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Show 2017 American Flame Research Committee Fired Heater Flooding Houston, TX Septembe, 2017 2017 AFRC Fired Heater Flooding Chuck Baukal Doug Basquez Mike Pappe Director, JZ Institute 918.234.2854 Energy Coordinator 316.321.8387 End User Sales & Service 661.588.5095 charles.baukal@johnzink.com douglas.basquez@hollyfrontier.com mike.pappe@johnzink.com Bill Johnson Bill Weimer John McGuire Aftermarket Support 918.234.5742 End User Sales & Service 985.288.5551 End User Sales & Service 713.443.1078 bill.johnson@johnzink.com william.weimer@johnzink.com john.mcguire@johnzink.com ©2017 John Zink Company, LLC **Proprietary & Confidential** 2 Outline ►Definition ►Causes ►Indication ►Response ►Examples ►Prevention ©2017 John Zink Company, LLC **Proprietary & Confidential** 3 API 535: Burners for Fired Heaters in General Refinery Services (May 2014) 14.2 Flooding Flooding (substoichiometric operation) is a term used to indicate operation with insufficient combustion air, resulting in unburned fuel or combustibles in the firebox and/or flue gas. As the furnace is typically on automatic coil outlet temperature control, the lack of combustion within the firebox allows the outlet temperature to reduce and the control system calls for more fuel exacerbating the situation. The cycle, if unabated can eventually lead to burner flameout. Before this point the unburned hydrocarbons can result in afterburning. ©2017 John Zink Company, LLC **Proprietary & Confidential** 4 Heater Flooding Incident ► Outside operators: ► Sent to check flames ► Saw low CO reading ► Smelled gas ► Saw heater huffing & puffing ► Saw deflagration blow open heater wall ► Issues: ► CO analyzer not in service due to maintenance (not in turnover report to next shift) ► Low O2 alarm incorrectly set too low ► Heater ran out of air ► Reduced heater temps = call for more fuel which flooded heater ©2017 John Zink Company, LLC **Proprietary & Confidential** 5 API 535 (cont'd) 14.2 Flooding (cont'd) Flooding on a natural draft heaters is generally accompanied by erratic firebox pressures or "panting" at the furnace air inlets. With too much fuel and too little air, combustion ceases, pressure is reduced in the firebox allowing more air to enter, as combustion develops, pressure increases in the firebox excluding the air once more. It is the small differential pressures across the natural draft burners that make this situation prevail. It is less prevalent with forced draft systems where cross limiting air fuel ratio control can prevent this situation. Pressure drop across the burners and combustion air system dampens the effect of the increases/decreases in combustion inducted pressure changes. ©2017 John Zink Company, LLC **Proprietary & Confidential** 6 Unstable Burner ©2017 John Zink Company, LLC **Proprietary & Confidential** 7 Unstable Heater 0 -0.3 +0.3 Draft ©2017 John Zink Company, LLC 0 3 %O2 **Proprietary & Confidential** 8 Refractory Damage When heater becomes flooded, firebox may shudder, huff, or woof repeatedly. This eventually can cause damage to refractory & heater tubes. ©2017 John Zink Company, LLC **Proprietary & Confidential** 9 Simple Definition of Fired Heater Flooding Too much fuel in the heater ©2017 John Zink Company, LLC **Proprietary & Confidential** 10 Good Operation Burners & heater Stack temp. Bridgewall temp. 500 oF working as designed * Pilots & BMS not shown 1550 Oil in oF Excess O2 -.1" 3% 0.0 XS O2 CO H2O Arch draft Tube temp. 815 oF Oil out 18 psig ©2017 John Zink Company, LLC **Proprietary & Confidential** Fuel pressure 11 Flooded Heater & After Burning High stack temperature High tube metal temperature High fuel pressure Low O2 850 oF 1850 oF Oil in +.5" 0% 5000 XS O2 CO H2O 1115 oF Oil out 28 psig ©2017 John Zink Company, LLC **Proprietary & Confidential** 12 Outline • Definition • Causes • Indication • Response • Examples • Prevention ©2017 John Zink Company, LLC **Proprietary & Confidential** 13 API 535 (cont'd) 14.2 Flooding (cont'd) Other possible causes of flooding may include: ►Fuel compositions beyond the recommended limits of the burner ►Low draft leading to insufficient air entering the burners ►API 556 discusses methods of addressing unburned combustibles within the fuel fired heater protective system. ©2017 John Zink Company, LLC **Proprietary & Confidential** 14 Possible Causes #1 Mechanical Issues ► Stack damper - positive draft in firebox ► Burner registers set too low for firing rate ► Fans - failure or set too low for firing rate ► Instrumentation failure/not calibrated (e.g., O2, CO, draft, fuel flow) ► Fuel control valve fails to respond ► Plugged/fouled gas tips ► Burner flame outs ► Tube failure ©2017 John Zink Company, LLC **Proprietary & Confidential** 15 Tube Leak snuffing steam inlet crack in process tube ©2017 John Zink Company, LLC **Proprietary & Confidential** 16 Tube Rupture Example Before rupture ©2017 John Zink Company, LLC After rupture **Proprietary & Confidential** 17 Possible Causes #2 Fuel Changes ►Sudden loss of H2 in fuel ►Switching to natural gas ►Sudden addition of heavies (e.g., C3s, C4s) ►Liquid fuel carryover ©2017 John Zink Company, LLC **Proprietary & Confidential** 18 Possible Causes #3 Operational Failures ►Dampers not adjusted to allow change in operation ►Burners ramped up too fast ►Heater operated to draft limit ►Sudden process feed changes in volume, temperature, or composition ►Notification that analyzers, dampers, valves are in manual, or being worked on ©2017 John Zink Company, LLC **Proprietary & Confidential** 19 Outline ►Definition ►Causes ►Indication ►Response ►Examples ►Prevention ©2017 John Zink Company, LLC **Proprietary & Confidential** 20 Indication of Possible Flooding Hazy firebox ©2017 John Zink Company, LLC **Proprietary & Confidential** After adjustment 21 Fuel Rich vs. Clean Firebox Heater flooded, fuel rich firebox ©2017 John Zink Company, LLC Clear firebox, burners adjusted **Proprietary & Confidential** 22 Fuel Rich vs. Clean Firebox Flooded heater, hazy firebox ©2017 John Zink Company, LLC Heater after adjustment **Proprietary & Confidential** 23 Fuel Rich Firebox Note this tube has fallen & is in front of tube below ©2017 John Zink Company, LLC **Proprietary & Confidential** 24 Fuel Rich vs. Clean Firebox Long tailing cloudy flames, haze visible in the firebox ©2017 John Zink Company, LLC Clear firebox, no haze **Proprietary & Confidential** 25 Outline ►Definition ►Causes ►Indication ►Response ►Examples ►Prevention ©2017 John Zink Company, LLC **Proprietary & Confidential** 26 General Response What to do: ►Reduce fuel flow rate until pulsing stops & flooding is corrected ©2017 John Zink Company, LLC **Proprietary & Confidential** 27 If flames become unstable… ©2017 John Zink Company, LLC **Proprietary & Confidential** 28 Slowly cut back on the fuel Reduce fuel until heater stabilizes ©2017 John Zink Company, LLC **Proprietary & Confidential** 29 General Response What not to do: ►Do not go to heater ►Do not adjust stack damper or burner air registers ►Do not shut down heater ©2017 John Zink Company, LLC **Proprietary & Confidential** 30 Response - Outside Operators ►DO NOT GO TO HEATER ►Evacuate any personnel in vicinity ►Do not open sight doors (added air could cause fire or explosion) ►Radio to control room to advise ©2017 John Zink Company, LLC **Proprietary & Confidential** 31 Response - Inside Operators ►Notify outside operators to stay clear of heater & to get any other personnel out of the area ►Slowly cut back on fuel until flooding is over (suitable excess O2 measured) ►If burners flame out, cut fuel to heater ©2017 John Zink Company, LLC **Proprietary & Confidential** 32 Outline ►Definition ►Causes ►Indication ►Response ►Examples ►Prevention ©2017 John Zink Company, LLC **Proprietary & Confidential** 33 Hydrotreater Incident #1 What Happened ►Heater tripped (flame scanner problems) ►Problems relighting ►Block valves manually bypassed (w/o using proper procedures) due to dropping heater temperatures ►Multiple relights attempted, purge steam permissive already satisfied so no purge on last attempt ►Heater detonated ©2017 John Zink Company, LLC **Proprietary & Confidential** 34 Hydrotreater Incident #2 ►Analysis ►Original trip caused by false loss of flame due to pilot flames blocking sight of main flames ►Subsequent loss of flame shutdowns were real; heater box was rich in fuel gas & flame was snuffed out ►Results ►No mechanical damage ►No one injured ©2017 John Zink Company, LLC **Proprietary & Confidential** 35 Heater Incident ►Primary gas tips plugged, excess oxygen low, added air instead of reducing fuel, resulting in heater incident ►Vacuum heater's burner tips fouled even after steam-out: rock inside gas tip ©2017 John Zink Company, LLC **Proprietary & Confidential** 36 Fired Heater Flooding Indications of flooding include: ► Low O2 (<0.5%) and/or high combustibles (>1000 ppm) are first indication of a potential firebox flooding situation ► Rapid drop in coil outlet temperatures and/or firebox bridgewall temperatures ► Drop in COT causes firing rate to increase due to closed loop control & worsens flooding condition of heater ► Loud rhythmic "whoosh" sound or vibration ► Pulsating / unsteady flames ► Local draft gauge swinging widely ► Hazy appearance in firebox or smoke from stack (during severe bogging) ©2017 John Zink Company, LLC **Proprietary & Confidential** 37 Fired Heater Flooding Causes for fired heaters being prone to flooding include: ►Large swings in fired duty on a regular basis ►Significant variances in fuel heating value ►Air registers or stack damper are fixed or manually operated ►Heater is air limited ►Delayed O2 analyzer response times ►Heater has exhibited signs of severe flooding in the past ©2017 John Zink Company, LLC **Proprietary & Confidential** 38 Outline ►Definition ►Causes ►Indication ►Response ►Examples ►Prevention ©2017 John Zink Company, LLC **Proprietary & Confidential** 39 Flooding Prevention ►Adjust heater operation before major fuel changes ►Maintain instruments: O2, CO, draft, etc. ►Communicate with maintenance, especially about any instruments out of service/not working ►Include anti-bogging controls in heater control scheme ©2017 John Zink Company, LLC **Proprietary & Confidential** 40 Flooding Prevention Consider: ►Adding red flashing light at heater during flooding incident or high CO ►Adding Burner Management Systems (BMS) to shut down heater during flame outs ►Adding alarms for: ►High fuel pressure ►Low combustion air flow / High combustibles ►Sudden drop in bridgewall temperatures ►Reviewing existing flooding procedures ©2017 John Zink Company, LLC **Proprietary & Confidential** 41 Conclusions/Recommendations ►Heater flooding is a very serious condition that must be dealt with properly ►Procedures must be in place & followed ►Training is critical ►Equipment must be properly maintained ©2017 John Zink Company, LLC **Proprietary & Confidential** 42 |