scholarly journals Thermal Performance of Integrated Direct Contact and Vacuum Membrane Distillation Units

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7405
Author(s):  
Alessandra Criscuoli
Keyword(s):  
Thermal Performance ◽  
Direct Contact ◽  
Process Intensification ◽  
Membrane Distillation ◽  
Operating Conditions ◽  
Recovery Factor ◽  
Flow Sheet ◽  
Water Recovery ◽  
In Series ◽  
Vacuum Membrane Distillation

An integrated membrane distillation (MD) flowsheet, consisting of direct contact membrane distillation (DCMD) and vacuum membrane distillation (VMD) units, was proposed and analysed in terms of thermal performance and water recovery factor, for the first time. The same lab-scale membrane module (40 cm2) was used for carrying out experiments of DCMD and VMD at fixed feed operating conditions (deionised water at 230 L/h and ~40 °C) while working at the permeate side with deionised water at 18 °C and with a vacuum of 20 mbar for the DCMD and the VMD configuration, respectively. Based on experimental data obtained on the single modules, calculations of the permeate production, the specific thermal energy consumption (STEC) and the gained output ratio (GOR) were carried out for both single and integrated units. Moreover, the calculations were also made for a flow sheet consisting of two DCMD units in series, representing the “traditional” way in which more units of the same MD configuration are combined to enhance the water recovery factor. A significant improvement of the thermal performance (lower STEC and higher GOR) was obtained with the integrated DCMD–VMD flowsheet with respect to the DCMD units operating in series. The integration of DCMD with VMD also led to a higher permeate production and productivity/size (PS) ratio, a metric defined to compare plants in terms of the process intensification strategy.

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%.

scholarly journals Effects of volatile organic compounds on water recovery from produced water via vacuum membrane distillation

Desalination ◽  
2018 ◽  
Vol 440 ◽  
pp. 146-155 ◽  
Author(s):  
Minwei Yao ◽  
Yun Chul Woo ◽  
Leonard D. Tijing ◽  
June-Seok Choi ◽  
Ho Kyong Shon
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Produced Water ◽  
Membrane Distillation ◽  
Water Recovery ◽  
Volatile Organic ◽  
Vacuum Membrane Distillation

scholarly journals Water reclamation from shale gas drilling flow-back fluid using a novel forward osmosis–vacuum membrane distillation hybrid system

2014 ◽  
Vol 69 (5) ◽  
pp. 1036-1044 ◽  
Author(s):  
Xue-Mei Li ◽  
Baolong Zhao ◽  
Zhouwei Wang ◽  
Ming Xie ◽  
Jianfeng Song ◽  
...  
Keyword(s):  
Hybrid System ◽  
Shale Gas ◽  
Forward Osmosis ◽  
Membrane Distillation ◽  
Water Recovery ◽  
High Quality ◽  
Gas Drilling ◽  
Vacuum Membrane Distillation ◽  
Quality Water ◽  
Shale Gas Drilling

This study examined the performance of a novel hybrid system of forward osmosis (FO) combined with vacuum membrane distillation (VMD) for reclaiming water from shale gas drilling flow-back fluid (SGDF). In the hybrid FO-VMD system, water permeated through the FO membrane into a draw solution reservoir, and the VMD process was used for draw solute recovery and clean water production. Using a SGDF sample obtained from a drilling site in China, the hybrid system could achieve almost 90% water recovery. Quality of the reclaimed water was comparable to that of bottled water. In the hybrid FO-VMD system, FO functions as a pre-treatment step to remove most contaminants and constituents that may foul or scale the membrane distillation (MD) membrane, whereas MD produces high quality water. It is envisioned that the FO-VMD system can recover high quality water not only from SGDF but also other wastewaters with high salinity and complex compositions.

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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