Processing of an East Mediterranean phosphate ore sample by an integrated attrition scrubbing/classification scheme (part one)

ABSTRACT

In this study, an Egyptian siliceous/calcareous sedimentary phosphorite was subjected to beneficiation by unsophisticated economic means. The mineralogical and chemical examination showed that the ore sample is a typical example for the East Mediterranean phosphorites with 21.80% P₂O₅, 10.93% acid insoluble and 16.61% loss on ignition. The primary crushed sample was classified into three size fractions without any milling and they were separately subjected to an integrated attrition scrubbing study. Screening and classification on the 2.30 mm and 0.071 mm sieves were sequentially introduced with the attrition process. The effect of solid%, attrition speed and time were studied and optimized for each size fraction. Results showed that three products were produced and could be categorized according to their P₂O₅ content into the coarse tailing (+2.30 mm), the attrition concentrate (?2.30 + 0.071 mm) and the phosphate fines (?0.071 mm). The P₂O₅ contents of these products reached 12.24%, 28.72% and 18.77%, with P₂O₅ distribution reached 6.74%, 51.75% and 41.51%, respectively. A global P₂O₅ of 28.72% was obtained with a recovery of about 52%. A tentative flow-sheet for the whole process was postulated.     

Mathematical Modeling and Simulation of Ozonation Processes in a Downstream Static Mixer with Sieve Plates

New standards for drinking water disinfection require better optimization of the ozonation stage on the basis of the concentration×contact time (CT) concept, and production of ozone from pure oxygen at higher concentrations presumes application of the new type of contactors operating efficiently at lower gas/liquid volumetric ratios. One possible construction to meet these requirements is a downstream static mixer with sieve plates. At higher flow rates of liquid in this mixer, the interfacial area may reach 10,000m²/m³ at energy dissipation 1–5kW/m³. Due to the very intensive hydrodynamic regime the ozone utilization degree in the gas phase reaches 98–100% in natural lake water ozonation. Mathematical simulation of lake water ozonation in this mixer indicated that the process proceeds mostly in the diffusion or kinetic regime depending on the operating parameters. The dominating parameters besides the sieve geometry are the liquid flow rate in the holes of the sieves and the volumetric liquid/gas ratio.     

徐州市云龙湖水质监测与评价

以云龙湖东西两湖区为对象,研究其不同功能区水质状况.在云龙湖东湖、西湖区各设置3个采样点,监测水体中总氮、总磷、高锰酸盐指数、氨氮、溶解氧和透明度指标;分别使用模糊识别法和特里指数法对水体进行水质评价与富营养化评价.评价结果表明：云龙湖水质级别为Ⅲ类,其中TN、TP超标明显,水体已呈现轻度富营养化;不同功能区水质差异明显,东湖区水质优于西湖区,云龙湖功能区划分对水体有显著影响.     

山东南四湖湿地生物多样性及保护措施

南四湖湿地由湖泊、沼泽湿地和人工湿地构成,生物多样性十分丰富。其湿地生态系统具有生境脆弱性、物种多样性、生物稀有性、生态自然性等特点,是我国华北平原最大的具有良好湿地植被的天然湿地生态系统,同时也是众多候鸟的越冬地、繁殖区及迁徙必经的中转站。分析了湿地生物多样性现状及保护中存在的主要问题,提出了相应的湿地保护措施。     

主成分分析法在鄱阳湖水质评价中的应用

通过SPSS13.0软件,利用主成分分析法有效地分析鄱阳湖水质的时空变化特征,结果表明：①鄱阳湖星子断面在1991—2006年时间跨度上水质不断下降,这一定程度上反映了鄱阳湖的污染程度在不断加重;②2008年鄱阳湖水质空间分布上表现为湖内水质好于入湖区域水质,说明五河带来的污染物对鄱阳湖周边地区水质影响较大,鄱阳湖主要受外源污染而非内源污染。     

鄱阳湖流域生态系统管理框架

鄱阳湖流域内水环境污染、水土流失、土地退化、自然灾害、矿区生态环境破坏等重大生态环境问题,不仅影响长江中下游的生态环境,同时制约流域内社会经济的发展。因此,亟须实行鄱阳湖流域生态系统管理,更好地协调流域内河流上下游、河湖以及行政区域之间的环境保护与社会经济发展关系。在对鄱阳湖流域特征分析和综合管理回顾的基础上,探讨鄱阳湖流域生态系统管理框架,分析鄱阳湖流域生态系统管理的尺度和范围、生态系统服务可持续利用、适应性管理等问题,提出鄱阳湖流域生态系统管理目标,为鄱阳湖生态经济区建设以及流域开发与保护提供理论依据和指导。     

策应鄱阳湖生态经济区建设 推动吉安进位赶超绿色崛起

建设鄱阳湖生态经济区是国家从战略全局和长远发展出发作出的一项重大决策。如何主动策应鄱阳湖生态经济区建设,推动吉安进位赶超、跨越发展,是摆在我们各级政府和科技部门面前一项亟待解决的问题。为此,一是要提高认识,统一思想,切实增强策应规划的使命感和责任感;二是要结合实际,突出重点,全面对接鄱阳湖生态经济区规划;三是要加强领导,落实措施,确保吉安进位赶超、绿色崛起取得明显成效。     

长兴入太湖河道口门的淤积问题与对策分析

长兴县环太湖堤岸长34 km,入湖河道口门32条.1991年环湖大堤建成运行以来,为流域防洪、供水、环境、航运效益的发挥作出了积极贡献,也改善了长兴县环太湖乡镇的交通条件.由于受地理位置、地质、水文特征和气象要素等条件的影响,入湖河道口门淤积比较严重,对淤积的成因进行了分析,提出治理对策和措施的建议.     

洞庭湖区农村住宅节能措施探讨

通过研究洞庭湖区农村住宅的能耗状况与技术现状,分析了影响新农村住宅节能的主要因素,提出了切合当地的新农村住宅节能措施．     

The role of wind-wave related processes in redistributing river-derived terrigenous sediments in Lake Turkana: A modelling study

A complete annual cycle of the dynamics of fine-grained sediment supplied by the Omo and smaller rivers is simulated for Lake Turkana, one of the world’s large lakes, with the hydrodynamic, wave and sediment transport model Delft3D. The model is forced with river liquid and solid discharge and wind data in order to simulate cohesive sediment transport and resuspension. It simulates stratification due to salinity, wave generation and dissipation, and sediment advection and resuspension by waves and currents, with multiple cohesive sediment fractions. A comparison of the simulation results with remotely-sensed imagery and with available in-situ sediment deposition rates validates the model. By devising simulation scenarios in which certain processes were switched on or off, we investigated the contribution of waves, wind-induced surface and bottom currents, salinity-induced stratification and river jet, in resuspending and transporting fine sediments in the lake basin. With only the wind or river influence, most of the sediment deposition occurs in the first 10 km off the Omo River mouth and at a depth < 10 m. When waves are switched on, increased bed shear stresses resuspend most of the fine sediments, that are then deposited further and deeper in the first 30 km, in water depths > 30 m. This study sheds new light on sediment transport in Lake Turkana and in great lakes in general, favouring the view that wind-waves can be the main agent that transports sediment away from river mouths and to deeper areas, as opposed to river-plume or gravity-driven transport.