Flue Gas Mercury Emission Test And The Experimental Study On Coal-char Sorbents For Mercury Removal

With the country all over the word paying more and more attention to atmospheric mercury pollution, mercury emissions from coal-fired power plants have become a major environment problem that urgently need to solve in China. In all kinds of flue gas mercury control technology, the research of activated carbon injection technology is relatively concentrated and mature, but expensive operation cost limits its extensive application. Different characteristics of mercury have different physical and chemical properties, the existence form of mercury in flue gas decided the mercury removal efficiency. Thus, if mercury control targets are to be met, knowing emission characteristics of mercury in flue gas and looking for efficient, low-cost mercury adsorbent must be done. With the support of the National Natural Science Foundation and Exclusive research fund for the public good granted by Ministry of Environmental Protection of PRC, the research of characteristics of mercury emission from the coal-fired boiler and the cement kilns in China and exploring the application of coal-char as mercury adsorbent is done in the paper.It firstly investigated the mercury speciation emission of a660MW pulverized coal fired boiler system and New dry method shaft kiln cement production line by Ontario-Hydro(OH) method. It is founded that most gaseous mercury goes into flue gas. The proportion of mercury in cinders is very small, only0.2%; with the SCR、 ESP、WFGD, the ratio of gaseous mercury down about50%, but the proportion of elemental mercury in WFGD export will rise with the sulfite’s role of transformation and absorption on oxidation mercury. Gaseous mercury is the main species, mercury is a little in Cement kiln ShuLiao; raw and dust removal device have an effect on mercury speciation.Using the advanced platform on researching mercury forms transform and control, Effect of coal type, pyrolysis temperature、pyrolysis time、gaseous mercury concentration、adsorption temperature and flue gas components on the adsorption characteristic of mercury on coal-char was studied under the simulated flue gas conditions. The mercury adsorption property of coal-char was compared with that of activated carbon. The result showed that:the ability of mercury adsorption on different coal is difference; because pyrolysis temperature and pyrolysis time have an effect on dispersion degree of char mineral gather and the development of pore, they are two important factors that affect char quality and mercury adsorption performance. As the adsorption temperature increase, the performance of coal-chars deteriorates under test condition, the mercury adsorption efficiency is the highest under50℃; the penetration ratio of coal-char increase as the inlet mercury concentration increase; O2and HCl all can promote HgO adsorption on coal-char, make penetration ratio reduce and increase removal efficiency when they are existed alone in the flue gas; SO2will cause competition adsorption and inhibit HgO adsorption on coal-char; NO have no effect on HgO adsorption on coal-char.