A critical assessment of desalination operations in Sicily

Novel Tri Hybrid Desalination Plants

On the reduction of desalting energy and its cost in Kuwait

Evaporation for desalination : Improved multistage flash(MSF) processes

Retrofitting the combined-cycle producing electric power and desalted seawater to include district cooling in GCC

Roof structural damage of Sitra Power and Water Station phase I multi-stage flash units

Coupling of a nuclear reactor to hybrid RO-MSF desalination plants

Solutions for coupling a mechanical vapour compression distiller with a multi-stage-flash evaporator

Solutions for coupling a mechanical vapour compression distiller with a multi-stage-flash evaporator

Desalination is probably the only means for fresh water supply to countries in decertified climate. The majority of GCC counties rely on desalinated water for fresh water supply to major cities. Over 70% of the desalinated water in the GCC comes from thermal desalination plants including Multi Stage Flash (MSF) and Multi Effect Distillation (MED). The new trend in the desalination plant in the GCC is 30% Reverse Osmosis (RO) and 70% thermal. However, these percentages vary from one to another country depending on feed water quality and expertise. For example, Oman Sea has lower salinity than the Gulf water and hence Oman uses more RO for desalination than MED and MSF. This decision is also driven by economy as RO process less energy intensive and hence the produced water is less expensive as compared to thermal plants. On the contrary, Qatar and Kuwait use more MSF followed by MED due to the high salinity and low quality feed water. This is also because trials of RO in both Qatar and Kuwait were not successful because of the problems of membrane fouling and restrict pre-treatment requirements due to the quality of the water intake.The advantages of RO over thermal technologies are well known in terms of lower energy consumption and the cost of produced water; but are not yet taken advantage of in the GCC zone. One of the reasons is blamed on high feed water salinity and bad water quality; other reasons such as lack of experience, red tides and reliability are contributed to the dominance of thermal plants. However, field experience showed that good pretreatment and optimized RO design may overcome the problems of high feed salinity and bad water quality. Several RO plants, such as Fujairah in UAE, are good examples of a working RO technology in the harsh water environment. Good RO design includes design and optimization of both pretreatment and post-treatment. Field experience showed that most of RO plants failure was due to inefficient pretreatment which resulted in providing low quality water to the RO membrane that caused fouling. Fouling, including biological and scaling, can be handled once an efficient pretreatment process is available. Recent advances in pre-treatment techniques include the combination of Forward Osmosis (FO) with RO among other methods. Recent studies by the authors including commercial implantations have shown that the combination of FO with RO addresses the most technical challenge of RO process and that is fouling, which results in lower energy consumption and less chemical additives. Experience showed fouling in FO process in reversible, i.e. can be removed by backlashing while fouling in conventional RO process is irreversible.In this study, the feasibility of integrating FO with RO process for the desalting of the Gulf water in Qatar is presented. The results are expressed in terms of specific energy consumption, process recovery, produced water quality, chemical additives and overall process cost.The implementation of RO for desalination is not only reducing the cost of desalination but also the environmental impact. More R&D should be done to provide useful data about RO application and suitability for the Gulf water. The R&D should be focused on laboratory to market development of RO technology using rigorous lab scale and pilot plant testing program.

A variety of industrial wastewater recovery technologies for different areas and applications has been developed over the years, including primarily thermal and membrane processes. The main thermal processes include atmospheric distillation, distillation with mechanical vapor compression, vacuum distillation, multi-stage flash distillation, multi-effect distillation with thermal vapor compression, etc. [1,2]. The membrane processes contain reverse osmosis, electrodialysis, and nanofiltration. The multi-stage flash distillation and reverse osmosis processes dominate in most applications. Wastewater recovery and re-use technologies have been expanding rapidly in recent decades. The market is also driven by the falling costs of wastewater recovery, which are due to the technological advances in the process. The costs of clean water produced by wastewater recovery process dropped considerably over the years as a result of reductions in price of equipment, reductions in power consumption and advances in system design and operating experiences. In this work state-of-the art and innovative wastewater recovery/re-use technologies are estimated and compared in their features and cost respects. The new technology is discussed that allows increasing in energy efficiency of the wastewater recycling and reduce electricity consumption associated with conventional methods. Successful development and implementation of the technology for food processing applications will provide large energy and water savings to the industry. These savings are tied to an energy efficiency increase and reduction in pumping power for process water supply. The ability to integrate waste heat recovery with wastewater reuse also leads to product cost reduction opportunities for producers.

Thermoeconomic analysis of some existing desalination processes

Hybrid desalting systems

The vast majority of commercial desalination systems utilise one of four desalination processes: reverse osmosis (RO), multi-stage flash (MSF), multiple-effect distillation (MED) and mechanical vapour compression (MVC). A small fraction of desalination systems utilise electrodialysis (ED) technology to treat low salinity brackish water. Worldwide, RO desalination systems account for close to 50% of overall capacity. However, in the arid countries of the Middle East, the majority of desalination systems utilise evaporation processes: MSF, MED and MVC. Although, the energy requirement of evaporation processes is higher than that for membrane processes, distillation desalination systems will continue to dominate Middle East markets for some time to come, due to the large base of thermal desalination units, with proven high operational reliability and the convenience of their integration with power plants (dual purpose systems). With the growing trend to privatise the desalination market in the Middle East, the proportion of desalination capacity supplied by RO will increase, due to the better economics of the RO process. In this chapter, an up-to-date review of industrial units has been performed in order to present the most common features of industrial operating units. This review includes typical design parameters, operating conditions and process performances. Moreover the developments that have taken place over the years are presented, along with examples of recent installations and their production capacities, performance parameters and locations.KeywordsReverse OsmosisDuplex Stainless SteelFeed WaterUnit Product CostReverse Osmosis MembraneThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Powering desalination by waste heat is often proposed to mitigate energy consumption and environmental impact; however, thorough technology comparisons are lacking in the literature. This work numerically models the efficiency of six representative desalination technologies powered by waste heat at 50, 70, 90, and 120 °C, where applicable. Entropy generation and Second Law efficiency analysis are applied for the systems and their components. The technologies considered are thermal desalination by multistage flash (MSF), multiple effect distillation (MED), multistage vacuum membrane distillation (MSVMD), humidification-dehumidification (HDH), and organic Rankine cycles (ORCs) paired with mechanical technologies of reverse osmosis (RO) and mechanical vapor compression (MVC). The most efficient technology was RO, followed by MED. Performances among MSF, MSVMD, and MVC were similar but the relative performance varied with waste heat temperature or system size. Entropy generation in thermal technologies increases at lower waste heat temperatures largely in the feed or brine portions of the various heat exchangers used. This occurs largely because lower temperatures reduce recovery, increasing the relative flow rates of feed and brine. However, HDH (without extractions) had the reverse trend, only being competitive at lower temperatures. For the mechanical technologies, the energy efficiency only varies with temperature because of the significant losses from the ORC.

A comparative study of RO and MSF desalination plants