Progress and prospects of seawater desalination in China
我国海水淡化若干问题及对策
第18卷第2期 2020年4月南水北调与水利科技（中英文）South-to-North Water Transfers and Water Science TechnologyVol.18 No. 2Apr. 2020DOI ： 10.13476/j. cnk i. nsbdqk. 2020.0043闫佳伟，王红瑞，朱中凡，等.我国海水淡化若干问题及对策[J].南水北调与水利科技（中英文），2020，18(2):199-210. YAN J W, WANG H R,ZHU Z F,et al. Relevant issues and countermeasures of seawater desalination in China[J]. South-to-North Water Transfers and Water Science Technology,2020,18(2) ： 199-210. (in Chinese)我国海水淡化若干问题及对策闫佳伟1>2，王红瑞h2，朱中凡1>2，白琪阶“2(1.北京师范大学水科学研究院，北京1〇〇875;2.城市水循环与海绵城市技术北京市重点实验室，北京100875)摘要:我国拥有1. 8万k m的海岸线，海洋资源丰富,海水淡化是解决水资源短缺，增加淡水资源的根本之道。
总结 了海水淡化的利用情况，深人探究制约海水淡化发展的因素,分析了淡化海水的利用前景。
在分析国际海水淡化现 状、经验及浙江舟山海水利用经验的基础上，针对我国海水淡化存在的问题，提出了我国海水淡化发展的对策：建议 加大技术投人，发展政产学研商模式，降低经济成本;合理规划建设海水淡化项目.提高产能利用;加强对海水综合 利用，减少环境污染;加强政策扶持，完善法规标准，不断推进海水淡化产业的发展。
关键词:海水淡化;制约因素;对策;前景;舟山中图分类号:TV213. 1文献标志码:A 开放科学（资源服务）标识码（OS1D):Relevant issues and countermeasures of seawater desalination in ChinaYAN Jiawei1*2 ,WANG Hongrui1-2 ,ZHU Zhongfan1*2 ,BAI Qijie1'2(1. College o f Water Science»Beijing Normal University, Beijing100875, China；2. Beijing Key Laboratory o f Urban Hydrological Cycle and Sponge City Technology，Beijing 100875，China) Abstract：China has a coastline of 18,000 kilometers,rich in marine resources. Desalination is the fundamental way to solve water shortages and increase freshwater resources. This paper summarized the utilization of seawater desalination,deeply explored the factors that restricted the development of desalination,and analyzed the utilization prospects of desalinated seawater. Based on the analysis of the current status and experiences of international desalination and seawater utilization in Zhoushan, Zhejiang, this study put forward the countermeasures for the development of seawater desalination in China. It was suggested to increase technical input,developed the model of government, industry, and research, to reduce economic costs, to reasonably plan and build seawater desalination projects. The projects may increase the utilization of production capacity, strengthen the comprehensive utilization of seawater,reducing the environmental pollution,strengthen policy support,improved laws and regulations,and continuously promoted the development of seawater desalination industry.Key words：desalination of seawater；constraints；countermeasures；prospects；Zhoushan近年来，随着社会经济的高速发展，水生态环境 水、雨洪水、生活污水、矿井水等非常规水源逐渐引逐渐恶化，我国水资源供需矛盾将进一步加剧，海 起政府和相关研究人员的重视。
海洋科学专业英语词汇
Chapter1 The History of Oceanography（一）【第一、二周】【十二周复习】meteorology botany sub-discipline basin interaction composition chart observation cruise atoll the British Isles Mediterranean Aegean Seas Arctic Antarctic seafloor drifting plants skeleton microscopically Atlantic Faroe Islands环礁航行盆地组成气象观测相互作用分支学科海图植物爱琴海骨骼显微镜水平地中海大西洋法罗群岛大不列颠群岛北极南极海床浮游生物Chapter1 The History of Oceanography（二）【第三周】【十三周复习】flux variation tropical accuracy joint specific sustain prime element mature hypothesis sea level continent margin federal联合假象热带的特殊的精确度、误差成熟通量变化元素维护边缘联邦的首要的海平面大陆Chapter 2 Earth: The Water Planet【第四周】【十四周复习】Surface area Coral sea equator volume crew mean depth marginal sea drain relatively meridian Persian Gulf bay gulf the Caribbean sea Baltic sea southern hemisphere子午圈表面积体积平均深度波斯湾加勒比海波罗的海赤道边缘海相反的、相对的南半球珊瑚海船员下陷宽海湾长海湾Chapter 3 The Sea Floor and Its Sediments（一）【第五周】【十五周复习】Sediment feature submersible survey scholar magnificent sample depression mariner sampling seabed mountain chains shallower regions mineral particle origin source deposit varies distribution general layer contrast constant accumulation oceanic crust intermediate well sorted gravel clay elsewhere displacement soluble descent spherical turbulent eddies latitude longitude水手源样品颗粒物海床矿物山脉浅海区域纬度经度洋壳可溶的中等的位移分选好的别处沙砾状的粘土沉积物下降特征采样潜水器壮观的纵览学者来源积累变化持续的分布对比、相反的通常的层下沉涡流球形的不稳定的Chapter 3 The Sea Floor and Its Sediments（二）【第六周】【十六周复习】Continental shelf grained mid-ocean –ridge process slope rise turbidity currents shore typical source compose thaw ice caps dominant preexisting abyssal lithogenous terrigenous weather technically sludge powder ooze overlying suspend calcareoussiliceous reddish concerning pattern quartz provide glacier overwhelm iron oxidize大陆架大陆坡大陆隆浊流岸粒度大洋中脊过程典型的冰盖冰川来源预先存在造岩的陆源的学术的污泥风化解冻主要的战胜组成深渊粉末悬浮状态铁氧化发红的石英方式提供有关的石灰质的硅质的软泥上层、表层Chapter 3 The Sea Floor and Its Sediments（三）【第七周】【十七周复习】Precipitation cosmogenous seaward estuary delta passive water column bombard erosion glacier currently steep plume suspension subtropical pelagic hydrothermal vents manganese nodules magnesium-rich disintegrate tektite quantity沉降水柱卷流热液孔锰结核富镁的宇宙碎屑轰击悬浮状分解熔融的向海的侵蚀亚热带河口冰川三角洲目前的被动的陡的远洋的量Chapter 3 The Sea Floor and Its Sediments（四）【第八周】Property superficial seaweed exploit dilute substitute sparse arid lead depletion fragment significant miner seam zinc strata multiplies ten to power six dislodge buoyancy十的六次方锌煤层矿工性质相当的铅耗竭的地层碎片干旱的稀少的浅海的开发替代物海藻稀释逐出，移走浮力Chapter 3 The Sea Floor and Its Sediments（五）【第十一周】Fertilizer sulfur acid hydrocarbon map methane nodule ashore anaerobic submarine nickel substantial swamp subject landslide ores volatile gas hydrate slump cobalt impurity solid component stage drill core alloy submerge operation厌氧的甲烷肥料水下的硫酸向岸的勘探结核状烃镍钴矿石大量存在滑坡沼泽天然气水合物承受挥发物山崩杂质操作，开采固体淹没成分合金阶段，步骤钻孔岩芯Chapter4 The Propertiies of Seawater【第十二周、第十三周】Molecule covalent bond be inversely proportional carbonic acid dip formula electrically neutral tenfold dissociate subtropic consist negatively alkaline bicarbonate per mill nucleus consequence basic arrow landlocked sea positively polar base respiration open ocean proton consequently logarithmic equilibrium neutron ever-changing by a factor of oxidation orbit concentration emission matter solution buffer gram ions runoff precipitation evaporate分子电中性碳酸氢根极中子溶液共价键10倍每千分之一碱不断变化缓冲反相关分解核子呼吸作用倍克碳酸的亚热带结果公海氧化离子舀（水）含有碱性的质子轨道径流分子式负的箭头方向然而浓度降雨量碱性的内陆海对数运算排放物蒸发正的平衡的物质Trace element iodine salt content conservation constituent complexes crystallization magma mantle irrigation crack permeable silica radiolatians碘能透过的地幔含盐量结晶作用地裂缝络合物灌溉保守成分痕量元素岩浆放射虫硅土Chapter4 The Propertiies of Seawater【第十四、五、六周】Compensation depth proportional regulate adsorption trench sill net mechanism solar decomposition anoxic annual specialized probes photosynthetic saturation predator substantially stagnant fjord成比例的海沟实质的太阳的补偿深度槛过饱和的分解，腐解捕食者年际的缺氧的调节净专用探针机制吸收光合作用停滞的峡湾。
与海洋能有关的英文
与海洋能有关的英文The Fundamentals and Applications of Ocean Energy.Ocean energy, a vast and untapped resource, holds the potential to power our future. It encompasses a diverse range of renewable energy sources derived from the ocean's natural motions, temperatures, and chemical processes. In this article, we delve into the various types of ocean energy, their working principles, and their potential applications.Types of Ocean Energy.1. Ocean Thermal Energy Conversion (OTEC): OTEC harnesses the temperature difference between warm surface water and cooler deep-sea water to generate energy. It works by using a heat exchanger to convert the temperature difference into a pressure difference, which is then used to power a turbine and generate electricity.2. Tidal Energy: Derived from the rise and fall of tides, tidal energy can be harnessed using turbines placed in tidal streams or through the construction of tidal barrages. These turbines rotate due to the flow of water, generating electricity.3. Wave Energy: Wave energy converters capture the kinetic and potential energy of ocean waves. They typically consist of floating devices that use the motion of waves to power generators.4. Salinity Gradient Energy: This type of energy is harnessed from the difference in salinity between seawater and freshwater sources. It involves using this salinity difference to create a pressure gradient, which can be converted into electricity.5. Ocean Current Energy: Ocean current energy harnesses the kinetic energy of oceanic currents. Turbines placed in the path of these currents capture their energy, converting it into electricity.Applications of Ocean Energy.Ocean energy has the potential to power a wide range of applications, from small-scale residential uses to large-scale industrial and commercial applications. Here are some examples:1. Electricity Generation: Ocean energy can be used to generate electricity for grid-connected power systems, supplying renewable energy to communities and businesses.2. Desalination: By harnessing salinity gradient energy, ocean energy can be used to power desalination plants, providing freshwater to areas with limited access.3. Marine Transport: Ocean energy can power marine vehicles, such as boats and submarines, reducing dependency on fossil fuels.4. Remote Area Power Supply: In remote areas where access to traditional power grids is limited, ocean energy can provide a sustainable and reliable power supply.5. Environmental Monitoring: Ocean energy can be used to power environmental monitoring stations, enabling continuous monitoring of oceanic conditions and protecting marine ecosystems.Challenges and Future Prospects.While ocean energy holds immense potential, there are several challenges that need to be addressed to realize its full potential. These include technological limitations, environmental impacts, and economic feasibility.Technological advancements are crucial to improve the efficiency and reliability of ocean energy converters. Research and development efforts are ongoing to develop more efficient turbines, converters, and energy storage systems.Environmental impacts, such as the potential for ecological disruption and water pollution, must becarefully managed. Careful site selection, environmentalimpact assessments, and the use of sustainable construction materials are essential to mitigate these impacts.Economic feasibility is another key challenge. While the initial capital costs of ocean energy projects can be high, the long-term savings from using renewable energy can offset these costs. Policy incentives, such as subsidies and tax credits, can also help to make ocean energy more economically attractive.In conclusion, ocean energy represents a vast and untapped resource that has the potential to power our future. With ongoing research and development, technological advancements, and careful management of environmental impacts, ocean energy has the potential to play a significant role in meeting our energy needs in a sustainable and environmentally responsible manner.。
核能海水淡化
核能海水淡化摘要：我国被联合国认定为13个最贫水的国家之一，核能海水淡化是应对将来可能出现的全国大范围水危机的重要途径。
在竞争性方面，核能海水淡化在环保，缓解交通运输等方面，有很强的竞争能力；在经济性方面，其成本仍比国内水价高出2.8到9.97倍。
在环保、缓解交通运输负担等方面，其竞争能力强。
关键词：核能海水淡化竞争性引言我国人均水资源占有量仅为世界的109位，被联合国列为世界13个缺水国之一。
目前，我国解决缺水问题的途径主要有实施区域性调水、蓄水工程、节水以及污水回用等。
这些途径只能解决区域性缺水和季节性缺水问题，而不能从根本上解决资源性缺水问题。
另外，投资和成本问题也是要考虑的重要因素。
据专家预测，仅南水北调中线工程投资就将达1000亿元。
工程实施后，长江水流到北京按现行不变成本计算，综合成本将在5元/立方米以上，甚至更高。
有的资料认为，远程调水40公里，其成本将超过海水淡化[1]。
海水淡化仅需要低品质的热源，利用核能生产这种热源比采用化石燃料具有更高的能源利用率。
因此，积极发展核能海水淡化，是解决我国部分地区缺水,以及应对将来可能出现的淡水资源危机的重要途径。
1．海水淡化方法海水淡化是将含盐浓度为35000mg/L的海水淡化至500mg/L以下的工艺过程。
目前，工业规模的海水淡化技术分为两类：一类是利用膜技术的耗电工艺，即反渗透法（RO）,消耗的能量主要来自于高压泵所需的电能；另一类是耗热工艺,即利用热能加热海水，通过蒸发——冷凝物理过程生产淡水，包括低温多效蒸馏(LT—MED)和多级闪蒸技术(MSF)[2]。
低温蒸馏的造水装置是将加热管放于海水蒸发器体内，并浸于海水之中，加热蒸汽（称为一次蒸汽）在加热管内流动，将管外海水加热并蒸发，产生的蒸汽（称为二次汽）在冷凝器中冷凝成蒸馏水。
蒸发器内的压力为较高的真空。
为了提高造水比，可以采用多级蒸发系统。
在这种系统中，第一级蒸发器产生二次汽，直接送入下一级蒸发器中作加热蒸汽之用。
海水淡化与饮用水
附录英文原文Desalination and water1 Introduction Water is the source of life. Who have life-sustaining water, people live longer and have to drink the health of the role of non-polluting water. Not only human life can not be separated from water, industrial and agricultural production are inseparable from the water. Therefore, water for human survival and development is crucial, especially in the human face water shortages, "water will soon become a serious social crisis. After the oil crisis of the next water crisis is" a serious case, solve the water has aroused worldwide attention. As early as 1977, the United Nations to convene the General Assembly of the water on to the world the warning was issued.Nearly 30 years, both developing and developed countries to address the water issue has become to ensure that people live a normal life and sustainable economic development an important task. To solve the task of drinking water there are three, the first having water to drink, to solve the problem of water shortage, and the second could not have contaminated drinking water, address water pollution problems, the third to drink a healthy effect on the human body of water to address the drinking activated to deal with the issue of water. These three aspects of drinking water mission, although of different priorities, but the health of the guarantor, is the need to address co-ordinate the development. This article links the task to solve the three aspects of drinking water to discuss the development of our country use and desalination of sea water so the problem of drinking water and recommendations. 2 "Water" is the eternal subject of humanOn the problem of water shortage, there is a recognized international standard, is generally believed that the country's per capita share of renewable fresh water annual volume of 1700 tons in the following, as a dry country, 1,000 tons in the following countries as a serious water shortage. At present, the world's populationaccounted for 40% of severe water shortage in more than 80 countries.The mostserious water shortage in the Middle East. Saudi Arabia of water per capita per year is only 249 tons, 95 tons of Kuwait, Israel, 300 tons, 936 tons of Egypt. Water shortage not only affects a country's economic development and people's normal life, but also caused by inter-State conflicts. United Nations panel on global warming, the President, the famous meteorologist John. Heap Lord that with global warming led to a number of opposing countries to compete for dwindling water resources in conflict, the outbreak of the 21st century will be water wars. 1993 47th session of the General Assembly decided on March 22 each year as "World Water Day", calling on other countries on the global prevalence of the problem of water shortage and water pollution caused by vigilant and carry out corresponding activities to raise public awareness of flooding is very correct.China's water shortage is a serious country. Although water resources are 2800 billion m3, ranks sixth in the world, the per capita resources are 2220m3. However, the inclusion of the United Nations to China's water-poor countries, because of our spatial and temporal distribution of water resources extremely uneven, the time focus on water resources, flood season every year for 4 months, water in 2 / 3 is difficult to make use of the flood. The regional distribution of water resources do not match, the Yellow River, Huaihe River, Haihe River Basin, the country's total land area of 13.4%, accounting for 39 percent of arable land, population accounts for 35%, GDP (gross domestic product) accounted for 32% of the water resources account for only 7.7% per capita of about 500m3. In recent years, the area north of consecutive drought in the Yangtze River, has been used in Tianjin last year Panjiakou reservoir dead storage, but also the beginning of the Yellow River to Tianjin urgent emergency water diversion project. Weihai last year to deal with "dry" the development of more than 1 m3 of water a fixed water charge increases 40-fold measures. In addition, water pollution, China's more rain in the South also exists in varying degrees of water pollution, some areas also very serious. Therefore, in the face of "dry" a serious situation, it is necessary to ensure that people live a normal life and the sustainable development of the national economy, to solve the problem of water shortage and also3Human beings be able to overcome the "water" crisisAs long as people of all countries in addressing the issue of water ways, andactively increase income and reduce expenditure, and actively carry out theconstruction of water conservancy projects, the development of agriculture and otherwater-saving drip irrigation projects to poor areas of developed countries to lend ahelping hand, we will certainly be able to overcome the world " water shortage "crisis.The Middle East has long been a "dry" areas. They use the technology developedwater use and desalination, drip irrigation projects on agricultural development toalleviate shortages of fresh water crisis in the country played an important use. Theirexperience is worthy of our attention.Issues in our country both in the water more than water (floods) of the trouble,and little water (drought) concerns. We must have a long-term flood protectionprogram, a defeat of the open source of water-saving programs of drought, a strongprogram to prevent water pollution, and implement effective, we can overcome the"water" problems.At present, we have overcome the "water" issues, awareness is not uniform, thepace is also inconsistent, were not effective, implement, and even the existence ofcreating "water shortage" a serious phenomenon. For example, industrial andagricultural production in our daily life and the people waste a lot of water, seriousneglect of expenditure; more important in open water, but the use of rainwater, the useof urban sewage, especially for not taking water do not pay enough attention to notpay enough attention to the use of rivers, lakes, soil and water conservation, do notattach importance to the prevention of water pollution, so that the country's watersources of funds and the situation is ignored, think. On its causes, mainly the lack ofawareness of water resources, the lack of a sense of crisis of water resources, lack ofawareness of the ecological environment of water and soil protection, therefore,resulting in the destruction of vegetation, soil erosion, rivers, lakes, groundwaterpollution a serious situation.The idea is to guide action. China should take advantage of the annual "WorldWater Day" to carry out the awareness of water resources, water resources, a sense of urgency to protect the ecological environment of water and soil awareness campaigns to raise public awareness of the flooding. In particular, so that our cadres at all levels up to flood alert is very important. We are a socialist country, from the theory is most concerned about sustainable human development countries, we have the issue ofsustainable use of water resources, efforts should be made an example to the world. 4 The development of desalination of sea water use and the significance of andmeansMore than 97% of Earth's water is difficult to direct human use of water. This huge body of water contains water inexhaustible volume of fresh water resources and other wealth of material resources. At present, land in the face of human and material resources of fresh water scarcity a constant threat, the development and utilization accounted for 96.5% of fresh water resources and accounting for 3.5% of a variety of rich mineral resources is the inevitable trend of development. For the development of China's water use, is to solve water shortage problems, developing the national economy and building a great maritime power of the strategic significance of strategic measures.However, the development and utilization of sea water to ease the water shortage situation in China's strategic significance, in our country has not yet attracted sufficient attention. The development and utilization of water resources have a direct use and desalination of sea water use. The direct use of sea water a lot to ease the water shortage in coastal industrial city plays an important role. According to statistics, the coastal city of water more than 80% of the total industrial water, industrial water and more than 80% of the industrial cooling water. At present, the developed coastal cities in the electric power, metallurgical, chemical, petroleum, coal, building materials, food industry, to do water cooling water has reached 90%. China's Dalian, Qingdao, Tianjin, Shanghai and other coastal cities have also started the use of seawater for cooling, washing, printing and dyeing, chemical salt, but also far less than developed countries. The use of sea water for flushing, the Hong Kong SAR of China's nearly 40-year history, and China's coastal cities, water shortages, there is nota city to use sea water for flushing.The development of desalination use abroad soon.According to theInternational Desalination Association 1998 survey statistics, the world's 100m3 / d of desalination device for more than a total of 12,451 units, making the total amount of water has reached 22.735 million m3 / d. Than in the previous survey cycle statistics, the number increased by 39%, making the total increase of 64% water. In particular, have expanded rapidly in some countries in the Middle East. It is reported that Saudi Arabia's 60 desalination on a large scale industries development, and set up a desalination Corporation, has overall responsibility for project construction and management of desalination. They have established the world's 25 large-scale desalination plant, the construction of a desalination water supply world's longest pipeline, pipeline diameter and 1.5 meters long and 466 kilometers from the eastern part of the desalinated water supply to the capital, Riyadh. Saudi Arabia's desalination industry have not only solved the problem of water shortage in the western region, but also for the 1 / 3 region with electricity. Over the past 20 years, China has made significant development in desalination, a number of island residents for the establishment of a desalination plant drinking water, coastal industries, such as power plants have begun to do with the boiler for water desalination. In general, however, development is not fast.On the understanding of its causes and the force of habit or problem. To speed up China's current water use and industrial development, we must step up publicity to increase awareness of flooding not only the awareness of efforts to increase the water use of the popular propaganda, to make people fully aware of the significance of water use and practical sexual. At the same time to speed up the development of a water use and the correct way to industry. We believe that the development of water use efficiency must be, from a technical and process management efforts to reduce costs; the use of state-sponsored demonstration project to use sea water and the construction of the demonstration zone, a point to face, the development of joint ventures and other means of speeding up the desalination of sea water and its use and an important way of industrial development. We hope that, like Tianjin, Qingdao,Yantai, Dalian, Zhoushan city, such as severe water shortage, to take the lead in developing the use and desalination of sea water, state-sponsored demonstration projects, demonstration areas, first of all to the development of results in these cities. 5Suggestions(1) to enhance awareness of the development and utilization of sea water. Positive publicity to enhance the whole nation, especially the cadres at all levels to fresh water to sea water, it is necessary to develop awareness of the wealth and enhance the breadth and depth of production into a sense of responsibility, sense of mission, people firmly believe that the development and utilization of water resources and material resources of fresh water is development prospects are unlimited, on the national economy has great significance for sustainable development.(2) engage in water demonstration project, the construction of the demonstration zone. Such as national support for the establishment of power plants in coastal sea water utilization demonstration project (including the activation of desalination of sea water for drinking water project), the establishment of urban residents in coastal sea water for flushing the demonstration zone, which speed up the development of the cause of water use, will be able to play an effective role .(3) enterprises are the mainstay of the market, the establishment of a joint venture between the development of the sea. Combination of demonstration projects, the national research institutes and enterprises together to unite business and enterprise, the water use and water equipment manufacturers to use business to form water such as the use of technology and engineering companies.(4) activation of desalination process, there must be provided for national policy and support. Desalination of sea water depends on the activation of market mechanisms to deal with, but also increased support for government policies, such as the development of the environmental protection industry, as required by the Government must be able to better deal with the activation process to deal with the promotion of drinking is conducive to people's health. Desalination of sea water for drinking water, can be reassuring.译文海水淡化与饮用水一引言水是生命之源。
海水提取镁的操作流程化学方程式
海水提取镁的操作流程化学方程式1.首先，我们需要收集海水作为镁的原料。
First, we need to collect seawater as the source of magnesium.2.然后，对海水进行过滤和沉淀操作，以去除杂质。
Next, the seawater is filtered and precipitated to remove impurities.3.海水经过过滤后，我们需要蒸发海水以浓缩镁的含量。
After filtration, the seawater needs to be evaporated to concentrate the magnesium content.4.在蒸发过程中，镁会在溶液中沉淀出来。
During the evaporation process, magnesium willprecipitate out of the solution.5.接下来，将沉淀的镁进行过滤和洗涤。
The precipitated magnesium is then filtered and washed.6.随后，通过加热和其他化学处理，可以将镁从沉淀物中提取出来。
Subsequently, magnesium can be extracted from the precipitate through heating and other chemical treatments.7.最后，得到的镁可以通过干燥和净化来得到最终产品。
Finally, the obtained magnesium can be further purified through drying and purification processes.8.海水中镁提取的过程需要严格控制温度和化学物质的使用。
The process of extracting magnesium from seawater requires strict control of temperature and the use of chemicals.9.提取镁的过程需要耗费大量的能源和资源。
公共英语一级阅读文章《海水盐度》
公共英语一级阅读文章《海水盐度》一级的难度不大，但是阅读理解还是不少考生容易出错的。
下面，为大家送上一篇公共英语一级阅读文章，欢送阅读。
If the salinity of ocean waters is analyzed, it is found to vary only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity.One of these is the subtraction of water from the ocean by means of evaporation - conversion of liquid water to water vapor. In this manner the salinity is increased, since the salts stay behind. If this is carried to the extreme, of course, white crystals of salt would be left behind.The opposite of evaporation is precipitation, such as rain, by which water is added to the ocean. Here the ocean is being diluted so that the salinity is decreased. This may our in areas of high rainfall or in coastal regions where rivers flow into the ocean. Thus salinity may be increased by the subtraction of water by evaporation, or decreased by the addition of fresh water by precipitation or runoff.Normally, in tropical regions where the sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as muchevaporation. Similarly, in coastal regions where rivers dilute the sea, salinity is somewhat lower than in other oceanic areas.A third process by which salinity may be altered is associated with the formation and melting of sea ice. When sea water is frozen, the dissolved materials are left behind. In this manner, sea water directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared. Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water. In the Weddell Sea Antarctica, the densest water in the oceans is formed as a result of this freezing process, which increases the salinity of cold water. This heavy water sinks and is found in the deeper portions of the oceans of the world.如果我们分析海水的盐度，会发现地区间只有轻微的变化，然而有些小的变化是重要的。
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Progress and prospects of seawater desalination in ChinaLin Zhang,Lin Xie,Huan-Lin Chen*,Cong-Jie GaoCollege of Materials Science and Chemical Engineering Zhejiang University,Hangzhou 310027,P.R.ChinaTel.þ8657187952121;Fax þ8657187952121;email:chenhl@Received 22February 2005;accepted 22March 2005AbstractChina is a populous country,and short of water resources.In China,the total volume of fresh water is 2.81012m 3,but per capita value of fresh water is less than 2400m 3,which is only a quarter of the world-wide average.Seawater desalination is particularly important and necessary in China,especially within coastal regions,which only account for 13%of the land area,but support 40%of the total population.This paper focuses on current applications for seawater desalination in China.We report that membrane technology and flash vaporization processes are used successfully to desalt seawater.For example,a device of flash vaporization has been built in Tianjin,and its yield is 6000t/d fresh water.Additionally,in Changdao County,two reverse osmosis (RO)systems have been completed.The future prospect of applying membrane technology to seawater in China is evaluated based on economic analysis.Keywords :Desalination;Seawater;Membrane;Flash vaporization1.IntroductionIt is well-known that seawater desalination is the technology and process for getting fresh water from the sea,and mainly includes mul-tistage flash (MSF),multieffect distillation (MED)and membrane separation process.In the membrane process,the reverse osmosis (RO)and electrodialysis (ED)are technolo-gies used frequently.At present,the yield ofseawater desalination is 3,00,000m 3/d by MSF,and it is 2,00,000m 3/d by RO in the world.Multistage flash and multieffect distilla-tion technology could be applied to seawater with high salt concentration but it is energy-consuming.It requires about 3–5kWh power and 7–12m 3steam for 1m -pared to distillation,the membrane process is an energy-saving technology,and its aver-age values of power consumption are 5–9and 15–18kWh per m 3water for RO and ED,Presented at the Conference on Desalination and the Environment,Santa Margherita,Italy,22–26May 2005.European Desalination Society.0011-9164/05/$–See front matter Ó2005Elsevier B.V.All rights reserved *Correspondingauthor.Desalination 182(2005)13–18doi:10.1016/j.desal.2005.03.005respectively,though the salt concentration of seawater has an effect on the cost and appli-cation of the membrane process.Distillation and membrane processes are used for seawater desalination in China.In this paper,the status of water resources in China has been analyzed,seawater desalina-tion technologies used in China are presented and their economics are evaluated.2.Water resources in ChinaThe total amount of fresh water supply is 28124108m3/year in China,but China is a populous country.The per capita water sup-ply is2171m3/year,which is less than a quar-ter of the average in the world.Water shortage is a serious problem in China. Another problem is uneven distribution of fresh water resources.To the best of our knowledge,in the northern part of China, the total flows of the Yellow River,the Huaihe River and the Haihe River etc.are only one eighth of the southern rivers: Yangtse River,Zhujiang River etc.In the China littoral,there are13provinces and 40%residents,and the population density is very high,the water consumption is so large that underground water is exploited.To alleviate water depletion in the north of China,our government developed a plan called‘‘South-North water transfer project’’in2002,and the project is being carried out as depicted in Fig.1.In the project,there are three canals to transfer water from the Yangtse River to the Yellow River.The total length of canals is over1000km,and the total volume is about40,000million m3. However the fresh water available from the Yangtse River basin is insufficient,and the impact of the water transfer project on the ecosystem is hard to estimate.On the other hand,China has18,000km of coastline and3,000,000km2of ocean areas, which contain abundant seawater.Thus,sea-water desalination is a better method to pro-vide fresh water to these water-shortage areas instead of transferring water from a thousand miles away.3.Desalination in China3.1.Multistage flash and multieffect distillationMultistage flash technology has received attention from1970s in China.The first laboratory installation of multistage flash was developed and operated in Tianjin city in1981;the capacity of the device is72m3/d. The first industrial MSF process was intro-duced from ES Co.in1989for supplying 2Â3000m3/d fresh water to Tianjincity,Fig. 1.Schematic illustration of‘‘South-North water transfer project’’. 14L.Zhang et al./Desalination182(2005)13–18based on the introduced technology,and an MSF device,with fresh water yield of 1200m 3/d,was designed and used in 1997.An MSF process for producing 3000m 3/d fresh water,which is shown in Fig.2,was developed by Hebei Electric Power Equip-ment Factory in 1998[1].The process includes 3evaporator sectors,which have 27flash vessel stages,and 1hot driving sector with 3flash vessels,a brine water circulating system and spool structure are used.The key parameters of the MSF are listed in Table 1.In June 2004,a multieffect distillation,the first independently designed by China,was installed at Huangdao Electric Power Plant in Qingdao city.The system can produce 3000m 3/d.The power consumption of the multieffect distillation is 1.6kWh/m 3water,and it is composed of a 9-effect system.Recently,Tsinghua University [2]developed a dual-tower stacked vertical evaporation tube-MED unit,which is an experimental test system designed to have an upper brine temperature of 120 C,a seawater mass flow of 3300kg/h and a fresh water yield of about 180kg/h.The system includes the steam generator,the evaporator,the pre-heater,the final condenser,and the sea-water tank,coupled with a natural circulation nuclear heating reactor (Fig.3).3.2.Seawater reverse osmosis (SWRO)Since 1965,SWRO has been studied as an important goal in China,and a collective study conference was hold about SWROinFig.2.Process diagram of MSF for seawater desalination.Table 1Technical parameters of MSF-3000m 3/d Technical parametersvalue Yield of fresh water (m 3/d)3000Salt concentration in product (mg/l)<5Heat consumption (kJ/kg fresh water)240Low-press steam (t/h)12.8Stage number of MSF 30(27þ3)Cycle brine flow (m 3)1100Concentration rate1.7L.Zhang et al./Desalination 182(2005)13–18151966.During the conference,an RO system with cellulose acetate membrane was demon-strated in Chaolian Island,which was the first RO system for seawater desalination.Today,there were some large-scale SWROs successfully operating in China,listed in Table2. Fig.4shows the SWRO process in Changdao, which was designed by the Development Cen-ter of Water Treatment Technology,SOA of China in2001[3].The process includes a pressure exchange type energy recovery device. The energy recovery rate reaches about94%, and the power consumption is 4.5kWh/m3 fresh water.Subsequently,another SWRO plant was built in the same place,yielding 75m3/d fresh water.3.3.Feasibility evaluation of seawater desalinationAs an important project,the‘‘South-North water transfer’’is being carried out in China.Even though the operating cost only includes running and management costs, which are0.5–1yuan RMB/m,the capital investment of the project is about500billion yuan RMB.The price of water transferred to Beijing is5–20yuan RMB/m3,while the price of desalination water is only about4–7yuan RMB/m3according to[7].In addition,water resources in south of China are not abundant,and the quality of transferred water cannot be kept high.Desalination can cover these shortcomings.To compare the cost-effectiveness of MSF, MED and RO for seawater desalination inTable2Some large-scale SWRO in ChinaOperation year Place Yield of fresh water(m3/d) 1997Shensi County of Zhejiang Province5001999Changhai County of Liaoning Province10002000Changdao County of Shandong Province10002000Changhai County of Liaoning Province5002001Shensi County of Zhejiang Province10002001Weihai City of Shandong Province20002001Daliang City of Liaoning Province20002001Cangzhou County of Hebei Province18,000aa For brackishwater.Fig.3.Schematic diagram of the vertical evaporationtube-MED test unit.1.Seawater tank;2.Seawaterpump; 3.Terminal condenser; 4.Pre-heater; 5.Tower No.2;6.Electrically heated steam boiler;7.Tower No.1;8.Seawater pump.16L.Zhang et al./Desalination182(2005)13–18China,based on a process producing 90m 3fresh water per hour,the investment and run-ning cost are shown in Fig.5,based on [4].Fig.5shows that the investments required for MSF and MED are higher than that of RO,but the operating costs of MSF and MED arelower than that of RO.The reason for high operating cost of RO is the length of mem-brane life cycle.At present,we assume the operating life of RO and UF membranes are generally 4years.Thus,increasing the oper-ating life of membrane will decrease the cost ofoperation.Fig.4.Process diagram of SWRO in Changdao of Shandong Province.VCMSF SWRO MEDg r o s s i n v e s t m e n t (m i l l i o n y u a n R M B )all-in cost per m 3water (yuan RMB)Fig. 6.The gross investments and all-in costs of MED,SWRO,MSF and VC processes for 6000m 3/d.RO2=pretreated with UFRO1=pretreated with conventional method g r o s s i n v e s t m e n t / m i l l i o n y u a n R M BMSF MED RO1RO2running cost (yuan RMB/m 3fresh water)parison of the capital investment and operating cost for MSF,MED and RO.L.Zhang et al./Desalination 182(2005)13–1817Fig.6shows the gross investments and total costs of MED,SWRO,MSF and VC processes for 6000m 3/d [5].From the results,it is found that the SWRO process is the most economical.For SWRO,the costs of seawater desalination depend on production scale.Uche [6]described the variation of installation cost of RO plants and desalted water costs with size,shown in Fig.7.Based on that,we con-clude that the costs will decrease dramatically with the increase in plant capacity.Economically,the SWRO is a promising and active technology for seawater desalina-tion,but for some specific desalination pro-cesses,MSF and MED are more effective.For example,in thermal power plants,the waste heat can be recovered by combining with MSF,which changes the power plant from a big consumer of fresh water into a fresh water producer.Therefore the cost of fresh water could be very low.4.ConclusionsIn China,fresh water resources are scarce.A water transfer project is being carried out to provide water to the north,and there are also many installed seawater and brackish water desalination processes.Compared with the water transfer project in China,if the energy consumption of the sea-water desalination can be decreased,MSF,MED and SWRO will be alternative pro-cesses for supplying fresh water,and these processes will not influence the ecology.In MSF,MED and SWRO processes for seawater desalination,the cost of SWRO is lower,but MSF or MED is more effec-tive in some cogeneration plants in coastal region of China.AcknowledgementsThe authors acknowledge financial sup-port for this work from The National Basic Research Program of China (No.2003CB615706).References[1]J.Z.Ma and M.Du,Multistage flashing systemfor sea water desalination and development of domestic device,Hebei Electric Power,17(Supp.)(1999)4–8(in Chinese).[2]H.J.Jia,S.Y.Jiang et al,Dual-tower verticalevaporation tube high-temperature MED sea-water desalination test unit,J.Tsinghua Univ.(Sci.Technol.),43(2003)1336–1338(in Chinese).[3]X.Fan,X.J.Zhang et al,Seawater desalinationproject by RO process in Changdao county of Shangdong Province,Technol.Water Treat.,29(2003)41–43(in Chinese).[4]L.Q.Deng,Comparison of economy and tech-nology for seawater desalination,Electric Power Technol.Guangxi,2(2001)53–55(in Chinese).[5]G.L.X.Ruan,L.Xie and Y.J.Zhang,Developthe sea water desalination industry and relieve the fresh water crisis,Coastal Eng.,20(2001)39–47.[6]J.Uche,L.Serra and A.Valero,Hybrid desalt-ing systems for avoiding water shortage in Spain,Desalination,138(2001)329–334.[7]Z.M.Lin and Z.L.Han,Analysis of alleviatefunction of desalination on the water resource shortage in China’s coastal areas,J.Liaoning Normal Univ.(Nat.Sci.Ed.),26(2003)297–301.SWRO Size (m 3/d)R M BInvestment cost per m 3 water (RMB*104)Fig.7.Installation cost of RO plants and desalted water cost vs.size [6].18L.Zhang et al./Desalination 182(2005)13–18。