SIMULATION OF VACUUM MEMBRANE DISTILLATION

Abstract

Vacuum membrane distillation technology has been widely used in seawater and brackish water desalinization, wastewater treatment, water purification, solution concentration and crystallization and callback of volatility solute in solution. Besides the merits of simple device, easy control, distillate pureness and being easy to assemble, vacuum membrane distillation can be used to treat high concentration solution and even concentrate the solution to saturation state. The fundamental problem in modeling of this process is due to the vapour liquid equilibrium at the membrane interface. Also, a large number of variables such as partial pressure difference, pore size, pore tortuosity and membrane geometry, as well as fluid flow rate and turbulence intensity, significantly affects the mass transfer in vacuum membrane distillation process. For example, for low flow rate of liquid feed, the resistance to mass transfer is more and possibly dominant and when the flow rate increases, the resistance to mass transfer decreases and flux increases. In this dissertation, to investigate mass transfer and heat transfer phenomenon in vacuum membrane distillation used the following system. The membrane is located in the middle of a circular cell of 74 mm diameter and is divided into two chambers of 2 mm depth. The useful membrane area for the process is 43 cm2 has been simulated using mathematical tool- of MATLAB. For simulation different models are used and results are compared. It is found that for the present application the film theory model and Knudsen diffusion model provided best result. Obtained results are compared with experimental results due to [Bandini S. et al., 1999] for transmembrane flux. The results showed that simulation offers well agreement with experimental results of within maximum deviation d 10%. Further, effect of parameters like Temperature, Concentration of volatile component in feed, feed flow rate, and downstream pressure for various binary mixtures has been studied. In addition to it, effects of temperature on selectivity of solute component is also discussed.