Red Hot Video of Combusting Liquor & Smelt Laurie Frederick Doug Singbeil Joey Kish at Primary Airports Black Liquor Colloquium - Utah 13 May 2003 2 1
Observations Lifespan of a Combusting Particle Coating of Tubes Two Steady States Overview Background to Boiler Video Camera Probe Activity not causing >500 C excursions Red (& White) Hot Video 3 Why Build a Camera Probe? Cracking of composite tubes at primary airports Associated with temperature excursions & cycling Cause of high temperatures - Unknown Since Feb.2001: Five successful camera probe variations ~ 35 + hours Video from 5 trips to 3 mills One design selected: Boiler View TC2 4 2
Black Liquor Life Span Hupa & Frederick 1987 Stage & Temperatures ( C) Drying <= Droplets Droplets swell ~1.5x PAPRICAN S OBSERVATIONS? Eg. Devolatilization > 800 Char Burning 800 > 1200 Smelt Puffs up, bright yellow flame produced Particle shrinks, mainly C & Na salts Molten Salts - C depleted Gray and Swelling Hollow White: Large or Medium reducing to Solid White: Small or Tiny Clear Liquid or Clear with fine black particles 5 Boiler-View Clip: Swelling Particles 6 3
Boiler-View clip: Medium to Large Particles 7 Boiler-View clip: Small to Tiny Particles 8 4
Is there something on the tubes? Yes - all fireside tube surfaces are coated ~ 2 mm thick below 1 and fairly uniform Coating either ductile or brittle TC2 @ Shutdown Burning Oil 9 Recognition of Two Steady States Expanded time scale revealed two dominant temperatures Video revealed two associated physical states: Coated Protected 24 hr 5 hr 1 hr Temperature ( C ) Temperature ( C ) Temperature ( C ) 500 500 500 TC2 0:00 8:00 16:00 0:00 11:00 12:00 13:00 14:00 15:00 16:00 13:10 14:10 Time 10 5
Coated Steady State ( CSS ) Very Few Particles & Bed Low: Tubes coated in a uniform white layer Temperatures on tube bends steady ( + 1-3 C ) Range 390-410 C; Average may drift over hours May have clear liquid flow over surface Example Video: Baseline 500 LH25-1 LH25-2 15:15 15:30 15:45 11 Boiler-View clip: Coated Steady State 12 6
Protected Steady State ( PSS ) Char Bed Particulate Covering Tube Bends: Temperature steady @~320 C High stable bed of compact particulate over coated thermocouples Particulate excluding radiation & atmosphere Example Video: 500 High Bed RH25-1 RH25-2 10:35 10:50 11:05 13 Boiler-View clip: Protected Steady State 14 7
What Seems to Protect Thermocouples from Radiation and Atmosphere? Some protection provided by coating on tubes Most Effective Protection: A high compact bed of particles, usually grey, over coating => Char Bed Protected Steady State (PSS) Two Other Conditions Approach PSS: Sticky grey particles forming a layer over coating on tubes, above bed level A buildup of fine black particles, produced as particles melt, washed down the tubes and deposited by liquid at bed interface 15 Cross Section at Thermocouple (TC) Tube Wall TC Coating Char Bed Particles TC Shield 16 8
What Items Are Not the Sole Cause of > 500 C on tube bends? Medium to tiny white particles landing Surface washed with liquid or left dry Bed surface rising & lowering Darkening surface deposits Primary or Secondary port rodding 17 Summary Tubes are normally coated on the fireside with a thin, adherent, white coating Protection of the coated tubes from radiation and atmosphere, may occur 3 ways: High compact char bed against the wall (most effective) Sticky particle layer on the tube surface, above the char bed Black fines deposited to form a smooth dense dark layer When the Bed was low, and the thermocouples not impacted by particulate, no temperatures above 500 C were noted 18 9