Produkteigenschaften und Verfahrenstechnik

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.     

Rohrleitungstechnik und Verfahrenstechnik

Pipework engineering and chemical engineering . Piping must be included as an essential part of a plant in the chemical engineering design of the process units. The necessary engineering specifications for an appropriate, minimum cost design of pipe systems and the job integration of pipe planning, which demonstrates the strong links between pipework engineering and chemical engineering in the planning and construction of plant, are discussed. The use of computers in pipe engineering began about 12 years ago. Development proceeded via computer mass listings, computer-plotted isometric drawings, automatic material listings to the contemporary computed plotted flow charts, leading to increasing confrontation of chemical engineers with these programs with repercussions in their work. A report is presented on the development of new systems and on the present state of implementation of these computer methods; the scope and limitations are indicated.     

Sicherheit in der Verfahrenstechnik

Safety in the field of chemical engineering . This article discusses whether the risks involved in technology have increased, why such severe criticism is expressed concerning safety in plants, and whether there has been any change in the criteria that the public applies to safety. The accident statistics of the employers' association indicate the improvements in safety that have been achieved and by no means suggest any increase in the risks involved. The reason for the frequent and severe criticism of safety appears to be a widespread ignorance of production processes and a mistrust that evolves from such ignorance. Thus it is necessary to provide the public with still more and still better information. For this purpose the chemical industry needs an unbiased press that strives for impartiality. Among the criteria applied nowadays, a consideration of the advantages and disadvantages of a technical development is frequently lacking and a trend towards forecasting methods can be ascertained. The chemical industry is prepared to provide frank information and to engage in an objective discussion of safety topics.     

Vakuumpumpen in der Verfahrenstechnik

Vacuum pumps in chemical engineering. Applications of vacuum pumps in chemical engineering are numerous. After a general systematization of the working principles of vacuum pumps, the most important types – liquid ring vacuum pumps, sliding vane vacuum pumps, and ejectors – are discussed with regard to their development and their working principle. Attention is focussed on aspects which allow a comparison of the advantages and disadvantages of vacuum pumps. A systematic survey of the criteria leading to the selection of a certain type of pump show that these criteria may be based on the process as a whole or on environmental and safety considerations as well as economic aspects. In areas where liquid ring vacuum pumps, sliding vane vacuum pumps, and ejectors may be applied the extent to which the pumps fulfill these criteria is shown. In this context, a comparison of the liquid ring pump and the sliding vane pump is of special interest. The doubts recently publicized concerning the environmental compatibility of liquid ring vacuum pumps are shown to be groundless if the pumps are installed correctly. Great care must be taken comparing the economic aspects of liquid ring pumps and sliding vane pumps.     

Energieeinsparung in der Verfahrenstechnik

Energy saving in process engineering . As is already well known, the overriding factor in thermal processes in the chemical industry is the cost of energy. Because of the considerable rise of prices for primary energy all over the world, efforts have been started to decrease the specific energy consumption for chemical products. In the first part of this paper possible ways of saving energy in the chemical industry are considered from a theoretical point of view. A principle motive was to decrease the percentage of primary energy needed in a process. In particular, the thermodynamic examination of heat pumps, multi-stage processes and the possible integration of backpressure engines in a chemical complex are treated. In the second part some planned and practically executed examples are shown with actual indications of energy savings. Hereby, the relatively greater increase of primary energy costs versus in vestment costs in recent years have been considered.