Abstract: Desalination using solar energy coupled with membrane techniques such as vacuum membrane distillation (VMD) is considered as an interesting alternative for the production of pure water. During this work, a developed model of a polytetrafluoroethylene (PTFE) hollow fiber membrane module of a VMD unit of seawater was carried out. This simulation leads to establishing a comparison between the effects of two different equations of the vaporization latent heat on the membrane surface temperature and on the unit productivity. Besides, in order to study the effect of putting membrane modules in series on the outlet fluid temperature and on the productivity of the process, a simulation was executed.
Abstract: The possibility of producing drinking water from
brackish ground water using Vacuum membrane distillation (VMD)
process was studied. It is a rising technology for seawater or brine
desalination process. The process simply consists of a flat sheet
hydrophobic micro porous 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
and natural ground water. The influence of operational parameters
such as feed flow rate (30 to 55 l/h), feed temperature (313 to 333 K),
feed salt concentration (5000 to 7000 mg/l) and permeate pressure
(1.5 to 6 kPa) on the membrane distillation (MD) permeation flux
have been investigated. The maximum flux reached to 28.34 kg/m2 h
at feed temperature, 333 K; vacuum pressure, 1.5 kPa; feed flow rate,
55 l/h and feed salt concentration, 7000 mg/l. The negligible effects
in the reduction of permeate flux found over 150 h experimental run
for salt water. But for the natural ground water application over 75 h,
scale deposits observed on the membrane surface and 29% reduction
in the permeate flux over 75 h. This reduction can be eliminated by
acidification of feed water. Hence, promote the research attention in
apply of VMD for the ground water purification over today-s
conventional RO operation.
Abstract: Vacuum membrane distillation (VMD) process can be
used for water purification or the desalination of salt water. The
process simply consists of a flat sheet hydrophobic micro porous
PTFE membrane and diaphragm vacuum pump without a condenser
for the water recovery or trap. The feed was used aqueous NaCl
solution. The VMD experiments were performed to evaluate the heat
and mass transfer coefficient of the boundary layer in a membrane
module. The only operating parameters are feed inlet temperature,
and feed flow rate were investigated. The permeate flux was strongly
affected by the feed inlet temperature, feed flow rate, and boundary
layer heat transfer coefficient. Since lowering the temperature
polarization coefficient is essential enhance the process performance
considerable and maximizing the heat transfer coefficient for
maximizes the mass flux of distillate water. In this paper, the results
of VMD experiments are used to measure the boundary layer heat
transfer coefficient, and the experimental results are used to reevaluate
the empirical constants in the Dittus- Boelter equation.