Katalysatoruntersuchungen an einer Technikumsanlage für Biomasse‐Kleinfeuerungen

In addition to the reduction of particulate matter, a catalytic supported emission reduction in small scale biomass combustion systems can also enable a conversion of toxic organic components into carbon dioxide and water. For catalyst investigations under practical conditions a special test facility was designed. The results show that products of incomplete combustion like carbon monoxide from stoves can be reduced by catalytic processes. Further developments and studies are necessary to achieve the targeted emission limits.     

Impedance spectroscopic investigations of zeolite-polydimethylsiloxane electrodes

Electrochemical impedance spectroscopy (EIS) was applied to study charge transfer and ion diffusion processes of all-solid-state ion-sensitive electrodes based on zeolite-polydimethylsiloxane (PDMS) membranes. In order to investigate the effects of zeolites embedded into a polymer matrix membranes with different types and contents of zeolites were characterised. On the basis of EIS studies, zeolites of the faujasite type were found most suitable for potentiometric determinations. This result can be attributed to the large pore size of 7.4 Å and a low Si/Al ratio. The differences in selectivity of potentiometric responses towards alkali metal cations and tetrabutylammonium cations were found to be reflected by differences in the bulk resistance of the membrane. The impedance behaviour of the zeolite-polymer electrodes was modelled by an appropriate equivalent electrical circuit.     

Effect of excess silicate on the structure formation and textural properties of MTS materials

The synthesis of micellar templated silica (MTS) materials has been conducted with different SiO₂/CTAB molar ratios for two different cetyltrimethylammoniumbromide (CTAB) concentrations of 0.02 and 0.07 M to examine the structure formation for cubic (SBA-1) as well as for hexagonal (SBA-3) surfactant arrangement in acidic reaction medium with increasing silicate excess. Reaction products were analyzed with X-ray diffraction, N₂ physisorption and TG-MS. It was found that an increase of the silicate concentration leads to the formation of additional silica gel in the resulting MTS material, which causes not only a decrease of specific surface area and pore volume, but also of the mesopore diameter. The latter effect is explained by a proposed embedding theory. Furthermore, with increasing silicate content in the synthesis mixture a phase transformation from hexagonal to cubic pore arrangement was found for the CTAB concentration of 0.07 M and the maximum SiO₂/CTAB molar ratio for ordered pore arrangement has been determined.     

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.     

Optimal and robust noncausal filter formulations

The paper describes an optimal minimum-variance noncausal filter or fixed-interval smoother. The optimal solution involves a cascade of a Kalman predictor and an adjoint Kalman predictor. A robust smoother involving H/sub /spl infin// predictors is also described. Filter asymptotes are developed for output estimation and input estimation problems which yield bounds on the spectrum of the estimation error. These bounds lead to a priori estimates for the scalar /spl gamma/ in the H/sub /spl infin// filter and smoother design. The results of simulation studies are presented, which demonstrate that optimal, robust, and extended Kalman smoothers can provide performance benefits.     

The use of fake algebraic Riccati equations for co-channel demodulation

This paper describes a method for nonlinear filtering based on an adaptive observer, which guarantees the local stability of the linearized error system. A fake algebraic Riccati equation is employed in the calculation of the filter gain. The design procedure attempts to produce a stable filter at the expense of optimality. This contrasts with the extended Kalman filter (EKF), which attempts to preserve optimality via its linearization procedure, at the expense of stability. A passivity approach is applied to deduce stability conditions for the filter error system. The performance is compared with an EKF for a co-channel frequency demodulation application.     

Untersuchungen zur adsorptiven Trennung von Glycerol/Propan-1,3-diol in wäßriger Lösung durch Flüssigphasen-Adsorption an Zeolithen

Investigations of Adsorptive Separation of Glycerol/Propane-1,3-diol in Aqueous Solution on Zeolites by Liquid Phase Adsorption The possibilities of adsorptive separation of propane-1,3-diol/water and glycerol/water mixtures on zeolitic adsorbents were studied in aqueous solution. The excess isotherms of both mixtures were determined on NaZSM-5 and on K⁺ and Ca²⁺ modified X and Y zeolites. The equilibrium constants of the examined mixtures and the theoretical mixture propane-1,3-diol/glycerol were calculated. The interactions of the three O atoms of glycerol with Ca²⁺ ions on Y zeolites led to the highest separation factor glycerol/propane-1,3-diol. Propan-1,3-diol is separable by NaZSM-5 zeolites.