CASE  STUDY  FOR ENERGY  SAVINGS  IN STEEL PLANTS




Bhilai Steel Plant

Unit  Profile :

Bhilai Steel Plant, a unit of Steel Authority of
India Ltd
. - a public sector undertaking was conceived
under aegis of Indo-USSR Treaty in the 2nd
Five year plan. This was in accordance with
erstwhile government policy for strengthening
economy and self reliance through development
of core sector.

Bhilai Steel Plant, an integrated steel works was
commissioned in 1959 with production capacity of
1.0 million tonne of steel. In successive phases,
capacity was enhanced to 2.5 and 4.0 million
tonne in the year 1962 and 1984 respectively.
As of now this is the largest steel plant in India
with present capacity utilisation more than 100%. State of art technology like 7 meter tall coke oven
batteries, 600 m2 sinter machine, LD converter, Continuous casting, Twin Hearth Furnace etc. were
adopted during capacity augmentation.


Energy Consumption   

Steel production in Bhilai Steel Plant, like any other integrated steel works, is highly energy intensive. The
gross energy consumption in the plant for the year 2001-2002 is 3,323 Gcal/Hr. which is equivalent of
2.87 million TOE ( ton of oil equivalent ) per year. The primary energy input for the year 2001-2002
constitute 3.5 million tonne of Coking Coal, 0.7 million tonne of Boiler Coal, purchased electrical power of
115.5 MW and 10521 kilo litres of petro-fuel.

The demand of other energy items, viz, steam, compressed air, oxygen etc. are completely met by
in-house auxiliary units. 54 % of the total power demand of the plant is met by captive power plants.

The annual energy bill for the company is around Rs. 1687 Crores which comprises around 40 % of the
total production cost. The specific energy consumption for the year 2001-2002 is 7.07 Gcal per tonne of
cast steel.

Energy Conservation Commitment, Policy and Set up

Energy intensive nature of integrated steel works and global energy crisis influenced policy makers of the
company to accord high degree of priority for energy conservation as one of the major thrust areas for
cost reduction.

In order to achieve company's goal, a elaborated energy conservation strategy and organisational
framework was evolved. A full-fledged Energy Conservation Cell headed by Senior Manager and
supported by three executives were formed and entrusted for close monitoring and control of energy
parameters by adhering to technological discipline. Control of wastage of utilities like steam, Oxygen etc.
were also given to this group.



ENERGY CONSERVATION TEAM STRUCTURE


The cost analysis is carried out on the monthly basis by the competent group. Their prime task is to
translate the deviation in energy performance indices in the term of cost and its impact on the profitability
of the plant.

Modification and retrofitting for energy efficient programme in the existing technologies are initiated by
the respective departments of the plant. These projects are cleared purely on merit and priority basis by
a committee designated by management.

Energy performance report for the plant are prepared on daily, weekly and monthly basis by MIS group of
Energy Conservation Cell. These reports are reviewed on regular basis to enhance plant performance.

Energy Conservation Achievements

The specific energy consumption in last few years registered steady decline with the exception of
2000-2001 when specific energy consumption was marginally higher than previous year due to planned
low production. Specific energy consumption of the plant per tonne of cast steel was 7.16 Gcal in
99-2000. The same has come down to 7.07 Gcal in the year 2001-2002, which is lowest among all Indian
integrated steel plants. This result speaks the total commitment made by Bhilai Steel Plant for energy
conservation.

YEAR               PRODUCT        KWH/TONNE        % REDUCTIONOVER 99-00        MKCAL / TONNE        
1999-2000        CRUDE STEEL        443                              ----               7.16                ---
2000-2001        CRUDE STEEL        427                             3.6                7.25                (-) 1.25
2001-2002        CRUDE STEEL        417                             5.87              7.07                     1.25

Energy Conservation measures implemented during 2001-2002 are given below :

1.        HOT SLAB CHARGING IN PLATE MILL REHEATING FURNACE        

Plate Mill reheating furnaces, where slabs are preheated prior to rolling, are fed with slab at room
temperature as per the original design.

To reduce the specific heat consumption, the furnaces are presently supplied with hot slabs as and when
available as per logistics. For feeding of hot slab to furnace, normal rolls of charging tables have been
modified to water-cooled rolls. This has helped to reduce specific heat consumption in Plate Mill by 25
Mcal per tonne of slab rolled.

2.        CONVERSION OF STEAM TURBINE-4 OF EXHAUSTER HOUSE-1 IN CCD TO BACK PRESSURE
TURBINE

STEAM TURBINE IS PROVIDED IN COAL CHEMICAL DEPARTMENT FOR EXHAUSTING COKE OVEN
GAS GENERATED DURING COKE MAKING IN COKE OVEN BATTERIES. TURBINE-4 IS DESIGNED TO
BE OPERATED WITH 18 ATMOSPHERE STEAM AND TOTAL STEAM USED TO GET CONDENSED. THE
MODIFICATION HAS BEEN CARRIED OUT IN THIS TURBINE AND INSTEAD OF TOTAL CONDENSATION
OF STEAM IN THE TURBINE, THE STEAM IS TAKEN OUT AT 8 ATMOSPHERES AND FURTHER
REUSED AS PROCESS STEAM. THIS HAS SAVED PROCESS STEAM @ 10T/HR. SAVING ABOUT RS. 1
LAKH/DAY.

3.        MODIFICATION OF WIND BOXES IN SINTER PLANT-2 FOR IMPROVING SUCTION   

All sinter machines are provided wind boxes for suction of air through sinter bed. This helps for ignition of
sinter and has direct impact on coke breeze consumption as well as specific heat consumption. In the
present condition, air infiltration through wind boxes were high and had detrimental effect on the sinter
making.

To reduce air infiltration, stationary damper of pre-designed size with predetermined slits were installed in
the wind box. This design was calculated based on the existing gas dynamics.

The modification has resulted better suction with reduced air infiltration. The project yielded reduction in
specific heat consumption in Sinter Plant-2 from 65 Mcal/Tonne to 45 Mcal/Tonne.

4.        USE OF JHAMA COAL IN SINTER PLANTS

Coke breeze in an essential fuel in sinter making process, which is a by-product of coke making process.
With reduction in Blast Furnace coke consumption, the generation of coke breeze has reduced and total
requirement of coke breeze in Sinter Plant could not be met.

To meet the requirement of coke breeze, instead of purchasing coke breeze (cost Rs. 2000/tonne).
Jhama coal (which is burnt out coal of IISCO Mines) costing Rs.1500/tonne is used.

To facilitate use of Jhama Coal, a hammer crusher (No.-5) was installed with in house resource. In the
year 2001-2002, 31,000 tonnes of Jhama Coal has been used.


5.        PUMPING OF STEAM CONDENSATE FROM COAL CHEMICAL DEPARTMENT    TO POWER
PLANT-1

At the design stage of the plant, there was provision of pumping back of steam condensate from Coal
Chemical Department to Power Plant-1, which did not operate.

For conservation of energy, this facility was revived in 2001-2002 and every day about 130-140 T/day of
steam condensate is pumped back to Power Plant-1.


6.        OPTIMAL USE OF EQUIPMENTS        

A)        STOPPAGE OF ONE HAMMER CRUSHER IN SINTER PLANT

There are 2 nos. of hammer crusher in Sinter Plant-2 for homogenisation of Iron Ore Charge. The
efficiency of these hammer crushers were improved by proper maintenance and improved material of
construction. This resulted in stoppage of one hammer crusher, thereby saving 0.5 MW power.

B)        OPTIMAL USE OF LIME KILN

There are 2 lime kilns, which are operated for manufacture of lime required for steel making. This lime
kilns are operated with LSHS as fuel.

Improve operation technique in steel making has reduced lime consumption. This has resulted in
stoppage of one lime kiln from operation circuit and thereby 5400 KL of LSHS requirement were reduced
on annual basis.


7.        RECYCLING OF TOWNSHIP WASTE WATER

Waste water of Bhilai Township was bio-oxidised prior to release of  water in Kharona River.

Bhilai Steel Plant management has strengthened the bio-oxidation system and decided to release this
water in Maroda Tank (for storage of industrial water). Necessary infrastructure was incorporated for
release of water to Maroda Tank. This has saved 1752 thousand m3 of fresh water requirement and will
be of great strength at the time of water crisis in summer months.

Energy Conservation Plans and Targets

The company has set up a challenging target of reducing specific energy consumption by 2% in every
successive year and to reach International Norm.

The proposed future plans for energy conservation are as follows :

1.  Augmentation of L.D.Gas evacuation scheme for maximisation of L.D.gas recovery.

2.  Conversion of one more gas exhauster turbine to back pressure steam facility in CO&CCD.        

3.  Modification in burner design of Power Plant-1 boilers for increased coke oven gas intake.

4. Operating minimum pits with maximum production in Soaking Pits.

5.  Introduction of Coal Dust Injection in 3 more Blast Furnaces.

6. De-centralisation of exhaust system of duct in casting machines.

Source : Bureau of Energy Efficiency,India













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