Flare Radiation, Dispersion and Noise

Flare and process vent design requires careful consideration of hazard and risk factors such as thermal radiation, flammables dispersion and noise. These parameters are required to be assessed to define adequate stack height, separation from adjacent facilities and to define any sterile zone. 
At PetroPlat Energy Limited, we have solid experience of flare and vent design using state of the art software such as Flaresim and Phast.
Thermal Radiation Modelling 
Flares produce significant amounts of heat, and poorly designed flares present a danger to people working nearby. We use the proven Flaresim software to design the optimum flare height, the necessary sterile zone, and the separation from adjacent plant. 
Flare location and height are important design parameters to firm-up early in the design process as the flare can have a significant impact on facility siting considerations.  Sensitivity analyses are performed to ensure variables are properly considered, thus ensuring a robust assessment. 

Dispersion Modelling 
Adequate dispersion of hazardous vapours from flares and vents is a common requirement. We use Phast software to conduct robust dispersion modelling to define the hazardous area zone extent of any flammable components in line with BS EN 60079 and API RP 505. 
Dispersion from flare flame out (e.g., Methane / hydrogen sulphide) or from combustion products (e.g., sulphur dioxide) can be a governing design factor for the flare height and location. Often, reliance on standard look-up tables from industry guides such as EI 15 is not sufficient, especially for complex situations and multi-component mixtures.

Noise Modelling 
Flares and vents are inherently noisy. Assessment of noise is an important consideration which should not be left to chance. 
We use Schlumberger’s Flaresim software to perform noise modelling of the flare or vent and validate our findings with design vendor information. 
Noise modelling conducted early-on in the design process helps the design team to confirm whether noise is an issue, whether it is a governing factor in flare/vent design and what hearing protection measures might be necessary on site. Noise is both a safety and an environmental consideration. Fence line noise limits may need to be adhered to and this is particularly relevant for flares since they tend to be in remote locations, sometimes nearer to the site boundary than the main equipment. 

Methodology
The study will focus on the worst-case scenarios for flaring, depending upon the flare system being studied. This is undertaken with varying flow rates and compositions as provided by Client. Both lit and flameout scenarios will be studied.
The following data is required:
⦁ Stack height
⦁ Tip diameter
For each scenario the following is required:
⦁ Flow rate
⦁ Composition
⦁ Temperature
⦁ Combusted flow rate
⦁ Combusted composition
⦁ Combusted temperature
Heat Radiation results will be presented in the form of tables and corresponding radiation contour diagrams.
Toxic dispersion will typically be determined to the Occupational Exposure limits for H2S and SO2.
Flammable dispersion will typically be determined to Lower Flammable Limit (LFL), 0.6 LFL and 0.2 LFL unless otherwise agreed with the company.
Noise will be reported for the lit and flameout case. Noise limits are typically 83 / 85 dB(A) (to be agreed with the company). No noise survey will be undertaken as part of this study.