一例带电水冲洗触发的220kV避雷器爆炸事故分析

对一例220 kV金属氧化物避雷器在带电水冲洗后发生爆炸故障的原因进行了分析。通过对完好避雷器和故障避雷器进行解体和对比分析,发现故障避雷器下节顶部压力释放装置内部的密封胶圈发生凹陷变形。最后,对该类事故提出预防措施。     

不同含量低污染水对人工湿地中细菌的影响研究

探究水平流人工湿地(HFCW)系统处理低污染水过程中,相同COD/ρ(TN)下不同碳氮含量对细菌群落结构的影响。结果表明,进水为较高碳氮含量的HFCW(HF1)和进水为较低碳氮含量的HFCW(HF2)对COD和TN的去除效率具有一定的差异,HF1和HF2对COD的去除效率分别为48.26%和28.89%,对TN的去除率分别为79.06%和81.87%。HF1中细菌的丰富度和多样性均高于HF2,HF1中富集的优势细菌为Chloroflexaceae、Comamonadaceae和Rhodocyclaceae,均具有异养反硝化功能,HF2中富集的优势细菌为Xanthomonadaceae和Rhodocyclaceae,其中Xanthomonadaceae具有自养反硝化功能。COD、NH4^+-N和NO3^--N对HF1中细菌群落的影响大于对HF2中细菌群落的影响,HF1中COD对细菌群落的影响大于NH4^+-N和NO3^--N。     

某铁矿隔水护顶矿柱厚度计算及安全影响预测

科学合理地确定矿山隔水护顶矿柱安全厚度是矿山安全生产的前提条件，为保障某铁矿地表民房、道路等建（构）筑物安全，防止矿山开采过程中产生的导水裂隙带贯通第四系含水层，采用荷载传递交汇线法、K.B.鲁别涅依他估算法和冒落带、导水裂隙带高度估算法3种理论分析方法对隔水护顶矿柱厚度进行计算，并利用数值模拟手段对留设隔水护顶矿柱后的开采过程安全影响进行了分析，对理论计算结果进行了验证。3种理论计算方法得出的隔水护顶矿柱厚度分别为14.3～17.3 m、17.5～31.4 m和41.8～57.4 m，推荐隔水护顶矿柱留设厚度为60 m。通过数值模拟分析得出，在留设60 m厚的隔水护顶矿柱的基础上，开采区域和隔水护顶矿柱位置产生的最大拉应力约0.47 MPa，矿山开采不会对隔水护顶矿柱造成破坏；地表产生的最大水平位移约5.8 cm，最大垂直位移约26.5 cm，最大倾斜为1.70 mm/m，最大曲率为0.20 mm/m2，最大水平变形值为0.70 mm/m，满足相关规范要求，预测矿山开采不会造成地表建（构）筑物破坏。     

Efficacy of alpha-cypermethrin and thiamethoxam against Trogoderma granarium Everts (Coleoptera: Dermestidae) and Tenebrio molitor L. (Coleoptera: Tenebrionidae) on concrete

Laboratory bioassays were conducted to evaluate alpha-cypermethrin and thiamethoxam for the control of adults, small larvae and large larvae of the khapra beetle Trogoderma granarium, and the yellow mealworm beetle Tenebrio molitor, on concrete. Factors such as dose (0.025 and 0.1 mg alpha-cypermethrin or thiamethoxam/cm²), exposure interval (1, 3 and 7 d), and formulation (alpha-cypermethrin SC and thiamethoxam WG) were evaluated. Apart from immediate assessment at end of exposure, an assessment of delayed mortality was performed with the survivors of the 7-d exposure by removing them from the treated substrate and keeping them on untreated surfaces for 7 more days. After the 7-d exposure, more T. granarium adults were dead on dishes treated with alpha-cypermethrin than with thiamethoxam. Small larvae were generally less susceptible than adults. After 7 d, small larval mortality reached 64.4% for alpha-cypermethrin, while for thiamethoxam it was <6%. Large T. granarium larvae were more tolerant than the small ones. Delayed mortality of T. granarium adults was generally high for both insecticides and doses, and ranged between 43.3 and 63.3% of those that were still alive immediately after the 7-d treatment. For both larval categories, delayed mortality was higher for larvae that had been previously exposed to alpha-cypermethrin, than with thiamethoxam. For T. molitor, after the 7-d exposure, significantly more adults were dead on dishes treated with alpha-cypermethrin than with thiamethoxam. For small larvae mortality was 38.9% at the lowest thiamethoxam dose, but in the other cases ranged between 88.9 and 95.6%. In the case of large larvae, the overall mortality was low in all tested combinations. Regarding delayed mortality of this species, it remained at low levels, for both adults and small larvae. Our results indicate that T. molitor was more susceptible than T. granarium in both insecticides tested, but alpha-cypermethrin was more effective than thiamethoxam.     

Seawater-softening process through formation of calcite ooids

Conventional water-softening processes usually involve the exchange of Na⁺ ions for Ca²⁺ and Mg²⁺ using commercial or synthesized ion exchangers. The differences in chemical compositions of the ooids can be attributed to the formation in different environments. In this paper, ooid grains form inside assembled semi-pilot softening unit through a continuous chemical process involving reaction between bicarbonate ions and added lime using natural seawater. Our sample of Mediterranean seawater has low Mg²⁺/Ca²⁺ ratio (1.98%) within the range chemically favorable for precipitation of low-Mg calcite ooids. Precipitation of calcite occurs around pure quartz sand grains which act as nucleation points (the bed required for sand vessel is 1.65 l). The shape of the sand grains controls the overall external morphology of the resulting ooids; they vary in size from 0.5 to 3.0 mm and have a high degree of polish due to surface abrasion caused by continuous agitation inside the softening system. Calcite ooid grains (1.53 kg) formed within the seawater-softening unit every 18 days have many of the ooid features formed in marine environments. Ooids grow to a significant size, at a rate of about 0.17 mm of one layer thickness per day inside the softening unit. The average weight percent of calcite precipitate is 35.48% after 18 days, at 10 °C, 60 l/min and pH 9.0. The pellets comprise mainly CaCO₃ and SiO₂ and some metal ions which may substitute for calcium ions in calcite are present only in trace amounts of the total composition.     

Improvement of adhesion and paint ability of EVA copolymers with different vinyl acetate contents by treatment with UV-ozone

The surface modifications produced by UV-ozone treatment of two ethylene-vinyl acetate (EVA) copolymers containing 12 and 20 wt% vinyl acetate (EVA12 and EVA20 respectively) were studied. The treatment with UV-ozone improved the wettability of both EVAs due to the creation of new carbon–oxygen moieties. The extent of these modifications increased with increasing length of the treatment and the modifications produced in EVA20 were produced for shorter lengths of treatment. The UV-ozone treatment also created roughness and heterogeneities on the EVA surfaces. Whereas roughness formation prevailed on the UV-ozone treated EVA12, important ablation was dominant on the treated EVA20. T-peel strength values in joints made with polychloroprene adhesive increased when the EVAs were treated with UV-ozone. Short length of UV-ozone treatment (1 min) produced higher T-peel strength in joints made with EVA20 whereas higher T-peel strength values in joints made with EVA12 were obtained after treatment for 5–7.5 min in which a cohesive failure into a weak boundary layer on the treated EVA surface was found. Furthermore, the adhesion of UV-ozone treated EVA20 to acrylic paint increased. Finally, the ageing resistance of the treated EVA/polychloroprene adhesive joints was good and the surface modifications on the UV-ozone treated EVAs lasted for 24 h after treatment at least.     

浅谈氯碱氢的一种深度脱水工艺

概述了氢的主要工业生产方法和实际应用,详细介绍了氯碱氢三级脱水工艺过程,并运用在线分析手段,准确显示了干燥过程中的氯碱氢水分含量变化规律。     

Abrasive waterjet micro-machining of channels in metals: Comparison between machining in air and submerged in water

Abrasive water jet technology can be used for micro-milling using recently developed miniaturized nozzles. Abrasive water jet (AWJ) machining is often used with both the nozzle tip and workpiece submerged in water to reduce noise and contain debris. This paper compares the performance of submerged and unsubmerged abrasive water jet micro-milling of channels in 316L stainless steel and 6061-T6 aluminum at various nozzle angles and standoff distances. The effect of submergence on the diameter and effective footprint of AWJ erosion footprints was measured and compared. It was found that the centerline erosion rate decreased with channel depth due to the spreading of the jet as the effective standoff distance increased, and because of the growing effect of stagnation as the channel became deeper. The erosive jet spread over a larger effective footprint in air than in water, since particles on the jet periphery were slowed much more quickly in water due to increased drag. As a result, the width of a channel machined in air was wider than that in water. Moreover, it was observed that the instantaneous erosion rate decreased with channel depth, and that this decrease was a function only of the channel cross-sectional geometry, being independent of the type of metal, the jet angle, the standoff distance, and regardless of whether the jet was submerged or in air, in either the forward or backward directions. It is shown that submerged AWJM results in narrower features than those produced while machining in air, without a decrease in centerline etch rate.     

尿素装置液位仪表失真分析及处理

介绍了尿素装置中3起液位仪表失真案例,分析了故障现象和设备工况,确定失真原因,采取了相应的处理措施,解决了仪表故障。     

玄武岩纤维填料应用于两种混合生长反应器的评价

采用单丝直径微米级的伞状玄武岩纤维(BF)作为填料,将其引入序批式反应器(SBR)和后置缺氧反硝化SBR外聚合物(EPS)含量和扫描电子显微镜形貌图,考察了两种SHBR的污水处理效果。试验结果表明:基于SBR的SHBR的出水COD、氨氮、总氮去除率分别为83.2%、89.9%、86.8%;基于后置缺氧反硝化SBR的SHBR优良,而基于后置缺氧反硝化SBR的SHBR的脱氮效果得到进一步的优化和提升。两种SHBR的BF填料中EPS含量分析结果显示:在好氧环境下,蛋白质(PN)的含量高于多糖(PS)的含量;在缺氧条件下,PS的含量明显高于PN的含量。