TY - GEN A1 - Aha, Ulrich A1 - Findeisen, Alexander A1 - Krautz, Hans Joachim T1 - Maintenance optimization for large coal-fired power plants Y1 - 2011 ER - TY - GEN A1 - Aha, Ulrich A1 - Findeisen, Alexander A1 - Krautz, Hans Joachim A1 - Kahlert, Joachim T1 - Korrosion und Instandhaltungsoptimierung CO2-armer Braunkohlekraftwerke unter geänderten Prozessbedingungen und -parametern Y1 - 2010 ER - TY - GEN A1 - Asegehegn, Teklay Weldeabzgi A1 - Schreiber, Matthias A1 - Krautz, Hans Joachim T1 - Investigation of bubble behavior in fluidized beds with and without immersed horizontal tubes using a digital image analysis technique Y1 - 2011 U6 - https://doi.org/http://dx.doi.org/10.1016/j.powtec.2011.03.025 ER - TY - GEN A1 - Asegehegn, Teklay Weldeabzgi A1 - Schreiber, Matthias A1 - Krautz, Hans Joachim T1 - Influence of two- and three-dimensional simulations on bubble behaviorin gas-solid fluidized beds with and without immersed horizontal tubes Y1 - 2012 U6 - https://doi.org/10.1016/j.powtec.2011.11.050 ER - TY - GEN A1 - Abang, Roger Atini A1 - Weiß, Sabine A1 - Krautz, Hans Joachim T1 - Impact of increased power plant cycling on the oxidation and corrosion of coal-fired superheater materials T2 - Fuel N2 - 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. KW - Power plant flexibility, Isothermal oxidation, Cyclic oxidation, High temperature corrosion, Superheaters Y1 - 2018 U6 - https://doi.org/10.1016/j.fuel.2018.02.047 SN - 0016-2361 VL - 2018 IS - 220 SP - 521 EP - 534 ER - TY - GEN A1 - Merzsch, Matthias A1 - Lechner, Stefan A1 - Krautz, Hans Joachim T1 - Heat-transfer from single horizontal tubes in fluidized beds: Influence of tube diameter, moisture and diameter-definition by Geldart C fines content T2 - Powder Technology Y1 - 2012 U6 - https://doi.org/10.1016/j.powtec.2012.12.002 SN - 1873-328X ER - TY - GEN A1 - Lechner, Stefan A1 - Merzsch, Matthias A1 - Krautz, Hans Joachim T1 - Heat-transfer from horizontal tube bundles into fluidized beds with Geldart A lignite particles T2 - Powder Technology N2 - This work investigates the heat transfer mechanism in fluidized beds equipped with horizontal heat exchanger surfaces such as single tubes and especially tube bundles. Previous works were performed for varying operating conditions and solids' material properties, leading to a heterogeneous and therefore not applicable spectrum of derived correlations for the influence of tube diameter and tube bundle geometry on heat transfer. Based on a wide range validation of the correlation for the influence of single tube diameter on heat transfer coefficient, tube bundles with different tube diameters and horizontal and vertical spacings and alignments were investigated. Experiments were carried out using electrical heat transfer probes in a 0.15 m2 fluidized bed test facility at ambient conditions. Geldart A lignite and Geldart D solids were used in order to distinguish between predominant particle-convective and gas-convective heat transfer mechanisms. The tube bundle reduction factor on heat transfer coefficient was derived as a key parameter based on dimensionless geometric numbers. This factor predicts the reduction of the heat transfer coefficient compared to that of the single tube due to the particle and gas flow disturbances caused by the immersed tubes. Tube diameter as well as tube bundle geometry were successfully implemented into useful correlations for predicting tube bundles' heat transfer of gas–solid fluidized bed systems operating with fine particles. KW - Fluidized bed KW - Lignite KW - Drying KW - Heat transfer KW - Horizontal tubes KW - Tube bundle Y1 - 2014 U6 - https://doi.org/10.1016/j.powtec.2013.10.041 IS - 253 SP - 14 EP - 21 ER - TY - GEN A1 - Horsfield, B. A1 - Scheck-Wenderoth, Magdalena A1 - Krautz, Hans Joachim A1 - Mutti, M. T1 - Geoenergy: From visions to solutions KW - CCS Y1 - 2010 U6 - https://doi.org/http://dx.doi.org/10.1016/j.chemer.2010.06.002 ER - TY - GEN A1 - Krautz, Hans Joachim A1 - Nimtz, Michael T1 - Flexible Operation of CCS Power Plants to Match Variable Renewable Energies T2 - Energy Procedia N2 - The German Energiewende is resulting in high grid load changes caused by renewable energies. Therefore flexibility of power plants is getting more and more important. Future CCS power plants are usually equipped with more components than conventional power plants, resulting in a more complex and inert reaction on changes in power output. Additionally, due to the change in price structures and higher fixed and operational costs for CCS power plants, it is harder for them to be economically efficient. This study will show different options to increase the flexibility of CCS power plants and evaluate their benefits. KW - CCS; Flexibility; Post combustion capture; Oxyfuel; Solvent storage; Pipeline Y1 - 2013 U6 - https://doi.org/10.1016/j.egypro.2013.08.034 SN - 1876-6102 VL - 2013 IS - 40 SP - 294 EP - 303 ER - TY - GEN A1 - Krautz, Hans Joachim A1 - Corrêa da Silva, Rodrigo A1 - Kangwanpongpan, Tanin T1 - Flame pattern, temperatures and stability limits of pulverized oxy-coal combustion T2 - Fuel : the science and technology of fuel and energy N2 - 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. KW - Oxy-fuel; Pulverized coal combustion; Flame pattern; Stability limits Y1 - 2014 U6 - https://doi.org/10.1016/j.fuel.2013.07.049 SN - 0016-2361 IS - Vol. 115 SP - 507 EP - 520 ER -