Plant Operators get extensive training, both on the job and in the classroom. One area that is usually not well covered is Coal Quality & Combustion. Our Coal Combustion for Plant Operators Class covers all the major coal testing and what operations can do to manage poor quality coal.
Class Outline for Coal Combustion by Rod Hatt
Coal Combustion School for Operators Coal Quality Introduction ·
Coal · Moisture, Ash, Volatiles, Sulfur, Btu/lb · Sizing, Slagging
Now we follow coal though the plant and examine how coal quality interacts with equipment performance, maintenance, and cost.
Wet Coal · Causes · Measurements · Solutions
Dusty and Spontaneous Combustion ·
Minimizing and controlling dust · Clean up procedures · Spon Comb potential ·
Fire fighting and precautions
Combustion Process ·
Coal Rank · Air to fuel ratios · Balancing furnaces · Balancing burners ·
NOx formation · CO analysis
Pulverizers · Basic operation · Adjustments ·
Coal Quality Impacts o Low Btu o High Ash o Reject materialÂ
High Moisture  Concern for fires o Impact of high air flow
Impacts on flame, NOx and SLAG Boiler
Efficiency and Heat Rate Variables ·
Boiler Efficiency vs. Excess Oxygen ·
Moisture and Hydrogen Impacts ·
Higher vs. Lower Heating Value ·
Exit Gas Temperatures ·
Steam Temperature Impacts on Heat Rate ·
Carbon and CO Losses
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
Coal Testing · The ASTM Fusion Temperature Test. ·
Ash Levels ·
Slagging and Fouling Indices. ß Elemental loading · Pounds of iron per million Btu · Pounds calcium, sodium, and other elements ·
Slagging with Bituminous Type Ash - High Iron ·
Ash Chemistry · Base to acid ratio, Slagging Index = Dry sulfur x B/A · Iron squared term
TABLE I - 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
Low CV coal
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 equipment
Design Related
Furnace size too small for fuel
Tube material and/or spacing inadequate
Soot blowing coverage inadequate
No means provided to observe slag buildup
Soot Blowing ·
Minimizing slags with combustion. ·
Controlling slag with soot blowers ·
Preventative blowers - IR · Reactive blowers IK · other soot blowing, air heater, SCR
How Slags and other Ash Deposits Cause Tube Leaks ·
Furnace Corrosion · High Temperature Corrosion · Erosion ·
Erosion and particle size and velocity
Pollution Control ·
Ammonia Slip and NOX SCR ·
Air Heater Pluggage and Leakage ·
Pollution control equipment basics ·
Particulate ·
SO2 ·
Mercury ·
SO3
Summary and Exam