Experimental Study on a Multi-stage Air Gap Membrane Distillation (AGMD) Unit

2014 ◽  
Vol 69 (9) ◽  
Author(s):  
Rubina Bahar ◽  
M. N. A. Hawlader ◽  
K. C. Ng ◽  
Yee Jiun Haw
Keyword(s):  
Polyvinylidene Fluoride ◽  
Energy Use ◽  
Membrane Distillation ◽  
Air Gap ◽  
Coolant Temperature ◽  
Hydrophobic Membrane ◽  
Operating Variables ◽  
Water Power ◽  
Air Gap Membrane Distillation ◽  
Multi Stage

Membrane distillation (MD) is a separation process that involves vapour transport through a hydrophobic membrane. The evaporation is caused by the partial pressure difference between a hot fluid and cold fluid/surface. In this study, an air gap MD (AGMD) process is utilized to produce freshwater from saline solution. A multi-stage AGMD unit with 0.45 mm pore size Polyvinylidene Fluoride (PVDF) membranes is built and experiments have been carried out with different operating variables including feed temperature, coolant temperature, air gap width and feed inlet concentration.A maximum of 12.9 kg/m2 of distillate flux was obtained per kWh energy input from the multi-stage MD unit while for a previously built single-stage MD unit, the highest water/power ratio obtained was only 2.3 kg /m2 kWh. This variation indicates that multistaging is necessary for efficeint energy use in MD system. 

scholarly journals Enhanced production from an Air Gap Membrane Distillation Desalination system by varying the feed entry angle

2021 ◽  
Vol 945 (1) ◽  
pp. 012026
Author(s):  
Rubina Bahar ◽  
Mohammad Jabed Perves Bappy
Keyword(s):  
Membrane Distillation ◽  
Air Gap ◽  
Coolant Temperature ◽  
Entry Angle ◽  
Hydrophobic Membrane ◽  
Flow Angle ◽  
Enhanced Production ◽  
Air Gap Membrane Distillation ◽  
Scale Unit ◽  
Feed Temperature

Abstract The membrane distillation (MD) process is an evaporative metho driven by the partial pressure difference between two different temperature solutions, namely the hot feed and the coolant. The hot feed evaporates, and the vapour gets condensed to the cooler side. A hydrophobic membrane maintains the evaporating surface. Air Gap Membrane Distillation(AGMD) separates the hot feed from the coolant by a narrow air gap and a coolant plate. The condensate forms on the coolant plate, and the air gap works as an insulation for the heat loss through the membrane. The salient parameters like feed temperature, coolant temperature, and air gap thickness have already been identified through research in previous years. In this study, an innovative technique has been tested to minimize the polarization and increase the production from an AGMD lab-scale unit. The effect of the feed flow entry angle has been investigated. Also, the combined effect of inclined flow entry and a finned coolant surface has been studied. It has been found from the experiments that with a feed flow entry angle of 60°, the system shows an average of 10% to 14% boost in performance. When 60° inlet flow angle and finned coolant plate work in combination, an average of 69% to 78% increase of distillate flux was observed with the same energy input.

scholarly journals A Comparison Study of Brine Desalination using Direct Contact and Air Gap Membrane Distillation

2019 ◽  
Vol 25 (11) ◽  
pp. 47-54
Author(s):  
Ahmed Shamil Khalaf ◽  
Asrar Abdullah Hassan
Keyword(s):  
Flow Rate ◽  
Direct Contact ◽  
Polyvinylidene Fluoride ◽  
Membrane Distillation ◽  
Air Gap ◽  
Feed Flow Rate ◽  
Permeate Flux ◽  
Air Gap Membrane Distillation ◽  
Flat Sheet ◽  
Feed Temperature

Membrane distillation (MD) is a hopeful desalination technique for brine (salty) water. In this research, Direct Contact Membrane Distillation (DCMD) and  Air Gap Membrane Distillation (AGMD) will be used. The sample used is from Shat Al –Arab water (TDS=2430 mg/l). A polyvinylidene fluoride (PVDF) flat sheet membrane was used as a flat sheet form with a plate and frame cell. Several parameters were studied, such as; operation time, feed temperature, permeate temperature, feed flow rate. The results showed that with time, the flux decreases because of the accumulated fouling and scaling on the membrane surface. Feed temperature and feed flow rate had a positive effect on the permeate flux, while permeate temperature had a reverse effect on permeate flux. It is noticeable that the flux in DCMD is greater than AGMD, at the same conditions. The flux in DCMD is 10.95LMH, and that in AGMD is 7.14 LMH.  In AGMD, the air gap layer made a high resistance. Here the temperature transport reduces in the permeate side of AGMD due to the air gap resistance. The heat needed for AGMD is lower than DCMD, this leads to low permeate flux because the temperature difference between the two sides is very small, so the driving force (vapor pressure) is low.                                                                                               

scholarly journals Analysis and optimization of a new cylindrical air gap membrane distillation system

2019 ◽  
Vol 20 (1) ◽  
pp. 361-371 ◽  
Author(s):  
Vandita T. Shahu ◽  
S. B. Thombre
Keyword(s):  
Flow Rate ◽  
Membrane Separation ◽  
Negative Impact ◽  
Membrane Distillation ◽  
Air Gap ◽  
Cylindrical Shape ◽  
Hydrophobic Membrane ◽  
Tube Heat Exchanger ◽  
Whole Process ◽  
Air Gap Membrane Distillation

Abstract Membrane distillation is a rate-governed non-isothermal membrane separation technique that utilizes trans-membrane temperature difference for evaporating water and thereby separating it from brackish feed for reproducing fresh water. A novel design of a cylindrical air gap membrane distillation module is presented. The module is fabricated in a way similar to a shell and tube heat exchanger. A PTFE hydrophobic membrane is used and is formed in a cylindrical shape. Design of experiments (DOE) is used to design the experiments statistically and to identify the significant operating parameters. Experiments were performed according to the Taguchi design approach using an L16 orthogonal array. Optimization of the whole process is performed by response surface methodology. It is shown that the feed temperature and feed flow rate have a positive effect, whereas the salinity has a negative impact on flux. The maximum value of flux achieved with this system is 3.6 kg/m2 hr. A high value of flux of 2.6 kg/m2 hr was achieved under optimum conditions at a temperature of 45 °C and a flow rate of 1.5 lpm with a salinity of 5 g/litre.

Development of Nano-Carbon Bucky-Paper Membranes for Membrane Distillation

2012 ◽  
Vol 724 ◽  
pp. 408-411 ◽  
Author(s):  
Jae Wuk Koo ◽  
Ji Hee Han ◽  
Sang Ho Lee ◽  
Jin Sik Sohn ◽  
June Seok Choi
Keyword(s):  
Polyvinylidene Fluoride ◽  
Membrane Distillation ◽  
Practical Implementation ◽  
Vapor Permeability ◽  
Feed Water ◽  
Hydrophobic Membrane ◽  
Salt Rejection ◽  
Multi Stage ◽  
And Performance ◽  
Bucky Paper

Membrane distillation (MD) is a special evaporation process to produce fresh water from seawater or contaminated water using membranes. MD has advantages over other evaporation technologies such as multi-stage flash vaporization (MSF) and multi-effect distillation (MED) due to its relatively low energy requirements, allowing the use of solar energy as its heat source. Nevertheless, lack of membrane materials for MD process hinders its practical implementation for desalination and water treatment. In this study, membranes made of carbon nanotube (CNT) are presented for MD. Flat sheet hydrophobic membranes made of polyvinylidene fluoride (PVDF) were selected as supports for bucky-paper membranes, allowing formation of CNT bucky-paper without chemical reactions. Laboratory-scale systems were used to evaluate their potential and performance in direct contact MD. Water permeability and salt rejection were analyzed for each case. D.I water and synthetic feed water were used for the lab-scale tests. It was demonstrated that the physical immobilization of CNT on a hydrophobic membrane changed led to an increase in vapor permeability while improving salt rejection.

scholarly journals Performances of air gap and water gap MD desalination modules

2018 ◽  
Vol 13 (1) ◽  
pp. 200-209 ◽  
Author(s):  
Atia E. Khalifa
Keyword(s):  
Specific Energy Consumption ◽  
Membrane Distillation ◽  
Air Gap ◽  
Dominant Factor ◽  
Feed Water ◽  
Permeate Flux ◽  
Hydrophobic Membrane ◽  
Air Gap Membrane Distillation ◽  
Gap Width ◽  
Feed Temperature

Abstract Membrane distillation (MD) is a promising thermally-driven membrane separation technology for water desalination. In MD, water vapor is being separated from the hot feed water solution using a micro-porous hydrophobic membrane, due to the difference in vapor pressures across the membrane. In the present work, experiments are conducted to compare the performance of water gap membrane distillation (WGMD) and air gap membrane distillation (AGMD) modules under the main operating and design conditions including the feed and coolant temperatures, membrane material and pore sizes, and the gap width. Results showed that the WGMD module produced higher fluxes as compared to the AGMD module, for all test conditions. The feed temperature is the dominant factor affecting the system flux. The permeate flux increases with reducing the gap width for both water and air gap modules. However, WGMD module was found to be less sensitive to the change in the gap width compared to the AGMD module. The PTFE membrane produced higher permeate flux as compared to the PVDF membrane. Bigger mean pore diameter enhanced the permeate flux, however, this enhancement is marginal at high feed temperatures. With increasing the feed temperature, the GOR values increase and the specific energy consumption decreases.

High water recovery of RO brine using multi-stage air gap membrane distillation

Desalination ◽  
2015 ◽  
Vol 355 ◽  
pp. 178-185 ◽  
Author(s):  
Hongxin Geng ◽  
Juan Wang ◽  
Chunyao Zhang ◽  
Pingli Li ◽  
Heying Chang
Keyword(s):  
High Water ◽  
Membrane Distillation ◽  
Air Gap ◽  
Water Recovery ◽  
Air Gap Membrane Distillation ◽  
Multi Stage

Separation of Water and Nitric Acid with Porous Hydrophobic Membrane by Air Gap Membrane Distillation (AGMD)

2006 ◽  
Vol 41 (14) ◽  
pp. 3187-3199 ◽  
Author(s):  
Ramesh Thiruvenkatachari ◽  
Matheswaran Manickam ◽  
Tae Ouk Kwon ◽  
Il Shik Moon ◽  
Jae Woo Kim
Keyword(s):  
Nitric Acid ◽  
Membrane Distillation ◽  
Air Gap ◽  
Hydrophobic Membrane ◽  
Air Gap Membrane Distillation
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