Film Distillation Research Articles

Reduction of PCBs in whale oil by steam thin film distillation

Reduction of PCBs in whale oil by steam thin film distillation

Pilot-scale testing of a multi-tube type falling film distillation column equipped with a biphasic thermosyphon as a new alternative for the desalination of brackish water and seawater

This paper proposes an innovative technology for desalinating brackish water and seawater using a multi-tube type falling film distillation column integrated with a biphasic thermosyphon. Based on the literature survey, this proposal has not been previously explored. In this study, the viability of the pilot-scale application of this technology for desalination was tested, and the process performance was evaluated in terms of distillate flow rate, salinity removal, and energy consumption, considering different experimental conditions. Synthetic solutions containing 10.0 and 35.0 g/L of sodium chloride were used to simulate brackish water and seawater salinities, respectively. The thermal desalination pilot plant integrating a compact falling film distillation column and a biphasic thermosyphon demonstrated high effectiveness, consistently producing desalinated water with a conductivity below 10 μS cm−1. Considering both concentrations, the optimal condition for desalinated water production was a feed temperature of 85 °C, a vapor chamber temperature of 121 °C, and an energy consumption of 16 kW. This new technological option’s energy consumption is approximately 33 % lower than that of a simulated flash distillation column operating under similar conditions. In conclusion, this study presents promising results, establishing falling film distillation technology as a viable alternative for desalinating brackish water and seawater.

Startup operation of an energetically-intensified single-tube type falling film distillation column: Insights from a pilot-scale study

Technological advancements in the field of energetically intensified falling film distillation columns have not been paralleled by sufficient published research on comparative startup evaluations for the single-tube falling film distillation column under different thermal energy transfer methods. The present study's originality and significance stem from presenting a startup procedure for a single-tube type falling film distillation column that employs a biphasic thermosyphon as a heat source for producing hydrated ethanol at a pilot scale. The concept of three discrete phases, the discontinuous, semi-continuous, and continuous phases, was employed to characterize the startup operation. The time and energy required for each phase of the startup operation were determined. This study also examined the startup operation with respect to two possible thermal energy transfer methods from the steam chamber to the distillation tube: isothermal and non-isothermal. The experiments were conducted in a pilot distillation column consisting of a single vertical tube, which processed a binary mixture of water and ethanol with a flow rate of 33 kg h−1. No relevant variation in startup time was detected for the three distinct stages when comparing the two heating modes, with a total startup duration of 2.2 h being observed irrespective of the heating configuration utilized. The isothermal heating configuration can produce hydrated ethanol at a rate of 3.0 kg h−1, with an ethanol content increase from 12.5 to 62.8 wt%. However, the non-isothermal heating mode yields a higher ethanol content an increase in ethanol content from 12.5 to 64.3 wt.%, albeit with a lower productivity rate of 1.3 kg h−1. Operating the single-tube type falling film distillation column with the steam chamber under the non-isothermal heating mode required only 2.12 kW for the startup, resulting in a 30.30 % reduction in energy demand compared to the isothermal heating configuration. The presented findings provide an empirical foundation for improving the efficiency and effectiveness of energetically intensified falling film distillation columns.

Film Distillation with a Porous Condenser for Seawater Desalination: Evaluation of Materials’ Stability in the Tropical Climate of Vietnam

Desalination and treatment of wastewater has become critical for Asia regions with water scarcity. In this work, the concept of thin-film distillation equipped with a porous condenser (FDPC) was considered for its implementation in a tropical climate of Vietnam. It was found that samples with a concentration of biocide of 0.5 wt.% possessed lower biofouling, in contrast to the neat membranes. The FD-PC module was developed and water desalination experiments were conducted in Russia and Vietnam. The experiments showed high reproducibility of the results; in particular, the evaporation rate was (4.9/3.0) kg/m2h in Russia and (4.1/2.0) kg/m2h in Vietnam. In addition, as part of this work, the optimal configuration of the installation was calculated using solar collectors as the main energy source. The calculation showed high energy efficiency: specific energy consumption 0.1-0.5 kWh/m3.

Triethylene glycol recovery by an energetically intensified thermosyphon-assisted falling film distillation unit: Experimental assessment on a pilot-scale unit and in-silico comparison with a conventional column from natural gas processing

Facing the emerging needs for energy-enhanced separation units, this work evaluated the triethylene glycol (TEG) regeneration, used as a dehydrating agent of natural gas from wells, by a novel thermosyphon-assisted falling film distillation technology, called Destubcal. The pilot-scale device has an innovative heat supply through a two-phase closed thermosyphon, which ensures a uniform energy distribution along the entire distillation tube. Based on current operating data from industrial water-rich TEG streams, different operating conditions were performed in the pilot-scale unit. The best recovery ratio (99.0%) was obtained with an evaporator temperature of 180 °C and a feed flow rate of 15 L/h. However, in order to maximize the bottom TEG composition, the best experimental condition achieved was 17 L/h and bottom temperature of 152.07 °C, due to an evaporator temperature of 170 °C. As a result, the Destubcal unit saved around 38.4% in energy requirement and reduced 49% the column height when compared to a conventional distillation column for the same recovery degree. Therefore, the proposed Destubcal technology can be considered a feasible alternative as recovery column for TEG regeneration in natural gas beneficiation units, with advantages of reduced dimensions and energy-saving operation.

A floating planting system based on concentrated solar multi-stage rising film distillation process

This work presents a floating planting system based on multi-stage rising film distillation process driven by concentrated solar energy. The proposed system applies desalinated freshwater to directly irrigate hydroponic crops, which saves land area and takes advantage of ocean resources. The hydrophilic wick is selected as the evaporator to form a rising seawater film by capillary suction. Through the vertically arranged multi-stage evaporation and condensation units, the latent heat of vapor can be recovered effectively. To obtain the maximum optical efficiency, the optical simulation of the concentrating section is carried out. Based on optimized structure, an experimental system is built to investigate the effects of different operating parameters on the internal temperature, water production rate, gained output ratio (GOR), and exergy efficiency. Under indoor steady-state conditions, the temperature difference of desalination units is found to be progressively larger under increasing irradiance. In addition, the system could achieve 1.7 of GOR and 6.1% of exergy efficiency with 900 W/m2 irradiance. Results at actual weather reveal that the daily water yield of the system could reach 9.51 kg/m2/day under azimuth tracking condition, which is 97% higher than the fully passive operation condition. Finally, under 28 consecutive days of operation, the average growth height of lettuces cultivated by the system is 13.7 cm.

Modeling of Film Distillation with Membrane Condenser for Treatment of Reverse Osmosis Concentrate under Vietnam Tropical Conditions

Modeling of Film Distillation with Membrane Condenser for Treatment of Reverse Osmosis Concentrate under Vietnam Tropical Conditions

Techno-economic and energetic assessment of an innovative pilot-scale thermosyphon-assisted falling film distillation unit for sanitizer-grade ethanol recovery

The increasing demand for ethanol-based disinfectants due to the COVID-19 pandemic has driven the emergence of innovative strategies to avoid the risk of shortage and reduce production costs. Distillation is well-known as the major energy consumer and cost driver for ethanol recovery in conventional distilleries. Our research team has been developing a novel heat-intensified falling film distillation apparatus assisted by a two-phase closed thermosyphon, patented as Destubcal. Therefore, this study aims to provide a techno-economic and energetic assessment of the pilot-scale thermosyphon-assisted falling film distillation unit applied to recover sanitizer-grade ethanol with 70 vol% in alcohol. Performance analysis showed that under a feed flow rate of 14L/h, a feed temperature of 80 °C, and an evaporator temperature of 93 °C, the pilot-scale unit reaches the minimum specific thermal energy consumption with the maximum distillate ethanol recovery and energy efficiency (88.5%). The impact of the elements in the capital cost-share showed instrumentation and control (27.8%), and piping and auxiliary equipment (27.6%) as the predominant capital costs, while the cost for major process equipment represents only 6.2% which reveals a low-cost and easy-to-implement technology. The major operating cost-driver is the labor (51.3%) since the pilot-scale unit has a lower capacity than industrial plants. However, the Destubcal unit spends on utility costs about 31.6$/m3feed, which represents a total saving of 43.8% compared to conventional distilleries. Furthermore, the Destubcal unit saves about 1.78 MJ/kg (46.4%), with 59.2% less column height than a conventional column, being considered techno-economically feasible for sanitizer-grade ethanol recovery.

Energy efficiency comparison between a conventional tray column and a novel heat-intensified thermosyphon-assisted falling film distillation unit: an assessment for mixtures with different relative volatilities

An energy performance comparison between a novel thermosyphon-assisted falling film distillation unit and a conventional tray unit was carried out for three mixtures with different relative volatilities: ethanol-water, acetone-isopropanol, and acetone-water. Experimental data from the pilot-scale plant were used as targets in the simulation runs through the Hysys® software. Thus, the separation performed in the falling film unit was reproduced in a conventional tray column. The thermosyphon-assisted falling film unit required less energy, with reductions of 24% for acetone-isopropanol, 30% for ethanol-water, and 55% for the acetone-water mixture. The energy-use ratio also showed that for each kW consumed in the falling film unit, the conventional unit would consume 1.33 kW for acetone-isopropanol, 1.44 kW for ethanol-water, and 2.21 kW for acetone-water, based in the same separation. Therefore, this novel distillation apparatus is more advantageous as an energy-saving viable option for separating mixtures with different relative volatilities.

Thin-film distillation coupled with membrane condenser for brine solutions concentration

A novel concept of film distillation equipped with the membrane condenser (FD-MC) was proposed and implemented for the concentration of brine salt solutions. In this thermo-gradient method, the water was evaporated from the thin liquid film flowing alongside the hot surface, and then directly condensed on the cold surface of the porous membrane placed at the distance of few millimeters from the feed. The change of the membrane positioning from the hot feed solution to the cold water stream (coolant circuit) enables to overcome the common challenges of the membrane distillation process like long-term stability towards pores wetting, membrane scaling, and latent heat loss. Comparing with the air gap membrane distillation with membrane condenser (AGMD-MC), FD-MC demonstrated higher water flux (14.7 kg/m2·h) and stable performance during the concentration of NaCl solution from 50 up to 230 g/kg (microcrystal formation was noticed) even in the presence of organic pollutants (kerosene or surfactants). A mathematical model of heat and mass transfer in FD-MC process was proposed and successfully verified. With the respect to the temperature of hot (40–100 °C) and cold (10–60 °C) circuits, the energy consumption and thermal efficiency of FD-MC process were in the range of 2.7–3.2 MJ/kg and up to 97%, respectively.

Machine learning modeling and genetic algorithm-based optimization of a novel pilot-scale thermosyphon-assisted falling film distillation unit

Engaged in the global trend towards more energy-efficient and sustainable technologies, our research team has developed a falling film distillation apparatus with an innovative heat supply through a two-phase closed thermosyphon. In order to evaluate the performance of this energy-intensified distillation process, a supervised machine learning (ML) predictive model based on artificial neural networks is implemented for the separation of the ethanol–water binary mixture. The feed temperature, the evaporator temperature, and the feed flow rate are the three input variables of the model, whereas the ethanol mass fraction in the distillate, the distillate mass flow rate, the recovery factor, and the separation factor are the four performance indicators evaluated. The feed-forward ML has been trained, tested, and validated using a total dataset of 64 experimental runs carried out in the pilot-scale unit, covering a wide operating range of the input variables. Despite the high non-linearity, the ML approach was capable of modeling this new process accurately. The optimal topology of the ML model was achieved with a network arrangement of 10 neurons within 1 hidden layer (3:10:4), with a correlation coefficient (R) greater than 0.95 for all data. The predictive abilities of the ML model were harnessed to investigate the individual and synergistic interaction effects of the operating variables by plotting generalization graphs. Finally, the optimal operating conditions were evaluated by the genetic algorithm (GA) technique, being the feed temperature of 90.6 °C, the evaporator temperature of 109.6 °C, and the feed flow rate of 26.3 L/h, the process operating values that led the maximum of the four performance indicators, simultaneously. Under these operating conditions, a distillate mass flow rate of 4.9 kg/h, with 50.6%wt ethanol-enriched, a recovery factor of 84.9%, and a separation factor of 57.4 have been achieved, showing the high-performance feasibility of the pilot-scale unit.

Nonequilibrium Stage Based Modeling of a Falling Film Distillation Unit

A novel nonequilibrium stage based model was developed for a falling film distillation unit. The model combines mass and energy balances in the liquid and vapor phases, without the need of separation efficiency factors. The modeled pilot scale falling film distillation unit is differentiated because the heat supply is carried out axially by means of a thermosyphon. In terms of the algorithm proposed, the central contribution is in reducing the number of variables to be determined by the method, which brings benefits such as reduction of computational time and increase of robustness in the convergence. The results obtained were compared with experimental data from the pilot scale plant, and showed good predictability, with deviations in the top temperature below 2.60%, 6.59% in the distillated ethanol fraction, 12.32% in the resistance power and only one case above 10% for distillate flow rate.

Dynamic modeling with experimental validation and control of a two-phase closed thermosyphon as heat supplier of a novel pilot-scale falling film distillation unit

Worldwide efforts in process intensification led to innovative designs for distillation, notably known as an energy-intensive process. Focusing on the boosting of thermal efficiency, our research team developed a novel pilot-scale thermosyphon-assisted falling film distillation apparatus. A network dynamic modeling is proposed to describe the thermal behavior of this new device, and the model is validated by dedicated experimental campaigns with the pilot-scale unit. The thermal network-based model was able to predict accurately the transient behavior and steady-state temperature of the two-phase closed thermosyphon. The experimental and predicted transfer coefficients showed reasonable agreement within the ±25% deviation band. A feedback control of the thermosyphon's evaporator temperature is performed in Simulink® to manage the steam chamber temperature. PID technique is adopted to achieve faster and smoother the control target, with the secondary effect to reduce mechanical stresses, increasing life cycle, and reducing energy consumption by 3.1%.

Energy conditions assessment of a two-phase annular thermosyphon used as heat supplier for a new pilot-scale falling film distillation unit

Energy-efficient chemical processes save resources and provide sustainability. Conventional distillation is notably known as an energy-intensive process, which motivated our research group to develop a new thermosyphon-assisted falling film distillation apparatus (Destubcal technology), where heat is supplied through the condenser of an annular thermosyphon coupled to the distillation tube. From this new design, two possible configurations of energy supply were studied: isothermal and temperature-profile conditions in the condenser of the annular thermosyphon. The distillation tube was fed with ethanol-water mixture, varying the feed flow rate and feed temperature, as well as the power of electrical resistances in the evaporator of the annular thermosyphon. Temperature-profile condition leads to a better heat transfer distribution, resulting in higher temperatures in the distillation tube and so higher ethanol recovery in the distilled product. In this way, temperature-profile operation proved to be more advantageous for this new thermosyphon-assisted distillation unit, corroborated by the separation factor, reaching a 10.3% increase. The analysis of operational variables showed that smaller potencies in the evaporator allow better separation, an important aspect of energy intensification. Thereby, this works contributes towards the urgent demand for novel thermal intensified proposals, indicating the best operational conditions for an advanced falling film distillation unit.

Ethanol enrichment from an aqueous stream using an innovative multi-tube falling film distillation column equipped with a biphasic thermosiphon

This paper aims to offer a new compact, safer, less energy-intensive technological alternative for ethanol-water separation, based on the intensified multi-tube falling film distillation technology. A pilot-scale investigation (with a processing capacity close to 250 kg h−1) proved the practical feasibility of a multi-tube falling film distillation column coupled with a biphasic thermosiphon for the distillation of ethanol and water in obtaining concentrated ethanol (64 wt.% - acceptable for medical applications) from aqueous ethanol (12 wt.%). Notable findings were achieved by using the intensified multi-tube falling film distillation to produce hydrated ethanol with adequate ethanol recovery (∼ 50 %), acceptable energy savings (∼ 15 %) and significant space savings (∼ 63 %) as compared with a conventional tray column, thus justifying its relevance for sugarcane ethanol distilleries. Finally, new research prospects for further improving the separation efficiency of this novel distillation concept are also mentioned in this study, purporting to make such novel intensified distillation process more competitive with conventional distillation columns in the future.

Energy Management Optimization of Open-Pit Mine Solar Photothermal-Photoelectric Membrane Distillation Using a Support Vector Machine and a Non-Dominated Genetic Algorithm

As a distributed energy source, open-pit mine solar photothermal-photoelectric membrane distillation can convert solar energy into heat and electrical energy to provide power for a membrane distillation water purification system. In mine sewage treatment, the solar membrane distillation system has the advantages of high desalination rate, good water quality and low cost. However, this system has not been widely promoted and applied because of its high energy consumption and low membrane flux. Different operating parameters have a greater impact on the operating efficiency of the solar membrane distillation system. In this study, a natural cooling film distillation system was built, the response surface method was used to analyze it, and a multi-objective optimization algorithm was used to optimize the operating conditions and improve the energy efficiency of the system. In our experiment, the hot end feed temperature, hot end feed flow rate, cold end cooling water flow rate, and membrane area were used as variables, and the membrane flux, thermal efficiency, and energy consumption values were investigated as target values. We used a support vector machine (SVM) with improved fitting, and substituted the fitting prediction model into the response surface method for the relationship between the variable and the target value. Collaborative analysis was followed by substituting the model into a non-dominated sorting genetic algorithm-II (NSGA-II). After the optimization operation, the optimal working conditions were obtained to improve the operating efficiency of the solar membrane distillation system, which will enable open-pit mine prosumers to realize intelligent management of solar energy generation, storage and consumption simultaneously.

Application of a new pilot-scale distillation system for monoethylene glycol recovery using an energy saving falling film distillation column

Monoethylene glycol (MEG) is a desiccant widely used in the Oil and Gas and Sugar Cane Alcohol industries and generates a large volume of MEG-water mixture effluent. This original study explores the use of a new pilot-scale distillation system for separating MEG from a MEG-water mixture. The distillation tests were performed with a single-tube falling film distillation column assisted by a thermosyphon system operating at atmospheric pressure (Destubcal Technology). The results attained high MEG contents, with a MEG loading of 66.00% (m/m), yielding a MEG separation of 88.61%. Additionally, a distillation arrangement with two single-tube falling film distillation columns in series was able to reach values of separation similar to those used by companies in the Oil and Gas sector, while operating at atmospheric pressure. It was also found that Destubcal Technology leads to a 46.93% reduction of the energy required and is more compact than a conventional-industrial distillation column.

ENERGY AND EXERGETIC EVALUATION OF THE MULTICOMPONENT SEPARATION OF PETROCHEMICAL NAPHTHA IN FALLING FILM DISTILLATION COLUMNS

Abstract Multicomponent separation of synthetic petrochemical naphtha (hexane, cyclohexane, toluene and xylene) was carried out in a falling film distillation sequence with heat supply using a vapor chamber (thermosyphon). Tests were carried out by varying feed flow rate and temperatures of the feed and the vapor chamber in two ways of heat supply: isothermal and with a vapor chamber temperature profile. Regarding the distillation behavior of the multicomponent separation with the proposed falling film column, it was verified that the lower values of the studied variables and the profile temperature mode promoted the best results for hexane recuperation. With an indirect sequence of three columns, hexane mass fraction in the top column increases to the value of 0.82. Higher thermodynamic efficiency was found for two columns of the sequence in comparison with the conventional ones. This behavior is related to smaller energy consumption, showing a total energy reduction of 12% compared to the same separation performed in a conventional unit. Energy and exergetic efficiency values were higher than 95% and 85% in the three columns used. These analyses demonstrated that the falling film separation proposal is an energy efficient arrangement and could be considered for multicomponent separation.

Falling film distillation column with heat transfer by means of a vapor chamber – part I: isothermal operation

We describe a new configuration for falling film distillation columns: a heating system provided by a vapor chamber along the entire column with the operation at atmospheric pressure. Experimental tests were carried out with an ethanol–water mixture by providing isothermal while varying the feed flow rate and the temperatures of the feed and vapor chamber. This heating proposal allowed the formation of a temperature gradient inside the distillation column, which was attributed to the mass and heat axial transfer that occurred along the entire length of the unit. Different from the usual recommendation for film units, higher flow rates are more suitable for distillation of ethanol and water, which was attributed to the heat transfer method and the operation being held at atmospheric pressure. Also, it was observed that there is a strong relationship between the feed temperature and vapor chamber temperature. The results are promising and encourage further studies with this new heat transfer proposal.

Falling film distillation column with heat transfer by means of a vapor chamber. Part II: operation with a temperature profile

Based on previous results and a new proposal for the configuration of falling film distillation columns heated by a vapor chamber operating at atmospheric pressure, the present study analyzed a different application for heat transfer by means of an the axial temperature profile in the same vapor chamber, generated by the presence of non-condensable gases. Experimental tests were performed with an ethanol–water mixture by varying the feed flow rate and vapor chamber temperature. This new heat transfer proposal allowed the formation of a temperature gradient inside the distillation tube (similarly to the isothermal proposal previously reported), thus indicating that this heat transfer method is feasible for a distillation unit. The results demonstrated that higher flow rates are suitable for the distillation of ethanol and water in this new proposal; the temperature profile operation shows the feasibility of this new heat transfer proposal in falling film distillation columns and encourages further studies on the optimization of the process and the evaluation of the energy consumption.