Participation of alkali and sulfur in ammonia combustion chemistry: Investigation for ammonia/solid fuel co-firing applications

Ammonia (NH3) is a promising carbon-free energy carrier. Co-firing of ammonia in solid fuel-fired facilities feasible solution to reduce carbon dioxide (CO2) emissions. Solid fuels, such as coal and biomass, contain various trace elements, alkali metals sulfur, which are released the gas phase during combustion. Experimental characterization modeling used study participation sulfur species conversion post-flame environment, focusing on characteristics NO emissions NH3 slip. The combustion environment was provided by laminar flame burner with temperature decreasing from about 2000 K reaction zone 1500 or 1100 flue an equivalence ratio around 0.65 1.3. Known amounts (up 20,000 ppm), potassium hydroxide (KOH, representative alkaline substances, up 25 (SO2, ppm) were uniformly introduced into for high-temperature thermochemical research. concentrations NH3, nitric oxide (NO), KOH, SO2, hydroxyl radicals (OH) downstream measured quantitatively situ using broadband UV (ultraviolet) absorption spectroscopy. In oxidizing environments, influence SO2 formation negligible, while KOH significantly reduced concentration NO, even led residual low case. Under reducing conditions, both inhibited decomposition ammonia, especially at relatively temperature. Meanwhile, consumption KOH/K observed after mixing possibly due direct ammonia. One dimensional detailed mechanism containing N/S/K chemistry qualitatively predicted impact S/K oxidation decomposition. effect mainly contributed enhanced radical KOH. However, model could not describe Potassium amide (KNH2) can be generated through + = KNH2 H2O. according quantum calculations KNH2, this endothermic 80 kJ mol−1, shifting equilibrium strongly towards more work required clarify removal NH3.