| 1. |
- Alevanau, Aliaksandr, 1965-
(author)
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Study of pyrolysis and gasification of biomass from the self-organization perspective
- 2015
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Doctoral thesis (other academic/artistic)abstract
- This thesis focuses on the analysis of kinetics of i) low-temperature pyrolysis of gaseous hydrocarbons, ii) high-temperature steam gasification of char of wood pellets (>700oC), iii) high temperature pyrolysis of straw pellets in an atmosphere of argon and steam, and iv) high temperature pyrolysis of slices of transversally cut wooden sticks. The results of the kinetic measurements in the high-temperature cases are approximated using a least-square based optimization software, which was specially developed to analyse kinetics prone for deviation from the Arrhenius law.In the thesis a general analysis of the researched materials and kinetics of their pyrolysis and gasification is presented from the self-organization perspective. The energy transfer phenomena in both the pyrolysis and gasification processes of biomass are discussed with an emphasis on an analysis of basic phenomena involving the self-organized dynamics on fractal structures in the chosen biomass samples.
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| 2. |
- Jagodzińska, Katarzyna, 1990-
(author)
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Energy and material recovery from high-ash waste through pyrolysis
- 2021
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Doctoral thesis (other academic/artistic)abstract
- Undoubtedly, the past practices of profit maximisation by all means, which fuelled swift industrialisation and urbanisation, left behind a legacy of non-sanitary old landfills polluting the environment. These, together with active landfills supplied with tremendous streams of waste produced annually, are a loose cannon calling for action. Specifically, this action is the transition to resource- and energy-efficient economy model – the so-called circular economy.The circular economy approach includes the closing of material loops by both: i) the recycling of pre- and post-consumer residues and ii) the mining of existing landfills, treated as material stocks. Following this, the possibility of energy and material recovery from two types of high-ash waste was investigated within this thesis. The first type of waste is a fine residue from the shredding of the mixture of industrial and municipal metallic waste with end-of-life vehicles (the so-called 'shredder fines'), which represents the aforementioned pre-and post-consumer residues. The second type of waste is excavated waste from an old landfill, and its recovery falls within the latter way of closing the material loops mentioned above.For the purpose of energy and material recovery, the aforementioned waste was subjected to thermochemical processes, namely pyrolysis and pyrolysis with in-line catalytic decomposition of the produced pyrovapours (volatile pyrolysis products). This thesis consists of four studies on that matter.The research within this thesis started with the characterisation of excavated waste fractions to preliminarily assess their potential further applications. The fractions are characterised by significant contamination with heavy metals (mainly Hg and Pb) and chlorine. Furthermore, they are characterised by highly heterogeneous compositions, reflected in a high complexity of the formed pyrovapours. However, in order to maximise the fractions' utilisation ratio, their collective pyrolysis in the form of refuse-derived fuel (RDF) was proposed for further studies.Following the above, the second study performed within the thesis aimed at the characterisation of the products from excavated RDF pyrolysis. The pyrovapours obtained at 500°C and 600°C showed potential for further catalytic upgrading to higher-quality products. Given the above, a study on the in-line catalytic decomposition of the pyrovapours from excavated RDF pyrolysis was performed. The process was aimed at the production of a H2-rich gas along with carbon nanotubes (CNTs). The study investigated the influence of the catalyst composition, its synthesis method, and catalytic bed temperature on the H2 and CNTs yields. Eventually, the bimetallic Fe-Ni/Al2O3 catalyst prepared using the sol-gel method showed the best performance as it tripled the H2 conversion rate (in comparison to the case without using a catalyst) and yielded 76 mg/gsample_daf CNTs of promising characteristics. Nevertheless, further research on this process is necessary to optimise it and to assess its feasibility subsequently.The final study included in the thesis focused on enhancing metals recovery from shredder fines by subjecting them to torrefaction (low-temperature pyrolysis). The process results in partial decomposition of the so-called 'fluff' (textiles fibres with plastic, wood and rubber particles in which metal particles are entangled), which interferes with the sorting techniques. Therefore, torrefaction seems to be a promising way of liberating metal particles from shredder fines so that metals can be recycled.
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| 3. |
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| 4. |
- Kasimagwa, Ismail
(author)
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A study of slag corrosion of oxides and oxide-carbon refractories during steel refining
- 2010
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Licentiate thesis (other academic/artistic)abstract
- The use of ceramic material as refractories in the manufacturing industry is a common practice worldwide. During usage, for example in the production of steel, these materials do experience severe working conditions including high temperatures, low pressures and corrosive environments. This results in lowered service lives and high consumptions of these materials. This, in turn, affects the productivity of the whole steel plant and thereby the cost. In order to investigate how the service life can be improved, studies have been carried out for refractories used in the inner lining of the steel ladles. More specifically, from the slag zone, where the corrosion is most severe. By combining thermodynamic simulations, plant trails and post-mortem studies of the refractories after service, vital information about the behaviour of the slagline refractories during steel refining and the causes of the accelerated wear in this ladle area has been achieved. The results from these studies show that the wear of the slagline refractories of the ladle is initiated at the preheating station, through reduction-oxidation reactions. The degree of the decarburization process is mostly dependent on the preheating fuel or the environment. For refractories without antioxidants, refractory decarburization is slower when coal gas is used in ladle preheating than when a mixture of oil and air is used. In addition, ladle preheating of the refractories without antioxidants leads to direct wear of the slagline refractories. This is due to the total loss of the matrix strength, which results in a sand-like product. Thermal chemical changes that take place in the slagline refractories are due to the MgO-C reaction as well as the formation of liquid phases from impurity oxides. In addition, the decrease in the system pressure during steel refining makes the MgO-C reaction take place at the steel refining temperatures. This reduces the refractory’s resistance to corrosion. This is a serious problem for both the magnesia-carbon and dolomite-carbon refractories. The studies of the reactions between the slagline refractories and the different slag compositions showed that slags rich in iron oxide lead mostly to the oxidation of carbon/graphite in the carbon-containing refractories. This leads to an increased porosity and wettability and therefore an enhanced penetration of slag into the refractory structure. If the slag contains high contents of alumina and or silica (such as the steel refining slag), reactions between the slag components and the dolomite-carbon refractory are promoted. This leads to the formation of low-temperature melting phases such as calcium-aluminates and silicates. The state of these reaction products during steel refining leads to an accelerated wear of the dolomite-carbon refractory. The main products of the reactions between the magnesia-carbon refractory and the steel refining slag are MgAl2O4 spinels, and calcium-aluminates, and silicates. Due to the good refractory properties of MgAl2O4 spinels, the slag corrosion resistance of the magnesiacarbon refractory is promoted.
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| 5. |
- Liu, Hailong, et al.
(author)
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A study of influencing factors on the particle concentration and deposition in a model room with a coupled drift flux and Eulerian deposition model
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Other publication (other academic/artistic)abstract
- The drift flux model coupled with a unified Eulerian deposition model is presented and used to discuss how it is possible to improve the understanding of the particle transport behavior in indoor environments. The validation of the model itself is achieved by a good agreement with published experimental data. A series of simulation cases have been conducted to illustrate the influential factors (particle size and density, wall roughness, release location and duration, flow obstacle) for particle concentration-distributions and depositions. The results show that the uniformity of the concentration distribution decreases as the particle size increases from submicron (0.01 and 0.1 µm) to micron (1 -10 µm), as well as when the particle density increases from 700 to 5600 kg/m3. Also, the well-mixed assumptions seem adequate for particles with a diameter smaller than 2 µm for the studied cases. Two parameters, namely, the deposited amount and deposition fraction are introduced to illustrate the deposition effect on micro sized particles. The results indicate that the deposition effect become more predominant for particles with a diameter greater than 2 µm. In view of the particle deposition, sub-micron particles are more sensitive to the variation of surface materials (wall roughness) than micron particles. For an internal source in the room, where a release over a long duration is considered, the particle dispersion is strongly related to the release location. However, this is not the case for a short release time. By studying a simple case consisting of a room with a table, it is obvious that obstacles or furnished settings bring a complicated situation for the particle dispersion and deposition. Therefore, specific simulations are needed for each real indoor environment.
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| 6. |
- Yang, Hanmin, 1992-, et al.
(author)
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Carbon-negative valorization of biomass waste into affordable green hydrogen and battery anodes
- 2023
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In: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487.
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Journal article (other academic/artistic)abstract
- The global Sustainable Development Goals highlight the necessity for affordable and clean energy, designated as SDG7. A sustainable and feasible biorefinery concept is proposed for the carbon-negative utilization of biomass waste for affordable H2 and battery anode material production. Specifically, an innovative tandem biocarbon + NiAlO + biocarbon catalyst strategy is constructed to realize a complete reforming of biomass pyro-vapors into H2+CO (as a mixture). The solid residues from pyrolysis are upgraded into high-quality hard carbon (HCs), demonstrating potential as sodium ion battery (SIBs) anodes. The product, HC-1600-6h, exhibited great electrochemical performance when employed as (SIBs) anodes (full cell: 263 Wh/kg with ICE of 89%). Ultimately, a comprehensive process is designed, simulated, and evaluated. The process yields 75 kg H2, 169 kg HCs, and 891 kg captured CO2 per ton of biomass achieving approx. 100% carbon and hydrogen utilization efficiencies. A life cycle assessment estimates a biomass valorization process with negative-emissions (−0.81 kg CO2/kg-biomass, reliant on Sweden wind electricity). A techno-economic assessment forecasts a notably profitable process capable of co-producing affordable H2 and hard carbon battery anodes. The payback period of the process is projected to fall within two years, assuming reference prices of 13.7 €/kg for HCs and 5 €/kg for H2. The process contributes to a novel business paradigm for sustainable and commercially viable biorefinery process, achieving carbon-negative valorization of biomass waste into affordable energy and materials.
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| 7. |
- Zhang, Zhi, 1982-
(author)
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A study of flow fields during filling of a sampler
- 2009
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Licentiate thesis (other academic/artistic)abstract
- More and more attention has been paid to decreasing the number and size of non-metallic inclusions existing in the final products recently in steel industries. Therefore, more efforts have been made to monitor the inclusions' size distributions during the metallurgy process, especially at the secondary steelmaking period. A liquid sampling procedure is one of the commonly applied methods that monitoring the inclusion size distribution in ladles, for example, during the secondary steelmaking. Here, a crucial point is that the steel sampler should be filled and solidified without changing the inclusion characteristics that exist at steel making temperatures. In order to preserve the original size and distributions in the extracted samples, it is important to avoid their collisions and coagulations inside samplers during filling. Therefore, one of the first steps to investigate is the flow pattern inside samplers during filling in order to obtain a more in-depth knowledge of the sampling process to make sure that the influence is minimized. The main objective of this work is to fundamentally study the above mentioned sampler filling process. A production sampler employed in the industries has been scaled-up according to the similarity of Froude Number in the experimental study. A Particle Image Velocimetry (PIV) was used to capture the flow field and calculate the velocity vectors during the entire experiment. Also, a mathematical model has been developed to have an in-depth investigate of the flow pattern in side the sampler during its filling. Two different turbulence models were applied in the numerical study, the realizable k-ε model and Wilcox k-ω model. The predictions were compared to experimental results obtained by the PIV measurements. Furthermore, it was illustrated that there is a fairly good agreement between the measurements obtained by PIV and calculations predicted by the Wilcox k-ω model. Thus, it is concluded that the Wilcox k-ω model can be used in the future to predict the filling of steel samplers.
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| 8. |
- Svantesson, Jonas, 1994-, et al.
(author)
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Effect of Froude Number on Submerged Gas Blowing Characteristics
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Other publication (other academic/artistic)abstract
- The submerged gas jet generated by a plasma generator is an important part of the IronArc processwhere it is used to provide the heat for melting, inject reducing compounds to the melt, and forstirring of the reactor. Therefore, accurate predictions of the gas plume from the plasma generatorare required to enable process control. Submerged gas side-blowing with high temperature gas andlarge density differences between superheated gas and liquid slag as is present in the IronArcprocess has not been studied previously to the authors knowledge. The flow behavior of gas in a compressible and incompressible system was investigated at an ambient temperature in the water-air system, and at a high temperature in the IronArc system. The simulation results were compared to verifying experiments in the water-air system and established empirical equations to predict the penetration length. The simulations in the air-water system were found to replicate the experimental behavior using both the incompressible and compressible models with only small deviations of 7-8 %. However, at higher temperatures as is present in theIronArc system the compressible simulations were required to replicate the varying density in the injected gas as it changes temperature when in contact with the liquid. It was found that there is a soft lower requirement for the Froude number of the gas blowing to produce a jetting behavior and allow accurate prediction of the penetration length by the empiricalequation. For gas blowing below the required Froude number the gas will form large pulsating bubbles instead of a steady jet, which makes the empirical equation severely underpredict the penetration length. The large pulsating bubbles also expand backwards from the inlet and may cause back-attack on the refractory wall.The lower limit for the Froude number was found to be approximately 300 for the studied IronArc system, at this point the empirical equation is quite accurate but the flow is still partly unstable. It was also found that the Froude number limit is system dependent and may be based on the density ratio between gas and liquid or the viscosity of the liquid. The amplitude of the pulsing for gasblowing below the Froude number limit is also expected to be dependent on the bath height and the density ratio. For submerged blowing applications it is important to ensure sufficiently high Froude numbers of the gas blowing if the gas penetration length is to be stable as a jet and predictable by the empirical equation.
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| 9. |
- Wen, Yuming, 1994-
(author)
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Towards a Sustainable Biomass and Waste Refinery Based on Pyrolysis Combined with a Pretreatment Process
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Some of the naturally accumulated biomass and the massive production of waste by human activities have caused serious environmental problems. The degradation of biomass and waste is one of the main greenhouse gasses (GHG) emission sources. Pyrolysis is a technique that can convert the organic feedstock into char, bio-oil, and gas at 350 - 800 °C and in the absence of oxygen. The diversity of the pyro-products makes pyrolysis one of the most promising techniques for biomass and waste refineries. One of the main challenges of the technique is that the unfavorable physical and/or chemical properties of the feedstock would increase the energy and cost required for the whole refinery process. Combining feedstock pretreatment with a pyro-refinery has the potential to make the entire process more efficient from a cost, energy, and climate perspective. In this thesis, the performance of the peat moss pyrolysis is firstly investigated. It was found that it has a potential to convert peat moss into fuels through pyrolysis. Thereafter, beach-cast seaweed is further considered as a feedstock for the process, which is a high-ash content biomass. Three refinery processes were designed and simulated based on the pyrolysis results. Results showed that it was necessary to have a washing pretreatment for the beach-cast seaweed pyro-refinery. The implementation of washing pretreatment could decrease the direct energy for the whole process from 1485.8 to 1121.0 MJ for treating one ton of dry beach-cast seaweed. The further life cycle assessment (LCA) analysis showed that using the pyro-refinery process with washing pretreatment to treat one ton of dry beach-cast seaweed for the electricity production had the lowest cumulated energy demand (CED). Specifically, it has a value of -3.0 GJ and the lowest global warming potential within a 100-year time frame (GWP100) with a value of -790.9 kg CO2eq compared to the other scenarios of producing liquid biofuel and syngas. Digestate from anaerobic digestion (AD) requires proper treatment. The third work of this thesis compares the pyrolysis behavior of the organic fraction of municipal solid waste (OFMSW) and its digestate. It was found that the AD process could decrease the pyrolytic activation energy of OFMSW. Due to digestate’s higher ash content, the char yield rate of digestate was higher than that of OFMSW. On the other hand, the yield rates of bio-oil and gas of OFMSW pyrolysis were higher than that of its digestate. The moisture content of the digestate is hard to be removed by traditional mechanical dewatering techniques due to digestate’s hydrophilic properties. Thus, the use of a pretreatment combined with hydrothermal carbonization (HTC) and mechanical dewatering has the potential to contribute to the digestate pyro-refinery. In the last work, the effect of HTC on the kinetics and thermodynamics of the agricultural waste digestate (AWD) pyrolysis was investigated. It was revealed that the HTC pretreatment could decrease the pyrolytic activation energy of AWD from 182.9 - 274.4 kJ/mol to 144.6 - 205.2 kJ/mol. Bench-scale pyrolysis experiments, process simulations, and LCA were then conducted based on the kinetic prediction results. In the process simulations and LCA, four scenarios of AWD refinery with different pretreatment combinations with HTC and mechanical dewatering were designed. It was found that the different pretreatment processes could benefit the designed AWD refinery for different targets. The implementation of both HTC and mechanical dewatering pretreatment for refinery based on a 650 °C-pyrolysis presented the lowest CED value of 10.3 GJ for treating one ton of AWD. The least emission of carbon dioxide equivalents (-843.3 kg) was achieved in the case of using a 650 °C-pyrolysis temperature with the pretreatment with only a dewatering process when treating 1-ton dry AWD.
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| 10. |
- Zhang, Zhi, 1982-
(author)
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On the Study of a Liquid Steel Sampling Process
- 2010
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Doctoral thesis (other academic/artistic)abstract
- The liquid steel sampling method is one of the commonly used procedures in monitoring the steelmaking process. Besides it can be used for analyzing the dissolved alloys, hydrogen content and oxygen content, it can be also employed to monitor the inclusion characteristics at the steelmakings. Here, a crucial point is that the steel sampler should be filled and the metal solidifies without changing the inclusion characteristics. Therefore, the objective of this work is to fundamentally understand the liquid steel sampling process by means of analyzing and modeling the two-phase flow during the sampler filling process, and verifying the mathematical model by using the experimental data. The present dissertation presents an experimental and theoretical study of the filling process of both the lollipop-shaped sampler and the rectangular-shaped sampler. Firstly, a physical modeling by using a water model has been carried out to fundamentally investigate the flow pattern inside the sampler vessels during its filling. The flow patterns were obtained by a PIV system. Then, a mathematical model has been built to theoretically understand the phenomena. The commercial CFD code was used. Here, different turbulence model have been compared between the realizable k-ε turbulence model and Wilcox k-ω turbulence model. It concludes that the Wilcox k-ω turbulence model agrees well with the PIV measurements.HH Thus, the preferred it was further employed to predict the turbulent flow inside the production lollipop-shaped sampler fillings. It is important to find that the average collision volume in the production steel sampler without solidification at filling is about 30 times higher than that in a ladle furnace. In the end, the whole sampling system was modeled. The initial solidification during the filling was taken into account. Focus was on the influence of the initial solidification on the inclusion concentrations. A discrete phase model was used to simulate the movement of inclusions in the liquid steel. Some selected different sized primary inclusions that exist in the ladles at a steelmaking process were simulated. The same method of studying the filling procedure of the lollipop-shaped sampler was further applied to comprehensively investigate the rectangular-shaped sampler.
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