Ennoblement of stainless steel in natural seawater – A new explanation

The ennoblement of corrosion potential (E_corr) of passive metal immersed in seawater was investigated with electrochemical technology and epifluorescence microscopy. The in situ observation showed that the bacteria number increased on the metal surface according to an exponential law which was in the same way with the ennoblement of E_corr. At the same time, the anodic polarization current of high‐Mo stainless steel decreased in the initial days. According to the mix‐potential theory and the characteristics of polarization curves of high‐Mo steel in natural seawater, the ennoblement of corrosion potential may be induced by the decrease of the passive current density.     

Application of Fuzzy Control into a New Kind of Sea Water Still

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A fatigue-life prediction methodology for notched aluminum-magnesium alloy in gulf seawater environment

Local-strain and linear-elastic fracture-mechanics (LEFM) methodologies have been investigated for prediction of the corrosion-fatigue life of notched components of specially developed Al-2.5Mg alloys exposed to Arabian Gulf seawater environment. Corrosion-fatigue crack initiation life estimates were obtained using strain-life relationships; corrosion-fatigue crack propagation life estimates were obtained using LEFM relationships. The total corrosion-fatigue life was considered to be the sum of the crack initiation and crack propagation lives. Estimated corrosion-fatigue lives were compared with experimentally obtained corrosion-fatigue life data using center-notched specimens of three types of Al-2.5Mg alloys (containing different amounts of chromium) exposed to Arabian Gulf seawater environment. Two notch geometries, a circular notch (K _t= 2.42) and an elliptical notch (K _t= 4.2), were investigated. Good corrosion-fatigue life predictions can be obtained using local-strain and LEFM methodologies by determining the relevant material constants via a few simple fatigue tests on smooth specimens and a few crack-growth-rate tests in the environment at the frequency of interest.     

低压反渗透复合膜NTR—7250的脱盐性能

测定了ＮＴＲ－７２５０膜的脱盐性能。结果表明，该膜水通量约为ＣＡ膜的５倍；脱盐率主要受阴离子控制，并随电荷数递增；水中结垢成分被优先除去，ＳＯ４＾２－，硬度和ＨＣＯ３＾－除去率分别大于９７％，８１％，７６％；该膜抗氧化能力与ＣＡ膜相当，而适用ＰＨ范围更宽，并且可在较高水温下长期使用。     

Hybrid systems in seawater desalination—practical design aspects, present status and development perspectives

Ever since seawater desalination has been applied on an industrial scale, and particular in the countries of the Arabian Gulf, the application of desalination processes in dual-purpose facilities—water and power—as a hybrid configuration has been discussed in many feasibility investigations and also planning concepts. It is above all the combination of reverse osmosis with thermal processes that has found increasing interest with the aim of ensuring, as economically as possible, uniform water supplies under the specific, greatly varying load conditions in the Gulf countries. Such design concepts for hybrid configurations encompass straightforward structures with a low degree of coupling between membrane and thermal desalination processes, but range up to very complex configurations with strong interconnections on both the water side and thermally, as well as with several desalination processes connected in series or in parallel. Classical hybrid concepts in which the permeate from an RO desalination component is mixed with distillate from thermal desalination have already been implemented in Saudi Arabian dual-purpose plants, like Jeddah and Yanbu-Medina. Although hybrid systems of greater complexity have been addressed in many design studies and publications, up to now none has been brought to fruition. Coming into consideration asthe design basis for determining the capacity shares of the various desalination processes operated in a hybrid configuration are: arrangement of thermal cycle of the power plant component; water/power ratio of the dual-purpose seawater desalination and power plant; provision of undiminished water production of the desalination plant as electricity generation varies; provision of a specified drinking water quality with regard to composition and salt content; combination of all these aspects. Also gaining in importance are concerns of environmental pollution and sustainable development when selecting seawater desalination and power plant configurations, as well as their optimization when considering desalination and electricity generation as a whole. In the practical design of hybrid membrane and thermal systems, aspects come to light, though, that restrict linking of the two systems and joint utilization of facilities, as conceived in studies and conceptual design investigations. This applies both for common utilization of intakes and the use of heated up cooling water from thermal processes as a feed stream for the RO part of the desalination process. Additionally, requirements of drinking water composition, particularly chloride content, TDS and compliance with a specific residual content of boron, influence specifically the design of the membrane process part and its share in the total desalination capacity. Such practical aspects have greatly influenced the design and configuration of the Fujairah hybrid plant for which, from a total desalination capacity of 100 MIGD (454,600 m³/d), the share of 37.5 MIGD (170,500 m³/d) makes its seawater RO plant the biggest currently being constructed anywhere in the world. From the findings of the engineering of this plant and the idea that, by increasing interconnection between the two processes on the water side, it is possible to advance a hybrid configuration of this type with regard to cost optimization in the membrane installation, but also by joint utilization of the intake equipment, perspectives result for applied research efforts over the near and long terms, for example: long-term behavior of membranes at elevated temperatures; tendency for biofouling in membrane process with common utilization of cooling water and brine; influences of such interconnections on the overall availability of the facility. But also for the operation and maintenance organization of such large facilities, consequences can be foreseen for the future development of hybrid plants, particularly for operation management and organisation of the interplay of the different power plant and desalination systems, monitoring of SWRO membrane replacement and cleaning, as well as controlling water quality.     

A review of the current status of small-scale seawater reverse osmosis desalination

The current status of small-scale desalination (produced water capacity 100 m³/day or less) is reviewed to provide an overview of the market segment. The use of energy-recovery devices in this market segment is also reviewed. We find that the Middle East accounts for the largest market share worldwide at present, and reverse osmosis is overwhelmingly dominant among the desalination technologies adopted. Implementation of energy-recovery devices at small scale is rare, which leads to relatively high energy consumption for small-scale seawater reverse osmosis desalination systems.     

风力发电——电渗析淡化苦咸水示范站的研建与运行

针对海岛风力资源丰富，但用电用水困难的问题，用风力发电－电渗析淡化苦咸水法成功地解决了海岛用电、吃水问题，具有较大的实用意义和社会效益。     

Empirical equations for the thermodynamic properties of aqueous sodium chloride

Equations for the thermodynamic properties of aqueous sodium chloride near its vapour pressure are presented. The equations are functions of temperature and concentration, and may be used to estimate aqueous sodium chloride's solubility, density, vapour pressure, specific enthalpy and entropy. They are valid for temperatures from 0 to 300°C, and concentrations extending to saturation with suitable accuracy. The thermodynamic equations are represented graphically and compared with published experimental data. These equations should prove to be a useful tool for modeling desalination equipment, particularly distillation processes.     

Coupling of nuclear heating reactor with desalination process

A seawater desalination plant using a nuclear heating reactor (NHR) coupled with the multi-effect distillation (MED) process was developed by the Institute of Nuclear Energy Technology, Tsinghua University, China. The seawater desalination plant was designed to supply potable water demand to some coastal location or island where both fresh water and energy sources are severely lacking. The NHR design possesses intrinsic and passive safety features, which was demonstrated by the NHR-5 experiences. The intermediate circuit and steam circuit were designed as the safety barriers between the NHR and MED desalination systems. With the power range of the heating reactor within 10 to 200 MWt, the desalination plant could provide 8,000 to 160,000 m³/d of potable water of appropriate quality. The design concept and parameters, safety features, and comparative investigation of coupling schemes are presented in the paper.     

海水反渗透淡化系统的能耗

通过对海水反渗透淡化系统（SWRO）吨水成本的分析，提出降低SWRO能耗的解决措施，采用能量透平装置（TURBO）或压力转换器（PE）回收浓水的能量传递于进水，不仅可以降低吨水电耗，也可减小一次性投资。值得关注的是，压力转换器，回收效率可达94％，在海水淡化系统中对于降低能耗有更重要的意义。