Experimental Study On Hg~0 Removal In Flue Gas By Fly Ash-CaO Adsorbent Combined With HBT Filter

Mercury pollution caused by coal is widely concerned. The physical and chemical properties of elemental mercury determine that mercury pollution control technology mainly focuses on how to control mercury aspects. The development of control technology for mercury emissions from coal-fired has been regarded as one of the important researches, which belongs to China's 863 Program. The research content in this report is an important part of these projects.Firstly simply introduced fixed bed experimental system and method of computation, secondly mixed fly ash and CaO to produce fly ash-CaO adsorbent according to an advanced mixture ratio. Electronic microscopy scanning and related physical parameters analysis on fly ash and fly ash-CaO showed that surface of fly ash-CaO adsorbent was really rough and had erosion. Many small particles was added on the surface of Fly ash which formed many folds and increased specific surface area. At mean time micro porous structure get rich.The paper studied Hg0 in simulated flue gas removal performance of coal fly ash and fly ash-CaO adsorbent on fixed bed model test system and discussed affection of fly ash and fly ash-CaO adsorbent's Hg0 removal performance by many factors such as different fly ash and CaO mixing ratio, mercury entrance concentration, adsorption reaction temperature, particle size distribution and HCl atmosphere & etc. This study provided useful reference for research on Hg0 removal performance in simulated flue gas of fiber filter load of fly ash - CaO adsorbent. The research showed that coal fly ash has some removal ability on Hg0 Though less efficient than activated carbon, fly ash is famous for its low price and high value in use. Hg0 adsorption efficiency of fly ash-CaO adsorbent mixed by fly ash and CaO was obviously higher than fly ash.2:1 mixture ratio is the best. Hg0 adsorption efficiency of fly ash-CaO adsorbent was affected by adsorption reaction temperature, particle size distribution and HCl atmosphere. With the increasing of concentration of mercury entrance, Hg0 adsorption efficiency of fly ash various but the adsorption amount increased. HgO adsorption efficiency in simulated flue gas of 2:1 mixture ratio of the absorbent rise with the adsorption reaction temperature decreased which meant physical adsorption had the dominate place during the adsorption process. Hg0 adsorption efficiency various from the particle size of fly ash - CaO adsorbent. Size at 43-75μm could have 41% absorption efficiency which was the best. Hg0 adsorption efficiency of fly ash-CaO absorbent rise with the HCl concentration in simulation gas increased. But the rise did not present a linear growth, which is because HCl could improve the Hg0 chemical adsorption of fly ash - CaO absorbent, thus increased adsorption efficiency.Affection of simultaneous Hg0 removal performance by fly ash combined with fiber filter and fly ash - CaO adsorbent combined with fiber filter were researched on fixed bed. Affection of fiber filter loaded adsorbent dust layer's Hg0 removal performance by many factors such as particle size distribution, mercury entrance concentration, adsorption reaction temperature and HCl atmosphere & etc.Research showed that HBT filter load fly ash - CaO adsorbent dust layer had higher simultaneous Hg0 removal performance than HBT filter load fly ash dust layer. It can be acknowledged by the analysis of fly ash-CaO adsorbent combined with HBT filter's simultaneous Hg0 removal performance experiment that with the increase of mercury entrance concentration, the simultaneous Hg0 removal efficiency did not rise but presented irregular variations. The simultaneous Hg0 removal efficiency decreased with the rise of adsorption reaction temperature which meant physical adsorption dominated the adsorption process. Hg0 removal efficiency of HBT filter load fly ash-CaO adsorbent increased with the rise of HCI concentration in simulation gas.At last, the paper established dynamic model of elemental mercury adsorption separately by fly ash adsorbent, fly ash-CaO adsorbent and fiber filter load fly ash-CaO adsorbent according to the gas phase equilibrium in adsorption bed and mass balance in hole of adsorbent. After that, the paper obtained some parameter within the adsorption process by combining the dynamic model with the result of the experiment and provided reference for further prediction.