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.     

基于最大偏差相似性准则的BP神经网络短期电力负荷预测算法

针对企业电力负荷随机性强、稳定性低、预测精度不理想等问题,提出了一种基于最大偏差相似性准则的BP神经网络短期电力负荷预测算法。首先对最大偏差相似性准则算法进行修改,并提出使用预测日的负荷特征向量与最大偏差相似性准则算法聚类之后的类中心负荷特征的距离来确定预测日的相似日类别;然后将聚类后的相似日类别负荷数据作为BP网络的训练数据,输出预测日起始的连续三天96整点负荷值。实验表明,该方法提出的短期电力负荷预测方法在精度和网络训练时间上都有较大的提升,具有较高的有效性和实用性。     

全自动液压压砖机CAD/CAE信息集成系统数据库的研究与开发

对全自动液压压砖机CAD CAE信息集成系统中的工程数据库的设计和实施进行了研究 ,分析了系统对数据信息的需求 ,提出了该系统数据库的E -R数据模型以及表的定义和结构关系 ,实现了压砖机CAD CAE信息集成系统。     

邻苯二甲酸酐的生产与市场

2005年全球邻苯二甲酸酐(PA)的生产能力约为450万t/a,需求量可达到350万~360万t,用于增塑剂占57%、醇酸树脂占17%、不饱和聚酯树脂占17%。未来5年全球PA需求将以年均3.0%~3.5%的速率增长,其中亚太地区将继续引领全球PA市场快速增长,其年均增速将达到4.0%~4.5%,美国仅以1.5%~2.0%的速率增长,西欧仅以1.0%的速率增长。我国产能和产量快速增长,2004年国内生产能力约为864 kt/a,消费量约为873 kt,用于邻苯二甲酸酯类增塑剂约占总消耗的60%,醇酸树脂约占22%,不饱和聚酯树脂占10%。     

甲醇市场分析及发展甲醇工业应注意的问题

分析和预测了国内外甲醇消费用户目前和今后几年的需求情况,从新建装置的布局、产品深加工、生产成本和市场价格等方面提出了发展甲醇工业应注意的问题。     

聚碳酸酯的生产和市场分析

分析了国内外聚碳酸酯(PC)的生产现状,包括已有、在建及计划建设的装置产能,并预测了今后生产和需求的发展趋势;展示了国内PC工业化技术的开发现状。2002年全球PC产能约为200万t/a,预计到2006年产能将增加到250万t/a,需求将达到300万t,并且在光学介质和汽车行业将会表现出强劲的扩张性需求。我国2002年PC进口量超过40万t,预计今后几年国内需求增长速度仍较快。建议国内企业应加大科研投入,加速我国PC工业的发展。     

上海地区不同商品粉煤灰水泥浆体的流变性能

采集了上海地区不同种类，等级和加工方式的7种商品粉煤灰，测定了种各种粉煤灰水泥浆体的流变性能，研究了商品粉煤灰品质与掺量对浆体流变参数的影响，并分析了影响浆体流变性能的粉煤灰主要品质因素。     

国内外无机颜料工业的现状及发展趋势

阐述了国内外无机颜料的生产及需求现状,预测了无机颜料工业的发展趋势、产品发展方向,提出了发展我国无机颜料工业的策略。     

我国LLDPE产需及装置建设现状

我国现有５套ＬＬＤＰＥ生产装置，合计生产能力为３８．５万ｔ／ａ。“八五”期间，我国又引进６套ＬＬＤＰＥ生产装置，合计生产能力为６４万ｔ／ａ。到“八五”后期，我国ＬＬＤＰＥ生产能力将超过１００万ｔ／ａ，其中７５％是采用美国ＵＣＣ技术生产的。建议我国跟踪世界新技术，并适应市场需求。     

Formulating middle-phase microemulsions using mixed anionic and cationic surfactant systems

Although mixtures of anionic and cationic surfactants can show great synergism, their potential to precipitate and form liquid crystals has limited their use. Previous studies have shown that alcohol addition can prevent liquid crystal formation, thereby allowing formation of middle-phase microemulsions with mixed anionic-cationic systems. This research investigates the role of surfactant selection in designing alcohol-free anionic-cationic microemulsions. Microemulsion phase behavior was studied for three anionic-cationic surfactant systems and three oils of widely varying hydrophobicity [trichloroethylene (TCE), hexane, and n-hexadecane]. Consistent with our hypothesis, using a branched surfactant and surfactants with varying tail length allowed us to form alcohol-free middle-phase microemulsion using mixed anionic-cationic systems (i.e., liquid crystals did not form). The anionic to cationic molar ratio required to form middle-phase microemulsions approached 1∶1 for univalent surfactants as oil hydrophobicity increased (i.e., TCE to hexane to n-hexadecane); even for these equimolar systems, liquid crystal formation was avoided. To test the use of these anionic-cationic surfactant mixtures in surfactant-enhanced subsurface remediation, we performed soil column studies: Greater than 95% of the oil was extracted in 2.5 pore volumes using an anionic-rich surfactant system. By contrast, cationic-rich systems performed very poorly (<1% oil removal), reflecting significant losses of the cationic-rich surfactant system in the porous media. The results thus suggest that, when properly designed, anionic-rich mixtures of anionic and cationic surfactants can be efficient for environmental remediation. By corollary, other industrial applications and consumer products should also find these mixtures advantageous.