Selection Of Optimal Operating Conditions Research Articles

Recovery of mixture of hydroxyethylammonium carboxylate protic ionic liquids from sugarcane pretreatment liquor using activated carbon in a fixed bed column

Integrated strategies using fixed bed columns can facilitate the recovery of protic ionic liquids (PILs) used in the pretreatment of lignocellulosic biomass. In this study, we investigated the adsorption of 2-hydroxyethylammonium acetate [Mea][Ac] and 2-hydroxyethylammonium hexanoate [Mea][Hex] on activated carbon in a fixed bed column for recovering the PILs mixture present in the liquor of the pretreatment. Breakthrough curves were determined experimentally. Breakthrough time (tb), exhaustion time (te), difference between tb and te, adsorption efficiency (ϕads), column efficiency (ϕcol) and qe equilibrium capacity were evaluated as a function of simultaneous variations in superficial velocity (vs) and temperature (T) using a central composite rotatable design. The optimum conditions for PIL purification were vs = 1.66 cm/min (Q = 1.3 mL/min) and T = 20 °C. After selection of optimum operating conditions, PILs separation was evaluated in a model solution and sugarcane pretreatment liquor, with similar intervals for recover of PILs. This is the first study to develop a successful proof of concept of mixture PILs [Mea][Ac]/[Mea][Hex] recovery from sugarcane straw pretreatment liquor in a fixed-bed column of activated carbon. The results indicate that the method has great potential for industrial application.

Uncovering the optimal structural characteristics of flocs for microalgae flotation using Python-OpenCV

Coagulation-based dissolved air flotation is generally recognized as an efficient and economical method for removal of algae from eutrophicated water, whose efficiency is directly affected by the structural characteristics of flocs. However, it is not clear which floc structures are suitable for microalgal floatation, whether large and compact flocs or small and loose flocs have good rising performance. In this study, a novel technology for dynamically tracking the growth and rising behaviors of flocs was developed based on Python-OpenCV to visually uncover the optimal structural characteristics of flocs for Microcysts aeruginosa coagulation-flotation. Different coagulation flow fields (velocity gradient, G) were adopted to artificially create flocs with various structural characteristics and floatation kinetics. Results showed that G value had significant effects on the growth and rising behaviors of flocs, thus achieving intuitively different flotation kinetics. An idea rising velocity of 91.5 m h−1 was achieved by flocs with optimal structural characteristics generated at a suitable G of 34.1 s−1, which was 29–75% higher than that of flocs at other G. The rising velocity of floc was synergistically determined by the size and fractal dimension of floc. The structural characteristics (size and fractal dimension) of flocs were introduced into the calculation model of rising velocity, which guided the principle of optimal floc structure characteristics (large and compact) suitable for Microcysts aeruginosa removal using DAF. These may provide new technology for the studies of the growth and settling/rising behaviors of flocs, and lay a theoretical foundation for the design of DAF system with high load rate and the selection of optimal operating conditions applied to cyanobacteria blooms prevention and control.

Validation of the Molar Flow Rates of Oil and Gas in Three-Phase Separators Using Aspen Hysys

A three-phase separator is the first vessel encountered by well fluids. The application of separators has been of great value to the oil and gas industry. In order to generate the gas phase envelope that is applicable to the study of reservoir fluid and the selection of optimum operating conditions of separators, this research utilizes a specified reservoir fluid stream to simulate a three-phase separator executed in Aspen HYSYS. Subsequently, a comparative study of the effects of specified inlet operating conditions on the output of gas and oil streams was carried out. The results show that changing the inlet pressure of the separator from 1000 to 8000 kPa reduces the gas outlet flow from 1213 to 908.6 kg mol/h, while it increases the liquid flow rate from 374 to 838.0 kg mole/h. By changing the temperature of the separator feed stream from 13 to 83 °C, the gas outlet stream was raised from 707.4 to 1111 kg mol/h, while the liquid flow rate dropped from 1037.0 to 646.1 kg mol/h. It was observed that the concentration of the outlet methane product is not affected by changing the flow rate of the feed stream at a specific pressure and temperature. Therefore, the thermodynamic property method is appropriate to simulate the separation of reservoir fluids which was achieved by selecting the Peng–Robinson (PR) model. The operating conditions of the separator were at 8000 kPa and 43 °C, which lies right on the dew point line. This is comparable to similar work on CHEMCAD which was in turn validated by plant data. Thus, the gas flow rate and the oil flow rate were dependent on pressure and temperature conditions of the plant.

FEATURES OF ANALYTICAL SYNCHRONIZATION OF DATA OF WORKING PROCESS MONITORING IN TRANSPORT DIESEL ENGINES UNDER OPERATION

The article discusses methods for determining top dead center, based on the analysis of pressure diagrams of a marine engine. The advantages and disadvantages of different methods are shown. Diagnostics of marine engines during operation and selection of optimal operating modes are based on the analysis of pressure diagrams, as well as fuel supply and gas distribution diagrams. As a result of the analysis of the pressure diagrams, the indicator engine power is calculated, which is further used in the control of engine operation modes, in the calculation of specific indicators, as well as in the calculation of energy efficiency coefficients of marine vessels according to IMO recommendations. The influence of the accuracy of determining the position of the top dead center on the calculation of the mean indicated pressure and indicated power is shown. Solving the problem of synchronization of data of working process monitoring using hardware sensors is unacceptable due to the complexity, and sometimes the impossibility of installing hardware sensors for the position of the top dead center of the piston, in addition to the standard sensors. This also leads to a more complex measurement pattern, combined with high accuracy, which is dependent on the load mode. In addition, the installation of hardware sensors is time-consuming and involves organizational problems, as it is necessary to temporarily disable the engine. The mentioned problems are absent in case of analytical data synchronization. It is shown that the existing methods of analytical synchronization are not effective enough for the operating conditions of transport engines. This is mainly due to the complexity of the formulation of the synchronization criteria or their lack of precision due to the impact of noise in the output data. In portable diagnostic systems, the top dead center determination is best done immediately by the analytical method. Principally, there are inconveniences during the diagnosis of engines, because additional pickup sensors and their cables must be used. Before installing the sensors, it is necessary to take the engine out of operation. The installed sensors must be calibrated, which is associated with a significant investment of time. All portable systems for parametric engine diagnostics measure the pressure in the working cylinder through the channel of the indicator valve. In this regard, in portable systems, in addition to the aforementioned errors, errors occur such as throttling and delay of the signal, which leads to an additional shift of the top dead center position. Thus, recently, most modern portable systems for diagnosing marine diesel engines do not use pickup sensors, but use different variants of the analytical determination of top dead center. Diagnostics of marine engines during operating and the selection of optimal operating conditions is based on the analysis of gas pressure diagrams, as well as fuel supply and gas distribution diagrams. As a result of the analysis of the pressure diagrams, the indicator engine power is calculated, which is further used in the management of engine operation modes, in the calculation of specific indicators, as well as in the calculation of energy efficiency coefficients of marine vessels according to International maritime organization recommendations. The authors claimed a method for determining the top dead center, based on solving the equation of equality to zero the first derivative of the gas pressure under compression, which provides the required accuracy in calculating the average indicated pressure and indicator power of the engine during operation. It is shown that the method can be applicable in marine engine working process monitoring systems as an alternative to hardware methods for determining the top dead center.

Selection of Optimal Operating Conditions for Extraction of Myrtus Communis L. Essential Oil by the Steam Distillation Method.

Myrtus communis L. is one of the important aromatic and medicinal species from the Mediterranean area. It is used in various fields such as culinary, cosmetic, pharmaceutical, therapeutic, and industrial applications. Thus, a Box–Wilson experimental plan was used in this study to select the optimal operating conditions in order to obtain high volumes of essential oils. The factorial design method was applied to evaluate at an industrial scale the effect of major process variables on the essential oil extraction from Myrtus communis L. herbs by the steam distillation method. The input variables considered as significant operating conditions were: X1—boiler occupancy rate (boilers were filled to 50%, 75%, and 100%), X2—distillation duration (distillation was continued 60, 75, and 90 min), and X3—particle size (herbs were cut in sizes of 10, 20, and 30 mm via guillotine). The dependent variable selected, coded as Y, was the essential oil volume obtained (mL). The steps of the classical statistical experimental design technique were complemented with the Taguchi method to improve the extraction efficacy of essential oil from Myrtus communis L., and the optimum parameter conditions were selected: boiler occupancy rate 100%, distillation duration 75 min, and particle size 20 mm. Following the optimum parameters, the GC-MS assay revealed for the Myrtus communis L. essential oil two predominant components, α-pinene—33.14% and eucalyptol—55.09%.

A model-based approach for the rational design of the freeze-thawing of a protein-based formulation

Proteins are unstable molecules that may be severely injured by stresses encountered during freeze-thawing. Despite this, the selection of freeze-thaw conditions is currently empirical, and this results in reduced process control. Here we propose a mathematical model that takes into account the leading causes of protein instability during freeze-thawing, i.e. cold denaturation and surface-induced unfolding, and may guide the selection of optimal operating conditions. It is observed that a high cooling rate is beneficial for molecules that are extremely sensitive to cold denaturation, while the opposite is true when ice-induced unfolding is dominant. In all cases, a fast thawing rate is observed to be beneficial. The simulation outputs are confirmed by experimental data for myoglobin and lactate dehydrogenase, suggesting that the proposed modeling approach can reproduce the main features of protein behavior during freeze-thawing. This approach can therefore guide the selection of optimal conditions for protein-based formulations that are stored in a frozen or freeze-dried state.

A multi-feature recognition criterion for identification of thermally safe operating conditions for single kinetically-controlled reactions occurring in isoperibolic liquid-liquid semibatch reactors

Many criteria have been developed to date for thermal behavior identification for single kinetically controlled reactions occurring in isoperibolic liquid-liquid semibatch reactors (SBRs), the essence of which resides in the extraction and recognition of ‘features’ which can characterize different thermal behaviors; accordingly, thermal behavior identification may be regarded as a pattern recognition problem. Here, a novel multi-feature recognition (MFR) criterion was proposed based on the support vector machine (SVM) pattern recognition algorithm with a feature dimension of five, allowing the effective identification of four categories of thermal behaviors, namely IS (inherently safe), NI (non-ignition), TR (thermal runaway) and QFS (quick onset, fair conversion and smooth temperature condition). Subsequently, a modified generalized IS region was defined by introducing a threshold where the maximum temperature of synthesis reactions (MTSR) after cooling failure is equal to the maximum allowable temperature (MAT). The rationality of the proposed MFR criterion was verified by comparing with established criteria. Finally, a practical procedure based on the proposed criterion was presented, enabling the selection of optimum operating conditions with the desired productivity and thermal safety.

The effect of operating conditions on the optically induced electrokinetic (OEK)-based manipulation of magnetic microbeads in a microfluidic system

Magnetic microbeads are widely utilized in microfluidic systems for various applications. For these tasks, the effective and efficient manipulation of magnetic microbeads is important. Among the techniques for microparticle manipulation, the optically induced electrokinetic (OEK) [e.g., optically induced dielectrophoresis (ODEP) or light-actuated AC electroosmosis (LACE)]-based technique is promising. However, its utilization for magnetic microbead manipulation in a microfluidic system has not yet been fundamentally studied. To address this issue, the effect of operating conditions on the OEK-based magnetic microbead manipulation investigated. The results showed that the maximum terminal velocity (Vterminal) of a light image that can manipulate microbeads decreased significantly with increasing AC frequency. In addition, the results revealed that the Vterminal increased with increasing intrinsic a-Si:H layer thickness (Ta-Si) when the AC frequency was higher than 30 kHz, whereas the results completely reversed when the frequency was lower than 30 kHz. Additionally, the Vterminal of larger magnetic microbeads was higher than that of smaller microbeads when the AC frequency was higher than 50 kHz; conversely, the results significantly reversed when the frequency was lower than 30 kHz. Moreover, microbead manipulation under high conductivity conditions could significantly affect the magnitude of the Vterminal. Based on the fast manipulation velocity in LACE-based microbead manipulation, its application for basic unit operations in a microfluidic system was demonstrated. Overall, this study has provided some fundamental information for the selection of optimum operating conditions for OEK-based magnetic microbead manipulation in a microfluidic system.

Acetic acid adsorption dynamics in stratified tapered beds

The bioproduction of acetic acid is not economically attractive at present due to the high cost of its recovery from the fermentation broth. Adsorption of acetic acid at pH ∼ 3 is examined in this research in different adsorber configurations to examine enhancements to bed capacity utilization and the potential for use of this technology. Four different fixed-bed configurations, namely, a conventional cylindrical fixed-bed with single particle size, a cylindrical bed stratified with increasing particle sizes in the direction of flow, a reverse stratified cylindrical bed, and a reverse stratified convergent tapered bed were studied in this research. The conventional stratified cylindrical adsorber was found to produce a dispersive solute front in the column whereas, the reverse stratified tapered bed was found to produce a sharpening solute front. Among the different configurations examined, the convergent tapered stratified bed was found to give the maximum bed capacity utilization under the same operating conditions. A general rate mathematical model was found to provide good representation of the physical phenomena. Sensitivity analyses show differing effects of operating variables and mass transfer parameters on performance based on bed configuration. The model presented will allow the selection of optimum operating conditions for maximum bed capacity utilization, and thereby enhance the economics of acetic acid recovery from fermentation broths.

Aerodynamic processes and heat exchange in the furnace of a steam boiler with a secondary emitter

The use of water-tube boilers is common in industrial and municipal boiler houses and they are used as the sources of heat and steam supply. The introduction of measures that ensure environmental performance at an acceptable level, the use of modern burner devices and automation of boilers for worn-out and obsolete boiler designs require a significant amount of reconstruction and significant financial costs. The solution of the problems of burner device modernization, analysis and selection of optimal operating conditions for furnaces and boilers requires the application of modern methods of mathematical modeling. Modern technologies for reducing nitrogen oxides should improve the ecological safety of boilers and increase the efficiency of their operation. The results of a numerical study of heat exchange processes when burning the fossil fuels have shown the efficiency of placing a secondary tubular reversible emitter in the volume of a boiler furnace. It is found that the density of the radiant heat flux increases by 15–20%, the temperature of the flue gases at the outlet from the furnace decreases and amounts to 970 °C. The dimensions of the flame torch exclude its collision with the surfaces of screen tubes. During the combustion of the gas-air mixture, the concentration of nitrogen oxides at the outlet from the boiler furnace does not exceed 125 mg/m3.

Structural design of a rotating disk dynamic microfilter in improving filtration performance for fine particle removal

This study investigated the selection of optimal operating conditions and the design of efficient rotating disk structures for removing particles from seawater. The distributions of fluid velocity and shear stress on the membrane surface under various operating conditions were simulated using computational fluid dynamics. Type 1 rotating disk had two vans, Type 2 rotating disk had four vanes shaped identically to those of the Type 1 rotating disk, and Type 3 rotating disk had two vanes with circular orifices located at the center of each vane. The simulated results indicated that the disk rotation speed is the main factor affecting shear stress on the membrane surface. Cake mass and filtration flux were estimated from shear stress and were calculated using empirical equations. The results showed that flux in Type 1 increased by 28% when the disk rotation speed increased from 1000 to 3000 rpm; the installation of extra vanes caused an ineffective increase in flux at 3000 rpm. Although Type 2 exhibited the highest filtration performance and the lowest cake resistance, Type 3 is the optimal design because it exhibited the highest specific filtration flux among all tested rotating disk types. The rotating disk with two vanes with a circular orifice at a low disk rotation speed demonstrated the optimal design and operating conditions for removing particles from seawater, because it resulted in high filtration fluxes and relatively low power consumption.

Modeling of Reactor of Straight–run Gasoline Fractions Refining on Zeolite Catalysts

Zeolites are widely used as catalysts and catalyst supports for fuel and lubricants production processes with enhanced performance properties. Design of industrial reactor requires the construction of a mathematical model and selection of optimal operating conditions for reducing the number of scaling stages. The authors have proposed a scheme of hydrocarbons conversion on zeolite catalysts, thermodynamics of reactions has been considered and the inverse kinetic problem has been solved. The model of reactor of straight–run gasoline fractions refining in software HYSYS Aspen Plus™ process simulator has been developed and its adequacy to experimental data has been shown.

Triphasic Segmented Flow Millireactors for Rapid Nanoparticle—Catalyzed Gas-Liquid Reactions — Hydrodynamic Studies and Reactor Modeling

In this paper, we present detailed experimental and modeling studies of a recently developed triphasic segmented flow millireactors for rapid nanoparticle-catalyzed gas–liquid reactions. We first present detailed observations of the hydrodynamics and flow regimes in a pseudo-biphasic mode of operation, which enable the design and selection of optimal operating conditions for the triphasic millireactor. We particularly focus on and analyze the presence of wetting films of the organic phase on the reactor walls at high flow speeds, a consequence of the phenomenon of forced wetting, which is a key ingredient for optimal reactor performance. Next, we describe the development of a simple phenomenological model, incorporating the key mass transport steps that accurately captures the observed experimental trends for the rhodium nanoparticle (RhNP) catalyzed hydrogenation of a model substrate (1-hexene). We further discuss and analyze the consequences of this model.

Prediction of cell growth rate over scaffold strands inside a perfusion bioreactor.

Mathematical and computational modeling of the dynamic process where tissue scaffolds are cultured in perfusion bioreactors is able to provide insight into the cell and tissue growth which can facilitate the design of tissue scaffolds and selection of optimal operating conditions. To date, a resolved-scale simulation of cell growth in the culture process, by taking account of the influences of the supply of nutrients and fluid shear stress on the cells, is not yet available in the literature. This paper presents such a simulation study specifically on cartilage tissue regeneration by numerically solving the momentum, scalar transport and cell growth equations, simultaneously, based on the lattice Boltzmann method. The simulation uses a simplified scaffold that consists of two circular strands placed in tandem inside a microchannel, with the object of identifying the effect of one strand on the other. The results indicate that the presence of the front strand can reduce the cell growth rate on the surface of the rear strand, depending on the distance between them. As such, the present study allows for investigation into the influence of the scaffold geometry on the cell growth rate within scaffolds, thus providing a means to improve the scaffold design and the culture process.

Instrumentation and methodological support of determination of waterand fat-soluble antioxidants

The paper describes the selection of optimal operating conditions of amperometric detector work for determination of water-soluble antioxidants, modernization of the instrument for analysis of fat-soluble antioxidants. The authors developed the design of the layout of the first domestic universal multi-purpose portable liquid chromatograph. This allowed for the first time to measure the total content of antioxidants in meat, fish and dairy products; expand the data content of antioxidants by adding sections: spices and seasonings, meat, fish and dairy products; to examine the question of the optimal balance in the human diet of water - and fat-soluble antioxidants.

Frequency drift and instantaneous linewidth broadening of phase-section tuned SG-DBR laser

We experimentally investigate the spectral dynamics of a phase-section tuned sampled-grating distributed Bragg reflector (SG-DBR) laser by using optical heterodyne method. The measured time-resolved spectra of the beat signal illustrate that the beat signal suffers from both frequency drift and instantaneous spectrum broadening, which indicates that the wavelengths of the lightwaves experience drift and jitter. We study the variation of frequency drift and instantaneous linewidth broadening with applied voltages. It is helpful in selection of optimum operating conditions and design of experimental setup. Experimental results demonstrate that the pulse-waveform can be used to reduce the frequency drift by shorting the beating time.

Selection of Optimal Operating Conditions for a Continuous CO2-Capture Process Using an Aqueous Ammonia Solution

The optimal conditions of the absorbent concentration, rich CO2 loading, and regeneration temperature in a continuous CO2-capture process using a 3−27 wt % aqueous NH3 solution were experimentally studied and compared to vapor−liquid equilibrium of a CO2−NH3−H2O system. The dependence of CO2 removal efficiency upon the NH3 concentration and regeneration temperature was well-explained by the regeneration critical condition, which was defined using mole fractions of CO2, NH3, and H2O in the vapor phase at equilibrium. The optimal conditions were 12 wt % NH3 concentration, 0.36 rich CO2 loading, and a 90 °C regeneration temperature. Use of the vapor−liquid equilibrium data of the CO2−NH3−H2O system at regeneration conditions can be employed as a method to select the optimal operating conditions of a regeneration system and can provide guidelines for the design and operation of a CO2-capture process using aqueous NH3 solution.

Characterization of electrokinetic mobility of microparticles in order to improve dielectrophoretic concentration

Insulator-based dielectrophoresis (iDEP), an efficient technique with great potential for miniaturization, has been successfully applied for the manipulation of a wide variety of bioparticles. When iDEP is applied employing direct current (DC) electric fields, other electrokinetic transport mechanisms are present: electrophoresis and electroosmotic flow. In order to concentrate particles, iDEP has to overcome electrokinetics. This study presents the characterization of electrokinetic flow under the operating conditions employed with iDEP; in order to identify the optimal conditions for particle concentration employing DC-iDEP, microparticle image velocimetry (microPIV) was employed to measure the velocity of 1-microm-diameter inert polystyrene particles suspended inside a microchannel made from glass. Experiments were carried out by varying the properties of the suspending medium (conductivity from 25 to 100 microS/cm and pH from 6 to 9) and the strength of the applied electric field (50-300 V/cm); the velocities values obtained ranged from 100 to 700 microm/s. These showed that higher conductivity and lower pH values for the suspending medium produced the lowest electrokinetic flow, improving iDEP concentration of particles, which decreases voltage requirements. These ideal conditions for iDEP trapping (pH = 6 and sigma(m) = 100 microS/cm) were tested experimentally and with the aid of mathematical modeling. The microPIV measurements allowed obtaining values for the electrokinetic mobilities of the particles and the zeta potential of the glass surface; these values were used with a mathematical model built with COMSOL Multiphysics software in order to predict the dielectrophoretic and electrokinetic forces exerted on the particles; the modeling results confirmed the microPIV findings. Experiments with iDEP were carried out employing the same microparticles and a glass microchannel that contained an array of cylindrical insulating structures. By applying DC electric fields across the insulating structures array, it was seen that the dielectrophoretic trapping was improved when the electrokinetic force was the lowest; as predicted by microPIV measurements and the mathematical model. The results of this study provide guidelines for the selection of optimal operating conditions for improving insulator-based dielectrophoretic separations and have the potential to be extended to bioparticle applications.

Mechanism of Particle Separation in Small Hydrocyclone

The mechanism of particle separation in a small hydrocyclone is analyzed in this study. The separation efficiency of particles is affected by two major effects, the centrifugal and underflow effects. The fundamentals of these effects on the selectivity curve are derived from the theories of hydrodynamics. Three JIS particulate samples are separated in a 10-mm hydrocyclone. The proposed mechanism can be demonstrated by the available data. An increase in split ratio leads to an increase in the separation efficiency only for fine particles; consequently, a decrease in the separation sharpness results in a remarkable fishhook phenomenon. When the feed rate is increased by increasing the pressure drop through the hydrocyclone, the entire partial separation efficiency will be improved, but the separation sharpness and fishhook depth have no substantial varieties. The proposed mechanism can be used for explaining these phenomena, for the selection of optimum operating conditions, and for the hydrocyclone design.

Understanding and revamping of industrial scale SMB units for p‐xylene separation

AbstractOne of the first applications of Simulated Moving Bed (SMB) technology was in p‐xylene recovery from mixed xylenes. The three main industrial processes for p‐xylene separation from mixed xylenes based on SMB technology are: UOP's Parex, IFP's Eluxyl, and Toray's Aromax. These units operate in liquid phase (T = 180°C and P = 9 bar), achieving high recovery of almost pure p‐xylene with high on‐stream efficiency and extended adsorbent life. In this work, the industrial scale SMB process is investigated from modeling, simulation, and optimization points of view, using experimentally measured xylene adsorption equilibrium and kinetics data on ion exchanged faujasite zeolite. The aim is to develop tools for training of SMB unit operators and choice of the best operating conditions. Useful studies for better understanding of the influence of the operating parameters, adsorbent packing, and separation requirements on unit productivity are presented. SMB unit revamping strategies and operative actions are proposed. The practical application of “separation volume” methodology in the selection of optimum operating conditions that lead to maximum p‐xylene productivity with minimal desorbent consumption is described. © 2006 American Institute of Chemical Engineers AIChE J, 2007