bluuebunny/crossref_metadata_2025 huggingface dataset:
Grenzflächenprobleme bei der Fest/Flüssig‐Trennung
Authors: Gösele Walter
Published: December 2004

Interfacial problems in solid/liquid separation. Mechanical solid/liquid separation is one of the unit operations of chemical engineering, which is far from having been mastered theoretically. This is because interfacial forces play such a pronounced role in this process step, and these forces have so far largely withstood scientific investigation. The present article enumerates the problems involved, and necessarily presents more open questions than ready answers.
Sicherung chemischer Produktionsanlagen mit Mitteln der Elektro‐/Meß‐, Steuerungs‐ und Regelungstechnik
Authors: Haas Klaus De , Magin Rudolf , Storck Heinz
Published: December 2004

Safeguarding of chemical production plant by means of control engineering. Control equipment is becoming increasingly important for safeguarding of plant. According to VDI/VDE 2180, sheet 3, control equipment is classified as operational equipment, as monitoring equipment, or as protective equipment. Operational and monitoring control equipment serves the proper operation of plant in its correct state or in a faulty but still acceptable state. Protective control equipment is intended to prevent occurrence of an unacceptable faulty state of the plant. It is helpful if the control equipment is classified at an early stage of planning. Preferably the protective control equipment should be considered separately from the other control equipment. It is then possible to design it in such a way that its behaviour in the event of faults can be clearly defined. A distinction is made between active faults (or functiontriggering faults) and passive faults (or function‐inhibiting or blocking faults). An active fault reduces the availability of chemical plant for production by inadvertent shut‐down. Passive faults of protective equipment prevent triggering of the protective function, even though the conditions for triggering are fulfilled. They adversely affect the safety of the plant. Passive faults of control equipment must therefore by prevented or kept under control. A selection of appropriate measures for achieving this is presented.
Reaktionstechnik bei industriellen Hochdruckverfahren
Authors: Maier Siegfried , Müller Franz‐Josef
Published: December 2004

Reaction engineering in industrial high‐pressure processes. The essential task of industrial chemistry is to transform cheap raw materials into high‐quality materials and substances economically. From the very beginning, the chemical industry has used the energy sources coal, oil, and gas as the starting point for synthesis. These substances are introduced into the product line through high‐pressure reactions. Joint developments in catalytic chemistry reaction kinetics, and plant design have permitted construction and operation of high‐capacity, high‐pressure plants at remote sites, where coal, oil, and gas are won. Industrial high‐pressure chemistry is thus capable of transforming in situ raw materials that could be used otherwise into high‐value products worth transporting to energy‐poor regions and whose distribution is secured. The second part of this paper considers the technical limits of pumps, compressors, and high‐pressure reactors. Approximate estimates of investment costs as a function of the pressure as process parameter are given for a high‐pressure process step. Aspects to be taken into consideration during design, construction, and installation of factory‐built high‐pressure reactors are considered in condensed form in the last part.
Produktansatzbildung beim Erhitzen und Eindampfen flüssiger Lebensmittel
Authors: Kessler Heinz‐Gerhard , Fiedler Josef , Hege Wolfgang
Published: December 2004

Formation of deposits from liquid foods on heated surfaces during heating and evaporation. In the past, deposit formation on heated surfaces in food processing has been investigated by considering the whole of the deposited material. This precluded reaction kinetic studies and it was therefore impossible to introduce preventive measures. However, ultrafiltration of milk and whey has now furnished model systems in which deposit formation by proteins and salts can be studied separately. The tendency for deposit formation of proteins is similar to the denaturation reaction of whey proteins. The heat sensitive native proteins in the liquid are deposited preferentially on surfaces already covered with reactive proteins. The deposition of milk salts is determined by the degree of supersaturation of the solution. For milk salts deposition, an activation energy was found which is typical for diffusion processes.
Selektive Reduktion von Stickoxiden in Rauchgasen – Stand der Technik und neue Wege
Authors: Kotter Michael , Lintz Hans‐Günther , Weyland Friedrich
Published: December 2004

Selective reduction of nitrogen oxides in flue gas–state of the art and trends. The selective reduction of nitrogen oxides by ammonia may be catalyzed by different substances. The suitable choice of the catalyst is determined largely by where the reduction step is placed in the overall process. The technical problems and the required catalyst properties are demonstrated and discussed. A new process, based on a periodically operated reactor, avoids some of the difficulties otherwise encountered.
Neuere Ergebnisse des Betriebes der Pilotanlage zum Hochtemperatur‐Winkler‐Verfahren
Authors: Lambertz Johannes , Schrader Lothar , Teggers Hans
Published: December 2004

Recent results obtained on operation of a pilot plant for the high‐temperature Winkler process. Rheinische Braunkohlenwerke AG is developing the high‐temperature Winkler (HTW) process for gasification of coal and biomass in a fluidized bed. Preliminary studies in a lab‐scale plant at the Technical University of Aachen served as a basis for construction of a pilot plant with a throughput of 25 tonnes of dry lignite per day which went into operation in mid 1978. The gasification pressure was raised to 10 bar and the temperature to over 1000 °C, and the exiting dust was recycled to the fluidized bed, with the aim of significantly improving the specific performance relative to operation at atmospheric pressure. In view of experience gained in operation with both low‐ash and high‐ash lignite, the availability of the pilot plant could be increased to almost 75% and the performance greatly improved. Thus significantly higher values were achieved than by the atmospheric‐pressure Winkler process: 96% C‐gasification and almost 1 600 m3 of synthesis gas per tonne of dry lignite; at over 7700 m3 of synthesis gas per tonne of dry lignite per m2 reactor cross‐section and per hour, the performance exceeds three times the former figure.
Large‐scale Continuous Production of Single Cell Protein
Authors: Westlake Richard
Published: December 2004

The PRUTEEN plant represents a major innovation in the green field of biotechnology. The 50 000‐t/a‐plant was sanctioned in 1976 as a £40‐million‐project and built by contractors John Brown. The 600 t fermenter vessel in particular was an impressive piece of engineering: fabricated in Dunkirk, it was transported to the Billingham site in one piece. This paper illustrates why, given the risks of innovation on such a scale, ICI chose a novel fermentation process. Particular reference is made to the pressure cycle fermenter and how it works, and to the product recovery stage. The approach to sterile engineering, which is crucial to the effective operation of the fermentation process, is also discussed. Faced with unique technical challenges, ICI pioneered practical solutions, and, through operational experience, has arrived at the point today of being able to license the process.
Verfahrenstechnische und wirtschaftliche Vorteile der Kochextrusion im Vergleich zu herkömmlichen Verfahren der Lebensmittel‐Industrie
Authors: Wiedmann Werner , Strobel Edgar
Published: December 2004

Economic and process engineering advantages of extrusion cooking in comparison with conventional processes in the food industry. Extrusion cooking is introduced as a modern high‐temperature short‐time process. Possible process steps in extruder machine systems, such as continuous conveying, mixing, homogenizing and reactions, mechanical and thermal energy dissipation for plasticizing and modifying biopolymers, are explained. This process creates new products with completely new textures, for example in the snack and breakfast cereal sector, while on the other hand the extrusion process competes with long‐standing conventional processes. The latter work slowly with low pressures, low temperatures and energy dissipation with high water contents in large batch‐operated machines. The quality of extruder‐cooked products depends on the extrusion system. The self‐cleaning corotating twin‐screw extruder with its narrow residence time spectrum is the optimum system. However, the counter‐rotating intermeshing machine has certain advantages for products of low viscosity. The cooking time at high temperature is a matter of seconds, which serves to maintain the properties of the ingredients and active substances, while ensuring fast destruction of microorganisms. The end‐products have a long shelf‐life on account of their low process moisture content. Continuous extrusion cooking has economic advantages mainly because it replaces many batch processes and because extrusion is carried out entirely or almost entirely with the final moisture content, thus avoiding the necessity to evaporate huge quantities of water.
Membranverfahren in der Umwelttechnik
Authors: Rautenbach Robert , Janisch Ingo
Published: December 2004

Membrane processes in environmental protection. Reverse osmosis and ultrafiltration are well established processes in areas like the production of fresh water from sea‐ or brackish water and the treatment of spent cutting emulsions from the metal working industry. New and interesting applications of these processes can be expected in environmental protection and in the treatment of process effluents. For reverse osmosis, the capacities of presently available membranes will be discussed with respect to chemical resistance and to the rejection of organic components in aqueous solutions. Results of experiments with various real‐life systems will be reported: landfill drainage water; protein‐rich process water of the fish industry; recovery of ε‐caprolactam; solvent‐contaminated waste water. These examples demonstrate the economical and engineering potential of membrane processes in treating process effluents. These examples also demonstrate that, in most cases only a combination of membrane processes and a conventional process, like evaporation, will give optimal results.
Struktur und Aufbau moderner Analyse‐Meßeinrichtungen
Authors: Daffner Klaus , Faulhaber Reimar
Published: December 2004

Structure and modular nature of modern analytical measuring equipment. Modern analytical instrumentation exhibits excellent adaptability to a wide range of demands arising from the process concerned and the site of application. Optimization of the specific plant structure according to criteria such as performance data, reliability, and economic factors demands a versatile modular system of components for matching the sensors to the process, the process control system, the discharge locations, and the environment. In addition, functions such as handling, control, and monitoring are steadily increasing in importance.
Werkstoffverhalten in Wasserstoff
Authors: Gráfen Hubert , Kuron Dieter
Published: December 2004

Properties of materials in hydrogen. The various kinds of damage to metallic materials of construction induced by hydrogen are described and their effects illustrated. A detailed account is given of the individual processes leading to the adsorption and absorption of diffusable atomic hydrogen and also of the various damage mechanisms, such as embrittlement, hydride formation, blistering and cracking, delayed rupture, and stress corrosion.
Wirtschaftlicher Einsatz von korrosionsbeständigen Werkstoffen im Apparatebau
Authors: Köcher Reiner
Published: December 2004

Economic use of corrosion‐resistant materials in plant construction. Particular attention must be paid to choice of materials, constructional design, and production processes in order to achieve optimum, favourably priced solutions in the planning and construction of equipment for chemical plant. In the choice of materials, special stainless steels and non‐ferrous metals of recent development, should be given special attention, particularly with respect to cost‐saving substitution of expensive quality materials. The use of clad steel sheet fulfills requirements for optimum design of components for many applications; however, the economic use of these composite materials must be compared with that of solid materials from case of case – due attention being given to the strength and working properties of the materials. The lining of equipment with high‐quality corrosion‐resistant materials is also an economic production method but its limited applicability should be borne in mind. Welding is a cost‐relevant production method. Use of welding techniques with high fusion rates, which is feasible for some high quality materials, can lead to considerable cost savings. Economic production of curved plates from Superferrit Remanit 4575 is possible by welding together individual rounds.
Schweißtechnische Gütesicherung im Chemieanlagenbau mit Beispielen aus der Praxis
Authors: Gawlas Georg
Published: December 2004

Welding quality assurance in plant construction illustrated by examples from practice. The welding quality assurance concept of a chemical company is shown by way of practical examples. In particular, the importance of quality monitoring by the owner operator is stressed. This must be carried out conscientiously because, in present‐day chemical plant construction, availability plays an important economic role, and also because safety is given the very highest priority.
Verminderung des Cadmium‐Gehaltes von Rohphosphaten und Mineraldüngern
Authors: Von Plessen Helmold , Schimmel Günther
Published: December 2004

Reducing the cadmium content of crude phosphates and mineral fertilizers. Crude sedimentary phosphates generally contain cadmium together with traces of other heavy metals. These Cd traces generally end up in fertilizers produced from the crude phosphates. Processes have therefore been developed to separate the Cd from the crude phosphate or from the crude phosphoric acids arising therefrom as intermediates. In this way, the Cd content of the crude phosphate can be reduced to less the 10% of its original value, and to 50% thereof by extractive treatment with acidic calcium nitrate solution. Older calcination processes for crude phosphate have been improved to give residual Cd contents of 10 to 50% at temperatures of 800 to 1000°C. Cadmium can be removed almost quantitatively from crude phosphate by means of dialkyl dithiophosphoric acid esters by extraction, binding to adsorbents, or ion flotation. Cadmium can be extracted from crude acids in high yield by long‐chained amines. After partial neutralization of the crude acids, precipitation as cadmium sulphide is also possible.
Herstellung von Aminosäuren mit Hilfe biotechnologischer Methoden
Authors: Leuchtenberger Wolfgang , Plöcker Ulf
Published: December 2004

Production of amino acid by biotechnological methods. Amino‐acids are needed for human and animal nutrition, pharmacy, cosmetics, agriculture, and industry. Particular interest focusses on the production of protein‐forming ß‐amino acids. Among the four methods of industrial production – chemical synthesis, extraction, enzymatic synthesis, and fermentation – the biotechnological process is attracting increasing attention. A joint development programme of KFA Jülich and GBF Braunschweig led to development of the enzyme membrane reactor (EMR) at Degussa. This reactor performs enzyme‐catalysed racemate resolution to produce L‐amino acids on a laboratory and pilot scale. The concept has meanwhile been successfully implemented in production and can be used for other applications too. Fermentation processes are being tested for more complex reaction mechanisms.
Hafttechnik – Grundlagen und Anwendungen
Authors: Zorll Ulrich
Published: December 2004

Adhesion science – Fundamentals and applications. Films of paints and adhesives, both polymeric organic substances, must be connected to the pertinent materials strongly enough, so that the bond can withstand ordinary climatic and mechanical stress. At the stage of applying the liquid paint or adhesive, good wetting will be the basis for high adhesive strength after film formation. Moreover, it is necessary to attain a balance in the effectiveness of the forces at the interface, related to the polar und unpolar groups of either adhering material. Adhesion strength can also be improved by selecting an appropriate surface profile, of which roughness as such is not so important as shape. The profile should secure sufficient clamping of the film even under conditions occuring in practice, for example at high shear stress as generated in the case of shock loading. For defined combinations of material, these rules and guidelines are generally sufficient to obtain optimum adhension strength at the interface.
Von der Schadstoffquelle zur Schadstoffsenke – neue Konzepte der Müllverbrennung
Authors: Vogg Hubert
Published: December 2004

From pollutant source to pollutant sink – Novel concepts of solid incineration. Until a few years ago, solid waste incineration plants were considered to be major sources of pollutant emission. Meanwhile, by enhancing the effectiveness of combustion and by integration of modern flue gas cleaning techniques, solid waste incineration now leads with regard to emission reducing engineering measures. Harmful effects on the environment no longer originate in the stacks of these plants. Recently, pollutants enriched in flue gas cleaning products have caused disposal problems. These problems can be solved by concentrating the harmful inorganic constituents, above all mercury and cadmium, to a still higher level through wet chemical extraction and removal of the resulting concentrate from the process. Organic pollutants can be conveniently destroyed by thermal treatment. Despite all the objections there are good chances of using solid waste incineration as a pollutant sink and hence as a tool helping to protect our environment.
Energieträger aus nachwachsenden Rohstoffen
Authors: Austmeyer Klaus , Röver Helmut
Published: December 2004

Energy from regenerable raw materials. In the long run, some of the agricultural areas in the Federal Republic of Germany will no longer be needed for food production, and could therefore be used for growing raw material plants in order to provide various sources of energy, such as wood, rape seed oil, ethanol, methanol, and biogas. With this indirect use of the solar power accumulated in the plants, the overall expenditure for fossilized fuel energy to produce these energy sources is lower than the amount of primary energy that can be substituted. Based on the assumption that 20% of farmland will be used to grow regenerable raw materials, it would be possible to replace approximately 7 million tons of coal equivalent (SKE) by wood or approximately 4 million tons of coal equivalent (SKE) by ethanol from sugar beet or methanol from wood. In the case of alcohol production from sugar beet, the total energy efficiency including the regenerative part of energy of about 74%, is lower than in the ethanol synthesis. At present, use of biomasses as an energy source is feasible only in a few rare cases, and can only be achieved if the regenerable raw materials are considered as an alternative to surplus food production or to the strategy of gradually using less acreage for growing food.
Gas/Flüssig‐Reaktoren
Authors: Mersmann Alfons
Published: December 2004

Gas‐liquid reactors. The gas hold‐up in bubble columns increases in proportion to the gas flux density in the homogeneous flow regime and rises less than proportionally in the heterogeneous flow regime. Both the gas and the liquid axial dispersion coefficient increase with gas flow. Gas phase dispersion becomes more intensive with increasing liquid viscosity, while liquid dispersion drops slightly. Experimental results for mass transfer in low viscosity liquids show that the two‐range turbulence model best fits experimental data. When aerating highly viscous Newtonian and non‐Newtonian liquids, mass transfer in the liquid phase is well described by known relations valid for very low bubble‐Reynolds number and very high Schmidt number.
Die Rolle der Sensoren in der Verfahrenstechnik
Authors: Raab Helmut
Published: December 2004

The role of sensors in process engineering. The principal function of sensors in process engineering is to obtain information about an ongoing process in order to ensure optimum management of that process in terms of process engineering. New methods of measuring conventional parameters, and recent advances in instrumentation technology, have improved ways of obtaining information and so influenced the interpretation of process engineering installations. Statistical evidence confirms a sharp increase in the number of sensors, and the increasing tendency to record flow and level measurements and product composition. Changes occurring in process engineering determine the requirements sensors have to meet and the ways in which they can be used. Microelectronics makes it possible to extend the range of functions available and the information content. This is giving rise to an new generation of sensors which are not only helping to meet the higher measurement standards required but are also making modern sensor technology more „user friendly”︁, specially for maintenance.
Anwendung des Temperatur‐Meßsystems QuaT in der Prozeßmeßtechnik
Authors: Schaudel Dieter
Published: December 2004

Application of the QuaT temperature measuring system in process measurement engineering. Resistance thermometers and thermocouples are today's standard in industrial electrical temperature‐measurement techniques. Their weaknesses, which were not so important, have become obvious with the advanced application of digital data loggers and data control units. These weaknesses include: uncertainty wether such a measuring line is predictable; the transmitter has to be defined with regard to the parameter, for each individual application; and transfer of the measured signal from the field to the central unit needs considerable effort. A temperatur measurement system has now been introduced which does not have these disdvantages, because it is using a piezoelectric resonator as a sensor element. Thus signal processing is „digital”︁. Advantages and disadvantages of both kinds of instrumentation are presented. The suitability of the new system, also regarding costs, is confirmed by the results from five industrial test programs.
Moderne Elektrolyseverfahren für die Wasserstoff‐Technologie
Authors: Sandstede Gerd
Published: December 2004

Modern electrolysis processes for the hydrogen technology. This survey discusses all processes of water electrolysis after having emphasized the central role, which hydrogen plays in chemical technology and which it might play in a hydrogen economy, with the aid of some historical considerations and applications in hydrogen energy systems. In order to understand the development potential of the processes, the physico‐chemical fundamentals as well as the problems of the engineering of water electrolysis are summarized in a structural form. Not only are the purely electrochemical processes reviewed by a classifying systematic, but also all other (indirect) processes, which include an electrochemical step. The following direct processes are discribed: conventional and advanced alkaline water electrolysis, medium temperature cells, acid water electrolysis, membrane water electrolysis, water vapor electrolysis with proton conductive solid electrolyte and high temperature water electrolysis as well as the indirect processes: electrochemical raw material gasification, thermochemical‐electrochemical hybrid processes, photochemical‐electrochemical hybrid processes, and the photoelectrochemical cleavage of water.
Ist hydrodynamische Modellierung tragfähig für die Auslegung von Schwerkraftabscheidern ohne Einbauten?
Authors: Blaß Eckhart , Löbmann Arthur , Meon Walter , Rommel Wolfgang
Published: December 2004

Is hydrodynamic modelling a sound approach for the design of gravity settlers without coalescing aids? Liquid/liquid dispersions occur in many chemical operations. Normally they have to be broken down again. This is accomplished by the flowing together of the droplets (coalescence) to a coherent phase. In practice simple gravity settlers without any coalescing aids are used for this purpose. In such settlers the dispersion is separated by the density difference between the phases, while a dense dispersion layer forms at the interface between the dispersion and the clear mother phase. The present paper deals with the modelling of such gravity settlers. First, the models describing the coalescence process of single drops are reviewed and analyzed. A physical notion of the coalescence process is derived thereform. Afterwards the models for the droplet coalescence in dense dispersions taken from the literature are presented and discussed. In conclusion the chances and limitations of the present settler models are indicated by quantitative comparison of selected models. A computer program specially developed for this purpose is presented.
Kombination von Eindicker und kontinuierlichem Druckfilter zur Verbesserung von Fest/Flüssig‐Trennprozessen
Authors: Anlauf Harald
Published: December 2004

Combination of thickener and continual pressure filter to improve solid/liquid separation processes. The fundamental concept of the proposed process combination, which basically entails a division of the whole solid/liquid separation stage into sub‐stages, is presented. The influence of the suspension's concentration on the formation and dewatering of filter cakes under ideal conditions is then discussed, after which possible deviations of the product from the ideal behaviour are described along with their influence on the process results. Actual engineering conditions are then considered, and the consequences of a suspension pre‐thickening for the results of a drum filter are demonstrated. The conditions necessary for satisfactory results are discussed. Based on the results of conventional filtration, the further increase in filter efficiency occurring on avoiding the conventionally unavoidable gas throughput by a new process is explained. Finally a conceivable combination of apparatus for performing the described process is sketched.
Produktionsintegrierter Umweltschutz – Verpflichtung der Chemischen Industrie
Authors: Lipphardt Günter
Published: December 2004

Production‐integrated environmental protection – commitment of the chemical industry. Production‐integrated environmental protection represents the optimum goal in attempts to reduce the amount of non‐utilisable substances to a minimum by chemical, physical, biological, and chemical engineering improvements in the overall process. This ranges from avoidance and reduction of residues in individual processes to the utilisation of residual substances in other production processes, also outside the perimeter fence. Combustion of organic by‐products with a high calorific value is also included in this concept as thermal utilisation. Only those waste products should be dumped on disposal sites which have no other use and cannot be disposed of by combustion. It is important to note that chemical production cannot exist without emission; it can only approach this ideal more or less closely.
Produktionsintegrierter Umweltschutz – Verwertung von Reststoffen
Authors: Lenz Heinz , Molzahn Martin , Schmitt Dieter W.
Published: December 2004

Production‐integrated environmental protection – Utilization of residues. Chemical plants as well as coal‐fired powerstations utilize chemical reactions in order to produce materials or energy. Most of these reactions additionally produce gaseous, liquid, or solid residues. It is the main objective of production‐integrated environmental protection to use these residues as suitable feedstocks in order to reduce environmental pollution and lower the consumption of raw materials. Several examples from the BASF Group will show how, by crossing the borders of the respective plant, reasonable solutions for material, or at least energetic, utilization of residues can be achieved. As a result of permanent efforts in production‐integrated environmental protection over many years and despite increasing outputs the emissions of the chemical industry have been continuously reduced.
Mechanische Aktivierung von Festkörpern
Authors: Heegn Hanspeter
Published: December 2004

Mechanical activation of solids. The main reasons why solids are comminuted are to decrease particle size, to create new free surfaces, and to increase reactivity of solids. In most cases, the comminution process is connected with crystal lattice transformations. A part of the energy supplied increases the energy level of the lattice. Consequently, a new theory of the energy balance of comminution processes is given and verified by experiments. It is shown, by some examples, that the individual mill parameters as well as the different mill types lead to characteristic changes of the crystal lattice of solids. Energy input by comminution is of great importance because it mainly influences the attainable degree of mechanical activation of solids.
Entwicklungslinien der Schüttgutdosiertechnik
Authors: Vetter Gerhard , Wolfschaffner Hubert
Published: December 2004

Developments in dosage of bulk solids. Dosage of bulk solids is a fast developing field of process‐ and production automation. Developments are determined directly by the current demands of the production process, with the properties of the bulk solids and the process itself playing an important role. A survey of proven dosage techniques from the viewpoint of the operating principles, properties, applications, and limitations demonstrates the great variety of problem solutions. An important difference between the individual dosage techniques is the nature and accuracy of mass limitation. The most accurate techniques are the gravimetric dosage methods, with discontinuous weighing giving the greatest accuracy. Developments have been greatly influenced by the state of weighing cell techniques, weighing electronics and computer engineering. The development of measured data acquisition and processing of control, and of instrumentation are described, compared, and assessed. A trend towards system responsibility and development on the part of manufacturers is noted. A accurate dosage of bulk solids requires constant flow of the solids and finely adjustable control devices. The principal interferences in bulk solids flow and measures for their avoidance are shown by means of examples. Successful solution of dosage tasks ultimately requires agreement between manufacturers and processors with regard to definition, determination, and control of dosage accuracy during calibration and during long term operation.
Scale‐up‐Probleme bei der experimentellen Verfahrensentwicklung
Authors: Hofen Willi , Körfer Martin , Zetzmann Klaus
Published: December 2004

Scale‐up problems in experimental process development. The experimental process development of a new product can be performed in test facilities of varying dimensions. Small miniplants from a laboratory scale up to larger pilot plants, in which a few tons of product per day can be produced, are used. The scale‐up factors, the risks involved in process and construction design, and a possible necessity of a limited production are important criteria for the size of the first technical realisation of the new process. The following examples highlight some special problems and their solutions in the experimental process development. Whereas a process, involving mainly fluids can be developed relatively well in a miniplant (laboratory scale), it is normally necessary to work on process development for a solid product involving difficult solid handling in a larger pilot plant. At the end of the paper some other scale‐up criteria for process design are explained.
Naßmahlung in Rührwerksmühlen
Authors: Stadler Reinhold , Polke Reinhard , Schwedes Jörg , Vock Friedrich
Published: December 2004

Wet grinding in agitated ball mills. To ensure certain product qualities it is necessary to have very fine particles or a narrow particle size distribution. For this process agitated ball mill grinding can be used as well as crystallisation and precipitation. Cost effective grinding of very fine products to a narrow particle size distribution requires that the effects of variation of strain intensity, frequency of impacts, residence time distribution, size of grinding media, viscosity of liquid and concentration of feed material should be known. The most important parameters and their effects on the grinding result are demonstrated, as well as explained by a model, and the consequences for the operating conditions of agitated ball mills are presented. By using small grinding media in agitated ball mills the production rate can be increased, or at the same energy level smaller particles can be obtained by grinding or deagglomeration. At high flow rates and a narrow residence time distribution the feed material becomes more homogeneous. These facts require the development of new or modified types of agitated ball mills.
Kopplung von Reaktions‐ und Kostenmodell: Der Weg zur effizienten Prozeßoptimierung
Authors: Büchs Jochen
Published: December 2004

Coupling of reaction and cost model: The efficient approach to process optimization. At present the investigation and optimization of chemical and biochemical reaction processes are still conducted using mostly empirical or intuitive methods. A more systematic and efficient method of process development can be achieved when experimental work is accompanied and guided by mathematical modelling. This is shown for the example of the development of an industrial L‐lysine production process. The guideline for the design of reaction models is presented as a flow sheet and explained in detail using the above example. The great advantage of a complete and verified model will become apparent, especially for reactor scale‐up and for estimation of the effects and possible benefits of advanced reactor configurations, such as fed‐batch or continuous‐flow reactors, including catalyst recycle systems or multi‐stage reactor cascades.
Modellgestütztes Messen in chemischen Reaktoren
Authors: Schuler Hans , Schmidt Christian‐Ulrich
Published: December 2004

Model‐aided measurement in chemical reactors. Some reaction‐specific variables of chemical reactors can be determined only with difficulty, sometime only with analytical measurements which are corrupted by time lags. In contrast, the approach tries to determine these variables indirectly and without time delay from easily measured variables like temperatures, pressures, flows. These sensor signals are processed together with reactor models to provide the characteristic reaction variables. This contribution discusses the applications of model‐based measuring techniques to chemical reactors. The systems are applied to operator assistence, process diagnosis, and reactor control. Their operation is submitted to a critical appraisal.
Die Kristallisationstheorie in der Praxis
Authors: Wöhlk Wolfgang , Hofmann Günter , de Jong Esso J.
Published: December 2004

Theory of crystallisation in practice. The use and applicability of crystallization theories for industrial crystallization practice are evaluated. The conclusion is that the plant user in particular benefits from the Population Balance Model because it allows for bug diagnostics and prediction of response on altering conditions. Also for design purposes, the available theoretical models greatly helped to increase insight into the wide range of events occurring in a crystallizer and how their interactions govern the resulting product. However, despite the enormous amount of research work done so far, the quantitative application of theoretical models has not found entrance into the design of tailor‐made crystallizers for strictly defined particle size distributions. From a designer's point of view, further investments of time and money should be considered carefully because the actual state of knowledge already allows more than 80% of the encountered problems to be solved. One area of common interest that urgently deserves more attention in the near future is habit modification by additives.
Katalysatoren für den Umweltschutz
Authors: Engler Bernd H.
Published: December 2004

Catalysts for environmental protection. The main emitters of anthropogenic air pollution are internal combustion engines, power plants, and production processes. Components of exhaust gases which are regarded as pollutants are hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), and dust. Three main types of catalyst are understood to improve the environment; namely automotive emission control, NOx abatement and oxidation. To reduce the pollutants HC, CO, and NOx in automobile exhaust gas, three‐way catalysts are currently applied. The reduction of particle emissions in diesel exhaust gas is achieved by diesel filters and oxidation catalysts. Pollutants from power plants are mainly the inorganic components NOx and SO2. In the SCR process, NOx is catalytically reduced to nitrogen and water. The DESONOX process is suited for the simultaneous catalytic abatement of NOx and SOx. Exhaust gases from production processes in many areas require after‐treatment. Therefore catalyst formulations depend on process parameters and exhaust gas components. This overview presents and explains catalyst types, design, mode of operation, and processes.
Neuere Entwicklungen und Perspektiven auf dem Gebiet des technischen Kohlenstoffs
Authors: Collin Gerd , Zander Maximilian
Published: December 2004

New developments and outlook for technical carbon. The present world production of technical carbon amounts to 20 Mio. t/a (metallurgical coke as well as petroleum and pitch coke not included). More recent developments in the field of technical carbon are discussed in detail. Topics covered include: production and utilization of technical carbon and graphite products in metallurgy; recent advances in the use of carbon black as reinforcing material for car tyres; the significance of activated carbon for waste gas purification including the recovery of valuable materials; high‐performance materials from carbon such as carbon fibres, carbon composites, and full‐matrix carbons; synthesis of diamond for technical applications; preparation of diamond or diamond‐like films by carbon vapor deposition; structure, preparation, and properties of fullerite, a new form of carbon, and conceivable future applications.
Katalytische Abluftreinigung: Verfahrenstechnische Aufgaben und neue Lösungen
Authors: Eigenberger Gerhart , Nieken Ulrich
Published: December 2004

Catalytic air purification; Challenges and new solutions. The integration of regenerative heat exchange into the catalyst bed allows for the autothermal operation of catalytic air purification with a low content of combustible gas. Concentrations corresponding to an adiabatic temperature rise of less then 20 °C can be processed without an additional heat source; in case of higher concentratons a side stream withdrawal allows for the utilization of the total heat of combustion at the highest reactor temperature. The feedback of heat due to the integrated heat exchange gives rise to an unusual reactor behaviour. An analogy of fixed bed reactor operation with countercurrent heat exchange is used to derive simple equations for reactor design and operation. If conventional catalyst packings are replaced by monolithic catalysts, substantial reduction in pressure loss and/or packed bed volume can be obtained. The corresponding relations are briefly discussed.
Produkteigenschaften und Verfahrenstechnik
Authors: Borho Klaus , Polke Reinhard , Wintermantel Klaus , Schubert Helmar , Sommer Karl
Published: December 2004

Product properties and process engineering. The properties of solids are determined by their chemical composition, their state of dispersion, and their interfacial forces. They are largely responsible for the behaviour of the products during the manufacturing process and for the desired quality characteristics of the finished product. The aim of this survey is to illustrate the influence of particle size distribution and interfacial forces on product properties. The effects shown can be explained with the aid of a few physical modes. The first part shows how product properties can be adjusted to achieve a particular aim, principally by modifying the particle size. These include product‐relevant properties such as filtration properties, miscibility, and potential for dust explosion, as well properties relevant to the (final) product such as colour and taste. As the particle size decreases, the forces acting between the particle become increasingly important. The second part of this article therefore focuses on those product properties which can be influenced by way of changes in the cohesive forces. Production‐relevant properties are flow properties, bulk density, agglomeration behaviour; product‐relevant properties are tablet stability and redispersibility of foods, dyes, etc. Among the cohesive forces, capillary forces deserve particular attention. The paper concludes with an account of their role in the manufacture and use of solids. The pore structure of an agglomerated solid is determined by capillary forces and the external forces required during the manufacturing process.
Probleme und Erfahrungen bei großtechnischen Packungskolonnen
Authors: Gann Martin , Kaiser Rudolf , Schoenmakers Hartmut , Zeck Sebastian
Published: December 2004

Problems and experience with industrial scale packed columns. Apart from column plates, random and structured packings are being used increasingly as internal components of distillation columns. The advantage of structured packings lies in an enhanced specific separation performance at significantly lower pressure drops than in the case of classical plate columns. In contrast to column plates, there is no defined liquid pathway in random and structured packings; in particular, the dependence upon the initial distribution in columns of large diameter proves to be problematical. Recent theoretical model calculations and laboratory scale studies have shown that the liquid distribution in structured packings is of paramount importance, above all in columns having diameters in excess of 1 m. The present article reports problems and experience gained with industrial scale distillation columns by considering four examples. In addition, the authors also provide an in‐depth account of the factors and problems relating to the assessment of separation performance of industrial columns.
Die Abscheidung von polychlorierten Dioxinen und Furanen aus Abgasen mit Aktivkoksverfahren
Authors: Richter Ekkehard
Published: December 2004

Removal of Polychlorinated Dioxins and Furans from Off‐Gases by Activated Charcoal. Discussions on solid waste incineration are dominated by the formation and emission of polychlorinated dibenzodioxins (PCDD) and dibenzofurans (PCDF). The predominant part of these substances remains in the fly ash, and less than 20% is present in the off‐gases. Very stringent emission limits have been stipulated during recent years in many countries. The adsorption of PCDD/PCDF on carbonaceous materials has proved to be a very effective technique for their removal. Experimental results relating to gas clean‐up, adsorber types, and concepts for the integration in plants are described.
Katalyse in der Abluftreinigung
Authors: Fink Klemens , Gajewski Wolfgang , Joisten Michael , Neufert Ronald , Sprehe Josef , Zürbig Jürgen
Published: December 2004

Catalysis in Air Purification. In most cases catalytic purification of waste gas allows the reliable reduction of industrial emission to meet existing regulations. This method can remove numerous organic and inorganic compounds from waste air. This review deals with design, applications and function of such air purification units with special regard to the catalysts used. Furthermore, aspects of chemical engineering relevant for planning and construction are also discussed.
Mittlere Temperaturdifferenz und Wirkungsgrad in mehrgängigen Rohrbündel‐Wärmeübertragern mit und ohne Umlenksegmente
Authors: Gaddis Edward Shafik
Published: December 2004

Mean Temperature Difference and Efficiency of Multipass Shell‐and‐Tube Heat Exchangers with and without Segmental Baffles. Branched flow in a multi‐passes shell‐and‐tube heat exchanger with segmental baffles causes a reduction in the mean temperature difference and the thermal efficiency of the apparatus compared with a pure counter‐flow. The influence of the shell‐side flow induced by the segmental baffles on the thermal performance of the heat exchanger is mostly ignored. Making certain assumptions (e.g. constant overall heat transfer coefficient) theoretical relations of the thermal performance of the exchanger can be derived from the energy balance and the kinetic equation. If these assumptions are not valid, a numerical integration of the differential equations is necessary. Ignoring the influence of the shell‐side flow induced by the baffles is only possible under certain conditions. If these conditions are not fulfilled, the cell‐method can be used.
Abscheidung organischer Dämpfe
Authors: Börger Götz‐Gerald
Published: December 2004

Emissionen organischer Dämpfe aus Industrieanlagen werden durch Vorschriften, z.B. die Technische Anleitung zur Reinhaltung der Luft, Grenzen gesetzt. Zu deren Einhaltung steht ein breites Spektrum von Verfahren zur Verfügung, das in sieben Gruppen gegliedert werden kann: (1) Kondensation, bei hohen Konzentrationen als Teil‐ oder als Vorabscheidung, (2) Adsorption für schlecht wasserlösliche Dämpfe oder bei geringen Konzentrationen, (3) Absorption für wasserlösliche, chemisch zu bindende oder konzentrierte Dämpfe, (4) Membran‐Permeation für einige Fälle konzentrierter Dämpfe, (5) Verbrennung für alle Arten organischer Dämpfe, (6) Katalytische Umwandlung für leicht, ausschließlich zu Gasen oxidierbare Dämpfe, (7) Biologische Oxidation für biologisch gut abbaubare Dämpfe geringer Konzentration. Aus einigen der Verfahren erhält man wiederverwendbare, flüssige Organika. Die übrigen Verfahren müssen so geführt werden, daß Oxidationsprodukte entstehen, die in der Umwelt toleriert werden können.
Nutzung unterschiedlicher Streulichtanteile zur Partikelgrößen‐Bestimmung in dispersen Systemen
Authors: Bauckhage Klaus
Published: December 2004

Utilisation of Different Components of Scattered Light for Particle Size Determination in Dispersed Systems. Light scattered by finely and coarsely dispersed particles can be used in variety of ways for characterization of sprays, emulsions, or suspensions. The characteristic of greatest interest is the particle size or the particle size distribution. While homogeneous, coarsely dispersed particles at sufficient dilutions and randomly distributed in a transparent continuous phase are generally amenable to particle size analysis, finely dispersed particles at higher concentrations or coarsely dispersed particles containing finely dispersed components are often difficult to measure. This article discusses ways of overcoming such difficulties on the basis of examples taken mainly from phase Doppler anemometry.