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Showing papers in "Chemical Engineering & Technology in 2001"


Journal ArticleDOI
TL;DR: An overview of recent advances in the synthesis of nanoparticles by flame aerosol processes is given in this paper, where a wide spectrum of new nanosized powders can be synthesized.
Abstract: An overview of recent advances in the synthesis of nanoparticles by flame aerosol processes is given. In flame processes with gaseous precursors emphasis is placed on reactant mixing and composition, additives, and external electric fields for control of product characteristics. Thermophoretic sampling can monitor the formation and growth of nanoparticles, while the corresponding temperature history can be obtained by non-intrusive Fourier transform infrared spectroscopy. Furthermore, synthesis of composite nanoparticles for various applications is addressed such as in reinforcement or catalysis as well as for scale-up from 1 to 700 g/h of silica-carbon nanostructured particles. In flame processes with liquid precursors using the so-called flame spray pyrolysis (FSP), emphasis is placed on reactant and fuel composition. The FSP processes are quite attractive as they can employ a wide array of precursors, so a broad spectrum of new nanosized powders can be synthesized. Computational fluid dynamics (CFD) in combination with gas-phase particle formation models offer unique possibilities for improvement and possible new designs for flame reactors.

393 citations


Journal ArticleDOI
TL;DR: In this article, the authors review the major research activities concerned with the direct methanol fuel cell (DMFC) and highlight the problems (slow kinetics of the anodic methenol oxidation, methanoline permeation through the membrane, carbon dioxide evolution at the anode) and their possible solutions.
Abstract: The direct methanol fuel cell (DMFC) has been discussed recently as an interesting option for a fuel-cell-based mobile power supply system in the power range from a few watts to several hundred kilowatts. In contrast to the favoured hydrogen-fed fuel cell systems (e.g. the polymer electrolyte membrane fuel cell, PEMFC), the DMFC has some significant advantages. It uses a fuel which is, compared to hydrogen, easy to handle and to distribute. It also comprises a fairly simple system design compared to systems utilising liquid fuels (like methanol) to produce hydrogen from them by steam reforming or partial oxidation to finally feed a standard PEMFC. Nevertheless, many severe problems still exist for the DMFC, hindering its competitiveness as an option to hydrogen-fed fuel cells. This work reviews the major research activities concerned with the DMFC by highlighting the problems (slow kinetics of the anodic methanol oxidation, methanol permeation through the membrane, carbon dioxide evolution at the anode) and their possible solutions. Special attention is devoted to the steady state and dynamic simulation of these fuel cell systems.

177 citations


Journal ArticleDOI
TL;DR: In this paper, the authors evaluated the extraction performance of a mixer settler set-up for miniplant technology using static micromixers as an alternative to conventional stirring apparatuses.
Abstract: The aim of the investigation was to evaluate the extraction performance of a mixer settler set-up for miniplant technology using static micromixers as an alternative to conventional stirring apparatuses. A comprehensive experimental study was conducted at BASF AG to broaden the technology base for the “extraction” unit operation which is well established for miniplants in order to be utilized for microplant systems. The work proved that micromixers, or micromixer arrays, are highly efficient apparatuses for extraction purposes. The extraction efficiency was found to be a function of volume flow, which could be explained in light of the volume flow dependence of the mean droplet size and, hence, the specific surface area of the dispersions intermediately formed. At optimal flow conditions, one practical mixer settler stage was found to yield one theoretical plate for most systems investigated.

135 citations


Journal ArticleDOI
TL;DR: In this paper, the authors attempted to remove arsenic from smelter industrial wastewater through electrocoagulation, using Mild Steel and Stainless Steel plates as anode and cathode respectively.
Abstract: In the present investigation, it is attempted to remove arsenic from smelter industrial wastewater through electrocoagulation. Experiments covering a wide range of operating conditions for removal of the arsenic present in the smelter wastewater are carried out in a batch electrochemical reactor. Mild Steel and Stainless Steel plates have been used as the anode and cathode respectively. It has been observed from the present work that arsenic can be removed effectively through electrocoagulation.

126 citations


Journal ArticleDOI
TL;DR: In this article, the effects of some parameters such as pH, loading of TiO 2, flow rate of O 2 and temperature on the photocatalytic destruction rate of phenol were examined.
Abstract: In this study the photocatalytic destruction of phenol in an aqueous suspension of illuminated TiO 2 was investigated. The experiments were carried out using a Pyrex annular photoreactor. The effects of some parameters such as pH, loading of TiO 2 , flow rate of O 2 and temperature on the photocatalytic destruction rate of phenol were examined. It was observed that the flow rate of O 2 has no considerable effect on the destruction of phenol over the range of 2-3.5 L/min. The photodestruction of phenol followed the pseudo first-order kinetics of the Langmuir-Hinshelwood model giving an activation energy of 16.2 kJ/mol.

100 citations


Journal ArticleDOI
TL;DR: The state of the art of the microwave super-heated boiling phenomenon is reported in this article, where it is shown that the steady state temperature can be up to 40 K higher than the boiling point of the liquid.
Abstract: This paper reports the state of the art of the microwave super-heated boiling phenomenon. When a liquid is heated by microwaves, the temperature increases rapidly to reach a steady temperature while refluxing. It happens that this steady state temperature can be up to 40 K higher than the boiling point of the liquid. With the same reactor, overheating is not observed under conventional heating. The bulk temperature of a microwaved solvent under boiling depends on many factors: physical properties of the solvent, reactor geometry, mass flow, heat flow, and electric field distribution. The influence of these factors is studied and discussed. The kinetics of homogeneous organic reactions shows an extension of Arrhenius behaviour into the superheated temperature region. Reaction rate enhancement of order 10-100 can thus be achieved, which is normally only possible under pressure. Finally, we present a model predicting reaction kinetics and yields under classical and microwave heating, based on predicted temperature profiles in agreement with experimental data.

91 citations


Journal ArticleDOI
TL;DR: In this article, the formation of silicon powder by pyrolysis of silane diluted in argon at different concentrations has been studied, where a hot wall gas-phase reactor was used for the thermal decomposition of SiH 4 at 1000°C and atmospheric pressure.
Abstract: The formation of silicon powder by pyrolysis of silane diluted in argon at different concentrations has been studied. A hot wall gas-phase reactor was used for the thermal decomposition of SiH 4 at 1000°C and atmospheric pressure. The composition, morphology, size, and shape of the particles produced has been studied utilizing electron microscopy, X-ray diffraction, infrared spectroscopy, and BET gas adsorption. Depending on the experimental conditions, agglomerates of polycrystalline, sintered particles have been obtained, which are composed of nanocrystallites of about 25 nm in size.

85 citations


Journal ArticleDOI
TL;DR: In this article, the possible industrial application of microreactors is discussed, and two research examples are presented, showing that information obtained from a microreactor can aid in the optimization of a conventional reactor for the same process, and that higher selectivities in production can thus be achieved.
Abstract: In this work, the possible industrial application of microreactors is discussed, and two research examples are presented. From these experiments, it is shown that information obtained from a microreactor can aid in the optimization of a conventional reactor for the same process, and that higher selectivities in production can thus be achieved. While the use of microreactors in production is currently rather unlikely, their use as measurement instruments for optimization indicates the potential for great improvements to come.

84 citations


Journal ArticleDOI
TL;DR: In this article, the influence of the initial concentration of dye, supporting electrolyte, current densities and pH on COD reduction has been critically studied using a RuO 2 /Ti electrode.
Abstract: Electrooxidation of simulated Acid Blue 113 dye effluent has been carried out using a RuO 2 /Ti electrode. The influence of the initial concentration of dye, supporting electrolyte, current densities and pH on COD reduction has been critically studied. Electrochemical analysis such as Instantaneous Current Efficiency (ICE) and Electrochemical Oxygen Demand (EOD) were used.

72 citations


Journal ArticleDOI
TL;DR: Using a piezoceramic tube and a continuous glass capillary, droplets in a diameter range between 10 μm and 100 μm can be generated as discussed by the authors, which corresponds to a volume of up to 0.6 pl.
Abstract: Using a piezoceramic tube and a continuous glass capillary, droplets in a diameter range between 10 μm and 100 μm can be generated. This corresponds to a volume of up to 0.6 pl. The velocity of the generated droplets depends on droplet size but is constant for each diameter. The liquid can be dosed as single droplet, as an accumulation of droplets or as a chain of droplets in a frequency range between 1 Hz up to 3 kHz. The lifetime of the droplets depends on droplet size and the chemical and physical properties of the dispersed liquid. In addition, for water droplets the humidity of the air near the droplet trajectory influences the lifetime of the droplets.

62 citations


Journal ArticleDOI
TL;DR: In this paper, a bench-scale system was used to demonstrate the application of a recently developed magnetic titanium dioxide photocatalyst for the degradation of organics in aqueous systems.
Abstract: A bench-scale system was used to demonstrate the application of a recently developed magnetic titanium dioxide photocatalyst for the degradation of organics in aqueous systems. The integrated water treatment system included a photoreactor and magnetic separator for the recovery of the magnetic photocatalyst particles. Methylene blue (MB) was used as a test pollutant. The mineralization and bleaching efficiencies of methylene blue using the magnetic photocatalyst were found to be comparable to those of Degussa P25. The magnetic photocatalyst also demonstrated high magnetic separation efficiency. The recycled photocatalyst particles were found to have the same separation efficiency as the fresh catalyst, although the mineralization and bleaching efficiencies were lower.

Journal ArticleDOI
TL;DR: In this article, the authors describe mechanisms and kinetics of the reactions, using modern concepts of solid state and surface chemistry and physics, and also describe the effects of these reactions on the quality of the calciner discharge in upgrading and for the customer.
Abstract: In the sulfate process for the production of TiO2 white pigments, gel-like metatitanic acid is calcined in a rotary kiln to microcrystals of the rutile polymorph. This process is monitored by the addition of alkali ions, Al3+, phosphate and rutile nuclei. During the last decade, a scientific understanding has developed how these additives influence the solid-state reactions of the material in the kiln, i.e., crystal growth, transformation of anatase to rutile, incorporation of dopants and aggregation of crystals. This review describes mechanisms and kinetics of the reactions, using modern concepts of solid state and surface chemistry and physics. It also describes the effects of the reactions on the quality of the calciner discharge in upgrading and for the customer, i.e., the grindability to pigment particles, their light-scattering properties and photocatalytic activity. The principles of the additive functions revealed here may be used in process engineering of other powder reactions as well as in particle chemistry and nanotechnology in general.

Journal ArticleDOI
TL;DR: The authors summarizes the work of the EFCE Working Party Education (WPE) over the last decade and attempts to identify effective educational solutions to meet the challenges caused by the rapid rate of change in technology and society world-wide.
Abstract: This paper summarizes the work of the EFCE Working Party Education (WPE) over the last decade and attempts to identify effective educational solutions to meet the challenges caused by the rapid rate of change in technology and society world-wide. The paper uses the results of the 1994 WPE survey of curricula in European Chemical Engineering Universities to identify a first degree level core curriculum. The problem of how to adapt the discipline to meet technological and societal changes without losing its identity is addressed. Basic sciences, chemical engineering science, integrated systems design and holistic thinking are emphasized as essential elements of the discipline. The paper discusses how Safety, Health and Environment (SHE), biotechnology, computerized models, product design, sustainability and other new subjects have been incorporated into chemical engineering curricula since the original survey. A simple model of the education process is presented to indicate how students might obtain a chemical engineering understanding and mindset. The paper explains how chemical engineering evolved from its origins in the petrochemical, heavy chemical and nuclear industries, to its current wide range of applications in industries, such as fine chemicals, food, pharmaceuticals, software, and cybernetics. It is suggested that the impact of changes arising from industry, new technology and society has driven the chemical engineering discipline to a point where it is now ripe for re-invention. The effects of rapid industrial, technological and societal change on chemical engineering education are studied against the backdrop of a discipline on the threshold of a significant change. The paper concludes by identifying curriculum development, personal development and life-long learning as three important factors for educating chemical engineers for a successful future.

Journal ArticleDOI
TL;DR: In this article, the minimum fluidization velocity of beds has been determined experimentally in beds of 0.089 m and 0.29 m diameters, respectively, using three distributors, each perforated by holes of varying hole densities.
Abstract: The minimum fluidization velocity of beds has been determined experimentally in beds of 0.089 m and 0.29 m diameters, respectively. The particles studied had sizes ranging from 100 μm to 1 mm in diameter, and densities from 1128 to 11400 kg/m3. Three distributors were used in the experimental scheme, each perforated by holes of 0.8 mm in diameter but with varying hole densities, as well as a porous plate. It was found that the minimum fluidization velocity was affected by both the diameter and distributor used. The effect of vertical tubular inserts on the minimum fluidization velocity was investigated in the 0.29 m diameter bed. The experimental data in the large bed, using four distributors, were parameterized within experimental error.

Journal ArticleDOI
TL;DR: In this paper, the Taguchi method has been used to determine the optimum conditions for the dissolution of malachite ore in H2SO4 solutions, and the chosen experimental parameters and their range were (i) reaction temperature: 15 to 45 °C, (ii) solid-to-liquid ratio: 1/10 to 1/3 g cm-3, (iii) acid concentration (in weight): 2 % to 10 %, particle size: –40 to 3.5 mesh, (iv) stirring speed: 240 to 720 rpm, and (vi) reaction time
Abstract: The Taguchi method has been used to determine the optimum conditions for the dissolution of malachite ore in H2SO4 solutions. The chosen experimental parameters and their range were (i) reaction temperature: 15 to 45 °C, (ii) solid-to-liquid ratio: 1/10 to 1/3 g cm–3, (iii) acid concentration (in weight): 2 % to 10 %, (iv) particle size: –40 to –3.5 mesh, (v) stirring speed: 240 to 720 rpm, and (vi) reaction time: 5 to 45 minutes. The optimum conditions were found to be reaction temperature: 40 °C, solid-to-liquid ratio: 1/3 g cm–3, acid concentration (in weight): 10 %, particle size: –30 mesh, stirring speed: 480 rpm, and reaction time: 45 minutes. Under these optimum working conditions, the dissolution of copper and iron in malachite ore was 100 % and 58 %, respectively. Besides, alternative working conditions reducing the total cost and dissolution of iron were found.

Journal ArticleDOI
TL;DR: In this article, the importance of selected palladium-catalyzed coupling reactions for fine chemical synthesis is shown, and a focus is made on the refinement of aryl halides.
Abstract: The importance of selected palladium-catalyzed coupling reactions for fine chemical synthesis is shown. Special focus is made on the refinement of aryl halides. Apart from known industrial processes the potential use of recently developed palladium catalysts from our group is demonstrated.

Journal ArticleDOI
TL;DR: An acoustic tube levitator was developed and used for investigating the drying behavior of single droplets (d D,0 ≃1.0 mm) containing water and a certain fraction of inert, solid material such as glass beads with a mean diameter of d s =30 μm.
Abstract: An acoustic tube levitator was developed and used for investigating the drying behavior of single droplets (d D,0 ≃1.0 mm) containing water and a certain fraction of inert, solid material such as glass beads with a mean diameter of d s =30 μm. A glass tube surrounds the transducer and reflector of the acoustic tube levitator, hence increases the radial stability of the droplet and shields it against disturbances from outside. A CCD camera and a back-light illumination are used to observe the evolution of the droplet diameter and the vertical position of the droplet. Ambient temperature, initial volume and initial solid mass fraction of the droplet were systematically varied. From the measured droplet diameter and the position of the mean density, the moisture content and the mean porosity of the drying droplet/grain can be determined as a function of time.

Journal ArticleDOI
TL;DR: In this paper, the basic phenomena at the disintegration of liquid jets in a pressurized gas at up to 35 MPa were clarified by the characterization of the forces involved in the liquid jets, which are influenced by the physical properties of the phases used.
Abstract: The aim of this investigation is to clarify of the basic phenomena at the disintegration of liquid jets in a pressurized gas at up to 35 MPa. This is carried out by the characterization of the forces involved in the disintegration of liquid jets, which are influenced by the physical properties of the phases used.

Journal ArticleDOI
TL;DR: In this article, the principle of freeze concentration after the Niro freeze concentration process was described, together with an example and an economical comparison with direct incineration of caustic wastewater coming from an SMPO production plant.
Abstract: According to an extensive study conducted in the early nineties, the best method for treating hazardous caustic wastewater coming from an SMPO (styrene monomer/propylene oxide) production plant is the combination of freeze concentration followed by incineration of the concentrate. This work provides a thorough description of the principle of freeze concentration after the Niro freeze concentration process together with an example and an economical comparison with direct incineration.

Journal ArticleDOI
TL;DR: The synergy effect of process coupling of reaction-reaction and reaction-heat transfer for dimethyl ether synthesis has been studied in this article, where the theoretical and experimental analyses show that the synergy of reactionreaction is prominent and that the synergies of reactionheat transfer is also feasible.
Abstract: The synergy effect of process coupling of reaction-reaction and reaction-heat transfer for dimethyl ether synthesis has been studied. The theoretical and experimental analyses show that the synergy of reaction-reaction is prominent and that the synergy of reaction-heat transfer is also feasible. Due to the synergy effect, CO-rich synthesis gas can be used for dimethyl ether synthesis and higher once-through conversion of CO can be obtained. Recycling and compression of the unreacted synthesis gas can be minimized considerably. Accordingly, savings will be made in energy consumption and the water gas shift reaction system, and the entire investment and production cost will decrease.

Journal ArticleDOI
TL;DR: In this article, the drop volume technique was used to determine the adsorption behavior and interfacial adaption kinetics of surfactants at fluid interfaces, and the time dependence of the interfacial coverage resulting from this adsoption process was well described by two approximation solutions.
Abstract: This study shows that the drop volume technique can be used to determine the adsorption behavior and interfacial adsorption kinetics of surfactants at fluid interfaces. Using this tensiometric method, one can determine not only the interfacial tension of the pure phases, but also the critical concentration for the formation of micelles (CMC) in a surfactant system, the quasi-static (equilibrium) interfacial tension, the diffusion coefficient as a function of surfactant concentration, and the maximum adsorption density at the interface. The determination of the dynamic interfacial tension allows to indirectly characterize the kinetics of surfactant adsorption. The time dependence of the interfacial coverage resulting from this adsorption process is well described by two approximation solutions (for short and long adsorption times), with the result that the diffusion coefficients calculated as a function of surfactant concentration using these two methods show good agreement. The droplet formation and dripping process of a surfactant solution in a capillary was found to be quite different depending on whether the process occurred in gaseous or fluid surroundings. In particular, the formation of satellite droplets was different for the two different media, in terms of both the volume and shape of the satellite droplets.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated how zeolites work as catalysts in the Beckmann rearrangement of cyclohexanone oxime in concentrated sulfuric acid and found that they are suitable catalysts for the MFI-structure type.
Abstract: e-Caprolactam is produced on an industrial scale nearly exclusively by Beckmann rearrangement of cyclohexanone oxime in concentrated sulfuric acid. In spite of the high yield of e-caprolactam this process exhibits many weakness arising from the use of the liquid acid and the corrosiveness of the reaction medium. Therefore, many attemps have been undertaken to employ solid acids as catalysts in the Beckmann rearrangement. The most suitable catalysts are zeolites of the MFI-structure type. The major aim of this study was to investigate how these zeolites work as catalysts in the Beckmann rearrangement of cyclohexanone oxime.

Journal ArticleDOI
TL;DR: In this article, the scale dependence of the hydrodynamics of the air-water system in bubble columns of 0.1, 0.15 and 0.38 m diameter was investigated.
Abstract: Measurements of gas holdup were made with the air-water system in bubble columns of 0.1, 0.15 and 0.38 m diameter, equipped with identical distribution devices. For operation with superficial gas velocity in the range 0-0.04 m/s, the total gas holdup was found to decrease with increasing column diameter. Of all the literature correlations for the gas holdup, only the Zehner correlation anticipates this decrease in the gas holdup with increasing column diameter. The reason for this scale dependence is because the strength of the liquid circulations increases with increasing scale. Such circulations accelerate the bubbles travelling upwards in the central core. Computational fluid dynamics (CFD) simulations were carried out using the Eulerian description for both the gas and the liquid phases in order to verify the scale dependence of the hydrodynamics. Interactions between the bubbles and the liquid are taken into account in terms of a momentum exchange, or drag, coefficient. The drag coefficient is determined from the Mendelson correlation for bubble rise velocity. The turbulence in the liquid phase is described using the k-e model. The simulation results verify the trends predicted by the Zehner (1989) correlation. It is concluded that Eulerian simulations are useful tools for scaling up bubble columns.

Journal ArticleDOI
TL;DR: In this article, the gas-phase hydrogenolysis of dimethyl maleate at 10 bar and 513 K was investigated over a series of co-precipitated Cu/ZnO/Al 2 O 3 catalysts.
Abstract: The gas-phase hydrogenolysis of dimethyl maleate at 10 bar and 513 K was investigated over a series of co-precipitated Cu/ZnO/Al 2 O 3 catalysts. High copper surface areas were obtained with a molar Al content of 5% in the catalysts. Upon variation of composition at fixed alumina content, copper surface areas increased until the molar ratio exceeded Cu/Zn=2:1. At the given reaction conditions, dimethyl maleate was completely converted to dimethyl succinate, which further reacted to methanol, γ-butyrolactone, tetrahydrofuran, and water over all catalysts. Initial deactivation of catalysts was mainly caused by a loss of copper surface area. The catalyst with a molar Cu/Zn ratio of 1:2 was found to be most active and stable under reaction conditions.

Journal ArticleDOI
TL;DR: In this paper, the solubility of compressed gases in melts of coating polymers at pressures up to 220 bar is exploited for the manufacture of powder coatings, which is applicable to new (lowmelting and fast-reacting) and conventional powder coating systems and allows to produce coatings with improved properties.
Abstract: An alternative process for the manufacture of powder coatings was developed. The continuously operated process is applicable to new (low-melting and fast-reacting) and conventional powder coating systems and allows to produce coatings with improved properties. The process uses the solubility of compressed gases in melts of coating polymers at pressures up to 220 bar. The single components of a powder coating mixture are melted in separated tanks and are dosed to a static mixer by means of high-pressure pumps. In the mixer the melts are homogenized and simultaneously compressed carbon dioxide is dissolved. The so-formed solution is depressurized directly afterwards over a nozzle into a spray tower. Thereby, the melt is atomized into fine droplets and cooled by the expanding gas. The droplets reach the solidification point of the melt and fine solid particles are formed. The particle size, particle size distribution and the morphology of the powders could be adjusted by the operating parameters of the plant.

Journal ArticleDOI
TL;DR: In this article, the effects of reaction temperature, reaction period, stirring speed, solid-liquid ratio and Cl2 gas flow rate on the dissolution of gold were investigated, and the experimental results showed that the gold recovery could be over 90 %.
Abstract: A study was performed on the chlorination and cementation of gold from an anode slime. The gold from decopperized anode slime first was dissolved with chlorine gas in aqueous medium, later the dissolved gold was precipitated by using a rotational copper disc. The effects of reaction temperature, reaction period, stirring speed, solid-liquid ratio and Cl2 gas flow rate on the dissolution of gold were investigated. Increasing the solid-liquid ratio decreases the dissolution, the solubility increases with increasing reaction temperature, reaction period and stirring speed. It was observed that the Cl2 gas flow rate hasn't a significant effect on the dissolution. As to the precipitation of the gold in the solution, the effects of temperature and rotational speed were sought for. The experimental results showed that the gold recovery could be over 90 %. For the kinetics analysis of the cementation, the activation energy value was found to be 19.51 kJ·mol–1.

Journal ArticleDOI
TL;DR: In this paper, the drop breakup behavior of a new high-pressure nozzle is investigated with the example of oil-in-water emulsions and compared to the breakup behaviour of a state-of-the-art nozzle and to available data published.
Abstract: Emulsification plays an important role in the formulation of lipophilic pharmaceutical agents. These substances are often included in the disperse phase of an oil-in-water emulsion. To reach a high bioavailability and a good long-term stability, drop sizes much less than 1 micron are required. For the generation of such emulsions, energy densities of a quality which can only be reached in high-pressure systems, are necessary. Actually available apparatus, such as high-pressure homogenizers fitted with valves, microfluidizer or jet disperser, reach particle sizes of about 0.2 micron in continuous processes. It is indispensable to produce emulsions with smaller globules in order to receive a maximum of diversity in application. Therefore, dispersion units with a higher efficiency in drop breakup are needed. Especially in the case of parenterally administered medicament formulations an average particle size between 0.04 and 0.1 microns is requested which is up to now not reachable by continuous emulsification. In this study the drop breakup behavior of a new high-pressure nozzle is investigated with the example of oil-in-water emulsions and compared to the breakup behavior of a state-of-the-art nozzle and to available data published.

Journal ArticleDOI
TL;DR: In terms of chemical oxygen demand depletion and final biodegradability characteristics of the effluent, the use of free radical promoters, for instance hydrogen peroxide, resulted in a significant enhancement of the process.
Abstract: The oxidation of wastewater from olive oil mills has been carried out in the liquid phase at high temperatures and pressures. Synthetic urban wastewater has been used to dilute the raw effluent (dilution rate 1:10). Experiments conducted using air as the oxygen source showed a positive effect of the previous neutralization of the wastewater if compared to the oxidation conducted at the original pH of the effluent (pH = 5.3). In terms of chemical oxygen demand depletion and final biodegradability characteristics of the effluent, the use of free radical promoters, for instance hydrogen peroxide, resulted in a significant enhancement of the process. Experiments completed in the presence of two commercially available catalysts (platinum supported on alumina and copper oxide supported on active carbon) showed not only an improvement in the chemical oxygen demand removal rate but also a high degree of the mineralization of the wastewater contaminant load.

Journal ArticleDOI
TL;DR: In this paper, gas was injected downward tangentially to the wall of the loop-seal to increase solids mass flux with stable flow, and the solid mass fluxes obtained have been correlated with the aeration rate and Archimedes number.
Abstract: Solid recycle characteristics through a conventional and a newly developed loop-seal (0.08 m i.d.) system are determined in a circulating fluidized bed of FCC or silica sand particles. In the loop-seal developed in this paper, gas was injected downward tangentially to the wall of the loop-seal to increase solids mass flux with stable flow. For conventional loop-seal, solids mass fluxes increase linearly with increasing aeration rate but it reaches a maximum value. At the same aeration rate with different aeration locations (0.1-0.6 m) in a conventional loop-seal, a maximum solids mass flux is seen at a height to diameter ratio of 2.5. For the newly developed loop-seal, mass fluxes of FCC and sand particles are higher and more stable than in conventional loop-seal at the same aeration rate. The solid mass fluxes obtained have been correlated with the aeration rate and Archimedes number.

Journal ArticleDOI
TL;DR: In this paper, the selectivity of the reaction regarding THF is nearly 100% and the ionic mechanism, which exists under conventional conditions, could be validated by the examinations of this work not only in the sub- but also in the supercritical range.
Abstract: The dehydration of 1,4-butanediol to tetrahydrofuran is a reaction that possesses disadvantages under conventional conditions caused by the use of mineral acids and the corrosion problem interconnected with it. These disadvantages can be remedied by the use of pure supercritical water as reaction medium, as well as catalyst. The selectivity of the reaction regarding THF is nearly 100%. The ionic mechanism, which exists under conventional conditions, could be validated by the examinations of this work not only in the sub- but also in the supercritical range.