Study On Influential Factors Of Coal Ash Fusion Temperature And Its Controlling Countermeasures

Melting characteristics of coal ash is an important indicator. Slagging threat the economyand security of the coal burned boiler. It is very important to study the impact factors of coalash fusion on the full utilization of coal resource. In this paper, six kind of coal ash were usedto study the theory of the coal ash fusibility. SEM、ternary diagram and XRD technique wereused to analyze the surface morphology as well as the crystalline compositions of the residue.According to about300groups data of coal ash composition and melting point, the model forcoal ash fusion was set up by use of genetic algorithm and global optimization.This article focuses on the impact of coal ash composition to coal ash fusibility, and toexamine impacting trends of the different mineral composition in coal on coal ash fusibility.Firstly choosing the A coal as research objects, and coal ashing standardly the coal samplesunder the conditions of815℃, then determining the contents of Fe2O3, SiO2, CaO, Al2O3,TiO2, MgO and P2O5in coal ash samples by XRF, at last, compounding the man-made coalash similar to original coal ash, by the way of controlling the variables to change the compo-nents in the man-made coal ash, the impact of chemical composition on coal ash fusibilityhave been investigated. Fluxs, mineralizing agent and coal blending were usd to regulate coalash fusion.The results show that, coal ash fusion temperature decrease initially, and then increasewith increasing Al2O3and CaO. The lowest point of the coal ash melting point appears whenthe content of Al2O3and CaO is15%and20%in coal ash. CaO could decrease the coal ashfusion temperature of A coal at a certain range. During the heating process, it reacted with thecompounds such as mullite and silica, to form several types of the high calcium containingcontent．These compounds formed eutecfic compounds, so the coal ash fusion temperaturedecreased. When CaO in coat coal ash preponderate over a certain extent, the coal ash meltingpoint was improved by the formation of pseudowollastonite and melilite.Al2O3content isgenerally less than15%, so it usually plays a role to improve the coal ash melting point. TiO2content can increase the coal ash fusion temperature, every0.5%increase in TiO2is linkedto12~15℃increase in melting point. While SiO2increased, coal ash fusion temperature in-creases and decreases, and then increases and decreases again. Coal ash fusion temperaturewill decrease along with the increase of Fe2O3, MgO and Na2CO3. A number of eutectic couldhave lowered the melting point of coal ash fusion temperature, such as SiO2-Al2O3-Fe2O3andAl2O3·SiO2-2FeO·SiO2-SiO2.Coal ash fusion point can be reduced effectively by coal blend technique. The changes ofcoal ash fusion point for tow blended coal do not meet the linear. Coal ash fusion point ofblended coal is similar to the temperature of liquid phase of Al2O3-SiO2, but lower than the resulting temperature in a ternary phase diagram。The ternary phase diagram can predict coal ash melting point, but the coal ash melting temperature is lower than the prediction. When the single coal have a same mineral in the Al2O3-CaO-SiO2, linear coefficient of the melting points and blended ratio of blending coal is larger. Coal ash melting temperature of the blended coal can lower than that of single coal when the connection of the two single coal passes through the low temperature eutectic area in the Al2O3-CaO-SiO2-Mineralizer and mixing additive can regulate coal ash fusion temperature by promoting or inhibiting formation of high-melting crystalline minerals to regulate coal ash fusion tem-perature can raise coal ash fusion temperature by promoting or inhibiting the generation of high-melting crystalline mineral. The effect of mineralizer is influenced largely by type, quantity and coal ash composition. V2O5and NaF increase coal ash melting temperature through promoting the formation of mullite. The effect of CaO/SiO2(13/7) is better than that of CaO to reduce the melting temperature of F coal ash. Compound additives can regulate coal ash fusion temperature effectively than single additives.Based on the research of coal ash composition phase diagram distribution and regulation mechanism of the coal ash melting point, according to experimental data of nearly300group coal ash composition and coal ash melting point, coal ash melting point prediction formula is established, neural network algorithm and general global optimization method is used in the optimization of the model. According to about43group data to testing the model for coal ash fusion, the performance was perfect.