Flash distillation sizing

Desalination. A special case of distillation is water desalination. In places where energy is abundant but fresh water is not, eg, the Arabian Peninsula, water may be produced from seawater ia flash evaporators. Low pressure turbiae steam is extracted to provide heat for the evaporators. Coadeased steam is returned to the cycle. Such units may be particularly prone to corrosion by salts. Sizes vary, but a plant scheduled for completion in 1996 had six units and a total capacity of 345,600 m /d. Power generation was expected to be 17,500 MW (36). 

Analytical thin layer chromatography (TLC) was conducted on pre-coated TLC plates, silica gel 60 F254, layer thickness 0.25 mm, manufactured by E. Merck and Co., Darmstadt, Germany. Silica Gel for flash column chromatography was obtained from Silicycle Chemical Division Silica Gel, 60 (particle size 0.040 - 0.063 mm) 230-240 mesh ASTM. All columns were prepared, loaded, and fractions collected according to the specification of Still.37 Ethyl acetate used for chromatography was dried over 4 A molecular sieves for at least 24 hours prior to use. Hexanes are the mixed hydrocarbon fraction (bp 60-70 °C), principally n-hexanes, which was purified as follows the commercial solvent was stirred concentrated sulfuric acid for at least 24 hours, decanted, stirred over anhydrous sodium carbonate for 6 hours, decanted, then distilled. 

After developing a robust steady-state simulation, the next step is the sizing of units whose dynamics is considered. Typically these are units with a significant material inventory, as flash vessels, distillation columns, and liquid-phase reactors. Heat exchangers, pumps and compressors may be considered in many situations as reaching fast steady state. 

Operation of the virgin and modified AI2O3 manbrane was compared by the separation of an oil-water emulsion, which consisted of 20 engine oil (1 g/L), Tween 80 (0.5 g/L), Span 80 (0.5 g/L), and distilled water. Stable oil-water emulsion had an average droplet size of 1.79 pm, and 90% of the oil droplets were between 0.67 and 7.4 pm. Filtration tests were conducted at the transmanbrane pressure of 0.16 MPa, feed flow rate of 5 m/s, and at an operating temperature of SO C. The membrane was back-flashed at the interval of 10 min. For the virgin AljOj manbrane, the flux declined sharply in the first 60 min, from 446 to 159 L/m h. The steady flux was only about 30% of the initial flux, implying that the AljOj membrane was seriously fouled. However, the flux of the modified membrane quickly reached a constant in 10 min. The flux declined from 506 to 441 L/m h, which is 88% of the initial flux. 

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