Search results for "kaasut"
showing 10 items of 63 documents
Modeling biomass char gasification kinetics for improving prediction of carbon conversion in a fluidized bed gasifier
2014
Gasification of biomass in a fluidized bed (FB) was modeled based on kinetic data obtained from previously conducted thermo- gravimetic analysis. The thermogravimetric analysis experiments were designed to closely resemble conditions in a real FB gasifier by using high sample heating rates, in situ devolatilization and gas atmospheres of H 2 O / H 2 and CO 2 / CO mixtures. Several char kinetic models were evaluated based on their ability to predict char conversion based on the thermogravimetric data. A modified version of the random pore model was shown to provide good fitting of the char reactivity and suitability for use in a reactor model. An updated FB reactor model which incorporates t…
Biotic oxidation of methane in landfills in boreal climatic conditions
2010
This study focused on the biotic oxidation of methane in landfill covers as a technology for reducing greenhouse gas emissions from landfills, particularly those located in the boreal climatic zone. First, methane oxidation was studied in laboratory batch assays in a landfill cover soil consisting of a composted mixture of sewage sludge and chemical sludge which had been installed on the landfill surface 4-5 years earlier. Second, methane oxidation was studied using mechanically-biologically treated municipal solid waste (MBT residual) as a material for methane-oxidizing landfill covers both in continuously methane-sparged laboratory columns and in an outdoor pilot lysimeter. Finally, meth…
Plasma response to amplitude modulation of the microwave power on a 14 GHz electron cyclotron resonance ion source
2018
This paper reports the effects of sinusoidal microwave power Amplitude Modulation (AM) on the performance of Electron Cyclotron Resonance (ECR) ion sources. The study was conducted on the 14 GHz ECR ion source ECR2 at the University of Jyväskylä. The klystron output was intentionally altered by a variable frequency sinusoidal amplitude modulation. The average microwave power 350 W was modulated between 530 W and 180 W from 0.011-25 kHz. The integrated x-ray energy, the mass analyzed beam current and the forward and reflected microwave power were measured. The energy integrated x-ray signal responded strongly with low frequency modulation and was no longer observable at approximately 2.2 kHz…
Microbial controls of greenhouse gas emissions from boreal lakes
2015
Vibrational Spectrum of HXeSH revisited : Combined computational and experimental study
2020
Vibrational spectrum of HXeSH embedded in low-temperature matrix is experimentally studied. To support the spectrum interpretation, anharmonic vibrational analysis is performed using different models and basis sets and the data is compared with previous experimental and theoretical analyses. Computations of overtones and combination modes allowed for new band assignments. The HXeSH molecule exhibits high anharmonicity similarly as other molecules from the noble-gas hydride family. Comparison of the employed computational methods shows once again that the modelling of the noble-gas compounds faces theoretical challenges to yield quantitatively reliable results. peerReviewed
Recent progress in metal-organic frameworks (MOFs) for CO2 capture at different pressures
2022
Global climate change ensued by the rise in atmospheric CO2 levels is one of the greatest challenges our planet is facing today. This worldwide distress demands technologies that can contribute to our society toward “negative carbon emissions”. Carbon capture and storage (CCS) technologies are in in important role for capturing CO2 from existing emission sources, such as industrial and energy production point sources, before new more prominent modifications to the energy infrastructure can be implemented. Recently, alongside point source capture, direct air capture (DAC) processes have emerged as highly sought-after technologies that are able to capture CO2 from the ambient air. Alongside t…
Navier-Stokes equations
2009
The emissions reduction potential of substituting short-haul flights with non-high-speed rail (NHSR) : The case of Finland
2021
Replacing short-haul flights with high-speed rail (HSR) has been widely discussed as one solution to mitigate the climate change impacts of aviation. However, although HSR can provide travel times similar to those provided by short-haul flights, and at lower emission levels, it also requires considerable investments in time and infrastructure to build. Instead, this study considers the feasibility of replacing short-haul flights with existing non-high-speed rail (NHSR). Our study is based in Finland, a country that has an extensive route network of short-haul flights but does not possess any HSR. We compared all 16 city pairs for which short-haul flights are offered with existing NHSR based…
Action-oriented knowledge for sustainable management of organic soils in Finnish agriculture
2023
Agriculture is a contributing force to climate change due to unsustainable changes in land use with the usage of peatlands for food production in Finland. The use of organic soils in food production is a complex and politically driven issue, thus multistakeholder and participatory approaches to policy development, implementation and evaluation are essential. This study is integrating qualitative and quantitative methods in an iterative process to produce action-oriented knowledge for supporting actions to sustainably manage peatlands and reduce the enormous greenhouse gas emissions from agricultural peatlands. This study has engaged inter-disciplinary researchers and transdisciplinary actor…