Tesi sul tema "Desalination"
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1
Nayar, Kishor Govind. "Improving seawater desalination and seawater desalination brine management". Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121886.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis. "Thesis contains very faint/illegible footnote numbering"--Disclainer Notice page.
Includes bibliographical references.
Water scarcity is an increasing problem globally. Seawater desalination is increasingly being relied upon as a means of mitigating the problem of water scarcity. However, seawater desalination has costs associated with it: capital costs, cost of energy to desalinate and environmental costs from the discharge of high salinity brine. Efficient and cost-effective seawater desalination and desalination brine management systems are necessary to make seawater desalination a sustainable scalable process. This work seeks to improve seawater desalination and seawater desalination brine management in several ways. For the first time, the thermophysical properties of seawater have been characterized as a function of pressure across the full desalination operating regimes of temperature, salinity and pressure. Functions that allow accurate thermodynamic least work of desalination and seawater flow exergy analysis have been developed.
The least work of desalination, brine concentration and salt production was investigated and the performance of state-of-the-art brine concentrators and crystallizers was calculated. Hybrid designs of reverse osmosis (RO) and electrodialysis (ED) were proposed to be integrated with a crystallizer to concentrate desalination brine more efficiently. The RO-ED-crystallizer concept was applied to two separate applications: (a) salt production from seawater and (b) zero brine discharge seawater desalination. A parametric analysis to minimize the specific cost of salt production and water production was conducted. Parameters varied were: the ratio of seawater to RO brine in the ED diluate channel, ED current density, ED diluate outlet salinity, electricity, water and salt prices, and RO recovery by adding a high pressure RO (HPRO) stage. Results showed that significant cost reductions could be achieved in RO-ED systems by increasing the ED current density from 300 A/m² to 600 A/m².
Increasing RO brine salinity by using HPRO and operating at 120 bar pressure reduced salt production costs while increasing water production costs. Transport properties of monovalent selective ED (MSED) membranes were also experimentally obtained for sodium chloride, significantly improving the accuracy of modeling MSED brine concentration systems. MSED cell pairs transported only about ~~50% the water but nearly as much salt as a standard ED cell pair, while having twice the average membrane resistance.
Supported by Center for Clean Water and Clean Energy at MIT and KFUPM Project No. R13-CW-10, King Fahd University of Petroleoum and Minerals (KFUPM), Dhahran, Saudi Arabia
by Kishor Govind Nayar.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
2
Mayere, Abdulkarim. "Solar powered desalination". Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12331/.
Testo completoAbstract (sommario):
Despite water being apparently abundant, up to half of the world’s population is faced with water crises which is growing at an alarming rate most especially in developing countries such as African countries where both physical and economic water scarcities prevail. Thus with the abundant salty water and solar intensity in the regions or seasons when water is mostly scarce, solar powered desalination presents an attractive and promising solution towards availability of clean water. A unique and simple solar desalination system has been developed. The system which based on humidification/dehumidification process is a low cost solution and very competitive with conventional desalination systems. It can be used to provide clean water to the over one billion population who have no access or have water shortages which threaten their health and economies. The developed solar desalination system consists of a purposely designed concentrating solar collector and the desalination core which consist of the humidification and dehumidification chambers. The novel concentrating v-trough solar collector which has its focal point at the bottom of the concentrator provides enough thermal energy required to heat up seawater which is then pumped and sprayed to humidify the incoming air in the humidification chamber. The humidified air enters the dehumidification chamber and is cooled by the incoming cold seawater. The moisture is condensed out and the pure water is accumulated at the base of the chamber, and the dehumidified air is discharged to the outside. The key point is the psychrometric energy re-use, most of the energy is from the condensing of the moisture in the carrier gas. Both theoretical analysis and experimental tests were carried out and good water output up to 20kg/h and COP around 3 was obtained. This would require 8m2 of the newly designed v-trough collector operating at 100°C at 1000W/m2 solar intensity. And economic and environmental analysis showed that the solar powered desalination system can achieve a 6 year payback period when compared with when driven by electricity and also a saving of up to 4730 kgCO2 per year. The system can be manufactured from inexpensive plastics rather than exotic and expensive metals. It can easily be sized and scaled to location’s needs, can be operated in diverse geographies unattended on a continuous basis and require minimal maintenance.
3
Rahal, Zeina. "Wind powered desalination". Thesis, Loughborough University, 2001. https://dspace.lboro.ac.uk/2134/7466.
Testo completoAbstract (sommario):
This thesis investigates the technical problems associated with large-scale stand-alone wind powered desalination employing a short-term energy store, particularly the complexities associated with the intermittent operation of the desalination plant. To achieve this, a non-linear, time domain system model of an existing wind powered desalination plant has been developed using the propriety code Simulink. Two desalination techniques have been considered: reverse osmosis and electrodialysis, due firstly to their relatively low specific energy consumption, and secondly, their efficient coupling to a wind turbine generator. As a way of reducing power mismatch, optimising water production, and above all reducing the switching rates of the desalination units, operation of the reverse osmosis and electrodialysis units under variable power conditions is suggested. Little information is available on plant performance under such conditions. A mathematical model has therefore been developed to ascertain the performance of reverse osmosis and electrodialysis processes under transient power conditions. The model consists of the set of partial differential equations (PDEs) describing the conservation of mass, momentum and chemical species coupled with the appropriate boundary conditions. A numerical solution based on the finite volume method has been employed to solve for the system of PDEs, as no analytical solution is available for the particular set of model equations derived. Sensitivity of plant performance to key design parameters (such as operating pressure and energy storage capacity) and operational strategies is predicted from simulation results. This technology is economically attractive for islands where wind energy density is high and water resources are scarce.
4
Crerar, Alan J. "Wave powered desalination". Thesis, University of Edinburgh, 1989. http://hdl.handle.net/1842/14741.
Testo completo
5
Digby, Simon. "Tjuntjuntjara groundwater desalination". Thesis, Digby, Simon (2012) Tjuntjuntjara groundwater desalination. Other thesis, Murdoch University, 2012. https://researchrepository.murdoch.edu.au/id/eprint/13106/.
Testo completoAbstract (sommario):
The Tjuntjuntjara Groundwater Desalination Thesis was conceived to solve the operational faults of a Vacuum-Multi-Effect-Membrane-Distillation (VMEMD) Pilot Plant. The National Centre for Excellence in Desalination (NCED), Murdoch University and other contributing parties intend to power the plant with renewable energies in order to supply the Tjuntjuntjara indigenous community with water.
The thesis involved research into VMEMD technology and an assessment of the control system and instrumentation that operated it. During the assessment process, operational faults as well as potential improvements in the operation of the plant were recorded. It was found that the control system had a number of software based faults. The design and implementation of a new Programmable Logic Controller (PLC) operating code was undertaken to correct these faults. In parallel to this work, the design and implementation of systems to improve the operation of the plant was also undertaken.
When all upgrades to the plant were complete, the vigorous process of validating the new additions commenced. As well as testing the new code and system improvements, a series of continuous trial periods was conducted. These proved that the plant can now operate continuously and at varying system temperatures for over 100 hours. During the trial periods, operating point data was collected and methods for increasing distillate output were found.
The plant has been brought up to a stable operating standard and the additional systems installed to improve the plant have further increased its reliability. A number of recommendations have been provided to stimulate further development of the VMEMD pilot plant.
6
Andersson, Niklas, e Pontus Heijdenberg. "Wind Power Desalination System". Thesis, Halmstad University, School of Business and Engineering (SET), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-2769.
Testo completo
7
Psaltas, Michael A. "Hybrid cogeneration desalination process". Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.576090.
Testo completoAbstract (sommario):
Supplies of potable water from the conventional resources are descending due to increased industrialization;' extensive irrigation and rapid population growth. In Cyprus, a country without any perennial river, fixed rainy season and depleted natural aquifers faces severe water shortage in future. Desalination along with power cogeneration certainly poses as the most suitable option in the long run to avoid any water scarcity and rationing. This dissertation introduces all the major desalination processes and is focused on the commercially employed desalination processes. The processes have been discussed in relation with their history, principle, capacity, costs, market capitalization, energy consumption, required pre treatments, future growth potential and their environmental effects. The dissertation extensively investigates Cyprus' existing water resources, water scarcity in Cyprus, the need and existing desalination including the overall power generation capacity. This dissertation is unique in the sense of covering all the major desalination processes and investigating the Cyprus water resources as a whole outlining the need for commercially viable desalination and power, cogeneration facilities. The aim of this study is to expand the existing MSF systems to a higher level for potential changes which they will help the industrial desalination in increasing the efficiency and reducing the costs. This is a new three stage distillation system which will be designed and constructed in Cyprus. The plant will be manufactured from local materials by local manpower and requires little maintenance and operating costs. Hence it offers relatively higher efficiency which enables this system to be more cost effective.
8
Bajpayee, Anurag. "Directional solvent extraction desalination". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78539.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012."September 2012." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 131-137).
World water supply is struggling to meet demand. Production of fresh water from the oceans could supply this demand almost indefinitely. As global energy consumption continues to increase, water and energy resources are getting closely intertwined, especially with regards to the water consumption and contamination in the unconventional oil and gas industry. Development of effective, affordable desalination and water treatment technologies is thus vital to meeting future demand, maintaining economic development, enabling continued growth of energy resources, and preventing regional and international conflict. We have developed a new low temperature, membrane-free desalination technology using directional solvents capable of extracting pure water from a contaminated solution without themselves dissolving in the recovered water. This method dissolves the water into a directional solvent by increasing its temperature, rejects salts and other contaminants, then recovers pure water by cooling back to ambient temperature, and re-uses the solvent. The directional solvents used here include soybean oil, hexanoic acid, decanoic acid, and octanoic acid with the last two observed to be the most effective. These fatty acids exhibit the required characteristics by having a hydrophilic carboxylic acid end which bonds to water molecules but the hydrophobic chain prevents the dissolution of water soluble salts as well the dissolution of the solvent in water. Directional solvent extraction may be considered a molecular-level desalination approach. Directional Solvent Extraction circumvents the need for membranes, uses simple, inexpensive machinery, and by operating at low temperatures offers the potential for using waste heat. This technique also lends itself well to treatment of feed waters over a wide range of total dissolved solids (TDS) levels and is one of the very few known techniques to extract water from saturated brines. We demonstrate >95% salt rejection for seawater TDS concentrations (35,000 ppm) as well as for oilfield produced water TDS concentrations (>100,000 ppm) and saturated brines (300,000 ppm) through a benchtop batch process, and recovery ratios as high as 85% for feed TDS of 35,000 ppm through a multi-stage batch process. We have also designed, constructed, and demonstrated a semi-continuous process prototype. The energy and economic analysis suggests that this technique could become an effective, affordable method for seawater desalination and for treatment of produced water from unconventional oil and gas extraction.
by Anurag Bajpayee.
Ph.D.
9
Al-Thani, Faleh N. "Economical desalination processes in Qatar". Thesis, University of Hertfordshire, 2002. http://hdl.handle.net/2299/14043.
Testo completoAbstract (sommario):
The limited underground water resources and the dramatic increase of fresh water consumption in Qatar forced the government to seek alternative ways to compensate for the lack of fresh water resources. Unfortunately, most of the currently available alternatives are costly in terms of excessive fuel consumption; also they require large capital investment and high maintenance cost. Such plants currently produce over 98% of the total fresh water in Qatar. This ratio may increase to 100% in the next few years. The main aim of this work is to investigate the most viable water desalination processes, which can produce sufficient, and a continuous supply of fresh water with low operation and construction costs. Climatic conditions and solar radiation in Qatar have been studied and analysed to determine the performance of any potential solar system applicable to this country. A technical and economical investigation into the current and common desalination methods with particular emphasis on the three main desalination systems including multistage flash, multiple effect distillation and reverse osmosis were conducted and included. A comprehensive literature survey on various water desalination methods was undertaken. The current experimental program was confined mainly to one novel type of tilted tray solar still system, namely pyramid tilted tray solar still, which was developed to increase productivity by increasing the receiving surface area of the still (the absorber) in order to collect the optimum amount of solar radiation. Two types of cover have also been selected and tested in this work, namely pyramid and dome shapes. These tilted tray solar stills were designed and constructed on a small scale and have been tested under controlled laboratory conditions at the University of Hertfordshire. Various parameters, which are likely to effect the still performance have been investigated. These include water flow rate, spacing between cover and tray surface, glass thickness, insulation layer, and inlet water temperature. Finally, a comparison of the stills performance characteristics of the two shapes has been carried out. The laboratory experimental results of hourly production revealed that pyramid type solar still yield higher distilled water output results than the dome type. However, the use of the pyramid shape with tilted tray solar can lead to further increase in the still productivity by optimising the orientation and surface area of the still absorber. The field experimental results of pyramid solar still, which were conducted under local climate conditions of Qatar, indicated clearly that solar desalination can be a suitable economical option, particularly for remote areas, where the fresh water demand is low and water transport is expensive. Moreover, a theoretical model was employed to predict the effects on solar still performance under three various parameters under typical climatic conditions of Qatar; These include the thermal insulation layer, the water depth and wind speed. Due to the economical reasons the dual-purpose multistage flash process will remain for the foreseeable future the preferred process, when fresh water and electricity demands are growing concurrently and rapidly.
10
Tow, Emily Winona. "Organic fouling of desalination membranes". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111695.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 211-224).
Energy-ecient desalination and water reuse are necessary to ensure universal access to clean water. Reverse osmosis (RO) is the most ecient desalination process for almost any water source, but it is susceptible to membrane fouling, which can reduce product water quality and raise energy consumption. Fouling can be reduced through (energy-intensive) pretreatment, delayed by membrane coatings, and partially reversed by cleaning. However, poor understanding of fouling physics hinders our ability to predict fouling or design for fouling resistance. Better models of fouling are needed to improve the RO process and provide sustainable sources of desalinated or recycled water to water-scarce communities. Through experiments and modeling, this thesis compares several desalination systems, quantifies the effect of pressure on fouling, and elucidates mechanisms of foulant removal. An experimental apparatus was created to simulate operating conditions in full-scale RO, forward osmosis (FO), and membrane distillation (MD) desalination systems and compare the fouling behavior of these processes under identical hydro-dynamic conditions. In the FO configuration, both uid streams could be pressurized to experimentally isolate the effects of pressure from other operating conditions that affect fouling. A window in the membrane module allowed in situ visualization of membrane fouling and cleaning at pressures as high as 69 bar. Experiments were complemented by the development of physics-based models that predict the eect of hydraulic pressure on foulant layer properties and ux decline and also enable the calculation of foulant layer thickness from measured flux. The findings provide new insight into the relative fouling propensity of membrane desalination systems, the factors influencing ux decline, and the mechanisms of foulant removal. Experiments and modeling show that, although flux decline is slower in FO than in RO, the FO membrane accumulates a thicker foulant layer. Furthermore, FO fouling trials at elevated pressure reveal that fouling behavior is not adversely affected by high hydraulic pressure. Despite this, low operating temperature and unfavorable surface chemistry cause RO to be more susceptible to organic fouling than MD and more susceptible to inorganic fouling than FO. However, neither FO nor MD is immune to fouling: FO flux declined as much as RO ux in the presence of alginate fouling, and MD exhibited rapid ux decline as a result of inorganic fouling. Finally, in situ visualization revealed that osmotic backwashing causes the foulant layer to swell, buckle, and detach in large pieces from both FO and RO membranes, regardless of operating pressure. These findings guide desalination process selection, membrane design, and cleaning protocol development to reduce the energy consumption associated with membrane fouling in desalination.
by Emily Winona Tow.
Ph. D.
11
Tabraham, John Mark. "The desalination of marine ice". Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624384.
Testo completo
12
Gutierrez, Hernandez Lucero, e Garcia Wenny Fernanda Ramirez. "Sustainable System for Water Desalination". Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-15991.
Testo completoAbstract (sommario):
Ankarstiftelsen, a non-profit organization with the mission of assuring the access to basic necessities in developing countries, presented a brief for a sustainable water desalination system, to obtain acceptable drinking water, in the region of La Guajira, Colombia. The main objective of the project is the creation of an initial proposal for a sustainable desalination system using solar energy with a minimal cost of construction. This project required large amounts of research regarding the principles of desalination and water purification systems. As well as the living conditions, weather, and water situation in La Guajira. Empirical studies helped verify initial information and provided a better understanding of desalination systems and their principles. Methodologies such as user personas, interviews, and Function analysis were used to determine key constraints and aspects to be considered in the project development. In addition, simple functionality tests were conducted to evaluate the concepts generated. The resulting design proposal is a collection of technical functionality aspects and user identity that aims to create a meaningful and coherent product to be implemented in its designated context.
13
Ahmad, Mansour M. M. "Assessment of freezing desalination technologies". Thesis, Swansea University, 2012. https://cronfa.swan.ac.uk/Record/cronfa42635.
Testo completoAbstract (sommario):
The production of both fresh water and waste streams are progressively increasing over the years due to ongoing population growth coupled with high levels of increase in water consumption. The ongoing growth of human activities, such as industry, recreation, and agriculture, are significantly contributing to the increase in both water demand and severity of degradation of natural water resources. The majority of the industrial wastewaters have a significant impact on the environment; some of which may pose a number of threats to human health and the surrounding environment. Thus, discharge of such waste streams into a surface water and/or groundwater presents a major source of water pollution in many countries. Therefore, these waste streams must be disposed of in an environmentally acceptable manner. The primary concern of the PhD thesis is to seek the most feasible and applicable freezing desalination technologies that are potentially capable to concentrate the dissolved ionic content of the liquid streams, especially for those causing severe pollution problems. Therefore, various forms of melt crystallisation processes, namely; agitated and static crystallisation processes, ice maker machines, a Sulzer falling film crystallisation process, the Sulzer suspension crystallisation process, and the Sulzer static crystallisation process, were experimentally used and investigated. The experimental investigations were carried out on the laboratory bench scale and/or straightforward pilot plant by using aqueous solutions of sodium chloride and/or process brines as feed samples. The study was focused on a number of important parameters influencing the separation performance of the investigated treatment systems. In general, the resulting experimental data for each innovative process were highly encouraging in minimising the volume of the waste stream, and substantially increasing the amount of product water. The obtained product water was ready for immediate use either as drinking water or as a saline water of near brackish water or seawater qualities. Also, relationships between the influences and the separation performance, in terms of salt rejection and water recovery ratios, were explored and determined for the investigated technologies. Based on the experimental results, the Sulzer melt crystallisation processes were scaled up and were combined into a commercial reverse osmosis membrane desalination plant. As a result, three novel treatment option configurations were proposed for minimising the waste stream, whilst increasing the production rate of drinking water and/or preserving a substantial amount of natural water resource from the RO plant's exploitation.
14
Xie, Fangyou. "Pressure Driven Desalination Utilizing Nanomaterials". DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2204.
Testo completoAbstract (sommario):
Nanomaterials such as graphene oxide and carbon nanotubes, have demonstrated excellent properties for membrane desalination, including decrease of maintenance, increase of flux rate, simple solution casting, and impressive chemical inertness. Here, two projects are studied to investigate nanocarbon based membrane desalination. The first project is to prepare hybrid membranes with amyloid fibrils intercalated with graphene oxide sheets. The addition of protein amyloid fibrils expands the interlayer spacing between graphene oxide nanosheets and introduces additional functional groups in the diffusion pathways, resulting in increase of flux rate and rejection rate for the organic dyes. Amyloid fibrils also provide structural assistance to the hybrid membrane, which supresses cracking and instability of graphene oxide sheets. The second project is to fabricate polymer nanocomposite membranes with carbon nanotubes encapsulated by polymerized surfactants. The designed polymerizable surfactant forms lyotropic liquid crystalline mesophases in an aqueous medium with hexagonal packing of cylindrical micelles. The adsorption of surfactants on the surface of carbon nanotubes allows a stable dispersion of carbon nanotubes encapsulated in the cylindrical micelles, resulting in the ordered structure. After photo-polymerization, the composite membranes display enhanced dye rejection. Both projects have shown promising ways to improve membrane filtration by using nanomaterials.
15
Girme, Gauri Manik. "Algae powered Microbial Desalination Cells". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397735584.
Testo completo
16
Corral, Andrea F. "Alternative Technologies for Inland Desalination". Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/333122.
Testo completoAbstract (sommario):
Water scarcity is one of the biggest issues we have to face as population and water consumption levels increase despite a fixed supply of renewable fresh water. Meeting the challenges that water scarcity poses to food production, ecosystem health, and political and social stability will require new approaches to using and managing water. Desalination already plays an essential role in water management. It constitutes a secure source of safe drinking water supply once demand management measures are fully implemented. Overcoming problems related to brine minimization and disposal is key to sustainable, efficient inland water desalination. The main focus of this was the investigation of technical limits and improvements for application in inland desalination. The first part of the dissertation covers the study of Membrane Distillation (MD) for desalination of water. The second part provides a broad perspective of Reverse Osmosis (RO), pretreatments -comparison of slow sand filtration and microfiltration-, post-mortem study of membranes to determining fouling and scaling causes, and RO brine minimization via Vibratory Shear Enhance Processing (VSEP®) for use in RO brine minimization. The study of Vacuum Membrane Distillation in a hollow fiber membrane was studied. Experimental work is supported by an original mathematical model to expose the physics of VMD and support predictions that extend VMD results beyond these generated in the laboratory. The advantages and disadvantages of each pretreatment, including their effects the effect on the performance of RO, a post-mortem membrane study and an economic analysis. The post-mortem study of membranes used during Yuma Desalting Plant operation. This work was used to identify the best pretreatment and more suitable membrane to treat saline water in the lower Colorado River. The work performed during the brine minimization study using VSEP®. This study included experimental data and an extensive economic analysis comparing Ion Exchange (IX) as pretreatment and VSEP® as post-treatment for RO.
17
Mkhize, Mfanafuthi Mthandeni. "Multistage solar still desalination system". Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2848.
Testo completoAbstract (sommario):
Thesis (Master of Engineering in Mechanical Engineering)--Cape Peninsula University of Technology, 2018.The present study was centred on the design of a thermal multistage solar still desalination system. The design is a multistage with new configurations such as direct vapour input into each stage using vapour make-up tubes and the integration of a multistage with a basin type solar still. The incorporation of float a valve in the secondary seawater tank to regulate the seawater in the assembly eliminated the need of pumps to the system. The circulation of seawater between the evaporator and the evacuated tube solar collector (ETC) was through the pressure difference and the flow back was controlled through the incorporation of oneway flow valve. The ETC was used as a heat source to supply the thermal energy into the multistage system. The system had no electrical connections and therefore, no forced circulation as no pumps or any electrical components were used. The system consisted of six stages in total, the evaporator supplied the vapour to five of the six stages of the system. The system was tested on the roof of Mechanical Engineering Department and this location was chosen because of less sun’s intensity obstructions. The system was tested for nine (9) days but the distillate collection was not performed for the whole each day. This was due to the controlled access to the roof and the minor repairs that had to occur before the tests were conducted. The duration on which the tests were conducted varied in each day. The data was supposed to be logged from 08h00 am to 18h00 pm but this was not so due to the controlled access to where the tests were conducted. This data logging period was chosen based on the assumptions that the sun’s intensity would be at maximum within this period. The longest period of test was approximately 7 hours and the system managed to produce about 1500 ml and the maximum temperature for the day was 28oC. The system produced a minimum of 225 ml in the space of 3 hours and the temperature of the day was 26oC. The total amount of distillate produced was about 7600 ml and this amount was produced within the period of 49 hours. The 49 hours is equivalent to two days and 1 hour. It is anticipated that the system would have produced more should there be no repairs involved during the tests. The system produced a maximum of 48 ml at night and a minimum of 8ml in some nights. The night tests were not controlled and monitored due to limited access. It was noticed that the system was empty in each morning of the first few days of the tests. This emptiness contributed to the leakage occurred to the evaporator. The leakage of the evaporator was caused by unmonitored heat supplied by the ETC. The evaporator was constructed using unsuitable material and this was another factor which contributed towards the failure of the evaporator.
18
Sassi, Kamal M. "Optimal scheduling, design, operation and control of reverse osmosis desalination : prediction of RO membrane performance under different design and operating conditions, synthesis of RO networks using MINLP optimization framework involving fouling, boron removal, variable seawater temperature and variable fresh water demand". Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5671.
Testo completoAbstract (sommario):
An accurate model for RO process has significant importance in the simulation and optimization proposes. A steady state model of RO process is developed based on solution diffusion theory to describe the permeation through membrane and thin film approach is used to describe the concentration polarization. The model is validated against the operation data reported in the literature. For the sake of clear understanding of the interaction of feed temperature and salinity on the design and operation of RO based desalination systems, simultaneous optimization of design and operation of RO network is investigated based on two-stage RO superstructure via MINLP approach. Different cases with several feed concentrations and seasonal variation of seawater temperature are presented. Also, the possibility of flexible scheduling in terms of the number of membrane modules required in operation in high and low temperature seasons is investigated A simultaneous modelling and optimization method for RO system including boron removal is then presented. A superstructure of the RO network is developed based on double pass RO network (two-stage seawater pass and one-stage brackish water pass). The MINLP problem based on the superstructure is used to find out an optimal RO network which will minimize the total annualized cost while fulfilling a given boron content limit. The effect of pH on boron rejection is investigated at deferent seawater temperatures. The optimal operation policy of RO system is then studied in this work considering variations in freshwater demand and with changing seawater temperature throughout the day. A storage tank is added to the RO layout to provide additional operational flexibility and to ensure the availability of freshwater at all times. Two optimization problems are solved incorporating two seawater temperature profiles, representing summer and winter seasons. The possibility of flexible scheduling of cleaning and maintenance of membrane modules is investigated. Then, the optimal design and operation of RO process is studied in the presence of membrane fouling and including several operational variations such as variable seawater temperature. The cleaning schedule of single stage RO process is formulated as MINLP problem using spiral wound modules. NNs based correlation has been developed based on the actual fouling data which can be used for estimating the permeability decline factors. The correlation based on actual data to predict the annual seawater temperature profile is also incorporated in the model. The proposed optimization procedure identified simultaneously the optimal maintenance schedule of RO network including its design parameters and operating policy. The steady state model of RO process is used to study the sensitivity of different operating and design parameters on the plant performance. A non-linear optimization problem is formulated to minimize specific energy consumption at fixed product flow rate and quality while optimizing the design and operating parameters. Then the MINLP formulation is used to find the optimal designs of RO layout for brackish water desalination. A variable fouling profile along the membrane stages is introduced to see how the network design and operation of the RO system are to be adjusted Finally, a preliminary control strategy for RO process is developed based on PID control algorithm and a first order transfer function (presented in the Appendix).
19
Lara, Ruiz Jorge Horacio Juan. "An advanced vapor-compression desalination system". Texas A&M University, 2005. http://hdl.handle.net/1969.1/3340.
Testo completoAbstract (sommario):
Currently, the two dominant desalination methods are reverse osmosis (RO) and
multi-stage flash (MSF). RO requires large capital investment and maintenance, whereas
MSF is too energy intensive.
An innovative vapor-compression desalination system is developed in this study. A
comprehensive mathematical model for the heat exchanger/evaporator is described. The
literature indicates that extraordinarily high overall heat transfer coefficients for the
evaporator are possible at selected operating conditions that employ dropwise
condensation in the steam side and pool boiling in the liquid side. A smooth titanium
surface is chosen to promote dropwise condensation and to resist corrosion.
To maximize energy efficiency, a combined-cycle cogeneration scheme is
employed composed of a gas turbine, a heat recovery boiler, and a steam turbine that
drive a compressor. The combined-cycle power source is oversized relative to the needs
of the compressor. The excess power is converted to electricity and sold to the open
market. A three-effect evaporator is employed. It is fed with seawater, assumed to be
3.5% salt. Boiling brine (7% salt) is in the low pressure side of the heat exchanger and condensing steam is in the high-pressure side of the heat exchanger. The condensing
steam flows at 1.52 m/s (5 ft/s), which maximizes the heat transfer coefficient. The plant
is sized to produce 37,854 m3/d (10 mill gal/day) and is assumed to be financed with a
5%, 30-yr municipal bond.
Two economic cases were emphasized: the United States and the Middle East.
For the United States, the fuel costs $5/GJ ($5.27/mill Btu) with the latent heat
exchanger at ( ) 1.11 K 2.00 F T à = ° . The required compressor energy is 14 MJ/m3 (14.7
kW h/thous gal). The capital cost for the U.S. is $884 d/m3 ($3,342/thous gal) and the
delivered water selling price is $0.47/m3 ($1.79/thous/gal).
For the Middle East, the fuel costs $0.5/GJ ($0.53/mill Btu) with the latent heat
exchanger at K T 33 . 3 = à ( ) F 00 . 6 ° . The required compressor energy is 26 MJ/m3 (27.3
kW h/thous gal). ). The capital cost for the Middle East is $620 d/m3 ($2,344/thous gal),
and the delivered water selling price is $0.25/m3 ($0.95/thous/gal).
In all cases, the water selling price is attractive relative to competing technologies.
20
Rees, Jones David. "The convective desalination of sea ice". Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/246582.
Testo completoAbstract (sommario):
This thesis aims to improve our understanding of the fundamental processes affecting the growth of sea ice in the polar oceans in order to improve climate models. Newly formed sea ice contains a significant amount of salt as liquid brine in the interstices of an ice matrix. My focus is on one of the processes by which the salt content of sea ice decreases, namely convective desalination, which is also often called gravity drainage by geophysicists. Modelling convective desalination requires an understanding not only of the thermo-dynamics of sea-ice growth but also of its internal fluid dynamics. This thesis considers a class of physical systems called mushy layers, of which sea ice is an example. Mushy layers are multi-component systems consisting of a porous matrix of solid phase whose interstices contain the same substance in the liquid phase. I develop a mathematical description of these systems in terms the of mushy-layer equations and explore the appropriate boundary conditions at a mush-liquid interface. I develop a simple Chimney-Active-Passive (CAP) model of convection in mushy layers for arrays of liquid chimneys in two and three dimensions. This allows the interstitial fluid flow and salt flux from the mushy layer to be determined in terms of the dimensionless parameters of the system. I discuss important mathematical and physical aspects of the CAP model. I then explain the physics of gravity drainage from sea ice, elucidating the connection between downward flow through liquid brine channels (chimneys) and a convective upwelling in the rest of the ice that is sustained by horizontal density differences and provides the fluid to replace that which drains from the ice. I use the CAP model to determine the convective upwelling velocity mathematically, deriving a new, physical parameterization of gravity drainage. I test my predictions by investigating previous laboratory observations of the propagation of dye fronts. Finally, I take a one-dimensional, thermodynamic sea-ice model of the kind currently used in coupled climate models and parameterize convective desalination using the CAP model. The parameterization allows determination of physical properties and salt fluxes from sea ice dynamically, corresponding to the calculated, evolving salinity of the sea ice, in contrast to older, established models that prescribe a fixed salinity. I find substantial differences compared to previous models, particularly in terms of predicted salt fluxes from sea ice. I explain the likely implications and potential advantages of my parameterization for climate models.
21
Chen, Yuanhong. "Electrohydrodynamic (EHD) desalination of sea water". Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60676.
Testo completoAbstract (sommario):
The distillation of sea water is of importance for the future demands for potable water and other uses in the world. A novel technique, based on electrohydrodynamic (EHD) principles, was used in this realm to desalinate artificial sea water of 3.3% (w/V) concentration. A single point corona electrode was operated at a potential of 5.3 kV (maximum output current 0.3 mA), and was installed one cm over the surface of sea water. The flux of air ions was about 3.0 $ times$ 10$ sp{12}$ cm$ sp{-2}$ s$ sp{-1}$ which produced an average electric wind of 1.72 m s$ sp{-1}$ at the sea water surface. Space charge from a corona electrode generated forces in the media to enhance the evaporation rate by about a factor of three compared with a control freely evaporating sea water. Water vapour was condensed and the condensate's purity was evaluated by chemical and physical analyses. Electrical conductivity and pH of the EHD distillate were found to be 14 $ mu$S cm$ sp{-1}$ and 5.5, respectively. In the absence of Joule heating, the energy required for EHD-distillation was comparable to the latent heat of vaporization of 2.3 $ times$ 10$ sp3$ kJ kg$ sp{-1}$ for water. The steady-state temperature of EHD solution was below that of the corresponding unventilated freely evaporating sea water. Electric wind caused by the ionic drag is considered to be the principal driving force for the enhancement.
22
Perera, Dehiwalage Harshani Nimalika. "Thin film composite membranes for desalination". Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709429.
Testo completo
23
Mistry, Karan H. (Karan Hemant). "Irreversibilities and nonidealities in desalination systems". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81703.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 207-220).
Energy requirements for desalination systems must be reduced to meet increasing global demand for fresh water. This thesis identifies thermodynamic limits for the energetic performance of desalination systems and establishes the importance of irreversibilities and solution composition to the actual performance obtained. Least work of separation for a desalination system is derived and generalized to apply to all chemical separation processes driven by some combination of work, heat, and chemical energy (fuel) input. At infinitesimal recovery, least work reduces to the minimum least work of separation: the true exergetic value of the product and a useful benchmark for evaluating energetic efficiency of separation processes. All separation processes are subject to these energy requirements; several cases relevant to established and emerging desalination technologies are considered. The effect of nonidealities in electrolyte solutions on least work is analyzed through comparing the ideal solution approximation, Debye-Hückel theory, Pitzer's ionic interaction model, and Pitzer-Kim's model for mixed electrolytes. Error introduced by using incorrect property models is quantified. Least work is a strong function of ionic composition; therefore, standard property databases should not be used for solutions of different or unknown composition. Second Law efficiency for chemical separation processes is defined using the minimum least work and characterizes energetic efficiency. A methodology is shown for evaluating Second Law efficiency based on primary energy inputs. Additionally, entropy generation mechanisms common in desalination processes are analyzed to illustrate the effect of irreversibility. Formulations for these mechanisms are applied to six desalination systems and primary sources of loss are identified. An economics-based Second Law efficiency is defined by analogy to the energetic parameter. Because real-world systems are constrained by economic factors, a performance parameter based on both energetics and economics is useful. By converting all thermodynamic quantities to economic quantities, the cost of irreversibilities can be compared to other economic factors including capital and operating expenses. By applying these methodologies and results, one can properly characterize the energetic performance and thermodynamic irreversibilities of chemical separation processes, make better decisions during technology selection and design of new systems, and critically evaluate claimed performance improvements of novel systems.
by Karan H. Mistry.
Ph.D.
24
Chung, Hyung Won. "Membrane distillation for high salinity desalination". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100061.
Testo completoAbstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 57-60).
Membrane distillation systems typically have low energy efficiency. Multistage membrane distillation (MD) systems can have significantly higher efficiencies than their single stage counterparts. However, multistage MD system design has received limited attention. In this work, the performance of a multistage vacuum membrane distillation (MSVMD) which is thermodynamically similar to a multi-stage flash distillation (MSF) is evaluated for desalination, brine concentration, and produced water reclamation applications. A wide range of solution concentrations were accurately modeled by implementing Pitzer's equations for NaCl-solution properties. The viability of MSVMD use for zero liquid discharge (ZLD) applications is investigated, by considering discharge salinities close to NaCl saturation conditions. Energy efficiency (gained output ratio or GOR), second law efficiency, and the specific membrane area were used to quantify the performance of the system. At high salinities, the increased boiling point elevation of the feed stream resulted in lower fluxes, larger heating requirements and lower GOR values. The second law efficiency, however, is higher under these conditions since the least heat for separation increases faster than the system's specific energy consumption with increase in salinity. Under high salinity conditions, the relative significance of irreversible losses is lower. Results indicate that MSVMD systems can be as efficient as a conventional MSF system, while using reasonable membrane areas and for a wide range of feed salinities. Given MD's advantages over MSF such as lower capital requirement and scalability, MSVMD can be an attractive alternative to conventional thermal desalination systems. Recently proposed single stage MD systems have shown high energy efficiency. Permeate gap (PGMD) and conductive gap (CGMD) systems are studied in the context of energy efficiency. A wide range of salinities was considered to investigate potential of these single stage systems for high salinity desalination applications.
by Hyung Won Chung.
S.M.
25
Al-Zuhairi, Ahmed. "A novel manipulated osmosis desalination process". Thesis, University of Surrey, 2008. http://epubs.surrey.ac.uk/2726/.
Testo completoAbstract (sommario):
The. present study, Manipulated Osmosis Desalination (MOD) looks at a process based on the replacement of the conventional reverse osmosis (RO) process, in which the water from a pressurised solution is separated from the solutes (the dissolved material) by a two stage membrane process. The fIrst stage uses forward osmosis (Fa) that naturally drives out the fresh solvent from a concentrated salt solution by manipulating the osmotic energy potential through innovative use of osmotic agents. The second step involves nanofiltration (NF) separation to regenerate the OA and produce the clean water. Optimising the fIrst step to achieve the highest quality and quantity ofwater is the focus of this research. Experiments were conducted on a flat bed bench scale rig. Quantitative results are displayed on the effect of draw solution solute concentration and feed salinity on the quality and quantity of produced water. Further data is displayed on the effect of varying the flow and temperature ofthe draw and feed solutions.
26
Gude, Veera Gnaneswar. "Desalination using low grade heat sources". access full-text online access from Digital Dissertation Consortium, 2007. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?3296129.
Testo completo
27
Batho, Mark P. (Mark Peter) 1968. "Economics of seawater desalination in Cyprus". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/67163.
Testo completoAbstract (sommario):
Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999.Includes bibliographical references (p. 48-52).
The Republic of Cyprus is currently suffering from severe drought conditions. This is not uncommon to Cyprus, as they frequently experience three to four year droughts every decade. They are currently in the middle of their fourth year of drought. Some Cypriots believe that the main reason for water shortages is due only to low levels of rainfall (average rainfall in Cyprus is 500 mm per year, and less than 400 mm per year is considered a drought year). It is not disputed that this is part of the problem. However, my belief, along with many Cypriots is that the biggest part of the problem is one of water allocation. Agriculture in Cyprus contributes approximately 5% to the GDP, yet consumes 75% of available water in Cyprus. The remainder of water is left for the sector of the economy that produces the remaining 95% of the GDP, of which municipal, industrial and tourist uses are of greatest importance. One may ask why this is so. According to some Cypriots, it is because Cypriot farmers are thought to be a politically influential group, and that they farm more as a way of life, rather than to earn a living directly. Others discount this "way of life" theory. What is important, however is that farming is using a lot of water and is contributing very little to the GDP of Cyprus. For example, Citrus crops grown within the Southern Conveyor System (a large network of water conveyance pipes stretching for over 100 km in the southern part of the island) (see Figure 3, page 16) uses approximately 21% of all available water available in Cyprus, and without Government subsidies would not show profitability. Although there may be some aesthetic value in citrus groves one must ask if it is economically and environmentally justified to continue farming citrus. To do so means building seawater desalination plants that contribute 5.0 to 6.0 kg of CO 2, a greenhouse gas, to the atmosphere per m3 of water produced by desalination, along with the cost of the water nearing one US dollar per m3 . Desalination is a painful solution to Cyprus' water shortage that could be otherwise be addressed with a proper water allocation scheme.
by Mark P. Batho.
M.Eng.
28
CAMPIONE, Antonino. "Electrodialysis modelling for low energy desalination". Doctoral thesis, Università degli Studi di Palermo, 2020. http://hdl.handle.net/10447/395212.
Testo completo
29
Hoffman, Anton Michael. "Design guidelines for a reverse osmosis desalination plant / Anton Michael Hoffman". Thesis, North-West University, 2008. http://hdl.handle.net/10394/4211.
Testo completoAbstract (sommario):
There are two basic needs globally and that is the control and supply of
reliable electricity and clean water. However, one of the biggest challenges
the world is facing today is the lack of fresh water resources. Lower rainfall,
together with population and industry growth, are only a few factors
contributing to the fast increasing strain on existing water supplies around the
world. This fast increasing need therefore necessitates the investigation into
finding alternative sources. One such option is that of desalination. In the last
50 years desalination technologies have been applied to produce high quality
fresh water from brackish and seawater resources. In the 1980's a breakthrough
was made with the introduction of the membrane desalination
technology, known as the reverse osmosis (RO) process.
Today newly developed technologies are improving the competitiveness of the
reverse osmosis process against the traditional distillation processes. There
are a number of options to increase the efficiency of a reverse osmosis plant
and one option is to use warm industrial waste water as the feed water to the
desalination plant. It is known that the viscosity of water is inversely
proportional to its temperature. Therefore, if the feed water temperature of a
reverse osmosis plant is increased the membranes will become more
permeable. This will result in a higher production volume or in a lower energy
demand. South Africa is on the edge of building the first fourth generation
nuclear power plant, called the Pebble Bed Modular Reactor (PBMR) at
Koeberg. The PBMR will produce a cooling water outlet temperature of 40°C
which can be used as feed water to a reverse osmosis plant.
In this study design guidelines of a reverse osmosis plant are given in nine
steps. These steps were then used during a basic component design of a
reverse osmosis plant coupled to the waste water stream of a PBMR nuclear
power plant. Furthermore design software programs were used to simulate
the coupling scheme in order to validate the outcome of the design guidelines.
The results of the two design approaches compared well to one another. It
furthermore showed that by using the waste water from the PBMR nuclear
power plant the efficiency of the RO plant is increased and the operating cost
is decreased. Fresh water can be produced at a cost of R 5.64/m3 with a
specific electricity consumption of 2.53 kWh/m3.Thesis (M.Ing. (Nuclear Engineering)--North-West University, Potchefstroom Campus, 2009.
30
Hughes, Amanda Jane. "Solar powered membrane distillation for seawater desalination". Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/2922.
Testo completoAbstract (sommario):
This thesis presents an investigation into the performance of a Membrane Distillation (MD) system used for seawater desalination. The research is focused on the effects of intermittent use of the MD module when powered with a solar energy collector. The aim is to assess the feasibility of directly powering an MD unit with a fluctuating input from a solar collector. An investigation into the effect of temperature on the microstructure of the membrane was carried out. In a series of experiments, samples of PTFE membrane were imaged while heated from 17 C to temperatures between 60 C and 80 C. It was found that the membrane pore size increased with increases in temperature. When heated to 80 C the pore diameter increased by 44%. Intermittent use of the system would cause the temperature of the MD module to fluctuate, therefore altering the membrane microstructure. An investigation was carried out to determine the in fluence of intermittent MD operation on the flux and conductivity of the distillate. The system was tested after overnight shutdown periods and was also tested with short term `on/off' periods of between 5 and 20 minutes, simulating the intermittent output from a concentrated solar collector. It was found that as the module was heated, the distillate flux produced increased, while the distillate conductivity decreased. Conversely, when the module cooled, the flux decreased and the quality of the distillate worsened. This was the result of the dependancy of membrane pore size on temperature.
31
Igobo, Opubo. "Low-temperature isothermal Rankine cycle for desalination". Thesis, Aston University, 2016. http://publications.aston.ac.uk/28569/.
Testo completoAbstract (sommario):
In brackish groundwater desalination, high recovery ratio (of fresh water from saline feed) is desired to minimise concentrate reject. To this effect, previous studies have developed a batch reverse osmosis (RO) desalination system, DesaLink, which proposed to expand steam in a reciprocating piston cylinder and transmit the driving force through a linkage crank mechanism to pressurise batches of saline water (recirculating) in a water piston cylinder unto RO membranes. However, steam is largely disadvantaged at operation from low temperature (< 150oC) thermal sources; and organic working fluids are more viable, though, the obtainable thermal cycle efficiencies are generally low with low temperatures. Consequently, this thesis proposed to investigate the use of organic working fluid Rankine cycle (ORC) with isothermal expansion, to drive the DesaLink machine, at improved thermal efficiency from low temperature thermal sources. Following a review of the methods of achieving isothermal expansion, ‘liquid flooded expansion’ and ‘expansion chamber surface heating’ were identified as potential alternative methods. Preliminary experimental comparative analysis of variants of the heated expansion chamber technique of effecting isothermal expansion favoured a heated plain wall technique, and as such was adopted for further optimisation and development. Further, an optimised isothermal ORC engine was built and tested at < 95oC heat source temperature, with R245fa working fluid – which was selected from 16 working fluids that were analysed for isothermal operation. Upon satisfactory performance of the test engine, a larger (10 times) version was built and coupled to drive the DesaLink system. Operating the integrated ORC-RO DesaLink system, gave freshwater (approximately 500 ppm) production of about 12 litres per hour (from 4000 ppm feed water) at a recovery ratio of about 0.7 and specific energy consumption of 0.34 kWh/m3; and at a thermal efficiency of 7.7%. Theoretical models characterising the operation and performance of the integrated system was developed and utilised to access the potential field performance of the system, when powered by two different thermal energy sources – solar and industrial bakery waste heat – as case studies.
32
Sempere, Catherine. "Nanofluidic insight into energy harvesting and desalination". Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10200/document.
Testo completoAbstract (sommario):
La première partie de cette thèse constitue une introduction aux différentes méthodes de conversion d'énergie et de dessalement qui seront évoquées dans cet ouvrage. Dans une deuxième partie, nous montrons que la conductance ionique d'un réseau de nanopores est sous-additive avec le nombre de pores. La contribution individuelle de chaque pore à la conductance globale tend vers une valeur nulle, pour un réseau suffisamment grand. On note que seuls des rapports de longueurs interviennent, et que le choix d'une échelle nanométrique n'a pas d'influence dans l'effet observé. Ensuite, dans une troisième partie, nous mesurons la perméabilité d'un réseau de pores à une échelle macroscopique. Là aussi, l'influence du réseau ne dépend pas de l'échelle du système. La perméabilité évolue en sens inverse de la conductance : elle est augmentée par la présence de pores voisins, mais dans une faible proportion. La quatrième partie se sert des résultats des deux parties précédentes, dans le but de déterminer une loi d'échelle pour la puissance électrique produite par courant d'écoulement et diffusio-osmose, deux méthodes de conversion d'énergie osmotique. On montre que les effets d'entrée ont un effet délétère sur cette conversion ; ils nécessitent des études plus approfondies. La dernière partie est un travail numérique sur un nouveau procédé de dessalement par osmose via une phase gaz, piégée dans des nanotubes hydrophobes. Son intérêt principal est l'utilisation de nanotubes plus gros que les pores des matériaux actuellement utilisés, donc moins susceptibles de s'encrasser. Par dynamique moléculaire, nous étudions la perméabilité et la sélectivité du dispositifThe first part of this thesis is an introduction to the different energy conversion and desalination methods that will be invoked in this work. In a second part, we show that the ionic conductance of a nanopore array is sub-additive with the number of pores. Individal contributions of each pore to the global conductance tend to a null value, if the network is big enough. We note that this phenomenon only involves length ratios, and that working at a nanometric scale does not have any influence. Then, in a third part, we measure the permeability of a pore array at a macroscopic scale. There too, the effect of the array does not depend on the scale of the system. Permeability evolves inversely to conductance: permeability is enhanced by the presence of neighboring pores, but in a smaller proportion than the ionic conductance falls under the same cause. The fourth part uses the results of the two preceding ones, to determine a scaling law for the electric power produced by streaming current and diffusio-osmosis, two methods of osmotic energy conversion. We show that entrance effects have a negative impact on such conversion, more efforts are needed to understand them better and circumvent them. The fifth and last part of this thesis is a numerical work on a new desalination device. It relies on osmosis through a gas phase which is trapped within a hydrophobic nanotube. Its main interest is to use nanotubes bigger than the pores of currently used materials, thus less prone to fouling. We use molecular dynamics methods to study the permeability and selectivity of this device
33
Li, Chennan. "Innovative Desalination Systems Using Low-grade Heat". Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4126.
Testo completoAbstract (sommario):
Water and energy crises have forced researchers to seek alternative water and energy sources. Seawater desalination can contribute towards meeting the increasing demand for fresh water using alternative energy sources like low-grade heat. Industrial waste heat, geothermal, solar thermal, could help to ease the energy crisis.
Unfortunately, the efficiency of the conventional power cycle becomes
uneconomically low with low-grade heat sources, while, at the same time, seawater desalination requires more energy than a conventional water treatment process. However, heat discarded from low-grade heat power cycles could be used as part of desalination energy sources with seawater being used as coolant for the power cycles. Therefore a study of desalination using low-grade heat is of great significance.
This research has comprehensively reviewed the current literature and
proposes two systems that use low-grade heat for desalination applications or even desalination/power cogeneration. The proposed two cogeneration systems are a supercritical Rankine cycle-type coupled with a reverse osmosis (RO) membrane desalination process, and a power cycle with an ejector coupled with a multi-effect distillation desalination system. The first configuration provides the advantages of
making full use of heat sources and is suitable for hybrid systems. The second system has several advantages, such as handling highly concentrated brine without external electricity input as well as the potential of water/power cogeneration when it is not used to treat concentrated brine. Compared to different stand-alone power cycles, the proposed systems could use seawater as coolant to reject low-grade heat from the power cycle to reduce thermal pollution.
34
Roy, Yagnaseni. "Modeling nanofiltration for large scale desalination applications". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100096.
Testo completoAbstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 91-94).
The Donnan Steric Pore Model with dielectric exclusion (DSPM-DE) is implemented over flatsheet and spiral-wound leaves to develop a comprehensive model for nanofiltration modules. This model allows the user to gain insight into the physics of the nanofiltration process by allowing one to adjust and investigate effects of membrane charge, pore radius, and other membrane characteristics. The study shows how operating conditions such as feed flow rate and pressure affect the recovery ratio and solute rejection across the membrane. A comparison is made between the results for the flat-sheet and spiral-wound configurations. The comparison showed that for the spiral-wound leaf, the maximum values of transmembrane pressure, flux and velocity occur at the feed entrance (near the permeate exit), and the lowest value of these quantities are at the diametrically opposite corner. This is in contrast to the flat-sheet leaf, where all the quantities vary only in the feed flow direction. However it is found that the extent of variation of these quantities along the permeate flow direction in the spiral-wound membrane is negligibly small in most cases. Also, for identical geometries and operating conditions, the flatsheet and spiral-wound configurations give similar results. Thus the computationally expensive and complex spiral-wound model can be replaced by the flat-sheet model for a variety of purposes. In addition, the model was utilized to predict the performance of a seawater nanofiltration system which has been validated with the data obtained from a large-scale seawater desalination plant, thereby establishing a reliable model for desalination using nanofiltration.
by Yagnaseni Roy.
S.M.
35
Cohen-Tanugi, David. "Nanoporous graphene as a water desalination membrane". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98743.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 147-162).
Desalination is one of the most promising approaches to supply new fresh water in the face of growing water issues. However, commercial reverse osmosis (RO) techniques still suffer from important drawbacks. In order for desalination to live up to the water challenges of this century, a step-change is needed in RO membrane technology. Thanks to significant advances in the field of computational materials science in the past decade, it is becoming possible to develop a new generation of RO membranes. In this thesis, we explore how computational approaches can be employed to understand, predict and ultimately design a future generation of RO membranes based on graphene. We show that graphene, an atom-thick layer of carbon with exceptional physical and mechanical properties, could allow for water passage while rejecting salt ions if it possessed nanometer-sized pores. Using computer simulations from the atomic scale to the engineering scale, we begin by investigating the relationship between the atomic structure of nanoporous graphene and its membrane properties in RO applications. We then investigate the thermodynamics, chemistry and mechanics of graphene and the water and salt surrounding it. Finally, we establish the system-level implications of graphene's promising membrane properties for desalination plants. Overall, this thesis reveals that graphene can act as an RO membrane with two orders of magnitude higher water permeability than commercial polymer membranes as long as the nanopores have diameters around 0.6nm, that graphene is strong enough to withstand RO pressures as long as it is supported by a substrate material with adequate porosity, and that a nanoporous graphene membrane could ultimately reduce either the energy footprint or the capital requirements of RO desalination. Ultimately, this thesis highlights a path for the development of next-generation membranes for clean water production in the 21st century.
by David Cohen-Tanugi.
Ph. D.
36
Dave, Shreya H. "Assessing graphene oxide for water desalination applications". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107077.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 121-133).
Water desalination plays a critical role in augmenting the fresh water supplies for water scarce regions. However, despite considerable improvements in system efficiencies, it still remains six to ten times more expensive than treating freshwater for drinking. As a result, the construction and operation of a desalination plant places considerable economic burden on the regions that require such an investment. As more and more regions experience water stress due to climate change, increased industrial consumption, and population growth, materials engineering will play a role in improving the economics. The membranes used in today's reverse osmosis plants are made from polymers that are fragile, limited in the flux, and typically operate at 70% of their rated performance due to biofouling. Following the exciting proposition of using graphene as a size-exclusion based desalination membrane, there has been a great deal of revived interest in the development of new membrane materials that overcome these challenges. Graphene oxide, made from the chemical exfoliation of graphite, has served as a promising candidate for membrane applications because it is cheaper than graphene to produce and yet demonstrates similar benefits of resilience and increased permeability. In this work, we take a critical look at three aspects of graphene oxide as it applies to the development of water desalination membranes. First, we present an atomic study of the structure of graphene oxide (GO) that is produced in bulk quantities. In contrast to previous work, which has examined particularly defect free GO, we find that GO develops a nanocrystalline structure in support of a Dynamic Structural Model in its hexagonal carbon lattice. Second, we detail the development of a new cross-linker that enables the fabrication of stable GO films with sub-nanometer interlayer spacing and demonstrated nanofiltration performance. The process of cross-linking and membrane fabrication is entirely solution based and therefore promising for scale up. Finally, we evaluate the techno-economic feasibility of a GO as a water desalination material with a comparison between estimated production cost and savings in terms of the levelized cost of water. We quantitatively assess GO membranes as a scalable technology and identify other separation areas that could be served by robust membrane materials. With these three diverse analyses, I aim to provide a research-based perspective as to the material system, technological hurdles, and the economic potential of graphene oxide membranes.
by Shreya H. Dave.
Ph. D.
37
Dahdah, Tawfiq. "Superstructure optimization of hybrid thermal desalination configurations". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/85452.
Testo completoAbstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 95-105).
As the global demand for freshwater continues to increase, a larger number of resources are dedicated to seawater desalination technologies. In areas with high temperature and salinity water, thermal desalination technologies are often employed. In other areas, reverse osmosis technologies are more popular. While both these technologies have witnessed improvements in recent years, economic and performance issues still pose significant barriers to their universal implementation, which has left many countries, including ones bordering oceans and seas, suffering from dire water scarcity issues. This thesis proposes a methodology which enables the identification of improved thermal-based desalination structures. It is based on the notion of superstructure, which allows for the representation of numerous feed, brine and vapor routing schemes. A superstructure is developed. By adjusting the flow routings, the superstructure is capable of representing the common thermal desalination structures, as well as an extremely large number of alternate structures, some of which might exhibit advantageous behavior. The superstructure is built around a repeating unit which is a generalization of an effect in a multi-effect distillation system (MED) and a stage in a multi-stage flash system (MSF). Allowing for just 12 repeating units, more than 1040 different structures can be represented. The superstructure is thus proposed as an ideal tool for the structural optimization of thermal desalination systems, whereby the optimal selection of components making up the final system, the optimal routing of the vapors as well as the optimal operating conditions are all variables simultaneously determined during the optimization problem. The proposed methodology is applicable to both stand-alone desalination plants and dual purpose (water and power) plants wherein the heat source to the desalination plant is fixed. It can be extended to also consider hybrid thermal-mechanical desalination structures, as well as dual purpose plants where the interface of power cycle and desalination is also optimized for. A multi-objective structural optimization of stand-alone thermal desalination structures is performed in Chapter 2, whereby the performance ratio of the structures is maximized while the specific area requirements are minimized. It is found that for any particular distillate production requirement, alternate structures with non-conventional flow patterns require lower heat transfer areas compared to commonly implemented configurations. Examples of these non-conventional configurations are identified, which include a forward feed - forward feed MED structure, involving the integration of two forward feed MED plants. Chapter 3 highlights how the superstructure can be adapted to optimize integrated thermal desalination and thermal compression systems. Specifically, the conducted study investigates whether there is any merit to the thermal compression of vapor streams produced in intermediate MED effects as opposed to the common practice of compressing vapors produced in the last effect. The study concludes that intermediate vapor compression results in significant reductions in area requirements, as well as significant increases in maximum distillate production capacities. Moreover, the study confirms that the optimal location of vapor extraction is heavily dependent on the exact distillate production requirement in question. Two novel configuration forms are informed by the optimization. The first is an integrated MED-TVC + MED + MSF system, while the second is an integrated MED-TVC + MSF system.
by Tawfiq Dahdah.
S.M.
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Park, Gavin Lawrence. "Wind-powered membrane desalination of brackish water". Thesis, Heriot-Watt University, 2012. http://hdl.handle.net/10399/2532.
Testo completoAbstract (sommario):
This thesis presents a detailed investigation of the technical feasibility, challenges and performance issues associated with the direct-connection of a wind turbine to a membrane (wind-membrane) system for treating brackish water in remote communities. The direct-connection of these two technologies negates the reliance on energy storage in batteries, which are traditionally used, but result in reduced system efficiency and increased life-cycle costs. Furthermore, the lack of knowledge of the safe operating window in which transient operation of membrane systems is beneficial or tolerable can be addressed. The impact of wind speed fluctuations on the performance of the wind-membrane system (using a BW30-4040 membrane and feed waters of 2750 and 5500 mg/L NaCl) showed that the performance deteriorated most under fluctuations at low average wind speeds with high turbulence intensity and long periods of oscillation. Therefore, the main challenge of operating with renewable energy is not the size of the fluctuations, but the effect of the power switching off. Further examination of the impact of wind intermittency (over one hour intervals with intermittent periods from 0.5 – 3 min) showed that the increase in permeate concentration was highest at off-times < 60 s, highlighting the potential for improved performance using short-term energy buffering. The safe operating window and the key constraints to safe operation were determined for several membranes and feed water concentrations to establish the optimum operating strategy for the wind-membrane system. Supercapacitors were used to expand the safe operating window by providing energy during periods of intermittency and enhancing the power quality delivered to the membrane system by absorbing wind fluctuations. When tested over 24 hours using real wind speed data (average 6 m/s), the wind-membrane system produced 0.78 m3 of water with an average permeate concentration of 240 mg/L NaCl and average specific energy consumption (SEC) of 5.2 kWh/m3. With the addition of supercapacitor storage, the system performance improved significantly with 0.93 m3 of water produced with an average permeate concentration of 170 mg/L NaCl and SEC of 3.2 kWh/m3.
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Mazlan, Nur Muna. "Forward osmosis for desalination and water recovery". Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/45550.
Testo completoAbstract (sommario):
In recent years, there has been an increased interest in forward osmosis (FO) from academic research and industry with a rising number of FO academic publications in the last decade. The common perception of FO as a low energy process compared to reverse osmosis (RO) sparked interest in this area. Nevertheless, there are some major challenges that need to be addressed before FO can be successfully implemented as an effective technology. Some of these challenges are addressed in this dissertation, starting with the assessment of FO as a low energy process. A modelling approach was used to assess the energy consumption of various FO hybrid processes and provide a detailed comparison with RO for desalination, in an effort to answer the critical question: Is FO truly a low energy process compared to RO? Results showed that there was practically no difference in specific energy consumption (SEC) between standalone RO, and FO with nanofiltration (NF) draw solution (DS) recovery; this can be generalised for any pressure-driven membrane process used for the DS recovery stage in a hybrid FO process, such as UF or RO. It was also found that even if any or all of the membranes considered, FO, RO or NF, were perfect (i.e. had infinite permeance and 100% rejection), it would not improve the SEC significantly. Furthermore, in order to reduce the higher membrane footprint required by FO hybrid processes, internal concentration polarisation (ICP) within the support has to be greatly reduced or eliminated. Hence, any advantage possessed by the FO hybrid process derives from the lower fouling propensity of FO, lower pretreatment costs arising from reduced fouling, use of draw solutes which can be recovered with low cost thermal energy sources and specific applications where RO cannot compete. Inspired by this insight, subsequent work was performed to study the multifaceted interactions alongside membrane and process parameters involved in the fouling of FO membranes, specifically the HTI TFC and CTA membrane. The chapter on organic fouling behaviour of structurally and chemically different FO membranes revealed that fouling on the HTI TFC membrane was more significant compared to HTI CTA in both membrane orientations, arising from a variety of factors associated with surface chemistry, membrane morphology and structural properties. Interestingly, it was observed that in FO mode, membrane surface properties dominated over fouling layer properties in determining fouling behaviour, with some surface properties (e.g. surface roughness) having a greater effect on fouling than others (e.g. surface hydrophilicity). In PRO mode, structural properties of the support played a more dominant role whereby fouling mechanism was specific to the foulant size and aggregation as well as the support pore size relative to the foulant. Whilst pore clogging was observed in the TFC membrane due to its highly asymmetric and porous support structure, fouling occurred as a surface phenomenon on the CTA membrane support layer, indicating that the latter’s structure was more symmetric in relation to the foulant (alginate) studied. Besides pore clogging, the severe fouling observed on the TFC membrane in PRO mode was due to a high specific mass of foulant adsorbed in its porous support. A new method was successfully introduced to quantify the density of the fouling layer and correlate it with hydrodynamic conditions and fouling behaviour of the membranes studied. It was observed that a trade-off between enhanced membrane performance and fouling mitigation is apparent in these membranes, with both membranes providing improvement in one aspect at the expense of the other. Hence, significant development in their surface and structural properties are needed to achieve good anti-fouling properties without compromising flux performance. Measured fouling densities on the studied surfaces suggest that there is not a strong correlation between foulant-membrane interaction and fouling density. Cleaning results suggest that physical cleaning was more efficient on the CTA membrane compared to the TFC membrane. Further, they implied that despite different mechanisms of fouling and quantities of foulant adsorbed in FO membranes, FO is a resilient process with high cleaning efficiencies and fouling reversibility. Finally, to address the challenge of ICP, a novel method of fabricating FO membranes was developed by interfacially polymerising a free-standing, salt rejecting polyamide (PA) film using a floating technique and directly depositing this layer onto an open mesh fabric. By doing this, the need for a phase inversion support was entirely eliminated. The fabrication method resulted in the successful formation of a defect-free, salt-rejecting FO membrane with significantly reduced or eliminated ICP, attributed to large open mesh sizes and straight channels in the fabric support. Interestingly, it was observed that even in the absence of ICP, flux was limited by the support layer at lower effective open areas of the mesh fabric. At higher mesh sizes and effective open areas, the effect of the fabric support became less significant and FO performance was likely governed by diffusion through the PA film, limited by its structure and transport properties. A trade-off between surface roughness and thickness of the PA film was observed, which is linked to the mechanism of film formation at the bulk interface. It was proposed that the design of FO membranes with ideal supports should also include tailoring the PA film properties in order to achieve superior FO performance. Additionally, the use of supports with higher percentage open areas or porosities should be considered.
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Ping, Qingyun. "Advancing Microbial Desalination Cell towards Practical Applications". Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73373.
Testo completoAbstract (sommario):
Conventional desalination plant, municipal water supply and wastewater treatment system are among the most electricity-intensive facilities. Microbial Desalination Cell (MDC) has emerged as a promising technique to capture the chemical energy stored in wastewater directly for desalination, which has the potential to solve the high energy consumption issue in desalination industry as well as wastewater treatment system. The MDC is composed of two critical components, the electrodes (anode and cathode), and the ion-exchange membranes separating the two electrodes which drive anions migrate towards the anode, and cations migrate towards the cathode. The multiple components allow us to manipulate the configuration to achieve most efficient desalination performance. By coupling with Donnan Dialysis or Microbial Fuel Cell, the device can effectively achieve boron removal which has been a critical issue in desalination plants. The uncertainty of water quality of the final desalinated water caused by contaminant back diffusion from the wastewater side can be theoretically explained by two mechanisms, Donnan exchange and molecule transport which are controlled by bioelectricity and concentration gradient. Scaling and fouling is also a factor needs to be taken into consideration when operating the MDC system in real world. With mathematical modeling, we can provide insight to bridge the gap between lab-scale experiments and industrial applications. This study is expected to provide guidance to enhance the efficiency as well as the reliability and controllability of MDC for desalination.Ph. D.
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Benson, Michelle Suzanne. "Solar Membrane Pervaporation for Brine Water Desalination". Thesis, The University of Arizona, 2011. http://hdl.handle.net/10150/144232.
Testo completo
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Wakter, Simon. "Technological Feasibility of Water Desalination using SMRs". Thesis, KTH, Fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-239617.
Testo completo
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Kennedy, Clinton P. "Water Desalination: Arizona, California, Nevada and Mexico". DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1223.
Testo completoAbstract (sommario):
This was a study on the history of the Colorado River, the water challenges of the Lower Basin states and the international water laws that govern the United States and Mexico concerning the Colorado river. The main purpose of this study was to determine possible long-term solutions to the growing water needs of the Lower Basin states and how Mexico could help. After discussing some concerns that the Lower Basin states had, research was done on the different types of desalination. This research included the different methods and their processes. MSF, MED, RO and MVC methods are discussed mentioning their different strengths and limitations. Next different possible solutions are discussed. These possible solutions include current practices and their successes. The solution that is discussed in length is water desalination as it offers another method of obtaining water. This part also discusses different ways to power the plant. As Mexico was already going to build nuclear power plants one idea was to build a plant in Mexico and use their power to run a desalination plant. This is one possible solution, to have a desalination plant desalinate water out of the Sea of Cortez in Mexico for the Southwest to use using the Mexico’s nuclear power plant to run the system. The economics of a desalination plant are discussed. The cost of building a plant, cost of desalinating the water, and water transportation costs are examined. After an examination on these different costs are completed it is discussed on who would pay for the desalination plant and who would receive the water. One possibility discussed is that Arizona, California and Nevada all pay an equal share in the cost of building the desalination plant in Mexico. California would then receive the water from the plant and thus would cut back on their consumption from the Colorado River allowing both Arizona and Nevada to increase theirs. A PEST analysis is done at the end of this study. It covers Political, Economical, Socio-cultural and Technological categories associated with this study. It covers different concerns and possible legislations that would need to be amended in order to continue with international desalination.
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GOMES, RODRIGO KLIM. "THERMAL DESALINATION AS AN OPTION FOR WATER SUPPLY: A STUDY OF THERMAL DESALINATION TECHNOLOGY AND PRELIMINARY ECONOMIC FEASIBILITY ANALYSIS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19356@1.
Testo completoAbstract (sommario):
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORA dessalinização térmica é uma técnica utilizada em diversas partes do mundo para produção de água. Países como Estados Unidos, Israel, Espanha e Grécia utilizam esse tipo de sistema em grande escala, garantindo um abastecimento constante para alguns pontos de seu território e contribuindo para o aperfeiçoamento dos sistemas de produção. No Brasil, apesar da vasta bacia hidrográfica e da existência de grandes reservatórios subterrâneos, a dessalinização térmica poderia ser vista como alternativa de produção para apoiar o desenvolvimento agrícola e industrial em algumas regiões, criando também melhores condições sociais para a população beneficiada, especialmente no nordeste brasileiro. Nessa dissertação propomos um método para avaliação preliminar de diversos cenários para implantação de tais sistemas. A avaliação aborda inicialmente a definição do dessalinizador, realizada através das formulações disponíveis em trabalhos acadêmicos que têm como base a Primeira Lei da Termodinâmca. Tais formulações foram adaptadas para o caso em estudo. Em seguida são avaliados os principais parâmetros para viabilidade do projeto, tais como Valor Presente Líquido (VPL) e Índice de Lucratividade (IL), de forma a demonstrar se o projeto seria ou não viável. Para consolidação da metodologia utilizada foi criado um programa que permite a avaliação de diversos cenários de maneira independente, sendo de fácil acesso e de grande flexibilidade para o usuário interessado neste tema.
Thermal desalination is a technology used in many places for water production. Some countries use desalination to produce big volume of water, like USA, Israel, Spain and Greece, aiming for the steady supply of water to some specific regions, contributing to the improvement of production systems. In Brazil, inspite of the huge volume of water available through the rivers, thermal desalination should be considered as an alternative for water production supporting the development of country for food production and for industry, specially in the northeastern region. In this work, a method of evaluation for different water supply needs was conceived, in order to perform the preliminary evaluation of this kind of system. It begins with the definition of the thermal desalinator which will compose the production system. This first step was based on First Law of Thermodynamics formulations available in technical articles used as reference. After technical analysis, the main parameters used for the study of feasibility are defined, for example, the Net Present Value. The methodology extracted from reference articles was simplified and converted into an algorithm, developted for an easy evaluation of different situations.
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Bin, Marshad Saud Mohammed H. "Economic evaluation of seawater desalination : a case study analysis of cost of water production from seawater desalination in Saudi Arabia". Thesis, Heriot-Watt University, 2014. http://hdl.handle.net/10399/2996.
Testo completoAbstract (sommario):
As a result of the increasing scarcity of freshwater resources worldwide, many countries have resorted to the use of unconventional sources, of which seawater desalination is the most significant, for meeting the supply-demand gap. However, despite the recorded advances in desalination technologies of recent decades, desalination remains a very expensive operation and operators will be greatly assisted if reliable means of predicting the costs are available to aid effective decision making during planning of new plants or the operation of existing plants. To achieve this, it is important to fully understand the factors that contribute to desalination costs, which could then be used to develop appropriate models for predicting costs that can support budgeting and/or cost reductions decision making. Consequently, this project has investigated the development of such models for predicting monthly production costs using data from 16 operational plants in Saudi Arabia. Monthly and annual data spanning 2001 – 2010 were collected on total water production, type of desalination technique, sea water salinity, product water salinity, energy consumption, and total (capital and operational) unit cost of water production. Because of the way in which the data were archived, some of the variables only had the annual totals for some of the years, which made them unsuitable for the monthly scale adopted for the analyses. Consequently, disaggregation schemes based on several variants of the method of fragments widely used in hydrological studies were used to obtain monthly data from the annual data. Exploratory analysis showed that the monthly costs correlated most with the total water production, which then formed the lone independent variable for various tested regression model formulations. In general, an inverse regression model performed best during both calibration and validation. To enhance the usefulness of the predictive model for decision making, uncertainty limits of the predictions were constructed using a Monte Carlo simulation approach involving the seasonal, lag-1 autoregressive generation of equally likely realisations of the available historic records that have been transformed to remove the skewness. Extensive testing of the data generation technique showed that the assumed lag-1 auto-regressive dependence structure was adequate. This study thus provides for the first time a predictive model for costs of desalination in Saudi Arabia and its uncertainty range for effective budgeting and operational management. Although the models were developed using Saudi Arabia data, the fact that only one independent variable was used means that the replication of the methodology in other desalination-intensive countries can be readily carried out.
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Martinez, Hiroki. "Design of a desalination plant : aspects to consider". Thesis, University of Gävle, Faculty of Engineering and Sustainable Development, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-6995.
Testo completoAbstract (sommario):
One of the main problems our actual society faces is the shortage of water. Despite the great effort made by authorities and researchers, multiple countries with poor economic resources are experiencing serious difficulties derivative of water scarcity. Desalination provides a feasible solution for inland and coastal areas. Through literature and reviewed articles analysis the reader will meet the actual issues regarding designing a desalination plant, and more over with reverse osmosis (RO) processes, which are the main arguments of this work. One of the big deals is the environmental concern when handling the concentrate disposal. Another important point about desalination processes is the increasingly interest in coupling the units with renewable energy sources (RES). The results point out that regardless of the efforts made until today, additional achievement is required in fields such as membrane’s structure materials for RO method, concentrate disposal systems, governmental water policies review and update, and greater distinction researches between brackish water and seawater RO desalination processes. Taking into consideration the previous outcomes it is finally concluded that some particular steps must be accomplished when beginning a desalination plant design.
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Kullab, Alaa. "Desalination using Membrane Distillation : Experimental and Numerical Study". Doctoral thesis, KTH, Kraft- och värmeteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-44405.
Testo completoAbstract (sommario):
Desalination has been increasingly adopted over the last decades as an option, and sometimes as a necessity to overcome water shortages in many areas around the world. Today, several thermal and physical separation technologies are well established in large scale production for domestic and industrial purposes. Membrane distillation is a novel thermally-driven process that can be adapted effectively for water desalination or water treatment in industrial applications, due to its potential lower energy consumption and simplicity. The general objective of this thesis is to contribute to the technical understanding of membrane distillation as a new technology in water treatment for both industrial and drinking water purposes, as a starting point for further improvement. The thesis includes experimental and numerical investigations that highlight some aspects of the technology application and fundamental aspects. In the field of industrial application, an experimental and numerical assessment has been carried out on an Air Gap Membrane Distillation (AGMD) prototype to assess the utilization of the technology in thermal cogeneration plants; in particular, demineralization of water boiler feed water and treating flue gas condensate. The main assessment parameters were water quality and energy consumption. The results from full-scale simulations of a system of 10 m3/hr production capacity, connected to the district heating network were as follows: 5 to 12 kWh/m3 specific thermal energy consumption, and 0,6 to 1,5 kWh/m3 specific electricity consumption, depending upon the heat source (district heat supply line or low-grade steam). For desalination applications, experimental and simulation work was conducted on an AGMD semi-commercial system as part of the EU MEDESOL project. The aim was to evaluate AGMD performance with saline water of 35 g/l NaCl in order to establish an operation data base for simulation of a three-stage AGMD desalination system. Specific thermal energy consumption was calculated as 950 kWht/m3 for a layout without heat recovery, and 850 kWht/m3 for a layout with one stage heat recovery. The lack of internal heat recovery in the current MD module means that most of the heat supplied to MD system was not utilized efficiently, so the thermal energy consumption is high. This would mean that a large solar field is needed. In order to analyze the flow conditions in feed flow and cooling channels, CFD was used as tool to analyze a spacer-obstructed flow channel for different types of spacer geometrical characteristics: flow of attack angle, spacer to channel thickness ratio, and void ratio. Velocity profiles, shear stress, and pressure drop were the main assessment criteria. Results show the flow of attack angle has a very minimum effect on the performance of spacers. The effect of spacer to channel thickness ratio was significant in all assessment parameters. Higher void ratios were found advantageous in promoting flow mixing, but resulted in lower sheer stress and hence reduced heat transfer. Physical modifications were implemented on a semi-commercial AGMD prototype to assess experimentally any improvement in its performance. These modifications were mainly focused on reducing the conductive heat transfer losses by modifying the physical support in the air gap that separates the membrane from the condensation surface. In addition, several feed channel spacers were tested and assessed based on their effect in increasing the mass transfer while maintaining or reducing pressure drop. The modifications yielded a two-fold augmentation: slight increase in the distillate mass flow rate (9-11%), and increased thermal efficiency (6%). The pressure drop in the module was reduced by 50% through selecting the appropriate spacer that would achieve the above mass flow rate increase.QC 20111021
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Harrison, Catherine J. "Bench-scale testing of seawater desalination using nanofiltration /". abstract and full text PDF (free order & download UNR users only), 2005. http://0-wwwlib.umi.com.innopac.library.unr.edu/dissertations/fullcit/1433104.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Nevada, Reno, 2005."August, 2005." Includes bibliographical references (leaves 80-84). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2005]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
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Chamier, Jessica. "Composite carbon membranes for the desalination of water". Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/353.
Testo completo
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Miller, Jacob A. S. M. Massachusetts Institute of Technology. "Numerical balancing in a humidification dehumidification desalination system". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68692.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 115-118).
This thesis details research on the thermal and concentration balancing of a humidification dehumidification desalination system. The system operates similarly to the natural rain cycle. Seawater is heated, sprayed into an airstream to increase the air's humidity, then pure water is condensed out of the same stream in a separate unit. These systems are typically inefficient due to entropy generation caused by mismatch between the temperature and humidity profiles in both the humidifier and dehumidifier components. Numerical models are developed for several different systems, and it is shown that for a given system with fixed inputs, entropy generation is minimized by way of balancing; i.e., the extraction and reinjection of the water or air streams within the humidifier and dehumidifier to equalize the capacity rates of the streams. Several modifications to existing baseline cycles are made to reach cases of minimum entropy generation. In these cases, the performance of the system is dramatically improved and the amount of energy needed to drive the system is reduced. For both on and off-design models, the addition of multiple extractions markedly improves the performance as compared to a baseline case with no extractions.
by Jacob A. Miller.
S.M.