Distillation Technology Research Articles

Design and optimization of a unique pilot scale forward osmosis integrated membrane distillation system for seawater desalination

The integration of forward osmosis (FO) and membrane distillation (MD) technologies for seawater desalination applications is recently gaining more importance since the system can be easily integrated with renewable energy resources. In this study a pilot scale FO integrated air gap membrane distillation (FO-AGMD) system is designed, commissioned, and tested for the desalination of the Arabian Gulf seawater (AGS) using 70,000 ppm solution of NaCl as the draw solution (DS). During the FO-AGMD operation, the FO feed-in conductivity decreased from 66.45 mS/cm to 63.31 mS/cm while the FO feed-out conductivity decreased from 62.92 mS/cm to 60.17 mS/cm. The DI water dosing system connected to the feed loop of the FO module decreased the feed-in and feed-out conductivities to maintain a uniform Δπ across the FO membrane. As the MD flux increased, to maintain the FO-AGMD system equilibrium the FO flux was also increased by raising the DS concentration using the dosing tank containing the stock solution of NaCl. Under the optimized operating conditions, the average system water recovery stabilized at 33% at the operating temperature of the MD at 85 °C. The water flux was stable between 6.3 and 7.3 L/m2h for the FO and 3.75 and 4 L/m2h for the MD. The major power consumption by the FO-AGMD system is the heating and cooling powers for heating the feed to ∼85 ºC and cooling the permeate to ∼10 °C in the MD section which varied in the similar range of 10–12 kW/h.

A Systematic Methodology for the Synthesis of Advanced Reactive Distillation Technologies

A Systematic Methodology for the Synthesis of Advanced Reactive Distillation Technologies

Pure Silica with Ordered Silanols for Propylene/Propane Adsorptive Separation Unraveled by Three-Dimensional Electron Diffraction.

Adsorptive separation of propylene (C3H6) from propane (C3H8), which could deal with energy-intensive cryogenic distillation technologies, remains challenging due to their similar physiochemical properties. Herein, we present a pure silica zeolite with ordered silanols (OSs), whose crystallographic structure was unraveled by the advanced three-dimensional electron diffraction (3D ED), displaying the highly efficient separation of propylene from propane under ambient conditions. The 3D ED technique enables us to investigate its 8-ring pore opening transformation from the round one to the elliptical one during the removal of organic structure-directing agents. Such unique elliptical 8-ring pore openings can exclude larger-size propane and only adsorb propylene. Its C3H6/C3H8 separation performance is also confirmed by column breakthrough experiments, showing a high dynamic adsorption capacity of 53.36 cm3 g-1 for C3H6 but negligible C3H8 under ambient conditions. The dynamic capacity for C3H6 is superior to that of the well-known pure silica DDR-type zeolite (31.07 cm3 g-1). The density functional theory calculation demonstrates that the adsorbed propylene is distributed in the heart-shaped cavity and has a weak interaction with the OSs.

Energy duty in direct contact membrane distillation of hypersaline brines operating at the water-energy nexus

In the context of global climate crisis and growing world population there is the urgent need for viable technical solutions to harvest energy from alternative, renewable and continuous sources and to recover pure water at affordable costs. Herein, we capitalize on the study of direct contact membrane distillation technology treating hypersaline solutions simulating reverse electrodialysis outgoing mixed streams, in the logic of valorising the otherwise environmentally threating brine, in an integrated system operating at the water-energy nexus.Experimental results in terms of transmembrane water flux and dissolved salts rejection, indicate that DCMD is a feasible option to treat feed solutions with concentrations as high as 228 g L−1 total dissolved solids, while recovering pure water from brines which are practically impossible to be dewatered through reverse osmosis. Specific thermal energy consumptions and gain to output ratios, calculated under different feed compositions and flow rates for polypropylene and polyvinilidenefluoride membranes, indicated the possibility to tailor the thermal energy requirements of the MD stage by controlling the ratio between the streams at different salinity that are partially mixed in the RED unit and to potentially adapt it to the available amount of heat.

Structured Data Management for Investigating an Optimum Reactive Distillation Design

Reaction and separation are the two most important processes in the chemical industry that significantly affect the overall energy and cost requirements. Therefore, the operation of integrated reactive separation in a single equipment, such as reactive distillation, potentially increases the chemical process efficiency remarkably. To achieve that advantage, it is vital to design an optimum reactive distillation configuration in the preliminary evaluation. This paper proposes structured data management that can be used to encounter an optimum reactive distillation design. The approach simplified and reduced the data necessity from thousands to dozens by applying a systematic data sorting for the simulation results obtained from the Aspen Plus simulator. Using a case study that is highly relevant to the real chemical processes, i.e., the metathesis of 2-pentene, this study showed that the rule of thumb for determining the optimum design of conventional distillation can be adapted for reactive distillation technology.

Electrical impedance spectroscopy for non-destructive detection of wetting, fouling and scaling in membrane distillation

Wetting, fouling, and scaling of hydrophobic membranes are significant constraints in membrane distillation (MD) technology. In recent research trends, novel membrane fabrication has been given utmost priority to address these constraints, majorly induced by the low surface tension chemicals like surfactants and dissolved organic matters present in the feed water. In this research, we fabricated a hydrophobic membrane using phase inversion technique with polyvinylidene fluoride (PVDF) polymer under an alcohol coagulation bath (ethanol). The wetting, fouling, and scaling of the membrane were monitored using electrochemical impedance spectroscopy (EIS) incorporated with direct contact membrane distillation (DCMD). The surface tension (52.14–27.5 mN m−1) of the synthetic brine water was reduced by adding surfactant, whereas model algal organic matters were dissolved to study the organic fouling. In the fabricated PVDF membrane, an asymmetric interconnected pore structure was obtained with a high hydrophobicity (water contact angle 146°). A narrow pore size distribution (∼0.43 μm), raised liquid entry pressure (∼1.3 bar), porosity (∼75 %), high surface roughness (1.06 μm), and low surface energy (∼28 mN m−1) were noticed with the same membrane. Hence, it qualified for DCMD application under different feed compositions. Different stages of pore wetting and their progress were assessed instantaneously by adopting EIS approach. Further, the permeate side conductivity was correlated with impedance measured during EIS. Advanced proficiency in distinguishing intrusion and different stages of wetting was illustrated.

Hybrid Technology Seawater Desalination Based on Reverse Osmosis and Membrane Distillation Methods

The article presents the results of a computational and analytical study of hybrid RO–MD (Reverse Osmosis–Membrane Distillation) technologies for desalination of the Caspian Sea, providing for the production of an additional amount of desalinated water by the MD method from RO concentrates heated to 50–80°C due to waste heat of fuel combustion products in steam boilers. Two options for solving the problem of the formation of CaCO3 and CaSO4 precipitates on membranes were studied: with preliminary nanofiltration (NF) or Na-cationation (Na) of sea water, as an alternative to the use of antiscalants (AS) and acid. The negative environmental effect of most plants (eutrophication of water bodies) and their low efficiency at high concentrations of desalinated water are taken into account. The Langelier index (СаСО3) and the degree of concentrate saturation (СаSO4) were used as criteria for precipitation of deposits on the membranes. The NF and RO processes were studied using the ROSA computer program, and the MD and Na processes were studied by computer simulation of the corresponding calculation models. It was found that at a 70% permeate yield at the NF and RO stages, the possibility of calcium precipitation on the RO and MD membranes is prevented, but their precipitation on the NF membranes is predicted, which makes the use of AS forced. At the same time, additional permeate production at the MD stage from RO concentrates reaches 40% of the amount of permeate from RO stadium, and the electricity consumption in general according to the scheme is 1.88 kWh/m3. Reducing the calcium hardness of sea water to 50 µg-eq/dm3 by the Na-cationization method makes it possible to refuse both the use of AS and acidification with sulfuric acid with additional production of MD permeate – 27% relative to RO permeate. Electricity consumption rises to 2.5 kWh/m3. To use the known advantages of NF without the use of AS, a hybrid Na–NF–RO–MD scheme is proposed. It has been established that at 80% yields of NF and RO permeates, to prevent the formation of CaSO4 precipitates at all stages of treatment, it is sufficient to reduce the hardness of sea water from 16 to 5.5 m-eq/dm3, and by acidifying the softened water to exclude the formation of CaCO3 precipitates.

An Analysis of Solar Distillation Technology for Mars Colonization

Aiming to analyze the practicality of distilling water on Mars, this research article studied vacuum membrane distillation and its ability to be utilized on Mars. Areas of study includes estimating water needs on Mars, analyzing existing water bodies on Mars, examination of vacuum membrane distillation technology, and more. It was concluded that vacuum membrane distillation is a technology possible to be utilized on Mars and could potentially distill enough water to support a Martian mission.

Improving the performance of reference-frame-independent quantum key distribution with advantage distillation technology.

The reference-frame-independent quantum key distribution (RFI-QKD) has the advantage of tolerating reference frames that slowly vary. It can generate secure keys between two remote users with slowly drifted and unknown reference frames. However, the drift of reference frames may inevitably compromise the performance of QKD systems. In the paper, we employ the advantage distillation technology (ADT) to the RFI-QKD and the RFI measurement-device-independent QKD (RFI MDI-QKD), and we then analyze the effect of ADT on the performance of decoy-state RFI-QKD and RFI MDI-QKD in both asymptotic and nonasymptotic cases. The simulation results show that ADT can significantly improve the maximum transmission distance and the maximum tolerable background error rate. Furthermore, the performance of RFI-QKD and RFI MDI-QKD in terms of the secret key rate and maximum transmission distance are still greatly improved when statistical fluctuations are taken into account. Our work combines the merits of the ADT and RFI-QKD protocols, which further enhances the robustness and practicability of QKD systems.

Dynamics and control of electrified pressure-swing distillation for separating a maximum-boiling azeotrope featuring small pressure-induced shift

Pressure-swing distillation (PSD) is a typical thermal-driven technique for separating pressure-sensitive azeotropes. By implementing heat pump assisted distillation (HPAD) and self-heat recuperation technology (SHRT), the process can be modified as an electrical-driven one. Previous works have verified the overwhelming steady-state economic advantages of electrified PSDs over a conventional design. However, highly integrated electrified processes could jeopardize the dynamics and controllability. In light of potential dynamic control issues, a demonstrating case of a maximum-boiling acetone/chloroform azeotrope featuring a small pressure-induced shift was studied. Severe snowball effects were observed in these complicated electrified systems. To maintain process stability under throughput and composition disturbances, several robust control structures based on decentralized proportional-integral feedback controllers were developed. These control structures feature temperature controllers with no composition measurement. The results indicate that there is no conflict between the steady-state advantage and dynamic controllability. Therefore, considering the great advantages in economic and environmental aspects of electrified PSD, it is encouraged to extend process electrification measures to other distillation processes.

Comparative life cycle assessment of seawater desalination technologies enhanced by graphene membranes

Graphene oxide (GO)-enhanced membranes are being developed to solve major limitations in both reverse osmosis (RO) and membrane distillation (MD) technologies, which include high electricity and thermal energy consumption. This study performed, for the first time, a life cycle assessment to determine the effects of using GO-enhanced membranes on the environmental impacts of seawater desalination via RO and MD. Four scenarios were evaluated and eighteen environmental impacts were quantified according to the ReCiPe impact assessment method. The average impacts for the RO-GO scenarios were lower than those of RO by 3–7 %. The reduction in the climate change impact was 3–8 %, which could avoid the release of 380–850 kt CO2 eq. per year globally if these membranes were used in current seawater RO systems. The MD-GO scenarios had, on average, 27–34 % lower impacts than the MD scenarios. Overall, the RO-GO systems were the most favourable, with lower impacts than MD-GO for most categories. However, using solar-thermal energy instead of natural gas in MD desalination would lead to 43–93 % lower impacts in nine categories than RO powered predominantly by fossil fuels. This includes climate change, which would be 64 % lower; however, freshwater ecotoxicity would be more than four-times higher. The results of this work indicate the potential environmental benefits of GO-enhanced membranes and discuss the future developments needed to improve the performance of RO and MD.

Comparative study on membrane distillation application between raw POME and POMSE

The palm oil industry is considered the traditional pillar of Malaysian industry that plays a key role in the domestic economy. In addition to the high incomes generated by this industry, it generates large quantities of effluent. To solve this problem, the purpose of this work is to introduce membrane distillation (MD) technology for the effluent treatment system. Polyvinylidene fluoride (PVDF) -bentonite hollow fiber membranes were tested in an MD system using raw palm oil mill effluent (POME) and palm oil mill secondary effluent (POMSE). Preliminary test was carried out using deionized water to evaluate the maximum permeate flux achievable in the absence of fouling problem before continuing with POME and POMSE as the feed solution. Membrane performance was evaluated in terms of permeate flux and rejection rate of several water quality parameters. The average permeate flux obtained while using raw POME is much lower than that obtained in the POMSE test which was recorded as 1.41 ± 0.62 kg/m2.hr and 3.45 ± 0.51 kg/m2.hr respectively. The membrane tested for POME experienced a significant decrease in flux relative to POMSE due to the excessive amounts of biological compounds blocking the membrane pores. In terms of removal efficiency of the PVDF-bentonite membrane, the membranes were able to achieve more than 95% removal efficiency for chemical oxygen demand, nitrate nitrogen, total suspended solids, total dissolved solids, color and turbidity. The results proved that the DCMD system was able to eliminate almost all pollutants in the effluent from oil palm industry. However, raw POME without pre-treatment is not suitable to be used directly in the DCMD process because it will cause a serious fouling problem. In conclusion, it can be said that MD has shown excellent performance in the treatment of palm oil wastewater and can be applied to other types of oil industries.

Optimal Binding Affinity for Sieving Separation of Propylene from Propane in an Oxyfluoride Anion-Based Metal-Organic Framework.

Highly efficient adsorptive separation of propylene from propane offers an ideal alternative method to replace the energy-intensive cryogenic distillation technology. Molecular sieving-type separation via high-performance adsorbents is targeted for superior selectivity, but the limit in adsorption capacity remains a great challenge. Here, we report an oxyfluoride-based ultramicroporous metal-organic framework UTSA-400, [Ni(WO2F4)(pyz)2] (pyz = pyrazine), featuring one-dimensional pore channels that can accommodate the propylene molecules with optimal binding affinity while specifically excluding the propane molecules. The exposed oxide/fluoride pairs in UTSA-400 serve as strong functional sites for strengthened propylene-host interactions, accounting for a significantly enhanced propylene uptake, while the propane molecules are excluded due to the regulated host framework dynamics. The strong propylene binding enables near-saturation of propylene in the pore confinement at ambient conditions, leading to full utilization of pore space and superior packing density. Combined in situ infrared spectroscopy measurements and dispersion-corrected density functional theory calculations clearly unveil the nature of boosted host-guest binding. Direct production of polymer-grade (>99.5%) propylene with remarkable dynamic productivity is demonstrated by column breakthrough experiments. This work presents an example of pore engineering with atomic precision to break the trade-off in adsorptive separation through guest binding optimization.

Model compression optimized neural network controller for nonlinear systems

Neural network-based controllers are widely used within the domain of robotic control systems. A network controller with more neurons typically achieves better performance, but an excessive number of neurons may make the model computationally intensive, resulting in slow dynamic responses in real-world environments. This paper reports a network compression method that integrates knowledge distillation technology for the development of concise neural network-based controllers to achieve a balance between the control performance and computational costs. The method first trains a full-size teacher model, which is then pruned, leading to a concise network with a minimum compromise of performance. From in this study, the resulting concise network is considered to be the prototype of a student model, which is further trained by a knowledge distillation process. The proposed compression method was applied to three classical networks, and the resultant compact controllers were tested on a robot manipulator for efficacy and potential demonstration. The experimental results from a comparative study confirm that the student models with fewer neurons resulting from the proposed model compression approach can achieve similar performance to that of the teacher models for intelligent dynamic control but with faster convergence speed.

Recent progress, bottlenecks, improvement strategies and the way forward of membrane distillation technology for arsenic removal from water: A review

Arsenic (As) is a common aquatic pollutant that enters the environment from anthropogenic sources and causes serious public health issues. Various conventional techniques have been applied for As removal from drinking water. However, those conventional techniques could not meet the requirement of the As discharge standard of <10 mg/L in drinking water set by the World Health Organization (WHO). To deal with this bottleneck, membrane distillation (MD) offers a complete As removal from an aqueous solution due to its higher rejection rate with less energy consumption than thermal techniques that require high thermal energy. This article reviews the recent progress of MD configurations, membrane modules, and membrane materials employed for As removal. This work also uncovers the technological solutions of MD in tackling a variety of bottlenecks in removing As from aqueous solutions. This includes integrating MD with alternative energy sources and/or forward osmosis (FO) to incorporate its hybrid systems with less energy consumption or a high separation rate. Limitations, challenges, and opportunities of MD systems for As removal were highlighted with a technological solution to these bottlenecks. The MD systems can effectively remove As (III) and As (V) with 100 % As rejection using hydrophobic ceramic and polymeric membranes. Overall, MD could play a role in helping the water industry meet the United Nations' Sustainable Development Goals (SDGs), such as clean water, affordable energy, and climate change mitigation.

Application of pressing and hydro distillation technology in the extraction of seedless lemon essential oil (Citrus latifolia Tanaka)

Citrus is one of the most popular tropical fruit tree genera in the world with delicious taste and a rich content of vitamins C, A, fiber, and other essential minerals. The citrus essential oil has the main component being D-limonene, which is a substance with high antibacterial and antioxidant properties, along with various compounds. The experimental process of essential oils extraction from seedless lemon peels by mechanical distillation method combined with hydrodistillation, followed by comparative analysis of the chemical composition of the resulted essential oils. Results have shown that the yield of essential oils obtained from the mechanical pressing and distillation process is 0.089% and 0.10%, respectively. The main compound present in these essential oils is D-limonene with the concentrations in pressed and distilled oils being 58.967% and 38.552%, respectively. The research results show that the technological process of extracting essential oils by mechanical pressing can provide basic understanding about different extraction methods.

Deep Learning With Fault Prior for 3-D Seismic Data Super-Resolution

Seismic data are always in low-resolution due to the limitations of seismic acquisition and processing technology, which bring challenges to subsequent seismic interpretation. Deep learning has been successfully applied to the seismic data super-resolution, all methods tend to directly learn the mapping relationship between low-resolution seismic images and super-resolution seismic images through some complex convolutional neural networks. But blindly increasing the depth of the network brings limited improvement to the super-resolution work. We propose a novel geophysical prior guided framework for seismic data super-resolution to solve this problem. Specifically, we select fault prior to guide the training of deep learning model: we use knowledge distillation technology to progressively propagate the fault prior from the teacher network (trained with the low-resolution synthetic seismic data/high-resolution fault prior and high-resolution synthetic seismic data pairs) to the student net-work (trained with the low-resolution synthetic seismic data and high-resolution synthetic seismic data pairs). To better propagate fault priors, we use feature space loss and soft ground truth loss in student network training. Finally, we use the trained student network to complete the super-resolution of synthetic validation seismic data and real seismic data. In addition, in our super-resolution framework, we directly process 3D seismic data instead of 2D seismic images, which further improves the effects of super-resolution and the subsequent seismic interpretation. Compared with the state-of-the-art seismic super-resolution method, the experimental results show that the super-resolution results of our method can depict the faults more clearly.

Research on High Flux Direct Contact Membrane Distillation Technology

The effects of membrane materials, membrane module structure and membrane distillation operation parameters on the performance of direct contact membrane distillation were investigated by using strontium chloride solution with Sr2 + concentration of 1g/L as test solution. The results showed that the flux of PTFE is the largest, PVDF is the second, PP is the smallest, and the rejection rate of PTFE decreases rapidly with the increase of running time, which indicated that PTFE is easy to be fouled, while PVDF is a better membrane material; When the packaging fraction of membrane module increases, the membrane flux decreases, but the water yield per unit time increases. Considering the economy and treatment efficiency, it is recommended to select the membrane module with packaging fraction of 11.42%; the increase of feed flow rate and temperature is beneficial to the increase of flux in DCMD process. The rejection rate is almost unaffected by the membrane module structure and operating conditions, and remains above 99.9%. This study is helpful to provide research direction for improving membrane distillation flux, and provide theoretical reference for membrane distillation technology to treat practical radioactive wastewater.

Vacuum Distillation of Aceh Patchouli Oil into Hi-Grade and Crystal Patchouli with Rotary Vacuum Evaporator

Patchouli or Pogostemon cablin benth is one of the most important essential oil-producing plants in Indonesia. In the world of trade, patchouli oil is widely used as raw material, a mixing agent, and a fixative. Patchouli oil can be upgraded to Hi-Grade Patchouli (HGP) with a Patchouli alcohol (PA) content of 40-80% through vacuum distillation technology. Furthermore, HGP can be further processed into crystal patchouli with a purity of up to 90-100%. This study aims to improve the quality of patchouli oil produced by the community. This study examines the effect of variations in vacuum pressure on the distillation process on the quality of the resulting patchouli oil, determines the impact of cooling temperature variations on the resulting crystal mass, and determines the crystal quality (patchouli alcohol content and crystal size). The method used was vacuum redistillation followed by crystallization of patchouli oil. In the redistillation stage, it is carried out using a rotary vacuum evaporator. Redistillation is conducted in two stages: the first is to produce a light fraction at a temperature of 125 ℃, and the second is to produce a heavy fraction at a temperature of 140 ℃. The variable that was varied was process pressure. The pressure used is 1; 2-3; 6-8 and 10-12 mbar. The process is continued with crystallization using the cooling method (cooling crystallization) with a cooling temperature variation of -12 ℃ and -15 ℃. The results showed that through the vacuum redistillation method, the quality of patchouli oil produced by the community could be increased in PA levels up to 81.79%. The lower the operating pressure, the highest the quality of patchouli oil is produced. The lower the crystallization cooling temperature, the more crystal mass is formed. The crystal purity of this HGP resulted in very high levels of crystalline PA, namely 99.6%. The crystal size obtained is 290-600 μm on average.

Operating windows for early evaluation of the applicability of advanced reactive distillation technologies

Advanced reactive distillation technologies (ARDT) are often overlooked during process synthesis due to their complexity. This work proposes the use of operating windows with additional features to identify suitable operating limits for ARDT. Data needed to construct the operating windows are thermodynamic properties, kinetic parameters, constraints of materials and experimental methods, and heuristics. In addition, two new concepts are proposed to represent complex features: representative components and a sliding window. Results include the identification of suitable operating limits for ARDT to help assess their feasibility early in process design. The proposed approach is demonstrated by case studies. Methyl acetate production can be carried out at low pressures (0.5–3.6 atm), while lactic acid purification requires vacuum conditions (0.3–0.8 atm) to avoid thermal degradation. Tert-amyl methyl ether production was evaluated in two scenarios where the effect of side reactions is evidenced in a reduction of the reaction window due temperature limits to favour the main reaction over side reaction. This study is the first to evaluate advanced reactive distillation technologies using a graphical representation in an operating window to aid process synthesis, where the results provide key selection insights.