Auswahl der wissenschaftlichen Literatur zum Thema „Dry-FGR“

Salinity tolerance of five buffalograss [Buchloe dactyloides (Nutt.) Englem.] cultivars (Texoka, Cody, Bison, Sharp's Improved II, and Bowie) and three blue grama [Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths] ecotypes (‘Lovington’, ‘Hachita’, and ‘Bad River’) was determined during in vitro seed germination and vegetative growth in a hydroponic system. Seeds were germinated on 0.6% agar medium supplemented with NaCl at 0, 5, 10, 15, and 20 g·L−1. Salinity reduced the final germination rate (FGR) and daily germination rate (DGR). Similarly, shoot dry weight (SDW), longest root length (LRL), and percentage of green tissue (PGT) of mature grasses declined with increasing salinity levels (NaCl = 0, 2.5, 5, 7.5, and 10 g·L−1). However, root dry weight (RDW) was not significantly affected by salinity. Blue grama exhibited a lower reduction in FGR and DGR than buffalograss at salinity levels lower than 10 g·L−1. Germination of all buffalograss cultivars and ‘Hachita’ blue grama was inhibited at salinity levels of 15 and 20 g·L−1 NaCl. However, buffalograss was more salt-tolerant than blue grama at the vegetative growth stage. Variations of salinity tolerance were observed within buffalograss cultivars and blue grama ecotypes, especially during the seed germination stage. Overall, buffalograss appeared to be salt-sensitive during germination but moderately salt-tolerant at the mature stage. However, blue grama was more salt-tolerant at the germination stage than the mature stage. Noticeable differences in salinity tolerance were observed between different germplasms. Therefore, salt tolerance of buffalograss and blue grama may be improved through turfgrass breeding efforts.

This study was carried out to examine the effect of plant species on soil properties in the Falgore Game Reserve (FGR) in Kano State, Nigeria; with the aim to promote sustainable conservation and management of the game reserve and to encourage the use of multiple tree species on farmlands. Strata, systematic and random sampling techniques were employed in order to capture the variability of land cover. Composite samples of soil were randomly collected at a depth of 0-30cm from sample plots of 50 m × 50 m sizes at five points using soil auger. This experiment was replicated four times. The samples were thoroughly mixed and spread out on a dry floor to air dried under the roofed shade. The samples were packaged in polythene bags and taken to the biological science laboratory (Bayero University Kano, Nigeria) for preparation and analysis. The data collected were analyzed using descriptive statistics, ANOVA and Correlation at p< 0.05. Based on this finding, shrubs and tree species diversity were found to be inversely related to soil total Nitrogen, N, % O.C and soil pH (H2O). The nitrogen content of the soil sample was more stable compared with the carbon content across the strata in the study area. The results of this finding revealed that plants species diversity have different effects on soil properties of FGR. Thus, it is recommended that conservation and restoration of threatened plant species should be encouraged for soil amendment. For easy adoption of plant species on farmlands, farmers should be enlightened more on the effects and environmental functions of trees on farm land.

AbstractDuring dry storage, the oxidation of the spent fuel in case of cladding and container failure (accidental scenario) could be detrimental for further handling of the spent fuel rod and for the safety of the facilities. Depending on whether the uranium dioxide is under the form of powder or pellet, irradiated or unirradiated, the weight gain curves do not present the same shape. To account for these different behaviours, two models have been developed. Firstly, the oxidation of unirradiated powders has been modelled based on the coexistence, during the oxidation, of two intermediate products, U4O9 and U3O7. The comparison between the calculation and the literature data is good in terms of weight gain curves and chemical diffusion coefficient of oxygen within the two phases. Secondly, the oxidation of spent fuel fragments is approached by a convolution procedure between a grain oxidation model and an empirical parameter which represents the linear oxidation speed of grain boundary or an average distance able to cover the entire spent fuel fragment. This procedure of calculation allows in one hand to account for the incubation period noticed on unirradiated pellets or spent fuel and in another hand to link the empirical parameter to physical as porosity, cracks or linear power, or operational parameters such as fission gas release (FGR) respectively. A comparison of this new modelling with experimental data will be proposed.

Global energy demand is predicted to rise in the coming decades, necessitating a shift to renewable energy sources to mitigate greenhouse gas emissions. However, due to the inability to supply renewable energy around the clock, it is estimated that only by adding an important technology, carbon capture and storage (CCS), it could be possible to reduce 80% of the 1990s greenhouse gas emissions. CCS aims to reduce anthropogenic carbon emissions by capturing CO2 from flue gases, transporting, and permanently storing or reutilizing industrially. The CCS approach includes three technologies: post-combustion capture, pre-combustion capture, and oxyfuel combustion, with the latter being the emphasis of this thesis. Based on the case study of Mälarenergi’s Refused-derived waste-fired CHP plant, this thesis investigates the viability of converting existing non-fossil fueled CHP plants to oxyfuel combustion. A thorough technical investigation based on analyzing the impact of oxyfuel combustion on system performance was conducted through system modeling using a process simulator, Aspen plus. The model in this thesis considers the development of an air separation unit (ASU), a CHP plant, and a cryogenic CO2 purification unit (CPU). All of which are validated through calibration and comparison with real-world data and similar work. To investigate the influence of employing oxyfuel combustion on the generation of both heat and electricity, two different scenarios were comprised, including recirculating flue gas before and after flue gas condensation. In addition, an analysis of the oxygen purity was conducted to assess the most optimal parameters with the least impact on system performance. Moreover, a detailed eco- nomic assessment comprising the costs of integrating oxyfuel combustion was also conducted. The findings of this thesis show that integrating waste incineration CHP plants with oxyfuel combustion for CO2 capture entails promising features under the condition of 97% oxygen purity and a flue gas recirculation system taking place after flue gas condensation. This is owing to (i) modest imposed energy penalty of approximately 8.7%, (ii) high CO2 recovery ratio, around 92.4%, (iii) total investment cost of approximately 554 M$ during a 20-year lifetime, and (iv) cost of captured CO2 of around 76 $/ton. Aside from system modeling, this thesis pre- sents an overview of the current state-of-the-art technology on the different separation and capture mechanisms. It is important to highlight that the goal of this thesis is not to provide a comprehensive review but rather to present an overall picture of the maturity of the different mechanisms. The findings point to the cryogenic separation mechanism as the most mature technology for both oxygen production and capturing of CO2 during oxyfuel combustion.

An EV burner as installed in Alstom’s dry low NOx gas turbines was experimentally investigated under different Flue Gas Recirculation (FGR) and engine conditions. FGR enables the reduction of the high exhaust volume flow while significantly increasing the exhaust CO2 concentration. This may substantially improve the post-combustion capture of CO2. However, FGR introduces consequent changes in the gas turbine combustion process mainly because of the oxygen depletion and CO2 increase within the oxidizer. N2 and CO2 were mixed with air in order to obtain at the burner inlet a synthetic oxidizer mixture reproducing O2 and CO2 levels spanning different FGR levels of interest for engine operation. In addition, various degrees of unmixedness of the reactive mixture were investigated by varying the ratio of fuel injected at different port locations in the investigated burner set. Stable operation was achieved in all tested conditions. The lean premix flame shifts downstream when O2 is depleted due to the decrease of the reactivity, although it always stays well within the combustion chamber. The potential for NOx reduction when using FGR is demonstrated. Changes of the NOx formation mechanism are described and compared to the experimental data for validation. Unmixedness appears to be less detrimental to NOx emission when under high FGR ratio. However, CO emission is shown to increase when FGR ratio is increased. Meanwhile, with the present gas turbine combustor, the CO emission follows the equilibrium limit even at high FGR ratio. Interestingly, it is observed that when the burner inlet pressure is increased (and consequently the inlet burner temperature), the increase of CO emission due to FGR is lowered while the NOx emission stays at a very low level. This present an argument for using a higher cycle pressure in gas turbines optimized for FGR operation.

Abstract Over the past decades there has been a dramatic increase in natural gas burning as the benign fossil fuel, offering far lower emissions than oil or coal. Its place had been established in a clean, or at least, cleaner energy future. Today, the national and international energy policy has been shifted to carbon neutrality — achieving net zero carbon emissions — and as result has moved natural gas from the “benign” to the “menace” category At present, there are chiefly two alternatives for fuel carbon neutrality under discussion: power-to-gas (PtG) producing methane (or synthetic natural gas, SNG, hydrogen etc.) and power-to-liquid, which stores electric power in the form of methanol. In opposite to other synthetic or fossil fuels, like synthetic methane, NG or hydrogen, methanol burning leads to significant reductions in emissions of nitrogen oxides without any substantial firing system design change. Burning of synthetic methane or hydrogen requires significant effort for NOx reduction. Hydrogen as a fuel offers many advantages in power production. It is a carbon-free fuel that can decarbonize power and heat generation, and transportation, to help meet long-term CO2 emission-reduction targets. However, things are different for NOx emissions are a different matter. The more hydrogen is added to a NG, the higher the NOx is anticipated. Dry Low NOx (DLN) combustor has traditionally mixed NG with sufficient air upstream the combustor, so burning can take place in a lean atmosphere to maintain a relatively cool flame and thus keep NOx down. That approach does not work so well when more hydrogen enters the picture due to auto ignition occurring in the premix zone. Some companies already have diffusion-type combustor technology where fuel and air are supplied separately. Combustion of hydrogen, specifically in diffusion mode, implies combustion with a hotter flame, leading to higher combustion temperatures and the formation of local hot spots. These, in turn, can cause NOx to increase. The generalized solution is to cool the flame using diluents, such as demineralized water, steam or nitrogen. However, reducing NOx, by dilution reduces efficiency compared to a DLN combustor. Another option of providing wide load range of GT operation, while maintaining low NOx emissions is fuel dilution with flue gas being recirculated from the exhaust (FGR - Flue gas recirculation). The present paper discusses the effect of burning renewable fuels produced from carbon dioxide and hydrogen which are being diluted with a flow of FGR on GT performance and emissions reduction in diffusion combustors. For the prediction of the combustion behavior a methodology that combines experimental work and computational simulations was used. Given the fact that due to the increase in renewable energy introduction into the grid, addition of renewable fuel-based energy produced from carbon dioxide becomes very significant. Hence, the development of enhanced firing systems burning synthetic clean fuels with low emissions is challenging and should be promoted. Using renewable fuels for energy supply would reduce the unfavorable impact of CO2 and allow meeting the targets established in the Kyoto and Paris Protocols.