Boiler burner
A burner is a device that mixes fuel (oil or gas) with air in a specific ratio and safely, stably, and efficiently ignites it via an ignition device to form a specific flame pattern. It is one of the core components of an oil or gas boiler.
Burner Overview
A burner is a device that mixes fuel (oil or gas) with air in a specific ratio and safely, stably, and efficiently ignites it via an ignition device to form a specific flame pattern. It is one of the core components of an oil or gas boiler.
Core Working Principle
All burners operate based on a fundamental process: Fuel Supply + Air Supply → Mixing → Ignition → Combustion → Flame Monitoring.
Preparation Stage: After the boiler control system sends a start signal, the burner motor starts, driving the fan impeller and fuel pump (for oil burners) into operation.
Purge Stage: The fan forces air into the combustion chamber to clear any potentially remaining flammable gases, ensuring a safe start. This process lasts several tens of seconds.
Ignition Stage: After purging, the ignition transformer activates, creating a high-voltage arc discharge between the ignition electrodes. Simultaneously, the fuel valve (gas) or solenoid valve (oil) opens slightly, releasing a small amount of fuel.
Ignition & Confirmation: The released fuel is ignited by the high-voltage arc, forming a small pilot flame. The flame detector (ionization electrode or photocell) detects the flame signal and relays it to the controller.
Main Combustion Stage: After flame confirmation, the main fuel valve opens (or oil pressure increases), and the fan adjusts the damper opening according to demand. Fuel and air mix thoroughly before entering the main combustion state.
Operation Regulation: Based on feedback from the boiler's temperature or pressure sensors, the control system automatically adjusts the fuel and air supply to maintain efficient and stable combustion.
Shutdown Stage: When demand is met, the controller closes the fuel valve, and combustion stops. The fan continues running for a post-purge period to cool the burner and remove residues before the entire unit shuts down.
Main Components
A complete burner typically consists of the following systems:
1. Fuel System
Oil Burner: Fuel tank, fuel pump, filter, preheater (essential for heavy oil), nozzle.
Gas Burner: Gas filter, regulator (pressure reducing valve), gas butterfly valve/modulating valve, gas train (safety shut-off valves).
2. Air System
Fan/Motor: Provides combustion air and overcomes the resistance on the boiler's flue gas side.
Damper Regulation Mechanism: Driven by a servo motor, it precisely controls the air intake to achieve the air-fuel ratio.
Air Pressure Switch: Monitors air pressure, ensures the fan operates correctly, and prevents ignition without air.
3. Ignition System
Ignition Transformer: Converts low voltage into thousands of volts of high voltage.
Ignition Electrodes: Generate the high-voltage arc to ignite the fuel.
4. Control System
Programmer/Combustion Controller: The "brain" of the burner, controlling the entire start, run, stop sequence, and performing safety monitoring.
Flame Detector: Monitors the flame status in real-time; immediately cuts off the fuel supply if the flame is lost unexpectedly. Common types include:
Ionization Electrode: Uses the principle of flame conductivity, often used for gas.
Ultraviolet (UV) Scanner: Detects ultraviolet light in the flame, effective for gas and light oil.
Infrared (IR) Sensor: Detects infrared light in the flame, offers strong anti-interference capability.
5. Other Mechanical Structures
Casing: Protects internal components.
Flame Tube/Stabilizer: Creates vortices in the airflow to stabilize the flame shape.
Oil Gun/Gas Gun: Injects fuel into the combustion chamber.
Main Types of Burners
Classified by Fuel
Oil Burners:
Light Oil Burners: Use low-viscosity fuels like diesel, kerosene.
Heavy Oil Burners: Use heavy oil, residual oil, etc., requiring a preheating system to reduce viscosity.
Gas Burners:
Natural Gas Burners
Liquefied Petroleum Gas (LPG) Burners
Town Gas Burners
Dual-Fuel Burners: Can use or switch between oil and gas fuels, suitable for situations with unstable fuel supply.
Classified by Combustion Method
Fully Premixed Combustion: Fuel and air are thoroughly mixed before entering the burner head. Advantages include high efficiency, low emissions (low NOx), short blue flame. Requires high technology and cost.
Diffusion Combustion: Fuel and air mix and burn simultaneously after being ejected. Technologically mature, simple structure, longer flame. But relatively lower efficiency and higher NOx emissions.
Classified by Control Mode
Single-Stage: Only has "On" and "Off" states. Simple structure, suitable for small boilers. Frequent cycling impacts the power grid and boiler.
Two-Stage (Hi-Lo): Has "High fire" and "Low fire" power levels. Reduces cycling frequency, offers smoother operation.
Proportional Modulation: The amount of fuel and air can be continuously and linearly adjusted between maximum and minimum based on load demand. This is the most advanced method, offering the highest thermal efficiency, minimal boiler wear, and optimal comfort.
Key Performance and Technical Parameters
Output Power/Heat Output: Usually in kW or MW, determines the boiler's capacity.
Fuel Consumption Rate: Units kg/h (oil) or m³/h (gas).
Electrical Data: Voltage, frequency, power.
Back Pressure Requirement: The resistance the burner can overcome on the boiler's flue gas side.
Turndown Ratio: The ratio of maximum load to minimum stable load. A larger ratio is better for modulating burners.
Emission Indicators: Mainly refer to NOx (Nitrogen Oxides) and CO (Carbon Monoxide) content, subject to increasingly strict environmental regulations.
Thermal Efficiency: Not the independent efficiency of the burner, but the system efficiency after matching with the boiler. An efficient burner is the foundation for high thermal efficiency.
Application and Selection Guide
Incorrect selection is a primary cause of burner failure. Selection must match the boiler:
Boiler Power: Burner output must match the boiler's rated output; slightly larger is preferable to smaller.
Boiler Back Pressure: The burner must be able to overcome the flue gas resistance of the boiler body.
Furnace Size and Shape: Determines the required flame shape (length, diameter). The flame must not impinge directly on the furnace walls.
Fuel Type and Characteristics: Clearly define the type of oil or gas used; parameters like pressure, calorific value, and viscosity are fundamental for selection.
Control Mode: Choose single-stage, two-stage, or proportional modulation based on load variation.
Environmental Requirements: Select low-NOx burners according to local regulations.
Daily Maintenance and Care
Regular maintenance is key to ensuring safe, efficient, and long-lasting operation.
Daily: Check fuel pressure, leaks, observe flame color (should be bright yellow or blue).
Monthly: Clean the air filter, check the fan impeller for dust buildup.
Quarterly/Biannually:
Oil Burner: Clean fuel pump filter, replace nozzle, clean ignition electrodes, check fuel lines.
Gas Burner: Clean gas filter, check the sealing of the gas valve train, clean ignition electrodes and flame detector.
Annually: A comprehensive service by professionals, including calibrating safety devices, checking motor bearings, thoroughly cleaning the burner head, etc.
Common Faults and Troubleshooting
Ignition Failure: No fuel, incorrect ignition electrode position/carbon buildup, faulty flame detector, insufficient gas pressure.
Combustion Interruption: Unstable fuel supply, clogged filter, dirty photocell, external airflow disturbance.
Poor Combustion (Smoking): Insufficient air, worn or clogged nozzle, imbalanced air-fuel ratio.
Noise/Vibration: Unbalanced fan impeller due to dust, damaged motor bearings, combustion resonance.
Development Trends
Low Nitrogen Oxide (Low-NOx) Combustion Technology: Uses FGR (Flue Gas Recirculation), fully premixed surface combustion, etc., to significantly reduce NOx emissions—currently the absolute mainstream.
Intelligent Control & IoT (Internet of Things): Enables predictive maintenance, energy efficiency optimization, and fault warning through remote monitoring and big data analysis.
Wide Modulation Range: Pursuing a larger turndown ratio to adapt to lower load demands and further improve energy efficiency.
Multi-Fuel Compatibility & Flexibility: Adapting to co-firing or dedicated burning of low/zero-carbon fuels like biogas or hydrogen is a future direction.
