EXERGY AND THERMO-ECONOMIC ANALYSIS OF MODIFIED MSF DESALINATION PLANTS CONFIGURATIONS
This paper presents the exergy and thermo-economic analysis of a Modified MSF thermal Desalination Plant Configurations. The modified configuration is based on the filed patent of Fath, [1] for MSF with inter-stage brine re-heater(s). The brine reheaters, placed at different inter-stages, are introduced to increase the unit flashing range. The Visual Desalination and Simulation (VDS) package, developed by authors [2], is used as a tool of analysis. The results are compared with the basic 5000 m3/day MSF configuration of Eoun Mousa (Egypt), [3]. An MSF process flow-sheet is developed of basic MSF desalination plant with interstage re-heater(s). The results showed that the use of reheating in the MSF desalination configuration reduces the unit water cost by 5.8 % and increases the distillate product by 3.7 % than that of the conventional MSF desalination plant. Using two re-heaters in the MSF flow-sheet cause a reduction in the unit cost of 6 % and increase in the distillate product of 5.2 % at the expense, of the performance ratio. Using re-heater in by pass of cooling stream (MSF_RH_CS) configuration shows 12.5 % increase in the distillate water product over that of the conventional MSF however, the performance ratio decreased. As a result, the water cost becomes higher than the conventional MSF by 3 %. The use of the re-heater in the MSF_M flow-sheet reduces the unit water cost by 9 % than that of the conventional MSF. The distillate product of MSF_M_RH is 4 % higher than that of the conventional MSF. Also the salt concentration is lowered by 20 % for the same brine recirculation.
Analysis of a new design of a multi-stage flash–mechanical vapor compression desalination process
In this work, a new design of a Multi Stage Flash-M echanical Vapor Compression (MSF-MVC) desalination process is investigated. The analysis of the proposed MSFMVC system is performed based on the energy, exergy and thermoeconomic methodologies. The considered system is investigate d under different operating conditions using a developed Visual Design and Simulation (VDS) software. To examine the performance of the proposed process, a comparison with the conventional MSF desalination process is performed. Thermoeconomic results show that, the best operatin g suction pressure is 8 kPa and the best top brine temperature is 110 °C. The effect of the stages number of the heat recovery section is investigated and the results sh ow that the low unit product cost is obtained at 20 stages. The effect of the temperatur e difference across the vent chamber is conducted and the results show that the lower un it product cost is 6 °C. Thermoeconomic analysis shows that the last stage ( vent chamber) has the highest value of the sum of capital and operation & mainten ance cost in addition to the exergy destruction cost. Also the last stage has higher re lative cost difference and lower exergetic efficiency. This in turn shows that a red uction in the exergy destruction within the vent chamber will reduce the unit produc t cost. The performance ratio of the proposed MSF-MVC system is 2.4 times the performance ratio of the conventional MSF process. The heat transfer area of the MSF-MVC system is 57 % higher than that of the conventional MSF. The exergetic efficiency o f the MSF-MVC system is 67 % higher than that of the MSF. The thermoeconomic results show that the unit product cost of MSF-MVC, under the specified conditions, is calculated by 2.0 $/m 3 and this value is 25 % less than that of the conventional MS F process.
Electrochemical detection of copper(II) at a gold electrode modified with a self-assembled monolayer of penicillamine
A penicillamine (PCA) self-assembled monolayer (SAM) was prepared on a gold electrode. It has been found that the modified electrode exhibited a selective response to copper ions. As demonstrated by cyclic voltammetric experiments, the SAM-based electrode showed an attractive ability to preconcentrate efficiently traces of copper(II) from solutions. Under optimum conditions, the anodic peak current was proportional to the concentration of Cu(II) in the range from 8.0 × 10−7 to 1.0 × 10−4 M with a detection limit of 4.0 × 10−7 M. Moreover, this modified gold electrode is also characterized by excellent repeatability, showing a relative standard deviation of 3.2% for nine successive measurements of 1.0 × 10−5 M Cu(II). The PCA/Au SAM gold electrode was used for the determination of Cu(II) in a tap water sample and the results showed a good agreement with the data obtained by atomic emission spectrometry.