The Role of Operating Conditions in Osmotic Distillation and Direct Contact Membrane Distillation - A Comparative Study

2006 ◽  
Vol 2 (5) ◽  
Author(s):  
V. A. Bui ◽  
M. H. Nguyen
Keyword(s):  
Comparative Study ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Flux Rate ◽  
High Concentration ◽  
Osmotic Distillation ◽  
Direct Contact Membrane Distillation ◽  
Feed Temperature

This paper presents a comparative study on the role of operating conditions in osmotic distillation (OD) and direct contact membrane distillation (DCMD). Comparisons were made for lab scale OD and DCMD experiments on two types of PVDF hollow fibres under similar operating conditions for the concentration of glucose solutions from 30 to 60% (w/w) at temperatures as low as 25 to 45°C. Analysis of the results indicated that temperature was the most influencing factor for process improvement for both OD and DCMD. The flux in DCMD was improved by 3 to 4 times when feed temperature increased by 15 degrees, while this figure was nearly 3 times for OD when feed temperature increased by 20 degrees. The flow rates of the two streams played a more important role in maintaining the driving force, and consequently the flux rate, in DCMD rather than in OD. It was found that feed velocity had significant effect on DCMD performance, but insignificant in OD. Feed concentration, as the determining factor on water activity and viscosity, caused a more serious reduction of the flux rate in the high concentration range of 45-60% rather than in the dilute region of 30-40%. The effect was more significant in DCMD than in OD. The ratio of DCMD flux over that of OD ranged from 0.41 to 0.66 for PV375 when concentrating glucose solutions 30-40% w/w and from 0.35 to 0.69 for PV650 when concentrating high solid content ones. However, DCMD can overcome the disadvantages of OD being poor consumers’ perception, (due to the use of brine solution being a chemical), the potential problem of corrosion by the brine and the cost of its reconcentration.

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.

scholarly journals Concentration of Bioactive Phenolic Compounds in Olive Mill Wastewater by Direct Contact Membrane Distillation

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1808
Author(s):  
Rosa Tundis ◽  
Carmela Conidi ◽  
Monica R. Loizzo ◽  
Vincenzo Sicari ◽  
Rosa Romeo ◽  
...  
Keyword(s):  
Direct Contact ◽  
High Performance ◽  
Biological Properties ◽  
Membrane Distillation ◽  
Olive Mill Wastewater ◽  
High Concentration ◽  
Direct Contact Membrane Distillation ◽  
Reducing Activity ◽  
Β Carotene ◽  
Olive Mill

Olive mill wastewater (OMW), generated as a by-product of olive oil production, is considered one of the most polluting effluents produced by the agro-food industry, due to its high concentration of organic matter and nutrients. However, OMW is rich in several polyphenols, representing compounds with remarkable biological properties. This study aimed to analyze the chemical profile as well as the antioxidant and anti-obesity properties of concentrated fractions obtained from microfiltered OMW treated by direct contact membrane distillation (DCMD). Ultra-high performance liquid chromatography (UHPLC) analyses were applied to quantify some phenols selected as phytochemical markers. Moreover, α-Amylase, α-glucosidase, and lipase inhibitory activity were investigated together with the antioxidant activity by means of assays, namely β-carotene bleaching, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic) acid (ABTS) diammonium salts, 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, and Ferric Reducing Activity Power (FRAP) tests. MD retentate—which has content of about five times greater of hydroxytyrosol and verbascoside and about 7 times greater of oleuropein than the feed—was more active as an antioxidant in all applied assays. Of interest is the result obtained in the DPPH test (an inhibitory concentration 50% (IC50) of 9.8 μg/mL in comparison to the feed (IC50 of 97.2 μg/mL)) and in the ABTS assay (an IC50 of 0.4 μg/mL in comparison to the feed (IC50 of 1.2 μg/mL)).

Experimental and Numerical Study of Water Distillation Performance of Small-Scale Direct Contact Membrane Distillation System

2017 ◽  
Author(s):  
Danielle Park ◽  
Elnaz Norouzi ◽  
Chanwoo Park
Keyword(s):  
Water Temperature ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Small Scale ◽  
Feed Water ◽  
Water Production ◽  
Water Distillation ◽  
Direct Contact Membrane Distillation ◽  
Feed Temperature ◽  
Feed Water Temperature

A small-scale Direct Contact Membrane Distillation (DCMD) system was built to investigate its water distillation performance for varying inlet temperatures and flow rates of feed and permeate streams, and salinity. A counterflow configuration between the feed and permeate streams was used to achieve an efficient heat exchange. A two-dimensional Computational Fluid Dynamics (CFD) model was developed and validated using the experimental results. The numerical results were compared with the experiments and found to be in good agreement. From this study, the most desirable conditions for distilled water production were found to be a higher feed water temperature, lower permeate temperature, higher flow rate and less salinity. The feed water temperature had a greater impact on the water production than the permeate water temperature. The numerical simulation showed that the water mass flux was maximum at the inlet of the feed stream where the feed temperature was the highest and rapidly decreased as the feed temperature decreased.

Modeling of Air-Gap Membrane Distillation and Comparative Study with Direct Contact Membrane Distillation

2020 ◽  
Vol 59 (50) ◽  
pp. 21930-21947
Author(s):  
Sadaf Noamani ◽  
Shirin Niroomand ◽  
Masoud Rastgar ◽  
Mehdi Azhdarzadeh ◽  
Mohtada Sadrzadeh
Keyword(s):  
Comparative Study ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Air Gap ◽  
Air Gap Membrane Distillation ◽  
Direct Contact Membrane Distillation

scholarly journals Highly Saline Water Desalination Using Direct Contact Membrane Distillation (DCMD): Experimental and Simulation Study

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1575 ◽  
Author(s):  
Noor A. Mohammad Ameen ◽  
Salah S. Ibrahim ◽  
Qusay F. Alsalhy ◽  
Alberto Figoli
Keyword(s):  
Mass Transfer ◽  
Direct Contact ◽  
Saline Water ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Water Desalination ◽  
System Of Nonlinear Equations ◽  
Transfer Model ◽  
Transfer Resistance ◽  
Direct Contact Membrane Distillation

The path for water molecules transported across a membrane in real porous membranes has been considered to be a constant factor in the membrane distillation (MD) process (i.e., constant tortuosity); as such, its effect on membrane performance at various operating conditions has been ignored by researchers. Therefore, a simultaneous heat and mass transfer model throughout the direct contact membrane distillation (DCMD) module was developed in this study by taking into account the hypothetical path across the membrane as a variable factor within the operating conditions because it exhibits the changes to the mass transfer resistance across the membrane under the DCMD run. The DCMD process was described by the developed model using a system of nonlinear equations and solved numerically by MATLAB software. The performance of the poly-tetra-fluoroethylene (PTFE) membrane was examined to treat 200 g/L NaCl saline at various operating conditions. The simulation results in the present work showed that the hypothetical proposed path across the membrane has a variable value and was affected by changing the feed temperature and feed concentration. The results estimated by the developed model showed an excellent conformity with the experimental results. The salt rejection remained high (greater than 99.9%) in all cases. The temperature polarization coefficient for the DCMD ranged between 0.88 and 0.967, and the gain output ratio (GOR) was 0.893. The maximum thermal efficiency of the system was 84.5%.

The role of membrane surface energy on direct contact membrane distillation performance

Desalination ◽  
2013 ◽  
Vol 323 ◽  
pp. 22-30 ◽  
Author(s):  
Ludovic F. Dumée ◽  
Stephen Gray ◽  
Mikel Duke ◽  
Kallista Sears ◽  
Jürg Schütz ◽  
...  
Keyword(s):  
Surface Energy ◽  
Direct Contact ◽  
Membrane Surface ◽  
Membrane Distillation ◽  
Direct Contact Membrane Distillation

scholarly journals Direct Contact Membrane Distillation for Desalination Brine Solution

2018 ◽  
Vol 24 (11) ◽  
pp. 18
Author(s):  
Asrar Abdullah Hassan ◽  
Ahmed Khalid Mohammed Reda
Keyword(s):  
Direct Contact ◽  
High Salinity ◽  
Membrane Distillation ◽  
Feed Concentration ◽  
Modus Operandi ◽  
Brine Solution ◽  
Direct Contact Membrane Distillation ◽  
Flat Sheet ◽  
Plate Cell ◽  
Feed Temperature

Desalination is a process where fresh water produces from high salinity solutions, many ways used for this purpose and one of the most important processes is membrane distillation (MD). Direct contact membrane distillation (DCMD) can be considered as the most prominent type from MD types according to ease of design and modus operandi. This work studies the efficiency of using DCMD operation for desalination brine with different concentration (1.75, 3.5, 5 wt. % NaCl). Frame and plate cell was used with flat sheet PTFE hydrophobic type membrane. The study proves that MD is an effective process for desalination brines with feed temperature less than 60˚C especially for feed with low TDS. 37˚C, 47˚C, and 57˚C was feed temperature and 17, 22, 27˚C as permeate temperatures used in study, temperature in both sides of membrane are recorded and TDS for permeate collected to assure that there is no penetration of brine to permeate side, the results took every 30 min for time experiment of 180 min. From results, the flux increases with increasing feed temperature and flow rate, and decreasing with increasing feed concentration, experiment time, and permeate temperature.     

scholarly journals Influence of Hydraulic Pressure on Performance Deterioration of Direct Contact Membrane Distillation (DCMD) Process

Membranes ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 37 ◽  
Author(s):  
Seung-Min Park ◽  
Sangho Lee
Keyword(s):  
Mass Transfer ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Hydraulic Pressure ◽  
Transfer Coefficients ◽  
Hydrophobic Membrane ◽  
Mass Transfer Coefficients ◽  
Efficient Operation ◽  
Direct Contact Membrane Distillation

Direct contact membrane distillation (DCMD) is a membrane distillation (MD) configuration where feed and distillate directly contact with a hydrophobic membrane. Depending on its operating conditions, the hydraulic pressures of the feed and distillate may be different, leading to adverse effects on the performance of the DCMD process. Nevertheless, little information is available on how hydraulic pressure affects the efficiency of DCMD. Accordingly, this paper investigates the effect of external hydraulic pressure on the process efficiency of DCMD. Gas permeabilities of MD membranes were measured to analyze the effect of membrane compaction by external pressure. Mass transfer coefficients were calculated using experimental data to quantitatively explain the pressure effect. Experiments were also carried out using a laboratory-scale DCMD set-up. After applying the pressure, the cross-sections and surfaces of the membranes were examined using a scanning electron microscope (SEM). Results showed that the membrane structural parameters such as porosity and thickness were changed under relatively high pressure conditions (>30 kPa), leading to reduction in flux. The mass transfer coefficients were also significantly influenced by the hydraulic pressure. Moreover, local wetting of the membranes were observed even below the liquid entry pressure (LEP), which decreased the rejection of salts. These results suggest that the control of hydraulic pressure is important for efficient operation of DCMD process.

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