unit operations of metals production l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Unit operations of metals production PowerPoint Presentation
Download Presentation
Unit operations of metals production

Loading in 2 Seconds...

play fullscreen
1 / 33

Unit operations of metals production - PowerPoint PPT Presentation


  • 127 Views
  • Uploaded on

Unit operations of metals production. Eetu-Pekka Heikkinen Laboratory of process metallurgy Department of process and environmental engineering. Not included in this presentation. Contents. Unit operations of Mining and enrichment Pyrometallurgical unit operations

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Unit operations of metals production' - anne


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
unit operations of metals production

Unit operationsof metals production

Eetu-Pekka Heikkinen

Laboratory of process metallurgy

Department of process and environmental engineering

contents

Not included

in this presentation

Contents
  • Unit operations of Mining and enrichment
  • Pyrometallurgical unit operations
  • Hydrometallurgical unit operations
  • Electrochemical unit operations
  • Casting processes
  • Thermo-mechanical treatment of metals
  • Metal product manufacture
slide3

Properties of

metals

Physical

metallurgy

Hot and cold

rolling

(...)

Metallurgy:

introduction

Material

sciences

Extractive

metallurgy

Thermo-

dynamics

Electro-

metallurgy

Mass

transfer

Mining &

Enrichment

Reaction

kinetics

Heat

transfer

Hydrometallurgy

Pyrometallurgy

Theory

Transport

phenomena

Fluid

dynamics

Ores

Mining

Enrichment

Crushing

Screening

Mechanical

separation

(...)

Hydrometallurgical

metal production

e.g.

zinc

nickel

Pyrometall.

pretreatment

Leaching

Impurity

removal

Metal

recovery

Similar

methods

Electrowinning

Methods

Solvents

e.g. Roasting

Cementation

Acidic

Chemical

precipitation

Solvent

extraction

Water

Organic

Basic

Ion

exchange

Pyrometallurgical

metal production

Iron and

steel

Sintering

Blast

furnace

Converters

(LD/AOD/...)

Casting

e.g.

iron/steel

copper

Coking

Sulphur

removal

Ladle

treatments

Sulphide-

ores (e.g. Cu)

Flash

smelting

Converters

(PS)

Electric

furnaces

(...)

how to choose a process

Energy

Raw materials

Products

Production chain

Residues

Water needed

Pyromet. unit operations

Hydromet. unit operations

Electro-chem. unit operations

How to choose a process?

Transport

Markets

pyrometallurgical unit operations

Raw materials

Products

Production of metals

Raw material

pre-treatments

Metal

extraction

Metal

refining

Thermal pre-treatment

Reduction

and oxidizing

Metal raffination

Temperature

control

Drying

Sintering

Composition

control

Pelletizing

Roasting

Reduction

of oxides

Matte

production

Coking

Calcination

Impurity removal

Pyrometallurgicalunit operations
drying
Drying
  • Dangerous to charge wet materials to the high temperature processes
    • The moisture that is allowed depends on the further processing
  • Mechanical moisture removal prefered
    • Thermal drying requires a lot of energy
  • Counter-current drum-driers are common in the drying of metallurgical raw materials
  • Utilisation of the process waste heat streams
sintering
Sintering
  • Problems in processing fine materials
    • Gas permeability
    • Dusting
  • Thermal agglomeration
    • Partial melting
    • Minimisation of the surface energy as a driving force for agglomeration
  • Chemical and mineralogical changes in material
  • Drum-, batch- or belt-sintering
    • Pretreatment: Micropelletising
pelletizing
Pelletizing
  • Feeding of concentrates, binding materials and water into the rotating and sloped pelletising drum or plate
  • Capillar forces caused by moisture as cohesive force
  • Aftertreatments in order to achieve wanted properties
    • Sintering
    • Shaft furnace
  • Small pellets are fed back to the process
calcination
Calcination
  • Thermal disintegration of a compound (which leads into a formation of gaseous product)
    • Thermal conductivity (endothermic reactions)
    • Removal of gas from the reaction surface
  • e.g. calcination of limestone to produce burned lime

 Use of lime in iron and steelmaking slags

    • CaCO3 = CaO + CO2HR >> 0
    • Counter-current shaft furnace or rotating drum
  • Other examples
    • Disintegration of CaMg(CO2)2 or Al(OH)2
coking
Coking
  • Pyrolysis of coal in order to modify it to be more suitable for metallurgical processes
    • Removal of water and volatile components
    • Agglomeration of coal particles
    • Porous coke as a result
  • Dry or wet quenching
  • Several by-products
    • Reducing gas (H2, CO)
    • Raw materials for chem. industry
roasting
Roasting
  • A process in which an anion of a solid compound is changed without changing the valency of the cation
  • High temperature processing of the sulphide ores without agglomeration
    • Often used as a pretreatment for the hydrometallurgical processes
  • Examples
    • Oxidising roasting
    • Sulphating roasting
    • Chlorine/Fluor/Alkalines/...
oxidising roasting
Oxidising roasting
  • Difficulties to reduce sulphide ores using carbon
    • e.g. 2 ZnS + C = 2 Zn + CS2 or ZnS + CO = Zn + COS
    • Equilibrium is strongly on the reactants’ side
  • Roasting of sulphides into the oxides
    • MeS + 3/2 O2 = MeO + SO2
    • Used e.g. in the production of lead, copper, zinc, cobalt, nickel and iron when using sulphide ores as raw materials
    • SO2 SO3  H2SO4
  • Fluidized bed, sintering or shaft furnace roasting
    • Products are either fine material or porous agglomerates
sulphating roasting
Sulphating roasting
  • Used in separation of metals from complex materials
    • Some metals react to sulphates that are soluble to water
      • MeS + 3/2 O2 = MeO + SO2
      • SO2 + 1/2 O2 = SO3
      • MeO + SO3 = MeSO4
    • Some are left as oxides (non-soluble)
  • A pretreatment for hydrometallurgical processes
  • Usually fluidized bed roasting
  • Often used to remove iron from more valuable metals (Cu, Ni, Zn, Co)
    • When T > 600 C  Ferrisulphate is not stable
reduction of oxides
Reduction of oxides
  • MeO + R = Me + RO
    • Me is a metal
    • R is a reducing component (an element or a compound which forms an oxide which is more stable than MeO in the considered temperature)
reduction of oxides15
Reduction of oxides
  • Carbo-thermal reduction
    • MeO + C = Me + CO
    • In practice:
      • MeO + CO = Me + CO2
      • C + CO2 = 2 CO (= Boudouard reaction)
  • Metallothermal reduction
    • MeO + M = Me + MO
  • Gas reduction
    • Usually H2 and CO (separately or as a mixture)
      • MeO + H2 = Me + H2O
      • MeO + CO = Me + CO2
reduction of oxides16
Reduction of oxides

Specific and total CO2-emissions

of the Finnish steel industry

The largest industrial CO2-emissions

in Finland and Sweden (Mt)

matte production
Matte production
  • Separation of metals from the sulphides
    • ”Worthless” metal is oxidised  Oxidic slag
    • Wanted metal is still as a sulphide  Matte
  • Matte is further refined  Metal
  • Used e.g. in the production of copper, nickel and lead
    • 2 CuS + O2 = Cu2S + SO2
    • FeS2 + O2 = FeS + SO2
    • 2 FeS + 3 O2 + SiO2 = Fe2SiO4 + 2 SO2
removal of impurities from iron steel
Removal of impurities(from iron/steel)
  • Carbon removal (hot metal  crude steel)
    • To achieve wanted properties
    • Decarburization in BOF-converters
      • Removal of other oxidising impurities/elements (Si, Mn, P)
      • Oxygen blowing  Oxide formation  Slag/Gases
      • Temperature is increased
        • Scrap melting
    • Vacuum treatment
      • Burning of carbon is more efficient in lowered pressure
      • Partial pressure of CO can also be lowered using inert gases
removal of impurities from iron steel19
Removal of impurities(from iron/steel)
  • Deoksidation / Oxygen removal
    • Solubility of oxygen in steel melt is appr. 0,2 % (T > 1500 C)
    • Solubility decreases when temperature is decreased
      • Causes CO formation, oxidation of alloying elements, etc.
    • Alloying, diffusion or vacuum deoxidation
  • Gas removal
    • Solubilities of gases decrease when T is decreased (cf. O)
    • Gas removal is based on decreasing the partial pressure of the concerned element in the gas phase (vacuum, inert gas)
  • Sulphur removal
    • Formation of CaS  Into the slag
composition control steel
Composition control(Steel)
  • Alloying of steel is made mainly in the BOF-converters after the blowing
  • More accurate alloying in the steel ladle
    • Lumps
    • Powder injection
    • Wire injection
  • Stirring
    • Inductive
    • Using an inert gas
temperature control
Temperature control
  • Increased significance due to continuous casting
  • Optimisation of a tap temperature
  • Inductive heating
  • Use of fuels
  • Plasma heaters
  • Chemical heating (Al, Si)
  • Electric arcs
  • Insulation
  • Scrap cooling
  • Stirring
hydrometallurgical unit operations

Waste

By-

products

Wastes

By-product

Impure

raw

materials

Poor

raw

materials

Waste

treatment

Cleaning / regeneration of the solvent

Electro-

chemical

Hydro-

metallurgical

Pyro-

metallurgical

Chemical

Hydrometallurgicalunit operations

Raw material

Activation

Leaching

Impurity removal

Metal recovery

Product

leaching
Leaching
  • Grinding, enrichment and activation as pre-treatments
  • Solvents
    • Water
      • For sulphates and chlorides
    • Acids
      • Sulphuric acid most commonly used
      • Nitric and hydrochloric acids
        • more expensive and corroding
    • Bases
      • Ammonia water
    • Organic solvents
leaching24
Leaching
  • Direct leaching
    • For poor ores and residues
  • Tank leaching (in atmospheric pressure)
    • For rich ores and concentrates
    • Smaller reactors and faster processes
    • Stirring
  • Autoclave leaching
    • Tank leaching in which reaction kinetics are enhanced by increasing temperature over the boiling point of the solution (in increased pressure)
metal recovery
Metal recovery
  • Crystallization
    • Separation of solid crystal from a homogenic solution
    • Pure products (impurities only on the surfaces)
    • Saturated solution
    • Kinetics?
  • Chemical precipitation (as sulphides or as metals)
    • Addition of anions or cations in order to form a compound with a low solubility
    • Selectivity
    • Gases (H2S, H2, SO2, CO) are efficient additives
  • Electrowinning
impurity removal
Impurity removal
  • Procedures between leaching and metal recovery
  • Physical removal of solid materials
    • Thickening
    • Filtering
  • Removal of impurities from the solution
    • Similar methods as in metal recovery
    • Ion exchange
    • Liquid-liquid-extraction
ion exchange
Ion exchange
  • To remove small amounts of impurities from large amounts of solutions
    • Best with dilute solutions (< 10 ppm)
  • Possibility to achieve very low impurity levels
  • Resin to which metal ions are tranfered from solution
    • Selectivity
  • Saturated resin is recovered with other solutions to which the metal ions are transfered
    • Saturation of metals as chlorides, sulphates, etc.
liquid liquid extraction
Liquid-liquid-extraction
  • Recovery of metal ions from the water solution using an organic extraction agent
    • Two immiscible liquids
      • Reaction area is increased using efficient stirring
    • Formation of complex compounds
    • Settling in order to separate two liquid phases
    • Recovery of valued metals from the complex compounds
  • Selectivity
cementation
Cementation
  • Substitution of a metal ion (M+) with a less noble metal (Me)
    • Me(s) + M+(aq) = Me+(aq) + M(s)
  • Efficiency depends on the difference of the ”nobilities” of the metals
electro chemical unit operations
Electro-chemicalunit operations
  • Electrolysis = reduction/oxidation that is controlled with the electricity
    • Electrolyte that contains ions
    • Anions (-) are transfered to the anode (+)  Oxidation
    • Cations (+) are transfered to the cathode (-)  Reduction
  • Can be hydrometallurgical ...
    • Electrowinning
    • Electrolytical refining
  • ... or pyrometallurgical
    • Molten salt -electrolysis
electrowinning
Electrowinning
  • Anodes are not dissolved (e.g. Pb)
    • Formation of oxygen as a main reaction
    • Formation of hydrogen occurs with less noble metals
    • The amount of H+-ions is increased in the electrolyte
  • Metal-ions from the solution are precipitated in the cathode
    • The amount of metal ions is decreased in the electrolyte
    • Metal-poor electrolyte is recycled back to the leaching process
  • Used in the production of nickel and zinc
electrolytical refining
Electrolytical refining
  • Anodes are dissolving (impure metal to be refined)
    • Wanted metal is dissolved to the electrolyte
    • All the less noble metals are also dissolved
    • More noble metals don’t dissolve  an anode sludge is formed
  • Cathodes
    • Precipitation of a wanted metal
    • Less noble metals are left in the electrolyte from which they can be recovered
  • Refining of pyrometallurgically produced metals
    • Especially copper
electrolysis using molten salts as electrolytes
Electrolysis using molten salts as electrolytes
  • Halide melts as electrolytes
  • The principle is same as in hydro- metallurgical electrolyses
  • Higher temperatures
    • Refractoriness of the reactors etc.
  • Used in the production of aluminium, magnesium, beryllium, cerium, lithium, potassium and calcium
    • i.e. metals that are produced from the raw materials with high melting temperatures