kemco energy saving cases in steel industries€¦ · kemco energy saving cases in steel industries...

1.Aug. 2013

Seo Jong Uk

KEMCO Energy Saving Cases

in Steel Industries

Ⅴ

Ⅵ

Ⅶ

Ⅰ

Ⅱ

Ⅲ

Ⅳ

LNG saving by adjusting the zone load at heating furnace

LNG saving by optimizing the heating furnace pressure

Increasing power production by preheating BFG

Saving cooling water pump power by installing fluid coupling system

Increasing combustion air temperature and steam generation by improving the heat recovery

Preventing the temperature drop of preheating zone at furnace by installing the partition wall

LNG saving by optimizing the location of burners in the forge furnace

Ⅷ LNG saving of burners by preheating combustion air

Ⅰ

2/24

▶ Process block diagram

▶ Type, Capacity, Size: Pusher Type Heating Furnace, 50ton/h, 6,110W× 2,300L× 4,278H

▶ Number of burners: Heating Zone 7 Units(Top 5units, Bottom 2 units), Soaking Zone 5 Units

Top Burner (5units)

Soaking Zone Burner(5Units)

Bottom Burner (2units)

← Charging Hole

← Out

Soaking Zone Heating Zone Preheating Zone

FL± 0

Stack

Recuperator

Combustion Blower

Exhaust Blower

[ Process flow for target process] ▶ Field measurements shall be conducted with test material as follows.

▶ 6 measurement points: ambient temp’(1 point), longitudinal temp’(3 points),

top and bottom temp’(2 points)

[Instrument installation]

[Charging] [Measurement]

[Extraction] [Instrument recovery] [Analysis]

Material Top Surface Temp’

Material Longitudinal Temp’(Right)

Ambient Temp’ (Material Top 50mm)

Charging Direction

Material Bottom Surface Temp’ Material Longitudinal

Temp’(Middle )

Material Longitudinal Temp’(Left)

[ Process flow for target process] ▶ The analysis of field measurements 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℃.

Preheating Heating Soaking

Control temp’: 1180℃

Control temp’ : 1130℃

1120℃

1110℃ Preheating Heating Soaking Preheating Heating Soaking

[Figure: Ambient temperature]

[Figure: Longitudinal temperature] [Figure: Top and bottom temperature]

[Figure: Total Temp’ Profile(6points)]

Top

Bottom

▶ Lower the burner load of soacking zone and increase the burner load of bottom heating zone

to reduce the top and bottom temperature deviation.

← Charging Hole ←

Extraction

Soacking Zone Heating Zone Preheating Zone

O2:Less than 6%

O2:5~6%

O2:9%

O2:5~6%

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)

Increase the burner load of

heating zone.

Decrease the burner load of

Soaking zone.

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

▶ Process block diagram

▶ Type, Capacity: Large Rolling Heating Furnace, 150ton/h

▶ Burner type: Regenerative burner 21 sets

1250℃ 1265℃ 1230℃

FD FAN

Regenerative burner

ID FAN

Combustech

Maker

36

Lenghth (m)

43820 ㎥

1100 mmAq 186 Kw

FD FAN

Large Mill

#1

Division

73620 ㎥ 1250 mmAq 220 Kw

21(+1) 150

ID FAN Burner (set)

Capa(T/h)

[Table: Large Rolling Heating Furnace Spec Data]

Preheating Zone

Heating Zone Soaking Zone

[ Process flow for target process] ▶ Large Rolling Heating 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.

[Figure: Comparison of exhaust gas heat loss ] [Figure: Current furnace pressure control screen]

Current furnace pressure PV value:

-0.35 mmH2O

Temp : 109 ℃ O2 : 16.1 % CO2 : 2.78

ppm

Temp : 846.6℃

O2 : 6.7% CO2 : 0 ppm

Temp : 694℃ O2 : 10.8 %

CO2 : 5.63ppm

Stack

Exhaust gas from body

Exhaust heat loss from body accounts for 80% of total heat loss.

Exhaust gas from burner

▶ The below table shows flue gas temperature and LNG usage depending on the furnace

pressure. Those data are obtained through field testing.

Time Furnace Pressure

Main LNG Usage

MAIN Exhaust gas from body

Exhaust gas from regenerative burner Remark

2007.9.5 mmAq N㎥/h 온도(℃) O2(%) 온도(℃) O2(%)

16:17 -0.6 1609 875.6 5 122.9 13.8

Main Exhaust Damper

40% Open

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 Main Exhaust

Damper 30% Open

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 Main Exhaust

Damper 28.2% Open

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

[Table: LNG usage of large rolling heating furnace depending on the furnace pressure changes ]

▶ By changing furnace pressure from -0.35mmAq to 0.18 mmAq, LNG consumption is reduced

from 1,775Nm3/h to 1,393Nm3/h.

로내압 변경에 따른 LNG 사용추이

700.0

900.0

1,100.0

1,300.0

1,500.0

1,700.0

1,900.0

(0.35) 0.18 로내압(단위:mmAq)

LNG사용량(N㎥/h)

main LNG량Main LNG Consumption

Furnace

Pressure(mmAq)

LNG

Consumption LNG Consumption comparison with furnace

pressure changes

▶ 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

Furnace pressure

Main LNG consumption

MAIN exhaust Regenerative burner exhaust

mmAQ N㎥/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

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

▶ 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.

Exhaust

Gas Burner

High Pressure

Steam

Extraction

Steam

BFW Heater

Power

639GWh

BFW Pump

B-C

[Figure: Power system using BFG]

* BFG: Blast Furnace Gas, FOG: Finex Off Gas, COG: Coke Oven Gas

▶ 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℃.

[Figure: Power system installed with BFG Preheating Heat Exchanger]

Exhaust

Gas

Burner

High Pressure

Steam

Extraction

Steam

BFW Heater

Power

645GWh

BFW Pump

B-C

BFG Preheating

System

▶ 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.

[Figure: Heat Exchanger System to preheat BFG]

BFG

80℃

증기

응축액

증증발발기기

응응축축기기

BFG

20℃ SSttaacckk

BFG배관

배GAS

185℃

배GAS

154℃

보보일일러러

보보일일러러

BFW Pipe

Condenser

Evaporator

Condensate

To BLR

Steam

From BLR Flue Gas

185℃

Flue Gas

154℃

Energy Savings

(MWh/yr)

Saving Cost

(k$/yr)

Investments

(k$)

Payback

(yr)

CO2 Reduction

(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

▶ 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

[Figure: Cooling water supply system]

Rough rolling Finish rolling Winder

Cooling Water Line

Roll Cooling Water Pump

Cooing Water Pump: 7 EA

(5 Centrifugal pumps are always operating)

Cooling Water Pipe

▶ 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.

[Figure: Cooling water supply system installed with fluid coupling]

Rough rolling

Finish rolling Winder

Cooling Water Pipe

Cooling W

ater Line

4 of 7 cooling water pumps are

installed with fluid coupling system

Roll Cooling Water Pump

▶ 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)

[Figure: Fluid coupling system]

Inlet Valve

Cooling Water

Improvement

Before/After

Motor

(Existing) Pump (Existing)

Fluid Coupling (New)

Energy Savings

(MWh/yr)

Saving Cost

(k$/yr)

Investments

(k$)

Payback

(yr)

CO2 Reduction

(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

25/24

Ⅴ

▶ 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

Part of NOF exhaust air is

provided to cleaning dryer.

[Figure: NOF zone supply and exhaust air system]

Recuperator tubes are

damged

Steam production is

reduced due to the decrease

of exhaust air flow.

Cold Air

▶ 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.

Division Volume (Nm3/h)

Percent (%)

Temp’ (℃)

Remark

Supply Air Balance

NOF Comb’ Air 4,800 36.9 200

After Burner 900 6.9 200

Air Curtain 4,800 36.9 20

Air Leak 2,000 15.4 20 O2% : 4%→7%(Increase)

By-Pass 500 3.8 200

Sub Total 13,000 100.0

Exhaust Air Balance

To Recup' 3,222 51.8 634

To Cleaning Dryer 3,000 48.2 634 O2% of Hot Air supplied to cleaning dryer O2% is about 15.5%.

Sub Total 6,222 100.0

[Table: NOF zone supply and exhaust air balance]

▶ 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.

y = 0.0006x R² = 0.5024

0.00

0.50

1.00

1.50

2.00

2.50

- 200 400 600 800 1,000 1,200

#1 CGL 폐열BLR 스팀생산량(m3/h)

분석

스팀생산량(m3/h) 线性 (스팀생산량(m3/h))

y = 0.0011x R² = 0.3976

0.00

0.50

1.00

1.50

2.00

2.50

- 500 1,000 1,500 2,000

#2 CGL 폐열BLR 스팀생산량(m3/h)

분석

스팀생산량(m3/h) 线性 (스팀생산량(m3/h))

#1 CGL Waste Heat Boiler Steam Generation

(ton/h) VS LNG Consumption(Nm3/h)

#2 CGL Waste Heat Boiler Steam Generation

(ton/h) VS LNG Consumption(Nm3/h)

Steam Generation

(ton/h) Line(Steam

Generation(ton/h)) Steam Generation

(ton/h)

Line(Steam

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

[Figure: NOF zone supply and exhaust air improvement system]

Cut off part of NOF exhaust air

provided to cleaning dryer.

The temp’ of combustion air

Increases from 200℃ to 300℃

Exhaust gas mixed with OA is

supplied to cleaning dryer.

Divsion Before After Increase

And Decrease

Remark

NOF Combustion Air Temp’(℃) 200 300 +100 100℃ Increase

Recuperator Air Leak(Nm3/h) 2,000 0 - 2,000 Replace recuperator tubes

NOF Exhaust Airflow to Cleaning Dryer(Nm3/h)

3,000 0 -3,000 Stop NOF exhaust air supplied to cleaning dryer

Recuperator Exhaust Flow(Nm3/h) 3,222 6,222 +3,000 Exhaust air increase by cutting off NOF exhaust air to cleaning dryer.

Exhaust gas temp’ before recuperator(℃)

634 634 - No Change

Exhaust gas temp’ after recuperator (℃)

219 385 +166 The exhaust gas temperature after recuperator rises due to the increase of exhaust airflow.

#1 CGL Waste Heat Boiler Steam Generation(kg/h)

496 1,097 +601 The steam generation of #1 CGL waste heat boiler increases.

[Table: Operating data before and after improvement]

▶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

Energy Savings

(Toe/yr)

Saving Cost

(k$/yr)

Investments

(k$)

Payback

(yr)

CO2 Reduction

(tCO2/yr)

297 218 94 0.4 323

LNG savings of burners: 38,255 Nm3/yr



Additional steam production: 4,760 ton/yr

Steam toe conversion factor: 0.0539 toe/ton

Steam price per ton: 40 $/ton


Steam carbon dioxide emission factor per ton: 0.0491tCO2/ton

▶ 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

← Charging Hole ←

Discharge

Soaking zone Preheating zone

O2:16% O2:11~12%

O2:9%

O2:8~9%

Heating zone

[Figure: Heating Furnace Operating Diagram ]

[Figure: Fluent analysis of current operating condition at heating furnace ]

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]

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

[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

[Figure: Fluent analysis in case of installing partition wall at 4.2 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 6.3 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

Energy Savings

(Toe/yr)

Saving Cost

(k$/yr)

Investments

(k$)

Payback

(yr)

CO2 Reduction

(tCO2/yr)

406 281 44 0.2 949

Annual LNG savings of burners: 386,863 Nm3/yr




▶ 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)

□ Lower side burners are absence

- Temperature profile : not uniformity

- Maximum temperature difference in the forge : 36 oC

* Fluent is a flow modeling and continuous fluid dynamic simulator (CFD).

▶ 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 the upper section

: active compare with the lower section

□ Flue gas distribution

: concentrated to the left side

□ Gas distribution of side burners

: Flames are not overlapped

▶ Comparison data of before and after improvement

- LNG saving by optimizing burners location(LNG savings:2.7%).

[ Heat profile before and after improving]

■ Relocate Roof BNR to side(Pitch: 3,300 mm)

■ Distance between Side BNR(●) and charge door :1,000mm


■ Maximum △T of Ingots : 21℃ (15℃ decreased)

■ Adjust the angle of roof and side burner : -8o

■ Side, Roof BNR( ) Pitch: 3,300 mm



■ Maximum △T of Ingots : 36℃

■ Maximize △T for high efficiency and quality

Before improving After improving

LNG consumed : 4,183 Nm3/yr LNG consumed : 4,070 Nm3/yr

(2.7% LNG savings)

▶ Comparison data of before and after improvement

- More uniform temperature profile by optimizing burners location

[ Temperature profile of before and after improvement]

(Bottom View )

(Side View - L ) (Side View - R )

(Upper View )

(Bottom View )

(Upper View )

(Side View - L ) (Side View - R )

Before improvement After improvement

Energy Savings

(Toe/yr)

Saving Cost

(k$/yr)

Investments

(k$)

Payback

(yr)

CO2 Reduction

(tCO2/yr)

119 82 60 0.7 278

Energy saving items As Is To Be Savings Saving cost

LNG consumption

4,183 kNm3/yr

4,070 kNm3/yr

113 kNm3/yr

k$ 82/yr




▶ Without preheating the combustion air, it increases the LNG consumption.

▶ Heat loss happens generally by heating cold air from 20℃ to 20℃.

COLD AIR (20oC)

RECUPERATIVE (500oC)

REGENERATIVE(1000oC)

1200C 1000C 20C 500C

Heat loss happens by heating air from

20℃ to 20℃.

Heat loss happens by heating

air from 500℃ to 1200℃.

Air 20C

Air 500C

Air 1000C

AIR

25% saving

50% saving

25% saving

Combustion(Flame)

=> HEATING ENERGY

HEATING MATERIAL Heat loss happens by

heating air from

1000℃ to 1200℃.

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 ALL HEATTREATING

FORGING (~1200C) ROLLING, FORGING

(OVER 1100C) HEATTREATING

( ~1100C) ROLLING, FORGING

(OVER 1100C)

COST VERY LOW LOW MIDIUM HIGH HIGH

OTHERS

• 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

[ Combustion air temperature before burner and energy saving]

• Continuous Heat treatment Furnace

• Forge Heat treatment Furnace

• Aluminum Heat treatment Furnace

• Preheat Furnace

2). Application

1). Characteristics

MEDIA CASE

BURNER HEAD

REGENERATIVE MEDIA

PILOT BURNER

Pilot Burner & UV Scanner

REGEN BURNER A

REGEN BURNER B

1ST AIR CYCLE VALVE

2ND AIR CYCLE VALVE

EX-GAS CYCLE VALVE

FUEL.1,2AIR.EXHAUST GAS FLOW CONTROL UNIT

FUEL CYCLE VALVE

SAFETY DEVICE

EACH UTILITY, PRESSURE,FLOW,TEMPERATURE MEASURING DEVICE

A. REGENERATIVE BURNER B. REGENERATIVE COMBUSTION SYSTEM

kemco energy saving cases in steel industries€¦ · kemco energy saving cases in steel industries...

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