Burner Applications in Ethylene Cracking Furnaces Operating at Significantly Less than 90 mg/Nm3

2016 AIChE Ethylene Producers Conference – April 11-14, 2016 – Houston, TX

Introduction

• Ultra-low NOx emissions of less than 90 mg/Nm3 can be difficult in ethylene cracking
• Typical NOx reduction methods can lead to longer flame lengths
• Longer flame lengths cause:
  • Flame rollover to process tubes
  • Flame impingement on process tubes, and hot spots
  • Shorter run time between decoking
  • Reduced ethylene production
• Zeeco’s GLSF enhanced-jet flat flame floor mounted burner
• Burner entrains unburned fuel next to furnace wall
• Mixes inert flue gas products of combustion with unburned fuel gas
• Results:
  • Lower peak flame temperature
  • Reduced NOx emissions
  • Reduction in tendency for flame rollover because mixture is kept close to furnace wall

GLSF Enhanced Jet Flat Frame Burner

Staged ports on side of burner tile allow:

• Fuel gas to avoid passing directly over combustion air stream
• Delayed fuel and air mixing to reduce peak flame temperature
• Reduction in peak flame temperature to decrease NOx emissions
• More fuel and air momentum on furnace wall to reduce potential for flame roll over
• Better control of flame width and length
• Uniform heat flux profile in the middle and upper regions of the burner flame
• Even heat transfer and reduction in possibility of tube hot spots

Conclusions

• (8) new ethylene cracking furnaces needed to operate at less than 90 mg/Nm3 NOx emissions
• After retrofit, closely mounted burners showed no signs of flame interaction or rollover
• Burners achieved desired emissions, and normally operate well below guaranteed levels
• Field measured NOx emissions were 35 mg/Nm3 (17 ppmv) to 65 mg/Nm3 (32 ppmv) at designed heat release

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