Optimization Of Operating Conditions Research Articles

Polysilicon Materials FBR Technology for Solar and Semiconductor Silicon

The chaotic nature of fluid flow within a fluidized bed reactor (FBR), the high surface area of the product which requires special handling to prevent contamination, the size of the reactors and the construction materials present significant engineering challenges, but, once overcome the benefits of the FBR polysilicon production are significant. FBR technology can used with either silane or TCS feed. In this paper, the reaction paths for silane conversion are discussed. Sophisticated predictive modeling and simulation capabilities allow optimization of both reactor design and operating conditions to maximize productivity and reduce reactor downtime. These attributes enable production of high purity polysilicon for both the solar and the semiconductor industries.

Run-to-run Optimization for Fed-batch Fermentation Process with Swarm Energy Conservation Particle Swarm Optimization Algorithm

An iterative optimization strategy for fed-batch fermentation process is presented by combining a run-to-run optimization with swarm energy conservation particle swarm optimization (SEC-PSO). SEC-PSO, which is designed with the concept of energy conservation, can solve the problem of premature convergence frequently appeared in standard PSO algorithm by partitioning its population into several sub-swarms according to the energy of the swarm and is used in the optimization strategy for parameter identification and operation condition optimization. The run-to-run optimization exploits the repetitive nature of fed-batch processes in order to deal with the optimal problems of fed-batch fermentation process with inaccurate process model and unsteady process state. The kinetic model parameters, used in the operation condition optimization of the next run, are adjusted by calculating time-series data obtained from real fed-batch process in the run-to-run optimization. The simulation results show that the strategy can adjust its kinetic model dynamically and overcome the instability of fed-batch process effectively. Run-to-run strategy with SEC-PSO provides an effective method for optimization of fed-batch fermentation process.

Optimization of operational conditions for adipate ester synthesis in a stirred tank reactor

Esterification of adipic acid and oleyl alcohol in a solvent-free system featuring a stirred tank reactor containing commercially immobilized Candida antarctica lipase B was performed. The process was carried out using an artificial neural network (ANN) trained by the Levenberg-Marquardt (LM) algorithm. The effects of four operative variables, temperature, time, amount of enzyme, and impeller speed, on the reaction yield were studied. By examining different ANN configurations, the best network was found to consist of seven hidden nodes using a hyperbolic tangent sigmoid transfer function. The values of the coefficient of determination (R2) and root mean squared error (RMSE) between the actual and predicted responses were determined to be 1 and 0.0058178 for training and 0.99467 and 0.622540 for the testing datasets, respectively. These results imply that the developed model was capable of predicting the esterification yield. The operative variables affected the yield, and their order of contribution was as follows: time > amount of enzyme > temperature > impeller speed. A high percentage of yield (95.7%) was obtained using a low level of enzyme (2.5% w/w), and the temperature, time, and impeller speed were 66.5°C, 354 min (about 6 h), and 500 rpm, respectively. A simple protocol for efficient substrate conversion in a solvent-free system evidenced by high enzyme stability is indicative of successful ester synthesis.

The prediction of the peak width at half height in HPLC

The prediction of the peak width at half height is an important aspect in the optimization of the chromatographic operating conditions. In this paper, a linear relationship, between the peak widths at half height and the retention values with various isocratic elution is observed. In gradient elution, however, the relationship between the peak widths at half height and the so-called invented retention values that correspond to the mobile phase composition by eluting the solute from the column end is developed. We believe that there is almost the same band width at half height inside the column (in unit of length) for different solutes. The peak width at half height in the chromatogram (in unit of time) is mainly determined by the capacity factor of the solute when it is eluted from the column end. The larger the capacity factor of a solute eluted from the column end, the more slowly will be the solute eluted from the column end and the wider will be the peak width at half height. It is possible to predict the peak width at half height in various isocratic and gradient elutions by using this linear relationship.

Optimization of combustion chamber geometry for stoichiometric diesel combustion using a micro genetic algorithm

This paper describes the optimization of combustion chamber geometry and engine operating conditions for stoichiometric diesel combustion, targeting lower gross indicated specific fuel consumption. The KIVA code, coupled with a micro genetic algorithm population of nine for each generation was used. The optimization variables were composed of ten variables related to the combustion chamber geometry and engine operating conditions. In addition, an auto mesh generator was developed for generating various kinds of combustion chambers, such as open-crater, re-entrant, deep, and shallow types. In addition, the computational models were validated against the experimental results for a stoichiometric process in terms of the combustion pressure history and emissions. Through the preset optimization, a 35% improvement in the gross indicated that specific fuel consumption was achieved. In addition, the optimization results showed that the optimum engine operating conditions employed a premixed charge compression ignition combustion regime with early injection and a narrow spray included angle. Furthermore, a higher boost pressure was used to prevent fuel film formation.

Modeling of the α-lactalbumin and β-lactoglobulin protein separation

This work used the General Rate Model (GRM) to evaluate the experimental data of α-lactalbumin (α-la) and β-lactoglobulin (β-lg) mass transfer using size exclusion chromatography (SEC). The chromatographic simulation has become necessary in large scale production processes. Mathematical models have been used for the optimization and control of different operating conditions of the process, as well as providing calculations for the process scale-up. For the SEC experiments, the aqueous biphasic system was composed of polyethylene glycol 1500 g/mol, potassium phosphate and whey protein isolate. The polymeric phase was enriched with α-la and the saline phase with β-lg. The experiments were conducted using a glass column packed with the Sephadex G-25 ® gel. Both proteins were quantified by reverse phase liquid chromatography. The experimental data were fitted by non-linear regression, using the successive quadratic programming algorithm. The mass transfer model utilized represented adequately the SEC experimental results.

Operation Condition Optimization of p-Xylene Oxidation Reaction Process Based on a Fuzzy Adaptive Immune Algorithm

The oxidation of p-xylene to terephthalic acid (TA) is a significant chemical process of purified TA production. Variation of operation conditions of the reaction directly affects the quality of TA. In this paper a fuzzy adaptive immune algorithm (FAIA) was proposed to realize the operation condition optimization of the p-xylene oxidation reaction. In FAIA, a chaotic hypermutation was developed to strengthen the searching ability of the algorithm, and a new immune network regulatory strategy was devised to maintain population adversity. Furthermore, two fuzzy logic modules were constructed to adjust parameters, further increasing the adaptability of the algorithm. The data of function optimization show that FAIA can quickly converge to the global optimum and overcome premature problems. Optimization results of process variable values of the p-xylene oxidation reaction indicate that the application of FAIA in an oxidation reaction process can greatly save the time of operation condition selection and reduc...

Performances and fouling control of a flat sheet membrane in a MBR pilot-plant

This paper deals with the performance and the optimisation of the hydraulic operating conditions of the A3 Water Solutions flat sheet membrane technology in a MBR pilot-plant to achieve a satisfying fouling control and also a reduction in the required aeration. Two vertically stacked modules were tested at pilot-scale at Anjou Recherche under typical biological operating conditions (mixed liquor suspended solids concentration (MLSS) =10 g/l; sludge retention time (SRT) =28 days; food to microorganism ratio (F/M)=0.12 kg COD/kg MLSS/d). The use of a double-deck and of specific backwashes for this membrane technology enabled to achieve satisfying membrane performances for a net flux of 25 L h(-1) m(-2), 20 degrees C at a low specific aeration demand per membrane surface (SADm = 0.2 Nm(3) h(-1) m(-2)) which corresponds to a specific aeration demand per permeate volume unit (SADp) of 8 Nm(3) air/m(3) permeate, which is lower than reported for many commercial membrane systems. The mixed liquor characteristics (foaming, MLSS concentration) appeared to influence the fouling behaviour of the membranes but no correlation was found with the fouling rate. However, with the new operating conditions, the system is robust and can cope with fouling resulting from biological stress and daily peak flows for MLSS concentrations in the membrane tank up to 18 g/l.

Incorporating Energy Generation into Volatile Organic Compound (VOC) Emission Treatment Using a Solid Oxide Fuel Cell: A Model-Based Approach

Industrial processes that use solvent-based coatings emit volatile organic compounds (VOCs), which when released into the environment are smog precursors. The purpose of this work is to develop a VOC abatement technology that not only destroys such VOCs with high efficiency but also extracts the energy found in these compounds to do useful work elsewhere in the facility. To this end, a model-based design approach using Aspen HYSYS was used to develop and optimize an abatement system that consisted of three separate technologies: an adsorber, a reformer, and a solid oxide fuel cell (SOFC). A model was developed that integrated the technologies, allowing for optimization of the overall operating conditions and performance. The reformer and SOFC portion of the model was validated by a comparison to published literature results for methane as a feedstock. After optimization, the model indicated that this system could achieve 95% VOC removal efficiency, with an electrical efficiency of 49%. When heat integrati...

Modeling and simulation of a simulated moving bed for adsorptive para-xylene separation

A multi-cell model was developed to analyze the behavior of a simulated moving bed process for adsorptive para-xylene separation from other xylene isomers. A novel technology for a semi-batch mode adsorption experiment was developed and used for fast and accurate data collection. Interaction parameters between different species for a multi-component extended Langmuir isotherm were estimated from single and multi-component adsorption experiments and implemented into the model. The parameters such as porosities, particle density and mass transfer coefficients were obtained from adsorbent analysis and commercial plant operation. To resolve the problem of high dimensionality, a cell-by-cell approach was proposed to solve the model. The recovery and purity of para-xylene as well as the concentration profile calculated from the model were in good agreement with the actual data. The effects of channeling and feed composition change were simulated, and they turned out to be physically meaningful. The simulation model will be used for operation condition optimization, trouble shooting, and productivity enhancement including a configuration change.

Optimization of Electrodes and Operating Conditions Using High-Throughput Electrochemistry for Low-Voltage Generation of Alkalinity for CO2 Sequestration

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Fabrication of size-selected Pd nanoclusters using a magnetron plasma sputtering source

We report on the fabrication of palladium (Pd) nanoclusters using a dc magnetron sputtering source. Plasma sputtering vaporizes the target’s material forming nanoclusters by inert gas condensation. The sputtering source produces ionized nanoclusters that enable the study of the nanoclusters’ size distribution using a quadrupole mass filter. In this work, the dependence of Pd nanoclusters’ size distribution on various source parameters, such as the sputtering discharge power, inert gas flow rate, and aggregation length have been investigated. This work demonstrates the ability of tuning the palladium nanoclusters’ size by proper optimization of the source operation conditions. The experimental nanocluster sizes are compared with a theoretical model that reveals the growth of large nanoclusters from “embryos” by a two-body collision. The model is valid for a specific range of deposition parameters (low inert gas flow rates and aggregation lengths equal or below 70 mm).

Equilibrium and Thermodynamic Studies of Cesium Adsorption on Natural Vermiculite and Optimization of Operation Conditions

Removal of cesium from synthetic aqueous solution through adsorption on vermiculite, under batch equilibrium experimental condition at six initial values of pH (3, 4, 6, 9, 11 and 12) and five temperatures (25, 50, 75, 85 and 95 °C) has been investigated. It is necessary to propose a suitable model for a better understanding of the mechanism of cesium adsorption on vermiculite. For this propose the suitability of the Langmiur, Freundlich and Redlich-Peterson (R-P) adsorption models for equilibrium data were investigated. The parameters in the adopted adsorption isotherm models were determined by Eviews software. The study of equilibrium isotherm shows that the best model for analysis of experimental data is Redlich-Peterson model with correlation coefficient higher than 0.99(both for temperature and pH). The results showed that increasing of pH and temperature increased the adsorption ability of vermiculite. Optimum conditions for adsorption were determined as T=75 °C, pH=9, vermiculite dose=1.5 g and contact time of 24 hr. Finally the thermodynamic constants of adsorption phenomena, DH° and DS° were found to be 2.672 kJ/mol and 0.563 kJ/mol K in the range of 25-95 °C respectively. The negative value of the Gibbs free energy DG demonstrates the spontaneous nature of cesium adsorption onto vermiculite.

Mathematical modeling of combustion in a grate-fired boiler burning straw and effect of operating conditions under air- and oxygen-enriched atmospheres

A three-dimensional mathematical model has been developed as a tool for furnace structure design and operation conditions optimization when the straw combustion is in oxygen-enriched or conventional air atmospheres. Mathematical methods have been used based on a combination of FLIC (A fluid Dynamic Incinerator Code) code for the in-bed incineration and commercial software FLUENT for the over-bed combustion. Oxygen-enriched atmospheres promote the destruction of most pollutants due to the high oxygen partial pressures and temperatures, which is reflected by very low residual amounts of organic combustion by-products in the bottom ash and flue gas of the straw-fired boiler unit. The predictions indicated that the maximum combustion temperature is around 1500 K, CO emission is 201 vppm and O 2 concentration is about 6.9 vol% at furnace exit, and it is shown that mathematical models can serve as a reliable tool for detailed analysis of straw combustion processes in the packed-bed furnace when compared with literature measurement data. In comparison to traditional straw combustion, the deviation of flue gas CO and NO is 27.5% and 62.1%, respectively. The numerical simulation results showed that combustion under the oxygen-enriched atmosphere excelled combustion under conventional air.

Subthreshold Regime has the Optimal Sensitivity for Nanowire FET Biosensors

Nanowire field-effect transistors (NW-FETs) are emerging as powerful sensors for detection of chemical/biological species with various attractive features including high sensitivity and direct electrical readout. Yet to date there have been limited systematic studies addressing how the fundamental factors of devices affect their sensitivity. Here we demonstrate that the sensitivity of NW-FET sensors can be exponentially enhanced in the subthreshold regime where the gating effect of molecules bound on a surface is the most effective due to the reduced screening of carriers in NWs. This principle is exemplified in both pH and protein sensing experiments where the operational mode of NW-FET biosensors was tuned by electrolyte gating. The lowest charge detectable by NW-FET sensors working under different operational modes is also estimated. Our work shows that optimization of NW-FET structure and operating conditions can provide significant enhancement and fundamental understanding for the sensitivity limits of NW-FET sensors.

Deposition of Size-Selected Cu Nanoparticles by Inert Gas Condensation

Nanometer size-selected Cu clusters in the size range of 1–5 nm have been produced by a plasma-gas-condensation-type cluster deposition apparatus, which combines a grow-discharge sputtering with an inert gas condensation technique. With this method, by controlling the experimental conditions, it was possible to produce nanoparticles with a strict control in size. The structure and size of Cu nanoparticles were determined by mass spectroscopy and confirmed by atomic force microscopy (AFM) and scanning electron transmission microscopy (STEM) measurements. In order to preserve the structural and morphological properties, the energy of cluster impact was controlled; the energy of acceleration of the nanoparticles was in near values at 0.1 ev/atom for being in soft landing regime. From SEM measurements developed in STEM-HAADF mode, we found that nanoparticles are near sized to those values fixed experimentally also confirmed by AFM observations. The results are relevant, since it demonstrates that proper optimization of operation conditions can lead to desired cluster sizes as well as desired cluster size distributions. It was also demonstrated the efficiency of the method to obtain size-selected Cu clusters films, as a random stacking of nanometer-size crystallites assembly. The deposition of size-selected metal clusters represents a novel method of preparing Cu nanostructures, with high potential in optical and catalytic applications.

Advantageous and detrimental effects of air sparging in membrane filtration: Bubble movement, exerted shear and particle classification

In various membrane applications air scour is applied to minimise fouling and to remove cake layers. Optimisation of module design and operating conditions (e.g., geometry and aeration intensity) requires knowledge of the most suited hydrodynamic conditions for the filtration task. However, many fundamentals of this multiphase flow in membrane modules are still unknown and difficult to access experimentally. Using experimental and numerical investigations it was shown that air sparging can have advantageous but also detrimental effects: depending on membrane plate spacing, wall shear can decrease with bubble size. Additionally, particle classification or segregation which increases the cake’s hydraulic resistance must be taken into account. Based on such findings, it will be possible to derive optimum bubble sizes, membrane spacing, aeration intensities and start-up strategies.

A new recovery process of carbon dioxide from alkaline carbonate solution via electrodialysis

AbstractBipolar membrane electrodialysis is applied to CO2 recovery from alkaline carbonate solution. CO2 in flue gas is captured by an alkaline hydroxide absorbing solution to form an alkaline carbonate solution. The captured CO2 is recovered from the alkaline carbonate solution via bipolar membrane electrodialysis, and the alkaline solution is regenerated simultaneously. To reduce the power requirement for CO2 recovery, this study considers optimal design and operation. Three membrane arrangements were compared, and the results indicate the membrane arrangement comprising a bipolar membrane and cation exchange membrane is the most energy saving. With further optimization of operation conditions, the minimum power requirement for CO2 recovery was reduced to 2.1 MJ/kg‐CO2 (or 2.1 GJ/t‐CO2). © 2009 American Institute of Chemical Engineers AIChE J, 2009

Protein phosphorylation stoichiometry by simultaneous ICP-QMS determination of phosphorus and sulfur oxide ions: A multivariate optimization of plasma operating conditions

Molecular mass spectrometry (MS) analysis of protein phosphorylation is partially limited by the molecular specie specificity of the analytical responses that might impair both qualitative and quantitative performances. Elemental MS, such as inductively coupled plasma mass spectrometry (ICP-MS) can overcome these drawbacks; in fact, analytical performance is theoretically independent of the molecular structure of a target analyte naturally containing the elements of interest. Nevertheless, isobaric interferences derived from sample matrix and laboratory environment can hinder the quantitative determination of both phosphorus (P) and sulfur (S) as 31P + and 32S + by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) under standard plasma conditions. These interferences may be overcome by quantifying P and S as oxide ions 31P 16O + and 32S 16O +, respectively. In this study, we present a systematic investigation on the effect of plasma instrumental conditions on the oxide ion responses by a design of experiment approach for the simultaneous ICP-QMS determination of P and S ( 31P 16O + and 32S 16O +, respectively) in protein samples without the use of dynamic reaction, collision reaction cells or pre-addition of oxygen as reactant gas in the torch. The proposed method was evaluated in terms of limit of detection, limit of quantification, linearity, repeatability, and trueness. Moreover, detection and quantification capabilities of the optimized method were compared to the standard plasma mode for determination of 31P + and 34S +. Spectral and non-spectral interferences affecting the quantification of 31P +, 31P 16O + and 32S 16O + were also studied. The suitability of inorganic elemental standards for P and S quantification in proteins was assessed. The method was applied to quantify the phosphorylation stoichiometry of commercially available caseins (bovine β-casein, native and dephosphorylated α-casein) and results were confirmed by Matrix Assisted Laser Desorption Ionization Time of Flight MS analysis. We demonstrate that ICP-QMS, by quantifying P and S as oxide ions, was able to accurately calculate the degree of phosphorylation of β-casein and α-casein and to detect specific partial enzymatic dephosphorylation. The collected results might lead to further development of ICP-QMS interfaces optimized for protein phosphorylation studies and for proteomics investigations.

Optimization of Operating Conditions in Forward Osmosis for Osmotic Membrane Bioreactor

Objective of this study was to conduct a baseline study of osmotic membrane bioreactor (OMBR) - optimization of operating conditions in forward osmosis (FO). Experiments were conducted with an FO pilot system. Tap water was used as the feed and NaCl and MgSO4 solutions were used as draw solution. Effects of various operating conditions on flux have been investigated. In addition, pure water permeability of the FO membrane was tested. It was observed that the plant operation could be stablized within 1 h. When the membrane selective layer faced to the feed, a flux of 6.3 lm-2h-1 (LMH) was achieved at 24 atm osmotic pressure and 25 °C and effects of feed velocity and air velocity on flux were not siganificant under the testing conditions due to low external concentration polarization (ECP). However, when the selective layer faced to the draw solution, the flux was enhanced by 64% due to much reduced internal concentration polarization (ICP), the flux sharply increased with an increase in velocity of the draw solution in the laminar flow pattern range due to a countable effect of dilutive external concentration polarization (DECP) and leveled off after the flow pattern became turbulent. NaCl performed much higher efficiency than MgSO4 as an osmotic agent due to a greater solute diffusion coefficient of NaCl.