TDL syngas sensor for in situmonitoring of CO, CH4, CO2, & H2O in an engineering‐scale high‐pressure coal gasifier

Ronald K. Hanson, Ritobrata Sur, Kai Sun, Jay B. JeffriesHigh Temperature Gasdynamics Laboratory, Stanford University

NETL's Crosscutting Research Review Meeting May 19‐23, 2014, Pittsburgh, PA

Vision for gasifier sensing Absorption sensor fundamentals NCCC gasifier facility Stanford optics design Results for CO, CH4, CO2, & H2O Summary and further work

Gasifier in Wilsonville, Alabama USA

Supported by DOE NETL – Dr. Susan Maley

2

Stanford’s Vision for TDL Sensing in IGCC

X

XCoal

Oxygen or Steam

Oxygen/CoalRatio Control

Sensor for T & SyngasComposition

3 4

Fuel/air Ratio Control1

Gasifier

ReactorCore

Quench

2SyngasCleanup Gas Turbine

X

XCoal

Oxygen or Steam

Oxygen/CoalRatio Control

Sensor for T & SyngasComposition

3 4

Fuel/air Ratio Control1

Gasifier

ReactorCore

Quench

ReactorCore

Quench

2SyngasCleanup Gas Turbine

Sensor for control signals to optimize gasifier output and gas turbine input 1st generation laser absorption sensor for CO, CO2, CH4, and H2O

Stanford sensor tested in a pilot-scale (1 T/day coal) gasifier (U Utah 2009-2012)

2nd generation CO, CO2, CH4, and H2O sensor developed Tested in an engineering-scale (30,000 lb/hr syngas) gasifier at NCCC

(December 2012 & March 2014)

Vision:

Absorption sensing: How does it work?

Absorption Fundamentals: Species

Scanned-wavelength line-of-sight direct absorption

Beer-Lambert relation

Spectral absorption coefficient

Wavelength-scanning yields

exp( )t

o

I k LI

PPTTSk ii ),,()(

3

Absorption of monochromatic light

( ) ik L d S T P L

Integrated absorbance

Two Absorption Sensor Strategies:Direct Absorption (DA)

WMS

Direct Absorption

Gas sample

Io It

Direct absorption: Simple, if absorption is strong and isolated WMS: More sensitive especially for small signals (near zero baseline)

WMS with TDLs improves noise rejection Normalized WMS, e.g. 2f/1f cancels scattering losses!

What wavelengths for syngas detection?

Injection current tuning

+ Injection current modulation @f

i’

i 0.4 0.5 0.6 0.7

0.00

0.25

0.50

0.75

Abs

orba

nce

W avelength (re lative cm -1)

D irect absorption lineshape

0.4 0.5 0.6 0.7 0.8 0.9 1.00.0

0.1

0.2

0.3 Direct Absorption Scan

Lase

r Int

ensi

ty S

igna

l

T ime(ms)

Baselinefit

for Io

Lockin@1f, 2f

-0.02

0.00

0.02

0.04

WMS-2f lineshapeNor

mal

ized

2f s

igna

l

Wavelength (relative cm-1)0.4 0.5 0.6 0.7

0

2

4

6

8

WMS Scan

WM

S S

igna

l

Time (ms)0.4 0.5 0.6 0.7 0.8 0.9 1.0

& Wavelength Modulation Spectroscopy (WMS)

4

Gas Species Important to Combustion/Gasification Absorb Light in the Near-Infrared

Important gasification species can be monitored (e.g., CO, CO2, CH4, H2O) Select 2-2.3µm to minimize H2O interference for CO, CO2, CH4

What does the facility look like? 5

T=600KP=1atmL=1cmX=100%

2.33µm

2.02µm

2.29µm

1.35µm

6

NCCC Gasifier Large-Scale DoE Demo

Instrumentation shelter

NCCC transport gasifier based on a circulating fluidized bed conceptGoal:Laser absorption in situ measurements of syngas products composition

Where is sensor located?

~100 m

TDL sensor monitors syngas flow 30m downstream of the PCD Flow laden with particulate (< 0.1% transmission) at sensor location

How do we measure 4 species?

TDL Sensor Location and Syngas conditions

7

Transport gasifier

Particulate control device (PCD)

Syngas coolerCyclone

Burner

Nominal conditions at TDL sensorT~600 KP~220 psig (15 atm)Gas composition

H2O 6-10%CO2 6-10%CO ~12%H2 ~ 8%CH4 ~ 1%Minor species <1%

(e.g., NH3, H2S, SO2…)N2 Balance

LDetection Strategy：Time Demultiplexing

Wavelength Scanned WMS-2f with 1f Normalization

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

x 10-3

-0.5

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

x 10-3

-0.5

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

x 10-3

-0.5

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

x 10-3

-0.5

0

0.5

1

1.5

2

2.5

0ms  5ms  10ms  15ms  20ms 

Detector signal

7393 7394 73950.0

0.5

1.0

1.5

2f/1

f [un

itles

s]

Frequency [cm-1]

Measurement Best fit

Lock‐in @ 1f and 2f

1f Normalized WMS‐2f

@ f

0‐5m

s

5‐10

ms

10‐15m

s

15‐20m

s

Separate laser for each species Time multiplexing (each laser takes a turn)

4 species in 20ms w/ one detector Wavelength scanned 1f‐normalized WMS‐2f

Enables measurements in opaque flows

Unique Stanford detection strategy

200Hz

10kHz

H2O 1.4m CO 2.35m CO2 2m CH4 2.29m

8

Experiment control House (DAQ, laser 

controller)

BNC

Detector pow

er sup

ply

DB 25

Detector gain sw

itch

Four laser controller cables

DB 25

Lasers

Fibers

Connections of Stanford Sensor to NCCC Facility

Electronics in the control house ~30m to measurement location Lasers near measurement location (~ 2m away) Sensor operated remotely (alignment, detector gain, laser scanning)

Next: Further details of optical system 9

Redundant valves and windows

Transmitter optics

Window pair

Valve pair

Receiver optics

Valve pair

Window pair Syngas flow

Optics Design：Multiplex Four Lasers

Fiber bundle delivers light from four lasers Optics combine all beams onto common line-of-sight w/ only one detector Large beam size reduces beam steering noise

10

2 cm 1.5 cm

Fiberbundle

0.2m Pitch sideCatch side

5cm

Insulation5m

Next: Data from gasifier warm-up

Time-Resolved H2O During Gasifier Warm-up

In situ measurements of syngas moisture content capture transient events Propane used for slow heating of ceramic linear Pulsed coal feeding begins at hour 38 Reactor shut down at hour 54 (before transition to stable gasification)

TDL shown @ 2s resolution

H2O% fluctuations from pulsed coal feed for controlled gasifier warm-up

11Next: Transition to gasification

H2O and CO2 During Transition to Gasification

6840 6860 6880

5

10

15

Mol

e fra

ctio

n [%

]

Time [mins]

GC : CO2CO2

H2O

CO2 fluctuations damped when reactor transitions to gasification GC time resolution does not capture transients, only average mole fraction

P = 120 psig

Onset of gasification

12

Rapid jump in CO and CH4 at onset of gasification GC data have large time lag (shifted here by 20 minutes for comparison with laser) GC data also have poor time resolution (note slow CO response vs laser)

6850 6900 69500

1

2

3

4

5

6

Pressurization & coal increased

Mol

e fra

ctio

n [%

]

Time [mins]

GC:CH42xCH4

GC : COCO

Onset of gasification

Sensor Captures Onset of Gasification via CO & CH4

13Next: Data from “Stable Gasification”

Four Species Measurements After Gasifier “Stable”

7320 7340 73600

3

6

9

12

15

P = 220 psig, T = 630 K

GC: CH4

GC: CO2

GC: CO

CO2

CH4

H2O

Mol

e Fr

actio

n [%

]

Time [mins]

CO

Laser sensor provides simultaneous CO, CH4, CO2, and H2O Correlation of CO with CH4 confirms that fluctuations are real GC time resolution does not capture temporal fluctuations

14Next: Long unattended monitoring

Continuous, stable measurements for 18 days (terminated by NCCC) Periodic liquid H2O samples taken from syngas agree with laser sensor Laser sensor show small fluctuations in the H2O mole fraction

15

Are sensor fluctuations real or noise?

18 Days of H2O Unattended Monitoring

H2O Sensor Captures Fluctuations in Gasifier Reactor

16

H2O fluctuation tracks the reactor thermocouple (note small T) H2O fluctuation tracks the reactor coal feed pulse Laser sensor captures small H2O change (mole fraction ~ 0.1%)

Laser sensor yields successful measurements in syngas

First-ever in situ laser absorption in pilot scale gasifier (Utah, 2010)

First-ever in situ laser absorption at NCCC (2012)

Successful in harsh environment, even with large (>99.9%) transmission losses due to scattering & pressure ~15atm

Demonstrated excellent detection sensitivity at 1-second (1Hz):

H2O : 200ppm ‐ m

CO : 200ppm ‐ m

CH4 : 300ppm – m

CO2 : 800ppm ‐ m

Unattended operation (>435 hours demonstrated)

Sensor strategy useful for other applications, especially at elevated pressure and/or dusty gases

Summary

Add additional species important to specific application, for example

NH3, H2S, SO2, ….

Improve data processing

Provide real time readout compatible with facility record

Provide web-based monitoring for unattended operation

Refine optical engineering and repackage in smaller containers

Recommendations for future work

Acknowledgements DoE, NETL: Dr. Susan Maley and Mr. Charles Miller

National Carbon Capture Center, Southern Company Services, Mr. John Socha

Stanford team:

Ritobrata Sur Dr. Kai Sun Dr. Jay Jeffries