Basics of Flares and its Applications in Oil and Gas Industries

What is a Flare?

• A flare is a combustion device used to burn off excess or waste gases safely during plant operations, shutdowns, start-ups, or emergencies.
• These gases are typically hydrocarbons that are either not feasible to recover or are released suddenly due to over-pressuring of equipment.
• Flaring prevents the uncontrolled release of flammable or toxic gases into the atmosphere and helps maintain the safe pressure levels in the system.

 

How Do Flares Work?

The basic components of a flare system include:

• Flare Stack (Elevated or Ground-level): Vertical pipe or chimney where the gas is released.

• Pilot Burner: Keeps the flare continuously ignited.

• Gas Header and Knockout Drum: Collects and routes gas to the flare, removing liquids.

• Flame Arrestors and Control Systems: Ensure safe ignition and prevent backfire.

• Assist Systems (Steam or Air): Improve combustion efficiency and reduce smoke.

When waste gas enters the flare system, it travels through the flare stack and is ignited by the pilot flame, resulting in controlled combustion. The goal is to convert hydrocarbons into carbon dioxide (CO₂) and water vapor, which are less harmful than releasing raw gas.

Applications of Flares in the Oil and Gas Industry

Major applications of lare system:

• Oil Refineries

• Petrochemical Plants

• LNG Terminals

• Gas Processing Units

• Offshore Platforms

• Landfills and Biogas Plants

1. Exploration and Production (Upstream)

During drilling, testing, or well clean-up, flaring is used to dispose of gas that cannot be stored or transported. This is especially common in remote areas where pipeline infrastructure is unavailable.

2. Refineries and Petrochemical Plants (Downstream)

Flares are essential for handling emergency pressure relief and vent gases during maintenance, plant upset conditions, or system startups. They act as a safety valve for high-risk processes.

3. Natural Gas Processing Facilities

Flares are used to burn non-recoverable gases or contaminants such as hydrogen sulfide (H₂S), ensuring compliance with environmental regulations.

4. LNG and Storage Terminals

Flares help manage boil-off gases (BOG) and excess pressure during loading or unloading of LNG (liquefied natural gas).

5. Offshore Platforms

Marine flares are installed on rigs to safely dispose of gas in the event of equipment failure or pressure surges.

Environmental and Safety Considerations

While flaring is a controlled and safer alternative to venting raw gas, it still results in carbon emissions and energy loss. Poor combustion may also release black smoke, carbon monoxide, or unburned hydrocarbons.

To minimize environmental impact, modern facilities are incorporating:

• Flare Gas Recovery Systems (FGRS) to reuse flare gases.

• Smokeless flare technology using steam or air assist.

• CFD modeling to optimize flare tip design and combustion efficiency.

What are types of flares?

• Flares come in various types based on their design, function, and combustion characteristics.
• The main types of flares include:

Elevated Flares

These are the most common type and are mounted on tall stacks.

• Purpose: Keep flame away from personnel and equipment.

• Features: Visible flame; may include steam or air assist to reduce smoke.

• Used In: Refineries, petrochemical plants, gas processing facilities.

Sub-types:

• Open Elevated Flare: Basic form; uses natural draft.

• Enclosed Elevated Flare: Includes a shield or structure around the flame to reduce noise and visibility.

Ground Flares

These are installed close to the ground and often enclosed for safety and noise reduction.

• Purpose: Used where flame visibility or safety is a concern.

• Features: Enclosed chambers, multiple burners, lower visibility, quieter operation.

• Used In: Urban refineries, chemical plants, LNG terminals.

Sub-types:

• Enclosed Ground Flare: Fully enclosed, smokeless.

• Open Ground Flare: Open but shielded for safety.

Enclosed Flares (Also Called Smokeless Flares)

These are designed with a combustion chamber to hide the flame and reduce emissions.

• Purpose: Reduce noise, light pollution, and visible smoke.

• Used In: Residential or environmentally sensitive areas.

Marine Flares

Specially designed for offshore platforms.

• Purpose: Handle excess gas on oil platforms at sea.

• Features: Corrosion-resistant, with wind protection.

Portable or Mobile Flares

Temporary flaring systems used during maintenance or field operations.

• Purpose: Emergency flaring or mobile use in oilfields or biogas plants.

• Features: Compact, movable, may be trailer-mounted.

Air-Assisted Flares

Use blowers to inject air into the flare to promote complete combustion and reduce smoke.

• Used In: Low-pressure gas systems or when smokeless operation is required.

Steam-Assisted Flares

Inject steam into the flame to reduce smoke and promote turbulence.

• Used In: High-flow gas flaring in refineries and petrochemical plants.

Pressure-Assisted Flares

Use pressurized gas flow to enhance mixing and combustion.

• Used In: Systems with high gas pressure or intermittent flow.

Liquid Flares

Burn liquid hydrocarbons directly.

• Used In: Where liquid waste needs to be combusted safely.

Summary  of Flare Classifications

Modeling and Prediction of flare Plume or Dispersion Flow

Computational Fluid Dynamics (CFD) has emerged as a powerful tool in the oil and gas industry, especially for flare system analysis. Modeling flare plume behavior and gas dispersion using CFD allows engineers to simulate real-world conditions and optimize design, safety, and environmental compliance.