Using Analyzers for Blend & Boiler Control Quality Control International

1.Types of on-line analyzers used in coal analysis 2.Analyzer and Sampling System maintenance 3.Calibration and Precision 4.Blend Control 5.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 Am 241 and Cs 137 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 (Cf 252 ) 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 $ ,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”) $ ,000

LIBS Elemental Analyzer Does not use radioisotopes – no licensing Can measure all elements in coal including mercury Also very precise $ ,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

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 2 nd 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/10 6 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

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