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Improving Energy EfficiencyImproving Energy Efficiency

Through Retrofitting TechnologiesThrough Retrofitting TechnologiesIn Existing ReIn Existing Re--heating Furnaces ofheating Furnaces of

Small Sector ReSmall Sector Re--rolling Millsrolling Mills

R & D Center for Iron and Steel

STEEL AUTHORITY OF INDIA LIMITED

RANCHI, JHARKHAND, INDIA

I .N.P. Gupt a

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INTRODUCTIONINTRODUCTION

Steel Industry being highly energy intensive.

Continuous increase in energy cost Energy cost of steel: one third of its total

production cost. Lot of competition in steel sector.

Net sale realization is decreasing. Necessity of adopting new technology in

reheating furnace to improve product quality& reduction in energy cost.

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INTRODUCTIONINTRODUCTION (Cont.)(Cont.)

PCRA, New Delhi sponsored a project (2002-04)to RDCIS to study & identify barriers in reducing oil

consumption and GHG emission in re-heatingfurnaces (RHFs) of small re-rollers.

RDCIS developed design, drawings & technicalspecifications for 7.5 t/hr capacity RHF having allbasic facilities for better fuel efficiency.

Retrofitting designs and estimates for existingRHFs were also made.

Another project (2005-06) to implement energyconservation schemes through retrofittingstrategies in existing furnaces to increase

productivity by 25% & decrease specific fuelconsumption by 20% was sponsored by PCRA.

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IMPORTANCE OF SMALL SCALEIMPORTANCE OF SMALL SCALERERE--ROLLING MILL IN INDIAROLLING MILL IN INDIA

More than 1400 re-rolling mills in the small andmedium sector in India

Employment to about 70,000 unskilled and semi

skilled workers

Low capital investment of Rs. 20 Million for every10,000 t/year capacity against Rs. 100 Million inintegrated steel plant

Low operational cost

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SOME UNIQUE FEATURES OFSOME UNIQUE FEATURES OF

RERE--ROLLERS IN INDIAROLLERS IN INDIA Smaller furnace capacity (5 - 10 t/hr)

Fuel Used: Coal, Producer/ LP gas, Liquid fuels

Higher billet discharge temperature (1275 - 1300C)

Limited working hours of mills (10 12 hrs)

Use of wide range of input materials: billets, pencil

ingots, plate scrap, used rails etc. Variety of products: CTD bars, TMT rods, small

merchant products, narrow thin strips etc.

Higher Specific fuel consumption (425 570 Mcal/t)

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SOME UNIQUE FEATURES OFSOME UNIQUE FEATURES OF

RERE--ROLLERSROLLERS (Cont.)(Cont.)

Underground flue duct

Higher Oxygen content in flue gas (> 4%)

Air preheat temperature below 200C

Un-insulated fuel oil and combustion air line

Poor hearth life of soaking zone (3 - 4 months)

Large manual operations with limited operationalskills

Low enthusiasm for modernization due toconsiderable capital investment/ design know-how

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Measurement of billet

Temperature

Flue gas analysis

Calculation of the heat

balance

Observations:

Overheating of billets

Higher O2 in Flue gases

Measures for increasingfurnace productivity and

reduction in specific fuelconsumption

THERMAL ENGINEERINGTHERMAL ENGINEERING

INVESTIGATIONSINVESTIGATIONS

Temperature profile ofdischarged billet

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OPTIONS FOR RETROFITTINGOPTIONS FOR RETROFITTING

Modification of furnace zonesModification of waste heat recovery

Modification of combustion system

Ceramic fibre insulations

Ultra low cement castable hearth

Introduction of control system

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IMPLEMENTAION OF RETROFITTINGIMPLEMENTAION OF RETROFITTING

STRATEGIESSTRATEGIES

Extension in furnace length

Existing length of most of RHFs: 18 20 meter

Length of RHFs increased by 5 meters (25%)

Addition of a new heat recuperative zone

Design and introduction of efficient

recuperator

Existing air preheat temperature: Below 200CDesign of recuperator for air preheat temperature

upto 250 275C

Flue gas temperature at furnace exit: 500 600C

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IMPLEMENTAION OF RETROFITTINGIMPLEMENTAION OF RETROFITTING

STRATEGIESSTRATEGIES (Cont.)(Cont.) Design of efficient producer gas burner

Producer Gas Burner

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RETROFITTING STRATEGIESRETROFITTING STRATEGIES

(Cont.)(Cont.) Introduction of manual & semi auto control

system Installation of thermocouple having ceramic

sheathe of better spalling life

Installation of orifice plates & basic instruments

Design and improvement of furnace hearth,roof and sidewall insulation

Introduction of Ultra Low Cement Castable(ULCC) in soaking hearth:

Al2O3 : 80%

Bulk Density : 2.85 gm/ccCCS : 1200 Kg/cm2 at 1500 C / 3 hrs.

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IMPLEMENTAION OF RETROFITTINGIMPLEMENTAION OF RETROFITTING

STRATEGIESSTRATEGIES (Cont.)(Cont.) Design and modification of flue duct system

Overhead Flue Duct System

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TEMPERATURE MEASUREMENTTEMPERATURE MEASUREMENT

PLAN OF TEST BILLETPLAN OF TEST BILLET

Size and location of holes in test billet

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HEATING OF BILEETS INSIDEHEATING OF BILEETS INSIDE

THE FURNACETHE FURNACE

Temperature of test billet after retrofitting

200

400

600

800

1000

1200

0:00 0:28 0:57 1:26 1:55 2:24 2:52 3:21 3:50

Time (hr:min)

Temperature(C)

Bottom

coreTop

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RESULTS OBTAINEDRESULTS OBTAINED

Parameters Beforeretrofitting

Afterretrofitting

Production (t/day) 54 63

Sp. Fuel Consumption (Mcal/t) 487 311

Av. Soaking Zone Temp. ( C) 1275 1225

Av. Heating Zone Temp. ( C) 1180 1150

Flue Gas Temp. ( C) 516 400

Preheated Air Temp. ( C) 206 180

Furnace Shell Temp. ( C) 125 85

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HEAT BALANCEHEAT BALANCE

Parameters Heat Content (Mcal/t)

Input Ideal Beforeretrofitting

Afterretrofitting

Fuel 300 487 331

Preheated Comb. Air 42 41 36Output

Steel 192 200 193

Flue Gas 122 115 89

Radiation &Unaccounted losses

28 213 85

Efficiency 64.0 41.1 58.3

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IMPACT OF INDIVIDUALIMPACT OF INDIVIDUAL

RETROFITTING SCHEMESRETROFITTING SCHEMESReduction in Sp. Fuel

ConsumptionRetrofitting Schemes

(Mcal/t) (%)

Extension of furnace length 97 62.2

Modification of burner andrecuperator

29 18.6

Reduction in discharge

temperature

14 9.0

Improvement in insulation 10 6.4

Others 6 3.8

Total 156 100

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FORMATION OF SCALEFORMATION OF SCALE

0.00

0.50

1.00

1.50

2.00

2.50

700 800 900 1000 1100 1200 1300

Temperature (C)

Scale

thickness

(mm)

1.5 hrs.

1 hr0.5 hr

REDUCTION IN HEATING DURATION BY 30 MIN. &

AVERAGE SOAKING ZONE TEMP. FROM 1275 TO 1225CREDUCES SCALE FORMATION BY 15 20 %

CONCLUSIONS

CONCLUSIONSCONCLUSIONS

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CONCLUSIONSCONCLUSIONSCONCLUSIONS

Reduction in specific fuel consumption by morethan 30 %

Increase in furnace productivity by about 17 %

and still further scope for increased productivity Increase in soaking zone hearth life from 6

months to 22 months

Reduction in Oxygen content in the flue gas from6 - 7% to 2 - 3 %

Increase in furnace efficiency by 44 %

Expected reduction in scale formation by 15 - 20%

Retrofitting is the best option for existing RHFs

RDCIS has expertise in design and developmentof combustion system for existing RHFs

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THANK YOU

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EFFECTS OF INCREASED FURNACE

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EFFECTS OF INCREASED FURNACEWIDTH / LENGTH

Increasing furnace Width Increasing furnace Length

Same

production

Higher

production

Same

production

Higher

production

Civil & structural

Change

Major Major Minor Minor

Productivity No change Increase No change Increase

Sp. fuel consumption Increase Decrease Slight increase Decrease

Billet length Higher Higher No change No change

Residence time No change No change Increase No change

Load on Pusher No change Increase Increase Increase

Air preheat Temperature No change No change Decrease No change

Flue exit temperature No change No change Decrease No change

Scale formation No change No change Increase No change

Parameters