【作者】 高宇；

【导师】 胡筱敏；

【作者基本信息】 东北大学 ， 安全技术及工程， 2010， 博士

【摘要】 我国二氧化硫和氮氧化物的排放所引起的污染越来越严重,国家治理大气污染的力度逐步加大。研究开发经济、高效、简单的烟气同时脱硫脱硝技术十分必要和紧迫。化学法制备的纳米氧化镁具有纯度高、粒径小、比表面积大、硬度高、反应活性高、吸附性强以及低温烧结性良好等优良性质,可用作环境污染治理的吸附剂。本研究进行了纳米氧化镁粉体及氧化镁基吸附剂制备的系统研究,并将其应用于烟气同时脱硫脱硝试验,在此基础上,通过各种再生方法的比较得出了纳米氧化镁吸附剂再生的最佳方法,获得了良好的处理效果,同时研究分析了纳米氧化镁吸附剂同时脱硫脱硝的吸附机理。对纳米氧化镁的性质、用途及制备方法进行了综述,并对其粉体和吸附剂的制备方法进行了深入的研究。对直接沉淀法和微波水浴加热法结合与均匀沉淀法和微波水浴加热法结合这两种方法进行了实验比较。结果发现以MgSO4·7H2O和Na2CO3为原料,添加表面活性剂聚乙二醇1000,采用直接沉淀法和微波水浴加热法相结合的方法制备出了结晶良好、比表面积大的纳米氧化镁粉体。研究了前驱物的反应温度及时间、焙烧温度及时间和高分子聚乙二醇用量等对粉体比表面积的影响。用热重分析仪(TGA).X-射线衍射仪(XRD)、扫描电子显微镜(SEM)、傅立叶红外光谱仪(FT-IR)等,对纳米氧化镁粉体的结构和形貌及其前驱物的热分解温度进行了分析。结果得到,在500℃下焙烧1.5h制得纳米氧化镁粉体前驱物,比表面积达到最大183.35m2/g,平均粒径为7.2nm,采用共混法(纳米氧化镁粉体：MgSO4·7H2O:甜津粉=75：32：1,质量比)制备纳米氧化镁基吸附剂。在自行设计安装的烟气脱硫脱硝装置中,对纳米氧化镁基吸附剂同时脱硫脱硝性能进行了考察,探索了各个因素对脱除效率的影响,并对吸附剂同时脱硫脱硝前后的状态进行表征。结果表明在烟气温度为120℃—180℃、床层高度为5cm、吸附塔内空速小于3400 h-1,烟气在有氧条件下,SO2浓度为2000mg/m3、NO浓度为500mg/m3的条件下,吸附60min内检测脱硫效率可保持在98.03%左右,脱硝效率可保持在85.74%左右,吸附剂具有良好的稳定性。在再生实验中,进行了热再生、水蒸气再生以及碱液洗涤的研究,通过对再生后吸附剂同时脱硫脱硝效果的比较,表明碱液再生方法的再生效果最好,并通过进一步实验发现：用0.25 mol/L、100mlNaOH在20℃的温度下浸泡5.37g纳米氧化镁基吸附剂30min的再生效果达到最佳。经过碱液洗涤再生后的吸附剂同时脱硫脱硝效率有所提高,再生后吸附剂同时脱硫脱硝的稳定性良好,纳米氧化镁基吸附剂可以反复再生。采用自行设计安装的同时脱硫脱硝吸附-再生一体化气动流化循环处理再生装置进行试验,连续60min试验测试,S02的脱除效率一直保持100%,NOx的脱除效率保持在74.3%以上。最后对纳米氧化镁基吸附剂同时脱硫脱硝的机理进行了研究。用BET、SEM、XRD、FT-IR等对纳米氧化镁基吸附剂同时脱硫脱硝前后及再生前后进行了表征和分析,纳米氧化镁基吸附剂同时脱硫脱硝为物理吸附和化学吸附共同作用,其中以化学吸附为主。8O2和NOx与吸附剂接触发生了一系列复杂的化学反应。经过了碱液洗涤后的吸附剂表面增加了碱性基团,有助于对S02和NO、的去除,并推测此时吸附剂对NO有催化氧化作用,催化作用进一步提高了脱硫脱硝效率。实验表明氧化镁基吸附剂可以反复再生,完善后的同时脱硫脱硝吸附-再生一体化系统可应用于实际生产中。更多还原

【Abstract】 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.更多还原