53 rd annual isa power industry division symposium 7-9 june 2010, summerlin, nevada 1 flue gas...
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53rd Annual ISA Power Industry Division Symposium7-9 June 2010, Summerlin, Nevada
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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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Determining CO Breakthrough- how low can your O2 go
Traditional Application of Flue Gas Analyzers- Optimize Fuel/Air Ratios
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Traditional Application of Flue Gas Analyzers- Optimize Fuel/Air Ratios
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.
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
New Measurement Goals-Slag Prevention
Ash fusion temperatures vary with flue gas O2 levels
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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)
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
• 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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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)
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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)
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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)!
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Fine Tuning Probe Placement With Variable Insertion Fine Tuning Probe Placement With Variable Insertion
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Variable Insertion Probe- looking for the ideal measuring point.
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Furnace Diagnostics- Detecting Air Leaks Air Heater Seal Leakage- the delta O2 before and after
an air heater helps determine seal leakage
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Duct Burners for Combined Cycle Combustion Turbines
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Duct Burners Increase Steam Production, But Now O2 Can Be Controlled To A More Efficient Level.
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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.
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
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