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The Study on Coal Ash Fusibility and Viscosity-temperature Characteristics

Author: LiDeXia
Tutor: ZhouZhiJie
School: East China University of Science and Technology
Course: Chemical processes
Keywords: coal ash fusibility viscosity rheology predictive model FactSage
CLC: TQ530
Type: Master's thesis
Year: 2012
Downloads: 51
Quote: 0
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Abstract


Coal ash fusibility and viscosity-temperature characteristic affect the operation temperature of gasifiers, the life of refractory bricks and water-cooled walls, and the normal operation of the gasifier directly. Therefore, the research on ash fusibility and viscosity-temperature characteristics is very important in measuring the adaptability of coal samples for high-temperature gasifiers and solving the blocking and hanging slag problems in industrial gasification.(1) An obvious fluctuation of viscosity-temperature curve of Yulin coal ash with high basic oxides is first studied. There exists blocking in real gasification process for this kind of coal samples. X-ray diffraction (XRD) combined with FactSage Thermochemical Modeling was used to calculate ternary equilibrium phase diagram and phase change rules of Yulin coal ash under different high temperature range to analyze the changes of ash fusion and viscosity-temperature characteristics caused by the addition of SiO2 and the reason for viscosity fluctuation from the formation of crystalline matters viewpoint. Otherwise, three comparative samples were choosen to explain viscosity fluctuation. It was revealed that bulk formation of gehlenite within special temperature range was directly corrected with viscosity fluctuation. Way to alleviate the viscosity fluctuation of them has been presented:adding appropriate SiO2 obtained with binary phase diagrams calculated by FactSage. Further work is needed with regards to coal ash slag viscosity fluctuation caused by crystalline minerals for such style of coals in the laboratory scale and industrial utilization.(2) According to the content of CaO and Fe2O3,21 kinds of laboratory coal samples were divided into four categories to study their fusion and viscosity-temperature characteristics. With the use of FactSage thermodynamic equilibrium calculation, the effect of original S/A in coal ash, the composition and content of minerals in high-temperature slag and the composition changes in homogeneous slag on fusibilities and viscosities of four coal categories were researched. The rules of viscosity-temperature characteristics about four coal categories with different ash composition were obtained, which provides a simple and practical assessment criterion for the prediction of viscosity-temperature characteristics of other coal samples and the choose of available coals for gasification. Furthermore, the cost of experimental measurement can be reduced through these conclutions.(3) Based on muti-burner impinging entrained-flow gasifier, the rheology of Shen coal ash slag was studied preliminarily. Through the viscosity calculation of Shenfu coal ash slag with the use of 9 Newtonian and 4 non-Newtonian viscosity models, the homogeneous and non-homogeneous models suitable for the viscosity prediction of Shenfu coal were obtained. Meanwhile, the non-homogeneous viscosity forecasting formulas which is available for Shenfu coal was established through factor correction.(4) On the basis of 181 kinds of coal ash flow temperature, the FT prediction model associated with ash composition and acid/basic was set up, and the correlation coefficient is 0.9341. Meanwhile, the incidence formula between FT and the liquidus temperature, which has good applicability, was established according to thermodynamics viewpoint.

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