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 KCl on combustion, these two components were injected
into the combustion reactor. In the experiments, pure gaseous SO2 was injected upstream of the burner. KCl was fed as an aqueous
solution (3.34%wt of KCl) that was sprayed directly into
the flame. Pure water was also injected, to distinguish any possible
interaction between KCl and water. Kinetic modeling was conducted
to examine the reaction routes and activities. The results show that
both KCl and SO2 suppress the formation of NO. KCl appears
to inhibit the formation of NO, whereas SO2 decreases the
concentration of NO by enhancing its oxidation to NO2.