Elevated vs Ground vs Skid-Mounted Flare: How to Choose the Right Flare System
Created on 08.21
Introduction
Selecting a flare system is not simply a matter of comparing equipment prices or choosing the largest available capacity.
An industrial flare is an engineered safety and combustion system designed around a specific combination of gas composition, flow conditions, operating scenarios, site constraints and environmental requirements.
The first decision should therefore not be which supplier to buy from, but which flare configuration is appropriate for the project.
The three configurations most commonly considered for industrial applications are:
- Elevated flare systems
- Enclosed ground flare systems
- Skid-mounted flare systems
Each has a different role. An elevated flare may be the preferred solution for high-capacity refinery or petrochemical applications, while an enclosed ground flare can be more suitable where radiation, noise or visual impact is a major concern. A skid-mounted flare offers greater flexibility where rapid installation, modular construction or relocation is required.
The right choice depends on the project—not on a standard product catalogue.
Why Flare System Selection Matters
Global gas flaring remains a significant challenge for the oil and gas industry. According to the World Bank's 2026 Global Gas Flaring Tracker, global gas flaring increased to approximately 167 billion cubic meters in 2025, the third consecutive annual increase and the highest level since 2019.
This does not mean that every flare can or should be replaced by another configuration. Rather, it highlights the importance of designing flare systems around actual process requirements, operating conditions and opportunities to reduce routine flaring.
For EPC contractors, process engineers and plant owners, the configuration decision should be made before comparing vendors.
1. Start with the Operating Mode
The first question is:
When and why will the flare operate?
A flare may be required for:
- Emergency pressure relief
- Process upset conditions
- Startup and shutdown
- Maintenance and depressurization
- Continuous or intermittent process venting
- BOG handling
- Temporary or pre-commissioning operations
The operating philosophy has a direct influence on flare capacity, turndown, ignition, flame stability, control philosophy and mechanical design.
Continuous or Frequent Operation
If the flare is expected to operate frequently, combustion stability at low and variable flow rates becomes particularly important.
The design may need to consider:
- Stable flame retention
- Pilot reliability
- Low-flow combustion performance
- Smokeless operation
- Continuous monitoring
- Maintenance requirements
Emergency Operation
For an emergency flare, the system may remain in standby for most of its operating life but must respond reliably when a relief or depressurization event occurs.
In this case, emergency capacity, response, ignition reliability, radiation and dispersion become major design considerations.
The flare that is suitable for continuous process venting is not necessarily the best configuration for emergency relief.
2. Analyze the Gas Composition
Gas composition is one of the most important inputs in flare system design.
A flare should be designed around the actual gas characteristics rather than a generic specification.
Important parameters may include:
- Gas composition
- Molecular weight
- Lower and higher heating value
- Temperature
- Operating pressure
- Maximum pressure
- Flow rate
- H₂S concentration
- CO₂ concentration
- Hydrogen content
- Oxygen concentration
- Corrosive or toxic components
- Presence of liquids or condensable hydrocarbons
Different gas compositions can significantly affect:
- Flare tip selection
- Combustion stability
- Flame temperature
- Radiation
- Smoke formation
- Material selection
- Purge requirements
- Pilot design
- Ignition system
- Emission performance
For example, a methane-rich gas, hydrogen-rich gas, acid gas and variable pyrolysis gas should not automatically be treated with the same flare configuration.
3. Evaluate Site Constraints
The physical location of the flare can be just as important as the gas itself.
Before selecting a configuration, engineers should evaluate:
- Available plot area
- Distance to occupied buildings
- Thermal radiation limits
- Noise requirements
- Stack height restrictions
- Wind conditions
- Ambient temperature
- Seismic requirements
- Maintenance access
- Transportation and lifting limitations
- Local environmental requirements
These factors can quickly narrow down the available options.
For example, a conventional elevated flare may be technically suitable but difficult to implement where thermal radiation or visual impact is highly restricted.
In such cases, an enclosed ground flare may provide a more appropriate solution.
4. Elevated Flare System
An elevated flare places the combustion zone at an elevated position above grade.
It is one of the most widely used configurations for large-scale oil and gas, refinery and petrochemical applications.
Typical applications
- Oil and gas production facilities
- Refineries
- Petrochemical plants
- Gas processing plants
- Large LNG facilities
- Emergency relief systems
- High-capacity flare applications
Key advantages
High capacity
Elevated flare systems can be engineered for very large relief and emergency flow rates.
Effective dispersion
Elevating the flame helps provide greater separation between the combustion zone and ground-level equipment or personnel.
Proven technology
Elevated flares have been widely used for decades in large industrial facilities.
Flexible configuration
Depending on project requirements, elevated flares can be designed as:
- Self-supported flare stacks
- Guyed flare stacks
- Derrick-supported flare stacks
- Demountable flare systems
Considerations
Elevated flares require careful evaluation of:
- Radiation
- Flame visibility
- Noise
- Stack structure
- Foundation
- Wind loading
- Maintenance access
For large-capacity applications where plot layout and radiation requirements permit, an elevated flare can be an efficient and proven solution.
5. Enclosed Ground Flare System
An enclosed ground flare performs combustion at or near ground level inside a refractory-lined enclosure.
Instead of exposing the flame directly to the surroundings, the combustion zone is contained within the enclosure.
Typical applications
- Petrochemical plants
- Chemical plants
- LNG terminals
- Facilities with strict radiation limits
- Industrial parks
- Sites close to occupied areas
- Projects requiring reduced visible flame
Key advantages
Reduced thermal radiation
The enclosure helps shield the combustion zone and can significantly reduce radiation at the site boundary compared with an exposed flame.
Lower visual impact
The flame is largely contained within the enclosure, making this configuration attractive where visible flame is a concern.
Noise control
The enclosure can also help reduce combustion noise, depending on the design.
Ground-level maintenance
Major components are accessible from ground level, which can simplify inspection and maintenance compared with a tall flare stack.
Considerations
An enclosed ground flare generally requires:
- Larger ground-level footprint
- Refractory lining
- Structural enclosure
- Careful combustion-air management
- Heat management
- Detailed refractory engineering
It can also involve higher initial engineering and manufacturing costs.
However, the initial equipment cost should not be evaluated separately from the project's radiation, noise, land-use and maintenance requirements.
6. Skid-Mounted Flare System
A skid-mounted flare integrates the major combustion components into a modular skid or compact package.
This configuration is particularly useful where flexibility and rapid deployment are important.
Typical applications
- LNG bunkering stations
- LPG facilities
- Small-scale LNG projects
- Temporary facilities
- Pilot plants
- Pre-commissioning and commissioning
- Remote installations
- Mobile or relocatable applications
- Pyrolysis gas treatment
Key advantages
Modular construction
Major components can be assembled and tested before shipment.
Reduced site construction
A skid-mounted package can reduce the amount of field fabrication and installation work.
Fast deployment
This can be particularly valuable for temporary projects or facilities with tight schedules.
Relocation
Where the project requires equipment to be moved between locations, a skid-mounted design offers substantially greater flexibility than a permanent flare structure.
Considerations
Skid-mounted systems are not automatically suitable for every application.
Engineers still need to evaluate:
- Maximum flow rate
- Gas composition
- Radiation
- Noise
- Flame stability
- Skid dimensions
- Transportation limitations
- Lifting requirements
- Site utilities
- Control and ignition requirements
7. Elevated vs Enclosed Ground vs Skid-Mounted Flare
The following comparison provides a starting point for configuration selection.
Factor | Elevated Flare | Enclosed Ground Flare | Skid-Mounted Flare |
Typical application | Oil & gas, refinery, petrochemical | Petrochemical, chemical, LNG | LNG/LPG, temporary and modular projects |
Capacity | Small to very large | Small to very large | Typically small to medium, project dependent |
Radiation control | Project dependent | Strong advantage | Project dependent |
Visible flame | Yes | Low / largely contained | Depends on design |
Noise control | Project dependent | Strong advantage | Project dependent |
Mobility | Low | Low | High |
Site construction | Structural installation required | Civil and enclosure installation required | Reduced field installation |
Maintenance access | Elevated components require access strategy | Ground-level access | Ground-level/package access |
Temporary projects | Limited | Limited | Highly suitable |
LNG/LPG applications | Yes | Yes | Yes |
Emergency relief | Yes | Yes | Yes |
Modular deployment | Limited | Limited | Excellent |
This table should be used as an initial screening tool rather than a final engineering decision. The appropriate configuration must be confirmed against actual process data, radiation calculations, dispersion requirements, applicable standards and site conditions.
8. Five Questions to Ask Before Selecting a Flare
Question 1: What is the maximum and minimum flow rate?
A flare should not be selected based only on maximum flow.
Engineers should understand the complete operating range, including:
- Minimum flow
- Normal flow
- Maximum continuous flow
- Emergency flow
- Startup/shutdown flow
A system that handles the maximum flow but becomes unstable at low flow may not be suitable for the application.
Question 2: What is the gas composition?
Provide the actual gas analysis whenever possible.
At minimum, the design team should evaluate:
- Main combustible components
- Molecular weight
- Heating value
- H₂S
- CO₂
- Hydrogen
- Nitrogen
- Oxygen
- Moisture
- Potential liquid carryover
This information directly affects combustion and equipment selection.
Question 3: How much space is available?
Site constraints can be decisive.
If the project has sufficient separation distance and can accommodate an elevated structure, an elevated flare may be appropriate.
If radiation, noise or visual impact is more restrictive, an enclosed ground flare may be preferable.
If the installation needs to be compact and relocatable, a skid-mounted system may provide greater flexibility.
Question 4: Is the flare permanent or temporary?
Permanent facilities generally favor fixed infrastructure.
Temporary, pilot or pre-commissioning projects may benefit from modular skid-mounted systems that can be installed and relocated more easily.
This is particularly relevant for:
- LNG/LPG bunkering
- Pilot plants
- Pyrolysis projects
- Remote facilities
- Commissioning projects
Question 5: What matters most over the equipment lifecycle?
The lowest purchase price does not necessarily represent the lowest total cost.
A proper evaluation should consider:
- Engineering cost
- Equipment cost
- Civil works
- Installation
- Transportation
- Commissioning
- Maintenance
- Spare parts
- Inspection
- Expected operating conditions
- Future modification requirements
A more customized configuration may require additional engineering at the beginning but can reduce operational and maintenance risks over the life of the project.
9. Real-World Flare Selection Examples
Different projects demonstrate why flare configuration should be selected according to actual operating conditions.
Skid-Mounted Ground Flare for a Pyrolysis Project in Vietnam
A skid-mounted ground flare was developed for variable pyrolysis gas generated by a waste-plastic conversion process.
The project required a compact and flexible combustion solution capable of handling changing gas conditions while minimizing field installation requirements.
The modular configuration was selected to match the project's operating and installation constraints.
Ground Flare for Coalbed Methane in China
A ground flare system for coalbed methane was designed for a capacity of approximately 900,000 Nm³/day.
The system uses three-stage venting and PLC-based control to accommodate different operating conditions.
This project illustrates how flare configuration and control philosophy need to be considered together rather than treating the flare as an isolated combustion device.
Flue Gas Treatment for a Tire Pyrolysis Project in South Korea
A customized flue gas treatment solution was developed for a tire pyrolysis application in South Korea.
The project required treatment of process emissions under variable operating conditions and demonstrated the importance of designing combustion and gas treatment systems around the actual process rather than relying on a standard configuration.
10. How Zexuan Approaches Flare System Selection
At Shandong Zexuan Environmental Protection Technology Co., Ltd., we do not treat elevated flares, enclosed ground flares and skid-mounted flares as interchangeable products.
Our engineering approach starts with the project requirements.
We evaluate:
- Gas composition
- Flow rate and operating range
- Pressure and temperature
- Operating scenarios
- Radiation requirements
- Noise requirements
- Site conditions
- Installation requirements
- Control philosophy
- Applicable project standards
Based on these inputs, the appropriate flare configuration can be developed.
Our flare solutions include:
- Elevated Flare Systems
- Enclosed Ground Flare Systems
- Skid-Mounted Flare Systems
- LNG/LPG Flare Systems
- Biogas and Landfill Flares
- Customized flare and combustion systems
For LNG and LPG applications, we also provide solutions for BOG and emergency vapor handling.
11. Need Help Choosing the Right Flare Configuration?
If you are evaluating an elevated flare, enclosed ground flare or skid-mounted flare for a new project, the most useful starting point is your process data.
Please provide, where available:
- Gas composition
- Minimum / normal / maximum flow rate
- Operating pressure
- Operating temperature
- Relief or vent scenarios
- Required operating hours
- Site location
- Radiation limits
- Noise requirements
- Installation or mobility requirements
Our engineering team can review the project conditions and recommend a suitable flare configuration.
Request a Flare System Assessment
Frequently Asked Questions
What is the difference between an elevated flare and an enclosed ground flare?
An elevated flare combusts gas at the top of a vertical flare stack, while an enclosed ground flare burns gas inside a refractory-lined enclosure at ground level. Enclosed ground flares are often considered where radiation, noise or visible flame requirements are more restrictive.
When should I choose a skid-mounted flare?
A skid-mounted flare is particularly useful for modular, temporary, remote or relocatable applications where reduced site construction and rapid deployment are important.
Which flare type is best for an LNG terminal?
There is no single configuration suitable for every LNG terminal. The selection depends on BOG flow, emergency relief scenarios, radiation requirements, available space, operating philosophy and project-specific regulations. Elevated, enclosed ground and skid-mounted configurations can all be considered depending on the application.
Is an enclosed ground flare more expensive than an elevated flare?
Initial costs can be higher because an enclosed ground flare requires an enclosure, refractory system and associated structural and combustion engineering. However, total project cost should also consider radiation requirements, plot layout, noise, maintenance and permitting constraints.
Can a skid-mounted flare be used for emergency relief?
Yes. A skid-mounted flare can be designed for emergency gas disposal when its capacity, pressure, combustion performance, ignition system, radiation and other project requirements are properly evaluated.
How do I select the correct flare capacity?
Flare capacity should be established from the applicable relief and venting scenarios rather than simply using the normal operating flow. The design should consider maximum credible relief cases as well as minimum and normal operating conditions.
Conclusion
Elevated, enclosed ground and skid-mounted flares are not interchangeable products.
The right configuration depends on the combination of gas characteristics, flow conditions, operating mode, site constraints, radiation and noise requirements, installation strategy and lifecycle objectives.
The best flare system is therefore not necessarily the cheapest or largest system. It is the configuration that safely and reliably addresses the actual requirements of the project.
Define the application first. Select the configuration second. Compare suppliers third.
For customized industrial flare system solutions, contact Shandong Zexuan Environmental Protection Technology Co., Ltd.
Email: alice@zexuaneco.com
Website: www.zexuaneco.com
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