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STOVESTOVEEquipmentEquipment
stovestovestove
Hot Blast
Waste product of combustion
AirBf Gas
Cold Blast
No of StoveNo of Stove
• Depends onDepends on– Type of stoveType of stove– Heat requirementHeat requirement– Capacity of StoveCapacity of Stove– Material quality of stove etc.Material quality of stove etc.
• Three or four stoveThree or four stove
Type of stoveType of stove
• Design baseDesign base– Internal combustion chamberInternal combustion chamber
– External combustion chamberExternal combustion chamber
– Top combustion ChamberTop combustion Chamber
Air
Gas
CERAMIC BURNERCERAMIC BURNER
Gas
Air
Capacity of StoveCapacity of Stove
• Depends uponDepends upon– SizeSize– Mass of checker brickMass of checker brick– Dome TempDome Temp– Stack tempStack temp– Heat recovery systemHeat recovery system– Surface/Volume or mass ratioSurface/Volume or mass ratio– Type and quality of brick etcType and quality of brick etc
Valve location in StoveValve location in Stove• Crossectional viewCrossectional view
Combustion air valve
Blast furnace gas valve
Hot Blast valve
X X X
Compression valve
Decompression valve
Cold Blast Valve
Chimney Valve
X
X
XX
Stove Operation CycleStove Operation Cycle
• On Gas 50 minuteOn Gas 50 minute
• Isolation from on gas 3 minuteIsolation from on gas 3 minute
• On Blast 30 minuteOn Blast 30 minute
• Isolation from on blast 7 minuteIsolation from on blast 7 minute
On Gas cycle On Gas cycle
• Valve operation sequenceValve operation sequence•Open Decompression valveOpen Decompression valve
•Close Decompression Valve (Stove Close Decompression Valve (Stove pressure=Atm pressure)pressure=Atm pressure)
•Open both chimney valveOpen both chimney valve
•Open combustion air valveOpen combustion air valve
•Open Blast furnace gas valveOpen Blast furnace gas valve
Isolation from on gasIsolation from on gas
• Valve operation sequenceValve operation sequence•Close Blast furnace gas valveClose Blast furnace gas valve
•Close combustion air valveClose combustion air valve
•Close both chimney valveClose both chimney valve
On Blast CycleOn Blast Cycle
• Valve Operation sequenceValve Operation sequence•Open compression valveOpen compression valve
•Close compression valve (Stove pressure Close compression valve (Stove pressure =Hot blast main pressure)=Hot blast main pressure)
•Open hot blast valveOpen hot blast valve
•Open cold blast valveOpen cold blast valve
Isolation from on blastIsolation from on blast
• Valve Operation sequenceValve Operation sequence•Close cold blast valveClose cold blast valve
•Close Hot blast valveClose Hot blast valve
•Open Decompression valveOpen Decompression valve
•Close decompression valve (Stove Close decompression valve (Stove pressure= atm pressurepressure= atm pressure
Heat transfer rateHeat transfer rate• In stove operation heat is transfer In stove operation heat is transfer
from the product of combustion of from the product of combustion of gas to checker brick & heat transfer gas to checker brick & heat transfer from checker brick to cold blast. from checker brick to cold blast. Depends onDepends on– Temp diff.Temp diff.– Surface / mass ratio of checker brick.Surface / mass ratio of checker brick.– Residence time of product of Residence time of product of
combustion in stove.combustion in stove.– Velocity of product of combustionVelocity of product of combustion– Temp difference between Dome and Temp difference between Dome and
stack tempstack temp– Quality of brick etcQuality of brick etc
Flame TemperatureFlame Temperature
• Flame temp depends onFlame temp depends on– Calorific value of fuel gas.Calorific value of fuel gas.– Air to gas ratio or product of combustion/nm3 of Air to gas ratio or product of combustion/nm3 of
gas.gas.– Input air and gas temp.Input air and gas temp.– Temp of combustionTemp of combustion
Blast furnace gas Blast furnace gas compositioncomposition
• ContentContent•%CO %CO 2626
•%CO%CO2 20
•%H2 3.5
•%N2 50.5
• In Combustion (CO+H2) Take part
Waste Product of Waste Product of CombustionCombustion
CalculationCalculationCO+1/2 OCO+1/2 O22=CO=CO22
HH22+1/2 O+1/2 O22=H=H22OO
Oxygen from air=1/2(CO+HOxygen from air=1/2(CO+H22))
Air need/NMAir need/NM33 of gas=1/2 x of gas=1/2 x %(CO+H%(CO+H22)/0.21)/0.21
Production of combustion=Bf gas Production of combustion=Bf gas +0.79 air+0.79 air
OrOr
Bf gas x (0.79 x %(CO+HBf gas x (0.79 x %(CO+H22)/0.42)))/0.42))
Heat valenceHeat valence
• Heat input to stove during on gas periodHeat input to stove during on gas period– Time or duration of on gas=t hrTime or duration of on gas=t hr– Fuel Gas CV.= C Kcal/NM3Fuel Gas CV.= C Kcal/NM3
– Flow rate of fuel gas.= FFlow rate of fuel gas.= Fgg Knm3/hr Knm3/hr
– Flow of air= FFlow of air= Faa KNM3 /hr. KNM3 /hr.
– Fuel and gas input temp. TFuel and gas input temp. Tii
– Heat in= HHeat in= Hii
– Specific heat of Air and fuel is SSpecific heat of Air and fuel is Spa pa and Sand S pg pg
– HHi i =((F=((Faa x S x Spapa+ F+ Fgg x S x S pg pg)x T)x Ti i + C x F+ C x Fgg x1000))x t x1000))x t
• Heat going out from stove during on gasHeat going out from stove during on gas– Product of combustion avg flow rate = FProduct of combustion avg flow rate = Fww KNM3/Hr KNM3/Hr
– Specific heat of waste gas = SSpecific heat of waste gas = Sww . .
– Avg temp of waste gas = TAvg temp of waste gas = Tww
– Out going heat = HOut going heat = Hw,w,
HHww= (F= (Fww x T x Tww x S x Sww) x t) x t
Heat valenceHeat valence
• Heat Absorbed by checker bricks of Heat Absorbed by checker bricks of stove during on gas.stove during on gas.
•Hc = Hi-HwHc = Hi-Hw
• Heat delivered by stove during on Heat delivered by stove during on blast periodblast period
•HHbb =( V =( Vbb x S x Sbb x HBT) x t x HBT) x tbb
•HHCC = H = Hbb
Heat valenceHeat valence
NEDO SystemNEDO System
• PurposePurpose– To recover heat from waste product of To recover heat from waste product of
combustion.combustion.
• Use toUse to– Raise hot blast temperatureRaise hot blast temperature– Fuel savingFuel saving
NEDO SystemNEDO System
• PrinciplePrinciple– There are three heat exchanger There are three heat exchanger
– One to recover heat from waste product of One to recover heat from waste product of combustion of stove.combustion of stove.
– Two heat exchanger used to deliver heat to Blast Two heat exchanger used to deliver heat to Blast furnace gas and combustion air.furnace gas and combustion air.
• DataData– Bf gas temp raised by 100 degree centigradeBf gas temp raised by 100 degree centigrade– Air temp raised by 125 degree centigradAir temp raised by 125 degree centigrad
Partition TempPartition Temp
• Should not go below 650 degree Should not go below 650 degree centigradecentigrade
Emergency SituationEmergency Situation
• Power failPower fail– HazardsHazards
• Gas leakGas leak
• ExplosionExplosion
– ActionAction• Gas valve design power to openGas valve design power to open
• Hydraulic system pressure for one operationHydraulic system pressure for one operation
