Multiple Effect Distillation Research Articles

An Integrated Planning Framework for Sustainable Water and Energy Supply

This study aims to reveal the economic, technical, and environmental impacts of different system configurations (centralized or decentralized, components, and technologies) on transition plans to achieve a higher share of renewable energy and desalination supplies for regions facing water scarcity. The main contribution of this research is the comparative evaluation of on-grid decentralized or distributed renewable-powered desalination systems for sustainable water and energy supply planning. Applying a novel nexus approach, an interactive multi-period planning model is developed to highlight synergies and to identify conflicts of planning both energy and water sectors at the same time as endogenous subsystems of one overall system. For studying these synergies in this study, the pace of technology deployment and the path of decline in overall costs are assumed to be a function of experience and knowledge as two-factor learning curves. Using data from 81 projects, the levelized cost and capacity factor of utility-scale photovoltaic and wind supplies in the Middle East were calculated. The results indicate that a scenario with a decentralized water sector and renewable-powered multiple-effect distillation technology has the best overall performance among the proposed scenarios.

Modeling, Simulation, and Optimization of a Solar-Based System of Desalination Using Humidification and Dehumidification

Solar desalination systems are characterized by low freshwater production compared with the usual techniques of mineral and salt removal from water. The usual methods include, but are not limited to, multi-stage flash distillation, multiple-effect distillation, vapor-compression desalination, and reverse osmosis. Solar desalination requires various modifications to make it more productive than the usual methods. The method is suitable for energy and environmental protection, making it the most effective system. The adjustments involve using the humidification and dehumidification principle (HD). The three configurations of the HD solar desalination system in this project are designed to accommodate variations in climate conditions and seasonal changes. Mathematical models are designed to test the workability of the system in an ideal environment. The models are based on universal fluid equations that regulate the functioning of each component of the system. After the model is designed, a regulation algorithm is designed based on the model. The simulation results show that the gain in freshwater production using a regulation algorithm is in the order of 33%.

Economic Assessment of the Possible Desalination Processes for the First Unit of Bushehr Nuclear Power Plant

The problem of ensuring the continuously growing needs of people for freshwater is becoming more acute in Iran. In order to resolve the serious water crisis in arid regions of the country near the Gulf, several desalination units have been used. However, most of the installed units of seawater desalination are based on fossil fuels consumption, which suffers from several disadvantages. According to the demand for clean energy to provide water and electricity, nuclear technology is gaining higher attention as compared to other energy sources. Bushehr NPP as the first commercial nuclear reactor in the country can be included the establishment of a large-scale desalination plant. In this study, after reviewing pertinent aspects of commercial desalination technologies, the history of seawater desalination in Iran is presented. This paper is focused on economic assessment of coupling the Bushehr NPP with different types of desalination systems, namely, Multiple Effect Desalination (MED), Multi-Stage Desalination (MSF), Reverse Osmosis (RO), and RO + MSF, RO + MED (hybrid methods) by using the Desalination Economic Evaluation Program (DEEP) package. By considering the obtained results and advantages of hybrid methods, RO + MED process with thermal/RO ratio of 0.7 and the total capacity of 150 000 m3/day is suggested.

Simulation analysis of flow velocity and liquid film of saline wastewater in falling film evaporation

It is an important way to promising treatment strategy to use the Multiple Effect Distillation(MED) system for saline wastewater treatment by numerical simulation. In the paper, the flow and heat transfer process’s difference of saline wastewater and pure water in falling film evaporator was simulated based on the volume of Fluid(VOF) multiphase flow model and the SIMPLE algorithm. Analysis results show that the temperature of pure water and saline wastewater reached 373.15 K at 226.3 mm from the evaporation pipe inlet. Compared with pure water, saline wastewater has slightly lower axial velocity, higher liquid film temperature and faster evaporation rate under the same conditions. In order to improve the heat transfer performance of saline wastewater in falling film evaporator, a comparison of tube diameter and length is made. At the same unit width flow, increasing tube diameter can improve heat transfer performance. In the tube diameter range of 35–50 mm, the heat transfer effect is best when the tube diameter is 50 mm. Under the condition of the same average circumferential flow and considering economy and efficiency, 1000 mm tube length is considered appropriate.

Energetic and exergetic performance analysis of a solar driven power, desalination and cooling poly-generation system

This paper presents a thermodynamic analysis of a poly-generation system powered by solar thermal energy using parabolic trough collectors. The proposed system consists of an organic Rankine cycle, a multiple effect distillation and an absorption cooling unit. The performance analysis of the solar system is conducted for different configurations: power generation only, cogeneration power and cooling, cogeneration power and desalination, and poly-generation. The effects of turbine inlet temperature and pump inlet temperature on the energetic and exergetic system performance as well as the net power output and total exergy loss of the system are examined. In addition, exergetic parameters, including system total exergy loss, fuel depletion ratio and improvement potential were analyzed. The study reveals that increasing the turbine inlet temperature increases the performance while it reduces the total exergy destruction rate of the system. The result of the study also shows that the two main sources of exergy destruction are the solar thermal collector and desalination unit; with 49.3% of the input exergy (76% of the total exergy loss) destructed in the collector while 9.6% of the inlet exergy (14.9% of the total exergy loss) is destroyed in the desalination system. The overall improvement potential of the system was found to be 64.8%.

Hybrid solar liquefied natural gas, post combustion carbon dioxide capture and liquefaction

Global energy consumption, in various forms, is rapidly increasing, owing to population and economic growth, and as a consequence energy-related CO2 emissions are dramatically rising. Hence, energy demand and mitigation of CO2 emissions are in urgent need of being dealt with. In this perspective paper, a novel approach, combining a system of simultaneous power cooling and fresh water is conducted an investigation by the exergetic and thermoeconomic approaches. The conventional energy storage methods are not able to perform under long-term condition as well as the possibility of transferring it to the considered location can be exorbitant. One of the leading methods for renewable energy storage is the simultaneous generation of liquid carbon dioxide and LNG using solar energy and heat loss. This integrated structure is composed of four sub-systems: Organic Rankine cycle system for power generation using parabolic trough collectors, using a mixture of ammonia and water as a working fluid in refrigeration cycle to produce liquefied natural gas (LNG) and liquid CO2, carbon dioxide capture process, multiple-effect distillation desalination. This hybrid system enjoys a capacity to produce 14.5 ton/h of LNG, 1.693 ton/h of desalinated water, and 2.611 ton/h of liquid CO2. The results of exergy analysis demonstrate that overall exergy efficiency of the process is 88.97%, and the component-based assessments also show that the highest exergy destruction is associated with towers (the average proportion of 39.23%), whilst the lowest exergy destruction ration is quantified for valves and drums (0.1352%). The economic appraisal results of the hybrid structure reveals that duration of return is 6 years, and the prime cost of the product is 24.2 cents/kg LNG. Moreover, sensitivity analysis is intended to discern the influential parameters of the developed hybrid arrangement.

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.

Theoretical analysis of a solar-powered multi-effect distillation integrated with concentrating photovoltaic/thermal system

A novel concentrated photovoltaic/thermal-multiple effect distillation system is proposed to simultaneously provide electricity, heating and freshwater for satisfying essential demands from isolated islands. Theoretical analysis under nominal condition is evaluated from perspective of energy and exergy and results indicate that electricity and heating are 353.2 and 432.9 kW with related energic and exergic efficiency of 0.2966 and 0.3635, 0.3177 and 0.0064. Produced freshwater is calculated as 0.7107 kg/s with gain output ratio of 6.59. Exergy destruction analysis exhibits detailed scenario of exergy consumption and solar collector field obtains the largest destroyed exergy, followed orderly by multiple effect distillation, heating unit and preheater. Parametric and sensitive analyses are performed to illustrate effects of parameters on system performance. Results indicate operating parameters exert remarkable impact on system efficiency. Efficiency of electricity is most sensitive to photovoltaic cell temperature, while that of heating and freshwater are most sensitive to coolant fluid temperature in comparison to the rest parameters. Primary energy and exergy saving ratio are conducted and results indicate proposed system is superior over individual systems with the same amount of electricity, heating and freshwater. In conclusion, this built system achieves a rational and efficient strategy to the comprehensive utilization of solar energy.

Systematic synthesis and integration of multiple‐effect distillation into overall processes: The case of biorefineries

AbstractChemical engineering is challenged by new chemistries that convert raw materials (biomass, biogenic waste) into chemicals through numerous promising, yet untested, chemical/biochemical reactions. Process and energy integration are essential to provide viable recommendations as downstream separation costs are often prohibitive to support the selected reactions. Distillation remains attractive for separation, whereas multiple‐effect distillation (MED) offers high energy savings, fully exploiting the potential to integrate separations with the background process. Whereas model‐based methods are plentiful for stand‐alone MED designs, integration of units with the background process is restricted by graphical or inspection methods, which are prone to miss optimality and impractical to use for high‐throughput screening. This work contributes with the introduction of an optimization approach that addresses challenges in allocation and integration of MED by considering methods to systematize design options and to automate decision‐making. The approach is illustrated in a real‐life biorefinery securing 70% savings under a small investment. © 2019 American Institute of Chemical Engineers

Hybrid molten carbonate fuel cell power plant and multiple-effect desalination system

In this work, an integrated system of simultaneous power generation, refrigeration and desalination cycle using a molten carbonate fuel cell, is developed and investigated. The process is simulated by HYSYS and MATLAB softwares. Molten carbonate fuel cell subsystem is the main power generation source, which produces 72000 kW power. Absorption refrigeration cycle with ammonia-water mixture as the working fluid is utilized for providing the required refrigeration. The required heat duty is supplied by exhaust heat from the power plant. This absorption refrigeration cycle can provide 32090 kW refrigeration with coefficient of performance of 0.4915. Four stage multiple-effect desalination subsystem produces 118944 kg/h fresh water. The proposed process is assessed by conventional exergy analysis method in order to evaluate performance of the process. Results of the energy analysis illustrate that overall thermal efficiency based on higher heating value (HHV) and lower heating value (LHV) are 54.37% and 60.32%, respectively. Results of the exergy analysis show that molten carbonate fuel cell with 91062 kW has the most exergy destruction rate. Also, generator has the most exergy efficiency (98.67%) and overall exergy efficiency of the process is 88.95%. Finally, a sensitivity analysis is applied on the major operating parameters of the system to demonstrate their effects on the performance of the process.

Study on the performance of a scale inhibitor during horizontal-tube falling film evaporation of seawater

Fouling on heat transfer surfaces is a severe problem and a complex phenomenon in multiple-effect distillation plants with horizontal tube falling film evaporators. In general, the scale on heat transfer surfaces is effectively prevented by adding scale inhibitors in large LT-MED seawater desalination plants. This paper presents an experimental study on the performance of a scale inhibitor with different seawater spray temperatures and salinities during falling film evaporation outside the horizontal tubes. The scale inhibitor is developed by the Institute of Water Treatment of Nanjing Tech University. Experiments are performed under the seawater temperature of 70°C, 80°C and 90°C and the salinity of 30g/kg, 60g/kg and 80g/kg. The dosage of the scale inhibitor is 6mg/L. The titanium tubes are used inside the evaporator and Dalian local seawater is selected as the working agent. The scale growing curves under different conditions are obtained through weighting the amount of the scale formed at different periods. The seawater temperature and salinity have a certain influence on the performance of the scale inhibitor during the horizontal-tube falling film evaporation. As the seawater spray temperature rises, the scale inhibition efficiency decreases. With the increase of salinity, the scale inhibition efficiency decreases.

Analyzing the Energy Consumption, GHG Emission, and Cost of Seawater Desalination in China

Seawater desalination is considered a technique with high water supply potential and has become an emerging alternative for freshwater supply in China. The increase of the capacity also increases energy consumption and greenhouse gases (GHG) emissions, which has not been well investigated in studies. This study has analyzed the current development of seawater desalination in China, including the capacity, distribution, processes, as well as the desalted water use. Energy consumption and GHG emissions of overall desalination in China, as well as for the provinces, are calculated covering the period of 2006–2016. The unit product cost of seawater desalination plants specifying processes is also estimated. The results showed that 1) The installed capacity maintained increased from 2006 to 2016, and reverse osmosis is the major process used for seawater desalination in China. 2) The energy consumption increased from 81 MWh/y to 1,561 MWh/y during the 11 years. The overall GHG emission increase from 85 Mt CO2eq/y to 1,628 Mt CO2eq/y. Tianjin had the largest GHG emissions, following are Hebei and Shandong, with emissions of 4.1 Mt CO2eq/y, 2.2 Mt CO2eq/y. and 1.0 Mt CO2eq/y. 3) The unit product cost of seawater desalination is higher than other water supply alternatives, and it differentiates the desalination processes. The average unit product cost of the reverse osmosis process is 0.96 USD and 2.5 USD for the multiple-effect distillation process. The potential for future works should specify different energy forms, e.g. heat and power. Alternatives of process integration should be investigated—e.g. efficiency of using the energy, heat integration, and renewables in water desalination, as well as the utilization of total site heat integration.

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.

A Demonstration of High Temperature MED-TVC Desalination Technology in the Gulf Area

This work focuses on a multiple effect desalination system with thermal vapor compressor (MED-TVC) operating at a top brine temperature (TBT) of 85°C which is significantly above the common operation temperatures of conventional MED-TVC systems, limited to a range below 70°C mainly due to scale risk. Such increase in TBT would enhance the production and system economics. A pilot plant installed at the Desalination Technologies Research Institute (DTRI) of the Saline Water Conversion Corporation (SWCC) in Jubail, Saudi Arabia was operated at the TBT of 85°C over a 5-month test period. Visual inspection of tube bundles after the test, in conjunction with chemical scale analysis showed that scaling was limited to a soft thin film scale, which was easily removed by flushing with water, which confirmed a low fouling potential analyzed from operation data. Techno-economic analysis of the MED-TVC system operating at a TBT of 85°C, indicated up to 34% reduction in steam consumption and up to 16% reduction in the levelized cost of water (LCOW), when compared with a MED-TVC unit operating at a conventional TBT of 65°C. Accordingly, the high temperature MED-TVC systems operating at a TBT of 85°C can be considered as a financially competitive and technologically reliable desalination option for the Gulf area which has challenging seawater characteristics.

Thermo-economic modeling and multi-objective optimization of multiple-effect desalination integrated with an organic Rankine cycle

Thermo-economic modeling and multi-objective optimization of multiple-effect desalination integrated with an organic Rankine cycle

New considerations for modelling a MED-TVC plant under dynamic conditions

The multiple-effect distillation (MED) technology is nowadays the most promising desalination process to be coupled with variable heat sources, thus leading to a more sustainable way to produce water. In order to prove the potential of this, it is of major interest to develop powerful modelling tools to predict the performance of this coupling. Only a few models have been presented so far. They show promising results but were based on some simplifying assumptions and non-physical constraints that could limit the analysis of the dynamic behaviour of a MED plant. This paper presents new considerations for the dynamic modelling of a MED plant associated with a thermal vapour compression unit, starting from a previous work “A dynamic model for MED-TVC transient operation”. After several improvements, this model is now more representative of the real operating modes of a MED-TVC plant by considering real process inputs. This paper also highlights the importance of accurately modelling the interconnection between effects, the evaporation and condensation processes and the other components, such as the pre-heaters. Here is also presented a control strategy for operating a MED plant under dynamic conditions. Indeed, when a perturbation occurs in the motive steam pressure, it is possible to stabilize the whole plant by a simultaneous variation in the intake seawater mass flow rate at the final condenser. The model has been validated in steady-state conditions with experimental data from a MED-TVC plant operated in Trapani (Sicily) and was used to perform dynamic simulation to prove the feasibility of operating a MED-TVC plant under dynamic conditions, which is a major step toward proving the possibility of a coupling with renewable energies.

Investigation of a hybrid water desalination, oxy-fuel power generation and CO2 liquefaction process

In this paper, an integrated liquefied natural gas (LNG) production process, carbon dioxide separation and liquefaction, and fresh water production is proposed and analyzed. The hybrid system consists of three sections: power and heat generation by the process of combustion with pure oxygen, natural gas liquefaction with a two-stage refrigeration cycle (absorption refrigeration cycle and multi-component refrigerant), and multiple-effect distillation (MED) desalination. This integrated process produce 593.3 ton/h LNG, 84.62 ton/h carbon dioxide, and 74.58 ton/h fresh water. Exergy analysis shows that the highest exergy destruction is related to the shell and tube heat exchangers, which is about 38.8% and the lowest exergy destruction is related to the air coolers, 0.84%. Integrated process has an overall electrical efficiency (LHV Base) of 36.3%, a specific power of 0.179 kWh/kg LNG. Also the amount of energy consumed for producing carbon dioxide is 0.005 kWh/kg CO2, and gained output ratio (GOR) of 2.87 is achieved by three-stage MED desalination. A sensitivity analysis is done to investigate and identify the important parameters affecting the integrated process performance.

Optimal Multiscale Capacity Planning in Seawater Desalination Systems

The increasing demands for water and the dwindling resources of fresh water create a critical need for continually enhancing desalination capacities. This poses a challenge in distressed desalination network, with incessant water demand growth as the conventional approach of undertaking large expansion projects can lead to low utilization and, hence, low capital productivity. In addition to the option of retrofitting existing desalination units or installing additional grassroots units, there is an opportunity to include emerging modular desalination technologies. This paper develops the optimization framework for the capacity planning in distressed desalination networks considering the integration of conventional plants and emerging modular technologies, such as membrane distillation (MD), as a viable option for capacity expansion. The developed framework addresses the multiscale nature of the synthesis problem, as unit-specific decision variables are subject to optimization, as well as the multiperiod capacity planning of the system. A superstructure representation and optimization formulation are introduced to simultaneously optimize the staging and sizing of desalination units, as well as design and operating variables in the desalination network over a planning horizon. Additionally, a special case for multiperiod capacity planning in multiple effect distillation (MED) desalination systems is presented. An optimization approach is proposed to solve the mixed-integer nonlinear programming (MINLP) optimization problem, starting with the construction of a project-window interval, pre-optimization screening, modeling of screened configurations, intra-process design variables optimization, and finally, multiperiod flowsheet synthesis. A case study is solved to illustrate the usefulness of the proposed approach.

Parametric study of an integrated organic Rankine/reverse Brayton refrigeration cycle and multiple-effect desalination unit

Parametric study of an integrated organic Rankine/reverse Brayton refrigeration cycle and multiple-effect desalination unit

Role of Seawater Desalination in the Management of an Integrated Water and 100% Renewable Energy Based Power Sector in Saudi Arabia

This work presents a pathway for Saudi Arabia to transition from the 2015 power structure to a 100% renewable energy-based system by 2050 and investigates the benefits of integrating the power sector with the growing desalination sector. Saudi Arabia can achieve 100% renewable energy power system by 2040 while meeting increasing water demand through seawater reverse osmosis (SWRO) and multiple effect distillation (MED) desalination plants. The dominating renewable energy sources are PV single-axis tracking and wind power plants with 243 GW and 83 GW, respectively. The levelised cost of electricity (LCOE) of the 2040 system is 49 €/MWh and decreases to 41 €/MWh by 2050. Corresponding levelised cost of water (LCOW) is found to be 0.8 €/m3 and 0.6 €/m3. PV single-axis tracking dominates the power sector. By 2050 solar PV accounts for 79% of total electricity generation. Battery storage accounts for 41% of total electricity demand. In the integrated scenario, due to flexibility provided by SWRO plants, there is a reduced demand for battery storage and power-to-gas (PtG) plants as well as a reduction in curtailment. Thus, the annual levelised costs of the integrated scenario is found to be 1–3% less than the non-integrated scenario.