Experimental Study On Coal Ash Fusion Characteristics Under Gasification Condition

IGCC becomes a significant development direction of CCT. Coal ash fusion characteristics are impoortant influential factors of safe and stable operation in the IGCC system. The coal ash fusion characteristics under this condition few have been studied in the world at present, This paper research this coal ash fusion characteristics by Coal Ash Fusion Characteristics Experimental Facility, Thermobalance, Pressurized Thermal Balance, SEM, XRD and EDS.Thermal analysis experiment results show that the root cause of the difference coal ash fusion characteristics is the chemical and mineral composition of coal ash. Ash melting temperature is not a defined, there are several endothermic peaks during melting process and showing multiple peaks. Atmosphere has an important impact on the results, Air atmosphere could inhibit the decomposition of CaSO4, and CO2 atmosphere could inhibit the decomposition of CaCO3. Heating rate can also affect the results, peak profile becomes not obvious under lower heating rate. However, peak profile is apt to overlap under higher heating.The behavior changes experiment of the mineral matter in coal shows that there exists a great deal of hematite and anhydrite in non-reducing atmosphere including air atmosphere, N2 atmosphere and CO2 atmosphere, but the hematite and anhydrite would gradually disappeare in reducing atmosphere including syngas atmosphere and weak reducing atmosphere. The reaction between CO and CaSO4 forms CaS. CaS and CO2 could form CaO. The reducing gas in the syngas atmosphere could reduce Fe2O3 to FeO which could easily form low melting with the other material and promote ash melting. The promotion depends on the content of Fe in the coal ash. Pressure could inhibit the decomposition of CaSO4 and CaCO3 to a certain extent. The mineral matters exists corresponding relation between cooling process and heating process. The melting mineral matters formed in heating process will be precipitated in cooling process, and the quantity of precipitated will increase within temperature decreasing. Pressure has an inhibitory effect on the decomposition of CaSO4 and CaCO3.The study of surface morphology shows that coal ash fusion is a gradual process in which a larger number of clasti material turned to melt completely. Mineral and melt are mixed highly, and they are mixed deeper under the redusing atmosphere comparing non-redusing atmosphere, the redusing atmosphere can accelerate the coal melting.