Raising forward osmosis brine concentration efficiency through flow rate optimization

Tow, Emily W.; McGovern, Ronan Killian; Lienhard, John H.

doi:10.1016/j.desal.2014.10.034

Cited by 38 publications

(36 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Examples of FO exchanger salinity profiles can be seen in [42]. Thermodynamically balancing the FO exchanger by setting the osmotic pressure pinch equal on feed and brine ends maximizes system efficiency when the draw regeneration efficiency is roughly independent of salinity [42], as it is in this model.…”

Section: Forward Osmosismentioning

confidence: 99%

Energy consumption in desalinating produced water from shale oil and gas extraction

et al. 2015

Self Cite

View full text Add to dashboard Cite

On-site treatment and reuse is an increasingly preferred option for produced water management in unconventional oil and gas extraction. This paper analyzes and compares the energetics of several desalination technologies at the high salinities and diverse compositions commonly encountered in produced water from shale formations to guide technology selection and to inform further system development. Produced water properties are modeled using Pitzer's equations, and emphasis is placed on how these properties drive differences in system thermodynamics at salinities significantly above the oceanic range. Models of mechanical vapor compression, multi-effect distillation, forward osmosis, humidification-dehumidification, membrane distillation, and a hypothetical high pressure reverse osmosis system show that for a fixed brine salinity, evaporative system energetics tend to be less sensitive to changes in feed salinity. Consequently, second law efficiencies of evaporative systems tend to be higher when treating typical produced waters to near-saturation than when treating seawater. In addition, if realized for high-salinity produced waters, reverse osmosis has the potential to achieve very high efficiencies. The results suggest a different energetic paradigm in comparing membrane and evaporative systems for high salinity wastewater treatment than has been commonly accepted for lower salinity water.

show abstract

Section: Forward Osmosismentioning

confidence: 99%

Energy consumption in desalinating produced water from shale oil and gas extraction

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…The state-of-the-art seawater reverse osmosis (SWRO) systems have energy consumptions about 3-4 kWh/m 3 (normalized by pure water produced) of which about 1 kWh/m 3 is used for pretreatment [52]. This corresponds to a Second Law efficiency value of about 30% [40,53]. In general, the Second Law efficiency of an RO system depends on the feed salinity in a nontrivial manner.…”

Section: Pressure-retarded Osmosismentioning

confidence: 99%

Thermodynamic analysis of brine management methods: Zero-discharge desalination and salinity-gradient power production

et al. 2017

Self Cite

View full text Add to dashboard Cite

Growing desalination capacity worldwide has made management of discharge brines an increasingly urgent environmental challenge. An important step in understanding how to choose between different brine management processes is to study the energetics of these processes. In this paper, we analyze two different ways of managing highly saline brines. The first method is complete separation with production of salts (i.e., zero-discharge desalination or ZDD). Thermodynamic limits of the ZDD process were calculated. This result was applied to the state-of-the-art industrial ZDD process to quantify how close these systems are to the thermodynamic limit, and to compare the energy consumption of the brine concentration step to the crystallization step. We conclude that the brine concentration step has more potential for improvement compared to the crystallization step. The second brine management method considered is salinity-gradient power generation through pressure-retarded osmosis (PRO), which utilizes the brine's high concentration to produce useful work while reducing its concentration by mixing the brine with a lower salinity stream in a controlled manner. We model the PRO system coupled with a desalination system using a detailed numerical optimization, which resulted in about 0.42 kWh/m 3 of energy saving.

show abstract

“…Note that this quantification judges membrane performance, not system efficiency, and is not comparable to efficiency metrics used for other technologies, such as the second law efficiency for RO [62][63][64][65]. Another relevant parameter is the overall energy efficiency or GOR (gained output ratio), which compares the enthalpy of simply evaporating water to the heat input ̇… actually used:…”

Section: Air Gap and Condensing Channel Modelingmentioning

confidence: 99%

Comprehensive condensation flow regimes in air gap membrane distillation: Visualization and energy efficiency

Warsinger

Swaminathan

Morales

et al. 2018

Journal of Membrane Science

Self Cite

View full text Add to dashboard Cite

The thermal performance of air gap membrane distillation (AGMD) desalination is dominated by heat and mass transfer across the air gap between the membrane and the condensing surface. However, little is known about the impact of condensate flow patterns in some design variations of the air gap. In this study, air gap membrane distillation experiments were performed at various inlet temperatures, varying module inclination angle, condensing surface hydrophobicity, and gap spacer design to identify the effect of each on the permeate production rate and thermal efficiency of the system. Energy efficiency modeling was performed as well. Additionally, this study is one of the first with enhanced visualization of flow patterns within the air gap itself, by using a transparent, high thermal conductivity sapphire plate as the condenser surface. System-level numerical modeling is used to further understand the impact of these flow regimes on overall energy efficiency, including flux and GOR. A brief review of membrane distillation condensation regimes is provided as well. For tilting the AGMD flat-plate module, permeate flux was barely influenced except at extreme positive angles (>80ᵒ), and moderate negative angles (<-30ᵒ), where condensate fell onto the membrane surface. The surface with the hydrophobic coating (for dropwise condensation) was shown to have better droplet shedding (with very small nearly spherical droplets) and fewer droplets bridging the gap. Superhydrophobic surfaces (for jumping droplet condensation) were similar, with much smaller droplet sizes. Meanwhile, the hydrophilic surface for small gap sizes (< 3 mm) often had pinned regions of water around the hydrophilic surface and plastic spacer. Overall, the various results imply that the common assumption of a laminar condensate film poorly describes the flow patterns in real systems for all tilt angles and most spacer designs. Real system performance is likely to be between that of pure AGMD and permeate gap membrane distillation (PGMD) variants, and modeling shows that better condensing in air gaps may improve system energy efficiency significantly, with strong relative advantages at high salinity.

show abstract

Raising forward osmosis brine concentration efficiency through flow rate optimization

Cited by 38 publications

References 33 publications

Energy consumption in desalinating produced water from shale oil and gas extraction

Energy consumption in desalinating produced water from shale oil and gas extraction

Thermodynamic analysis of brine management methods: Zero-discharge desalination and salinity-gradient power production

Comprehensive condensation flow regimes in air gap membrane distillation: Visualization and energy efficiency

Contact Info

Product

Resources

About