distributed fiber optic sensor for on-line …
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DISTRIBUTED FIBER OPTIC SENSOR FOR ON-LINE MONITORING OF COAL GASIFIER REFRACTORY HEALTH
DE-FE0005703
DISTRIBUTED FIBER OPTIC SENSOR FOR ON-LINE MONITORING OF COAL GASIFIER REFRACTORY HEALTH
DE-FE0005703Zhihao Yu, Anbo WangVirginia Tech Center for Photonics TechnologyBlacksburg, VA [email protected], [email protected]://photonics.ece.vt.edu/
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2014 NETL Crosscutting Research Review MeetingSheraton Station Square Hotel Pittsburgh, PA
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OutlineOutline
• Motivation and Objectives
• Background and Fundamental
Technology
• Project Progress
• Summary
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MOTIVATION AND OBJECTIVESMOTIVATION AND OBJECTIVES
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MotivationMotivation
• Refractory health monitoring in slagging coal gasifiers:• Rapid corrosion of refractory materials.
• High-temperature reducing environment.
• Difficult to predict remaining refractory life.• Localized thinning, spallation and cracking.
• Expensive to shut down gasifier for repair.
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ImpactsImpacts• Current gasifier operation strategy:
• Scheduled inspection & replacement of liners.• Conservatively short intervals – increased downtime• Difficult to predict wear rate.
• Re-bricking takes up to 3 weeks and $1-2M, and downtime costs even more.
• New technology will enable:• Early detection & location of hot-spots.• Estimation of remaining lifetime.• Allow conditions-based maintenance model.• Reduced downtime & cost savings.
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Project Overview & ObjectivesProject Overview & Objectives• Three-year project beginning 5/1/2011.• Industrial collaborator Eastman Chemical Co.
assists in developing technical requirements. • Objectives:
• Develop a first-of-a-kind distributed high-temperature sensing platform.
• Demonstrate potential for coal gasifier refractory health monitoring.
• Potential operation at the back side of inner-most gasifier refractory wall.
• Direct mapping of temperature profile.
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BACKGROUND AND FUNDAMENTAL TECHNOLOGY
BACKGROUND AND FUNDAMENTAL TECHNOLOGY
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Light-induced Traveling Fiber GratingLight-induced Traveling Fiber Grating
• A strong pulsed light as pump and a weak CW light as probe are injected into the sensing link, counter-propagating.
• The beat note of the pump induces a transient grating which scans along the sensing fiber.
• The signal light probes the travelling fiber grating and translates the temperature distribution along the fiber from spectral shift changes in time domain.
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• Refractory defect monitoring by temperature mapping
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Gasifier Refractory Health Monitoring Gasifier Refractory Health Monitoring
Temperature (C)
1200
1000
800
600
400
200
(a) Sensor Simulation: 2D Model
1.0m
Cracking
1326
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Thinning
Outer Shell(steel, ¼”)
Air Gap (1")Gasifier Interior
Refractory Layers (high-chrome spinel, 12")
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PROJECT PROGRESSPROJECT PROGRESS
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• Electrostriction phonon induced transient periodic refractive index change is chosen as the mechanism to generate the travelling fiber grating.
• With an intense pulsed light, the pulses generates acoustic gratings as they propagate along the sensing fiber, also known as Stimulated Brillouin Scattering (SBS) effect.
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Phonon
Probe Light Signal
Travelling Grating
Pump Pulse
Sensing MechanismSensing Mechanism
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Optical Sensing System DesigningOptical Sensing System Designing
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1550 nm source
PC EOM
Pulse generator
EDFA
PS
OC
FUT
PD
Oscilloscope
OC
RF generator
50%
50%
PC EOM EDFA
Tunable filterPump
Probe
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• First demonstration of temperature sensing• 5m spatial resolution and 10ºC temperature resolution
achieved at 500ºC
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First DemonstrationFirst Demonstration
100 200 300 400 500 600 700 800 900 1000
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11.1
11.2
11.3
11.4
11.5
11.6
11.7
temperature
Bril
loui
n Fr
eque
ncy
shift
, GH
z
BFS vs. Temp
FF vs. Tfit 1
Temperature100ºC 1000ºC
Freq
uenc
y Sh
ift
Posi
tion
in S
pace
Heated Section
Frequency Shift
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Sensitivity Optimization: Spatial ResolutionSensitivity Optimization: Spatial Resolution
• Width of pump pulse and intensity of probe light optimized with the help of theoretical analysis
• Spatial resolution improved from 5m to 1m (over the span of 230m, at 1000ºC)
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• Temperature demodulation algorithm improved
• Test environment temperature stabilized
• Temperature resolution of 5ºC achieved at 1000ºC with 1m spatial resolution.
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Sensitivity Optimization: Temperature ResolutionSensitivity Optimization: Temperature Resolution
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• Simulation for key parameters of • Furnace geometry• Power consumption• Heating element arrangement
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Lab Test Environment DesignLab Test Environment Design
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• Independent dual heating zone for temperature gradient simulation
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Lab Test Environment DesignLab Test Environment Design
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• Finished furnace assembly
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Lab Test Environment BuildingLab Test Environment Building
Testing chamber
~2ft
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• Minor temperature difference observed due to a gap reserved for sensor leading-in and leading-out.
• ~2ºC temperature stability at 1000ºC
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Lab Test Environment CharacterizationLab Test Environment Characterization
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• Inconel 600 alloy tubes• No deformation
• Oxidation on surface only
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Sensor Packaging: Alloy TubingSensor Packaging: Alloy Tubing
Before annealing
After 1000ºCannealing
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• 1m spatial resolution over the span of 600m achieved at 1000ºC
• Sensor passed 36h annealing test at 1000ºC
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Preliminary Packaged Sensor TestPreliminary Packaged Sensor Test
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• Demonstrate temperature gradient measurement in the lab testing environment
• Improve sensor temperature response linearity
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Next StepsNext Steps
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SUMMARYSUMMARY
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TasksTasks
1. Project management and planning2. Determine sensor technical requirements3. Sensor design and refractory performance
modeling4. Demonstrate the chosen mechanism5. Develop distributed sensor prototype6. Design and build test environment7. Test sensor and evaluate performance8. Prepare final report
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Project Start Date: 5/1/2011Project End Date: 12/31/2014
Task Description Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Q11 Q12 Q13 Q14 Start Date End Date
Technical Progress Reports Q Q Q Q Q Q Q Q Q Q Q Q Q F
Project MilestoneLinked Tasks: Application Info.
Budget Period 2
Reports: Q - Quarterly F - Final
Umbrella Task Budget Period
7 Test & Evaluate Sensor
Task Continuation
Develop Sensor Prototype
3.2 Develp refractory model
Construct prototype sensor
Investigate various sensing mechanism
Budget Period 1
No cost extension
3.2 Develop sensor design 2011/10/1 2012/9/30
2014/9/30
8 Prepare Final Report 2014/10/1 2014/12/31
2014/4/1
2014/3/316 Design & Build Test Environment 2013/7/1 2014/6/305.2 Calibrate & verify basic operation 2013/10/1
2013/7/1 2013/12/31
2011/10/1 2013/6/304 Demonstrate the Choson Mechanism 2011/10/1 2013/6/30
2013/7/1 2014/3/315.15
2011/5/1 2011/9/30
2 Determine Technical Specifications 2011/5/1 2012/3/31
1 Project Management & Planning
Sensor Design & Refractory Model 2011/10/1 2013/6/303.1 2011/10/1 2012/9/303
Project Progress SummaryProject Progress Summary
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THE ENDTHE END
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