Tunable Diode Laser Sensors for Monitoring Combustion and Gasification Systems

Jay B. Jeffries*, Ronald K. Hanson*, and Kevin Whitty***High Temperature Gasdynamics Laboratory, Stanford University g e pe a u e Gasdy a cs abo a o y, S a o d U e s y

**Institute for Clean and Secure Energy, The University of UtahDoE/EPRI Workshop on Instrumentation June 2012

1. Fundamentals of TDL absorption sensing2. TDL sensing for coal gasification

T and H O sensing* T and H2O sensing* CO, CO2, CH4, H2O sensing**

3. Monitor of syngas heating value

*Sponsored by EPRI (Jose Marasigan & Jeff Phillips)**Sponsored by DoE NETL (Susan Maley)

My main message today is that:TDL Absorption is Practical in Harsh Environments

Utilizes economical, robust and portable TDL light sources and fiber optics Can yield multiple properties: species, T, P, V, & m in real-time over wide conditions

T to 8000K, P to 50 atm, V to 15km/sec, multiphase flows, overcoming strong

.T to 8000K, P to 50 atm, V to 15km/sec, multiphase flows, overcoming strong emission, scattering, vibration, and electrical interference

Demonstrated in harsh environments and large-scale systems: Aero-engine inlets, scramjets, pulse detonation engines, IC engines, gas turbines g j p g g g

arcjets, shock tunnels, coal-fired combustors, rocket motors, furnaces…. Potential use in control of practical energy systems

IC-Engines @ NissanCoal Gasifier @ U of UtahCoal-fired Utility Boiler

IC-Engines @ Nissan

J ff i Pitt b h C l C f 2011

2

Jeffries, Pittsburgh Coal Conf, 2011

Chao, Proc Comb Inst, 2011 Jeffries, SAE J. Eng, 2010

Absorption Fundamentals: SpeciesAbsorption of monochromatic light

• Scanned-wavelength line-of-sight direct absorptionB L b t l ti I• Beer-Lambert relation

• Spectral absorption coefficient

LnLkII

io

t exp)exp(

PPTTSk )()(absorbance

• Spectral absorption coefficient PPTTSk ii ),,()(

3

Absorption Fundamentals: Velocity

• Shifts & shape of contain information (T,V,P,i)

4

Absorption Fundamentals: Temperature

• T from ratio of absorption at two wavelengths

5

Absorption Fundamentals: Multiplexed

• Wavelength multiplexing is often utilizedWavelength multiplexing is often utilized• To monitor multiple parameters or species• To assess non-uniformity along line-of-sight

6

TDL Sensors Provide Access to a Wide Range of Combustion Species/Applications

S ll i h Small species such as NO, CO, CO2, and H2O have discrete rotational transitions in the vibrational bands

Larger molecules, e.g., hydrocarbon fuels, have blended features

77Two primary TDLAS sensor strategies

Two Absorption Measurement Techniques:Direct Absorption (DA)

Baseline

& Wavelength Modulation Spectroscopy (WMS)

Direct Absorption

Injection current tuning

0.25

0.50

0.75

Abs

orba

nce

D irect absorption lineshape

0.1

0.2

0.3 Direct Absorption Scan

r Int

ensi

ty S

igna

l Baselinefit

for Io

Gas sample

Io Iti 0.4 0.5 0.6 0.7

0.00

A

W avelength (re lative cm -1)

0.4 0.5 0.6 0.7 0.8 0.9 1.00.0La

ser

T ime(ms)

0.04

gnal8

l

WMS+ Injection current

modulation @f

i’ Lockin @1f, 2f

0.00

0.02

orm

aliz

ed 2

f si

2

4

6

WM

S S

igna

Direct absorption Method of choice hen applicable

@-0.02 WMS-2f lineshapeN

o

Wavelength (relative cm-1)0.4 0.5 0.6 0.7

0WMS Scan

Time (ms)0.4 0.5 0.6 0.7 0.8 0.9 1.0

Direct absorption: Method of choice when applicable WMS: More sensitive especially for small signals (near zero baseline)

WMS with TDLs improves noise rejection 1f-Normalized WMS-2f/1f: Provides Io without a baseline

8

High P,T Sensing Enabled by WMSSimulated Absorbance SpectraSimulated Absorbance Spectra

2500 K12% H2OL = 4 cm

High P, T challengesB d d bl d d t t hi h P

25 atm1 atm

Broad and blended spectra at high P Decreased absorbance at high T

Simulated WMS Spectra2500 K

Solution 1f-Normalized WMS-2f

25 atm

2500 K12% H2O

Recovers strong peaks No baseline Io needed! Also suppresses noise and pp

transmission losses

9

WMS-2f/1f Accounts for Non-Absorption LossesPitch Lens Fixed WMS 2f/1f

0 061392 nm, Partially Blocking Beam 1392 nm, Vibrating Pitch Lens

Modulated TDL near 1392nm

Pitch LensDetector

Fixed WMS-2f/1fAmbient H2O (T=296 K, 60% RH) L=29.5 cm, ~6% absorbance)

0.6

ude

0.00

0.02

0.04

0.06

2f M

agni

tude

2f Magnitude

0.6

ude

0.00

0.02

0.04

0.06

2f M

agni

tude

2f Magnitude

0 06

0.09

0.12

agni

tude

0.0

0.2

0.4

1f M

agni

t

2f/1f

1f Magnitude

0 06

0.09

0.12

Mag

nitu

de

0.0

0.2

0.4

1f M

agni

tu

1f Magnitude

Demonstrate normalized WMS-2f/1f in laboratory air

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.350.00

0.03

0.06

2f/1

f Ma

Time (s)

2f/1f

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.70.00

0.03

0.06

2f/1

f M

Time (s)

2f/1f

Demonstrate normalized WMS-2f/1f in laboratory air 2f/1f unchanged when beam attenuated (e.g., scattering losses) 2f/1f unchanged when optical alignment is spoiled by vibration

WMS-2f/1f signals free of window fouling or particulate scatteringWMS has other advantages too

10

Sensing with Large Transmission Losses from Scattering Enabled by WMS

Transmission of laser light at non-absorption wavelengths

M t i d t li b f ti l t filt i Measurement in syngas product line before particulate filtering Particulate loading increases with pressure (99.9% loss at 150psig)

Varies with gasifier performance, fuel, temperature, etc.

11

Solution: Stanford’s 1f-normalized WMS-2f scheme

What might we measure in syngas?

Vision and Goals for TDL Sensing in IGCC

X

Oxygen or Steam

Sensor for T & SyngasComposition Fuel/air Ratio

GasifierX

Oxygen or Steam

Sensor for T & SyngasComposition Fuel/air Ratio

GasifierX

Oxygen/CoalRatio Control

Composition

3 4

Fuel/air Ratio Control1Reactor

Core2

Syngas

XOxygen/CoalRatio Control

Composition

3 4

Fuel/air Ratio Control1Reactor

CoreReactor

Core2

SyngasX

Coal

QuenchSyngasCleanup Gas TurbineX

Coal

QuenchQuenchSyngasCleanup Gas Turbine

Sensor for control signals to optimize gasifier output and gas turbine input Two flow parameters considered: gas temperature and heating value

Vision:Goals:

Gas temperature determined by ratio of H2O measurements Measurements of CO, CH4, CO2, and H2O provide heating value

H2 determined by gas balance as other species ignored

1212

2 y g p g Four measurement stations considered: spanning reactor core to products

Oxygen-blown, Down-fired, Entrained-flow Coal Gasification Facility at the University of Utah

Rated to 450 psig current data to 200 psig

Pilot scale gasifier

current data to 200 psig Rated to 3100 °F Coal throughput: 1 ton/day Overall dimensions

5.1 m (17’) tall0.76 m (30’’) OD

Reactor dimensions1.5 m (60’’) long 0.20 m (8’’) ID

Four measurement campaigns to test Stanford TDL sensors: Four measurement campaigns to test Stanford TDL sensors: Aug. 2010, Dec. 2010, Aug. 2011, May 2012

Ideal facility for instrumentation testing:R id t iti f 1 t fl t 20 t ifi ti diti

13

Rapid transition from 1 atm flame to 20 atm gasification conditions Reactor kept hot with 1 atm natural gas flame between runs

Sensor Setup in Utah Gasifier: T and H2O

Two reactor locations tested Position 1: Reactor core

P iti 2 Q h l ti

N2 Purge

Gasifier reactor

N2 Purge

Slag

1 Position 2: Quench location

12.5cm

CollimatorIrisFocusing mirror

Optical filter

1

20cm

Sapphire window

2

Detector34cm

Liquid H2Oquench

14

Sensor Setup in Utah Gasifier: T and H2O

Two reactor locations tested Position 1: Reactor core

Hi h t T

N2 Purge

Gasifier reactor

N2 Purge

Slag

1 Highest T Largest scattering losses Emission interference

12.5cm

CollimatorIrisFocusing mirror

Optical filter

1

Time limited by slag flow Successful measurements

demonstrated

20cm

Sapphire window

2

Detector34cm

Liquid H2Oquench

Laser current

Diode Lasers1352, 1347 nm

Laser

1×2 fibercombiner

15Control Room

Diode Lasers1392, 1469 nmDAQ PC

Laser controller 1×2 fiber

combiner

Temperature in Reactor Core

Transmission at 50 psig 0.13% dropping to 0.02% at 150 psig Normalization scheme successful Very strong optical emission - optical filtering scheme successful

Optical access tube successfully stayed open in presence of flowing slag’p y y p p g g Later unsuccessful with different coal (and different atomizer)

Temperature in Reactor Core

Reactor CoreIncrease O2

DetectorFiber to Control Room

Normalization scheme successful with low transmission (< 0.02%) TDL sensor time response can capture flow changes TDL sensor time response can capture flow changes

17

Sensor Setup in Utah Gasifier: T and H2O

Two reactor locations tested Position 2: Quench location

M d t fl k

N2 Purge

Gasifier reactor

N2 Purge

Slag

1 Modest purge flow keeps

windows clean Lower T – different line pair 12.5cm

CollimatorIrisFocusing mirror

Optical filter

1

Amplifier available Increase power x10

Successful measurements

20cm

Sapphire window

2

even with 10-5 attenuationDetector

34cm

Liquid H2Oquench

Laser current

Diode Lasers1352, 1347 nm

Laser

1×2 fibercombiner

Fiber amplifier

18Control Room

Diode Lasers1392, 1469 nmDAQ PC

Laser controller 1×2 fiber

combiner

Temperature @ Quench Location

Normalized WMS accounts for varying transmission (10-3 at 160 psig)y g ( p g) Measured T at reactor pressures of 90, 120 and 160 psig stable Measured T at 200 psig identifies potential fuel/O2 input instabilities

Temperature @ Quench Location

Location 2, P ~ 200psigTransmission~ 7 X 10-6Transmission 7 X 10

Different gasifier conditions, different coal, more particulate scattering High SNR, time-resolved measurements of T using fiber amplifier

20

g , g p Less than 10-5 of the laser light transmitted

Sensor Setup in Utah Gasifier: Syngas Composition

CO, CO2, and CH4 lasers use lasers 2-2.3 m

21

Fiber technology less available TDLs controlled remotely but located near measurement

Sensor Setup in Utah Gasifier: Syngas Composition

Syngas can by pass sensor location for window maintenance Syngas can by-pass sensor location for window maintenance Similar setup before and after particulate filter (similar results) Multiple-lasers directed through one window

Rapid (10 Hz) switching from one species to another Time-resolution ~1/3 second

22

TDL Sensor Measured Syngas Composition

CH4 addition Vary O2/coal feed rates

Laser absorption measurements of CO, CO2, H2O and CH4 over 1 hour CH4 added to syngas to test sensor response and vary gas composition

23

Gasifier feed rates changed to test sensor response

Syngas Composition Including N2 and H2

N2 in flow from gas purges – determined by metering and GC data Assume the rest of the syngas is H2

24

Enables determination of lower heating value (LHV)

Time-Resolved Monitor of Syngas LHV

One hour time record of syngas lower heating value (LHV) CO, CO2, CH4 and H2O from TDL sensor and N2 from facility data

Assume balance of syngas H

25

Assume balance of syngas H2

LHV contribution of small concentrations of H2S and NH3

are estimated to be less than 2% (accounted as H2)

Summary

A novel modulation strategy enables measurements in high pressure environments with extinction by scattering Scheme validated for extinction as large as 105 Scheme validated for extinction as large as 10

Sensor demonstration measurements made in four locations of a pilot-scale, entrained-flow, coal gasifier Time-resolved measurements capture small changes in gasifier Time-resolved measurements capture small changes in gasifier

operating conditions Current work focused on sensor validation and demonstrationNe t StepsNext Steps: Transition sensor to real-time for continuous unattended monitoring Add H2S and NH3 to sensor suite Package next-generation sensor for industrial-scale applications (test Utah?) Find suitable industrial-scale demonstration opportunities

A k l d t St f d PhD t d t K i S d Rit SAcknowledgements: Stanford PhD students Kai Sun and Rito SurProfessor Kevin Whitty at University of UtahSusan Maley @DoE; Jeff Phillips and Jose Marasigan @EPRI26