bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling of multi gas/solid reactions – effect of structural parameters
Authors: Hastaoglu Mehmet A. , Abba Ibrahim A. 
Published: August 2005

AbstractA 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

AbstractThis 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

AbstractCalcination 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

AbstractThe 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

AbstractIn 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

AbstractThe 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

AbstractThe 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

AbstractDuring 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.
Aerodynamic characteristics of FGD spray towers
Authors: Michalski Jacek A. 
Published: August 2005

AbstractOn the basis of the balance of forces acting on droplets falling down inside a co‐ or counter‐current spray tower, a model of scrubber aerodynamic characteristics was developed. Relations between pressure drop caused by spray, droplet concentration and residence time distribution of the dispersed phase were found analytically for slurry droplet motion in the range of 400<Re<2500. The differences between the simplified model solutions and complete solutions are presented. The model was verified by the experimental data collected in two large pilot plant scrubbers applied for flue gas desulfurization (FGD).
Dynamic modeling and simulation of a riser‐type fluid catalytic cracking unit
Authors: Ali Hany , Rohani Sohrab 
Published: August 2005

AbstractA dynamic model is developed for a fluid catalytic cracking (FCC) unit to describe the dynamic behavior of both the riser and the regenerator reactors and their interactions. The cracking reactions are simulated by the four‐lumped kinetic model [1]. The reactions in the riser occur in a transported bed with the fluid and the solids in ideal plug flow. The two‐phase nature of the regenerator‐fluidized bed is considered and the kinetic model for the coke combustion on the cracking catalyst [2,3] is incorporated. The proposed model is validated using steady‐state plant data from an industrial unit and the results are found to be in good agreement. One of the main advantages of the model is that it does not include any partial differential equations. This facilitates the solution of the equations and makes the model particularly suitable for control studies. Simulation studies are performed to investigate the effect of changing various process variables, such as catalyst circulation rate, gas oil feed rate, and oxygen feed concentration.
Hydrogenation of 3‐hydroxypropanal in trickle beds — experimental and modelling
Authors: Zhu Xiao Da , Hofmann Hanns 
Published: August 2005

AbstractHydrogenation of 10% aqueous solution of 3‐hydroxypropanal (HPA) was adiabatically carried out over cylindrical Ni/SiO2/Al2O3‐catalyst pellets (∅︁ 0.8 + 5 mm) in a trickle bed (∅︁ 76 × 5200 mm) at 2.6 to 8.0 MPa. The concentration and temperature profiles in the trickle‐bed were measured at different flow rates of liquid. A mathematical model was developed under consideration of heat transfer, interphase mass transfer, intraparticle diffusion and deactivation of catalyst pellets at partial wetting with different wetting geometries. The model fits the measured data satisfactorily when its kinetics of deactivation is modified by a factor determined by regression of data measured in the trickle bed.
Effect of two‐pass trays on distillation efficiencies
Authors: Klemola Kimmo T. , Ilme Jarno K. 
Published: August 2005

AbstractTwo important structural factors that affect distillation efficiencies, the outlet weir heigh and the liquid flowpath length, are investigated. Performance and efficiency data of an industrial scale i‐butane/n‐butane distillation column equipped with two‐pass trays are used as a basis for the calculations. A mathematical development for a new method for predicting the numbers of vapor and liquid phase transfer units is given. This method together with some other NTU calculation methods is used to assess the effect of the outlet weir height on efficiencies. The effect of outlet weir height on the Murphree tray efficiencies is investigated using the observed point efficiencies and different point efficiency to the Murphree tray efficiency relation methods. The effect of varying liquid flowpath lengths on efficiencies is studied by calculating the Murphree tray efficiencies for one‐pass and two‐pass trays. The results obtained using the NTU calculation method presented in this study show that a certain outlet weir height point efficiency reaches its maximum. Most of the other methods give opposite results giving a minimum for point efficiency at a certain outlet weir length. The results also show that the Murphree tray efficiencies for one‐pass trays are higher than for two‐pass trays. Obviously, this is caused by the longer liquid flowpath length of one‐pass trays. The Murphree tray efficiencies are also calculated for an industrial‐scale MTBE purification column. The column is equipped with two‐pass trays in the stripping section and with one‐pass trays in the rectifying section. The Murphree tray efficiencies of one‐pass trays are considerably higher than the two‐pass tray Murphree tray efficiencies.
Application of mathematical modelling in a two‐component layer crystallisation process
Authors: Guardani Roberto , Belline Alexandre 
Published: August 2005

AbstractAn algorithm for the computation of design variables in layer crystallisation processes is presented, based on an algebraic solution of the moving boundary equation for heat transfer, as well as on an expression for the concentration profile. The algorithm was applied to the discontinuous crystallisation of a NaCl‐H2O solution around the wall of an internally cooled cylindrical tube. Good agreement between simulation results and laboratory experiments was observed. After input of experimentally measurable values of the distribution coefficient, the algorithm enables the prediction of the following process variables along the crystallisation time: layer thickness, temperature, and composition profiles across the layer, as well as the end‐values of solid and liquid mass and concentrations. Multistage processes can be studied by the series association of crystallisation cycles, enabling the determination of the optimal number of stages that meets a specific design criterion.
Models for minimum explosible concentration of organic dust clouds handled in industries
Authors: Mittal Manju 
Published: August 2005

AbstractDust explosion hazard exists in plants and facilities wherever combustible dusts are hardled. Minimum explosible concentration of dust clouds is an important factor requiring special attention for hazard evaluation if any technological equipment is to be protected by inertisation. The mathematical models available for prediction of this parameter have been analysed for their application to organic dust clouds. Solution of the most general mode for determination of minimum explosible concentration of dust clouds proposed by Mitsui and Tanaka is presented, together with the comparison with experimental data. It has been found that the model is not successful in predicting the minimum explosible concentration for organic dusts. Recommendations on requirement of development of a new model for prediction of minimum explosible concentration of an organic dust such as polyethylen have been given.
Determination of local phase holdups in airlift reactors by means of time‐domain‐reflectometry
Authors: Kochbeck Birgit , Lindert Mark , Hempel Dietmar C. 
Published: August 2005

AbstractAirlift loop reactors are useful in many chemical and biotechnological processes where three phase reaction systems are required. One example is biological waste water treatment. In order to enhance biological reaction rates it is often useful to immobilize the bacteria on carrier particles. Knowledge of solid distribution and local gas holdup in those systems is important for calculation of mass and energy transfer or reaction kinetics. For this reason a method has been developed which enables to measure such local phase holdups. The measuring system consists of a time‐domain‐reflectometry (TDR)‐instrument in combination with a pressure difference meter. The method has successfully been applied to determine local axial gas and solid distribution in internal airlift loop reactors, filled with a three phase system consisting of water, air, and polymer particles.
Gas‐Liquid mass transfer in fixed beds with two‐phase cocurrent downflow: Gas/newtonian and non‐newtonian liquid systems
Authors: Iliuta Ion , Thyrion Fernand C. 
Published: August 2005

AbstractNew data of gas‐liquid mass transfer for cocurrent downflow through packed beds of porous and non‐porous particles are presented. Mass transfer parameters for air/carbon dioxide/water, air/carbon dioxide/carboxymethylcellulose solution and air/carbon dioxide/sodium hydroxide systems were evaluated by least square fit of the calculated CO2 concentration profiles in gas phase to the experimental values. The volumetric liquid‐side mass transfer coefficient increases with the increase of the flow consistency index of the liquid. A comparison of the volumetric liquid‐side mass transfer coefficient values evaluated with and without taking into account the axial dispersion shows that the influence of the liquid axial dispersion is significant at low liquid velocity and high CMC concentrations, and the influence of the gas axial dispersion is insignificant.
Successful use of special stainless steels in nitrogen‐based fertilizer plants
Authors: Tersmeden Knut , Kangas Pasi 
Published: August 2005

AbstractThe modern urea plants are using a stripping process to reduce the energy consumption. The potential, very severe corrosion problems have been mastered by special grades and strict process control. The different grades are reviewed. After more than 20 years operation the results are very satisfying.In ammonia plants, an often forgotten corrosion problem is found in the heat exchangers. After about 3–6 years failures caused by chloride continuing cooling water may appear on carbon steel or low alloyed austenitic stainless steels. Corrosion mechanism is reviewed. Duplex stainless steels has been used with success and the properties are presented. An example of life‐cycle cost shows that duplex stainless steel is an inexpensive way to solve chloride related corrosion problems.Condensation and evaporation of nitric acid in heat exchangers in nitric acid plants cause severe corrosion on conventional stainless steel grades. Low impurity in combination with high chromium content has proved to result in stainless steel with improved corrosion resistance.
pH Fuzzy control of automated industrial electroplating of gold
Authors: Jinxiang Zhang , Zaiman Zheng , Yanbin Qu , Linru You , Suqin Wang , Lianyu Li 
Published: August 2005

AbstractThis paper presents a fuzzy control system for electroplating of gold which was developed to solve the problems of non‐linearity and to overcome difficulties in establishing a mathematical model of the pH of the industrial gold electroplating process. Operating results show that the fuzzy controller effectively counteracts the non‐linearity of the plant.
Gas‐liquid mass transfer in trickle‐bed reactors: Gas‐side mass transfer
Authors: Iliuta Ion , Iliuta Maria C. , Thyrion Fernand C. 
Published: August 2005

AbstractNew data of gas‐liquid mass transfer for cocurrent downflow through packed beds of non‐porous particles are presented. Mass transfer parameters for air/carbon dioxide/water and air/carbon dioxide/sodium hydroxide systems were evaluated by least squares fit of the calculated CO2 concentration profiles in the gas phase to the experimental values. The dependence of kGa on gas and liquid flow rates is caused by the dependence of gas‐liquid interfacial area, not by the gas‐side mass transfer coefficient kG. In the case of the absorption of dilute carbon dioxide the gas‐side resistance is considerably smaller than the liquid‐side resistance. In the pulse flow regime, gas‐liquid interfacial area calculated from kLa and kL values obtained by physical, respectively, chemical absorption are lower than the gas‐liquid interfacial area evaluated from the measurements under reaction conditions.
Oxidation of aqueous sulfide solutions by dioxygen Part II: Catalysis by soluble and immobilized cobalt(II) phthalocyanines
Authors: Fischer Holger , Schulz‐Ekloff Günter , Wöhrle Dieter 
Published: August 2005

AbstractThe oxidation of sulfide in oxygen‐saturated aqueous solutions is accelerated by dissolved or silica‐bonded cobalt phthalocyanines. On the basis of thermodynamical considerations it is postulated that the catalyst enhances the formation of disulfide as the initial elementary reaction step. The following reaction steps are largely unaffected by the catalyst, as indicated by a product ratio sulfate/thiosulfate=0.86, comparable to that of the uncatalyzed autoxidation. A Langmuir‐Hinshelwood formalism is developed for the catalytic reaction step and is demonstrated to fit best with the kinetics. In addition, from the kinetic data free enthalpies for the adsorption of HS− (i) at the dissolved phthalocyanine (ΔG = −17.6 kJ/mole) and (ii) at the immobilized complex (ΔG = −20.0 kJ/mole) are calculated.
Controlled Hydrothermal Synthesis of Bismuth Oxyhalide Nanobelts and Nanotubes
Authors: Deng Hong , Wang Junwei , Peng Qing , Wang Xun , Li Yadong 
Published: August 2005

AbstractTernary bismuth oxyhalide crystalline nanobelts (such as Bi24O31Br10, Bi3O4Br, Bi12O17Br2, BiOCl, and Bi24O31Cl10) and nanotubes (such as Bi24O31Br10) have been synthesized by using convenient hydrothermal methods. The composition and morphologies of the bismuth oxyhalides could be controlled by adjusting some growth parameters, including reaction pH, time, and temperature. All the nanostructures were characterized by using various methods including X‐ray diffraction, transmission electron microscopy, high‐resolution TEM, electron diffraction, and energy‐dispersive X‐ray analysis. The possible reaction mechanism and growth of the crystals are discussed based on the experimental results.
Rationally Designed, Polymeric, Extended Metal–Ciprofloxacin Complexes
Authors: Xiao Dong‐Rong , Wang En‐Bo , An Hai‐Yan , Su Zhong‐Min , Li Yang‐Guang , Gao Lei , Sun Chun‐Yan , Xu Lin 
Published: August 2005

AbstractReactions of the antimicrobial fluoroquinolone ciprofloxacin (cfH) with metal salts in the presence of aromatic polycarboxylate ligands or under basic conditions produce fourteen new metal–cfH complexes, namely, [Ba2(cf)2(1,4‐bdc)(H2O)2]⋅H2O (1), [Sr6(cf)6(1,4‐bdc)3(H2O)6]⋅2 H2O (2), [M2(cfH)2(bptc)(H2O)2]⋅8 H2O (M = Mn(3) and Cd(4)), [M(cfH)(1,3‐bdc)] (M = Mn(5), Co(6), and Zn(7)), [Zn2(cfH)4(1,4‐bdc)](1,4‐bdc)⋅13 H2O (8), [Ca(cfH)2(1,2‐Hbdc)2]⋅2 H2O (9) and [M(cf)2]⋅2.5 H2O (M = Mn(10), Co(11), Zn(12), Cd(13), and Mg(14)) (1,4‐bdc = 1,4‐benzenedicarboxylate, bptc = 3,3′,4,4′‐benzophenonetetracarboxylate, 1,3‐bdc = 1,3‐benzenedicarboxylate, 1,2‐bdc = 1,2‐benzenedicarboxylate). Their structures were determined by single‐crystal X‐ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric analyses. The structures of 1 and 2 consist of unique two‐dimensional arm‐shaped layers. Compounds 3 and 4 are isostructural and feature one‐dimensional structures formed from the interconnection of [M2(cfH)2(H2O)2] dimers with bptc ligands. Compounds 5–7 are isostructural and contain double‐chain‐like ribbons constructed from [M2(cfH)2(CO2)2] dimers and 1,3‐bdc. Compound 8 consists of a pair of [Zn(cfH)2]2+ fragments bridged by a 1,4‐bdc into a dinuclear dumbbell structure. Compound 9 is a neutral monomeric complex. To the best of our knowledge, compounds 1–9 are the first examples of metal‐quinolone complexes that contain aromatic polycarboxylate ligands. Compounds 10–14 are isostructural and exhibit interesting two‐dimensional rhombic grids featuring large cavities with dimensions of 13.6×13.6 Å. Up to now, polymeric extended metal–cfH complexes have never been reported.
Synthesis and Characterization of a New Layered Ethylene‐Diammonium Manganese(II) Phosphate, (C2N2H10)Mn2 (PO4)2×2H2O.
Authors: Song Yanning , Zavalij Peter Y. , Chernova Natasha A. , Whittingham M. Stanley 
Published: August 2005

AbstractFor Abstract see ChemInform Abstract in Full Text.
Catalytic Asymmetric Dihydroxylation of Aliphatic Olefins with Reusable Resin‐Osmium Tetroxide.
Authors: Choudary Boyapati M. , Jyothi Karangula , Madhi Sateesh , Kantam M. Lakshmi 
Published: August 2005

AbstractFor Abstract see ChemInform Abstract in Full Text.
Preparation of 2,6‐Bis(l‐menthopyrazol‐3‐yl)pyridines and Their Catalytic Activity for Asymmetric Diels—Alder Reaction.
Authors: Kashima Choji , Shibata Saori , Yokoyama Hiroyo , Nishio Takehiko 
Published: August 2005

AbstractFor Abstract see ChemInform Abstract in Full Text.