Solar desalination using the vacuum freezing ejector absorption (VFEA) process

This paper consists of design analysis and economic evaluation of a solar-assisted vacuum freezing ejector absorption (VFEA) desalination plant with a capacity of 1 mgd and located in Abu Dhabi, UAE adjacent to the coast of the Gulf. The effect on the design and plant cost of variations in several of the operating parameters was investigated. These parameters are: the sea water salinity, the sea water temperature, and solar collector outlet temperature. Two collector outlet temperatures were used, namely 90°C and 120°C typical of flat plate and evacuated tube collectors, respectively. The absorber loop of the VFEA system uses a sodium hydroxide solution with concentration ranging from 0.5 (dilute stream) to 0.6 (concentrated stream).The results indicate that the capital cost of the VFEA system increases by increasing the sea water salinity and sea water temperature. The capital cost of the system decreases when using the higher value of collector outlet temperature (120°C) typical of evacuated tube collectors. The thermal load on the concentrator is also affected by the sea water salinity and collector outlet temperature with the load increasing with increasing the sea water salinity. The load drops substantially for the collector outlet temperature of 120°C as compared to 90°C.Life cycle savings in fuel costs of the solar-assisted VFEA plant were also estimated using a set of economic ground rules with the objective of specifying the optimum collector area which yields the maximum life cycle savings. It was observed that the optimum area increases with increasing the sea water salinity.     

Energy-saving electro dialyzer for sea water desalination

Tokuyama Soda Co. ltd. has developed an energy-saving skid mounted electrodialyzer for sea water desalination. This equipment is suitable for making fresh water for drinking and industrial use. To desalinate 25°C sea water and turn out one ton of product water. This equipment consumes only 8.5 KWH of electricity and 0.09 Kg of concentrated sulfuric acid. Low energy consumption is achieved by adoption of low electric resistance membranes, new spacer and new designed one pass type system. Low running cost, easy maintenance and low initial installment cost place the equipment good position in the desalination field. And also we applied high temperature electrodialysis up to 50°C of sea water and get figure 6.0 KWH for one ton of product water.     

Ro, MSF and VTE/VC desalination: a comparative evaluation

The two main processes currently in vogue, for sea -water desalination 3?-- multistage flash. (MSF) and reverse osmosis (R.O.) -- are compared, on the basis of cost economics. Cost data are reported for unit sizes up to 10 million (U.S.) gallons per day. Both single-pass and double-pass systems are considered for the R. 0. unit, while the cost of water from MSF plants is calculated for different performance ratios. Controlling factors such. as fuel prices, pretreatment costs, membrane life, energy recovery and terms of financing, are discussed.On the basis of present technology, notwithstanding new developments, it is concluded that R. 0. is the more economical of the two for small unit sizes and regions of high fuel costs. There is a break-even point, depending on these two parameters, beyond which the MSF process yields lower water costs.Attention is focussed on a third process —- Vertical Tube Evaporation/Vapor Compression (VTE/VC), a self-contained, low-energy consuming system which is particularly suitable for barge-mounted or land-based single- purpose (water only) installations. The process, -which, is in an advanced stage of development under Envirogenics Systems Company's R and D program, is potentially competitive with R.O , even for small unit sizes. Future improvements and operational experience could make this the process of choice for single-purpose sea water desalination plants.     

Means by which reverse osmosis desalting costs can be substantially reduced well. before the year 2000

Examination of the market, state-of-the-art in current practice, and a well documented recent study agree on cost for sea water desalting by reverse osmosis which is approximately $4.00 per thousand gallons of purified water produced. At this cost one generally only produces, reliably, water to meet the rather lenient purity standard of less than 1000 mg/l total dissolved solids after demineralization and conditioning if the recovery fractions and membrane replacement frequency are to have any degree of respectability and acceptability. The study predicts that future “fully developed costs” will be approximately $1.00 per thousand gallons of purified water, largely on the basis of a substantial investment in time and money for research and development over a period of many years.

The thrust of this paper is that present technological product, process, and engineering capability can be used in high recovery full two-stage systems to reduce these costs by 40% to approximately $2.60 per thousand gallons of purified water produced, with such conditioned water meeting the 500 mg/1 TDS and the 250 mg/1 chloride ion upper limits. This thesis is examined and illustrated in detail in several iterations, including sea waters containing 35,000 and 42,000 mg/1 TDS respectively. The above approach produces substantial savings in power requirements, membrane replacement and pre-treatment capital and operating costs which far outweigh the added capital amounts to be amortized. These improvements can be realized starting now with minimum development cost or effort. Further cost reductions to be achieved thereafter by research and development effort are also considered.     

Extraction of strontium ion from sea water by contained liquid membrane permeator

To develop a liquid membrane permeator that extracts strontium ion from sea water effectively and continuously, we investigated the extraction of strontium ion from artificial and natural sea water in a contained liquid membrane permeator. The permeator consists of a liquid membrane and two cells for aqueous solutions. The liquid membrane containing D₂EHPA(di-2-ethylhexyl-phosphoric acid) and DCH18C6(dicyclohexano-18-crown-6) is trapped between two hydrophobic microporous polyethylene films and separates sea water and the 0.2 M H₂SO₄ aqueous stripping solution. The effects of various operating parameters on the extraction of strontium ion were experimentally examined. The extractant of DCH18C6 -D₂EHPA mixture in kerosene had a synergistic effect on the extraction of strontium ion. The permeator extracted strontium ion from sea water effectively and continuously with long membrane lifetime.     

Mathematical Modeling of Flux in Ultrafiltration Membrane for Water Treatment

Abstract

Calculation of water flux in a spiral ultrafiltration element was conducted by the novel proposed method, in which all necessary parameters were determined solely from membrane sheet test. By comparing water flux of the commercial element with the data from membrane sheet measurement, this study found that the tendency of water flux variation with time in the membrane element was similar to that which occurred in the membrane sheet, including the consideration of scale‐up effect due to hydrodynamics influence. Therefore, it is possible to express the variation of water flux in the membrane element based on the results from membrane sheet measurement using a practical water source. Surface water and sea water were separately employed to carry out a pilot test with an 8‐inch spiral membrane element, made of polyvinylidene fluoride(PVDF) with a molecular weight cut‐off of 150 kDa, and water fluxes under various transmembrane pressures. Calculations were approximate agreement with that of the pilot test, which enables us believe that the proposal method is reliable for designing a practical ultrafiltration system.     

热泵膜蒸馏系统结构及其优化分析

热泵膜蒸馏系统具有能耗低、可用于中高浓度料液等特点。针对不同料液温度、水蒸气凝结温度、热泵驱动能源等要求,给出了五类典型结构的热泵膜蒸馏系统,介绍了其结构和应用特点。在此基础上,建立吨水总费用与主要影响参数的关系方程,并进行了计算分析。结果表明,料液温度、膜组件成本与寿命、电价等对降低吨水总费用均具有重要影响。     

Separation of phenol–water mixture by membrane pervaporation using polyimide membranes

Separation of components of aqueous waste streams containing organic pollutants is not only industrially very important but also is a challenging process. In this study, separation of a phenol–water mixture was carried out by using a membrane pervaporation technique with indigenously developed polyimide membranes. The membranes were found to permeate water selectively. The total flux as well as that of the individual components were measured. The effect of lithium chloride modification of polyimide film on total flux was investigated. The total flux obtained with 2% lithium chloride modification was about 3.6 times higher than that obtained with virgin membrane. The effects of different parameters such as feed composition and temperature on flux, and separation factor were determined. With modified membrane, a separation factor as high as 18.0 was obtained for water at 27°C and with 8.0 wt % phenol solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 822–829, 2002     

水处理中膜分离技术的应用

对水处理膜分离技术的发展历史和应用现状做了介绍,总结了国内外纳滤和反渗透技术在海水苦咸水淡化、废水处理等水处理领域的应用,指出了膜污染、浓差极化现象及成本较高等膜技术应用中普遍存在的问题。由于纳滤膜具有选择透过性,对纳滤技术应用于盐湖卤水资源开发中镁锂分离过程的可行性做了探讨,并从膜原件和配套工艺两方面对相关技术的应用做了展望。     

Practical aspects of sea water desalination by reverse osmosis

The cost of reverse osmosis equipment for sea water desalination is now equal or lower than the cost of multistage flash evaporators up to 6000 MTD capacity, depending on conditions. The high temperatures and salinity of the sea in several locations where fresh water is in short supply are important in the design of reverse osmosis plants; high temperatures will increase the flux of the membranes but will also increase the rate of compaction and flux decline. As a consequence, the most rugged membranes are required for the desalination of warm sea water. Experience has shown that the addition of aluminum sulfate followed by dual media filtration will provide a suitable feed for reverse osmosis treatment.     

海水冷却塔设计

选择带冷却塔的循环冷却系统,采用海水作为循环冷却水的补充水,是我国沿海火力发电厂以及其它工业企业冷却用水的一次革命。它改变了从海洋取水使用后又将废水排回海洋的传统做法,避免了近海的热污染;极大的减少了从海洋取水的数量,节约了大量的基建投资。我国渤海湾地区拟建的超大型机组发电工程取水均在浅滩海岸,采用直流供水系统,取水头部将深入海中十几千米甚至更远,耗资将达到十几亿甚至几十亿元人民币。根据某科研设计单位十多年“海水冷却塔试验研究”的成果以及国际上成功的工程实践并结合国情,这些工程选择带冷却塔的海水闭式循环系统从方案和技术支持上是可行的,合理的。     

Viscosity of sea water solutions

The kinematic viscosity of sea water solutions and concentrates up to 11% salt by weight and from 0 to 200°C have been measured in a pressurized glass capillary viscometer. All precipitation was prevented during testing; carbonates and hydroxides by slight acidification (to pH 4.5) with concentrated (36N) sulfuric acid, and calcium sulfate by preheating and filtration under pressure. The precision of the results is ± 0.001 centistokes. Existing data on density of sea water solutions were correlated and used to calculate the dynamic viscosity in centipoises. Smoothed values presented should be accurate to ± 0.003 centipoises above 20°C and ± 0.005 below 20°. The results compare well with other authors' values for synthetic sea water.     

One-step preparation of asymmetric ceramic membranes based on sea urchin-like mullite whisker skeletons and their oil-water separation properties

In this work, novel sandwich-type asymmetric ceramic microfiltration membranes with a sea urchin-like mullite whisker skeleton were prepared one step. Their structural properties and oil-water separation performance were investigated. The results show that after sintering at 1400 °C, the prepared membrane possesses good hydrophilic, underwater oleophobic, and anti-fouling properties. During the continuous separation of a 300 mg/L oil-in-water emulsion, a maximum stable flux of 267 L·m⁻²·h⁻¹ was achieved without membrane cleaning. After chemical cleaning and simple physical cleaning, the membranes recovered to a steady flux of 397 L·m⁻²·h⁻¹ and 305 L·m⁻²·h⁻¹, respectively, and maintained a 95% oil rejection. The good underwater oleophobicity and selective permeability brought about by the flat-lying whiskers on the top surface, coupled with the efficient water channels between the sea urchin-like structures inside the membrane, are considered to be the main reasons for its improved separation characteristics over conventional low-cost ceramic membranes.     

Short‐term effects of sea water on E‐glass/vinylester composites

The use of ambient cured E‐glass/vinylester composites is increasingly being considered for infrastructure applications both along the shore and offshore, thereby exposing the composite to a marine aqueous environment. The use of ambient cure potentially results in incomplete polymerization and susceptibility for degradation early in life. This study characterizes the mechanical response of E‐glass/vinylester quadriaxial composites immersed in deionized water, sea water, and synthetic sea water. It is seen that there are substantial differences based on the solution type, with deionized water immersion causing the maximum drop in interlaminar shear performance and sea water causing the maximum reduction in tensile performance. The effect of cycling, simulating the tidal zone or the splash zone, is seen to be more pronounced in a resin‐dominated response. Drying of specimens, even over prolonged periods of time, is not seen to result in complete regain of performance degradation due to sorption processes. A clear competition is seen between the phenomena of moisture‐induced residual cure/postcure and physical (fiber‐matrix debonding, microcracking, plasticization) and chemical (hydrolysis) aging. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2760–2767, 2002     

Evaluating the Effectiveness of Using Flexography Printing for Manufacturing Catalyst‐Coated Membranes for Fuel Cells

This study is an evaluation of the effectiveness of the flexography printing process for manufacturing catalyst‐coated membranes (CCMs) for use in proton exchange membrane fuel cells (PEMFCs). Flexography is a maskless and continuous process that is used in large‐scale production with water‐based inks to reduce the cost of production of PEMFC components. Unfortunately, water has undesirable effects on the Nafion® membrane: water wets the membrane surface poorly and causes the membrane to bulge outwards significantly. Membrane printability was improved by pre‐treating membrane samples by water immersion for short periods (<2 min). This pre‐treatment was used to control the membrane deformation before printing to limit the impact of the ink transfer. Water and ink drop deposition experiments were performed to estimate the liquid‐air‐Nafion® apparent contact angle and the locally induced membrane deformation. Despite the short immersion times used in the tests, the immersion pre‐treatment appeared to induce structural modifications that enhanced both the membrane wettability and the dimensional stability. Flexography printability tests were performed on these treated membranes and showed that the dimensional instability of the Nafion® membrane was the critical parameter for limiting the ink transfer. The immersion pre‐treatment improved the printability of the Nafion® membranes, which were used to fabricate cathodes that were tested in an operational fuel cell.     

Cost analysis of seawater desalination with reverse osmosis in Turkey

Economically usable water resources per capita are decreasing due to excessive population increase each year in Turkey. For this reason, new water resources should be found in the near future. The potential water resources are seawater or well water both of which need removal of salinity. The most promising treatment method for salinity is reverse osmosis. While reverse osmosis becomes widespread, the cost of the process will decrease. There is no detailed information about cost of seawater desalination in Turkey. In this study, a cost analysis of seawater desalination in Turkey was performed for reverse osmosis systems. The basic parameters of cost analysis such as capacity, recovery, membrane life, energy, chemical costs and flux were evaluated based on the effects on capital, operating and total production costs.     

Fresh water,energy, and food from the sea and the sun

Surface waters of tropic and sub-tropic seas hold most of the solar energy retained by the earth; but the heat therein may be increased even more by heat which can be added by intensive solar heaters. The sea water so heated naturally or additionally by the sun, when flash evaporated, gives vapors which may be passed through a heat engine to give power, then condensed at a lower pressure to give fresh water, which may be much more valuable than the power produced. Heat of condensation is removed by circulating cold sea water from a depth of a few thousand feet. This water from the deep also has considerable nutrients for sea plants and animals coming from the degradation of former sea life; and these nutrients may be used in well studied mariculture systems to grow commercial food fish in ponds adjacent the land-based plant. Various arrangements of flows of the several liquid streams are presented to illustrate variations to the process which will produce fresh water and/or electric power, also food fish. These modifications may be optimized with various component systems, some of which are well known and evaluated in this usage, including the use of a second thermodynamic fluid, conventional multistage flash evaporation, also two of its variations: Controlled Flash Evaporation and Vapor Reheat. Calculations indicate that even without the use of intensive solar heaters, a profitable desalination and mariculture operation may be expected which would pay for its substantial cost in two or three years of profits; however, the incorporation of certain intensive solar heaters may increase the profitability significantly.     

The Libyan experimental on the environmental impact assessment for desalination plants

The desalination industries are considered to have a major role in developing human life. Recently this technology became widely distributed, and its construction along the coastal area has been widely reported. Many countries are adopting these technologies for securing the fresh water supply for consumer consumption all over the world. This situation has raised the need for researches to evaluate the environmental impact assessment (EIA) of these technologies on coastal line environment.

This study has been directed to monitor sea water quality used for feeding desalination plants to determine the concentrates of selected pollutants such as heavy metals by using chemical monitoring system to know their effects on the desalination units and other components. This study was conducted in the year 2003 from January to June. Samples were collected from feed water intake of Benghazi North desalination plant and Tobrouk desalination plant, both plants were chosen because of their importance for supplying fresh water for potable water and industrial uses.

The results of this study showed monthly differences in most tested parameters, these differences lead to the scale and corrosion by precipitation on the components of the desalination unites. The objectives of this study is to know the main reasons which caused increasing these concentrates in the sea water (study area) and know how to deal with.     

海水用于循环冷却系统的相关问题探讨

海水循环冷却技术,是海水资源利用领域一项新技术。海水循环冷却术具有海水取水量小、工程投资和运行费用低及排污量小等优点,与海水直流冷却和淡水循环冷却技术相比,在经济、环保及社会效益等方面更具优势,是海水冷却技术的主要发展方向之一。     

A Unique Cross-Linking Strategy to Prepare Poly(Vinyl Alcohol)-Based Anion Conducting Membrane for Fuel Cell Applications

Anion conducting polymer electrolyte membrane (PVA/KOH/CHDMG) was prepared by cross-linking of poly(vinyl alcohol) (PVA) with 1,4-cyclohexanedimethanol diglycidyl ether (CHDMG) in the presence of KOH. FTIR, FESEM, and DSC-TGA techniques were used for the structural, morphological and thermal characterization of the membrane. The effect of cross-linking on the water uptake, thermomechanical characteristics, ionic conductivity, and chemical stability of the membranes was studied with respect to CHDMG contents. The membrane ionic conductivity at room temperature was 2.2–4.7 × 10^?3 S.cm^?1. Further, the membrane exhibited good mechanical attributes and chemical stability. Thus, these low cost membranes exhibited good prospect for application in alkaline fuel cell.