MT's Guide .pdf

7/18/2019 MT's Guide .pdf

1/309


2/309

ORIENTATION TRAINING GUIDE FOR MANAGEMENT TRAINEES2

A story says that a Russian student tried to make an iron ring to present his lover by chemically

extracting iron from his blood, but had died of anemia as human body contains only 3 grams of

iron

In 1714 Iron Reboyer, a Worlcer working in a Copper Plant had suddenly became weak andwas unable to drag his feet even. He drank Water from Mariatian Water fall, he recovered. It was

found that the water was containing iron.

In olden days Iron Water and Steel Wine were prepared with iron filings in Grape wine etc.,

Irons medicinal properties were also ascribed because of its Magnetic Property. Egyptians

were treating some patients using this property.

Earths Crust contains nearly 5% i.e. 755 x 110 15 tons or 755 Million Billion tons of iron.

96 out of every 100 Kgs. of metal consumed by Industry Agriculture and every day life was iron.

King Solomon gave a feast and honoring the workmen on completion of temple in Jerusalem.

He was asked who contributed more: Black Smith, Carpenter and Mason Finally, the king said

it was Black Smith.

DEVELOPMENT OF STEEL INDUSTRY IN INDIA

Iron & Steel making as craft has been known to India for a long time. However its

production started only after 1900. In a short span of 3 decades or so that capacity was

increased from 11 folds to about 16 Million tonnes by nineties. Progress in next 15 years is

slow, just more than double i.e. 34.821 million tonnes.


3/309

ORIENTATION TRAINING GUIDE FOR MANAGEMENT TRAINEES 3

MAJOR STEEL PRODUCING COUNTRIES

(million metric tons crude steel production)

Rank COUNTRY 2003 2004 2005 2006 2007 2008

1 CHINA 220 273 318 423 489 502

2 JAPAN 111 113 112 116 120 119

3 UNITED STATES 90 100 94 99 98 92

4 RUSSIA 63 66 66 71 72 69

5 INDIA 32 33 38 50 53 55

6 SOUTH KOREA 46 48 48 49 52 54

7 GERMANY 45 46 45 47 49 46

8 UKRAINE 37 39 39 41 43 37

9 BRAZIL 31 33 32 31 34 34

10 ITALY 27 28 29 32 32 31

WORLD TOTAL 968 1046 1107 1253 1345 1330

Note:- In the year 2008 India stood as fifth largest producer of crude steel in the world for the third

consecutive year.

WORLD CRUDE STEEL PRODUCTION :

1945 113 2001 860

1950 190 2002 904

1955 270 2003 971

1960 347 2004 1070

1965 451 2005 1148

1970 595 2006 12531975 644 2007 1345

1980 717 2008 1330

1985 719

1990 770

1995 752

2000 848

YearProduction

(Million Tonnes)Year

Production

(Million Tonnes)


4/309


PRODUCTION OF CRUDE STEEL

(Million metric tones)

CONSUMPTION OF STEEL

(Million metric tones of finished steel products)

China alone constitutes 25% of world steel production and consumption. China has more

than doubled its steel output from 220 mt in 2003 to 502 mt in year 2008. Presently India consumes

85% of its production in the domestic market and exports the rest.

2003 232 31

2004 263 32

2005 293 34

2006 361 46

2007 408 51

YEAR CHINA INDIA

2003 220 31.8

2004 290 34.25

2005 300 34.8

2006 423 50

2007 489 53

2008 502 55

YEAR CHINA INDIA


5/309



6/309



7/309



8/309



9/309



10/309


Chapter - 3

MAJOR OPERATING STANDARDS AND NORMSCOKE OVENS & COAL CHEMICALS PLANT:

RECEIPT QUALITY OF COAL :

Moisture Ash VM Fixed Carbon% % % %

Indigenous Prime coking (PCC) 6.0 25-30 25.0 40.0 (approx)Indigenous medium coking (MCC) 6.0 17-20 25.0 50.0 (approx)Imported hard coking 7.0 8 -10 26.0 57.0 (approx)Imported soft Coking 7.0 8 -10 30.0 53.0 (approx)

BLEND PROPORTION :

MCC or PCC 15 % ) Blend proportions could vary from time to timedepending Imported hard coking 65 %) upon coal supply

linkages, coal quality and coal) availability.Imported soft coking 20 %)

BLEND COAL QUALITY :

Ash 10-11 %VM 25-26 %Moisture 6-8 %Thickness of plastic layer 20-22 mmSize analysis %0-3 mm size 74-75 %0-0.5 mm 28-29 %Bulk density 0.76

BATTERIES :

i) Oven charge weight (T) dry 32.0ii) Coking time (Hrs) 17-18iii) Specific Heat consumption 615 Mcal/TDCCiv) a)C.V.of mixed gas for heating (Kcal/NM3 ) 1000

b) CV of Coke oven gas for heating (Kcal/NM3 ) 4240v) Yields from dry coal carbonized (%)a) Run of oven coke 75.00b) 25 to 70 mm coke 62.00c) 0 to 25mm coke 13.00

vi) Coke Quality :Moisture < 0.50 %Ash


11/309


ii) Temperature of cooled coke (0C) 150-180iii) Steam generation from one chamber (T/hr) 22-25iv) Steam pressure (ata) 39-40v) Temperature of super heated steam (0C) 430-450

COAL CHEMICALS PLANT :

1) Yield from one tonne of dry coal carbonized:a) Coke oven gas 330-350 NM3b) Ammonia 0.3%c) Crude benzol 0.6%d) Crude tar 3.2%2) Typical Characteristics of coke oven (Raw) gas:

Calorific value (Kcal/NM3) 4425Density (kg/m3) 0.45CmHn 2.8%O

20.1- 0.3 %

CO 6.4%

H2 59- 61 %CH

425-26 %

N2

3.5%CO

22.15%


12/309



13/309



14/309



15/309



16/309



17/309



18/309



19/309



20/309



21/309



22/309



23/309



24/309



25/309


MAJOR

PRODUCTION

UNITS


26/309



27/309


RMHP


28/309



29/309



30/309



31/309



32/309



33/309



34/309



35/309



36/309



37/309


Chapter - 5

COKE OVENS AND COAL CHEMICALS PLANT

COAL PREPARATION PLANT :

From the storage yard, the coking coal is sent to foreign object separation section (FOSS) to

remove foreign matter of above 150mm size. Iron traps for ferromagnetic articles and cylindrical

screens are provided for this. For averaging and proportioning of coal, 16 nos. of Silos, each of 800T

capacity are provided along with continuous action weigh-feeders of up to 120 tones per hour capacity

each. After blending, the material is crushed with the help of impact crushers. The crushing is carried

out in reversible hammer crushers, 2 operating and 1 standby. Crushing is done to take care of

petrographic non-uniformity, high hardness and mineral content of coal. The crushed and blended

coal (74-75% of -3mm size) is conveyed to two coal towers each of 4000 T capacity. Weigh bridges

are provided under coal towers to weigh the coal charge. System of pneumatic blow down of blend is

provided in the coal tower to take care of jamming or hanging of coal in the coal tower.

BATTERY :

The prepared coal charge from the coal tower is drawn by a charging car on the top of the

batteries and charged into the ovens as per sequence. The charged coal is gradually heated by the

heating walls of the oven in the absence of air to attain a temperature of 1000-1050 0C at the central

axis of the coke mass towards the end of coking period. The coking period is generally specified

between 16 hrs and 19 hrs depending upon oven condition and production requirement. The volatilematter of coal liberated during carbonization is collected in gas collecting mains in the form of raw

coke oven gas passing through stand pipes and direct contact cooling with ammonia liquor spray. The

gas cooled from 8000C to 800C is drawn to coal chemicals plant by Exhauster.

The residual coke is pushed out of the oven by pusher car through a guide into coke bucket.

The red-hot coke is taken to coke dry cooling plant for cooling.

There are 4 batteries, each having 67 ovens. Each oven can hold 32 tons of dry coal charge.

The volumetric capacity of each oven is 41.6 m3.

The heat for carbonization is supplied by under firing of coke oven gas having CV of 4200

Kcal/Nm3 or mixture of BF gas & CO gas having CV 1000 Kcal/Nm3.

The heating system of batteries is of underjet compound type having twin-heating flues with

recirculation of waste gases. The dimensions of an oven are as follows.

a) General Dimensions:

Length 16,000 mm


38/309


Height 7,000 mm

Width on coke side 435 mm

Width on pusher side 385 mm

Average width 410 mm

Oven taper 50 mm

b) Effective Dimensions:

Length 15,160 mm

Height 6,700 mm

Number of heating flues in one heating wall 32 Nos.

Distance between axes of ovens 1,400 mm

Number of charging holes 3

Number of gas-off take holes 2

Heating level (distance from the top ofthe hairpin of the heating flue to the 1,100 mm

carbonizing chamber roof)

Temperature in heating flues is between 13000C and 13600C and final temperature of coke mass at its

central axis is between 1000 - 10500C.

Following pressures are maintained:

a) Pressure of carbonizing chamber sole,

15 minutes prior to pushing coke +0.5 to +3 mm W.C.b) Pressure in the gas collecting main +16 to +17 mm W.C.

c) Pressure in the heating system at hair

pin level for waste heat gases +/- 0.3 mm W.C.

The refractory requirement per battery is 14000 T silica bricks, 5700 T fire clay bricks and 130 T

lightweight insulation bricks.

Following oven machinery is provided.

Operating TotalCharging Cars 4 8

Coke pusher 6 4

Door Extractor 4 6

Electric Loco 4 6

COKE DRY COOLING PLANT :

There are four coke dry cooling plants, each having four chambers. Capacity of each chamber is 50-


39/309


52 TPH. Each coke dry cooling plant consists of cooling chambers with individual lifter and lifting

shaft, waste heat boiler, dust catching arrangements and mill fan.

The cooling chamber has two technological zones. Red-hot coke is charged into the upper zone while

cooling takes place in lower zone by circulating gases. Gas is forced by mill fan into distribution

channels in the lower part of the chamber and fed into the cooling zone. The gas flows upwards and

gets heated. Circulating gases enter boiler, cyclones and return to bottom part of cooling chamber

because of mill fan.

The coke is cooled from 1000 - 1050 0C to 150-180 0C while the circulating gases are heated from

160-180 0C to 600 - 800 0C. 22-25 Tonnes/hour of steam at 35-40 atm pressure and 430-440 0C is

produced from one chamber. The cooled coke from the cooling chamber is discharged onto the

conveyor continuously through a rotary discharging system.

COKE SORTING PLANT :

From the dry cooling plant, cooled coke is conveyed to a dedusting unit by conveyor. From the dedusting

unit, coke is conveyed to crushing section. Here the incomig coke fractions are first separated into

+70mm and -70mm fractions. The +70mm fraction is fed to a two roller-toothed crusher (2 nos. each

of 120 TPH capacity). The crushed product along with -70mm fraction is conveyed to coke screening

section where 25 -70mm and 0 - 25 mm fractions are separated using roller screens. 25 to 70mm

fractions(metallurgical coke) are conveyed to blast furnace. Bunkers of 600 tonnes capacity are also

provided for loading into wagons/trucks and dumpers for sending to coke yard.

0 to 25mm fractions are fed to vibrating screens provided to separate into nut coke (10 to 25 mm size)

and breeze coke (0 to 10mm). Nut coke is sent to blast furnace or to yard depending upon the

requirement. Breeze coke is sent by conveyor to Sinter Plant.

CONVEYORS

The following types of conveyors are used in coke ovens & coal chemical plant.

Width (mm) 1600 1400 1200 1000 800 650 500

Quantity (nos.) 9 49 6 11 - 4 2

Total no. of conveyors: 87

Total length (Mts) - 15000 (approximately)

COAL CHEMICALS PLANT :

The main by product in the process of coke making is raw coke oven gas and this has lot of valuable

chemicals. Coal Chemicals Plant recovers Ammonia (NH 3), Tar and crude Benzol from Co-Gas as


40/309


per the process described below:

The primary By-products from Crude CO Gas are Ammonium Sulphate (NH 4)2

SO4, Crude Tar,

Crude Benzol and cleaned coke oven gas.

QUALITY AND COMPOSITION OF COKE-OVEN GAS

Calorific value Kcal/N.cum 4300-4350

Density kg/Nm3 0.45

CmHn % 2.8

O2

% 0.5 (max)

CO % 6.4 - 7.0

H2

% 59 - 61

CH4

% 25 - 26

N2 % 3.0-3.5

Yields of main Carbonization by-products based on coal are follows (percent on dry blend basis).

Crude Tar 3.2 %

Ammonia (NH3) 0.3% or 7-10 gm/Nm3 of coke oven gas

Crude Benzol 0.6% or 20 gm/Nm3 of coke oven gas

Generation of coke oven gas per ton of dry coal charged is 330-350 Nm3 at calorific value of 4300

Kcal/Nm3

GAS CONDENSATION SECTION :

The Coke Oven Gas (CO Gas) leaves the ovens at a temperature of 8000C and is cooled from

8000C to 800C in goosenecks and in gas collecting mains at the batteries by spraying Ammonical

liquor (Flushing liquor). 60-70% of Tar present in CO-Gas is condensed here. The CO-Gas along with

Tar and liquor comes to a separator to remove liquor and condensed Tar. The cooled CO-Gas is then

taken to primary gas coolers ( each having a heat transfer area of 2425m2) where it is cooled indirectly

by water to about 25 to 300C. Along with the Tar, some amount of Naphthalene in coke oven gas is

also condensed.

The gas is then sent to Electro Static Precipitators ( each of 27000 Nm3/hr capacity) to remove

the foggy Tar (about 5%) from CO gas. In ESP, foggy Tar particles are electrically charged and collected

on the surface of the electrodes and separated. The gas purified from Tar is compressed in Exhauster

to a pressure of max.2800 mm water column. There are five electrically driven exhausters provided

and each having capacity of 76000 Nm3/hr.


41/309


Tar and Ammonia Liquor (Flushing liquor) from the separator are delivered to mechanized

decanters , each of having capacity of 370 m3. Here the crude Tar, Flushing liquor and sludge (coal

and coke dust particles in Tar) are separated based on their density difference. The separated flushing

liquor from decanter is collected in Tanks of capacity of 200 m3 from where it is pumped continuously

by flushing liquor-pump to gooseneck and gas collecting mains of coke ovens. There are 8 Nos. ofFlushing liquor pumps of having capacity of 1100 m3/hr.

Tar separated from the decanters is collected in an intermediate Tar tank of having capacity of 50 m 3

from where it is once again pumped to Tar decanters (each of capacity 370 m3), which are exclusively

provided to remove further water from Tar. The gas condensate which is collected after the primary

gas coolers, Electrostatic precipitators and exhauster is taken to a underground 50 m3 tank from

where it is pumped to Tar Decanters for separation. The flushing liquor separated from Tar decanters

is collected in Flushing liquor tanks. The clear Tar taken in another 50 m 3 tank from where it is pumped

to final gas cooler.

AMMONIUM SULPHATE SECTION:

The CO-Gas from the Exhausters under pressure is sent to saturators in Ammonium Sulphate section

through pre-heaters.

Acidity of the saturator bath is maintained at 4 to 5% and Sulphuric Acid is used for this purpose.

Ammonia present in CO Gas reacts with sulphuric acid and forms Ammonium sulphate crystals.

Nitrogen at 600 -750 Nm3/hr is used for agitation purpose in each saturator and this keeps the crystals

in motion. Once the crystals grow bigger in size, it settles at the bottom of the saturator.

There are five saturators of 6400 mm diameter having cylindrical body and conical bottom.

The Ammonium sulphate, (NH4)

2SO

4, crystals settled at the bottom of saturators is sent to the

centrifuges by pumps where the crystals are separated continuously from the liquor (mother liquor).

There are 5 Nos of centrifuges.The crystals from centrifuges are dried in a fluidized bed drier and

stored. The dried Ammonium Sulphate crystals are bagged in 50 kg bags and shipped. This is used as

a fertilizer for agricultural purpose and having Nitrogen content 21%.

15 days production can be stocked in the godown. Sulphuric acid required for the productionof Ammonium sulphate, caustic soda & soda ash required for coal chemical plant are stored in Reagent

storage. A month requirement of Sulphuric Acid can be stored here.

FINAL GAS COOLING AND NAPHTHALENE WASHING :

From the saturator the CO-Gas enters the Acid trap where the acid droplets that might be

carried along with the CO-Gas are separated and sent to saturator. The acid free of COGas enter the

final gas cooler. There are two final gas coolers of diameter 5000 mm and height 45.5 meters. Each


42/309


cooler has got two sections. In the top section CO-Gas is sent from the bottom and cooled service

water is sprayed from the top. There are perforated plates in this section, which provides the necessary

contact for the water and CO-Gas.

The CO-Gas enters the final gas cooler minimum at 550C. Cooling of the CO-Gas is done by

direct water spray through a closed cycle system. In this way Naphthalene that is present in CO-Gas

is scrubbed by water & this enters the bottom of the bottom section. The bottom section, Naphthalene

washer, having Tar will come in contact with warm water from top section. Lighter than Tar the water

comes to the top and leaves the cooler. During this process whatever Naphthalene is present in (or

dissolved) in the water gets dissolved in tar because the solubility of Naphthalene in Tar is many times

higher than water. Then this Tar is taken out and stored in tanks and then sent to Tar Distillation Plant

(TDP) for processing.

BENZOL RECOVERY :

Cooled Coke Oven Gas from final gas cooler (FGC) will successively pass through two benzol

scrubbers in each of the two streams. All four Benzol scrubbers are of 5000mm diameter and height

48.5m.

Recovery of benzol hydrocarbons is carried out by solar oil, a petroleum fraction, in counter

current. The Benzol content in CO-Gas before scrubbers is 27gms/Nm3 and after scrubbers it is 6gm/

Nm3. Aluminum packing is provided in all the scrubbers for efficient contact.

DRY PURIFICATION UNIT :

700 -1000 Nm3/hr of coke oven gas is sent to dry purification system when H2

S content of the gas is

required to be removed from 0.6-0.7 gms/Nm3 to 0.02 gm/Nm3. The H2S free CO Gas is sent to

laboratories and other special consumers like GETS at BF, CO Gas is supplied to dry purification unit

after the electrostatic precipitators. Synthetic bog ore is used as purification mass. Spent purification

mass containing 24 to 25% sulphur is transferred to dump.

TAR DISTILLATION PLANT :

It is designed to process 1,15, 200 Ton/year of Tar. The crude tar having maximum water content 5%

is heated in the pipe still furnace to 1150C and sent to the 1st stage Evaporator, where the Tar is

separated from water and stored as dehydrated Tar. Further, this Tar is heated in the pipe still up to

4000C and taken to the 2nd stage evaporator.

Here the vapours and the residues (called pitch with softening temperature 67 to 730C) are separated

and this vapour is sent to the Rectification Column.All the products are withdrawn at different levels

based on their boiling points difference and cooled and stored.


43/309


Naphthalene fractions are crystallized in the crystallizes and then pressed to form a cake in a Hydraulic

press and bagged and shipped. Pitch or Residue at the bottom of the 2 nd stage evaporator is soft in

nature and it is made hard by sending compressed air in pitch reactors. Due to the polymerization and

condensation, which takes place in the reactor, the pitch becomes harder and withdrawn from the

reactor. Pitch creosote mixture is prepared by mixing soft pitch and Anthracene Oil.

Major facilities of the plant are :

a) 2 drum crystallizes, 8 mechanical crystallizer and 2 centrifuges and 2 hydraulic presses for

naphthalene. There is 10 days storage capacity for crude naphthalene.

b) 9 mechanical crystallizes, 3 centrifuges and 16 days storage capacity for crude Anthracene.

c) Washing section for making Sodium Phenolates.

d) 4 still reactors, head Tanks, pipe still for production of pitch with softening temperature of 75

to 950C.

e) Facility for preparing Pitch Creosote Mixture.

f) 23 days storage for Tar and Tar products.

MECHANICAL BIOLOGICAL AND CHEMICAL TREATMENT OF

PHENOLIC EFFLUENTS :

Before treatment After treatment

mg/ltr mg/ltr

Phenols 400 not more than 1Rhodonites 400 not more than 10

Tar & Oil 500 not more than 25

Biological Oxygen demand 2500 not more than 300

AMMONIA (NH3) 500 not more than 100

In CO&CCP amount of phenolic effluents are 120 m3/hr and this water is treated in the unit and is

transferred into the net- work of sanitary domestic sewerage plant.

BENZOL DISTILLATION PLANT :

The plant consists of

i) Benzol recovery & distillation using Solar Oil as scrubbing medium.

ii) Benzol refining & Rectification plant using continuous hydro refining process for production of

Caprolactum grade Benzene, Nitration grade Toluene, Light Solvent Oil.

The Recovery & Distillation unit has two streams each consisting of one final gas cooler two

scrubbers connected in series. In scrubber the Solar Oil and CO-Gas is subjected to counter current


44/309


flow and thus Solar Oil absorbs and Benzol from CO-Gas and becomes benzolised oil. This benzolised

oil is taken to a stripping column, where with the help of direct steam, the benzol is stripped, removed

and cooled. The de-benzolised oil is the bottom product, which is reused for scrubbing the CO Gas.

BENZOL REFINING & RECTIFICATION :

The benzol refining & rectification section is designed to handle Crude Benzol recovered from

the benzol distillation unit. It can handle 110 tons of crude benzol per day and operating period is 330

days/annum.

The Crude Benzol recovered in Benzol Distillation Plant is processed in Hydro-refining unit to

produce BTXS refined. Crude Benzol is refined by using hydrogen, recovered from CO gas by Pressure

Swing Adsorption (PSA) process. The refining process is carried out of 25 kg/cm2 pressure. The

refining process involves removal of sulphur compounds in two catalytic bed reactors called

pre-reactor and main reactor. The product, which is sulphur free, is called BTXS refined and is furthersubjected to rectification process where different products like Benzene, Toluene, SOL-110 and Light

Solvent Oil are made.

This rectification process involves a series of distillation processes like pressure distillation,

extractive distillation where NFM solvent is used to remove non-aromatics from Benzene & Toluene.


45/309



46/309



47/309



48/309



49/309



50/309



51/309



52/309



53/309



54/309



55/309


CALCINING AND REFRACTORY

MATERIAL PLANT


56/309



57/309


Chapter - 7

CALCINING AND REFRACTORY MATERIAL PLANT

CRMP, i.e. Calcining & Refractory Materials Plant is an integrated unit of Visakhapatnam Steel Plant.

This plant plays a significant role in the manufacturing of liquid steel. The main customer of CRMP isSteel Melting Shop (SMS).

1) Calcining Plant

CRMP has two units

2) Brick Plant

Calcining Plant

Calcining plant produces lime and calcined dolomite, which are used for refining of hot metal to steel

in the converter. This plant has 5 rotary kilns of 325 tons/day capacity. Lime is produced by calcining

limestone and calcined dolomite is produced by calcining dolomite. Limestone (SMS grade) is procured

from United Arab Emirates and Dolomite (SMS grade) from Madharam mines of VSP. The size of

limestone is (30 - 60) mm and size of dolomite is (25 50) mm. Both the raw materials are received

and stacked at RMHP. RMHP reclaims these materials and conveys to LSDS (Limestone & Dolomite

Screening Plant) via a stream of conveyors. LSDS has two screens (VS6 & VS7) to screen out the

minus fraction from raw materials. The minus size is sent to RMHP for use in Sinter Plant. The +30mm

size limestone is stored in bunker 5 and +25mm dolomite is stored in bunker 6. These materials are

then conveyed to the stone bins of all the kilns by operating the weigh feeders below the two

bunkers. Limestone and dolomite are charged to separate kilns.

The material from the stone bin flows by gravity into the preheater. Material in side the preheater gets

preheated by the hot flue gas coming out of the kiln and is then charged into the kiln by activation of

hydraulically operated rams. The feeding of raw material into the kiln can be varied by regulating the

frequency of the ram pushing.

The fuel used for firing of the kiln is PCM (Pitch Creosote Mixture). This is supplied by CCP (Coal

Chemicals Plant) through pipelines. The calorific value of PCM is 9000 Kcal/Kg. This fuel is stored in

four tanks in pump house. Pump house pumps the fuel to the kilns through PHF unit (Pumping,

Heating & Filtering Unit) of each kiln at 4 - 8 kg/cm2 pressure. This fuel generates a temperature of

12500C - 13000C inside the kiln to calcine limestone & dolomite. The product of the kiln, i.e. lime and

calcined dolomite are discharged to a contact cooler provided for each kiln. The cooled product is

discharged and sent to the Flux Storage Building. Lime and calcined dolomite are screened and

stored separately in Flux Storage Building. There are two 10mm screens in FSB as SMS requires

+10mm size only. The stored material is then sent to SMS as per demand. Some +10mm size lime is

also sent to PCM (Pig Casting Machine). The -10mm size is sent to Briquetting plants, Sinter Plant,

Water Treatment Plant and to outside sales.


58/309


The hot flue gas coming out of the rotary kiln is passed through the preheater, cyclone and bag filter

by ID Fan. Dust, carried by the hot gas, is separated in cyclone and bag filter and stored in dust

hoppers and despatched to Sinter Plant by pneumatic tankers. The clean gas is then let off through

chimney.

Brick PlantBrick plant produces Pitch Bonded Magnesia Carbon Bricks for lining of Converters and Steel Ladles.

Total twelve shapes of bricks are currently produced :- CD1 to CD8 and LB1 to LB4.

The main raw materials of brick are Sea Water Magnesia (SWM) and Fused Magnesia (FM). Sea

Water Magnesia is imported from Ireland and Israel. Fused Magnesia is imported from China. Graphite

Flakes is used as additives and Aluminium Powder is used as antioxidant. Liquid pitch is used as

binder, which is supplied by CCP (Coal Chemicals Plant) by tankers. In mill house, SWM is crushed,

ground and screened into different sizes of (0 - 0.2), (0 - 0.5), (0.5 - 1.6), (1.6 - 3) & (3 - 5) mm and

stored in separate blending bunkers. Graphite & aluminium powder are stored in separate blending

bunkers. These fractions of SWM and additives are collected by scale car from blending bunkers inpredetermined quantities and discharged into mixer. Pitch is added during mixing and mixing is done

as per set mixing program. The mixer temperature is maintained between 1400C and 1800C.

The Brick Plant has two 1600 T capacity hydraulic presses to press these bricks. After pressing the

green bricks are placed on takeoff belt. The green bricks are lifted from the takeoff belt and placed on

a tempering pallet manually. Pallet filled with the green bricks is then placed on a tempering car. The

tempering of bricks is done at a temperature of 3000C - 3500C. The tempered bricks are then packed

on packing pallets, strapped with polyethylene straps and stored in Brick store. These bricks are

despatched to SMS as per requirement of SMS and RED.

Moreover, bottom jointing mass and back filling mass are also produced in the Brick Plant for useduring converter relining. For production of bottom jointing mass resin is used as binder in place of

pitch.


59/309


BLAST FURNACE


60/309



61/309


Chapter - 8

BLAST FURNACE

8.0 BURDEN HANDLING AND FURNACE CHARGING :

Burden materials are received in the stock houses, one for each furnace through a junction

house. Coke is handled by two conveyors (one stand by) of 1600 mm width and 350 TPH capacity,

sinter, lump ore by two conveyors (one stand by) of 1400 mm width and 800 TPH capacity, Sized ore

and additives will be handled by one reserve conveyor of 1400 mm width and 800 TPH.

Junction house has a cross over through rolling reversible conveyor and stationary reciprocating

conveyor. For each furnace, there are 5 bins for sinter, 5 bins for coke, 3 bins for lump ore, 1 bin for nut

coke, 3 bins each for limestone/LD slag and quartzite/used silica bricks and manganese ore.

Coke, sinter and iron ore are screened in screens up to 400 m3/hr capacity to remove the fines.

The screened material is fed to the inclined conveyor for burden handling to top through a horizontalconveyor. Conveyors for burden handling to top are of 2000 mm width & 2160 m3/hr capacity and are

operated continuously. The materials are positioned in conveyor in separate batches at certain intervals

and in a certain sequence as per preset program. PLC system is a certain sequence as per preset

programs. PLC system is provided for batching, weighing and feeding of the burden to the furnace

top.

The Paul wurth, bell less top system is installed for furnace charging. The system consists of

two bunkers of 47 cubic meter capacity each, charging moving hopper & rotating trough. All drives are

hydraulically operated except for trough rotation and tilting which are electrically operated. Semi clean

BF gas and nitrogen are used for pressure equalization in charging bunkers. Nitrogen is used forcooling rotating trough drive and for blowing off stock bin gates and sealing valves of charging

arrangement. Mechanical gauge rod on side and radar probe on the other side are provided for

measuring stock level.

Exhaust station and air cleaning plant are provided for burden handling system. The exhaust

air is directed to electrostatic precipitators (2 nos.) for cleaning. The plant capacity is 3. 65 x 10 m3/hr.

The dust content of air is reduced from 2.85 gm/cum to 0.1 gm/cum, 200 tons of dust is collected

every day. The dust collected is balled in granulation plant and is transported in trucks to Sinter plant.

The burden handling system premises are hydraulically flushed 600 m3

/hr water). Total effluentsgeneration is 600 .3/hr. After primary settling, the water is pumped to sinter plant for further use.

8.1 HOT BLAST STOVES :

There are four hot blast stoves for each furnace with a total heating surface of 224, 000 m 2.

The dome can be heated to a temperature of 14500C maximum while the waste flue temperature is up

to 4000C. The stoves are capable of giving a blast temperature up to 13000C. Stoves are heated by a

mixture of blast furnace gas and coke oven gas having a calorific value of 1,100 Kcal/Ncum. Pressure

of mixed gas before burners is 600mm W.C.


62/309


Gas mixing station is provided to mix BF gas, CO gas in required proportion and to get the

necessary Calorific value. Separate stations are provided for each furnace. Mode of operation of

stoves is successive (parallel also can be operated).

High temperature zone is lined with silica and mullite corundum refractories, medium

temperature zone, with kaoline refractories and low temperature zone with fire clay refractories. The

shell of dome and cyclindrical part is heat insulated with a heat proof gunnite concrete in high temperature

zone. Gaps between shell and walls are filled with mats from fibrous materials. Checker-work is lined

with hexahedral refractories with round cells of 41mm dia. Combustion chamber is in-built construction

of elliptical shape. The chimney is of 80 m high, 3.5m diameter at the mouth. It is of reinforced

concrete and fire clay lined. Stack for back drought is made of metal with refractory lining. Air supply

for burners is centralized. Three fans (one stand by) of 120, 000 m3/hr, 1080 mmwc capacity each are

provided for the purposes.

Water cooling arrangement has been provided for cooling of hot blast valves and burner cut

off valves.

8.2 FURNACES :

Two blast furnaces of 3,200 m3 useful volume, each capable of producing 1.7 MT of hot metal

per year while operating for 350 days are installed. The basic characteristics of furnace are :

Useful height from iron notch center line to trough bottom in

vertical Position ........ 33,100 mm

Height of hearth ........ 4,600 mm

Height of Bosh ........ 3,400 mm

Height of belly ........ 1,900 mm

Height of shaft ........ 20,000 mm

Height of top ........ 2,300 mm

Height of dead layer ........ 1,203.5 mm

Diameter of Hearth ........ 12,000 mm

Diameter of belly ........ 13,000 mm

Diameter of top ........ 8,900 mm

Bosh Angle ........ 7901037mm

Shaft Angle ........ 8304322mm

Number of Tuyeres ........ 32.................

Number of Tap Holes ........ 4.................

No slag notches are provided.


63/309


The lower part of the hearth bottom is lined with graphitized carbon blocks while upper part is

with high refractory mullite bricks in the center and with carbon blocks in the periphery. Side walls of

the hearth are lined with carbon blocks in lower part and alumina silicate bricks are used for lining of

bosh, belly and shaft. Furnace top is lined with non cooled steel slabs of suspended construction,

while non cooled cast iron slabs are used for furnace dome. Insulation layer was provided between

slabs and shell of dome.

Lower part of the hearth bottom is air cooled. Peripheral cooling plates are used for cooling of

upper part of hearth bottom, hearth, tuyere zone, bosh, belly and lower part of shaft. For middle part

of the shaft, peripheral plates with independently cooled projections are used. There are 664 cooling

plates. Besides, there are 32 breast coolers, 32 tuyere coolers, 32 tuyeres and 8 nozzles in furnace

dome. The water requirement for cooling is 5555 m3/hr max.) per furnace at 80 mmwc. Clean

recirculating water with suspended matter up to 50 mg/litre is used.

The hot metal is discharged into 140T hot metal ladles by rocking runners in cast house. Hot

metal ladle cars are moved by a pusher car. At every notch, a notch opening machine and an electric

gun is provided. The cast house is circular in shape and two circular cranes 20/5+5 T and a circularplatform (5m width) for maintenance and observation of tuyers stock is also provided.

There are 10 to 20 casts in a day. Cast house has good aeration. Provision has been made for

gas and dust exhaust from iron notches, rocking runner covers and from housing of the drum of the

conveyor from burden handling to top. Four mill fans (one stand by) of 160,000 m3/hr capacity and 900

kgf/cm2 pressure and two exhaust fans (1 stand by) of 492000 m3/hr capacity and 430 Kgf/cm2

electrostatic precipitators, two horizontal type three fold precipitators having needle type discharge

electrodes and S shape collecting electrodes (12m height) are provided. Dust is granulated and

dispatched to sinter plant by dump track. Clean gas is fed to chimney of 5m dia, and 100m height. The

total capacity of the plant is 972, 000 m3/hr. Dust content is reduced from 2.5 gms/m3 to 0.1 gms/m3.

About 60T of dust is collected daily from two precipitators.

There are four railway tracks for hot metal transportation [two on either side,] one service

sub-track and one track for flue dust disposal. Independent running railway tracks are provided for

delivery of metal to each SMS. Two rail weigh bridges are provided for weighing hot metal sent to SMS

& PCM. For auxiliary freights, automobile transport is provided.

The furnace process control is computerized.

Four gas off takes run vertically from furnace dome, which are connected to each other in

pairs, firstly forming two vertical off takes and these two joining to form one central vertical off takes

and these two joining to form one central vertical off take which is connected to a dust catcher of 12mdia through a down comer. Dust catcher and gas pipe lines are lined with fire clay bricks. Moistening

and discharge of dust is carried out by a screw conveyor. The furnace can be separated from dust

catcher by 3,000 mm dia cut off valve in upper part of the dust catcher.

8.3 CAST HOUSE SLAG-GRANULATION PLANT :

The molten slag produced by the furnaces is fed to cast house slag granulation plant to produce

granulated slag. Two granulation plants are provided for each furnace adjoining the cast houses on

two opposite sides.


64/309


Slag is dicharged from the furnace 10 to 20 times a day, duration of each discharge being up

to 60 minutes. Each granulation unit comprises two process lines (one stand by), designed to receive

all slag through two iron notches. Each process line comprises of one granulator, one slag air lift, one

granulated slag dehydrator, one receiving bin and water supply recirculating system. Steam from

receiving hopper is discharged to atmosphere through a chimney.

The granulated slag from the dehydrator is discharged into an intermediate hopper and from

there it is fed to final storage through a conveyor system. The granulation of liquid slag is done by

water jets and the granulation water is delivered by dredged pumps in a quantity of 2000 m3/hr at a

minimum pressure of 5atg in the granulator. Temperature of pumped water is around 90 degrees C.

with an average suspended matter content of upto 2 g/litre. Through put of make up water is 300m3

per granulation plant.

For air lifting thickened pulp from receiving bin to separator, compressed air is used. The plant

is designed for maximum slag discharge rate of 10 T/min and hot metal content in the slag will be 12.7

kg/T.

The granulation plant works for 350 days in a year. The combined conveying system for handling

granulated slag from both furnaces has a capacity of 600 TPH. Two conveyor systems one acting as

standby is provided.

The storage is open dump type and can hold about one month production. From the storage

slag is loaded in railway wagons and in trucks by grab cranes.

8.4 PIG CASTING :

Four double strand pig casting machines of 1700 TPD capacity are installed to pour off grade

metal and metal diverted due to stoppages in SMS (one machine reserve). The machines can handle

one furnace production. Each PCM is served by a 75 T, overhead trolley to tilt the 140 T hot metalladle. Pig weight is about 45 kgs. Facilities for lime washing of moulds and a re-circulating water

system for cooling the pigs, including a settling tank, is provided.

The cold pig from machines are collected in wagons and sent to open gantry pig iron storage

yard. The yard is of 300 x 40 m size and cold pigs are stored in separate lots according to grade. Two

150 T Rail weigh Bridges are provided to weigh outgoing loaded wagons.

8.5. HOT METAL LADLE REPAIR SHOP :

The main objectives of this shop are as follows :

a) To ensure placement of hot & clean metal ladles to each furnace in time for the casting as per

the casting schedule.

b) To ensure quick despatch of Hot metal loads to their planned destination and also ensure early

withdrawal of empties from PCM/SMS in order to thoroughly clean inspect and clean the same

before placement.

c) To effectively coordinate with Rail Traffic department / 2BFs/ SMS/PCM to ensure achieving of

above objectives.


65/309


The entire shop working rotates around the three above objectives. The main equipment/tools/devices

provided in the shop to achieve those objectives are as below :

a) 2 Nos. of 120/50 tons capacity E.O.T. cranes (for Hot Metal ladles cleaning purposes).

b) 30 Nos. of conventional open top metal ladles (capacity 140 tons each) and 7 Nos. of Torpedo

ladles (capacity 300 tons each) to hold & transfer liquid Hot Metal.

c) 4 Nos. of metal ladle pits with stands to hold conventional ladles during mechanical repair jobs

/ RED lining jobs.

d) 1 No. 42 tons capacity punch and 2 Nos. of four beak anchor hooks to remove skull from metal

ladles and clean them.

e) 2 Nos. of drying installation to dry and preheat freshly lined conventional ladles before taking

hot metal in them to avoid explosion and thermal shock.

f) Separate torpedo ladle repair shop is there to maintain the torpedo ladle cars in all respects.

8.6 BLAST FURNACE MASSES AND COMPOUND SHOP :

Refractory masses required in cast house viz., Runner mass, Mudgun mass, Tap hole frame mass

are prepared in Masses Compound shop.

The raw materials required for preparing mass are received at various sizes from the different sources.

These are crushed in various stages and stored in final storage bins. 12 final storage bins are provided

for storage of raw materials. There are 6 operating groups for raw material handling and preparation

of masses.

The raw materials for preparation of different masses are :

G Coke Breeze

G Pitch

G Grog

G Plastic fire clay

G Silicon Carbide

G Calcined Bauxite

G Powder Resin

G Liquid Resin

G Wash Oil / L.C Oil

G Special binder

There are two storage tanks (25 m3) for wash oil/L.C Oil. Two pan mixers are used for preparation

of the mass.


66/309


All the groups can be operated through PLC and if required they can be operated in local

mode.

There is a 5 Tons capacity crane for handling the mass boxes.

8.7 GAS EXPANSION TURBINE STATION :

This is intended for generation of electric power utilizing the potential energy of the compressed BF

gas. One turbine is provided for each furnace. Each turbine operates the turbo generators of 12 MW

nominal rating with exciter placed on one shaft with the turbo generator. Air coolers are provided for

turbo generators. (The gas is heated up to 120 degrees C. in heater. The station operates for 8000

hours in a year annual generation of electric power is about 123. 8 to 184. 6 X 10000000 KWH.

8.8 GAS CLEANING PLANT :

The rated dust content in gases after the dust catcher, when the blast furnace is operating at high top

pressure is 6.3 gms/normal cubic meter and at low top pressure up to 15 gms/Normal cubic meter.Further cleaning up to 4 mg/Normal cubic meter is accomplished in wet gas cleaning plant, consisting

of high pressure scrubber of 9000 mm dia, two venturi pipes with adjustable drop of pressure by

changing throat cross section, 2, 600 mm dia spray catcher and the cyclone sprary catcher. In the

scrubber, gas is cooled and cleaned of coarse fractions of dust. In venturi pipes and septum valves,

the coagulations of fine fraction of dust takes place with subsequent separation of them in spray

catchers.

A BF gas flare stack is provided for prevention of excess of the preset pressure in out door distributing

BF gas pipe lines and centralized burning of the discharged temporary surpluses of BF gas. Capacity

is 200 to 240 x 103 normal cubic meter per hour, height-60m. Four burners of 60 normal cubic meter

per hour are provided.

8.9 NITROGEN SUPPLY AND BLOCK OF RECIPIENTS :

Nitrogen of 97% purity is used for charging apparatus and for other equipment requirement is 38, 370

normal cubic meter per hour. Nitrogen is supplied from Oxygen plant. To provide for emergency

Nitrogen reserve, and to compensate non-uniform consumption, a block of recipients consisting of

two 100 cubic meter vessels for 10 Ksca pressure and five 125 cubic meter vessels for 35 to 40 Ksca

pressure are provided. A Nitrogen control station is provided as a part of block of recipients, where

pressure is reduced from 35 to 40 Ksca to 8 to 10 Ksca.

8.2.0 AIR CONDITIONING STATION :

To supply air to all units, two central air conditioners 200000 m 3/hr capacity are installed. In cold

season one unit will be in operation. Air is subjected to cleaning in cell filters, adiabatically cooled and

humidified in the spray chambers in summer. Air at a temperature of +30 degrees C and 90% humidity

is supplied through yard pipe lines. In cold season, air is subjected to only cooling. The total requirement

is 392, 000 m3/hr.


67/309


8. 2.1 CONVEYORS :

The details of conveyors in blast furnace as follows :

Width (mm) Length (M) Quantity (Nos.)

1600 1542 121400 2250 18

1200 1138 4

1000 1890 10

8.2.2 PROCESS CONTROL COMPUTERIZATION IN BLAST FURNACE :

8.2.2.1 Scope :

Two systems have been envisaged in the Blast Furnace Automation Control system.

8.2.2.1.1 Burden Handling System :

To control the proportioning of burden materials with due consideration for coke moisture content &

batching accuracy. This system also gives relevant data connected with the operation of the Burden

handling Complex to the process personnel. This consists of the following major local systems for

monitoring and control.

i) Material levels in the bins

ii) Material batch weights

iii) Coke moisture content

iv) Availability of materials and transfer of the material batches to the Blast furnace top

v) Over filling of chutes

8.2.2.1.2. The centralised monitoring and control system for the Blast Furnace comply with the following

main functions.

a) Automatic data acquisition on the process run, state of equipment.

b) Automatic processing of incoming data and making them available to the technological

personnel in a convenient form.

c) Occasional calculation of process parameters and taking the process data to the service

personnel.

d) Delivery of corrective responses to local control circuits.

e) Optical and acoustic signaling for variations of basic process parameters from nominal

values and for operating conditions of the equipment.

f) Occasional filling-out of reports.

8.2.2.1.3 Lan system is implemented in Blast Furnace department connecting all the sections of the

department with the main net work. Data is logged on to the system in all the section and

made available for use & reference by the concerned.


68/309



69/309



70/309



71/309



72/309



73/309


C = 4.0 - 4.5%

Si = 0.4 - 0.7%

Mn = 0.10%

P = 0.11% max

S = 0.04% max

Temperature = 1250 - 1425 Degree C.

1300 to 13500C Through Mixer route

1350 - 14500C Through TLC (Torpedo Ladle Car) route.

BULK MATERIAL HANDLING SECTION (BMHS) :

The following bulk materials are used in converter shop of SMS.

Calcined Lime and calcined dolo - used as flux in LD-Converter.

Cao = 89 - 90%LOI (Loss On ignition) = 6-8%

SiO2

= 2.5% Max

Size = 10-25 mm

Mgo of dolo = 28 to 32%

Requirement = 6-10 T as per heat weight and hot metal composition, iron Ore Lump - Used as

Coolant in steel making.

Fe = 66.9%SiO

2= 0.9%

AI2O

3= 1.6%

MnO

2= 0.05%

Size = 15 - 60 mm

Requirement = 0.5 - 3T as per blowing conditions.

Raw or Calcined Dolo - Used to increase lining life of Converter.

Lump Coke - Used to preheat the lining of newly lined converter.

One of the requirements for continuous casting process is that the liquid steel should be killed (fully

deoxidized). For this and to make different grades of steel, ferro alloys (FeSi, SiMn, FeMn, etc) Coke

breeze/Petroleum coke and Aluminium are added in the ladle during tapping of steel from converter to

ladle.

CONVERTER BAY :

Hot metal contains different impurities (C,Si,Mn,S,P) above safe level which make Pig Iron brittle. But

steel is nothing but refined hot metal. Refining is only possible when things are in molten


74/309


phase. Refining is done by blowing oxytgen in the LD converter Charged with Hot Metal, Scrap, Flux,

Iron Ore, etc. In this refining process, temperature of liquid steel is aimed at 17000 C (average).

Different grades of steel is made by adding various ferro alloys & additives (FeSi, FeMn, Coke Breeze

or Petroleum Coke, Aluminium, etc) in different quantities during tapping of liquid steel from converter

to steel ladle.

There are 3 LD convertors in SMS. Characterstics of converter design are given below:

Capacity = 150 Tonne

Effective Volume = 133 cum

Converter specific volume = 0.886 Meter Cube per Tonne

Height to Diameter Ratio = 1.36

Refractory for converter lining is MgO based e.g. Sea water Magnesia, Magnesia carbon,

Pitch Bonded

Oxygen is blown in the converter through oxyzen lance. It consists of three concentrically

arranged steel tubes with connecting branches for Metal - Flexible - Hoses. Central pipe is for supplying

oxyzen, intermediate pipe is for incoming cooling water and outside pipe is for outgoing water. At

lower part of lance there are 5 nos. Convergent - Divergent copper nozzles syrnetrically arranged at

17.50 to the lance axis.

CHARACTERISTICS OF OXYGEN LANCE :

Lance Travel = 16000 mm

Oxyzen working pressure = 16 KSCG

Water Working Pressure = 12 KSCG

No.of Nozzles = 5

Water consumption = 130 Cum/hr

Oxygen flow rate = 400-450 NM3/min

During blowing LD gas is generated. This is a very poisonous gas because its main component

is carbon monoxide. LD gas cooling, cleaning and collection system comprises of tube bar-tube type

skirt, gas cooling hood and stack, Closed loop type gas cooling arrangement with finfan cooler, kinpactor,

gas duct, ID fan, change over valve, flare-stack, gas holder, etc. When the gas composition isacceptable, it is recovered and collected in gas holder. Unacceptable LD gas is discharged through

Flare Stack.

LD gas Collection system - Gas collection with suppressed Combustion.

LD gas Cooling - Gas cooling with closed loop hot water pressurised

cooling system.

LD gas cleaning - Wet type cleaning system with adjustable

throat venturi.


75/309


Slag Splashing : After tapping of liquid steel, slag splasting is done after adding calcined dolo in the

slag to improve the lining life of converters.

SCRAP YARD :

Scrap is used as coolant. Scrap may be heavy (wt. up to 1.5 T) or light. Length should be less

than 1.5 M. Some times cast pig iron is used as scrap in case of shortage in steel scrap. Purpose ofscrap yard is to supply scrap to the converter periodically without any interruption Following equipments

are available in scrap yard.

1) Scrap Box Tansfer Car

2) Scrap Weigh Bridge

3) Scrap Box

4) Magnetic EOT Crane

Scrap should not have dust, moisture or water, grease, oil, etc. Generally 15T of Scrap is charged in each heat.

SLAG YARD :

The Slag generated in LD converter during refining of hot metal is collected in vessels called slag pots

(16/18 Meter cube capacity). This slag is dumped in the pits (4 nos.) which are present in slag yard.

For doing so, slag pots, slag pot transfer cars (3 nos.) slag dump cars (2nos.), EOT cranes (2 nos.),

etc. are needed.

LADLE PREPARATION BAY :

Ladles after prolonged use get wornout and need to be repaired. After one or two heats, plates for

slide gate control mechanism, for teeming liquid steel, need to be changed or repaired. All these and

many other activities are done in Ladle preparation bay. There are 26 steel ladles and 5 hot metalladles in SMS.

This bay will house the following main facilities:

Horizontal Ladle Stand - For slide gate fixing, Plate changing, etc.

Vertical Ladle Stand - For heating ladle

Relining Pits - For Relining the ladles

Ladle Drier - By burning coke-oven gas, ladle is heated

EOT Crane(3 nos.) - To handle the ladle

(Main hoist capacity 100T)On line drier - To heat the ladle before releasing for tapping.

ARGON RINSING STATION (ARS) :

The liquid steel which is tapped from LD converter is not homogenious in composition and temperature.

To make the liquid steel suitable for continuous casting purpose by making it homogenous, inert

gas rinsing is done. Generally Argon gas is used for this purpose. Both bottom and top purging

facilities are available. Bottom purging is superior than top purging. When both are used at a time, it

is more effective.


76/309


In general, 12 minutes rinsing is done. For all the 3 LD Converters steel transfer car track, 3

ARS are available. In case of LD-2 steel transfer car track, IRUT (Injection Refining & Up Temperature)

is installed. Along with steel temeperature rising, Argon Rinsing is also done simultaneously. To

raise the temperature at IRUT, oxygen blowing is done and simultaneously Aluminium is added.

In ARS, Aluminium is also added for complete deoxidation (to reduce oxyzen potential of liquidsteel below 10 PPM) and to increase Al% in liquid steel in certain grades of steel to make it suitable for

continuous casting purpose.

There is one ladle furnace in ARS Bay. In Ladle Furnace, composition adjustment and liquid

Steel-temperature raising can be done. Simultaneously Argon Rinsing is also done along with the

above said activities. In Ladle furnace, temperature of liquid steel is raised by electric arcing. There

are 3 graphite electrodes for this purpose.

When rinsing is over after achieving desired temperature and composition (varies from one

steel grade to another) ladle covering compound is added at the top layer of liquid steel in the ladle.

This reduces heat loss from ladle.

TUNDISH PREPARATION BAY :

Tundish is a refractory lined container having 4 nozzles through which liquid steel is poured in

all 4 moulds of a C.C.machine at a time. Pouring of liquid steel from tundish to mould is controlled by

stopper-rod mechanism. During casting, Tundish is placed over mould, and below steel ladle. Tundish

maintains the constant ferrostatic pressure and it helps in floating of the nonmetallic inclusions at the

top layer of liquid steel and thus non-metallic inclusions are prevented from entering into mould.

In Tundish preparation bay, used tundishes are cooled by water/compressed air and lining Is

demolished. All the relining activities, stopper-rod asembly fixing, etc. are done in this bay.

CONTINUOUS CASTING MACHINES (CCM) :

Continuous Casting may be defined as teeming of liquid metal in a mould with a false bottom

through which partially solidified ingot (same shape as mould) is continuously withdrawn at the same

rate at which liquid metal is poured in the mould.

Facilities and Equipments at CCM platforms: Lift and Turn Stand:

To accommodate the steel ladles and place them in casting position as and when required to

facilitate sequence casting. It lifts the ladle and places the ladle at casting position by turning it and

swing back the empty ladle after completion of casting.

Mould Oscillating system :

To facilitate easy withdrawl of continuously Cast bloom (partially solidified) from the mould.

Oscillation frequency : 40-100 cycle/min

Mould Oscillation stroke : 7 mm


77/309


Copper Mould :

The foremost important factor in the continuous casting is the copper mould which decides the

efficiency of the process. The material selected for mould and the design of mould play a prominent

role in obtaining the bloom of greater surface finish, better mechanical properties with minimum of

casting defects. A mould with good design associated by good cooling system gives quality blooms,

provided a great care, is excercised during casting.

In VSP, square (250mm x 250mm) and rectangular (320mm x 250mm) cross sectional moulds

are used. These moulds are provided taper towards bottom (327 x 255 top, 324x252.5 bottom in case

of 320x250 bloom) to maintain the contact between partially solidified strands and is made of copper

which is necessary for achieving the necessary cooling rate.

Copper is an ideal material for mould because it is having

i) good thermal conductivity.

ii) mechanical strength must be retained at operating temperature 250 degree C.

iii) recrystallization temperature above 300 degree C.

iv) low friction coefficient and good resistant to wear.

v) chemical immunity w.r.t. steel.

Cu-Ag 0.1 P-F 25-possess all the above properties.

Length of mould at VSP is 1.0 m

Radius of mould / Machine 12 m

STRAND COOLING :

Strand cooling is carried in two stages: Primary and Secondary cooling.

Primary Cooling :

The soft water is used for this purpose with PH 7-9, total hardness- 0.2 dh. This water is

repeatedly pumped through the moulds in a closed cycle with recooling blot. This water has to be

treated and anticorrosive agent etc., should be added. This water is supplied at a pressure of 5-6 bar.

The inlet water comes from the bottom & leaves the mould through the outlet valve which is located at

the top of mould. This is indirect type of cooling.

Secondary Cooling :

The water that is sprayed over the strand should cool the strand uniformly thoughout the length, toavoid under cooling of some parts of strand. The pressure will be 6 bar. The countoract flow problem

due to corrossion, the pipeline will be made up of stainless steel. In secondary cooling, strand (bloom)

will be completely solidified, leaving no liquid steel at all. The secondary cooling zone begins from

just below the mould.

Water for secondary cooling should have

PH 7-9, Total hardness 20 DH

Carbonate hardness 0.7 DH


78/309


Dummy Bar :

The function of Dummy Bar is to seal the mould bottom, for the starting of casting and to

withdraw solidified shell until the hot strand has passed the straightening and withdrawing machines.

Backup Roller sections N1 & N2 :

These sections are intended for supporting and directing the dummy bar and strand in course

of casting. N1 is a four roll section installed on posts underneath the secondary cooling sections, while

N2 is a six roll section installed after the 4-high stand.

Withdrawal and straightening rollers :

There are four strands which are used for withdrawing and straightening the curved bloom.

These 4 stands are designated as TK1, TK2, TK3, TK4.

TK1 - 4 high strand

TK2 - 2 high strand

TK3 - 2 high strand

TK4 - 2 high strand

Casting Powder :

The main purpose of casting powder is to act as a lubricant to prevent the sticking of steel to

mould. Casting powder must be added continuously at regular intervals. The meniscus must always

be covered enough that it appears dark, but layer thickness should not exceed 30 mm.

Casting powder should meet the following requirement :

i) reduce strand friction

ii) should protect liquid steel against reoxidation.

iii) prevent surface heat loss.

iv) promote uniform heat transfer from meniscus to mould in order to avoid longitudinal

cracks.

v) rapid and uniform spreading on the bath surface.

vi) it should also absorb some oxides in the steel without great change of its viscocity.

Technical details of CC machines

Average Casting speed for 320x250 bloom size is 0.78 M/min for 250x250 bloom size is 0.82

M/min

Gas Cutting Machines(GCM) :

The strand, which continuously comes from the copper mould after getting completely solidified,

should be cut as per our requirement, to facilitate easy handling, etc. In order to cut the blooms

accurately, a gas cutting machine, using acetylene and oxygen, is used.


79/309


Since the bloom travels with certain speed, the machine used for cutting the bloom should

travel along with the bloom. For this grippers are used, which grips the bloom and travels along with it,

taking the oxy-acetyline flame with it. Each CC machine has been provided with 4 cutting machines to

cut the four blooms at a time.

Details of gas cutting machines :

The pressure of the acetylene : 0.6 kg/sq.cm

Length of the bloom : 5.5 to 5.8 m for 250 x250mm size

6.0 to 6.4m for 320x 250 mm size

Time required for cutting one bloom : 1-1.5 min

The pressure of oxygen : 15 kg/cm2

Bloom Storage Yard (BSY) :

To sychronise the production in continuous casting machine and requirement of rolling mills

for blooms, Bloom storage yard (BSY) has been established. Inspection and selective conditions are

also carried out in BSY. After cutting the blooms at GCM they are moved to cooling beds and after

cooling they are transferred to racks. The BSY is served by 11 nos. EOT cranes with rotating cabins

and magnet facility. Blooms of particular grade of steel are stored at a particular place. Every bloom is

marked by heat no. and machine no.

The sequence of operations in brief at different sections of continuous casting shop is given

below :

1) Steel ladle from converter after tapping is transferred to Argon Rinsing station.

2) In rinsing station : Argon purging (bottom or top or both) is carried out for a period not less than

12 minutes. During rinsing, Aluminium is also added.

3) The sample and temperature are taken. The sample is sent to lab and composition is verified.

If temperature and composition are satisfied, liquid steel is sent to casting platform. If

temperature or composition corrections are required, they are done either at ARS or IRUT or

LF.

4) In CCM, first of all, dummy bar is inserted through the mould. Some small scrap is charged into

mould to enhance cooling rate of liquid steel, to enable the operator to withdraw the dummy

bar.


80/309


5) In CCM, the ladle with liquid steel is placed on the lift and turn stand and will be fixed with

hydraulic cylinder for operating slide gate mechanism to control teeming of liquid steel to

Tundish from ladle.

6) Meanwhile tundish is preheated to about 10000C. Stopper are checked before the tundish is

placed into casting position. After placing the tundish at casting position, nozzles are posi-

tioned exactly in the centre of the mould.

7) Ladle is brought to casting position by turning the lift and turn stand. Stoppers of the tundish

are kept closed. Slide gate of ladle is opened by hydraulic mechanism. If liquid steel stream

is not proper or liquid steel is not coming, oxygen lancing is carried out in ladle nozzle.

8) Liquid steel is continuously fed into the tundish and the level in tundish is carefully observed.

When it is 2/3 full, stoppers will be opened to allow the steel to fill the mould.

9) Before feeding liquid steel into mould water circulation in the mould is to be ensured

10) After the steel meniscus reaches certain level, dummy bars withdrawal will be started.

Secondary cooling water spray is also started.

11) After the dummy bar passes over the withdrawal rollers, it will be disengaged.

12) Continuously coming bloom is cut by gas cutting machine. The required length of cut blooms

are sent to BSY after marking the heat no. and CC machine no. by hot chalk.

13) These blooms are stacked, inspected and heat no. is written by paint over cross section ofbloom. Blooms are sent to rolling mills as per requirement.


81/309



82/309



83/309


Chapter - 10

LIGHT AND MEDIUM MERCHANT MILL

INTRODUCTION :

Visakhapatnam Steel Plant has three sophisticated Rolling mills, designed to produce 2.656 milliontones per annum of finished products from continuously cast blooms with a wide range of product mix.

The mills are :

a. Light & Medium Merchant Mill (LMMM)

b. Medium Merchant & structural Mill (MMSM)

c. Wire Rod mill (WRM)

SOME OF THE SALIENT FEATURES OF THE MILL ARE :

a. High capacity and high speed.

b. Automatic minimum tension control in stands

c. Double sided cooling beds of walking beam type.

d. High capacity and high productive sawing lines.

e. Automatic bundling machines.

f. Computerization at the sequential process control and material tracking

g. Adoption of closed circuit TV at furnaces.

h. evaporative cooling system and waste heat recovery.

These features help to optimize the production and assure quality products from the mill.

BLOOM STORAGE AND INSPECTION :

The SMS supplies continuous cast blooms in killed and semiskilled quality of ordinary grade, high

carbon and low alloy steels. The bloom storage is at right angles and common to all mills. Bloom

inspection and storage, if necessary, is carried out in the common storage.

LIGHT AND MEDIUM MERCHANT MILL :

Keeping in view the latest developments the light and medium merchant mill is designed with the

operation floor on a second storie elevation, namely +5.0 mts. This arrangement has many

advantages. It provides better drainages for both lubricants and water and mill scale. The oil cellars

can be placed at slightly below the ground level with out deep excavations but ensuring adequatedrainage. The oil and water pipes and cable trenches are readily accessible.

Blooms for LMMM are placed on charging grids (3 nos) of 150 tonnes per hour capacity each by 16

tonnes claw cranes (2 nos). The blooms are then delivered to the furnace approach roller table (+5.8mts)

by an inclined elevator from bloom storage roller table (+0.8mts)

The approach roller table is provided with a weighing scale, a tilter and disappearing stops. The

blooms are positioned in front of the furnaces and then pushed by hydraulic pushers on to the charging

skids of the furnaces. There are two nos. of walking beam type furnaces of 200 T/hr capacity with


84/309


double row charging. The blooms also can be discharged from the charging side of the furnaces in

case of emergency. Heated blooms are placed piece by piece by discharging devices on to the furnace

delivery roller table. The blooms are descaled by high pressure de-scaler.

The continuous Break-Down group (non-reversing) consists of 7 stand -2 Horizontal (850x1200mm)

and 5 alternating vertical and horizontal (730X1000mm and 630X1000mm).

In 5 Box passes and one each of diamond and square passes, the blooms are reduced to 125 mm

square in the 7 stands. The finishing speed will be 1.3 to 1.6 mts/sec. A four crank shear installed

behind the mill stands is designed to crop both ends and to cut billet lengths as per requirement of

WRM & Sales as per requirement to achieve optimum yield in cutting. Billets feeding the LMMM are

cropped at the front and back ends.

Normally one Bloom is rolled for LMMM and the next one for the WRM alternatively, Billets are also

sold. The billets for WRM and for sale are cooled on 2 turn over - type cooling beds to a maximum

discharge temperature of 4000 C. These billets are picked up by magnet cranes of 16 T capacity in the

intermediate billet storage and transferred to the transfer grids in the shipping area or dispatched for

sale.

Billets after cropping by the 4 crank shear and having a length of about 32 mts are transported to the

in-line 2 strand roller hearth furnace of 200 T/h Capacity. Billets normally arrive at the furnace with a

surface temperature of 11000 C. Billets are heated and soaked to a discharging temperature of 11500

C to 11300 C.

The continuous multi-line mill comprises 8 stand double strand roughing train, 2 Nos, 4 Stand Single

strand finishing trains.

Loopers are provided in between the finishing stands for tension free rolling in order to obtain good

surface quality and tolerances. Housings are of closed top type. Roll necks are mounted in anti friction

bearings.

Shears for cropping and emergency cutting are arranged ahead of the first of roughing mill stand and

upstream of intermediate mills. Snap shears for emergency cuts only are ahead of finishing mill. The

rotating shears after the finishing mills crop the materials leaving at rolling speed. And cut into multiples

of specified sales lengths.

The finished bar now enters the cooling stretches. There are two cooling stretches each installed just

downstream the last stand of the finishing mill. The purpose of the cooling stretches is to cool down

the rebars to such an extent so as to produce desired mechanical properties. It also serves to control

the scale formation.

The bar leaving the last stand of the finishing mill passes through a cooling stretch. The coolingefficiency of this installation is such that a surface layer of the bar is quenched into martensite, the

core remaining austenite. The quenching treatment is stopped when a determined thickness of

martensite has been formed under the skin when the rebar leaves the cooling stretch, a temperature

gradient is established in the cross-sections of the bar causing heat to flow from center to the

surface, which results in self-tempering of the martensite Finally during slow cooling of the rebar on

the cooling bed, the austenitic core transforms into ferrite and pearlite. To achieve the required

mechanical properties, it is sufficient to maintain the tempering temperature within a predetermined


85/309


range. The obvious control variables are the length of the quenching line and the cooling water flow

late at suitable number of cooling pipes whose diameter, are chosen as a function of product diameter.

Air Strippers are fitted at the end of cooling pipes to make sure that the material leaves the stretch in

dry condition. The pinch roll units; downstream the cooling stretch guarantees the correct bar speed

during the cooling process. These pinch rolls are speed synchronized with the exit stands of finishing

mill 1 & II so that bar speed remains same when the bar tail has left exit stand of finishing mill. They

also serve to enter the material into the rotary shear. A total cooling bed of 130 mts X 12 mts has been

provided for cooling down the rolled section at about 8080C maximum for straightening.

In the downstream of the cooling beds there are multi strand straightening machines (maximum 8

straightening strands) The number of straightening rolls are 8 (top 4 and bottom 4). The bar groups

from the straighteners are collected in layers for the downstream cold shear by cross - transfers. The

2 cold shears have cutting pressure of 500 MPa each. Desired finished lengths normally 12 mts are

set by girder type gauge carriages. Tail lengths less than 6 mts are discharged into cradles near the

cold shears. Downstream file cold shears, rounds, and rebars are transported to bar bundling facility.

There are two bundling facilities. The bar bundling facilities have provision for counting the bars, andstrapping the collected bars into bundles of 4500 Kgs and 10000 Kgs.

Strapping of bar bundles and packs is by means of wire and straps.

The finished section packs/bundles are finally transported to the weighers and the loading grid permits

the bundles to be picked up by magnetic cranes in the finished product storage area having lifting

magnets of 20 Tonnes capacity.

ELECTRICAL EQUIPMENTS IN LMMM

The mill stands are driven by individual main drive motors. The motors are separately excited and

compensated DC shunt motors in two frame sizes.

The armature circuits of the motors are provided with individual thyristor power supply comprising 11

KV converter transformer, thyristor converter, reactor, single pole high speed circuit breaker and double

pole no-load contractor, in ratings to match the motor overloads. Field circuits of the motors are fed by

individual thyristor power supply systems fed from 415V, 3-Phase supply source, over isolation

transformer.

For AC drives the motors provided are generally squirrel cage type for continuous operation drives

and slip ring type for intermittent duty drives. Geared motors for individually roller table drives have

also been foreseen. AC motors provided are totally enclosed Fan-cooled.

Variable frequency motors for roller table drives are fed over variable voltage -variable frequency

(VVVF) supply sources.

AUTOMATION AND CONTROL SYSTEM IN LMMM :

PLCs in LMMM :

Different makes of PLCs are used in various areas of automation for operation control.

AEG-PLC : ( 38 Nos)

Total mill control

Reference generation for all drives


86/309


Sequence and interlocking for process equipments.

Position control for drives.

Video interface for the operator in the control pulpit

ALLEN BRADLEY-PLC ( 5 Nos)

Walking beam furnace control system - 2 Nos.

Cobble detection system for merchant bar mill - 1 No.

Strapping machine control system - 2 Nos. with 9 nos. Remote I/O

GE FANUC-PLC (7 Nos)

Total mill control

Reference generation for all drives

Sequence and interlocking for process equipments.

Position control for drives.

Video interface for the operator in the control pulpit

Roller hearth furnace control system

Air oil lubrication system control

SIEMENS PLC (1 No)

Booster water station

LEVELS OF AUTOMATION IN LMMM :

Programmable Logic Controllers (PLCs) provided at level-1 finally control the process equipment

directly, each in its own area for sequencing and interlocking functions. The system envisaged is

interfaced with the main and auxiliary drive analogue control system so as to perform as one integrated

unit.

The control at Level-2 is basically decentralized and distributed in concept so as to offer a higher

degree of operational flexibility. A number of microcomputer subsystems provided at this level, operate

and control function for equipment distributed in various areas of the mill.

For operators communication with the system dialogue terminals (VDU and Keyboard units) have

been envisaged in control pulpits of the mill. Printers for hard copy print out of rolling schedule, shift

reports etc.

The control system envisaged is basically automatic with provision of manual control locally for

equipment to take care of local disturbance during operation and also the maintenance needs.

UPGRADATION OF PLCs :

Most of the important PLCs of the Billet mill and Bar mill are being upgraded to latest GE FANUC

make.


87/309



88/309



89/309



90/309



91/309



92/309



93/309



94/309


Modifications done in MMSM to improve productivity

1) Roll-pass design modification in MC100,MC125&MC150 for more pass-life in finishing stands

2) Roll-pass design modification in Rounds to make exit stand horizontal,for easy adjustment in

mill during rolling

3) Double bars to batching in rounds,thus increasing output from Cooling bed

4) Diameter of cold saw blades reduced to 1460mm from 1604mm and 1500mm,thus increasing

stability of the blade

5) Hydraulic feeder modified to mechanical feeder,thus reducing hydraulic leakage in piling


95/309



96/309



97/309



98/309



99/309



100/309



101/309



102/309



103/309



104/309



105/309


Chapter - 13

ROLL SHOP AND REPAIR SHOP

Roll shop & Repair shop (RS&RS) is a prime service department to the three rolling mills of

VSP. Located in the complex of Rolling Mills, RS&RS caters to the mill requirements of Roll passdesign, Guide design, Supply of roll assemblies, guide assemblies and maintenance spares all in one

department which is unique in the steel industry. For the first time in the country, CNC technology has

been adopted for grooving of steel mill rolls for achie

MT's Guide .pdf

Documents

Transcript of MT's Guide .pdf