4.3 Flare Emissions

It is generally accepted that an appropriately designed stable flare will achieve a combustion efficiency of >98%. However it must be understood that under extreme operating and ambient conditions, combustion efficiency will suffer to some degree.

The combustion efficiency of a hydrocarbon stream can be defined by the percentage conversion of the constituents to the completed products of combustion, i.e. CO2 and H2O.

Whilst it is possible to determine the combustion efficiency of a thermal oxidiser/incinerator because they are, by design, enclosed environments in which the operating conditions and products of combustion can contained, controlled, measured and recorded, the same is not true of an open flare. As such, field measurements of combustion efficiency are not possible. Similarly the recording of meaningful NOx, CO, NMVOC or CH4 emission data specifically from an industrial flare is not possible.

In lieu of being able to monitor flare emissions and combustion efficiency, the industry generally concentrates on achieving a stable flare flame and the use smoke suppression media such as steam, assist gas or air where applicable to ensure smokeless operation under the day to day continuous operating conditions.