Wirbelschicht-Technologie: Neuentwicklungen für Kraftwerkstechnik und Umweltschutz

Fluidized bed technology: recent developments for power station engineering and pollution abatement . The principle of fluidization has been successfully applied to numerous areas of chemical engineering. Combustion of coal in a fluidized bed consisting of particles of ash and limestone or dolomite permits low-pollution utilization of coals having lower heating values or high sulphur contents without any need for removing sulphur from the exhaust gases. The present state of the art and world-wide development work on fluidized combustion are considered, as are the future prospects of this new energy technology.     

Die Arten der rißbildenden Korrosion und ihre Bedeutung für die Betriebsbereitschaft von Komponenten der Chemietechnik

Kinds of crack-producing corrosion and their significance for the availability of components of chemical plants. Interor transcrystalline cracks in metallic components of chemical plants can occur under the combined influence of mechanical stress and corrosion. Since they usually remain unrecognized before the occurrence of visible damage – leakage of a vessel or fracture of a structural part – such crack-producing corrosion processes are greatly dreaded. Based on differences in the mechanism of the process of damage, one distinguishes two groups, i. e. stress corrosion cracking (SCC) and corrosion fatigue (CF). SCC stands for an interaction between local corrosion attack and quasi-static tensile stresses (load- and/or residual stresses). CF means a combination of mechanical stresses differing in time and corrosion. Hydrogen induced SCC is a special kind of crack corrosion, initiated by atomic hydrogen absorbed in a metal. The paper describes the different systems of SCC and CF, the forms of failure, the parameters, and the possibilities of avoiding damages, especially emphasizing their significance in practice.     

Bedeutung und Technik des Fritierens Fritiergeräte für gewerblichen Einsatz und Haushalt

Significance and Technology of Frying: Frying Equipment for Commercial Purposes and Household Currently, the frying equipments available for commercial use fulfil the requirements with regard to protection of the fat and reliability of the frying operation. This has been accomplished by proper choice of material, suitable construction, and appropriate technical layout. However, certain technical improvements seem to be necessary in the case of household fryers. Considerable differences are observed in layout of the heating system. Obviously, a great deal of attention has unnecessarily been paid to specific surface load of the electrical heating elements. Detailed studies are required which should enable to optimize the frying process.     

Wärmetransformatoren für die Chemische Industrie aus der Sicht des Anwenders

Absorption heat transformers for the chemical industry as seen from a user's point of view. Absorption heat transformers can transfer waste heat, that could not hitherto be reused, to a higher temperature level. This is of special interest for the chemical industry, where there is both waste heat available at temperatures below 100°C and a demand for heat at 120 to 150°C. Though absorption heat transformers are able to recycle only a part of the total waste heat, they only need a negligible amount of additional, expensive exergy. The present status of development and advantages and disadvantages of the concept are discussed from a user's point of view. In view of the present low price of energy, special attention is given to economic considerations.     

Zusammensetzung und Aufbau der Triglyceride von Muttermilch und einiger Rohstoffe für Säuglingsnahrung

Composition and Structures of Triglycerides of Human Milk and Some Base Components for Infant Milk Formulas Following HPLC separation of human milk triglycerides with a silver-loaded ion exchange and an RP-18-phase column, the 50 substantial fractions obtained were characterized by gas chromatography of triglycerides and fatty acid methyl esters as well as by the analysis of intramolecular distribution on a reduced scale using ethyl magnesium bromide. Exploitation of all data available resulted in the detailed structures of 106 triglycerides, representing 81 g/100 g human milk fat. A substitute for producing infant milk formulas should be adapted to the composition and fatty acid distribution of those 14 substantial triglycerides which are present in human milk fat with more than 1 g/100 g, amounting to a total of 42 g/100 g. Among several fats and oils analyzed, only lard and a recent product were found to contain palmitic acid also predominantly in the 2-position. Therefore, other base components would require a directed fractionation and/or interesterification to be best adapted to human milk fat.     

Moderne und wirtschaftliche Aufbereitung der Abwässer in der Speiseöl- und Fettindustrie

Modern and Economic Treatment of Waste Waters from Edible Oil and Fat Industry In the near future no industrial undertaking will be permitted to dispose waste water from the plants into public waters and city drainage without prior purification. The edible oil and fat industry has the advantage that its waste waters can be clarified in an inexpensive manner and the sludge recovered can be utilized economically. In the present communication a purification process is described which has been used with advantage in several plants in and outside of Germany.     

Werkstoff- und Schweißfragen bei der Herstellung von dickwandigen Druckbehältern für höhere Betriebstemperaturen aus Stählen mit 2 bis 3% Chrom und ca. 1% Molybdän

Materials and welding in the production of thick-walled pressure vessels for elevated operating temperature made of steels containing 2 to 3% of chromium and ca. 1% of molybdenum . High-temperature steels containing 2 to 3% of chromium and ca. 1% of molybdenum are resistant to hydrogen under pressure at temperatures up to about 500°C. Being readily weldable, they are excellently suited for high pressure equipment in chemical plant construction. Their tendency to embrittlement at operating temperatures of 400 to 500°C is a drawback. However, specific metallurgical measures adopted during the production of the semifinished material and the welding materials, and use of optimized welding techniques and heat treatment keep this embrittlement within limits. The article reports recent experiences gained in producing pressure vessels with welding seam thicknesses of up to 230 mm at the authors company.