考虑水需求的水电联产海水淡化系统的优化设计

水电联产不仅能缓解淡水资源不足的问题,而且可有效降低能耗和淡化成本。建立了水电联产系统数学模型,将优化设计描述为一个混合整数非线性规划(MINLP)问题,并采用混合编码的遗传算法进行求解,结果表明,以水定电模式下水电联产系统最优操作模式为发电、多级闪蒸(MSF)和反渗透(RO)三者的集成,且MSF和RO的产水比存在最优值,发电采用背压式蒸汽轮机。随着淡水需求量的增加,联产系统的淡水成本逐渐降低,MSF与RO的产水比呈现出逐渐降低的趋势。     

海水淡化技术包括哪些?

<正>全球海水淡化技术超过20余种,包括反渗透法、低多效法、多级闪蒸法、电渗析法、压汽蒸馏法、露点蒸发法、水电联产法、热膜联产法以及利用核能、太阳能、风能、潮汐能海水淡化技术等等,以及微滤、超滤、纳滤等多项预处理和后处理工艺。从大的分类来看,海水淡化技术主要分为蒸馏法(热法)和膜法两大类,其中低多效蒸馏法、多级闪蒸法和反渗透膜     

热膜耦合海水淡化系统的优化设计

采用混合节点和分配节点的概念,建立了多级闪蒸(MSF)和反渗透(RO)海水淡化集成系统的超结构模型,以年度总费用最小为目标,引入产水比的概念,并将该参数作为集成系统的一个优化变量,采用改进的遗传算法进行求解,获得了集成系统的最优结构及相应的操作条件。实例结果表明:集成海水淡化系统的淡水成本比独立运行的RO和MSF低,产水比为0.45时集成系统的费用最小,流程结构为MSF-RO。     

多级闪发式海水淡化装置水流特性数值模拟

引　言目前国内外在陆上采用的海水淡化技术主要有蒸馏法和反渗透法两种 .蒸馏法的优点是装置费用随产量增加而明显减少 ,具有规模效应 ,且维护费用较少 ,产水水质很高 .在陆上使用的蒸馏法海水淡化设备一般为大型多级卧式闪发蒸馏装置 ,它由一系列逐级降压的闪发室串联而成 ,过热水在水位差作用下向下一级流动 ,靠逐级降压而保持的过热度使海水不断蒸发 ,产生水蒸气后冷凝成淡水 (图1) [1] .闪发室的结构形状并不复杂 ,但闪蒸过程涉及汽、液两相的流动、相变、热交换过程以及两Fig 1　SketchofMSFdesalinationdevice[1]相之间自由界面的…     

利用火电机组余热能的热膜耦合海水淡化性能分析

以沿海电厂汽轮发电机组抽汽作为热源,针对反渗透(RO)和低温多效蒸馏(LT-MED)海水淡化技术各自的特点,提出2种水电联产海水淡化方案,并进行性能分析:1种是传统的蒸汽压缩喷射器(TVC)与低温多效蒸馏系统结合的MED-TVC方案;另1种是利用电厂汽轮机抽汽余热能发电驱动反渗透膜,通过热膜耦合技术将低温多效蒸馏与反渗透海水淡化产水集成的RO-MED方案。结合某实际火电机组已经运行的海水淡化项目,建立数学模型,对2种方案的淡水产量进行了比较分析。结果表明,RO-MED方案的淡水产量约为38.26 kt/d,远大于MED-TVC方案11 kt/d的产水量。但受投资成本、运行成本、安全性等条件的制约,在实际生产中还需要依据具体情况进行选择。     

热膜耦合方式下浓海水脱硬处理零排放实验研究

针对海水淡化副产高盐度浓海水直接排放会对生态环境造成破坏的问题,采用化学沉淀法与膜法相结合技术,从浓海水中提取70%以上有效碳酸钙,并控制透过液中Mg2+的质量浓度为15~20mg/L;浓海水硬度基本去除的同时,降低反渗透进水硬度,提高淡水回收率,降低药剂成本;反渗透产二次浓盐水可供给盐碱厂,可降低海水淡化成本、解决淡化后浓盐水的排放问题。     

反电渗析法海水淡化副产浓水盐差能利用

海水淡化是解决淡水资源短缺的有效途径,其副产的浓海水具有较高的浓度,而基于离子交换膜的反电渗析（RED）法发电是对盐差能利用的有效手段。通过模拟计算研究了以反渗透法海水淡化副产的浓水和海水为进料的情况下,RED装置发电的功率密度和能量效率,并探讨了多级操作对于RED系统功率密度和能量效率的影响。结果表明：单级RED的发电功率密度随水回收率的提高和隔板厚度的降低而增大,但过程的能量效率均低于30%。RED多级操作能显著提高系统的能量效率。探讨了影响淡化浓海水盐差能利用效果的因素,并提出多级RED作为提高浓水盐差能利用效率的手段,研究结果为海水淡化副产浓水的利用提供了一种新的思路。     

中国海水淡化技术研究现状与展望

分析了国内近年在多级闪蒸、低温多效和反渗透等海水淡化技术方面研究和发展现状,并与世界海水淡化技术先进国家进行了比较,讨论了所存在的问题和差距。此外,结合国内对海水淡化技术需求,提出了中国海水淡化技术未来可能的发展方向和目标。     

短流程反渗透海水淡化预处理试验研究

针对我国沿海水质的特点,开发了集浸没式超滤及絮凝反应为一体的短流程反渗透海水淡化预处理设备,并进行了中试试验。结果表明,处理后产水水质可达到后续反渗透进水要求,SDI15<1%,浊度<0.1 NTU,并可以在33⁴0 L/(m40 L/(m²·h)的高通量下保持6个月稳定运行,可以应用于反渗透海水淡化系统的预处理过程中。     

风光互补海水淡化系统的技术经济分析

介绍了5 m~3/d风光互补发电反渗透海水淡化装置,阐述其工艺方案、设备选型、控制模式、功率及电耗,并从装置的建设投资费用、运行维护费用、制水成本3方面进行经济分析,表明该装置综合制水成本约为13.77元/m~3。归纳总结出风光互补发电海水淡化系统的经济性影响因素,并建议进一步研究蓄电池的充放电控制、RO海水淡化工艺优化、高压泵和能量回收装置的合理选择等关键技术,以提升风光互补发电RO海水淡化系统的经济性。     

满足不同需求的水热电联产系统的模型和设计简

In order to improve the energy efficiency, reduce the CO2 emission and decrease the cost, a cogenera- tion system for desalination water, heat and power production was studied in this paper. The superstructure of the cogeneration system consisted of a coal-based thermal power plant （TPP）, a multi-stage flash desalination （MSF） module and reverse osmosis desalination （RO） module. For different demands of water, heat and power production, the corresponding optimal production structure was different. After reasonable simplification, the process model ot each unit was built. The economical model, including the unit investment, and operation and maintenance cost, was presented. By solving this non-linear programming （NLP） model, whose objective is to minimize the annual cost, an optimal cogeneration system can be obtained. Compared to separate production systems, the optimal system can reduce 16.1%-21.7% of the total annual cost. showing this design method was effective.     

Integrating hybrid systems with existing thermal desalinationplants

In Gulf countries, most power plants are co-generation power desalting plants (CPDP) that generate electric energy and also produce fresh water through the desalination of seawater. This paper provides detailed technical and economical analyses to evaluate a new generation of dual purpose technology that includes the integration of reverse osmosis (RO) processes with existing thermal desalination processes and power generation (triple hybrid system) at Layyah plant, Sharjah, UAE. Hybridization of sweater reverse osmosis (SWRO) and the multi-stage flash (MSF) technology was considered to improve the performance of latter and reduce the cost of the produced water. Moreover, “idle” power in winter (seasonal surplus of unused power) was mainly utilized by RO to further reduce the cost of the hybrid system for six months of the year. Spinning reserve was also used to further reduce the cost of the proposed hybrid system. Integration ofthe three processes of MSF, MED, and RO desalination technologies could be made at different levels through which the resulting of water cost will depend on the selected configuration and the cost of materials of construction, equipment, membrane, energy, etc. Thus, the capital and annual operating costs were calculated for all potential alternatives for various plant capacities. It was found that for all plant capacities, integrated hybrid systems resulted in most cost effective solution. For example, at a capacity of 50 MIGD, the present worth of the cost was calculated to be 588.7, 443.2, and 380 million US$ for MSF, MED, and hybrid RO systems, respectively.     

Optimal design of hybrid RO/MSF desalination plants Part III: Sensitivity analysis

This is the last paper in a series of three parts entitled “Optimal design of hybrid RO/MSF desalination plants”. This research is concerned with exploring the feasibility of hybridization of multi-stage flash (MSF) and reverse osmosis (RO) technologies in order to improve the performance characteristics and process economics ofthe conventional MSF process. The research project involved an optimization study where the water cost perunit product is minimized subject to a number of constraints. In the first part, the design and cost models were presented, the optimization problem formulated and solutions for a number of cases were outlined. In the second part, results were presented and discussed. In this paper we discuss the sensitivity of water cost from the alternative plant designs to variations in some cost elements and operating conditions. In general, it is concluded that, for the same desalting capacity, hybrid RO/MSF plants can produce desalted water at a lower cost than brine recycle MSF plants, while hybrid plants are characterized, by lower specific capital costs and higher water recovery fractions. Reduction in steam cost allows MSF to compete more with hybrid RO/MSF plants. This result explains the advantage of coupling MSF plants and steam power plants where the exhaust steam from the back pressure turbine represents a relatively cheaper source of heat for the MSF process. Results showed that the RO technology exceeds all other designs over the whole range of energy, chemicals and membrane costs studied here. However, water cost of the RO process was the most sensitive to variations in membrane and electricity costs compared to other hybrid configurations.     

Optimal design of hybrid RO/MSF desalination plants Part II: Results and discussion

This paper presents the results of an optimization study, based on minimum water cost, to explore the feasibility of the hybridization of RO and MSF processes. The study explores the possible improvement of MSF process economics. Nine different scenarios for the production of the same capacity of desalted water are presented and compared from the standpoint of minimum water cost, specific capital cost and water recovery. The process and cost models, formulation of the optimization problem and solution outlines were previously presented in the first part of this study. In this work, results show that RO technology is recommended when building new desalination plants. RO technology becomes preferable at low feed concentrations and for brackish water desalination. Although they come in second position after the RO process, some hybrid plants economically exceed by far the MSF process. Computations gave a water cost of 1.1 $/m³ for the brine recycle MSF process against 0.75 $/m³ for the two-stage RO process. Water cost of the MSF process can be reduced by 17 to 24% through hybridization with RO technology.     

An approach to improve the economy of desalination plants with a nuclear heating reactor by coupling with hybrid technologies

In order to investigate the possible approach to increase thermal efficiency of desalination plants, decrease water production costs and further optimize the coupling design of a nuclear heating reactor (NHR) with the desalination process, the coupling schemes of NHR reactors with hybrid desalination technologies were investigated. The cogeneration operation mode was adopted in this investigation. Two coupling schemes were selected for the cogeneration mode: NHR + low-temperature MED+RO and NHR + low-temperature MED+MED/VC. Technical specifications and economic aspects of the investigation are briefly presented in this paper.     

Myth and reality of the hybrid desalination process

The paper discusses some misconceptions that have contributed to the continued use of thermal desalination processes and promotion of the hybrid desalination process for new plants being built or considered at Middle East locations. The misconceptions are examined both on the basis of fundamental thermodynamic principles and in terms of practical engineering parameters. The analysis shows that there is no economic or performance advantage in the installation of greenfield hybrid power/thermal desalination/ seawater reverse osmosis (SWRO) plants in preference to power/SWRO plants, because the latter would produce water more cheaply under all conditions and at all fuel costs, and would provide more operational flexibility than the former. The paper identifies situations where the hybrid desalination process can be fully justified: in existing power/desalination plants, where aging boilers and multistage flash (MSF) units need to be repaired or replaced, through retrofitting and repowering. In such situations, abandonment of the MSF process would result in a reduction in the power output of the plant. The paper refers to previous work which showed that the repowering of a typical existing power/desalination station with refurbishment/replacement of the MSF units, together with the addition of SWRO units, would result in a several-fold increase in the water and power output and a dramatic improvement in the fuel efficiency, without any additions to the existing seawater intake system. The paper emphasizes the importance of test stations/demonstration plants at existing power/desalination stations in the Middle East in order to obtain data and make improvements in the technology of higher temperature SWRO, with the feed obtained from the cooling water returning from the power plant condenser and the thermal desalination plant. The paper shows that the potential benefits would easily justify the investment in research and development required to validate this concept.     

Nuclear desalination competitiveness in the western region of the Kingdom of Saudi Arabia

The competitiveness of nuclear desalination in the western region of Saudi Arabia was studied. A forecast of water demand between the years 2000 and 2025 was established as part of the input data required for the DEEP computer code. Several options of energy sources such as PWR (600 MWe), SPWR (160 MWth), PHWR (450 MWe), HR (200 MWth) and GT (125 MWe and 175 MWe) were investigated in conjunction with different desalination technologies such as RO, MSF, MED and the hybrid MED-RO. The total plant output, specific electricity investment cost, specific water investment cost, levelized power cost, average daily production, net saleable power and levelized water cost are presented for all cases. Two scenarios were investigated; the first assumed no interest and discount rates and the second assumed interest and discount rates equal to 4%, 8% and 12%. The first scenario assumed that the water utility continues under the control of the government while the second assumed that the water utility will be privatized.     

MSF海水淡化系统热经济学优化分析

热经济学理论和方法在能量系统分析中占有重要地位。本文以年度化平均淡水成本为目标函数,对ＭＳＦ海水淡系统建立了较完善的优化模型。并就国产化日产３０００吨ＭＳＦ海水淡化系统进行了较详细的浮动价格结构下的优化设计分析。