Understanding the influence mechanism of sodium-calcium coupling on ash deposition in 660 MW utility boiler: Experiments and a first-principles study

To guarantee the safe and effective running of the boiler and help to solve the issue of ash deposition on the heating surface of the boiler burning high alkali coal, we investigated the properties of ash deposition on many heating surfaces of 660 MW utility boiler utilizing Zhundong coal. Furthermore, the formation process of first layer of ash deposition under the coupling action of sodium and calcium was investigated using first principles. The findings revealed that for the actual boiler, ash deposition could be clearly split into inner and exterior layer. Clearly for the outer layer of the high temperature reheater, the concentrations of Na, Ca, and S on the surface of ash particles are higher than those inside ash particles. The large concentrations of alkali and alkaline earth metal sulfates on the surface of ash particles aggravate ash deposition. It was demonstrated by examination of binding energy, electron density difference, and electron orbital density of states that single calcium may be hybridized with Fe 3 O 4 (111) surface more easily than single sodium atom. Moreover, the interaction of sodium and calcium might worsen their deposition on the surface of Fe 3 O 4 (111). AIM studies shown that the interaction between particles and surface in certain binding systems is non-covalent. Furthermore, the interaction of the surface-based particles is essentially closed shell with occasional covalent connection. IGM theory clarifies the shape and place of weak interaction even further. The preceding studies are rather important for the burning of high alkaline coal, biomass, and waste.