Water is the most important chemical component on Earth. Seawater distillation processes have a considerable promise as a technique suitable for producing large scale quantities of potable water from the seawater. Distillation process flowsheets consist of a number of interconnected units. The development of the mathematical model describing the behaviour of these units, and the subsequent solution of this model are fundamental steps in process flowsheeting. The first objective of this work is to develop a specialized flowsheeting program for performing design and simulation calculations for different types and configurations of seawater distillation processes. Many numerical methods have been used for solving linear and nonlinear sets of equations representing distillation processes. Most of these methods involve the direct manipulation of the mathematical model equations without exploiting the special properties, such as the sparsity and the weak nonlinearities, of these equations. The second aim of this study is to develop a new approach taking advantages of these properties. Hence, the model equations can be linearized, and grouped according to the variable type. These groups can then be solved by linear matrix technique. The performance of the developed program is investigated by solving many distillation process problems. The results from design and simulation calculations for large practical desalination plants are discussed. In addition to that the convergence characteristics of the new approach (such as stability. number of iterations. computing time. sensitivity to starting values, and general ease of use) are presented. Also. the validity of the approximation assumptions proposed to develop the new approach is examined.

The aim of this study is to develop a seawater desalination system that uses sea-wave energy as the sole energy source for system operation. This system is composed of a sea-wave energy acquisition system, a reverse-osmosis device, and a proposed mechanism linking the system to function synchronously. The relationships between various system parameters and system characteristics are analyzed. The limitations and constraints of system operations are then suggested. For the purpose of comparison, another system, which indirectly drives the reverse-osmosis system through an additional stage of energy storage, is introduced. To analyze the system dynamic properties, the following steps are implemented. First, a mathematical model than can properly describe the system characteristics is derived. This model is found to be a nonlinear one, which increase the difficulties of system analysis enormously. However, it is also noted through a preliminary examination that the effect of system nonlinearity becomes insignificantly if the system parameters are properly adjusted. Under these parameters, the linearied model is analyzed. The effects of different system parameters on the amount of energy acquisition and desalinated water are investigated. The analysis indicates that the amount of energy acquisition or desalinated water is closely related to both the selected energy acquisition system and the desalination system. For a given energy acquisition system and sea wave condition, an improper system parameter selection of desalination system will either make the whole system operation inefficient or devastate the functioning of acquisition system. This suggests that certain parameters of the desalination system must be adjustable in a real operation. The study also shows that the linearied system can be approximated by a model with two degrees of freedom. This model may offer the convenience for the optimization of system parameters.

In spite of abundant water resources, world is suffering from the scarcity of usable water. Seawater Reverse Osmosis (SWRO) desalination technology using polymeric membranes has been recognized as a key solution to water scarcity problem. However, economic sustainability of this advanced technology is adversely impacted by the membrane fouling problem. Fouling of RO membranes is a highly studied phenomenon. However, literature is found to be lacking a detailed study on kinetic and dynamic aspects of SWRO membrane fouling. The factors that impact the fouling dynamics, i.e., pretreatment and water quality were also not adequately studied at full–scale of operation. Our experimental protocol was designed to systematically explore these fouling aspects with the objective to improve the understanding of SWRO membrane fouling mechanisms. An approach with multiple analytical techniques was developed for fouling characterization. In addition to the fouling layer characterization, feed water quality was also analysed to assess its fouling potential. Study of SWRO membrane fouling dynamics and kinetics revealed variations in relative abundance of chemical and microbial constituents of the fouling layer, over operating time. Aromatic substances, most likely humic–like substances, were observed at relatively high abundance in the initial fouling layer, followed by progressive increase in relative abundances of proteins and polysaccharides. Microbial population grown on all membranes was dominated by specific groups/species belonging to different classes of Proteobacteria phylum; however, similar to abiotic foulant, their relative abundance also changed with the biofilm age and with the position of membrane element in RO vessel. Our results demonstrated that source water quality can significantly impact the RO membrane fouling scenarios. Moreover, the major role of chlorination in the SWRO membrane fouling was highlighted. It was found that intermittent mode of chlorination is better than continuous mode of chlorination of seawater, as anti–biofouling strategy. It was also confirmed that significant biofilm development was inevitable even with the use of chlorine to disinfect SWRO membranes. Our findings on the dynamic patterns of SWRO membrane fouling should help in further elaborating research projects focusing on the development of better strategies to minimize this troublesome phenomenon.

yes / Boron is a vital element for growth of creations, but excessive exposure can cause detrimental effects to plants, animals, and possibly humans. Reverse Osmosis (RO) technique is widely used for seawater desalination as well as for waste water treatment. The aim of this study is to identify how different operating parameters such as pH, temperature and pressure can affect boron concentrations at the end of RO processes. For this purpose, a mathematical model for boron rejection is developed based on solution-diffusion model which can describe solvent and solute transport mechanism through the membranes. After a wide and thorough research, empirical correlations developed in the past are filtered, adopted and calibrated in order to faction with reliability as part of the solution-diffusion model of this work. The model is validated against a number of experimental results from the literature and is used in further simulations to get a deeper insight of the RO process. The general findings of the boron rejection model are supporting the case that with increasing pH and operating pressure of the feed water, the boron rejection increases and with increasing feed water temperature the boron rejection decreases.

Yes / Multistage Flash (MSF) desalination process is still a dominant process, especially in the Gulf region, to produce high quality freshwater. Although there has been energy price surge in recent years, MSF process will continue to operate in that region for some foreseeable future. The key challenge is how to make such processes still profitable. Understanding the dynamics of any processes under uncertainty and disturbances is very important to make a process operationally feasible and profitable. The main aim of this work is to understand the dynamics of industrial scale MSF process using high fidelity and reliable process model. For this purpose, a detailed dynamic model for the MSF process incorporating key and new features is developed and validated against the actual data of a large-scale seawater desalination plant. The model is then used to study the behaviour of large scale MSF processes for disturbances in steam temperature, feed temperature and the recycle brine flow rate. The simulation results show that the last stage requires a longer time to settle compared to the preceding stages. In addition, steam temperature shows insignificant influence on the performance ratio compared to the inlet seawater temperature and recycle brine flow rate. Furthermore, it is found that the productivity of plant can increase in the winter compared to that in the summer. However, this benefit comes at the expense of increased steam consumption in the winter, resulting in a low performance ratio.

Owing to the maldistribution of precipitation in the harsh climatic region has resulted in the deficit between freshwater demand and natural supply or water scarcity in these countries. Seawater desalination has emerged as one of the most reliable methods to bridge this gap. However, the thermal desalination (MED and MSF) process faces challenges related to surface scaling phenomena, such as temperature and seawater concentration. Innovative thermodynamic processes and technologies have the potential to overcome these limitations. On one hand, the top brine temperature (TBT) limit can be raised by partially removing the multivalent ions such as SO42-, Mg2+, Ca2+, Cl-, and Na+ dissolved in the seawater. One of the main drawbacks of the current MED processes is their vulnerability to scaling at temperatures above 70°C.. This limitation deprives the technology to be energy efficient and reduces its optimal productivity. However, by implementing an optimized pre-treatment of seawater feed using NF membranes, the efficiency of the process can be significantly improved. In the pilot plant, the experiment was conducted to investigate the efficacy of NF (nanofiltration) as a physical pre-treatment method for partially removing undesirable ions of dissolved salts in Red Sea water, thereby mitigating scaling issues beyond the upper TBT limit in thermal desalination systems. Utilizing the NF-270 membrane, the optimal operating feed pressure of 15 bar was determined to ensure effective ion removal while minimizing operational expenditures (OpEx). The results demonstrated high removal rates, with 97% removal of Sulfate (SO42-), 73% removal of Magnesium (Mg2+), 49% removal of Calcium (Ca2+), 17% removal of Sodium (Na+), and 16% removal of Chloride (Cl-). By employing NF as a pre-treatment method, the concentrations of these ions were significantly reduced, allowing for thermal desalination plants to operate at higher temperatures, with a maximum TBT of 120°C. This, in turn, has the potential to substantially increase water production yield in thermally driven plants by incorporating a greater number of stages in a green new design plant or by exploiting larger temperature differences in existing plants.

Yes / The use of Reverse Osmosis (RO) process in seawater desalination to provide high-quality drinking water is progressively increased compared to thermal technologies. In this paper, multistage spiral wound RO desalination process is considered. Each stage consists of several pressure vessels (PVs) organised in parallel with membrane modules in each PV being organised in series. This allows disconnecting a set of PVs and membrane modules depending on the requirement of cleaning and maintenance. While this flexibility offers the opportunity of generating several RO configurations, we presented only four such configurations of the RO system and analysed them via simulation and optimisation. Production of different grades of water catering different needs of a city is also considered for each of these configurations. The optimisation has resulted in the optimal operating conditions, which maximises the water productivity and minimises the specific energy consumption of the proposed configurations for a given water grade in terms of salinity. For instance, the results indicate that the proposed RO networks can produce drinking water of 500 ppm salinity with a minimum specific energy consumption of 3.755 kWh/m3. The strategy offers the production of different grades of water without plant shutdown while maintaining the membrane modules throughout the year.

Yes / The coupling of thermal (Multi Stage Flash, MSF) and membrane processes (Reverse Osmosis, RO) in desalination systems has been widely presented in the literature to achieve an improvement of performance compared to an individual process. However, very little study has been made to the combined Multi Effect Distillation (MED) and Reverse Osmosis (RO) processes. Therefore, this research investigates several design options of MED with thermal vapor compression (MED_TVC) coupled with RO system. To achieve this aim, detailed mathematical models for the two processes are developed, which are independently validated against the literature. Then, the integrated model is used to investigate the performance of several configurations of the MED_TVC and RO processes in the hybrid system. The performance indicators include the fresh water productivity, energy consumption, fresh water purity, and recovery ratio. Basically, the sensitivity analysis for each configuration is conducted with respect to seawater conditions and steam supply variation. Most importantly, placing the RO membrane process upstream in the hybrid system generates the overall best configuration in terms of the quantity and quality of fresh water produced. This is attributed to acquiring the best recovery ratio and lower energy consumption over a wide range of seawater salinity.

Yes / Despite the fact of being intensive energy consumption, MSF is a mature technology that characterised by a high production capacity of high-quality water. The multistage flash (MSF) desalination process is one of the prominent thermal desalination used in the industry of seawater desalination to produce high quantity and high quality of freshwater. However, this process consumes large amount of energy and faces thermal limitations due to its high degree of exergy destruction at several units of the process. Therefore, the research of MSF is still existed to elevate the performance indicators and to resolve the concern of high energy consumption. To rectify these limitations, it is important to determine the units responsible in dissipating energy. This study aims to model an industrial MSF process validated against real data and then investigate the exergy destruction and thermodynamic limitations of the process. As a case study, Azzour MSF seawater desalination plant, located in Al Khiran in Kuwait is under the focus. A comprehensive model is developed by analysing several published models. Specifically, the calculation of exergy destruction has embedded both physical and chemical exergies that identified as a strong point of the model developed. As expected, the highest exergy destruction (55.5%) occurs within the heat recovery section followed by the brine heater with exergy destruction of 28.26% of the total exergy destruction. This study identifies the sections of the industrial process that cause the highest energy losses.

Yes / The shortage of fresh water resources is a global problem which requires a prompt solution. Thus, the multi effect distillation (MED) was successfully used for the production of fresh water from seawater. Despite the use of MED desalination system extensively, the influence of the number of effects on the fresh water production cost has not been covered in the open literature. Thus, this paper tries to rectify this specific challenge via simulation at given operating conditions of seawater salinity and temperature. The study is performed using a detailed mathematical model contains the suitable cost correlations. gPROMS model builder suite has been used to carry out an extensive simulation. The results of the study show that the lowest fresh water production cost can be achieved at an optimal number of effects of 17 for a certain operating conditions.