(126a) A Proposed Comprehensive Model for Elevated Flare Flames and Plumes

When designing elevated flares, the open flame and the associated radiant heat represent the most obvious safety considerations and several different flames models are available in the literature to aid in the design process on this basis.

An often overlooked consideration however is the effect of the flue gas plume itself and how this can impact plant safety in the near field due to its inherent temperature, reduced oxygen and potential concentration of unburned materials, affecting both personnel access areas and local structures.

Disadvantages of the commonly used flame models include

- a universal assumption that all flare discharges are axially vertical, rendering these models inaccurate in many Offshore and Oil field applications, and

- a discontinuity between the flame and downwind plume models, making it difficult to estimate near-field downwind effects.

This paper introduces a new algorithm for a flame model, referenced in the paper as the BUOYANT Flame Model, using the indicator BUO, which

- is based on widely used parameters for buoyant rise and momentum rise of a plume;

- includes a vector component to allow use for both vertical or non-vertical discharges;

- can be applied equally to the flame and the resulting plume as a comprehensive solution.

The paper expands on the published dispersion formulae to show how the model may be used to approximate downwind plume temperature and flue gas concentrations in a three dimensional field. The new model can be a spring-board to further research and includes a time based component which may have general applicability to all diffusion flames and assist in flare flame efficiency estimations.