53 rd annual isa power industry division symposium 7-9 june 2010, summerlin, nevada 1 flue gas...

53rd Annual ISA Power Industry Division Symposium7-9 June 2010, Summerlin, Nevada

1

Flue Gas Analysis As A Furnace Diagnostic Tool

Doug Simmers- Worldwide Product Manager Rosemount Analytical

53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada2#

Contents

• Overview of traditional applications for combustion flue gas analyzers

• Traditional analyzer technologies• New measurement goals• Analyzer applications to detect furnace anomalies • New analyzer developments

53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada

Traditional Application of Flue Gas Analyzers- Optimize Fuel/Air Ratios


Determining CO Breakthrough- how low can your O2 go




0

2

4

6

8

10

12

14

16

0 10 20 30 40 50 60 70 80 90 100

% Steam Flow

Original Setpoint

Actual Data

New Setpoint

The point of CO breakthrough changes with firing rate. Higher firing rates induce greater turbulence in the burner(s), providing better mixing of fuel and air, and a lower possible excess O2 setpoint. This curve should be re-established periodically, but more often is not.


New Measurement Goals-Staged Combustion for NOx Reduction

NOx as a function of air / fuel ratio

0

200

400

600

800

1000

1200

1400

1600

1800

0.50 0.70 0.90 1.10 1.30 1.50 1.70

NO

x (

mg

/m3) Excess air flow quenches the flame,

Lowering reaction temperatures belowThat required to make NOx

Not enough O2

to react into NOx

Flue gas O2 setpoints may be shifted up or down, based on minimizing the amount of NOx and CO produced at the burner


New Application- Flue Gas Recirculation Controlling Final O2 Entering The Wildbox

Flue Gas

3 % O2

Windbox

Burner

Primary Air

O2 Probe

21% O2

18% O2


New Measurement Goals-Slag Prevention

Ash fusion temperatures vary with flue gas O2 levels


Application Overview- Large, Multi-burner FurnacesApplication Overview- Large, Multi-burner Furnaces

Combustion analyzers are typically placed in the back pass of the furnace, and used to establish the optimum fuel/air ratio, minimize NOx, and also providing diagnostic information about the burner array, classifiers, and coal mills.

Probes


Typical flue gas Analyzers

In Situ O2 Probe

Extractive O2/ combustibles system

Point Measurements Averaging, Line-of-sight Measurements

SpectroscopyIR for COLaser IR for CO and O2(NOx is also possible)


• Zirconium Oxide “Fuel cell” technology is

commonly used Output is inverse, and logarithmic.

– Cell generates it’s own signal, which increases at the low O2 levels commonly experienced in combustion processes.

– Accuracy actually improves at lower O2 levels.

No sampling system required. Passive diffusion- filters last a long time

before plugging in high particulate applications

Speed of response is fast. Cost effective

Sensing cells are robust. Operate well at elevated temperatures Sulfur resistance is good. Cell life can easily exceed 3-5 years.

Typical flue gas Analyzers –In Situ Oxygen Probe



In Situ O2 Probe


Point measurements Averaging, line-of-sight measurements

SpectroscopyIR for COLaser IR for CO and O2(NOx is also possible)


Typical flue gas Analyzers –Close-Coupled Extractive (no sample conditioning)

• Same ZrO2 Oxygen sensor

• Calorimetric combustibles sensor• Detects CO breakthrough, but cannot

resolve fine PPM CO levels• May require frequent maintenance in

high particulate applications (coal, biofuels, garbage incineration, etc.)

OCX 8800 Launch PresentationJuly 09, 2009 // Slide 13



In Situ O2 Probe


Point measurements Averaging, line-of-sight measurements

SpectroscopyIR for COLaser IR for CO and O2

(NOx is also possible)


Typical flue gas Analyzers –IR or Laser Spectroscopy for CO

• Most implementations are across-stack, or “line-of sight”.– Averages across the flue duct. – Difficult to challenge with a known

calibration gas.

• CO is a good absorber of IR energy @ about 470nm wave number

• CO as well as O2 and NOx can be reliably detected with tunable diode laser systems.

Typical Installation


Historical Progression of Point O2 AnalysisIn Large Multi-Burner Furnaces

Historical Progression of Point O2 AnalysisIn Large Multi-Burner Furnaces

• Early years- 1970-1980- a single O2 Probe per flue gas duct is sufficient- placement is “somewhere near the middle”

• Confused- 1985- a second O2 probe is added, to get a better average for fuel/air ratio adjustment– The two probes rarely agree, so operators trust the readings from neither probe. – After many calibrations, it’s understood that both probes are telling the truth, and significant

stratification exists in the ductwork• 1990- More probes are added in order to again get a better O2 average

– More stratification is witnessed by the operators, and more confusion ensues– Probes that are particularly out of the norm are often removed from the average (exactly the wrong

thing to do)!


Average O2 for Fuel/Air Ratio Control Predictive Maintenance Tool Average O2 for Fuel/Air Ratio Control Predictive Maintenance Tool

Seeking out stratification- Rather than avoid stratification, plant operators are more and more trying to determine what flue gas stratification is telling them.

Balancing Burners Detecting Burner Fouling Poor coal distribution/roping Mill to mill variations


Focusing In On The Real Process(es)

Each burner and coal mill constitutes a separate process of it’s own

The furnace is an envelope


Burner Diagnostics-Analyzer Placement Is Important

• Burner columns are easier to identify with a wall-fired furnace

• Corner to corner variations in a tangentially fired furnace are harder to discern


Changing Measurement Locations

• Coal-fired boilers– Most boiler manufacturers

provide testing ports after the economizer, hopper, which are often utilized for permanently mounted analyzers.

– An upstream location ahead of the economizer has advantages

– Large particle ash, or “popcorn ash” is less prominent- abrasion on probes is less.

– Stratification is greater, burner column by burner column


Fine Tuning Probe Placement With Variable Insertion Fine Tuning Probe Placement With Variable Insertion


Variable Insertion Probe- looking for the ideal measuring point.


Furnace Diagnostics- Detecting Air Leaks Air Heater Seal Leakage- the delta O2 before and after

an air heater helps determine seal leakage


Furnace Diagnostics- Flue duct seal leaks are indicated by outer probes reading higher

3.4 % 3.4 %

2.9 %

3.2 % 3.3 %

3.1 %

4.1 % 3.8 %

Furnace Diagnostics- Detecting Air Leaks


Furnace Diagnostics- Beyond Total Furnace Average

2.9%3.2 % 3.3 %

3.0 %

3.3 % 3.4 %

3.1%3.4 % 3.1 %

3.0 %

3.3 % 2.9 %

Duct A Average Duct B Average

Mill average- Burners fed from common pulverizer mills may show similar readings when mill/classifier problems arise.

Duct averages can shift left or right with ID fan load changes


Furnace Diagnostics- Soot Blow Problems/Tube breaks

• O2 readings will be affected by the dilution of water entering in the furnace– O2 dry= O2 wet (1/1-H2O

– Soot blow/water lance

– Tube breaks


Duct Burners for Combined Cycle Combustion Turbines


Duct Burners Increase Steam Production, But Now O2 Can Be Controlled To A More Efficient Level.


New Developments In ZrO2-Getting New Information From AReliable Sensor Technology

Recovering from process upsets- A ZrO2 sensor that measures the level of O2 deficiency during reducing events.

O2 range is depressed -2% to 10%

During process upsets into reducing conditions, the operator can see the level of O2 deficiency, and see if his corrections are adequate

Zero % O2


New Developments In ZrO2-Getting New Information From AReliable Sensor Technology

New ZrO2 probe sensor that measures CO breakthrough.

CO Probe

O2 Probes

Boiler load (megawatts)

IR CO analyzer


Summary

• Flue gas analysis has historically provided a good tool for optimizing fuel/air ratios in large furnaces

• Analyzers help achieve new goals such as NOx reduction and slag reduction.

• Multi-burner furnaces often have significant flue gas stratification, which is often a cause for operator concern

• Stratification profiles provide a great diagnostic of upstream processes at the burners and pulverizers– The furnace is just an envelope for the process– each burner is it’s own

process.– Point measurements provide good granularity of upstream burner columns,

but more instruments are required in order to get a good average – Line-of-sight measurements are inherently averaging, so fewer are required

to get a good total average, but stratification is masked• New developments in CO measurements will improve NOx reduction,

combustion efficiency, and burner diagnostics.


Thank You- Questions?

Chris Morrissey- S. California Sales [email protected](951) 285-1629

Chris Lesser- RM Regional Sales [email protected](303) 883-7180

Dave Anderson- Marketing [email protected](949) 322-8178

Doug Simmers- Worldwide Product [email protected](330) 309-2494

53 rd annual isa power industry division symposium 7-9 june 2010, summerlin, nevada 1 flue gas...

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