Multi-effect Distillation System Research Articles

Prediction of key performance indicators of multi-effect vacuum membrane distillation systems integrated with PVT and Organic Rankin Cycle

The study presented a numerical simulation conducted using MATLAB® to analyze the performance of a poly-generation system. This system comprises solar collectors, a Photovoltaic-Thermal (PVT) system, an Organic Rankine Cycle (ORC), and a multi-effects vacuum membrane distillation (V-MEMD) system. The study investigates the impact of changes in operating conditions of the water stream on the performance of the V-MEMD system. The optimal performance values observed include a water flux of up to 13 kg/ m2·h, a GOR of 5.5, a SEEC of 49 kWh/ m3, and a STEC of 145 kWh/ m3, with each parameter reaching its optimum at different operational settings. The paper explores the impact of different working fluids in the ORC system on water and power generation. It also discusses recent research on combined PVT and ORC systems in Riyadh, Saudi Arabia, considering the region's specific meteorological conditions. The findings reveal that the highest electricity generation occurs in June, with the ORC system producing 18,540 kWh when R123 is used and the PVT system generating 13,536 kWh. The cumulative electricity output for the year reaches 266,564 kWh. Moreover, the V-MEMD system produces 1333 m3 of water over the year, with the highest water yield of 178 m3 observed in June.

Model-based zero liquid discharge desalination for land-locked arid/semi-arid regions in India

The arid and semiarid regions usually are water-stressed. The available natural groundwater resources in these areas are, at times, saline and unfit for potable use. Desalination of saline water is a possible solution in such cases. However, discharge of concentrated brine is an issue, particularly in land-locked areas. In this regard, a case study has been presented for brackish water desalination in Western Rajasthan, India. As this is a land-locked desert area, zero liquid discharge (ZLD) desalination has been considered, offering a practical and sustainable solution. This study presents a novel approach to the model-based ZLD hybrid desalination system consisting of reverse osmosis and multi-effect distillation (RO-MED) systems producing drinking quality water and common salt. The simultaneous production of common salt has the potential to bring down the cost of drinking water produced by the system. A system design has been carried out for a real case based on the raw water analysis of groundwater in Western Rajasthan. Our hybrid (RO-MED-ZLD) model results indicate that RO reduced TDS from 4419 mg/l to 22 mg/l with a 67 % recovery rate. The proposed ZLD method recovers 93 % of salt crystals from MED brine solutions, potentially reaching 99 % with adjustments.

Enhanced performance of two-stage ejector based on flow-field coupling effect in MED-TVC systems

Steam ejectors serve as prevalent flow devices in multi-effect distillation systems, collecting excess steam and energy to promote sustainable energy utilization. In contrast to traditional ejectors, two-stage ejectors exhibit superior pressurization and vacuum capacities. However, the flow-field coupling effect, which is closely related to the entrainment performance of the two-stage ejector, is rarely explored. In this study, the flow-field coupling effect of the two-stage ejectors is investigated, and two new strategies are proposed to optimize the ejector performance. A concept of two-stage choking and a design principle for a two-stage choking structure is proposed by analyzing the size matching between two stages based on the flow-field coupling effect. Based on the design principle, the optimal structure parameter can be obtained by evaluating the two-stage choking state. Subsequently, a dynamic pressure control criterion based on the flow-field coupling effect is proposed to improve the entrainment performance. The results show that the entrainment performance of the two-stage ejector based on this control criterion is increased by 29.31 % and 4.15 % respectively when the second-stage primary pressure is 300 kPa and 450 kPa. Moreover, simulation results demonstrate that the upper limit of the entrainment performance is determined by the second-stage primary flow pressure.

Effect of droplets in the primary flow on ejector performance of MED-TVC systems

The performance of an ejector, as a crucial component that determines the operating efficiency of the multi-effect distillation system, is closely related to the state of the motive steam. However, the motive steam may be accompanied by droplets during system operation, which decreases the dryness of the motive steam. Nine wet-steam numerical models with different droplet mass fractions and numbers were established to investigate the influence of droplets in the primary flow on the performance and condensation phenomenon of the ejector. The results showed that as the droplet mass fraction of the primary flow increased from 0 to 0.12, the entrainment ratio (ER) of the ejector decreased by 9.15%, and the condensation intensity at the throat of the primary nozzle and the outlet of the primary nozzle decreased by 2.9% and increased by 201%, respectively. In addition, as the droplet number increased from 6 to 14, the ER of the ejector and condensation intensity at the throat of the primary nozzle varied merely between 1.5% and 1.8%, whereas the condensation intensity at the outlet of the primary nozzle fluctuated by 50%. Therefore, the presence of droplets in the primary flow of the ejector cannot be ignored. Some steam–water separation measures must be adopted to ensure efficient operation of the ejector.

Theoretical performance assessment of a multi-effect distillation system integrated with thermal vapour compression unit running on solar energy

Abstract Mathematical models can be successfully applied to predict the multi-effect distillation system integrated with thermal vapour compression unit (MED-TVC) performance under different operating conditions. In this work, a one-dimensional (1-D) mathematical model was developed to perform the theoretical analysis of a small-scale parallel feed MED-TVC desalination system driven by solar heat. A parametric study was conducted allowing the ejector motive steam temperature, first effect temperature, between effects temperature difference and ejector compression ratio to vary within an expectable range. The results showed that higher motive steam temperatures, had a positive impact on the water yield up to an optimal point. Any additional increase of driving steam temperature reduced water yield. Gain output ratio ($GOR$) was maximum at the highest considered motive temperature. It was found that the calculated specific heat transfer area does not depend on the motive temperature variation. Water yield, $GOR$ and specific heat transfer area decrease with the ejector compression ratio. The temperature difference between the evaporator effects had no effect on the water yield and $GOR$. It only decreases the specific heat transfer area. First effect temperature should be as low as possible with respect to operational constraints. Based on the parametric study, the optimal design operating conditions, corresponding to the maximum water yield is identified for a small-scale three-effect desalination system. The unit can produce up to 204 l/h drinking water with a gain output ratio of 8.6 and specific heat transfer area of 575 m2/kg/s using about 22 kW of solar heat.

Low-temperature desalination driven by waste heat of nuclear power plants: A thermo-economic analysis

Nuclear desalination is one of the ideal options to achieve net-zero emissions. However, most nuclear desalination plants extract steam from the power cycle to drive desalination, leading to a reduction of electricity output. To avoid the parasitic effects of desalination on the power cycle, this study considers recovering waste heat from the power plants' condensers to drive low-temperature desalination systems, including spray-assisted low-temperature desalination system (SLTD), multi-effect distillation system (MED) and spray-assisted multi-effect distillation system (SMED). Thermodynamic and economic models of the three desalination systems are firstly established and validated with experimental data. Then, the impacts of key design, operation and economic parameters are evaluated using the validated models. Results reveal that the productivity and thermodynamic efficiency are promoted by increasing the cooling water flowrate of desalination condenser, enlarging the heat exchanger area and lifting the heat source temperature, while the number of effects has an optimal value of 3. Under the optimal configuration, the gained-output ratio and Second Law efficiency of a 20 m3/day SLTD plant are 0.71 and 1.25 % respectively. In terms of economic performance, the levelized-cost of desalinated water (LCOW) for three plants can be reduced substantially under a larger plant capacity and longer lifespan. When the plant capacity exceeds 20,000 m3/day, the LCOW of SLTD can be reduced to 0.757 $/m3, which is lower than all other desalination systems coupled with power plants or renewable energy sources.

Hybrid vacuum membrane distillation-multi effect distillation (VMD-MED) system for reducing specific energy consumption in desalination

This study focuses on the integration of vacuum membrane distillation into the multi-effect distillation (VMD-MED) system, incorporating heat recovery mechanisms to augment fresh water productivity and minimize the specific thermal energy consumption of the desalination process when compared to stand-alone vacuum membrane desalination systems. The hybrid system was devised by integrating the experimental output of VMD (permeate flux and hot brine) as heat source to MED. Two hybrid systems were investigated in this study: VMD/MED, wherein the heated brine from VMD served as a heat source for MED, facilitating the recovery of sensible heat from VMD; and VMD-HR/MED, where the latent heat of VMD vapor during condensation was utilized to pre-heat the feed water for MED. Based on the performance parameters, it was concluded that the VMD-HR/MED hybrid system outperformed both the stand-alone VMD and VMD/MED hybrid system in terms of efficiency. The latent heat recovery from the condenser of VMD in VMD-HR/MED hybrid system reduces the specific thermal energy consumption (STEC) to 38.42 kWh/m3, however, it enhanced the gain-output-ratio (GOR) and productivity of the system. Additionally, a rise in GOR and a simultaneous decrease in STEC were observed with increasing feed flow rates and vacuum pressure.

Internal feed preheating necessary for energy-efficient modular multi-effect membrane distillation

Multi-effect membrane distillation (MEMD) systems achieve a high product recovery ratio by effectively utilizing the heat of condensation for further vaporization within the module. In this study, a novel internal feed-preheating design for improving the energy efficiency of modular MEMD systems is proposed and evaluated using a 2D CFD model. Custom user-defined functions are implemented to account for water vapor and associated energy transport across the membrane in an MEMD design with serpentine flow across various effects. Preheat channels embedded into the condensation plates help increase the temperature of feed entering the first effect by ∼25 K, close to heater plate temperature. As a result, high-grade external heat input is not used for sensible heating, instead being utilized towards evaporation and pure water production, resulting in ∼32 % improvement in energy efficiency. However, the added thermal resistance of the preheat channels results in lower average flux and hence recovery, which can be ameliorated by increasing the effective conductivity of the preheat channels. Increasing the thermal conductivity of preheat channels results in ∼23.5 % rise in recovery ratio. Such preheat designs are necessary to reap energy efficiency improvements by increasing the total number of effects in multi-effect vacuum and gap MD systems.

Energy and Exergy Analyses of a PWR-Type Nuclear Power Plant Coupled with an ME-TVC-MED Desalination System

Electricity–water cogeneration power plants are an important tool for advancing sustainable water treatment technologies because they provide a cost-effective and environmentally friendly solution for meeting the energy and water needs of communities. By integrating power and water production, these technologies can reduce carbon emissions and help mitigate the impact of climate change. This work deals with the energy and exergy analysis of a cogeneration plant for electrical power generation and water desalination using real operational data. The power side is a pressurized water reactor (PWR) nuclear power plant (NPP), while the desalination side is a multi-effect distillation (MED) system with a thermo-vapor compressor (TVC) plant coupled with a conventional multi-effect plant (ME-TVC-MED). A mathematical model was implemented in MATLAB software and validated through a comparison with previously published research. The exergy analysis was carried out based on the second law of thermodynamics to evaluate the irreversibility of the plant and the subsystems. In this study, the components of the sub-systems were analyzed separately to identify and quantify the component that has a high loss of energy and exergy. According to the energy and exergy analyses, the highest source of irreversibility occurs in the reactor core with 50% of the total exergy destruction. However, turbines, steam generators, and condensers also contribute to energy loss. Further, the thermodynamic efficiency of the cogeneration plant was obtained as 35.38%, which is more effective than other systems. In the ME-TVC-MED desalination unit, the main sources of energy losses are located in the evaporators and the thermo-compressor (about 50% and 36%, respectively). Moreover, the exergetic efficiency of the ME-TVC-MED unit was found to be low at 6.43%, indicating a high degree of technical inefficiency in the desalination process. Therefore, many opportunities exist to improve the performance of the cogeneration system.

Geothermal energy integrated multi-effect evaporator (MEE) and multi-effect distillation (MED)-based desalination systems: an ecofriendly and sustainable solutions.

Desalination is a tried-and-true method for obtaining clean water from the ocean's brackish waters and recycling and reusing water. It requires a fair amount of energy, so it is necessary to create sustainable energy systems to lessen energy use and environmental impact. For thermal desalination procedures, thermal sources can be great heat sources. This paper's research focuses on thermoeconomically optimized multi-effect distillation and geothermal desalination systems. Collecting hot water from subsurface reservoirs is a well-established method of generating electricity through geothermal sources. Low-temperature geothermal sources, which have a temperature of less than 130°C, can be utilized for thermal desalination systems, for example, multi-effect distillation (MED). Geothermal desalination is affordable, and it is possible to produce power simultaneously. Because it only uses clean, renewable energy and produces no greenhouse gasses or other pollutants, it is also safe for the environment. The viability of any geothermal desalination plant will be influenced by the location of the geothermal resource, feed water supply, cooling water source, water market, and concentrate disposal site. Geothermal energy can directly supply heat for a thermal desalination system or indirectly give electrical power to reverse the osmosis (RO) membrane-based desalination plant.

Impacts of the internal heat recovery scheme on the performance of an adsorption heat transformer cycle for temperature upgrade

Adsorption heat transformer (AHT) cycles, unlike adsorption cooling cycles, upgrade the heat source to a higher temperature. Despite the renewed interest in the AHT cycles, its performance enhancement schemes along with their impacts are yet to be explored extensively. Heat and mass recovery schemes on the adsorption cooling/heating cycles have been extensively studied. However, AHT cycles are fundamentally different from those cycles since the AHT cycles employ isothermal-adiabtic processes. Thus, similar impacts of the heat and mass recovery scheme as in the cooling/heating cycles cannot be expected in AHT cycles. Therefore, the impacts and limitations of the internal heat recovery scheme on the AHT cycle are investigated in the current study. The heat recovery scheme aims to minimize the requisite uptake consumption for preheating the adsorber bed by recovering the sensible heat between two adsorber beds having different temperatures. This sensible heat exchange is modeled using modified energy-balance equations to capture the non-linearity of the adsorption process. The preheating uptake loss decreases from 0.014 kg/kg to 0.007 kg/kg at the heat source-heat supply temperature combination of 60 °C–80 °C due to the maximum possible heat recovery in the AHT cycle. As a result of the reduced preheating uptake loss, approximately 5% and 10% increase in the useful heat ratio and exergy efficiency of the AHT cycle, respectively are obtained. This modified AHT cycle further improves the performance ratio of the hybrid AHT-MED (multi-effect distillation) system from 4.6 to 4.9 at the heat source temperature of 58 °C. Furthermore, a parametric analysis of the cycle's performance metrics has been conducted for various degrees of heat recovery, representing the effect of realistic heat exchanger effectiveness during the recovery process. This study will help propel the theoretical development of the adsorption-based thermodynamic systems.

Energy analysis of a small-scale multi-effect distillation system powered by photovoltaic and thermal collectors

Powering thermal desalination technologies by renewable energy is believed to be a viable solution to overcome the worldwide freshwater scarcity problem without causing more damage to the environment. In this paper, a multi-effect distillation system (MED) with mechanical vapor compression is powered by the generated electrical power of photovoltaic/thermal collectors and assisted by the by-product thermal power generated. The system is sized according to thermal power needed and designed for small-scale application and weather conditions of Alexandria, Egypt. Excess electricity is injected into the grid and hot water storage tank is used as a back-up to compensate low and fluctuating radiation. Results show that, at a saturation temperature of MED’s heating steam of 55 °C, freshwater production is 11.1 m3/day in 10 hours of operation, system specific power consumption is 9.72 kWh/m3, specific area is 317.04 m2s/kg, and performance ratios of the desalination unit is 3.33 and 6.97 for the overall system. However, at T = 65 °C the system’s electrical energy is totally absorbed by the compressor, and the system’s performance decreases.

Desalinated Water Costs from Steam, Combined, and Nuclear Cogeneration Plants Using Power and Heat Allocation Methods

This work presents a detailed thermo-economic analysis of unit water costs from dual-purpose cogeneration plants. The power levelized cost was first calculated for stand-alone steam, nuclear, and combined-cycle power plants. The cost of energy needed to operate the desalination systems connected to power plants was evaluated based on two different approaches: power- and heat-allocated methods. Numerical models based on the heat and mass balances of the power and desalination plants’ components were developed and validated. Comprehensive and updated data generated using Desaldata libraries were correlated to estimate the capital, labor, overhead, and maintenance costs for different desalination systems. The levelized water cost produced by multi-effect distillation, multi-effect distillation with vapor compression, multi-stage flash, and reverse osmosis systems connected to different power plants was estimated. The impact of various controlling parameters, including the price of natural gas, nuclear power plant installation cost, and the desalination capacity on water cost, was investigated. For all simulated cases, the levelized water cost evaluated using the heat-allocated method was found to be lower by 25–30% compared to that estimated using the power-allocated method. The cost of water produced using reverse osmosis remains below that produced by other desalination technologies. However, using the heat-allocated method to estimate the levelized water cost narrows the gap between the costs of water produced by multi-effect distillation and that produced by seawater reverse osmosis. The results also show that the use of the multi-effect distillation process in a cogeneration configuration rather than multi-effect distillation with vapor compression can result in a lower water cost. The profit analysis shows slight differences between the profit of a power plant connected to a reverse osmosis system and the profit of a power plant connected to a plain multi-effect distillation system.

Modeling and Simulation of Multi-Effect Membrane Distillation Systems

Modeling and Simulation of Multi-Effect Membrane Distillation Systems

CuO/water and Al2O3/water nanofluids as working fluid in an abandoned oil well to improve thermal performance in the seawater desalination process

BackgroundAbandoned Oil/gas wells could be employed as heat sources for various technical processes such as seawater desalination. MethodsIn this study, the thermal performance of an abandoned oil well is enhanced by the addition of nano Cu and Al2O3 particles into the working fluid (water) and by using two distinct thermal insulations in the coaxial double-pipe borehole heat exchanger to decrease heat losses of the heated working fluid. Diligent simulation of the process was carried out using the k-ω SST turbulence model and sweep meshing method. The effect of Cu/water and Al2O3/water nanofluid concentrations on extracted fluid temperature was investigated. Significant FindingThe results revealed that 0.5 wt.% of Cu/water and Al2O3/water as working fluid at a flow rate of 2 kg/s raised the extracted fluid temperature by 14% and 12.9% compared to pure water, respectively. Also, SiO2/GO composite thermal nano-insulation could improve heat loss by 7.4% compared to polystyrene thermal insulation. Furthermore, 806 m3/day of potable water was produced by a multi-effect distillation modified with flash-boxes desalination, where brines were reused as a secondary feed for potable water production. Noticeable increase achieved compared to conventional multi-effect distillation systems.

Thermal optimization research of vertical tube climbing film desalination system

Abstract Based on the pinch theory and energy cascade utilization principle, the performance of a multi-effect shipboard vertical tube climbing film desalination system combined thermal vapor compression with different preheating configuration has been analyzed. The mathematical model is established for thermodynamic simulation, in which various thermodynamic losses caused by boiling point elevation and pressure drop are considered, and the effective heat transfer temperature difference and the hot side temperature difference are used to analyze the influences of heating steam temperature, final effect evaporation temperature, and concentration ratio on thermal performance including gained output ratio (GOR)—specific heat transfer area for different preheating configuration. The results show that the internal average effective heat transfer temperature difference determines characteristics of multi-effect distillation (MED) system. While for system with similar average effective heat transfer temperature, the temperature difference of hot side is the controlling parameter. And the energy cascade utilization principle shows the controlling attribute in MED thermodynamic system, as GOR is improved mainly due to utilization of the secondary energy and residual energy of the heating steam for preheating process.

Design, modeling, and thermo-economic optimization of an innovative continuous solar-powered hybrid desalination plant integrated with latent heat thermal energy storage

Ever-increasing needs for freshwater over the globe have made scientists investigate and find out viable solutions to overcome this concern. In line with this fact, multi-objective optimization of a solar-assisted hybrid desalination plant, which encompasses multi-effect distillation with thermal vapor compression and humidification-dehumidification units, was carried out during this study. Parabolic trough solar collectors play the role of a supplier of required input energy to run this system. In addition, there is a heating and storage unit, which includes a latent heat thermal storage tank to store the excess heat gained by solar collectors and an auxiliary boiler to assist in supplying the required heat for desalination units. Design parameters such as Parabolic trough solar collectors rows, phase change materials, number of multi-effect distillation system effects, motive steam flow rate, and last effect brine temperature of multi-effect distillation system which have the greatest impact on the performance of the system are selected. The non-dominated sorting genetic algorithm was employed to conduct multi-objective optimization. According to the optimization results, the total cost rate of the system and the sustainability index is 0.548 $/s and 1.54 respectively. In addition, adding the humidification-dehumidification unit to the system contribute to producing 0.5% more fresh water and brings 0.1% extra cost.

Thermoeconomic optimization of a solar-assisted supercritical CO2 Brayton cycle, organic Rankine cycle and multi-effect distillation system

In this paper, the simulation and optimization of a combined supercritical carbon dioxide Brayton cycle, an organic Rankine cycle and multi-effect distillation system driven by solar energy have been applied for power and freshwater generation. In this cycle, the solar collector, the central receiver reflected the sun’s light by heliostats, enters the storage system and then enters the fluid stream according to the amount of heat required to initiate the cycle. The working fluid of solar receiver is a mixture of the 60% NaNO3 and 40% KNO3, supercritical carbon dioxide is working fluid of the Brayton cycle and R600 is the working fluid of the organic Rankine cycle. The innovation of this article is using power and fresh water cycle without fuel consumption (with solar system and storage tanks). The simulation of this combined cycle was carried out by engineering equation solver software and energy and exergy efficiency changes in terms of different parameters are obtained. Then, a multi objective optimization of this system considering exergy efficiency and cost of system as objective functions is performed by genetic algorithm in Matlab software. Decision variables of the whole cycles are including Compressor inlet temperature, Turbine inlet temperature, Number of MED effect, The temperature of the water fed the desalination, Evaporator pinch point, Mass flow (Critical Carbon Dioxide), Turbine inlet pressure, Compressor inlet pressure and Pressure drop. The two objective functions optimization including exergy and economic parameters of this cycle is carried out for achieving reduction of electricity generation cost and increase of the exergy efficiency. The results of this optimization showed, the maximum exergy efficiency of this combined system is 61.78% and the minimum cost of electricity production is 0.2617 $/kWh. In this regard, the multiple effect distillation system produces 530.9 KgS freshwater in 15 stages.

Exergy and economic analysis of a novel integration of compressed air energy storage with multi-effect distillation and multi-stage flash systems

Potable water and power shortage are major concerns for the world community. Large-scale energy storage systems (ESSs) are a suitable solution for grid-scale energy storage, among which Compressed air energy storage (CAES) is a lead technology. Hybrid CAES-Desalination was introduced in previous investigations. The system can supply power and potable water simultaneously which can be a strategic system for dry and warm climates. Multi-stage flash (MSF) and multi-effect distillation (MED) are modeled and thoroughly investigated in this paper. The CAES system's exhaust hot air is the drive power of the distillation systems. Therefore, not only the CAES system's performance is improved but also a large amount of drinkable water is generated. The compressors and turbine's dissipated heat play as the main sources in the distillation unit in charging and discharging periods, respectively. This paper has mainly focused on the exergy and economic analyses of this integration and has worked on the optimum arrangement considering exergy and economic investigation. This paper has also studied the exergy and economic analyses of the CAES system's recuperator removal. The exergy analysis declares that the majority of the exergy destruction in desalination units happens at the first stage where the heat exchange occurs. It also shows that pressure regulator, HTES, and turbine are responsible for significant shares of exergy destruction in the CAES system. The economic assessment expresses 5.1 years for the payback time of the integrated system.

Thermo-economic assessment of forward osmosis as pretreatment to boost the performance and sustainability of multi-effect distillation for seawater desalination

This work presents the thermodynamic and techno-economic assessment of a forward osmosis – multi-effect distillation (FO-MED) system able to improve the thermal performance of the MED seawater desalination process and reduce its environmental impact. Energy, exergy and techno-economic analyses have been carried out to identify the best boundary conditions that enhance the process efficiency and water cost, predicting the scale formation with the Ryznar index. Results show that using FO pretreatment in a 100 m3/d MED plant of 8 effects at 65 °C allows increasing the heating steam temperature up to 100 °C and the number of effects to 16 without increasing the risk of scaling. This results in 44 % reduction of the specific thermal energy consumption and 21 % decrease in the specific heat transfer area. The volume of saline water rejected to the sea is reduced 40 % and the water footprint 36 %. The exergy analysis reveals that the MED is the component with the highest exergy destruction. Finally, the levelized cost of water of the FO-MED is higher (7.6 $/m3) than the standalone MED process (4.6 $/m3). If high-performing and cost-effective membranes are used, the product cost could be reduced 33 % (5.1 $/m3).