FG Thermische Energietechnik
The present study investigates the fireside corrosion behavior of selected superheater materials, namely: T24, P92,
VM12-SHC, A800HT, and 7RE10 under oxy-coal combustion atmospheres. Data on mass change, scale thickness,
metal loss, surface morphology and micro-structural characteristics of corrosion products were obtained. The alloy
specimens were analyzed by SEM-EDX, light microscopy and X-Ray diffraction techniques. The results after
2000 hours of exposure at a metal surface temperature of 600 °C indicate that metal wastage increased with
decreasing Cr-content under oxy-coal conditions.
As power generation from variable renewable energy sources such as wind and solar power continues to increase in the future, fewer baseload power plants will be needed. As a result, high operational flexibility is becoming a vital requirement for conventional power plants to allow for the smooth integration of the variable renewable energy sources (v-RES) into the grid. To understand the impact of high operational flexibility (increased cycling) for coal-fired power plant materials, five commercial coal boiler superheater and reheater materials were investigated under isothermal and cyclic conditions for 1000 h each. The candidate alloys investigated were: T91, VM12-SHC, TP347-HFG, DMV304 HCu and DMV310 N. The results (weight change kinetics and metallographic analysis) after exposure at a metal surface temperature of 650 °C clearly showed the impact of increased flexibility on the corrosion and oxidation of the materials. Oxide growth (weight gain), metal loss, oxide spallation, and grain boundary attack were found to be more severe under cyclic conditions than under isothermal conditions.
District heating dynamic models arise as an alternative approach to in-situ experimental investigations. The main advantage of dynamic modeling and simulation is the possibility to avoid technical and operational risks that might occur during in-situ experimental investigations (e.g. heat demand is not met, damages in the energy systems etc.). Within this study, the authors present two models for an existing district heating system in Cottbus, Germany. One model is developed using the tool EBSILON Professional, while the other one is developed using the Simscape toolbox for physical modeling in Matlab/Simulink. The models were experimentally validated against measured data from the considered district heating system. The results show that the Simscape model has a better fit and better response than the EBSILON model. Yet, some discrepancies were found between the measured and the simulated data and, therefore, the uncertainties of the models were addressed. A comparative study between both tools is presented. The EBSILON models permit only unidirectional flow, whereas the Simscape toolbox permits reverse flow. Nevertheless, the EBSILON model outperforms the Simscape model in computation time. In addition, this study presents an approach for dynamic thermo-hydraulic modeling of district heating networks. This approach is utilized to examine the role of district heating networks as heat storage as an optimization configuration. The numerical results show less start-ups for additional heat sources. Yet, higher heat losses from the network are observed due to the installation of unburied pipelines.
Untersuchungen zum Korrosionsverhalten ausgewählter Werkstoffe bei verschiedenen Betriebsbedingungen
(2009)
Corrosion Processes and Carbonisation of Boiler Materials under Air and Oxyfuel Process Conditions
(2011)
Wasserstoff – Elektrolyse
(2015)
Druckelektrolyse zur Wasserstoffherstellung- eine Kurzübersicht zu energetischen Vor- und Nachteilen
(2015)
Investigation of oxyfuel combustion by numerical simulation with different turbulent flow models
(2009)
In diesem Beitrag wird ein Flammenbewertungsverfahren auf Basis eines Flammenwächtersignals vorgestellt. Mit zunehmender Flexibilisierung der Verbrennungsanlagen und der Absenkung von Emissionsgrenzwerten wird eine unmittelbare Flammenanalyse für die Regelung der Brennersysteme zunehmend erforderlich. Auf Basis eines Flammenwächtersignals wird mittels Frequenzanalyse ein ergänzendes Auswertungsverfahren dargestellt. Anhand der vorgestellten Untersuchungen an einem Erdgas-/Kohle-Kombibrenner wird die Qualifizierung der Prozessmesstechnik für die Flammenbewertung und Brennersteuerung überprüft. Die Ergebnisse im Erdgas- und Kohlebetrieb belegen, dass mit der erweiterten Signalanalyse eine Veränderung des Flammenverhaltens mit dem Flammenwächtersignal in Zusammenhang gebracht werden kann. Dabei konnte einmal das Emissionsverhalten bei verschiedenen Brennereinstellungen beurteilt werden und andererseits ein Zugriff auf das Stabilitätsverhalten der Kohleflamme ermöglicht werden. Durch die Analyse des Strahlungssignals der Chemilumineszenz des OH* bzw. CH*-Radikals ist ein Bezug zur Veränderung in der Reaktionszone hergestellt. Die entwickelte Bewertungsmethodik kann für die Entwicklung und Etablierung von Beobachter- und Regelmodellen von Brennersystemen genutzt werden.
Mit der steigenden Erzeugung volatilen Stroms aus erneuerbaren Energien werden die Anforderungen an die Flexibilität der konventionellen Kraftwerke erhöht. Der Einsatz von Stützfeuerungssystemen auf Basis von Trockenbraunkohle (TBK) ermöglicht die Erweiterung des Lastbereiches und der Lastgradienten am Dampferzeuger. Untersuchungen zum Teillastverhalten von TBK-Brennern wurden an der BTU Cottbus – Senftenberg an einem 400 kWth Verbrennungsversuchstand und an dem industriellen 30 MWth TBK-Staubbrenner der Firma BBS (Babcock Borsig Steinmüller GmbH) durchgeführt. Der verfügbare Einsatzbereich des Brenners ist maßgeblich von der Intensität den brennernahen Mischungsvorgang abhängig. Mit der Absenkung der Brennerleistung ist beispielsweise eine signifikante Steigerung der NOx-Emission verbunden. Dieser Effekt ist auf die Veränderung des brennernahen Strömungsprofiles zurückzuführen. Mit Maßnahmen wie der Erhöhung der Drallzahl, Verteilung der Luftimpulsströme und Veränderung des Primärimpulses konnte eine Stabilisierung und Intensivierung der Reaktionszone und somit eine Verbesserte des Teillastverhaltens nachgewiesen werden.
1.
CO2-freies Kraftwerk ab 2020
(2004)
The challenges in maintaining a stable oxy-coal flame have been reported in the open literature. In case of pulverized coal combustion, narrower flammable regimes arise not only of differences in the feed gas composition, but also due to changes in the flow dynamics because of reduced volume flow rate through the burners to match similar temperatures and radiative heat transfer within the furnace. The present work focuses on the study of flame structure and stability of pre-dried lignite fired by a staged feed-gas burner. Experimental runs were carried out in a 0.40 MWth laboratory facility, with the objective of investigating the effects of swirl strength and feed gas distribution in the burner registers. To assess the experimental data, a numerical study of the non-reacting flow in the near burner region is performed. Predicted flow pattern and flame images show that the primary fuel jet penetrates the internal recirculation zone, forming an annular doughnut reverse flow region for both firing conditions and resembling a type-1 flame pattern. Temperature measurements indicate that the feed gas distribution among the burner registers control the flame temperature in parallel with the swirl number in both air-fired and oxy-fired environments. The oxy-fuel cases exhibite markedly reduced temperatures on the flame axis. This difference in the core arises not just from the more pronounced penetration depth of the primary jet, but also due to reaction mechanisms including pyrolysis and gasification reactions at the higher concentrations of CO2 and water vapor. Flame stabilization is shown to be strongly dependent on an appropriate distribution of the feed gas and strength of swirling flow in the burner front. The results correlated in terms of swirl number, secondary/tertiary flow ratio and secondary/primary axial momentum point to similarities in the stability limits between air-firing and oxy-firing.
CCT & CCS Technologies
(2009)