Energy production at the Dead Sea by pressure-retarded osmosis: challenge or chimera?

In recent years two types of very large-scale plants have been proposed for handling seawater brought to the Dead Sea, both processes taking advantage of the 400 m drop to Dead Sea level and both sized to replenish the 3,000,000 m³/d evaporation rate of the Dead Sea. Pressure-retarded osmosis (PRO), the process discussed herein, would use the replenishment stream to produce an appreciable amount of benign and renewable electric power. If the seawater plant prior to PRO would be reverse osmosis (RO), handling 5,000,000 m³/d to produce 2,000,000 m³/d of fresh water, PRO could produce 48,000 kW from the RO-concentrated seawater feed at a capital cost for power of about $4,000 per kilowatt and a PRO plant cost of $190,000,000. The electrical energy would be produced at a cost of about $0.07/kWh. The PRO plant would use a DuPont B-9 type or similar hollow fiber modified to have 110 and 320 micron internal and outer diameters (instead of 40 and 90). Osmotic permeation of half of the 3,000,000 m³/d RO reject brine into Dead Sea brine would produce 35 atmospheres of hydrostatic pressure relieved by passage of an equivalent volumetric rate of diluted Dead Sea brine through a hydroturbine/generator set. The second type of plant prior to PRO would use 3,000,000 m³/d of seawater to produce hydropower, estimated at about 130,000 kW. The permeation rate in PRO could then be 2,000,000 m³/d enabling power production in PRO of 70,000 kW at a capital cost for power of $3,300 per kilowatt and a PRO plant cost of $230,000,000. The cost of produced energy in PRO would be $0.058/kWh. It is believed that the Great Salt Lake should also be examined as a site for PRO.     

外驱旋转式能量回收装置的设计和性能测试

旋转式能量回收装置（RERD）作为反渗透海水淡化系统的节能设备,对于降低系统能耗和产水成本具有重要意义。设计和加工了一套新的外驱旋转式能量回收装置,建立了满足其性能评测要求的一套完整的反渗透海水淡化系统。当装置的性能很好地满足工业化运用需求时,对RERD与反渗透淡化系统的耦合运行性能进行了现场测试。实验结果表明：反渗透膜的操作压力为6.0 MPa、RERD的处理量为13 m³/h及转子转速为500 r/min时,装置的泄漏量为0.57 m³/h,能量回收效率达到91.2%。保持反渗透膜的操作压力和装置转速不变,当装置的处理量为16 m³/h时,进出RERD的4股流体的流量和压力波动较小,装置的能量回收效率略有提高,达到92.5%。     

Sustainable fuel cell integrated membrane desalination systems

According to the United Nations, between two and seven billion people will face water shortages by the year 2050. Further, it is estimated that the amount of water available per person will shrink by a third during the next two decades. Inadequate supply of good-quality water coupled with higher water demand due to rapid population growth and industrialisation in developing countries are among the major reasons for the worsening water situation. Current shortages of potable water around the world and looming water scarcity especially in the developing countries is the driving force behind the implementation of membrane technologies for seawater and brackish water desalination. Typical energy consumption in seawater reverse osmosis (RO) plants operating at 40–45% product water recovery and with energy recovery from the high pressure reject stream currently is about 3–4 kWh/m³. The near-term goal of the industry is to reduce energy consumption to less than 2 kWh/m³ by using a combination of energy efficient RO pumps, more efficient energy recovery devices, high performance low energy RO membranes, hybrid membrane systems, advanced pretreatment technologies and alternate energy integrated membrane systems. The beneficial aspects of using alternate energy systems such as on-site distributed fuel cell systems integrated with membrane desalination units in remote locations are discussed.     

基于AMESim的海水淡化斜盘柱塞式能量回收装置运行性能分析

为满足中小型海水淡化系统节能降耗需求,设计开发了一种新型斜盘柱塞式能量回收装置,并基于AMESim仿真分析软件构建了斜盘柱塞式能量回收装置的液压仿真模型及与之配套的反渗透海水淡化系统流体计算模型,对斜盘柱塞式能量回收装置在海水淡化系统中的耦合运行性能进行了模拟研究.结果 表明:在装置高压进流压力为6.0 MPa,设计处...     

基于响应面法光热-光电膜蒸馏系统优化研究

设计并搭建了太阳能光热-光电方腔型膜蒸馏系统,为研究该系统机理与优化问题,首先以料液进口温度、流量、太阳辐照度为影响因子,膜通量、能耗为响应值,采用响应面法分析各影响因子与响应值间的关系;其次结合中心复合设计法设计实验工况,建立响应值与影响因子的二次多项式回归模型,通过方差分析、实验验证对所建立的模型进行可靠性分析;最后对响应值进行响应面分析与系统优化,获得了系统最佳运行工况和最优膜通量、能耗值,并进行了实验验证。结果表明,系统最佳工况为：料液进口温度为63℃,料液进口流量为232 L/h,太阳辐照度为700 W/m²,在此工况下实际膜通量达到7.28 L/(m²·h),高于预测值6.39 L/(m²·h),两者误差为12.23%,对应的能耗值为10.40 L/(kW·h)。     

Sea water desalination by reverse osmosis in chigasaki laboratory

For the purpose of constructing a reverse osmosis [RO) sea water desalination plant of 800 m³/day capacity, a series of tests on the following themes have been carried out in the Chigasaki Laboratory:

1. Performance and durability of 8B modules made in Japan

2. Simplification of pretreatment system

3. Establishment of energy recovery system.

Domestic modules showed good and stable performance during long term operation, and water recovery ratio of these modules have been raised to 40%.

In-line coagulation and filtration system has been established for the pretreatment of feed sea water, instead of coagulation, sedimentation and filtration system.

The energy recovery equipment is consisted of a high-pressure pump, a motor and a hydraulic turbine on a common base. Recovered energy from pressurized brine is used for the auxiliary motive power of the high-pressure pump. The experimental data show that about 20% of required power for the pump was recovered.     

Optimization of solar-powered reverse osmosis desalination pilot plant using response surface methodology

A solar thermal and photovoltaic-powered reverse osmosis (RO) desalination plant has been constructed and optimized for brackish water desalination. The central composite experimental design of orthogonal type and response surface methodology (RSM) have been used to develop predictive models for simulation and optimization of different responses such as the salt rejection coefficient, the specific permeate flux and the RO specific performance index that takes into consideration the salt rejection coefficient, the permeate flux, the energy consumption and the conversion factor. The considered input variables were the feed temperature, the feed flow-rate and the feed pressure. Analysis of variance (ANOVA) has been employed to test the significance of the RSM polynomial models. The optimum operating conditions have been determined using the step adjusting gradient method. An optimum RO specific performance index has been achieved experimentally under the obtained optimal conditions. The RO optimized plant guarantees a potable water production of 0.2 m³/day with energy consumption lower than 1.3 kWh/m³.     

Electrodialysis desalination designed for off-grid wind energy

An electrodialysis desalination plant has been set up and tested to treat brackish water while driven from an off grid wind energy system. The tests were carried out in the framework of a wider scope project, located on Gran Canaria Island (Spain). The main goal of this project was to test and identify the most suitable desalination systems for connection to the above-mentioned medium-scale off grid wind farm. After having previously analysed the behaviour of the system on-grid, the following stage was to develop an operational envelope for the electrodialysis reversal (EDR) unit while operating off grid, i.e., only coupled to the wind farm. The unit included power converters for the membrane stacks (DC-drivers) and variable frequency drivers (VFD) for the feed pumps. The tests were carried out to establish the power intervals for the EDR unit depending on the product flow rate specified as well as water quality. Product flow rate between 3 and 8.5 m³/h, power requirements between 4 and 19 kW, while product water conductivity ranged between 200 and 500 μS/cm were recorded. The desalination unit showed good flexibility, adapting smoothly to variations in wind power, even when sudden drops or rises occurred. The control system, slightly modified from a standard design, can cope with such sudden variations. Good agreement between performance predicted with software and the actual operating performance was observed. The presence of harmonics in the electric system due to DC drivers and VFD became harmful for the control and electric system, and care must be taken through appropriate mitigating measures.     

液化天然气深冷-膜蒸馏海水淡化系统集成与分析

提出了一种PRICO天然气液化-膜蒸馏（MD）海水淡化系统集成方法,利用PRICO过程压缩机出口的余热驱动MD海水淡化。采用Aspen Plus和GAMS建立了集成系统的数学模型,综合考虑系统的结构、物流物性、设备规模、操作参数等系统设计问题,分析不同设计下系统的投资、能耗、运行费用以及MD单位产水成本。模型应用于一个处理量为1 kmol/s的PRICO天然气液化系统与MD集成的案例研究。计算结果表明,单位产水成本最小时,系统产水成本为1.98 USD/m³,淡水产量为5.78 m³/h,与反渗透等海水淡化技术相比,MD在经济性方面具有较强的竞争力。     

泵驱动回路热管能量回收装置性能的影响因素

提出一种泵驱动回路热管能量回收装置,用于回收公共建筑空调系统排风的能量,降低处理新风的能耗,并搭建实验平台,测试该装置在两种工况下的性能,分析工质质量流量、换热器换热面积和换热器迎面风速3种因素对装置换热量、温度效率和性能系数的影响,得出质量流量、换热面积和迎面风速的最优值。结果表明,夏季工况下,质量流量250 kg·h^-1,换热面积58.0 m²,迎面风速1.8 m·s^-1时,装置的换热量为4.09 kW,性能系数为9.26;冬季工况下,质量流量300 kg·h^-1,换热面积58.0 m²,迎面风速1.8 m·s^-1时,装置的换热量为6.63 kW,性能系数为14.20。     

电化学法处理钢厂循环冷却水的中试研究

为研究电化学法对循环冷却水的处理性能,以钢厂循环冷却水为处理对象,考察不同电流密度和循环流量对处理效果和运行成本的影响。结果表明,在初始硬度(以CaCO₃计)为350 mg/L,电流密度为3 mA/cm²,循环流量为18 m³/h时,硬度去除率为25.95%, COD去除率为50.3%,能耗分别为25.29 kW·h/kg[Mg(OH)2]和70.17 kW·h/kg[COD]。电化学处理法能够影响污垢的晶型,降低Mg(OH)2晶体的完整度,使其结构疏松,有利于后续对污垢的处理。     

Analysis of water production costs of a nuclear desalination plant with a nuclear heating reactor coupled with MED processes

A nuclear heating reactor (NHR) was designed with the required inherent safety and simplified design features. Power capacity of the NHR-200 (200 MW(th), with steam production of 380 t/h) is compatible with reasonably sized desalination plants. Thermal-hydraulic parameters of the produced steam (2.4 bar and 124°C) are suitable for coupling with distillation processes. Economic competitiveness of the NHR desalination plant is the key point to which the public and decision-makers are paying good deal of attention. Coupling of the NHR with selected MED processes and design parameters of an integrated desalination plant are described. Results of analyses of water production costs are presented as well. Based on the economic evaluation, the average energy cost of the nuclear plant may reach 5.44 $/t of steam, and the provided water production cost may reach 0.72 $/m³ and 0.76 $/m³ for coupling with HT–VTE–MED and LT–HTE–MED processes, respectively.     

Solar multistage flash evaporation (smsf) as a solar energy application on desalination processes

The application of solar energy on desalination constitutes one of the activities of the research and development program of digases. Within this philosophy a project is being developed in cooperation with the Federal Republic of Germany. The objective of the project is to test and prove the feasibility of the solar energy utilization as the source of the thermal energy required for a multistage flash evaporation plant.

The plant is composed of three systems:

1. Desalination system. Multistage flash evaporation plant with 10m³/d production capacity, 5.0 in performance ratio and 10 stages.

2. Solar energy captation. Composed of one low temperature subsystem of double pipe flat collectors with 670m² of effective captation surface, and a high temperature subsystem composed of parabolic concentrators with 320m² of captation surface.

3. Storage of energy. System designed with such capacity which allows continuous operation of desalination unit.

The poject is separated into two phases. The first includes the design manufacturing and tests for the three systems. The second phase comprises the installation and integration of the systems which compose the plant, the start-up operation and evaluation of plant performance.

At the present time, the first phase of the project is under development and it is expected to finish it at the end of June. The second phase will start in August with system start-up scheduled for the end of October.     

LNG轻烃分离与乙烯冷分冷量联合

乙烯深冷分离过程需要冷剂为分离过程提供不同等级的冷量,可以把乙烯深冷分离过程作为一个冷阱;LNG气化过程中,需要加热,可以作为冷源.考虑到冷阱冷源的相互匹配,提出通过将LNG经过轻烃分离,为乙烯深冷分离提供冷量,降低了制冷公用工程消耗,同时LNG气化装置降低了加热公用工程消耗,且LNG分离出的轻烃直接供给乙烯装置作为裂解原料使用,优化乙烯装置裂解原料.以300万吨/年的LNG装置和64万吨/年的乙烯装置为例进行模拟计算得到,LNG轻烃分离装置可为乙烯冷分提供冷量41464 kW,降低乙烯冷分三元冷剂消耗75%,为乙烯装置提供优质裂解原料约65万吨/年.     

冷冻-重力脱盐与反渗透结合的海水淡化分析研究

随着我国沿海液化天然气(LNG)接收站的迅速发展,LNG冷能有望成为冷冻法海水淡化的低成本冷源。在此前提下,研究了人工海冰在不同融化率下的重力脱盐效果,结果表明,当融化率达到79.53%时,Cl-、TDS、总硬度这3项指标可达到饮用水标准。当融化率为39.81%时,将冷冻-重力脱盐产水作为反渗透系统进水的运行模式,相较单纯冷冻-重力脱盐模式,饮用水产水率由20.47%上升到45.1%;相较直接将原海水进行反渗透处理,水泵吨水能耗从3.39 kW·h下降到0.87 kW·h。     

静压支承技术在海水淡化旋转式能量回收装置中的应用

海水淡化旋转式能量回收装置（RERD）高、低压流体间的泄漏主要在转子与端盘的配合间隙中发生，这种泄漏直接影响到装置的能量回收效率水平。本文通过在平面端盘上引入阻尼孔和静压支承槽，构建了静压支承端盘方案，将静压支承技术应用到自主开发的电驱RERD装置中，以解决其运行过程中泄漏量大、能量回收效率低等问题。在转子与上、下端盘配合总间隙为0.04mm、转子转速为500r/min的条件下，RERD分别使用平面端盘和静压支承端盘进行对比实验研究。结果表明，在操作压力为4.5MPa和处理量为13m³/h的工况下，与平面端盘相比，采用1^#静压支承端盘（静压支承槽槽宽为2.0mm）时，装置的泄漏量从0.45m³/h减小至0.28m³/h，能量回收效率从91.3%提升至92.7%。采用2^#静压支承端盘（静压支承槽槽宽为3.0mm）的RERD在相同工况下，装置的泄漏量可降低至0.11m³/h，能量回收效率提升到95.0%。上述研究显示静压支承技术对于减小RERD装置泄漏量、提高装置效率具有显著的效果，对RERD装置密封结构设计与优化具有指导意义。     

Pilot investigation on the treatment of fertilizer manufacturing process effluent using lime and electrodialysis reversal

The treatment of a fertilizer company's effluent was evaluated using lime and electrodialysis reversal (EDR) for phosphate removal, water and chemical recovery, and effluent volume reduction. Phosphate could be reduced from 3 800 to less than 50 mg/1 at pH 8.5 with lime; however, phosphate removal from the lime treated effluent using EDR was poor (75% removal). The EDR product water complied with the requirements for cooling tower make-up except for TDS and phosphates. However, the required specifications should be met using 10 stage EDR.

In addition, plant nutrients (NH₄⁺ NO₃⁻) may be recovered from the brine, which comprised 20% of the initial effluent volume. Membrane scaling was virtually absent. A full scale EDR plant should run well with electrical adjustments and/or frequent acid cleaning. Electrical energy consumption for EDR treatment was found to be 4.5 kWh/m³ feed (pumping costs excluded). The capital cost for a 30 m³/h EDR plant and clariflocculator (PO₄ removal) was estimated at US $750 000.     

Comparative economics of current and advanced desalting systems

A comparative investigation of the economics of desalting based on current and projected technology has been made. Current operating cost of various plant types operating in Israel are reported. These costs range from less than $.4/m³ for membrane plants desalting brackish water to more than three times as much for thermal plants desalting seawater. For new systems, two plant sizes were evaluated: 4,000 m³/day plants applying current technology and 100,000 m³/day plants applying projected technology. The water costs obtained for the various plant types and applied economic parameters, especially energy prices, range between $.2/m³ and $.6/m³ for brackish water desalting and from $.5/m³ to $2.4/m³ for seawater desalting.     

Economic evaluation of desalination by small-scale autonomous solar-powered membrane distillation units

Solar-powered desalination is an attractive and viable method for the production of fresh water in remote arid areas. One of the most important factors determining desalination decisions is economics. This paper presents an economic assessment performed to estimate the expected water cost, which is the ultimate measure of the feasibility of the stand-alone system. Based on the calculations, the estimated cost of potable water produced by the compact unit is $15/m³, and $18/m³ for water produced by the large unit. Membrane lifetime and plant lifetime are key factors in determining the water production cost. The cost decreases with increasing the membrane and/or the plant lifetime.     

Nitrate removal with reverse osmosis in a rural area in South Africa

The nitrate-nitrogen concentration (>6 mg/l) and the salinity (>1000 mg/l TDS) of many borehole waters in rural areas in South Africa are too high for human consumption. Therefore, an urgent need for water denitrification and water desalination exists in these areas. Reverse osmosis (RO), electrodialysis (ED), ion-exchange (IX) and certain biological technologies can be very effectively applied for water denitrification. Each of these technologies, however, has its own advantages and disadvantages. Reverse osmosis technology, however, has been selected for this study because the technology is well known in South Africa and because it can be very effectively applied for water desalination. The objectives of this study were: (a) to transfer RO technology through process demonstration performance for water denitrification and water desalination to people living in rural areas; (b) to build capacity regarding the operation and maintenance of an RO application in a rural area; (c) to produce a preliminary operational and maintenance manual for the operation of an RO unit in a rural environment; (d) to train local operators to operate and maintain an RO plant in a rural environment; (e) to evaluate stock watering as brine disposal option; and (f) to determine the preliminary economics ofthe process. The following conclusions were drawn. It was demonstratedthatthe RO process could be very effectively applied for water denitrification and water desalination in a rural area. Nitrate-nitrogen was reduced from 42.5 mg/l in the RO feed to only 0.9 mg/l in the RO product water. The TDS of the RO feed was reduced from 1292 mg/l to 24 mg/l in the RO permeate. Therefore, an excellent quality water could be produced for potable purposes. The RO brine at approximately 50% water recovery should be suitable for stock watering if the conditions for stock watering are met in terms of nitrate-nitrogen concentration, TDS and other constituent concentrations. The capital cost for an approximately 50 m³/d output RO plant is approximately US $29,900. Preliminary cost estimates have shown that the operational cost for water denitrification is approximately US $0.50/m³. This cost, however, should be significantly reduced by optimisation of the chemical dosing and by blending borehole water with RO product water.