京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19740号 / 工博第4195号 / 新制||工||1647(附属図書館) / 32776 / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 阿部 竜, 教授 陰山 洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

A study of how Svensk Plaståervinning i Motala AB (SPÅ) can use intermodal transports to work towards their goal of CO2 reduction. The study shows a quantitaive reduction in CO2 emissions compared to road transports. / <p>Examensarbetet är utfört vid Institutionen för teknik och naturvetenskap (ITN) vid Tekniska fakulteten, Linköpings universitet</p>

<p>Current industrial practice in the steel Industry involves the use of natural gas with high methane content as a primary energy source. Natural combustion produces greenhouse gases, and with the continued focus on managing and reducing harmful emissions from industrial processes, there is a need for research into alternative sources of energy. Among several alternatives that have been studied is hydrogen: a non-carbon-based fuel. This work uses a coupled computational fluid dynamics (CFD)-finite element analysis (FEA) combustion model to investigate hydrogen utilization as a fuel in a reheat furnace and how it impacts the quality of the steel produced by understanding the three dimensional (3D) flow behavior, furnace temperature profile, thermal stress distribution, heat flux, formation of iron oxides, emission gases and mode of heat transfer onto the steel slabs. The modeling process integrates the five different zones of a pusher type reheating furnace (top and bottom) and modeled using Ansys Fluent 2020R1 and Ansys Workbench 2022R1. Changes in these parameters are determined by comparison to a baseline case that uses methane as fuel and maintaining the same heat input in terms of chemical energy into the furnace. Global mechanism was used for hydrogen and two step mechanism was used for methane combustion. Results revealed a 2.6% increase in average temperature to 1478K across the furnace for hydrogen which resulted in 6.45% increase in maximum heat flux into the slabs. Similar flue gas flow patterns were seen for both cases and heat transfer mode from the combustion gases to the slabs was primarily by radiation (~97%) for both methane and hydrogen. 11.5% increase in iron oxide formation on the slab was recorded for the hydrogen case, however, the bulk of the iron oxide formed was more of wüstites which are the easiest form of iron oxide to descale. However, elevated nitrogen oxide (NOx) levels were recorded for hydrogen combustion which led to further study into NOx mitigation techniques. Application of the staged combustion method using hydrogen fuel showed potentials for NOx reduction. The use of regenerative burners further conserved exergy losses in hydrogen fuel application. Insignificant deviation from base case thermal stress distribution and zero carbon emission from the hydrogen case indicates the usability of hydrogen as an alternative fuel in reheating furnace operations. </p>

A major contribution to global warming is CO2 emitted from the combustion of fossil fuels. Electrochemical processes can help to mitigate the elevated CO2 emissions through either the conversion of CO2 into value-added chemicals or the replacement of fossil fuels with clean fuels such as hydrogen produced from water oxidation. The present dissertation focuses on the mechanistic aspects of electrochemical processes. Electrochemical water oxidation is hindered by the low efficiency of oxygen evolution reaction (OER) at the anode whereas electrochemical reduction of CO2 (ERCO2) is hampered by high overpotentials and poor product selectivity. In this dissertation, we studied the catalytic activity of transition metal-based catalysts, including FeNi spinels, metal-oxide/copper, and d metal cyclam complexes, for both OER and ERCO2 using the density functional theory (DFT) computational approach.We report a combined effort of fabricating FeNi oxide catalysts and identifying the active component of the catalyst for OER. Our collaborators at the University of California, Santa Cruze fabricated a series of FeNi spinels-based materials including Ni(OH)Fe2O4(Cl), Ni(OH)Fe2O4, Fe(OH)Fe2O4(Cl), Fe(OH)Fe2O4, Ni(OH)O(Cl), Ni(OH)O and some show exceptional activity for OER. Combined experimental characterization and computational mechanistic study based on the computational hydrogen electrode (CHE) model revealed that Ni(OH)Fe2O4(Cl) is the active ensemble for exceptional OER performance. We also investigated CO2 reduction to C1 products at the metal-oxide/copper interfaces ((MO)4/Cu(100), M = Fe, Co and Ni) based on the CHE model. The effect of tuning metal-oxide/copper interfaces on product selectivity and limiting potential was clearly demonstrated. This study showed that the catalyst/electrode interface and solvent can be regulated to optimize product selectivity and lower the limiting potential for ERCO2. Applied potential affects the stability of species on the surface of the electrode. The proton-coupled electron transfer (PCET) equilibrium assumed in the CHE model does not capture the change in free energy under the influence of the applied potential. In contrast, the constant electrode potential (CEP) model captures changes in free energy due to applied potential, we applied the CEP model to ERCO2 and OER on (MO)4/Cu(100) and compared the results with those from the CHE model. The results demonstrate that the CHE and the CEP models predict different limiting potentials and product selectivity for ERCO2, but they predict similar limiting potentials for OER. The results demonstrate the importance of accounting for the applied potential effect in the study of more complex multi-step electrochemical processes. We also studied transition metal-based homogeneous catalysts for ERCO2. We examined the performance of transition metal(M) - cyclam(L) complexes as molecular catalysts for the reduction of CO2 to HCOO- and CO, focusing on the effect of changing the metal ions in cyclam on product selectivity (either HCOO- or CO), limiting potential and competitive hydrogen evolution reaction. Our results show that among the complexes, [LNi]2+ and [LPd]2+ can catalyze CO2 reduction to CO, and [LMo]2+ and [LW]3+ can reduce CO2 to HCOO-. Notably, [LMo]2+, [LW]3+, [LW]2+ and [LCo]2+ have a limiting potential less negative than -1.6 V and are based on earth-abundant elements, making them attractive for practical application. In summary, the dissertation demonstrates high-performance catalysts can be designed from earth-abundant transition metals for electrochemical processes that would alleviate the high CO2 level in the environment. On the other hand, completely reversing the increasing trend of CO2 level in the atmosphere requires a collective human effort.

No description available.

Excessive CO2 emissions can negatively impact society and our planet. Reduction of CO2 is one potential avenue for its abatement. One of the most significant challenges to reducing CO2 is its extremely stable linear form. Experimentally, Cu/TiO2 has shown promise for CO2 photocatalytic reduction. Dispersed atomic catalysts can achieve high catalytic efficiency on a per atom basis. Active sites also typically having lower coordination number, and therefore may be more reactive. Using density functional theory and experimental techniques, we have investigated the role of surface oxygen vacancies (Ov) and photoexcited electrons on supported single atom catalysts and CO2 reduction. Cu atoms with Ov have shown to aid in the process of bent, anionic CO2 formation. In the first step involving CO2 dissociation (CO2* --> CO* + O*), a single Cu atom in Ov lowered the activation barrier to 0.10 - 0.19 eV, which could enable fast reduction of CO2 even at room temperature, in agreement with experimental findings. A photoexcited electron model was shown to readily promote Cu binding to the surface vacancy, and CO2 adsorption and direct dissociation. Finally, we briefly compare our results to calculations of supported single Pt atoms to determine how metals besides Cu may behave as photocatalysts for CO2 reduction, and we found a single Pt with Ov can promote CO2 dissociation. Our results show that tailoring TiO2 surfaces with defects in conjunction with atomic catalysts may lead to useful catalysts in the photoreduction of CO2.

The risk for climate change is a growing concern for theglobal society. According to what is known as the Kyoto Protocol,developed countries have committed themselves to reduce theirgreenhouse gas (GHG) emissions. The purpose of this thesis hasbeen to analyse opportunities for CO2 reductions in Swedish pulpand paper mills. The pulp and paper industry accounts forsignificant shares of the Swedish utilisationof both electricityand, in particular, biomass fuels. In this thesis, it has been agoal to focus not only on the technical potential of alternativesfor CO2 reductions in the energy systems of pulp and paper mills,but also on analysing the costeffectiveness of the studiedmeasures. Moreover, the analysis has covered questions concerningthe capacity and willingness among the actors involved with thepulp and paper mills’energy systems to realise CO2reduction potentials. A broad techno-economical evaluation of available technologiesfor increased power production as well as more efficient energyutilisation is carried out. Furthermore, a more indepth analysisof pulp mill-based biomass energy with CO2 removal and permanentsequestration (BECS) is presented. An evaluation is made of thepotential for pulp and paper production with a negative CO2balance through the implementation of BECS. In recent yearsoutside suppliers, mainly energy service companies (ESCOs), havebegun to operate energy facilities in some Swedish pulp and papermills. Based on interviews with managers from pulp and papercompanies and ESCOs, the main driving forces behind theincreasing co-operation as well as the opportunities and riskswith energy related co-operation are presented. Furthermore, the technical possibility of carbon-negativitythrough the implementation of BECS is discussed in relation tocarbon management on both corporate and global levels. The extentto which CO2-reducing measures in pulp and paper mills arerealised will have an impact on Sweden’s capacity to reachCO2 reduction targets. Whether or not technologies for CO2capture and sequestration are developed and implemented inSwedish pulp mills has a very large impact on the size ofSweden’s long-term CO2 reduction potential. Moreover, thedevelopment of business and competence focus in pulp and papercompanies and ESCOs suggests that cooperation will become ofincreasing importance for future sustainable industrial energymanagement. <b>Keywords:</b>CO2 reduction, pulp and paper industry, energysystem, biomass, CO2 capture and sequestration, black liquor,gasification, power production, outsourcing, sustainable energymanagement

The increased concentration of greenhouse gases in theatmosphere, in particular CO2, is changing the Earth’s climate. Accordingto the Kyoto protocol, where the international community agreedon binding emission targets, developed countries are committedto reduce their greenhouse gas emissions. The increased use ofbiomass in energy systems is an important strategy to reduce CO2emissions. The purpose of this thesis has been toanalyse the opportunities for Sweden to further reduce CO2emissions in the energy system, by rationallyutilising woody biomass energy. The characteristics of currentcommercially operating biofuel-based CHP plants in Sweden aresurveyed and systematically presented. A consistent andtransparent comprehensive reference base for system comparisonsis given. Furthermore, the fuel effectiveness and contributionto CO2reduction is calculated. The governmentalsubsidies of the CHP plants’investment, expressed as costof specific CO2reduction, appears to be low. The competitiveness of biomass-fuelled energy production inrelation to fossil-based production with carbon capture isanalysed, showing that the biomass-fuelled systems provide acompetitive option, in terms of cost of electricity andefficiencies. The remaining Swedish woody biofuel potential ofat least 100 PJ/yr is principally available in regions with abiomass surplus. Transportation is therefore required to enableits utilisation in a further national and international market.Refining the biofuel feedstock to pellets, or even furtherrefining to motor fuels (DME, methanol or ethanol) or power,could facilitate this transport. Different options for fuelrefining are studied and compared. The entire fuel chain, fromfuel feedstock to end users, is considered and CO2emissions are quantified. Substituting fuelpellets for coal appears to be the most costeffectivealternative and shows the largest CO2reduction per energy unit biofuel. Motor fuelsappear more costly and give about half the CO2reduction. Transportation of the upgraded biofuelpellets is highly feasible from CO2emissions point of view and does not constitute ahindrance for further utilisation, i.e. the pellets can betransported over long distances efficiently with only limitedemissions of CO2. Bioenergy utilisation has additional features forenvironmental improvement, apart from the CO2aspect. Waste heat from biofuel-based CHP can becost-effectively used in conjunction with sewage treatment. Theincoming sewage water to the nitrification process can bepreheated with the waste heat, and thereby substantiallyenhance the nitrification and the reduction of ammoniumnitrogen during the winter season. <b>Keywords:</b>CO2reduction, energy system, biofuel, CHP, refining,fuel pellets, ethanol, methanol, DME, fuel substitution, sewagewater, nitrification.

The objective of this thesis is to investigate the photocatalytic activity in nanosized TiO2 structures. Two different structures were used for two different reaction systems. In the first part of the study, TiO2 coated on glass beads by a sol-gel procedure were used to test the photocatalytic CO2 reduction reaction with H2O and H2 in the gas phase. The results of photocatalytic CO2 reduction reaction revealed that CO2 reduction step of the overall reaction proceeds in dark / while illumination is required for water splitting reaction. In the second part of the study, Photocatalytic oxidation activity of the commercial TiO2 powders mixed with grout and plaster were studied for a potential commercial self cleaning material. A method based on gas phase benzene oxidation was developed for testing TiO2 added cement based self cleaning surfaces. This method was used to screen 15 commercial TiO2 samples with and without cement. Based on this method a commercial TiO2 sample (S9) was selected for further use. Surface of 15 commercial TiO2 samples were characterized by using NO and CO2 as probe molecules. Photocatalytic benzene oxidation experiments showed that using TiO2 on the surface lead to more effective surfaces in terms of photocatalytic activity. TiO2 was bound to surface by inorganic materials without much activity loss. This kind of amount optimization is of commercial importance.

<p>The risk for climate change is a growing concern for theglobal society. According to what is known as the Kyoto Protocol,developed countries have committed themselves to reduce theirgreenhouse gas (GHG) emissions. The purpose of this thesis hasbeen to analyse opportunities for CO2 reductions in Swedish pulpand paper mills. The pulp and paper industry accounts forsignificant shares of the Swedish utilisationof both electricityand, in particular, biomass fuels. In this thesis, it has been agoal to focus not only on the technical potential of alternativesfor CO2 reductions in the energy systems of pulp and paper mills,but also on analysing the costeffectiveness of the studiedmeasures. Moreover, the analysis has covered questions concerningthe capacity and willingness among the actors involved with thepulp and paper mills’energy systems to realise CO2reduction potentials.</p><p>A broad techno-economical evaluation of available technologiesfor increased power production as well as more efficient energyutilisation is carried out. Furthermore, a more indepth analysisof pulp mill-based biomass energy with CO2 removal and permanentsequestration (BECS) is presented. An evaluation is made of thepotential for pulp and paper production with a negative CO2balance through the implementation of BECS. In recent yearsoutside suppliers, mainly energy service companies (ESCOs), havebegun to operate energy facilities in some Swedish pulp and papermills. Based on interviews with managers from pulp and papercompanies and ESCOs, the main driving forces behind theincreasing co-operation as well as the opportunities and riskswith energy related co-operation are presented.</p><p>Furthermore, the technical possibility of carbon-negativitythrough the implementation of BECS is discussed in relation tocarbon management on both corporate and global levels. The extentto which CO2-reducing measures in pulp and paper mills arerealised will have an impact on Sweden’s capacity to reachCO2 reduction targets. Whether or not technologies for CO2capture and sequestration are developed and implemented inSwedish pulp mills has a very large impact on the size ofSweden’s long-term CO2 reduction potential. Moreover, thedevelopment of business and competence focus in pulp and papercompanies and ESCOs suggests that cooperation will become ofincreasing importance for future sustainable industrial energymanagement.</p><p><b>Keywords:</b>CO2 reduction, pulp and paper industry, energysystem, biomass, CO2 capture and sequestration, black liquor,gasification, power production, outsourcing, sustainable energymanagement</p>