Dual Fuel Burner For Boiler

A dual fuel burner for boiler is an industrial combustion system designed to operate with two different fuels, typically Natural Gas and Diesel Oil (Light Oil/HSD). The burner can automatically or manually switch between fuels, ensuring continuous boiler operation whenever one fuel becomes unavailable or too expensive.

This flexibility makes dual fuel burners one of the most reliable combustion solutions for industries requiring uninterrupted steam production, including food processing, chemical plants, pharmaceuticals, textiles, palm oil mills, paper manufacturing, and power generation. Modern dual fuel burners are widely adopted because they improve operational reliability while helping facilities optimize energy costs.

What Is a Dual Fuel Burner?

A dual fuel burner is an industrial combustion system designed to burn two different types of fuel—typically natural gas and diesel oil—using a single burner assembly. Unlike a single-fuel burner, which is limited to either gas or oil, a dual fuel burner integrates both combustion systems, providing greater operational flexibility and reliability for industrial boiler applications.

The most common fuel combinations include:

• Natural Gas + Diesel
• CNG (Compressed Natural Gas) + Diesel
• LNG (Liquefied Natural Gas) + Diesel
• LPG (Liquefied Petroleum Gas) + Diesel
• Biogas + Diesel

Although two fuel systems are installed, only one fuel is combusted at any given time. The burner management system (BMS) automatically or manually selects the active fuel based on fuel availability, operating costs, process requirements, and safety interlocks. If the primary fuel supply is interrupted, the burner can safely switch to the secondary fuel, minimizing production downtime and ensuring continuous steam generation.

This capability makes dual fuel burners an ideal choice for industries where uninterrupted boiler operation is essential, such as food and beverage processing, pharmaceuticals, chemical manufacturing, textile production, palm oil processing, paper mills, and power generation.

Modern dual fuel burners are also equipped with advanced combustion controls, including automatic ignition, flame monitoring, air-to-fuel ratio control, modulating operation, and multiple safety protection systems. These features help maximize combustion efficiency, reduce fuel consumption, lower emissions, and ensure compliance with industrial safety standards.

By combining the advantages of both gas and oil firing in a single system, a dual fuel burner provides industries with a dependable, efficient, and cost-effective solution for maintaining reliable boiler performance under varying operating conditions.

How Does a Dual Fuel Burner Work?

The operating sequence generally includes:

1. Boiler receives a heating demand.
2. Burner performs a pre-purge cycle.
3. Ignition transformer energizes.
4. Selected fuel valve opens.
5. Flame detector confirms stable combustion.
6. Burner modulates according to steam demand.
7. If the primary fuel fails, the system switches to the backup fuel after completing the required safety sequence.

Modern systems use PLC or burner management controls to supervise flame safety, fuel pressure, combustion air, and ignition timing.

Main Components of a Dual Fuel Boiler Burner

A dual fuel boiler burner consists of several integrated components that work together to ensure safe, efficient, and reliable combustion using either gas or liquid fuel. Each component plays a critical role in fuel delivery, air regulation, ignition, flame monitoring, and burner control. Proper coordination between these parts ensures stable boiler performance, optimal fuel efficiency, and compliance with industrial safety standards.

1. Combustion Head

The combustion head is the heart of the burner where fuel and combustion air are mixed before ignition. Its design creates the proper flame shape and air-fuel ratio, ensuring efficient combustion while minimizing emissions and preventing flame instability.

2. Burner Fan (Blower)

The burner fan supplies the combustion air required for complete fuel burning. It provides the correct airflow and pressure needed to maintain a stable flame throughout the burner’s operating range. Modern burners often use variable-speed or servo-controlled fans to improve combustion efficiency.

3. Ignition Electrodes

Ignition electrodes generate a high-voltage spark that ignites the fuel-air mixture during the burner start-up sequence. They are designed to withstand high temperatures and repeated ignition cycles while ensuring reliable burner startup.

4. Flame Scanner (Flame Detector)

The flame scanner, also known as a flame detector, continuously monitors the burner flame using ultraviolet (UV), infrared (IR), or ionization sensing technology. If the flame is lost during operation, the burner management system immediately shuts off the fuel supply to prevent hazardous conditions.

5. Gas Train

The gas train is the complete gas supply assembly that regulates, filters, and controls the flow of gaseous fuel to the burner. A typical gas train includes manual shut-off valves, gas filters, pressure regulators, pressure switches, safety shut-off valves, and flow control valves to ensure safe and accurate fuel delivery.

6. Oil Pump

When operating on liquid fuel, the oil pump delivers diesel or fuel oil from the storage tank to the burner at the required pressure. It maintains a stable fuel supply to ensure consistent combustion and reliable burner performance.

7. Oil Nozzle

The oil nozzle atomizes liquid fuel into a fine mist before it enters the combustion chamber. Proper atomization promotes efficient mixing with combustion air, resulting in cleaner combustion, improved efficiency, and reduced smoke formation.

8. Solenoid Valves

Solenoid valves automatically open and close the fuel supply during burner operation. Separate solenoid valves are typically used for gas and oil circuits. These electrically operated valves form an essential part of the burner’s safety system by instantly shutting off fuel flow whenever an abnormal condition is detected.

9. Gas Pressure Regulator

The gas pressure regulator maintains a constant gas supply pressure regardless of fluctuations in the incoming gas line. Stable pressure ensures accurate fuel delivery, consistent flame quality, and efficient combustion.

10. Air Pressure Switch

The air pressure switch monitors the airflow generated by the burner fan. Before ignition, it verifies that sufficient combustion air is available. If airflow falls below the required level, the burner controller prevents startup or initiates a safety shutdown.

11. Fuel Pressure Switch

The fuel pressure switch continuously monitors the pressure of either gas or oil. If the fuel pressure becomes too low or too high, the burner management system activates a safety lockout to protect both the burner and the boiler.

12. Servo Motor

The servo motor precisely controls the air damper and fuel control valves during burner operation. In fully modulating burners, it continuously adjusts the air-to-fuel ratio according to boiler load, maximizing combustion efficiency while reducing fuel consumption and emissions.

13. Burner Controller (Burner Management System)

The burner controller, often referred to as the Burner Management System (BMS), is the electronic control unit responsible for coordinating the complete burner operating sequence. It manages pre-purge, ignition, flame monitoring, fuel switching, modulation, safety interlocks, and shutdown procedures in accordance with international combustion safety standards.

14. Control Panel

The control panel provides operators with a centralized interface for monitoring and controlling the burner. It typically includes power switches, indicator lamps, alarms, digital controllers, PLCs, touchscreen HMIs, and communication interfaces for integration with the boiler control system and plant automation.

Why These Components Matter

Each component of a dual fuel burner performs a specific function, but together they create a highly reliable combustion system capable of operating safely with either gas or liquid fuel. Proper maintenance, calibration, and inspection of these components help maximize combustion efficiency, reduce fuel consumption, extend equipment life, and ensure continuous steam production for industrial boiler applications.

Each component works together to maintain a stable flame, proper air-to-fuel ratio, and safe combustion.

Common Boiler Applications

Dual fuel burners are widely installed on:

• Steam Boilers
• Hot Water Boilers
• Thermal Oil Heaters
• Heat Recovery Boilers
• Package Boilers
• Fire Tube Boilers
• Water Tube Boilers
• Electric Steam Backup Systems

Other Industrial Applications

Besides boilers, dual fuel burners are used in:

• Industrial Furnaces
• Rotary Dryers
• Asphalt Mixing Plants
• Incinerators
• Powder Coating Ovens
• Ceramic Kilns
• Food Processing Ovens
• Palm Oil Processing
• Chemical Reactors

Burner Capacity Selection

Selecting the correct burner requires matching the burner heat input with the boiler’s required thermal load.

Actual sizing should consider boiler efficiency, steam pressure, excess air, and safety margin.

Control Modes

Modern dual fuel burners are available with different firing controls:

On-Off

Suitable for small boilers.

Two-Stage

Operates in Low Fire and High Fire modes.

Progressive

Smoothly adjusts burner output.

Fully Modulating

Continuously matches boiler load for maximum efficiency and reduced fuel consumption.

Fuel Consumption

Approximate fuel consumption depends on burner capacity and efficiency.

Actual consumption varies with boiler efficiency, excess air, fuel quality, and operating load.

Safety Features

Industrial dual fuel burners include multiple protection systems such as:

• Flame Failure Protection
• Automatic Fuel Shutoff
• Air Pressure Monitoring
• Gas Pressure Monitoring
• Oil Pressure Monitoring
• Purge Cycle
• Ignition Safety Timer
• Emergency Shutdown
• Overheat Protection

These systems are essential for safe and reliable boiler operation.

Industries That Use Dual Fuel Burners

Typical industries include:

• Food & Beverage
• Pharmaceutical
• Chemical
• Textile
• Palm Oil
• Paper Mills
• Rubber Processing
• Automotive
• Packaging
• Power Plants
• Petrochemical
• Steel Manufacturing

How to Choose the Right Dual Fuel Burner

Before purchasing, evaluate:

• Boiler capacity
• Steam pressure
• Operating temperature
• Available fuel supply
• Daily operating hours
• Required modulation
• Local emission regulations
• Maintenance availability
• Spare parts support

Proper engineering selection improves combustion efficiency, extends equipment life, and reduces operating costs.

Frequently Asked Questions

What is a dual fuel burner?

A dual fuel burner is a combustion system capable of operating on two different fuels, typically natural gas and diesel oil.

Can both fuels burn simultaneously?

No. Standard dual fuel burners operate on one fuel at a time, switching between fuels as required.

Which fuel is more economical?

Natural gas generally offers lower operating costs and cleaner combustion, while diesel provides a dependable backup during gas supply interruptions.

Is a dual fuel burner suitable for all boilers?

Most fire tube, water tube, and thermal oil boiler systems can be equipped with a properly sized dual fuel burner.

What is the expected efficiency?

Modern industrial dual fuel burners typically achieve high combustion efficiency when correctly commissioned, tuned, and maintained. Efficiency depends on burner design, combustion control, and overall boiler condition.

RLS 500÷1200/M Series

Low NOx Progressive Two-Stage or Modulating Operation Burners

RLS/M burners are characterized by a modular monoblock structure which means all necessary components can be combined in a single unit thus making installation easier, faster, and, above all, more flexible. The series covers a firing range from 2500 to 11500 kW, and it has been designed for use in hot water boilers,overheated water boilers as well as steam boilers. The operation can be “two-stage progressive” or alternatively “modulating”, for both fuels, light oil and gas, with the installation of a PID logic regulator.

The mechanical cam device of regulation allows to catch up a high modulation ratio on all firing rates range. The burners can, therefore, supply with precision the demanded power, guaranteeing a high-efficiency system level and the stability setting, obtaining fuel consumption and operating costs reduction. The combustion head guarantees reduced polluting emissions (NOx < 80 mg/kWh on gas operation). An exclusive the design ensures low sound emissions, low electrical consumption, easy use, and maintenance.

The burners are fitted with a butterfly valve to regulate the fuel, controlled by the main management module of the burner through a high-precision servomotor. Fuel can be supplied either from the right or left sides, on the basis of the application requirements. A maximum gas pressure switch stops the burner in case of excess pressure in the fuel line.  The gas train can be selected to best fit system requirements depending on the fuel output and tension in the supply line.

Gas Train Components of a Dual Fuel Boiler Burner

Industrial dual fuel burners use Multibloc or Composed gas train assemblies to safely regulate, monitor, and control the flow of gaseous fuel before it enters the burner. These gas trains may be supplied with or without an integrated valve proving (seal control) system, depending on the burner model, safety requirements, and local regulations.

A Multibloc gas train combines multiple gas control components into a single compact unit, while a Composed gas train consists of individually assembled components that offer greater flexibility for high-capacity industrial applications.

Main Components of a Gas Train

1. Gas Input Pipework

The gas input pipework connects the facility’s gas supply to the burner gas train. It must be properly sized to deliver the required gas flow and pressure while minimizing pressure losses.

2. Manual Shut-Off Valve

A manual shut-off valve allows operators to isolate the gas supply during maintenance, inspection, or emergency situations. It serves as the first safety isolation point in the gas train.

3. Anti-Vibration Joint

An anti-vibration joint absorbs mechanical vibration and thermal expansion between the gas piping and the burner. This flexible connection helps prevent stress, pipe fatigue, and gas leakage.

4. Pressure Gauge with Push-Button Cock

The pressure gauge measures the incoming gas pressure, while the push-button cock allows technicians to safely isolate or vent the gauge during maintenance and calibration.

5. Gas Filter

The gas filter removes dust, rust particles, scale, and other contaminants from the gas supply before it reaches sensitive control components. Clean fuel protects valves, regulators, and burner nozzles, extending equipment life and improving combustion reliability.

6. Integrated Multibloc Assembly

In Multibloc gas trains, several essential components are combined into one compact assembly, including:

• Gas filter
• Operating (control) valve
• Safety shut-off valve
• Gas pressure regulator

This integrated design reduces installation time, minimizes leakage points, and simplifies maintenance.

7. Minimum Gas Pressure Switch

The minimum gas pressure switch continuously monitors the incoming gas pressure. If pressure falls below the preset safety limit, the burner management system immediately prevents ignition or shuts down the burner to avoid unstable combustion.

8. Leak Detection Device (Valve Proving System)

The leak detection device, also called a Valve Proving System (VPS) or seal control, checks that both automatic gas shut-off valves are fully closed before each burner start-up. If leakage is detected, the burner remains locked out until the fault is corrected. Depending on the gas train model, this device may be supplied as an optional accessory or integrated into the gas train.

9. Gasket (Flanged Models Only)

For flanged gas train configurations, a high-quality gasket provides a gas-tight seal between mating flanges, preventing gas leakage and ensuring safe operation.

10. Gas Pressure Regulator

The gas pressure regulator reduces and stabilizes the inlet gas pressure to the precise pressure required by the burner. Stable outlet pressure ensures consistent combustion, improved fuel efficiency, and reliable flame stability even when upstream gas pressure fluctuates.

11. Gas Adjusting Butterfly Valve

The gas adjusting butterfly valve regulates the gas flow rate entering the burner. In modulating burners, the butterfly valve works together with the servo motor to maintain the correct air-to-fuel ratio across the entire firing range.

12. Burner

The burner is the combustion device where the regulated gas mixes with combustion air and is ignited to produce a stable flame for heating the boiler. Proper burner design ensures high combustion efficiency, low emissions, and reliable steam generation.

13. Maximum Gas Pressure Switch

The maximum gas pressure switch protects the burner against excessive gas pressure. If the gas pressure rises above the allowable limit, the burner management system initiates a safety shutdown to prevent equipment damage or unsafe operating conditions.

14. Gas Train-to-Burner Adapter

The gas train adapter connects the gas train assembly to the burner inlet. It is typically supplied separately and ensures proper alignment, sealing, and compatibility between the gas train and burner.

Pressure Measurement Points

Several pressure measurement points are provided to simplify commissioning, adjustment, and troubleshooting.

These pressure readings allow technicians to verify that the gas train is operating within the manufacturer’s specified pressure ranges.

Installation Responsibilities

The gas train is generally supplied separately from the burner and is selected according to the required burner capacity and fuel specifications.

• L – Gas train supplied separately according to the specified gas train code.
• L1 – Gas piping installation, supports, and final connection to the burner are the responsibility of the installing contractor.

Proper installation, pressure testing, and commissioning should always be carried out by qualified personnel in accordance with applicable standards such as EN 676, EN 746-2, and local gas safety regulations.

Why the Gas Train Is Critical

The gas train is far more than a simple fuel supply assembly—it is a complete safety and control system that regulates gas pressure, filters contaminants, monitors operating conditions, prevents gas leakage, and automatically isolates the fuel supply whenever an unsafe condition is detected. A correctly designed and maintained gas train ensures safe operation, maximizes combustion efficiency, reduces emissions, and provides long-term reliability for industrial dual fuel boiler burners.

Gas Train System for Dual Fuel Boiler Burners

The gas train is one of the most critical safety and control assemblies in a dual fuel boiler burner. It regulates the flow of natural gas or other gaseous fuels to the burner while ensuring safe operation through pressure control, filtration, automatic shut-off, and flame safety devices. Every gas train supplied with industrial burners must comply with recognized international safety standards to ensure reliable and efficient combustion.

Gas Train Compliance with EN 676

Gas trains installed on industrial gas burners are typically approved in accordance with EN 676, the European standard for automatic forced-draught burners for gaseous fuels. Compliance with EN 676 ensures that the burner and gas train have been tested together as a complete combustion system, meeting stringent requirements for safety, performance, and emissions.

Main Functions of a Gas Train

The gas train performs several essential functions before gas reaches the burner:

• Filters impurities from the incoming gas supply.
• Regulates gas pressure to maintain stable combustion.
• Monitors gas pressure for safety.
• Automatically opens and closes gas flow during burner operation.
• Prevents gas leakage during shutdown.
• Supplies the correct gas pressure required by the burner.

These functions help maintain a stable flame while protecting both personnel and equipment.

Types of Gas Trains

Industrial dual fuel burners generally use one of the following gas train configurations.

1. MULTIBLOC Gas Train

The MULTIBLOC gas train integrates several components into a compact assembly, including a pressure regulator, gas filter, safety shut-off valves, and pressure switches.

Key Features:

• Maximum inlet gas pressure: 360 mbar
• Compact integrated design
• Suitable for medium-pressure gas systems
• Easy installation and maintenance

Typical outlet pressure ranges include:

The outlet pressure can be adjusted by replacing the regulator spring, allowing the gas train to match different burner operating requirements.

2. COMPOSED Gas Train

A COMPOSED gas train consists of individual gas control components assembled together rather than a single integrated block.

Advantages include:

• Maximum gas pressure up to 500 mbar
• Flexible component selection
• Suitable for high-capacity industrial burners
• Easier customization for special applications

This configuration is commonly used on large industrial boilers and high-capacity combustion systems.

3. CB Series Gas Train

The CB Series is designed for applications requiring stable gas pressure regulation over a moderate operating range.

Specifications:

• Maximum inlet pressure: 500 mbar
• Adjustable burner outlet pressure: 10–30 mbar
• Pressure range can be modified using interchangeable regulator springs

The CB Series provides reliable pressure control while maintaining stable combustion under varying load conditions.

4. DMV Series Gas Train

The DMV Series gas train is commonly used on industrial gas burners requiring external pressure regulation.

Specifications:

• Maximum inlet gas pressure: 500 mbar
• Supplied without an integrated pressure regulator
• Requires an external gas governor or pressure regulator installed upstream

This configuration offers greater flexibility for facilities with centralized gas pressure control systems.

Typical Components of a Gas Train

A complete industrial gas train typically includes the following components:

• Manual Shut-Off Valve
• Gas Filter
• Pressure Regulator (Governor)
• Minimum Gas Pressure Switch
• Maximum Gas Pressure Switch
• Double Safety Solenoid Valves
• Leak Detection System (Optional)
• Flexible Connection
• Test Ports
• Gas Pressure Gauge
• Burner Connection Flange

Each component contributes to ensuring that the correct gas pressure reaches the burner while preventing unsafe operating conditions.

Importance of Proper Gas Train Selection

Selecting the correct gas train is essential for achieving:

• Stable combustion performance
• High thermal efficiency
• Low fuel consumption
• Reduced emissions
• Reliable burner ignition
• Compliance with international safety standards
• Long service life for the burner and boiler

The appropriate gas train should be selected based on the burner capacity, fuel type, inlet gas pressure, required outlet pressure, and applicable safety regulations.

Applications

Gas trains are widely used in industrial combustion equipment, including:

• Steam Boilers
• Hot Water Boilers
• Thermal Oil Heaters
• Industrial Furnaces
• Rotary Dryers
• Asphalt Mixing Plants
• Kilns
• Process Heating Systems

Properly designed and maintained gas trains are fundamental to the safe, efficient, and reliable operation of modern industrial gas-fired and dual fuel boiler systems.

RLS 500÷1200/M Series CATALOGUE

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