Optimization Of Operating Conditions Research Articles

Optimization of UHMWPE/Graphene Nanocomposite Processing using Ziegler-Natta Catalytic System via Response Surface Methodology

Optimization of operational conditions for the preparation of Ultrahigh-molecular-weight polyethylene (UHMWPE)/Graphene nanocomposites with Ziegler–Natta catalyst was carried out via response surface methodology (RSM). This study deals with the optimization of process variables to optimize the productivity and molecular weight. A three-factor, three-level Box–Behnken design with temperature (X1), monomer pressure (X2), and [Al]/[Ti] molar ratio (X3) as the independent variables were selected for the study. The dependent variables were productivity and molecular weights of the final nanocomposites. It was developed by using the three parameters at three levels including 50, 60, and 70°C for temperature; 4, 6, and 8 bar for pressure; and 176, 318, and 460 for [Al]/[Ti] molar ratios. The optimum reaction conditions derived via RSM were: temperature 60°C, pressure 8 bar, and [Al]/[Ti] molar ratio 242. Productivity and molecular weight were 2107 g PE/mmol Ti.h and 3.7 × 106 g/mol, respectively, under optimum conditions. Morphological information was determined by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Obtained results show that graphene layers in these nanocomposites were completely exfoliated and dispersed uniformly in the polyethylene matrix while no nanoparticle cluster was formed.

Optimization of operational conditions for biodiesel production from cottonseed oil on CaO–MgO/Al2O3 solid base catalysts

In the present work, biodiesel production from the transesterification of the cottonseed oil with ethanol over a novel CaO–MgO/Al2O3 catalyst has been studied, and the effects of experimental factors such as loading of CaO–MgO on Al2O3, reaction temperature and molar ratio of ethanol to cottonseed oil on the oil conversion were investigated. CaO–MgO/Al2O3 catalysts were prepared via a conventional co-precipitation method. These catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and temperature-programmed desorption of CO2 (TPD-CO2). The operational conditions on the cottonseed oil conversion were investigated using Design of Experiment (DOE). The optimized conditions predicted by Box–Behnken design were found to be 14.4wt% loading of CaO–MgO on Al2O3, with molar ratio of ethanol to cottonseed oil=12.24 and reaction temperature=95.63°C in order to achieve a conversion of 97.62%. The predicted results agree with the experimental results (12.5wt% loading of CaO–MgO on Al2O3, molar ratio of ethanol to cottonseed oil=8.5 and reaction temperature of 95°C with 92.45% conversion).

Furfural removal from liquid effluents by adsorption onto commercial activated carbon in a batch heterogeneous reactor

Currently, the presence of furfural at low concentrations in different industrial effluents presents an environmental problem. In this work, the optimization of the main operating conditions of a batch heterogeneous reactor for furfural removal by adsorption onto commercial activated carbon were determined. In this sense, the effect of the commercial activated carbon concentration, operating temperature, and the agitation rate in the reactor were studied. In all experiments, the adsorption data have engaged in behavior that can be represented by pseudo-second order model. In liquid effluents with initial concentrations of furfural equal to 1 or 2gdm−3, the 90% furfural removal requires a minimum concentration of adsorbent in the reactor equal to 11 or 12gdm−3, respectively. The optimum agitation rate and temperature were around 100rpm and 303–308K, respectively. Equilibrium data at different temperatures were represented by Langmuir equation. The thermodynamic parameters of activation energy (Ea=43.1kJmol−1) at different furfural concentrations, standard free energy (ΔG°=−16.1kJmol−1), standard enthalpy (ΔH°=−21.8kJmol−1), and standard entropy (ΔS°=−18.8Jmol−1K−1) of the adsorption process were determined.

Initial Performance Evaluation of a Gridded Radio Frequency Ion Thruster

Helicon plasma sources are devices that are capable of efficiently producing high-density plasmas. There is growing interest in using a helicon plasma source in space propulsion as a replacement to the direct current plasma discharge in ion engines. A radio frequency ion engine is developed that combines a helicon plasma source with electrostatic grids and a magnetically shielded anode. Thruster performance evaluation includes estimation of the discharge plasma ion density and electron temperature and measurement of the plume current density, grid currents, and thrust. The radio frequency ion engine is tested across the following operating parameter ranges: 343–600 W radio frequency power, 50–250 G magnetic field strength, argon flow rate, and 100–600 V discharge voltage range at an operating pressure of , discharge ion density and electron temperature range and 5.4–9.9 eV, respectively. Maximum beam current extracted is 120 mA at a 600 V discharge and is primarily limited by ion impingement on the grids due to insufficient grid potentials. The maximum measured thrust is 2.77 mN with an average uncertainty of . Further optimization of the thruster operating conditions and grid assembly can improve thruster performance.

Optimization of operation conditions for the startup of aerobic granular sludge reactors biologically removing carbon, nitrogen, and phosphorous

The transformation of conventional flocculent sludge to aerobic granular sludge (AGS) biologically removing carbon, nitrogen and phosphorus (COD, N, P) is still a main challenge in startup of AGS sequencing batch reactors (AGS-SBRs). On the one hand a rapid granulation is desired, on the other hand good biological nutrient removal capacities have to be maintained. So far, several operation parameters have been studied separately, which makes it difficult to compare their impacts. We investigated seven operation parameters in parallel by applying a Plackett-Burman experimental design approach with the aim to propose an optimized startup strategy. Five out of the seven tested parameters had a significant impact on the startup duration. The conditions identified to allow a rapid startup of AGS-SBRs with good nutrient removal performances were (i) alternation of high and low dissolved oxygen phases during aeration, (ii) a settling strategy avoiding too high biomass washout during the first weeks of reactor operation, (iii) adaptation of the contaminant load in the early stage of the startup in order to ensure that all soluble COD was consumed before the beginning of the aeration phase, (iv) a temperature of 20 °C, and (v) a neutral pH. Under such conditions, it took less than 30 days to produce granular sludge with high removal performances for COD, N, and P. A control run using this optimized startup strategy produced again AGS with good nutrient removal performances within four weeks and the system was stable during the additional operation period of more than 50 days.

Bench scale production of nicotinic acid using a versatile amide-hydrolysing Geobacillus subterraneus RL-2a isolated from thermal spring of Manikaran, India

A new thermostable amidase-producing isolate identified as Geobacillus subterraneus RL-2a has been studied extensively for the optimization of enzyme operational conditions in the production of nicotinic acid in fed batch mode. The amidase of G. subterraneus RL-2a is constitutive in nature, active at broad pH (pH 4.5–13.0), temperature (40–90 °C) with optimal activity at 70 °C and pH 6.5. The enzyme was fairly stable at 70 °C with a deactivation constant (kd) and enzyme half-life of 4.15 × 10−5 s−1 and 6 h 4 min. Another advantage of this enzyme was its broad substrate specificity, including aliphatic, aromatic and amino acid amides respectively. In a fed batch reaction at one litre scale using resting cells corresponding to 8 U ml−1 amidase activity (7.76 mg dcw ml−1), a total of 88.6 g nicotinic acid was produced at a rate of 2.85 g h−1 g−1 dcw. This thermostable amidase represents the first reported broad substrate spectrum amidase with exceptional thermostability from a thermophilic G. subterraneus RL-2a.

Optimization of xylanase production by filamentous fungi in solid-state fermentation and scale-up to horizontal tube bioreactor.

Five microorganisms, namely Aspergillus niger CECT 2700, A. niger CECT 2915, A. niger CECT 2088, Aspergillus terreus CECT 2808, and Rhizopus stolonifer CECT 2344, were grown on corncob to produce cell wall polysaccharide-degrading enzymes, mainly xylanases, by solid-state fermentation (SSF). A. niger CECT 2700 produced the highest amount of xylanases of 504 ± 7 U/g dry corncob (dcc) after 3 days of fermentation. The optimization of the culture broth (5.0 g/L NaNO3, 1.3 g/L (NH4)2SO4, 4.5 g/L KH2PO4, and 3 g/L yeast extract) and operational conditions (5 g of bed loading, using an initial substrate to moistening medium of 1:3.6 (w/v)) allowed increasing the predicted maximal xylanase activity up to 2,452.7 U/g dcc. However, different pretreatments of materials, including destarching, autoclaving, microwave, and alkaline treatments, were detrimental. Finally, the process was successfully established in a laboratory-scale horizontal tube bioreactor, achieving the highest xylanase activity (2,926 U/g dcc) at a flow rate of 0.2 L/min. The result showed an overall 5.8-fold increase in xylanase activity after optimization of culture media, operational conditions, and scale-up.

Titania Nanotubes Grown on Carbon Fibers for Photocatalytic Decomposition of Gas-Phase Aromatic Pollutants.

This study aimed to prepare titania (TiO2) nanotube (TNT) arrays grown on un-activated carbon fibers (UCFs), with the application of different TiO2 loadings based on the coating-hydrothermal process, and to evaluate their photocatalytic activity for the degradation of sub-ppm levels of aromatic pollutants (benzene, toluene, ethyl benzene, and o-xylene (BTEX)) using a plug-flow photocatalytic reactor. The characteristics of the prepared photocatalysts were determined by scanning electron microscopy (SEM),energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), UV-visible absorption spectroscopy (UV-Vis) and X-ray diffraction (XRD) analyses. Spectral analysis showed that the prepared photocatalysts were closely associated with the characteristics of one-dimensional nanostructured TiO2 nanotubes for TNTUCFs and spherical shapes for TiO2-coated UCF (TUCF). The photocatalytic activities of BTEX obtained from TNTUCFs were higher than those obtained from a reference photocatalyst, TUCF). Specifically, the average degradation efficiencies of BTEX observed for TNTUCF-10 were 81%, 97%, 99%, and 99%, respectively, while those observed for TUCF were 14%, 42%, 52%, and 79%, respectively. Moreover, the photocatalytic activities obtained for TNTUCFs suggested that the degradation efficiencies of BTEX varied with changes in TiO2 loadings, allowing for the optimization of TiO2 loading. Another important finding was that input concentrations and air flow rates could be important parameters for the treatment of BTEX, which should be considered for the optimization of TNTUCFs application. Taken together, TNTUCFs can be applied to effectively degrade sub-ppm levels of gas-phase aromatic pollutants through the optimization of operational conditions.

Adsorptive Removal of Cr(VI) from Aqueous Solution on Hydrous Cerium—Zirconium Oxide. Part I: Process Optimization by Response Surface Methodology

Hydrous cerium-zirconium oxide (Ce0.25Zr0.75O2) was used for Cr(VI) removal by adsorption. The response surface methodology (RSM) was applied as a tool for the optimization of adsorption operational conditions (temperature, pH and adsorbent dose) with the combined effects of the key processing variables on the Cr removal efficiency (%RCr). The following conditions were found to be optimal: pH = 2, temperature = 28 °C, adsorbent dose = 4 g l-1. The %RCr obtained experimentally (92%) was in agreement with the value predicted by RSM (88%). The adsorption process followed the pseudo-second-order kinetic model and obeyed the Langmuir isotherm model. Thermodynamic parameters (ΔH°, ΔS° and ΔG°) indicated the exothermic and spontaneous nature of adsorption governed by physisorption interactions. Hydrous Ce0.25Zr0.75O2 showed high adsorption capacity (25 mg g-1), high desorption efficiency (80%), reached adsorption equilibrium quickly (30 minutes) and high chemical stability. The Cr(VI) adsorption on hydrous Ce0.2...

Combustion of palm kernel shell in a fluidized bed: Optimization of biomass particle size and operating conditions

This work presents a study on the combustion of palm kernel shell (PKS) in a conical fluidized-bed combustor (FBC) using alumina sand as the bed material to prevent bed agglomeration. Prior to combustion experiments, a thermogravimetric analysis was performed in nitrogen and dry air to investigate the effects of biomass particle size on thermal and combustion reactivity of PKS. During the combustion tests, the biomass with different mean particle sizes (1.5mm, 4.5mm, 7.5mm, and 10.5mm) was burned at a 45kg/h feed rate, while excess air was varied from 20% to 80%. Temperature and gas concentrations (O2, CO, CxHy as CH4, and NO) were recorded along the axial direction in the reactor as well as at stack. The experimental results indicated that the biomass particle size and excess air had substantial effects on the behavior of gaseous pollutants (CO, CxHy, and NO) in different regions inside the reactor, as well as on combustion efficiency and emissions of the conical FBC. The CO and CxHy emissions can be effectively controlled by decreasing the feedstock particle size and/or increasing excess air, whereas the NO emission can be mitigated using coarser biomass particles and/or lower excess air. A cost-based approach was applied to determine the optimal values of biomass particle size and excess air, ensuring minimum emission costs of burning the biomass in the proposed combustor. From the optimization analysis, the best combustion and emission performance of the conical FBC is achievable when burning PKS with a mean particle size of about 5mm at excess air of 40–50%. Under these conditions, the combustor can be operated with high (99.4–99.7%) combustion efficiency, while controlling the gaseous emissions at acceptable levels. No evidence of bed agglomeration was found in this conical FBC using alumina as the bed material for the entire time period of experimental tests.

Artificial neural network model for turbulence promoter-assisted crossflow microfiltration of particulate suspensions

In this study, an artificial neural network (ANN) model for the turbulence promoter-assisted crossflow microfiltration (CFMF) process was successfully established, in which the inlet velocity, transmembrane pressure (TMP) and feed concentration were taken as inputs, and the flux improvement efficiency (FIE) by turbulence promoter was taken as output. Using the trained ANN model, the FIE can be predicted under CFMF operation conditions that are not included in the training database. It reveals that the FIE first increases and then decreases with increasing either TMP or inlet velocity, and increases with increasing feed concentration. Among three input variables, TMP has the most important effect on the FIE. The optimization of MF operation conditions was largely dependent on the feed concentration. The high FIE can be obtained by exerting both high inlet velocity (>0.7m/s) and low TMP (<30kPa) at a relatively low feed concentration (<1g/L), and both high inlet velocity (>0.7m/s) and high TMP (>70kPa) at a relatively high feed concentration (>8g/L). This study provides a useful guide for the applications of turbulence promoter in CFMF processes.

Model-Based Optimization of Scaffold Geometry and Operating Conditions of Radial Flow Packed-Bed Bioreactors for Therapeutic Applications

Radial flow perfusion of cell-seeded hollow cylindrical porous scaffolds may overcome the transport limitations of pure diffusion and direct axial perfusion in the realization of bioengineered substitutes of failing or missing tissues. Little has been reported on the optimization criteria of such bioreactors. A steady-state model was developed, combining convective and dispersive transport of dissolved oxygen with Michaelis-Menten cellular consumption kinetics. Dimensional analysis was used to combine more effectively geometric and operational variables in the dimensionless groups determining bioreactor performance. The effectiveness of cell oxygenation was expressed in terms of non-hypoxic fractional construct volume. The model permits the optimization of the geometry of hollow cylindrical constructs, and direction and magnitude of perfusion flow, to ensure cell oxygenation and culture at controlled oxygen concentration profiles. This may help engineer tissues suitable for therapeutic and drug screening purposes.

Combined in Silico Optimization of Solvents and Operating Conditions for Carbon Capture Processes

Abstract The carbon capture process requires a large amount of energy resulting in reduction in power plant power output. This energy penalty must be reduced in order for carbon capture and sequestration (CCS) to become a viable option for reducing carbon emissions. This paper presents an in silico approach aimed at reducing the capture energy penalty through simultaneous screening of capture solvents combined with optimization of process conditions. The computation involves coupling an optimization algorithm to a process model of the pre-combustion carbon capture (Pre-CC) process. A library of 9 physical solvents was selected for screening. Subsequently, optimization of process conditions around these solvents was performed in a typical pressure swing C02 absorption process, with the optimization objective specified for reduction in operating energies. Sulfolane (2,3,4,5-tetrahydrothiophene-1,1-dioxide), an organosulfur compound commonly used for C02 extraction in acid gas removal processes, was found to have the lowest operating energy consumption (352 kJ/ kgC02) recovered from syngas.

1022 ビル用マルチ空調システムにおける運転条件の最適化 : 定常シミュレーションに基づく最適化(GS-8 エネルギーシステム)

1022 ビル用マルチ空調システムにおける運転条件の最適化 : 定常シミュレーションに基づく最適化(GS-8 エネルギーシステム)

DKP操業条件の確立

近年，レーヨンは東南アジアや中国で需要が大きく伸びてきたことから，再び世界で注目を集め始めている。天候で供給が変動しやすいコットンリンターとは異なり，溶解パルプは工業的に製造されるため安定した供給が可能である。日本製紙株式会社では釧路工場に針葉樹では世界初となるKP連続蒸解釜による溶解パルプを製造することを決定し，2013年3月から商業生産を開始した。DKPの製造フローはKP蒸解の前に前加水分解釜（PHV：Pre―Hydrolysis Vessel）でヘミセルロースを加水分解・除去する。これはチップに温水を加えることで発生する酸性物質を利用して酸性条件下で高温・高圧で処理するものである。その後，白液を添加し，クラフト蒸解を行い，以降はKPと同様の漂白工程で処理をする。溶解パルプの品質は，セルロース以外の不純物（ヘミセルロース，リグニン・灰分・樹脂分など）が低いことが求められるなど，要求が製紙用のKPとは異なっている。実機ではPHVの操業条件を確立することで，ヘミセルロースの除去が可能である知見を得た。

바이오에너지 생산 및 폐수처리를 위한 미생물연료전지

A microbial fuel cell (MFC) is a bio-electrochemical device that converts chemical energy in the chemical bonds in organic compounds to electrical energy through catalytic reactions of microorganisms under anaerobic conditions. Power density and Coulombic efficiency are significantly affected by the types of microbe in the anodic chamber of an MFC, configurations of the system and operating conditions. The achievable power output from MFC increased remarkably by modifying their designs such as the optimization of MFC configurations, the physical and chemical operating conditions, and the choice of biocatalysts. This article presents a critical review on the recent advances made in MFC research with the emphasis on MFC configurations, optimization of important operating parameters, performances and future applications of MFC.

A Back-Gate Controlled Silicon Nanowire Sensor with Sensitivity Improvement for DNA and pH Detection

Silicon nanowire field-effect transistors (SiNW-FETs) are emerging as powerful chemical and biological sensors with various attractive features including high sensitivity and direct electrical readout. However, limited systematic studies have appeared on how the working voltage affects their sensitivity. Here we demonstrate that the current change rate of SiNW-FETs can be exponentially enhanced in the subthreshold regime by both analyses of FET's theory model and electrical characteristics. On that basis, the back-gate controlled sensors' detection sensitivity for DNA and pH value appears great improvement when working in the subthreshold regime, which shows that optimization of SiNW-FET operating conditions, can provide significant improvement for the limits of SiNW-FET nanosensors, making it possible for higher-accuracy chemical and biological molecules detection.

Evaluation of inoculation method and limiting conditions on bacterial activity in microbial electrochemical cells

There is growing interest in the potential of microbial electrochemical systems (microbial electrochemical cells – MXCs) for sustainable wastewater treatment and energy production, and extensive research has been undertaken to improve their power production. To optimize MXCs, their performance under technical and operational deficiencies should also be characterized. Using experiments with fed-batch reactors, this study investigated the effects of seeding method, electron donor and acceptor limitations, mixing, salinity, and substrate concentration on performance.The MXCs required 0–8 days for current generation depending on the inoculum source; the most rapid generation was achieved with attached electrogenic bacteria. When the electrogenic bacteria were exposed to air for 3h, the current production was deferred for 5h. The bacteria could handle the lack of an electron donor for at least 3 days, and the lack of a solid electron acceptor for at least 5 days, which would facilitate long distance delivery. A 1.54-fold increase in electron donor concentration contributed to a 1.7-fold enhancement in peak current. The addition of 75mM NaCl increased the power density from 1.64mWm−2 to 2.16mWm−2, whereas optimal mixing increased the power from 0.613mWm−2 to 1.786mWm−2. Thus, electrogenic bacteria may endure some unfavorable conditions, but optimization of operational conditions is necessary to maximize MXC performance.

Cell Squeezing as a Robust, Microfluidic Intracellular Delivery Platform

Rapid mechanical deformation of cells has emerged as a promising, vector-free method for intracellular delivery of macromolecules and nanomaterials. This technology has shown potential in addressing previously challenging applications; including, delivery to primary immune cells, cell reprogramming, carbon nanotube, and quantum dot delivery. This vector-free microfluidic platform relies on mechanical disruption of the cell membrane to facilitate cytosolic delivery of the target material. Herein, we describe the detailed method of use for these microfluidic devices including, device assembly, cell preparation, and system operation. This delivery approach requires a brief optimization of device type and operating conditions for previously unreported applications. The provided instructions are generalizable to most cell types and delivery materials as this system does not require specialized buffers or chemical modification/conjugation steps. This work also provides recommendations on how to improve device performance and trouble-shoot potential issues related to clogging, low delivery efficiencies, and cell viability.

Cell Squeezing as a Robust, Microfluidic Intracellular Delivery Platform

Rapid mechanical deformation of cells has emerged as a promising, vector-free method for intracellular delivery of macromolecules and nanomaterials. This technology has shown potential in addressing previously challenging applications; including, delivery to primary immune cells, cell reprogramming, carbon nanotube, and quantum dot delivery. This vector-free microfluidic platform relies on mechanical disruption of the cell membrane to facilitate cytosolic delivery of the target material. Herein, we describe the detailed method of use for these microfluidic devices including, device assembly, cell preparation, and system operation. This delivery approach requires a brief optimization of device type and operating conditions for previously unreported applications. The provided instructions are generalizable to most cell types and delivery materials as this system does not require specialized buffers or chemical modification/conjugation steps. This work also provides recommendations on how to improve device performance and trouble-shoot potential issues related to clogging, low delivery efficiencies, and cell viability.