Modeling of pore wetting in vacuum membrane distillation

Chamani, Hooman; Matsuura, Takeshi; Rana, Dipak; Lan, Christopher Q.

doi:10.1016/j.memsci.2018.11.018

Cited by 39 publications

(18 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These operations are omitted by immersing the capillary membranes inside the feed tank. Thus, the application of submerged modules significantly simplifies a construction of installation, which also additionally reduces the heat losses in the MD process [13][14][15].During a long-term exploitation of the MD module, the water fills a fraction of the membrane pores, thereby the elimination of membrane wettability becomes a very important issue [16][17][18]. The MD process is not pressure-driven, however, the hydrostatic pressure is necessary in order to obtain the feed flow through the module channels.…”

mentioning

confidence: 99%

“…The MD process is not pressure-driven, however, the hydrostatic pressure is necessary in order to obtain the feed flow through the module channels. Although the value of this pressure is usually not high, this is one of the reasons accelerating the membrane wetting, especially if the surface tension of the feed solution is low [17,18]. The immersion of membranes inside a non-pressure feed vessel allows elimination of a hydrostatic pressure generated by feed pumping.Fouling is also one of the reasons causing the membrane wetting [19][20][21].…”

mentioning

confidence: 99%

“…During a long-term exploitation of the MD module, the water fills a fraction of the membrane pores, thereby the elimination of membrane wettability becomes a very important issue [16][17][18]. The MD process is not pressure-driven, however, the hydrostatic pressure is necessary in order to obtain the feed flow through the module channels.…”

mentioning

confidence: 99%

See 2 more Smart Citations

The Application of Submerged Modules for Membrane Distillation

Gryta

2020

Membranes

View full text Add to dashboard Cite

This paper deals with the efficiency of capillary modules without an external housing, which were used as submerged modules in the membrane distillation process. The commercial hydrophobic capillary membranes fabricated for the microfiltration process were applied. Several constructional variants of submerged modules were discussed. The influence of membrane arrangement, packing density, capillary diameter and length on the module performance was determined. The effect of process conditions, i.e., velocity and temperature of the streams, on the permeate flux was also evaluated. The submerged modules were located in the feed tank or in the distillate tank. It was found that much higher values of the permeate flux were obtained when the membranes were immersed in the feed with the distillate flowing inside the capillary membranes. The efficiency of submerged modules was additionally compared with the conventional membrane distillation (MD) capillary modules and a similar performance of both constructions was achieved.Membranes 2020, 10, 25 2 of 21 the module channels. With regard to this, in order to achieve a higher degree of water recovery, the feed is circulated in the closed loop and simultaneously reheated before the feed water enters the module [11,12]. These operations are omitted by immersing the capillary membranes inside the feed tank. Thus, the application of submerged modules significantly simplifies a construction of installation, which also additionally reduces the heat losses in the MD process [13][14][15].During a long-term exploitation of the MD module, the water fills a fraction of the membrane pores, thereby the elimination of membrane wettability becomes a very important issue [16][17][18]. The MD process is not pressure-driven, however, the hydrostatic pressure is necessary in order to obtain the feed flow through the module channels. Although the value of this pressure is usually not high, this is one of the reasons accelerating the membrane wetting, especially if the surface tension of the feed solution is low [17,18]. The immersion of membranes inside a non-pressure feed vessel allows elimination of a hydrostatic pressure generated by feed pumping.Fouling is also one of the reasons causing the membrane wetting [19][20][21]. The application of air bubbling is commonly employed in the MBR in order to mitigate the fouling phenomenon and it also proves to be effective in the MD process [15,22,23]. Moreover, in the case of the presence of surface active agents, they are accumulated on the surface of air bubbles, which additionally limits the influence of these substances on the pore wetting [23]. Such a concept was successfully used in the MD process applied to the treatment of wastewater from the petrochemical industry and to the treatment of produced water generated during the extraction of gas and petroleum [2,24].The driving force in the MD process does not directly depend on the bulk feed temperature, but on the feed/membrane interfacial temperature [25][26][27][28][29][30][31]. Therefore, t...

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

The Application of Submerged Modules for Membrane Distillation

Gryta

2020

Membranes

View full text Add to dashboard Cite

show abstract

“…The driving force of mass transfer in the MD process is a difference in the vapour pressure, which increases exponentially along with the increase of the feed temperature (T F ) [ 40 ], and this exponential character is reflected in the changes in the permeate flux presented in Figure 7 . The obtained process efficiency for the feed temperature in the range of 343–353 K was more than 5 times higher than that obtained for T F = 313–323 K. With regard to this, there should be a serious reason to utilize a low temperature for the operation of the MD process.…”

Section: Resultsmentioning

confidence: 99%

“…Diffusion is a relatively slow process; hence, with a rapid increase in solutes concentration, supersaturation and crystallization may occur. The rate of water evaporation depends on the vapour pressure [ 40 ]. Its value for 313 K is 7.4 kPa, and at 353 K, it amounts 47.3 kPa; hence, a permeate flux of about 5 times higher is achieved for 353 K. For this reason, lowering the feed temperature (flux decreasing) limits the increase in the solute concentration in the evaporation layer (C 1 ), which in turn can limit the membrane scaling [ 18 ].…”

Section: Wetting By Scalingmentioning

confidence: 99%

Mitigation of Membrane Wetting by Applying a Low Temperature Membrane Distillation

Gryta

2020

Membranes

View full text Add to dashboard Cite

The formation of deposits on the membrane surface during membrane distillation is considered as one of the main reasons for membrane wetting. To assess the intensity of this phenomenon, long-term studies were performed comparing the membrane wettability with non-fouling feed (NaCl solutions) and feeds containing various foulants (lake and Baltic Sea water). The polypropylene membranes used were non-wetted by NaCl solutions during several hundred hours of water desalination. However, the occurrence of CaCO3 or other salt crystallization caused the membranes to be partially wetted, especially when periodical membrane cleaning was applied. The scaling intensity was significantly reduced by lowering the feed temperature from 353 to 315 K, which additionally resulted in the limitation of the degree of membrane wetting.

show abstract