Performance of Air Gap Membrane Distillation Unit for Water Desalination

2014 ◽  
Author(s):  
Atia E. Khalifa ◽  
Dahiru U. Lawal ◽  
Mohamed A. Antar
Keyword(s):  
Flow Rate ◽  
Membrane Distillation ◽  
Air Gap ◽  
Water Desalination ◽  
Feed Water ◽  
Feed Flow Rate ◽  
Permeate Flux ◽  
Air Gap Membrane Distillation ◽  
Gap Width ◽  
Feed Temperature

Due to water scarcity in the Arabic gulf region, water desalination technologies are considered extremely important. The present work represents a fundamental study on the effect of basic operating and design variables on the flux of an air gap membrane distillation (AGMD) unit for water desalination. The flat sheet, channeled air gap membrane distillation module was designed and manufactured locally. The effect of feed flow rate, feed temperature, coolant water temperature, the air gap width, and the water salinity on the module flux are investigated. Analytical model for heat and mass transfer is used to predict the flux and the model results are compared to the experimental ones. Results showed that the technique has good potential to be used for water desalination. The permeate flux is increased by increasing feed flow rate, feed temperature, decreasing the air gap width, decreasing coolant temperature, and decreasing salinity of feed water. For a given feed flow rate, the width of the air gap and the feed water temperature are found to be the most effective parameters in increasing the distillate flux. Predicting the permeate flux with analytical models for heat and mass transfer showed good agreement with experimental results.

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 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.

scholarly journals Performance Investigation of O-Ring Vacuum Membrane Distillation Module for Water Desalination

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Adnan Alhathal Alanezi ◽  
H. Abdallah ◽  
E. El-Zanati ◽  
Adnan Ahmad ◽  
Adel O. Sharif
Keyword(s):  
Flow Rate ◽  
Membrane Distillation ◽  
Membrane Module ◽  
Water Desalination ◽  
Feed Flow Rate ◽  
Permeate Flux ◽  
Vacuum Degree ◽  
Flat Sheet ◽  
Vacuum Membrane Distillation ◽  
Feed Temperature

A new O-ring flat sheet membrane module design was used to investigate the performance of Vacuum Membrane Distillation (VMD) for water desalination using two commercial polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) flat sheet hydrophobic membranes. The design of the membrane module proved its applicability for achieving a high heat transfer coefficient of the order of 103 (W/m2 K) and a high Reynolds number (Re). VMD experiments were conducted to measure the heat and mass transfer coefficients within the membrane module. The effects of the process parameters, such as the feed temperature, feed flow rate, vacuum degree, and feed concentration, on the permeate flux have been investigated. The feed temperature, feed flow rate, and vacuum degree play an important role in enhancing the performance of the VMD process; therefore, optimizing all of these parameters is the best way to achieve a high permeate flux. The PTFE membrane showed better performance than the PVDF membrane in VMD desalination. The obtained water flux is relatively high compared to that reported in the literature, reaching 43.8 and 52.6 (kg/m2 h) for PVDF and PTFE, respectively. The salt rejection of NaCl was higher than 99% for both membranes.

Development and Testing of a Lab-Scale Air-Gap Membrane Distillation Unit for Water Desalination

2018 ◽  
Author(s):  
Reza Baghaei Lakeh ◽  
Keaton Cornell ◽  
Benny Ly ◽  
Aaron Chan ◽  
Sepideh Jankhah
Keyword(s):  
Elevated Temperatures ◽  
Membrane Distillation ◽  
Air Gap ◽  
Water Desalination ◽  
Coolant Temperature ◽  
Feed Water ◽  
Permeate Flux ◽  
Flow Rates ◽  
Air Gap Membrane Distillation ◽  
Membrane Porosity

As the population grows, one issue that is continually being addressed is the lack of clean water resources. In order to explore viable solutions, rapid experimentation and research has been underway to alleviate the water crisis. With the addition of new emerging technology, the development, improvement, and understanding of various techniques used to treat non-potable water has expanded. One subcategory of water filtration in particular that has seen rapid growth is Membrane Distillation (MD). MD is a filtration process that utilizes thermal energy to desalinate and decontaminate water. Compared to current industry leading techniques such as reverse osmosis, MD does not require such large operating pressures, leading to less power consumption. MD is accomplished primarily by flowing contaminated feed water at elevated temperatures across semi-permeable membranes. The membranes used are made to allow water vapors to penetrate through and separate from the contaminated liquid portion. By maintaining a temperature difference across the membrane, a pressure gradient is created, which drives the vapor of feed water through the pores in the membrane. Once the vapor passes through the membrane, it condenses through various methods and is collected. Air Gap Membrane Distillation (AGMD) has shown significant ability to desalinate water effectively in small scales. The air gap between the membrane and condensation plate minimizes heat loss through conduction, making AGMD a more attractive option for upscaling. In this project a laboratory-scale test cell was developed to test AGMD using different membranes, and operational parameters. In order to test such parameters, a unique design with baffled channels to induce turbulence was designed and manufactured. Feed water and coolant temperature differences, flow rates, membrane porosity, and air gap thickness are among the parameters that has been studied in this research. Temperatures of the hot feed were varied from 40°C to 80°C while the cold feed temperature was kept at a near constant temperature of 0°C. Flow rates of feed water and coolant water range from 1 to 3 L/Min. It was observed that the permeate flux is an increasing function of feed water temperature and membrane porosity. The air gap thickness plays a major role in permeate flux and energy consumption of the system.

scholarly journals Experimental evaluation of two consecutive air-gap membrane distillation modules with heat recovery

2020 ◽  
Vol 20 (5) ◽  
pp. 1678-1691 ◽  
Author(s):  
Mostafa Abd El-Rady Abu-Zeid ◽  
Gamal ElMasry
Keyword(s):  
Water Temperature ◽  
Flow Rate ◽  
Heat Recovery ◽  
Waste Heat ◽  
Water Flow Rate ◽  
Membrane Distillation ◽  
Air Gap ◽  
Feed Water ◽  
System Productivity ◽  
Air Gap Membrane Distillation

Abstract Two rectangular modules with a total interior membrane surface area of 13.53 m2 were consecutively combined to evaluate the use of heat recovery in an air-gap membrane distillation (AGMD) system. Several operating inlet parameters including feed water temperature, mass water flow rate and salinity were investigated. The experimental results revealed that the performance of the system was improved by virtue of efficient heat recovery resulting from combining two AGMD membrane modules in series. Under optimal inlet operating parameters of cooling water temperature of 20 °C, salinity of 0.05% and flow rate of 3 l/min, the system productivity (Pp) increased up to 192.9%, 179.3%, 176.5% and 179.2%, and the thermal efficiency (ηth) by 261.5%, 232.6%, 239.4% and 227.3% at feed water temperatures of 45 °C, 55 °C, 65 °C and 75 °C, respectively. Concurrently, the specific waste heat input (Ew.h.i) decreased by 6.7%, 4.7%, 5.6% and 2.7% due to the efficient heat recovery. The results confirmed that heat recovery is an important factor affecting the AGMD system that could be improved by designing one of the two AGMD modules with polytetrafluoroethylene (PTFE) hollow fibers with a flow length shorter than the other one having a salt rejection rate of 99%.

scholarly journals A Systematic Framework for Optimizing a Sweeping Gas Membrane Distillation (SGMD)

Membranes ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 254
Author(s):  
Nawras N. Safi ◽  
Salah. S. Ibrahim ◽  
Nasser Zouli ◽  
Hasan Shaker Majdi ◽  
Qusay F. Alsalhy ◽  
...  
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Membrane Distillation ◽  
Feed Flow Rate ◽  
Permeate Flux ◽  
Gas Flow Rate ◽  
Feed Concentration ◽  
Sweeping Gas ◽  
Feed Temperature ◽  
Systematic Framework

The present work has undertaken a meticulous glance on optimizing the performance of an SGMD configuration utilized a porous poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) membrane. This was carried out by conducting a systematic framework for investigating and optimizing the pertinent parameters such as sweeping gas flow rate, feed temperature, feed concentration and feed flow rate on the permeate flux. For this purpose, the Taguchi method and design of experiment techniques were harnessed to statistically determine optimum operational conditions. Besides that, a comprehensive surface and permeation characterization was conducted against the hand-made membranes. Results showcased that the membrane performance was ultimately controlled by the feed temperature and was nearly (~680) % higher when the temperature raised from 45 to 65 °C. Also, to a lesser extent, the system was dominated by the feed flow rate. As the adopted feed flow rate increases (from 0.2 to 0.6 L/min), around 47.5% increment was bestowed on water permeability characteristics. In contra, 34.5% flux decline was witnessed when higher saline feed concentration (100 g/L) was utilized. In the meantime, with raising the sweeping gas flow rate (from 120 to 300 L/h), the distillate was nearly 129% higher. Based on Taguchi design, the maximum permeate flux (17.3 and 17 kg/m2·h) was secured at 35 g/L, 0.4 L/min, 65 °C and 300 L/h, for both commercial and prepared membranes, respectively.

scholarly journals Experimental analysis of a novel helical air gap membrane distillation system

2021 ◽  
Author(s):  
Vandita T. Shahu ◽  
S. B. Thombre
Keyword(s):  
Flow Rate ◽  
Experimental Analysis ◽  
Membrane Distillation ◽  
Air Gap ◽  
Operating Conditions ◽  
Coolant Temperature ◽  
Feed Water ◽  
Air Gap Membrane Distillation ◽  
Feasible Solutions ◽  
Water Problems

Abstract Membrane distillation presents one of the feasible solutions to fresh water problems. The present study aims to develop an innovative Helical Air Gap Membrane Distillation (HAGMD) system and to analyze its behavior under different operating conditions. In this design the condenser is made up of a cylindrical copper tube with continuous helical fins over it, that increases the total available condensation area by almost 45% and enhances the overall heat transfer throughout the module. The presence of fins in the gap also reduces the total air gap width by almost 64%and therefore improves the flux production. A detailed experimental analysis is carried out for a better understanding of the underlying phenomenon. The effect of feed water temperature, feed flow rate, cold flow rate, coolant temperature and feed salinity on the performance of HAGMD is investigated experimentally. The analysis shows that the finned condenser results in very high flux. The maximum flux obtained from the system was 20 kg/m2 hr with feed of 5gm/liter salinity and a diving force temperature difference of 45 °C.

Water Desalination Using Direct Contact Membrane Distillation System

2015 ◽  
Author(s):  
Hafiz M. Ahmad ◽  
Atia E. Khalifa ◽  
Mohamed A. Antar
Keyword(s):  
Flow Rate ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Water Desalination ◽  
Feed Flow Rate ◽  
Direct Contact Membrane Distillation ◽  
Rejection Factor ◽  
System Output ◽  
Feed Temperature

Membrane distillation (MD) is a separation technique used for water desalination, which operates at low feed temperatures and pressures. Direct contact membrane distillation (DCMD) is one of the common MD configurations where both the hot saline feed stream and the cold permeate stream are in direct contact with the two membrane surfaces. An experimental study was performed to investigate the effect of operating conditions such as feed temperature, feed flow rate, permeate temperature, and permeate flow rate on the system output flux. To check the effect of membrane degradation, the MD system was run continuously for 48 hours with raw seawater as feed and the reduction in system flux with time was observed. Results showed that increasing the feed temperature, decreasing the permeate temperature, increasing the feed and permeate flow rate yield an increase in flux. The effects of feed temperature and feed flow rate are the most significant parameters. After 48 hours of system continuous operation flux was reduced by 42.4 % but the quality of permeate (as measured by its TDS) is still very high with salt rejection factor close to 100 %. For the DCMD system under consideration, the GOR values remain between 0.8 and 1.2, for the tested range of operating temperatures.

Separation of HCl/water mixture using air gap membrane distillation, Taguchi optimization and artificial neural network

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Sarita Kalla ◽  
Rakesh Baghel ◽  
Sushant Upadhyaya ◽  
Kailash Singh
Keyword(s):  
Water Temperature ◽  
Flow Rate ◽  
Cooling Water ◽  
Membrane Distillation ◽  
Air Gap ◽  
Water Mixture ◽  
Feed Flow Rate ◽  
Ann Model ◽  
Cooling Water Temperature ◽  
Feed Temperature

AbstractThe aim of this paper is to analyze the performance of the air gap membrane distillation (AGMD) process for the separation of HCl/Water mixture first by applying Taguchi optimization approach and second by developing an artificial neural network (ANN) model. The experimental data which are fed as input to the above approaches are collected from the fabricated AGMD lab-scale setup using poly-tetra-fluoro-ethylene membrane of 0.22 µm pore size. The process input variables considered are bulk feed temperature, feed flow rate, air gap thickness, cooling water temperature and cooing water flow rate and AGMD performance index is the total permeate flux. The optimum operating condition is found to be at feed temperature 50 °C, air gap thickness 7 mm, cooling water temperature 5 °C and feed flow rate 10 lpm. Analysis of variance test is carried out for both Taguchi and ANN models. Regression model has also been developed for the comparison between experimental and model predicted data. The developed ANN model has been found well fitted with experimental data having R2 value of 0.998. Based on the calculated percentage of contribution of each input parameter on the AGMD permeate flux, it can be concluded that feed temperature and air gap thickness have highest weightage whereas feed flow rate and cooling water temperature have moderate effects. Predictive ability of the developed ANN model is further checked with 2D contour plot. The distinctive feature of the paper is the development of the Taguchi experimental design and ANN model and then consequently integration of both Taguchi and ANN has been carried out to optimized the developed ANN model parameters.

Sign in / Sign up

Export Citation Format

Share Document