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