高碱煤中碱金属及氯元素析出特性

Release characteristics of alkali metal and Cl species in high alkali coal

煤灰的理化特性与灰化温度密切相关,试验研究了不同灰化温度下高碱煤中碱/碱土金属以及氯元素的析出特性,分别采用X射线荧光光谱分析(XRF)与电感耦合等离子光谱分析(ICP-OES)对样品成分进行分析,并对结果进行对比。结果表明,煤的灰分和煤灰中的碱金属含量随灰化温度的升高而降低,碱土金属含量变化不大;Cl元素析出温度低于500℃,且在815℃前基本完全析出;Na元素的析出特性与煤中Cl元素含量密切相关;低温灰化造成高灰分煤种碳燃尽困难,但对碱金属测量造成的相对误差有限,ICP-OES对于元素含量测试的结果低于XRF,但2种测试方法获得的碱/碱土金属元素含量随灰化温度的变化趋势一致,前者具有更高精度,因而推荐采用ICP-OES测试方法测量碱/碱土金属的含量。

The physical and chemical characteristics of coal ash are closely related to the ashing temperature.The release characteristics of alkali/alkaline earth metal（ AAEM） and chlorine in high alkali coal were investigated experimentally at different ashing temperatures. The content of AAEM and Cl in different samples were analyzed and compared by X-ray fluorescence spectroscopy（ XRF） and inductively coupled plasma optical emission spectroscopy（ ICP-OES）.It is found that ash contents and alkali metal contents in coal ash decrease with increasing the ashing temperature,while the change of alkaline earth metal is insignificant.The release of chlorine starts at temperature below 500 ℃,and completely release before 815 ℃. Na release characteristic is closely related to the content of chlorine in the coal. Low-temperature ashing is difficult to burnout the carbon in high ash coals,however,its relative error in alkali metal measurement is limited.The content of element detected by ICP-OES is lower than that of XRF,however,the alkali/alkaline earth metal content obtained by the two test methods is consistent with the change of the ashing temperature.Therefore,it is recommended to use the ICP-OES to measure AAEM content due to its higher accuracy.