Combustion of mixtures: A modified IFC approach

While most studies on flares have been done with single hydrocarbon fuels or binary mixtures, the reality of most industrial flares is that they see different mixtures of many gases. Over the past 5 years the International Flare Consortium (IFC) has been conducting research on just this issue. In a recently published literature review, the IFC has explored approaches that have been used to describe the impact of vent gas composition and assist gas ratio on flare combustion efficiency. LeChatelier's Principle has been widely used to estimate the flammability limits (lower and upper) of mixtures of flammable gases. However, LeChatelier's Principle must be slightly modified when one or more of the gas components are inflammable or inert. This paper discusses some minor suggested modification of the reduced steam volume fraction parameter outlined in the IFC Literature Review, then discusses how this approach can be used to describe industrial flare operation, and the impact of assist gas ratio on the observed combustion efficiency. Finally, this paper will present the analysis of combustion efficiency data collected from 7 recent flare test campaigns and illustrate the ability of this modified IFC RSVF method to describe the results obtained. A hypothesis will be offered as to how this approach might be used to predict the performance of other flares, given additional data.