Waste management in metallurgical

1. Assignment On
Waste management in metallurgical plants
Submitted to
Sir Muhammad shakeel
Submitted by
Gulfam Hussain
Roll #
MME-12-30
Institute of Advanced Materials
Bahauddin Zakariya University
Multan
Waste:

2. Waste (also known as rubbish, trash, refuse, garbage, junk, litter, and ort) is unwanted or
useless materials. In biology, waste is any of the many unwanted substances or toxins that are
expelled from living organisms, metabolic waste; such as urea and sweat.
Waste management:
Waste management is a set of activities that include collection, transport, treatment and
disposal of waste and prevention of waste production through in-process modification, reuse
and recycling.
The term usually relates to all kinds of waste, whether generated during the extraction of raw
materials, the processing of raw materials into intermediate and final products, the
consumption of final products, or other human activities, including municipal (residential,
institutional, commercial), agricultural, and special (health care, household hazardous wastes,
sewage sludge). Waste management is intended to reduce adverse effects of waste on health,
the environment or aesthetics.
Classification of Wastes according to their Effects
on Human Health and the Environment
Hazardous wastes
Substances unsafe to use commercially, industrially, agriculturally, economically and have any
of the following properties- ignitability, corrosively reactivity & toxicity.
Non-hazardous
Substances safe to use commercially, industrially, agriculturally, or economically and do not
have any of those properties mentioned above. These substances usually create disposal
problems.
Classification of wastes according to their origin
and type

3. Municipal Solid wastes:
Solid wastes that include household garbage, rubbish, construction & demolition debris,
sanitation residues, packaging materials, trade refuges etc. are managed by any municipality.
Bio-medical wastes:
Solid or liquid wastes including containers, intermediate or end products generated during
diagnosis, treatment & research activities of medical sciences.
Industrial wastes:
Liquid and solid wastes that are generated by manufacturing & processing units of various
industries like chemical, petroleum, coal, metal gas, sanitary & paper etc.
Agricultural wastes:
Wastes generated from farming activities. These substances are mostly biodegradable.
Fishery wastes:
Wastes generated due to fishery activities. These are extensively found in coastal & estuarine
areas.
Radioactive wastes:
Waste containing radioactive materials. Usually these are byproducts of nuclear processes.
Sometimes industries that are not directly involved in nuclear activities, may also produce some
radioactive wastes, e.g. radio-isotopes, chemical sludge etc.
E-wastes:
Electronic wastes generated from any modern establishments. They may be described as
discarded electrical or electronic devices. Some electronic scrap components, such as CRTs,
may contain contaminants such as Pb, Cd, Be or brominated flame retardants.
Classification of Wastes according to their
Properties

4. Bio-degradable
Such wastes that can be degraded (paper, wood, fruits and others).
Wastes of Metallurgical Plants:
Metallurgical industry is the one of the largest source of waste. The Polish metallurgy
restructuring process has caused both quality & quantity of waste to change. In accordance
with the applicable legal regulations, every manufacturer, including metallurgical
manufacturers, should prevent generation of waste in first instance or limit both generation of
waste & its negative impact on natural environment as well as human life. Holders of waste
whose generation could not have been prevented is obliged to recycle it first and foremost.
Metallurgical industries contribute significantly towards generation of solid wastes and
creation of substantial environmental pollution. Typically, 300–400 kg of slag is produced in
the production of 1 tonne pig iron (hot metal) by blast furnace route. Similarly, the red mud
generated in alumina/aluminium production amounts to 1–1.5 times the alumina extracted
by the Bayer process and about 4 times of aluminium produced by electrolytic smelting.
Production of metals is highly energy intensive. The energy required includes significant
amount of electrical energy.
The following types of waste are generated in the metallurgical industry:
 sintering dust and sludge from the sintering process
 blast furnace dust and sludge from the blast furnace process
 steelmaking dust & sludge from steel production in converter
 steelmaking dust from steel production in electric arc furnace
 blast furnace and steelmaking slag
 Ceramic debris.

5. Recovery:
Recovery of the heavy metals and other useful materials from the industrial
wastes are becoming extremely important to the society, industry and environment. This has
to be done in order to achieve the basic goals of cost reduction of the expensive materials,
efficient and proper use of limited resources and to reduce the need for the landfill utilization.
Red mud or bauxite tailings produced during alkali leaching of bauxite by the Bayer
process have continued to be one of the prime concerns of aluminium/alumina industry
from the point of view of resource conservation and protection of the environment. For
every tonne of alumina produced, 1–1.5 tonnes of red mud is generated as a waste. The
disposal costs as per regulations may add up to 5% of the alumina
production cost. Red mud could contain as much as 63% Fe2O3, 43% Al2O3 and 24% TiO2
depending upon chemical and mineralogical make up of bauxite and bauxite treatment
technology.
Over the years efforts have been made to develop processes for metallurgical as well as
non-metallurgical applications of red mud. Till date, red mud has found limited commercial
utilisation in road making, land reclamation and also used as a constituent in making Portland
cement. Development of suitable metallurgical processes for metal recovery from red mud

6. is important for bulk utilisation, value addition and moving towards zero waste. Red mud may
have 20–65% Fe2O3, 10-27% Al2O3, 5–25% TiO2, 4–20% SiO2 & 2–8% Na2O depending on
chemical and mineralogical make up of bauxite & bauxite treatment technology. Iron recovery
from red mud is a major concern. Two methods are utilized for this purpose:
o Solid-state reduction of red mud followed by magnetic separation to recover iron
o Smelting in a blast/electric/low shaft furnace (with or without pre-reduction) to produce
pig iron.
The main components in the steel slags are CaO, Fe, SiO2, MgO and MnO. Fe in the steel slags is
normally in the form of steel (7–10%), iron oxide and iron bearing minerals. f steel (7–10%), iron
oxide and iron bearing minerals. They can be separated from slag by applying mineral
processing technology and recycled as feed materials for sintering, blast furnace and steel
making.
The magnetic separation method is used for separating metallic iron and iron minerals from
steel slag. Commonly-used magnetic machines are cross-belt magnetic separator, drum
magnetic separator and magnetic pulley separator. To improve magnetic separation efficiency,
the classification of steel slag fed to magnetic separation is carried out. A single or double deck
vibratory screen is used in this process.
For the recovery of metals from non-ferrous slags froth floatation, leaching & roasting methods
are utilized.
Recycling:
Recycling is a process to convert waste materials into new products to prevent waste of
potentially useful materials, reduce the consumption of fresh raw materials,
reduce energy usage, reduce air pollution (from incineration) and water pollution
(from landfilling) by reducing the need for "conventional" waste disposal and lower greenhouse
gas emissions as compared to plastic production.
Recyclable materials include many kinds of glass, paper, metal, plastic, textiles and electronics.
The composting or other reuse of biodegradable waste—such as food or garden waste—is also
considered recycling. Materials to be recycled are brought to a collection centre or picked up
from the curbside, then sorted, cleaned and reprocessed into new materials destined for
manufacturing.
Levels of metals recycling are generally low. The military recycles some metals. Ships may be
sunk to create an artificial reef. Uranium is a very dense metal that has qualities superior to
lead and titanium for many military and industrial uses. The uranium left over from processing

7. it into nuclear weapons and fuel for nuclear reactors is called depleted uranium, and it is used
for armour-piercing shells and shielding.
The need for waste recycling arises due to following three reasons:
 To handle the waste in an environment friendly manner, keeping in view the
scarcity of land available for disposal of waste.
 To reduce the cost of production by lowering the specific raw materials
consumption and elimination of cost of handling and disposal.
 Conservation of scarce natural resources.
Management of different wastes are given below:
Solids:
 Dumping at site specified by land authorities or within the company premises
in low lying areas may be done.
 Slags may be utilised for building roads and filling low lying areas
 Beneficiation of slags to recover molybdenum, tungsten, cobalt, vanadium and
other valuable metals were/may be used.
 Slags may be used as fertilizer or for making cement.
Liquid:
 Water used for various cooling systems may be recycled. Recycling of effluent
waters serves to minimise fresh water consumption and lowers pollution load
to the environment.
 Effluent may be treated before letting into sewerage systems /natural water
bodies.
 Effluents were/may be used for agri/horticultural purposes.
 Provision may be made of soaking pits to absorb the contamination of water
before letting into environment.
 Provision may be made of soil separators to capture oil and grease from used
waters before discharge to public water bodies.
Gaseous:
 Effluent and appropriate dust collection and scrubbing systems may be used to reduce
the dust load to the atmosphere and helping resource recovery from such dusts.

8.  Fugitive emissions to be minimised through good housekeeping procedures in the
various manufacturing operations as well as in handling, conveying, transport and
storage of raw and intermediate materials.
Waste Management in Foundry:
The casting production process is inseparably connected with pollutants emission into the
environment, that is into air, water,
soil and also noise emission. The fumes and gases from coke-fired furnaces are deposited in the
air as well as other pollutants created when metal are molten in electric furnaces. Foundry
wastes generated includes waste foundry sand, slag, dust and sludge. The water
contaminations are caused by open melting furnaces cooling systems. Usually, these wastes are
hazardous to the environment. For instance, slag containing sulphurous leachate can result in
sulphur odour and discoloration of water in poor drainage conditions. Slag containing high
levels of nickel can cause corrosion of iron and steel in the presence of moisture.
The use of foundry sand in Portland cement and Portland cement concrete mixtures is an
emerging application area. In addition, use of foundry sand from iron, steel and aluminium
foundries in flowable fill, road embankments, road base, manufactured soil, agricultural
amendments, and similar uses may be appropriate depending on the site and the sand
composition.
The solid wastes from various production stages (moulding mass de-dusting, furnace de-
dusting, blast cleaners de-dusting, slag etc.) are deposited on waste dumps. The latter can be
utilized after granulation process as a road building material whereas furnace dusts are treated
in recirculation into furnace systems decreasing their final quantity and improving utilization of
some important elements mainly iron.
Waste Management in Non-ferrous Industry:
Non-ferrous metals besides gold, silver and platinum are somewhat toxic to living organism. It
is therefore important that all the metallurgical industries not only take care of the process of
manufacture but also safe disposal of the pollutants generated in the form of solids, liquids or
gaseous wastes. Metallurgical industries generate vast quantities of solid wastes such as slag,
ash, sludge, dross, grindings, turnings, clippings, residues and secondary.
Aluminium industry:
Bayer’s Process is the only process adopted worldwide for the production of aluminium in
which substantial amount of red mud is generated. Production of 1 t of alumina is accompanied

9. by generation of about 1.0–1.5 t of red mud. It is more than a century that the industry has not
come up with any viable alternate economic method to treat bauxite for production of
aluminium, which does not generate red mud. The major constituents of red mud are the
oxides of Fe, Al, Si, Ti, Na and Ca along with a large number of minor constituents. The alumina,
silica and soda account for about 40% of the total red mud and rest are mostly in the form of
iron and titanium oxides. Besides the red mud, other two major solid wastes generated in the
aluminium industries are spent pot lining (SPL) and fly ash. Red mud disposal causes seepage of
the alkaline liquid into groundwater, which might contaminate industrial, domestic, and
agricultural water supplies; spillage from damaged pipelines or from retaining-dyke failure,
reduction in the availability of arable land, requirement of huge area (viz. 2 million square
kilometre per annum) dust pollution in arid regions, aesthetic impacts, etc. are the other
problems prevalent in these units. Many plants in recent times are practising dry staking
disposal of red mud which requires much less land and promotes consolidation and hardening
of red mud, consequently resulting in stable and safer deposal. On account of damage to
aquatic/marine life disposal into sea or river streams is not favoured. Out of 84 alumina plants
all over the world, only seven are still practising the sea disposal in a planned manner because
of scarcity of land. Because of the high alkalinity, this red mud is usually not suitable for cement
production or metal extraction. However, it is used for making tiles, building material, doors
and windows, road construction, pig iron production etc. Since red mud contains appreciable
amount of iron oxide depending on the chemical and mineralogical make up of bauxite and
treatment process, attempts have been made to recover iron. Spent pot lining and fly ash are
mostly stored in the secured landfill.
Copper industry:
Copper as a metal provides limited scope for environmental pollution, but the waste generated
by the copper based industries with various toxic elements can pollute the environment.
Copper mining, smelting and refining activities are often associated with the generation of a
large quantity of wastes. Overburden, mine tailings, sediments from concentrator plants and
scrap, slag, dross, reverts, slime, flue dust, mill scales, sludge etc. from the process are the
major sources of pollution unless handled and treated suitably.
Copper based industrial waste suitable for copper recovery can broadly be classified on the
basis of physical form, copper content, chemical nature, chemical composition and possible
recovery process. Some of the more important copper bearing wastes amenable to copper
recovery include the following:
 Compound waste—oxide scale.
 Oxidised bulk waste—slag, dross etc.

10.  Oxidised powder waste—anode slime, pickling sludge, floor dust, flue dust, spent
catalyst,
effluent sludge, mine tailings.
 Liquid waste—spent pickling liquors, spent electroplating solutions, industrial effluent,
mine water etc.
 Metallic waste—heavy, medium and fine scrap
Certain solid wastes from the copper industries are real assets and are the important
secondary’s. These are the useful sources of strategic metal such as nickel and cobalt and
precious metals such as gold, silver, platinum etc. These secondary’s are converter slag, anode
slag, ETP sludge, anode slime etc. The metallic wastes and certain other wastes like dross,
reverts etc. are best recycled by pyro metallurgical process including melting, fire refining and
electro refining. Among the other waste except for high grade mill scale, all are mostly
amenable to recovery by hydrometallurgical processing. The residues generated in copper
primary smelters and also in the secondary plants from brass ash/dross are mostly stored
within the plant premises. The liquid streams of these plants are processed in the effluent
treatment plant and sludge generated is either processed/stored or sold to the respective
metal recovery unit by pyro-hydrometallurgical techniques. The dust from the dust collecting
system of several of the copper pyrometallurgical units are either stored for possible metal
recovery or processed by hydrometallurgical routes.
Zinc industry:
All zinc wastes containing zinc have been categorised as hazardous waste. Some selected dross,
zinc scrap and skimmings are in green list of waste and zinc ash happens to be in amber list. The
European Union has placed all zinc containing wastes in the list of hazardous wastes. Because of
the likely contaminants present in the zinc skimmings, a product of galvanizing operation, they
have been placed under the categories of wastes for which the level of contamination is
essential to quantify. The residue generated from these materials by secondary units may have
hazardous character depending on the concentration of the toxic constituents.
The environmental measures include provision for dust suppression and collection system,
disposal of beneficiation plant tailing into tailing ponds, recycling of tailing dam water to
beneficiation plants as process water so as to maintain zero discharge, green belt development
to improve landscape, to work as dust sinks and achieve noise attenuation.
Over the years zinc sulphate industry dealing with micronutrients has developed technology for
handling air, water and solid wastes. The sludge obtained in the process from the filter press is
washed to recover both water soluble and acid soluble zinc and washing is then recycled. This
sludge is given a treatment of excess lime, which converts water-soluble zinc to insoluble form.
Lead that is present originally in the zinc ash (0.3–0.8%) will also report in the sludge as
insoluble form of lead metal/oxide or lead sulphate. To ensure that treated sludge does not

11. carry any soluble salts of heavy metal ions, it is kept for 10–15 days for curing before final
disposal. The treated sludge is disposed off which may cause some damage to the environment
in the long run unless environmental impact analysis (EIA) finds it otherwise.