| The pollution caused by sulfur dioxide and nitrogen oxides in our country turns out to be very pressing. The nation is devoting a lot of energy on taking care of the air pollution. Hence it is quite necessary and urgent to develop a new economical, efficient and simple way to carry it out. Nano-magnesia has some good nature, such as small size, large specific surface area, high purity, high hardness, high reactivity, strong adsorption, good low-temperature sintering, which can be used as environmental pollution control adsorbent. This paper systematically studied on preparation of nano-magnesia powder and magnesia adsorbent, and the adsorbent was used on experiment of simultaneous desulfurization and denitrification,which obtain a good effect. In the stuy, the best method of Nano-MgO adsorbent regeneration is found through comparing with many ways and the adsorption mechanism of simultaneous desulfurization and denitrification is analyzed.The paper introduced the nature, use and preparation methods of nano-magnesia, and carried out in-depth research on preparation methods of nano-magnesia powder and adsorbent. The research comparated these two methods which direct precipitation combined with microwave heating in water bath combining method and homogeneous precipitation combined with microwave heating in water bath combining method. Using MgSO4·7H2O and Na2CO3 as raw material, polymer (PEG1000) as surfactants, nano-magnesia powder with good crystallinty and large specific surface area has been synthesized by direct precipitation and microwave heating in water bath combining method. The effects of reaction temperature and time, calcination temperature and time, and the dosage of polymer (PEG1000) on the powder specific surface area were studied in detail The morphology and structure of nano-magnesia powder were characterized by means of thermogravimetry analysis, X-ray powder diffraction (XRD), scan electron microscope (SEM), Fourier Transform Infrared Spectrophotometer (FT-IR). And thermal decomposition temperature of the basic of nano-magnesia was analyzed by thermogravimetry. The results showed that nano-magnesia powder whose specific surface area was 183.35 m2/g and average particle size was about 7.2nm was prepared by decomposing nano-magnesia basic at the temperature 500℃for 1.5 hours. Adopting blend methods to prepare nano-magnesia adsorbent (nano-magnesia powder:MgSO4·7H2O: sweet-powder= 75:32:1).The nano-magnesia adsorbent simultaneous desulfurization and denitrification performance were studied through self-designed and installed devices, and the influencing factors of desulfurization and denitrification efficiencies were analysed in detail. And characterizing the adsorbent before and after simultaneous desulfurization and denitrification. The result showed that adsorption of desulfurization efficiency can be maintained at about 98.03 percent and denitrification efficiency can be maintained at about 85.74 percent in flue gas temperature 120℃—180℃, bed height 5cm, flue gas airspeed of adsorption tower less than 3400 h-1, flue gas in the aerobic conditions, sulfur dioxide concentration 2000 mg/m3, nitric oxide concentration 500mg/m3 under the conditions within 60 min.Lye regeneration was the best method compared with hot regeneration and steam regeneration. The final conclusion was to immerse the adsorbent with 100ml NaOH of 0.25mol/L for 30 minutes. The efficiency of simultaneous desulfurization and denitrification was higher after regenerating with lye. The Nano-MgO adsorbent could be regenerated repeatedly. The adsorbent has good stability with simultaneous desulfurization and denitrification after regeneration. The stuy showed that Nano-MgO adsorbent could be regenerated repeatedly. The desulfurization and denitrification efficiency were 100 percent and above 74.3 percent respectively within 60 min through self-designed and installed integrative absorption and regeneration devices.Finally to research simultaneous desulfurization and denitrification’s mechanism of the nanometer magnesia absorbent. Through the determination results of simultaneous desulfurization and denitrification by Nano-MgO adsorbent, BET, SEM, XRD and FT-RI, the conclusion was found that physical adsorption and chemical adsorption were included in process of simultaneous desulfurization and denitrification, the chemical adsorption was dominant. An array of chemical reactions were happened complicatedly between SO2, NOx and adsorbent. There were alkaline functional groups which were beneficial to the removal of SO2 and NOx producted in the surfaces of adsorbent through immersing in the lye. Catalysis might exist in the process, which further improved the removal efficencies of SO2 and NOx.The stuy showed that Nano-MgO adsorbent could be regenerated repeatedly, and the integrative absorption and regeneration devices needed farther improvement so that it can be applied to practical production. |
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