L-29Steel mill

Industrial Waste Treatment

Introduction• Steel industry uses large amount of

water and discharges wastewater in proportion.

• Wastewater contains SS, lubrication oils, and several toxic substances.and several toxic substances.

• There are seven major integrated iron and steel plants in India, out of which five are under the Steel Authority of India Ltd. (SAIL)

• The total world annual production of steel is 715.4 million tonnes of which India contributes 14.5 million tonnes. In India, on an average each tonne of steel production consumes 25 to 60 cubic meters of water and 4 to 5 tonnes of other raw materials. It may tonnes of other raw materials. It may be noted that in developed countries the water consumption for each tonne of steel production varies from 3 to 6 cubic meters, i.e., 8 to 10 times less than that of water consumption in India.

• In an Integrated Iron & Steel Industry, wastewater generated from Coke Oven By-product Plant is considered to be the most polluting.

• This wastewater contains toxic • This wastewater contains toxic chemicals like phenol, cyanide and ammonia, which are harmful to the receiving water bodies when discharged untreated/partially treated.

MANUFACTURING PROCESS

IRON ORESORE APPEARANCE COMPOSITION % OF IRON

MAGNETITE STEEL GREY OR BLACK Fe3O4 72-62

HEMATITE(a) RED HEMATITE EARTHY OR ROCK ,RED Fe2O3 70-60

(b) BROWN HEMATITE BROWN EARTHY 2 Fe2O33H2O 60-42

SIDERITE OR SPATHIC CRYSTALLINE GREY FeCO3 48-35

IRON STONE GREY TO LIGHT BROWN FeCO3 42-30

EARTHLY OR STONEY

MAGNETITE:

HEMATITE:(RED)

HEMATITE:(BROWN)

• Pig iron:- is the intermediate product of smelting iron ore with a high-carbon fuel such as coke, usually with limestone as a flux. Charcoal and anthracite have also been used as fuel. been used as fuel.

• Pig iron has a very high carbon content, typically 3.5–4.5%, which makes it very brittle and not useful directly as a material except for limited applications.

Pig iron • Traditionally pig iron would be worked into wrought iron in finery forges, and later puddling puddling furnaces, more recently into steel

Ingot

• An ingot is a material, usually metal, that is cast into a shape suitable for further processingsuitable for further processing

Billet Mill• A rolling mill designed

for the rolling of blooms or ingots into billets of square or round cross section.section.

• The billets are later processed in specialized rolling mills (section and tube rolling mills).

Rolling• In metalworking, rolling is a metal

forming process in which metal stock is passed through a pair of rolls. Rolling is classified according to the temperature of the metal rolled.

• If the temperature of the metal is above its recrystallization temperature, then the process is termed as hot rolling.

• If the temperature of the metal is below its recrystallization temperature, the process is termed as cold rolling.

PICKLING• The process of removing hot rolled

mill scale from billets, bars or hot rolled sheets with sulphuric or hydrochloric acid. hydrochloric acid.

• The scale is removed for hot rolled pickled and oiled sheets or for further processing of the hot rolled steel product into cold drawn bars and wire and cold rolled sheets and strip.

Blooming Mill• Blooming Mill a high-capacity rolling

mill for the reduction, into blooms, of steel ingots of large cross section, with masses up to 12 tons and larger.

• In some cases a blooming mill is used • In some cases a blooming mill is used for the rolling of slabs and also shaped pieces (for heavy I beams, channel iron, and the like).

Treatment

• Segregation

• Equalization

• Clarification• Clarification

• pH adjustment

• Precipitation

• Filtration

Theory Questions

Q1. Draw process flow sheet of steel mill.

Q2. discuss nature of waste from steel mill and suggest treatments.mill and suggest treatments.