Sea water intrusion in Derna located in the Green Mountain region, Libya — a threatening recurrent phenomenon calling for desalination

The city of Derna, Libya, located on the Green Mountain Coastal region is facing a severe water shortage problem as its water resources are exposed to sea water intrusion. This threatening phenomenon is being recurrent with several cities in the coast. This paper considers the evaluation of this problem and suggests proper means to resolve it, such as desalination.     

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.     

Hydraulic turbine energy recovery - R.O. System

In reverse osmosis desalination plants large flow rates of concentrated brine are discharged at high pressure from the membrane modules. Currently this pressure energy is wasted. This paper reviews the impact of soaring energy costs on the technical alternative of hydraulic turbine energy recovery. The capital costs, operating costs, and economics in electrical energy are evaluated for both sea-water and brackish water systems. Schemes of hydraulic turbine coupled with electric generator, tied to the electric power supply are considered for various plant sizes from 1 to 10 mgd. The analysis, in parametric form, presents the interrelationships between the cost of money, cost of electrical energy, and recovery factors for the different plant sizes and for sea-water and brackish water systems. The results will serve as a guide to determine when such a power recovery system should be seriously considered and evaluated in greater details for specific applications.     

聚乙烯醇改性及降解研究进展

从材料学的改性技术和环境学的相容性两个角度综述了国内外聚乙烯醇生物降解的研究概况。通过聚乙烯醇溶液及薄膜的降解过程的介绍,指出化学改性和微生物降解的结合将是今后处理含聚乙烯醇类废水和固体废弃物的主要方法。     

Horizons and future of water desalination in Libya

A premature study has been conducted to overlook the viability and feasibility of the future of desalination in Libya, by estimating the water situation in several locations in the country. A simplified review of the spectrum of well-known desalination techniques and a presentation of these analysis of the water situation would be highlighted to guideline the planners on how, why and when to embark on desalination to resolve the water shortage problem that would be faced at any moment in the future. Finally the methods to resolve shortage problem alongside their economical evaluation would be considered briefly.     

A methodology for comparing water desalination to competitive fresh water transportation and treatment

The comparison between desalination and other water supply methods i usually based on a conventional economic evaluation which typically takes into account the direct capital and operating costs and utilizes techniques and criteria which differ from designer to designer. While this method is usually adequate when one of the alternative water supply methods is clearly superior, the comparison must be much more systematic and comprehensive where the alternatives are competitive. This paper presents a methodology for such a comprehensive evaluation, addressing the complete water supply-disposal chain and taking into consideration technical, environmental, economic, and political/legal aspects of the problem. Actual examples, mainly from the experience of the Southwest Florida Water Management District, are provided to illustrate the methodology. The economic analysis is based on a present-value life-cycle cost model which accounts for interest, tax, insurance and escalations in energy, labor and material costs.     

Comparative cost analysis of nuclear versus oil-fired dual-purpose desalination plants

Prospects for the application of nuclear energy to sea water desalination for the Kingdom of Saudi Arabia have been evaluated here based only on economic considerations. Updated capital costs of power plants and current prices of oil and nuclear fuel are used. Information on the Kingdom's water demand and current status of water desalination is provided. A comparison is also made of costs of water production from power-cum-desalination nuclear plants versus oil-fired plants. Only dual-purpose nuclear plants are considered because of their overall economic advantages over single purpose (water only) plants. The scope of available data and information can not be provided in such detail as to allow for system planning or for a site-specific feasibility study. However, the results provide guidelines for more in-depth analysis. The results show that, compared to oil-fired plants, there is a net saving of costs in using nuclear plants for desalination. If interest on capital is disregarded in calculation of total capital costs and also in calculation of annual capital charges, the economic advantages of nuclear power plants improved significantly over the oil-fired power plants.     

Supercritical Extraction: A Bibliographic Guide (1980-1993)

Abstract

This article provides a bibliographic listing of journal papers published between 1980–1993 concerned with supercritical extraction. This paper provides coverage of a topic of relatively recent interest (since 1980) but which is growing rapidly in terms of applications and the number of publications each year. Supercritical extraction (often using carbon dioxide) has been used for the extraction of caffeine from coffee beans, and removal of aromatics and oils from plant materials. Recent interest has centered on environmental problems and it is currently being investigated as a possible technique for the separation and recycling of polymer materials. Other applications are emerging in the biotechnology area. This bibliography is timely in that it provides a quick and easy reference source, and a more detailed coverage than has been provided in other bibliographic papers (1–3). The following topics are included in this paper:     

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.     

Graphical approach to minimum flowrate targeting for partitioning water pretreatment units

Pretreatment is often necessary when the fresh water available to industrial plants is impure, and when some processes are particularly sensitive to contaminants. Partitioning processes such as membrane separation units are often used for such applications. However, the use of pretreatment units adds to capital and operating costs for a water system. Hence, it is of interest to develop design procedures to minimize the cost for such system. This work presents a graphical pinch analysis approach for targeting minimum flowrate of partitioning water pretreatment systems in single component problem. The approach determines how product and reject streams from the treatment unit can be allocated, along with bypassed freshwater, to satisfy multiple process sinks with their respective flowrate and purity requirements. Hypothetical case studies are presented to illustrate the approach, and generalized design principles based on pinch analysis heuristics are drawn from the examples.     

Simulation and optimization of multi effect desalination coupled to a gas turbine plant with HRSG consideration

There are a large number of gas turbine power plants in the south of Iran that could be exploited to produce fresh water and overcome water shortage. In order to combine gas turbine power plant and thermal desalination, heat recovery steam generator (HRSG) is required for producing steam. Few papers in literature have investigated this combination and none of them has considered HRSG in their studies. Thus, in this paper, multi-effect evaporation thermal vapor compression desalination (ME-TVC) is coupled to gas turbine plant through HRSG. After performing a thorough thermoecnomic analysis, an optimization study is done in view of three approaches. The first and second approaches are single objective optimizations, which utilize two heuristic algorithms, namely, genetic algorithm (GA) and particle swarm optimization (PSO). The first approach is a global optimization problem, which completely optimize the combined system. The second one, as an innovative method, is a local optimization approach, which optimize HRSG and ME-TVC in two separate stages while the third approach is a multi objective optimization. Eventually, the results of the first and second approaches show that the minimum amount of objective function achieved by PSO is better, although the third approach presents a system with higher productivity.     

中水回用现状及研究进展

随着经济发展和人口增长,水危机问题日益严重,中水利用成为解决水危机的重要途径。本文介绍了国内外的中水回用现状和处理技术,并分析了其存在的问题,提出了一些解决这些问题的对策。     

THE USE OF NONLINEAR PROGRAMMING TO OPTIMAL WATER ALLOCATION

Environmental protection, shortage of fresh-water and rising costs for wastewater treatment are all convincing motives for reducing fresh-water consumption and wastewater discharge of the chemical, petrochemical, petroleum refining and other process industries. Maximizing water reuse, regeneration re-use, and regeneration recycling within the chemical plant, as well as optimal distribution of waste streams for end-of-pipe treatment can reduce fresh-water usage and wastewater discharge, while they are also significant in shrinking capital investment in wastewater treatment systems.

Optimal assignment and design of water consuming, regenerating, and treatment systems is a complicated task that can be mathematically formulated as mixed integer non-linear programming (MINLP). In the present article the superstructure based 'Cover and Eliminate' approach with NLP is applied with the tools of the GAMS/M1NOS/CONOPT package and compared to previous results. After introducing the problem in the context of chemical process synthesis, a mathematical model is described and the use of the methodology is explained. Experience with the use of GAMS is discussed. Several case studies are solved including basic examples from the literature and their variants.

The main conclusion is that the application of the mathematical programming for the optimal water allocation problem is essential owing to the broad variety of the specification opportunities. The complex nature of re-use, regeneration re-use, and recycling with multiple pollutants and multiple treatment processes cannot be simultaneously taken into account by conceptual approaches. It is also shown that the assumption on the independency of contamination rates, generally applied in earlier works, are not necessarily valid; and the NLP approach can deal with the more reliable specifications.     

Magnesium oxide production from concentrated brines

Magnesium oxide production from concentrated brines wasted in sea water desalting plants has been investigated.Unlike traditional Mg recovery plants from sea water, it is necessary to undertake purification of the precipitated magnesium hydroxide by means of a carbonation-decarbonation section in order to remove calcium sulphate impurities. Such an operation gives flexibility to the whole plant and allows a high purity product to be obtained.This note illustrates all the stages of the proposed process together with the relevant operating conditions. In comparison with the traditional Mg recovery plants from sea water, it has been also found that the capital and operating costs related to the carbonation-decarbonation section are substantially balanced by the elimination of the sea water intake and of the feed pretreatments, as well as by the reduction of the flow rates to be handled in the first plant section.     

Technical and economic analysis of solvent-based lithium-ion electrode drying with water and NMP

Processing lithium-ion battery (LIB) electrode dispersions with water as the solvent during primary drying offers many advantages over N-methylpyrrolidone (NMP). An in-depth analysis of the comparative drying costs of LIB electrodes is discussed for both NMP- and water-based dispersion processing in terms of battery pack $/kWh. Electrode coating manufacturing and capital equipment cost savings are compared for water vs. conventional NMP organic solvent processing. A major finding of this work is that the total electrode manufacturing costs, whether water- or NMP-based, contribute about 8–9% of the total pack cost. However, it was found that up to a 2?×?reduction in electrode processing (drying and solvent recovery) cost can be expected along with a $3–6?M savings in associated plant capital equipment (for a plant producing 100,000 10-kWh Plug-in Hybrid Electric Vehicle (PHEV) batteries) using water as the electrode solvent. This paper shows a different perspective in that the most important benefits of aqueous electrode processing actually revolve around capital equipment savings and environmental stewardship and not processing cost savings.     

STAGED CASCADED FLUIDIZED BED COMBUSTOR (SCFBC) EVALUATION

The SCFBC is basically a countercurrent contacting unit of downward moving solids with the hot combustion products moving up the stages. Each contacting stage is a shallow fluidized bed providing intimate contact between gas and solids. The design of SCFBC's requires rigorous determination of temperatures, stream flow rates, and heat transfer rates at each stage. The determination is made by solving material balance, energy balance, and appropriate rate equations for each stage.

In this work a technical and economic evaluation of the SCFBC is presented. Analysis of an SCFBC producing 75,000 Ib/hr steam at 200psig is presented with respect to its thermal efficiency, carbon combustion efficiency, sulfur capture efficiency, and sorbent utilization. Effects of the Ca/S ratio on the percent sulfur retention, and carbon burnout efficiency, and effects of stack gas temperature on plant thermal efficiency, total capital costs, and unit cost of steam, and effects of boiler size on the total capital cost and on the unit cost of steam are presented. Effects of variations in cost of operating parameters, e.g., water, sorbent, fuel, etc., on the steam cost are discussed.     

Wind-Aided Intensified eVaporation (WAIV) and Membrane Crystallizer (MCr) integrated brackish water desalination process: Advantages and drawbacks

Due to the increasing of water shortage problems, the need for inland brackish water RO will continue to increase in future. However, the primary limitations to further application of RO inland are the cost and technical feasibility of concentrate disposal. In this work, Membrane Crystallizer (MCr) and Wind-Aided Intensified eVaporation (WAIV) technologies have been applied in order to mitigate the impact of concentrates on the environment. In particular, the research activity has been carried out on a desalination system in which brackish water was first pre-treated, then desalinated through reverse osmosis (RO) operation. Finally, RO concentrates were further treated in WAIV and MCr units. The effect of the presence of organic contaminants and antiscalants were studied by analysing RO operations working at different recovery factors and with different pre-treatments. In the absence of an antiscalant, RO operates at 75% recovery factor and at a pH low enough to ensure no calcium carbonate precipitation. In the presence of an antiscalant, RO process might work until a recovery factor of 88%. The analysed integrated RO + WAIV + MCr system allowed to reach recovery factors as high as 76.6–88.9% and limit brine discharge to less than 0.75–0.27% of the raw water fed to the system.     

A novel systemic approach to water resources optimisation in areas with limited water resources

Water is a constrained natural resource and in many areas of the planet water shortage is considered to be one of the most important issues to be resolved. This is certainly true for many Greek islands, where there is serious water shortage especially during the summer, thus hindering the development of the islands. The aim of the present work is to propose a method for the optimisation of water systems, i.e. the optimal water supply and distribution under conditions of water shortage, as they appear in the Aegean islands. In the water systems under consideration, the total demand as expressed by the users may exceed water availability. In this case, priorities between conflicting demands need to be taken into account. More specifically, the work describes the mathematical model that has been developed for the optimal allocation of water to various users from different sources with varying supply costs and water use values. Technical and environmental parameters are taken into account in the optimisation problem. Special emphasis is given to the implementation of the method in specific Aegean islands with water shortage. The novel feature of the work lies in the fact that it proposes an integrated framework for the solution of water resources optimisation, taking into account various problem parameters and thus resulting in important conclusions concerning supply sources, required infrastructure projects, water cost and value creating from the exploitation of water resources.     

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.     

Use of dielectric spectroscopy to assess adhesively bonded composite structures,Part I: Water permeation in epoxy adhesive

This three-part series of papers describes studies on water penetration into epoxy resins and the use of low- and high-frequency dielectric spectroscopy as a method of monitoring the health of adhesive bond lines in bonded epoxy/graphite composite structures. The first paper is concerned with an investigation of the effect of water ingress into the epoxy adhesive resin used in the manufacturing of the adhesive bond. This study reports a dynamic mechanical thermal analysis (DMTA) and gravimetric analysis of the effects of water uptake and interprets the data in terms of various processes that can occur within the adhesive. Surprisingly high values of water absorption were observed in samples where the edges were unconstrained and presented direct access to the fibre matrix for the moisture. The study demonstrated the effects of postcure and leaching on the sorption and desorption processes and provided background data, which are necessary for the interpretation of the study described in Parts II and III of this series of articles.