APPLICATION OF CONCENTRATED SOLAR RADIATION TO HIGH TEMPERATURE DETOXIFICATION AND RECYCLING PROCESSES OF HAZARDOUS WASTES

In many cases, hazardous wastes are subject to thermal treatment at elevated temperatures. Some types of wastes do not have a sufficient calorific value to cover the heat demand of the high temperature process. For thermal treatment of e.g. filter residues, dusts, sulfuric acid, aluminium dross, foundry sand, or waste water, supplementary energy supply is needed. The specific energy demand ranges from 0.5 to 2.5 kWh/kg (2–10 MJ/kg). An important aim of process optimisation is the reduction of (fossil) energy consumption and exhaust gas flow. Concentrated solar energy promises advantages when applied to high energy consuming waste treatment processes with regard to substitute fossil or electric energy consumption, to reduce CO₂ emissions, and exhaust gas flow. In parallel to conceptional studies, a solar-heated rotary kiln mini-plant has been designed and constructed for tests in the DLR solar furnace. The tests will give indications of boundary conditions for solar thermal treatment or conversion of selected hazardous materials.     

Modularisierung von Gaswäschern für die CO2‐Entfernung aus Biogas

Modularization has been identified as one of the research fields of the ?50 % idea”?. A development methodology for modules must consider both the economies of scale for investment costs and costs of operation and maintenance. In this paper, the impact of an absorber module, which is offered as discretized diameter scaling, on the total process is investigated at the example of the CO₂ separation from biogas. The simulation shows the effect of this approach to the stripper diameter and the energy demand of the process. The calculations form the basis for applying cost models.     

Kinetik der polykondensation von natriumsulfidhydrat und 1,4-dichlorbenzol zu poly(thio-1,4-phenylen)

The kinetics of the polycondensation of sodium sulfide hydrate and 1,4-dichlorobenzene to poly(thio-1,4-phenylene) in 1-methyl-2-pyrrolidone as solvent was studied in a differential scanning calorimeter at temperatures between 220 and 280°C. This polycondensation shows an autocatalytic behavior and the kinetics can be modelled by a first order reaction up to complete conversion. This is explained by the low solubility of sodium sulfide in l-methyl-2-pyrrolidone. The concentration of sodium sulfide is regarded as being constant during the whole course of the reaction. The autocatalytic effect can be explained by the increase of the condensation rate constant at the beginning of polycondensation due to the higher reactivity of the oligomers compared to the monomers. The number- and the weight-average molecular weight of the products formed during the course of the polycondensation can be modelled by means of stochastic methods. A simple model with only two different rate constants of the condensation process is assumed. The concentration of sodium sulfide in the reactive phase is found to be 2–5% of the value of dichlorobenzene at the beginning of the reaction and remains constant nearly until the end of polycondensation.     

Interaction of thermally induced and mechanical fatigue

The influence of superimposed total strain controlled HCF loadings on TMF life is presented and discussed for several cast Al-Si alloys, the Ni-base superalloy Inconel 617 and the cast iron GJS-700. Except for GJS-700, a threshold of the superimposed HCF loading is observed, below of which TMF life is not significantly affected. The strong decrease of TMF life as soon as the HCF amplitude exceeds this threshold is due to fundamental changes in the crack propagation mechanisms. The paper closes with a brief overview on lifetime prediction methods for TMF and their application in the case of TMF/HCF loadings.     

Study of Interatomic Potentials in ZnS—Crystal-GRID Experiments Versus Ab Initio Calculations

Crystal-GRID measurements have been performed with ZnS single crystals. For the first time, an asymmetric Crystal-GRID line shape could be observed. The preliminary data evaluation indicates that the reported lifetime of the 3221 keV level in ³³S is too short. A value of about 60 fs has been found. Due to this “long” lifetime the line shape is much less structured than calculated with the reported lifetime.     

Numerical analysis of ductile failure of undermatched interleaf in tension

Ductile failure of an interleaf tension specimen consisting of a metal interleaf bonded between two elastic substrates, with a crack located in the centre of the metal, is studied by means of detailed finite element (FE) analyses. The rate-independent version of the Gurson model is used. This accounts for ductile failure mechanisms of micro-void nucleation, growth and coalescence within the framework of a finite deformation plasticity theory. Also, the rapid evolution of void density due to coalescence, which leads to ultimate failure, is considered. The effect of the interleaf thickness on failure (crack initiation and limited amount of crack growth) is investigated. The results show that the interleaf thickness affects crack initiation only slightly. For all specimens considered, crack initiation takes place at the crack tip. However, after crack initiation, the interleaf thickness affects stress and strain distributions significantly. Reducing the interleaf thickness significantly increases the load-carrying capacity. Moreover, reducing the interleaf thickness increases the maximum hydrostatic stress in the interleaf, which is no longer developed at the crack tip but at a distance far away from the crack tip. The resulting fracture toughness thus decreases as the interleaf thickness decreases. The shielding of the crack tip due to constrained plasticity is observed at higher load levels for interleaf specimens. This revised version was published online in August 2006 with corrections to the Cover Date.     

Amplitude and phase recovery of rotationally symmetric beams

Two methods are presented for the amplitude and phase recovery of optical beams with rotational symmetry. These are the tomographic method based on the ambiguity function and the one-step wavefront recovery based on the measurement of a phase-space distribution closely related to the Wigner distribution function. The results obtained from these two methods are compared, and the appropriateness of using either one of them for specific situations is discussed.     

Experimentelle und analytische Untersuchungen zum Zündverhalten stark verdünnter C2H2/O2-Gemische

Zusammenfassung Das Zündverhalten homogener Gasgemische bestehend aus Argon mit C₂H₂+O₂-Anteilen von 2% wird bei ?quivalenzverh?ltnissen von ϕ=0,2; 0,5; 1,0 und 2,0 hinter Sto?wellen experimentell untersucht. Kriterium für das Ende der Induktionsperiode ist das starke Ansteigen der OH-Konzentration, die durch Absorptions- oder Emissionsverfahren gemessen wird. Die Gaszust?nde sind in einem Temperaturbereich 1000 K≦T≦1560 K bei Drücken zwischen 0,6 und 1,3 bar variiert worden. Die Me?werte lassen sich durch eine Korrelationsgleichung darstellen mit τ in μs und Konzentrationen in mol cm⁻³. Mit Hilfe eines reaktionskinetischen Modells bestehend aus 29 Elementarreaktionen werden Computersimulationen des Zündverhaltens der verschiedenen Gemische durchgeführt. Die übereinstimmung zwischen berechneten und gemessenen OH-Induktionszeiten erscheint zufriedenstellend, wenn man bedenkt, da? keine kinetische Anpassung vorgenommen worden ist.