Abgasreinigung an Biomassekleinfeuerungsanlagen und experimentelle Untersuchungen zur Kombination von katalytischen und elektrostatischen Abgasreinigungsverfahren

Small‐scale furnaces for combustion of solid biomass can emit toxic or harmful gases and particulate matter. In this paper a representative selection of technologies for exhaust gas purification available on the market and in the development stage, respectively, is presented. Until now, no technology exists, which is able to reduce emissions of gaseous as well as solid pollutants from small‐scale combustion. The enquiry about the state of the art revealed that the combination of electrostatic precipitators with catalytic post‐combustion is a promising method. Results of experimental studies on such a combination are presented.     

Gasfluss‐Sputtern von Katalysatorschichten für Polymer‐Elektrolytmembran‐Brennstoffzellen

Gas flow sputtering (GFS) at increased pressures results in the formation of nanoscale particles of the sputtered material. This process has been evaluated regarding its applicability for synthesizing Pt catalysts for polymer electrolyte membrane fuel cells (PEMFCs). Catalyst layers of varying Pt‐loadings were deposited directly onto carbon fiber paper (gas diffusion layers, GDLs). Immediately after deposition, the catalytic activity of the resulting particulate deposits was tested by H₂‐oxidation at predefined ratios of H₂/O₂. The Pt deposits were subsequently evaluated regarding their applicability in a PEMFC environment.     

CO2‐Abtrennung für fossil befeuerte Kraftwerke

An overview of technologies for fossil fuel power plants with drastically reduced CO₂ emissions is given. Post combustion capture, Pre combustion capture, and Oxyfuel technology are introduced and compared. Current research results indicate that Post combustion capture may lead to slightly higher losses in power plant efficiency than the two other technologies. However, retrofitting of existing plants with Oxyfuel technology is complex and costly, and retrofitting of Pre combustion capture is not possible. On the other hand, Post combustion capture is suited for retrofitting. Based on the mature technology of reactive absorption, it can be implemented on a large scale in the near future. Therefore, Post combustion capture using reactive absorption is discussed here in some detail.     

Spillover‐bedingte Reichweite von aktivierten Sauerstoffatomen in der katalytischen Rußoxidation an Nanopartikel‐Schichtsystemen

The catalytic oxidation of carbon particles is an important process, e.g., in regeneration of diesel particulate filters. If the catalyst and the carbon particles are not in direct contact, a transportation step of the activated oxygen atoms (oxygen spillover) is needed. The distance of oxygen spillover in a nanoparticle layer system was studied. The system consisted of a platinum catalyst (20 μm thick) and a carbon (300 μm thick) layer that were separated by an inert SiO₂ layer with variable thickness. At moderate conversion (< 40 %), which occurs without substantial structural changes of the carbon particle layer, a distance of 160 μm was found. The spillover distance of the oxidizing species may be a starting point for the geometric design of more efficient impregnated catalytic particulate filters.     

Impuls‐, Wärme‐ und Stofftransport in Abgassensoren bei motorischen Betriebsbedingungen

Knowledge of all relevant parameters affecting function and load is a precondition for optimal engineering of exhaust gas sensors. Access to those parameters by measurement is difficult and often impossible. Thus the development of a validated model to simulate operating behaviour of exhaust gas sensor was the aim of this work. Coupling of a 1D‐engine simulation with a 3D‐CFD simulation is done to predict convective momentum, heat and mass transfer to the sensor surface. Being results from coupled simulations, transient boundary conditions are applied to a further 1D‐model to predict mass transfer inside the sensor. Signals of two exhaust gas sensors were simulated.