using analyzers for blend & boiler control quality control international
Post on 17-Jan-2016
221 Views
Preview:
TRANSCRIPT
Using Analyzers for Blend & Boiler ControlQuality Control International
1.Types of on-line analyzers used in coal analysis
2.Analyzer and Sampling System maintenance3.Calibration and Precision4.Blend Control5.Combustion Optimization
Using on-line analyzer data in a control strategy
On-line Ash or Elemental Analyzers
• Dual Energy (DUET)• Prompt Gamma Neutron
Activation Analysis (PGNAA)• X-Ray Fluorescence (XRF)• Laser Induced Breakdown
Spectroscopy (LIBS)
Dual Energy Ash Analyzer
• Uses Am241 and Cs137 radioisotopes
• Higher energy Cs is unaffected by atomic number of material
• Lower energy Am scattering increase with atomic number (proportional to ash)
• $50-70,000
PGNAA Elemental Analyzer
• Coal exposed to a neutron beam (Cf252) releases prompt gamma rays specific to the elements in the coal
• High precision, ash is measured from its constituents
• Can measure sodium if concentration is high
• $350-500,000
XRF Elemental Analyzer• Uses beam of low energy
X-Rays to fluoresce photons characteristic of elements within coal
• Capable of measuring low energy elements (Na, Mg) as well as trace elements (Hg)
• Limited to particle sizes of <10mm (3/8”)
• $175-225,000
LIBS Elemental Analyzer
• Does not use radioisotopes – no licensing
• Can measure all elements in coal including mercury
• Also very precise• $500-600,000
On-line Moisture Analyzers
• Microwave• Capacitance• Near Infrared
Microwave• Beam penetrates full
bed of material• Does require
minimum of 4” for precise measurements
• Affected by metal reinforcement in belt
• $15-20,000
Capacitance• Measurement of
free moisture• Particle size up
to 50mm or 2”• Ceramic disk
contacts material, but resistant to abrasion
• $10-15,000
Near Infrared (NIR)• Non contact surface
moisture measurement
• Optical lens does require cleaning
• Not affected by particle size
• $15-20,000
QCI Experience at DTE• Two systems currently operating
at Monroe & Belle River Power Plants for over a decade
• Both mounted on as-fired sampling systems
• Both tied into PI system for monitoring feedstock quality every 90 seconds
MONPP Sampling System Features
• Uses a roll crusher to minimize moisture loss on high moisture PRB coals
• Surge bin between crusher and analyzer to ensure constant coal flow
• Programmed to meet ASTM D7430 requirements for both routine shift samples and weekly calibration samples
Standard Operating Procedure
DTE and QCI have developed a weekly and monthly checklist for maintaining the As-Fired Sampler and the XRF Coal Analyzer in order to ensure that availability of the entire system is 95% and the precision of the measurements are within applicable ASTM reproducibility limits.
Maintenance Checklist• Collection of calibration/check
samples• Inspection of sampling system using
ASTM D7430 Guidelines• Monitoring voltage and current of X-
ray tube• Preventive maintenance as per
manufacturer’s recommendations• Periodic testing of blend changes to
check analyzer response (step changes)
Three Steps to Better Analyzer Precision
How do you ensure that the results from your on-line analyzer are at least as good as lab-to-lab (ASTM reproducibility) comparison?
Calibration
Evaluation
Maintenance
Sources of error for each component of analysis
Conventional Analysis
Sampling80%
Prep15%
Testing5%
Sources of error for each component of analysis
On-line Analysis
Instrumentation5%
Interrogation15%
Calibration15%
Sampling65%
Calibration• Proper calibration begins with proper
installation– ALL analyzers sample a stream of coal– This stream must be representative of the
entire material flow• If analyzer is on sampling system, then
– System should be free from significant bias (tested using ASTM D7430) or at least
– Compliant with ASTM operational guidelines• If system is on-the-belt, then
– Reference blocks can be used for initial calibration
– Continued calibration is very difficult and often imprecise
Evaluation• Measurement performance is best
determined by 2 comparative test methods:– 2 instrument test
• Less complex• Can attribute bias errors to analyzer• Requires minimum of 15 duplicate samples
– 3 Instrument test• Uses 2nd independent reference sample• Eliminates bias errors• Requires minimum of 40 sets of samples
Fuel Tracking System Implemented at Detroit
Edison• Uses on-line Coal Analyzer on as-fired sampling system
• Tracks 50+ ton blocks of coal tagged with complete coal quality analysis through plant
Blending results
Tripper locations
On-the-belt coal
specs
Inventory results
Belt scales System
health
Analyzer results
Silo destinations
All trends will fill screen when
double clicked
Average pile specs
Determining Coal Blends in Bunker
Real Time Coal Quality Measurement at DTE
• Used X-Ray Fluorescence On-Line Coal Analyzers for over a decade– Heat Content (Btu/lb as-received)– Moisture Percent– Ash Loading (lb/106 Btu)– Ash Chemistry (ash elemental
analysis, base/acid ratio, slagging index, opacity index)
– Fuel Volatility (volatiles, fixed carbon)
Real Time Coal Quality Control at a Power Plant• Implemented Feed Forward System
that looks at:– Current Fuel– Fuel to be Burned in 1 Hour– Fuel to be Burned in 2 Hours– Fuel to be Burned in 4 Hours– Fuel Being Loaded into Silos
• Integrated with Digital Fuel Tracking System
• All Operators, Shift Supervisors and Combustion Engineers and Managers See Fuel Characteristics
Operator Coal Quality Screen
653.400
2 Hrs1 hrsNOW
FiringCharacteristics
Unit 2 Fuel Quality Screen
Unit 1 Unit 3 Unit 4
Unit 2 Fuel Quality #1
8/2/2004 6:07:32 AM 8/2/2004 2:07:32 PM8.00 Hour(s)
10000
10500
9500
11500
15
30
5
10
Furnace Temperatures
8/2/2004 6:07:32 AM 8/2/2004 2:07:32 PM
U2NFURN-GAS:TC
F
U2SFURN-GAS:TC
F
2200
2300
2050
2400
1950
23502337.4
2305.9
U2NFURN-GAS:TC
F
U2SFURN-GAS:TC
F
Operator Guidance1. If Heating Value A/R is below 10,200 Btu/lb, then unit efficiency will deteriorate and mills will be stressed harder. Watch Furnace Temperature at full load.
2. If Moisture is above 20 percent, then unit efficiency will deteriorate and mills will be stressed harder. Watch Furnace Temperature at full load.
3. If Ash Loading is more than 7 lb/MBtu, then opacity excursions are expected at full load.
4. If Base/Acid Ratio is less than 0.2, then opacity excursions are expected at full load.
5. If Base/Acid Ratio is between 0.2 and 0.25, then there is a potential for opacity problems at full load.
6. If Base/Acid Ratio is more than 0.5, then slagging can be expected at full load.
7. If Base/Acid Ratio is between 0.4 and 0.5, then slagging can be caused by the fuel at full load.
8. If Fuel Volatility Ratio is below 0.25, then combustion will occur in upper furnace, watch Furnace temperature.
9. High Furnace Temperature values should provide a caution to increase excess O2 or reduce load..
4 Hrs On C4
Unit SiloC5
C5A
Belt28
284
4
TPH
697.600
Heating Value A/R (Btu/lb)
Moisture (%)
North Furnace Temperature
South Furnace Temperature
Base/Acid Ratio
Fuel Volatility Ratio (VM/FC)
Slagging Alkalinity
Silica + Alumina
SO2 Rate
Ash Loading (lb/MBtu)
18.65
6.97
0.33
1.10
65.89
12.16
0.69
10314
18.43
6.92
0.32
1.12
65.80
11.79
0.690.58
9.55
55.01
1.16
0.26
6.96
18.01
1039610293 10300
18.34
7.12
0.32
1.10
65.72
11.78
0.68
10444
17.62
7.18
1.15
67.79
11.52
0.68
0.30
Blend 0-59-41 0-59-41 0-60-400-60-40
Unit 2 Fuel Quality #2
8/2/2004 6:07:32 AM 8/2/2004 2:07:32 PM8.00 Hour(s)
0.2
0.4
0
0.6
50
100
10
20
2337
2306
Key Aspects of Coal Quality Control System
• Color Coded for Quality– Good = green– Caution = yellow– Trouble = red
• Trends for Major Parameters– Can Review Conditions over Time– Can Correlate Fuel Conditions with
Combustion• Operators can React to Fuel Quality • Plant can Blend Coal Based Upon
Performance Parameters (e.g., heat content, moisture, ash loading, base/acid ratio)
Next Steps Combustion Optimization
• Standard Operating Procedure for establishing maximum capacity as f(fuel conditions).– Moisture– Ash– Calcium Oxide– Sodium Oxide
Fuel Parameters vs Capacity
Conclusion - Analysis• On-line analyzers are NOT install
them and forget them devices• Success of an analyzer installation is
directly dependent on quality of the calibration
• On-line analyzers should be capable of providing measurement precision within ASTM reproducibility limits and can even be better than lab-to-lab comparisons
• The key is to obtain frequent and reliable samples. An ASTM compliant sampling system is the best way to do this.
Conclusion – Blending & Control
• Analysis, Blending and Control advances make it possible for utilities to “Blend at the Burner”
• Coal prep plants can use the same technology for on-line:– Sorting on the raw coal side– Blending on the clean coal side– Washability analysis for gravity
control
top related