bluuebunny/crossref_metadata_2025_split huggingface dataset:
Systems engineering approach for chemical process energy optimization
Authors: Koehler Jürgen , Schadler Norbert 
Published: August 2005

AbstractProcess energy integration and continuous improvement of process technology are everlasting issues to ensure profitability of chemical productions. And both objectives become increasingly important due to long‐term environmental effects of energy degradation, such as resource depletion, emissions and the release of “waste” heat. The key success factor for process improvement lies in combining up‐to‐date expertise from different areas in an overall approach. One such approach is the systems engineering concept. It helps to structure and to organize problem‐solving process. We strongly believe that the increasing complexity of large and interlinked chemical production system and the tightening of global economic pressure force us to use more than ever systematic analysis and design methods to guarantee optimality throughout the entire product life. First we present a brief introduction to systems engineering in general. Then, in the main part of the paper, we give examples for optimizing the use of energy in chemical plants in order to illustrate advantages of the systems engineering concept. The examples range from improving the performance of individual pieces of equipment over changes in the process structure up to optimizing process clusters.
General criteria to analyze the role of mass transfer and hydrodynamics in trickle‐bed reactors
Authors: Cassanello Miryan C. , Cukierman Ana L. , Martinez Osvaldo M. 
Published: August 2005

AbstractGeneral simple criteria to predict and analyze the influence on trickle‐bed reactors behavior of three phenomena, namely, plug flow deviations, external wetting efficiency and external mass transfer resistance, are developed. Criteria predictions are compared with results arising from a comprehensive mathematical model widely employed to describe trickle‐bed reactors behavior and with other particular criteria reported in the literature. Present criteria applications to different sets of experimental data exemplify their practical utility for various actual situations and verify their validity. Besides, they constitute simple tools to diagnose detrimental on trickle‐bed reactors operation.
Power consumption of multiple shaft agitators
Authors: Pahl Manfred H. , Brenke Andreas , Luo Yining 
Published: August 2005

AbstractFor highly viscous products, multiple shaft agitators represent an interesting alternative to expensive special mixers. A triple shaft agitator with a volume of 250 liters is used to determine the powder consumption of the impellers and its relationship with the process parameters. The result shows that the power consumption of a single impeller running in multiple shaft mode is significantly smaller than of one running in single shaft mode. But the power required for the whole multiple shaft machine is much higher than that for a single shaft machine. A model is presented for detailed description of the interactions between the individual agitators in multiple shaft mode.
Numerical simulation of influence of mass transfer on phase transfer catalytic reaction
Authors: Wu Ho‐Shing 
Published: August 2005

AbstractMass transfer with chemical reaction by liquid/liquid phase tranfer catalysis (LLPTC) for an isothermal batch reactor was analyzed. The results for the phase transfer catalyzed reaction system can be generally described by a pseudo first‐order hypothesis, whereas the reaction system can be controlled by simultaneous mass transfer of the catalysts between two liquid phases and chemical reaction in the organic phase. The mass transfer limitation is mainly from the mass transfer step of QX from the organic phase to the aqueous phase. The concept of catalyst‐effectiveness vs. physically meaningful parameters in a liquid/liquid phase transfer catalyzed reaction is introduced. The catalyst effectiveness is increased as the mass transfer factors increase, the ratio of reaction rate coefficients of aqueous forward reaction to organic increases, and the equilibrium constant in the aqueous solution increases.
Analytical study of type‐1 facilitated transport through liquid surfactant membrane
Authors: Bhowal Avijit , Datta Siddhartha 
Published: August 2005

AbstractIn the present study, a mass transfer model for Type‐1 facilitated transport in liquid surfactant membrane is developed by taking into consideration a size distribution of emulsion drops, and analytical solution of the model equations has been presented. The model takes into account the continuous phase and outer liquid membrane phase resistances along with diffusion through composite emulsion drop. Effort has been made to highlight the effect of the various system parameters on the extraction rate including computation of reaction front position. The results of this work are found to be in good agreement with the published experimental results on batch extraction of phenol using NaOH as internal reagent. The model would thus provide an insight of the separation mechanism involved in the mass transfer processes in this type of system.
The effect of mannitol and pH of the solution on the properties of sintered magnesium oxide obtained from sea water
Authors: Petric Nedjeljka , Martinac Vanja , Labor Miroslav 
Published: August 2005

AbstractIn order to reduce the B2O3 content in sintered magnesium oxide as much as possible, in precipitation with 80% of the stoichiometric quantity of dolomite lime, the effect of the pH of the agent used for rinsing the magnesium hydroxide precipitate was examined, as well as the effect of mannitol in sea water before precipitation. Mannitol binds orthoboric acid present in sea water into a weakly dissociated complex acid HB(OC)4. Experiments have shown that the B2O3 content in the sintered magnesium oxide samples is satisfactorily low. The lowest B2O3 content is obtained when mannitol is added; no B2O3 was found in these samples after sintering. Magnesium oxide samples were sintered at 1500°C; duration of isothemal sintering was one hour. Values for density and porosity of individually sintered samples are listed. The ratio CaO/SiO2 indicates that forsterite (Mg2SiO4), monticellite (CaMgSiO4) and mervinite (Ca3MgSi2O8) are formed during sintering of the samples.
Kinetics of liquid‐phase cyclohexanone ammoximation over a titanium silicate
Authors: Kul'kova Natal'ya V. , Kotova Valentina G. , Kvyathovskaya Marina Yu. , Murzin Dmitry Yu. 
Published: August 2005

AbstractLiquid‐phase cyclohexanone ammoximation over titanium silicate was carried out in a batch reactor. The influence of the solvent, duration of kinetic run, catalyst amount and reactant concentrations was investigated. Byproducts were formed in considerable amounts, leading to catalyst deactivation by pore blocking. The values of initial reaction rates were calculated taking into account deactivation phenomenon. Theses values indicated that within the range of studied concentration (Ccyclohexanone = 0.4 to 1.70 mol/l; Cammonia = 1 to 4 mol/l; Chydrogen peroxide = 0.4 to 1.8 mol/l) the reaction rates plotted as a function of all the reagent concentrations go through a maximum. Special experiments on hydrogen peroxide decomposition and cyclohexanone oximation by hydroxylamine demonstrated that the rates of these reactions are essentially higher than the ammoximation rates.A kinetic equation for initial ammoximation rates was developed on the basis of a mechanistic model. The advanced model permits description of the observed kinetic regularities.
Economic process optimization strategies
Authors: Buskies Ulrich 
Published: August 2005

AbstractThe following deliberations are concerned with the application of economy criteria to the optimization of process‐engineering plants. We are therefore not concerned here with criteria for investment decisions, i.e., decisions on the implementation orabandonment of an investment project, nor with criteria for the selection of the most profitable investment options from a series of alternatives. Instead, we are interested here in the question of how a plant, while at the planning stage, can best be designed, i.e., the most rational method of selecting process parameters, such as throughputs, pressures, temperatures, concentrations, etc. The problem of plant optimization only occurs, however, when there are design parameters which can be selected at will or can, at least, be varied within certain limits. This is however, virtually always the case. There is then a need for an optimization strategy in the form of an objective function which is either reduced to a minimum, where lowest possible production costs are the target, for instance, or advanced to a maximum, where high profitability is the aim. The inclusion of engineering economy functions, in the form, namely, of the net present value function and the internal rate of return function for definition of such objective functions, provides better defined information on the best possible choice of process parameters than was possible with methods previosly used, such as the annuity method, for instance. One obtains different values for the process parameters to be optimized, depending on the objective functionused, and therefore different investment costs and utility consumptions. These differences are delineated and quantified using a process‐engineering example in the course of the following discussion. The example selected is a gas scrubber, the function of which is to remove and recover useful components from a flow of gas. The specific problem examined is one of heat recovery.
Bubble emissions from submerged orifices – a critical review
Authors: Ponter Anthony B. , Surati Ashini I. 
Published: August 2005

AbstractA comparative study of reported theoretical and experimental investigations evaluating the numbers and sizes of bubbles emerging from submerged orifices reveals that the lack of consistency can be attributed largely to faulty experimental techniques. Errors are attributed to an inadequate knowledge of the influence of the surface properties of the solid and liquid media on the emission process and to the lack of standardization of the equipment geometries especially regarding the pressure chambers and orifice plates. The analyses provide guidance to designing standardized equipment to produce reproducible bubbles.
A vapor pressure equation for heavy compounds
Authors: Campanella Enrique A. 
Published: August 2005

AbstractA vapor pressure calculation procedure based on a lattice equation is applied to several compounds. Originally, the method was used to predict low vapor pressures of heavy hydrocarbons. In this work, the method is used at low vapor pressure for nonhydrocarbons, and a modified version is employed at high vapor pressure for n‐alkanes. As the procedures require the knowledge of one vapor pressure datum only, they work in a predictive mode. Prediction for hydrocarbons is good and for nonhydrocarbons is poor. Prediction of n‐alkanes high vapor pressure is good with an overall average relative absolute deviation under 6 percent.
Effect of fasting condition on multi‐substrate carbon oxidation and nitrification system in an upflow packed‐bed biofilm reactor
Authors: Beg Shafkat Ali , Hassan Mirza Manirul , Chaudhry Muhammad Arshad Saeed 
Published: August 2005

AbstractThe performance of an upflow packed‐bed biofilm reactor has been analyzed under multisubstrate limitation by considering simultaneous carbon oxidation and nitrification reactions. The fasting shock load of inlet methanol concentration has a much more pronounced effect on the response of the system compared to that of inlet NH4+ ‐nitrogen concentration. The exit concentration of NH4+ ‐nitrogen drops very close to zero, thereby showing essentially complete nitrification during methanol fasting condition. Further, the concentration profiles of oxygen within the biofilm show significant variation during methanol fasting and nonfasting conditions whereas during NH4+ ‐nitrogen fasting conditions the oxygen concentration profile in the biofilm remains essentially unaffected.
Effect of laminar flow on the rate of mass transfer inside cubical cavities
Authors: Zaki M. M. , Nirdosh I. , Sedahmed G. H. 
Published: August 2005

AbstractAn electrochemical technique which involved measuring the limiting current of the cathodic reduction of potassium ferricyanide was used to study the rate of mass transfer inside a cubical cavity machined in the wall of a vertical rectangular duct. Variables studied were side length, physical properties of the solution and flow rate of the solution. The mass transfer coefficient was found to decrease with increasing cavity size; in all cases, the mass transfer coefficient inside the cavity was less than that at the duct wall. Mass transfer data inside the cavity were correlated by the equation Shc = 0.525 (Sc Re de/L)0.33. Comparison of the present results with the results obtained using other cavity geometries shows that cavity geometry plays an important role in determining the rate of mass transfer inside the cavity.
Bioheat equation of the human thermal system
Authors: Xuan Yimin , Roetzel W. 
Published: August 2005

AbstractAs an alternative to the existing bioheat transfer models a new system of two energy equations is proposed by considering the human body as a deformable porous medium. One equation is developed for the blood and the other for the peripheral skeletal tissue. It includes such significant factors as the vascular geometry and size, the blood flow and direction, thermal diffusion and the local thermal nonequilibrium between the blood and peripheral tissue. Discussion and application of both equations are given.
Reaction kinetics of the CO2 reforming of methane
Authors: Mark Michael F. , Maier Wilhelm F. , Mark Franz 
Published: August 2005

AbstractThe kinetics of the CO2 reforming of methane was investigated in the temperature range 700–850°C at normal pressure with a 1:1 mixture of CH4 and CO2 on Ir/Al2O3 catalysts. The feed composition was kept constant to avoid a change in mechanism associated with composition changes. Various rate models were fitted to the experimental data by numerically integrating the rate equations. All rate models included the reverse water gas shift reaction as the most important side reaction at these reaction conditions. The best agreement was obtained with a rate model based on the stepwise mechanism, where in the rate‐determining step methane is decomposed to hydrogen and active carbon followed by the direct and fast conversion of this active carbon with CO2 to 2 CO. This model is also the first and only one containing a complete subset of reactions necessary to describe the network of reactions known to occur at these reaction conditions. Comparable fit quality was obtained with a simple first order model and with a model based on a Langmuir‐Hinshelwood rate expression, where the latter provided physically meaningless parameters. Values of the reaction parameters are given for the 5 best rate models studied.
Fuzzy logic control of an unstable biological reactor
Authors: Inamdar Satish R. , Chiu Min‐Sen 
Published: August 2005

AbstractIn the present work, we employ a fuzzy logic controller (FLC) to control the unstable state of a nonlinear biological reaction. The state variable vectors consist of cell density and substrate concentration. The dilution rate is used as a manipulated variable to control the reaction dynamics. An analytic form of FLC employing Zadeh AND logic along with Center of Mass defuzzification method is considered. Simulations reveal that for servo response test, the FLC shows satisfactory performance for natural unsteady states for which a conventional PI controller is known to fail. Further simulations also show that the FLC gives satisfactory regulatory response and is relatively insensitive to the deviations in model parameters.
A new correlation for the two‐phase pressure recovery downstream from a sudden enlargement
Authors: Attou A. , Bolle L. 
Published: August 2005

AbstractBy applying the macroscopic conservation laws to a simplified jet downstream from a sudden enlargement, a new correlation of the two‐phase subcritical pressure recovery is obtained. Comparisons with the set of existing data (air‐water and steam‐water subcritical flows) show that the predictions obtained by means of this formula are more accurate than the ones given by available analytical models. The proposed correlation presents an important improvement of the pressure recovery predictions in the case of small mass velocities. However, it can not be applied in the conditions of quality too close to one.
Caprolactam production: A comparison of different layouts of the liquid‐liquid extraction section
Authors: Alessi Vanni , Penzo Renzo , Slater Michael J. , Tessari Roberto 
Published: August 2005

AbstractTwo different layouts for the liquid‐liquid extraction section of an industrial caprolactam process are evaluated. Laboratory mass transfer measurements on streams obtained from an industrial and a demonstration plant with different extraction sections are interpreted by a model describing the effect of surface contaminants on mass transfer coefficients. Indications of the impact of these layouts on the complexity of the extraction section, quality of products and efficiency of the extraction processes are given.
Comparison of two‐phase upflow and downflow fixed bed reactors performance: Catalytic SO2 oxidation
Authors: Iliuta Ion , Iliuta Maria C. 
Published: August 2005

AbstractA time‐ and space‐dependent model based on the piston‐dispersion‐exchange model for liquid flow was developed to analyze the performance of two‐phase upflow and downflow fixed bed reactors and was applied to the catalytic SO2 oxidation. The hydrodynamic parameters were determined from residence time distribution measurements, using an imperfect pulse method for time‐domain analysis of nonideal pulse tracer response. A transient diffusion model of the tracer in the porous particle coupled with the PDE model was used to interpret the obtained RTD curves. Gas‐liquid mass transfer parameters were determined by a stationary method based on the least square fit of the calculated concentration profiles in gas phase to the experimental values. It is shown that two‐phase downflow fixed bed reactor performs better at low liquid flow rates, while two‐phase downflow fixed bed reactor performs better at low liquid flow rates, while two‐phase upflow performs better at high liquid flow rates.
Three‐dimensional vibrational mixing
Authors: Pahl Manfred H. , Wittreck Hubert 
Published: August 2005

AbstractWhen working with disperse solid matter systems, one uses the effect of vibration in numerous processes. Solid matter mixing with vibration has only occurred in very simple units up to now. By means of the 3D‐vibrational mixer from the company Kuston, Kleve, the influence of vibration on bulk materials and new mixing techniques are demonstrated. The 3D‐vibrational mixer is suitable for liquids and solids, does not require mixing tools that need to be cleaned, and does not carry out rotary motions which would hinder incoming lines. It is used for mixing small amounts, where the mixing tank can be used simultaneously as the transportation container, so that a transfer is unnecessary.With the aid of 4 linear motors, the vibrational amplitudes and the frequencies can be varied within wide boundaries in all three spatial directions. By analyzing the vibrational system by means of Lissajous figures, it can be demonstrated that the optimal mixing effect occurs in the case of small frequency differences between the three axes. For freeflowing bulk materials, the best possible mixing state, the uniform coincidence mixing, is achieved after 2 min.
High shear rheology of paper coating colors – more than just viscosity
Authors: Willenbacher Norbert , Hanciogullari Haryutum , Wagner Hans G. 
Published: August 2005

AbstractCapillary viscometry is used to characterize viscosity, entrance pressure loss and apparent wall slip of paper coating colors at high shear rates. Special emphasis is laid on the dependence of these phenomena on solids content in order to account for changes in the rheology due to the dewatering of the color during the coating process. Coating colors with substantially different runnability have been investigated. Differences in apparent wall slip and high shear viscoelasticity (manifesting itself in extremely high entrance pressure losses) are observed at increased concentration, even if these phenomena do not show up at the initial solids content. Poor runnability is observed when viscosity, entrance pressure loss and wall slip increase strongly with increasing solids content. But all rheological features change simultaneously with the coating color recipe and it is not possible to separate out the contribution of the particular rheological features on the runnability of the coating colors or to correlate the runnability to a single rheological prorameter. Future work will have to focus on a numerical analysis of the blade coating process taking into account all the rheological features described here. First simulations including slip at the color/blade interface indicate that wall slip may cause severe runnability problems, at least when the apparent slip velocity exceeds the web velocity.
Calculation of equilibrium composition in combustion products
Authors: Rashidi Manoochehr 
Published: August 2005

AbstractFor a specific combustion problem involving calculations of several species at equilibrium, it is much simpler to write a special computer program and calculate the concentrations, rather than to use a generalized computer program. To calculate these concentrations, one must solve a set of non‐linear algebraic equations. This work describes a procedure in which the Newton‐Raphson method and the successive substitution method are combined. It is was found that for these types of problems the value of unknowns and the nature of the equations are such that by adopting the two procedures simultaneously a much faster and reliable convergence is achieved. This study also shows what possible species should be considered for these calculations.
Numerical determination of the three‐dimensional velocity distribution in a baffled pitched blade impeller stirred vessel
Authors: Götz Sven , Sperling Reinhard , Liepe Friedrich , Jembere Solomon 
Published: August 2005

AbstractThe objective of the work presented here was the development of a method of modeling the effect of an impeller on the velocity distribution in a stirred vessel. The developed model makes it possible to numerically investigate the flow field almost independently of any experimental data. The starting point was a force balance around an impeller blade, which took into consideration the lift and drag forces. The obtained volume forces were circumferentially averaged in the impeller region. The calculations were carried out time‐averaged for the case of a pitched blade impeller. The results were compared with experimental data which were obtained by laser Doppler anemometry. The comparison of the axial velocity components shows a good agreement between numerical and experimental data. Furthermore some characteristic integral values were calculated, which demonstrate the efficiency of the impeller.