In thermal power plants, the boiler burner plays a critical role by controlling the combustion of fuel oil. Burners supply the initial flame during start-up, stabilize combustion at low loads, and provide flame support during coal firing. The most common fuels are Light Diesel Oil (LDO) for start-up and Heavy Fuel Oil (HFO) for extended support. Reliable burner performance ensures smooth boiler operation, safety and efficiency.

When Power Plants Use Boiler Burners

• Start-up operations – LDO/HFO burners raise boiler pressure before coal mills come online.
• Low load operations – maintain flame stability during reduced coal firing.
• Flame stabilization – support coal combustion during load swings.
• Emergency operation – ensure steam supply if coal firing is interrupted.

Major Components of a Boiler Burner

• Fuel Train (LDO/HFO): Pumps, strainers, heaters (for HFO), valves, and regulators.
• Combustion Air System: Forced draft fan, dampers, and registers.
• Fuel Nozzle/Atomizer: Breaks liquid fuel into fine droplets for efficient burning.
• Ignition System: Spark electrode or high-energy igniter gun.
• Combustion Head: Zone where air and atomized fuel mix.
• Burner Management System (BMS): Controls sequencing, purge, ignition, flame supervision, and trips.
• Flame Scanner: UV/IR sensor to continuously monitor flame.

Types of Burners Used in Boilers

1. Gas Burners(rare in coal-based plants)
   • Premix burners: Fuel gas and primary air mixed before burner tip, secondary air added at flame.
   • Postmix burners: Fuel and air supplied separately, mixed at burner mouth.
2. Oil Burners (Power Plant Use – LDO/HFO)
   • Vaporizing burners: Fuel vaporized by heating surface, then ignited.
   • Atomizing burners: Fuel (LDO/HFO) atomized by steam or air, most common in utility boilers.

Fuel Preparation for Burners

• LDO: Can be fired directly without preheating.
• HFO: Must be preheated to ~120–130 °C for proper viscosity.
• Strainers: Prevent nozzle clogging.
• Atomizing Medium: Steam or air is used to break HFO into fine droplets.

Working Principle of Boiler Burners

1. Pre-purge – Furnace purged with FD fan to remove gases.
2. Ignition – Pilot or spark ignites atomized LDO/HFO.
3. Main Flame – Main fuel valves open once ignition is proven.
4. Flame Stabilization – Burner supports coal flame during start-up/low load.
5. Monitoring – Flame scanner supervises continuously.
6. Post-purge – Furnace cleared of unburned gases after shutdown.

Burner Arrangement in Power Plants

• Large utility boilers may have 16–32 burners, placed in front wall, opposed wall, or tangential corner configuration.
• Swirl vanes or tilting mechanisms are used in some designs to control flame shape and heat distribution.

Operational Guidelines

• Maintain correct fuel (LDO/HFO)–air ratio.
• Check all interlocks: furnace purge complete, fuel oil pressure, atomizing steam/air pressure, scanner status.
• Warm up HFO heaters and lines before firing.
• Use burners until coal combustion is stable, then shut down as per BMS sequence.

Maintenance Practices

• Clean atomizers and strainers regularly.
• Inspect HFO heaters and maintain viscosity range.
• Check igniter and spark rods for proper functioning.
• Verify flame scanner alignment and cleanliness.
• Test safety interlocks and BMS trips periodically.

Common Problems and Corrective Action in Boiler Burners

1. Flame instability

• Cause: Poor atomization, low fuel (LDO/HFO) pressure, faulty igniter.
• Remedy: Clean nozzle, check igniter, adjust atomizing steam/air.

2. Black smoke emission

• Cause: Low excess air, clogged fuel nozzle.
• Remedy: Increase air supply, clean atomizer/nozzle.

3. Ignition failure

• Cause: Faulty spark electrode, defective pilot system.
• Remedy: Replace spark rod, check ignition transformer/pilot flame.

4. Frequent burner trips

• Cause: Dirty flame scanner, misalignment, weak flame signal.
• Remedy: Clean and realign scanner, check flame intensity.

5. High unburned fuel in furnace

• Cause: Incorrect fuel–air ratio, faulty BMS logic, nozzle damage.
• Remedy: Tune burner, check BMS sequencing, replace damaged nozzle.

Burner Operation Checklist

1. Start-Up

• Ensure furnace purge is completed.
• Verify fuel oil (LDO/HFO) pressure is within limits.
• Confirm atomizing steam/air is available.
• Check igniter and spark system health.
• Ensure flame scanner is clean and aligned.

2. Running Condition

• Observe stable flame with no pulsation.
• Maintain oxygen within design limits (avoid black smoke).
• Confirm correct atomizer spray pattern.
• Ensure all interlocks are active.

3. Shutdown

• Fuel valves must close as per BMS sequence.
• Conduct proper post-purge of the furnace.
• Verify furnace is clear of unburned gases.

4. Weekly Preventive Checks

• Clean nozzle and strainer.
• Inspect igniter and spark electrode.
• Wipe flame scanner lens.

5. Annual Maintenance

• Overhaul atomizers and replace worn parts.
• Calibrate BMS logic and flame scanners.
• Test all safety interlocks and trip functions.

6. Safety Precautions

• Never bypass burner management logic.
• Always purge furnace before ignition.
• Use correct atomizing medium for HFO firing.
• Keep fire extinguishers ready at burner front.
• Train operators for flame failure and emergency shutdown.

Frequently Ask Questions (FAQs) on Boiler Burners