How to Design Industrial Burners

Essential Subject for Burner Design

  • In an industrial furnace, the burner plays a crucial role in generating and controlling the heat necessary for various industrial processes.
  • The primary role of an industrial burner is to produce a controlled flame that generates heat.
  • The burner is responsible for igniting the fuel (such as natural gas, oil, or propane) and ensuring its combustion within the furnace chamber
  • Types of industrial burners are discussed in the previous post. There are several types of oil, gas, and coal burners.  Based on industrial application, design details would be different.

Principle of Industrial Burners_and its parts

  • Basic combustion and subject related to heat and mass transfer, turbulent and multi-phase flow are important for the design and development of industrial burners

Fluid Mechanics

  • Using fluid mechanics you can determine the pressure drop of air in the burner
  • Bernoulli’s equation is used to find the pressure drop  due to changes in static and dynamic velocity head
  • The ideal burner should have a lower-pressure drop of air and  fuel

What is the statement of Bernoulli's equation? - Quora

 

Turbulent flow

    • Turbulent flow is a very important subject for the design of modern industrial subjects
    • In all industrial burners, the flow is turbulent, and turbulent mixing is very important to decide the flame length and emissions like CO and NO.
    • The selection of a correct turbulent model is essential to predict combustion in the burner

Heat and Mass Transfer

    • Most of the heat transfer in combustion is due to thermal radiation
    • Some energy from high temperatures to flue gases is transferred by convection
    • Mass transfer or species transfer needs to understand what chemical species are involved in combustion

Combustion Fundamentals

  • Combustion requires three main components: fuel, oxygen (usually from air), and heat. The mixture of fuel and air must be within a specific range known as the “flammability limits” for stable and efficient combustion.
  • The combustion process involves several stages, including fuel vaporization, mixing of fuel and air, ignition, flame stabilization, and combustion completion
  • Understanding of Combustion is essential for anyone working on industrial burners
  • The engineer must know the type of air and fuel mixing in the burner to design fuel tips and air register
  • Burner Types:
    • There are various types of burners, such as premix burners, diffusion burners, and partially premix burners, each with its advantages and applications.
    • Premix burners pre-mix the fuel and air before entering the combustion zone, providing better control over the combustion process and lower emissions.
    • Diffusion burners introduce fuel and air separately into the combustion zone, relying on turbulent mixing for combustion.
  • Air-Fuel Ratio:
    • The stoichiometric ratio is the ideal ratio of air to fuel that allows for complete combustion with no excess oxygen or unburned fuel.
    • The actual air-fuel ratio used in burners is often adjusted based on the specific requirements of the application to balance efficiency and emissions.
  • Flame Stability:
    • Burners should maintain stable flames throughout the operating range to avoid flameouts or unstable combustion that can lead to safety hazards and reduced efficiency.
    • Various design features, such as flame stabilizers and recirculation zones, can help achieve stable combustion

Understanding of Pollution Formation and Its controls

  • Premixed flames have low emissions but can not be used for high firing rates. Most burners used in furnaces of boilers and fired heaters are non-premixed.
  • To control emissions due to combustion, we need to understand the basic of emissions formation due to the burning of solid, liquid, and gas fuels

Multiphase flow

    • The combustion mechanism is different for solid, liquid, and gaseous fuels
    • For solid combustion,  pyrolysis or devolatilization is required before combustion. Ash particles are formed during the combustion of solid fuels like wood, coal, and waste materials
    • For liquid combustion, atomization and phase change from liquid to vapor is essential for mixing with oxygen. Soot particles are formed during the combustion of liquid fuels
    • All combustion occurs always in the gas phase. Hence combustion of gas fuel is easiest to understand

CFD modeling of combustion

    • Turbulent combustion modeling needs to be understood for CFD simulation of any industrial low NOx burner
    • Numerical models depend on the type of air and fuel mixing
    • Each combustion model has limitations in the prediction of CFD results. Combustion Engineers must understand assumptions in combustion modeling

Steps in Design of Industrial Burner

  • Designing an industrial burner involves several key considerations to ensure efficient and safe combustion. Here is a general outline of the steps involved in the design process:
  • The design of an industrial burner involves several steps to ensure its efficiency, reliability, and safety. Here are the general steps involved in the design process:
  1. Define the Requirements:
  2. Burner Data sheet
    • Details of the environment in which the burner will operate
    • Type of combustion chamber,
    • heat transfer requirements,
    • available fuel supply, air/fuel ratio,
    • combustion air temperature
  3. Preliminary Design:
    •  perform a preliminary design of the burner system. This involves selecting the burner type (e.g., atmospheric, power, or high-velocity burner)
    • determine the burner’s configuration, such as the number of burner heads, flame shape, and combustion chamber geometry
    • Other factors like flame stability, mixing of fuel and air, and eta load’
  4. Computational Modeling and Simulation:

    • Use computational tools and software to model and simulate the burner system. This step helps optimize the design, evaluate the burner’s performance, and predict factors such as flame temperature, emissions, and heat transfer characteristics. Computational fluid dynamics (CFD) simulations are commonly employed in this stage.
  5. Component Selection:
    • Select appropriate components for the burner system, such as the fuel delivery system, combustion air blower, igniter, flame monitoring system, and control system.
    • Consider factors like component reliability, compatibility with the fuel type, and compliance with safety standards.
  6. Detailed Design:
    • Once the preliminary design is validated through simulations, proceed with the detailed design. Specify the dimensions, materials, and manufacturing processes for each component.
    • Consider aspects like heat resistance, corrosion resistance, and durability to ensure the burner can withstand operating conditions.
  7. Safety Considerations:
    • Incorporate safety features into the design to minimize the risk of accidents.
    • This may include features such as flame monitoring and detection, automatic shutdown systems, and safety interlocks.
  8. Prototype Development:
    • Build a prototype of the burner system based on the detailed design.
    • Test the prototype to validate its performance, efficiency, and compliance with regulations. Make any necessary adjustments or refinements to the design based on the test results.
  9. Manufacturing and Installation:
    • Once the design is finalized and the prototype is successfully tested, proceed with manufacturing the burner system.
    • Follow appropriate manufacturing and quality control processes to ensure consistent performance and reliability.
    • Install the burner system in the designated industrial application.
  10. Post-installation Evaluation and Maintenance: After the burner system is operational, regularly monitor and evaluate its performance. Conduct maintenance activities as needed to ensure optimal functioning, energy efficiency, and compliance with regulations.

It’s important to note that the specific steps may vary depending on the complexity of the industrial burner and the application requirements. Engaging with experienced engineers and adhering to relevant codes and standards is crucial throughout the design process.

 

Determine the Application of Burner

  • Start by clearly defining the requirements of the industrial burner. Consider factors such as the type of fuel to be used (gas, oil, biomass, etc.), the desired heat output, operating conditions (temperature, pressure), emissions regulations, and any specific industry standards that need to be followed.
  • Understand the specific requirements of the industrial application, such as the desired heat output, fuel type, combustion efficiency, emission limits, and operating conditions (temperature, pressure, and ambient environment).
  • This information will guide the design process.
  • Decide the burner as per the type of furnace,  availability of fuels, and environmental norms

Conduct Fuel Analysis

  • Analyze the fuel properties, including its composition, energy content, viscosity, and other relevant parameters. This helps determine the appropriate burner design and combustion characteristics.
  • Sizing the fuel ports for burners involves determining the appropriate dimensions to ensure proper fuel flow and combustion. Here are the general steps to size fuel ports for burners
  • The type of fuel used in the burner affects the design considerations.
  • Different fuels have different combustion characteristics and may require specific burner configurations.

Fuel Flow Rate Calculation

  • Begin by calculating the fuel flow rate required for the burner.
  • This depends on the heat output needed and the specific energy content of the fuel being used. The fuel flow rate is typically measured in terms of mass flow rate (kg/hr) or volumetric flow rate (m³/hr).
Fuel Tips for Burners used on Fired Heaters after operation
Fuel Tips for Burners used on Fired Heaters after operation

Fuel Velocity Calculation

  • Determine the desired fuel velocity through the fuel ports. Fuel velocity affects the fuel-air mixing and flame stability. It is typically specified based on experience or industry standards.
  • For liquid fuels, the velocity is often in the range of 5-20 m/s, while for gaseous fuels, it can be higher.

Fuel Port Area Calculation:

  • Calculate the required cross-sectional area of the fuel ports based on the fuel flow rate and the desired fuel velocity. The area can be calculated using the equation:

         Fuel Port Area = Fuel Mass Flow Rate / (Fuel Velocity  × Fuel Density)

                                                      A = M/(V*ρ)

  •  Size of the fuel port (drill size) can be calculated using the area of fuel ports to each fuel tips of burner
  • Ensure consistency in units during the calculation (e.g., convert fuel flow rate to m³/hr if the fuel density is in kg/m³).
Fuel Port for Industrial Gas Burner
Fuel Port for Industrial Gas Burner

Port Configuration and Number:

  • Determine the configuration and number of fuel ports based on the burner design and application requirements. Fuel ports can be circular, rectangular, or a combination of shapes. The number of ports depends on factors such as the desired flame shape, combustion chamber geometry, and heat distribution requirements.

Fuel Port Sizing and Spacing:

  • Once the total fuel port area is determined, divide it among the individual fuel ports.
  • Consider factors like port size limitations, manufacturing constraints, and the need for uniform fuel distribution. The port size should be practical for fabrication while ensuring adequate fuel flow without excessive pressure drop.

Fuel Port Selection for Industrial Gas BurnerFuel Port Selection for Industrial Gas Burner

Considerations for Liquid Fuels

  • For burners using liquid fuels, additional considerations are required. Factors such as fuel atomization, spray angle, and droplet size affect combustion efficiency.
  • The fuel ports should be designed to facilitate proper atomization and mixing of the fuel with the combustion air.

Validation and Testing

  • Validate the sizing of fuel ports through computational modeling and/or physical testing. Computational fluid dynamics (CFD) simulations can help analyze the fuel-air mixing, flame stability, and combustion characteristics. Physical testing, such as flame visualization and emissions monitoring, can provide practical insights and verify the burner’s performance.

Iterative Refinement:

  • If the initial design or testing reveals any issues, iterate and refine the fuel port sizing as necessary. Adjustments may be required to achieve the desired flame characteristics, combustion efficiency, and emissions control.
  • Determine the size of fuel ports or orifices  considering the turn-down ratio
  • For the gas burner, a minimum pressure drop of 12 psi must be maintained. It can vary from 12 psi- 40  psi depending and flame profile and firing rat
  • It’s important to note that the specific methodology and calculations for sizing fuel ports may vary depending on the burner type, fuel type, and application requirements. Consulting with combustion engineers and referring to relevant industry standards and guidelines can provide valuable insights for accurate fuel port sizing.

Design of Burner Air Register 

  • Determine the pressure Drop for air and fuel in the burner. Then deduce air register and fuel ports
  • Choose the most suitable burner type for the application
    • Type of Draft: Used for low-pressure applications with a natural draft or forced draft.
    • Power burners: Suitable for high-pressure applications, offering better combustion control and turn-down ratio.
    • Air register burners: Provide adjustable air and fuel mixture for enhanced combustion performance.
    • NOx level: As per emissions we have to select low or high NOx burner

  • The design of a burner air register is an essential aspect of burner system design, as it controls the airflow to the combustion zone, thereby affecting combustion efficiency and flame stability as mentioned in the post.
  • Here are the key considerations and steps involved in designing a burner air register:

Determine Air Flow Rate 

  • Understand the airflow requirements for the specific burner application.
  • This includes the required air-to-fuel ratio, primary and secondary air needs, and the desired combustion air distribution within the combustion chamber. Consider factors such as the type of fuel being used, combustion characteristics, and industry standards.
  • Determine the fuel firing rate with heating value with a desired excess air. Refer the guideline for excess air for type of fuels.
  • The webpage of this site will help with the calculation of the heating value and flow rate of air

Register Type and Configuration

  • Choose the appropriate type and configuration of the air register based on the burner design and application requirements.
  • Common types include annular registers, radial registers, and tangential registers. The selection depends on factors like the burner geometry, flame shape, and desired airflow patterns.

Air damper for different non premix burner

Air Register Sizing

  • Calculate the dimensions of the air register based on the required air volume flow rate. The sizing is typically based on the cross-sectional area of the register.
  • Consider the desired air velocity through the register, which affects the mixing of air with the fuel and flame stability. The register size should facilitate proper airflow while minimizing pressure drop and noise generation.

Air Register Shape and Openings:

    • Determine the shape and number of openings in the air register.
    • The shape and arrangement of the openings influence the airflow pattern and distribution within the combustion zone. The openings can be circular, rectangular, or a combination of shapes.
    • The design should ensure uniform air distribution and minimize the risk of flame impingement.

Air damper for non premix burner

Adjustability and Control:

    • Incorporate adjustability features in the air register design to control the airflow rate and distribution.
    • This may involve using adjustable vanes, dampers, or variable geometry designs. The adjustability allows for fine-tuning the air-to-fuel ratio and flame characteristics based on varying operating conditions or process requirements.

CFD Simulation to check pressure Drop

    • Utilize computational fluid dynamics (CFD) simulations to analyze the airflow patterns, velocity profiles, and air-fuel mixing within the combustion chamber.
    • CFD can help optimize the air register design, predict burner performance, and evaluate factors like pressure drop and recirculation zones.

Material Selection:

    • Choose appropriate materials for the air register considering factors such as temperature, corrosion resistance, and durability.
    • The materials should withstand the combustion environment and any potential exposure to high heat or chemical reactions.

Manufacturing and Installation:

    • Manufacture the air register components based on the design specifications.
    • Follow appropriate manufacturing processes and quality control measures to ensure accurate fabrication.
    • During installation, consider alignment, sealing, and connection to the combustion system to ensure proper functionality and minimize air leaks.

Validation and Testing

    • You can compare experimental or testing results of pressure drop with CFD results or analytical results
    • Validate the air register design through practical testing.
    • Conduct performance tests to evaluate the airflow characteristics, pressure drop, flame stability, and combustion efficiency.
    • Adjustments or refinements may be necessary based on the test results.

Maintenance and Inspection:

  • Incorporate accessibility features in the air register design to facilitate regular inspection, cleaning, and maintenance.
  • Periodic inspections should be conducted to ensure proper operation, check for any obstructions, and verify the integrity of the air register components.

Throughout the design process, collaboration with combustion engineers and adherence to relevant standards and guidelines, such as those provided by industry organizations, can assist in the effective design of the burner air register.

Design of Burner Tiles 

  • Burner tiles, also known as refractory tiles or burner blocks, are crucial components in industrial burners that are designed to withstand high temperatures and provide efficient and controlled combustion.

Role of burner tiles

  • They are typically made from refractory materials such as ceramic or refractory concrete. Here’s an overview of burner tiles and their role in industrial burner applications:
    1. Function: Burner tiles serve several important functions in industrial burners, including:
    2. Flame Stabilization: The shape and arrangement of burner tiles help stabilize the flame and maintain its position within the combustion chamber. This is important for ensuring efficient and complete combustion.
    3. Heat Insulation: Burner tiles provide thermal insulation, helping to contain and direct the heat produced by the burner toward the desired target, such as a heating chamber or process equipment.
    4. Protection: They protect the underlying structure of the burner, such as the burner housing or refractory lining, from the high temperatures and corrosive effects of the combustion process.
    5. Flue Gas Recirculationon (FGR)

Burner tiles for FGR low NOx burners

Material Selection

  • Burner tiles are made from refractory materials chosen for their ability to withstand high temperatures, thermal shock, and chemical attack. Common refractory materials used for burner tiles include high-alumina, silicon carbide, and zirconia.

High-Alumina:

    • These tiles are composed primarily of alumina (Al2O3) and are known for their excellent thermal resistance and mechanical strength.
    • They are commonly used in a wide range of industrial applications.

Silicon Carbide:

    • Silicon carbide (SiC) tiles offer exceptional thermal conductivity, high strength, and resistance to thermal shock.
    • They are ideal for applications involving high-temperature and high-velocity combustion.

Zirconia

    •  Zirconia-based tiles, such as stabilized zirconia, exhibit excellent resistance to thermal shock and are often used in high-temperature applications where rapid temperature fluctuations occur.

Design and Configuration:

  • Burner tiles are designed with specific shapes, patterns, and arrangements to achieve desired flame characteristics, heat distribution, and overall burner performance.
  • The design may vary depending on the specific requirements of the burner and the combustion system.
    • Tile Shapes: Common tile shapes include rectangular, square, or trapezoidal. The shape can influence flame stability, heat transfer, and combustion efficiency.
    • Tile Patterns: Tiles can be arranged in various configurations, such as a honeycomb pattern or staggered arrangement, to optimize flame stabilization and heat distribution.
    • Mounting and Installation: Burner tiles are typically mounted and secured within the burner assembly using appropriate anchoring systems to ensure stability and proper alignment during operation.

Maintenance and Replacement:

  • Burner tiles are subject to wear and degradation over time due to harsh operating conditions.
  • Regular inspection and maintenance are necessary to monitor the condition of the tiles and replace them when they become damaged or worn out. This helps maintain the performance and efficiency of the burner.
  • It’s important to consult the specific manufacturer’s guidelines and recommendations for burner tile selection, installation, and maintenance to ensure proper functioning and longevity of the burner system.

Heat Load Calculation  (Q)

  • Determine the heat load (Q) required for your application. This could be specified by the process requirements or heat transfer calculations.
  • Determine the heating value of the fuel you are using. This value is typically provided by the fuel supplier or can be found in fuel specifications. It is usually given in terms of energy per unit of fuel (such as BTU per cubic foot for natural gas or BTU per gallon for liquid fuels).
  • Make sure to use consistent units for the heat load and heating value.
  • To calculate the fuel firing rate for a burner, you need to consider the heat load (Q) required and the heating value of the fuel. The formula for calculating the fuel firing rate is:
  • The mass flow rate of  Fuel is calculated as follows:

Firing Rate  = Heat Load   (Btu/hr)/ Heating Value (Btu/hr-ft2)

                                      M = Q/HV

Example with steps

  • let’s say you have a heat load of 10,000 BTU/hr and you are using natural gas with a heating value of 1,000 BTU/cubic foot. The fuel firing rate would be:

Fuel Firing Rate = 10,000 BTU/hr / 1,000 BTU/cubic foot = 10 cubic feet per hour

  • This means that you would need to supply the burner with 10 cubic feet of natural gas per hour to meet the specified heat load.
  • Refer to the webpage  for the calculation of air and fuel flow rate as per composition and total firing rate of a furnace (Q)

Design Combustion System (Furnace):

  • Design the combustion system, including the burner head, fuel and air supply lines, mixing chamber, and flame stabilization mechanism.
  • Consider factors like fuel and air distribution, flame shape, residence time, and flame stability.

Select Combustion Controls:

  • Choose appropriate combustion control systems to ensure safe and efficient operation.
  • This may involve incorporating sensors, actuators, and control algorithms for fuel flow, air-to-fuel ratio, flame monitoring, and safety interlocks.

Consider Emissions Control

  • Design measures to minimize emissions, such as incorporating low-NOx burners,
    • flue gas recirculation (FGR), or other emission control technologies.
    • Air staged
    • Fuel staged burner
  • Ensure compliance with local environmental regulations.
  • Other emissions like ash, SOx, Soot, and Particulate matter (PM) should be accounted for solid and liquid fuels
  • Combustion can produce harmful pollutants such as nitrogen oxides (NOx), carbon monoxide (CO), and particulate matter
  • Burner design and operational parameters can influence the emission levels. Low-NOx burners, for example, are designed to reduce nitrogen oxide emissions.

Perform Computational Fluid Dynamics (CFD) Analysis:

    • Utilize CFD simulations to evaluate the flow patterns, combustion characteristics, and heat transfer within the burner.
    • This helps optimize the design for improved performance and efficiency.

Prototype and Testing:

  • Build a prototype burner based on the design and conduct rigorous testing to validate its performance, efficiency, emissions, and safety.
  • Make necessary adjustments based on the test results.

Document and Manufacture:

  • Create detailed documentation, including drawings, specifications, and operating instructions for the final burner design.
  • Coordinate with manufacturers to ensure accurate and reliable manufacturing of the burner components.
  • Throughout the design process, it is crucial to follow relevant industrial codes, standards, and safety guidelines specific to burners and combustion systems.
  • Consulting with experienced combustion engineers and specialists can provide valuable insights and ensure compliance with industry best practices.

Scope of CFD Modeling for  Design of Industrial Burner

  • In the realm of industrial burners, optimizing performance, efficiency, and emissions control is crucial for modern industries.
  • Computational Fluid Dynamics (CFD) modeling has emerged as a powerful tool in the design and analysis of industrial burners.
  • By simulating the complex fluid dynamics and combustion processes, CFD modeling enables engineers to gain insights, refine designs, and enhance the overall performance of industrial burners. In this blog post, we explore the significance of CFD modeling in the realm of industrial burner design, its benefits, and its impact on improving burner performance.

2 thoughts on “How to Design Industrial Burners”

  1. Very nicely structured this industrial burner design and its combustion technology in depth manner.
    Every Engineer in combustion and burner design sector must read this philosophy.
    Very nicely & well professionally offer for us.
    Thanks Dr. Sharad. Appreciate your effort with this way of publication.

    Reply

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