Coal Quality & Combustion

• Power and Cement plants operation, production and maintenance engineers
• Fuel Procurement Managers
• Plant Chemists
• Plant Performance Engineers
• Power Plant Project Engineers
• Coal Mining Engineers and Coal Marketers

Course Outline

Boiler Basics
Major components of PC - fired boiler

Coal Formation

• What is Coal
• Coal Rank
• Where are the different coals located?

Coal Mining

• Surface
• Deep
• Out of seam dilution
• Coal Washing
• Drying coal
• Transportation Impacts
  • Time and Climate
  • Barge Coal tends to gain moisture

Sampling coal and coal analyses

• The Good, The Bad and the Ugly
• Good sampling is hard work

• Guidelines
  • Hand Samples
    • Feeder and Belt
    • Car top
  • Mechanical Sampling
    • Sampling systems
    • Augers
    • Core holes

Terms

• Proximate - Moisture, ash, volatile, fixed carbon (by difference)
• Short Prox - Moisture, ash, sulfur, Btu/ lb
• Ultimate - Moisture, ash, sulfur, + carbon, hydrogen, nitrogen, oxygen (by difference)

Coal Cost

• Sold by the ton - $/ton
• Boilers want Calorific Value not tons
• Evaluated by the Kcal or millions of Kcal (MMcal)

Coal Handling

• Moisture plays a dominant role
• Fines
• What sizes are important?
• Clays and mineral matter
• Chemical additives

Spontaneous Combustion
Combustion

• The three T's in practice
• Size the coal and add air!
• Coal Reactivity

The Story of NOX

• To minimize the formation of NOX
• Post Combustion Control

Combustion Tune-up Procedures

• Air Heater Leakage
• Other Leakage
• Balancing
  • O2 levels
  • Temperature
  • Flows

Pulverizer Performance

• Coal Sizing
• Air and Fuel Flow
• Clean and DIrty Coal Pipe Measurements
• Pyrite Rejects
• Primary Air Flow
• Adjustments include: Roller and journal pressure, alignment, air flow, Classifiers, temperature, ball charge, ball size

LOI Testing and Combustion Verification

• LOI Test
• Carbon in Ash
• Sampling Location
• Sampling Methods
• Operator Feedback
• CO Analyses
• NOx Analyses

Result Engineering

• Output/ Input
• Heat Loss Method
• Problem areas

Improving Boiler Efficiency

• Improving Combustion
• Optimizing Combustion
• Optimizing NO

Unit Heat Rate

• Input/ Output
• Performance Diagrams

Ash Deposits - Introduction
Types of Ash Deposits

• Wall Slag
• Superheater Slag
• Convection Pass Fouling
• Low Temperature Deposits

Causes of Ash Deposits

• Fuel Related
• Equipment Related
• Design Related

Analytical Procedures

The ASTM Fusion Temperature Test

• Ash levels used as slagging and fouling indices
  • Elemental loading
    • Pounds of iron per millio Btu
    • Pounds calcium, sodium, and other elements

Slagging with Bituminous Type Ash - High Iron

• Ash fusion temperatures
• Advanced ash fusion techniques
• Ash Chemistry
  • Basic Slagging factors
    • B/A - Base to acid ratio, sum of total bases divided by sum of all acid elements
    • Slagging Factor - Ash and Elemental Loading
  • Slagging index
    • Dry sulfur x B/A
    • Iron or sulfur squared term
  • Silica% Raask Quartz, Clay type
• Computer Controlled Scanning Electron Microscopy provide some of the best mineralogical information but has not come into common use

Cyclone and Wet bottom Furnaces

• Ash Viscosity
  • Calculating T- 250
  • Measuring T- 250
  • Temperature verses Ash Viscosity Curves

Fouling Deposits

• Chemical Fractionation
  • Active alkali
    • Water soluble
    • Ammonium Acetate soluble
    • Weak acid soluble
    • Micro crystals
• Major and Minor Ash Elements
  • Acid Oxides or Glass Formers
  • Basic Oxides or Fluxing agents or Gluing Elements

Major Causes of Ash Deposits
Fuel Related

• Large pyrite particles that impact the furnace wall before they  completely combust
• Clay minerals that contain significant amounts of iron, calcium, sodium or potassium causing them to have low melting temperatures
• Interaction of pyrite, clays and alkalis with alumino silicates to form low viscosity melts
• Extremely fine or organically bound alkalis

Equipment Related

• Soot blowers not in operation or used improperly
• Poor pulverization of fuel
• Improper air to fuel ratio
• Burners damaged or improperly adjusted
• Changes in operation of boiler or other euqipment

Design Related

• Furnace size too small for fuel
• Tube material and/ or spacing inadequate
• Soot blowing coverage inadequate
• No means provided to observe slag build up

Advanced Methods for Slag

• Computer Controlled Scanning Electron Microscopy (CCSEM)
  • Uses Energy Dispersive X-ray Analyses (EDAX) to size and quantify elemental composition
• Low Temperature Ashing
  • Microscopically identify minerals present
• Chemical Fractionation
  • Provides information on Organically Bound Elements
• Elemental Analyses of float sink and/ or size fractions
  • Can be performed by ASTM coal laboratories
  • Pounds of iron per million Btu
  • Pounds calcium, sodium, and other elements

Ash Deposit Analyses

• Sampling Procedure for Ash Deposits
• Polarized Light and Scanning Electron Microscopy
• Forms of Iron by chemical fractionation
• Mossbauer spectroscopy

Fouling Deposit Formation

Electrostatic Precipitators

• Basic Operation Principles
• High Voltage DC - Transformer Rectifier Sets
• Voltage Control - Controlling the wave form and sparking rate
• Sizing ESP - Plate area (fixed) and Flue gas volume (operational variable?)
• Migration Velocity or why the particle goes to the plate
• Ash Resistivity concerns
• Gas Velocity - impacts ESP size and treatment time
• Rapping - important equipment that can be high maintenance
• Hopper Evacuation - useful for determining ash partitioning
• Dust Collection and Storage

Advanced ESP Methods and Tune-up

• Combustion Influences
• Calculating and Measuring Fly Ash Resistivity
• Correlating and making sense of resistivity data
• Rappers
• High Voltage controls
• Measuring gas flows and particular loadings
• ESP Inspections
• Tune-up Procedures
• Ash Handling
• Scrubber
• Out of stack pollutants
• Trace Elements

Summary

• Coal Specifications
• Computerized Evaluations
• Test Burns
• Conclusion

Trainer Profile
Rod Hatt

Rod Hatt from U.S. has experience in most aspects of how coal quality impacts the operation and performance of industrial and utility coal-fired steam plants. He works regularly with fuel purchasing, plant operation and engineering departments at utilities and with coal sales and mining companies. His services include training classes, expert services and computer software sales and development.

He has over 28 years of experience, 15 as an independent coal quality specialist, 7 years in technical coal sales and marketing and 6 years as a utility combustion and results engineer.

Rod's marketing and engineering experience, along with a unique blend of creative analytical and communication skills, have allowed him to understand, communicate and solve countless complex coal quality problems. He organizes and participantes in a number of classes and workshops and conferences. The "Coal Quality & Combustion Workshop" has been attended by hundreds of attendees representing dozens of companies.

Rod specializes in ash deposits and provides advanced analytical services including electron microscopy of deposits. He presently works as a CTO at Coal Combustion Inc.

Experiences & Achievements

1980 - 1986

• Combustion Engineer with Northen Indiana Public Service Co.
• Evaluated potential fuels to predict operational effects and costs. Conducted test burns and evaluated results to confirm predictions. Solved opacity problems at six units and determined cause of deposit formation on ten occasions. Develop and taught combustion training programs to all levels.
• Improved coal handling by developing wet coal monitoring procedures. Improved coal and ash sampling procedures.
• Responsible for evaluation of coal and coal ash chemistry, coal sampling procedures and coal blending. Implemented microscopic techniques for determining asbestos at plant, saving over $250, 000 annually by eliminating disposal of non-asbestos material as hazardous.
• Responsible for boiler and precipitator performance testing, fly ash sampling and resistivity measurements.

1986 - 1994

• Director pf Technical Services for Island Creek Coal Corporation
• Developed and implemented marketing plan for sales of low volatile coal to utilities, $450,000,000 of new sales resulted from these efforts.
• Created over 8,000,000 tons per year of new sales opportunities by persuading customers to modify their specifications. This increased price realization by creating a larger customer base.
• Provided leadership and direction to steam sales which resulted in over 25 test programs, which led to two major long term contracts and several short term sales
• Developed and implemented the use of coal quality impact models, that created improved markets for high quality coals

1999

• Rod Hatt took on the additional responsibility of Director of Marketing for CT&E. This position designs, develops and produces company literature, website and manages exhibits at conferences nationwide

1994 - 2002

• Rod Hatt operated the Fuel Utilization Services section of Commercial Testing & Engineering Co. located in Lexington, KY. Fuel Utilization specializes in providing customers with the understanding of the impacts of coal quality on power plant performance and cost. He teaches a one-day Coal Quality and Combustion class that have been attended by hundreds of industry personnel over the last nine years