Transcript Slide 1

Flue Gas Analysis As A Furnace Diagnostic Tool
Doug Simmers- Worldwide Product Manager
Rosemount Analytical
53rd Annual ISA Power Industry Division Symposium
7-9 June 2010, Summerlin, Nevada
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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
2#
Traditional Application of Flue Gas AnalyzersOptimize Fuel/Air Ratios
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Traditional Application of Flue Gas AnalyzersOptimize Fuel/Air Ratios
Determining CO Breakthrough- how low can your O2 go
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Traditional Application of Flue Gas AnalyzersOptimize Fuel/Air Ratios
16
14
12
Original Setpoint
10
New Setpoint
8
Actual Data
6
4
2
0
0
10
20
30
40
50
60
70
80
90
100
% Steam Flow
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 GoalsStaged Combustion for NOx Reduction
NOx as a function of air / fuel ratio
1800
1600
Not enough O2
to react into NOx
NOx (mg/m 3)
1400
1200
Excess air flow quenches the flame,
Lowering reaction temperatures below
That required to make NOx
1000
800
600
400
200
0
0.50
0.70
0.90
1.10
1.30
1.50
1.70
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
Burner
Windbox
Flue Gas
O2 Probe
18% O2
3 % O2
21% O2
Primary
Air
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
New Measurement GoalsSlag Prevention
Ash fusion temperatures vary with flue gas O2 levels
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Application OverviewLarge, 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
Point Measurements
Averaging, Line-of-sight
Measurements
In Situ O2 Probe
Extractive O2/ combustibles system
Spectroscopy
IR for CO
Laser IR for CO and O2
(NOx is also possible)
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Typical flue gas Analyzers –
In Situ Oxygen Probe
•
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.
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Typical flue gas Analyzers
Point measurements
Averaging, line-of-sight
measurements
In Situ O2 Probe
Extractive O2/ combustibles system
Spectroscopy
IR for CO
Laser 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 Presentation
53rd Annual ISA POWID Symposium,
7-2009
9 June
July 09,
// Slide 13 2010, Summerlin, Nevada
Typical flue gas Analyzers
Point measurements
Averaging, line-of-sight
measurements
In Situ O2 Probe
Extractive O2/ combustibles system
Spectroscopy
IR for CO
Laser 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”.
Typical Installation
– 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.
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Historical Progression of Point O2 Analysis
In 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
Seeking out stratification- Rather than avoid stratification, plant
operators are more and more trying to determine what flue gas
stratification is telling them.
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


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 DiagnosticsAnalyzer 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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Variable Insertion Probelooking 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- Detecting Air Leaks
Furnace DiagnosticsFlue duct seal leaks are indicated by outer probes reading higher
4.1 %
3.8 %
3.2 %
3.3 %
3.4 %
3.4 %
2.9 %
3.1 %
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Furnace DiagnosticsBeyond Total Furnace Average
Duct averages can shift left or right with ID fan load changes
3.3 %
3.2 %
3.4 %
3.3 %
2.9%3.0 %
Duct A Average
3.3 %
3.4 %
2.9 %
3.1 %
3.1%3.0 %
Duct B Average
Mill average- Burners fed from common pulverizer mills may show
similar readings when mill/classifier problems arise.
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
Furnace DiagnosticsSoot 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 ZrO2Getting New Information From A
Reliable Sensor Technology
Recovering from process upsets- A ZrO2 sensor that measures the level of
O2 deficiency during reducing events.
Zero % O2
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
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada
New Developments In ZrO2Getting New Information From A
Reliable Sensor Technology
New ZrO2 probe sensor that measures CO breakthrough.
O2
Probes
CO Probe
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 Engineer
[email protected]
(951) 285-1629
Chris Lesser- RM Regional Sales Manager
[email protected]
(303) 883-7180
Dave Anderson- Marketing Manager
[email protected]
(949) 322-8178
Doug Simmers- Worldwide Product Manager
[email protected]
(330) 309-2494
53rd Annual ISA POWID Symposium, 7- 9 June 2010, Summerlin, Nevada