Influence of KCl and SO₂ on NO Formation in C₃H₈ Flames

Abstract

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.

Formation of Soot in Oxygen-Enriched Turbulent Propane Flames at the Technical Scale

“…The concentration of CO is chosen for tuning the model since CO is an important indication of the local stoichiometry in the experimental flame. This method has been applied successfully in previous studies [44,45] to describe the combustion conditions and the chemistry of nitrogen, sulfur and alkali as well as hydrocarbon oxidation. In the case of Air-32, temperature measurements were not available due to measurement issues related to large amounts of soot clogging the suction pyrometer.…”

Alkali Monitoring of Industrial Process Gas by Surface Ionization─Calibration, Assessment, and Comparison to In Situ Laser Diagnostics

“…Propane was used as fuel, with λ of 1.15 and with a resulting flue gas composition composed of 11.8 vol % CO 2 (dry), 2.95 vol % O 2 (dry), and 14.6/13.6 vol % H 2 O, for operation with and without liquid injection, respectively. The used operating conditions are consistent with established conditions used in previous work, in which a detailed temperature profile and gas composition are available . Alkali salts are injected as a liquid, and the flow rate is set and monitored using a pump (delta 1612, ProMinent).…”

“…The used operating conditions are consistent with established conditions used in previous work, in which a detailed temperature profile and gas composition are available. 5 Alkali salts are injected as a liquid, and the flow rate is set and monitored using a pump (delta 1612, ProMinent). To achieve a stable reference concentration, 0.9 L h −1 KCl(aq) with a concentration of 3.34 wt % was injected, which corresponds to 100 ppm of KCl in the flue gas, assuming complete combustion and that all injected KCl remains as KCl.…”

“…Alkali compounds may also interfere with the combustion chemistry and can either promote or inhibit the fuel oxidation depending upon specific conditions. For example, the presence of volatile alkali compounds may affect the formation of flue gas pollutants, such as NO x , SO 2 , and CO, by either direct reactions or indirectly by influencing the radical pool. − In contrast, alkali compounds may also have beneficial effects on the thermal conversion of carbon fuels by increasing the conversion kinetics and reducing the level of unconverted hydrocarbons. , For example, various additions of alkali metals have been used to increase commercial gasification processes for both coal and biomass . However, the mechanisms and reaction chains are not yet fully determined.…”

Recirculation of NOx and SOx Scrubber Effluent to an Industrial Grate Fired MSW Boiler─Influence on Combustion Performance, Deposition Behavior, and Flue Gas Composition

“…It has, for example, been shown that the injection of KCl (aq) in a propane flame can both influence fuel oxidation and depress the formation of NO. It was also shown that the effect of injection could change from inhibiting to promoting, depending on the combustion conditions. , Another study focused on the recirculation of a liquid containing H 2 SO 4 in a full-scale waste-to-energy plant . It was found that it had a clear effect on the aerosol and deposition formation in terms of reduced corrosion and the deposition growth rate.…”