| Mercury is one of the many toxic trace elements in coal, in the coal combustion process, most of the mercury in the coal volatiles into the atmosphere with the flue gas. It attaches great attention of domestic and foreign researchers because of its long residence time in the atmosphere and easy to accumulate in living organisms, and after entering the food chain mercury compounds will endanger human health. One of the important research content of the state863projects is the mercury emission control technology development, and the research content of this paper is an important component part of the projects.Firstly the fixed-bed experimental system and method of calculation was introduced, and the different mass mixing ratio of fly ash-CaCO3formulated samples of adsorbent to remove Hg0in simulated flue gas were studied. The results showed that in the atmosphere of N2and4%O2under the temperature of120℃, The highest removal rate of different mixing ratio of fly ash and CaCO3sample of adsorbent was lower than the condition of the pure fly ash, showed this formula type adsorbent cannot obviously improve the mercury removal efficiency.Using different concentrations of KMnO4solution to modify the fly ash-CaCO3sample of adsorbent, and it was the same with different concentrations of KBr. The results showed that with the modified by different concentrations of KMnO4, the removal efficiency of Hg0by fly ash and CaCO3sample of adsorbent had an increase to a certain extent and the removal efficiency reached64%, but it also didn’t have an obvious increase. What was worth noteworthy is that, when the concentration of KMnO4was different, the removal efficiency had an obvious change. With the modified by different concentrations of KBr, the removal efficiency of Hg0by fly ash and CaCO3sample of adsorbent, the removal efficiency had a significantly improved. However, with the increasing amount of KBr, the mercury removal efficiency didn’t have a corresponding increase. It would have the highest rate of vemoval efficiency when the amount of5%, and it would have a slightly decline when it was10%.The experiment on Hg0removal from coal-fired flue gases was conducted with a fixed-bed experimental system, in which the Hg0removal efficiency of formulated fly ash-calcium based adsorbents loaded by PPS filter material and the effect of the different temperature and gases were studied. And the removal and influence mechanism were carried on the deep discussion.The results showed that in the atmosphere of N2and4%O2under the temperature of120℃, the removal efficiency of Hg0could reach72%when the mass mixing ratio of fly ash and Ca(OH)2was2:1, the higher adsorption of reaction temperature, the lower removal efficiency of Hg0, indicated the high temperature was not conducive to mercury removal. In the condition of10ppm HCl and40ppm HCl, the removal efficiency could reach80%, made an increase by about20%compared the condition without HCl, indicated that HCl had a strong role in promoting on the removal of mercury. With the different concentrations, the removal effect had little difference, indicated small amount of HCI sufficient to substantially improve its removal effect. In the condition without SO2, the removal efficiency could reach65%, and in the condition of SO2, the removal efficiency could increase7%to15%, showed that SO2had a certain role in promoting. However, the NO almost had no promoting effect on the removal efficiency, in the condition of100ppm NO, the removal efficiency just had an increase about1%to2%, and could even be considered to be due to error, when the concentration of NO increased to200ppm, the removal efficiency could reach73%, and the effect was still not clear.In the atmosphere of N2and4%O2under the temperature of120℃, the removal efficiency of Hg0could reach61%when the mass mixing ratio of fly ash and CaCO3was3:1, with the temperature increased from80℃to160℃, the removal efficiency decreased from64%to53%, the rise of temperature was not conducive to the mercury removal. Different concentrations of HCI all had a certain degree of role in promoting to the removal efficiency of Hg0by the sample of adsorbent, the removal efficiency of Hg0could reach72%, and made an increase by14%compared the condition of no HCI, and the concentrations of HCI made little difference on the removal efficiency of Hg0. The SO2had acceleration on the removal efficiency in some degree, but it was inconspicuous and the addition product had an inhibitory effect on the removal of Hg0. The acceleration of NO was not significant but the Hg0removal efficiency was stable, and90minutes later, the removal efficiency still could reach26%.On the basis of the predecessors, established a simple mathematical model of the fixed bed experimental system of adsorbent for removing elemental mercury. The result showed that the removal efficiency of the simulation result had a good agreement with the test result and the mathematical model cloud simulated the effect of mercury removal by formulated fly ash-calcium based adsorbents in the adsorbing reactor. |
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