Electron beam process for SO2 removal from flue gases with high SO2 content

Flue gases with high SO₂ concentration are emitted from different industrial processes, e.g. combustion of coal with high sulfur content, copper smelting and sintering plant. The application of the electron beam process for SO₂ removal from such flue gases was investigated. A parametric study was carried out to determine the removal efficiency as a function of temperature and humidity of irradiated gases, dose and ammonia stoichiometry. At the dose 11.5 kGy 95% SO₂ removal efficiency was obtained when the temperature and humidity of irradiated flue gases and ammonia stoichiometry were properly adjusted. The synergistic effect of high SO₂ concentration on NO_x removal was observed. The collected by-product was the mixture of (NH₄)₂ SO₄ and NH₄NO₃. The content of heavy metals in the by-product was many times lower than the values acceptable for commercial fertilizer.     

Kinetics of SO2 removal from flue gas by electron beam technique

Laboratory scale experiments were carried out in order to get more information about the oxidation of SO₂ by OH radicals (homogeneous reaction) and the oxidation of SO₂ at aerosol surfaces (heterogeneous reaction). For the experiment of homogeneous reaction, SO₂ was added to synthetic flue gas without initial NO and without ammonia and the mixture was irradiated with electron beam. The SO₂ removal was measured as a function of temperature and water vapour concentration at constant dose. For the experiment of heterogeneous reaction, SO₂ was added to nucleating sulfuric acid aerosol. No SO₂ removal was observed in this case. So, it can be concluded that the heterogeneous oxidation of SO₂ is negligible in the absence of ammonia. Therefore, the oxidation of SO₂ must be interpreted merely by homogeneous gas phase chemistry. The gas phase kinetics are derived from comparison of experimental results and computer modelling.     

Water aerosols spraying for SO2 and NOx removal from gases under E-beam irradiation

The gas-phase transport process of an admixture to the surface of spraying aerosol droplets has been experimentally investigated with reference to E-beam gas cleaning processes. The rate of SO₂ uptake by alkali aerosol droplets with average radius 30 μm has been measured in gas-aerosol jet using light absorption technique. It has been shown that the rate of gas-phase transport is described by the molecular flux of the admixture. Gas-liquid reactions are considered to explain the observed improvement of radiation-induced NO removal in the presence of spraying alkali aerosol.     

SO2和NO浓度对TiO2-硅酸铝纤维脱除元素汞的影响

使用溶胶凝胶法制备了TiO₂-硅酸铝纤维纳米复合材料。使用此复合材料在波长为253.7 nm的紫外光照射下脱除模拟烟气中的元素汞,实验研究了SO₂和NO浓度对光催化脱汞的影响以及温度对脱汞率的影响。结果表明,常温时烟气中SO₂浓度对光催化脱汞表现出促进作用,当SO₂浓度为1 200 μg/m³时脱汞率最高可达93%。NO浓度对光催化脱汞表现出抑制作用,随着NO浓度的增加脱汞率逐渐降低。高温时SO₂和NO浓度对光催化脱汞的作用规律与常温时相似。随着模拟烟气温度的升高,脱汞率逐渐减低,升高温度对光催化脱汞表现出抑制作用。     

应用水汽相变促进湿法脱硫净烟气中PM_(2.5)和SO_3酸雾脱除的研究

在石灰石-石膏法脱硫净烟气中分别采用添加适量蒸汽和湿空气方式建立PM_(2.5)和SO_3酸雾凝结长大所需的过饱和水汽环境,在测试分析湿法脱硫净烟气中PM_(2.5)及SO_3酸雾物性的基础上,考察了蒸汽及湿空气添加量、脱硫净烟气温度等的影响。结果表明,湿法脱硫净烟气中PM2.5除含有燃煤飞灰外,含Ca SO_4、Ca SO_3及未反应的Ca CO_3等组分;由于SO_3酸雾基本处于亚微米级粒径范围,湿法烟气脱硫(WFGD)系统对SO_3酸雾的脱除率仅为35%-55%;添加适量蒸汽及湿空气方式均可促进湿法脱硫净烟气中PM_(2.5)和SO_3酸雾脱除,最终排放浓度随蒸汽或湿空气添加量的增加而降低,其中,添加蒸汽方式适合于脱硫净烟气温度较低(≤50-55℃)的场合,在脱硫净烟气温度较高(≥55-60℃)时,利用添加湿空气方式替代添加蒸汽更具技术经济优势。     

臭氧氧化结合湿法喷淋对玻璃窑炉烟气同时脱硫脱硝实验研究

采用臭氧氧化结合湿法喷淋对模拟玻璃窑炉烟气开展了同时脱硫脱硝实验研究.采用不同溶液(NaOH、Na₂S)进行了喷淋实验.结果表明,保证溶液pH值在10以上,NaOH浓度对NO_x脱除效率无影响,SO₂的存在促进了NO_x吸收.当O₃/NO物质的量比为1.6、溶液NaOH浓度为0.5%时,NO_x脱除效率可达70%,SO₂脱除效率在99%以上.往喷淋液中添加Na₂S,NO_x脱除效率随Na₂S浓度增加而提高,SO₂的存在对NO_x脱除效率无影响.当O₃/NO物质的量比为1.2、溶液中NaOH浓度为0.5%、添加剂Na₂S浓度为0.6%时,NO_x脱除效率可达70%,SO₂脱除效率在95%以上.60 min长时间运行实验证明,模拟烟气中的NO_x经碱液和添加剂吸收后主要以NO^-₂的形式存在于喷淋液中,且NO_x脱除效率不随溶液pH值的变化而变化.     

H2O、CO2组分对NOx存储-还原性能的影响

NOx存储-还原技术是控制汽车稀燃NOx排放的重要手段之一,在汽车尾气中H2O、CO2组分含量均相对较高,有必要弄清这些组分对NOx存储-还原特性的影响。论文以MnOx改性Pt/Ba/Al2O3催化剂为研究对象,评价在不同气氛下的NOx存储能力和催化还原性能。结果表明：CO2、H2O组分均抑制催化剂的NOx存储性能,H2O的抑制作用主要表现在低温区,CO2抑制NOx存储的现象在高温区更为显著。CO2对NOx存储速率的抑制作用较H2O更为明显,且其NOx存储速率随着温度的升高表现的差异性更为明显。对于NOx催化还原过程,CO2、H2O或CO2 H2O添加均导致N2选择性降低,其N2选择性按CO2 > H2O > CO2 H2O的顺序降低。     

Photocatalytic conversion of NOx on AgCl/Al2O3 catalyst

The rate of NO conversion under UV illumination was evaluated over Ag/Al₂O₃ and AgCl/Al₂O₃ catalysts at room temperature. The AgCl/Al₂O₃ catalyst is highly active for the conversion of NO_x. The conversion is enhanced in the presence of O₂ and further enhanced when oxygen coexists with hydrocarbons. Diffuse reflectance spectra of AgCl/Al₂O₃ and Ag/Al₂O₃ show an absorption band at 250 nm, and a weak and broad band at 230 nm, respectively. The high photocatalytic NO_x conversion is achieved over the AgCl/Al₂O₃ catalyst. The conversion level of NO_x is maintained above 60% over 5 h in the presence of O₂ and hydrocarbons under UV-irradiation. The absorption band at 250 nm is ascribed to the band gap energy of crystallized AgCl particles on Al₂O₃. These results suggest that high photocatalytic NO_x conversion proceeds on crystallized AgCl particles formed on Al₂O₃.     

蒸汽活化生物质焦吸附模拟烟气中SO2和NO的研究

以麦秆和稻壳生物质为研究对象,在不同的热解温度、热解速率以及蒸汽活化温度条件下制备了生物质焦,采用比表面积与孔隙度分析仪测定生物质焦的比表面积和孔隙结构参数。利用固定床吸附装置,研究了热解温度、热解速率、活化温度和模拟烟气中SO₂和NO浓度等因素对生物质焦吸附SO₂和NO性能的影响。结果表明,蒸汽活化可以显著提高生物质焦的BET比表面积、D-R比表面积、D-R微孔容积和总孔容,降低其平均孔径,并显著增加蒸汽活化生物质焦对SO₂与NO吸附的起始穿透时间和吸附量。快速热解下制得的蒸汽活化焦对SO₂和NO的吸附效果优于慢速热解,热解温度为873 K的蒸汽活化焦的吸附性能明显好于热解温度为673与1 073 K的蒸汽活化焦。在973~1 173 K下,随着蒸汽活化温度的提高,蒸汽活化生物质焦对SO₂和NO的吸附量呈现先上升后下降的趋势。随着模拟烟气中SO₂与NO浓度的降低,蒸汽活化生物质焦对SO₂与NO吸附的起始穿透时间延长,但相应的SO₂和NO吸附量下降。在873 K、快速热解和1 073 K条件下制得的蒸汽活化麦秆焦对SO₂和NO吸附量最大,其值分别为109.02和21.77 mg/g。     

有序介孔CuFe2O4同时催化去除碳烟与NOx

采用纳米复刻(浇筑)法制备一系列介孔CuFe_2O_4.通过X射线衍射(XRD)、 N_2物理吸附、透射电镜(TEM)等研究了不同制备条件对有序介孔CuFe_2O_4结构形成的影响.研究发现,作为对比,柠檬酸法仅能合成普通的四方相CuFe_2O_4纳米颗粒,但是硬模板法则能合成出高温淬火才能形成的立方晶相介孔结构CuFe_2O_4.进一步研究了该催化剂同时催化去除碳烟和氮氧化合物(NO_x)的性能,研究发现,与柠檬酸法合成的普通CuFe_2O_4催化剂相比,介孔结构CuFe_2O_4不仅大幅降低了碳烟起燃温度(324降低到278℃),而且将N_2的最高产率从5.9%提升到了92.2%.基于原位漫反射红外(in-situ DRIFTS)的机理分析研究表明,合成过程中采用NaOH除去硬模板的过程中会在介孔CuFe_2O_4表面造成大量残留的钠盐,这种高分散的钠物种促进了NO_x的吸附并转化为硝酸盐物种,从而促进碳烟氧化以及NO_x转化.但是与表面Na修饰的CuFe_2O_4相比,体相Na掺杂的CuFe_2O_4虽然具有更好的有序介孔结构,但是其氧化性能下降,进一步也导致了NO_x的催化还原性能的下降.     

Analytical methods and monitoring system for E-beam flue gas treatment process

The results of reliable and precise measurement of gas composition in different key points of e-beam installation are necessary for its proper operation and control. Only the composition of flue gas coming into installation is adequate to composition of flue gas emitted from coal-fired boiler. At other points of e-b installation the gas composition is strongly modified by process conditions therefore specific measuring system (sampling and conditioning system and set of gas analyzers) for its determination are required. In the paper system for gas composition measurement at inlet and outlet of e-b installation are described. Process parameters are continuously monitoring by CEM system and occasionally by the grab sample system. Both system have been tested at pilot plant at EPS Kaw czyn.     

Limiting of SO2 and NOx emission in worldwide coal-power production

A broad overview is offered of both SO₂ and NO_x emission regulation as well as of diverse available technologies for control and/or removal of these stack pollutants in coal firing. The logistics and trends in worldwide supply and use of diverse available steam coal resources are reviewed in relation to the need, environmentally, for continuing restraint and reduction in sulfurous emissions.     

煤制活性焦性质对其脱除烟道气中二氧化硫性能的影响

讨论了四种煤制活性焦的性质对其脱除烟道气中SO2性能的影响,活性焦的表面碱性与微孔面积决定了其对烟道气中SO2的吸附与氧化。生成的硫酸主要贮存在活性焦的微孔内。活性焦内的硫酸在脱附温度为300℃时达到最大脱附速率。     

The study of electron beam flue gas treatment for coal-fired thermal plant in Japan

The fundamental research work with simulated coal-fired flue gas was performed in JAERI to get basic data for electron beam treatment of flue gas from thermal power plants in Japan. The standard condition of the experiments was set to be the same as that of next large scale pilot test in Nagoya. The concentrations of NO_x and SO_x were 225 ppm and 800 ppm, respectively. The temperature of the system was 65°C. The effect of multiple irradiation was observed for NO_x removal. The target SO_x and NO_x removals (94% and 80%, respectively) with low NH₃ leakage (less than 10 ppm) were achieved at 9 kGy irradiation with 0.9 NH₃ stoichiometry during 7 hours continuous operation. The facility for the pilot plant (12,000 Nm³/hr) has just built at the site of Shin-Nagoya power plant of Chubu Electric Power Company and will be started in full operation in November 1992.     

CoOx-CeOx/ZrO2催化氧化NO性能及抗SO2毒化研究

采用浸渍法制备了一系列CoO_x-CeO_x/ZrO₂催化剂,探讨了催化剂载体、Co含量、Co/Ce配比等对Co基催化剂催化氧化NO活性的影响及其机理。ZrO₂负载的Co氧化物具有优良的低温NO催化氧化活性,铈的添加进一步提高了催化剂的低温活性。其促进机制主要是提高了催化剂吸附氧的能力及改善了Co在催化剂表面的分散。同时,掺杂铈使得催化剂抗SO₂能力有一定增强,呈现出选择性毒化机制。     

Pilot-plant for NOx, SO2 and HC removal from flue-gas of municipal waste incinerator by electron beam irradiation

According to the basic research performed using a small size reactor at TRCRE of JAERI, the electron beam irradiation process was proved to be very effective for NO_x, SO₂ and HC removals from flue-gas of municipal waste incinerators. Based on this result, a pilot-plant was constructed for the demonstration of NO_x, SO₂ and HC removal performance using electron accelerator of maximum energy 0.95 MeV and maximum power 15kW.The pilot-plant was constructed at Matsudo City waste Disposal Center. The flue-gas of 1,000 Nm³/hr is guided from the waste incinerator flue-gas line of 30,000Nm³/hr to the pilot-plant to be processed by spraying Ca(OH)₂ slurry or powder and irradiation with high-energy electron beam of the accelerator. NO_x, SO₂ and HC are removed simultaneously from the flue-gas by the enhanced reaction with Ca (OH)₂ under irradiation.A brief explanation of the pilot-plant and preliminary results of the experiments are introduced in this paper.     

SO2对钙基CO2吸收剂循环煅烧/碳酸化反应的影响

在循环煅烧/碳酸化反应系统中,研究了SO₂对钙基吸收剂CaCO₃捕集CO₂的影响,获得了SO₂对钙基吸收剂碳酸化特性、煅烧特性以及循环稳定性的影响规律,并结合SEM分析结果,从循环煅烧/碳酸化反应角度,分析了可能存在的原因。结果表明,钙基吸收剂吸收CO₂的能力随着循环反应次数的增加逐渐发生衰减,在SO₂影响下,这种衰减会进一步加剧,且衰减程度随着SO₂浓度的增加而增大,经过十次循环后,碳酸化转化率分别为25.5%(0%SO₂)、16.9%(0.1%SO₂)和5.2%(0.2%SO₂)。造成这种衰减加剧的主要原因是反应产生较厚的硫酸化产物层,硫酸化产物层使颗粒表面孔隙发生堵塞,阻碍了CO₂在吸收剂内部的扩散,降低了碳酸化转化率。     

流化床快速制不定形活性焦脱除烟气中SO2的研究

利用大型流化床制得了适用于脱除烟道气中二氧化硫的不定形活性焦AC-A,并对其进行了特性分析,在固定床上考察了不同条件下脱除SO2的性能。与硫容相近的商业活性焦AC-B的脱硫性能对比,发现其脱硫性能较好。实验结果表明,在烟气中的二氧化硫的体积分数为0.05%~0.12%,反应温度为80 ℃～100 ℃,空速（GHSV）为1 200 h-1,O2的体积分数为6%,水蒸气为10%的情况下,活性焦AC-A保持SO2脱除率在90%以上达5 h。再生循环脱硫实验表明,活性焦AC-A具有良好的再生脱硫活性。     

UV/H2O2工艺湿法脱除燃煤烟气中NO的研究

在自行设计的内置紫外光-鼓泡器中,利用UV/H₂O₂高级氧化工艺湿法脱除燃煤烟气中的NO气体。主要对紫外光强度、H₂O₂初始浓度、NO初始浓度以及烟气总流量对NO脱除效率的影响进行了考察。研究结果表明,在实验范围内,NO脱除效率随着紫外光强度和H₂O₂初始浓度的增加而增加,但当达到一定值后,NO脱除效率的增加幅度均变得相对平缓;NO脱除效率随着NO初始浓度以及烟气总流量的增加呈近似线性减小。通过离子色谱对液相离子产物进行了定性与定量检测,并对NO中的氮元素进行了物料平衡计算,在此基础上对NO脱除路径与产物形态进行了理论分析。
     

SO_2对Mn-Ce/TiO_2低温SCR催化剂的毒化作用研究

考察了SO_2对Mn-Ce/TiO_2低温脱硝催化剂活性的影响,利用XRD、BET、SEM和XPS对其毒化作用的原因进行分析。结果表明,SO_2对催化剂活性有明显的抑制作用,使NO_x去除率由84%降至42%左右。主要是SO_2的加入造成催化剂比表面积减小,孔径为5-10 nm的孔数量减少,且催化剂晶相由锐钛矿型转化成金红石型结构,活性组分MnO_x发生晶化现象,破坏了Mn-Ti间的强相互作用。催化剂理化性质的变化造成吸附态氧转化为晶格氧的路径受阻、MnO_2含量减少和CeO_x储氧功能减弱,并且产生氧阻效应而使NO吸附和解吸受阻,造成催化剂活性降低。同时生成的硫酸铵盐在催化剂表面沉积,覆盖了催化剂表面的Lewis酸性位,使其对NH_3吸附能力减弱。