Multiple Effect Distillation Desalination Research Articles

Impact of phosphonium-based ionic liquid on the corrosion control of aluminum alloy AA5052 in MED desalination plants during acid cleaning process

Aluminum alloy AA5052 has recently been chosen to replace titanium tubes in desalination plants' multiple effect distillation (MED) units. The high corrosion rate of AA5052 during the acid cleaning process to remove the scale layer, on the other hand, remains a significant challenge. In this paper, we describe for the first time the use of an ionic liquid, tributyl(ethyl)phosphonium diethyl phosphate (Ph-IL), as a corrosion inhibitor for aluminum alloy AA5052 during the acid cleaning process with a 4% sulfamic acid solution. Remarkably, the addition of ionic liquid Ph-IL to sulfamic acid results in enhanced corrosion resistance of AA5052 with the efficiency reached to 93.0%. Through the adsorption of both the cationic and anionic parts of the ionic liquid, Ph-IL molecules can cover the anodic and cathodic sites. Furthermore, the Ph-IL forms a significant activation energy barrier against the corrosion process. In addition, SEM-EDX analysis confirms the formation of protective layers of Ph-IL molecules on the surface of AA5052. This finding may be helped in the expansion of the use of many ionic liquids with their new properties in the field of desalination.

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.

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.

Exergetic and exergoeconomic analysis of a renewable polygeneration system and viability study for small isolated communities

A great interest has recently arisen for the sustainable supply of energy and fresh water, due to the growing demand from developing countries. Facing this demand by traditional technologies implies evident risks related with the high cost of fossil fuels and their environmental impact. Then, alternative solutions based on the use of renewable sources and innovative technologies must be considered. In this paper a renewable polygeneration system is examined, which includes a solar field based on parabolic trough photovoltaic/thermal collectors, a biomass heater, an absorption chiller and a Multiple Effect Distillation desalination unit.Plant operation under dynamic conditions has been analysed in previous papers; in this paper an exergetic and exergoeconomic analysis is carried out. The exergetic analysis is intended to identify the steps that mostly affect the overall plant exergy efficiency, so as to propose possible improvements. The exergoeconomic cost accounting is aimed at assigning a monetary value to each energy or material flow, thus providing a rational basis for price assignment. Both the exergetic and exergoeconomic analyses are applied to integral values of energy flows, comparing the results obtained in the summer and winter season. Finally, economic viability of the system in different context scenarios is discussed.

Techno-economic analysis of MED and RO desalination powered by low-enthalpy geothermal energy

Utilizing low enthalpy geothermal resources in various applications, including desalination, has triggered continuously growing interest in the past decade. This work offers a preliminary techno-economic evaluation of coupling a low-enthalpy geothermal resource, commonly found in regions such as the Arabian Gulf countries, and a suitable desalination technology. The desalination processes chosen, multiple effect distillation (MED) and reverse osmosis (RO), were designed as integrated energy–water systems and were compared and assessed in terms of their levelized cost of water produced. It was found that geothermal RO could potentially be a more cost-effective option for seawater geothermal desalination in the Gulf Cooperation Council (GCC) countries, based on our model results. A number of parameters, which can potentially alter the results of the analysis, were chosen to investigate their effect on the LCOW of the proposed schemes. These parameters include feed water quality, operational lifetimes of both the geothermal and desalination systems, quality of the geothermal resource, cost of well-drilling and finally, reinjection temperature of the utilized geofluid. By varying their values, the robustness of our initial model results was assessed.

Impacts of tube bundle arrangement and feed flow pattern on the scale formation in large capacity MED desalination plants

The aim of the present work is to evaluate the effect of tube bundle arrangement and the seawater feed distribution on the dry zone and scale formation in the large sized Multiple Effect Distillation (MED) evaporator.A mathematical model of the seawater feed distribution is developed and validated for a triangular pitch tube bundle of MED evaporator. The developed model includes CaCO3 scale formation and CO2 release. The simulation results showed that the dripping seawater flow rate on the column based on the 2nd row is lower than that of the 1st row. Consequently, the wetting rate of the tubes in the column based on the 2nd row is less than that based on the 1st row. This explains why the tubes based on the 2nd row experience more CaCO3 scale deposit than that based on the 1st row.The simulation results showed that increasing the feed seawater to twice that of the original flow will reduce the scale thickness by 15%. Increasing the tube pitch by twice the diameter will reduce the scale thickness by 30%. The combined effect of modified feed flow and increase in the tube pitch would significantly reduce the scale precipitation thickness.

Application of field synergy principle for optimization fluid flow and convective heat transfer in a tube bundle of a pre-heater

The big problems facing solar-assisted MED (multiple-effect distillation) desalination unit are the low efficiency and bulky heat exchangers, which worsen its systematic economic feasibility. In an attempt to develop heat transfer technologies with high energy efficiency, a mathematical study is established, and optimization analysis using FSP (field synergy principle) is proposed to support meaning of heat transfer enhancement of a pre-heater in a solar-assisted MED desalination unit. Numerical simulations are performed on fluid flow and heat transfer characteristics in a circular and elliptical tube bundle. The numerical results are analyzed using the concept of synergy angle and synergy number as an indication of synergy between velocity vector and temperature gradient fields. Heat transfer in elliptical tube bundle is enhanced significantly with increasing initial velocity of the feed seawater and field synergy number and decreasing of synergy angle. Under the same operating conditions of the two designs, the total average synergy angle is 78.97° and 66.31° in circular and elliptical tube bundle, respectively. Optimization of the pre-heater by FSP shows that in case of elliptical tube bundle design, the average synergy number and heat transfer rate are increased by 22.68% and 35.98% respectively.

Economic evaluation of nuclear desalination systems

This paper describes the detailed analyses of power and water costs for several nuclear reactors operating in a cogeneration mode (e.g. the 900 MWe French PWR, the advanced PWR, AP-600, the gas cooled, high temperature reactors, such as the GT-MHR and the PBMR) and coupled to two main desalination processes, e.g. multiple effect distillation (MED) and reverse osmosis (RO). Results for a specific site in a south Mediterranean country, Tunisia, are presented. It is shown in particular how the desalination costs could be further reduced by utilising waste heat from the GT-MHR and the PBMR type of reactors. Comparisons are made with desalination costs from the cheapest of fossil energy based systems, namely the 600 MWe gas turbine, combined cycle plant (CC-600) in various cost scenarios and in conditions specific to the selected site. Calculations are performed using the DEEP-3 software, recently developed by the International Atomic Energy Agency (IAEA). In the light of the results obtained, it is concluded that: a) Compared to the CC-600 system, all nuclear desalination options lead to much lower power production costs, as long as gas prices are ≥150 $/toe, and for discount rates of 5, 8 and 10%. Thus for example, at 8% discount rate and a gas price of 40 $/bbl (291 $/toe) for the CC-600, the kWh cost of the PWR-900 is 56% lower. Under the same conditions, that of the AP-600 is 49% lower; b) If the economic performances of the GTMHR and the PBMR, as announced by their respective developers, are indeed true than the GT-MHR would lead to the lowest kWh costs of all options considered. The kWh cost of the PBMR would be comparable to the large sized PWR-900; c) At 8% discount rate, the MED desalination cost by the PWR-900 and the AP-600 are respectively 46 and 42% lower than the corresponding cost by the CC-600 plant; d) The lowest costs with the MED plants are obtained by the GT-MHR and PBMR, utilising virtually free waste heat. Compared to the cost by the CC-600 + MED system, these reactors give desalination costs which are respectively 62% and 44% lower; e) For all energy sources, the desalination cost with the RO process is lower than with the MED process.