"Enclosed Ground Flare" refers to a type of flare system designed to combust waste gases near the ground within an enclosed structure, offering distinct advantages in safety, noise reduction, and emission control compared to traditional elevated flares. Below is a detailed professional explanation:

Definition and Core Features

An enclosed ground flare consists of a combustion chamber (enclosure) and supporting systems, where waste gases are ignited and burned within a confined space. Its key features include:
  • Enclosed Structure: Typically formed by a cylindrical or polygonal steel frame with perforated metal panels or louvers, allowing air intake while containing flames and heat.
  • Low-Height Design: Operates close to the ground (usually within 10–30 meters), eliminating the need for tall risers or stacks.

Key Components

  • Combustion Chamber:
    • Made of heat-resistant materials (e.g., stainless steel) to withstand high temperatures.
    • Perforated walls facilitate controlled air induction for complete combustion.
  • Burner Assembly:
    • Multi-point burners distribute gas evenly, ensuring stable flame and minimal smoke.
  • Ignition System:
    • Electric igniters or pilot burners for reliable start-up.
  • Air Management System:
    • Louvers or fans regulate air supply to match gas flow, optimizing combustion efficiency.

Advantages

Aspect Enclosed Ground Flare Traditional Elevated Flare
Safety Enclosed design reduces radiation hazards to personnel and equipment. Open flames at height may pose risks in high-wind conditions.
Noise Emission Noise is dampened by the enclosure (typically <85 dB at boundary). Loud combustion noise (up to 110 dB) requires greater setback distances.
Visible Emission Flames are contained, minimizing light pollution and visual impact. Visible flames at night may be a concern for urban or residential areas.
Footprint Compact design (smaller land area required). Tall stacks and guy wires demand larger spacing.
Emission Control Better control of NOx and CO through staged combustion. Emissions are more dependent on atmospheric dispersion.

Application Scenarios

  • Urban/Industrial Complexes: Where strict environmental regulations or proximity to communities limit elevated flares.
  • Refineries and Chemical Plants: For routine gas flaring during normal operations, the shutdown, or upset conditions.
  • Offshore Platforms: Space-constrained environments where low-profile designs are preferred.
  • LNG Terminals: Combusting boil-off gas (BOG) with minimal visual/noise impact.

Design Considerations

  • Gas Flow and Properties:
    • Accurate calculation of gas flow rate, calorific value, and H2S content to size the combustion chamber and burners.
  • Combustion Efficiency:
    • Staged air injection and burner layout to ensure >98% combustion efficiency, minimizing unburned hydrocarbons.
  • Heat Management:
    • Thermal insulation of the enclosure to prevent overheating of adjacent structures.
  • Safety Interlocks:
    • Pressure sensors, flame detectors, and emergency shutdown (ESD) systems to prevent overpressure or flame failure.
  • Environmental Compliance:
    • Design to meet local regulations on NOx, CO, and opacity (e.g., <20 ppmv NOx, <50 ppmv CO).

Operational Challenges

  • Blockage Risks: Moisture or particulates in gas streams may clog perforated walls, requiring regular cleaning.
  • High Wind Impact: Strong winds can disrupt air intake, affecting combustion stability (mitigated by wind baffles).
  • Initial Cost: Higher investment compared to simple elevated flares due to complex enclosure and burner systems.

Typical Configurations

  • Cylindrical Enclosure with Radial Burners: Common for medium gas flows (10–50 MMscfd), offering uniform combustion.
  • Multi-Annular Burner System: For high-flow applications, using concentric burners to enhance air-gas mixing.
  • Water Injection System: Optional for NOx reduction, spraying water into the combustion zone to lower flame temperature.

Enclosed ground flares represent a modern solution for industries seeking sustainable flaring practices with minimal environmental and operational impacts, particularly in sensitive locations where traditional flares are impractical.