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Show Objectives for Optimizing Combustion Systems in Refinery and Petrochemical Applications 1914 - 2014 A Century of Innovation in the Oil and Gas Industry © 2014 UOP LLC. All rights reserved. UOP 6123-1 Kurt Kraus, PE Callidus Technologies LLC UOP, A Honeywell Company AFRC 2014 INDUSTRIAL COMBUSTION SYMPOSIUM September 7-10, 2014 Hyatt Regency Houston 1. Design Verification - Set Goals - Furnace Spec Sheets - Burner Data Sheets - Historical Operational Data 2. Verify Equipment Condition Low NOX Burner Process Steps for New and Retrofit Applications 3. Additional Considerations 4. Areas for Further Study Prudent Initial Project Goals for Combustion Optimization - Prudent, but Technology Limiting 1. Meet Heating Performance Spec Requirements - Capacity (Firing Duty) - Emissions and Efficiency: NOx, CO, UBHC,… 2. Keep Flames Safely Off Tubes - Use acceptable burners - Maintain low heat density and heat flux rates • Some may purport limiting heat density and flux rates is a way to allow use of lower levels of burner technologies • Reduces radiant section thermal efficiency - Use ample burner spacing • As some will advocate • Precludes process improvements, yield, conversion, runtime • Radiant section that is too big can cause poor flame quality, blowing around in large currents Design Verification: Heat Flux & Density heat area Qin xy = / − r < 900 kW/m² ** The duty per unit area contained within the tubes is the Area Heat Flux ** Proposed values by members of an industry group (285,000 BTU/hr/ft2) z heat vol Qin xyz = / − r Volumetric Heat Density 100 kW/m3 ** (9660 Btu/h/ft3) 4 Additional Goals for Combustion Optimization But after achieving initial objectives, some customers see unit performance changes (gains or losses) and want to further explore, drive and optimize or correct to: 1. Optimize Process Yield 2. Optimize Process Conversion Selectivity 3. Maximize Run Time Actual Calculated Increase the Process Value to Operating Company, Make More Money Process Heating and Furnaces Process Heaters (Ignore or Mitigate Reactions in Process Tubes) - Thermal Cracking - Mitigate • Mostly Creates Lighter HCs - What is the Optimal Level? - Recombination and Radical Addition - How much of this is going on? PROCESS FLOW Furnaces (Drive Reaction in Process Tubes) - Steam Cracking - Steam Methane Reformers (Catalyst in Tubes) PROCESS FLOW Process Heater Case Study - Coker A seminal example Retrofit conventional "raw gas" burners with Ultra-Low NOx (circa 1992) Minimize coking in heater Maximize process yield, coking in flash drum Refinery retrofit all heaters vs. just those needed to meet NOx limits Relative Incident Heat Flux On Tubes vs. Elevation in Heater 25 30 35 40 45 50 Heater Elevation PROCESS FLOW 0 5 10 15 20 1.00 0.80 0.60 0.40 0.20 0.00 (Feet) Relative Incident Heat Flux On Tubes Dimensionless PROCESS FLOW Flow Down In Through Convection, Crossover Top of Radiant, Serpentine Radiant, Out at Bottom INLET (CONVECTION) PROCESS FLOW Conventional "Raw Gas" Burner Heat Flux Curve Ultra-Low NOx Burner Heat Flux Curve Uniform - Well Stirred Process Heater Case Study - Coker BOTTOM OUTLET Hypothetical Optimal Heat Flux Curve (Flameless??) Possible Optimal Heat Flux Curve Flameless Combustion CONVENTIONAL LOW NOx FLAMELESS Address Shift of Duty or Consider Indirect Heating Reality Check: Verify Equipment Condition Clean & Repair Seal Fire Box & Convection Functional Stack Dampers & Air Registers or FD/ID Fans Locate & Calibrate Oxygen & Draft Transmitters Make it Air Preheater Clean & Maintain Burners Operate With Design Limits Section Right Tramp Air Tramp Air Through Convection Section O2 = 3% 0.1 in. WC draft Reality Check: Eliminate Air Leakage Locate Oxygen and Draft Analyzers Heater Wall Sight Port Radiant Section O2 High O2 = 4% Raises NOx Levels Reality Check: Locate Oxygen and Draft Analyzers Locate O2 Meters at Arch, Not Stack Reality Check: Eliminate Air Leakage Stuffing Box Sight Door Floor Tube Penetration Dark Spots Hydrogen content Unsaturates Liquids Heating value / specific gravity Inerts Additional Considerations: Fuel Natural Gas Clean and Dry - Heat Trace & Insulate - 120C (250F) with Heavy Hydrocarbons Consider stainless steel piping Flame Quality - Better Burners - Low NOx Short Flames -Diffuse Flame, (Flameless?) -Broad Operating Range, Conventional Operation -Automated Operation Multi-Dimensional Heat Flux Characterization Going Forward: Areas for Further Study -Flame Detection and Characterization -Real Time Flame/Heat Flux Optimization Close Coupling of Process and Flame -Thermodynamics, Heat Transfer and Process Chemical Kinetics (Heater and PetroChem) End User Value (Profit) System Driven Optimization UOP 6123-17 |