Factors Influencing the Total Energy Consumption in Arc Furnaces.ppt

Factors Influencing the Total Energy Consumption in Arc Furnaces

1. Wayne AdamsWayne Adams
Said AlameddineSaid Alameddine
Ben BowmanBen Bowman
Nicolas LugoNicolas Lugo
Stefan PaegeStefan Paege
Paul StaffordPaul Stafford
UCAR Carbon Company Inc.UCAR Carbon Company Inc.
Factors InfluencingFactors Influencing
thethe
Total Energy ConsumptionTotal Energy Consumption
in Arc Furnacesin Arc Furnaces

2. Total Energy Consumption
Electrical
Chemical
Electrical Energy 60 - 80 %
Lance Energy 10 - 30 %
Burner Energy up to 20 %

3. KWH Equivalents of Chemical Energy
Natural Gas

CH
4
C
2
H
6
C
3
H
8
C
4
H
10
C
5
H
14
CO
2
N
2
~ 10.5 kWh / Nm3
(energy equivalent)
27.6 kWh / 100 SCF

4. KWH Equivalents of Chemical EnergyKWH Equivalents of Chemical Energy
Total
Oxygen
Lance
Oxygen
2:1
Burner
Oxygen
Excess

5. KWH Equivalents of Chemical Energy
Lance Oxygen
C
Fe
Si
Mn
~ 5.2 kWh / Nm3
(energy equivalent)
18.5 kWh / 100 SCF

6. KWH Equivalents of Chemical Energy
kWh / tkWh / t
C + 0.5 OC + 0.5 O
22 = CO = CO 35.935.9
Fe + O = FeOFe + O = FeO 40.340.3
2 Fe + 1.5 O2 = Fe2 Fe + 1.5 O2 = Fe
22OO
33
16.216.2
Si + OSi + O
22 = SiO = SiO
22
25.425.4
Mn + 0.5 OMn + 0.5 O
22 = MnO = MnO 13.513.5
Total Total 131.3131.3
kWh/mkWh/m
33
Oxygen equivalentOxygen equivalent 5.25.2
Calculated energy from 25 m
3
/t lance oxygen (100 t furnace)

7. KWH Equivalents of Chemical EnergyKWH Equivalents of Chemical Energy
Pig Iron

Si (~0.8%)
Mn (~0.5%)
C (0.6 kWh/kg)
~ 1.1 kWh/t
per 1% scrap replacement
(energy advantage)

8. KWH Equivalents of Chemical EnergyKWH Equivalents of Chemical Energy
Hot Metal
1150-1350
o
C
Si (~0.8%)
Mn (~0.5%)
C (0.6 kWh/kg)
~ 4.5 kWh/t
per 1% scrap replacement
(energy advantage)

9. KWH Equivalents of Chemical EnergyKWH Equivalents of Chemical Energy
DRI
&
HBI
Gangue
(4-5%)
Metallization
(92-93%)
~ - 1.0 kWh/t
per 1% scrap replacement
(energy disadvantage)

10. Oxygen lanced or injectedOxygen lanced or injected 5.2 kWh per Nm5.2 kWh per Nm
33
O O
22
18.5 kWh per 100 SCF18.5 kWh per 100 SCF
Natural gas through burnersNatural gas through burners10.5 kWh per Nm10.5 kWh per Nm
33
gas (with 2.0 m gas (with 2.0 m
33
O O
22))
27.6 kWh per 100 SCF27.6 kWh per 100 SCF
Pig ironPig iron 1.1 kWh added for each 1 % scrap replacement1.1 kWh added for each 1 % scrap replacement
1.0 kWh per short ton1.0 kWh per short ton
DRI (HBI)DRI (HBI) 1.0 kWh subtracted for each 1 % scrap replacement1.0 kWh subtracted for each 1 % scrap replacement
0.9 kWh per short ton0.9 kWh per short ton
Hot metalHot metal 4.5 KWh added for each 1 % scrap replacement4.5 KWh added for each 1 % scrap replacement
4.1 kWh per short ton4.1 kWh per short ton
Energy Equivalents

11. 0
2
4
6
8
10
12
14
16
18
20
Total energy (kWh/t liquid)
Total Energy Consumption
( furnaces over 80 t liq/hr)
Mean = 583

12. Factors Affecting Energy ConsumptionFactors Affecting Energy Consumption
 Charge Materials

Yield up to 60 kWh/t
(1% drop in yield causes 10 kWh/t energy increase)

Shape up to 40 kWh/t

Non-Ferrous Content up to 30 kWh/t
Scrap
Fluxes
 Amount up to 72 kWh/t
(1% of scrap weight increase causes 16 kWh/t energy increase)

13. Factors Affecting Energy ConsumptionFactors Affecting Energy Consumption
 Charging Practice
Number of Baskets ~ 10 kWh/t per basket
Scrap Layering up to 20 kWh/t
Slag Flux Charging up to 10 kWh/t
Liquid Heel up to 15 kWh/t

14. Factors Affecting Energy ConsumptionFactors Affecting Energy Consumption
 Operating Practice
Electrical Power Program ~ 20 kWh/t per 100 volts
Foaming Slag Quality + / - 20 kWh/t
Oxygen Lance Practice + / - 30 kWh/t
Burners up to 10 kWh/t
Post Combustion ~ 3.1 kWh/m
3
Tapping Temperature up to 70 kWh/t
Time (delays) ~ 0.4 kWh/t per min.
Twin-shell operation up to 27 kWh/t
Slag cover (roof & walls)up to 3 kWh/t per m
2
uncovered
Extraction system/furnace tightness + / - 30 kWh/ /t
Water-cooling of electrodes up to 20 kWh/t

15. Calculations or correlationsCalculations or correlations
ParameterParameter RateRate
Potential effect onPotential effect on
total kWh/ttotal kWh/t
DecreaseDecreaseIncreaseIncrease
Arc voltage during refiningArc voltage during refiningper 100 volts above 450 AC or 600 DCper 100 volts above 450 AC or 600 DC 2020
Delay in refiningDelay in refining per 10 minutesper 10 minutes 1717
Slag additionsSlag additions per 10 kg/t scrapper 10 kg/t scrap 1616
YieldYield per drop of 1 %per drop of 1 % 1010
DRI (or HBI)DRI (or HBI) per 10 % additionper 10 % addition 1010
No. of basketsNo. of baskets per basketper basket 1010
Roof slag coverRoof slag cover per 3 m2 uncoveredper 3 m2 uncovered 1010
Tapping TempTapping Temp per 10 deg C > 1600per 10 deg C > 1600 77
Delay < 30 min between heatsDelay < 30 min between heatsper 10 minutesper 10 minutes 55
Delay during meltingDelay during melting per 10 minutesper 10 minutes 44
Delay > 30 min between heatsDelay > 30 min between heatsper 10 minutesper 10 minutes 33
Hot MetalHot Metal per 10 % additionper 10 % addition 4545
Twin ShellTwin Shell Power-off lossPower-off loss 2727
Pig IronPig Iron per 10 % additionper 10 % addition 1111
Summary of key factors (part 1)

16. EstimationsEstimations
ParameterParameter RateRate
Potential effect onPotential effect on
total kWh/ttotal kWh/t
DecreaseDecreaseIncreaseIncrease
RangeRange
Energy recovery systemEnergy recovery system Shafts, Consteel, preheatersShafts, Consteel, preheaters 30 to 5030 to 50
Lance practiceLance practice Variations in efficiencyVariations in efficiency 3030 3030
Scrap shapeScrap shape Melting rateMelting rate 2020 2020
Scrap analysisScrap analysis Rust, water, etc.Rust, water, etc. 2020 2020
Foaming qualityFoaming quality Variations in depthVariations in depth 2020 2020
Fume system/furnace sealingFume system/furnace sealingAir throughputAir throughput 1515 1515
Layering in furnaceLayering in furnace Arc stability, scrap collapseArc stability, scrap collapse 1515 1515
Post combustionPost combustion Per 10 mPer 10 m
33
O O
22/t/t 3030
Electrode water-coolingElectrode water-cooling Water into furnaceWater into furnace 1010 1010
Liquid heatLiquid heat Arc stabilityArc stability 1010
Fluxes blown into furnacesFluxes blown into furnaces (relative to basket charging)(relative to basket charging) 1010
Coherent systemCoherent system OO
22 control, uniformity control, uniformity 1515
BurnersBurners Variation in efficiencyVariation in efficiency 55 55
Boredown pit(s) sizeBoredown pit(s) size Scrap collapseScrap collapse 55 55
Summary of key factors (part 2)

17. Energy consumption for furnaces can best be compared by
referring to the total energy.
Conclusions
Total energy (kwh/t liq.) = electrical + 10.5gas + 5.2(total O
2
- 2*gas) +
1.1pig iron % - 1.0DRI % + 4.5hot metal %
An equation for total energy consumption is:
An average to compare to is 583 kWh/t liquid.
(this was the study average of 92 furnaces working at > 80 t liq/h,
having a standard deviation of ~ 50 and a minimum of ~ 480)
Being aware of the key factors that impact energy consumption is
helpful in explaining differences and in identifying potential areas
for improvement.