Optimization Of Operating Conditions Research Articles

Optimization of Operation Conditions for Zeolitic Imidazolate Framework/Polydimethylsiloxane Hybrid Pervaporation Membranes

AbstractThe separation performance of a membrane is not only related to the membrane, but also to the operating conditions. The operation conditions of superhydrophobic zeolitic imidazolate framework‐90 (S‐ZIF‐90)/polydimethylsiloxane hybrid membranes for pervaporation were optimized using response surface methodology. The separation performances of hybrid membranes were evaluated by regulating the rotation rate, operation temperature, and feed concentration. The regression equations between the operation variables and the separation performance of the hybrid membranes were established and applied to predict and optimize the separation performance of these membranes. The main effects, quadratic effects, and interactions of the three variables on the permeation flux and the separation factor of hybrid membranes were analyzed.

Enhanced Furfural Production in Deep Eutectic Solvents Comprising Alkali Metal Halides as Additives.

The addition of alkali metal halide salts to acidic deep eutectic solvents is here reported as an effective way of boosting xylan conversion into furfural. These salts promote an increase in xylose dehydration due to the cation and anion interactions with the solvent being a promising alternative to the use of harsh operational conditions. Several alkali metal halides were used as additives in the DES composed of cholinium chloride and malic acid ([Ch]Cl:Mal) in a molar ratio of 1:3, with 5 wt.% of water. These mixtures were then used as both solvent and catalyst to produce furfural directly from xylan through microwave-assisted reactions. Preliminary assays were carried out at 150 and 130 °C to gauge the effect of the different salts in furfural yields. A Response Surface Methodology was then applied to optimize the operational conditions. After an optimization of the different operating conditions, a maximum furfural yield of 89.46 ± 0.33% was achieved using 8.19% of lithium bromide in [Ch]Cl:Mal, 1:3; 5 wt.% water, at 157.3 °C and 1.74 min of reaction time. The used deep eutectic solvent and salt were recovered and reused three times, with 79.7% yield in the third cycle, and the furfural and solvent integrity confirmed.

Identification and classification of host cell proteins during biopharmaceutical process development.

As significant improvements in volumetric antibody productivity have been achieved by advances in upstream processing over the last decade, and harvest material has become progressively more difficult to recover with these intensified upstream operations, the segregation of upstream and downstream processing has remained largely unchanged. By integrating upstream and downstream process development, product purification issues are given consideration during the optimization of upstream operating conditions, which mitigates the need for extensive and expensive clearance strategies downstream. To investigate the impact of cell culture duration on critical quality attributes, CHO-expressed IgG1 was cultivated in two 2L bioreactors with samples taken on days 8, 10, 13, 15, and 17. The material was centrifuged, filtered and protein A purified on a 1ml HiTrap column. Host cell protein (HCP) identification by mass spectrometry (MS) was applied to this system to provide insights into cellular behavior and HCP carryover during protein A purification. It was shown that as cultivation progressed from day 8 to 17 and antibody titer increased, product quality declined due to an increase in post-protein A HCPs (from 72 to 475 peptides detected by MS) and a decrease in product monomer percentage (from 98% to 95.5%). Additionally, the MS data revealed an increase in the abundance of several classes of post-protein A HCPs (e.g., stress response proteins and indicators of cell age), particularly on days 15 and 17 of culture, which were associated with significant increases in total overall HCP levels. This provides new insight into the specific types of HCPs that are retained during mAb purification and may be used to aid process development strategies.

Annual assessment of the wastewater treatment capacity of the microalga Scenedesmus almeriensis and optimisation of operational conditions

The depth of the culture and the dilution rate have a striking effect on the biomass productivity and the nutrient recovery capacity of microalgal cultures. The combination of culture depth and dilution rate that allows to maximise the performance of the system depends on environmental conditions. In the current study, a response surface methodology was used to explore the relationship between the two most relevant operational conditions and the biomass productivity achieved in 8.3 m2 pilot-scale raceways operated using urban wastewater. Four polynomial models were developed, one for each season of the year. The software predicted biomass productivities of 12.3, 25.6, 32.7, and 18.9 g·m−2·day−1 in winter, spring, summer, and autumn, respectively. The models were further validated at pilot-scale with R2 values ranging within 0.81 and 0.91, depending on the season. Lower culture depths had the advantage of minimising nitrification and stripping but allow to process a lower volume of wastewater per surface area. Biomass productivity was higher at culture depths of 0.05 m, when compared to 0.12 and 0.20 m, while the optimal dilution rate was season-dependent. Results reported herein are useful for optimising the biomass productivity of raceway reactors located outdoors throughout the year.

Enhanced monovalent over divalent cation selectivity with polyelectrolyte multilayers in membrane capacitive deionization via optimization of operational conditions

In this work, we tuned the ion selectivity of a polyelectrolyte multilayer (PEM)-coated, cation-exchange membrane (CMX) in a membrane capacitive deionization (MCDI) process by carefully studying different operational modes, namely constant voltage (CV) and constant current (CC). The monovalent cation selectivity and its time-dependent behavior were monitored at different voltage and current values. Upon optimizing the current density (10 A/m2) and the number of polyelectrolyte bilayers (5.5) on the CMX membranes, a time-independent and nearly full monovalent cation selectivity was obtained for various feed solutions, provided a polycation-terminated PEM was applied. Furthermore, the selectivity values of several commercially available cation-exchange membranes were tested under the optimized conditions and compared with CMX and PEM-CMX, yielding the best performance for PEM-CMX, regardless the composition of feed solution. Before this optimization, this MCDI system showed a time-dependent selectivity, with a maximum of ρMgNa ≈3. The results were rationalized by applying an MCDI model based on the dynamic potential profile, describing the potential drops across the membrane and demonstrating a threshold for the current density.

Optimization of Nutritional and Operational Conditions for Producing PHA by the Halophilic Bacterium Halomonas boliviensis from Oil Palm Empty Fruit Bunch and Gluten Hydrolysates

Optimization of Nutritional and Operational Conditions for Producing PHA by the Halophilic Bacterium Halomonas boliviensis from Oil Palm Empty Fruit Bunch and Gluten Hydrolysates

Optimization of Operating Conditions for Ultrafiltration Units

Optimization of Operating Conditions for Ultrafiltration Units

Eight-lumped kinetic model for Fischer-Tropsch wax catalytic cracking and riser reactor simulation

Wax produced during Fischer-Tropsch synthesis (FTS) has no sulfur, nitrogen and aromatic contents and could be an attractive material to produce high quality transportation fuels by means of fluid catalytic cracking reaction. The kinetic modeling and riser reactor simulation are urgently needed. However, most of the current models in this field are based on crude oil feedstock which can not rigorously reflect the features of FTS wax catalytic cracking, especially the aromatization of the cracked light olefins for aromatic gasoline components. The effects of operating conditions on the catalytic cracking performance of FTS wax are investigated in a riser reactor with an industrial β-zeolite based catalyst. An eight-lumped (including paraffins, olefins, naphthenes and aromatics in gasoline, liquefied petroleum gas, dry gas, FTS wax and coke) kinetic model is developed for product selectivity description and riser reactor simulation in FTS wax catalytic cracking. The theoretical prediction is in good agreement with the experimental data. The modeling work is very helpful in reactor scale-up and operating condition optimization of the process.

An Investigation into Conversion of a Fleet of Plug-in-Electric Golf Carts into Solar Powered Vehicles Using Fuzzy Logic Control

This paper presents an investigation factors that need to be considered in the design and selection of components for the conversion of a fleet of plug-in electric golf carts at Princess Nourah Bint Abdelrahman University, (PNU), Riyadh, Kingdom of Saudi Arabia (KSA), into solar power energy. Currently, the plug-in electric golf carts are powered by a set of deep-cycle lead-acid battery packs consisting of six units. Solar energy systems (photovoltaics and solar thermal) provide significant environmental benefits and opportunities over the traditional and conventional sources. Therefore, they can contribute positively to many aspects of the built environment and societies. There are many factors that affect the energy generated from the solar panel system. These include type and dimension of the solar panels, weight, speed, acceleration, and other characteristics of the used golf carts, and the energy efficiency of the solar energy system, as main factors that affect the green energy generated to operate the carts. The energy values needed to power the electric cart were calculated and optimized using traction energy calculation and optimized using a fuzzy logic analysis. The fuzzy logic system was developed to assess the impacts of varying dimensions of solar panel, vehicle speed, and weight on the energy generation. Initial calculations show that the replacement cost of the batteries can be up to approximately 75 percent of the operating cost. Together with the indirect cost benefits of achieving zero tail-pipe emission and the comfort of silent operation, the cost of operation using solar energy can be significant when compared with the cost of battery replacement. In order to achieve better efficiency, supercapacitors can be investigated to replace the conventional batteries. The use of fuzzy logic successfully facilitated the optimization of system operation conditions for best performance. In this study, fuzzy logic and calculated data were used as an optimization tool. Future work may be able to use fuzzy logic with experimental data to demonstrate feasibility of utilizing fuzzy logic systems to assess energy generation processes. Future investigations could also include investigation of other factors and methodologies, such as various types of batteries, supercapacitors, solar panels, and types of golf carts, together with different techniques of artificial intelligence to assess the optimum system specifications.

Optimal operating conditions of PEM fuel cells in commercial aircraft

This work investigates the integration of polymer electrolyte membrane fuel cells (PEMFC) into recently proposed hydrogen aircraft concepts. Based on a numerical optimization of the stack's operating conditions, the interrelated aspects of efficiency and system mass are explored. A novel 1D two-phase PEMFC stack model is developed that captures water management effects in detail and yet features sufficiently low computational cost to be used for system-level optimization. The stack model is validated for a wide range of temperatures, current densities and oxygen concentrations. In combination with auxiliary component models, it can relate the effects of the investigated parameters on cell-level water management to system-level effects. This allows for an improved understanding of the underlying design tradeoffs, particularly regarding pressurized operation and stack oversizing. The results show that the conditions that maximize the overall system efficiency for a given flight phase deviate significantly from those that merely maximize stack efficiency.

Strategy study of critical flux/threshold flux on alleviating protein fouling of PVDF-TiO2 modified membrane

Aiming at the fouling problem of PVDF membrane, one novel integrated strategy was used for the first time, including hydrophilic membrane modification and low-pressure operation. Permeability and anti-fouling ability of PVDF were simultaneously improved by nano-TiO2 embedment. From perspective of operating condition optimization, the concepts of critical flux (JC) and threshold flux (JTH) were recommended as fouling-control tools. The JC and JTH of PVDF-TiO2 membrane were tested by two constant pressure-steps methods, i.e. Constant pressure-step method and Alternating constant pressure-step method. Three indicators, consisting of instant FTTT curves, dFlux/dt condition and TMP-Fluxave curve, were employed to evaluate the JC and JTH of PVDF-TiO2 membrane. In brief, the JC and JTH of PVDF-TiO2 were 10.62 and 23.91 L/(m2·h), respectively, which were nearly 3 times of PVDF membrane. Fouling resistance results displayed that protein irreversible fouling of two PVDF membranes were effectively reduced by JC mode and JTH mode. Besides, reversible fouling of PVDF-TiO2 membrane was controlled well by JC mode meanwhile. The pure water filtration line (PWF line) and the normalized resistance were both used to judge the form of JC of two membranes. As compared with PVDF, it was speculated the enhancement of JC and JTH mainly related to the better hydrophilicity and local hydraulic condition of PVDF-TiO2 modified membrane.

Reusing sago mill effluent as a substrate for bio-based polymeric flocculant fermentation: Optimisation of operational conditions

Sago mill effluent (SME) contains high levels of organic material that can be reused as feedstock for a nutrient source in polymeric bioflocculant fermentation. In this study, SME was reused for bio-based polymeric flocculant or bioflocculant production and was optimised using central composite design (CCD) to obtain a high yield of bioflocculants, chemical oxygen demand (COD) removal, and enhanced flocculating activity. The operational conditions involved in the optimisation were temperature (30–40°C), fermentation time (24–72 h), incubator speed (100–200 rpm), and fermentation medium (sterile and non-sterile SME). Based on the analysis, the optimal conditions for bioflocculant production were a temperature of 30°C, fermentation time of 32 h, incubator speed of 100 rpm, and cultivation in non-sterile SME medium, with bioflocculant yield of 201 mg/L, 65.5% COD removal, and 88.4% flocculating activity. X-ray diffraction analysis showed that the bioflocculants contained C, O, Ca, Mn, Si, P, S, Ca, and Mn. Zeta potential analysis indicated that the bioflocculants had a negative charge, while analyses via liquid chromatography-mass spectrometry (LC-MS) revealed that the bioflocculants consisted of glucose, xylose, and rhamnose. Therefore, reusing SME at optimum operational conditions to produce a new product and minimise waste discharge to the environment could support and move towards the circular economy concept. • Sago mill effluent contains valuable organic materials. • Sago mill effluent was used for a bio-based polymeric flocculant fermentation. • Bio-based polymeric flocculant production was optimised using central composite design. • Good COD removal of 65.5% and flocculating activity of 88.4%, were achieved. • Bio-based polymeric flocculant consisted of glucose, xylose and rhamnose.

Optimization of operation conditions for improved cytochrome P450BM3 enzymatic reaction yield

AbstractThe P450 cytochrome monooxygenase CYP102A1 from Bacillus megaterium, better known as P450BM3, is a heme‐thiolate enzyme that catalyzes the hydroxylation of numerous substrates. Many of the resulting products are of commercial interest to the pharmaceutical and fine chemical industries. Unlike most other P450 cytochromes, P450BM3 is both soluble and fused to its natural redox partner, which supplies the necessary electrons from NADPH to drive its reaction forward. However, the industrial use of this enzyme is limited by its poor stability and its expensive cofactor. In this work, we explore the effects of buffer formulation and temperature on the stability of wildtype and P450BM3 mutant R966D/W1046S as well as on the stability of nicotinamide cofactors NADPH, NADH, and the biomimetic cofactor N‐benzyl‐1,4‐dihydronicotinamide. We demonstrate that cofactor stability is more important to increase product yield than that of the enzyme. We also demonstrate that low temperatures enhance oxido‐reduction reactions coupling, thus resulting in an increase in the molar ratio of p‐nitrophenolate produced from 10‐pNCA per oxidized cofactor. Overall, the optimized reaction conditions lead to a 2 to 2.6‐fold increase in total product output when wildtype P450BM3 or R966D/W1046S mutant is used with either of these three aforementioned cofactors.

Construction of a Tl(I) voltammetric sensor based on ZIF-67 nanocrystals: optimization of operational conditions via response surface design.

An electroanalytical sensor was constructed constituted on a carbon paste electrode (CPE) with a ZIF-67 modifier and devoted to the quantification of Tl(I). Several characterization tests including XRD, BET, FT-IR, SEM/EDS/mapping, TEM, impedance spectroscopy (EIS), and cyclic voltammetry (CV) were performed on the synthesized ZIF-67 nanocrystals and CPE matrix. Central composite design (CCD) was used to assess the impact of variables affecting the sensor response, including the weight percent of ZIF-67 (14%), the pH of the thallium accumulation solution (6.4), and accumulation time (315 s) as well as the accumulation potential (-1.2 V). The direct linear relationship between the sensor response and the concentration of Tl(I) is in the interval of 1.0×10-10 to 5.0×10-7 M (coefficient of determination = 0.9994). The detection limit is approximately 1.0 × 10-11 M. The right selection of the MOF makes this sensor highly resistant to the interference of other ions. High selectivity against common interferences in the measurement of thallium (such as Pb(II) and Cd(II)) is an important feature of this sensor. To confirm the performance of the prepared sensor, the amount of thallium in the real sample was determined.

Analysis of PPCI mode and multi-objective comprehensive optimization for a dual-fuel engine

The aim of this research is to find a favorable combination of the complex control parameters of a diesel/natural gas dual-fuel engine, so that polluting emissions can meet regulatory requirements and achieve relatively low fuel consumption. This research covers the effects of control parameters on the performance and emissions of a dual-fuel engine for different combustion modes as well as discussions on the optimization of the entire operating conditions in the partial premixed compression combustion ignition (PPCI) mode combined with long short-term memory networks (LSTM) and non-dominated sorting genetic algorithms (NSGA-II). LSTM is used for the first time to establish a predictive regression model for the calibration parameters and output response of a dual-fuel engine, achieving the optimized mapping of input and output parameters. All of the optimization scenarios can achieve a trade-off between fuel consumption and emissions. The engine test results show that for the entire working conditions for the optimized dual-fuel engine, the nitrogen oxides (NOx) emissions are reduced by 77%, and the fuel consumption is roughly equal to that of the original diesel engine. The test results of the four condition test cycle of a marine engine for propulsion show that the NOx emissions of the optimized dual-fuel engine are reduced by 26.6% compared with the Tier-III legal requirements.

Optimization of catalyst pellet structures and operation conditions for CO methanation

A fundamental understanding of the effects of catalyst pellet structures and operation conditions on catalytic performance is crucial for the reactions limited by diffusion mass transfer. In this work, a numerical investigation has been carried out to understand the effect of catalyst pellet shapes (sphere, cylinder, trilobe and tetralobe) on the reaction-diffusion behaviors of CO methanation. The results reveal that the poly-lobe pellets with larger external specific surface area have shorter diffusion path, and thus result in higher effectiveness factors and CO conversion rates in comparison with the spherical and cylindrical pellets. The effects of operating conditions and pore structures on the trilobular catalyst pellet with high performance are further probed. Though lower temperature can contribute to larger effectiveness factors of pellets, it also brings about lower reaction rates, and pressure has little impact on the effectiveness factors of the pellets. The increase in porosity can reduce the pellet internal diffusion limitations effectively and there exists an optimal porosity for the methanation reaction. Finally, the height of the trilobular pellet is optimized under the given geometric volume, and the results demonstrate that the higher the trilobular catalyst, the better the reaction performance within the allowable mechanical strength range.

Optimization of Operating Conditions for Electrochemical Decolorization of Methylene Blue with Ti/α-PbO2/β-PbO2 Composite Electrode

α-PbO2 was introduced into the intermediate layer of an electrode to prevent the separation of the electrodeposited layer and maintain oxidizing power. The resulting Ti/α-PbO2/β-PbO2 composite electrode was applied to the electrochemical decolorization of methylene blue (MB) and the operating conditions for MB decolorization with the Ti/α-PbO2/β-PbO2 electrode were optimized. The morphology, structure, composition, and electrochemical performance of Ti/α-PbO2 and Ti/α-PbO2/β-PbO2 anode were evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The optimum operating parameters for the electrochemical decolorization of MB at Ti/α-PbO2/β-PbO2 composites were as follows: Na2SO4 electrolyte 0.05 g L−1, initial concentration of MB 9 mg L−1, cell voltage 20 V, current density 0.05–0.10 A cm−2, and pH 6.0. MB dye could be completely decolorized with Ti/α-PbO2/β-PbO2 for the treatment time of less than one hour, and the dye decolorization efficiency with Ti/α-PbO2/β-PbO2 was about 5 times better, compared with those obtained with Ti/α-PbO2.

Determination of Key Parameters Required to Optimize Calcination Process in Ferrous Metallurgy Heating Plants

Lime is the product of calcination. Its formation is always related to removal of carbon dioxide generated in the course of carbonate decomposition. Ferrous metallurgy, construction material, chemical and food industry companies account for about 90 % of lime produced in the country. Ferrous metallurgy is the major consumer of commercial lime using up to 40 % of all produced lime. Currently, despite occurrence of new binding and artificially produced chemical compounds, lime remains the major chemical compound produced by the industry in terms of output. Various units (shaft, rotary tubular kilns and fluidized bed kilns) are used for calcination. Shaft kilns are used the most widely. Considering continuously growing demand for lime, the need occurs for intensification of the burning process and optimization of the shaft kiln operating conditions. This requires knowledge of calcination physicochemical and heat transfer process mechanisms. Thus, the work deals with the issues related to determination of the optimal specific fuel consumption for burning of limestone from a particular deposit. It may be done only basing on thermal calculations for an operating shaft kiln, what, in its turn, causes the need for determination of the whole set of limestone and lime heat transfer properties. The obtained work results may be used to optimize the operating conditions of not only shaft but also rotary kilns intended for limestone heat treatment.

Investigation and Optimisation of Operating Conditions for Low-Temperature CO2 Reduction to CO in a Forward-Bias Bipolar-Membrane Electrolyser

The most recent investigations of operating conditions in a forward-bias bipolar-membrane zero-gap electrolyser using a silver cathode catalyst for the reduction of CO2 to CO at low temperatures and near-ambient pressures are reported. First, the CO2 electrolyser performance was investigated as a function of cathode feed humidification and composition. The highest CO partial current density was 127 mA cm−2, which was obtained at an iR-corrected cell voltage of 2.9 V, a cathode feed humidification of 50%RH, CO2 feed concentration of 90% and a CO Faradaic efficiency of 93%. The cells were tested continuously for 12 h at 3 V and 8 h at 3.4 V cell voltage to investigate system stability. While Faradaic efficiencies were maintained during the measurements at 3.0 V, a shift in selectivity was observed at 3.4 V, while a deterioration in current densities occurred in both cases. Using a specially designed electrochemical cell with an integrated reversible hydrogen reference electrode, it was found that the cathode catalyst is the main responsible for the observed loss in performance. It was furthermore determined via post-mortem SEM and EDX investigations that cathode deterioration is caused by catalyst agglomeration and surface poisoning.

Energy Efficient Seawater Desalination: Strategies and Opportunities

With the change in climate patterns, rapid industrialization, and population growth, the increasing water and energy demand became a major concern in the past decades. Desalination has been touted as the answer to the global water crisis, due to its capability in producing high‐quality fresh water from saline water. The continual research and innovations in the desalination field have resulted in the commercialization of large‐scale desalination in many water scarce regions. In the energetic context, all desalination processes are energy intensive. With the necessity to make desalination a more affordable and sustainable process, the energy efficiency of desalination is becoming an important topic. Herein, it is aimed to provide insights into the recent efforts and strategies established to tackle the energy‐related issues of both, thermal‐based and membrane‐based desalination processes. Depending on the principle of various commercial and emerging desalination processes, the directions of energy efficiency improvements, which include operating condition optimization, high‐performance material development, and renewable energy exploitation are discussed. The ideas and strategies reviewed herein, whether in their implementation or theoretical stage, are expected to provide insights into the possible improvement for application in commercial desalination plants.