INDUSTRIAL WASTE
➡️Industrial solid wastes are also sorted out as
biodegradable and non-degradable wastes.
Biodegradable wastes are generated by cotton
mills, food processing units, paper mills, and
textile factories.
➡️Non-biodegradable wastes are generatedby thermal power plants which produce fly
ash; integrated iron and steel plants which
produce blast furnace slag and steel melting
slag. Industries manufacturing aluminium,
zinc and copper produce mud and tailings.
Fertilizer industries produce gypsum.
Hazardous wastes such as inflammables,
composite explosives or highly reactive
substances are produced by industries
dealing in metals, chemicals, drugs, pharmaceuticals,
dyes, pesticides, rubber goods etc.
➡️The disposal of non-degradable industrialsolid wastes, if not done by a proper and
suitable method, may cause serious threat to
the environment. New innovations have led to
different uses of waste material. Nowadays,
fly ash and slag from the steel industry are
utilised by the cement industry. Large
quantities of toxic wastes are usually destroyed
by controlled incineration, whereas small
quantities are burnt along with factory
garbage in open bins. Moreover, solid wastes
if not managed effectively, affect the
components of the environment.
Do you know about waste recycling?
➡️• Fuel obtained from plastic waste has
➡️Limestone is also decomposed to CaO which
➡️Thermodynamics helps us to understand how
high octane rating. It contains no lead
and is known as “green fuel”.
➡️• Due to recent developments made in
chemical and textile industries, clothes
will be made from recycled plastic
waste. These will be available soon in
the global textile market.
➡️• In India, our cities and towns face
endless hours of power cut. We can also
see piles of rotting garbage here and
there. There is a good news that we can
get rid from both these problems
simultaneously. Technology has now
been developed to produce electricity
from the garbage. A pilot plant has been
set up, where after removing ferrous
metals, plastic, glass, paper etc. from
garbage, it is mixed with water. It is then
cultured with bacterial species for
producing methane, commonly known
as biogas. The remaining product is
used as manure and biogas is used to
produce electricity.
Extraction of iron from its oxides
➡️After concentration, mixture of oxide ores of iron (Fe2O3, Fe3O4) issubjected to calcination/roasting to remove water, to decompose
carbonates and to oxidise sulphides. After that these are mixed with
limestone and coke and fed into a Blast furnace from its top, in
which the oxide is reduced to the metal. In the Blast furnace,
➡️reduction of iron oxides takes place at different temperatureranges. A blast of hot air is blown from the bottom of the furnace
by burning coke in the lower portion to give temperature upto about
2200K. The burning of coke, therefore, supplies most of the heat
required in the process. The CO and heat move to the upper part of
the furnace. In upper part, the temperature is
lower and the iron oxides (Fe2O3 and Fe3O4)
coming from the top are reduced in steps to FeO.
These reactions can be summarised as follows:
At 500 – 800 K (lower temperature range in
the blast furnace),
Fe2O3 is first reduced to Fe3O4 and then
to FeO
➡️➡️Limestone is also decomposed to CaO which
removes silicate impurity of the ore as slag. The
slag is in molten state and separates out from
iron.
➡️At 900 – 1500 K (higher temperature rangein the blast furnace):
➡️➡️Thermodynamics helps us to understand how
coke reduces the oxide and why this furnace is chosen. One of the
main reduction steps in this process involves reaction 6.27 given below.
➡️
➡️This reaction can be seen as a reaction in which two simpler
reactions have coupled. In one the reduction of FeO is taking place
and in the other, C is being oxidised to CO:
➡️The iron obtained from Blast furnacereactions have coupled. In one the reduction of FeO is taking place
and in the other, C is being oxidised to CO:
contains about 4% carbon and many impurities
in smaller amount (e.g., S, P, Si, Mn). This is
known as pig iron. It can be moulded into
variety of shapes. Cast iron is different from pig
iron and is made by melting pig iron with scrap
iron and coke using hot air blast. It has slightly
lower carbon content (about 3%) and is
extremely hard and brittle.
➡️Further Reductions
Wrought iron or malleable iron is the purest form
of commercial iron and is prepared from cast iron
by oxidising impurities in a reverberatory furnace
lined with haematite. The haematite oxidises carbon
to carbon monoxide
➡️Limestone is added as a flux and sulphur, silicon and phosphorusare oxidised and passed into the slag. The metal is removed and freed
from the slag by passing through rollers.
