Study On The Ecological Technology Of Glass Ceramics From Coal Fly Ash

In this paper, glass-ceramics we re pr oduced with coal fl y ash andsome additive chemicals by the molten sintering process and directsintering process respectively, the CaO-Al₂O₃-SiO₂ternary syste m andCaO-Al₂O₃-SiO₂-MgO-Fe₂O₃ternary syst em were chose, gehlenite andanorthite were determined as the main crystal phase of theglass-ceramics. Method of combining theoretical and experimental, themi neralogical characteristics of the raw materials, basic glasscomposition and ingredient selection, heat treatment system, the impactof heat treatment on microstructure and properties of glass-ceramicssa mples were studied. The ecolog ical utilization technology ofglass-ceramics from coal fly ash was assessed as well.The results show that:①In addition to quartz and Mullite, etc.,Silicate glass was the mainly phase in coal fly ash. The main chemi calcompositions were SiO₂and Al₂O₃, and the other containing a smallamount of Fe₂O₃, MgO and CaO, etc.②The glass-ceramics wereprepared with coal fly ash, limestone and sodium carbonate as the rawmaterials. The method was molten sintering process. And the maincrystal phases of the glass-cera mics produced were gehlenite andanorthite. Five different formulas of the parent glass were chose, andthe incorporation of the coal fly ash was from54.5%to79.1%. With theimprovement of crystallization temperature, the main crystal phase ofthe glass-cera mi c sampl e s in t he sa me for mul a did not change, but theintensity of the main crystalline phase of the diffraction peaksincreased and then decreased; And the gl ass-cerami c samples FCN2-1、FCN2-2、 FCN2-3、 FCN1-5and FCN1-6had the highest compactmicrocrystalline phase structure and comprehensive performance whenthe heat treatment was nucleated at780℃、760℃、760℃、780℃a n d780℃for120min, and then cr ystallization at1050℃for120min.when the temperature up to1100℃, the "dilution" effecting appeared,and resulted in degradation of the performance. The density of the five gl ass-cerami cs samples pr oduced at the optimized heat treat mentconditions was2.70g/cm3to2.82g/c m3, water absorption was less than0.04%, and the maximu m flexural strength loss rate under acid andalkali condition was0.04%to0.26%, and less than0.01%, Moh’shardness was greater than5.5, compressive strength was218Mpa to242Mpa.③The gl ass-cerami cs were pr epared with coal fly ash,calcium oxide and sodium hydroxide as the raw materials. The methodwas direct sintering process. And the main crystal phases of theglass-ceramics produced were gehlenite and anorthite. Four differentformulas of the parent glass were chose, and the incorporation of thecoal fly ash was from57.0%to86.0%. With the i mprovement ofcrystallization temperature, the main crystal phase of the glass-ceramicsa mples in the same formula did not change, but the intensity of themain cr ystalline phase of the di ffraction peaks increased and thendecreased; And the glass-ceramic samples DFCN2-1、 DFCN2-2、DFCN2-3and DFCN4-1had the highest compact microcrystalline phasestructure and comp rehensive performance when the heat treatment washeated at600℃for30min, and then sinering at1160℃、1160℃、1080℃and1140℃for120min. When the temperature was too high, the"oversintering" effecting appeared, and resulted in degradation of theperformance. The density of the five glass-ceramics samples producedat the optimized heat treat ment conditions was2.44g/cm3to2.59g/cm3,water absorption was less than0.05%, and the maxi mum flexura lstrength loss rate under acid and alkali condition was0.12%to0.30%,and less than0.01%, Moh’s hardness was greater than5.5, compressivestrength was162Mpa to194Mpa. Glass-ceramics preparation withcoal fly ash can realize its re source utilization and ecologicalutilization.④Study on the evaluation of ecological technology ofglass ceramics from coal fly ash indicates that the components in coalfly ash can be utilized sufficiently by use it to be preparation ofglass-ceramics, and can realize the utilization of coal fly ash. Thetechnological process is simp le and the technology parame ter is easy toachieve. Glass-ceramics products perfor m excellent performance, and reach the requirement of standard JCT872-872. The production,consumption process and perfor mance of glass-cera mi cs ful ly meet th emodern environmental philosophy, have the very good practica lapplication value, and easy to large-scale industrial production.