Absch?tzung der Pyritoxidation in einem Braunkohletagebau mithilfe numerischer Modellrechnungen

Beim Abbau von Braunkohle kann die Oxidation von im Sediment vorhandenen Pyriten zu einer Versauerung des Sickerwassers führen und damit zu einer Mobilisierung von Schwermetallen. Um den Oxidationsgrad der Pyrite in der unbehandelten Abraumkippe eines Braunkohletagebaus abzuschätzen, wurden am Lehrstuhl für Angewandte Geologie der Ruhr-Universität Bochum neben umfangreichen Felduntersuchungen und Laborversuchen auch numerische Simulationsrechnungen durchgeführt. Um die in einem Tagebau oxidierten Pyritmengen zu berechnen, wurde mithilfe des numerischen Modells gw-chem.f sowohl die Oxidation auf der Abbauseite als auch die Oxidation auf der Kippenseite berechnet. Die genaue Kenntnis der umgesetzten Pyritmenge ist notwendig, um die Kalkmenge zu ermitteln, die benötigt wird, um die bei der Pyritoxidation entstehende Schwefelsäure zu neutralisieren. Dadurch soll das Grundwasser geschützt werden, wenn der Tagebau wieder geflutet wird.     

Herstellung,Verarbeitung und Eigenschaften höherfester Stähle für den Einsatz in Windenergieanlagen

Production, processing and properties of higher‐strength steel plates for application in wind energy plants. The mechanical and technological demands on steels for offshore wind energy plants are high. Advanced technologies in steel production make normalized or thermomechanically rolled plates with minimum yield strengths up to 460 MPa as well as quenched and tempered steels with minimum yield strengths from 520 up to 1100 MPa available for construction. Plates with up to 460 MPa are well established for building wind energy plants. Material properties and processing of these steel grades are well known. High‐strength steels offer further possibilities for construction. These steels are characterised by high yield strength and at the same time high toughness and excellent processing behaviour. By modern fracture mechanical safety concepts, it could be shown, that even under critical service conditions there can be guaranteed a high level of safety against brittle failure.     

On the use of peak-force tapping atomic force microscopy for quantification of the local elastic modulus in hardened cement paste

A surface of epoxy-impregnated hardened cement paste was investigated using a novel atomic force microscopy (AFM) imaging mode that allows for the quantitative mapping of the local elastic modulus. The analyzed surface was previously prepared using focussed ion beam milling. The same surface was also characterized by electron microscopy and energy-dispersive X-ray spectroscopy.We demonstrate the capability of this quantitative nanomechanical mapping to provide information on the local distribution of the elastic modulus (from about 1 to about 100 GPa) with a spatial resolution in the range of decananometers, that corresponds to that of low-keV back-scattered electron imaging. Despite some surface roughness which affects the measured nanomechanical properties it is shown that topography, adhesion and Young's modulus can be clearly distinguished.The quantitative mapping of the local elastic modulus is able to discriminate between phases in the cement paste microstructure that cannot be distinguished from the corresponding back-scattered electron images.     

Manufacture of fatty alcohols based on natural fats and oils

The present worldwide capacity of fatty alcohols is ca. 1.0 million metric tons per year. About 60% of this capacity is based on petrochemical feedstocks, 40% on natural fats and oils. Three basic dominating commercial-scale processes are used to manufacture fatty alcohols: the Ziegler process and the Oxo synthesis starting from petrochemical feedstocks, and the high-pressure hydrogenation of natural fatty acids and esters. Basically, the high-pressure hydrogenation can be used with triglycerides, fatty acids or fatty acid esters as feedstock. The direct hydrogenation of fats and oils has not been developed to a commercial-scale process, mainly because it was not possible to prevent decomposition of the valuable byproduct glycerol. Conversion of fatty acids into fatty alcohols by catalytic hydrogenation without preesterification requires corrosion-resistant materials of construction and acid-resistant catalysts. Required reaction temperatures are higher, resulting in a higher hydrocarbon content. The majority of fatty alcohol plants based on natural fats and oils use methyl esters as feedstock. These can be made either by esterification of fatty acids or by-transesterification of triglycerides. For catalytic high-pressure hydrogenation of methyl esters to fatty alcohols, several process options have been developed. The bawic distinguishing feature is the catalyst application either in a fixed bed arrangement or suspended in the methyl ester feed.     

Kontinuierliche Reaktionsführung mit löslichen Enzymen

Continuous processes with soluble enzymes. This paper surveys the use of continuously operating enzyme-membrane reactors with enforced flow where the retention of soluble enzymes in the reaction vessel is achieved by means of an ultrafiltration membrane. This technique has been commercialized in the acylase process for the synthesis of L -amino acids on a 200 ton/year level. It is especially useful for the application of multi-enzyme systems with cofactor regeneration. The synthesis of L -tert-leucine from the corresponding α-keto acid has been achieved on a kilogram scale. Coenzymes coupled to water soluble polymers are retained in the membrane-reactor together with the enzymes. Use of suitable conditions prevents loss of enzyme and coenzyme by passage through the membrane or by deactivation. Therefore the costs of enzymes and coenzymes are no longer limitations for economic processes. In the continuously operating enzyme-membrane reactor regeneration of the coenzyme up to 600 000 times was achieved. In continuous peptide synthesis space-time yields of 25 kg/(l d) were obtained. To suppress side reactions very high catalyst concentrations are possible, yielding residence times below 4 min.     

Input reconstruction for statistical‐based fault detection and isolation

In this work, an input reconstruction scheme for detecting and isolating sensor, actuator, and process faults is proposed. The scheme uses model‐based and statistical‐based FDI methods, which yields an improved analysis of abnormal operation conditions in chemical processes. The main advantage of the proposed approach over existing works lies in the reconstruction of system inputs and the subsequent estimation of fault signatures. This advantage is demonstrated through simulation examples and the analysis of recorded process data from a reactive batch distillation column. © 2011 American Institute of Chemical Engineers AIChE J, 2012