Ausgewählte Problempunkte bei Simulation und Gestaltung rektifikativer Trennprozesse

Selected Problem Points in the Simulation and Design of Distillative Separation Processes . Thermodynamic simulation represents an important tool in the process engineering treatment of distillative separation processes. The degree of detail in the representation of the real process is orientated upon the question of the stage of process development at which thermodynamic simulation is utilized. For three examples of practical relevance it is shown that an improper representation of process reality in the simulation may lead to ambiguous and even false interpretations. In most cases problems arise when process-relevant functions of single units are not incorporated adequately. It is shown that a Langrange-type consideration of the process avoids most of the problems discussed.     

Fragen der apparativen Gestaltung und Betriebsweise von Verdampfern für thermisch empfindliche Stoffe

Problems of Design and Processing of Evaporators for Thermal Sensitive Components The special conditions of evaporation of thermal sensitive components resulted in the development of suitable evaporators for this purpose. The temperature effect during the evaporation process is shown for different types of evaporators and the advantages and disadvantages of the use of motive steam are explained. It was evident that systems operating with the fall film principle are especially suited for the given task. The application scope and the parameters for the designs of such an evaporator as well as examples for the successful full scale application with most protecting product treatment with an energy saving lay-out are discussed.     

Waschverfahren partikulär‐disperser Systeme – Verfahrensspektrum und Aspekte der Verfahrensauswahl

Washing of Disperse Solid Systems – Existing Washing Processes and Guidelines for Choosing the Appropriate Washing Procedure Washing of disperse solid systems is a widely used and complex operation. Since the washing‐step is mostly integrated into other process operations, it is subject to numerous demands, which exceed the primary demands like a good separation result and a low specific wash liquid demand. Because of the phenomenology and limits of different washing procedures it is difficult to choose an appropriate washing process. Additionally, the acting transport mechanisms of some washing procedures are not yet sufficiently understood. This work shows a broad overview over the existing washing processes, the numerous parameters and the demands they have to fulfill. A categorization of washing procedures as well as a classification of the processes concerning their macroscopic transport phenomena are the base for a broad decision chart which compares and evaluates existing washing processes and shows their individual limits. The work can be seen as a rough guideline for choosing the appropriate washing procedure.     

Quantenchemische Untersuchungen zur Carbonylierung von Nitrosoverbindungen,III. Der Einfluß von Metallkatalysatoren des Typs MXCOL2 auf ausgewählte Ausschnitte der Potentialfläche der Carbonylierung von Nitrosomethan

Quantum Chemical Investigations on the Carbonylation of Nitroso Compounds. III The Influence of Metal Catalysts MXCOL₂ on Selected Parts of the Potential Surface of the Carbonylation of Nitrosomethane The first step of the reaction of nitroso compounds with carbon monoxide, fixed in transition-metal complexes of the type MXCOL₂, is assumed to be an addition of the nitroso compound to the complex. By means of the EHT formalism, a relevant part of the potential surface of some adducts consisting of nitrosomethane and rhodium complexes RhXCOL₂ with various ligands X and L has been calculated. The NO double bond in the adducts is destabilized by a considerable charge transfer from the complex to the nitroso component. Additionally, a positive overlap population between the oxygen of the nitroso group and the carbon atom in CO has been calculated. The reaction profil shows that acceptor ligands L favour the deoxygenation of the nitroso compound. Basing on the results obtained, a mechanism of the catalytic carbonylation of nitroso compounds is discussed.     

Aktuelle Beurteilung ernährungswissenschaftlicher Aspekte der Linolensäuren

Current Views of Nutritional Aspects of Linolenic Acids The linolenic (n-3) type of fatty acid has many metabolic and chemical properties similar to those of the linoleic (n-6) type. Activation to CoA esters and esterification to lipids occurs relatively independent of the n-3 or n-6 structure. Both types of dietary polyunsaturated fatty acid appear able to reduce serum cholesterol levels and diminish some risk factors associated with cardiovascular disease. Nevertheless, the presence of the added terminal double bond in the n-3 fatty acids diminishes their reactivity in physiological conditions with the cyclooxygenase enzyme that forms prostaglandins. Also the formation of leukotriene derivatives from 20:5n-3 appears decreased relative those from 20:4n-6. This lower reactivity of n-3 acids also is associated with a lower ability to relieve the symptoms of essential fatty acid deficiency in experimental animals. The n-6 acids are thus defined as the essential fatty acids that physiologically form the active eicosanoids. Because villagers traditionally ingesting maritime foods have decreased incidence of cardiovascular disease and thrombotic deaths, current attention is directed to the dietary balance of n-3 and n-6 fatty acids. Recent concepts of platelet function and dietary lipids in coronary thrombosis, vasospasm and angina (Herz 5, 34–41 [1980]) suggest that some dietary balance between the n-3 and n-6 polyunsaturated fatty acids may be beneficial in decreasing the development of coronary artery disease and thromboembolisms.     

Heizen und Kühlen –- verfahrenstechnische Aspekte

Heating and cooling-chemical engineering aspects. This paper reviews the commonest types of heat exchangers and their applications. They are classified in the following types: tube bundle heat exchangers, plate heat exchangers, spiral heat exchangers, lamella heat exchangers, and heat exchangers for special purposes. Most of these apparatus can be used for heat exchange between single phases or for condensation or boiling of substances. The different criteria determining the choice of heat exchanger are explained.     

Trans-Fettsäuren – gegenwärtiger Stand der Erkenntnisse

Trans-Fatty Acids - Current State of Knowledge Trans-fatty acids are regularly consumed by human beings along with butter and margarine. Numerous researchers have been engaged in proving their harmlessness. A study of the literature (1967-1976) covering about 20 publications has enabled the conclusion that trans-fatty acids are harmless if the supply of linoleic acid is adequate.     

Grenzflächenphysik in der Verfahrenstechnik – Beispiele aus der Praxis

Interface physics in chemical engineering – practical examples . A series of practical examples is used to demonstrate the possible ways in which interface physics can help the chemical engineer in his work. The article first presents some fundamental principles of interface physics and appropriate methods and model concepts. It is then shown how this armamentarium can be profitably applied in specific cases: questions of coating, formulation, adhesion, granulation of powders, production of trickling films, and flotation are considered. It becomes very clear that interfacial effects have a very wide and far-reaching influence on industrial processes. The problems encountered can be solved only by close cooperation between chemical engineers and interface physicists.     

Lärmbekämpfung in der Industrie – eine Managementaufgabe

Control of Noise in the Industry – a Management Task For an efficient control of noise, a good cooperation is necessary between engineers, production staff, physician, purchasor, and staff of the legal, insurance and finance sections. The coordination of activity of all the groups should be done at the executive level. Communications should be easily possible; responsibilities should be well defined and the individual measures should be adapted within the broad policy, from which long-term plans should be made. The cost factors should be taken into account while making the plans. Several examples of noise control are given together with the quantitative data achieved. The examples cited include new construction of the factory, acoustic ceiling of production halls, noise preventive walls, insulation of machines and sound sources, noise damper and other constructive measures.     

Bestimmung der Nullfeldparameter optisch angeregter 3(π,π*)-Zustände ausgewählter aromatischer Systeme

Determination of the Zero Field Parameters Optically Excited ³(π,π*)-States in Selected Aromatic Systems Experimental zero field parameters of optically excited naphthalene and quinoxaline derivatives are presented. The (D*), (D) and (E) parameters are determined by the position of the transitions by means of simple approximation formula, magnetophotoselection and simulation of spectra. Possibilities of comparison of the zero field parameters of optically excited ³(π,π*)-states with parameters of ground state for simple aromatic hydrocarbones are presented.