1. Methanol production via power-to-liquids : a comparative simulation of two pathways using green hydrogen and captured CO2David Tian Hren, Miloš Bogataj, Andreja Nemet, 2024, izvirni znanstveni članek Opis: Methanol is a versatile substance that can be used in combustion engines and fuel cells and as a feedstock for the production of various chemicals. However, the majority of methanol is currently produced from fossil fuels, which is not sustainable. The aim of this study was to analyze and evaluate the feasibility of methanol production from renewable sources as a bridge to a low-carbon economy and its potential as an alternative to fossil-derived chemicals. For this purpose, the process of methanol production from captured CO2 and water as an H2 source was simulated in Aspen Plus. For CO2 capture, the monoethanolamine (MEA) absorption process was assumed. The H2 required for methanol synthesis was obtained by alkaline water electrolysis using electricity from renewable sources. The captured CO2 and the produced H2 were then converted into methanol through the process of CO2 hydrogenation in two ways, direct and two-step synthesis. In the direct conversion, the hydrogenation of CO2 to methanol was carried out in a single step. In the two-step conversion, the CO2 was first partly converted to CO by the reverse water-gas shift (RWGS) reaction, and then the mixture of CO and CO2 was hydrogenated to methanol. The results show that direct synthesis has a higher methanol yield (0.331 kmol of methanol/kmol of H2 ) compared to two-step synthesis (0.326 kmol of methanol/kmol of H2 ). The direct synthesis produces 13.4 kmol of methanol/MW, while the two-step synthesis produces 11.2 kmol of methanol/MW. This difference amounts to 2.2 kmol of methanol/MW, which corresponds to a saving of 0.127 $/kmol of methanol. Besides the lesser energy requirements, the direct synthesis process also produces lower carbon emissions (22,728 kg/h) as compared to the two-step synthesis process (33,367 kg/h).
Ključne besede: power-to-X, Aspen Plus, methanol, CO2 capture, methanol production, water electrolysis
Objavljeno v DKUM: 12.02.2025; Ogledov: 0; Prenosov: 14
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2. Methodology for estimating the effect of traffic flow management on fuel consumption and CO2 production : a case study of Celje, SloveniaBorut Jereb, Ondrej Stopka, Tomáš Skrúcaný, 2021, izvirni znanstveni članek Opis: The manuscript discusses the investigation of vehicle flow in a predesignated junction byan appropriate traffic flow management with an effort to minimize fuel consumption, the productionof CO2, an essential greenhouse gas (hereinafter referred to as GHG), and related transport costs.The particular research study was undertaken in a frequented junction in the city of Celje, located in the eastern part of Slovenia. The results obtained summarize data on consumed fuel and produced CO2 amounts depending on the type of vehicle, traffic flow mixture, traffic light signal plan, andactual vehicle velocity. These values were calculated separately for three different conditions of traffic flow management. Amounts of fuel consumed were experimentally investigated in real traffic situations, whereas CO2 production was calculated by applying the actual European standardentitled EN 16258:2012 associated with a guideline for measuring emission values, as well as by examining specific traffic flow parameters. The key objective of the manuscript is to present multiple scenarios towards striving to minimize environmental impacts and improve transport operation's economic consequences when implementing proper traffic flow management. As for crucial findings, we quantified fuel consumption and CO2 emissions based on real data on the number and type of vehicles crossing the examined intersection and traffic light switching intervals. The results show that most of the CO2 was produced while waiting and in the accelerating phase in front of traffic lights, whereby in the running phase through the intersection, significantly less fuel was used. This study represents a mosaic fragment of research addressing endeavors to reduce CO2 production in urban transport. Following the experiments conducted, we can see a notable contribution towards reducing CO2 production with known and tested interventions in the existing transport infrastructure. A procedure embracing individual research steps may be deemed as an approach methodology dealing with traffic flow management with an aim to decrease the environmental and economic impacts oftraffic and transport operation; this is where the novelty of the research lies.
Ključne besede: traffic flow management, urban transport, CO2 production, greenhouse gas, fuel consumption, methodology, logistics, crossroads
Objavljeno v DKUM: 19.08.2024; Ogledov: 82; Prenosov: 12
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3. 3D-CO2-modelling for waste management in Styria/AustriaWolfgang Fischer, Danko Simic, 2016, izvirni znanstveni članek Opis: The paper in hand focuses on a calculation model which had been developed for calculating the CO2 production of a garbage truck during a waste collection tour. The challenge is the integration of not only the distance and loading weight but also the different petrol consumption and therefore CO2 production in regard to the topography of the whole collection tour. Additionally the increase of waste load at each stop during the whole collection tour has to be taken into account for the calculation.
The model has been developed on basis of Excel. In order to get the real data from the collection tours these had been accompanied. There not only the whole tour but also all waste bins and stops for loading the waste had been registered. Both GPS (Global Positioning System) and RFID (Radio-Frequency Identification) had been used. The huge amount of data had to be scrubbed. This process of amending or removing data in a database that is incorrect, incomplete, improperly formatted, or duplicated was an important step to have reliable data for further calculation processes.
The identification of the CO2 production during a waste collection tour including the topography and continuous revenue load had not been done so far and allows the identification of tour segments with lower but mainly higher or very high ecological impact. However, this is the basis for further discussions about options for optimizing the actual tours and habits of waste collection. That approach is part of a more comprehensive investigation of waste collection tours with general focus on economic, ecologic and social potentials for optimization.
Ključne besede: waste management, CO2 production of trucks, Styria, Austria
Objavljeno v DKUM: 17.04.2018; Ogledov: 1321; Prenosov: 108
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4. Enzymatic synthesis of isoamyl acetate with immobilized Candida antarctica lipase in supercritical carbon dioxideM.P. Romero, L. Calvo, C. Alba, Maja Leitgeb, Mateja Primožič, Željko Knez, 2005, izvirni znanstveni članek Opis: Isoamyl acetate was successfully synthesized from isoamyl alcohol in supercritical carbon dioxide by enzymatic catalysis. First, the impact of the acyl donor was investigated. Among several reactants, including acetic acid and two different acetates, acetic anhydride gave best yields. Then, two different immobilized lipases (Novozym 435 from Candida antarctica and Lipozyme RM-IM from Rhizomucor miehei) as biocatalysts for the above-mentionedreaction were compared. An esterification extent of 100% was obtained in continuous operation using acetic anhydride as acyl donor and Novozym 435 as enzyme. The amount of enzyme preparation was optimised to 6.25 g/mol alcohol. The effect of substrates load in the solvent was investigated. Operating at a CO2žsubstrates molar ratio below 7.0, the conversion of alcoholdecreased, probably due to an inhibitory effect on enzyme by high concentration of acetic anydride or by produced acetic acid. Pressure in the range of 8-30 MPa showed no effect on this reaction, while an increase in temperature (over 313 K) led to lower production of isoamyl acetate. Novozym 435 was very stable not finding any loss of activity during one month of continuous operation. Finally, carbon dioxide was compared to a conventional organic solvent (n-hexane). Initial reaction rate was higher in SC-CO2, although final esterification extent was similar in both media.
Ključne besede: chemical processing, high pressure technology, superkritical CO2, ester synthesis, isoamyl acetate, enzymatic catalysis, immobilized lipase, isoamyl acetate production, natural flavors
Objavljeno v DKUM: 01.06.2012; Ogledov: 2406; Prenosov: 355
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5. H2 separation and use in fuel cells and CO2 separation and reuse as a reactant in the existing methanol processAnita Kovač Kralj, Peter Glavič, 2007, izvirni znanstveni članek Opis: Fuel-cell efficiencies yield substantial reductions in the emissions of climate-change gases and promise an end to exclusive reliance on carbon fuels for energy. Fuel cells, CO2 reuse, process heat integration, and open gas turbine electricity cogeneration can be optimized simultaneously, using a nonlinear programming (NLP) algorithm. The simplified NLP model contains equations of structural and parametric optimization. This NLP model is used tooptimize complex and energy-intensive continuous processes. This procedure does not guarantee a global cost optimum, but it does lead to good, perhaps near-optimum, designs. The plant, which produces methanol, has a surplus of hydrogen (H2) and CO2 flow rates in purge gas. H2 is separated from the purge gas by an existing pressure swing adsorption (PSA) column. Pure H2 can be usedas fuel in fuel cells. CO2 can be separated from the outlet stream (purge gas) by a membrane or absorption system (absorber and regenerator) or an adsorption system and reused as a reactant in a reactor system. Therefore, theproduct yield can be increased and CO2 emissions can be reduced, simultaneously. CO2 emissions can then be reduced at the source. The retrofitted process can be operated within existing parameters. Using a methanol process as a case study, the CO2 emission flow rate can be reduced by4800 t/a. The additional electricity cogeneration in the gas turbine and in fuel cells and additional flow rates of the raw material could generate an additional profit of 2.54 MEUR/a.
Ključne besede: chemical processing, methanol production, optimization, nonlinear programming, CO2 reuse, fuel cells, heat integration, energy cogeneration
Objavljeno v DKUM: 31.05.2012; Ogledov: 2763; Prenosov: 129
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6. CO2 separation from purge gas and flue gas in the methanol process, using NLP model optimizationAnita Kovač Kralj, Peter Glavič, 2007, izvirni znanstveni članek Opis: The concentration of CO2 in the atmosphere has to be stabilized, requiring a reduction in current emission rates in existing plants. This will be done by reducing the environmental burden imposed in such areas as materials input andCO2 emission reduction and using cleaner production, resources, and energy recycling. Any opportunities for emission reduction and CO2 reuse largely depend on existing plant and energy systems. CO2 can be separated from the outlet stream (purge gas) and from flue gas by a membrane or absorption system(absorber and regenerator) or adsorption system and reused as a reactantin a reactor system. Therefore, product yield can be increased and CO2emissions reduced, simultaneously. CO2 emissions can be reduced at the source. The authors of this paper studied CO2 reuse in a methanol process, in which electricity can be generated using an open gas turbine, followed by a separator. Simultaneous optimization of a process structure and its parametersusing simplified nonlinear programming (NLP) ensures an additional annual profit, influenced by reusing the flow rate of CO2. The additional electricity cogeneration and additional flow rates of the raw material could generate an additional profit of 2.79 MEUR/a.
Ključne besede: chemical processing, methanol production, optimization, nonlinear programming, CO2 emissions, CO2 reuse
Objavljeno v DKUM: 31.05.2012; Ogledov: 2261; Prenosov: 99
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