Metallurgy Flashcards
3 branches of Metallurgy
1) Extractive
2) Physical
3) Adaptive
Preparation required before the extraction process
Ore Dressing
A localized plastic deformation
Necking
Minimum strength that will promote plastic deformation
Yield strength
Capacity to absorb energy when it is deformed elastically
Resilience
How is a Rockwell Hardness Test performed
find difference in depth of penetration bet a minor and a major load using diamond cone
How is Brinell Hardness test done
w. a Hard spherical indenter and measure indent for a specified load and time
Izod Impact test is done by
placing specimen vertically and 167 J impact
Charpy impact test is done by
hor specimen, 300 J load
Knoop and Vickers is done using a
diamond indenter for brittle materials only
Fatigue def
metal’s response to cyclic loading
Creep def
time dependent deformation under constant load and/or high temp
3 types of Extractive processes
1) Pyrometallurgy
2) Electrometallurgy
3) Hydrometallurgy
Ore type where pyro met is easiest
Oxide minerals
How is smelting done
1) Use carbon as a reducing agent
2) Convert oxide to molten state
3) Alllow SG for metal to separate from the slag
How are Carbonate ores treated
by separating into metallic oxides and CO2 thru heating
How are Silicate ores treated
same for oxide plus removal of silica
How are Sulfide ores treated
for matte in smelting operations
How are Sufide ores prepared
by adding elemental sulfur to molten metal
How is sulfur removed
by oxidizing to sulfur dioxide gas
Treatment of metal product to remove impurities
Refining
What is a Shaft furnace and its efficiency
charge in contact with fuel (thermal efficiency of 60-70%)
Reverbatory furnace is a
Heat from firebox passes to the charge then is exhausted
Describe Muffle, Crucible, and Retort
heat is conducted through wall, low thermal efficiency
Pyrolysis means
destructive distillation of coal in the absence of air
What is Calcination process
process of heating the ore at a temp not suff to melt ore, in absence of air
When is Calcination done
Covert carbonate ores into oxide and CO2
CaCO3 —> CaO + CO2
What is Roasting
heating of ore in presence of excess air
When is Roasting done
convert metal sulfides into metal oxides and sulfur dioxide
2Cu2S + 3)2 —> 2Cu2O + 2SO2
What is sulfatizing roast
Oxide is turned into metallic sulfate
CuO + SO3 —> CuSO4
What is blast roasting
air is supplied by fan or blower
What is flash roasting
used in very fine sulphide material (flot concentrates)
What is smelting
process of melting and separating into two immiscible liquids
Converter process
presurized air is blown through molten charge
Molten solutions of sulfides
Matte
Molten solution of arsenides
Speiss
What is dross
Collective term for Sollid impurities floating on molten metal
What are refractories
Accepts molten charge
2 types of Heat Exchanger
Recuperators (continuous transfer) and Regenerators (stores heat)
Why is Roasting done
to convert metal into soluble form and remove volatile impurities, and to weakn bonds
What is used to leach Cu-Zn, and gold- silver allow
Sulfuric Acid
Base NH4OH used to leach what
Copper
NaOH is used to leach what
bauxite
NaCN or KCN is used to leach what
Au and Ag
Vat or Percolation leaching is used for
5 mm diameter material, lasts days
Fastest type of leaching (hours)
Agitation leaching
Why is Pressure leaching done
for minerals difficult to dissolve at ordinary temp and pressure
SPC means
Separation - Purification - Enrichment
What is SPC by Ion exchange
used of polymeric resin to exchange ions
Steps in Ion-Exchange
1) Sorption - pregnant soln passed thru resin column to exchange ions
2) Elution - ions are removed from resin by passing eluan or renerant which has excess electrolyte
What is Adsorption process
use of activated carbon to takeup ionic or molecular substances preferentially
Explain Solvent Extraction
partitioning of metal into immiscible phase - aqueous and organic (aqueous w/ valuable)
Metal winning precipitation is done by
formation of solid product from solution using reagents
Electromet is done by
deposition of metals at cathode
Cadmium is precipitated using
Zinc dust
Zinc purification is done by
Neutral circuit leaching
Zinc dissolution is done by
Acid circuit leaching
Explain Amalgamation
1) Mercury leaches Gold to form Amalgam
2) Retort furnace is used to vaporize Mercury and condensed for reuse
3) Gold Amalgam is left in the furnace
Furnace using electricity for heat
Arc furnace
Explain Oxidation
involves loss of electrons
Fe0 ->Fe2+ + 2e-
Explain Reduction
involves gain in electrons
Cu2+ + 2e- -> Cu0
Oxidation occurs here
Anode
reduction and deposition occurs here
Cathode
Electrolyte is the
aqueous medium thru w/c ions move from one electrode to another
Explain Electrowinning
1) Anode site provides the electrons
2) The cathode uses electron to recover metal
Explain Electrorefining
Anode is dissoved into solution
Betts process means
Crude lead is refined (only if Bismuth is present)
Process to remove Silver and Gold from lead bullion
Parkes process
Nickel is is prod electrolytically by
Bessemer matte using a nickel sulfate solution w/ boric acid
Silver bullion is refined electrolytically by
Thum or Moebius process
Wohlwill process is
Electrolytically refining Gold bullion
Selective deposition of Gold using REDOX reactions
What is electroplating
surface coating of metal on metallic object thru cathodic depostion
Used to refine Al
Bayer Process
Define Isotopes
same number of protobs, diff number of neutrons
Explain allotropy
Change in structure when heated
What is metallic bond
all positive cores share electrons
Metal which is non-crystalline at room temp
Hg
Liquid w/c is non-amorphous
Crystalline polymer
3 Principal metallic structure
BCC
FCC
HCP
How many Bravais lattice
14
What is Diffraction
Constructive interference of scattered x-rays
Alloying is done by
- Metal base is melted
2. Additive are added as solids to be dissolved
2 common types of Metal Fabrication Processes
- Forming
2. Casting
Forming operations
F orging
R olling
E Extrusion
D rawing -
Casting operations
D ie - force molten material under pressure
I nvestment - Wax is molded, ceramic mold takes its place as wax melts, molten material poured
C ontinuous - cast into continuous strands
S and - as mold material
L ost Foam Casting - Foam is replaced with hardened metal
2 Miscellaneous operations
Powder metallurgy
Welding
Hot Working use
Large strains can be achieved
Forging def
use of compressive stress to deform metal
Rolling def
Reducing of thickness and change in shaped using pair of revolving rollers
Extrusion def
Forcing hot block of metal thru a die orifice under high pressure
Drawing def
Pulling metal thru exit side of die
Casting def
Molten metal solidify in mold
How is Powder met done
- Powder is prod by mech, electro, chem, atomization process
- Compacted using punches
- Heat for inter-particle weld
Mechanical joining
Bolts, Rivets, Screw, Snap fit
S
Soldering def
Bonding sep pieces by melting metal
Most common bonding material
60-40 lead-tin
Brazing def
similar to soldering but using Ag or Cu alloys
What is CIP/CIL
Selective dissolution of Gold using cyanide for >3% Au feed
What is Miller process
Chlorine gas is passed thru molten gold to ppt other metals
What is HPAL and MOA Bay process
Use of Sulfuric acid leaching of Ni into Sulfate
What is Sherritt Gordon Process
Ammonina (NH3)leaching of Ni
Mitsubishi Process is the
Continuous Furnace smelting of Cu into copper matte
Flash smelting is
under Mitsubishi Process, Autogenous fine particle smelting of Cu
Blast furnace smelting is used to extract what
Iron
What is Midrex/COREX process
Direct Iron Oxide Reduction
5 Unit Operations in Ore Dressing
Comminution Sizing Concentration Dewatering Auxilliary Operations
2 Means of Liberation
Size reduction and detachment
When is “Grain” used
for Uncrushed rock
When is “Particle” used
Crushed rock
Reaction that reduces iron to pig iron
Boudard reaction
Two types of Liberation due to fracture
Intergranular
Transgranular
4 types of middlings
Rectilinear
Vein
Shell
Occlusions
Rittinger’s formula (Surface area)
E = K(Final area - Initial area)
Kick’s Energy Law (Change in size)
E = K*ln(Initial Diameter / Final Particle Diameter)
Bond’s Energy Law (Crack length)
E = K * (1/sqrt(Final diam) - 1/ sqrt(Initial Diam))
Reduction ratio (Rr)
feed opening/ product opening
Geometry factor for Kick’s
n = 1.0
Geometry factor for Bond’s
n = 1.5
Geometry factor for Rittinger’s
n = 2.0
Rod mill L:D
1.5-2.5 : 1
Ball Mill L:D
1-1.5 : 1
AG/SAG L:D
0.5 : 1
SAG volume ball mill charge %
6-10%
Mass Balance Eqn
F = C + T
Elemental Balance equation
fF = cC + tT
What is MOG
Size to w/c ore is ground to ensure sufficient liberation
Normally 80% passing
Mesh no. equals
of square apertures/in^2
GGS formula
Cumulative passing vs LOG(passing size)
Concentration ratio in terms of assay
K = (c-t)/(f-t)
Recovery in terms of assay
R = c(f-t)/f(c-t)
Enrichment ratio
Er = c/f
2 methods of Sizing
Screening - Use of physical barriers
Classification - diff’l movement of solid particles thru fluid
2 Screen movements
Frequency - hor’l movement
Stroke - Vertical movement
Limit of Industrial screening
Mat’l over 250 microns
Dual Vibrating screens has how many products
3 (2 over size, 1 under size)
Terminal velocity meaning
Equilibrium attained bet gravitational and fluid resistance forces.
Bouyant force + Drag force - Gravitational force = 0
Free settling is the
settling in a vol of large fluid vol wrt total vol
Effect of flowing film wrt to SG and Diameter
the high SG low D is less affected than high SG high D,
What is High-tension separation done
Uses diff in electrical conductivities to sep feed
Theory behind froth flotation
Driving force for attachment of part’s to bubbles is the REDUCTION OF SURFACE ENERGY of the system
Allotrope of Sphalerite
Wurtzite
What are Surfactants
Surface active chemicals that affect dynamics at interface
What do collectors do
makes surface hydrophobic
What is the Polar group and Hydrocarbon chain
Polar group attaches to mineral while Hydrocarbon chain makes it hydrophobic to water
What do Frothers do
Control stability of bubbles
What do Conditioners do
Control pH w/c in tur dictates the surface charge
What do Modifiers do
affect adsorption efficiency of collectors on min surface
2 types of Modifiers
Activators - adsorbent to collector
Depressants - suppresses adsorption of collector
Working slope for Chutes
45-55%
What are tensioning devices
to prevent undue sag on conveyor belt
What are snub pulleys
to increase tension
What are drive pulley
receives torque from motor to move belt
What is a counter-weight in conveyors
To add tension in conveyor
Interlock systems are used to
stop preceding conveyors when one fails
What do belt-loading systems do
Load ore same speed as belt
Centers ore on belt
Elliptical Bar feeder advantage
Move large rocks along while letting thru smaller ones
Most widely used feeder for coarse materials
Apron feeder
What is a live storage stock pile
There is a draw bell and a conveyor under the stockpile
How are orebins used
intermediate bet crushing and grinding
When are sloping bottom ore bins used
for easily oxidized ore
Slurry/Conditioning tanks are used
Store suspensions of fine solids
Non-white or nearly white metals
Au and Cu
Ferromagnetic mineral
Fe, Ni, Co
What is toughness
ability to absorb energy up to fracture
Reagnet which lowers surface tension; reagent conc at bubble
Organic frother
Reagent increases surface tension; reagent conc away from surface
Inorganic frother
Effect of electrolyte ph in frothing
Acids - dec froth
Alkali - inc froth
Collector for most sulfide minerals
Xanthates
Other name for “Aeroflot” a collector for sulfides
Dithiophosphates
Collector for alkali earth metals,some carbonates, and oxides
Carboxyl
Collector Applied for silicates
Cationic
Depressants fxn
Make hydrophobic to hydrophilic
Activator fxn
To help adsorb collector making it hydrophobic
What do regulators do
pH modification
pH of flotation slurry for all sulfide ores
alkaliine
Column flotaion descrp
Feed at top
Air sparger makes bubble at bot
Cleaning zone at top
Conc output at top
Net downward flow of water maintained inColumn flotation
Positive Bias
Jameson Cell fxns by
Feed and air slurry jet is injected
Wash water at top removes entrained tais
Conc at top
Tails at bot
Adv of Jameson
Fast, bc contact dependent not residence time dependent
Denver flotation cell works by
Impeller at bot sucks in slurry and pressurized air from top
Most widely used flotation machine
Wemco cell
Wemco feature
rotor-disperser, no need for pressurized air
Outokumpu Cell feature
Impeller design
There is an impeller surrounded by vert slots called diffuser
Air is pumped also
Particle size range for flotation
10 to 150 microns
carat to mg
1 carat = 200 mg
Pa to Bar
100,000 Pa = 1 bar
Hp to kW
1 Hp = 0.746 kW
cal to kJ
1 cal = 4.184 kJ
Relation of attachment porbabitlity to diameter
inversely proportional
Pulp density must be kept:
- As dense as possible, so coarse can sep from fines
- but dilute enooguh for particle rearrangement
Effect of temperature in flotation
- Increased flotation room
- inc solubility of reagents
DMS is most effective for
Metalliferous ore with light gangue
What is a LARCODEM
Large Coal Dense Medium Separator
Energy law: >1 cm
Kick’s
Energy law: 10 - 1000 microns
Rittinger’s
Energy law: 1 cm - 10 microns
Bond’s
Measures or energy nec to break an ore
Work Index
Net profit =
Revenue - Cost - Deductions
Roughing descrp
- Uses mod seperating force to rem liberated minerals
2. Rec of bulk of conc
Scavenging Descrp
- Receives tailings from rougher
2, Strong sep force for incompletely liberated minerals
Receives rougher concentrate
Cleaning
When to use Rougher-Scavenger
If Recovery is more important than grade
In pyritic gold, transport cost is less than add’l cleaning
When is Rougher - Cleaner used
When Conc. grade is important
for easily recoverable ores
Feed Character for impactor
Soft feed
Why are Rod mills run in open circuit
due to evenness of product
What are reclaimers
Stockpile with conveyance at bottom
Bayer process
- Al2O3 dissolve is in molten cryolite
- Carbon anodes electrolytically collect O2 ions
- Molten Al is left
Gangue Mineral for Lead zinc complex
Siderite