铁基改性活性炭吸附净化烟气中单质汞研究

发布时间：2019-03-15 16:15

【摘要】：液态金属汞是因具有持久性、生物累积性和神经毒害作用目前被高度重视。铅锌冶炼烟气中排放汞的形态主要以Hg0为主,难以被现有的污染控制设备去除。而利用Hg2+的高溶解度,将Hg0氧化为Hg2+,是控制Hg0排放的有效途径。目前国内外对燃煤烟气中汞的去除进行了大量研究,但对铅锌冶炼烟气中汞的排放研究比较少,所以本文在模拟冶炼烟气汞浓度的条件下,研究了改性炭对汞的吸附净化效果。本文从载体,活性组分,浸渍浓度,焙烧温度,反应温度,进口汞浓度,体积空速,含氯金属盐几个方面分析对吸附效率的影响进行分析。通过不同载体筛选确定工业煤质活性炭(AC)为最佳的汞吸附汞载体。空白活性炭的穿透时间为330min,穿透吸附容量达到1.4840 mg/g。不同活性组分筛选对比实验发现FeCl3是最佳改性组分,其穿透吸附容量是空白活性炭的2.454倍,达到了3.642mg/g。五种活性组分的吸附性能呈现以下趋势：Fe/AC Zn/AC Ni/AC Ce/AC Co/AC;浸渍浓度改变,改性活性炭的穿透吸附容量也在变化。不同浸渍浓度Fe3+改性活性炭对Hg0的吸附效果从大到小排列0.15mol/L 0.10mol/L 0.20mol/L 0.30mol/LAC。焙烧温度对吸附效果的影响较为复杂,温度过低和过高对Hg0吸附净化都不利,最佳焙烧温度为300。C。随进口汞浓度的增加,活性炭对Hg0的吸附量也在增大；汞浓度的增大在一定程度上能提高吸附过程中的推动力,进入增加汞的吸附速率。体积空速的增加会缩短了Hg0气体分子在吸附剂床层表面的接触和停留时间,进而导致脱汞性能的降低。给普通活性炭表面负载金属氯化物,会在活性炭表面形成新的活性位,这些物质与汞有较强的亲和力,可以与汞反应生成更稳定的HgCl2等,其可优先对Hg0进行化学吸附,极大的提高了活性炭的脱汞效率。采用扫描电镜(SEM)、N2等温吸附脱附曲线、X射线光电子能谱表征(XPS)、X-射线衍射(XRD)和红外光谱分析(FT-IR)等方法对吸附剂进行表征。分析发现活性炭AC具有高活性、高比表面特征,是负载汞的最佳载体。XPS表征发现,300℃焙烧的改性活性炭在711.4和725.22eV出现两个明显的峰,认为改性吸附剂上的铁以+2,+3混合价态存在。由XRD表征分析知,活性炭样品有炭的特征衍射峰,表明活性炭性有完整的炭结构,其可以为汞吸附提供大的比表面积和多的吸附位点。由红外表征知,300℃焙烧更有利于羟基的形成,该官能团在某种程度上对汞的吸附有利。总体来说,三氯化铁改性活性炭具有良好的汞吸附性能,并且价格成本低廉,具有良好的工业应用前景。
[Abstract]:Liquid metal mercury is persistent, bioaccumulative and neurotoxic. Hg0 is the main form of mercury emission in lead-zinc smelting flue gas, which is difficult to be removed by the existing pollution control equipment. Using the high solubility of Hg2 to oxidize Hg0 to Hg2 is an effective way to control Hg0 emission. At present, a lot of research on mercury removal from coal-fired flue gas has been carried out at home and abroad, but there is little research on mercury emission from lead-zinc smelting flue gas. Therefore, under the condition of simulated mercury concentration in smelting flue gas, the adsorption and purification effect of modified carbon on mercury has been studied in this paper. In this paper, the effects of carrier, active component, impregnation concentration, calcination temperature, reaction temperature, inlet mercury concentration, volume space velocity and chlorine-containing metal salt on the adsorption efficiency were analyzed. The industrial coal activated carbon (AC) was selected as the best carrier for mercury adsorption by screening different carriers. The breakthrough time of blank activated carbon is 330 min and the breakthrough adsorption capacity reaches 1.4840 mg/g.. By screening and comparing different active components, it was found that FeCl3 was the best modified component, and its breakthrough adsorption capacity was 2.454 times that of blank activated carbon, which reached 3.642 mg 路g 路kg-1. The adsorption properties of the five active components showed the following trends: the Fe/AC Zn/AC Ni/AC Ce/AC Co/AC; impregnation concentration changed, and the breakthrough adsorption capacity of the modified activated carbon changed. The adsorption effect of activated carbon modified with Fe3 with different impregnation concentration on Hg0 ranged from large to small arrangement of 0.15mol/L 0.10mol/L 0.20mol/L 0.30mol / L LAC. The influence of calcination temperature on the adsorption effect is more complex. The low temperature and too high temperature are not good for the adsorption and purification of Hg0. The optimum calcination temperature is 300.C. With the increase of import mercury concentration, the adsorption capacity of Hg0 on activated carbon is also increasing, and the increase of mercury concentration can increase the driving force of the adsorption process and increase the adsorption rate of mercury to a certain extent. The increase of volume space velocity will shorten the contact and residence time of Hg0 gas molecules on the surface of adsorbent bed, which will lead to the decrease of mercury removal performance. When metal chloride is loaded on the surface of activated carbon, new active sites are formed on the surface of activated carbon. These substances have strong affinity to mercury and can react with mercury to form more stable HgCl2, which can be chemisorbed to Hg0 first. The mercury removal efficiency of activated carbon is greatly improved. The adsorbents were characterized by scanning electron microscopy (SEM), N 2) isotherm adsorption desorption curve, X ray photoelectron spectroscopy (XPS), (XPS), X ray diffraction (XRD) and infrared spectroscopy (FT-IR). It was found that the activated carbon AC had high activity and high specific surface area, and was the best carrier for carrying mercury. The results showed that the modified activated carbon calcined at 300 鈩，

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