Multi-stage Flash Research Articles

Exergoenvironmental analysis and evaluation of coupling MSF, MED and RO desalination plants with a combined cycle plant

In this paper, freshwater production through multi-effect desalination (MED), multistage flash (MSF), reverse osmosis (RO), hybrid (MED-RO), and hybrid (MSF-RO) units have been investigated based on environmental impacts associated with life cycle assessment (LCA) modelling tool and exergoenvironmental analysis. The integration of Qom combined cycle as a real case study with selected desalination plants has been studied. In this regard, thermodynamic simulation has been performed in computer code with high accuracy. Furthermore, computer code has been developed to perform exergy, exergoeconomic, and exergoenvironmental analyses. Results show; the environmental impact rate associated with the integrated combined cycle with the MED unit decreased by 23% compared to the stand-alone power plant. Also, in the integration of combined cycle with MSF, RO, MED-RO, and MSF-RO, it has been found that 25%, 60%, 27%, and 25% decrease can be obtained in the environmental impact rates, respectively.

Effect of Treating the Titanium Electrode of the Desalination Performance in Microfluidics System

The commercially applied macro desalination methods such as reverse osmosis, multi-stage flash distillation and multi-effect distillation suffer from several drawbacks such as high power consumption and low separation performance. It is believed that the micro-scaled structures will optimize the mixing efficiency of the micro-flow liquid and lead to higher desalination performance. Large surface-area-to-volume ratio in micro-scale promotes the fluids interaction since the laminar flow properties in the microfluidic device allowing the high-velocity gradients and dominant interfacial effects which is the manipulation of fluid streams [1]. The present work introduces a microfluidics chip for water desalination which fabricated using polydimethylsiloxane soft lithography method. Three layers of polydimethylsiloxane (PDMS) were fabricated using soft lithography method where PDMS liquid mixture was mixed and poured onto the designed wafer and heated to become solid. The solid PDMS was then peeled off from the wafer and hence assembled together with another PDMS by using surface plasma treatment process. The flow rate was set at 90 mL/h and the system was supplied with 9 V of potential difference. Aluminium and titanium were being used as the electrodes which achieved 65% and 15% of salt removal efficiency, respectively. Titanium was further treated by using the etching method and the performance was studied. The desalination efficiency was analyzed and evaluated with the flow rate of 90mL/h using capacitive deionization method. The result revealed that the performance of untreated titanium was better than the treated titanium which achieves 10% improvement in salt removal efficiency. The finding in this work show that the desalination efficiency was relied on the electrode surface property where the oxide layer inhibits the deionization from occurs.

Linear programming determination of blend ratios for desalinated water produced by multistage flash and reverse osmosis in a hybrid plant

Linear programming determination of blend ratios for desalinated water produced by multistage flash and reverse osmosis in a hybrid plant

Modelling and Simulation of the Multi-effect/Thermal Vapor Compression Distillation Process

The Multi-effect distillation (MED) associated with thermal vapor compression (TVC) process has recently been applied for a number of desalination plants in the GCC countries and emerged as a strong competitor to the multistage flash distillation (MSF) process. The MED/TVC desalination process is characterized by low power consumption compared to the MSF process. It is currently operated at low TBT of 65°C to avoid scale formation compared to MSF technology which operate at top brine temperature of 110°C, this lead to lower tendency to scale formation and less fouling risk. The use of more efficient pretreatment to MED/TVC desalination plants such as nano-filtration or high performance additive antiscalant would allow operating MED at higher TBT which allow increasing the performance ratio. A simulation steady-state program has been established to analyze the thermodynamic behavior of parallel feed flow MED/TVC unit at a wide range of TBT from 65°C up to 125°C and different number of effects with different condition of motive steam pressure on the performance ratio, and specific heat transfer and therefore the best design of MED for the future different design options were considered to optimize the operational of MED system to enhance the economics and performance of MED technology.

A literature survey on humidification dehumidification desalination processes

Potable water scarcity can be considered as a challenge nowadays and at least in the nearest future. Many factors contribute to such situation. Common techniques for desalination purpose include multistage flash, multi-effect distillation and reverse osmosis dedicated essentially to large scales. Humidification Dehumidification Desalination systems appear as low scale installations mainly powered by renewable or geothermal energy. This paper focuses on the state of the art of such installations. It discusses their types, their composition and the available models treating them and their outputs, the plants optimization procedures as well as productivity and costs of these systems. The study aims also the futures of such installations.

Energy, exergy and exergo-environmental assessment of a novel solar powered Kalina cycle incorporated with micro-CCHP for poly-generation

In this study, a solar parabolic trough collector combined with a Kalina cycle, multi-stage flash desalination unit, a proton exchange membrane electrolyser for hydrogen production, and a micro-combined cooling, heating, and power system is presented. Systematic energy, exergy, and exergo-environmental evaluation are used to analyse the viability of the integrated systems as the most effective approach for performance assessment of integrated systems. The energy and exergy efficiencies of the overall system is observed to be 50.51% and 3.27% respectively. The rate of exergy destruction of each component and the overall cycle is determined where the parabolic trough collector is shown to have an exergy destruction rate of 234.4 kW, which is the highest among all the components. The performance of the proposed systems is also checked through a parametric study of the different key parameters.

Corrosion inhibition effect of a benzimidazole derivative on heat exchanger tubing materials during acid cleaning of multistage flash desalination plants

A benzimidazole derivative, 2-(2-bromophenyl)-1-methyl-1H-benzimidazole (2BPB) has been studied as a corrosion inhibitor for Cu-Ni 70/30 and 90/10 alloys in 1 mol/dm3 HCl solution at low and high temperatures using the weight loss, electrochemical (potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), & cyclic voltammetry (CV)), and surface characterization (scanning electron microscopy (SEM) & Fourier-transform infrared spectroscopy (FTIR)) techniques. The effect of immersion time (up to 72 h) and addition of iodide ions on the inhibition efficiency of 2BPB have also been investigated. At low temperature, 1.0 g/L 2BPB inhibits Cu-Ni 70/30 and 90/10 alloys by 88.9 ± 4.8% and 57.5 ± 1.3%, respectively. The performance of 2BPB improves with increase in immersion time and addition of iodide ions but slightly depreciates with rise in temperature. 2BPB acts as a mixed type corrosion inhibitor and adsorbs on the alloys surfaces through physical adsorption mechanism. SEM and FTIR results confirm the adsorption of 2BPB on the alloys surfaces. 2BPB is a potential low toxic candidate for the formulation of acid corrosion inhibitor for Cu-Ni alloys.

Simulation of Multi-Stage Flash with Brine Circulating Desalination Plant

Multi-stage flash (MSF) desalination is the main process to solve the problem of limited freshwater resources in the world. This work describes the developed steady-state mathematical model for analysing and evaluating the performance of Multistage flashing with brine circulation desalination process (MSF-BC). It is based on the laws of energy balance, material balance, and heat transfer equations with physical properties correlations equations. The nonlinear equations are linearized and arranged into a tridiagonal matrix form. The model solution is obtained by a computer code written by MATLAB program software. It can predict the productivity of the plant with temperature profiles and flow rates for all stages in the unit. The model results were compared with some previous results presented in literature. The comparison shows good agreement with these available data. An MSF desalination plant in Ayoun Mousa, Egypt of capacity 5000 m 3 /day was presented as a case study.

Seawater Desalination Using Waste Heat Recovery on Passenger Ship

This paper presents a study for sea water desalination on board of passenger ships using waste heat from the engine. Three thermal methods for water desalination were explored, namely Forward Feed Multiple Effect Evaporation, Once Through Multi-Stage Flash, and Brine Circulation Multi-Stage Flash. Computer simulation has been developed to calculate the parameters of the desalination plant; the required amount of fresh water and the corresponding total heat transfer area. The optimum plant selection is the one which achieves the required distillate flow rate with minimum heat transfer area. The effect of different variables on the plant selection has been studied, i.e. steam temperature, exhaust temperature, and intake water flow rate. An existing passenger ship has been selected to examine the proposed method where the optimum desalination method has been selected for her using the developed software. To assess the effectiveness of the proposed method, the economical, environmental, and technical gains are numerically analyzed. Using the waste heat recovery leads to reducing the unit product cost of freshwater by circa 30%. The plant reduced the emissions by about five thousand tons of CO2, 100 tons of NOx and 35 tons of SO2 per year. Applying the optimum design of the proposed salt water desalination on the case study saved 2.7 $/ m3 as a minimum comparing to the average cost of fresh water in ports. These savings can cover the plant capital cost in six years at most.

Technoeconomic analysis of solar thermal desalination

Desalination systems are necessary in order to meet growing demands for freshwater. Coupling desalination systems with solar energy technologies is one possible route for eliminating the need for fossil fuel energy sources. Herein, we build a technoeconomic model that assesses the viability of coupling solar collectors with thermal desalination systems. The model considers the impacts of system lifetime and scale, unit price and performance parameters for each subsystems, local market and environmental factors of plant site on specific discounted water production costs and payback period. This approach eliminates technical and geographic constraints. The technoeconomic model attempts to predict the economics of a solar multi-stage flash distillation system. The specific discounted water production cost for a plant producing 1000 m3/day is $0.97/m3 if the solar collector unit cost is $100/m2 and operates at 40% efficiency. According to market and environmental factors in seven coastal cities in the United States, the most economically feasible geographic location for a solar desalination plant is Miami, Florida.

Applications and prospects of titanium and its alloys in seawater desalination industry

Seawater desalination (SD) is an effective method to solve the shortage of human water resources. Because of the excellent corrosion resistance of metallic materials in natural waters, as well as the best corrosion resistant, low density, high strength and good heat resistance in seawater, titanium and its alloys are considered the desirable marine material, including in SD equipment. This review introduces material characteristics of titanium and its alloys, and three currently most widely used commercial SD technologies: multiple effect desalination (MED), multi-stage flash (MSF) and reverse osmosis (RO). The applications and prospect of titanium and its alloys in SD industry are overviewed and analysed. This paper can be a reference for the future material selection of SD equipment.

Advance control scheme for Desalination Plant

The multistage flash desalination (msf) process is used to separate brine from sea water and provide distilled water. The factors that determine the performance of the plant (distillate produced) depends on the output temperature of the brine heater which is known as top brine temperature.Single loop controllers are usually used to control top brine temperature. Control of top brine temperature of MSF plants is a multivariable control problem, due to interaction between other variables like, brine inlet flow to the brine heater, brine heater level, brine concentration etc., the use of simple PID controllers cannot cope with the compound interactions with other variables which affects the top brine temperature. Hence it is necessary to have dependable model of the plant behavior to account for the interaction between the controlled and manipulated variables. For this purpose, a non-linear dynamic model was developed for the MSF plant with multi variable interaction approach. Simulation studies were carried out to maintain top brine temperature by varying brine flow and brine heater level. A feed forward controller was developed and the performance was compared with the conventional PID controller. The merits of the proposed scheme were highlighted. [19],[20],[21]

Energy storage and generation through desalination using flow-electrodes capacitive deionization

Flow electrodes-based capacitive deionization (FCDI) is a highly energy-efficient desalination process compared to conventional processes, including reverse osmosis and multi-stage flash distillation. Furthermore, it provides a continuous desalination flow with high salt-removal capacity, whereas CDI using fixed electrodes requires additional electrode rinsing. In FCDI, salt ions are adsorbed onto flow carbon electrodes and stored in the electrode slurry container, which is similar to an electrochemical flow capacitor. Therefore, stored ions can generate energy during discharging in FCDI operation. In this study, such energy generation was systematically investigated in terms of the various discharging rates, feed concentrations, and volume of flow-electrode slurry. We found that the results were correlated with the changes in the salt concentration of the effluent flow. The discharging current of 50 mA showed the highest capacity for energy generation out of all the experimental conditions; it recovered around 25% of the energy consumed during FCDI desalination. We believe that such energy recovery can greatly reduce the energy consumption needed for FCDI desalination. Such recycling of generated energy would make FCDI more attractive than other conventional desalination techniques.

Prevention is better than cure: Persian Gulf biodiversity vulnerability to the impacts of desalination plants.

Due to extremely high rates of evaporation and low precipitation in the Persian Gulf, discharges from desalination plants (DPs) can lead to ecological stresses by increasing water temperatures, salinities, and heavy metal concentrations, as well as decreasing dissolved oxygen levels. We discuss the potential ecological impacts of DPs on marine organisms and propose mitigating measures to reduce the problems induced by DPs discharges. The daily capacity of DPs in the Persian Gulf exceeds 11 million m3 per day, which is approximately half of global daily freshwater production; multistage flash distillation (MSF) is the dominant desalination process. Results from field and laboratory studies indicate that there are potentially serious and chronic threats to marine communities following exposure to DP discharges, especially within the zoobenthos, echinodermata, seagrasses, and coral reefs. DP discharges can lead to decreases in sensitive species, plankton abundance, hard substrate epifauna, and growth rates of seagrasses. However, the broad applicability of any one of these impacts is currently hard to scale because of the limited number of studies that have been conducted to assess the ecological impacts of DP discharge on Persian Gulf organisms. Even so, available data suggest that appropriately sited, designed, and operated DPs combined with current developments in impingement and entrainment reduction technology can mitigate many of the negative environmental impacts of DPs.

Thermodynamic, economic and environmental impact studies on various distillation units integrated with gasification-based multi-generation system: Comparative study and optimization

Abstract This research proposes four scenarios for a multi-generation system to produce power, pasteurized milk, biofuel and fresh water for the northern areas of Iran. In all scenarios, power, pasteurized milk and biofuel are produced by a similar arrangement of a supercritical CO2 (S–CO2) Brayton cycle, a biomass gasifier and a milk pasteurization unit while the portable water is produced by a brine recirculation multi-stage flash (BR-MSF) in scenario 1, by forward, backward and parallel feed schemes of multi-effect distillation (BF, FF and PF-MED) in scenarios 2, 3 and 4, respectively. A comparative study is conducted for the exergy, exergoeconomic and exergoenvironmental performances of all scenarios with various stages and effects using Engineering Equation Software (EES). The optimum performances of all scenarios are found by applying the fast and elitist non-dominated sorting genetic algorithm (NSGA-II) and using linear programming technique for multi-dimensional analysis of preference (LINMAP), technique for order of preference by similarity to ideal solution (TOPSIS) and Shannon entropy decision makers. According to the results, the maximum distillate water with capacity of 400.6 m3/day is obtained for scenario 1 through Shannon entropy method. Moreover, scenario 4 gives the maximum exergy efficiency with a value of 44.16% using LINMAP method and scenario 2 with the lowest total cost and environmental impact (EI) rates of 77.15 $/h and 33.35 mPts/s, respectively obtained from TOPSIS method is the best layout from the economic and EI aspects.

Highly efficient corrosion inhibitor for C1020 carbon steel during acid cleaning in multistage flash (MSF) desalination plant

A new environmentally friendly and cost effective molecule, thiabendazole (TBZ), was evaluated as a potential acid corrosion inhibitor for a typical carbon steel (C1020 grade) used as construction material in MSF desalination plant using electrochemical and (weight loss) immersion techniques. Electrochemical measurements after 1, 4 and 8h immersion in 1.0M HCl at 25°C showed that TBZ is an excellent corrosion inhibitor for C1020 grade steel and its inhibition efficiency reaches ≈90% at 4mM concentration with no substantial increase at 10mM. In the presence of iodide ions, TBZ showed improved corrosion inhibition attaining inhibition efficiency of 94.3% with 4mM concentration after 4h of testing with no increase in inhibition efficiency after 8h. However, weight loss measurements indicate that the corrosion inhibition performance of TBZ, and TBZ in combination with KI decreased with immersion time up to 24h and temperature up to 60°C. SEM-EDX and ATR-IR spectroscopy confirm that the inhibition process was due to the formation of an adsorbed film that protects the steel surface against corrosive medium. DFT and Monte Carlo simulation results gave further molecular and atomic level insight on mechanism of interaction between the inhibitor and the steel surface.

A pilot study of spiral-wound air gap membrane distillation process and its energy efficiency analysis

Brine disposal is a major drawback for seawater desalination. Membrane distillation (MD) is an emerging technology to treat a high saline water including brine disposal instead of reverse osmosis, multi-stage flash and multi-effect distillation. This study investigated a pilot scale of a spiral-wound air gap MD (AGMD) module and evaluated its efficiency. A pilot-scale AGMD module with design production capacity of 10 m3/d was operated. Experiments with varying flow velocity showed increasing trend of water vapor flux as flow velocity increases. The temperature is one of the significant points in maximizing water permeate vapor flux in MD. Increasing temperature from 65 °C to 75 °C in evaporator channel has increased flux from 0.59 to 1.15 L/m2/h. Under various conditions, specific thermal energy consumption (STEC) and gained output ratio (GOR) was used to analyze energy efficiency. The pilot plant showed high GOR value in spite of a limited heating and cooling source available at the site. The highest GOR achieved was 3.54 with STEC of 182.78 kWh/m3. This study provides an overview of operation experience and its data analysis related to temperature, concentration, flow rate and energy supply.

Thermodynamic assessment of an integrated renewable energy multigeneration system including ammonia as hydrogen carrier and phase change material energy storage

Sustainable development and effective management of resources has become an integral need of future energy systems. This study considers a unique multi-generation system involving ammonia synthesis using electrolytically produced hydrogen from desalinated water, alongside supply of basic utilities like potable water, heating, cooling, and electricity. The integrated system employs a phase change material based-energy storage unit to provide uninterrupted energy supply to the system. Energy and exergy analysis of the overall and sub-systems based on the first and second law of thermodynamics reveal valuable insights into the performance of such a system. A rigorous analysis of external parameters including environmental temperature, direct normal irradiance on the overall and component energy/exergy efficiencies is performed. The analysis reveals that the utilities demand of a remote area can be met in a more sustainable and environmentally friendly manner using the proposed multi-generation system. An overall system exergy and energy efficiencies of 18.9% and 28.0% respectively are obtained, whereas the sub-systems are also found to have energy efficiencies ranging between 15 and 80%. The highest exergy destruction rates of 25 megawatts and 32 megawatts are observed for the multi-stage flash distillation and the steam Rankine cycle sub-systems respectively. An elementary environmental impact assessment of the same system reveals that the proposed system can help reduce the carbon footprint by almost 60% with no significant compromise on the overall exergy and energy efficiencies.

Economic evaluation of 20,000 M3/Day seawater desalination coupling with floating reactor nuclear power plant

The coupling of floating nuclear reactor with different desalination processes was economically evaluated by using a desalination economic evaluation program (DEEP-5) software and a method of levelized annualized production water cost. Three desalination processes, namely, Multi-effect distillation (MED), multi-stage flash (MSF) or reverse osmosis (RO). The capacity of the plant was 20,000m3/day and its energy source was 100MWt nuclear power plant. The analysis indicated that water costs with the RO process have stronger economic competitive comparing to distillation processes, without regard to changes in water quality. The sensitivity analysis results showed that the sensitivity factors affecting the cost of desalinated water are, in order, discount rate, interest rate, Specific Construction Cost and Condensing temperature.

Potential for sustainable use of trees in hot arid regions: A case study of Emirati neighborhoods in Abu Dhabi

This paper explores the future of landscapes in arid, coastal regions based on 4 water-energy regimes, using a case study of villa neighborhoods in Abu Dhabi, United Arab Emirates. It examines the potential for the planting of 15 selected tree species for carbon storage under various water-energy regimes to create carbon neutral (or negative) villa neighborhoods. Recent improvements to solar photovoltaic and reverse-osmosis desalination technology have lowered the carbon emissions for water production by over 99% relative to current gas-powered multi-stage flash desalination (0.08 kg CO2/m3 vs.12.8 kg CO2/m3). This allows trees planted in hot, desert climates to utilize treated ocean water while net sequestering between 1.7 and 38.2 kg C/tree/yr depending on species. When planted in existing neighborhood open spaces, we find that net carbon storage rates from trees are significant (15–800%) relative to operational emissions rates for building energy (cooling, lighting, equipment) when households are supplied from 100% renewable energy sources. Thus, as technology advances, landscape design strategies in the region could evolve to maximize planting to sequester carbon while also creating more comfortable outdoor spaces that enhance the livability of neighborhoods. This study provides a first step in identifying the potential for landscape architectural design to employ a tree-based, neighborhood scale, carbon storage strategy in arid regions such as those in the Arabian Peninsula. As nations move towards a carbon-neutral future, it is imperative to develop innovative solutions that address urban sustainability, especially in resource-challenged and extreme climate regions where new urban development is planned.