以Hg^(2+)离子为前驱体标定煤热解气中气相元素汞量

Using Hg^(2+) as a Precursor to Calibrate Gaseous Elemental Mercury from Pyrolysis of Coal

汞易挥发且通常以气态形式在大气环境中迁移转化,检测汞在气相中的含量可为汞的治理工作提供依据,但检测气相汞的技术并不成熟。该项工作需要准确地对气相元素汞量进行测定,而测定的前提是必须具备准确、可靠的标定方法。本研究提出以Hg^(2+)离子为前驱体标定煤热解气中气相元素汞量的方法。该方法是基于水溶液中Hg^(2+)可被还原剂定量还原成元素汞蒸汽的原理,实现对气相元素汞量的标定。与传统的基于饱和蒸汽原理的标定方法相比,该方法的优点是取样时不易受温度影响,易于精确控制汞量,且避免了实验室内储存汞蒸汽所造成的汞污染。以测定四种煤在热解过程中元素汞的释放量为例考察了本方法的准确性,结果表明本方法具有较好的重复性和适应性。与美国Ontario-Hydro方法分析的结果进行对比,两种方法的相对标准偏差均小于3.0%,说明本研究的标定方法的可靠性较高。

Mercury is easily volatile and vaporizes in air. The monitor of mercury in gas phase provides insight for developing advanced Hg control technologies. However,the analytical method of gas mercury is rudimentary. In order to determine the gas mercury content,a reliable calibration method is needed. This study provides a method of calibrating gas mercury from pyrolysis of coal with Hg^(2+)as a precursor. The method is based on the principle that Hg^(2+)in aqueous solution can be quantitatively reduced by reductant into elemental mercury vapor to determine the calibration of mercury content in gas phase. Compared with the conventional calibration method based on the saturated vapor principle,this method eliminates the influence of the sampling temperature,the quantity of mercury during sampling can be easily controlled,and pollution of the gaseous mercury stored in the laboratory is avoided.To illustrate the accuracy of the calibration method,the quantity of elemental mercury emission during pyrolysis of four coals were determined. Results show that the method has good reproducibility and adaptability. Compared with the Canadian Ontario-Hydro method,the relative standard deviations of both methods are less than 3. 0%,indicating a high reliability of this calibration method.