Experiment Study On The Slagging And Fouling Characteristics During Zhundong Coal Combustion

Zhundong region is one of the most coal-enriched areas in Xinjiang, of which the storage was predicted to be 390 billion tons. Limited by the geographical location and transportation conditions, Zhundong coal was planed to be extensively applied in local power plants. However, the strong slagging and fouling characteristics seriously limited its application in power plants. In this paper, many works was conducted to study the slagging and fouling characteristics of Zhundong coal.Based on the mineral quantitative and thermal analysis of four typical Zhundong low-temperature ash(WCW-LTA, WD-LTA, TC-LTA and TCTN-LTA), the melting dynamic curves of which were calculated. Compared with the conventional ash molten measuring method, the initial ash melting temperature of high-sodium coal was 150? lower than its deformation temperature(DT), the LTA had melted nearly 50% when the temperature rose to DT. The initial ash melting temperature of low-sodium coal was 200? lower than DT, TCTN-LTA had melted nearly 40% when the temperature had not reached DT. The melting curve calculated by MQTA method better reflects the ash fusion process than the ash molten measuring method.The slagging characteristics of four Zhundong coals mentioned above was researched on the one-dimensional flame furnace, two different furnace outlet oxygen content was considered. The results shows that all the Zhundong coals are easy to be burned off. The 4,6-grade ash samples of WCW and TC coal are black film-like slags, which is severely slagging. The fouling and slag degree of TCTN coal is moderate, and WD coal is weak. Ash elemental analysis suggested that Ca, Fe, Na and S are the dominant elements that caused the slagging and fouling of Zhundong coal. Further studies show that these elements concentrate more in 6 grade(about 800?) ash. The high melting point Al mitigates slagging tendencies of Zhundong coal. When the furnace outlet oxygen content is 2.5%, more sodium trend to coexist with Ca, Al and Si, forming a sintered wound feldspar-like components. Sintered particles collected from low sodium coal experiment are mostly enriched with Al and Si, which are weakly bonded.Studies on the ash samples gathered from Zhundong coal-fired plant show that sodium components mostly deposit on the convection heating surface(about 700?), and the enrichment of block ash is more than floating ash. XRD analysis shows that CaSO4 trends to exist in the ashes gathered from the medium-low temperature heating surface, labradorite and anorthite are detected in the high temperature zone of the furnace. Na mostly exists in the form of labradorite and potassium sodium aluminosilicate when the temperature is high, but in the form of sodium iron sulfate and sodium magnesium iron sulfate when the temperature is medium and low. The factor of temperature has great influence on the enrichment form of sodium and calcium. ESEM-EDX analysis further validated the exist of mineral composition in the ash. Mineral components with low melting point such as sodium sulfate, albite, calcium sulfate, anorthite, sodium iron sulphate and labradorite are flow-like, components like mullite and quartz with high melting point are spheres. Components enriched with sodium and calcium play an important role in the formation and growth of the slags produced during Zhundong coal combustion.