Copyright (c) 2008 All rights reserved. http://works.bepress.com/m_h_nguyen Recent documents in Minh H. Nguyen en-us Thu, 03 Jan 2008 08:23:18 PST 3600 http://works.bepress.com/m_h_nguyen/2 http://works.bepress.com/m_h_nguyen/2 Thu, 25 Jan 2007 21:39:02 PST This paper presents a comparative study on the role of operating conditions in osmotic distillation (OD) and direct contact membrane distillation (DCMD). Comparisons were made for lab scale OD and DCMD experiments on two types of PVDF hollow fibres under similar operating conditions for the concentration of glucose solutions from 30 to 60% (w/w) at temperatures as low as 25 to 45°C. Analysis of the results indicated that temperature was the most influencing factor for process improvement for both OD and DCMD. The flux in DCMD was improved by 3 to 4 times when feed temperature increased by 15 degrees, while this figure was nearly 3 times for OD when feed temperature increased by 20 degrees. The flow rates of the two streams played a more important role in maintaining the driving force, and consequently the flux rate, in DCMD rather than in OD. It was found that feed velocity had significant effect on DCMD performance, but insignificant in OD. Feed concentration, as the determining factor on water activity and viscosity, caused a more serious reduction of the flux rate in the high concentration range of 45-60% rather than in the dilute region of 30-40%. The effect was more significant in DCMD than in OD. The ratio of DCMD flux over that of OD ranged from 0.41 to 0.66 for PV375 when concentrating glucose solutions 30-40% w/w and from 0.35 to 0.69 for PV650 when concentrating high solid content ones. However, DCMD can overcome the disadvantages of OD being poor consumers' perception, (due to the use of brine solution being a chemical), the potential problem of corrosion by the brine and the cost of its reconcentration. V. A. Bui Separation and purification http://works.bepress.com/m_h_nguyen/1 http://works.bepress.com/m_h_nguyen/1 Thu, 25 Jan 2007 21:39:02 PST A step-by-step procedure for scaling up of an osmotic distillation system from laboratory to pilot plant is discussed. The newly built pilot scale OD system featured a flexibility of using 1 or 2 hollow fibre modules at a time to suit the concentration demands. Three types of hollow fibres were tested on the new system. Pilot trials for OD concentration of apple, grape juices and freeze concentrated (FC) grape juice were successfully carried out to achieve a final concentration up to 65°Brix with fluxes ranging from 2.4 to 0.69kg.m-2.h-1 depending on the fibre types and the operating conditions. Cascade effect was also employed to deal with high viscosity to achieve high concentration. The obtained pilot OD fluxes were comparable to the ones obtained in the lab under similar conditions, and they fitted well with the developed models. Sensory evaluation indicated that OD well preserved the quality attributes of the fruit juices. A. V. Bui Food processing concentration