气流床气化是煤炭清洁高效利用的重要途径,而高钙镁准东煤因其灰熔融温度较高难以直接应用于液态排渣的工业气化炉,深入研究准东煤灰高温熔融机理对其气化应用具有重要指导意义。采用试验分析与热力学模拟计算手段研究了高温(1100~1500℃)气化条件下高钙镁准东煤灰熔融性及矿物质演化,并考察了SiO2添加对原煤灰熔融性及矿物质演化的影响。结果表明,气化温度小于1300℃时,高钙镁五彩湾煤灰中Ca主要以CaS形态存在于灰渣中,而Mg始终以MgO形态存在;气化温度升高至1400℃后Ca基矿物质逐渐熔于液相并在1500℃完全熔融,Mg则结合生成高熔点镁铝尖晶石,导致煤灰熔融温度较高。添加适量SiO2可与煤灰中Ca、Mg结合生成易发生低温共熔的钙镁黄长石,从而显著降低煤灰熔融温度及液相线温度,所添加SiO2与CaO结合的优先度高于MgO。此外,热力学平衡计算结果显示,即使在1600℃高温平衡状态下,五彩湾煤灰中部分Ca、Mg仍以高熔点单一氧化物形态存在,因此原煤灰液相线温度较高,热力学计算结果可为煤灰熔融性预测及高温矿物质转化提供参考。

Entrained-flow gasification is an important way for clean and efficient utilization of coal,while Zhundong coal with high contentof calcium and magnesium can not be directly applied to industrial gasifiers due to its high ash fusion temperature. The in-depth study ofthe high-temperature fusion mechanism of Zhundong coal ash has important guiding signification for its gasification application. The fusi⁃bility and mineral transformation of high calcium magnesium Zhundong coal ash under high-temperature(1 100- 1 500 ℃ ) gasifica⁃tion conditions were studied using experimental analysis and calculated simulations, and the effect of SiO2 addition on the fusibilityand mineral transformation of raw coal ash was also investigated. The results indicate that when the gasification temperature is below1 300 ℃ , Ca mainly exists in the form of CaS in the high calcium-magnesium Wucaiwan coal ash, while Mg always exists in the formof MgO. When the gasification temperature increases to 1 400 ℃ , Ca-based minerals gradually melt in the liquid phase and complete⁃ly melt at 1 500 ℃ , while Mg reacts to form magnesium aluminum spinel of high melting point, resulting in a higher fusion temperature ofraw coal ash. An appropriate amount of SiO2 can combine with Ca and Mg in coal ash to form the akermanite that is prone to low-tempera⁃ture eutectic, thus significantly reducing the fusion and liquidus temperature of coal ash. Moreover, the combined priority of SiO2 and CaOis higher than that of MgO. The thermodynamic simulation results show that some Ca and Mg in Wucaiwan coal ash still exist in the formof monoxideat the equilibrium state of 1 600 ℃ , leading to a higher liquidus temperature of the raw coal ash. The thermodynamic calcula⁃tion results can provide a reference for fusibility prediction and high-temperature mineral transformation of coal ash.

0 引言

1 试验

   1.1 试验原料

   1.2 煤灰熔融特征温度测定

   1.3 煤灰高温矿物质演化试验

   1.4 热力学平衡计算

2 结果与讨论

   2.1 原煤灰渣高温矿物质演化

   2.2 SiO2添加对煤灰熔融特性的影响

   2.3 SiO2添加对煤灰高温矿物质演化的影响

   2.4 热力学平衡状态下的矿物质组成

3 结论