New Approach to Control of the Dissolved Oxygen Concentration in a Biomass-Driven Self-Cycling Biochemical Process

In a biomass-driven bioprocess, the dissolved oxygen concentration (DOC) is controlled indirectly by controlling biomass concentration. Because the DOC depends not only on biomass concentration, but also on other factors (e.g. substrate concentration, efficiency of the aeration system), this solution may cause a decrease in the DOC below a critical level. To remedy this, in the presented article, a biomass-driven model that takes into account the DOC is developed and its accuracy is evaluated with experimental data. Then, the extended analyses and exemplary simulations of Acinetobacter calcoaceticus and Saccharomyces cerevisiae aerobic growth are carried out. The main aim of these analyses and simulations is the maximization of the biomass growth by ensuring good aerobic conditions and preventing against fermentation.     

Distillation profiles in ternary heterogeneous mixtures with distillation boundaries

Distillation boundaries are created by saddle azeotropes and divide the composition space into distillation regions. In this study, the behavior of rectification profiles was investigated in the following heterogeneous systems: benzene, tert-butanol, water and ethanol, water, toluene. These systems were chose in order to scrutinize whether distillation regions overlapped. The experiments were performed using Distil (afterwards Conceptual Engineering) software from AspenTech, Inc. For each type of distillation column (staged and packed), a different pair of distillation boundaries is referred (TRB & PDB and SDB & PDB accordingly). Similar to homogeneous mixtures, distillation regions were found to overlap each other in heterogeneous mixtures. As a consequence, their common part was parametrically sensitive.     

Bioleaching von Rostasche der thermischen Abfallbehandlung im Jahreszyklus

Due to environmental protection, the recycling of fractions < 10 mm from waste incineration bottom ashes is inevitable in the future and at the same time a source for metal resources, which may help Germany to get more independent in metal feedstock supply. Caused by the inhomogeneity of bottom ashes, random sampling does not provide reliable concentration average values. Therefore, only a long‐time study based on dissolution provides appropriate data about the potential of bottom ashes. Thus, not the concentration of the solid material is used for evaluation of the potential, but the amount of metals (Al, Fe, Cu, Zn), which are dissolved upon bioleaching from the bottom ashes.     

THERMOELASTIC ANALYSIS IN RANDOM CONDITIONS

A probabilistic finite-element approach for modeling the temperature and displacement fields in structures is proposed. The theoretical formulation of the problem is described. It presents probabilistic distributions for temperature and displacement taking into account the random thermal properties of a material. An example of the thermal analysis in random conditions is demonstrated.     

Properties of CO2 copolymers with heterocyclic monomers

Basic properties of poly(propylene carbonate) and poly(propylene urethane) were estimated by means of additive methods. The properties estimated for the former polymer—an alternating CO²/propylene oxide copolymer—were compared with those determined experimentally. Properties of poly(styrene carbonate)—an alternating CO²/styrene oxide copolymer—were estimated and confronted with those of poly(4,4′-isopropylidene diphenylene carbonate) produced commercially.     

Simultaneous HDS and HDN over supported PtSn catalysts in comparison to commercial NiMo/Al2O3

The performance of platinum-tin catalysts, supported on Al₂O₃ and SiO₂ and subjected to reduction prior to use, has been studied. The catalysts were characterized in reduced forms by X-ray diffraction (XRD) and XPS. The surface properties were determined by N₂ BET specific surface area and CO chemisorption. The model compounds were 4,6-dimethyldibenzothiophene (4,6DMDBT) and carbazole. The PtSn catalysts supported on either Al₂O₃ or SiO₂ were characterised by high activity, but the catalyst PtSn/SiO₂ was found the most effective, even more effective than the commercial KF848 catalyst. Both PtSn catalysts studied were more effective in the reaction of 4,6DMDBT hydrogenation, the dominant product obtained with the use of PtSn/Al₂O₃ was methyl-cyclohexyltoluene (MCHT) and with PtSn/SiO₂ the dominant product was dimethylbicyclohexyl (DMBCH). The amount of dimethylbiphenyl (DMBPh) obtained was small and practically independent of the contact time. In the HDN reaction of carbazole the most active was PtSn/SiO₂. It was also more active in the consecutive reaction of isomerisation of the main product of the HDN reaction, bicyclohexyl (BCH) to methylcyclopentylcyclohexane (MCPCH). The large differences shown in the hydrotreating activity specially in the HDN reaction between PtSn catalysts supported on Al₂O₃ and SiO₂ result from the physicochemical properties of both samples. The significantly higher CO chemisorption for PtSn/SiO₂ indicates the presence of larger amount of metallic species and better hydrogenation properties so important for deep hydrotreating process.     

An effective 3-D inverse procedure to retrieve cooling conditions in an aluminium alloy continuous casting problem

The paper discusses a three-dimensional numerical solution of the inverse boundary problem for a continuous casting process of an aluminium alloy. Because verified information of heat flux distribution is crucial for a good mould design, effective cooling system and the whole caster in general, the main goal of the analysis presented within the paper is identifying of the heat fluxes along the external surface of the ingot. To model the solidification process, an enthalpy-porosity technique implemented in a commercial package was used. In this method, the phase change interface was determined based on the liquid fraction approach. In the inverse procedure, a sensitivity analysis was used to estimate the boundary condition retrieval. While the measured temperatures required to solve the problem are always burdened by measurement errors, a comparison of the measured and retrieved values showed a computational high accuracy. The average percentage error of the sensors was considerably lower than the maximum percentage error of the numerically simulated measurements. In addition, the computationally effective method was independent of the mesh size, the starting value of the assumed boundary condition and the maximum error of measurements used for calculations.     

Relaxation of stresses in polystyrene–carbon microcomposite resistive layers

This paper presents the investigation results on thermoresistive elements made with a styrene–butadiene–styrene (SBS) modified polystyrene binder and carbon filler. Resistive layers were deposited by screen-printing method onto a polyethylene terephthalate (PET) foil. The temperature–resistance dependence of the examined layers was observed. The carbon filler content was precisely selected to obtain high values of TCR, such as 70,000 ppm/°C, for resistive layers with a SBS-modified polystyrene binder in the temperature range from 24 to 100 °C. Because of high TCR the influence of mechanical stresses, which is unfavorable feature of the examined layers, may be omitted. The highest TCR value and stability of electrical parameters during operation were observed for layers containing 42.9% of carbon filler by mass content. The measurements were carried out with the aid of an infrared camera and an oscilloscope because of very fast changes of resistive elements parameters. The analysis of the obtained results allows to draw conclusions about the carbon layer properties and to determine the stress–relaxation rate of the polymer structures.