(101d) Comparison of Methods for Estimation of Levels of Radiation Emitted by An Industrial Flare

The thermal radiation is the energy emitted by matter which is a non-zero temperature. Although this phenomenon is commonly addressed to solid, it also occurs for liquids and gases. Regardless of form of matter, the emission can be attributed to changes in the configuration of atoms or molecules. In the heat transfer by radiation, the energy is carried by electromagnetic waves and is the only form of energy which can be transmitted without an intermediate material [1].

Among the parameters that influence the heat exchange by radiation there are the material body, its physical state, its spectral and direction distribution beyond the temperature. The most common sources of heat by radiation are the sun and processes or reactions that produce flame. Radiant energy is emitted only by the gases and solids present in the flame. The molecules of water and carbon dioxide, the combustion products, are the gases that emit radiation more significantly in the flame, while radical species, such as carbon monoxide, are present only for a very short time, making its issue negligible [2].

The flare system is responsible to burn the waste gas of oil and gas production and processing facilities to achieve, with safety, the burning of gas released by seeking relief devices and keep the unit operating safely. As a result, levels of radiation released by this system may compromise the structural integrity of these facilities around and cause damage to the health of local workers. Thus, the radiation resulting from the process of burning, in emergency and operating conditions, should be estimated during the design of these systems and structures in its vicinity, in order to validate or not the configuration provided by the various designer disciplines involved. In emergency situations the flow of gas released is considerably high, consequently, the levels of radiation emitted by the flame are also considerably high. Due to the great impact on the energy emitted by radiation, and therefore, the characterization as a design flare scenario, the emergency conditions are usually taken as the basis for this kind of study.

The aim of this work is to present a comparison among methodologies for calculating the radiation levels emitted by a flare flame. The study employs the use of computational fluid dynamics (CFD) tools in order to perform a comparison among its results and the ones obtained by other methodologies commonly used in industry. The results used as basis for the comparison are the temperature profile on equipments structures beyond the analysis of maximum allowed levels for human exposure, according the limits suggested by API 521, in a generic offshore platform used as an example [3].

[1] Fundamentals of Heat and Mass Transfer, sixth edition, David P. Dewitt, Frank P. Incropera.

[2] The John Zink Combustion Handbook, Charles E. Baukal.

[3] API Recommended Practice 521 ? Guide for Pressure-Relieving and Depressuring Systems, fifth edition.