CURRENT TECHNOLOGIES IN IMPROVING REHEAT FURNACE EFFICIENCY AND CONTROLLING EMISSIONS

Steven J O’ConnorSenior Applications Engineer

John C DormireVice President – Sales and Marketing

Energy and Environment

• US Industry is facing difficult regulations

• Fuel costs are significantly higher than a few years ago

• To survive in today global economy companies must reduce fuel use and emissions cost effectively

Emissions Reduction

NOx Increase with Peak Flame Temperature

• Difficult to measure• Not practical to use for process control• Can evaluate with CFD

NOx Increase with Furnace and Air Temperature

NO

X

Air, oF

• Easy to measure• Practical to use for process control• Tracks flame temperature• Use as predictor instead of

flame temperature

Effect of Burner Capacity on NOxEmissions

Effect of Wall Area to Port Area Ratio on Potential to Emit NOx

Effect of Port Length to Diameter Ratio on Potential to Emit NOx

Geometry and System Design Factors

• POC induced into the flame (internal exhaust gas re-circulation, IEGR)

• How & where air & gas are mixed together– air staging– Uniform flame temp Air Staging

1st stage air < 100%

100% of fuel Partialcombustion

1 or more additionalstages of air

Combustioncompleted

• Bloom Uses Air Staging!– gas always surrounded by air

» better air-fuel mixing» better control of the

flame geometry as furnace wears

» protects process from unwanted reducing atmosphere

– no field adjustments– good flame shape in all

modes of operation– Ultra low NOx at all furnace

temperatures

Geometry and System Design Factors for Reduction of NOx Production

Application of Low NOx technology:

• Application of Modern Low NOx technology is critical to success

• Must use modern control techniques, yet still be flexible enough for day to day use (little change for current mass flow type systems)

• Burner designs should be specific to the application requirement

Low NOx technology – Key factors:

• Flame shape must be appropriate for the furnace

• Flame development must result in the correct furnace atmosphere – O2 levels should be minimum at the steel surface – no reducing atmosphere

Available Low NOx Technology:

As low as 0.035 to 0.040 lbs/MMBTU in most reheat furnace applications using hot air

As low as 0.050-0.060 lbs/MMBtu when using regenerative type burners

Low Nox burners on Steel Reheat Furnace

PROVEN RESULTS

• SLAB FURNACE EASTERN U. S0.07 LBS/MMBTU• SLAB FURNACE TEXAS0.045 LBS/MMBTU• BILLET FURNACE UTAH0.037 LBS/MMBTU• SLAB FURNACE MIDWEST0.06 LBS/MMBTU• BILLET FURNACE MIDWESTO.O4 LBS/MMBTU• AND MANY OTHERS

EFFICIENCY IMPROVEMENT

• FUEL SAVINGS• REGENERATIVE BURNERS

Regenerative Burners

Burners are installed in pairs

Bloom Regenerative Burners Cycle A

Hot air

Warm POC

Hot POC

Gas

Bloom Regenerative BurnersCycle B

ADVANTAGES

• FUEL SAVINGS FROM HIGHER AIR PREHEAT

• SHORTER UNFIRED SECTION DUE TO PULLBACK

• LOWER NOx WITH IMPROVED BAFFLE DESIGN

RECENT APPLICATIONS

• PLATE MILL FURNACE - KOREA• HSM RETROFIT - CHINA• FORGE FURNACE - KOREA

PLATE MILL FURNACE - KOREA

• SIX ZONE WALKING BEAM FURNACE

• REPLACED BOTTOM PREHEAT ZONE BURNERS WITH REGENERATIVE BURNERS

• NATURAL GAS• 10-12% FUEL SAVINGS ON

ENTIRE FURNACE

PLATE MILL FURNACE - KOREA

PLATE MILL FURNACE - KOREA

HSM FURNACE RETROFIT - CHINA

• EIGHT ZONE WALKING BEAM FURNACE

• REPLACED BOTTOM HEAT1 AND BOTTOM HEAT2 ZONES WITH REGENERATIVE BURNERS

• MIXED GAS (200 BTU/SCF HHV)• 12-18% FUEL SAVINGS ON

ENTIRE FURNACE

SOAK

58.74 METERS EFFECTIVE LENGTH

HEAT 2 HEAT 1PREHEAT

HSM FURNACE RETROFIT - CHINA

HSM FURNACE RETROFIT - CHINA

HSM FURNACE RETROFIT - CHINA

FORGE FURNACE - KOREA

• BATCH FURNACE TWO ZONES• REGENERATIVE BURNERS ON

TOP• REGENERATIVE FLAT FLAME

BURNERS ON BOTTOM• NATURAL GAS• 20-25% FUEL SAVINGS

FORGE FURNACE - KOREAThis image cannot currently be displayed.

This image cannot currently be displayed.This image cannot currently be displayed.This image cannot currently be displayed.

This image cannot currently be displayed.

WORK IN PROGRESS - NEW HSM FURNACE - CHINA