Research On Calibration Techniques For Continuous Emission Monitoring System Of Mercury In Flue Gas

Mercury, also known as quicksilver, is the only metal that is liquid at standardconditions for temperature and pressure and easy flow. Mercury as a global pollutanthas three characteristics: highly volatile, highly diffusible and bioaccumulation. Thehuman factor is the main cause of global mercury pollution emissions at presentstage, in which coal-fired is the largest source of anthropogenic mercury emissions.China is one of the world ’s most polluted areas of mercury pollution. The currentsystem of coal-fired power plant flue gas mercury emission monitoring technology inChina is not yet mature, the total gaseous mercury in the flue gas monitoring is stillin the blank stage, now domestic coal-fired power plant boiler is not yet equippedwith Hg CEMS equipment for continuous monitoring of mercury emission of fluegas. Therefore, it can provide powerful basis for setting limits and correspondingemission standards on mercury emissions from coal-fired power plants to study themonitoring methods of mercury emissions from coal-fired power plants. Mercuryanalysis technology has been very mature, commonly used methods include coldvapor atomic absorption spectrometry (CVAAS), cold vapor atomic fluorescencespectrometry (CVAFS), etc., as well as atomic emission spectroscopy (AES), atomicabsorption spectroscopy, zeeman atomic absorption spectrometry (ZAAS), ultravioletdifferential optical absorption spectroscopy (UV-DOAS), etc., but the object of allanalytical techniques are elemental mercury (Hg0). Regardless of the measurementtechnology and transformation systems, measuring instruments must be calibrated asa test. In order to obtain a practical method for elemental mercury standard gasgeneration, The following work is described in this paper:1.The mercury vapor saturation method as a simple and practical method forgenerating elemental mercury standard gas has aroused great concern. Based on themethod of measuring saturated vapor pressure, saturated flow method, the experimentprinciple of element mercury standard gas generator is designed.2. In order to analyze the generated elemental mercury standard gas，build acontinuous emission monitoring system for element mercury, based on Lambert-Beer law to analyze the elemental mercury calibration gas of different concentrations.3. Select the permeation tube method as a reference standard to verify theaccuracy and feasibility of mercury vapor saturation method. Concentration ofmercury vapor generated by penetration tube method as the standard, by using therelationship between concentration and absorbance area deduced mercury vaporconcentration of mercury vapor saturation method, and comparing with the theoretical values to determine the accuracy of the mercury vapor saturation method.4.By comparing with the pulsed xenon lamps, low pressure and high pressuremercury lamp and xenon lamp, it is concluded that low pressure mercury lamp isa kind of high stability and reproducibility of the light source, it is very suitable toanalysis mercury vapor as a light source.5. Summarizes the influence factors in the process of experiment, of which thestability of light source is the main influence factors. In addition, the adsorption ofmercury absorption cell will also affect the concentration of generated standardmercury gas.