Enhanced production from an Air Gap Membrane Distillation Desalination system by varying the feed entry angle

The membrane distillation (MD) process is an evaporative metho driven by the partial pressure difference between two different temperature solutions, namely the hot feed and the coolant. The hot feed evaporates, and the vapour gets condensed to the cooler side. A hydrophobic membrane maintains the evaporating surface. Air Gap Membrane Distillation(AGMD) separates the hot feed from the coolant by a narrow air gap and a coolant plate. The condensate forms on the coolant plate, and the air gap works as an insulation for the heat loss through the membrane. The salient parameters like feed temperature, coolant temperature, and air gap thickness have already been identified through research in previous years. In this study, an innovative technique has been tested to minimize the polarization and increase the production from an AGMD lab-scale unit. The effect of the feed flow entry angle has been investigated. Also, the combined effect of inclined flow entry and a finned coolant surface has been studied. It has been found from the experiments that with a feed flow entry angle of 60°, the system shows an average of 10% to 14% boost in performance. When 60° inlet flow angle and finned coolant plate work in combination, an average of 69% to 78% increase of distillate flux was observed with the same energy input.

Recovery of Spent Sulphuric Acid by Diffusion Dialysis Using a Spiral Wound Module

In this study, we assess the effects of volumetric flow and feed temperature on the performance of a spiral-wound module for the recovery of free acid using diffusion dialysis. Performance was evaluated using a set of equations based on mass balance under steady-state conditions that describe the free acid yield, rejection factors of metal ions and stream purity, along with chemical analysis of the outlet streams. The results indicated that an increase in the volumetric flow rate of water increased free acid yield from 88% to 93%, but decreased Cu2+ and Fe2+ ion rejection from 95% to 90% and 91% to 86%, respectively. Increasing feed temperature up to 40 °C resulted in an increase in acid flux of 9%, and a reduction in Cu2+ and Fe2+ ion rejection by 2–3%. Following diffusion dialysis, the only evidence of membrane degradation was a slight drop in permselectivity and an increase in diffusion acid and salt permeability. Results obtained from the laboratory tests used in a basic economic study showed that the payback time of the membrane-based regeneration unit is approximately one year.

Cesium Removal from Wastewater Using Banana Peel

The potential of banana peel (BP) on the cesium removal from aqueous solutions is study by using different design parameters by adsorption process. The design parameters studied to adsorb cesium using BP as an adsorbent material were initial concentration of cesium , absorbance material packing height which was BP, pH of cesium feed inlet, treatment time, feed flow rate and feed temperature, results show that the higher removal efficiency was 97.50 % for cesium from aquatic solution and this efficiency was decreased with increasing of initial concentration and flow rate while the removal efficiency increased with increasing pH, sorption media bed height and feeding temperature. By this way we can possess different benefits which are: remove the hazard and toxic cesium contaminated the water and get rid of waste BP.

Theoretical Investigation of Vapor Transport Mechanism Using Tubular Membrane Distillation Module

This paper’s primary objective is to examine the vapor delivery mechanism through a tubular membrane distillation (MD) module. Experiments were conducted utilizing a hydrophobic tubular membrane module with a pore size of 0.2 µm. To establish the mass transport mechanism of water vapor, tests were carried out first with pure water as a feed. The permeate flow was then determined using NaCl aqueous feed solutions. Distilled water flux at diverse feed temperatures, feed flow rates, and feed salt concentrations was investigated. The permeate flux improved linearly with rising temperature and flow rate of the feed, however, it declined with feed concentration. Increasing temperature from 40 to 70 °C increased the permeate flux by a factor of 2.2, while increasing the feed flow rate from 60 to 120 L/h increased the permeate flux by a factor ranging from 0.7 to 1.1 depending on feed temperature. Using the Dusty gas model (DGM) the mass transport of water vapor is estimated in the membrane pores. The results showed that the water vapor delivery is controlled by way of the Knudsen molecular diffusion transition mechanism and its version changed into one capable of predicting the permeate fluxes. The mass transfer coefficient calculated and located using the Knudsen molecular transition version agreed properly with the corresponding experimental value. The delivery resistances were affected by working parameters, along with feed temperature, flow rate, and concentration. The mass transfer resistance of the membrane became the predominant controlling step to the MD process.

Laminated graphene oxide membrane for recovery of mercury-containing wastewater by pervaporation

Mercury (Hg) is a toxic heavy metal contaminant and has very harmful effects for human health. In this work, Hg-containing wastewater with Hg concentration of 6.36 ppb and 9.4 ppb were recovered with polyethylenimine (PEI) cross-linked graphene oxide (GO) layered membrane (c-GO-PEI) by pervaporation. The influence of ionic type, the concentration of Hg and the feed temperature were investigated. The c-GO-PEI exhibited not only high rejection for salts (> 99.97%), Hg (77.5–100%) and non-purgeable organic carbon (NPOC) (67.3–90.8%) but also high flux (30.30 kg·m−2·h−1) to treat with the wastewater. In addition, the flux could be largely recovered after simple washing, indicating the excellent antifouling property of the membrane.

PVDF-TiO2 Hollow Fibre Membrane For Water Desalination

The clean water crisis is increasing along with the increasing human population. Sea water is one of the largest water sources that can be utilized on the earth. However, the high salt concentration dissolved in seawater must be treated before it can use. Desalination is the directly technology for treating seawater with PVDF-TiO2 hollow fibre membrane via pervaporation process. The aim of this research was to determine the performance of PVDF-TiO2 hollow fibre membrane against variations in feed temperature in the artificial seawater pervaporation process. Method for fabrication membrane is using dry-wet spinning method. The result showed that the highest flux permeat occurred at feed temperature of 60ºC, namely 8.96 kg.m-2.h-1 with salt rejection > 92.86%. The result via SEM showed that of the membrane surface morphology, there is a white spot on the membrane surface is TiO2 because the dope solution is too thick. The PVDF-TiO2 hollow fiber membrane in this research is can be applied for seawater pervaporation.

An Improved Modelling Approach for the Comprehensive Study of Direct Contact Membrane Distillation

Direct Contact Membrane Distillation (DCMD) is a promising and feasible technology for water desalination. Most of the models used to simulate DCMD are one-dimensional and/or use a linear function of vapour pressure which relies on experimentally determined parameters. In this study, the model of DCMD using Nusselt correlations was improved by coupling the continuity, momentum, and energy equations to better capture the downstream alteration of flow field properties. A logarithmic function of vapour pressure, which is independent from experiments, was used. This allowed us to analyse DCMD with different membrane properties. The results of our developed model were in good agreement with the DCMD experimental results, with less than 7% deviation. System performance metrics, including water flux, temperature, and concentration polarisation coefficient and thermal efficiency, were analysed by varying inlet feed and permeate temperature, inlet velocity, inlet feed concentration, channel length. In addition, twenty-two commercial membranes were analysed to obtain a real vision on the influence of membrane characteristics on system performance metrics. The results showed that the feed temperature had the most significant effect on water flux and thermal efficiency. The increased feed temperature enhanced the water flux and thermal efficiency; however, it caused more concentration and temperature polarisation. On the other hand, the increased inlet velocity was found to provide increased water flux and reduced temperature and concertation polarisation as well. It was also found that the membrane properties, especially thickness and porosity, can affect the DCMD performance significantly. A two-fold increase of feed temperature increased the water flux and thermal efficiency, 10-fold and 27%, respectively; however, it caused an increase in temperature and concertation polarisation, at 48% and 34%, respectively. By increasing Reynolds number from 80 to 1600, the water flux, CPC, and TPC enhanced by 2.3-fold, 2%, and 21%, respectively. The increased feed concentration from 0 to 250 [g/L] caused a 26% reduction in water flux. To capture the downstream alteration of flow properties, it was shown that the ratio of inlet value to outlet value of system performance metrics decreased significantly throughout the module. Therefore, improvement over the conventional model is undeniable, as the new model can assist in achieving optimal operation conditions.

Experimental Investigation on Floating Solar-Driven Membrane Distillation Desalination Modules

Membrane distillation (MD) processes need a relatively mild temperature gradient as the driving force for desalination. In the field, it is reasonable to utilize solar energy as the heat source for the feed, and seawater as the infinite cold source for condensation. Solar-driven MD provides a route for the practical application of seawater desalination at a small scale. In this work, we focus on floating MD modules with a solar heating bag as the power source, and perform proof-of-principle experiments on the MD performance under various conditioning parameters, including feed flow rate, feed temperature, salinity, air gap, and sea waves. The results indicate that floating solar-driven MD modules are feasible in terms of permeate flux and salt rejection ratio, and the upward evaporation MD configuration leads to a better performance in terms of permeate flux. The simulation and experiments also show that the natural sea waves disturb the heating bag and the MD module floating on the surface of seawater, and effectively enhance the feed circulation and transport in the system.

Low Cost Solution to Increase the C2 & C3 Product Recovery from LNG Feed

An operating methane/ethane recovery plant from Liquefied Natural Gas (LNG) feed was facing limitations to process design throughput due to a variation in operating parameter of LNG feed. About 92% of design capacity of LNG feed is only being processed as flooding is observed inside the Demethanizer column, eventually leading to tripping of the plant. The limitations in the throughput has direct implication on the revenue as lesser throughput reduces the product generation. Various field trials were attempted within the existing setup to increase the throughput to the plant, however the throughout could not be increased. Operating an LNG plant is comparatively complex due to its unique characteristics, as even one degree change in the temperature has effect on the liquid vaporization. To achieve the design feed throughput rate, as a permanent solution, the temperature of the feed before entering the demethanizer column has to be increased. Various locations for increasing the temperature in the plant were studied in this paper. The identification of location for preheating plays an important role in the costing. For every one degree Celsius increase in the feed temperature, the duty of the exchanger increases three folds. This paper explains the low cost solutions to increase the throughput to the plant, thereby increasing the product generation of C2, C3 products from LNG feed prior to regasification.