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Breath and diet samples were collected from 29 taxa of animals at the Zurich and Basel Zoos to characterize the carbon isotope enrichment between breath and diet. Diet samples were measured for δ13C and breath samples for CH4/CO2 ratios and for the respired component of δ13C using the Keeling plot approach. Different digestive physiologies included coprophagous and non-coprophagous hindgut fermenters, and non-ruminant and ruminant foregut fermenters. Isotope enrichments from diet to breath were 0.8 ± 0.9‰, 3.5 ± 0.8‰, 2.3 ± 0.4‰, and 4.1 ± 1.0‰, respectively. CH4/CO2 ratios were strongly correlated with isotope enrichments for both hindgut and foregut digestive strategies, although CH4 production was not the sole reason for isotope enrichment. Average CH4/CO2 ratios per taxon ranged over several orders of magnitude from 10–5 to 10–1. The isotope enrichment values for diet-breath can be used to further estimate the isotope enrichment from diet-enamel because Passey et al. (2005b) found a nearly constant isotope enrichment for breath-enamel for diverse mammalian taxa. The understanding of isotope enrichment factors from diet to breath and diet to enamel will have important applications in the field of animal physiology, and possibly also for wildlife ecology and paleontology., Frontiers in Ecology and Evolution, 9, ISSN:2296-701X

To improve the economics and viability of accessing deep georesources, we propose a combined thermo–mechanical drilling (CTMD) method, employing a heat source to facilitate the mechanical removal of rock, with the aim of increasing drilling performance and thereby reducing the overall costs, especially for deep wells in hard rocks. In this work, we employ a novel experiment setup to investigate the main parameters of interest during the interaction of a cutter with the rock material, and we test untreated and thermally treated sandstone and granite, to understand the underlying rock removal mechanism and the resulting drilling performance improvements achievable with the new approach. We find that the rock removal process can be divided into three main regimes: first, a wear-dominated regime, followed by a compression-based progression of the tool at large penetrations, and a final tool fall-back regime for increasing scratch distances. We calculate the compressive rock strengths from our tests to validate the above regime hypothesis, and they are in good agreement with literature data, explaining the strength reduction after treatment of the material by extensive induced thermal cracking of the rock. We evaluate the new method’s drilling performance and confirm that thermal cracks in the rock can considerably enhance subsequent mechanical rock removal rates and related drilling performance by one order of magnitude in granite, while mainly reducing the wear rates of the cutting tools in sandstone., Geothermal Energy, 8 (1), ISSN:2195-9706

The reaction pathway of high-pressure CO2 hydrogenation over a Cu/ZnO/Al2O3 catalyst is investigated through the gradients of reactants/products concentration and catalyst temperature within the catalytic reactor. This study reveals that methanol is formed through direct CO2 hydrogenation at low temperature, while above 260 °C methanol formation is mediated via CO which is formed by reverse water–gas shift reaction., Catalysis Science & Technology, 10 (9), ISSN:2044-4753, ISSN:2044-4761

Liquid transport (continuous or segmented) in microfluidic platforms typically requires pumping devices or external fields working collaboratively with special fluid properties to enable fluid motion. Natural liquid adhesion on surfaces deters motion and promotes the possibility of liquid or surface contamination. Despite progress, significant advancements are needed before devices for passive liquid propulsion, without the input of external energy and unwanted contamination, become a reality in applications. Here we present an unexplored and facile approach based on the Laplace pressure imbalance, manifesting itself through targeted track texturing, driving passively droplet motion, while maintaining the limited contact of the Cassie–Baxter state on superhydrophobic surfaces. The track topography resembles out-of-plane, backgammon-board, slowly converging microridges decorated with nanotexturing. This design naturally deforms asymmetrically the menisci formed at the bottom of a droplet contacting such tracks and causes a Laplace pressure imbalance that drives droplet motion. We investigate this effect over a range of opening track angles and develop a model to explain and quantify the underlying mechanism of droplet self-propulsion. We further implement the developed topography for applications relevant to microfluidic platform functionalities. We demonstrate control of the rebound angle of vertically impacting droplets, achieve horizontal self-transport to distances up to 65 times the droplet diameter, show significant uphill motion against gravity, and illustrate a self-driven droplet-merging process., ACS Nano, 14 (10), ISSN:1936-0851, ISSN:1936-086X

Methyl formate synthesis by hydrogenation of carbon dioxide in the presence of methanol offers a promising path to valorize carbon dioxide. In this work, silica-supported silver nanoparticles are shown to be a significantly more active catalyst for the continuous methyl formate synthesis than the known gold and copper counterparts, and the origin of the unique reactivity of Ag is clarified. Transient in situ and operando vibrational spectroscopy and DFT calculations shed light on the reactive intermediates and reaction mechanisms: a key feature is the rapid formation of surface chemical species in equilibrium with adsorbed carbon dioxide. Such species is assigned to carbonic acid interacting with water/hydroxyls on silica and promoting the esterification of formic acid with adsorbed methanol at the perimeter sites of Ag on SiO2 to yield methyl formate. This study highlights the importance of employing combined methodologies to verify the location and nature of active sites and to uncover fundamental catalytic reaction steps taking place at metal–support interfaces., Journal of the American Chemical Society, 140 (24), ISSN:0002-7863, ISSN:1520-5126

We characterize shapes and volumes of droplets generated in PDMS T-junctions and assess the use of this type of microfluidic device to generate droplets suitable for the study of nucleation. Water droplets were formed in oil in a PDMS T-junction and subsequently stored. Droplet volume reproducibility and stability were investigated from acquired micrographs. By theoretically analyzing the influence of the mean volume of a population of droplets on the estimation of nucleation rates, we have shown that deviations in mean volumes can seriously affect the estimates, unless such deviation is smaller than 10%. This condition is fulfilled if experiments are repeated using the same microdevice. Measured droplet polydispersity remained low enough to treat the droplets as monodisperse. Immersing the microdevice in a water bath mitigates solvent evaporation, and allows for very accurate temperature control. Finally, a screening procedure was used to select the ideal operating conditions to obtain droplets with the desired sizes. Applying this method in devices with increasing T-junction cross sectional area, we have demonstrated a scaling-up of droplet volumes close to an order of magnitude while tuning the droplet shape, i.e., the average length to width ratio, at values between 1 and 1.2., Chemical Engineering Research and Design, 138, ISSN:0263-8762, ISSN:1744-3563

Background Steam explosion pretreatment has been examined in many studies for enhancing the enzymatic digestibility of lignocellulosic biomass and is currently the most common pretreatment method in commercial biorefineries. It is however not effective for overcoming the extremely high recalcitrance of softwood to biochemical conversion. Recent fundamental research in small-scale liquid hot water pretreatment has shown, though, that the addition of a carbocation scavenger like 2-naphthol can prevent lignin repolymerization and thus enhance the enzymatic digestibility of softwood cellulose. This work studies the technical application potential of this approach in a larger steam explosion pilot plant for surmounting softwood recalcitrance. Results The addition of 35.36 g 2-naphthol to the steam explosion pretreatment of 1.5 kg spruce wood chips allowed to considerably enhance the enzymatic cellulose digestibility. Different ways of adding the solid 2-naphthol to steam pretreatment were tested. Mixing with the biomass before pretreatment could enhance digestibility by up to 55% compared to control experiments. Impregnation of the biomass with 2-naphthol was yet more effective. Acetone and ethanol were tested to dissolve 2-naphthol and impregnate the biomass. The solvents were then removed again by evaporation before the pretreatment. The impregnation allowed to enhance digestibility by up to 179 and 192%, respectively. A comparison to prevalent acid-catalyzed steam explosion pretreatments for softwood revealed that the scavenger approach allows for obtaining exceptionally high yields in enzymatic hydrolysis. The biomass impregnation with 2-naphthol even renders a complete enzymatic cellulose conversion possible, which is remarkable for a softwood pretreatment not removing lignin. Steam pretreatment experiments without explosive decompression revealed that the enhancing effects of the explosion and the scavenger complement each other well. The explosion enhances the accessibility of the cellulose while the use of the scavenger reduces particularly the deactivation of enzymes. Conclusions This is the first study to show that a carbocation scavenger in steam pretreatment can enhance the enzymatic digestibility of lignocellulosic biomass. The approach opens up a novel possibility for overcoming the high softwood recalcitrance in a process that does not require an acid catalyst or the removal of lignin from the biomass., Biotechnology for Biofuels, 10, ISSN:1754-6834

The current work describes the measurement of emissivity of rock samples and black paint Pyromark 2500 within the temperature range between 230∘ C and 650∘ C together with its detailed uncertainty analysis. The infrared camera Optris PI450 was used to obtain the surface temperature of the samples. The described method is based on adjusting the emissivity of the rock sample until the temperature of the rock surface detected by the IR camera matches the temperature of a reference body. The reference body represented the tested rock sample partially coated with Pyromark 2500. The emissivity of the paint was previously determined with a technique described in this work: Pyromark 2500 was applied on a ceramic heater and heated up to a certain temperature that was calculated from measured electrical resistance of the ceramic heater (previously calibrated as a resistance thermometer). The emissivity measurement of rock samples is flexible concerning the type of sample, its size, position relative to the IR camera (distance, observation angle), and environmental conditions. Emissivities of Gotthard granite and Paradiso migmatite are reported, and they are in an agreement with emissivities of some granite samples from literature. The uncertainty of the rock sample emissivity reaches the value of 10% and the main contribution to it is related to the electrical resistance measurement of the ceramic heater., International journal of thermophysics, 37 (2), ISSN:0195-928X, ISSN:1572-9567

This study presents a modified autohydrolysis pretreatment which helps to overcome the recalcitrance of softwood for enzymatic hydrolysis of its cellulose. Autohydrolysis pretreatments of spruce wood were performed with 2-naphthol, which prevents lignin repolymerisation reactions, thereby increasing the enzymatic digestibility of cellulose by up to 64%. The negative influence of repolymerised lignin structures on enzymatic hydrolysis was confirmed by the addition of resorcinol in autohydrolysis, which is known to promote repolymerisation reactions and decreased the biomass digestibility. Several analyses were performed to study the underlying mechanism of this effect on hydrolysis, indicating that cellulolytic enzymes are adsorbed and deactivated especially by repolymerised lignin structures, which accounts for the high differences in biomass digestibility. It was shown that lignin repolymerisation significantly increases its specific surface area through modification of the lignin nanostructure, which is supposed to increase the unproductive binding of enzymes., Green Chemistry, 17 (6), ISSN:1463-9262, ISSN:1463-9270

Visualization of large complex networks has become an indispensable part of systems biology, where organisms need to be considered as one complex system. The visualization of the corresponding network is challenging due to the size and density of edges. In many cases, the use of standard visualization algorithms can lead to high running times and poorly readable visualizations due to many edge crossings. We suggest an approach that analyzes the structure of the graph first and then generates a new graph which contains specific semantic symbols for regular substructures like dense clusters. We propose a multilevel gamma-clustering layout visualization algorithm (MLGA) which proceeds in three subsequent steps: (i) a multilevel γ-clustering is used to identify the structure of the underlying network, (ii) the network is transformed to a tree, and (iii) finally, the resulting tree which shows the network structure is drawn using a variation of a force-directed algorithm. The algorithm has a potential to visualize very large networks because it uses modern clustering heuristics which are optimized for large graphs. Moreover, most of the edges are removed from the visual representation which allows keeping the overview over complex graphs with dense subgraphs., Advances in Bioinformatics, ISSN:1687-8035, ISSN:1687-8027

Chemical Engineering and Processing, 69, ISSN:0255-2701, ISSN:1873-3204

Experiments in Fluids, 43 (2-3), ISSN:0723-4864, ISSN:1432-1114

Background Steam explosion pretreatment has been examined in many studies for enhancing the enzymatic digestibility of lignocellulosic biomass and is currently the most common pretreatment method in commercial biorefineries. The information available about the effect of the explosive decompression on the biochemical conversion is, however, very limited, and no studies prove that the latter is actually enhanced by the explosion. Hence, it is of great value to discern between the effect of the explosion on the one hand and the steaming on the other hand, to identify their particular influences on enzymatic digestibility. Results The effect of the explosive decompression in the steam explosion pretreatment of spruce wood chips on their enzymatic cellulose digestibility was studied systematically. The explosion had a high influence on digestibility, improving it by up to 90 % compared to a steam pretreatment without explosion. Two factors were identified to be essentially responsible for the effect of the explosion on enzymatic digestibility: pretreatment severity and pressure difference of the explosion. A higher pretreatment severity can soften up and weaken the lignocellulose structure more, so that the explosion can better break up the biomass and decrease its particle size, which enhances its digestibility. In particular, increasing the pressure difference of the explosion leads to more defibration, a smaller particle size and a better digestibility. Though differences were found in the micro- and nanostructure of exploded and non-exploded biomass, the only influence of the explosion on digestibility was found to be the macroscopic particle size reduction. Steam explosion treatments with a high severity and a high pressure difference of the explosion lead to a comparatively high cellulose digestibility of the—typically very recalcitrant—softwood biomass. Conclusions This is the first study to show that explosion can enhance the enzymatic digestibility of lignocellulosic biomass. If the enhancing effect of the explosion is thoroughly exploited, even very recalcitrant biomass like softwood can be made enzymatically digestible., Biotechnology for Biofuels, 9, ISSN:1754-6834

The safe operation of a nuclear power plant (NPP) has the highest priority for the owning utility. Therefore, safety measures must be in place for the anticipation of different, sometimes very challenging or even severe, accident scenarios. As part of the installations to mitigate the consequences of severe accidents, filtered containment venting systems have been developed in the past and installed to protect the containment from integrity failure due to over pressurization after a core damage. The designs of nowadays filters rely either on dry filters (sand bed, metal fiber or zeolite filters) or wet scrubbers. In case of wet scrubbers, the efficiency for scrubbing contaminants from the gas stream is depending, among other parameters, on the hydrodynamic properties of the flow, chemical composition of the scrubber solution and additional internal structures for enhancement of the mixing. The removal of iodine species has not been an easy task for wet scrubbers so far. Several studies tried lately to link the removal efficiency of iodine to different quantities like gas injection velocity, bubble residence time and iodine concentration in the contaminated gas stream or gas temperature applied to different gas inlet nozzle designs. In the field of the soluble gas models, which are part of the models dealing with the retention of gaseous iodine variations, the available data set were rather scarce to validate the codes, which use those correlations. Furthermore, the tests conducted to benchmark these codes laid their focus on suppression pools, i.e. rather simple nozzles, and using a high share of steam where condensation is having a big impact on the flow field and trapping. In the bubble rising zone, the regime of a homogeneous bubble column is assumed to establish after the injection. In reality, especially for filtered containment venting systems, the high volumetric flow rates can lead to very heterogeneous and chaotic flow behavior that is not well captured by the existing models. The aim of this work was to characterize the established two-phase flow structure for two typical filtered containment venting system nozzles, i.e. a Venturi design and a simple converging nozzle with impaction plates combined with a bubble breaker. The main instrumentation utilized for this purpose were wire-mesh sensors in two different facilities, TRISTAN and ISOLDE, at the Paul Scherrer Institut. Furthermore, a new methodology for high-speed shadowgraphy was proposed and applied to measure droplet sizes inside the throat of self-priming Venturi nozzles. The adiabatic conditions and non-condensable gases, dry nitrogen or compressed air, were chosen on purpose to disentangle the very complex mechanisms of pool scrubbing and focus on the pure soluble gas diffusion. The measured droplet sizes and the corresponding Sauter mean diameter in the Venturi design suggest to rather focus on annular flow based correlations than common Venturi correlations from the chemical field due to the unique self-priming operation mode. In the pool, the heterogeneous flow fields that came forth in both nozzle designs at the most probable flow rates made a closer look at mass transfer phenomena necessary. Carbon dioxide was used as a substitute for inside a small-scale bubble column with 50 x 50 mm2 cross-section at ETH Zürich to investigate the effect of the flow structure on the mass transfer. For these tests, a new methodology for mass transfer experiments was developed, using wire-mesh sensors for both, two-phase flow structure characterization and measurement of the scrubbed gas concentration in the liquid. The results showed a high contribution from smaller bubbles in the mass transfer process whereas Taylor bubbles are not strongly participative. The new gained data on the spatio-temporal evolution of the concentration of the dissolved gas was used to extract mass transfer coefficients with the help of a one-dimensional code based on the continuous stirred tank and the axial dispersion model. The simultaneous measurement of mass transfer and interfacial area allowed to separate mass transfer coefficients from the interfacial area concentrations. The model could be further developed in the future with more experimental data especially at lower gas concentrations relevant to pool scrubbing and eventually molecular iodine tests.

The Diesel-ignited gas engine is a promising concept for reducing the emission of climate-damaging greenhouse gases from passenger cars. The reduction of CO2 emissions that becomes possible with this concept is a result of using an alternative fuel with increased efficiency. In the dual-fuel combustion process methane, as the primary fuel, is ignited by a small amount of Diesel. In addition to the dual-fuel combustion process, the Diesel-ignited gas engine can also be operated in pure Diesel combustion mode, like a conventional Diesel engine. While the operating strategies of conventional Diesel or gasoline engines are well known and optimized, the operation of the Diesel-ignited gas engine is still the subject of research. Specifically, the operation at low torque levels is demanding. The contradictory requirements of the two fuels lead to high raw emissions of unburnt methane. In addition, the removal of these raw emissions from the exhaust gas is difficult due to the low exhaust gas temperatures. The Diesel-ignited gas engine is thus not capable of covering low torque requirements using the dual-fuel combustion process, which is why only the transition to the conventional Diesel operation remains possible. The goal of this thesis is to describe the operational limits of the dual-fuel operation and to develop the essential operating strategies. For this purpose, the air path as well as the exhaust aftertreatment system is described by control-oriented models which are then used in numerical optimization methods. Finally, this thesis shows that the dual-fuel operation at low loads is only feasible with a dedicated control strategy that avoids the emission of unburnt methane at the tailpipe. The reaction heat originating from the conversion of carbon monoxide thereby plays an important role in the effective post-oxidation of the methane in the catalyst. Given the limited effectiveness of today’s catalyst, the stoichiometric operation, with its high raw emission of carbon monoxide, is the preferred dual-fuel strategy. For achieving torque levels beyond the operational limit of the dual-fuel combustion process, the transition to Diesel operation is crucial in terms of the practicability of this engine type. However, the transition between the combustion modes is a challenging task as various actuator settings, from both the fuel and air paths, change significantly during the transition. This thesis shows that only the optimal design of the oxygen concentration trajectories in the intake and exhaust manifolds yields a smooth transition with significant reductions of both the torque deviation and the emissions of pollutants.

Biofuels as a sustainable replacement for fuels derived from fossil resources have gathered increasing interest in the past years due to environmental concerns about fossil fuels and unstable oil supply. Lignocellulosic biomass like wood, energy crops or agricultural waste is the most abundant biological material on Earth and is considered as a potential source for sustainable biofuels. Intensive research is carried out on the biochemical conversion process, which consists of the enzyme-catalyzed hydrolysis of cellulose and hemicellulose into sugars and the fermentation of these sugars into the target product. Residual lignin is usually separated and burned for steam and power production but has also a great potential for the production of aromatic monomers. The complex entanglement of cellulose, hemicellulose and lignin makes a pretreatment necessary in order to obtain high yields of fermentable sugars in the subsequent enzymatic hydrolysis. Steam explosion will become most likely the dominating pretreatment technology due to its feedstock flexibility, its cost-savings potential and its comparatively low impact on the further bioprocessing. However, for very recalcitrant biomass, like softwood, steam explosion is not very effective and even after a pretreatment under severe conditions insufficient sugar yields are obtained in the subsequent hydrolysis. Preventing lignin repolymerization by adding a carbocation scavenger like 2-naphthol can significantly increase the enzymatic cellulose conversion in the subsequent hydrolysis. However, this process is still in its infancy and far from its industrial application. The effect of the explosive decompression and the presence of 2-naphthol during the pretreatment on different biomass feedstocks were investigated in order to gain further insight into the process and its application potential. The explosive decompression could significantly enhance the enzymatic cellulose digestibility of woody biomass by particle size reduction. Due to a less pronounced effect of particle size reduction in the pretreatment of herbaceous biomass (corn stover), only minor influences on the enzymatic hydrolysis could be observed. Hardwood (beech) and herbaceous biomass (corn stover) could not benefit from the presence of 2-naphthol during pretreatment as opposed to softwood (spruce). After a steam-pretreatment of beech wood with 2-naphthol even negative influences on the enzymatic digestibility could be observed. The investigation of substituted 2-naphthol molecules in the biomass structure by infraredspectroscopy suggests that 2-naphthol is not integrated into the lignin structure of hardwood. Nevertheless, fundamental investigations on lignin scavenger interactions remain necessary to find out why 2-naphthol only works with softwood. To obtain a homogeneous distribution of the almost non-water soluble 2-naphthol on the biomass, a dip-impregnation of the biomass is necessary. The requirement of large amounts of organic solvents has tremendous ecological and economical impacts on the process. In order to reduce or avoid organic solvents, different 2-naphthol addition methods were developed. Their impact on the enzymatic cellulose conversion and on the economy of the pretreatment process was evaluated. Sprayimpregnation could reduce solvent consumption by almost 90%, while obtaining identical glucose yields compared to a dip-impregnation procedure. Full cellulose conversion could be reached after a pretreatment at a severity of log R0=4.8 and an enzyme dosage of 30 FPU/g cellulose. With a suspension of 2-naphthol in water a cellulose conversion of 82% at a severity of log R0=4.8 and an enzyme dosage of 30 FPU/g cellulose could be reached and at the same time the use of organic solvents completely avoided. This is from an economic point of view the most feasible method, since no expensive solvent recycling is necessary. In order to prevent the degradation of hemicellulose, a two-stage 2- naphthol steam explosion pretreatment was investigated. In the first stage, the process conditions allow for optimal autocatalytic hydrolysis of hemicellulose. The hydrolysate containing the solubilized sugars was withdrawn from the reactor and the remaining solids were pretreated with 2-naphthol under process conditions which allow for high enzymatic cellulose conversion. The two-stage pretreatment could greatly enhance the recovery of hemicellulosic sugars from spruce wood and a maximal yield of 47.5% of hemicellulosic sugars could be reached at a pretreatment severity of log R0=3.75. However, the enzymatic cellulose conversion is reduced and the yield enhancing effect of 2-naphthol is less pronounced compared to a one-stage pretreatment. Therefore, the most likely reason is the high water content of the biomass after the first pretreatment stage, which could have reduced the pretreatment severity of the second pretreatment stage. In addition to influences of 2-naphthol on enzymatic hydrolysis, influences on fermentation were investigated. Therefore, the two-stage pretreated spruce wood was subjected to simultaneous saccharification and fermentation (SSF). SSF of the whole slurry from the second pretreatment stage and a cellulose concentration of 1% w/w, 90% ethanol yield could be reached with a 2-naphthol dosage of 0.205 mol/mol lignin C9-unit compared to a yield of 74% for the control without 2-naphthol. Experiments with higher solid loadings of 5% w/w revealed the inhibitory effect of residual 2-naphthol alone and snyergistically with 5- hydroxymethylfurfural (HMF), furfural, acetic acid. The higher the concentration of HMF, furfural and acetic acid, the lower were the concentrations of residual lignin that were tolerated by the yeast. Lastly, investigations of the molecular weight and the oxidation of the accruing softwood lignin were carried out in order to gain information on its structure and its valorization potential. The studies revealed that spruce which was pretreated with 2-naphthol has a higher extractability with organic solvents and a lower and more defined molecular weight. However, the acidic oxidation of lignin residues pretreated with 2-naphthol could not increase the yield of aromatic monomers. This thesis shows the limitations of the presence of 2-naphthol in the pretreatment of lignocellulosic biomass. It underlines the importance of using not only enzymatic hydrolysis but also fermentation for the evaluation of the pretreatment efficiency so as not to overlook inhibitory effects. The results achieved demonstrate that 2-naphthol can increase the enzymatic cellulose digestibility, but residual 2-naphthol can inhibit the subsequent fermenting yeast cells. Furthermore, it proves that a twostage pretreatment can significantly increase the overall sugar yield from spruce wood. It shows furthermore that the combination of a two-stage pretreatment with subsequent SSF can lead to remarkably high ethanol yields from softwood, even without the addition of 2-naphthol.

In the scope of Switzerland’s current energy turnaround, this work introduces geothermal well construction, local resources and techniques intended for underground heat mining. In this context flame-jet drilling, an established contactless drilling technique is substantially developed and technical solutions are demonstrated at the conditions prevailing in a well, several kilometers deep. To achieve this ambitious objective, custom sensors to ignite flames in an aqueous environment at conditions exceeding the critical pressure of water have been successfully developed, tested and patented. The dual functions of the igniter thermocouple allowing: (i) to ignite the flame in a particularly relevant manner and, (ii) to monitor combustion. This is essential to trigger the operation of the contactless drill remotely while minimizing intrinsic hazards. A novel confinement system to simulate the vertical stress downhole has been conceived, developed and tested on laboratory rock samples. The confinement system does not only allow to mimic the vertical stress at various depths, up to several kilometers, it is essential to drill in the laboratory. Using a specific finite element code written and tuned to analyze the development of thermal stresses in the rock probes, it is shown that thermal drilling techniques require less energy at depth because the natural stress is beneficial for the drilling process. Additionally, the finite element code contributes to the understanding of the mechanism driving the micro-scale processes induced by the thermal shock and to explain the reasons why igneous rocks are very sensitive to thermal stresses. As a definite proof that ETH Zurich has the knowledge and technical skills to drill hard rocks in a practically relevant manner, a large scale demonstration of the technology has been performed using a system specifically designed and constructed to drill pilot holes in the field. The demonstration proved that if spalls are removed rapidly from the surface, the propagation of the thermal front is essentially prevented (i.e. temperature gradients are limited to the spall thickness) and the thermal process sustained without any reduction in the rate of penetration. Qualitative relations between nozzle diameter, spall size and burner diameter, which are practically relevant to optimize the technique in the field have also been elucidated in this scope. In the end and in relation with the motivation of reducing well construction costs to promote the development of geothermal projects, two concepts to implement the technology in deep wells are presented and discussed. Based on an established costs distribution and an evaluation of the rock reduction costs, the impact of the technology is reviewed. It turns out that up to 39% of the rock reduction costs can be saved using the concepts presented and that most of the economy is achieved by limiting tripping and drilling time. Conversely due to the complex design of deep geothermal wells and the restrained number of wells per field - leading to perpetual exploration and significant unexpected costs - the extensive savings in rock reduction have a limited impact on the overall well and project costs, respectively 10% and 7%. Even though the technology may contribute to reduce costs, it will not result in a breakthrough for electricity production in Switzerland. The principal bottleneck remaining related to the construction of the underground heat exchanger, i.e. stimulation. The others being the intrinsic lack of temperature in the underground and unattractive specific investment. Besides the development related to a practical implementation of the technique, novel heat flux sensors have been developed in an attempt to characterize the flame-jets. To date, such sensors for high temperature, high pressure, high heat flux applications do not exist on the market opening up new possibilities in different fields.

In order to promote the development of geothermal energy production from deep resources, cost effective solutions to increase the drilling performance have to be developed. Currently, the drilling costs account for up to 70% of the total investment for a deep geothermal project. Besides the different attempts to intensify the conventional drilling process, several emerging technologies are currently investigated by researchers around the world. One of these alternative technologies is the spallation technology, which is based on the effect of hard, crystalline rocks disintegrating into small fragments, if rapidly heated by a hot fluid jet. Thermal spallation drilling has the benefits of high penetration rates in hard rock formations, an efficient energy transport to the bit and reduced wear-rates. Previous research has indicated that these benefits could lead to a decrease of the drilling costs and therewith to a boost in the development of geothermal energy production from deep resources. Even though, thermal spallation drilling is used since decades for hard rock excavation, no deep bore hole has been drilled with the technology, as some important questions remain still open. The presented thesis aims at closing these open questions and to demonstrate the application possibilities of thermal spallation drilling and its operational readiness. Thereby, the deeper understanding of the physics of the spallation process and their transfer to practical applications shall be an essential building block for the discussion about this technology. In order to assess the viability and the economical aspects of thermal spallation drilling without extensive full-scale experiments, a comprehensive modeling approach is required. This model has to be capable to predict the operating conditions of a thermal spallation drill head, which are required to drill a certain formation with a desired drilling velocity without any further calibration measurements. Only if such a model is available, an economical assessment of the technology, evaluating if thermal spallation drilling can reduce the drilling costs, is possible. Therefore, two interlinked models are presented. The first model is based on a linear fracture mechanical consideration and can be used to predict the operating conditions, which are required to drill a certain rock formation and to assess the spallability of rock formations. The second model is based on an analytical heat transfer approach and predicts the drilling velocity, which can be reached by using thermal spallation drilling, as a function of the drill head operating conditions and the prevailing rock formation. This model can also be used to design spallation drill heads with respect to the applied combustion reaction and the required jet velocities. After the introduction of the spallation model, opportunities and challenges for thermal spallation drilling in deep drilling operations are discussed. A case study is conducted, comparing the investments, which are required to drill an exemplary well with thermal spallation drilling and with conventional drilling methods. Therewith, it gives a perspective on the financial aspects of thermal spallation projects in great depths. Thereafter, the differences between laboratory experiments and drilling operations in deep bore holes are discussed. Finally, supply solutions for the reactive fluids, required to establish the flame-jet, are assessed and their applicability is investigated. The chapter closes with a recommendation of the application possibilities of thermal spallation drilling and with a discussion, which limitations restrict the use of this technology. In order so solve the revealed issues of stand-alone thermal spallation drilling, a combination of spallation drilling and mechanical drilling is investigated. The principles of such a combined drilling method are assessed together with its potential benefits. In order to demonstrate the general feasibility of a thermo-mechanical drilling system, a first feasibility study by means of thermal treatments is conducted and implementation possibilities are discussed. The applicability of this hybrid system is demonstrated in a full-scale hybrid drilling system, designed in cooperation with the Geothermal Center in Bochum (GZB). This system has a length of about 11m and a diameter of 140mm. The design aspects of the system are discussed and the drill head is tested in an laboratory environment. With these experiments, the feasibility of a combined system is shown and its potential impact on the enhancement of geothermal energy production is revealed. Additionally, a novel process is developed in this thesis, which utilizes thermal spallation drilling to enhance and enlarge the bore hole diameter in the reservoir section of the well. Thermal bore hole enlargement aims at removing near well bore impedances, enhancing the access to natural fractures and providing efficient fracture initiation points for hydraulic stimulation. Therewith, the developed technology has the potential to reduce the efforts of hydraulic stimulation and to increase the production rate of a well. The principles of this process are introduced and a process procedure is developed, which facilitates the application in deep bore holes. The operational readiness of the technology is shown in a field test conducted in the Grimsel Test Site. Two different enlargement geometries could be successfully drilling in a water-filled bore hole in a maximal depth of 13.8m. In summary, this thesis discusses the viability of thermal spallation drilling for deep drilling operations. Two major application possibilities are revealed: a combined thermo-mechanical drilling system for drilling deep wells in hard rock sections and thermal bore hole enlargement, to increase the diameter in the production zone of the well. For each of this two technologies a field test is conducted or prepared, demonstrating the operational readiness of the systems, which could be achieved during the progression of this project. Therewith, the thesis shows that thermal spallation drilling can contribute to the development of geothermal energy production from deep resources, as it can be used to enhance the drilling process and to increase the production rate.

In this thesis slug flow in microchannels was investigated experimentally and theoretically with the aim to provide design equations enabling construction of multistep microfluidic networks. Two major aspects were studied: pressure drop in channels of various geometries and subsequent phase separation of generated droplets. Mathematical modeling of phenomena observed on microscale was validated by extensive experimental studies. Pressure drop of three-phase gas-liquid-liquid slug flow was investigated in capillaries of round cross section. Pressure losses were modeled combining frictional and interfacial components using Hagen-Poiseuille ∆P model for laminar flow and expression based on work of Bretherton to account for the presence of bubbles and droplets in the flow. Developed model is free of empirical parameters and only droplet frequency needs to be known a priori in order to calculate pressure losses. Experimental validation was performed using oleic acid-water-nitrogen and heptane-water-nitrogen slug flow in Teflon or Radel-R capillaries. Proposed model allowed for prediction of pressure drop with 20% accuracy. During the experiments influence of surface roughness on pressure drop and occurence of dry slug flow were also analysed, both induced unexpected pressure losses which were rarely quantified before. Based on the three-phase flow study, a more complex problem of slug flow in square channels was analysed. Liquid-liquid slug flow of toluene-water and silicone oil-water was studied in channels fabricated in silicon/glass. The same modeling approach was adopted with respective frictional and interfacial pressure drop correlations modified to account for the polygonal channel geometry. No empirical parameters were necessary but both droplet frequency and velocity had to be measured experimentally to enable the pressure drop prediction. Two models, one taking into account the presence of moving liquid film around the droplets and the other assuming lack thereof, were developed and subsequently enabled analysis of the influence of the lubricating film on pressure drop. While both correlations performed well for flows with similar viscosities of both phases, large discrepancies were discovered for liquid flows with viscosity ratio significantly different from one. First attempt has been made to use pressure drop predictions to calculate droplet frequency however it was found that an accuracy of about 10 % in pressure loss estimation is necessary to allow reliable fd determination. Finally separation of liquid-liquid slug flow in so-called capillary phase separators was studied. In those devices, dispersed phase is prevented from exiting through the capillary outlets by the balance between the capillary pressure and the pressure drop across narrow side-channels. Operating limits of the device were modeled with Young-Laplace equation to describe the upper pressure limit; a new model was developed for the lower pressure limit, based on the changing length of the slug and thus varying number of available capillaries as the slug is withdrawn through the separator. Operating boundaries were determined experimentally by studying water-toluene slug flow in glass/silicon devices, five different geometries were tested. Calculated operating diagrams were compared with experiments and showed better performance than the models used in literature. Prediction of the operating limits of the separator fully independent of experimental data was made possible by applying a modified scaling law to predict droplet and slug lengths formed in a T-junction. Developed models constitute a theoretical framework to design a network of microfluidic channels where various process units such as reactors, extractors, mixers, etc. may be implemented. Correct prediction of pressure drop and of the operating region of a capillary phase separator enables integration of multiphase flows into such setup. Thus it is a step towards a realisation of a fully versatile microfluidic platform for the applications in flow chemistry.

The Chilled Ammonia Process enables the separation of CO2 from flue gas of large-scale, stationary CO2 emitters. Such capture of CO2 is a crucial step in CO2 Capture and Storage, a system of technologies that has the potential to reduce global CO2 emissions rapidly in order to mitigate climate change. In typical CO2 capture processes, the flue gas is contacted with a solution that has a high affinity to CO2. After loading the solution with CO2 in the absorption section of the process, the solvent is heated in the regeneration section and almost pure CO2 evaporates. In the case of the Chilled Ammonia Process, an aqueous ammonia solution is recycled between the absorption and the regeneration section. Ammonia and CO2 undergo a complex interaction in the aqueous phase, including a series of chemical reactions and at high concentrations also the formation of several different solid compounds. The formation of solids may lead to clogging of process equipment and it has been recognized as an important challenge for the controlled operation of the process. In this thesis, the thermodynamics of the CO2-NH3-H2O system was analyzed systematically with a focus on solid formation. Based on a detailed thermodynamic model, phase diagram tools were developed with the objective of supporting process development and optimization. The CO2 capture process was investigated and critical streams and unit operations that may be concerned with solid formation were identified based on an exemplary process simulation and on ranges of operating conditions typically reached according to the literature. Implications for process design and energy consumption are discussed and ternary phase diagrams mapping the composition regimes of solid formation and the typical operating conditions are presented. It is shown that the energetic optimization of the capture process pushes the composition of several process streams towards the solubility limit. In the following, a new ammonia-based process for CO2 capture from flue gas was developed, which utilizes the formation of solid ammonium bicarbonate to increase the CO2 concentration of the solution before the regeneration. Precipitation, separation, and dissolution of the solid phase are realized in a dedicated process section, while the packed absorption and regeneration columns remain free of solids. A rigorous performance assessment based on the integration of the capture process with a coal-fired power plant and on the specific primary energy consumption per CO2 avoided was implemented and the new process was compared to a standard Chilled Ammonia Process without solid formation in detail. An optimization algorithm was developed to screen a wide range of operating conditions in equilibrium-based process simulations. The new process shows a significant, i.e. greater than 10% reduction of the specific energy requirement. Favorable conditions under which the improvement would further increase are discussed. The further investigation of the new process requires a detailed design of the solid handling section based on rate-based process simulations. Due to a lack of growth data in the literature, the growth kinetics of ammonium bicarbonate was investigated experimentally. A setup has been developed that allows to measure the liquid composition in a pressurized batch-type reactor on-line. In addition, an injection system that enables the addition of seed crystals has been designed. Upon seeding of a supersaturated solution, the trend of the decreasing solute concentration with time was used to regress the growth rate parameters applying a population balance model. Besides the work on the Chilled Ammonia Process, this work provided an important contribution to the knowledge transfer from academia to the general public in the field of CO2 capture and storage. A physical model for the geological storage of CO2 was developed and built and successfully demonstrated at numerous exhibits and events.

Heterogeneously-catalysed hydrogenations represent key reactions for many industrial processes. In particular, selective hydrogenations of alkynes lie at the heart of pharmaceutical and fine chemicals industry for production of vitamins. These reactions are usually carried out in batch processes in the presence of supported palladium-based catalysts modified with the addition of lead. The presence of this toxic element strongly limits the sustainability of these processes. Furthermore, the need of energy savings led, in the past decade, to a growing interest in new technologies for Process Intensification. For the aforementioned reasons, new reactor solutions need to be further investigated in order to reduce the energy consumption and to establish safe and environment-friendly process solutions. This thesis contributes to the application and characterization of structured reactors for three-phase solvent-free continuous hydrogenation of alkynes. The proposed reactors consist of metal porous structures, with regular geometries, coated with a zinc oxide/alumina layer and impregnated with palladium nanoparticles. The performance of this structured catalyst, in terms of reaction selectivity and activity, is found to be higher than that of Lindlar catalyst. This consideration, associated with the stringent environ-mental regulations regarding the industrial use of lead, makes this material a valuable alternative to the commercial catalysts. Mathematical models are initially developed using a stirred slurry reactor with the aim of predicting the experimental behavior of the investigated reacting systems in the typical operating ranges of industrial processes. The knowledge acquired during these preliminary studies is transferred to the porous structured reactor operated firstly with recirculation of the process liquid and then in fully continuous mode. The kinetic and adsorption parameters governing the process are estimated in the kinetic regime by means of a numerical optimization procedure. The extension of the model to the mass transfer limited regime allows the estimation of an overall mass transfer coefficient under reacting conditions. The mathematical model is successfully validated, to confirm its reliability, using the results of additional experimental runs not included in the pool used during the optimization procedure. In this case the model is used to predict the experimental results without any further adjustment of the estimated parameters. This work enriches the understanding of three-phase selective hydrogenation of alkynes in designed structured reactors and proposes a mathematical model able to predict the performance of the experimental setup. The model is developed in a step-by-step process and can be used to simulate the intrinsic kinetics and the mass transfer phenomena of this class of reactions in designed structured reactors. These novel reactor concepts are applied for the first time in continuous operation showing potential for Process Intensification.