Experimental study of multi-effect membrane distillation (MEMD) for treatment of water containing inorganic salts

2016 ◽  
Vol 11 (4) ◽  
pp. 765-773 ◽  
Author(s):  
Bhausaheb L. Pangarkar ◽  
Samir K. Deshmukh ◽  
Prashant V. Thorat
Keyword(s):  
Flow Rate ◽  
Separation Efficiency ◽  
Operating Time ◽  
Specific Energy Consumption ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
Carbonate Solutions ◽  
Inorganic Solutes ◽  
Latent Heat Of Vaporization ◽  
Feed Temperature

A novel multi-effect membrane distillation (MEMD) process has been implemented to treat water containing four different inorganic solutes. The 4-stage MEMD module was developed based on the air-gap configuration. The influence of operating parameters like concentration, feed temperature, flow rate and operating time on permeate fluxes of zinc sulfate, sodium fluoride, magnesium chloride and sodium carbonate solutions was observed. Concentration had negligible effect on the MEMD's permeate flux, while its performance increased with increasing feed temperature and flow rate. Its separation efficiency was stable at more than99.91% throughout the experiment. In addition, its specific energy consumption after the recovery of the latent heat of vaporization and sensible heat of brine was measured at different component concentrations and found to be independent of the type of component.

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 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.

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 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 Employing full factorial design and response surface methodology for optimizing direct contact membrane distillation operational conditions in desalinating the rejected stream of a reverse osmosis unit at Esfahan refinery–Iran

2018 ◽  
Vol 19 (2) ◽  
pp. 492-501 ◽  
Author(s):  
M. Ebadi ◽  
M. R. Mozdianfard ◽  
M. Aliabadi
Keyword(s):  
Response Surface Methodology ◽  
Reverse Osmosis ◽  
Flow Rate ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
Operational Conditions ◽  
Direct Contact Membrane Distillation ◽  
Full Factorial ◽  
Feed Temperature

Abstract Optimized condition for desalination of the reverse osmosis (RO) rejected stream from Esfahan Oil Refining Company (EORC) using direct contact membrane distillation (DCMD) with polytetrafluoroethylene (PTFE) membrane was investigated here, having designed a set of 34 experiments using response surface methodology (RSM) and full factorial design (FFD) modelling, carried out in a laboratory scale set-up built for this purpose. Statistical criteria for validation, significance, accuracy and adequacy confirmed the suitability of the quadratic polynomial model employed. Response plots and regression equations suggested that the permeate flux response improved with increased feed temperature, reduced permeate temperature and enhanced feed flow rate. Optimizing DCMD process showed that maximum permeate flux of 60.76 L/m2·h could be achieved at the following optimum operational conditions: feed temperature and flow rate of 70 °C and 2 L/min, respectively, as well as the permeate temperature of 15 °C. At this point, the mean annual energy required for 90% water recovery (36 m3/h off the RO brackish rejected stream) at EORC refinery was found to be 96 GJ, which could be supplied using solar or conventional energy systems at Isfahan, facing a very critical water shortage at present.

scholarly journals Theoretical Investigation of Vapor Transport Mechanism Using Tubular Membrane Distillation Module

Membranes ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 560
Author(s):  
Adnan Alhathal Alanezi ◽  
Mohamed Bassyouni ◽  
Shereen M. S. Abdel-Hamid ◽  
Hassn Safi Ahmed ◽  
Mohamed Helmy Abdel-Aziz ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Water Vapor ◽  
Mass Transport ◽  
Flow Rate ◽  
Transport Mechanism ◽  
Membrane Distillation ◽  
Permeate Flux ◽  
Transfer Resistance ◽  
Tubular Membrane ◽  
Feed Temperature

This paper’s primary objective is to examine the vapor delivery mechanism through a tubular membrane distillation (MD) module. Experiments were conducted utilizing a hydrophobic tubular membrane module with a pore size of 0.2 µm. To establish the mass transport mechanism of water vapor, tests were carried out first with pure water as a feed. The permeate flow was then determined using NaCl aqueous feed solutions. Distilled water flux at diverse feed temperatures, feed flow rates, and feed salt concentrations was investigated. The permeate flux improved linearly with rising temperature and flow rate of the feed, however, it declined with feed concentration. Increasing temperature from 40 to 70 °C increased the permeate flux by a factor of 2.2, while increasing the feed flow rate from 60 to 120 L/h increased the permeate flux by a factor ranging from 0.7 to 1.1 depending on feed temperature. Using the Dusty gas model (DGM) the mass transport of water vapor is estimated in the membrane pores. The results showed that the water vapor delivery is controlled by way of the Knudsen molecular diffusion transition mechanism and its version changed into one capable of predicting the permeate fluxes. The mass transfer coefficient calculated and located using the Knudsen molecular transition version agreed properly with the corresponding experimental value. The delivery resistances were affected by working parameters, along with feed temperature, flow rate, and concentration. The mass transfer resistance of the membrane became the predominant controlling step to the MD process.

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 Experimental Investigation on Floating Solar-Driven Membrane Distillation Desalination Modules

Membranes ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 304
Author(s):  
Qingxiu Miao ◽  
Yaoling Zhang ◽  
Shuo Cong ◽  
Fei Guo
Keyword(s):  
Power Source ◽  
Membrane Distillation ◽  
Small Scale ◽  
Sea Waves ◽  
Permeate Flux ◽  
Practical Application ◽  
Rejection Ratio ◽  
Cold Source ◽  
Mild Temperature ◽  
Feed Temperature

Membrane distillation (MD) processes need a relatively mild temperature gradient as the driving force for desalination. In the field, it is reasonable to utilize solar energy as the heat source for the feed, and seawater as the infinite cold source for condensation. Solar-driven MD provides a route for the practical application of seawater desalination at a small scale. In this work, we focus on floating MD modules with a solar heating bag as the power source, and perform proof-of-principle experiments on the MD performance under various conditioning parameters, including feed flow rate, feed temperature, salinity, air gap, and sea waves. The results indicate that floating solar-driven MD modules are feasible in terms of permeate flux and salt rejection ratio, and the upward evaporation MD configuration leads to a better performance in terms of permeate flux. The simulation and experiments also show that the natural sea waves disturb the heating bag and the MD module floating on the surface of seawater, and effectively enhance the feed circulation and transport in the system.

Removal of high concentration Congo red by hydrophobic PVDF hollow fiber composite membrane coated with a loose and porous ZIF-71PVDF layer through vacuum membrane distillation

2020 ◽  
pp. 152808372096707
Author(s):  
Hongbin Li ◽  
Wenying Shi ◽  
Qiyun Du ◽  
Shoufa Huang ◽  
Haixia Zhang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Hollow Fiber ◽  
Congo Red ◽  
Fiber Composite ◽  
Water Flux ◽  
Membrane Distillation ◽  
Feed Flow Rate ◽  
High Concentration ◽  
Operation Conditions ◽  
Feed Temperature

Although membrane distillation (MD) technology has the outstanding advantages of almost 100% solute retention and mild operation conditions, its further development is limited by low permeate flux. In order to solve the problem, the improvement of membrane hydrophobicity becomes one of the effective solutions. In this study, a loose and porous hydrophobic zeolitic imidazolate frameworks-71 (ZIF-71)/polyvinylidene fluoride (PVDF) coating layer was composited on the outside surface of PVDF hollow fiber support membrane by the dilute solution coating to enhance membrane hydrophobicity. The prepared hollow fiber composite (HFC) membranes were employed to remove high concentration Congo red (CR) through VMD. The effects of different operation conditions including the dye concentration, feed temperature, vacuum pressure and feed flow rate on CR rejection and permeate water flux were investigated. In the variation range of operating conditions, all the CR rejection of the PVDF HFC membranes shows a slight change and remains above 99.9%. Under the optimal operation conditions including dye concentration 600 mg·L−1, vacuum pressure 31.325 kPa, feed temperature 60°C and feed flow rate 50 L·h−1, HFC membrane exhibit a permeate water flux of 13.15 kg·m−2·h−1. HFC membrane suffers dye fouling during the continuous dye filtration for 100 h. The fouling mechanism was proposed and a combined cleaning way including forward washing, back flushing and chemical desorption has been proved to be effective in recovering membrane water flux.

Membrane Distillation Desalination System With Gap Circulation and Cooling Using a Built-in Heat Exchanger

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Atia E. Khalifa
Keyword(s):  
Energy Consumption ◽  
Heat Exchanger ◽  
Specific Energy Consumption ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Water Desalination ◽  
Module Design ◽  
Membrane Surfaces ◽  
Best Value ◽  
Feed Temperature

Abstract A comprehensive experimental investigation is conducted to evaluate the performance of a new flux-enhanced compact water gap membrane distillation (WGMD) module design with gap circulation and cooling for water desalination. The new design uses a separate circulation loop to circulate the gap water, and a built-in heat exchanger coil implanted inside the coolant stream channel for cooling the circulated gap water. The WGMD modules with circulation and with circulation and cooling are compared with conventional WGMD without circulation. Variations of distillate flux, temperatures, and energy consumption are presented at different design operating conditions. Circulation and cooling of the gap water greatly enhance the output flux due to gap water motion and increase the temperature difference between membrane surfaces. However, the enhancement in flux was achieved at the expense of energy consumption. Circulation and cooling of gap water are more effective with bigger gap widths. Feed flowrate showed significant effects with gap water circulation and cooling. The electrical specific energy consumption (SEC) showed the best value of 7.9 and 8.8 kWh/m3 at a feed temperature of 70 °C for both conventional WGMD and WGMD with circulation modules, while the best value of SEC for the WGMD module with gap circulation and cooling was 9.4 kWh/m3 at a feed temperature of 80 °C.

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