bluuebunny/crossref_metadata_2025 huggingface dataset:
Removal of ethoxylated aliphatic amines from zinc containing effluents by adsorption on macroporous resins
Authors: Heitzsch Olaf , Stephan Holger , Gloe Karsten , Mühl Peter , Hellmig Reinhard
Published: August 2005

The separation of ethoxylated aliphatic amines from zinc containing effluents with macroporous polymeric adsorbents Wofatit EP 61, EP 62, Y 59, Y 77 and active carbons has been examined. The adsorption behaviour has been investigated as a function of temperature, time and concentration of Na2SO4, ZnSO4 and H2SO4. The macroporous polymers EP 61, Y 77 and Y 59 are capable of separating ethoxylated aliphatic amines from effluents of viscose fibre industry at higher temperatures and under weakly acidic conditions. In contrast to active carbon, inorganic components are not adsorbed on the investigated macroporous resins. Data obtained in a concentration range of 0 to 10 g of adsorbate per litre produced a Langmuir profile for adsorption of ethoxylated aliphatic amines by polymeric adsorbents.
Catalytic dehydrogenation of methanol to water‐free formaldehyde
Authors: Su Shoujin , Zaza Philippe , Renken Albert
Published: August 2005

Catalytic dehydrogenation of methanol is a promising process of producing water‐free formaldehyde. The present paper reviews research in this field. As effective catalysts mainly transition metal compounds as well as oxides and salts containing sodium have been reported. Several catalysts exhibit high activity and high selectivity, for formaldehyde at low conversions while further efforts have to be made to improve catalyst stability and selectivity at high conversions. Catalytic dehydrogenation of methanol to formaldehyde is compared with methanol oxidation.
Supported nickel catalyst from hydroxycarbonate of nickel and aluminium
Authors: Rathouský Jiří , Schulz‐Ekloff Günter , Stárek Jindřich , Zukal Arnošt
Published: August 2005

The hydroxycarbonate of nickel and aluminium (Ni/ Al = 3) with a hydrotalcite‐like structure is an outstanding precursor of the active component of supported nickel catalysts. Good mechanical strength and suitable nickel content of these catalysts, which are necessary for practical applications, can be achieved by mechanical mixing of this compound with an additional support. The catalyst prepared from a mixture of 56.5 wt‐% of nickel‐aluminium hydroxycarbonate and 43.5 wt‐% of γ‐alumina was proven to have a stable catalytic activity in the methanation reaction at 2 MPa and 800 K.
Further remarks on the linear relationship between stoichiometry and dimensional analysis
Authors: Pethö Árpád
Published: August 2005

The phrase “further remarks” in the title of this short paper is meant to imply that reactions and dimensionless groups are not only purely algebraic concepts, but definite numerical values can also be associated with them; in stoichiometry this evaluation may relate, for example, to the heat of reaction and, in dimensional analysis, to what is called a dimensionless number. On the basis of the evaluation concept, it will be shown that a counterpart of Hess' law in thermochemistry is valid in dimensional analysis.
Non‐Darcian non‐isothermal compressible flow and heat transfer in cylindrical packed beds
Authors: Foumeny Esmail A. , Ma Jian
Published: August 2005

Knowledge of transport processes is of considerable practical importance in the design and performance evaluation of packed bed reactor systems. Acquisition of the required information necessitates a realistic mathematical description of the system. In this study, numerical analysis is performed for forced convective non‐Darcian, non‐isothermal compressible flow and heat transfer in cylindrical packed beds. Local structural and transport properties are considered. The influence of compressional work as well as viscous dissipation on the thermal field is evaluated and a general criterion provided for assessing the effect of expansion.
A new design concept of structured packing column auxiliaries
Authors: Spekuljak Zvonko , Monella Horacio
Published: August 2005

This paper discusses the criteria for obtaining an improved performance of structured packing columns in gas‐liquid contacting, by improving the liquid and gas distributors. A new liquid distributor design, specific for structured packing columns is presented. Experimental measurements which quantify the improvements attained by the new distributor are also presented. Furthermore, gas flow distribution requirements for structured packing columns are discussed. Three “case studies” indicative of the implementation of the proposed distributor concept in industrial columns are included. Case (a) CO2/MEA removal column, case (b) ammonia splitter and case (c) acid gas neutralization column.
Air purification by catalytic oxidation in a reactor with periodic flow reversal
Authors: Van De Beld Bert , Westerterp K. Roel
Published: August 2005

The behaviour of an adiabatic packed bed reactor with periodic flow reversal has been studied by means of model calculations. A heterogeneous model as well as a pseudo‐homogeneous model have been developed. It is shown that a high degree of conversion can be obtained in an autothermal process even with very low adiabatic temperature rises of some 10 to 20 K. The reactor is insensitive to fluctuations in inlet concentrations and in through‐put. Short‐cut methods proposed in the literature for calculating the plateau temperature in the pseudo‐steady state are studied. The so called countercurrent‐flow reactor approach showed reasonable agreement with the plateau temperature obtained by dynamic calculations with the full reactor model.
Mixing of large volume gas flows in pipes and ducts. Visualization of concentration profiles
Authors: Fellhölter André , Mewes Dieter
Published: August 2005

Concentration profiles are measured during the mixing process of carbon dioxide and air, which were injected into the rectangular cross section of a duct. The volume flow rates of both components differ considerably. The non‐stationary and three‐dimensional concentration fields are measured by optical tomography using holographic interferometry as the measuring principle. Projection data from four different viewing angles are used for tomographic reconstruction by the ART method. Pressure losses due to mixing processes are also measured. Results are presented for different angles of injection and different ratios of momentum flow rate for single and multiple jets of carbon dioxide which were injected into the carrier gas stream of air.
Development of a mathematical model for a secondary reformer
Authors: Raghunandanan Kunduvelil S. , Reddy Kandi Venkat
Published: August 2005

A rigorous one‐dimensional heterogeneous model is developed for a secondary reformer in an ammonia plant with special emphasis on the catalyst particle models. These are based on the effective diffusivity model and the Stefan‐Maxwell model in the catalyst pore and the film around the catalyst particle. The performance of these four models is evaluated for the data collected from a commercial reformer in the complete operating range and recommendations are made regarding the use of appropriate particle models. The models for the catalyst particle show considerable deviations at the particle level but the reformer simulations produce almost identical results at the global level for all the four particle models. The need for a rigorous treatment of interphase resistance to mass transfer has been clearly demonstrated by comparison of the present model with the model of Singh and Saraf.
Comparison of the single‐bubble‐class and modified two‐bubble‐class models of bubble column reactors
Authors: Modak Shrikant Yadneshwar , Juvekar Vinay Anant , Rane Vishwanath Chango
Published: August 2005

Gas phase conversions and product selectivities predicted by the single‐bubble‐class and modified two‐bubble‐class models of bubble column reactors are compared for a multistep gas‐liquid reaction involving series/parallel steps. A situation is considered where the first reaction step is fast and occurs in the interfacial region while the other reaction steps are slow and occur only in the liquid bulk. Equivalent hydrodynamic and transport parameters provide a common basis for the comparison. The differences in the gas phase conversions predicted by these models are insignificant. However, the two models predict very different values of selectivities for the intermediate products. This analysis enables us to judge the range of applicability of the single‐bubble‐class model in design and scale‐up of bubble column reactors.
Single and multicomponent adsorption equilibria of carbon dioxide, nitrogen, carbon monoxide and methane in hydrogen purification processes
Authors: Sievers Werner , Mersmann Alfons
Published: August 2005

Single, binary, ternary and quaternary adsorption equilibria of CO2, CO, CH4 and N2 on molecular sieve 5A and activated carbon were experimentally determined over a pressure range from 10−4 to 101 MPa, a temperature range from 303 to 363 K and at various compositions. The adsorption equilibria of steam reformer gases as needed for the hydrogen purification in pressure swing adsorption units were measured by using a circulating volumetric method. For the temperature‐dependent correlation of pure gas isotherm fields the Toth equation, which is a favorable model for heterogeneous adsorbents, was extended by two parameters accounting for the temperature‐dependencies of the saturation loading and the heterogeneity parameter. Multicomponent equilibria were successfully predicted from single component isotherms by the Ideal Adsorbed Solution Theory based on the accurate representation of the pure component data by this temperature dependent Toth equation. Other thermodynamic models like the HIAS, the MIAS, the SPD or the VS theory and the Statistical Thermodynamics Model were also applied to the prediction of the adsorption equilibrium and the temperature and pressure dependence of the selectivity, with comparable success, which is due to the quasi‐ideal adsorption behavior even at a high pressure.
Dynamic response and safety assessment of a batch process on cooling breakdown
Authors: Koufopanos Charalambos A. , Karetsou Ageliki , Papayannakos Nikos G.
Published: August 2005

Cooling breakdown in highly exothermic reaction processes may lead to runaway. The sensitivity and the safety assessment of a batch process on cooling breakdown are studied. The dependence of the minimum cooling time and the maximum allowable time of cooling breakdown for safe operation on the process parameters is investigated.
Continuous fermentation with product recovery by in‐situ extraction
Authors: Weilnhammer Christian , Blass Eckhart
Published: August 2005

The productivity of fermentations is often limited by end product inhibition. This can be avoided by continuous removal of the inhibiting product from the broth. Such in‐situ separation can be conveniently accomplished by liquid‐liquid extraction. As an example, the continuous fermentation of ethanol by the thermophilic, anaerobic bacterium Clostridium thermohydrosulfuricum is investigated in a 20‐1 fermenter with simultaneous in‐situ extraction by oleyl alcohol as organic solvent. Continuous fermentations with and without in‐situextraction were carried out with systematic variation of the independent operating conditions, viz. feed glucose concentration, broth flow rate and solvent flow rate. The experimental results of 18 steady states are reported. They show that in‐situ extractions doubles the yield, selectivity and space‐time yield of ethanol in comparison to fermentations without in‐situ extraction. A biomodel elucidates the influence of feed glucose concentration, broth flow rate and solvent flow rate on the productivity of the fermentation process. Finally, a cost model was developed for the investigated fermentation which allows economic evaluation of the results of experiments and simulation. A sensitivity study elucidates the economic limits and advantages of fermentation with in‐situ extraction compared to a common fermentation without product separation.
Concept of a sterile concentration process for milk by multistage flash evaporation
Authors: Kiesner Christian , Eggers Rudolf
Published: August 2005

In the proposed combined sterilisation and concentration method, the original milk is first sterilised under conditions of continuous flow and after reaching the desired sterilisation temperature the product is concentrated by means of flash evaporation during subsequent cooling. Addition of stabilisers to maintain the thermal stability of the concentrate during sterilisation is not necessary in this process. The method presupposes that cooling with concentration is carried out under sterile conditions. This is technically quite feasible on use of multistage flash evaporation.
Temperature oscillation calorimetry in stirred tank reactors with variable heat transfer
Authors: Carloff Rüdiger , Proß Alexander , Reichert Karl‐Heinz
Published: August 2005

A new method for applying reaction calorimetry to stirred tank reactors with variable heat transfer is presented. Sinusoidal temperature oscillations are induced by an electrical heater placed either in the reactor or in the jacket in order to decouple the chemical heat production from the variable heat transfer during reaction. Multiplication of the reactor heat balance by periodic functions and integration yields the overall heat transfer. Temperature oscillation calorimetry was successfully applied to the free radical polymerization of methyl methacrylate in ethyl acetate which shows a strong decrease in heat transfer.
Design of a packed column for ethanol extraction. Equilibrium and kinetics studies
Authors: Ismael R. Costa , De Carvalho J. M. Rodrigues , Dias S. M. Martins , Novais J. Maggiolly
Published: August 2005

Computer‐aided design of a packed column to remove ethanol from aqueous solution with dibutyl butylphosphonate (DBBP) was accomplished with a programme based on the Pratt method and on the slip velocity equation. Reliable data for successful computation were obtained from literature correlations (drop size, hold‐up and axial mixing coefficients for different types of packing) and from experimental work (equilibria and kinetics). Equilibrium studies on the H2O‐ethanol‐dibutyl butylphosphonate system were performed at different temperatures. A decrease in temperature increased the selectivity of the extractant while the distribution coefficient of ethanol, KD ≈ 1.0, remained constant. The behaviour of the system kinetics towards temperature is assessed in order to determine the initial mass transfer flux (892 × 10−3 kg m−2s−1, 30°C) and the activation energy, 22.9 kJ/kmol. The process is governed by the diffusion of the species involved. The influence of the type of packing of the column on its design is analyzed from the inventory volume of the solvent, the total volume of the column and the axial dispersion coefficients under normalised inlet and outlet conditions.
New technology for hydrogen production by the catalytic oxidation and steam reforming of methanol at low temperatures
Authors: Trimm David L. , Wainwright Mark S.
Published: August 2005

A simple design of an adiabatic reactor for the production of hydrogen from methanol without external heating has been explored. Heat and steam are generated by oxidising part of the methanol and are removed in the process of reforming methanol to hydrogen. The reactor design emphasises the degree of control that can be achieved in a two‐bed system by controlling the air to methanol and water to methanol ratios in the feed. Predictions of the model are compared with experimental testing to allow optimisation of the process. Up to 75% of methanol can be converted to hydrogen.
Basic sites on the surface of oxide catalysts responsible for oxidative methane coupling
Authors: Davydov Anatolii Aleksandrovich
Published: August 2005

The basic sites of various oxide catalysts for the oxidative dimerisation of methane were studied by FTIR spectroscopy of adsorbed molecular probes (chloroform and CO2). The methods used are compared and the advantage of CO2 as probe for specifying the basic sites is demonstrated. The strengths of the basic sites were seen to correlate with the spectral parameters of the surface carbonates. Differences in spectral responses of carbonates are attributed to the different states of oxygen participating in their formation. The concentration of the strongest sites was estimated. A study of the catalytic activity of this system indicates that the system's activity in oxidative methane coupling depends on the presence and concentration of strong basic sites on the catalyst surface.
Limitation by zeolite protons of the oxygenate yield in syngas conversion over RhMn/NaY catalysts
Authors: Treviño Horacio , Sachtler Wolfgang M. H.
Published: August 2005

CO hydrogenation over Mn‐promoted Rh/NaY catalysts was studied at 1 MPa and 250°C. Significant selectivity to ethanol and ethyl acetate was obtained only after neutralising the protons formed on reduction of Rh ions. Layered bed experiments show that protons act as Brønsted acid sites catalysing secondary reactions that convert the oxygenates to hydrocarbons and coke.
Modification of the catalytic properties of supported noble metal catalysts by carrier doping
Authors: Ioannides Theophilos , Verykios Xenophon E.
Published: August 2005

The influence of altervalent cation doping of TiO2 carriers on the chemisorptive and catalytic properties of supported Pt and Rh crystallites has been investigated. It was observed that doping of the carrier with higher valence cations leads to suppression of the H2 and CO chemisorption capacity of Pt catalysts, while their activity in hydrogenation and oxidation reactions is significantly reduced. The opposite effects were observed in the case of Rh catalysts supported on higher valence doped TiO2. These catalysts were found to possess higher activity in CO and CO2 hydrogenation, in aromatics hydrogenation and in CO and C2H4 oxidation. Their stability characteristics were also found to be superior to those of the undoped Rh/TiO2 catalyst. These effects are believed to originate from an electronic type interaction at the metal‐support interface, induced by doping, which results in electron transfer from the support to the metal crystallites.
Single liquid drop velocities and breakage mechanism in sections of structured packings
Authors: Mao Z.‐Q. , Godfrey J. C. , Slater M. J.
Published: August 2005

Single liquid drop velocities in structured packings have been measured to aid calculation of throughput of liquid extraction columns using characteristic (single drop) velocities. Solvent drops were passed through two types of glass and two types of steel structured packing and further work was done using sloping glass tubes. Existing wall‐effect equations for drop velocity reduction in vertical tubes were considered and that given by Clift et al. [1] was used as a basis for correlation of structured packing data. Drop breakage was studied in order to improve understanding of drop size distribution development in packed columns. Drops broke only rarely within the structured packing; most of the breakage occurred as a drop hit the exposed edges on entry to a piece of packing. An energy balance equation was used to correlate critical conditions for breakage of drops hitting glass blades at various angles. Under the conditions used all those drops moving at terminal velocity had enough energy to break but a condition exists when drops may be small enough to have insufficient energy to break.
Single liquid drop breakage probabilities and characteristic velocities in Kühni columns
Authors: Fang J. , Godfrey J. C. , Mao Z.‐Q. , Slater M. J. , Gourdon C.
Published: August 2005

Studies have been made on the extent and mechanism of breakage of single liquid drops of organic liquids immiscible in water rising through short sections of Kühni liquid‐liquid extraction columns. Information on drop breakage probabilities is required for calculation of drop size distributions developed under counter‐current column operating conditions. The breakage probability data from two small diameter Kühni columns containing one, three or five stages have been correlated as a function of a modified Weber number based on the shearing forces on drops. The critical condition for breakage, giving a maximum stable drop size, is based on an impeller Weber number. Characteristic velocities of drops were measured relative to terminal velocity and the ratio was tentatively correlated with a function of an impeller Reynolds number together with the fractional free area of the perforated plates used to separate compartments. The drops were found to break predominantly at the holes in the plates, not at the turbine, in the region of transitional Reynolds number used in this work. The results apply only to non‐turbulent conditions so further work on larger diameter equipment is called for.
Synthesis of tertiary amyl methyl ether (TAME): Equilibrium of the multiple reactions
Authors: Oost Carsten , Sundmacher Kai , Hoffmann Ulrich
Published: August 2005

The octane enhancer tertiary amyl methyl ether (TAME) is produced by liquid phase synthesis from methanol and a mixture of isoamylenes, namely 2‐methyl‐1‐butene and 2‐methyl‐2‐butene, using a sulfonic acid ion exchange resin as catalyst. Three reactions take place simultaneously in TAME synthesis: etherification of the two methylbutenes and their isomerisation. In order to study the equilibrium of the multiple reactions in TAME synthesis, the thermodynamic properties of the compounds in the liquid phase and equilibrium constants were calculated using a modified UNIFAC method to describe the nonideality of the system. Four parameters influencing the equilibrium conversion were derived and discussed in detail. Supplemental experiments were performed at three temperatures in the range from 303 to 343 K and at different initial molar ratios of educts. Equilibrium conversions of methanol were determined from these experiments and compared with calculated values. At 298 K the predicted activity based equilibrium constant was 22.9 for TAME synthesis from 2‐methyl‐1‐butene and 1.6 for TAME synthesis from 2‐methyl‐2‐butene; for isomerisation of 2‐methyl‐1‐butene to 2‐methyl‐2‐butene a value of 14.3 was obtained.
Oxidation of methane on a Au + SrFeO3−δ//YSZ electrode characterised by mass spectroscopy and 18O2 pulses
Authors: Norby Truls , Middleton Peter Hugh , Hansen Eddy W. , Dahl Ivar , Andersen Arnfinn G.
Published: August 2005

A solid state electrochemical reactor is described in which reactants can be oxidised at high temperatures over an anode/catalyst using co‐fed oxygen gas as well as electrochemically supplied oxygen. The setup permits injection of isotopic pulses in the reactant streams. The composition and isotopic distribution in the products are recorded with a quadrupole mass spectrometer. The use of the system is exemplified by oxidation of methane over a Au + SrFeO3−δ//YSZ anode at 800–850°C. Pulses of 18O2 in the stream of co‐fed O2 were used to study the reactivity and products of gaseous oxygen as distinguished from the electrochemically supplied oxygen. The results indicate that the anode used supports oxygen pumping, but is only moderately active for methane oxidation. The products are mainly CO and CO2. The content of 18O in the products is low, indicating that methane oxidation takes place by 16O‐rich lattice oxygen. In comparison, a reference Au//YSZ electrode was found to be a slower anode for oxygen pumping, but a better catalyst for the reaction between CH4 and gaseous O2, seemingly involving adsorbed oxygen.
Air stripping – a method for treatment of wastewater
Authors: Kutzer Stephan , Wintrich Hans , Mersmann Alfons
Published: August 2005

During recent years the air stripping process has been increasingly applied to the cleaning of water contaminated by volatile organic compounds (VOC). The present contribution compares various methods of treating VOC‐contaminated water, with a special focus on removal efficiency and economic aspects. In particular, air stripping, a universally used cleaning method, is described in greater detail. Design and operational aspects are worked out for packed stripping towers for the special case of water contaminated with chlorinated hydrocarbons. Experimental results substantiate predictions of various operating conditions, packing types and scale‐up effects.
Nonlinear model‐based feedforward control of distillation columns
Authors: Broll Johannes , Rix Armin , Gelbe Horst
Published: August 2005

An approach to feedforward distillation control based on inverse computation of nonlinear stage models is presented. The feedforward model calculates dynamic trajectories of manipulated variables from measured disturbances and product purity set points independently of the control configuration. Because the model includes the dominant dynamics and nonlinearities of the column, dynamic decoupling of the control loops is achieved. A superimposed linear controller only has to compensate model uncertainties and disturbances that cannot be measured. The proposed approach improves the control performance. Simulation studies show the applicability of the method to multicomponent distillation as well as to distillation trains. Experiments on a pilot plant scale binary distillation column verify the simulation results.
The vapour‐liquid equilibria of several binary systems of fluorocarbons and hydrocarbons, part II
Authors: Kramp Sabine , Wagner Heinz Georg
Published: August 2005

The vapour‐liquid equilibria of the binary systems perfluoromethylcyclohexane‐pentafluorobenzene, benzene‐pentafluorobenzene, benzene‐methylperfluorobutanoate and perfluoromethylcyclohexane‐methylperfluorobutanoate have been measured at 333.07 K and 343.12 K using a dynamic circulation still of the Sieg‐Röck type. The thermodynamic consistency of the measurements was tested by two different methods. New UNIFAC interaction parameters [1] were calculated for the following groups: ACH‐ACF, ACF‐CF2, CF2‐COO, ACCH2‐ACF, ACH‐CF2. The abbreviations stand for the following increments: ACH = aromatic CH group, ACF = aromatic CF group, CF2 = aliphatic CF2 group, COO = ester group and ACCH2 = side chain CH group.
Application of fuzzy relational modelling to industrial product quality control
Authors: Qian Yu , Tessier Patrick J. C.
Published: August 2005

Industrial product quality control is a typical mathematical programming and optimization problem. Unfortunately, complete and precise models are not always available for many industrial processes. A fuzzy relation modelling approach is proposed to describe approximate relationships among system variables and reconcile empirical equations. Symmetric fuzzy decision‐making is transformed into a non‐linear function maximization problem. The approach is applied to optimization of a wood chip refining process. It is used either to improve pulp quality within the refiner operation range, or to reduce operation costs while maintaining an acceptable pulp quality.
Pyrolysis of methane in the presence of hydrogen
Authors: Olsvik Ola , Rokstad Odd A. , Holmen Anders
Published: August 2005

The kinetics of methane pyrolysis were studied in a tubular flow reactor in the temperature range 1200 to 1500°C at atmospheric pressure. To avoid excessive carbon formation the reaction time was short and the methane feed was diluted with hydrogen. Ethene, ethyne, benzene and hydrogen were the main gaseous products. Ethane was observed as a product at very low conversions of methane. More than 90% selectivity was obtained for C2 products. The ratio of ethyne to ethene increased with increasing temperature. The yield of C2 products is limited by gas‐phase equilibrium at lower temperatures. Formation of carbon was strongly depressed by hydrogen at higher temperatures. The maximum yield of ethyne was found to increase from about 10% to about 50% when the temperature was increased from 1200 to 1500°C, with hydrogen dilution H2: CH4 = 2: 1. A mechanistic reaction model was used to simulate the pyrolysis of methane at the actual conditions. A sensitivity analysis was performed to evaluate the elementary reactions which influence the formation and consumption of the species in the model system.
Kinetics of thermal decomposition of hydromagnesite
Authors: Rao T. Rajeswara , Chohan V. S.
Published: August 2005

The thermal decomposition of hydromagnesite has been studied using thermogravimetric analysis. The experiments were conducted in a nitrogen atmosphere with pellets of hydromagnesite in the temperature range 300 to 550°C, and also with powder samples under non‐isothermal conditions at a heating rate of 10°C/min. It is found that the reaction proceeds in two stages: dehydration followed by decomposition. The dehydration reaction is controlled by external mass transfer whilst the decomposition reaction is controlled by both external and internal mass transfer. The activation energy for the dehydration reaction was found to be 2.67 × 107 J/kmol. From the non‐isothermal analysis the activation energy for the decomposition of magnesium carbonate was found to be 1.62 × 108 J/kmol.
Fluid catalytic cracking: Selectivity and product yield patterns
Authors: Hari C. , Balaraman K. S. , Balakrishnan A. R.
Published: August 2005

Fluid catalytic cracking, a common secondary process employed in the petroleum industry, is used to convert heavier feedstocks into products such as liquefied Petroleum Gas (LPG), motor gasoline, diesel etc. The present study focuses on developing a three lump fraction kinetic model to estimate the yield of C5 up to 370°C cut (motor gasoline and middle distillates). A Micro Activity Test (MAT) apparatus was used to estimate the parameters in the kinetic model. The study is useful in evolving a procedure to simulate plant performance using experimental data obtained in the MAT apparatus for a particular catalyst and feedstock in terms of the product yield pattern.
Mass transfer coefficients for arranged packings with vertical walls under gas film control
Authors: Kolev Nikolai , Nakov Svetoslav , Djonova‐Atanassova Daniela
Published: August 2005

Packings with vertical walls, especially structured packings, are distinguished by their high efficiency and low pressure drop per mass transfer unit. Yet for these types of packings there is still no universal relationship for calculating gas‐film‐controlled mass transfer coefficients. The present work proposes such an equation. For arranged and structured packings the new equation fits the experimental data, both new results and those taken from the literature, with a mean error of 9%.
Inulin hydrolysis to fructose by a novel catalyst
Authors: Abasaeed A. E. , Lee Y. Y.
Published: August 2005

Acidic zeolite LZ‐M‐8 was used to catalyse the hydrolysis reaction of inulin into fructose. Fructose contents of 96% and 75% were obtained when commercial inulin and Jerusalem artichoke extract were used respectively as substrates. Zeolite LZ‐M‐8 was found to be extremely selective towards inulin hydrolysis as compared to fructose decomposition. Formation of hydroxymethyl furfural (HmF) was not detected and it was confirmed that zeolite LZ‐M‐8 does not adsorb HMF. The catalytic activity of the zeolite remained intact upon repeated use of the catalyst. The superiority of the zeolite over other catalysts used in inulin hydrolysis was demonstrated experimentally.
Effect of double agitation on particle size in suspension polymerization of styrene with a loop reactor
Authors: Tanaka Masato , Takahashi Tohru , Kimura Isao
Published: August 2005

Suspension polymerization of styrene was performed in the loop reactor. In order to allow wide change to the polymer particle size, a sub impeller was included within the main impeller. The sub impeller served to increase the fluid velocity and to uniformly disperse the polymer droplets during polymerization.

It was investigated how the double agitation method by the main and the sub impellers affected the transient droplet diameter distribution and the final particle size distribution. The particle size could be changed widely by the double agitation method without the decrease in degree of the uniformity of the particle size.
Kinetics of vanillin oxidation
Authors: Fargues Claire , Mathias Álvaro , Silva José , Rodrigues Alírio
Published: August 2005

Vanillin can be produced by oxidation of kraft lignin, with air, in alkaline medium. The optimal conditions for vanillin production strongly depend on pH and temperature. This paper addresses the effect of temperature and pH on vanillin degradation by oxidation. Experiments were carried out in a wide range of vanillin concentration, oxygen partial pressure, temperature and pH. Simple models are proposed to explain the observed rate of vanillin consumption under conditions of high alkalinity (pH>12) and lower alkalinity (pH<12). At pH>12,the reaction rate of vanillin oxidation is first order in dissolved oxygen concentration [O2] and in vanillin concentration [C], i.e., (−rC) ∝[O2][C]; at pH<12, the rate is zero order in oxygen concentration and second order in vanillin concentration, i.e., (−rC)∝f(pH)[C]2.
Determination of lumped rate coefficients of proteins: Effect of adsorption
Authors: Hashim Mohd. Ali , Chu Khim Hoong , Tsan Peh Sim
Published: August 2005

The equilibria and kinetics of adsorption of lysozyme and bovine serum albumin on the Fractogel‐EMD tentacle‐type cation exchanger and the Fractogel‐TSK conventional cation exchanger have been studied experimentally by batch stirred‐tank method. Adsorption equilibrium data corresponded well to the Langmuir isotherm. For both proteins, the tentacle‐type exchanger exhibited a higher binding capacity than the conventional exchanger. This is attributed to the flexibility of the functional groups in the tentacle‐type exchanger which enhance optimal electrostatic interactions. The dynamic data were analyzed by a simplified data model which lumped mass transfer resistances and intrinsic adsorption kinetics into a single rate constant. For both proteins, it was found that the tentacle‐type exchanger showed a smaller lumped rate coefficient than the conventional exchanger. The difference in the values of the lumped rate coefficients was shown to be due to the influence of nonlinear equilibrium constants rather than due to any difference in rate of adsorption.
Interfacial tension of fluid system considering the nonstationary case with respect of mass transfer
Authors: Jaeger Philip T. , Schnitzler Joachim V. , Eggers Rudolf
Published: August 2005

Interfacial properties exert a fundamental influence on fluid/liquid separation processes, with the interfacial tension being an important quantity associated with mass transfer and mutual solubility of participating compounds. A better understanding of transport phenomena is achieved by obtaining interfacial tension data under different conditions of pressure and temperature and as a function of time. Generally, interfacial tension decreases with increasing pressure due to increased adsorption of the compressed fluid at the interface. In the case of considerable mutual solubility, interfacial tension further decreases with time as mass transfer into the bulk phase proceeds. Prediction of colloidal behaviour in a separation process requires acquisition of additional information on the presence of surfactants.
Two‐dimensional motion of spherical particles
Authors: Michalski Jacek A.
Published: August 2005

A method for the prediction of velocity and path length components for two‐dimensional particle motion is developed for stagnant and slowly moving gas. The numerical algorithm appears much more straightforward and more efficient than those previously developed on the basis of simplified analytical methods. In the case of particle motion in a flowing gas, several limitations of the method occur. The method of limit estimation is briefly described.
Measurement of pumping characteristics of agitators in tubes
Authors: Rieger František
Published: August 2005

The Pumping characteristic of an agitator in a tube is necessary of the calculation of its pumping capacity in configuration in the vessel with a draught tube. The general dimensionless equation of the pumping characteristic suitable for the higher Reynolds number region was derived by inspection analysis of basic equations. The new dynamic experimental method for determination of pumping characteristics is put forward. The application of this method is illustrated on a special three‐blade axial‐flow impeller.
About the possibility of a direct concentration control for distillation columns
Authors: Fieg Georg , Landwehr Birgitta , Wozny Günter
Published: August 2005

The results of simulations of direct concentration control of a distillation column in industrial scale are presented. Both controlled variables, the two product concentrations, are determined by on‐line gas chromatographs and are characterised by high dead times of about 30 min. For the resulting scanning control of the product concentrations corresponding decentralised PI controllers were developed and applied. The control of the product concentrations developed presents a conventional DV structure and was exemplarily tested for disturbances in feed flow and feed concentrations. The calculations carried out exhibit a good time behaviour of the whole system. On this occasion it can be stated that the control quality could be clearly improved if a steady‐state decoupling by output transformation was employed. In this case the results achieved are totally comparable to those of internal model control (IMC), which was in use at the production plant for over two years.
Simulation of hydrodynamic behaviour and mass transfer efficiency of reduced pressure distillation
Authors: Benadda Belkacem , Moszkowicz Pierre , Prost Michel , Otterbein Michel , Mohammedi Kamal
Published: August 2005

A random packing hydrodynamic simulator is designed specially to carry out experiments under reduced pressures with a counter‐current flow air/water system. The simulator results (air/water system) compared to those obtained in a real packed distillation column (benzylchloride/ ethylbenzene system) show a good agreement between hydrodynamic parameters like pressure drop, flooding flow rate, and total liquid hold‐up. Empirical relationships derived from the simulator experimental results are proposed allowing the calculation of the pressure drop in a packed distillation column, operating in the pressure range between 10 kPa and atmospheric pressure. The influence of reduced pressure on the HETP in the distillation column and interfacial area in the simulator was also investigated.
A comparison of cavern development in mixing a yield stress fluid by rushton and intermig impellers
Authors: Galindo Enrique , Argüello Martha A. , Velasco David , Albiter Verónica , Martínez Alfredo
Published: August 2005

Intermig impellers have been postulated as very efficient for mixing highly viscous non‐Newtonian fluids (such as xanthan and mycelial broths). However, no formal characterisation has been published and no fair comparisons have been made, based on accurate power drawn measurements and using equal number of impeller stages and equal diameter, if compared (for example) with the performance of Rushton turbines. Characterisation of the shape, size, and evolution of the well‐mixed zones or “caverns” were correlated with power drawn, for single and dual Rushton turbines and for one‐ as well as two‐stage Intermig unslotted impellers. Cavern evolution studies were carried out in a mixing tank (diameter=0.205 m, H/T=1.6) equipped with an accurate air bearing dynamometer. Carbopol 940 (0.25 wt.‐%) was used as a model, transparent fluid. Impeller to tank diameter ratio was 0.53 for both impellers. Caverns were visualised by injecting methylene blue in the well‐mixed zones. A single Rushton turbine developed larger caverns if compared with one‐stage Intermig of the same diameter under power drawn below 1.5 kW m−3. At higher power drawn, both impellers behaved very similarly, reaching a limit in cavern volume of about 40% of the total liquid volume, even at very high (20 kW m03) power drawn. A similar trend characterised dual combinations: below 3 kW m−3, dual Rushtons gave larger cavern volume if compared with the performance of two‐stage Intermigs. In either case, power drawn higher than 3 kW m03 was sufficient to mix more than 90% of the liquid volume. The presence or absence of the slot in the Intermig did not influence cavern development. Experiments with a smaller if compared with those obtained with the larger Intermig (D/T = 0.53).
Modelling of multi gas/solid reactions – effect of structural parameters
Authors: Hastaoglu Mehmet A. , Abba Ibrahim A.
Published: August 2005

A unified gas/ solid reaction model has been formulated for multi reactions with multi gas and solid species. The transient formulation has been followed by finite‐difference method and subsequent solution via an iterative procedure. The simulation produces intermediate results for concentration profiles of various components and pressure and temperature distribution, in addition to various structural parameters within a reacting pellet. The effect of structural parameters is analysed. The general formulation allows homogeneous and heterogeneous reactions. Solid state processes can also be accommodated.
Numerical simulation of toluene adsorption on activated carbon in a technical column in low concentration range
Authors: Bart Hans‐Jörg , Germerdonk Rolf , Ning Ping
Published: August 2005

This paper deals with the modeling of toluene adsorption in a technical column of activated carbon in a low concentration range (2.6 to 3.4·10−3 kg/m3), which is usual for environmental applications. It is also concerned with methods of numerical solutions of the nonlinear partial differential equations (PDE), a modified control volume method was used to determine the PDE. Three nonequilibrium isotherm models are developed to describe mass transfer in a fixed bed of activated carbon (Degussa WS‐4). The important parts of this paper are the simulation of the maldistribution of concentration and loading of the pollutant in the technical column, as a result of the flow velocity maldistribution and the study of the mass transfer mechanisms in a technical fixed bed. It is found that in a low concentration range, toluene adsorption in a fixed bed of activated carbon (Degussa WS‐4) is an external rate‐controlled process, thus surface diffusion cannot be neglected. The calculated results are in good agreement with the experimental ones. The measured effect of an earlier breakthrough near the wall‐near zone has been calculated using the model.
Thermo gravimetric study of calcination of dolomite at pressurised conditions
Authors: Mårtensson Roland , Bjerle Ingemar
Published: August 2005

Calcination and carbonation behaviour of dolomite has been studied in a pressurised thermo balance at pressures in the range of 1.1 to 2.3 MPa and for temperatures ranging from 730 to 840°C. The atmosphere consisted of nitrogen containing up to 20 vol.‐% carbon dioxide. The calcination of dolomite has been studied as a function of temperature, particle size, and Pco2. An investigation concerning possible mass transfer restrictions for the experimental system and a model investigation of the calcination rate in CO2 atmosphere has been made. Further, the effect of calcination on the BET surface and the BET surface including the surface structure due to successive temperature cycles has been studied. The temperature for the initialisation of calcination of dolomite in CO2 atmosphere was independent of both Pco2 and the particle size. No conclusive indications on mass transfer restrictions have been detected for the experimental system. A significant difference in calcination rate as a function of particle size existed for decomposition in CO2 atmosphere. A model for homogeneously progressing chemical reaction parallel with a shrinking core chemical reaction together with a mass transfer control mechanism was found to describe the calcination rate in CO2 atmosphere most accurately.
H2S gas treatment with Thiobacillus Ferrooxidans – process performance and stability
Authors: Pagella Claudio , Zambelli Luca , Silvestri Piero , De Faveri Dante Marco
Published: August 2005

The present paper deals with a novel hydrogen sulphide abatement process applying a combined chemical‐biological process. The authors already dealt with this subject in the paper “Biotechnological H2S gas treatment with Thiobacillus ferrooxidans” [1], previously published in Chemical Engineering and Technology. This study, in particular, deals with over all process test runs in a laboratory scale plant with a single‐stage immobilised biomass reactor.
Model for the influence of mass transport on enzymatic hydrolysis of polysaccharides
Authors: Heitmann Torsten , Wenzig Edda , Mersmann Alfons
Published: August 2005

In this paper enzymatic hydrolysis reactions have been considered as integration‐limited reactions analogous to crystal growth. Based on the mathematical formulation of diffusion of polysaccharide substrate molecules to binding sites of the enzyme, integration kinetics were derived and compared to measured data. Significant is the measured and calculated decrease of the ratio of the specific activity and the Michaelis‐Menten parameter with increasing molar mass of the enzymes with an exponent more than unity.
Simultaneous oxidation of nitrogen oxides and sulfur dioxide with ozone and hydrogen peroxide
Authors: Nelo Sirpa K. , Leskelä Kaisu M. , Sohlo Jorma J. K.
Published: August 2005

The use of ozone and hydrogen peroxide for the simultaneous oxidation of nitrogen and sulfur oxides was studied in experiments carried out in a stirred cell. It was found that in a gas mixture, containing both nitrogen and sulfur oxides, only the nitrogen oxides are oxidized by ozone. Contrary to earlier results, sulfur dioxide does not disturb the oxidation of nitrogen oxides under dry conditions. The consumption of ozone in the oxidation of nitric oxide was slightly below the stoichiometric level because the ozone was introduced into the reactor in the oxygen flow. When the molar ratio between ozone and nitric oxide was more than 0.4, some of the nitric oxide was oxidized to higher oxides of nitrogen, the final product being a solid mixture of N2O5 and (NO)2S2O7. Some nitrosyl sulfuric acid was formed in the aqueous solution of hydrogen peroxide in addition to sulfuric acid under wet conditions. Some white solid was found on the walls of the reactor. This solid is said it the literature to consist of H2SO4, HNOSO4 and (NO)2S2O7.
Models for minimum ignition temperature of organic dust clouds
Authors: Mittal Manju , Guha Barun Kumar
Published: August 2005

The minimum ignition temperature of dust clouds is one of the important factors required for the design of preventive measures against dust explosion. The mathematical models available to predict this parameter have been analyzed for thier application to organic dust clouds. A solution of the most general model proposed by Mitsui and Tanaka is presented, together with its comparision with experimental data. It has been found to be quite successful in predicting the minimum ignition temperature for metal dusts but not for organic dusts. Recommendations for the development of a new model to predict the minimum ignition temperature of an organic dust, such as polyethylene, have been given.
Mechanical foam breaking – a physical model for impact effects with high speed rotors
Authors: Gutwald Stefan , Mersmann Alfons
Published: August 2005

During recent years in chemical engineering processes for instance with aerated stirred tanks containing surface‐active components foams and their mechanical control have become very important. However, there are still no rules for calculating mechanical foam breakers. As a contribution to foam control the present paper discusses the fundamentals of foam breaking by means of foam densities and gives a physical model for the mechanisms of a mechanical foam breaker when the main breaking effect is based on impact. The mechanisms were proved by measuring pressures in a foam breaker box. Diameters of secondary foam bubbles produced by foam breakers are calculated and discussed. Experimental investigations were made with different surfactants in aqueous solutions. The paper points out their influence on the process of foam breaking.