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Ex situliver machine perfusion at subnormothermic/normothermic temperature isincreasingly applied in the field of transplantation to store and evaluateorgans on the machine prior transplantation. Currently, various perfusionconcepts are in clinical and preclinical applications. Over the last 6 years ina multidisciplinary team, a novel blood based perfusion technology wasdeveloped to keep a liver alive and metabolically active outside of the bodyfor at least one week.Within thismanuscript, we present and compare three scenarios (Group 1, 2 and 3) we werefacing during our research and development (RD) process, mainly linked tothe measurement of free hemoglobin and lactate in the blood based perfusate. Apartfrom their proven value in liver viability assessment (ex situ), these twoparameters are also helpful in RD of a long-term liver perfusion machine and moreover supportive in the biomedical engineering process.Group 1 ("good" liver on the perfusion machine) represents the best liver clearance capacity for lactate and free hemoglobin wehave observed. In contrast to Group 2 ("poor" liver on the perfusion machine), that has shown the worst clearance capacity for free hemoglobin. Astonishingly,also for Group 2, lactate is cleared till the first day of perfusion andafterwards, rising lactate values are detected due to the poor quality of theliver. These two perfusate parametersclearly highlight the impact of the organ quality/viability on the perfusion process. Whereas Group 3 is a perfusion utilizing a blood loop only (without a liver).Knowing the feasible ranges (upper- and lower bound) and the courseover time of free hemoglobin and lactate is helpful to evaluate the quality ofthe organ perfusion itself and the maturity of the developed perfusion device. Freehemoglobin in the perfusate is linked to the rate of hemolysis that indicates how optimizing (gentle blood handling, minimizing hemolysis) the perfusion machine actually is. Generally, a reduced lactate clearancecapacity can be an indication for technical problems linked to the blood supplyof the liver and therefore helps to monitor the perfusion experiments.Moreover, the possibility is given to compare, evaluate and optimize developed liverperfusion systems based on the given ranges for these two parameters. Otherresearch groups can compare/quantify their perfusate (blood) parameters withthe ones in this manuscript. The presented data, findings and recommendations willfinally support other researchers in developing their own perfusion machine ormodifying commercially availableperfusion devices according to their needs.

Objective The aim of this study was to maintain long-term full function and viability of partial livers perfused ex situ for sufficient duration to enable ex situ treatment, repair, and regeneration. Background Organ shortage remains the single most important factor limiting the success of transplantation. Autotransplantation in patients with nonresectable liver tumors is rarely feasible due to insufficient tumor-free remnant tissue. This limitation could be solved by the availability of long-term preservation of partial livers that enables functional regeneration and subsequent transplantation. Methods Partial swine livers were perfused with autologous blood after being procured from healthy pigs following 70% in-vivo resection, leaving only the right lateral lobe. Partial human livers were recovered from patients undergoing anatomic right or left hepatectomies and perfused with a blood based perfusate together with various medical additives. Assessment of physiologic function during perfusion was based on markers of hepatocyte, cholangiocyte, vascular and immune compartments, as well as histology. Results Following the development phase with partial swine livers, 21 partial human livers (14 right and 7 left hemi-livers) were perfused, eventually reaching the targeted perfusion duration of 1 week with the final protocol. These partial livers disclosed a stable perfusion with normal hepatic function including bile production (5-10 mL/h), lactate clearance, and maintenance of energy exhibited by normal of adenosine triphosphate (ATP) and glycogen levels, and preserved liver architecture for up to 1 week. Conclusion This pioneering research presents the inaugural evidence for long-term machine perfusion of partial livers and provides a pathway for innovative and relevant clinical applications to increase the availability of organs and provide novel approaches in hepatic oncology.

Long-term ex situ liver perfusion may rescue injured grafts. Little is known about bile flow during long-term perfusion. We report the development of a bile stimulation protocol and motivate bile flow as a viability marker during long-term ex situ liver perfusion.Porcine and human livers were perfused with blood at close to physiologic conditions. Our perfusion protocol was established during phase 1 with porcine livers (n = 23). Taurocholic acid was applied to stimulate bile flow. The addition of piperacillin-tazobactam (tazobac) and methylprednisolone was modified from daily bolus to controlled continuous application. We adapted the protocol to human livers (n = 12) during phase 2. Taurocholic acid was replaced with medical grade ursodeoxycholic acid.Phase 2: Despite administering taurocholic acid, bile flow declined from 29.3 ± 6.5 to 9.3 ± 1.4 mL/h (P.001). Shortly after bolus of tazobac/methylprednisolone, bile flow recovered to 39.0 ± 9.7 mL/h with a decrease of solid bile components. This implied bile salt independent bile flow stimulation by tazobac/methylprednisolone. Phase 2: Ursodeoxycholic acid was shown to stimulate bile flow ex situ in human livers. Eight livers were perfused successfully for 1 week with continuous bile flow. The other 4 livers demonstrated progressive cell death, of which only 1 exhibited bile flow.A lack of bile flow stimulation leads to a decline in bile flow and is not necessarily a sign of deterioration in liver function. Proper administration of stimulators can induce constant bile flow during ex situ liver perfusion for up to 1 week. Medical grade ursodeoxycholic acid is a suitable replacement for nonmedical grade taurocholic acid. The presence of bile flow alone is not sufficient to assess liver viability.

Objective: The hepatic arterial buffer response is a well-known phenomenon in hepatic circulation, describing the response of hepatic arterial resistance to changes in portal vein flow. Several vasoactive metabolites underlying its mechanism have been proposed, however, there is currently no clear consensus. The aim of this study is to investigate the hepatic arterial buffer response of porcine livers preserved in a controlled ex vivo perfusion machine. Methods: Porcine livers are perfused on an ex vivo perfusion machine and hemodynamic experiments investigating the hepatic arterial resistance response to portal vein flow and vena cava pressure variations are conducted. A simple hemodynamic model is developed to support the interpretation of the received measurements. Further, a mechanism is proposed that explains hepatic arterial resistance changes in response to vena cava pressure as myogenic and in response to portal vein flow as a combined washout and myogenic effect. Results: A clear correlation between hepatic sinusoidal pressure levels and hepatic arterial resistance is observed where an increase of approximately 4 mmHg of hepatic sinusoidal pressure level results in doubling of the hepatic arterial resistance. This relation is considered during the analysis of the portal vein flow variations resulting in a reduced isolated effect of adenosine washout on hepatic arterial resistance. With an average buffer capacity of 27% during our experiments, the hepatic arterial buffer response shows to be unimpaired in the ex vivo scenario. Conclusion: First, washout and myogenic effects both influence the hepatic arterial buffer response; and second, hepatic sinusoidal pressure levels strongly influence the hepatic arterial resistance. Significance: These results present new findings in hemodynamics of the liver, which are fundamental for successful ex vivo liver perfusion.

Thermal spallation drilling is a contact-less means of borehole excavation that works by exposing a rock surface to a high-temperature jet flame. In this study, we investigate crucial factors for the success of such thermal drilling operations using numerical simulations of the thermomechanical processes leading to rock failure at the borehole surface. To that end, we integrate a model developed for spalling failure with our thermomechanical simulations. In particular, we consider the role of material heterogeneities, maximum jet-flame temperature and maximum jet-flame temperature rise time on the onset of inelastic deformation and subsequent damage. We further investigate differences in energy consumption for the studied system configurations. The simulations highlight the importance of material composition, as thermal spallation is favored in fine-grained material with strong material heterogeneity. The model is used to test the relationship between the jet-flame temperature and the onset of thermal spallation.

The ability to preserve metabolically active livers ex vivo for 1 week or more could allow repair of poor-quality livers that would otherwise be declined for transplantation. Current approaches for normothermic perfusion can preserve human livers for only 24 h. Here we report a liver perfusion machine that integrates multiple core physiological functions, including automated management of glucose levels and oxygenation, waste-product removal and hematocrit control. We developed the machine in a stepwise fashion using pig livers. Study of multiple ex vivo parameters and early phase reperfusion in vivo demonstrated the viability of pig livers perfused for 1 week without the need for additional blood products or perfusate exchange. We tested the approach on ten injured human livers that had been declined for transplantation by all European centers. After a 7-d perfusion, six of the human livers showed preserved function as indicated by bile production, synthesis of coagulation factors, maintained cellular energy (ATP) and intact liver structure., Livers are stored long term in a sophisticated perfusion system.

The aim of this study was to maintain long-term full function and viability of partial livers perfused ex situ for sufficient duration to enable ex situ treatment, repair, and regeneration.Organ shortage remains the single most important factor limiting the success of transplantation. Autotransplantation in patients with nonresectable liver tumors is rarely feasible due to insufficient tumor-free remnant tissue. This limitation could be solved by the availability of long-term preservation of partial livers that enables functional regeneration and subsequent transplantation.Partial swine livers were perfused with autologous blood after being procured from healthy pigs following 70% in-vivo resection, leaving only the right lateral lobe. Partial human livers were recovered from patients undergoing anatomic right or left hepatectomies and perfused with a blood based perfusate together with various medical additives. Assessment of physiologic function during perfusion was based on markers of hepatocyte, cholangiocyte, vascular and immune compartments, as well as histology.Following the development phase with partial swine livers, 21 partial human livers (14 right and 7 left hemi-livers) were perfused, eventually reaching the targeted perfusion duration of 1 week with the final protocol. These partial livers disclosed a stable perfusion with normal hepatic function including bile production (5-10 mL/h), lactate clearance, and maintenance of energy exhibited by normal of adenosine triphosphate (ATP) and glycogen levels, and preserved liver architecture for up to 1 week.This pioneering research presents the inaugural evidence for long-term machine perfusion of partial livers and provides a pathway for innovative and relevant clinical applications to increase the availability of organs and provide novel approaches in hepatic oncology.

INTRODUCTION The use of normothermic liver machine perfusion to repair injured grafts ex situ is an emerging topic of clinical importance. However, a major concern is the possibility of microbial contamination in the absence of a fully functional immune system. Here, we report a standardized approach to maintain sterility during normothermic liver machine perfusion of porcine livers for one week. METHODS Porcine livers (n = 42) were procured and perfused with blood at 34°C following aseptic technique and standard operating procedures. The antimicrobial prophylaxis was adapted and improved in a step-wise manner taking into account the pathogens that were detected during the development phase. Piperacillin-Tazobactam was applied as a single dose initially and modified to continuous application in the final protocol. In addition, the perfusion machine was improved to recapitulate partially the host's defense system. The final protocol was tested for infection prevention during one week of perfusion. RESULTS During the development phase, microbial contamination occurred in 27 out of 39 (69%) livers with a mean occurrence of growth on 4 ± 1.6 perfusion days. The recovered microorganisms suggested an exogenous source of microbial contamination. The antimicrobial agents (piperacillin/tazobactam) could be maintained above the targeted minimal inhibitory concentration (8-16 mg/L) only with continuous application. In addition to continuous application of piperacillin/tazobactam, partial recapitulation of the host immune system ex situ accompanied by strict preventive measures for contact and air contamination maintained sterility during one week of perfusion. CONCLUSION The work demonstrates feasibility of sterility maintenance for one week during ex situ normothermic liver perfusion.

It is known that electrified droplets deform and may become unstable when the electric field they are exposed to reaches a certain critical value. These instabilities are accompanied by electric discharges due to the local enhancement of the electric field caused by the deformed droplets. Here we report and highlight an interesting aspect of the behavior of unstable water droplets and discharge generation: by implementing wettability engineering, we can manipulate these discharges. We demonstrate that wettability strongly influences the shape of a droplet that is exposed to an electric field. The difference in shape is directly related to differences in the critical value of the applied electric field at which inception of discharge occurs. Using theoretical models, we can predict and sufficiently support our observations. Thus, by tailoring the wettability of the surface, we can control droplet's behavior from expediting the discharge inception to completely restricting it.

Networks of microdevices can be used to form, sort, split and recombine droplets by varying the fluidic resistance of the channels. To facilitate design of such systems we propose two models to calculate pressure drop of liquid-liquid slug flow in square microchannels. By approximating a droplet surrounded by liquid film as annular flow, the moving film model includes the velocity profile in the lubricating layer. In the no-film model, the presence of liquid film is neglected. Pressure drop measurements of water-toluene and water-silicone oil slug flow generated in glass/silicon devices of 200 and 400 μ m width serve to validate these two models. We found that the droplet viscosity influences the applicability of the models. Good agreement is obtained for water-toluene slug flow, with the average error of 15–20% between the measured and calculated values for both models, proving that the presence of the lubricating film may be neglected for flows with similar viscosities of both phases. On the contrary, both predictions agree poorly with experiments for silicon oil-water flow which we attribute to the lower than expected liquid film thickness around the silicon oil droplets. Therefore we use the moving film model to estimate the thickness of the lubricating layer which we find to lie between 0.5% and 0.75% of the channel width, lower than the assumed 2%. Finally we compare the performance of our models against two correlations adapted from literature. We thus demonstrate that our approach allows reliable pressure drop prediction for liquids with similar viscosities and delivers important information on flow hydrodynamics.

Long-term perfusion of liver grafts outside of the body may enable repair of poor-quality livers that are currently declined for transplantation, mitigating the global shortage of donor livers. In current ex vivo liver perfusion protocols, hyperoxic blood (arterial blood) is commonly delivered in the portal vein (PV). We perfused porcine livers for one week and investigated the effect of and mechanisms behind hyperoxia in the PV on hepatic arterial resistance. Applying PV hyperoxia in porcine livers (n = 5, arterial PV group), we observed an increased need for vasodilator Nitroprussiat (285 ± 162 ml/week) to maintain the reference hepatic artery flow of 0.25 l/min during ex vivo perfusion. With physiologic oxygenation (venous blood) in the PV the need for vasodilator could be reduced to 41 ± 34 ml/week (p = 0.011; n = 5, venous PV group). This phenomenon has not been reported previously, owing to the fact that such experiments are not feasible practically in vivo. We investigated the mechanism of the variation in HA resistance in response to blood oxygen saturation with a focus on the release of vasoactive substances, such as Endothelin 1 (ET-1) and nitric oxide (NO), at the protein and mRNA levels. However, no difference was found between groups for ET-1 and NO release. We propose direct oxygen sensing of endothelial cells and/or increased NO break down rate with hyperoxia as possible explanations for enhanced HA resistance., Scientific Reports, 10 (1), ISSN:2045-2322

Objective: With the growing demand for livers in the field of transplantation, interest in normothermic ex situ machine perfusion (NMP) has increased in recent years. This may open the door for novel therapeutic interventions such as repair of suboptimal grafts. For successful long-term NMP of livers, blood glucose (BG) levels need to be maintained in a close to physiological range. Methods: We present an “automated insulin delivery” (AID) system integrated into an NMP system, which automatically adjusts insulin infusion rates based on continuous BG measurements in a closed loop manner during ex situ pig and human liver perfusion. An online glucose sensor for continuous glucose monitoring was integrated and evaluated in blood. A model based and a proportional controller were implemented and compared in their ability to maintain BG within the physiological range. Results: The continuous glucose sensor is capable of measuring BG directly in human and pig blood for multiple days with an average error of 0.6 mmol/L. There was no significant difference in the performance of the two controllers in terms of their ability to keep BG in the physiological range. With the integrated AID, BG was controlled within the physiological range on average in 80% and 76% of the perfusion time for human and pig livers, respectively. Conclusion: The presented work offers a method and shows the feasibility to maintain BG in the physiological range for multiple (up to ten) days during ex situ liver perfusion with the help of an automated AID. Significance: Maintaining BG within the physiological range is required to enable long-term ex situ liver perfusion.

Granular food products, such as seeds, grains and nuts, are frequently contaminated with diverse microorganisms which can deteriorate product quality or even threaten health, especially when consumed raw. Cold plasma treatment is a novel technology which can be applied for the disinfection of granular food to overcome drawbacks of conventional decontamination method like heat deterioration, toxic by-products or customer acceptance. In this chapter, the mechanisms of plasma inactivation are introduced, and different types of plasma discharges applied for granular food treatment are described. The influence of power supply settings, gas pressure, composition and flow rate, substrate morphology and moisture content as well as composition of microflora on treatment efficiency are discussed and the impact of plasma treatment on food quality parameters is evaluated. In conclusion, currently applied plasma treatments achieve reductions of microorganisms on granular food products comparable to other decontamination strategies, while maintaining or even improving quality parameters.

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

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.

Enhancing the thermal efficiency of a broad range of condenser devices requires means of achieving sustainable dropwise condensation on metallic surfaces, where heat transfer can be further enhanced, by harvesting the advantage of the sweeping action of vapor flow over the surface, facilitating a reduction in the droplet departure diameter. Here, we present a rationally driven, hierarchical texturing process of copper surfaces, guided by fundamental principles of wettability and coalescence, which achieves controlled droplet departure under vapor flow conditions and thus significantly enhances phase change thermal transport. The desired texture is attained by fabricating an array of 3D laser-structured truncated microcones on the surface, covered with papillae-like nanostructures and a hydrolytically stable, low surface energy self-assembled-monolayer coating. Passive droplet departure on this surface is achieved through progressive coalescence of droplets arising from microcavities formed by the microcone array, resulting in depinning and subsequent departure of the depinned condensate drops through vapor shear. The synergistic combination of vapor shear and the sustained dropwise condensation on the hierarchical copper surface results in a nearly 700% increase in heat transfer coefficients as compared to filmwise condensation from identical, standard unstructured surfaces.

The performance of flame jet drilling on Grimsel Granodiorite cylindrical rock samples was experimentally investigated depending on applied uniaxial load. With a simple confining system for the rock samples, uniaxial load up to 47 MPa was tested in order to simulate the axial component of the stress tensor existing in a deep borehole. Provided that flame properties were unchanged, increasing the uniaxial load influenced the drilling positively. The experimental results were explained with numerically calculated stress profiles. It was concluded that tensile stresses below the heated surface increase with uniaxial load and additionally weaken the rock, which should improve the flame jet drilling with depth.

In this paper, the feasibility of a thermally assisted drilling method is investigated. The working principle of this method is based on the weakening effect of a flame-jet to enhance the drilling performance of conventional, mechanical drilling. To investigate its effectiveness, we study rock weakening after rapid, localized flame-jet heating of Rorschach sandstone and Central Aare granite. We perform experiments on rock strength after flame treatments in comparison to oven heating, for temperatures up to 650 $$^{\circ}$$ C and heating rates from 0.17 to 20 $$^{\circ}$$ C/s. The material hardening, commonly observed at moderate temperatures after oven treatments, can be suppressed by flame heating the material at high heating rates. Our study highlights the influence of the heating rate on the mechanism of thermal microcracking. High heating rate, flame treatments appear to mostly induce cracks at the grain boundaries, opposed to slow oven treatments, where also a considerable number of intragranular cracks are found. Herewith, we postulate that at low heating rates, thermal expansion stresses cause the observed thermal cracking. In contrast, at higher heating rates, thermal cracking is dominated by the stress concentrations caused by high thermal gradients.

This work presents a study on the continuous operation of a structured reactor for alkyne hydrogenation in the field of Process Intensification. The reactor consists of a laser sintered metal structure characterized by a regular geometry, coated with a layer of ZnO/Al2O3 and impregnated with palladium nanoparticles. The partial hydrogenation of 2-methyl-3-butyn-2-ol with co-current gas-liquid upward flow was used as the test reaction system. A plug flow reactor model was applied to study the mass transfer phenomena under the reacting conditions. The reaction kinetics with the Pd/ZnO-based catalyst were simplified using a power rate law expression. The results in terms of the overall mass transfer coefficient Kov were modelled with a predictive Sherwood number correlation whose parameters were estimated by means of an optimization procedure. The structured reactor shows an overall mass transfer coefficient ranging between 0.2 and 1.2 s−1 depending on the operating conditions. The model is able to predict the impact of temperature (333–363 K), pressure (3.0–7.0 bar), gas velocity (0.005–0.024 m s−1) and liquid velocity (0.025–0.085 m s−1) on the overall mass transfer coefficient with a maximum deviation of 15%.

The creation of deep reservoirs for geothermal energy or oil and gas extraction is impeded by insufficient stimulation. Direction and extension of the created fractures are complex to control and, therefore, large stimulated and interconnected fracture networks are difficult to create. This lack of control and efficiency poses an inherent risk of uneconomic reservoirs, due to insufficient heat-sweep surfaces or hydraulic shortcuts. Therefore, we present a technique, which locally increases the cross section of a borehole by applying a thermal spallation process to the sidewalls of the borehole. By controlled and local enlargement of the well bore diameter, initial fracture sources are created, potentially reducing the injection pressure during hydraulic stimulation, initiating fracture growth, optimizing fracture propagation and increasing the number of accessible preexisting fractures. Consequently, local thermal borehole enlargement reduces project failure risks by providing better control on subsequent stimulation processes. In order to demonstrate the applicability of the suggested technique, we conducted a shallow field test in an underground rock laboratory. Two types of borehole enlargements were created in a 14.5 m deep borehole, indicating the feasibility of the technology to improve the productivity of geothermal, oil and gas reservoirs.

Both autohydrolysis and acidic pretreatments have already been commercialised to allow for the bioconversion of lignocellulosic biomass to valuable products. Recent fundamental research has shown that the pretreatment of lignocellulosic biomass can be enhanced by the suppression of lignin repolymerisation. This work evaluates the application potential of a carbocation scavenger additive that prevents lignin repolymerisation for the autohydrolysis and acidic pretreatment of woody biomass. The results show that the enhancing effect of the scavenger is strongly dependent on the type of biomass. While it proved hardly beneficial in the pretreatment of hardwoods, the pretreatment of recalcitrant softwoods could be greatly enhanced. Softwood has an exceptionally high recalcitrance to biochemical conversion compared to other biomass types, though the reasons for this behaviour have hardly been understood so far. Our study revealed that lignin repolymerisation is a major factor accounting for the exceptional softwood recalcitrance. A sensitivity analysis of pretreatment temperature and time showed that the scavenger can enhance the enzymatic digestibility of softwood cellulose by up to 113% in autohydrolysis and up to 142% in dilute acid pretreatments. The scavenger proved effective for both softwood sawdust and wood chips. Its mode of action in pretreatment was shown to be particularly suitable for the implementation in two-stage pretreatments, which are of high commercial relevance.

This work presents a study of the hydrogenation of 2-methyl-3-butyn-2-ol in flow over a structured catalyst. A porous tubular metal structure is coated with a layer of ZnO/Al 2 O 3 and impregnated with palladium. This reactor is operated with recirculation of the process liquid and continuous supply of hydrogen with co-current upward flow. A Langmuir-Hinshelwood mechanism based on noncompetitive adsorption of hydrogen and organics is used to model the experimental results. 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, at lower hydrogen flowrates, allows the estimation of an overall mass transfer coefficient K ov . The reaction appears to be strongly dependent on the hydrogen flowrate with estimated K ov lower than 0.25 s −1 in the range of flowrates 0.1–0.5 nL min −1 . The mathematical model, successfully validated, is able to accurately predict the concentration profiles of the species involved in the system at varying temperatures, in both kinetic and mass transfer limited regimes.

The axial dispersion in tubular reactors is frequently modeled by the dispersion model, which is an analytical solution under the assumption that the vessel dispersion number is sufficiently small. In this study, limits until which the analytical solution is valid are investigated by comparison with the numerical method. The results show that it is applied only if the vessel dispersion number is small enough and the entrance effect of the tracer is avoided. Therefore, an algorithm based on the numerical solution of the control equation of dispersion is proposed, which allows for higher vessel dispersion numbers.

Isophytol is a key intermediate in the industrial synthesis of vitamins, produced by selective hydrogenation of dehydroisophytol. This work presents a study of the kinetics of this process in the absence of any solvent. The experimental data were modeled using power-law kinetic expressions and mechanistic models based on Langmuir–Hinshelwood kinetics. The hypothesis of noncompetitive adsorption between hydrogen and organics was chosen in order to describe the changes in the reactivity of the system at varying temperatures (313–353 K) and pressures (5.0–9.0 bar). A simplified approach was used to describe the kinetics of the overhydrogenation reaction to the corresponding alkane. A list of the relevant kinetic and adsorption parameters, the result of an optimization procedure, is reported. The mathematical model, successfully validated, allows the prediction of the influence of the operating conditions and of the addition of quinoline, as reaction modifier, on the selectivity of the process.

The utilization of abandoned lignocellulosic residues for chemical production has a strong potential to partially substitute chemicals, which are traditionally produced from non-renewable resources. Softwood especially, with its high availability, presents a sustainable resource for the conversion to higher value-added products such as biofuels and bioplastics. In this study, we investigate mature and innovative technologies for the conversion of softwood to the platform chemical sugar from an economic and environmental perspective. We show that the conventional enzymatic hydrolysis has high economic as well as environmental burdens and that the increase of enzyme availability via a carbocation scavenger process is the key solution to overcome them. Furthermore, we present a process design based on concentrated acid hydrolysis, which is both environmentally and economically competitive compared to conventional production from sugarbeet. The low energy and raw material requirements combined with heat integration and moderate capital costs makes this technology attractive for utilization of softwood residues. This proves that lignocellulosic residues have the potential to become an important raw material in the future bioeconomy.

In the frame of process development for the generation of chemical energy carriers, we studied the synthesis of methanol and formic acid from methyl formate hydrolysis in a continuous-flow millireactor. The aim was to establish the link between kinetics and phase behavior in the biphasic liquid regime. Reaction performance using the acidic ion-exchange resin Amberlyst 15 as catalyst was examined at various operating conditions such as space velocity, catalyst particle size, temperature, and initial reactant ratio. Results revealed substantially higher yields without mass transfer impediment with feed compositions exceeding methyl formate saturation in water. The simultaneous decrease in methyl formate and increase in polar product concentrations sufficed to bring the initially biphasic mixture to a homogeneous system as confirmed by thermodynamic UNIFAC equilibrium calculations. The separate analysis of effluent liquid phases unveiled a quasi-homogeneous catalytic process rooted in an aqueous layer at the...

The need for long term, large-scale storage solutions to match surplus renewable energy with demand drives technological innovation towards a low-carbon economy. As a high hydrogen density energy carrier, formic acid streamlines functional storage of unscheduled intermittent power supply. However, the unfavourable thermodynamics of its direct synthesis from CO2 and H2 call for alternative processes to achieve substantial space time yields. This preliminary study investigates the feasibility of continuously producing formic acid in a two-step process by exploiting methyl formate as a thermodynamically stable intermediate. In order to prove the concept, the qualitative efficiency of several three-reactor configurations is evaluated and discussed with respect to the efficiency of a single reactor methanol synthesis over a commercial Cu catalyst. Although concrete solutions are not available yet and identification of formic acid remains arduous, the proposed reactive pathway exceeds the thermodynamic limits of the direct synthesis path over heterogeneous catalysts, and opens up avenues for advances in clean energy production.

Electrochemical micro-probes are used to study the flow regime and liquid–solid mass transfer inside a designed porous structure. In order to place the electrodes inside the porous structure avoiding gluing and polishing, the electrodes are glued flush with pins. These pins are then simply plugged into the structure. In a first step, the influence of the pin on the local flow behavior is studied. It is shown, that the departure from the laminar flow regime can be determined within 10% accuracy in empty pipes. Additionally, the influence of the pin length on the point of transition is studied inside the porous structure showing errors below 10% for pin lengths with an accuracy of ±0.5 mm. In a second step, the flow regime is determined with a simple algorithm, allowing a reproducible detection of the laminar plateau and the onset of fluctuations. The departure from the laminar regime is found at Re lam , end = 162 ± 3 . In the third and last step, the liquid–solid mass transfer is studied for a single-phase liquid flow and gas–liquid two-phase flow. It is shown, that the second phase is enhancing the mass transfer at low volumetric transport fractions but degrading the mass transfer at volumetric transport fractions higher than 6%. The Sherwood number is compared to the literature and correlations are presented to describe the Sherwood number in the laminar and turbulent flow regime.

Highly porous structures (porosity ≥75%), as metal foams or designed foam-like structures, are often used in industry to augment heat and mass transfer. In the present study, we focus on the mixing in highly porous structures in continuous millireactor characterized with a relatively low Reynolds number (ReD=240 – based on the ligament diameter and bulk velocity) and a high Schmidt number fluid (Sc=2400). We apply a combined numerical and experimental approach. The numerical simulations employ a Large Eddy Simulation (LES) method with dynamic Lagrangian approach for subgrid-scale turbulent stress and turbulent mass flux. The results of the numerical simulation are compared with our own combined Particle Imaging Velocimetry (PIV) and Laser Induced Fluorescence (LIF) measurements. The application of combined PIV/LIF makes it possible to simultaneously measure velocity components, turbulent stresses, concentration and concentration fluxes. The mechanism of the mixing is analyzed in detail with specific focus on validity of a simple gradient diffusion hypothesis (SGDH) in modeling of the turbulent mass transfer in complex porous structure.

“Designed Porous Structured Reactor” (DPSR) is porous stream-wise periodic structure that can serve both as static mixers and catalyst carriers. Two DPSRs with different inner diameters (A: 14 mm, B: 7 mm) were compared. Residence time distributions were determined in an aqueous system at different Reynolds numbers using wire-mesh electrodes. Similar dispersion was observed in both structures, which was attributed to fully developed flow in DPSR A and B. Axial dispersion coefficients increased monotone with pore Peclet numbers and were in good agreement with literature. DPSR A showed higher pressure drops due to lower porosity values than DPSR B. Pressure drops followed the Forchheimer equation using an Ergun model. The coating reduced the surface roughness and the porosity of the DPSRs’ metal fabric. Chemical mass transfer was evaluated for the hydrogenation of 2-methyl-3-butyn-2-ol (MBY) at various gas/liquid combinations. While gas–liquid mass transfer was determined as limiting process step, liquid–solid mass transfer was ruled out. Superior gas–liquid mass transfer coefficients were determined for DPSR B. Differences in mass transfer rates DPSR A and B were attributed to the ratios of inner diameter to the pore size and the porosities. A Stanton correlation was suggested to estimate gas–liquid mass transfer coefficients.

In this work, we examine thermal spallation drilling through finite element modeling of the uncoupled quasi-static thermoelastic problem describing the stresses induced by rapid and localized heating of a uniaxially pre-stressed rock core. The numerical procedure is verified using the method of manufactured solutions, and the optimal order of accuracy is demonstrated. From a series of numerical experiments, we present the temperature and stress profiles along the centerline of the rock core which are discussed qualitatively with respect to the corresponding laboratory experiments. Our numerical results, in agreement with the experiments, emphasize that the efficiency of thermal spallation drilling increases linearly with the vertical stress.

This study compares a two-phase flow through a foam-like porous structure and a Sulzer SMX TM static mixing element. Refractive index matching between two immiscible fluids and the internal structures enables optical measurements to be performed. The droplet size and position within the internal structures were observed by laser-induced fluorescence. The results show that at low flowrates, droplets follow preferred paths, whereas at higher flowrates, they are more homogeneously distributed within the structures. The droplet size distribution was found to be well represented by the Sauter mean diameter. Measuring along the axis of the two static mixers, we found that droplets disintegrate more quickly in the foam-like porous structure. As both geometries have the same porosity and hydraulic diameter, we conclude that the change in the free cross section is also an important parameter. We observed that in the geometry with large changes in the free cross section, the droplets are smaller.

Motivated by the frequent microbial contamination of granular food products like cereal grains or sprout seeds, an atmospheric pressure dielectric barrier discharge (DBD) was developed to study plasma inactivation of microorganisms on granular materials. Wheat grains as well as polypropylene model substrates were artificially contaminated with endospores of Geobacillus stearothermophilus as a model organism and treated in a pulsed argon plasma discharge applying different combinations of treatment time, pulse voltage and frequency. While the treatment of polypropylene substrates resulted in an efficient reduction of microbes, wheat grains, having a rough surface and a deep ventral furrow, turned out to be more challenging to decontaminate. However, an improvement in treatment efficiency could be achieved by applying longer treatment, faster pulse frequency or higher pulse voltage. Furthermore, experiments demonstrated that endospore reduction was not caused by thermal, mechanical or electrical stress factors, but a direct effect of plasma-generated species, and chemical sputtering is supposed to be the predominant inactivation mechanism. Finally, it could be shown that functional wheat grain properties (Falling number, gluten content) are not negatively affected by our plasma treatment.

The spallation process is based on the effect, that hard rocks with a high quartz content disintegrate into small disc-like fragments, if the rock surface is rapidly exposed to high thermal loads. Spallation is pursued as a contact-free drilling technology for various applications. In view of increasing the knowledge about the process and for determining the limitations of the applicable operating range, a profound knowledge of the minimal required boundary conditions are of significant importance. These conditions are characterized by the lowest surface temperature and heat transfer coefficient at which spallation can be successfully initiated. In order to determine the minimal required boundary conditions, spallation experiments were conducted in which granitic rock samples were rapidly heated by a methane–air burner. A novel measuring concept is proposed to measure the surface temperature, using high-speed pyrometers to temporally resolve the detachment of single spalls. The heat transfer coefficient of the impinging flame was determined by measuring the heat flux in the stagnation point of the jet using an industrial heat flux sensor. The reported data of the boundary conditions show good accordance with data published by other researches and supports their proposed characteristic for the specific heating process.

In this work we present the hot surface ignition of turbulent diffusion oxygen–ethanol hydrothermal flames. For this purpose up to 520 W electric are dissipated through a heating wire. The mean wire temperature and the electrical energy it releases at ignition are reported by measuring the voltage drop across its resistance. The wire temperatures – up to 385 °C – are compared to the auto-ignition temperatures reported in literature and the ignition map of our system is drawn. In case the reactants are injected at room temperature, the hot surface enables ignition for ethanol contents in the aqueous fuel stream above 30 wt.%. In the end, potential applications of the ignition system in the scope of supercritical water oxidation and hydrothermal spallation drilling are highlighted.

The surface heat flux and its distribution in space and time is an important parameter in numerous engineering problems. In this content, we present a method for estimating transient, multidimensional heat flux distributions by measuring the temperature distribution on the surface of an object and by applying inverse techniques. The proposed method can be used for transient heat transfer processes and particularly for heat transfer problems where lateral heat conduction along the surface plays a significant role. The method is based on two-dimensional sensitivity matrices, which have been expanded to a three-dimensional sensitivity approach. Thereby, the profile of the heat flux does not have to be known beforehand. As the introduced method is applied on the surface of the investigated objects, the frequent problem with instabilities due to the ill-posedness of the inverse problem is significantly reduced and no further stabilization procedures are required. The method improves available methods based on one-dimensional heat conduction, due to the consideration of three-dimensional heat conduction.

A general kinetic model has been developed to simulate the three-phase solvent-free hydrogenation of 2-methyl-3-butyn-2-ol (MBY) over a commercial palladium-based catalyst. A Langmuir–Hinshelwood mechanism with noncompetitive adsorption between hydrogen and the organic species is assumed. Gas–liquid mass-transfer resistance is included in the model. Experiments were carried out in a stirred slurry reactor to estimate the kinetic parameters. The proposed model is able to predict the concentration profiles of the species involved during MBY hydrogenation, at varying temperatures (313–353 K), pressures (3.0–10.0 bar), and catalyst loadings (0.075–0.175 wt %). The model predictions were successfully validated using additional experimental runs conducted under different operating conditions and at a lower initial concentration of MBY.

Accessing hydrocarbons, geothermal energy and mineral resources requires more and more drilling to great depths and into hard rocks, as many shallow resources in soft rocks have been mined already. Drilling into hard rock to great depths, however, requires reducing the effort (i.e., energy), time (i.e., increasing the rate of penetration) and cost associated with such operations. Thus, a Combined Thermo-Mechanical Drilling (CTMD) technology is proposed, which employs a heat source (e.g., a flame jet) and includes two main drilling modes: (I) Thermal spallation drilling, investigated here as a field test and (II) Flame-assisted rotary drilling, investigated as a field test in the companion paper. The CTMD technology is expected to reduce drilling costs, especially in hard rocks, by enhancing the rock penetration rate and increasing the bit lifetime. ModeI of the CTMD technology (thermal spallation drilling) is investigated here by implementing the concept on a full-scale drilling rig to investigate its feasibility and performance under realistic field conditions. During the test, the successful thermal spallation process is monitored, employing a novel acoustic emission system. The effects of thermal spallation in the granite rock are analyzed to provide conclusions regarding the rock removal performance and the application potential of the technology. The field test shows that thermal spallation of the granitic rock can be successfully achieved even when a liquid (water) is used as the drilling fluid, as long as the heat source is appropriately shielded by compressed-air jets. Thermal damage of the surrounding rock is investigated after the spallation test, employing micro-computer tomography imaging and modeling the stability of the cracks, generated by the spallation field test. This study shows that thermally induced damage is mainly confined within a narrow region close to the rock surface, suggesting that thermal spallation only marginally affects the overall mechanical stability of the borehole. Thus, this confirms that, as part of the Combined Thermo-Mechanical Drilling (CTMD) technology, thermal spallation drilling is a promising mode that has a high potential of facilitating the drilling of deep boreholes in hard rocks.

To enhance the drilling performance in deep hard rocks and reduce overall drilling efforts, this work proposes a Combined Thermo-Mechanical Drilling (CTMD) technology. This technology employs a heat source (e.g., a flame jet) and includes two main drilling modes: (I) thermal spallation drilling, investigated in the companion paper and (II) flame-assisted rotary drilling, investigated here as a field test. The CTMD technology is expected to reduce drilling efforts, especially in hard rocks, enhancing the rock penetration rate and increasing the bit lifetime, all of which reduces the drilling costs. The present work investigates Mode II (flame-assisted rotary drilling) of the CTMD technology by implementing the concept in an existing drilling rig and testing the technology under relevant process conditions. This contribution studies the underlying rock removal mechanism of CTMD and demonstrates its drilling performance, compared to conventional rotary drilling methods. Acoustic emission monitoring, and analysis of the collected drill cuttings provide multiple evidences for thermal-cracking-enhanced rock removal during the flame-assisted rotary drilling. This removal mechanism appears to represent an optimal compromise to minimize rock fragmentation and cutting transport efforts during drilling, compared to a less efficient mechanical scraping of the hard granite rock, observed during the standalone-mechanical drill test. The drilling performance, in terms of removal and wear rates, are evaluated for the flame-assisted rotary drilling. This shows that the proposed drilling approach is capable of enhancing the removal process in hard granite rock, by a factor of 2.5, compared to standalone-mechanical drilling. The implementation of this drilling approach into a conventional drilling system shows that integration of thermal assistance to conventional rotary drilling requires marginal technical efforts. Additionally, this technology can profit from established knowledge in conventional mechanical drilling, facilitating its implementation to improve drilling performance in hard rocks. Hence, this study demonstrates that the Combined Thermo-Mechanical Drilling method is feasible and concludes that this technology constitutes a promising approach to improve the drilling process, thereby increasing the viability of accessing deep geo-resources in hard rocks.