Influence of KCI and SO2 on NO Formation in C3H8 Flames

Journal article, 2017

The use of low-quality fuels in power generation plants is typically motivated by the potential for reducing fuel costs or CO2 emissions, the latter in the case of a fuel based on biomass. These features make low-quality fuels attractive, although their use for power generation is usually problematic due to their composition. One of the main issues is high-temperature corrosion (HTC), which is caused by alkali-containing chlorides. The alkali chlorides, which are formed from alkali metals and chlorine released from the fuel during the combustion process, are a particular problem. HTC is often related to the combustion of fuels with a low sulfur-to-potassium ratio, such as biomass, and it has a significant effect on the thermal efficiency and/or the maintenance cost of the power plant. Sulfuric and alkali species not only influence the formation of highly corrosive salts but also affect other aspects of combustion chemistry. While the present work relates to HTC chemistry, it focuses on how potassium chloride and sulfur dioxide influence the formation of NO. The experiments were carried out in a 100 kW test facility using C3H8 as the fuel. In order to examine the influence of SO2 and KCI on combustion, these two components were injected into the combustion reactor. In the experiments, pure gaseous SO2 was injected upstream of the burner. KCI was fed as an aqueous solution (3.34%, of KCI) that was sprayed directly into the flame. Pure water was also injected, to distinguish any possible interaction between KCI and water. Kinetic modeling was conducted to examine the reaction routes and activities. The results show that both KCI and SO2 suppress the formation of NO. KCI appears to inhibit the formation of NO, whereas SO2 decreases the concentration of NO by enhancing its oxidation to NO2.