant volume:-

Heat input = Heat output

∆H = q (at constant pressure)

Means the enthalpy increases of the system must be equal to the heat lost by the

surroundings. A Heat Balanced may be prepared in which the increases in enthalpy of the

system are tabulated in one column and the losses of the heat by the surroundings are

tabulated in other column. Any lack of balance of the two columns is due to experimental

error.

3.5. Mass Balance:-

Mass balance for any reactive system is denoted by the below diagram.

In – Out + gen – cons = accumulation [3]

A mass balance for a system is

FA - FA + GA = ��

�� ……… (5)

Where,

N is the mass of A inside the system.

GA

Rate of gen erat ion/consu mpt ion

FA 0

Rate of f low inF A

Rate of flow outSystem

GA

Rate of gen erat ion/consu mpt ion

FA 0

Rate of f low inF A

Rate of flow outSystem

Where, GA = ∫ �����

V is volume of the system, rA is total material flow rate in the system

o

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3.6. Second Law of Thermodynamics:-

There are two statements as applied to thermodynamics:

1) Heat cannot be transferred from low temperature to high temperature without

aid of external agency. Thus the law states the irreversible nature of

spontaneous heat flow.

2) A spontaneous (non – equilibrium), irreversible change, the entropy (S) of an

isolated system always increases.

∆S = +ve

Where ∆S = Sprod - Sreact

Entropy is a state function which is defines as:

dS = ��

� …………(6)

The standard entropy, So in terms of specific heat:-

So(T) = Sref + ∫��(�)

�

�

����dT ………….(7)

The enthalpy of formation, Ho in terms of specific heat:-

Ho(T) = Href + ∫ ��(�)�

���� dT …………(8)

Where,

Sref & Href are the entropy and enthalpy of the species at the reference temperature

Tref.

3.7. Gibbs free energy:-

Gibbs free energy is a state function and acts as a store of non-mechanical work or

energy available to the system for doing non-mechanical work. dG is a measure of the

work obtainable from a reversible, isothermal process occurring at constant pressure and

gives a direct indication of possibility of chemical reaction.

dG = dH – TdS ………….(9)

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3.8. Helmholtz Free Energy:-

Helmholtz Free Energy A acts like a store of work or energy available for doing work

(i.e. mechanical work and non- mechanical work together ) for the system , Hence, when

work ∂W is done, A decreases by dA.

dA = dE – TdS …………..(10)

3.9. Third Law Of Thermodynamics:-

According the third Law of Thermodynamics “The entropy of any homogeneous

substance, which is in complete internal equilibrium, may be taken as zero at the absolute

zero temperature (i.e., So = 0 at T = 0 K).

The third law of thermodynamics is finding of the Nernst who has given Nernst heat

theorem as following:

dG = dH – TdS …..{From equation (9)}

[Since, (�∆�

��) p = - ∆S ]

Put the value in above equation and differentiate with respect to T at constant pressure at

T=0 K.

(�∆�

��) p, = (

�∆�

��) p

This means that ∆G and ∆H are not zero at absolute zero but approach zero at absolute

zero, but their curves of ∆G vs. T and ∆H vs. T meet and both have the same slope at

absolute zero.

3.10. Gibbs Energy Minimization:-

The minimization algorithm determines internally the best set of independent system

components that it should use during the minimization procedure. So each phase

constituent is composed of one or more system components. At equilibrium the

chemical potential µ of each system component at each phase is equal:

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μ�� = μ�

�= μ�

�…

Equilibrium of a closed thermodynamic system is established if its Gibbs energy at

constant temperature and pressure has reached its minimum:

G’ (T, p,���) ≤ G (T, p, ni)

Gibbs energy of the system of one or more phases is then given as[3]:

G = ∑�∑� ���(μ�

�� + �� �������

�) ……….. (10)

The minimum value of Gibbs energy is found so that the masses of the system

components remain constant (mass balance constraints):

bj = ∑�∑�������

� ………… (11)

Where,

bj is the molar amount of the system component j,

ni is the molar amount of the constituent i in phase α,

aij is the stoichiometric coefficient of the system component j in constituent i.

There are several software/database packages with applications in materials science. These packages all contain large critically evaluated databases for thousands of compounds and hundreds of solution phases, as well as user interfaces of varying degrees of user-friendliness[6]:

HSC Chemistry MTS-NPL Thermo-Calc Thermodata FactSage

This is a complete database because all the other thermodynamic properties (H, Cp, µ, etc.) can be calculated by taking the appropriate derivatives of the G functions. For a given set of constraints (such as temperature, total pressure and total mass of each element) the software calculates the equilibrium conditions by minimizing the total Gibbs energy of the system. This is mathematically equivalent to solving all the equilibrium constant equations simultaneously.

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4. FactSage:-

FactSage was introduced in 2001 as the fusion of the FACT-Win and ChemSage

thermochemical packages[6]. The FactSage package runs on a PC operating under

Microsoft Windows and consists of a series of information, database, calculation and

manipulation modules that enable one to access and manipulate pure substances and

solution databases. The software calculates the equilibrium conditions by minimizing the

total Gibbs energy of the system for given a set of constraints.

The FactSage package runs on a PC operating under Microsoft Windows the FactSage

Menu (Fig.1) offers access to the various modules of the package. The modules are

grouped into four categories:

1. Info

2. Databases

3. Calculate

4. Manipulate

Fig.1.1 FactSage Menu

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4.1. Info:-

The General module provides slide shows (Microsoft Power Point and Adobe PDF

presentations) of all the modules as well as database documentation. The module also

includes information on the FactSage Family of Products and Services. These products

include[6]:

FactSage-Teach - The thermochemical teaching package based on FactSage

ChemApp - The thermochemistry library dynamically linked for software

ChemSheet - The spreadsheet tool for process simulation.

SimuSage - The component library for rapid process modeling.

CSFAP - ChemSage File Administrator Program.

OLI Systems - FactSage Interface: the link to the OLI aqueous databanks.

METSIM - FactSage Link for coupled chemical process simulation.

4.2. Databases:-

In FactSage there are two types of thermochemical databases – compound (pure

substances) databases and solution databases. Compound databases contain data for

stoichiometric compounds (of fixed composition) giving the properties as functions of

T and P. Solution databases contain parameters of models giving the properties of

solution phases as functions of composition as well as of T and P. The

Documentation, View Data, Compound and Solution modules permit one to list

and manipulate the database files.

4.2.(a) Documentation:-

Introducing extensive documentation and displaying calculated phase diagrams of

different compositions of material at particular Temperature, Pressure range.

Applications.

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4.2.(b) View Data:-

In this module enter the E-L-E-M-E-N-T or Compound or All with selecting the database

type, which we wish to view in the database. We can able to get the entire database [i.e.

Cp (T), H (T), G (T), S (T)] at different phase in the Temperature range.

4.2.(c) Solution & Compound:-

In these modules create the private compound & solution database which is not present

database. These compound/solution got by the experimental data for any chemical

reaction process. Once when we find the new compound/solution which is not present in

the database, input here in the define group as present in database.

4.3. Calculate:-

There is Reaction, Predom, EpH, Equilib, Phase Diagram and Optisage modules to

calculate the different data require for the compositions.

4.3.(a) Reaction Module:-

The Reaction module calculates changes in extensive thermochemical properties (H, G,

V, S, and Cp) & potential (volts) relative to the H2(g)/2H [+] standard reference electrode

for a single species, a mixture of species or for a Chemical Reaction.

4.3.(b) Predom Module:-

The Predom module one can calculate and plot isothermal predominance area diagrams

for one-, two- or three-metal systems using data retrieved from the compound databases.

4.3.(c) EpH Module:-

The EpH module is similar to the Predom module and permits one to generate Eh vs. pH

(Pourbaix) diagrams for one, two or three-metal systems using data retrieved from the

compound databases that also include infinitely dilute aqueous data.

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4.3.(d) Equilib Module:-

The Equilib module is the Gibbs energy minimization workhorse of FactSage and offers

great flexibility in the way the calculations may be performed. Equilib calculates the

concentrations of chemical species with a wide variety of tabular and graphical output

modes when specified elements or compounds react or partially react to reach a state of

chemical equilibrium under a large range of constraints. Equilib accesses both compound

and solution databases.

4.3.(e) Phase Diagram Module:-

The Phase Diagram module used to generate various types of phase diagrams for

systems containing stoichiometric phases as well as solution phases, and any number of

system components where the axes can be various combinations of T, P, V, composition,

activity, chemical potential, etc. The Phase Diagram module accesses the compound and

solution databases. The graphical output of the Phase Diagram module is handled by the

Figure module.

4.3.(f) OptiSage Module:-

The OptiSage Module is used to generate a consistent set of Gibbs energy parameters

from a given set of experimental data using known Gibbs energy data from well-

established phases of a particular chemical system. The assessor (user of OptiSage) has

to use his best judgment as to which of the known parameters should remain fixed, which

sets of parameters need refinement in the optimization and which new parameters have to

be introduced, especially when assessing data for non-ideal solutions.

.

4.4. Manipulate:-

It consist Results, Mixture, Fact-XML, Figure, Viscosity, Reset & Quit module which

are not directly use in FactSage. There are mainly use first five modules for examine the

data and phase diagram etc. which described below:-

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4.4.(a) Results Module:-

The Results module generates graphs from the output of complex equilibrium

calculations performed with Equilib Results (Equi*.Res) files. Depending upon the

selected axis variable(s) it may be necessary to specify in addition to the variable itself a

species or phase to which this variable is related.

4.4.(b) Mixture Module:-

Use Mixture to edit mixtures and streams for input to Equilib. The mixture module use

in making the mixture of the elements or compounds which are act as the reactants in the

reaction process. In the stream module is use to take the mixture of the product gasses as

and use them as a reactants which is very much helpful in recycling of heat/energy in the

chemical process.

4.4.(c) Fact-XML:-

The Fact-XML is an add-in to the Equilib program that enables you to edit the results of

a calculation and save customized outputs as templates. There is no limitation to the

number of templates. In this module we can change the unit, activity of species, graph

setup and draw etc.

4.4.(d) Figure Module:-

Use of Figure to Manipulate, edit and plot figure and phase diagrams already calculated

by FactSage. Graphical output from calculation modules such as Reaction, Predom,

Equilib or Phase Diagram can be Post-viewed and edited using the Figure module.

4.4.(e) Viscosity Module:-

The viscosity module for single-phase, liquid slags and glasses has been developed. It is

distinct from other viscosity models in that it directly relates the viscosity to the structure

of the melt, and the structure in turn is calculated from the thermodynamic description of

the melt using the Modified Quasichemical Model.

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Chapter 2:- Experimental Detail

5. Methodology:-

1. Extraction of magnesium get by the raw material Dolomite, Ferro-Silicon &

Bauxite with the following compositions (in Wt. %):-

Ferro – Silicon:-

Si = 70.10 % Fe = 27.19% Al = 2.02% Ca = 0.53 %

Calcined Bauxite:-

Al2O3 = 87.34% CaO = 1.35% SiO2 = 4.66% Fe (T) = 3.5%

Dolomite Ore (Dolo-3):-

MgO = 20.80% CaO = 29.87% SiO2 = 0.54% Al2O3 = 1.12% Fe2O3 = 1.24% Na = 0.12% K = 0.04%

2. By using the Mixture Module in FactSage, make mixture of Ferro-Silicon, Calcined Bauxite & Dolomite ore. Its to be mentioned mention that compositions are in mass percent unit and not in the “mole”. Save those mixtures for further process as shown in below fig:

3. Import all the mixture in the Equilib Module in different weight ratio of Ferro-

Silicon, Calcined Bauxite & Dolomite ore. Then calculate the weight of Magnesium vapours at the specific temperature and pressure. Be sure that the mass unit in the Equilib module should not in “Mole”.

Fig 2.1:- The Main Menu of Mixture Module[6]

Fig: 2.2:- The Main Menu of Equilib Module[6]

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4. The effective mass of magnesium is depend upon the minimum Gibbs Free Energy for the above mixture reaction at the specific temperature and pressure by the below formula:

G = ∑ ni ( ��� + RT ln Pi ) + ∑ ni��

� + ∑ ni ( ��� + RT ln Xi + RT lnγi)

+ ∑ ni ( ��

� + RT ln Xi + RT ln γi) …… [6] ……(12) Where,

ni : Moles Pi : Gas Partial Pressure Xi : Mole Fraction γi : Activity Coefficient

���: Standard Molar Gibbs Energy

5. When we get the best process condition for Magnesium Production from these

raw materials. Then add the Lime at that process condition and observed the influence of lime at the production of Magnesium.

6. Then by using the Phase Diagram Module for components of slag ( i. e. MgO, CaO, Al2O3 & SiO2 ) draw the binary phase diagram keep constant amount of two components for looking the effect of other two components on slag formation temperature & Calcium Silicate + slag temperature by which it’ll easy to determine the Low melting temperature of slag economically, Make sure about the below condition[8]:-

���

���� = 1.8 but for the furnace process this ratio can be use the

range of 2.2- 2.4

�����

���� = 0.26 but for the furnace process this ration can be use the range of

…………. (iv) Slag components weight percentage should be in the following range:

CaO = 54-58% SiO2 = 23-28% Al2O3 = 11-15% MgO = 3-8%

Ideal Gas

Pure Condensed Phases

Solution - 1

Solution - 2

Since,

Pi=Mg = ����������

����������������� * PTotal

0.30– 0.33

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7. Draw the Liquidus projection Ternary Phase Diagram of the slag components CaO, Al2O3 & SiO2 at the range of the MgO amount (3-8 wt. %) and the temperature range (1400oC – 1800oC) for looking the Liquidus area shrinkage and growing with the MgO amount And Temperature by superimpose all diagrams.

8. For low viscosity of the slag use the Viscosity module, in which keep different slag composition ratio of the MgO, CaO, Al2O3 & SiO2 components with keep in mind above ratio and slag components amount at the temperature range 1400oC – 1700oC.

9. Finally with keep in mind Low slag Viscosity, Low Slag melting Temperature &

optimum temperature and Pressure, determine the amount of raw material.

0.026136 atm

Fig 2.3:- The menu of Phase Diagram: Last system

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Chapter 3:- Results & Discussions

1. Take amount of the raw materials in different weight Ratio at Temperature range 1500oC-1700oC & Pressure 10mm – 30mm Hg.

1.1. Keep Calcined Bauxite & Ferro –Silicon Amount constant, increase the

amount of Dolomite (Dolo-3).

Ratio ( Dolo-3:Bauxite:Ferro-Silicon) (x100 gm.)

Temperature(oC)

Magnesium Yield (wt. %) at

10mm Hg 20mm Hg 30mm Hg

1:1:1

1500 1.58 0.29 0.05

1600 4.68 1.59 0.06

1700 9.69 5.12 2.84

2:1:1

1500 9.11 6.96 6.19

1600 10.13 8.30 7.37

1700 11.27 10.22 9.01

3:1:1

1500 13.14 11.01 10.28

1600 13.13 12.13 11.36

1700 13.51 13.11 12.57

4:1:1

1500 13.91 13.31 12.84

1600 14.37 13.89 13.51

1700 14.64 14.34 14.08

5:1:1

1500 14.43 13.98 13.67

1600 14.75 14.38 14.13

1700 14.93 14.66 14.47

6:1:1

1500 13.93 13.45 13.07

1600 14.16 13.94 13.77

1700 14.29 14.12 13.99

7:1:1 1500 12.45 12.13 11.88

1600 12.72 12.56 12.42

1700 12.80 12.74 12.68

Table: 3.1:- Magnesium Yield at different ratio of Raw

~ 27 ~

Magnesium Yield (Wt. %) is economically maximum for the ratio 5:1:1 but Amount of Magnesium (gm.) is economically maximum at the ratio 6:1:1. So, it has been decided to choose the latter Ratio for the further procedure from above table.

1.2. Increase amount of Ferro –Silicon from 100gm to 130gm at constant Dolomite & Bauxite amount.

Ratio ( Dolo-3:Bauxite:Ferro-Silicon)

Temperature(oC) Magnesium amount(gm.)

10 mm 20 mm 30 mm

6:1:1.1

1500 118.43 115.42 113.42

1600 120.52 117.99 116.27

1700 121.63 119.73 118.39

6:1:1.2

1500 122.98 119.59 117.31

1600 125.33 122.53 120.59

1700 126.49 124.30 122.75

6:1:1.3

1500 125.89 122.26 119.73

1600 128.48 125.50 123.37

1700 129.77 127.54 125.87

Since, we know that the Ferro-Silicon provide the Si which increase the reactant concentration by which reaction proceed forward that’s why magnesium amount increases as shown in reaction (i).

1.3. Increase the Amount of Calcined Bauxite at Ratio 6:1:1.3 with keeping the constant amount of Dolomite & Ferro-Silicon.

Ratio ( Dolo-3:Bauxite:Ferro-Silicon) Temperature(oC) Magnesium amount(gm.)

10 mm 20 mm 30 mm

6:1.5:1.3 1500 121.84 117.19 114.03

1600 125.43 121.85 107.27

1700 127.48 124.91 122.97

Table: 3.3:- Magnesium Amount at changing the amount of Bauxite

Table: 3.2:- Magnesium Amount at changing the amount of Ferro-Silicon

~ 28 ~

Means for the efficient production of Magnesium, the Optimum ratio of Dolo-3: Calcined Bauxite: Ferro-Silicon should be in 6:1:1.3.

2. Take the Magnesium amount at the optimum ratio of raw material at pressure

range 10 mm-30 mm Hg at constant temperature range 1500oC-1700oC.

3. Take the Magnesium amount at the optimum ratio of raw material at constant pressure range 10 mm-30 mm at temperature range 1500oC-1700oC.

127.5888

125.688

124.1784

122.904

121.7856

128.7744

127.08

125.7144

124.5528

123.528

129.6144

128.1456

126.9408

125.9016

124.98

130.1064

128.856

127.8216

126.9168

126.108126.0864

123.9984

122.3544

120.9696

119.7528

118

119

120

121

122

123

124

125

126

127

128

129

130

131

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Mag

nes

ium

Am

oun

t (g

m)

Pressure (mm Hg)

1550 oC

1600 oC

1650 oC

1700 oC

1500 oC

Fig: 3.1:- Magnesium amount at constant Temperature

~ 29 ~

By comparing both Fig 3.1 & Fig 3.2, we observe that at 20mm Hg pressure and 1600 oC we get the efficient amount of Magnesium 125.72 gm. Per 830 gm. Raw Materials. 4. Now add the Lime in the amount range (0 gm.-80 gm.) at 1600 oC & 20 mm

Atmospheric pressure at the optimum Ratio of raw material for observing its effect on the Magnesium Production Rate.

122.3544

124.1784

125.7144

126.9408

127.8216

120.9696

122.904

124.5528

125.9016

126.9168

126.0864

127.5888

128.7744

129.6144130.1064

123.9984

125.688

127.08

128.1456

128.856

119.7528

121.7856

123.528

124.98

126.108

118

119

120

121

122

123

124

125

126

127

128

129

130

131

1475 1500 1525 1550 1575 1600 1625 1650 1675 1700 1725

Ma

gnes

ium

Am

oun

t (g

m)

Temperature (oC)

20 mm

25 mm

10 mm

15 mm

30 mm

Fig: 3.2:- Magnesium amount at constant Pressure

~ 30 ~

Lime Addition(gm.)

0 10 20 30 40 50 60 70 80

Magnesium amount (gm.)

125.50

126.41

127.36

128.24

129.08

129.89

130.65

131.37

132.04

Solid Slag (wt. %)

13.816 16.95 19.91 22.67 25.24 27.58 29.7 31.57 33.19

Viscosity (poise) 1.024 1.014 1.003 0.99 0.977 0.962 0.945 0.928 0.909 When we add lime then from Reaction (ii), we observe that Partial Pressure of SiO is Low than Reaction (i) that’s why the Magnesium production increases.

5. Then Feed requirement for the 1 ton Magnesium and the slag composition of the process with increasing the amount of lime will be following:

Dolomite ore

(ton)

Calcined Bauxite

(ton)

Ferro-Silicon (ton)

Lime (ton)

Total Amount

(ton)

Energy Requirement

(kWh/ton)

Slag(ton)

Solid Liquid

4.781 0.797 1.036 0 6.614 1.4226*10^4 0.765 4.771 4.745 0.791 1.028 0.079 6.643 1.4336*10^4 0.944 4.624 4.711 0.785 1.021 0.157 6.674 1.4447*10^4 1.115 4.486 4.679 0.779 1.014 0.234 6.706 1.4559*10^4 1.278 4.358 4.648 0.775 1.007 0.309 6.739 1.4674*10^4 1.431 4.241 4.619 0.769 1.001 0.385 6.774 1.4790*10^4 1.575 4.134 4.592 0.765 0.995 0.459 6.811 1.491*10^4 1.707 4.04 4.567 0.761 0.989 0.523 6.84 1.5033*10^4 1.827 3.959 4.544 0.757 0.985 0.606 6.892 1.5159*10^4 1.935 3.894

6. Now draw the binary phase diagram between the Temperatures Vs. mass fraction of slag constituents for observing the Lowest Liq-Slag & Solid Slag (Ca2SiO4) formation temperature with keep in mind equation (iv).

6.1. Keep MgO mass fraction in range of 0-0.08 Wt. % with keep the constant mass fraction of Al2O3 & SiO2, draw the Binary Phase Diagram.

Table: 3.4:- Effect of Lime Addition

Table: 3.5:- Feed requirement

~ 31 ~

Take the Solid & Liquid slag temp & Wt. % at different mass fraction of MgO from above Binary Phase Diagram.

MgO(mass Fraction) 0.05 0.06 0.07 0.08

Solid Slag Temp. 1480.77 1524.62 1560 1590.15

Liquid Slag Temp. 1861.54 1831.08 1791.38 1745.23

Solid slag % 39.85 31.83 23.91 16.03

Liquid slag % 60.15 68.17 76.09 83.97

From the above data, we observe that as increasing the amount of MgO in slag Solid Slag temperature increase as decreasing the Liquid Slag temperature. Since as increasing the MgO in slag decreases the Magnesium amount as in reaction (i). That’s why solid slag percentage also decreases with increasing the amount of MgO in slag.

Fig: 3.3:- Effect of MgO at Binary Phase Diagram

Table: 3.6:- Effect of the MgO at the slag

~ 32 ~

6.2. Keep Al2O3 mass fraction in range of 0-0.20 Wt. % with keep the constant mass fraction of MgO & SiO2, draw the Binary Phase Diagram.

Take the Solid and Liquid Slag wt. % in the slag at the efficient solid slag temperature at different mass fraction of Al2O3 from above Binary Phase Diagram.

Al2O3(mass Fraction) .095 .098 .1 .105

Solid Slag Temp. 1652 1502.46 1436.92 1436.92

Liquid Slag Temp. 1748.92 1824.62 1897.54 1906.77

Solid slag % 12.03 31.68 44.69 70.02

Liquid slag % 87.97 68.32 55.31 29.98

Fig: 3.4:- Effect of Al2O3 at Binary Phase Diagram

Table: 3.7:- Effect of the Al2O3 at the slag

~ 33 ~

From the above data we observe that as increasing the amount of Al2O3 in slag decreases the solid slag temperature but increases the liquid slag temperature. Since alumina in slag also increases the CaO in slag that’s why solid slag will be increase as in reaction (ii).

6.3. Keep SiO2 mass fraction in range of 0-0.32 Wt. % with keep the constant mass fraction of MgO & Al2O3, draw the Binary Phase Diagram.

Take the Solid and Liquid Slag wt. % in the slag at the efficient solid slag temperature at different mass fraction of SiO2 from above Binary Phase Diagram.

SiO2(mass Fraction) .31 .3 .29 .29

Solid Slag Temp. 1436.92 1436.85 1577.69 1637.69

Liquid Slag Temp. 1832 1791.54 1746.15 1735.38

Solid slag % 58.33 46.79 29.46 12.82

Liquid slag % 41.67 53.21 70.54 87.18

Fig: 3.5:- Effect of SiO2 at Binary Phase Diagram

Table: 3.8:- Effect of the SiO2 at the slag

~ 34 ~

From the above data we observe that increasing the amount of SiO2 in slag decreases solid slag temperature with increasing the liquid slag temperature. Since increasing silica in slag increase the CaO [reaction (iv)] that’s why solid slag will form more as in reaction (ii).

6.4. Keep CaO mass fraction in range of 0-0.58 Wt. % with keep the constant mass fraction of MgO & Al2O3, draw the Binary Phase Diagram.

Take the Solid and Liquid Slag wt. % in the slag at the efficient solid slag temperature at different mass fraction of CaO from above Binary Phase Diagram.

CaO(mass Fraction) 0.54 0.55 0.56 0.57

Solid Slag Temp. 1662 1524 1437 1481

Liquid Slag Temp. 1786 1853.54 1906.5 1941.33

Solid slag % 16.58 34.91 47.01 53.93

Liquid slag % 83.42 65.09 52.98 46.07

Fig: 3.6:- Effect of CaO at Binary Phase Diagram

Table: 3.9:- Effect of the CaO at the slag

~ 35 ~

As we observe from the above data as increasing the amount of CaO in slag Solid temperature first decrease then again increase and liquid slag temperature increases. As increase CaO in slag also increase the silica [reaction(iv)] by which the slag formation will be more.

7. Draw the ternary phase diagram of slag components Al2O3, SiO2 and CaO at Magnesium amount range 3gm-8gm and Temperature range 1500 oC – 1700 oC at constant pressure 20mm Hg for observing the effective Liquidus Projection with combine effect of slag components:

1800oC

1700oC

1600oC 1500oC

Fig: 3.7:- Liquidus Projected Ternary Phase Diagram at MgO = 3gm

~ 36 ~

1800oC

1800oC

1700oC

1700oC

1600oC

1600oC 1500oC

1500oC

Fig: 3.8:- Liquidus Projected Ternary Phase Diagram at MgO = 4.5gm

Fig: 3.9:- Liquidus Projected Ternary Phase Diagram at MgO = 6gm

~ 37 ~

8. Now take slag composition of the components at the temperature range for measuring the viscosity of slag in melts state.

8.1. First keep Magnesium amount constant in the range of 1-8 wt. % and

make different composition of slag.

Slag Compositions (wt. %) Viscosity(poise) MgO CaO Al2O3 SiO2 1400oC 1500 oC 1600 oC 1700 oC

1 62.17 8.5 28.33 2.18 1.235 0.744 0.472 2 62.94 8.5 26.56 2.012 1.145 0.693 0.441 3 61.6 7.4 28 2.061 1.173 0.709 0.452 4 57.47 9.5 29.03 2.351 1.333 0.803 0.51 5 56.23 8 30.77 2.41 1.365 0.823 0.522 6 56 8.53 29.47 2.31 1.314 0.794 0.505 7 55.37 8 29.63 2.281 1.299 0.786 0.501 8 55.43 8 28.57 2.173 1.242 0.753 0.481

1800oC 1700oC

1600oC

1500oC

Fig: 3.10:- Liquidus Projected Ternary Phase Diagram at MgO = 8gm

Table: 3.10:- Effect of the MgO at the Viscosity of slag

~ 38 ~

As the amount of MgO increases (0-8 gm.), the viscosity of slag also increases (0.44-2.41 poise) at constant temperature and decreases with increasing temperature.

8.2. Now make the compositions of slag components (i. e. Al2O3, SiO2 &

CaO) with observing viscosity of slag at different temperature.

Slag Compositions (wt. %) Viscosity(poise) MgO CaO Al2O3 SiO2 1400 oC 1500 oC 1600 oC 1700 oC

4 56 10 30 2.521 1.425 0.857 0.543 4.1 56.1 9.6 30.2 2.504 1.415 0.851 0.539 4.2 56.3 9 30.5 2.478 1.402 0.843 0.534 4.4 56.5 8.4 30.7 2.441 1.382 0.831 0.527 4.5 56.8 7.9 30.8 2.403 1.361 0.819 0.520

As the amount of Alumina increases (7.9-10 gm.), the viscosity of slag also increases (2.521-0.520 poise) at constant temperature and decreases with increasing temperature.

Slag Compositions (wt. %) Viscosity(poise) MgO CaO Al2O3 SiO2 1400 oC 1500 oC 1600 oC 1700 oC

5 55 10 30 2.520 1.426 0.858 0.544 5.5 55.5 9.5 29.5 2.406 1.365 0.823 0.523 6 56 9 29 2.301 1.309 0.791 0.504

6.3 56.2 9.3 28.2 2.242 1.277 0.773 0.493 6.4 56.3 9.4 27.9 2.219 1.265 0.767 0.489

As the amount of Silica increases (27.9-30 gm.), the viscosity of slag also increases (2.520-0.489 poise) at constant temperature and decreases with increasing temperature

Slag Compositions (wt. %) Viscosity(poise) MgO CaO Al2O3 SiO2 1400 oC 1500 oC 1600 oC 1700 oC

5.5 56.5 9.5 28.5 2.291 1.303 0.788 0.501 5.8 55.6 9.6 29 2.357 1.339 0.809 0.514 6 55 9.7 29.3 2.402 1.364 0.823 0.523

6.2 54.5 9.8 29.5 2.435 1.382 0.834 0.530 6.3 54 9.9 29.8 2.483 1.408 0.849 0.539

As the amount of CaO increases (54-56.5 gm.), the viscosity of slag also decreases (2.483-0.501 poise) at constant temperature and also decreases with increasing temperature

Table: 3.11:- Effect of the Al2O3 at the Viscosity of

Table: 3.12:- Effect of the SiO2 at the Viscosity of slag

Table: 3.13:- Effect of the CaO at the Viscosity of slag

~ 39 ~

Chapter 4:- Conclusions

The process conditions for the production of Magnesium by Magnotherm Process is evaluated.

The optimum ratio of the raw materials is found to be Dolomite: Bauxite: Ferro-Silicon: Lime:: 6:1:1.3:0.5.

The optimum range of the operating process conditions are; 1600oC temperature & 20mm Hg Pressure for the given raw material and the feed ratio.

Maintenance of the liquid slag is evaluated through the phase diagrams and the calculation of the viscosity of the given slag. From the calculations, it is known that the minimization of silica in the slag and optimized use of the amount of Magnesia and Alumina leads to the maintenance of the slag in liquid form.

~ 40 ~

Chapter 5:- Future work

These studies can further continued in the open system, where continuous evaluation of the Mg can be obtained, which is an actual situation.

The kinetic study of the rate of dissolution of the ore in the slag bath is an important parameter for the Mg production.

CFD of the Magnesium reactor is important, as to access the internal process parameters and its distribution over the entire domain.

~ 41 ~

Chapter 6:- References 1. ASM Specialty Handbook, “Magnesium and Magnesium Alloys”. 2. H S Ray, “Extraction of Non Ferrous Metals”.

3. Gaskell, “Introduction to thermodynamics of materials”.

4. J.M Toguri and L.M. Pidgeon, Can. J. Chem. 39, 540 (1961). & O.

Kubaschewski and E. Ll. Evans. “Metallurgical thermochemistry”. Pergamon Press Ltd., London. 1958.

5. Ursula R. Kattner NIST-Gaithersburg. “Thermodynamic Modeling of

Multicomponent Phase Equilibria”. JOM 49 (12) (1997) 14-19.

6. FactSage® 6.4 Manual.

7. Melissa Marshall and Zi-Kui Liu, “A Computational Thermodynamic Analysis of Atmospheric Magnesium Production”. TMS (2001)

8. United states Patent 4190434, “Thermal Processes for the Production of Magnesium”.(14th Jun-1978)