Consistent emission correction factors applicable to novel energy carriers and conversion concepts

Abstract

Volume correction factors have been an important aspect when reporting pollutant emissions from gaseous combustion for many years. Their application has become standard procedure in such a way that their applicability is seldom questioned. However, their emergence dates back to a time when power generation primarily relied on conventional fuels such as coal and gas. The advent of alternative fuels and new combustion concepts reveals the classical correction formula prescribed by many current legal regulations to produce results that can be misleading when comparing different mixtures with regard to their emission behavior. For this reason, this work derives a more generalized correction formula that extends the applicability to any fuel–oxidizer combination and is based on the same principles as conventional volume correction. The impact of the choice of correction formula is then exemplified by comparing results for various fuels for a selection of numerical and experimental examples. They consist of a simple equilibrium calculation, as well as experimental data from a premixed swirl combustor and a pulse detonation combustor. The results show that conventional correction terms can lead to misleading perceptions of emission performance when comparing fuels. In contrast, the extended correction terms derived in this work allow for a comparison of emission behavior on a common basis that is independent of effects introduced by fuel and oxidizer stoichiometry, in a manner similar to alternative fuel-mass based metrics such as emission index. This is not restricted to the investigated examples but can be applied to all areas where oxygen correction is common. It is suggested that future emission regulations should incorporate the issues discussed in this work to ensure unbiased comparison of emission values across a wide range of combustion applications.