Performance evaluation of vacuum membrane distillation for desalination by using a flat sheet membrane

Abstract

Vacuum membrane distillation (VMD) process received a great deal of attention by many investigators because of its promising applications in several separation areas. It is a rising technology for seawater or brine desalination process. The process simply consists of a flat sheet hydrophobic microporous PTFE membrane and diaphragm vacuum pump without a condenser for the water recovery or trap. In this work, VMD performance was investigated for aqueous NaCl solution. In order to enhance the performance of the VMD process in desalination, that is, to get more flux, it is necessary to study the effect of operating parameters on the yield of distillate water. The influence of operational parameters such as feed flow rate, feed temperature, feed salt concentration and permeate pressure on the membrane distillation (MD) permeation flux have been investigated. The VMD performance showed that this device could reach a desalting degree of 99.99% which was not affected by feed concentration. The membrane distillation flux reached 14.62 kg/m 2 h at 333 K bulk feed temperature, 1.5 kPa permeate pressure, 54 l/h feed flow rate, and 30,000 mg/l feed concentration. With these chosen operating conditions, experiments with concentrated salt water showed a permeate flux decreases with time, but these reduction is less than 14% over a long term experimentation. However, this fouling is reversible and easily removed by a water washing. This study promotes the research attention in apply of VMD for over-concentrated salt water means rejected brines of reverse osmosis process.

Direct contact membrane distillation for seawater desalination

“…They indicated that a pre-treatment step to remove organic matters is essential to prevent membrane fouling. Moreover, other MD configurations are potentially used for desalination when considering various points of view [16][17][18][19][20][21][22].…”

Scaling and fouling in membrane distillation for desalination applications: A review

“…DI water readily absorbs salts, and is even known to leach salts from surroundings [121]. Mericq et al [109] for example, completely restored membrane flux using RO permeate water to remove and re-dissolve scale deposits from synthetic seawater in their VMD system.…”

Statistical analysis of air-gap membrane desalination experimental data: Hypothesis testing

“…Fisher's least significant difference (LSD) method is similar to Tukey's method in principle, the differences in response averages (permeate flux in this work) are compared to a corresponding LSD value that is represented in Eq. (9). This method uses the t-statistic calculated using Eq.…”

“…Similar to the SGMD, condensation takes place outside the membrane cell and heat loss by conduction is insignificant [8]. VMD is used to separate volatile compounds from water and is effective in desalination of sea water [9].…”