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.     

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.     

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.     

An autonomous wave-powered desalination system

The potential for an autonomous wave-powered desalination system is considered and it is identified that the most promising configuration is a reverse osmosis (RO) plant utilising a pressure exchanger-intensifier for energy recovery. A numerical model of the RO plant with a pressure exchanger-intensifier is developed that shows that a specific energy consumption of less than 2.0 kW h/m³ over a wide range of sea-water feed conditions, making it particularly suitable for use with a variable power source such as wave energy. A numerical model of the combined wave-power and desalination plant is also developed that shows that it is possible to supply the desalination plant with sea-water directly pressurised by the wave energy converter, eliminating the cost and energy losses associated with converting the energy into electricity and back to pressurised water. For a typical sea-state the specific hydraulic energy consumption of the desalination plant is estimated to be 1.85 kW h/m³ whilst maintaining a recovery-ratio of less than 25 to 35% to avoid the need for chemical pre-treatment to eliminate scaling problems. It is suggested that the economic potential for wave-powered desalination depends on these energy and cost savings more than compensating for the reduction in membrane life that occurs with variable feed conditions.     

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。     

An investigation of high operating temperatures in mechanical vapor-compression desalination

It is common practice to operate mechanical vapor-compression (MVC) seawater desalination systems at temperatures lower than 80°C. This study presents the detail engineering and economics of a MVC system operating at 172°C. The literature indicates that high overall heat transfer coefficients for the evaporator are possible at high temperatures with dropwise condensation on the steam side and pool boiling on the liquid side. Employing high operating temperature delivers the following advantages: (1) low compression work, (2) small latent heat transfer area, and (3) small compressor. These advantages potentially reduce operating costs and capital investment. The disadvantages follow: (1) pretreatment required to prevent fouling of heat exchangers, (2) careful selection of materials to prevent corrosion, and (3) larger sensible heat transfer area is required. A desalination plant is designed herein to produce 37,854 m³/d (10 mil gal/day), which is financed with a 5%, 30-y municipal bond. To maximize energy efficiency, combined-cycle cogeneration is employed. For the US ($5.00/GJ energy), the product water selling price is estimated to be $0.49/m³ ($1.86/thous gal). For the Middle East ($0.50/GJ energy) the product water selling price is estimated to be $0.38/m³ ($1.44/thous gal). These are attractive prices relative to competing technologies.     

Field testing and economic evaluation of RO seawater technology

An experimental RO seawater system has been in operation for two years at Eilat on the Red-Sea shore. Simplified seawater pretreatment, comprising only sand filtration and acid dosing was applied. Hollow fiber and spiral wound membranes were tested. Evaluation of pretreatment effectiveness and comparative membrane performances are reported. Investment and water cost analysis of a 4,000 m³/day RO seawater desalting system under various operating conditions is given. The analysis is based on the results of experimental site operation, current technology development and updated industrial quotations. The resulting water production cost from a one-stage system, adequate to produce desalted water acceptable for local drinking water standards, is approximately $ 1.1/m³.     

Validating the performance simulation program “SOLDES” using data from an operating solar desalination plant

A computer program (named SOLDES) was developed to simulate the operation of solar desalination plants which utilize evacuated tube collectors, heat accumulators and multiple-effect distillation (MED) systems. The heat accumulator used is of the thermally stratified type using pure water as the storage fluid. The procedure was written in Fortran language and consists of a main program, 22 sub-programs, two system data files and four meteorological data files. The absorber area of the solar collector field can be varied between 500 m² and 20,000 m²; the storage capacity per unit collector area of the heat accumulator can vary between 0.05 and 1.00m³/m²; the capacity of the evaporator can be varied between 100 m³/d to 2000 m³/d. The heat collecting system uses a bypass circuit to allow the heat collecting fluid (pure water) to recirculate back to the solar collector field when the outlet temperature from the collector field is below a set-point. When the collector outlet temperature rises above the set-point, operation is switched over to the accumulator side. A solar-cell-type controller is used to start and stop the water circulating pump of the collector field. The operation of the MED evaporator is controlled by the state of charge of the heat accumulator by the use of set-point switches which allow the evaporator to start up when the accumulator water temperature is above a set-point and to shut down if the water temperature drops below the set point. In order to validate the SOLDES program, a comparison was made between the predicted results of the program and the actual measured data from a solar plant of similar design features to the simulation program. The selected plant was the one in actual operation in Abu Dhabi, UAE, which has almost identical design features as the simulation program and has been in operation since 1984. The data from the plant collected during 1985 were used to compare the simulation results for the months of January and June. These two months were found to be typical of a winter month (January) and of summer months (June). Except for days when a plant interruption took place, such as a power failure, the agreement between the measured and simulation data appears to be quite good.     

The futuke of water supply to tripoli

The recent expansion of the city of Tripoli has resulted in an inadequate water supply for the present demand. Means of improvements are indicated.

Presuming effective measures for conserving water, the peak day demand for municipality water is expected to increase from its present value of 0.26 Mm³/d to 0.6 Mm³/d in the year 2000. Schemes to meet future demands are surveyed.

For all feasible schemes, the increase of irrigation water is not allowable except by re-use, the sea water desalting is inevitable, the capital investment for the next 5 years is more than $ 400 × 10⁶ and the cost of potable water is unlikely to be less than $ 0.7/m³ under careful management.

Schemes and research projects for brighter conclusions are welcome.     

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.     

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.     

煤制天然气过程全局能量集成优化

我国正在大力发展煤制天然气项目实现清洁能源供给。然而现有煤制天然气示范项目存在能耗大、CO₂排放高、生产成本缺少竞争力的问题。本文从煤制天然气能量系统出发,通过全局能量集成实现煤制天然气项目的节能减排与经济效益的提高。根据煤化工示范项目特点,提出了煤制天然气过程全厂能量系统集成优化策略：建立了煤制天然气各单元过程模型,对全流程的物流和能流展开了详细的模拟计算;利用夹点技术对全厂内各单元过程的能量系统展开了用能分析;利用全局温焓曲线对全厂能量系统进行了分析,揭示出全厂能量利用效率低是由于高品位热量降质利用和低品位余热未得到合理利用引起的。通过装置间热回收集成和增设有机朗肯余热回收装置可有效地提高热回收率。通过全厂能量系统优化集成,燃料煤消耗由现有过程1.26t/kNm³（0℃、101325Pa标准状态）天然气下降到1.07t/kNm³天然气。由于公用工程系统消耗的减少,全厂能量利用效率由原来的57.2%提高到59.6%,同时CO₂排放可以由原来5.02t/kNm³天然气下降到4.66t/kNm³天然气。相比于现有过程,改进过程的总投资仅增加了2%左右,而单位生产成本由1.65CNY/Nm³下降到了1.59CNY/Nm³,对于年产20亿立方米煤制天然气厂每年可节约生产成本1.2亿元。     

Present status of electrodialysis process in Japan

This paper describes the present activities of the electrodialysis process in Japan. The ion-exchange membranes and the electrodialyzers are supplied mostly by the three companies. The physical and chemical properties of the membrenes have good performance. The electrodialyzer units which have 50 to 1,800 pairs of 0.03 to 1.6 m² membranes are used for the desalination. Many commercial plants which have the capacities of 1 to 12,000 m³/day are in operation for the desalination of brackish water or sea water, and a few test plants have been operated in order to the desalination of municipal or industrial waste water for reuse.     

MSBR工艺在污水处理厂中的应用——以江苏某污水处理厂为例

江苏某县因地形限制需新建污水处理厂,总规模为10万m³/d,近期规模为5万m³/d,出水水质需达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级A标准。该厂对脱氮要求较高,且拟建地块的吨水用地指标偏低。通过工艺比选,生物处理工艺采用高度集约化的MSBR工艺,深度处理工艺采用滤布滤池,介绍了相关设计参数。MSBR采用7池构型,设计总水力停留时间为16.2 h,回流污泥可在泥水分离区进行脱氮。该厂实际运行后,出水水质达到设计的一级A标准,出水NH₃-N浓度低于1.0 mg/L,去除率为97.9%;出水TN浓度为10.98 mg/L,去除率为65.4%。全厂吨水用地指标为0.611m²/(m³·d),低于传统生物二级处理工艺,单位处理成本为1.28元/m³。MSBR工艺适用于脱氮要求高和用地紧张的工程项目。     

Desalination costs in Australia: A survey of operating plants

A survey of desalination costs in Australia was conducted using data obtained from plant operators, and is reported in second quarter 1986 A$. Unit water costs range from $0.76/kL (for a precursor to deionisation for boiler feed) to $14/kL (for emergency supplies for an island resort).

However, an average figure for desalination of brackish water is $3–$4/kL, and for seawater, $5–10/kL in medium-sized installations.

Capital costs for brackish water plants have been correlated with plant design capacity ranging from 10 to 3400 kL/d.

There is insufficient information to allow a proper comparison between reverse osmosis and electrodialysis for brackish water desalination.     

Two detailed case studies of large Libyan desalination plants and their influence on development

Two large Libyan desalination plants are studied :

1. The Ganzour (Tripoli West) MSF plant with two units, each having a rated distillate output of 11,250 m³/day at full load, the distilla- te purity being 25 ppm. The reliability tests on this plant are just beginning and consequen- tly we shall stress on the erection problems.

2. The Zliten MSF plant with three units, each having a distillate production rate of 4525 m³/day, the distillate purity being 25 ppm. This plant being in operation, we shall stress on the occuring maintenance problems.

All difficulties encountered (during erection for Ganzour plant and during maintenance for Zliten plant) are studied in details. Also the influence of each plant on the development of surrounding regions is considered. Recommendations to both sides (Libyan government and foreign plant manufacturers) are made in order to avoid the future repetition of these problems and troubles.     

Operating experiences of a 15,000 cubic meter per day municipal desalting plant at Corfu, Greece

The initial eighteen month period of operation of the 15,000 m³/day municipal plant on the Island of Corfu, Greece, is described.

The 15,000 m³/day desalting plant employing the electrodialysis reversal process (EDR) produces potable water (500 ppm) from a blend of brackish sources with salinities up to 2000 ppm TDS. The paper describes the plant and integration of the plant into the municipal system. The unique system employed to segregate the treatment of the different brackish waters employing only the highest salinity water for blowdown water is also described.

The plant was started up in the fall of 1977 and provided water to the municipal system during the 1978 season.

The paper presents operating cost data for this period and compares these costs with projected costs which form part of the contractual agreement, with the Municipality.     

Economical study of a small-scale direct contact humidification-dehumidification desalination plant

Economical study of humidification-dehumidification desalination (HDD) pilot plant was made in order to estimate the economic benefits of the process in comparison with a small-scale reverse osmosis (RO) system. The energy recovery of the unit was investigated to be 75%. Some theoretical modifications were made to the HDD system in order to reduce the energy costs of the unit. Exact and clear economic analysis results were obtained using COMFAR ΙΙΙ software including fixed investment costs, production costs, internal rate of return on investment, operating costs, energy costs and some other economical parameters. Based on the energy prices in Iran, the total fresh water production cost was calculated to be $ 6.4/m³ that was nearly the same as produced by an imported RO plant. Finally some points were recommended whether to choose HDD or RO plant in different cases and capacities.     

Ultrafiltration membrane cleaning technology and mechanism based on seawater desalination pilot equipment

In order to clean the ultrafiltration membrane in the process of seawater desalination, this paper studied the cleaning effects of backwash water and chemical agents on the ultrafiltration membrane by using the ultrafiltration pilot equipment. Effects of different backwash water on the transmembrane pressure difference were studied. The results showed that the cleaning effect was in the order of fresh water (tap water) > ultrafiltration water > reverse osmosis concentrated water. In addition, cleaning effect was as follows: citric acid > oxalate > hydrochloric acid > sodium hypochlorite > sodium hydroxide. Citric acid had the best cleaning effect, and the pure water penetration rate could be restored from 283.24 L/(m²·h) to 571.56 L/(m²·h). Moreover, the effect of alkali washing and acid washing together is better than that of cleaning alone. After cleaning with sodium hydroxide and then citric acid, the pure water transmission rate can recover from 283.24 L/(m²·h) to 818.81 L/(m²·h). The results of this study have a good application prospect for the maintenance of ultrafiltration membrane in seawater desalination.     

Economic aspects of membrane processes

Care must be exercised, in predicting operating costs for membrane desalination systems for electricity, labor, chemicals, etc. The assumptions made in establishing unit costs can greatly affect the predicted operating cost and hence the ultimate investment decision. The use of data estimating the quantities of chemicals, power, etc., expected to be used per unit of production can assist in predicting costs, as then site-specific cost data can be used. The fact that 0.2 pounds of acid per kgal of permeate is required in a Florida RO plant is more useful for predicting operating costs of an RO plant on the Island of Anegata than is the fact that acid costs at the Florida plant are $0.03/kgal of water produced. Data based on units rather than costs are presented for seven RO facilities and one ED facility in this paper for use in this type of analysis.