Cairo University

Cairo University Cairo University - Start

2017-11-29 28K 28 0 0

Cairo University - Description

. Faculty of Engineering. 2nd year. Dept of Metallurgy . HelloOo….. 2. Extraction of Aluminum. ID: 611263 Download Presentation

Download Presentation

Cairo University




Download Presentation - The PPT/PDF document "Cairo University" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.



Presentations text content in Cairo University

Slide1

Cairo University

Faculty of Engineering

2nd year

Dept of Metallurgy

Slide2

HelloOo….

2

Slide3

Extraction of Aluminum

Prepared for :

Dr/

Randa

Abd

El-

karim

Slide4

Gaber Alaa El Din gaber B.N 20Ahmed Hatem Omar B.N 3 Tarek Emad El-Din B.N 26 Mohamed Ibrahim Hanafy B.N 31Bishoy Shawky Alfy B.N 19Kareem Mohamed B.N 29

Prepared by :

Slide5

General Principles

Metals are found in the Earths crust.

The least reactive metals are found as elements (i.e. native, e.g. silver, gold), but most metals are found in compounds, usually oxides or sulphides, Ex: Al , Fe.

Aluminum and iron are very widely distributed in the Earths crust, and so they are used in many applications.

Slide6

Methods of Extraction

There are a number of different methods of metal extraction, including:

by heating with carbon (in the form of coke) (e.g. Fe, Cu)

by heating with a more reactive metal (e.g. Ti)

by electrolysis of melts (e.g. Al)

by reduction with hydrogen gas

(e.g. W)

Slide7

Methods of Extraction

Which method is used depends on:

1) the energy requirements: fuel, electric sources,…..

2) the cost of the reducing agent: carbon

(in the form

Of coke) is cheap, but some reducing agents (more

reactive metals) are expensive

3) the metal purity required: the higher the required purity, the greater the cost in obtaining that purity

4)position of the metal in the reactivity series

Slide8

Reactivity Series

the reactivity series or activity series is an empirical series of metals, in order of "reactivity" from highest to lowest

K Na Ca Mg Al C Zn Fe Sn Pb H Cu Ag Hg Au Pt

Slide9

K Na Ca Mg Al

Zn Fe Sn Pb

Cu Ag Hg Au Pt

Electrolysis

Reduction with

carbon

Occur native or

electro refined

Reactivity Series

Slide10

Extraction of Aluminum

Aluminum is at the top of the reactivity series

Then it is highly reactive

Then the bonds in its compound are very strong

So Aluminum is extracted by electrolysis

The raw materials for the extraction of aluminum are

purified aluminum oxide (Al

2

O

3

) and cryolite (Na

3

AlF

6

)

Slide11

The most important ore of aluminum is a rock called “Bauxite”

Bauxite consists of minerals Aluminum oxide Al

2

O

3

Gibbsite Al(OH)

3 ,

Diaspore α-AlO(OH) , Hematite Fe

2

O

3

, and Quartz SiO

2

95% of the world's bauxite production is processed first into Aluminum oxide “Alumina” Al

2

O

3

Slide12

Alumina is then processed into Aluminum by electrolysis

Bauxite is converted to Alumina through a process called “Bayer process”

In the Bayer process bauxite is washed with a hot solution of Sodium hydroxide NaOH

This converts Alumina to Aluminum hydroxide Al(OH)

3

Slide13

Aluminum hydroxide dissolves in the solution

Other components of bauxite do not dissolve

These solid impurities are filtered off

Slide14

Extraction of Aluminum

The hydroxide solution is cooled and Aluminum hydroxide precipitates Aluminum hydroxide is then strongly heated to 1050 c (calcined) giving off water vapor and Aluminum oxide is produced2Al(OH)3  Al2O3 + 3H2O

Bayer

process

electrolysis

Slide15

Extraction of Aluminum

In electrolysis the aluminum oxide must be molten or dissolved to conduct electricity, and so is dissolved in molten cryolite (this requires a lower temperature than using molten aluminum oxide alone so has lower energy costs)

The electrodes are made of graphite

Note:

Cryolite is added to aluminum oxide to lower melting point and to dissolve Al2O3, so energy is saved

Slide16

carbon-lined steel vessel

acts as cathode

CO

2

bubbles

Al (l)

Al

2

O

3

(l)

Draw

off

Al (l)

-

+

from

power

source

Al

+3

O

-2

O

-2

Al

+3

O

-2

graphite anodes

e

-

e

-

Slide17

Overall cell reaction: 4 Al3+ + 6O2- + 3C(s)  4Al(l) + 3CO2(g)

Anode reaction: 2O2-(l) +C(s) CO2(g) + 4e- X3

Cathode reaction:

Al

3+

(l) + 3e

-

 Al (l)

X4

Slide18

Extraction of Aluminum

Al

3+

gains 3 electrons from the cathode to form molten aluminum, which is tapped off

O

2-

loses 2 electrons to the anode to form oxygen

2O

2-

(l)

 O

2

(g) + 4

e

-

Oxygen released attacks carbon anode, to form Carbon monoxide/dioxide

Note:

Carbon anode burns due to the oxygen produced forming CO

2

so the carbon anode needs to be replaced regularly

Slide19

Applications on Aluminum

Properties

Applications

Low density , light , resistant to corrosion,

Good electrical conductivity

Electric cables

Non toxic , resistant to corrosion , good heat conductivity

Food containers

Low density , light , high tensile strength , resistant to corrosion

Aircraft body

Slide20

Thank You


About DocSlides
DocSlides allows users to easily upload and share presentations, PDF documents, and images.Share your documents with the world , watch,share and upload any time you want. How can you benefit from using DocSlides? DocSlides consists documents from individuals and organizations on topics ranging from technology and business to travel, health, and education. Find and search for what interests you, and learn from people and more. You can also download DocSlides to read or reference later.