High Feed Flow Rate Research Articles

Plasma-assisted NH3 cracking in warm plasma reactors for green H2 production

NH3 is emerging as a carrier of green H2, but it requires a green and economical NH3 cracking process based on renewable energy. Plasma technology is promising for this purpose, as it can crack NH3 without the need for a catalyst and is highly compatible with renewable electricity, reducing the environmental footprint of the cracking process. This work investigates the NH3 cracking performance of four different warm plasma reactors with different configurations and operating in a wide range of conditions. We show that the NH3 conversion in warm plasma reactors is primarily determined by the specific energy input, with the main difference observed in the energy cost (EC) of cracking. The lowest EC obtained is 146 kJ/mol but at a conversion of only 8 %. A more reasonable conversion of around 50 % yields an EC of around 200 kJ/mol in two of the reactors investigated. Plasma reactors operating at higher feed flow rates are more efficient and yield a higher H2 production rate. Our data indicate that NH3 cracking in these warm plasma reactors occurs mainly via thermal chemistry, with non-thermal plasma chemistry playing a less prominent role. NH3 decomposes not only inside the plasma core but also in a hot volume around it, which reduces the EC. Our study shows that warm plasmas are significantly more efficient for NH3 cracking than cold plasmas, even when the latter are combined with catalysts.

Dynamic control analysis of energy-efficient side-stream extractive distillation process for separating close-boiling mixture

To separate the close-boiling mixture comprising heptane and toluene, this study introduces an environmentally-friendly method of side-stream extractive distillation by utilizing aniline as the separating agent. This approach modifies traditional extractive distillation by adding a side rectifier, converting two-way vapor and liquid communication into one-way liquid transfer using an additional distillation section along with corresponding reboiler. Our present study investigates the dynamic control behavior for a strongly non-ideal system without and with heat integration. It focuses on achieving stable and reliable regulatory control by closely keeping the dual-product composition to their original design standards. Key control loops are pinpointed, with a specific emphasis on those centered around adjusting reboiler heat duty and side-stream flow rate within extractive column C1 to regulate the temperatures of Stages 48 and 36. Furthermore, control effectiveness is enhanced by introducing a feedforward action of reboiler heat duty-to-feed flowrate. By developing a new and robust control architecture, high feed flowrate and composition disturbances can be managed efficiently, solving the issues of oscillation and large transient response.

Comparison of non-isothermal and isothermal cycles in a novel methane-assisted two-step thermochemical process

As driven by thermodynamics and reaction kinetics considerations, conventional two-step solar thermochemical processes typically rely on non-isothermal cycling conditions to effectively couple the endothermic reduction and exothermic oxidation reactions. Nevertheless, recent discussions on isothermal cycles based on thermodynamics simulation and material characterization have sparked dissenting opinions, as certain reaction processes operating under isothermal cycling conditions have demonstrated the possibility of achieving higher energy conversion efficiency. To delve further into such phenomenon and potentially unveil the underlying scientific principles, this study conducts a reaction kinetic analysis and lab-scale systematic experiments on a novel methane-assisted two-step thermochemical process using iron-based oxygen carriers. Despite the fact that the reaction kinetics analysis of iron oxides indicates that isothermal cycles at reaction temperatures of 573–1173 K do not provide significant advantages in terms of energy conversion efficiency, surprisingly, the experiments conducted with the prepared cobalt–nickel ferrite materials conclude oppositely. More specifically, the observed increase in material reactivity with rising oxidation temperature contributes to an approximately two-fold enhancement in the CO yield under isothermal conditions, as well as a noteworthy improvement of about 15% in solar-to-fuel efficiency. This energy efficiency improvement could be attributed, at least in part, to the stable reaction temperature during isothermal cycling, which effectively mitigates the challenges associated with solid-phase sensible heat recovery caused by significant temperature fluctuations, particularly when operating at high feed flow rates. Accordingly, the applicability of isothermal cycles is linked to two crucial factors: the reactivity of the oxygen carrier and the specific operating conditions employed. The experiments herein conducted showed that the catalytic activity of the material reached a relatively stable state after 24 h of reaction, resulting in a peak CO yield of 20.5 mL min−1 g−1 and a CO2 conversion exceeding 90%. Thorough analyses reveal several optimization measures for enhancing efficiency under the setting of the reaction system.

Optimization of Membrane Condenser Process with PTFE Hollow Fiber Membrane.

A membrane condenser (MC) is a novel membrane separation technology that utilizes the hydrophobic nature of porous membranes to capture water vapor from humid gas. Factors such as temperature, pressure, flow rate, and gas composition entering the membrane condenser play a crucial role in water recovery efficiency. This study utilized hydrophobic polytetrafluoroethylene (PTFE) hollow fiber membranes to create multiple identical membrane modules. This research investigated the impact of temperature, flow rate, pressure on the intake side, gas flow on the cooling side, membrane area, and other variables on the performance of the membrane condenser process. This study compared water extraction efficiency under different conditions, focusing on feed flow temperature and sweeping flow. Results showed that at a temperature of 60 °C, the water recovery rate was 24.7%, while a sweep gas flow rate of 4 L/min resulted in a recovery rate of 22.7%. The efficiency of the membrane condenser decreased with higher feed flow rates but increased with larger membrane areas. A proportional relationship between inlet flow and membrane area was observed, suggesting an optimal range of 0.51-0.67 cm/s for both parameters. These findings offer valuable insights for the practical implementation of hydrophobic membrane-based membrane condenser technology.

A novel process for rutin recovery from model solutions using nanofiltration: Experimental study, mathematical modeling, and scale‐up design

AbstractPressure‐driven membrane processes represent a credible method for the separation and concentration of natural polyphenols. The separation characteristics and their productivity depend on several factors such as molecular weight cut‐off, operating conditions, and test cell parameters. In this study, a compact polyamide HFT‐NF150 nanofiltration membrane has been tested to separate different model solutions of rutin, and the effects of operating conditions like trans‐membrane pressure, feed concentration, and feed flow rates were analyzed. All the findings of the experiment revealed that the maximum permeate flux of 3.04 × 10−5 m3/m2 s and 98.5% rejection were obtained at a high feed flow rate of 36 L/h and a high pressure of 6 × 105 Pa. Also, the Spiegler–Kedem model is used to report the mass transport phenomenon across the membrane. The unconstrained minimization technique based on the simplex search method was applied for the estimation of the unknown parameters. The theoretical and experimental values for permeate characteristics were then compared for each experimental data point for the model validation. Later, a mathematical model was used to check the scale‐up viability of the process to the commercial limit.Practical applicationsIn the past few years, naturally occurring bioactive compounds have revolutionized the whole scientific community for their exploration. Rutin is one such phenolic compound that is present in significant amounts in buckwheat and has a wide range of applications in the food and pharmaceutical industries. In this work, an energy‐efficient and cleaner method of nanofiltration is applied to concentrate the rutin from the model plant extract. Experiments were performed on a polyamide nanofiltration membrane with a molecular weight cut‐off of 150 Da at different operating conditions. Experimental results were fitted in a three‐parameter Spiegler–Kedem model to determine the transport parameters of the membrane for rutin. The values of transport parameters were also successfully validated using the experimental results. Experimental results and model predictions were then used to analyze the effects of different operating parameters. A scale‐up setup has been designed and simulated to check the feasibility of the process at the commercial level.

Asymptotic Water Split Behavior of Hydrocyclones; A Unique Design Characterization Methodology

ABSTRACT An attempt has been made in this work to experimentally investigate the water split behavior of hydrocyclones for extracting the relevant features that are characteristic of hydrocyclone design conditions only. The experimental findings demonstrated that at high feed flowrates, the water split of the hydrocyclone attains a consistent value, referred to here as the stable split value, because of a fully developed and steady vortical flow through the hydrocyclone. These stable split values were shown to be characteristic of the hydrocyclone design conditions. An empirical model developed in the study considering the key hydrocyclone design variables could predict the stable split values with a validation R2 of 0.98 and 0.96 for the training and testing data, respectively. It is believed that such a design-dependent parametric representation of the water split behavior can be significantly useful for hydrocyclone design comparison and selection which has not been reported in the literature so far.

Predictive modeling of single pass tangential flow filtration for continuous biomanufacturing.

Opportunities for process intensification have made continuous biomanufacturing an area of active research. While tangential flow filtration (TFF) is typically employed within the biologics purification train to increase drug substance concentration, single-pass TFF (SPTFF) modifies its format by enabling continuity of this process and achieving a multifold concentration factor through a single-pass over the filtration membranes. In continuous processes feed concentration and flow rate are determined by the preceding unit operations. Therefore, tight control of SPTFF output concentration must be achieved through precise design of the membrane configuration, unlike TFF. However, predictive modeling can be utilized to identify configurations that achieve a desired target concentration across ranges of possible feed conditions with minimal experimental data, hence enabling accelerated process development and design flexibility. We hereby describe the development of a mechanistic model predicting SPTFF performance across a wide design space using the well-established stagnant film model, which we demonstrate is more accurate at higher feed flow rates. The flux excursion dataset was generated within time constraints and with minimal material consumption, showing the method's ability to be quickly adapted. While this approach eliminates characterizing complex physicochemical model variables or the need for users with specialized training, the model and its assumptions become inaccurate at low flow rates, below 25 L/m2 /h, and high conversions, above 0.9. As this low flow rate, high conversion operating regime is relevant for continuous biomanufacturing, we explore the assumptions and challenges involved in predicting and modeling SPTFF processes, while suggesting added characterization to gain further process insight.

Preparation and Characterization of Polyvinylalcohol/Polysulfone Composite Membranes for Enhanced CO2/N2 Separation

The unique properties of polyvinyl alcohol (PVA) and polysulfone (PSf), such as good membrane-forming ability and adjustable structure, provide a great opportunity for CO2-separation membrane development. This work focuses on the fabrication of PVA/PSf composite membranes for CO2/N2 separations. The membranes prepared by coating a 7.5 wt% PVA on top of PSf substrate showed a relatively thin selective layer of 1.7 µm with an enhanced CO2/N2 selectivity of 78, which is a ca. 200% increase compared to the pure PSf membranes. The CO2/N2 selectivity decreases at a rapid rate with the increase of feed pressure from 1.8 to 5 bar, while the CO2 permeance shows a slight reduction, which is caused by the weakening of coupling transportation between water and CO2 molecules, as well as membrane compaction at higher pressures. Increasing operating temperature from 22 °C to 50 °C leads to a slight decrease in CO2 permeance, but a significant reduction in the CO2/N2 selectivity from 78 to 27.1. Moreover, the mass transfer coefficient of gas molecules is expected to increase at a higher velocity, which leads to the increase of CO2 permeance at higher feed flow rates. It was concluded that the CO2 separation performance of the prepared membranes was significantly dependent on the membrane operating parameters, and process design and optimization are crucial to bringing CO2-separation membranes for industrial applications in post-combustion carbon capture.

Effect of drying methods on yield, physicochemical properties, and total polyphenol content of chamomile extract powder.

Chamomile (Matricaria chamomilla L.) is a traditional medicinal plant used to treat hay fever, inflammation, muscle spasms, menstrual disorders, insomnia ulcers, wounds, gastrointestinal disorders, rheumatic pain, and hemorrhoids. Dried chamomile flowers have a longer shelf life and the dried extract in form of powder offers much flexibility for new therapeutic formulations as it could be used as a replacement for liquid extract and serve as a shelf-stable ingredient in new applications. This study aims to determine the effect of drying methods, i.e., convection oven-drying at 45 °C, freeze-drying at -50°C, and spray-drying at 140°C at 10.5 and 12ml/min, respectively) on powder yield, physicochemical properties (moisture content, water activity, and color attributes), and total polyphenol content of chamomile extract powder. Our findings showed that spray-drying conducted at 140°C, 12ml/min resulted in the lowest yield of powder (16.67%) compared to convection oven-drying (90.17%) and freeze-drying (83.24%). Decreasing the feed flow rate to 10.5ml/min during spraying caused an increase in powder yield to 26.99%. The moisture content of spray-dried chamomile extract powder obtained at 140°C, 10.5ml/min was higher (11.00%) compared to that of convection oven-dried (8.50%) and freeze-dried (7.50%). Both convection oven-dried and freeze-dried chamomile extract powder displayed no significant difference (p > 0.05) in moisture content. The higher feed flow rate (12ml/min) in spray-drying also led to an increase in the moisture content of chamomile extract powder to 12.00%. The higher residual moisture found in the spray-dried samples resulted in partial agglomeration of particles. In terms of water activity, freeze-dried chamomile extract powder was found to have the highest water activity (0.63) compared to that of convection oven-dried (0.52), spray-dried at 140°C, 10.5ml/min (0.57), and spray-dried at 140°C, 12ml/min (0.58). Spray-dried and freeze-dried chamomile extract powder with high moisture content and water activity could be highly susceptible to microbial growth. In terms of color attributes, higher drying temperature in spray-drying led to darker, redder, and more yellowish chamomile extract powder that could be caused by heat-induced Maillard reaction and caramelization. Since lower drying temperature was used in both convection oven-drying and freeze-drying, both convection oven-dried (56.94mg GAE/g powder) and freeze-dried chamomile extract powder (55.98mg GAE/g powder) were found to have higher total polyphenol content compared to those of spray-dried (42.79-46.79mg GAE/g powder). The present findings allow us to understand the effect of drying methods on the properties of chamomile extract powder and provide a better drying option to dry chamomile extract. Due to higher powder yield with ideal powder properties such as low moisture content and water activity, desirable color, and high total polyphenol content obtained from convection oven-drying, convection oven-drying was a better option than freeze-drying and spray-drying for drying chamomile extract.

Flow-through in-situ evaporation membrane enabled self-heated membrane distillation for efficient desalination of hypersaline water

Water crisis and high salinity water treatment are growing challenges for the world. The recently emerged self-heating or surface heating membrane distillation (MD) can be a promising way to obtain fresh water from saline and other wastewater sources. However, its inherent drawbacks such as intolerance to high feed flow rate, low flux, and loss of heat energy through bulk feed stream, limit its realistic applications. Herein, we successfully demonstrate a novel trilayered flow-through in-situ evaporation membrane (FTIEM) enabled membrane distillation process. The PEI-PDA-SBA-15 is spray coated as a top layer of FTIEM, which functions as hydrating, salt screening and thermally insulating layer, thus, it prevents the loss of heat from the middle joule heating layer (i.e., COOH-MWCNTs-PVA layer, where the water evaporation occurs) to the bulk feed stream, while the bottom PVDF microporous membrane permits only vapor to pass through under an appropriate vacuum pressure. The power required for membrane heating is provided by using a D.C. supply. During MD desalination of sea water, the FTIEMs achieve the lowest specific heating energy of 0.024 KWhL−1. In addition, the FTIEMs upon long –term MD operation using hypersaline water as feed, exhibit excellent stability and performance with maximum flux and salt rejection of 29.25 Lm−2h−1 and 99.99 % respectively. Our findings may encourage the development of FTIEMs for desalination of hypersaline water.

Bio-gas augmentation and waste minimization by co-digestion process in anaerobic digestion system of a municipal waste water treatment plant

Anaerobic digesters of Tehran waste water treatment plant (WWTP) working in mono-digestion operation are investigated for not only methane augmentation but also for waste minimization by the use of co-digestion process. Three types of co-substrate wastes including slaughterhouse flotation greases, biowaste, and cattle manure were selected because they were available in large amounts. A model was required to predict the volume flow rates of feeding co-substrate wastes into digesters during operation time for providing sufficient biogas in order to generate maximum gas engine power output. Thus, Anaerobic Digestion Model Number 1 (ADM1) for mono-substrate is modified so that it could be used with characterization of primary sludge, secondary sludge, and several co-substrate waste inputs into digesters. Then, appropriate coefficients (hydrolysis coefficient and bio-degradability factor) in this model were determined by the use of sludge biochemical methane potential (BMP) tests. After complete modification, calibration and validation of ADM1 method with experimental values of primary and secondary sludge for anaerobic digestion (which is the current reality in Tehran WWTP), the developed model is integrated with a co-substrate feeding strategy for estimation of required feed flow rates of co-substrate wastes. Results indicated that feeding grease, biowaste and manure increased the average generated biogas from 10524 m3/day (62.1% CH4) to 29161 m3/day (61.5% CH4), 30183 m3/day (59.5% CH4), and 32531 m3/day (53.8% CH4), respectively. Also, the gas engine power output increased from an average value of 906 kW to about 2.5 MW (during the studied operation time period). Low hydrolysis coefficient and low degradability of manure caused high bio-degradable feed flow rate of this co-substrate waste to about 58,200 kgCODb/day in average. This value for biowaste and grease was 38,800 and 36,100 kgCODb/day, respectively. Feeding grease and biowaste into digesters increased COD removal efficiency from 37% to 58% and 54%, respectively, while feeding manure dropped it to 31%. Furthermore, values of pH and VFA/Alk indicators showed stable conditions in digesters. Moreover, it was found that all three co-digestion processes did not impose a new load on other WWTP equipment for reducing nitrogen in the effluent stream of WWTP. Finally, it was concluded that biowaste is an appropriate co-substrate for our case study.

Hydrophobic silica sand ceramic hollow fiber membrane for desalination via direct contact membrane distillation

A porous hollow fibre ceramic membrane derived from a low-cost natural material (silica sand) and fabricated by combine phase inversion and sintering technique followed by fluoroalkylsilane (FAS17) grafting to improve its hydrophobicity is reported in this study. Prior to the subjection of the silica sand ceramic hollow fibre membrane (SSCHFM) to a desalination performance test via direct contact membrane distillation (DCMD), characterization studies were performed on the SSCHFM before and after grafting using different characterization techniques, such as scanning electron microscopy (SEM), atomic force microscopy (AFM), 3-points bending, water liquid entry pressure (LEPw), and water contact angle measurement. Mercury porosimetry analysis (MIP) was also used to determine the pore size distribution and porosity of the SSCHFM. The grafting process caused an increasing of the contact angle from 0° to 142.5° ± 2.0, and LEPw value of (2.6 ± 0.4 bar) was achieved. AFM images showed an increment in the surface roughness of the grafted SSCHFM from 0.305 µm to 0.375 μm, with a slight decrease in the average pore size and porosity from 0.17 µm and 17% to 0.12 µm and 14.7% respectively. After the grafting process, the performance of the membrane in DCMD was evaluated on a salt solution for 32 h at different NaCl concentrations (8,16, 24, 32 and 40) g/L, feed flow rates and feed temperatures. The results showed a decrease in the permeate flux at increasing feed concentration, but the reverse was at higher feed flow rates and feed temperatures. The surface-modified membrane recorded a water flux value of 35 kg/m2.h and 100% salt rejection. The results indicate that the hydrophobic hollow fibre ceramic membranes derived from silica sand have significant potential to be developed for membrane distillation application in water purification and reclamation.

Understanding and improving the modular properties of high-performance SSZ-13 membranes for effective flue gas treatment

High-performance tube-supported standard oil synthetic zeolite-13 (SSZ-13) membranes were prepared using low-temperature ozone calcination and modularized in different-sized permeation cells. The hydrophobic SSZ-13 membrane exhibited robust, marked CO2/N2 separation performances at a H2O vapor partial pressure of 10 kPa at 50 °C (CO2 permeance of 1.3 × 10−7 mol∙m−2 s−1∙Pa−1 and CO2/N2 separation factor (SF) of ca. 31.5). However, these intrinsic values were obtained at high feed flow rates, where the optimal recovery of CO2 molecules cannot be obtained. Thus, we correlated membrane (permeance and SF) and feed stream (Reynolds number) properties, finding that convective mass transfer from feed to outer membrane surface (Sherwood number) was described by the Reynolds number and cell dimensions. This further accounted for the CO2 molar flux and CO2/N2 SF. Based on this, we proposed critical parameters (comprising total feed flow rate and pressure, and characteristic module dimension) to describe the representative module properties of the recovery, purity, and process efficiency (PE) for CO2. Finally, the PE of the membrane unit was improved in double-stage configuration, yielding noticeable improvements in CO2 purity and PE at the slight expense of CO2 recovery. Crucially, the process-based module properties were well understood and predicted using the feed stream properties.

Investigation of the factors affecting reverse osmosis membrane performance using machine-learning techniques

Several factors affecting the RO membrane performance can be investigated mainly in two groups; feed characteristics and operational parameters. In this work, the effect of feed characteristics of a municipal wastewater such as conductivity, oxidation reduction potential (ORP), total suspended solids (TSS), turbidity, chemical oxygen demand (COD) and feed operational parameters such as feed pressure, flow rate, temperature on RO membrane performance monitoring parameters (pressure difference across membranes, salt passage and permeate flow rate) were analyzed in a wastewater recovery plant using different machine learning techniques. Artificial neural networks (ANNs) were found to perform better to predict pressure difference whereas random forest and multiple linear regression models performed better in salt passage and permeate flow rate prediction, respectively. Association rule mining was also employed, and it was found that high feed flow rate, low feed conductivity and low temperature operation are desired for effective RO membrane operation.

Sensitivity Analysis and Multi‐Objective Optimization of Oxidative Dehydrogenation of Propane in a Fixed‐bed Reactor over Vanadium/Graphene for Propylene Production

AbstractOxidative dehydrogenation of light alkanes is an attractive route for the production of olefins. This method does not need much energy, while common processes such as propane dehydrogenation and cracking require external energy resources and cause rapid catalyst deactivation. In this research, an isothermal one‐dimensional model of a fixed‐bed reactor was considered for oxidative dehydrogenation of propane over a V2O5/graphene catalyst. Operational parameter sensitivity analysis showed that high temperature (450–500 °C), high pressure (7–8 atm), a moderate molar propane to air feed ratio (about 0.7), and a low feed flow rate enhanced the propane conversion and propylene productivity. However, for the production of propylene as desirable product, low temperature, low pressure, a high molar ratio, and a high feed flow rate are preferred. Thus, to determine the exact interval of operational parameter values, a multi‐objective optimization was performed for the yields of propylene and COx, revealing a maximum propylene yield of ∼40 %. For safety reasons, a feed molar ratio of propane to air of > 0.6 was preferred, which is not in the flammable region.

Kinetic Modeling of Ethylene Oligomerization to High-Chain-Length Olefins Over Al-SBA-15-Supported Ni Catalyst with LiAlH4 Co-catalyst

Kinetic modeling of ethylene oligomerization was performed; an Al-SBA-15-supported Ni catalyst and LiAlH4 co-catalyst were used to produce high-chain-length olefins in a one-pot reaction. A semi-batch slurry reactor produced kinetic data at different feed flow rates and temperatures. Grouping of the kinetic and mass transfer coefficients concerning the products was introduced to estimate undetermined parameters with limited experimental data. Among the four combinatorial cases, the estimation of individual kinetic parameters and grouped mass transfer coefficients showed the lowest errors and Akaike’s information criteria. The activation energies for the formation of hexene and octene were determined to be approximately 15 and 45 kJ/mol, respectively, confirming reported values of 23.1–64.1 kJ/mol. The model showed that the formation of short-chain-length olefins accounted for the rate-determining steps, and the evaluation for the effects of operating conditions guided optimal operation; high temperature and feed flow rate maximized heavy species production, and the flow rate should be optimized to maximize light olefin production.

Instant tea from Condonopsis javanica L. root extract via spray drying

Introduction. Codonopsis javanica L. root is a gingsen-like medicinal material with valuable bioactive compounds and alkaloids in its composition. However, the diversification of commercial products from Codonopsis javanica root extract is limited and poorly represented on the market. This study presents a new production process of an instant tea product from Codonopsis javanica root extract, which involved spray drying with maltodextrin as a drying additive.
 Study objects and methods. The research featured different process parameters including a drying additive concentration, a drying temperature, and a feed flow rate. Moisture content and drying yield were selected as the main outcomes.
 Results and discussion. In general, the improved drying yield was associated with an increased drying additive concentration, a lower drying temperature, and a higher feed flow rate. The best drying yield (78.35%) was obtained at the drying additive concentration of 30% (w/w), the drying temperature of 140°C, and the feed flow rate of 300 mL/h. The total saponin content in the product was 0.29% (w/w), and the ABTS free radical scavenging ability reached 59.48 μgAA/g. The obtained powder was spherical and exhibited fairly uniform particle morphology with shriveled and concave outer surface.
 Conclusion. The research results justified the use of Codonopsis javanica as an ingredient in beverage industry and suggested maltodextrin as an appropriate substrate for spray-drying natural extracts.

Implementing PAT for single-pass tangential flow ultrafiltration for continuous manufacturing of monoclonal antibodies

Control of single pass tangential flow ultrafiltration is crucial for continuous manufacturing of monoclonal antibodies. We propose a strategy to control the output concentration of a continuous ultrafiltration step regardless of variations in the volume or concentration of the feed material. Scheduling algorithms for the filtration runs and cleaning cycles are developed, accounting for the expected cycle times of different unit operations in the continuous train. The complete design space for the membrane module is characterized experimentally. An empirical model of the design space is developed to predict the logarithmic relationship between the feed flowrate and the maximum concentration factors achievable in a single pass for feed concentrations in the range of 1–50 g/L and feed flowrates in the range of 10–210 mL/min. The control strategy leverages in-line concentration, flowrate and pressure sensors, including near infrared spectroscopy (NIRS) flow cells to measure the concentration of mAb in the feed and retentate streams in the range 0.5–200 g/L. The control elements are the permeate pump and a variable control valve on the retentate line, which are used to obtain the desired concentration factor across the module in a single pass. Two case studies are designed to test the control system under conditions of high feed flow rate and low feed concentration, and low feed flow rate and high feed concentration, respectively. Successful control is demonstrated in both cases. The proposed system is the first complete approach that integrates process understanding, advanced monitoring sensors, and control strategies to consistently achieve concentration targets over long continuous campaigns for production of monoclonal antibodies.

The effect of energy recovery device and feed flow rate on the energy efficiency of reverse osmosis process

The energy requirements for reverse osmosis (RO) seawater desalination continue to be a major matter of debate. Previous studies have shown the dependence of optimum RO desalination energy on the RO recovery rate. However, they overlooked including the effect of Energy Recovery Device (ERD) and pretreatment on the power consumption. In this work, a computer model was used to analyze the energy requirements for RO desalination, taking into account the effect of ERD efficiencies and pretreatment. The specific power consumption (SPC) of the RO was found to increase with the increase of RO recovery rate when the ERD system was included. The optimum SPC became more dependent on the RO recovery rate when the pretreatment energy was added. The recovery for optimum desalination energy was 46%, 44%, and 40% for the RO system coupled with an ERD of 65%, 80%, and 95% efficiency, respectively. The results showed that RO process could be operated at lower recovery rate and still meet the projected desalination capacity by increasing the feed flow rate and coupling with high-efficiency ERD. A trivial decrease of the total desalination energy was achieved when the feed flow rate increased from 7m3/h to 8m3/h and recovery rate decreased from 46% to 44% by coupling the RO with an ERD of 95% efficiency. This suggests that the RO–ERD system can be operated at a high feed flow rate and low recovery rate without affecting the plant capacity.

Thermo-economic analysis and optimization of a vacuum multi-effect membrane distillation system

Vacuum multi-effect membrane distillation is an advanced system that possesses the features and merits of vacuum membrane distillation and multi-effect distillation. It has low operating pressure and temperature, high levels of non-volatile rejection and high energy efficiency. This study presents a thermo-economic analysis and optimization of this novel system. A thermodynamic analysis is firstly conducted to evaluate the productivity and the energy consumption under varying design and operational conditions. Special emphases are placed on the impacts of the system configuration, including the number of effects and the overall membrane area, which are rarely covered in the literature. Results reveal that there is a trade-off between the production rate and the energy consumption with respect to most of the operating parameters, e.g. the feed flowrate and the cooling water flowrate. An increase in the number of effects and the membrane area will reduce the energy consumption, but the specific permeate flux for the unit membrane area also becomes lower. To obtain the optimal parameters that minimize the desalination cost, an economic study is then carried out considering a wide range of thermal energy prices. It is observed that a higher feed flowrate, more numbers of effects and larger membrane areas are preferable when the energy price is higher. However, when thermal energy with low prices is available, lower feed flowrates and smaller membrane areas are recommended. The derived results will provide useful information on the vacuum multi-effect membrane distillation system for its future design and operation.