Risk and characteristics analysis of the flow-induced vibration of the dip tube in opposed multi-burner gasifier

The vibration of dip tube in multi-burner gasifier changes the stress at the connection, causing flange seal failures and high temperature gas erosions with heavy economic losses and industrial accidents. This work aims to reveal the dip tube vibration mechanism, with special focus on obtaining the effect of operational parameters on the fatigue damage and long-term stable operation of gasifiers. A three-dimensional numerical simulation of the water-scrubbing cooling chamber was conducted to obtain the excitation source in the flow field. Then a FSI (fluid-structure interaction) transient dynamics simulation was carried out to investigate the vibration characteristics. Two major flow forms were found: a vertical annular flow near the dip tube outlet in the water-scrubbing cooling chamber; and a gas-liquid coupled flow caused by the syngas entrained the liquid. These two unstable multiphase flow forms exerted an energy excitation on the dip tube, resulting in a self-excited flutter. The dip tube vibration was similar to the first mode of a cantilever beam. The peak frequency was less affected by the initial liquid level and the syngas stream inlet velocity, which was close to its own first natural frequency. Note that, the alternating load generated by vibration may cause fatigue damage, which needs to be specifically considered in the design and manufacturing process of opposed multi-burner gasifier.     

仓面浇筑立体空间冲突致灾过程建模与伤害评价*

为定量评价大坝浇筑过程空间冲突致灾事故后果,通过对缆机运输典型情景进行危害能量运动分解,确定在水平和竖直方向运动方式,阐述危害能量在流动路径相互转化形式;根据能量守恒定律,分析危害能量在吊罐与承灾体碰撞接触之间转移规律,将吊罐与人头部接触过程抽象为带强阻尼的弹簧振子系统,建立危害能量与碰撞冲量相等的动量方程,量化空间冲突致灾后果。结果表明:吊罐坠落危害能量极大,产生的碰撞冲击力与吊罐的运输速度、高度呈正相关,与阻力系数呈负相关,风速、载重对其影响较大。对比2种不同碰撞情景发现,机械碰撞因顶部承载力缓冲,对人头部产生伤害远小于直接碰撞,并对碰撞结果分级评价,研究结果可为大坝浇筑交叉作业空间冲突致灾风险评价提供参考。     

Significance of iron compounds in chemical and electro‐oxidation treatment of sugar industry wastewater: Batch reaction

Industrialization plays a major role in a nation's growth. However, with an increase in industrial activities, pollution levels are also increasing. Among all industries, the sugar‐processing industry is one that requires large amounts of water to process the sugar, and, consequently, it discharges large amounts of water as effluent. Highly polluted wastewater brings changes to the physicochemical characteristics of the surrounding environment. Iron compounds have had a significant impact when they are used in wastewater treatment in various applications, including when they are used to minimize the pollution levels in sugar industry wastewater (SIWW). To minimize the pollutant levels from SIWW, iron compounds have been key for uses in treatments involving chemical and electro‐oxidation. Two different methodologies of electrocoagulation and chemical coagulation have been used to treat SIWW. In electrocoagulation, an iron plate is used as an electrode material under specific operating conditions. Ferrous sulfate and ferric chloride have been used as chemical coagulants at various pH and mass loading levels. The use of iron metals shows an 82% reduction in chemical oxygen demand (COD) and an 84% reduction in color at the optimum condition of pH 6, an electrode distance of 20 millimeters, and a current density of 156 square centimeters. As a chemical coagulant, iron salt (ferrous sulfate) provides a reduction of 77% COD and a 91% reduction of color at pH 6 and a 40‐millimole mass loading. Electrochemical treatment using iron was found to be suitable to treat SIWW. The sludge generated after treatment can be burned or composted with the possible recovery of some of the treatment costs.     

城市PM2.5健康损害评估研究

参考美国Ben MAP软件,提出城市PM_(2.5)健康损害评估的基本框架,并就评估方法和参数使用中的关键问题进行了论述,包括人群健康损害评估指标的确定、空间尺度和时间尺度的选择、健康终点的界定、人群年龄结构的划分、比较的基准的确定,以及"剂量-反应"关系参数和生命价值参数的选择等.本文收集和整理了2014年北京市空气质量监测点PM_(2.5)浓度监测数据及暴露人口、基期死亡率等数据,运用"向标准靠拢(Rollback to Standard)"的方法,估算北京市PM_(2.5)达到空气质量标准情景下的浓度值,以此作为比较的基准,使用美国Ben MAP数据库收录的"剂量-反应"关系参数,分别基于"工资-风险"法模型和人力资本法模型估计生命价值参数,代入本文城市PM_(2.5)健康损害评估的基本框架,计算2014年北京市PM_(2.5)对人群健康的损害.     

Genotoxicity of ferric oxide nanoparticles in Raphanus sativus: Deciphering the role of signaling factors, oxidative stress and cell death

We have studied the genotoxic and apoptotic potential of ferric oxide nanoparticles(Fe_2O_3-NPs) in Raphanus sativus(radish).Fe_2O_3-NPs retarded the root length and seed germination in radish.Ultrathin sections of treated roots showed subcellular localization of Fe_2O_3-NPs,along with the appearance of damaged mitochondria and excessive vacuolization.Flow cytometric analysis of Fe_2O_3-NPs(1.0 mg/m L) treated groups exhibited 219.5%,161%,120.4% and 161.4% increase in intracellular reactive oxygen species(ROS),mitochondrial membrane potential(ΔΨm),nitric oxide(NO) and Ca2+influx in radish protoplasts.A concentration dependent increase in the antioxidative enzymes glutathione(GSH),catalase(CAT),superoxide dismutase(SOD) and lipid peroxidation(LPO) has been recorded.Comet assay showed a concentration dependent increase in deoxyribonucleic acid(DNA) strand breaks in Fe_2O_3-NPs treated groups.Cell cycle analysis revealed 88.4% of cells in sub-G1 apoptotic phase,suggesting cell death in Fe_2O_3-NPs(2.0 mg/m L) treated group.Taking together,the genotoxicity induced by Fe_2O_3-NPs highlights the importance of environmental risk associated with improper disposal of nanoparticles(NPs) and radish can serve as a good indicator for measuring the phytotoxicity of NPs grown in NP-polluted environment.     

力学载荷条件下 EB-PVD 热障涂层损伤行为研究

目的研究力学载荷条件下EB-PVD热障涂层的损伤行为。方法采用电子束物理气相沉积工艺(EB-PVD)制备热障涂层(TBCs),利用SEM和体式显微镜对力学性能试验后带涂层试样的断口特征、裂纹形貌和金相组织进行观察,分析热障涂层在拉伸、持久和旋转弯曲疲劳等典型力学载荷条件下的损伤行为。结果在室温拉伸条件下,陶瓷层内先出现垂直于应力轴、沿柱状晶簇扩展的平行环状周向微裂纹,随着拉伸塑变量的增加,局部区域裂纹贯穿粘结层并进入合金基体;900℃高温拉伸条件下裂纹也产生于陶瓷层,但裂纹均钝化于粘结层与陶瓷层的界面,并穿透粘结层。在持久条件下,试样在弹性变形阶段涂层即发生开裂,随后沿着陶瓷层柱状晶簇间扩展,但未扩展至粘结层;在高温高周疲劳条件下,裂纹首先出现在粘结层,随后向基体逐渐扩展,扩展深度较浅,而基体疲劳裂纹在粘结层裂纹末端萌生并倾斜滑移扩展。结论提高粘结层韧性、减少粘结层中裂纹萌生和向基体扩展,是热障涂层材料和工艺优化的有效途径。     

Growth inhibition and oxidative damage of Microcystis aeruginosa induced by crude extract of Sagittaria trifolia tubers

Aquatic macrophytes are considered to be promising in controlling harmful cyanobacterial blooms. In this research, an aqueous extract of Sagittaria trifolia tubers was prepared to study its inhibitory effect on Microcystis aeruginosa in the laboratory. Several physiological indices of M. aeruginosa, in response to the environmental stress, were analyzed. Results showed that S. trifolia tuber aqueous extract significantly inhibited the growth of M. aeruginosa in a concentration-dependent way. The highest inhibition rate reached 90% after 6 day treatment. The Chlorophyll-a concentration of M. aeruginosa cells decreased from 343.1 to314.2 μg/L in the treatment group. The activities of superoxide dismutase and peroxidase and the content of reduced glutathione in M. aeruginosa cells initially increased as a response to the oxidative stress posed by S. trifolia tuber aqueous extract, but then decreased as time prolonged. The lipid peroxidation damage of the cyanobacterial cell membranes was reflected by the malondialdehyde level, which was notably higher in the treatment group compared with the controls. It was concluded that the oxidative damage of M. aeruginosa induced by S.trifolia tuber aqueous extract might be one of the mechanisms for the inhibitory effects.     

S型皮托管截面受损与皮托管系数变化的实验研究

污染源排放废气流速通常在7～15m／s之间。通过S型皮托管在低速风洞中与标准皮托管的对比实验说明,在10m／s,15m／s两种情况下,皮托管迎风面截面变化对皮托管系数却的影响很大,实验结果可供污染源废气监测和皮托管定期检定进行参考。     

盐雾试验方墨探讨

分析了不同盐雾试验方法标准对盐溶液配制、试样的处理和检测、试验参数、试验过程控制等方面的不同要求,探讨了盐雾试验的操作技术,提出了必须严格控制盐雾试验过程的建议和不能用不同标准进行的盐雾试验结果进行比较的观点.     

多种损伤影响下正交层合板刚度退化研究

通过对纤维增强树脂基复合材料层合板的细观力学分析,建立了基体裂纹和纤维断裂2种损伤共存时正交层合板刚度退化模型.给出了纤维断裂损伤的计算方法,对正交层合板刚度退化过程进行了量化计算.结果表明,所建立的模型采用较少的几个参数即可描述层合板刚度退化过程,并与试验结果吻合较好.