Technical and economic analysis for the integration of small reverse osmosis desalination plants into MAST gas turbine cycles for power generation

A technical and economic analysis concerning the integration of small reverse osmosis (RO) desalination plants into mixed air steam turbine (MAST) technologies for power generation was carried out. The simulation tool used is the computer aid reverse osmosis calculations optimization algorithm. This user-friendly software takes into account the capital cost, fuel cost and operation and maintenance requirements of each candidate RO desalination plan scheme and calculates the least-cost configuration. The results indicate that the integration of a RO desalination plant into MAST gas turbines has a minor effect on the final operating cost of the power plant.     

A systematic approach to the synthesis and design of flexible site utility systems

The paper presents a systematic approach for the synthesis of flexible utility systems satisfying varying energy demands. The approach combines benefits of total site analysis, thermodynamic analysis and mathematical optimisation. A thermodynamic efficiency curve (TEC) is developed, which gives an overview of the maximum thermodynamic efficiencies of all possible design alternatives. TEC and hardware composites guide the selection of candidate structures in the superstructure, excluding uneconomic options from the synthesis model. The integration of thermodynamics yields significant reduction in the synthesis model, addresses the impact of variable loads on the unit efficiencies, and enables a compact formulation of the design problem over long horizons of operation. The optimisation is formulated as a multi-period MILP problem that relies on new target models to describe the performance of steam turbines, condensing turbines, gas turbines and boilers. Target models account for the variation of efficiency with unit size, load and operating conditions in a simple, yet accurate way. As a result, these models are capable of accounting for the efficiency trends of realistic units.     

Analysis of water desalination and power generation expansion plans for the Emirate of Abu Dhabi — a preliminary study

This paper contains a comparative economic study of a number of different expansion schedules for power and desalination plants required to meet a forecasted demand in electricity and water for the Emirate of Abu Dhabi. For power generation, steam turbine and gas turbine plants were considered and for desalination both multistage flash distillation and reverse osmosis processes were investigated. Nine combinations of power and desalination plants were selected and a present worth economic analysis was conducted. Capital and operating cost figures used are those typical of the local conditions at Abu Dhabi. Based on the assumptions used in this study the plant combination using steam turbine power plant connected to a reverse osmosis unit seems to represent the most economic alternative.     

Conceptual design of a novel hybrid fuel cell/desalination system

A novel concept for integrating fuel cells with desalination systems is proposed and investigated in this work. Two unique case studies are discussed — the first involving a hybrid system with a reverse osmosis (RO) unit and the second — integrating with a thermal desalination process such as multi-stage flash (MSF). The underlying motivation for this system integration is that the exhaust gas from a hybrid power plant (fuel cell/turbine system) contains considerable amount of thermal energy, which may be utilized for desalination units. This exhaust heat can be suitably used for preheating the feed in desalination processes such as reverse osmosis which not only increases the potable water production, but also decreases the relative energy consumption by approximately 8% when there is an increase of just 8°C rise in temperature. Additionally, an attractive hybrid system application which combines power generation at 70%+ system efficiency with efficient waste heat utilization is thermal desalination. In this work, it is shown that the system efficiency can be raised appreciably when a high-temperature fuel cell co-generates DC power in-situ with waste heat suitable for MSF. Results indicate that such hybrid system could show a 5.6% increase in global efficiency. Such combined hybrid systems have overall system efficiencies (second-law base) exceeding those of either fuel-cell power plants or traditional desalination plants.     

An evaluation of the energy requirements of desalination processes on the basis of the fuel-use performance ratio

The fuel-use performance ratio is defined as the quantity of water produced, in kg, per 1000 kJ of the heat content of the fuel used for supplying thermal, mechanical and/or electrical energy to the desalination plant. The concept is used to evaluate the energy requirements of the major sea water conversion processes - reverse osmosis, multistage flash, multiple effect boiling (as exemplified in the vertical tube foam evaporation process), vapor compression and hybrids of the thermal processes - for three types of plants: (a) single-purpose (water only), (b) dual-purpose (power/water) involving “power loss” and (c) dual-purpose (power/water) utilizing waste heat. It is concluded that only distillation systems based on waste heat can compete with the low energy requirements of reverse osmosis.     

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.     

Optimal design of reverse osmosis‐based water treatment systems

We address the problem of optimal design of reverse osmosis (RO)‐based water treatment systems. A superstructure optimization method is proposed to solve the problem, where the superstructure for a RO system is structurally enhanced with additional features. We formulate the problem as mixed‐integer nonlinear program which is solved to yield optimal results. A case study on desalination is considered in this work, and the numerical results obtained using our approach are validated using a commercial simulation tool. We further extend the problem by considering the effects of degradation of membrane performance over time and solve it by representing the problem as a two‐stage stochastic program. This new approach is highly useful for identifying minimum cost robust designs for membrane‐based water purification systems, which are especially important in desalination applications. © 2012 American Institute of Chemical Engineers AIChE J, 2012     

The SDAWES project: an ambitious R&D prototype for wind-powered desalination

This paper describes the design and operational strategies of an ambitious prototype for a desalination system powered exclusively by wind energy. The system, installed on the island of Gran Canaria, was designed with several objectives in mind: (a) to determine experimentally the feasibility of the stand-alone operation of wind farms isolated from the conventional power grids and supplying energy for a number of desalination techniques (reverse osmosis, electrodialysis reversal and vacuum vaporcompression; (b) to verify the operational feasibility of the various desalination techniques when the energy source driving the system is an intermittent one; and (c) to analyze the influence that a variety of operational strategies have on the volume and quality of the desalinated water produced and on the useful working life of the main components of the desalination plants. The first of these three questions has been resolved with the feasibility of such stand-alone systems now clearly demonstrated. As for the second question, initial tests would seem so far to indicate that the reverse osmosis technique is the most suitable for use in stand-alone wind-powered desalination systems. The results that are still to come from the remaining studies will be of vital importance for regions like the Canary Islands, which suffer from a scarcity of potable water, lack conventional energy sources, but do have at their disposal wind energy resources.     

满足不同需求的水热电联产系统的模型和设计简

In order to improve the energy efficiency, reduce the CO2 emission and decrease the cost, a cogenera- tion system for desalination water, heat and power production was studied in this paper. The superstructure of the cogeneration system consisted of a coal-based thermal power plant （TPP）, a multi-stage flash desalination （MSF） module and reverse osmosis desalination （RO） module. For different demands of water, heat and power production, the corresponding optimal production structure was different. After reasonable simplification, the process model ot each unit was built. The economical model, including the unit investment, and operation and maintenance cost, was presented. By solving this non-linear programming （NLP） model, whose objective is to minimize the annual cost, an optimal cogeneration system can be obtained. Compared to separate production systems, the optimal system can reduce 16.1%-21.7% of the total annual cost. showing this design method was effective.     

Waste heat powered reverse osmosis plants

The purchased power required for operation of reverse osmosis systems can be greatly reduced or sometimes eliminated by reclaiming waste heat from diesel engines, gas turbines, flare gases, etc. This can be accomplished by using a Biphase turbine to convert low level waste heat to shaft horsepower.The system can be designed to use waste heat from existing installations or to reduce the size of the generating equipment in new supplies.The Biphase conservation turbine is driven by a two phase stream generated by flashing a superheated liquid through a nozzle to the turbine. The turbine can be directly coupled to a pump shaft, to an electrical generator or to a combination of the two. Performance of the turbine is discussed. The waste heat recovery turbine and a hydraulic turbine to recover energy from the high pressure concentrated brine can be combined into one system.This paper describes the design of a seawater reverse osmosis system using waste heat from an existing diesel generating unit. The SeaRO system is designed to produce 750 cmd of 400 ppm water at an energy consumption of approximately 2.5 KWH of purchased power per cubic meter.A discussion of available desalination capacity at various quantities and temperature levels of the waste heat source is presented. A comparison of water costs obtained using this system and a conventional electrical drive is presented.     

反渗透膜的研究进展与展望

反渗透具有低能耗、高效率等突出优点,是目前应用最为广泛的分离技术之一。反渗透膜的性能是影响反渗透过程效率的决定因素,反渗透膜的研制一直是国内外膜领域的研究热点。特别是近年来,石墨烯、碳纳米管等新型材料展现出优异的水传递行为,成为新型反渗透膜材料的研究热点。本论文回顾了反渗透膜的研制发展历程,介绍了不同单体通过界面聚合反应成膜的研究进展,综述了国内外新型混合基质膜和无机分子筛反渗透膜材料及其成膜研究,最后提出了新型反渗透膜的研究方向。     

海水反渗透淡化技术的分析与探讨

反渗透海水淡化技术是一种高效、节能、先进的液体分离技术.论述了目前国内外海水反渗透淡化技术的应用现状,着重介绍了反渗透膜材料及特点、膜污染及清洗、典型的海水反渗透淡化流程,探讨了反渗透海水淡化技术目前存在的问题及未来发展趋势.     

Seawater desalination and reverse osmosis plant design

Plant site, water intake, pretreatment, choice of materials of construction, design alternatives and energy recovery are important variables to be considered in the design of seawater desalination plants employing “permasep” B-10 reverse osmosis modules. Techniques are outlined to permit custom design of seawater desalination plants which offer reliable long term performance as well as competitive economics.     

Prospects of the exploitation of advanced energy resources in water production in the middle east

The utilization of oil and natural gas in water production and in supplying steam for desalination plants is progressing with a remarkable rate in the Middle East and especially in the oil producing countries. Nevertheless, some of the available economically feasible energy sources are yet to be exploited. Available hot brine and steam fields in the Red Sea Deeps and in other locations in the Middle East are a valuable source of useful energy for desalination. The rapidly growing geothermal technology can be utilized in supplying fresh water to the Red Sea coasts for both of the western cities of Saudi Arabia and the new settlements on the eastern Egyptian coast. An assessment is made of the geothermal fields in the area and their characteristics with special consideration of their utility in water desalination projects. Other energy sources are also considered; such as the future exploitation of heavy water and heavy hydrogen isotopes obtained from the Red Sea in energy sources for desalination. In addition, the potential use of natural depressions in the production of power and water is discussed. A comparison is made between these advanced systems and contemporary alternates in a longterm plan for agricultural and industrial expansion.     

热膜耦合海水淡化系统的优化设计

采用混合节点和分配节点的概念,建立了多级闪蒸(MSF)和反渗透(RO)海水淡化集成系统的超结构模型,以年度总费用最小为目标,引入产水比的概念,并将该参数作为集成系统的一个优化变量,采用改进的遗传算法进行求解,获得了集成系统的最优结构及相应的操作条件。实例结果表明:集成海水淡化系统的淡水成本比独立运行的RO和MSF低,产水比为0.45时集成系统的费用最小,流程结构为MSF-RO。     

Design of a small solar-powered desalination system

A design is presented for a solar/thermal system configured to power a reverse osmosis (RO) desalination unit to produce 7000 gallons of fresh water in an eight hour period. A field of line-focus tracking solar collectors is used to heat a high pressure liquid-vapor water storage tank supplying two compound reciprocating steam engines, one direct-connected to the RO high-pressure pump and the other to an electric generator for auxiliary power. An auxiliary heating loop with an oil-fired boiler is also used to supply the steam engines.The system operates in either all-solar, all-oil, or mixed solar/oil modes. Primary operating mode is assumed to be a mixed solar/oil mode in which the oil-fired boiler is used only to prevent shutdown of the RO system during the course of a partly sunny day. In this mode, the RO system does not come on line in the morning until the solar collector field has brought the high-pressure storage tank to a point near maximum operating pressure. Thereafter, the oil-fired boiler comes on automatically whenever the storage tank is drawn down to a pressure near minimum full-power operation (due to inadequate or intermittent insolation) and remains on, supplying the steam engines, until the solar collectors have again brought the storage tank to the high-pressure cutoff.In the all-solar mode, the system continues to operate at reduced power as storage tank pressure drops below the point at which the oil-fired boiler would otherwise come on. A portion of the RO system is shut down to maintain pressure in the remainder.The all-oil mode is used whenever fresh water is required during non-sunny periods, or to increase fresh water production in sunny periods.     

On the use of filters to facilitate the post-optimal analysis of the Pareto solutions in multi-objective optimization

Multi-objective optimization (MOO) has emerged recently as a useful technique in the design and planning of engineering systems because it allows identifying alternatives leading to significant environmental savings. MOO models typically contain an infinite number of Pareto solutions, from which decision-makers should choose the best one according to their preferences. An approach is here presented that identifies and retains for further inspection a reduced set of Pareto solutions showing better overall performance. The capabilities of our approach are illustrated through its application to the design of reverse osmosis desalination plants considering simultaneously the unitary production cost and a set of environmental impacts in several damage categories. Our method reduces significantly the number of Pareto points, thereby facilitating the decision-making process in MOO.     

膜法海水淡化系统在华能威海电厂的应用

随着我国水资源的日益匮乏,海水淡化技术不断应用于工业中。华能威海电厂三期海水淡化系统设备为笔者所在公司提供,海水作为该厂锅炉补给水水源,采用了超滤(UF)-海水反渗透(SWRO)-一级反渗透-二级反渗透-电去离子技术(EDI)全膜法制备。其中能量回收作为海水淡化系统的重要部分,本文将介绍几种常用的能量回收装置,并详细介绍膜法海水淡化系统在该厂中的应用。     

Boron in seawater and methods for its separation — A review

The seawater reverse osmosis (SWRO) membrane desalination process is a relevant and reliable technology for desalination of seawater. However, some serious limitations had recently been discovered during field practice, among them the boron problem seems to have a critical meaning. According to the WHO regulations, the boron concentration should be reduced to less than 0.5 mg/L for drinking water. It was also reported that, this limit is rarely reached for conventional reverse osmosis desalination plants equipped with commercially available membranes. This paper reviews the extensive published literature on separation methods of boron removal from seawater.     

Fractionation of aqueous organic mixtures by reverse osmosis

Modern synthetic polymer membranes for reverse osmosis, although primarily developed for seawater desalination, are remarkably selective and chemically resistant in the case of organic solvents. Accordingly, reverse osmosis is increasingly employed for the treatment of industrial effluents such as solvent-contaminated waste water. In this case flux and selectivity can no longer be calculated with the simple relationships valid for seawater desalination. Semi-empirical relationships are presented, capable of quantitatively describing the local partial fluxes of organic-aqueous solutions. The relationships are based on the solution diffusion model but contain less stringent simplifying assumptions than in the case of dilute salt solutions.

Compared to empirical relationships, very few experiments are required to determine the model parameters. In combination with the differential mass and material balances, these equations are sufficient for process design. This is illustrated by a comparison of calculated results and experiments on a pilot plant scale and is even valid for quasi-binary systems.