湿式烟气脱硫喷淋塔内部流场数值模拟研究

以300MW机组湿法烟气脱硫喷淋塔为研究对象,利用计算流体力学通用软件对其内部两相流场进行模拟。气相湍流由标准k 模型描述,喷淋液滴由拉格朗日颗粒轨道模型描述。预测了无喷淋和有喷淋2种条件下的气相湍流流场分布、沿塔高方向不同截面上的气速分布以及喷淋液滴的轨迹。模拟结果表明,引入喷淋液后,出口截面气速分布明显均匀化,其最大值由无喷淋时的12m/s降至6m/s。该最大值出现在靠近塔壁处,是由塔壁附近喷淋密度较低造成的,可通过改进周边喷嘴的布置方式及喷嘴型式进行优化。     

光纤ZnO薄膜的制备及光催化性能研究

实验利用射频磁控溅射镀膜工艺,分别在光纤和石英玻璃上成功制备了ZnO薄膜。采用X射线衍射仪、原子力显微镜和荧光分光光度计对薄膜进行了测试分析,并对其光催化降解苯酚的性能进行了对比测试。结果表明,该薄膜具有良好的C轴取向性,光致发光峰分别位于362nm、421nm和486nm附近,且随着薄膜样品晶粒的减小而出现蓝移,光纤上ZnO薄膜的光催化能力是以石英玻璃为基底的ZnO薄膜的193倍,光催化效果显著。     

Pd/CZ/Al2O3催化剂的制备、表征与三效催化性能

以共浸渍法制得的氧化铝负载铈锆固溶体为载体,并浸渍贵金属Pd得到了Pd/CZ/Al2O3催化剂.实验结果表明,该催化剂在老化前后都表现出良好的三效催化活性,新鲜样品Pd/CZ/Al2O3活性与Pd/CZ相当,老化后样品前者优于后者.结合XRD,BET,TPR等表征手段,讨论了Pd/CZ/Al2O3的催化活性特别是高温老化后活性与其组成结构之间的内在关系,揭示了其老化后仍具有较高活性的主要原因在于保持了Pd与CZ/Al2O3复合载体之间的强相互作用(SMSI).     

改进的BP算法在黄河下游枯季径流预测中的应用

本在黄河下游地区应用多层前向人工神经网络理论,通过改进BP算法,建立下游枯季径流预测的BP神经网络模型,使用花园口-利津水站26年的完整序列测流资料训练和检验网络并用于预测,结果表明,通过本次研究建立的BP网络模型是合理的,可靠的,它较好地反映了黄河下游的枯季径流规律,可为今后黄河流域水资源的统一调度,管理,尤其是预防黄河下游再次出现断流提供科学依据。     

Denitrification and phosphorus uptake by DPAOs using nitrite as an electron acceptor by step-feed strategies

Denitrifying phosphorus accumulating organisms (DPAOs) using nitrite as an electron acceptor can reduce more energy. However, nitrite has been reported to have an inhibition on denitrifying phosphorus removal. In this study, the step-feed strategy was proposed to achieve low nitrite concentration, which can avoid or relieve nitrite inhibition. The results showed that denitrification rate, phosphorus uptake rate and the ratio of the phosphorus uptaken to nitrite denitrified (anoxic P/N ratio) increased when the nitrite concentration was 15 mg·L^-1 after step-feeding nitrite. The maximum denitrification rate and phosphorus uptake rate was 12.73 mg NO2-–N·g MLSS-1?h-1 and 18.75 mg PO43-–P·g MLSS-1?h-1, respectively. These rates were higher than that using nitrate (15 mg·L^-1) as an electron acceptor. The maximum anoxic P/N ratio was 1.55 mg PO43--P?mg NO2--N-1. When the nitrite concentration increased from 15 to 20 mg NO2--N?L-1 after addition of nitrite, the anoxic phosphorus uptake was inhibited by 64.85%, and the denitrification by DPAOs was inhibited by 61.25%. Denitrification rate by DPAOs decreased gradually when nitrite (about 20 mg·L^-1) was added in the step-feed SBR. These results indicated that the step-feed strategy can be used to achieve denitrifying phosphorus removal using nitrite as an electron acceptor, and nitrite concentration should be maintained at low level (<15 mg·L^-1 in this study).     

超音速虹吸式空气雾化喷嘴雾化影响因素实验研究

为掌握超音速虹吸式空气雾化喷嘴雾化机理及特性,采用流体力学线性不稳定理论分析雾化机理,通过喷雾实验研究不同因素对雾化性能的影响及对比不同类型喷嘴的雾化效果。研究结果表明：随着距喷嘴出口距离增加,超音速虹吸式空气雾化喷嘴在雾滴破碎后碰撞聚合作用由强到弱,300 mm内雾滴粒径增长速率明显,300 mm外雾滴粒径增长速率较缓。随着供气压力增加,超音速虹吸式空气雾化喷嘴雾滴粒径逐渐减小,在实测距离内SMD(平均粒径)最小为17.5μm。不同供气压力下,超音速虹吸式空气雾化喷嘴随距离增加,雾滴粒径增长趋势基本一致。有效射程内供气压力为0.1～0.5 MPa时,SMD仅为17.5～31.16μm。对比实验中,超音速虹吸式空气雾化喷嘴SMD比内混式空气雾化喷嘴和X旋流型压力喷嘴小53.5%～74.0%。     

Green and efficient degradation of cefoperazone sodium by Bi4O5Br2 leading to the production of non-toxic products: Performance and degradation pathway

Photocatalytic process represents a promising approach to overcome the pollution challenge associated with the antibiotics-containing wastewater. This study provides a green, efficient and novel approach to remove cephalosporins, particularly cefoperazone sodium (CFP). Bi₄O₅Br₂ was chosen for the first time to systematically study its degradation for CFP, including the analysis of material structure, degradation performance, the structure and toxicity of the transformation products, etc. The degradation rate results indicated that Bi₄O₅Br₂ had an excellent catalytic activity leading to 78% CFP removal compared with the pure BiOBr (38%) within 120 min of visible light irradiation. In addition, the Bi₄O₅Br₂ presents high stability and good organic carbon removal efficiency. The effects of the solution pH (3.12 - 8.75) on catalytic activity revealed that CFP was mainly photocatalyzed under acidic conditions and hydrolyzed under alkaline conditions. Combined with active species and degradation product identification, the photocatalytic degradation pathways of CFP by Bi₄O₅Br₂ was proposed, including hydrolysis, oxidation, reduction and decarboxylation. Most importantly, the identified products were all hydrolysis rather than oxidation byproducts transformed from the intermediate of β-lactam bond cleavage in CFP molecule, quite different from the mostly previous studies. Furthermore, the final products were demonstrated to be less toxic through the toxicity analysis. Overall, this study illustrates the detailed mechanism of CFP degradation by Bi₄O₅Br₂ and confirms Bi₄O₅Br₂ to be a promising material for the photodegradation of CFP.     

Ecological service assessment of human-dominated freshwater ecosystem with a case study in Yangzhou Prefecture, China

Freshwater ecosystems provide a host of services to humanity. These services are now rapidly being lost, not least because of the inability of making the impacts measurable. To overcome this obstacle, assessment frameworks for freshwater ecosystem services are needed. A simple water equivalent framework to assess the ecological services provided by freshwater ecosystems was developed in this study. It translated the occupation of freshwater ecosystem services into biologically freshwater volumes and then compares this consumption to the freshwater throughput, that is, the ecological capacity available in this region. In this way, we use the example of Yangzhou Prefecture, to account the main categories of human occupation of water ecosystem services. The result showed that there is a huge gap between the consumption and the supply of freshwater ecosystem services. This must encourage local government to make land-use and water management decisions both economically rational and environmentally sound.     

2014年北京市城区臭氧超标日浓度特征及与气象条件的关系

根据2014年1~12月北京市环境保护监测中心监测的O₃浓度数据,综合探讨了北京市O₃的时空分布及与其气象条件的关系.结果表明:2014年北京市全年O₃小时平均浓度约为56.18 μg·m^-3,O₃超标日小时平均浓度约为148.05 μg·m^-3且超标日主要集中在5~9月;超标日O₃日变化呈现单峰型分布,06:00或07:00为低谷,15:00、16:00左右达到峰值;超标日O₃浓度在09:00~23:00明显高于夏季同时间段浓度平均;空间分布上中心城区站点O₃浓度相对较低,而城区西部植物园站点浓度最高;统计的2014年北京市O₃超标日地面形势场3种类型高压类、低压类、均压类各占16%、36%、48%;超标日O₃浓度与气压、湿度、能见度呈负相关关系,与风速、温度呈正相关关系; 2014年5月29日~6月1日北京市发生的一次O₃重污染过程是由本地光化学污染及区域输送造成的,区域输送对北京市O₃浓度有着十分重要的影响.     

太原城区PM2.5中多环芳烃、硝基多环芳烃的污染特征、来源解析和健康风险评价

以2013—2014年期间太原城区大气细颗粒物(PM_(2.5))为研究对象,定量分析了其中多环芳烃和硝基多环芳烃的浓度.结果显示,太原城区PM_(2.5)中16种多环芳烃和12种硝基多环芳烃的浓度分别为13.8~547和0.70~4.33 ng·m~(-3),硝基多环芳烃浓度低于多环芳烃浓度1~2个数量级.太原城区PM_(2.5)中多环芳烃最高值出现在冬季,最低值出现在夏季,冬季污染物浓度平均值高于夏季20倍,主要是由于北方采暖期间取暖用煤量的增加使得多环芳烃排放量大幅提高;与之不同的是,硝基多环芳烃浓度季节变化并不显著,冬季浓度均值与夏季差异小于5倍(除9-硝基蒽),反映出硝基多环芳烃生成主要与机动车尾气排放有关,其排放不受季节控制,这与实际情况是吻合的.此外,基于因子分析和化合物比值结果发现,太原城区大气PM_(2.5)中9-硝基蒽有来自周边地区木材燃烧的贡献.健康风险评价结果表明,必须对多环芳烃排放进行有效控制来降低人群在冬季大气中的暴露风险;对于硝基多环芳烃,其健康风险更要引起足够的重视.