Modeling of air-gap membrane distillation process: A theoretical and experimental study

Alsaadi, Ahmad Salem; Ghaffour, Noreddine; Li, Junde; Gray, Stephen; Francis, Lijo; Maab, Husnul; Amy, Gary L.

doi:10.1016/j.memsci.2013.05.049

Cited by 187 publications

(99 citation statements)

References 33 publications

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“…The feed solution, after being heated, is brought into contact with the membrane which allows only the vapor to go through the dry pores so that it condenses on the permeate side (coolant), as shown in Figure 7. A temperature difference of 7-10 o C between the warm and cold streams is potentially enough to produce freshwater [133][134][135][152][153][154].…”

Section: Membrane Distillation (Md)mentioning

confidence: 99%

Renewable energy-driven desalination technologies: A comprehensive review on challenges and potential applications of integrated systems

et al. 2015

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Despite the tremendous improvements in conventional desalination technologies, its wide use is still limited due primarily to high energy requirements which are currently met with expensive fossil fuels. The use of alternative energy sources is essential to meet the growing demand for water desalination. In the last few decades a lot of effort has being directed in the use of different renewable energy (RE) sources to run desalination processes. However, the expansion of these efforts towards larger scale plants is hampered by several techno-economic challenges. Several medium-scale RE-driven desalination plants have been installed worldwide. Nevertheless, most of these plants are connected to the electrical grid to assure a continuous energy supply for stable operation. Furthermore, RE is mostly used to produce electric power which can be used to run desalination systems. This review paper focusses on an integrated approach in using RE-driven with an emphasis on solar and geothermal desalination technologies. Innovative and sustainable desalination processes which are suitable for integrated RE systems are presented. An assessment of the benefits of these technologies and their limitations are also discussed.

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Section: Membrane Distillation (Md)mentioning

confidence: 99%

Renewable energy-driven desalination technologies: A comprehensive review on challenges and potential applications of integrated systems

et al. 2015

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“…The density, specific heat capacity, and the latent heat of evaporation of saline solutions are dependent on temperature and salinity, and their calculations are given elsewhere [31]. Unless otherwise stated, for comparison purpose, the STEC and GOR of DCMD reported in this study were calculated for the constant recovery mode.…”

Section: Energy Consumption and Thermal Efficiency In Dcmdmentioning

confidence: 99%

Optimising thermal efficiency of direct contact membrane distillation by brine recycling for small-scale seawater desalination

Duong

Cooper

Nelemans³

et al. 2015

Desalination

118

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A technique to optimise thermal efficiency using brine recycling during direct contact membrane distillation (DCMD) of seawater was investigated. By returning the hot brine to the feed tank, the system water recovery could be increased and the sensible heat of the hot brine was recovered to improve thermal efficiency. The results show that in the optimal water recovery range of 20 to 60% facilitated by brine recycling, the specific thermal energy consumption of the process could be reduced by more than half. It is also noteworthy that within this optimal water recovery range, the risk of membrane scaling is negligible -DCMD of seawater at a constant water recovery of 70% was achieved for over 24. h without any scale formation on the membrane surface. In contrast, severe membrane scaling was observed when water recovery reached 80%. In addition to water recovery, other operating conditions such as feed temperature and water circulation rates could influence the process thermal efficiency. Increasing the feed temperature and reducing the circulation flow rates increased thermal efficiency. Increasing the feed temperature could also mitigate the negative effect of elevated feed concentration on the distillate flux, particularly at a high water recovery. Abstract:A technique to optimise thermal efficiency using brine recycling during direct contact membrane distillation (DCMD) of seawater was investigated. By returning the hot brine to the feed tank, the system water recovery could be increased and the sensible heat of the hot brine was recovered to improve thermal efficiency. The results show that in the optimal water recovery range of 20 to 60% facilitated by brine recycling, the specific thermal energy consumption of the process could be reduced by more than half. It is also noteworthy that within this optimal water recovery range, the risk of membrane scaling is negligible  DCMD of seawater at a constant water recovery of 70% was achieved for over 24 hours without any scale formation on the membrane surface. In contrast, severe membrane scaling was observed when water recovery reached 80%. In addition to water recovery, other operating conditions such as feed temperature and water circulation rates could influence the process thermal efficiency. Increasing the feed temperature and reducing the circulation flow rates increased thermal efficiency. Increasing the feed temperature could also mitigate the negative effect of elevated feed concentration on the distillate flux, particularly at a high water recovery.

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“…In the case of DCMD, despite the higher flux the efficiency is lower as the thermal efficiency decreases with increasing ΔT due to the high heat input required and low heat recovery [13] as well as the thermal conduction (from feed to permeate sides) and the latent heat of water evaporation [50,51]. As shown in Figure 6 …”

Section: Scale-up Issuesmentioning

confidence: 99%

Performance evaluation of the DCMD desalination process under bench scale and large scale module operating conditions

Francis

Ghaffour

Alsaadi

et al. 2014

Journal of Membrane Science

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126

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The flux performance of different hydrophobic microporous flat sheet commercial membranes made of poly tetrafluoroethylene (PTFE) and poly propylene (PP) was tested for Red Sea water desalination using the direct contact membrane distillation (DCMD) process, under bench scale (high ΔT) and large scale module (low ΔT) operating conditions. Membranes were characterized for their surface morphology, water contact angle, thickness, porosity, pore size and pore size distribution. The DCMD process performance was optimized using a locally designed and fabricated module aiming to maximize the flux at different levels of operating parameters, mainly feed water and coolant inlet temperatures at different temperature difference across the membrane (ΔT). Water vapor flux of 88.8 kg/m 2 h was obtained using a PTFE membrane at high ΔT (60 °C). In addition, the flux performance was compared to the first generation of a new locally synthesized and fabricated membrane made of a different class of polymer under the same conditions. A total salt rejection of 99.99% and boron rejection of 99.41% were achieved under the extreme operating conditions. On the other hand, a detailed water characterization revealed that low molecular weight non-ionic molecules (ppb level) were transported with the water vapor molecules through the membrane structure. The membrane which provided the highest flux was then tested under large scale module operating conditions. The average flux of the latter study (low ΔT) was found to be eight times lower than that of the bench scale (high ΔT) operating conditions.

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Modeling of air-gap membrane distillation process: A theoretical and experimental study

Abstract: water production rate and the heat input to the process along the membrane length. This was used to understand the gain in both process production and thermal efficiency for different membrane surface areas and the resultant increases in process capital and water unit cost.

Cited by 187 publications

References 33 publications

Renewable energy-driven desalination technologies: A comprehensive review on challenges and potential applications of integrated systems

Renewable energy-driven desalination technologies: A comprehensive review on challenges and potential applications of integrated systems

Optimising thermal efficiency of direct contact membrane distillation by brine recycling for small-scale seawater desalination

Performance evaluation of the DCMD desalination process under bench scale and large scale module operating conditions

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