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 24061zhyu@vt.edu, awang@vt.eduhttp://photonics.ece.vt.edu/

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2014 NETL Crosscutting Research Review MeetingSheraton Station Square Hotel Pittsburgh, PA

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")

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

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

• 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

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

• Simulation for key parameters of • Furnace geometry• Power consumption• Heating element arrangement

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Lab Test Environment DesignLab Test Environment Design

• Independent dual heating zone for temperature gradient simulation

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Lab Test Environment DesignLab Test Environment Design

• Finished furnace assembly

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Lab Test Environment BuildingLab Test Environment Building

Testing chamber

~2ft

• 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

• 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

• 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

• Demonstrate temperature gradient measurement in the lab testing environment

• Improve sensor temperature response linearity

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Next StepsNext Steps

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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