Study On The Coal Ash Melt Characteristics Formed In Different Geological Ages In Erdos

The requirements of coal quality are various for different coal chemical technology.The coal ash melt characteristics is a very important coal quality index,especially for combustion and gasification.For unsuitable raw coal,it is necessary to be adjusted by a certain method such as coal blending,one of the principal ways to improve the melt characteristics of coal ash.In this paper,the coal ash melt characteristics in Erdos had been systematically studied using ash fusion temperature tester,coal ash high temperature viscometer,X-ray diffractometer,scanning electron microscopy,optical microscope,heating stage microscope,and thermodynamic software FactSage.The difference of mineral composition between two coals at different forming periods in Erdos area,the impact of coal ash composition to coal ash fusibility,the influence of coal blending on coal slagging and thermal conversion characteristics of minerals were investigated.And AFTs model based on large data,blending coal AFTs model and viscosity model suitable for Erdos area were finally established.The main conclusions were as follows:Adding SiO₂、Fe₂O₃、CaO、MgO、Na₂O to the permo-carboniferous coal,the ash fusion temperature represented a basic trend first of first decreased and then increased.With the addition of SiO2、Fe2O3、CaO、MgO、Al2O3,the melting temperature of Jurassic coal ash was improved to some extent,especially when Al2O3 was used,while the ash fusion temperature decreased firstly and then increased with the addition of Na2O.The minerals in the Jurassic coal in Erdos were mainly quartz,calcite,gypsum,hematite and feldspar,while that in permo-carboniferous coal were boehmite and kaolinite.Kaolinite,boehmite and quartz were refractory mineral,however,calcite,gypsum,hematite and feldspar were fluxing minerals.The difference of mineral composition between Jurassic coal and permo-carboniferous coal in Erdos was the most important factor that caused the huge difference of coal ash melt characteristics.Through the study of mineral thermal transformation,it was found that the phenomenon of mineral transformation and low temperature co-melting in the heating process of coal ash had a great influence on the properties of coal ash slag.From the coal ash fusibility and viscosity temperature characteristics,ash slag melt characteristics were improved by blending Jurassic coal and permo-carboniferous coal,so as to meet the requirements of industrial and expand the scope of application of the coals in Erdos region.Trough Thermodynamic software FactSage simulation,it was found that the liquid phase was formed between 900～1000℃ in the heating process for coal ash samples in Erdos area.The temperature when coal ash system completely converted to liquid phase was 100～200℃ higher than FT.Using the high-temperature thermo-stage microscope combined with viscosity-temperature characteristics tester,it could be observed in the process of cooling,anorthite drop from fully melting state of Jurassic coal ash to the occurrence of crystallization in short temperature range,which resulting in the rapid increase of viscosity value.The coal ash fusion temperature and viscosity prediction models have been established for Jurassic coal in Erdos region.In addition,the blending coal ash fusion temperature prediction model was also established for Jurassic coal and permo-carboniferous coal in Erdos region.