Multi-effect Distillation Desalination System Research Articles

Thermo-Environ-Economic Optimization of an Integrated Combined-Cycle Power Plant Based on a Multi-objective Water Cycle Algorithm

The integration of power plants and desalination systems has attracted increasing attention over the past few years as an effective solution to tackle sustainable development and climate change issues. In this light, this paper introduces a novel modelling and optimization approach for a combined-cycle power plant (CCPP) integrated with reverse osmosis (RO) and multi-effect distillation (MED) desalination systems. The integrated CCPP and RO–MED desalination system is thermodynamically modelled utilizing MATLAB and EES software environments, and the results are validated via Thermoflex software simulations. Comprehensive energy, exergic, exergoeconomic, and exergoenvironmental (4E) analyses are performed to assess the performance of the integrated system. Furthermore, a new multi-objective water cycle algorithm (MOWCA) is implemented to optimize the main performance parameters of the integrated system. Finally, a real-world case study is performed based on Iran's Shahid Salimi Neka power plant. The results reveal that the system exergy efficiency is increased from 8.4 to 51.1% through the proposed MOWCA approach, and the energy and freshwater costs are reduced by 8.4% and 29.4%, respectively. The latter results correspond to an environmental impact reduction of 14.2% and 33.5%. Hence, the objective functions are improved from all exergic, exergoeconomic, and exergoenvironmental perspectives, proving the approach to be a valuable tool towards implementing more sustainable combined power plants and desalination systems.

Exergy optimization of nuclear-solar dual proposed power plant based on GWO algorithm

In this work, an innovative design of an optimized Nuclear-Solar hybrid power plant with a desalination system has been performed. The NuScale small modular reactor and Concentrated Solar Power (CSP) have been used for cogeneration of electricity and fresh water. Solar heat is used to increase the temperature of the steam and to utilize for multi-effect distillation desalination system with thermo vapour compressor (MED-PVC). Continuous solar superheating is provided by molten salt-based thermal energy storage (TES). In this analysis, the Grey Wolf Optimizer (GWO), after comparison with other algorithms, has been applied to obtain optimal exergy destruction for a hybrid plant. During optimization, all effective parameters, such as turbine inlet temperature, net electric power, and total heat input, are calculated with Thermoflex. Using this optimized hybrid method, electrical efficiency has been increased from 27.03 % to 30.18 %, and fresh water is provided for the Makran population. The results prove that using solar energy to produce freshwater (82.11 kg/s) can reduce carbon dioxide emissions by 779.1 tons/year. In addition to carbon dioxide, large amount of other pollutants such as SO2, NOx, and non-volatile organic compounds emitted by fossil fuels are removed.

Minimum motive steam consumption on full cycle optimization with cumulative fouling consideration for MED-TVC desalination system

Multi-effect distillation (MED) desalination system always faces the inevitable fouling problem, which leads to a decrease in fresh water production and restricts its long-term efficient operation. This study focuses on improving the system's operation benefits in the full cycle. Firstly, an asymptotic model for fouling accumulation is added to a MED-TVC model, which takes into account the influence of operating conditions on the fouling rate. Subsequently, the impact of fouling accumulation on the operating state of the system is analyzed in the whole cycle, indicating the decrease of operating benefits. Finally, the full cycle operation optimization method is applied for the purpose of reducing motive steam consumption as well as meeting fresh water demand using control vector parameterization strategy. The result shows a significant reduction in motive steam consumption while maintaining fresh water production capacity, which confirms that full cycle optimization has a considerable effect on dealing with fouling problem in MED desalination systems.

Energy and exergy analysis of a spray-evaporation multi-effect distillation desalination system

The saline, thermal, and chemical pollution associated with the direct discharge of concentrated brine from various desalination processes are the main negative environmental impacts of seawater desalination. Thus, a novel spray-evaporation multi-effect distillation (SE-MED) desalination system is proposed to eliminate wastewater discharges and achieve zero liquid discharge, in which the spray evaporation technology was adopted for the recovery of freshwater and salts from the brine concentrate disposal. A three-level energy recovery process was adopted in the SE-MED desalination system to improve the thermal efficiency and freshwater productivity. A comprehensive thermodynamic study for the integrated system was carried out to investigate its parametric sensitivity. A three-effect SE-MED desalination system with effects temperature difference of 4.5 °C and heat source temperature of 500 °C was prove suitable for the integrated SE-MED system to balance the system performance, capital cost, and system reliability. Exergy analysis was also conducted for a better understanding of the SE-MED system. The highest exergy destruction (67.76%) occurred in the spray evaporation tank. The useful exergy efficiency was 1.13% and a large amount of surplus exergy is wasted in the process of achieving ZLD.

Effects of preheater arrangement on performance of MED desalination system

Preheating seawater before it flows into the evaporators in multi-effect distillation (MED) system could improve the system performance. The number and position of the preheaters play an important role in the thermal performance. A comparison of systems with different numbers and positions of preheaters was performed. On the premise of the constant distillate production, taking the 10-effect evaporation desalination system as an example, the effects of preheater arrangement on the gained output ratio (GOR) of the system and the total heat transfer area of the evaporators (Atotal) were analyzed. By adopting the equal temperature difference design method, a mathematical model was developed for the system performance analysis under different preheater arrangements. The results indicated that the GOR and Atotal are changed obeying some rules when the position of the preheater changes in one evaporator group or in different evaporator groups. In addition, with the increase in the number of preheaters, the mean GOR rises, the mean Atotal grows and the promotion space of system performance improves. The research provides a certain guiding direction for the optimization of desalination devices.

Techno-economic assessment of bifacial photovoltaic and geothermal based multigeneration system for cleaner communities

This study proposes an integrated renewable energy based multigeneration system for fresh water, heating, electricity and fuel requirements of a community with a greenhouse in Gokcebayir, Canakkale, Turkey. Solar and geothermal sources are used as renewable energy resources while sea source is employed in the desalination process to produce fresh water. The bifacial photovoltaic and hydrogen subsystems are integrated to transfer excess daytime photovoltaic electricity to hydrogen gas as an energy storage medium that is employed as hydrogen fuel for hydrogen vehicles and proton-exchange membrane fuel cell for electricity production during the lack of solar radiation. Geothermal energy system is integrated with photovoltaic subsystem and hydrogen subsystem to create more reliable energy system due to its continuous characteristic, and to provide various outputs such as heating via residential heat pump and fresh water via multi effect distillation desalination system. The bifacial photovoltaic modules are employed in two novel arrays which are the top of the greenhouse and an enhanced albedo field 1.3 MWp photovoltaic plant. The pitch distance and height determinations are made specifically for bifacial photovoltaic plant arrays in terms of solar electricity gain. The proposed bifacial photovoltaic plant is analyzed, modeled and integrated with hourly electric load, thermal load and hydrogen subsystem. The proposed system supplies electricity to a community with 150 households and a greenhouse. 1642 MWh annual electricity demand and 485 MWh annual thermal load is met at the 0.058$/kWh levelized cost of energy with 7938 kg annually produced hydrogen and 14551 kg daily fresh water. The proposed system poses 4.29% internal rate of return where 0.21% electricity could not meet due to the insufficient electricity availability especially during winter months at 39°47′N latitude, 26°15′E longitude.

Optimisation of multi effect distillation based desalination system for minimum production cost for freshwater via repetitive simulation

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.

Impact of Cumulative Fouling Characteristics on Full-cycle Operation Optimisation of Multi-effect Distillation Desalination System

Cumulative fouling characteristics are often overlooked by researchers when optimising the operation of multi-effect distillation seawater desalination system. In order to analyse the influence of fouling cumulation on the optimisation operation, an eight-effect dynamic model for multi-effect distillation with thermal vapour compression (MED-TVC) seawater desalination system has been established and the cumulation of fouling has been considered in this model. Operation parameters of the eight-effect MED-TVC desalination system have been optimised repeatedly at different times (namely at different levels of fouling cumulation) throughout the full-cycle. Results indicate that the cumulation of fouling will gradually let the system deviate from the optimal operation condition, resulting in decrease in fresh water production, and operation re-optimisation at different times gets different results, which can efficiently reduce the influence of fouling and obtain better operational benefits. This work concludes that fouling cumulation has a big impact on operation optimisation of MED-TVC systems, and it is necessary to timely re-optimise operation parameters.

Study on a novel spray-evaporation multi-effect distillation desalination system

As the negative environmental impacts associated with disposal of brine concentrate become increasingly recognized and attracting public attention, zero liquid discharge (ZLD) is emerging as a technique for desalination plants to minimize waste and recover resources. In this study, an innovative concept of a spray-evaporation multi-effect distillation (SE-MED) system is proposed to achieve ZLD, in which a spray evaporation tank (SET) is used to fully split brine disposal for water and salts. A steady-state mathematical model for the SE-MED process is developed under several simplification assumptions. A five-effect forward SE-MED system with a bleed fraction of 20% is designed based on the mathematical model. A simplified vaporization model is also developed to describe the motion and evaporation behavior of a single water droplet in the SET. The calculated trajectories of the droplet provide guidance to the SET design. Two-phase simulations are performed to provide further insight into spray evaporation performance inside the SET. Results indicate that a high evaporation efficiency of 99.86% is achievable by the modified SET. In addition, the application of the Reaction Engineering Approach in the hindered spray evaporation simulation is discussed and validated for future study.

Modeling analysis on solar steam generator employed in multi-effect distillation (MED) system

Recently the porous bilayer wood solar collectors have drawn increasing attention because of their potential application in solar desalination. In this paper, a thermodynamic model has been developed to analyze the performance of the wood solar collector. A modeling analysis has also been conducted to assess the performance and operating conditions of the multiple effect desalination (MED) system integrated with the porous wood solar collector. Specifically, the effects of operating parameters, such as the motive steam temperature, seawater flow rate, input solar energy and number of effects on the energy consumption for each ton of distilled water produced have been investigated in the MED desalination system combined with the bilayer wood solar steam generator. It is found that, under a given operating condition, there exists an optimum steam generation temperature of around 145°C in the wood solar collector, so that the specific power consumption in the MED system reaches a minimum value of 24.88 kWh/t. The average temperature difference is significantly affected by the solar heating capacity. With the solar capacity increasing from 50 kW to 230 kW, the average temperature difference increases from 1.88°C to 6.27°C. This parametric simulation study will help the design of efficient bilayer wood solar steam generator as well as the MED desalination system.

Exergy Analysis and Optimization of Multi-effect Distillation with Thermal Vapor Compression System of Bandar Abbas Thermal Power Plant Using Genetic Algorithm

Multi-effect distillation desalination system with thermal vapor compression is one of the systems of producing fresh water based on distillation desalination. This type of desalination system is one of the most appropriate and economic types of desalination systems for low to high capacities of seawater and brackish water in which evaporation and distillation have occurred in a vacuum and in temperature below 70 °C. This research provides a mathematical model in the steady-state conditions for multi-effect distillation desalination system with thermal vapor compression in Bandar Abbas thermal power plant in south of Iran. The genetic algorithm is used for maximizing the produced fresh water and minimizing total exergy destruction rate. Exergy analysis shows that the thermo-compressor and effects are the main sources of exergy destruction in the system (more than 80%). The actual operating data in summer and winter were used for the exergy destruction study. The results show that the exergy destruction in winter is more than summer. Parametric analysis for studying the effects of key parameters shows that increasing the top brine temperature leads to increase in the total exergy destruction of the system. The optimization of the system with two-target genetic algorithm causes distillate production to increase by 16.62%, and the total exergy destruction rate decreases by 3.58%.

Design and numerical investigation of an adaptive nozzle exit position ejector in multi-effect distillation desalination system

Few investigations have been conducted on an ejector that has an auto-tuning capability to regulate the performance of a multi-effect distillation-thermal vapour compression (MED-TVC) desalination system with the variation of operating conditions. In this study, an adaptive nozzle exit position (ANXP) ejector was first proposed to enhance ejector performance by self-adjusting the position of the primary nozzle with the change of primary pressure. A computational fluid dynamics (CFD) model was established and validated using experimental data. Simulation results indicate that there is an optimum NXP range of 43 mm–70 mm for an ejector to achieve its highest performance. The maximum increase of the entrainment ratio is 35.8% compared to that at an NXP of −30 mm. The secondary flow rate first increases and then decreases while the primary flow rate remains unchanged with the increase of the NXP in fixed working conditions. Furthermore, a correlation between optimum NXP and primary pressure was developed to provide designing parameters for the ANXP ejector.

Experimental study on a new method for improving the performance of thermal vapor compressors for multi-effect distillation desalination systems

A new method is proposed in this study to improve the entrainment performance of thermal vapor compressors (TVCs) that are widely used in multi-effect distillation (MED) desalination systems by preheating entrained vapor. In order to confirm its effectiveness and study the influences of the entrained vapor superheat on the TVC entrainment ratio, a four-effect-parallel-flow MED-TVC experimental system was set up. Hot water from a solar heating system and steam from an electric boiler were used as heat source of the entrained vapor preheating, respectively. The preliminary experimental results show that the entrained vapor preheating could greatly increase the TVC entrainment ratio and the TVC entrainment ratio increases with the entrained vapor superheat. Due to the poor performance of the TVC used in this study, further verification experiments of the proposed method need to be conducted in future work.

Experimental benchmarks and simulation of GAMMA-T for overcooling and undercooling transients in HTGRs coupled with MED desalination plants

Abstracts The nuclear desalination based on the high temperature gas-cooled reactor (HTGR) with gas turbomachinery and multi-effect distillation (MED) is attracting attention because the coupling system can utilize the waste heat of the nuclear power system for the MED desalination system. In previous work, KAIST proposed the new HTGR + MED coupling scheme, evaluated desalination performance, and performed cost analysis for the system. In this paper, in order to confirm the safety and the performance of the coupling system, we performed the transient analysis with GAMMA-T (GAs Multidimensional Multicomponent mixture Analysis–Turbomachinery) code for the KAIST HTGR + MED systems. The experimental benchmarks of GAMMA-T code were set up before the transient analysis for several accident scenarios. The GAMMA-T code was well validated against steady state and transient scenarios of the He–Water test loop such as changes in water mass flow rate and water inlet temperatures. Then, for transient analysis, the GTHTR300 was chosen as a reference plant. The GTHTR300 + MED systems were made, based on the KAIST HTGR + MED coupling scheme. Transient analysis was performed for three kinds of accidents scenarios: (1) loss of heat rejection through MED plant, (2) loss of heat rejection through heat sink, and (3) overcooling due to abnormal cold temperature of seawater. In all kinds of accident scenarios, maximum peak fuel temperatures were well below than the fuel failure criterion, 1600 °C and the GTHTR300 + MED system could be operated continuously and safely. Specially, in the loss of heat rejection through MED plants, which is related with the failure of the MED plant, the performance reduction was negligible because the reactor thermal power and the generator power decreased by only 1% and 2%, respectively. As the KAIST coupling scheme uses the double stage precooler, it turns out to have lower potential of total loss of heat rejection accidents than the single purpose nuclear power system using a single stage precooler.

Thermal coupling of HTGRs and MED desalination plants, and its performance and cost analysis for nuclear desalination

The nuclear desalination based on the high temperature gas-cooled reactor (HTGR) with gas turbomachinery and multi-effect distillation (MED) has been drawing attention, because it can utilize waste heat for desalination. In this paper, research objectives are as follows: (a) proposing an optimal design of HTGR+MED systems and (b) performance and cost analysis for the HTGR+MED system. In the first step, the KAIST coupling scheme was proposed. It uses printed circuit heat exchangers (PCHE) instead of conventional heat exchangers without any intermediate loop and has the independent structure between MED plants and heat sink. In the second step, the KAIST version of DEEP (K-DEEP) code was developed for more practical cost and performance analysis of the KAIST HTGR+MED system. The desalination performance and cost analysis with the K-DEEP code were performed for the Gas Turbine-Modular Helium cooled Reactor (GT-MHR)+MED system. The maximum desalted water production capacity increases by 258% compared to the production capacity using the previous coupling scheme. The desalted water cost could be reduced by 9.0%. Finally, from the comparison of various nuclear MED desalination systems we confirmed the potential of the KAIST HTGR+MED system that may be one of the best desalination options in mass production of desalted water.

Thermoeconomic optimization of a hybrid pressurized water reactor (PWR) power plant coupled to a multi effect distillation desalination system with thermo-vapor compressor (MED-TVC)

Thermoeconomic optimization of a typical 1000 MW Pressurized Water Reactor (PWR) nuclear power plant coupled to a Multi Effect Distillation (MED) desalination system with thermo-vapor compressor (TVC) is performed. A thermodynamic modeling based on the energy and exergy analysis is performed while economic modeling is developed based on the Total Revenue Requirement (TRR) method. The objective function based on the thermoeconomic analysis is obtained. The proposed cogeneration plant, for simultaneous production of power and fresh water, including sixteen decision variables is proposed for thermoeconomic optimization in which the goal is minimizing the cost of system product (including the cost of generated electricity and fresh water). The optimization process is performed using a stochastic/deterministic optimization approach namely as Genetic Algorithm. It is found that thermoeconomic optimization aims at reduction of sub-components total costs by reducing either the cost of inefficiency or the cost of owning the components, whichever is dominant. For some components such as evaporators, the improvement is obtained by reducing the owning cost of the sub-system at the cost of reduction of the thermodynamic efficiency. For components like as TVC + de-superheater, improvement is achieved by increasing the thermodynamic efficiency or decreasing the inefficiency cost.

Thermoeconomic optimization of multi effect distillation desalination systems

Thermoeconomic optimization of a multi effect distillation (MED) desalination system with thermo-vapor compressor (TVC) is performed. A model based on the energy and exergy analysis is presented here. An economic model of the system is developed according to the Total Revenue Requirement ( TRR) method. The objective functions based on the thermodynamic and thermoeconomic analysis are developed. The proposed multi effect distillation system including six decision variables is considered for optimization. A stochastic/deterministic optimization approach known as genetic algorithm is utilized as an optimization method. This approach is applied to minimize the cost of the system product (fresh water).

Coupling of nuclear heating reactor with desalination process

A seawater desalination plant using a nuclear heating reactor (NHR) coupled with the multi-effect distillation (MED) process was developed by the Institute of Nuclear Energy Technology, Tsinghua University, China. The seawater desalination plant was designed to supply potable water demand to some coastal location or island where both fresh water and energy sources are severely lacking. The NHR design possesses intrinsic and passive safety features, which was demonstrated by the NHR-5 experiences. The intermediate circuit and steam circuit were designed as the safety barriers between the NHR and MED desalination systems. With the power range of the heating reactor within 10 to 200 MWt, the desalination plant could provide 8,000 to 160,000 m 3/d of potable water of appropriate quality. The design concept and parameters, safety features, and comparative investigation of coupling schemes are presented in the paper.