Recycling of iron & steel

PRESENTATION ON
RECOVERY & RECYCLING
TECHNOLOGIES OF IRON &
STEEL
Presented by: Muhsia Tabassum
M.Sc. Student,
Bangladesh University of Engineering & Technology
(BUET).

IRON & STEEL
 Iron – from which steel is being manufactured – is
produced from iron ore which consists of iron oxide
and usually other substances, known as gangue
minerals such as oxides of calcium and aluminum,
silicates, phosphates and sulphates.
 It is smelted in a blast furnace with coke and
limestone to produce iron.

IRON & STEEL (CONTINUED)
 Steel is an alloy of iron produced by refining iron to
remove excess carbon and other elements,
particularly silicon and phosphorus.
 The carefully controlled amount of carbon and
other elements which are left, and some aluminum,
nickel and chromium which may be deliberately
added, determine the steel’s properties and
therefore it’s applications.

PRODUCTION OF IRON & STEEL
Iron Production : (In Blast
Furnace)
 Iron ore contains iron oxides
(Fe2O3) with gangue minerals (SiO2,
Al2O3, P2O5 etc.) is used to produce
Iron.
 Solid charge (iron ore/iron & steel
scrap along with coke and
limestone)
 The hot air – 1,200°C – blown into
the base of the furnace induces the
combustion of the coke.

(CONTINUED..)
 The O2 in the air reacts with coke to
produce CO which reduces the iron
oxide to form iron.
 Gangue minerals are absorbed in
limestone-forming slag.
 Thus iron produced in liquid form
tapped from the bottom of the
furnace. (Pig iron)

(CONTINUED..)
Steel Production (In Basic Oxygen
Furnace)
 Molten pig iron (hot metal) poured into a
large refractory-lined container called
a ladle
 High purity oxygen at a pressure of 100-
150 psi introduced at supersonic speed
onto the surface of the iron bath through a
water-cooled lance.
 Flux are charged
 Heat generation by the oxidation of
impurities.

STEEL PRODUCTION (IN BASIC OXYGEN
FURNACE) CONTINUED..
 The addition of oxygen to the charge of the scrap
and molten iron leads to the formation of iron oxide
and carbon monoxide.
 When the carbon content of the molten metal is
reduced to the desired level, the steel is tapped into
a laddle and cast continuously.

(CONTINUED..)
Steel Making (In Electric Arc
Furnace)
• Furnace receives energy from a three-phase
transformer.
• Cylindrical solid graphite electrodes,
suspended from above the shell and
extending down through the ports in
the roof are used to carry the current
and strike an arc with the metal.
• Lime is used as flux & O2 injected into
the bath late in the melt to refine the
steel.

RECYCLING OF IRON & STEEL
 A large number of secondary sources- ‘scrap’
 Discarded metal in the form of machinery, auto
parts etc.
 In the steel making industries scraps are the main
source raw materials.

RECYCLING OF IRON & STEEL (CONTINUED..)
Sources of Scrap
 Mainly three types of scraps- home, new and old.
Old Scrap
 Old or obsolete scrap is iron or steel from
postconsumer products.
 The largest source is junked automobiles followed
by appliances, machinery, worn out railroad cars
and tracks, demolished steel structures, and other
products.

SOURCES OF SCRAP (CONTINUED..)
New Scrap
 Mainly generated from manufacturing plants.
 Scrap accumulates when steel is cut, drawn, cast,
extruded, or machined.
 As it’s chemical and physical characteristics are
known, so it is usually transported quickly back to
steel plants through scrap processors and dealers
or directly back to the steel plant for remelting to
avoid storage space and inventory control costs.

SOURCES OF SCRAP (CONTINUED..)
Home Scrap
o Home or revert scrap consists of scrap that is
produced in steel mills and foundries as a
byproduct of their operations, as well as old plant
scrap.
o This scrap has a known composition and is always
recycled to the furnace for remelting.
o Technological advances have significantly reduced
the generation of home scrap.

DIFFERENT TYPES OF IRON & STEEL SCRAPS
Sheet Iron Scrap (Sheet Tin)
 Sheet Iron (Sheet Tin) shall consist of
miscellaneous iron & steel and may contain
galvanized sheet, painted & coated materials,
whole machinery & equipment containing other
metals provided Iron is the main content.
Scrap White Goods
 Major household appliances including stoves,
fridges, freezers, clothes washers, dryers & dish
washers.

(CONTINUED..)
Mixed Steel Can Scrap
 Flattened or whole steel cans. This material is typically
generated from food cans from municipal recycling
programs. May contain Bi-Metal (aluminum/steel)
beverage cans.
CAUTION May not contain aerosol cans.
Bundled Steel Can Scrap
 Bundled Steel Can Scrap shall consist of compressed
assorted flattened or whole steel cans with a minimum
weight density of 75 lb./cubic foot. This material is
typically generated from food cans from municipal
recycling programs. May contain Bi-Metal
(aluminum/steel) beverage cans.
CAUTION May not contain aerosol cans.

(CONTINUED..)
Briquetted Oil Filters
 Briquetted Oil Filters shall contain used or spent
automotive or industrial oil filters that have been
saturated with motor oil and shall have been
compressed to a minimum weight density of 75 lb./cubic
foot.
Mixed Scrap Iron & Steel
 Assorted iron & steel scrap up to any maximum size,
must be free of white goods & light gauge materials
under 1/8" in thickness.
No.1 Steel Scrap (HMS1)
 No.1 HMS shall consist of clean iron & steel with a
minimum thickness of 1/4", and a maximum size of
60"x24", material handling compatible to feed a furnace
charge box. This grade may include ISRI code 200.

(CONTINUED..)
No.1 Steel Scrap (2 foot)
 No.1 Steel (2 foot) shall consist of clean iron & steel with
a minimum thickness of 1/4", and a maximum size of
24"x18", material handling compatible to feed a furnace
charge box.
This grade may include ISRI code 201.
Special Scrap Plate Punchings
 Special Plate Punchings shall include clean, dry, uniform
plate punchings suitable for ballast material or high
density furnaces charging. Material must be free flowing
and no piece shall be larger than 2" in any direction and
a minimum of 1/4" in any direction. May be any shape
provided that there are no protruding edges.

(CONTINUED..)
No.2 Steel Scrap
 No.2 Steel shall consist of clean iron & steel scrap with a
minimum thickness of 1/8", and a maximum size of 60"x18",
material handling compatible to feed a furnace charge box.
No.2 Steel Scrap (2 foot)
 No.2 Steel (2 foot) shall consist of clean iron & steel with a
minimum thickness of 1/8", and a maximum size of 24"x18",
material handling compatible to feed a furnace charge box.
No.3 Steel Scrap (Unprepared Bushling)
 No.3 Steel (Unprepared Bushling) shall consist of clean,
uncoated steel clippings, stappings & sheet skeletons under
1/8" thick.
No.4 Steel Scrap (Silicon Bushling)
 No.4 Steel (Silicon Bushling) shall consist of clean silicon
bearing steel scrap with a maximum thickness of 1/8"

(CONTINUED..)
No.4 Shredded Steel Scrap
 No.4 Shredded Steel shall consist of course shredded
steel scrap.
Mixed Cast Iron Scrap
 Mixed Cast Iron shall consist of assorted scrap iron
castings.
Sorted Machine Cast Scrap
 Sorted Machine Cast shall consist of sorted broken or
unbroken scrap cast iron machinery scrap, not to
exceed 18"x18"
Sorted Scrap Automotive Cast
 Sorted Automotive Cast shall consist of sorted broken or
unbroken cast iron automotive scrap, not to exceed
18"x18"

(CONTINUED..)
Unclean Motor Block Scrap
 Whole or particle cast iron auto or truck engines.
Transmissions may or may not be attached.
Clean Motor Block Scrap
 Clean Motor Block shall consist of stripped cast iron
motor blocks, free of oil pan, pistons, and all foreign
attachments.
Whole Prepared Scrap Car Bodies
 Unflattened car bodies, with tires, radiator and
battery removed, gas tanks acceptable but must be
removed and punctured, (no propane tanks
allowed). Engine and transmission may or may not
be included.

(CONTINUED..)
Flattened Scrap Car Bodies
 Flattened Car Bodies shall consist of prepared car
bodies that have been flattened & stacked for
transportation as auto shredder feedstock. Tires,
radiator and battery removed, gas tanks acceptable but
must be removed and punctured, (no propane tanks
allowed). Engine and transmission must be removed.
Scrap Green Car Bodies
 Green Car Bodies shall consist of stripped car hulks that
have dismantled through a "Green" Auto Recycling
System. The "Green" Car Body shall have most of the
manually strippable non-metallic parts removed,
including, windows, seats, interior & trunk carpet, head
& tail lights, external non-metal body parts, internal dash
parts. Fluids reduced or removed.

(CONTINUED..)
Scrap Steel Wheel Rims
 Scrap Steel Wheel Rims shall consist of whole or
crushed steel automobile wheel rims with tires removed,
and may contain lead wheel weights.
Mixed Steel Turnings & Iron Borings
 Mixed Turnings & Borings shall consist of assorted cast
iron or steel turnings, borings or grindings.
Short Shoveling Borings Scrap
 Short Shoveling Borings and Turnings shall consist of
clean free flowing cast iron borings or steel
turnings. Must be free of fluffy, tangled, springy turnings
and free of lumps or clumps.
Steel Mill Scale
 Mill Scale shall consist of magnetic iron surface scale
produce while working steel.

(CONTINUED..)
Iron Oxides
 Iron Oxides shall consist of clean sized iron and
iron oxide particles or powdered material.
Maximum particle size of -10 mesh.
Manganese Steel Scrap
 Manganese Steel Scrap shall consist of non-magnetic
manganese/steel alloy materials.
May include Manganese Grinder Plates.
Other Scrap Iron & Steel
 Other Scrap Iron & Steel shall include any iron &
steel materials not covered in the other iron & steel
grades.

GENERAL PROCEDURE OF IRON & STEEL
RECYCLING
Collection and Sorting
 The first step in metal recycling is the collection of all the
materials which are made up of metals. There should be
an organized system for the collection of metals.
Containers should be used to collect them.
 For that there should be recycling centers in all big
cities and there should be recycling bins at home and
in the shopping malls that should be taken directly to
industry.
 The second important step is sorting the kind of metals
which are good for recycling. The quality of metals
matters a lot when it comes to recycling.

RECYCLING (CONTINUED..)
Processing
 The next step is to compact the metal.
 All the appliances are squeezed and squashed in the
machines so that they don’t occupy that much space
in conveyor belts.
Sweat Furnace
 The furnace is used by many metal scrap recyclers for
the purpose of separating aluminum, zinc, and or/or
lead from Iron in composite parts. It can also be used to
remove contaminants like dirt, rubber, plastics and
other combustibles from aluminum, zinc, and/or lead
bearing scrap.

Shredding
 By shredding with massive hammer mills
automobile hulls, appliances and other large goods
are reduced to fist-sized pieces.
 Three streams of material are produced: ferrous
metals (iron and steel), a light fraction residue
and a heavy fraction residue.
 The ferrous metals (iron & steel) are recovered by
the shredder operator through magnetic separation
and sold to steel mills.

Melting and Purification
 The next step is to melt all this scrap metal in a
large furnace.
 Each metal has a specially designed furnace
depending on its properties.
 Then after melting the metals are purified by using
different methods. Electrolysis is also used for
metal purification.

 Magnetic Separation
 When large quantities of ferrous
scrap are to be separated from
other materials magnetic separation
is the obvious choice.
 Magnetic separators can be of the
belt type or drum type.
 In the drum a permanent magnet is
often located inside a rotating shell.
Material passes under the drum on
a belt.
 A belt separator is similar except
that the magnet is located between
pulleys around which a continuous
belt travels.

Eddy Current Separation
 Eddy current separators are used to separate non-ferrous
metals from waste and automobile shredder
residue.
 The simplest device follows this principle is the inclined
ramp separator. This uses a series of magnets on a
sloped plate covered with a non-magnetic sliding
surface.
 When a feed of mixed materials are fed down the ramp,
non-metals slide straight down, while metals are
deflected sideways by the interaction of the magnetic
field and the induced eddy current.
 The two streams are then collect separately.

Heavy Media Separator
 Heavy media separation (HMS) utilizes a medium
normally consisting of finely ground magnetic or
ferrosilicon and water.
 By varying the relative proportion of the solids the
relative density of the medium can be adjusted.
 The specific gravity of the medium is typically
halfway between the densities of the two materials
being separated.
 Once separated, the products are allowed to drain;
the medium recovered is returned to the process.

Incineration
 Some scrap processors use incineration to remove
combustible materials including oil, grease, wood,
plastic & paper and volatile metals such as lead &
zinc.

Dezincing Technologies:
 Two main processes of dezincing technologies
I. Thermal and Thermo-Mechanical Removal:
 In the first method galvanized parts are heated to
a temperature greater than 900ᵒC to evaporate
the zinc.
 In the second method galvanized parts are
heated to a temperature sufficient to embrittle the
coating, which is then removed by abrasion.
 In a third process coating is heated and
subsequently removed by abrasion.

II. Chemical and Electrolytically Aided Removal
of Chemicals:
 In the first sulfuric acid is used to dissolve the zinc
coating.
 But the disadvantages is that it is difficult to
separate the dissolved iron & zinc.
 In the second the zinc coating is leached by
ammonia.
 In the third, caustic soda is used to dissolve the
zinc coating.

CHEMICAL AND ELECTROLYTICALLY AIDED
REMOVAL OF CHEMICALS (CONTINUED..)
 The caustic soda dezincing process is considered to be
the most promising.
Two major steps:
 Zinc is first dissolved from the steel scrap in a caustic
soda electrolyte by applying an electric current
 Then the sodium zincate solution is electrolyzed to
recover zinc in powder form on the cathode.
 The process can be applied to all types of galvanized
steel scrap.
 After electrolysis the material is passed through a multi-station,
counter-current rinsed cycle to remove entrained
sodium zincate.
 The zinc-enriched electrolyte is then treated in the
electrowinning section using convetional cells with nickel
anodes and cathodes.

Detinning Technologies
 The electrolytic detinning process consists of
leaching in a hot alkaline solution.
 The scrap is suspended in baskets in a bath
containing about 10% caustic soda, at a
temperature of 80ᵒC.
 Steel cathodes surround the baskets.
 A spongy tin deposit is formed on the deposits. It is
manually removed, compacted melted and cast into
ingots and sold to tin refiners.

RECOVERING IRON POWDER FROM SCRAP
There are four methods to recover iron powder from
scrap:
Atomization:
 A stream of molten metal produced from home,
industrial or processed obsolete scrap, is broken
up with high pressure air, water or gases, such as
nitrogen or argon.
 Iron powder is produced by direct high pressure
water atomization of molten scrap.
 The powder is collected, dried and annealed.
 The non-magnetic materials, if any, are
segregated in a magnetic separator.

(CONTINUED..)
Chemical Methods:
o One of the most important chemical methods for the
production of iron powder is direct reduction of the
scrap by using gaseous or solid reducing agents.
o The dried and ground mill scale is loaded in ceramic
saggers using special charge heads, which are so
designed that alternate sub-divisions can be filled with
the mill scale and reducing agent, which is a mixture
dried and ground coke limestone.
o The loaded saggers are stacked and heated at 1100ᵒC
in a continuous tunnel kiln.
o The sponge iron then removed from the cooled saggers,
crushed to powder, magnetically separated and
subsequently reduced.
o The reduced powder is screened and blended
depending upon the end use.

CHEMICAL METHODS (CONTINUED..)
 Another chemical process has been developed to
utilize low-grade scrap such as turnings, borings, tin
cans and other types of ferrous scrap.
 The process consists of dissolving the scrap in
hydrochloric acid, followed by evaporation and
crystallization of the resultant solution to yield
ferrous chloride crystals, which are dried, briquetted
and converted to iron sponge by reduction in hot
hydrogen.

(CONTINUED..)
Electrolytic Deposition:
 In this process, iron scrap is treated with
hydrochloric or sulfuric acid to produce chloride or
sulfate or mixed chloride-sulfate electrolyte bath.
 Iron powder is produced by using a graphite or
carbon anode or a stainless steel cathode.

(CONTINUED..)
Pulverization:
o These methods use cast iron turnings or machining
swarf as the material.
o The machining chips are degreased, heavy pieces
are removed by air-separator, and the chips are
hammer-milled to produce the particles of less than
0.8 mm size.
o These chips are then impact-fractured by throwing
them against a target surface by a high velocity
stream.
o The powders are collected, classified and
annealed.

PULVERIZATION (CONTINUED..)
 In another method, the cutting fluid is separated
from machining swarf and the cleaned and dried
material is pulverized in a hammer-mill at room
temperature.

INTERMEDIARY PRODUCTS & WASTE TREATMENT (IN
THE STEEL-MAKING INDUSTRY)
Type Process
Source
Characteristics Treatment/Reuse/Recycle
Spent
waste acid
and pickle
liquor
Finishing Non-metallic Processed & recovered iron chlorides are used
for phosphate removal. Neutralized with lime
and land-filled.
Pickling Non-metallic,
Hazardous
waste
Neutralized with lime and land-filled. Processed
and recycled for pickling or sewage treatment.
Alkali cleaner Non-metallic Land-filled.
Tin line Non-metallic Waste sludge is treated by an ion-exchange
process, chromic acid is recovered and
recycled. Land-filled.
Spent
refractory
Melting Non-metallic Reused or processed and recycled. Land-filled
or stockpiled.
Ingot hot
tops
Batch ingot
casting
Metallic Metal is recovered magnetically and remaining
material sold for use as roadbed aggregate.
Mill scale Finishing Metallic Sintered and recycled.

STAINLESS STEEL (SORTING & PREPARATION
TECHNOLOGIES)
Manual Sorting:
 This involves the removal of components from the
scrap by hand. Example- the removal of catalytic
converters from scrap automobiles.
 Large items such as storage tanks and platforms
must be cut to allow them to be changed into a
furnace.
 This is done using torches, crushers and shredders.
Magnetic Separation:
o This is used to separate the magnetic stainless
steels and nickel from the non-magnetic stainless
steels.

TECHNOLOGIES) (CONTINUED..)
Baling & Compaction:
 Loose scrap and thin-walled low density scrap (tanks and
tubing) are normally compacted by bailing or briquetting.
 A baler is a heavy piece of equipment that uses up to three
hydraulic rams to compress the scrap.
 In the briquetter, small scraps are compacted into pockets as
it passes between two counter rotating drums.
 The use of bales and briquettes reduce transportation costs
and facilitates the charging of the furnace.
Shredding:
 It is used to reduce the size of large stainless steel parts.
 Stainless steel found in automobiles is recovered from
automotive shredder residues.

TECHNOLOGIES) (CONTINUED..)
Eddy Current Separation:
• Some non-ferrous metal separators utilize eddy current
technology to recover the non-ferrous metals and
stainless steels from shredder residue.
Heavy Media Separation:
• It is used in some non-ferrous metal separators to
recover the non-ferrous metals and stainless steels from
shredder residue.
Sweat Furnace:
• This is used for the purpose of separating aluminum,
zinc and lead from stainless steels, which coexist in
composite parts and to remove contaminants.

GENERAL DESCRIPTIONS OF RECOVERY
TECHNOLOGIES OF STAINLESS STEELS
The following are some of the ladle-refining processes:
 Ladle without-cover:
• Composition adjustment by sealed argon bubbling(CAS)
process;
• Sealed argon bubbling (SAB) process; and
• Argon-oxygen decarburization (AOD) process.
 Ladle with-cover:
• Thyssen-Niederrhein (TN) process;
• Kimitsu Injection Process (KIP); and
• Capped Argon Bubbling (CAB) process.
 Vacuum Processes:
• Stream degassing process;
• Rheinstahl Huttenwerke & Heraeus (RH) process;
• Vacuum-oxygen decarburization (VOD) process; and
• Dortmund-Hoerder (HD) process.

ECONOMIC FACTS IN RECYCLING IRON AND STEEL
 Almost 40% of the world’s steel production is made from scrap.
 Every ton of recycled steel can help save 1.4 ton of iron ore.
 Conversely, a steel can land-filled will take 100 years to vanish.
 Steel is the most recycled material on earth! In Luxembourg, 2,292 tons of steel
packaging have been collected in 2013.
 Recycling one ton of steel saves 1,100 kgs of iron ore, 630 kgs of coal, and 55 kgs of
limestone.
 CO2 emissions are reduced by 58% through the use of ferrous scrap.
 Recycling one ton of steel saves 642 kWh of energy, 1.8 barrels (287 litres) of oil, 10.9
million Btu's of energy and 2.3 cubic metres of landfill space.
 Recycling steel uses 75% less energy compared to creating steel from raw materials -
enough to power 18 million homes.
 Steel recycling uses 74% less energy, 90% less virgin materials and 40% less water; it
also produces 76% fewer water pollutants, 86% fewer air pollutants and 97% less
mining waste.
 Steel automobile frames contain at least 25% recycled steel and a typical electrical
appliance will usually be made of 75% recycled steel. Steel cans consist of at least
25% recycled steel.

ECONOMIC FACTS IN RECYCLING IRON AND
STEEL (CONTINUED)..

USES OF STEEL
Steel is present in many different areas:
 A car is made of 65% recyclable and recycled steel
– engine parts, body, doors, etc.
 Electrical appliances: Washing machine: 57% steel;
Cooker: 80% steel. This steel is recyclable.
 Fridge: 51% steel
 Food packaging: cans and beverage cans mainly.
This steel is recyclable and recycled.
 Building products: 70% of all building products
made of steel – concrete rebars, metallic frames,
etc. – are recycled.

Recycling of iron & steel

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