A computer simulation of continuous ion exchange membrane electrodialysis for desalination of saline water

A computer simulation program including the principle of ① mass transport, ② current density distribution, ③ energy consumption and ④ limiting current density is developed for predicting desalinating performance of a continuous (one-pass flow) electrodialysis process. In this simulation the following parameters are inputted; ① membrane characteristics such as overall transport number, overall solute permeability, overall electro-osmotic permeability, overall hydraulic permeability, direct current electric resistance etc. ② electrodialyzer specifications such as flow-pass thickness, flow-pass width and flow-pass length of a desalting cell etc. and ③ electrodialytic conditions such as current density, electrolyte concentration in a feeding solution, linear velocity in desalting cells, standard deviation of normal distribution of solution velocity ratio etc.In a practical-scale electrodialyzer, electrolyte concentration in a desalting cell is decreased along a flow-pass and it gives rise to electrolyte concentration distribution. It causes electric resistance distribution and current density distribution. Solution velocities in desalting cells vary between the cells, and give rise to solution velocity distribution. In this simulation, these distributions are taken into account assuming that the frequency distribution of solution velocity ratio is equated by the normal distribution. Further, the influences of electrodialyzer specifications and elctrodialysis conditions described above on the performances of an electrodialyzer (desalting ratio, current efficiency, electrolyte concentration at the outlets of desalting cells, cell voltage, energy consumption, electrolyte concentration distribution, current density distribution, and limiting current density) are predicted. The simulation model is developed on the basis of the experiments and its reasonability is supported by the performance of electrodialyzers operating in salt-manufacturing plants.     

Experimental study of a basin type solar still with internal and external reflectors in winter

A basin type solar still with internal and external reflectors was constructed and then examined in outdoor experiments in winter in Kurume, Japan. The external reflector was inclined slightly forward to make the reflected sunrays hit the basin liner of the still effectively. The daily productivity of a basin type still can be increased about 70% to 100% with a very simple modification using internal and external reflectors. The experimental results and the theoretical predictions are in fairly good agreement, especially on clear days.     

咸潮原水的处理工艺及技术

河口地区在枯水季节易发生咸潮上溯,致使当地自来水中氯化物浓度超标,生活和生产用水受到威胁。本文对可应用于各种城市自来水的深度处理设施、工业水处理设备、小区集中净水装置及各种家用净水器的咸水淡化技术进行了综述,如离子交换技术、膜分离法、药剂法、蒸馏法等,并对各种淡化工艺的适用方向和发展前景进行了展望。     

Some criteria to minimize the impact of brine dischargeinto the sea

On a uniformly sloping beach, high salinity build-up along the coast associated with brine discharge into the sea can be avoided by building a longer outfall. For an existing seawater desalination plant, extending the outfall will affect the design specification of the plant. Using a two-dimensional advection-diffusion equation, model solutions that can minimize the shoreline salinity levels without building a longer sea outfall are presented.     

膜蒸馏海水淡化研究

研制了聚偏氟乙烯中空纤维微孔膜,并用减压膜蒸馏技术进行了海水淡化实验室试验及中间试验．海水温度在５５℃,经一次过程,脱盐率大于９９．７%,膜通量大于５ｋｇ/(ｍ２·ｈ)．试验数据表明,微孔膜的孔径与孔隙率,以及膜组件和膜装置的结构设计对膜蒸馏过程有重大影响．同时,研究了海水温度、真空度、流量等因素对膜蒸馏过程的作用．     

Saltbush (Atriplex lampa) leaf protein concentrate by ultrafiltration for use in balanced animal feed formulations

The purpose of this study was to evaluate the use of ultrafiltration and discontinuous diafiltration (DD) to obtain a protein concentrate from Atriplex lampa saltbush, improving its palatability by decreasing the salt content (mainly sodium and potassium chloride). The experimental work was done using a Pellicon^® cassette (25 units) system equipped with polyethersulfone organic membranes with a molecular weight cut‐off value of 10 kD. The characteristic of the membranes and the feed material, the parameters and operational conditions were studied in the pretreatment of the sample as well as in the ultrafiltration process to obtain a maximum performance. The product obtained contained 85% protein on aa dry weight basis and a marked decrease in salt content, from 40% in fresh leaves to 2.5% after processing by DD, which is in agreement with the average conductivity values observed, from 18.1 mS cm^?1 in the initial aqueous alkaline extract to a final value of 3.5 mS cm^?1. Measurements of normalized water permeability were determined after each wash cycle in order to verify the flow recovery through the membrane. Analysis of amino acids from the protein concentrate with a chemical score of 85.13 was calculated using a Food Agricultural Organization reference pattern (sulfur amino acids as limiting amino acids). Nitrogen retention was evaluated by means of a biological test and the following values were obtained: net protein utilization = 63.00 ± 4.00, true digestibility = 79.00 ± 5.21, and biological value = 79.80. The presence of oxalic acid, nitrates, saponins, phenolic compounds and condensate tannins is not significant. The results indicate that the concentrate obtained has a high content of lysine, making these products particularly useful as a complement for cereal flour, which is deficient in this amino acid. The determined values suggest that the product can be used in balanced animal feed formulation. Copyright © 2007 Society of Chemical Industry     

Water Mangement Intricacies in the Sultanate of Oman The Augmenation—Conservation Conundrum

Abstract

As with most arid regions, the gap between increasing demands for freshwater and the limited available natural resources has increased dramatically in the Sultanate of Oman. This is mainly due to the expansion in agricultural production and improvements in the standard of living with increasing demands per capita for good quality water. Major aquifers are affected from excessive pumping at rates, which have reached 190 percent of the safe yield in some areas. Several water management approaches have been introduced and implemented, including augmentation of resources and conservation of water. The overall annual water deficit has been estimated to be about 378 Mm³, nearly 50 percent of this being in the most agriculturally productive area of the country. This paper highlights the water shortages in Oman and the efforts exerted to resolve them. It also presents an economic assessment of costs and benefits that might provide a preliminary sound base for examining alternative methods of water augmentation and conservation. It is concluded that, even though conservation practices cost much less than augmentation, favoring one practice over the other is contingent on considerations other than mere costing. However, the general policy seems to favor augmentation rather than conservation. This policy must be reviewed through continuous assessment and feasibility studies     

中东原油破乳剂的合成与评价

开发了一种适合加工中东原油的新型破乳剂，通过采用提高破乳剂相对分子质量和复配的方法，提高破乳剂的破乳效果和广谱性，对如何提高破乳剂的适应性和使用效果进行了高温和低温试验研究。该破乳剂适合多种中东原油，且具有用量少、效率高的优点，对于中东原油，在破乳剂用量为5～10μg／g时，脱盐率大于95％，脱后原油的盐含量可以达到深度电脱盐指标。     

低温多效海水淡化工程材料的选用

通过对众和海水淡化工程有限公司参与设计并制造的三台低温多效海水淡化设备的研究,介绍了低温多效海水淡化工程用材料的选取,探讨了常用在低温多效海水淡化工程上的一些材料及其性能。在此基础上提出了对低温多效海水淡化工程材料选取的一些建议。     

Incipient crystallization of sparingly soluble salts on membrane surfaces: The case of dead-end filtration with no agitation

This paper aims at contributing to development of reliable criteria for determining the onset of scaling on desalination membranes. A novel approach is proposed to investigate incipient crystallization on membranes through modeling and RO filtration experiments. The evolution of membrane surface concentration of rejected ionic species (e.g. Ca²⁺, CO₃²⁻) is theoretically determined, and coupled with a detailed kinetic model for nucleation and growth of particles on the membrane. Model results contribute to our understanding of this problem and are in general accord with experimental data on membrane surface crystal density and mean size. Experimental data and model results show that incipient crystallization on RO membrane surfaces, when the bulk supersaturation ratio is maintained near its critical value (S ~ 1), is controlled by fluid permeation, and that the “induction time” may be insignificant under typical RO conditions. This work also suggests that the ability to determine the onset of crystallization on membranes is dependent on the combined sensitivity and adequate spatial resolution of the experimental technique employed, which explains the significant uncertainty associated with the reported in literature “induction period” data of different origin. Directions for future research are discussed.