LNG savings of burners - Institute for Industrial Productivity

KEMCO Energy Saving Cases
in Steel Industries
1.Aug. 2013
Seo Jong Uk

Ⅱ
Ⅰ
LNG saving by adjusting the zone load at heating furnace
LNG saving by optimizing the heating furnace pressure
Ⅲ
Increasing power production by preheating BFG
Saving cooling water pump power by installing fluid
Ⅳ coupling system
Ⅴ Increasing combustion air temperature and steam generation
by improving the heat recovery
Preventing the temperature drop of preheating zone at furnace
Ⅵ by installing the partition wall
Ⅷ
Ⅶ
LNG saving by optimizing the location of burners in the forge furnace
LNG saving of burners by preheating combustion air

Ⅰ
2/24

▶ Type, Capacity, Size: Pusher Type Heating Furnace, 50ton/h, 6,110W× 2,300L× 4,278H
▶ Number Process of block burners: diagram Heating Zone 7 Units(Top 5units, Bottom 2 units), Soaking Zone 5 Units
Stack
Combustion
Blower
Exhaust
Blower
Recuperator
Soaking Zone
Burner(5Units)
Top Burner
(5units)
Soaking Zone Heating Zone Preheating Zone
← Charging
Hole
← Out
FL± 0
Bottom Burner
(2units)

▶ [ Process Field measurements flow for target shall process] be conducted with test material as follows.
▶ 6 measurement points: ambient temp’(1 point), longitudinal temp’(3 points),
top and bottom temp’(2 points)
Charging
Direction
Ambient Temp’
(Material Top 50mm)
[Instrument
installation]
[Charging]
[Measurement]
Material Top
Surface Temp’
Material Bottom
Surface Temp’
Material Longitudinal
Temp’(Right)
Material Longitudinal
Temp’(Middle )
Material Longitudinal
Temp’(Left)
[Analysis]
[Instrument recovery]
[Extraction]

▶
[ Process
The analysis
flow for
of field
target
measurements
process]
using test material shows that temperature distribution
in the longitudinal side presents a uniform profile.
▶ But, the top and bottom temperature range indicates more than 40℃.
Control temp’:
1180℃
Control
temp’ :
1130℃
Preheating Heating Soaking
[Figure: Total Temp’ Profile(6points)]
[Figure: Ambient temperature]
Top
Bottom
1120℃
1110℃
Preheating Heating Soaking Preheating Heating Soaking
[Figure: Longitudinal temperature]
[Figure: Top and bottom temperature]

▶ Lower the burner load of soacking zone and increase the burner load of bottom heating zone
to reduce the top and bottom temperature deviation.
Division
Heating Zone
Top Burner Load(%)
Heating Zone
Bottom Burner Load(%)
Soacking Zone Burner
Load(%)
Before 57 17 26
After 57 20(Increase) 23(Decrease)
O 2 :Less than 6%
O 2 :5~6%
Decrease the burner load of
Soaking zone.
O 2 :5~6%
←
Extraction
Soacking Zone Heating Zone Preheating Zone
← Charging
Hole
Increase the burner load of
heating zone.
O 2 :9%

Energy Savings
(Toe/yr)
Saving Cost
(k$/yr)
Investments
(k$)
Payback
(year)
CO2
Reduction
(tCO2/yr)
259 157 - - 605
• Adjusting the Zone load at heating furnace brings 3% efficiency
improvement.
• Annual LNG savings of burners: 246,665Nm3/yr
• LNG toe conversion factor: 1.05 toe/kNm3
• LNG price per Nm3 : 0.727 $/Nm3
• LNG carbon dioxide emission factor per toe: 2.3357tCO2/toe

Ⅱ

▶ Type, Capacity: Large Rolling Heating Furnace, 150ton/h
▶ Burner Process type: block Regenerative diagram burner 21 sets
[Table: Large Rolling Heating Furnace Spec Data]
Divi
sion
Capa(T/h)
Burner
(set)
Lenghth
(m)
FD FAN
ID FAN
Maker
Large
Mill
#1
150
21(+1)
36
43820 m3
1100 mmAq
186 Kw
73620 m3
1250 mmAq
220 Kw
Combustech
FD FAN
ID FAN
Soaking Zone
Heating Zone
Preheating Zone
Regenerative
burner
1265℃ 1250℃ 1230℃

▶ [ Process Large Rolling flow for Heating target process] Furnace is operated at a negative pressure(-0.2~0.4mmH2O)
▶ It causes heat loss by invaded fresh air, so the heat loss of body exhaust gas
increase.
Stack
Exhaust heat loss from
body accounts for 80%
of total heat loss.
Current furnace
pressure PV value:
-0.35 mmH2O
Temp : 694℃
O2 : 10.8 %
CO2 : 5.63ppm
Temp :
846.6℃
O2 : 6.7%
CO2 : 0 ppm
Temp : 109 ℃
O2 : 16.1 %
CO2 : 2.78
ppm
Exhaust gas
from body
Exhaust gas
from burner
[Figure: Comparison of exhaust gas heat loss ]
[Figure: Current furnace pressure control screen]

▶ The below table shows flue gas temperature and LNG usage depending on the furnace
pressure. Those data are obtained through field testing.
[Table: LNG usage of large rolling heating furnace depending on the furnace pressure changes ]
Time
Furnace
Pressure
Main LNG
Usage
MAIN Exhaust gas
from body
Exhaust gas
from regenerative burner
2007.9.5 mmAq Nm3/h 온도(℃) O2(%) 온도(℃) O2(%)
16:17 -0.6 1609 875.6 5 122.9 13.8
16:18 -0.4 1758 870(880) 4.2 14.6
16:21 -0.2 1965 828.2 7.4 145.7 13.9
16:26 -0.24 1689 835 4.7 130.8 13.9
16:47 0 1456 831 6 119.6 14.1
16:58 0 1355 833.8 5.4 120.2 14.5
17:16 0.33 1439 831.7 5.2 124.8 14
17:27 0.24 1377 823.2 5.9 124.6 14
17:39 0.3 1301 826.9 5.2 124.1 14
18:00 0.3 1301 821.5 4.9 124.8 13.5
Remark
Main Exhaust
Damper
40% Open
Main Exhaust
Damper
30% Open
Main Exhaust
Damper
28.2% Open

▶ By changing furnace pressure from -0.35mmAq to 0.18 mmAq, LNG consumption is reduced
from 1,775Nm3/h to 1,393Nm3/h.
LNG
Consumption LNG사용량
(Nm3/h)
1,900.0
1,700.0
1,500.0
1,300.0
1,100.0
900.0
700.0
로내압 변경에 따른 LNG 사용추이
LNG Consumption comparison with furnace
pressure changes
(0.35) 0.18 로내압(단위:mmAq)
Furnace
Pressure(mmAq)
main Main LNG량
Consumption

▶ We must adjust furnace pressure in order to minimize the heat loss by invaded fresh air
and blow off of furnace gas.
▶ Optimum furnace pressure: About 1 mmAq
[Figure: Heat loss table book with furnace pressure changes ]

Energy Savings
(Toe/yr)
Saving Cost
(k$/yr)
Investments
(k$)
Payback
(year)
CO2
Reduction
(tCO2/yr)
2,171 1,503 - - 5,071
• Applied data to calculate improvement effects is as below.
and we apply safety factor to 0.7 considering disturbance.
• Operating hours per year: 8,160h/yr
Furnace
pressure
Main LNG
consumption
MAIN exhaust
Regenerative burner exhaust
mmAQ Nm3/h Temp’(℃) O2(%) Temp’(℃) O2(%)
-0.35 1,755.3 846.3 5.3 133.1 14.1
0.18 1,393.0 828.0 5.4 123.0 14.0
Distinction 362.3 18.3 -0.1 10.1 0.0

Ⅲ

▶ BLR uses waste gas(BFG, FOG, COG) generated in the smelting process as fuel gas.
But fuel gas is supplied at 20℃ without preheating.
▶ The flue gas from APH is discharged to 185℃ into the atmosphere.
High Pressure
Steam
Exhaust
Gas
B-C
Burner
Extraction
Steam
Power
639GWh
BFW Heater
BFW Pump
* BFG: Blast Furnace Gas, FOG: Finex Off Gas, COG: Coke Oven Gas
[Figure: Power system using BFG]

▶ Power generation increases from 639GWh to 645GWh by preheating BFG.
▶ Heat pipe heat exchanger is installed to preheat BFG with flue gas.
▶ Flue gas temp’ drops from 185℃ to 154℃. but BFG temp’ increases from 20℃ to 80℃.
BFG Preheating
System
High Pressure
Steam
Exhaust
Gas
B-C
Burner
Extraction
Steam
Power
645GWh
BFW Heater
BFW Pump
[Figure: Power system installed with BFG Preheating Heat Exchanger]

▶ Heat pipe exchanger using water as heat exchanger material is installed to preheat BFG.
▶ The water in evaporator is vaporized with flue gas heat and is condensed at condenser
by heating BFG.
To BLR
보일러
BFG
80℃
응축기
Condenser
Stack
배GAS
154℃
Flue Gas
154℃
증기
Steam
증발기
Evaporator
BFG
20℃
BFG배관
BFW Pipe
Condensate
응축액
배GAS
185℃
Flue Gas
185℃
보일러
From BLR
[Figure: Heat Exchanger System to preheat BFG]

Energy Savings
Saving Cost
Investments
Payback
CO2 Reduction
(MWh/yr)
(k$/yr)
(k$)
(yr)
(tCO2/yr)
6,257 563 1,507 2.7 1,507
• Additional power production: 6,256,664 kWh/yr
• Power unit: 0.09$/kWh
• Carbon dioxide emission factor for power: 0.8 tCO2/MWh

Ⅳ

▶ 7 cooling water pumps are installed to supply cooling water for rolling equipment.
5 cooling water pumps always operate regardless of load change.
▶ Cooling Water Pump Design Data: 1,400kW, 6,600V, 125A, 28m3/min, 20kg/cm2g
Roll Cooling Water Pump
Cooling Water Line
Cooing Water Pump: 7 EA
(5 Centrifugal pumps are always operating)
Cooling Water Pipe
Rough rolling Finish rolling Winder
[Figure: Cooling water supply system]

▶ Cooling water pump power can be saved by installing fluid coupling which automatically
adjust motor speed according to the cooling water load.
▶ 4 of 7 cooling water pumps should install fluid coupling for cooling water load variations.
Roll Cooling Water Pump
Cooling Water Pipe
4 of 7 cooling water pumps are
installed with fluid coupling system
Cooling Water Line
Rough rolling
Finish rolling
Winder
[Figure: Cooling water supply system installed with fluid coupling]

▶ Fluid coupling is additionally installed to the existing motors and pumps.
▶ Fluid coupling specifications: variable speed type(20%~80%), direct connection type, 15 sec
acceleration time(lowest RPM → maximum RPM)
Inlet Valve
Cooling Water
Motor
(Existing)
Fluid Coupling (New)
Pump (Existing)
Improvement
Before/After
[Figure: Fluid coupling system]

Energy Savings
Saving Cost
Investments
Payback
CO2 Reduction
(MWh/yr)
(k$/yr)
(k$)
(yr)
(tCO2/yr)
5,041 458 2,279 5.0 4,033
• Power consumption before improvement: 41,748,742 kWh/yr
• Power consumption after improvement: 36,707,669 kWh/yr
• Power unit: 0.09$/kWh
• Carbon dioxide emission factor for power: 0.8 tCO2/MWh

Ⅴ
25/24

▶ NOF exhaust air volume supplied to recuperator is reduced due to providing part of
NOF exhaust air to the cleaning dryer
▶ Air leak of recuperator tube side causes the temperature drop of combustion air
Steam production is
reduced due to the decrease
of exhaust air flow.
Recuperator tubes are
damged
Cold Air
Part of NOF exhaust air is
provided to cleaning dryer.
[Figure: NOF zone supply and exhaust air system]

▶ Through the supply and exhaust air balance analysis, we know that 15% of supply air leaks
at recuperator tubes.
▶ 48% of the hot exhaust air is supplied to the cleaning dryer.
[Table: NOF zone supply and exhaust air balance]
Division
Volume
(Nm 3 /h)
Percent
(%)
Temp’
(℃)
NOF Comb’ Air 4,800 36.9 200
Remark
After Burner 900 6.9 200
Supply
Air Balance
Air Curtain 4,800 36.9 20
Air Leak 2,000 15.4 20 O2% : 4%→7%(Increase)
Exhaust
Air Balance
By-Pass 500 3.8 200
Sub Total 13,000 100.0
To Recup' 3,222 51.8 634
To Cleaning Dryer 3,000 48.2 634
Sub Total 6,222 100.0
O2% of Hot Air supplied to cleaning
dryer O2% is about 15.5%.

▶ According to linear regression analysis of steam generation compared to burner LNG
consumption, #1 CGL steam generation is half of #2 CGL.
▶ As part of hot exhaust air is supplied to the pretreatment cleaning dryer,
We confirm that the reduced exhaust airflow is the main reason.
2.50
2.00
1.50
1.00
0.50
#1 CGL 폐열BLR 스팀생산량(m 3 /h)
(ton/h) VS LNG 분석 Consumption(Nm3/h)
#1 CGL Waste Heat Boiler Steam Generation
y = 0.0006x
R²= 0.5024
2.50
2.00
1.50
1.00
0.50
#2 CGL 폐열BLR 스팀생산량(m 3 /h)
(ton/h) VS LNG 분석 Consumption(Nm3/h)
#2 CGL Waste Heat Boiler Steam Generation
y = 0.0011x
R²= 0.3976
0.00
- 200 400 600 800 1,000 1,200
Steam Generation
Line(Steam
스팀생산량(m3/h)
(ton/h)
线 性 (스팀생산량(m3/h))
Generation(ton/h))
0.00
- 500 1,000 1,500 2,000
Steam Generation
Line(Steam
스팀생산량(m3/h) 线 性 (스팀생산량(m3/h))
(ton/h)
Generation(ton/h))

▶ By stop exhaust gas to cleaning dryer and replacing tubes of recuperator,
the temperature of combustion air rises from 200℃ to 300℃ and the steam generation
at waste heat boiler increases from 496kg/h to 1,097kg/h
Exhaust gas mixed with OA is
supplied to cleaning dryer.
The temp’ of combustion air
Increases from 200℃ to 300℃
Cut off part of NOF exhaust air
provided to cleaning dryer.
[Figure: NOF zone supply and exhaust air improvement system]

▶Data before and after improvement are shown in the table below.
▶ LNG used in burners is saved and steam is additionally generated only through
cutting off NOF exhaust air supplied to cleaning dryer
[Table: Operating data before and after improvement]
Divsion Before After
Increase
And
Decrease
Remark
NOF Combustion Air Temp’(℃) 200 300 +100 100℃ Increase
Recuperator Air Leak(Nm 3 /h) 2,000 0 - 2,000 Replace recuperator tubes
NOF Exhaust Airflow
to Cleaning Dryer(Nm 3 /h)
3,000 0 -3,000 Stop NOF exhaust air supplied to cleaning dryer
Recuperator Exhaust Flow(Nm 3 /h) 3,222 6,222 +3,000
Exhaust gas temp’
before recuperator(℃)
Exhaust gas temp’
after recuperator (℃)
#1 CGL Waste Heat Boiler
Steam Generation(kg/h)
634 634 - No Change
219 385 +166
496 1,097 +601
Exhaust air increase by cutting off NOF exhaust
air to cleaning dryer.
The exhaust gas temperature after recuperator
rises due to the increase of exhaust airflow.
The steam generation of #1 CGL waste heat
boiler increases.

Energy Savings
Saving Cost
Investments
Payback
CO2 Reduction
(Toe/yr)
(k$/yr)
(k$)
(yr)
(tCO2/yr)
297 218 94 0.4 323
• LNG savings of burners: 38,255 Nm3/yr
• LNG toe conversion factor: 1.05 toe/kNm3
• LNG price per Nm3 : 0.727 $/Nm3
• Additional steam production: 4,760 ton/yr
• Steam toe conversion factor: 0.0539 toe/ton
• Steam price per ton: 40 $/ton
• LNG carbon dioxide emission factor per toe: 2.3357tCO2/toe
• Steam carbon dioxide emission factor per ton: 0.0491tCO2/ton

Ⅵ

▶ If door will be opened, you can see that cold air from the outside would be significantly
introduced to the deep point without partition wall.
▶ Influx of cold air at the bottom of the furnace increases the amount of burner LNG
O 2 :8~9%
O 2 :16%
O 2 :11~12%
←
Discharge
Soaking zone
Heating zone
Preheating zone
←
Charging
Hole
Cold air from the outside is
introduced to the bottom of furnace
O 2 :9%
[Figure: Heating Furnace Operating Diagram ]
[Figure: Fluent analysis of current operating condition at heating furnace ]

[Case 1: Installing partition wall at 2 meter from charging side]
▶ Partition wall cut off the cold air supplied from the outside. but you can see that
part of cold air is introduced to the bottom of preheating zone over the partition wall
Part of cold air from the outside is
prevented from partition wall
Part of cold air from the outside is
introduced to the bottom of furnace
[Figure: Fluent analysis in case of installing partition wall at 2 meter from charging side]

[Case 2: Installing partition wall at 4.2 meter from charging side]
▶ The rear temperature of partition wall keeps higher than case 1. you can see the
uniform temperature profile at the bottom of preheating zone due to the prevention of cold air.
▶ The effect to enforce preheating with partition wall causes the LNG saving of burner
The temperature profile at the
bottom of preheating zone is higher
than case 1.
[Figure: Fluent analysis in case of installing partition wall at 4.2 meter from charging side]

[Case 3: Installing partition wall at 6.3 meter from charging side]
▶ Because partition wall is installed at 6.3 meter from charging hole, the front temperature of
charging side keeps low.
▶ the preheating effect appears lower than case 2 because of the long distance(6.3meter)
from charging hole.
The front temperature of charging
side keeps low and this results in the
increase of LNG consumption at
burners
[Figure: Fluent analysis in case of installing partition wall at 6.3 meter from charging side]

Energy Savings
Saving Cost
Investments
Payback
CO2 Reduction
(Toe/yr)
(k$/yr)
(k$)
(yr)
(tCO2/yr)
406 281 44 0.2 949
• Annual LNG savings of burners: 386,863 Nm3/yr
• LNG toe conversion factor: 1.05 toe/kNm3
• LNG price per Nm3 : 0.727 $/Nm3
• LNG carbon dioxide emission factor per toe: 2.3357tCO2/toe

Ⅶ

▶ Analyze results for heat flow of the forge furnace with Fluent simulation*
- Temperature profile : Not uniform (maximum temperature difference : 36 o C)
[Heat profile for operating conditions of the forge furnace]
□ There were 16 burners
Roof burner : 4 set x 2(reft/right)
Side burner :4 set x 2(reft/right)
* Fluent is a flow modeling and continuous fluid dynamic simulator (CFD).
□ Lower side burners are absence
- Temperature profile : not uniformity
- Maximum temperature difference in the forge : 36 o C

▶ Analyze heat flow of the flue gas with Fluent simulation
- Uneven flue gas distribution
[Heat profile for operating condition of flue gas]
□ Flame direction of roof burners
: biased to left side
(A part of Ingots overheated)
□ Gas distribution of side burners
: Flames are not overlapped
□ Gas distribution of the upper section
: active compare with the lower section
□ Flue gas distribution
: concentrated to the left side

▶ Comparison data of before and after improvement
- LNG saving by optimizing burners location(LNG savings:2.7%).
[ Heat profile before and after improving]
Before improving
After improving
■ Side, Roof BNR( ) Pitch: 3,300 mm
■ Relocate Roof BNR to side(Pitch: 3,300 mm)
■ Distance between Side BNR(●) and charge door :1,350mm ■ Distance between Side BNR(●) and charge door :1,000mm
■ Distance between Side BNR(●) and charge door :3,000mm ■ Distance between Side BNR(●) and charge door :2,100mm
■ Maximum △T of Ingots : 36℃
LNG consumed : 4,183 Nm3/yr
■ Maximize △T for high efficiency and quality
LNG consumed : 4,070 Nm3/yr
(2.7% LNG savings)
■ Maximum △T of Ingots : 21℃ (15℃ decreased)
■ Adjust the angle of roof and side burner : -8 o

▶ Comparison data of before and after improvement
- More uniform temperature profile by optimizing burners location
[ Temperature profile of before and after improvement]
Before improvement
(Side View - L ) (Side View - R )
After improvement
(Side View - L ) (Side View - R )
(Upper View )
(Upper View )
(Bottom View )
(Bottom View )

Energy Savings
Saving Cost
Investments
Payback
CO2 Reduction
(Toe/yr)
(k$/yr)
(k$)
(yr)
(tCO2/yr)
119 82 60 0.7 278
• LNG toe conversion factor: 1.05 toe/kNm3
• LNG price per Nm3 : 0.727 $/Nm3
• LNG carbon dioxide emission factor per toe: 2.3357tCO2/toe
Energy saving items As Is To Be Savings Saving cost
LNG consumption 4,183 kNm 3 /yr 4,070 kNm 3 /yr 113 kNm 3 /yr k$ 82/yr

Ⅷ

▶ Without preheating the combustion air, it increases the LNG consumption.
▶ Heat loss happens generally by heating cold air from 20℃ to 20℃.
COLD AIR (20 o C)
Heat loss happens by heating air from
20℃ to 20℃.
Air 20C
Combustion(Flam
e)
=> HEATING
ENERGY
RECUPERATIVE
(500 o C)
Air 500C
25% saving
Heat loss happens by heating
air from 500℃ to 1200℃.
HEATING MATERIAL
AIR
REGENERATIVE(1000
o
C)
50% saving
25% saving
Heat loss happens by
heating air from
1000℃ to 1200℃.
Air 1000C
20C
500C
1000C
1200C

[ Combustion air temperature before burner and energy saving]
COLD
AIR TYPE
AIR PREHEATING (BY FLUE GAS)
CONCENTRATIVE TYPE
INDIVIDUAL TYPE
RADIATION CONVECTION SELF-RECUPER REGENERATIVE
AIR TEMP(@1200C) 20C 450C 600C 800C 1100C
FUEL SAVING - 20% 25% 35% 45%
APPLICATION
OTHERS
ALL
HEATTREATING
FORGING (~1200C)
ROLLING, FORGING
(OVER 1100C)
HEATTREATING
( ~1100C)
ROLLING, FORGING
(OVER 1100C)
COST VERY LOW LOW MIDIUM HIGH HIGH
• SIMPLE
• SIMPLE
• AIR PIPING SIZE UP
• RECUPERATOR
MAITENANCE(2YEAR)
• AIR PIPING SIZE UP
• EX-GAS PIPING
• AIR FAN CAPA UP
(1.5TIMES)
• SIMPLE
• COMPLEX and SIZE UP
• EX-GAS PIPING
• NEED ADDITIONAL IDF

1). Characteristics
2). Application
• Continuous Heat treatment Furnace
• Forge Heat treatment Furnace
• Aluminum Heat treatment Furnace
• Preheat Furnace

A. REGENERATIVE BURNER B. REGENERATIVE COMBUSTION SYSTEM
BURNER
HEAD
PILOT
BURNER
FUEL CYCLE
VALVE
1 ST AIR CYCLE
VALVE
REGEN BURNER
B
Pilot Burner & UV Scanner
REGEN BURNER
A
MEDIA CASE
2 ND AIR CYCLE
VALVE
EX-GAS CYCLE
VALVE
REGENERATIVE
MEDIA
FUEL.1,2AIR.EXHAUST GAS
FLOW CONTROL UNIT
SAFETY DEVICE
EACH UTILITY,
PRESSURE,FLOW,TEMPERATU
RE MEASURING DEVICE

49/24