Dissertations / Theses on the topic 'Intensification'

Over the centuries the equipment used by the process industry went through little changes: it have been perfected but it have never been substantially changed. Indeed the type of chemical reactor currently used is the stirred tank, that works in the same way of a similar one built in 1800; logically, materials, control systems or safety systems changed, but the basic engineering remained the same. In recent years, a new equipment was proposed: it performs the same functions as the existing one, occupying less space, requiring less power and operating in a safer way. The changes required in a plant to achieve the above mentioned objectives are called Process Intensification; it can be described as the following: “Any chemical engineering development that leads to a substantially smaller, cleaner, safer and more energy efficient technology is process intensification”. From the Process Identification point of view, it is possible to mention the development of new equipment, such as the Spinning Disk Reactors and Heat Exchange (HEX) Reactors, characterized by a remarkable technological jump with respect to the existing equipment: designers began to use physical phenomena previously neglected, such as the centrifugal force in the spinning disk reactor, or to combine into one equipment more unit operations, such as Reverse-Flow Reactors, Reactive Distillation ... These recent developments certainly provide more compact and cleaner plants, but there are more uncertainties about their capability to produce an actual increase of the safety. The use of more complex equipment, in example with moving parts or with more intense sources of energy, can even bring to safety problems not detected in traditional plants, also modifying the reliability of the system. Under the definition of Process Intensification it is possible to indicate different kinds of improvements to the plants: in order to analyze the effects of these improvements on safety and reliability, we made an assessment of the reliability in a traditional plant, and in an intensified plant, comparing their results. The process analyzed is related to a plant for the VOC (Volatile Organic Compound) abatement in a stream of inert gas. The traditional system is based on a fixed bed reactor; the intensified plant uses a Reverse-Flow Reactors. The selected plants were firstly subjected to a traditional safety analysis, using an operability analysis and then operating the extraction and quantification of the fault trees. During the analysis, we realized that the traditional methods (HAZOP and FT) worked well if applied to conventional systems, which arrive to a steady-state, but they were less suitable for modern plants, that work in a transitional regime. After the traditional safety analysis, we proceeded with a Integrated Dynamic Decision Analysis, that allows to evaluate more in detail the behavior for not stationary plants, in case of failure. From the application of the methodology to the specific case some general conclusions have been drawn.

Biosurfactants are naturally occurring surface active compounds with unique properties such as biodegradability, low toxicity and tolerance to extreme conditions. These unique properties promote their use as alternatives to traditional petrochemical and oleochemical surfactants, as they satisfy requirements for environmentally friendly manufacturing processes. However, the cost of biosurfactants is still significantly higher than chemical surfactants which hinders their large-scale commercialisation. This work presents an investigation into the production of surfactin, a lipopeptide biosurfactant, exploiting its foamability characteristics for the design and implementation of a recirculating continuous foam fractionation column operated in parallel with a bioreactor. Surfactin is a powerful amphiphilic compound produced by Bacillus subtilis. It is a plant-elicitor with antimicrobial properties offering a huge potential in the food and agricultural industries. However, surfactin has extreme foamability even at low concentrations. This foamability can lead to production problems such as large volumes of uncontrolled overflowing foam with significant product and biomass losses. Here, it is demonstrated that this overflow can be controlled, or eliminated, by integrating a foam fractionation system to the bioreactor in a recirculating loop. A dual production and separation process was engineered and enabled reaching high surfactin productivity in a controlled manner. After elucidating the surface properties of surfactin-rich broth, a foam fractionation column was designed for bench-scale production. Operation of the recirculating column in parallel with the bioreactor enabled air flow to be independently controlled for each unit. Surfactin solutions of various concentrations were tested to relate foamability to concentration over a range of bubble sizes. The sintered glass pore size was revealed to be the main factor influencing the enrichment, with a positive correlation with increasing pore size. Characterisation of the fermentation production rate enabled fractionation column air flow rate to be controlled to ensure sufficient foam surface area for product adsorption. The airflow rate was identified as the main factor impacting on the surfactin recovery rate. This characterisation enabled broth feed flow rate to be controlled to balance the removal rate with the production rate. Two processes were created coupling the newly designed fractionation column with the bioreactor operated either in aerated or non-aerated conditions. Under aerated settings, controlled surfactin production was successfully achieved at a productivity of 0.0019 g L-1 h-1 whilst simultaneously recovering 91% of the product at a maximum enrichment of 79 and 116 through the column and overflow routes, respectively. Under non-aerated settings, overflowing foam was fully avoided and 90% of the product was recovered solely through the fractionation column at an enrichment ratio of 40 under non-optimised settings. Additionally, up to 14% (g/g) increase in surfactin production was observed with the coupling of the fractionation column demonstrating a further benefit as a bioprocess intensifying device for surfactin production. This work provides a benchmark for a robust system for surfactin production, substantially improving the productivity at bench scale, potentially leading the way to more productive and less costly industrial processes for surface active compounds in a wide range of industrials fields.

L'amélioration des propriétés hydrodynamiques des réacteurs chimiques est toujours un grand défi pour les ingénieurs en génie des procèdes. La réalisation d'expériences sur des réacteurs chimiques situés dans un champ magnétique inhomogène peut donner des informations importantes concernant les mécanismes des réactions chimiques ou les propriétés hydrodynamiques du système. Un champ magnétique inhomogène sera généré par un aimant solénoïdal à supraconductivité NbTi et appliqué à un réacteur chimique. Les directions de recherche sont: les propriétés magnéto hydrodynamiques des réacteurs situés dans le champ magnétique généré par le solénoïde (réalisation de conditions d'hypogravité ou de macrogravité), l'effet du champ magnétique sur les réponses catalytiques de certaines réactions sélectionnées et l'effet du champ magnétique sur l'écoulement du fluide pour les réacteurs a lit fixe. Le champ magnétique extérieur inhomogène exerce une force magnétique qui peut modifier la direction et la valeur de la force gravitationnelle.

A methodological approach to process intensification (PI) has been developed to aid in the design of intensified chemical processes. Current process development procedures fail to consider if, and how, a chemical process can be intensified, resulting in limited application of PI in the chemicals industry. The PI methodology has been developed to meet these needs, focusing upon the chemical reaction stages of a process. The PI methodology is a paper-based tool, based around a flowsheet known as the framework. Throughout development, the methodology was applied to industrial case studies which revealed considerations that should be included in the methodology and aided in determining its format. Each section of the framework contains checklists and procedures detailing the information required and the decisions to be made by the participants, who should be in a multi-disciplinary team. Examination of chemical reaction kinetics and the effects of mixing upon the reaction are key aspects of the methodology that are normally not examined during process development. Incorporated within the methodology is a PI experimental protocol designed to model PI operation in the laboratory. Mixing theory was reviewed to identify that the protocol approach should be based upon recreating the mixing conditions experienced in a full scale plant within a small scale laboratory stirred vessel. The developed laboratory protocol utilises semi-batch operation in a highly-mixed stirred vessel of 10cm diameter and height with twin pitched-blade turbine impellers. Turbulent energy dissipation rates of 150 W/kg can be achieved in the vessel. Experiments were run, showing that the performance of static mixer reactors can be predicted through the application of the protocol, though future work is required to develop this laboratory protocol approach into a rigorous experimental tool.

Monoclonal antibodies can be produced in culture fluid by the fermentation of specificially selected hybridoma cells. Hybridoma cells exhibit suspension type fermentation characteristics and therefore the simplest method for large scale fermentation is that of the stirred tank fermenter. However, such is the growing demand for monoclonal antibodies, methods for increasing the production capacity of a commercial process are being developed. This study examines some of the current process intensification methods in relation to an established production facility. As well as examining the actual productivity increases possible with any method, the applicability of that method to a commercial environment is taken into account. Hollow-fibre systems are investigated, with a potential increase in productivity which was outweighed by the significant retooling and retraining costs. Gel Bead entrapment systems are shown to have great promise, as they can be readily placed into existing equipment and production methods. However, all methods examined, including alginate bead entrapment, were found unsuitable for hybridoma cell culture. A novel method for cell entrapment was developed, using an agarose/alginate gel mixture which allowed greatly improved growth and consistent antibody production. The entrapment method was examined in a continuous chemostatic system. This system was then scaled-up and applied to the existing facility, to give a 25L airlift operating in a chemostatic mode at a rate of 1.2-1.5 day^-1.

Intensification refers to utilizing wastewater treatment processes that decrease chemical and energy demands, increase energy recovery, and reduce the process footprint (or increased capacity in an existing footprint) all while providing the same level of nutrient removal as traditional methods. Shortcut nitrogen removal processes; including nitrite shunt, partial nitritation/anammox, and partial denitrification/anammox, as well as low-carbon biological phosphorus removal, were critically-evaluated in this study with an overall objective of intensification of existing infrastructure. At the beginning of this study, granular sidestream deammonification was becoming well-established in Europe, but there was virtually no experience with startup or operation of these processes in North America. The experience gained from optimization of the sidestream deammonification moving bed biofilm reactor (MBBR) in this study, including the novel pH-based aeration control strategy, has influenced the startup procedure and operation of subsequent full-scale installations in the United States and around the world. Long startup time remains a barrier to the implementation of sidestream deammonification processes, but this study was the first to show the benefits of utilizing media with an existing nitrifying biofilm to speed up anammox bacteria colonization. Utilizing media with an established biofilm from a mature integrated fixed film activated sludge (IFAS) process resulted in at least five times greater anammox activity rates in one month than virgin media without a preliminary biofilm. This concept has not been testing yet in a full-scale startup, but has the potential to drastically reduce startup time. False dissolved oxygen readings were observed in batch scale denitrification tests, and it was determined that nitric oxide was interfering with optical DO sensors, a problem of which the sensor manufacturers were not aware. This led to at least one sensor manufacturer reevaluating their sensor design and several laboratories and full-scale process installations were able to understand their observed false DO readings. There is an industry-wide trend to utilize influent carbon more efficiently and realize the benefits of mainstream shortcut nitrogen removal. The A/B pilot at the HRSD Chesapeake Elizabeth Treatment provides a unique chance to study these strategies in a continuous flow system with real wastewater. For the first time, it was demonstrated that the presence of influent particulate COD can lead to higher competition for nitrite by heterotrophic denitrifying bacteria, resulting in nitrite oxidizing bacteria (NOB) out-selection. TIN removal was affected by both the type and amount of influent COD, with particulate COD (pCOD) having a stronger influence than soluble COD (sCOD). Based on these findings, an innovative approach to achieving energy efficient biological nitrogen removal was suggested, in which influent carbon fractions are tailored to control specific ammonia and nitrite oxidation rates and thereby achieve energy efficiency in the nitrogen removal goals downstream. Intermittent and continuous aeration strategies were explored for more conventional BNR processes. The effect of influent carbon fractionation on TIN removal was again considered, this time in the context of simultaneous nitrification/denitrification during continuous aeration. It was concluded that intermittent aeration was able to achieve equal or higher TIN removal than continuous aeration at shorter SRTs, whether or not the goal is nitrite shunt. It is sometimes assumed that converting to continuous aeration ammonia-based aeration control (ABAC) or ammonia vs. NOx (AvN) control will result in an additional nitrogen removal simply by reducing the DO setpoint resulting in simultaneous nitrification/denitrification (SND). This work demonstrated that lower DO did not always improve TIN removal and most importantly that aeration control alone cannot guarantee SND. It was concluded that although lower DO is necessary to achieve SND, there also needs to be sufficient carbon available for denitrification. While the implementation of full-scale sidestream anammox happened rather quickly, the implementation of anammox in the mainstream has not followed, without any known full-scale implementations. This is almost certainly because maintaining reliable mainstream NOB out-selection seems to be an insurmountable obstacle to full-scale implementation. Partial denitrification/anammox was proven to be easier to maintain than partial nitritation/anammox and still provides significant aeration and carbon savings compared to traditional nitrification/denitrification. There is a long-standing interest in combining shortcut nitrogen removal with biological phosphorus removal, without much success. In this study, biological phosphorus removal was achieved in an A/B process with A-stage WAS fermentation and shortcut nitrogen removal in B-stage via partial denitrification.
Doctor of Philosophy
When the activated sludge process was first implemented at the beginning of the 20th century, the goal was mainly oxygen demand reduction. In the past few decades, treatment goals have expanded to include nutrient (nitrogen and phosphorus) removal, in response to regulations protecting receiving bodies of water. The only practical way to remove nitrogen in municipal wastewater is via biological treatment, utilizing bacteria, and sometimes archaea, to convert the influent ammonium to dinitrogen gas. Orthophosphate on the other hand can either be removed via chemical precipitation using metal salts or by conversion to and storage of polyphosphate by polyphosphate accumulating organisms (PAO) and then removed in the waste sludge. Nitrification/denitrification and chemical phosphorus removal are well-established practices but utilize more resources than processes without nutrient removal in the form of chemical addition (alkalinity for nitrification, external carbon for denitrification, and metal salts for chemical phosphorus removal), increased reactor volume, and increased aeration energy. Intensification refers to utilizing wastewater treatment processes that decrease chemical and energy demands, increase energy recovery, and reduce the process footprint (or increased capacity in an existing footprint) all while providing the same level of nutrient removal as traditional methods. Shortcut nitrogen removal processes; including nitrite shunt, partial nitritation/anammox, and partial denitrification/anammox, as well as low-carbon biological phosphorus removal, were critically-evaluated in this study with an overall objective of intensification of existing infrastructure. Partial nitritation/anammox is a relatively new technology that has been implemented in many full-scale sidestream processes with high ammonia concentrations, but that has proven difficult in more dilute mainstream conditions due to the difficulty in suppressing nitrite oxidizing bacteria (NOB). Even more challenging is integrating biological phosphorus removal with shortcut nitrogen removal, because biological phosphorus removal requires the readily biodegradable carbon that is diverted. Partial denitrification/anammox provides a viable alternation to partial nitritation/anammox, which may be better suited for integration with biological phosphorus removal.

The absorption of nitrogen oxides in water has important applications in nitric acid manufacture and pollution control. The design for optimum absorption efficiency and air pollution control has made necessary the installation of large reaction chambers and absorption towers for the adequate oxidation and absorption of nitrous gases. The worldwide production of weak acid has seen the progression of the process from the use of low through medium- to high-pressure technology in the efforts of achieving a more compact construction and avoiding the need for catalytic tail-gas treatment in plants with ever increasing capacities. Even at high pressures (8 bar), absorption columns employing sieve plates can reach up to 40 m in height for large-tonnage plants, and the relatively large pressure drop across the plates at these pressures leads to high power consumption and increased costs. As the dimensions of the absorption tower are typically governed by the conditions required for NO oxidation and thermal design, intensification of the process via miniaturisation can address the issues above through the high surface area to volume ratio offered by microreactor technology. The substantial improvement in heat and mass transfer due to the increase in effective exchange surface leads to an acceleration of the slow NO oxidation reaction and the enhancement of absorption rates. In addition to the development of such novel equipment for process intensification, the flow of the process can also be structured to improve process efficiency. An interesting method would be the replacement of the nitrogen ballast typically used in industry with steam, as the concentration of the gases upon condensation can lead to improved gas phase reaction rates. Furthermore, the provision of increased residence times due to the decrease in gas velocity upon condensation also makes the process more efficient. In this way, the size of the absorber can be significantly reduced and the high capital and operating costs associated with the employment of compressors in high pressure plants can be reduced. The objective of this thesis is to gain a fundamental understanding of the complex behaviour of nitric acid production in microchannels and obtain data for the development of a model used for process design and optimisation. Experiments on the oxidation and absorption of xviii nitrogen oxides have been conducted for a wide range of nominal residence times (0.03 – 1.4 s), gas compositions (5 – 10% NO, 5 – 49% O2, 46 – 82% H2O, balance argon), system pressures (2 – 10 bar absolute), mass fluxes (1.5 – 30 kg m-2 s-1), coolant mass fluxes (66 kg m-2 s-1 and 341 kg m-2 s-1), and coolant temperatures (23 – 51ºC) in circular tubes with internal diameters of 1.4 and 3.9 mm. Absorption efficiencies of up to 99% have been achieved without the use of counter-current flow typically employed in conventional nitric acid plants. The use high steam fractions was shown to cause significant improvements in gas phase reaction rates such that the usual industrial practice of applying high system pressures to enhance the NO oxidation reaction becomes unnecessary. Absorption efficiency can also be increased by increasing system pressures, but there are certain limits to which this can be done; a decline in performance may result when pressures are increased sufficiently high such that mass transfer becomes limiting. In addition to decreasing the tube diameter, increasing both the NO concentration and cooling duty also led to improved nitric acid yields. A simple model of condensing two-phase shear-driven annular flows, in which both laminar and turbulent regimes are valid and the vapour-liquid interface is assumed to be smooth, have been constructed and compared against experimental data. The model qualitatively captures most of the effects observed, but the presence of uncertainties in model parameters and the use of particular assumptions on the flow pattern and structure of the interface had to be compensated for through the use of a model fitted parameter iAθ. Larger corrections to the model were required in cases where the fluid was tending towards slug or plug flow, such as systems employing high H2O/NO ratios, since the interfacial area between vapour and liquid would be larger than that obtained if annular flow was assumed to occur under the same conditions. Higher values of iAθwere also found to give better fit to the experimental data at short nominal residence times (< 0.10 s) for absorption carried out under high system pressures, high oxygen partial pressures or high NO partial pressures, presumably due to incorrect representation of the overall heat and mass transfer flux under these conditions, among other things such as the parameter uncertainties, the presence of interfacial waves and the possibility of a flow regime transition from annular to intermittent flow. On the other hand, interfacial area multipliers less than unity were better suited to larger xix channels due to the possibility of flow stratification which acts to decrease the interfacial area and hence the nitric acid yield. The predictions of the model were subsequently used to determine the operating conditions optimal for the production of nitric acid in microreactors on a larger scale. In most of the cases considered, the pressure drop across the absorber length was found to be relatively small, hence much smaller channels can be utilised for increased absorption efficiency without considerable loss in pressure. It was also shown that most of the heat liberated near the inlet of the absorber stems from the release of latent heat of condensation, while chemical reactions account for most of the heat released downstream of the reactor. The absorption volume required for the commercial production of nitric acid in microchannels was compared against that typically employed by current industrial absorbers. The volume of the microreactor system was found to be about 2 orders of magnitude smaller than its larger counterpart. Although additional volume may be required for distillation of the weaker acid produced from the smaller system, substantial reduction in plant size can still be achieved since the volume of the cooler-condenser was excluded from the industrial plant calculations while the physical and chemical reactions involved in the cooler-condenser are already inherent in the microreactor system. In summary, the results of the experiments and model simulations have demonstrated that the absorption of nitrous gases in microchannels with the use of a steam ballast and close-to-stoichiometric quantities of oxygen can lead to intensification of the process, thus presenting an opportunity for a paradigm shift in nitric acid production.

At the United Nations Framework Conference on Climate Change COP15 (2009) Brazil presented ambitious commitments or Nationally Appropriate Mitigation Actions (NAMAs), to reduce greenhouse gases emissions (GHGs) mitigation by 2020. At COP21 (2015), the country presented new commitments and a framework to achieve further mitigation targets by 2030 as so-called Intended Nationally Determined Contributions (INDCs). Both NAMAs and INDCs focus on the land use change and agricultural sectors, but the INDCs include a commitment of zero illegal deforestation in the Amazon by 2030. This research focuses on the contribution of the livestock sector to reducing GHGs through the adoption of sustainable intensification measures. A detailed linear programming model, called Economic Analysis of Greenhouse Gases for Livestock Emissions (EAGGLE), of beef production was developed to evaluate environmental trade-offs. The modelling encompasses pasture degradation and recovery processes, animal and deforestation emissions, soil organic carbon dynamics and upstream life-cycle inventory. The model was parameterized for the Brazilian Cerrado, Amazon and Atlantic Forest biomes and further developed for farm-scale and regional-scale analysis. Different versions of the EAGGLE model was used to: (i) Evaluate the GHG mitigation potential and economic benefit of optimizing pasture management through the partitioning of initially uniform pasture area; (ii) to define abatement potential and cost-effectiveness of key mitigation measures applicable to the Brazilian Cerrado; (ii) to demonstrate the extent of cost-effective mitigation that can be delivered by the livestock sector as part of INDCs, and to show a result that underpins the national INDC target of zero deforestation; and (iv) to evaluate the consequences of reducing (or increasing) beef production on GHGs in the Cerrado. Counter-intuitively, a sensitivity analysis shows that reducing beef consumption could lead to higher GHG emissions, while increasing production could reduce total GHGs if livestock is decoupled from deforestation.

Process industries are cornerstones in today’s industrialized society. They contribute significantly in the manufacturing of various goods and products that are used in our day-to-day life. Our society’s paradigm of consumerism accompanied by a rise in global population drives an ever increasing demand for goods. One of many strategies developed to satisfy these demands and at the same time improve production capabilities is known as process intensification. As an example, this can be accomplished by implementation of devices using the principle of hydrodynamic and acoustic cavitation. High-intensity cavitation in the ultrasonic range can change the physical and chemical properties of a wide range of substances and hence, improve the production rate or quality. Despite the generally accepted benefits of hydrodynamic and acoustic cavitation, applications in the process industry are yet limited. The reasons are that the method requires extensive optimization, which depends on multiple process parameters and encounters problem in the implementation on a larger scale. Scalable cavitation reactor concepts for industrial applications need to meet challenges like stability and robustness, energy efficiency and high flow rates. This thesis focuses on the methodology for the design and optimization of a flow through cavitation reactor. An ultrasound reactor concept has been developed and tested for two different applications: i) Fibrillation processes typical for paper and pulp industry; ii) Metal leaching of mineral concentrates. Simulations were carried out using a commercially available software for multiphysics modeling which combines acoustics, structural dynamics, fluid dynamics and piezoelectrics. However, the optimization procedure requires extensive experimental work in parallel with multi-physical simulations. In general, the application leads to hydrodynamic initiation of small gas bubbles in the fluid to be excited and collapsed by high-intensity ultrasound. This transient collapse of the cavitation bubbles provides both mechanical and chemical effect on materials. The developed reactor has a power conversion efficiency of 36% in batch mode and is well suited for a scale-up. In flow-through mode, the cavitation effect improves extensively and provides stable results. Energy efficiency requires hydrodynamic initiation of cavitation bubbles, high acoustic cavitation intensity by multiple excitation frequencies adapted to the optimized reactor geometry, as well as optimal process pressure and temperature with respect to the materials to be treated. The impact of flow conditions and hydrodynamic cavitation is significant and almost doubles the yield at the same ultrasonic power input. In the case of fibrillation of cellulose fibers, results obtained indicate that generated cavitation intensity changes the mechanical properties of the fiber wall. In the case of leaching, experiments show that six hours of exposure gave a 57% recovery of tungsten from the scheelite concentrate at 80°C and atmospheric pressure. Future research will focus on different types of excitation signals, extended reactor volume, increased flow rates and use of a higher process temperature.

Dissertation (Ph.D. in Meteorology)--Naval Postgraduate School, June 2010.
Dissertation supervisor: Harr, Patrick A. "June 2010." Description based on title screen as viewed on July 14, 2010. Author(s) subject terms: Tropical Cyclones, TCS-08, T-PARC, Extratropical Transition, Airborne Dual Doppler Radar, ELDORA, Axisymmetrization, Mesoscale Vortices, Mesoscale Convective System. Includes bibliographical references (p. 207-212). Also available in print.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2000.
Includes bibliographical references (leaves 32-33).
Hurricane intensification modeling has been a difficult problem for the atmospheric science community. Complex models have been built to simulate the process, but with only a certain amount of success. A model developed by Dr. Kerry Emanuel is much simpler compared to previous studies. The Emanuel model approaches hurricane intensification as an ocean-controlled process where the upper-ocean heat content limits intensification. It is shown that this ocean-based model can produce very accurate results when the true structure of the ocean can be determined. The Ocean Topography Experiment (TOPEX) provides an opportunity for the model to be tested through the use of satellite altimetry. Measurements of the mixed layer depth and upper-ocean heat content are incorporated into the model for Hurricanes Bret, Gert, Opal, Mitch and Dolly. This technique is shown to be quite reliable for many storms, especially in the Gulf of Mexico. Limitations are examined where this method breaks down and improvements are suggested for its development into a forecasting tool.
by Christopher Gerald DesAutels.
S.M.

The aim of this work was to develop an intensified syngas cleaning system for different applications of the cleaned gas. The main target of syngas cleaning is the destruction of tars although the removal of heavy metals is also important. The syngas cleaning strategies include water scrubbing followed by further cleaning and moisture reduction, low temperature capture of tars and destruction of tars at high temperatures preferably at the gasifier exit temperature. In the present study, initially a novel downdraft intensive 50kWe air-blown auto-thermal gasifier was used for the gasification of refinery sludge indicating that refinery sludge could be gasified with low levels of tar as a result of catalytic tar cracking during gasification since refinery sludge initially contained large amounts of catalytic rare earth elements. It contained tar and particulate matter of less than 90 ± 6.0 mg/Nm3 and calorific value of 3.71 ± 0.4 MJ/Nm3 (wet gas), which is sufficient for power generation using an internal combustion engine (ICE). Gas composition, tar content and heat content of the produced gas were determined. Results were compared with those obtained with wood chips (reference feedstock). In the development of intensified syngas cleaning systems, we used a model syngas (carbon dioxide) and model tar (crude oil). A new/novel, multi-functional tar removal rig was designed and fabricated. It can be used as a water scrubber or for tar removal under electric field in the absence or presence of biphilic (both hydrophilic to adsorb water and lipophilic to adsorb tars) adsorbents in the form of functionalized PolyHIPE Polymers (PHPs). These PHPs were produced, functionalized and characterized using environmental scanning electron microscopy (ESEM) and surface area analysis (SAA) and then used in the form of packed bed for the adsorption of model tars from model syngas. According to the literature, using the syngas in a power production application, the tar concentration in syngas needs to be less than 100 mg/Nm3 which requires particle and tars reduction efficiencies of 90 % for a satisfactory operation of an Internal Composition Engine (ICE) using syngas produced in a downdraft gasifier. vii Maximum tar removal efficiencies under the prevailing process conditions were: water scrubbing 45.9 ± 4.5 %; adsorption by the sulphonated PolyHIPE Polymers (s-PHP) 61.8 ± 2.5 %; high voltage application with conductive electrodes 97.5 ± 1.5 % at 25kV; and the combination of s-PHP with electric field resulted in 96.7 ± 1.9 % % tar removal efficiency. The advantage of high voltage gas cleaning is that it can be used at high temperatures and that no other material is used as adsorbent which requires regeneration once they are saturated with tar, etc. Finally, another electrical method was designed to crack the model tars using plasma induced catalytic conversion. The results indicate that hydrocarbon profile of crude oil in the model syngas shifted towards low carbon number.

It may be tempting to think that humans generally say or do things once in communication. However, repetition for the communication of a particular stylistic effect is a commonplace and everyday occurance. Think of texts with repeated kisses and emoji, lively conversations with friends who excitedly produce the same utterance again, and adverts and branding campaigns that feature repeated utterances and forms. Within Relevance Theory pragmatics, pragmatic stylistics generally, and in some areas of linguistics proper, stylistic repetition is understudied and under-understood. The term is applied to a rag-tag muddle of phenomena that have little in common from the point of view of form, interpretation or effects. Utterances repeated due to illness, repeated forms mandated by the grammar (reduplication), forms necessarily repeated due to limits on linguistic resources (e.g., re-use of the common conjunction ‘and’), and the repetitions in poetry or rhetoric, or the repetitions produced by emphatic speakers are often lumped together, without consideration of speaker intentions, the nature of communication, or the division of labour between linguistic en-/decoding and pragmatic inference. Yet, these are all qualitatively distinct. This thesis (re)assesses a set of phenomena which have been called repetition, for example, reduplication, epizeuxis, and ‘long distance’ repetition, as well as repetition phenomena which have not yet been given detailed treatments within cognitive pragmatics, pragmatic stylistics or linguistics, such as repeated gradable adjectives, repeated intensifiers, repeated yes/no particles, and repeated face emoji. Study is restricted to the deliberate and ostensive repetition of such items for communicating vague and non-propositional effects. It is noted that many repetitions, particularly epizeuxis, are often called emphatic, or intensifying, or both. A key aim of this work is to combat the conflation surrounding the effects of stylistic repetitions, and to explain how such repetitions are recognised in the first instance as intended to communicate non-propositional effects. The work is carried out within Relevance Theory pragmatics (Sperber & Wilson, 1986/1995) and draws on the showing-saying continuum developed by Wharton (2009). From the point of view of how they achieve relevance, the repeated forms examined are all analysed as cases of indeterminate showing (Sperber & Wilson, 2015), and stylistic repetition is, as such, a non-verbal behaviour which allows a speaker to communicate a vague range of effects by providing relatively direct evidence for what their communication. Along the way, it is suggested that intensification is a processing phenomenon and not an effect, while emphasis is also judged not an effect, and is defined instead as highly ostensive showing on the part of a speaker. With support from repetition data, the author proposes a continuum of cases from mere display, through what is called highlighting (Wharton & Wilson, 2005), to emphasis, allowing for more fine-grained analyses of pragmatic phenomena in similar contexts.

Heat transfer equipment is one of the main unit operations in many industrial processes such as heating, cooling, transportation and power generation. Thus, convective heat transfer plays a major role in the heat equipment. In the past years, liquids such as water, oil and ethylene glycol had been used as the heat transfer fluids. These fluids have a major drawback since they possess low thermal conductivity. Thus innovation in developing advanced heat transfer fluids is needed in many industrial applications so that more energy efficient and compact systems can be achieved. This is the main impetus of this work. A nanofluid is a liquid suspension that consists of nano-sized solid particles. In this work, carbon nanotubes (CNT) and titanium dioxide (Ti02 ) were utilized in formulating nanofluids. The shape and morphology of these nanoparticles make it a challenge in producing long term stable nanofluids. CNT nanofluids were produced using sonication and higher shear mixing, while the Ti02 nanofluids were produced by using the beads mill. The CNT nanofluids dispersion stability was enhanced by the aid of gum arabic surfactant and the Ti02 was stabilized by means of electrostatic stabilization mechanism at pH - 11.0. The nanofluids were characterised using electron microscopy and size analyzer. The multi-wall CNTs have a diameter of < lOnm and length up to micron size, thus the aspect ratio is huge. The primary particles of Ti02 have an average diameter of 30-40 nm. The heat transfer study involves several measurements and analysis: i) the thermal conductivity measurements, ii) viscosity analysis and iii) convective heat transfer measurements. A significant enhancement was observed for thermal conductivity of CNTs nano fluids, where nanoparticles concentration of 0.25 wt %, 25% enhancement was observed. On the other hand, for concentration of 0.2 wt% of TiO2 nanofluids, a maximum of 3.2% enhancement was observed, both measurements were conducted at 25°C. The viscosity of CNT and Ti02 nanofluids showed shear thinning behaviour. The viscosity decreases with increasing shear rate, and decreases with increasing temperature. The viscosity of CNTs nanofluids was much greater than that of Ti02 nanofluids. At shear rate greater than 150 s the Ti02 nanofluids behaved like Newtonian fluids and the viscosity approached the viscosity values of water. The heat transfer behaviour of nanofluids was investigated for various experimental conditions such as flow conditions (Reynolds Number), nanoparticle concentration, pH, and particle size. For flow in 45 mm diameter pipe, the heat transfer coefficient decreases with increasing axial direction from the entrance, and increasing Reynolds Number. A significant enhancement for heat transfer coefficient was observed for CNT nanofluids. At Re = 800, a maximum of 350% enhancement of heat transfer coefficient was observed for 0.5wt % of CNTs. As the concentration increases, the maximum enhancement occurred at increasing axial direction along the pipe. On the other hand, the maximum enhancement (-16%), was observed at x/D = 150 for the Ti02 nanofluids. Moreover, the heat transfer coefficient of Ti02 increases with decreasing particle size for Reynolds Number > 2000. Apart from the thermal conductivity of nanoparticles, several other possible mechanisms are believed to be operating towards the enhancement of heat transfer coefficient. These include changes in the boundary layer thickness, particle migration and re-arrangement, thermal conduction increase due to shear and aspect ratio of nanoparticles.

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2016.
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Abstract : In this work, answers to some gaps found in the literature on the field of process intensification in microfluidic devices were proposed. The behavior of a carbon-based composite photocatalyst, specifically a composite of TiO2 and graphene, immobilized on the inner walls of a microchannel reactor, was evaluated and compared with a system containing pristine TiO2. Additionally, a comprehensive computational simulation was performed, based on fundamental physics of semiconductors and considering the coupling of radiation distribution, fluid flow, mass transport and chemical reactions. Moreover, a numerical study was carried out aiming to determine optimal photocatalytic film thicknesses for different illumination mechanisms (backside illumination, BSI, and front-side illumination, FSI) as a function of relevant operational variables and parameters, namely the incident irradiation, the apparent first-order reaction constant, the effective diffusivity and the absorption coefficient. Finally, the possibility of numerically predict the effect of wall wettability on gas-liquid flow pattern developed in microfluidic devices was investigated.

Dispositivos microfluídicos são baseados em microcanais nos quais o diâmetro efetivo é da ordem de centenas de micrômetros, resultando em elevada razão área/volume. Embora um considerável avanço tenha sido observado nessa área nas últimas décadas, resultando, inclusive, em aplicações industriais comercialmente disponíveis, ainda há importantes questões em aberto. Neste trabalho, respostas a algumas dessas questões foram propostas. Em particular, procurou-se determinar o comportamento de dispositivos microfluídicos aplicados à intensificação de processos fotocatalíticos considerando um fotocatalisador compósito (especificamente um compósito de dióxido de titânio e grafeno) imobilizado nas paredes internas. Tal sistema foi, então, comparado a um equivalente no qual dióxido de titânio puro foi imobilizado. As partículas de dióxido de titânio e do compósito de dióxido de titânio-grafeno foram depositadas por meio de um método térmico. Suspensões de TiO2 e TiO2- grafeno foram preparadas e injetadas ao longo de microcanais de chips microfluídicos comerciais construídos com vidro borossilicato. Os dispositivos foram, então, tratados termicamente para promover a evaporação do solvente (água) e a deposição do fotocatalisador nas paredes internas. O processo foi realizado ciclicamente para promover a formação de múltiplas camadas. A evolução da deposição foi avaliada pelo monitoramento dos perfis óticos dos sistemas. Azul de metileno foi usado como reagente modelo em ensaios de fotodegradação. Ensaios preliminares permitiram determinar o efeito dos fenômenos de adsorção e fotólise sobre o comportamento global. Nos experimentos de reação fotocatalisada observou-se que uma maior velocidade de reação inicial foi obtida no microrreator contendo fotocatalisador composto (TiO2-GR) imobilizado nas paredes internas, mas ambos os sistemas (TiO2 e TiO2- GR) exibiram velocidades de reação similares quando o estado estacionário foi alcançado. Verificou-se que a taxa de descolorização do azul de metileno no chip microfluídico foi, aproximadamente, uma ordem de magnitude maior que aquela reportada em sistemas macroscópicos equivalentes em condições experimentais similares. Além disso, investigou-se, neste trabalho, a possibilidade de avaliar teoricamente o comportamento de sistemas microfluídicos aplicados a processos fotocatalíticos com base na física fundamental de semicondutores, bem como a possibilidade de modelar computacionalmente os fenômenos acoplados (distribuição de intensidade luminosa, escoamento, transporte de massa e reação química) que ocorrem em reatores de microcanais (provendo uma estimativa para o desempenho do reator, dos pontos de vista global e local). O modelo computacional foi validado com os resultados experimentais. Na sequência, o modelo computacional foi aplicado para a predição da melhor espessura para o filme fotocatalítico imobilizado nas paredes internas de dispositivos microfluídicos em diferentes condições de iluminação (backside illumination, BSI, e front- side illumination, FSI) como função de variáveis operacionais e parâmetros relevantes, nomeadamente a irradiação incidente, a constante de velocidade de reação aparente de pseudo-primeira ordem, a difusividade efetiva e o coeficiente de absorção do fotocatalisador. Finalmente, a possibilidade de predizer numericamente o efeito da molhabilidade da parede sobre padrões de escoamento multifásicos desenvolvidos em microcanais foi avaliada. Tal modelo computacional pode ser utilizado como fonte de informação prévia sobre o impacto de diferentes propriedades do filme fotocatalítico na morfologia interfacial de escoamento gás-líquido em microrreatores fotoquímicos. Em particular, escoamentos gás-líquido isotérmicos (Taylor e estratificado) foram avaliados através do modelo volume of fluid (VOF). Microcanais com condições limites de hidrofilicidade e hidrofobicidade foram investigados tomando-se como base um referencial experimental disponível na literatura. Um estudo preliminar detalhado foi conduzido para a determinação da malha computacional ótima, capaz de permitir modelagem adequada do filme líquido formado entre as cavidades de gás e a parede sólida, no caso de Taylor flow. Os resultados numéricos foram comparados com dados experimentais (comprimento máximo de cavidade e área de cavidade, para o caso de Taylor flow, e espessura do filme gasoso no caso de escoamento estratificado) e algumas correlações disponíveis (comprimento máximo de cavidade e perda de carga por cavidade) e boa concordância foi observada. Nas mesmas condições de alimentação, o modelo foi capaz de captar os diferentes padrões de escoamento gás-líquido esperados quando o ângulo de contato da parede foi variado. Portanto, tal modelo computacional pode ser utilizado em estudos de scale out com o objetivo de projetar e otimizar reatores compactos modulares baseados na tecnologia de microcanais nos quais escoamento multifásico, particularmente gás e líquido, é estabelecido. Discussões acerca das limitações e de propostas futuras referentes ao desenvolvimento deste trabalho também são apresentadas.

Le but de cette étude est d'étudier l'amélioration du mélange par superposition d'une dépendance temporelle, sous la forme d'une pulsation, à un écoulement de Dean alterné où les trajectoires des particules fluides sont spatialement chaotiques. La dépendance temporelle de l'écoulement dans les conduites courbes peut générer des écoulements secondaires - composées de deux cellules contra-rotatives (cellules Dean) dans un régime stationnaire - plus complexe. Cette modification de l'écoulement secondaire qui se traduit par des gradients de vitesse plus forts, augmente les étirements et les repliements; et donc le mélange. La configuration chaotique étudiée dans ce travail est composée d’une série de six coudes alternés de 90°. Lors du passage d’un écoulement pulsé (stationnaire+sinusoïdal) dans cette géométrie, les champs de vitesse de l'écoulement secondaire sont mesuré en utilisant la vélocimétrie par images de particules (PIV) pour différentes conditions de pulsation. Pour éviter les effets de réfraction de lumière lors des mesures de PIV, un canal en forme de T est installé en aval du coude d’étude. Les expériences sont réalisées pour une large gamme de nombres de Reynolds stationnaire 420≤Rest≤1000, de rapports d’amplitude de vitesse 1≤(β=Umax,sin/Ust)≤4 et de paramètres de fréquence 8,37≤(α=r0(ω/ν)0,5)≤24,5. Les effets de chaque paramètre (Rest, β et α) sur le mélange transversal sont discutés en comparant les valeurs de vorticité adimensionnelles (|ζP|/|ζS|) et les taux de déformation transversale adimensionnels (|εP|/|εS|) au cours d’une période d’oscillation complète. Les résultats montrent que β≥2 et α≤15 sont les conditions favorables de pulsation pour l'amélioration du mélange. En plus, dans certaines conditions de pulsation, les centres de cellules visitent une zone (dans la section du canal) 9 fois plus grande que celle d’un cas stationnaire
The purpose of this study is to investigate mixing enhancement by superposition of a temporal dependence, in the form of a pulsation, on a twisted pipe flow where the trajectories of fluid particles are spatially chaotic. In the steady case, the secondary flow in a curved tube is composed of two counter-rotating cells (Dean cells), however, the temporal dependence of the flow can make this structure more complex. This modification of the secondary flow which results in stronger velocity gradients enhances stretching and folding (the main mechanism of mixing). Here, the chaotic configuration is composed of six alternating 90° curved pipes. When a pulsating (steady+sinusoidal) flow passes through this geometry, the velocity field is measured by particle image velocimetry (PIV) for different pulsating conditions. To obviate light-refraction effects during PIV measurements, a T-shaped end channel is installed at the exit of the curved pipe. Experiments are carried out for the steady Reynolds numbers range 420≤Rest≤1000, velocity component ratios 1≤ (β = Umax,sin / Ust) ≤ 4 and frequency parameters 8. 37≤(α=r0(ω/ν)0. 5)≤24. 5. The effects of each parameter (Rest, β and α) on transverse mixing are discussed by comparing the dimensionless vorticity (|ζP|/|ζS|) and dimensionless transverse strain rates (|εP|/|εS|) during a complete oscillation period. The results show that β ≥ 2 and α ≤ 15 are favorable pulsating conditions for mixing enhancement. Moreover, in some pulsation conditions, the cells’ centers visit a zone (in the flow cross-section) 9 times larger that that of the steady case

The natural environment will become an increasingly important arena for economic competition in the future. The growing world population and the increased global consumption raise concerns about the sustainability of the current and future use of natural resources. Due to the growing global population the production of agricultural crops and food security is high on the global policy agenda. The purpose of this study has been to investigate the opportunities for a sustainable intensification in the Swedish cereals production and how the Lantmännen cooperative, a company active in the whole cereals value chain can act in order to enable the intensification. The research was conducted as a descriptive case study. Given the comprehensive nature of the purpose of this study, we have studied the Swedish agriculture from a system perspective in order to get the comprehensive understanding of its complexity. The findings presented in this report are based on data from multiple research methods such as interviews with stakeholder in the agriculture, database search, and archive searches. We show in this study that a sustainable intensification of the Swedish cereals production can be realized through utilizing the existing unused farmland registered by the farmer as fallow for a number of consecutive years in a row, which can be described as acreage that is not used for crop production but is still kept in farmable condition. Our study has identified four barriers hindering the intensification; Single payment system, Leasing contract, Logistics and Investment costs. To overcome these barriers we argue that the RO PSS business model is appropriate. By using this model Lantmännen will be able to deliver four different types of values to the farmers. The first value is the intangible value of identity, which let inactive farmers continue to live on their farms while being able to focus on other sources of main income. The second value we name ownerless consumption. This value offers farmers with little capital to start up or expand their production without having to invest in new machinery and equipment. The third value we call safety, which is connected to the barrier of lease contracts identified and the distrust between landowners and tenants. The fourth value, specialization, gives the farmer possibility to leverage overall cereals bulk production by including niche crops. We conclude by arguing that the opportunities for an intensification of the Swedish Cereals production lie in delivering these four values.
Naturen kommer i framtiden bli en alltmer viktig arena för ekonomisk konkurrens. En växande världsbefolkning och en ökad global konsumtion skapar oro kring hållbarheten i vårt användande av naturresurser. På grund av den ökande befolkningsmängden placerar sig frågor såsom produktionen av jordbruksgrödor och livsmedelsförsörjning högt upp på den globala politiska dagordningen. Studiens syfte är att undersöka möjligheter för en hållbar intensifiering av den svenska spannmålsodlingen och hur Lantmännen, ett kooperativt företag som verkar i spannmålets hela värdekedja ska agera för att möjliggöra intensifieringen. Med tanke på den övergripande karaktären av våra frågeställningar har vi studerat det svenska jordbruket ur ett systemperspektiv för att få en övergripande förståelse av dess komplexitet. Forskningen har genomförts i form av en beskrivande fallstudie. Våra resultat baseras på data från flera forskningsmetoder som intervjuer med intressenter inom jordbruket, databassökning, arkivsökning. Vår studie visar att en hållbar intensifiering av den svenska spannmålsodlingen kan realiseras genom att utnyttja befintlig oanvänd jordbruksmark som av jordbrukaren registrerats som träda i flera år i följd. Träda kan beskrivas som jordbruksareal som inte används till växtodling men som fortfarande hålls i odlingsbart skick. För att få denna mark i bruk och därmed möjliggöra en intensifiering krävs det att få bukt med fyra identifierade barriärer inom det svenska jordbrukssystemet; Gårdsstödet, Arrendekontrakt, Logistik och Investeringskostnader. Vi hävdar, baserat på våra resultat och analyser, att affärsmodellkonceptet RO PSS är lämplig att använda då Lantmännen ska lyckas få bukt med barriärerna. Denna modell kommer leverera fyra olika värden till jordbrukarna. Det första värdet har vi döpt till Identitet och är av en immateriell natur som vilket låter inaktiva jordbrukare fortsätta bo kvar på sina gårdar medan de inriktar sig på andra inkomstbaserade verksamheter. Det andra värdet gav vi namnet Ägandefri konsumtion. Detta ger värde till jordbrukaren i form av att jordbrukaren inte behöver låna pengar för höga  investeringskostnader i maskiner och infrastruktur vid uppstart eller expansion av verksamheten. Det tredje värdet kallar vi för Säkerhet, vilket är relaterat till barriären arrendekontrakt där vi har funnet en misstro mellan markägare och arrendatorer. Det fjärde värdet, Specialisering, ger jordbrukaren möjlighet att blanda in specialgrödor i sin produktion, och på så vis skapa en hävstång åt bulkproduktionen. Vår slutsats är att möjligheterna för en intensifiering av den Svenska spannmålsodlingen ligger i att kunna leverera dessa värden.

L'objectif de ce travail fut d'intensifier des procédés de polymérisation radicalaire par transfert d'atomes (ATRP) du méthacrylate de 2-(dimétylamino)éthyle (DMAEAMA) au moyen de technologies de microréaction (microréacteurs, micromélangeurs) et de paramètres de procédé (géométrie du réacteur, température, pression ... ).L'impact du prémélange sur les caractéristiques d'un copolymère statistique du DMAEMA et du méthacrylate de benzyle synthétisé dans des microréacteurs hélicoïdaux (CT) fut étudié en utilisant des principes différents de micromélange: bilamination, multilamination interdigitale (!MM) et jet d'impact. Des caractéristiques bien mieux contrôlées ont été obtenues avec !'IMM et l'intensification du procédé (Pl) a été clairement démontrée encomparaison d'un réacteur fermé ; en effet des masses molaires et conversions plus élevées ainsi que de plus faibles indices de polymolécularité (PDI) ont été obtenus pour des temps de passage inférieurs. Pour la production de PMADAME linéaire, le PI a également été réalisé par augmentation de la température et de la pression (jusqu'à 1 OO bars). Toutefois de trop hautes températures se sont avérées préjudiciables notamment pour de longs temps de passage. L'effet de l'augmentation du taux de cisaillement (via la longueur du réacteur) ne fut bénéfique qu'en régime dilué à un stade précoce de la réaction lorsque les masses molaires sont encore faibles. Comparés aux CT, un mélange interne favorisé par une technique d'inversion de flux s'est révélé être une stratégie très efficace pour réduire davantage le PDI et obtenir des masses molaires et conversions plus élevées. Des polymères branchés synthétisés en microréacteurs à inversion de flux (CFI) par ATRP en présence d'inimère présentèrent une structure plus ramifiée soulignant ainsi la supériorité des CFI sur les CT et réacteurs fermés en termes de PDI et d'efficacité de branchement. Considérant les caractéristiques des CFI, l'augmentation d'échelle des microréacteurs fut considérée par accroissement de leur diamètre. La productivité du procédé a été augmentée d'un facteur 4 tout en gardant un bon contrôle sur les caractéristiques macromoléculaires. Ainsi fut-il démontré que l'inversion de flux est un moyen très efficace pour contrebalancer l'effet négatif d'une augmentation du diamètre du microréacteur
The aim of this work was to intensify Atom Transfer Radical polymerization (ATRP) processes for the production of DMAEMA-based (co)polymers by relying on microreaction technology tools (microreactor, micromixers) and process parameters (reactor geometry, temperature, pressure ... ). Impact of premixing on macromolecular characteristics of P(DMAEMA-co-BzMA) synthesized in coiled tube (CT) microreactors was studied using different micromixing principles: bilamination, interdigital multilamination (IMM) and impact jet.Better controlled characteristics were obtained with !MM and process intensification (PI) was clearly demonstrated in comparison with batch mode as higher molecular weights, increased monomer conversions and lower polydispersity indices (PDI) were obtained for lower residence times. For the production of linear PDAEMA, PI was also achieved by application of elevated temperature and pressure (up to 100 bars). However, high temperature was found to be detrimental for long residence times. Effect of increased shear rate (i.e. reactor length) was found only beneficial in dilute regime at the early stage of the polymerization reaction when molecular weights are low. ln comparison with CT reactors, internal mixing promoted by flow inversion technique was found to be quite an effective strategy to reduce further PDI and obtain higher molecular weights and monomer conversions. Branched polymers synthesized by self condensing vinyl copolymerization (SCVCP) adapted to ATRP in tubular coil flow inverter (CFI) microreactors exhibited higher branched structure highlighting the superiority of CFI microreactor over CT and batch reactors in terms of PD! and branching efficiency. Finally, considering such features of CFI, attempt was made to scale-up microreactors by increasing their diameter. lt was found that process throughput can be increased by more than a factor of 4 while keeping a good control over macromolecular characteristics. Thus itwas demonstrated that flow inversion is quite effective to counter balance the detrimental effect of an increase in microreactor diameter

Olefins (Ethylene and Propylene) are the most important products of the petrochemical industry, because of their wide range of applications. The global demand tor ethylene and propylene is expected to increase over tne next live years and production capacity must also increase to Keep up witti tins demand growth. There are several industrial processes for ethylene and propylene production; the most widely used process is the steam cracking process in which the hydrocarbon ieed is thermally-cracked to produce olefins. Coke is an undesirable by-product because it deposits on the internal walls of the reactor tubes, consequently reducing the heat transfer rate and increasing the pressure drop across the reactor. The reactor has to be shut down frequently for decoking. Several research studies have been conducted and new technologies developed to improve the performance of the steam cracking process.

Thesis (MSc)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: The multifaceted land degradation problem and its associated manifold impacts have attracted research from different disciplines, resulting in varying definitions of the concept. However, most researchers agree that human intervention that deteriorates the state of the environment is the central element. Among the anthropogenic activities that exacerbate land degradation, land cover has been singled out as the salient element. Rapid and unplanned land cover changes are primary manifestations of this problem. UMhlathuze Municipality, the study area which has superior biodiversity richness, is one of fastest growing municipalities in South Africa and is the locale of significant land modifications in recent decades because of a variety of industrial and residential developments. Using Landsat TM imagery acquired for 1984, 1996 and 2004, this study mapped and quantified land cover change and manifestations of land degradation in the uMhlathuze Municipality in conjunction with settlement intensification computed from orthophotographs acquired for 1984 and 2004. Census population statistics were analysed as a reflection of population dynamics and further to gauge related causes of land cover change. Geographical information technology (GIT) was applied as an analytical tool. The results revealed the anthropogenic influences that led to changes in land cover over the 20- year period between 1984 and 2004. The dominant natural cover classes in 1984 declined continuously and human-dominated land categories had increased sharply by 2004. Much of grasslands, forest and wetlands were converted to monotypical agroforestry (sugar cane and forestry plantations), built-up settlement and mining. These changes engendered complete loss of biodiversity (floral and migration of fauna). Bare ground, signifying land degradation, was noticeable although it exhibited a fluctuating trend which could be attributable to differences between the various imagery used. Along with population growth, the area of settlements increased over the study period and spatially sprawled from urban areas. Settlements showed a fairly stable spatial configuration over the 20-year period, but became magnified in medium- and high-density areas. Grassland and wetlands occurring around Richards Bay, as well as indigenous forest near Port Durnford, were identified as critically threatened ecosystems. The proposed industrial development zone and port expansion were recognized as having adverse ecological implications for wetlands. The study concluded that significant land cover changes occurred in the form of natural land cover giving way to monotypical agroforestry, built-up settlements and mining - all to the detriment of pristine natural habitat.
AFRIKAANSE OPSOMMING: Die veelvlakkige probleem van omgewingsdegradasie en die gepaardgaande veelsoortige impakte lok navorsing uit verskillende dissiplines, wat lei tot verskillende definisies van die konsep. Tog is die meeste navorsers dit eens dat menslike invloede die sentrale element is wat die toestand van die omgewing verswak. Van die vele menslike aktiwiteite is grondgebruikverandering uitgesonder as die belangrikste beïnvloeder van agteruitgang van die omgewing. Veral vinnige en onbeplande grondgebruikveranderinge verteenwoordig die primêre manifestasies van hierdie probleem. UMhlathuze Munisipaliteit, die studiegebied met 'n hoë biodiversiteitsrykdom, is een van die vinnigste groeiende munisipaliteite in Suid-Afrika, waar 'n verskeidenheid nywerheids- en residensiële ontwikkelings beduidende grondgebruikverandering oor die afgelope dekades dryf. Met behulp van Landsat TM beelde van 1984, 1996 en 2004, is hierdie studiegebied gekarteer en oppervlaktes gekwantifiseer om grondgebruikverandering en verwante manifestasies van die agteruitgang van landbedekking in die uMhlathuze Munisipaliteit te konstateer. Tesame hiermee is die verdigting van nedersettings ook met behulp van ortofoto’s van 1984 en 2004 aangeteken. Bevolkingsensusstatistieke is ontleed as weerspieëling van die gepaardgaande bevolkingsdinamika en om moontlike oorsake van verandering in grondbedekking te bepaal. Vir hierdie doel is geografiese inligtingstegnologie (GIT ) as analitiese instrument toegepas. Die resultate toon antropogeniese invloede lei tot veranderinge in grondbedekking oor die tydperk van 20 jaar tussen 1984 en 2004. Die dominante natuurlike dekkingsklasse in 1984 het voortdurend verminder en menslik-gedomineerde kategorieë het teen 2004 skerp gestyg. Baie van die grasvelde, woude en vleilande is daadwerklik omskep tot monotipiese agro-bosbou (suikerrieten bosbouplantasies), beboude nedersetting en mynbou. Hierdie veranderinge behels 'n volledige verlies van biodiversiteit (plantegroei en migrasie van fauna). Kaalgrond, wat dui op die agteruitgang van grondbedekking, was ook opvallend, hoewel dit 'n wisselende tendens toon wat ook kan wees as gevolg van die verskille tussen die beeldmateriaal wat gebruik is. Saam met die groei van die bevolking is bevind dat nedersettings oor die studieperiode toegeneem het en in tipiese spreipatrone weg van die stedelike gebiede uitbrei. Nedersettings het 'n redelik stabiele ruimtelike liggingsopset oor die tydperk van 20 jaar getoon, maar het in medium- en hoë- digtheid gebiedeverdeel. Die voorkoms van grasveld en vleiland rondom Richardsbaai, asook inheemse woud naby Port Durnford, is geïdentifiseer as krities-bedreigde ekosisteme. Die voorgestelde nywerheidsontwikkelingsone en hawe-uitbreiding is geïdentifiseer as ontwikkelings met nadelige ekologiese implikasies vir vleilande. Daar is dus tot die gevolgtrekking gekom dat beduidende voortgaande grondbedekkingveranderinge in die gebied voorkom, waarin natuurlike landdekking transformeer tot monotipiese agrobosbou, beboude nedersettings en mynbou - alles tot nadeel van die ongerepte natuurlike habitat.

This study is aimed to provide comprehensive evaluation and mechanistic understanding of the impact of process intensification techniques applied in main and side stream wastewater treatment on biosolids management in terms of anaerobic digestion enhancement, dewaterability improvement, odor mitigation, as well as phosphorus and nitrogen removal. The first part of this study was conducted to understand the effect of anaerobic digester solids retention time (SRT) on odor emission from biosolids. A kinetic model and inhibitory studies showed the emission of methanethiol (MT), a representative odor compound, was primarily determined by the dynamic concurrence of MT production from amino acid and utilization by methanogens in the course of anaerobic digestion. MT emission pattern follows a bell-shape curve with SRT in anaerobic digesters. However, for digested and dewatered biosolids, SRT ranging from 15 to 50 days in anaerobic digesters demonstrated insignificant effect on the odor emission from biosolids. In contrast, the peak odor emission was found to exponentially increase with both shear intensity and polymer dose applied during dewatering. The second part of this study investigated the impact of process intensification practices on sludge dewatering performance. The integration of high-rate activated sludge process and anaerobic digestion elevated the sludge orthophosphate level, leading to struvite scaling and dewaterability deterioration. Superior orthophosphate removal, significant improvement of sludge dewaterability, and favorable economics were achieved through sludge conditioning by cerium chloride. Continuous flow aerobic granulation technology offered significant process intensification of mainstream treatment trains. However, its impact on biosolids management was not studied. This study showed that there was little dewaterability difference between aerobic granular sludge and activated sludge when polymer was not added. However, about 75% polymer saving and improved dewatering performance were observed with polymer addition. When subjected to high shear, a greater dewaterability deterioration was observed for granular sludge than activated sludge. The last part of this study is focused on the impact of anaerobic digestion process intensification through thermal treatment including pre-pasteurization, thermophilic anaerobic digestion, temperature phased anaerobic digestion, and thermal hydrolysis pretreatment. Improved methane production, pathogen reduction, dewatering performance, and odor mitigation were observed with the involvement of these high-temperature processes. However, special cautions and measure should be taken during the start-up of these high rate processes as they are more liable to digester souring. In addition, the in-depth understanding of the mechanism of recalcitrant dissolved organic nitrogen formation during sludge thermal pretreatment was provided.
Doctor of Philosophy
This study is aimed to provide comprehensive evaluation and mechanistic understanding of the impact of process intensification techniques applied in main and side stream wastewater treatment on biosolids management in terms of anaerobic digestion enhancement, dewaterability improvement, odor mitigation, as well as phosphorus and nitrogen removal. The first part of this study was conducted to understand the effect of anaerobic digester solids retention time (SRT) on odor emission from biosolids. A kinetic model and inhibitory studies showed the emission of methanethiol (MT), a representative odor compound, was primarily determined by the dynamic concurrence of MT production from amino acid and utilization by methanogens in the course of anaerobic digestion. MT emission pattern follows a bell-shape curve with SRT in anaerobic digesters. However, for digested and dewatered biosolids, SRT ranging from 15 to 50 days in anaerobic digesters demonstrated insignificant effect on the odor emission from biosolids. In contrast, the peak odor emission was found to exponentially increase with both shear intensity and polymer dose applied during dewatering. The second part of this study investigated the impact of process intensification practices on sludge dewatering performance. The integration of high-rate activated sludge process and anaerobic digestion elevated the sludge orthophosphate level, leading to struvite scaling and dewaterability deterioration. Superior orthophosphate removal, significant improvement of sludge dewaterability, and favorable economics were achieved through sludge conditioning by cerium chloride. Continuous flow aerobic granulation technology offered significant process intensification of mainstream treatment trains. However, its impact on biosolids management was not studied. This study showed that there was little dewaterability difference between aerobic granular sludge and activated sludge when polymer was not added. However, about 75% polymer saving and improved dewatering performance were observed with polymer addition. When subjected to high shear, a greater dewaterability deterioration was observed for granular sludge than activated sludge. The last part of this study is focused on the impact of anaerobic digestion process intensification through thermal treatment including pre-pasteurization, thermophilic anaerobic digestion, temperature phased anaerobic digestion, and thermal hydrolysis pretreatment. Improved methane production, pathogen reduction, dewatering performance, and odor mitigation were observed with the involvement of these high-temperature processes. However, special cautions and measure should be taken during the start-up of these high rate processes as they are more liable to digester souring. In addition, the in-depth understanding of the mechanism of recalcitrant dissolved organic nitrogen formation during sludge thermal pretreatment was provided.

The present thesis has focused on the intensive study of the methane dehydroaromatization process under non-oxidative conditions for producing benzene and H2 in a direct way. Nevertheless, MDA process is thermodynamically limited and, moreover, the catalyst quickly accumulates large amounts of carbonaceous deposits, which hinders its commercialization. Therefore, this thesis has as fundamental purposes the improvement of the catalytic activity and the stability of the catalyst on MDA reaction. The catalysts widely used on MDA reaction are Mo/zeolite, which are bifunctional, i.e., Mo sites are involved in the methane dehydrogenation and formation of CHx species, which are dimirized to C2Hy species, and Brønsted acid sites of the zeolite oligomerize these C2Hy species, forming mostly benzene and naphthalene. Thereby, different Mo/zeolite catalysts were prepared using commercial zeolites as well as zeolites synthesized on the laboratory. Thus, observing that the zeolite and the Mo content employed on the catalyst affected significantly the MDA performance. The topology and the channel dimensions of the zeolite as well as its Si/Al ratio and crystal size were also important on the MDA results obtained. Concretely, the best MDA performance was achieved by the 6%Mo/MCM-22 catalyst. Different catalyst activation procedures were tested, achieving the best MDA performance and catalyst stability using a gas mixture of CH4:H2, 1:4 (vol. ratio) during 1 h up to 700 ºC and maintaining this temperature for 2 h. This catalyst activation leads to the pre-carburization and pre-reduction of the Mo species, obtaining the most active and stable on MDA reaction. Moreover, the effect of the space velocity was studied in the present thesis. The best MDA results were reached at 1500 mL¿h-1¿gcat-1, as at higher space velocities methane barely can interact with the catalytic sites. While at lower space velocities the condensation of the heavy aromatic hydrocarbons is facilitated, causing higher coke accumulation on the catalyst. Furthermore, higher catalyst stability was obtained by co-feeding H2O, H2 and CO2 separately using the 6%Mo/HZSM-5 catalyst as well as the 6%Mo/MCM-22, due to the partial suppression of coke deposited. However, the catalytic activity was worsen by adding these co-reactants because of, on one hand, thermodynamically the addition of H2O, H2 or CO2 to the methane feed is detrimental and, on the other hand, H2O and CO2 partially re-oxidize the Mo species of the catalyst. Thermodynamically, H2 causes an equilibrium shift and, therefore, a decrease on the methane conversion; H2O favors the methane reforming reaction and coke gasification; and CO2 promotes the methane reforming reaction and the reverse Boudart reaction. The development and implementation of a catalytic membrane reactor (CMR) that integrates the 6%Mo/MCM-22 catalyst and the BZCY72 tubular membrane has been carried out on the present thesis. The MDA performance and the stability of the catalyst were exceptionally improved using this CMR by imposing a current to the electrochemical cell, changing or not the standard operating conditions. These good results were obtained due to the simultaneous H2 removal from MDA reaction side and O2 injection to this side through the BZCY72 tubular membrane. Thus, the H2 extraction results in the thermodynamic equilibrium displacement of MDA reaction, which causes the increase of the methane conversion and in turn of the aromatics yield. Moreover, the O2 injection involves the formation of H2O in low concentration, which reacts with coke accumulated (coke gasification), rising the stability of the catalyst.
La presente tesis se ha centrado en el estudio intensivo del proceso de deshidroaromatización de metano en condiciones no oxidativas para producir benceno e hidrógeno de forma directa. Sin embargo, el proceso de MDA está limitado termodinámicamente y, además, el catalizador acumula rápidamente grandes cantidades de depósitos carbonosos, lo que dificulta su comercialización. Por tanto, esta tesis tiene como objetivos fundamentales la mejora de la actividad catalítica y la estabilidad del catalizador en la reacción MDA. Los catalizadores Mo/zeolita son ampliamente utilizados en la reacción MDA, los cuales son bifuncionales, es decir, los sitios de Mo están involucrados en la deshidrogenación del metano y la formación de las especies CHx, las cuales se dimerizan a especies C2Hy, y los sitios ácidos de Brønsted de la zeolita oligomerizan éstas especies C2Hy, formando principalmente benceno y naftaleno. Por lo que, diferentes catalizadores Mo/zeolita se prepararon utilizando zeolitas tanto comerciales como sintetizadas en el laboratorio. Observando así que la zeolita y el contenido de Mo utilizados en el catalizador afectan significativamente el rendimiento de la reacción MDA. Tanto la topología y las dimensiones de los canales de la zeolita como su relación Si/Al y su tamaño de cristal son también importantes en los resultados obtenidos de la reacción MDA. Concretamente, el mejor rendimiento de MDA fue obtenido por el catalizador 6%Mo/MCM-22. Se probaron diferentes procedimientos de activación del catalizador, obteniendo el mejor rendimiento de la reacción MDA y estabilidad del catalizador usando una mezcla gaseosa de CH4:H2, 1:4 (relación en volumen) durante 1 h hasta 700 ºC y manteniendo esta temperatura durante 2 h. Esta activación del catalizador provoca la pre-carburización y pre-reducción de las especies de Mo, obteniendo las más activas y estables en la reacción de MDA. Los mejores resultados de MDA se obtuvieron con 1500 mL¿h-1¿gcat-1, ya que con mayores velocidades espaciales el metano apenas puede interaccionar con los sitios catalíticos. Mientras que con menores velocidades espaciales la condensación de los hidrocarburos aromáticos pesados se ve favorecida, provocando una mayor acumulación de coque en el catalizador. Por otra parte, co-alimentando H2O, H2 y CO2 por separado se obtuvo una mayor estabilidad tanto del catalizador 6%Mo/HZSM-5 como del 6%Mo/MCM-22, debido a la supresión parcial del coque depositado. Sin embargo, la actividad catalítica empeoró al añadir estos co-reactivos ya que, por un lado, la adición de H2O, H2 y CO2 a la alimentación de metano es perjudicial termodinámicamente y, por otro lado, el H2O y el CO2 re-oxidan parcialmente las especies Mo del catalizador. Termodinámicamente, el H2 provoca un cambio en el equilibrio y, por tanto, una disminución de la conversión de metano; el H2O favorece la reacción de reformado de metano y la gasificación de coque; y el CO2 promueve la reacción de reformado de metano y la reacción inversa de Boudart. En la presente tesis se ha llevado a cabo el desarrollo y la implementación de un reactor catalítico de membrana (CMR) que integra el catalizador 6%Mo/MCM-22 y la membrana tubular BZCY72. El rendimiento de la reacción MDA y la estabilidad del catalizador fueron excepcionalmente mejorados usando este CMR imponiendo una corriente a la celda electroquímica, cambiando o no las condiciones de operación estándar. Estos buenos resultados fueron obtenidos debido a la simultánea extracción de H2 del lado de reacción y la inyección de O2 a este lado mediante la membrana tubular BZCY72. Así, la extracción de H2 se traduce en un desplazamiento del equilibrio termodinámico de la reacción MDA, lo que causa el aumento de la conversion de metano y a su vez del rendimiento de aromáticos. Además, la inyección de O2 implica la formación de agua en baja concentración, la que reacciona con el coque acumulado (gas
La present tesi s'ha centrat en l'estudi intensiu del procés de deshidroaromatització de metà en condicions no oxidatives per produir benzé i hidrogen de forma directa. No obstant això, el procés de MDA està limitat termodinàmicament i, a més, el catalitzador acumula ràpidament grans quantitats de dipòsits carbonosos, el que dificulta la seva comercialització. Per tant, aquesta tesi té com a objectius fonamentals la millora de l'activitat catalítica i l'estabilitat del catalitzador en la reacció MDA. Els catalitzadors Mo/zeolita són àmpliament utilitzats en la reacció MDA, els quals són bifuncionals, és a dir, els llocs de Mo estan involucrats en la deshidrogenació del metà i la formació de les espècies CHx, les quals es dimeritzen a espècies C2Hy, i els llocs àcids de Brønsted de la zeolita oligomeritzan aquestes espècies C2Hy, formant principalment benzè i naftalè. Per tant, diferents catalitzadors Mo/zeolita es van preparar utilitzant zeolites tant comercials com sintetitzades al laboratori. Observant així que la zeolita i el contingut de Mo utilitzats en el catalitzador afecten significativament el rendiment de la reacció MDA. Tant la topologia i les dimensions dels canals de la zeolita com la seva relació Si/Al i el seu tamany de cristall són també importants en els resultats obtinguts de la reacció MDA. Concretament, el millor rendiment de MDA va ser obtingut pel catalitzador 6%Mo/MCM-22. Es van provar diferents procediments d'activació del catalitzador, obtenint el millor rendiment de la reacció MDA i estabilitat del catalitzador usant una mescla de gasos de CH4: H2, 1: 4 (relació en volum) durant 1 h fins a 700 ºC i mantenint aquesta temperatura durant 2 h. Aquesta activació del catalitzador provoca la pre-carburització i pre-reducció de les espècies de Mo, obtenint les més actives i estables en la reacció de MDA. A més, en la present tesi es va estudiar l'efecte de la velocitat espacial. Els millors resultats de MDA es van obtindre amb 1500 mL¿h-1¿gcat-1, ja que amb majors velocitats espacials el metà gairebé no pot interaccionar amb els llocs catalítics. Mentre que amb menors velocitats espacials la condensació dels hidrocarburs aromàtics pesants es veu afavorida, provocant una major acumulació de coc en el catalitzador. D'altra banda, co-alimentant H2O, H2 i CO2 per separat es va obtindre una major estabilitat tant del catalitzador 6%Mo/HZSM-5 com del 6%Mo/MCM-22, a causa de la supressió parcial del coc dipositat. No obstant això, l'activitat catalítica empitjorà en afegir aquests co-reactius ja que, d'una banda, l'addició d'H2O, H2 i CO2 a l'alimentació de metà és perjudicial termodinàmicament i, d'altra banda, el H2O i el CO2 re-oxiden parcialment les espècies Mo del catalitzador. Termodinàmicament, el H2 provoca un canvi en l'equilibri i, per tant, una disminució de la conversió de metà; l'H2O afavoreix la reacció de reformat de metà i la gasificació de coc; i el CO2 promou la reacció de reformat de metà i la reacció inversa de Boudart. En la present tesi s'ha dut a terme el desenvolupament i la implementació d'un reactor catalític de membrana (CMR) que integra el catalitzador 6%Mo/MCM-22 i la membrana tubular BZCY72. El rendiment de la reacció MDA i l'estabilitat del catalitzador van ser excepcionalment millorats usant aquest CMR imposant un corrent a la cel¿la electroquímica, canviant o no les condicions d'operació estàndard. Aquests bons resultats van ser obtinguts a causa de la simultània extracció d'H2 del costat de reacció i la injecció d'O2 a aquest costat per mitjà de la membrana tubular BZCY72. Així, l'extracció d'H2 es tradueix en un desplaçament de l'equilibri termodinàmic de la reacció MDA, el que causa l'augment de la conversió de metà i alhora del rendiment d'aromàtics. A més, la injecció d'O2 implica la formació d'aigua en baixa concentració, la qual reacciona amb el coc acumulat (gasificació de coc)
Zanón González, R. (2017). Intensification of methane dehydroaromatization process on catalytic reactors [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/83124
TESIS

Doutoramento em Engenharia Mecânica
A desmaterialização da economia é um dos caminhos para a promoção do desenvolvimento sustentável na medida em que elimina ou reduz a utilização de recursos naturais, fazendo mais com menos. A intensificação dos processos tecnológicos é uma forma de desmaterializar a economia. Sistemas mais compactos e mais eficientes consomem menos recursos. No caso concreto dos sistemas envolvendo processo de troca de calor, a intensificação resulta na redução da área de permuta e da quantidade de fluido de trabalho, o que para além de outra vantagem que possa apresentar decorrentes da miniaturização, é um contributo inegável para a sustentabilidade da sociedade através do desenvolvimento científico e tecnológico. O desenvolvimento de nanofluidos surge no sentido de dar resposta a estes tipo de desafios da sociedade moderna, contribuindo para a inovação de produtos e sistemas, dando resposta a problemas colocados ao nível das ciências de base. A literatura é unânime na identificação do seu potencial como fluidos de permuta, dada a sua elevada condutividade, no entanto a falta de rigor subjacente às técnicas de preparação dos mesmos, assim como de um conhecimento sistemático das suas propriedades físicas suportado por modelos físico-matemáticos devidamente validados levam a que a operacionalização industrial esteja longe de ser concretizável. Neste trabalho, estudou-se de forma sistemática a condutividade térmica de nanofluidos de base aquosa aditivados com nanotubos de carbono, tendo em vista a identificação dos mecanismos físicos responsáveis pela condução de calor no fluido e o desenvolvimento de um modelo geral que permita com segurança determinar esta propriedade com o rigor requerido ao nível da engenharia. Para o efeito apresentam-se métodos para uma preparação rigorosa e reprodutível deste tipo de nanofluido assim como das metodologias consideradas mais importantes para a aferição da sua estabilidade, assegurando deste modo o rigor da técnica da sua produção. A estabilidade coloidal é estabelecida de forma rigorosa tendo em conta parâmetros quantificáveis como a ausência de aglomeração, a separação de fases e a deterioração da morfologia das nanopartículas. Uma vez assegurado o método de preparação dos nanofluídos, realizou-se uma análise paramétrica conducente a uma base de dados obtidos experimentalmente que inclui a visão central e globalizante da influência relativa dos diferentes fatores de controlo com impacto nas propriedades termofísicas. De entre as propriedades termofísicas, este estudo deu particular ênfase à condutividade térmica, sendo os fatores de controlo selecionados os seguintes: fluido base, temperatura, tamanho da partícula e concentração de nanopartículas. Experimentalmente, verificou-se que de entre os fatores de controlo estudados, os que maior influência detêm sobre a condutividade térmica do nanofluido, são o tamanho e concentração das nanopartículas. Com a segurança conferida por uma base de dados sólida e com o conhecimento acerca da contribuição relativa de cada fator de controlo no processo de transferência de calor, desenvolveu-se e validou-se um modelo físico-matemático com um caracter generalista, que permitirá determinar com segurança a condutividade térmica de nanofluidos.
The economy dematerialization is a means to promote sustainable development as it eliminates or reduces the use of natural resources. Hence, the intensification of technological processes is a way to dematerialize the economy. More compact and efficient systems require fewer resources. In what concerns technological systems involving heat exchange processes, intensification results in the reduction of the exchanging area and amount of working fluid, which in addition to other advantages inherent to systems’ miniaturization, is a direct contribution of the scientific and technological development to a more sustainable society. The development of nanofluids is a response to such challenges of contemporary society, contributing to the innovation of products and systems by solving fundamental questions raised at the level of basic sciences. The available literature is unanimous identifying nanofluids potential as an engineering thermal fluid due to their thermo-physical properties, namely a high thermal conductivity. However, the lack of rigorous preparation techniques as well as of a systematic knowledge of their thermo-physical properties, supported by validated physical-mathematical models, are serious constrains to their use in engineering applications. In this work, the thermal conductivity of carbon nanotubes, water based nanofluids were systematically studied. The governing physical mechanisms for heat conduction in the nanofluid were established as the basic condition for the development of a general model able to securely determine this property with the precision required in engineering applications. For this purpose the methodologies to correctly prepare such nanofluids in a reproducible way as well as to measure their long term stability are presented. The colloidal stability is accurately established and quantified taking into account parameters such as the absence of agglomeration, separation of phases and deterioration of the morphology of the nanoparticles. A parametric analysis was developed through appropriate DOE methodologies in order to build a comprehensive data base of the nanofluid physical properties as a function of control factors, previously identified variables considered to have the greatest impact on the variability of thermo-physical properties. Among the latter, this work gives particular attention to the acquisition of thermal conductivity data against the selected control factors: base fluid, temperature, size and concentration of nanoparticles. It was verified experimentally that amongst these control factors, those that hold the greatest influence on the thermal conductivity of the nanofluid are the size and concentration of nanoparticles. A solid database and the awareness about the relative contribution of each mechanism controlling the heat transfer process in nanofluids successfully supported the development and validation of a general physical-mathematical model to determine the thermal conductivity of nanofluids.

L’intensificazione sostenibile delle pratiche agricole rappresenta un paradigma per il passaggio da sistemi agricoli tradizionali all’applicazione di tecnologie e tecniche moderne per la produzione agricola. A livello globale si è diffuso l’interesse verso il modello di Agricoltura Sostenibile (AS), in vista di alcuni problemi che possono minacciare la sicurezza alimentare mondiale: crescita della popolazione mondiale, cambiamenti nella domanda delle produzioni agricole, percentuale elevata di persone sottonutrite, cambiamenti climatici, diminuzione delle risorse naturali. Il progetto “Produzione di cibo appropriato: sufficiente, sicuro, sostenibile”, ancora in corso, lavora per raggiungere alcuni scopi: (1) rilevare e valutare la disponibilità quantitativa e qualitativa degli alimenti destinati al consumo umano, (2) proporre nuovi sistemi di produzione agro-zootecnica, (3) sviluppare tecniche appropriate per processare e conservare gli alimenti, al fine di ottenere uno stato di sicurezza alimentare e sostenibilità ambientale ed economica. L’obiettivo generale di questo lavoro è quello di mostrare quali sono le possibili alternative ai sistemi agricoli tradizionali, sia nei Paesi Sviluppati sia in quelli in Via di Sviluppo, al fine di aumentarne l’efficienza e diminuirne gli impatti sull’ambiente, aumentando lo stato globale di sicurezza alimentare. Per i Paesi in Via di Sviluppo l’attenzione si concentra sulle pratiche di sviluppo rurale integrato, al fine di implementare quantitativamente la produzione alimentare e, conseguentemente, la sicurezza alimentare, preservando nel contempo l'ambiente. Per i Paesi Sviluppati, in cui i rendimenti agricoli sono già potenzialmente molto elevati, l’attenzione viene focalizzata sul migliorare la produttività del suolo, riducendo gli input esterni e le emissioni di gas ad effetto serra, attraverso l’adozione di sistemi agricoli conservativi.
Sustainable intensification of agricultural practices represents a paradigm shift from traditional farming systems to the application of modern technologies and techniques to crop production. At global level it has been widespread interest towards Sustainable Agriculture (SA) model, in view of some issues that will may threaten the world food security: growing world population, changes in agricultural product’s demand, high prevalence of undernourishment, climate changes, decreasing of natural resources. The project “Production of proper food: sufficient, safe, sustainable" is still working to achieve some purposes: (1) to detect the availability quantity and quality of food for human consumption, (2) to propose new agro-livestock production systems, (3) to develop appropriate techniques for processing and storage of foodstuffs, in order to achieve food security, environmental and economic sustainability. The objective of this work is to show what are the possible alternatives ways at traditional agricultural systems, both in Developed and Developing Countries, in order to increase the efficiency and to decrease the impacts on the environment, raising a global condition of food security. For Developing Countries the attention is focused on integrated rural development practices in order to implement food production and the state of food security, while preserving the environment. For Developed Countries, in which yields are already potentially higher, the attention is focused on enhance soil productivity while reducing external farming input and greenhouse gases emission by the adoption of conservation agricultural systems.

L’intensificazione sostenibile delle pratiche agricole rappresenta un paradigma per il passaggio da sistemi agricoli tradizionali all’applicazione di tecnologie e tecniche moderne per la produzione agricola. A livello globale si è diffuso l’interesse verso il modello di Agricoltura Sostenibile (AS), in vista di alcuni problemi che possono minacciare la sicurezza alimentare mondiale: crescita della popolazione mondiale, cambiamenti nella domanda delle produzioni agricole, percentuale elevata di persone sottonutrite, cambiamenti climatici, diminuzione delle risorse naturali. Il progetto “Produzione di cibo appropriato: sufficiente, sicuro, sostenibile”, ancora in corso, lavora per raggiungere alcuni scopi: (1) rilevare e valutare la disponibilità quantitativa e qualitativa degli alimenti destinati al consumo umano, (2) proporre nuovi sistemi di produzione agro-zootecnica, (3) sviluppare tecniche appropriate per processare e conservare gli alimenti, al fine di ottenere uno stato di sicurezza alimentare e sostenibilità ambientale ed economica. L’obiettivo generale di questo lavoro è quello di mostrare quali sono le possibili alternative ai sistemi agricoli tradizionali, sia nei Paesi Sviluppati sia in quelli in Via di Sviluppo, al fine di aumentarne l’efficienza e diminuirne gli impatti sull’ambiente, aumentando lo stato globale di sicurezza alimentare. Per i Paesi in Via di Sviluppo l’attenzione si concentra sulle pratiche di sviluppo rurale integrato, al fine di implementare quantitativamente la produzione alimentare e, conseguentemente, la sicurezza alimentare, preservando nel contempo l'ambiente. Per i Paesi Sviluppati, in cui i rendimenti agricoli sono già potenzialmente molto elevati, l’attenzione viene focalizzata sul migliorare la produttività del suolo, riducendo gli input esterni e le emissioni di gas ad effetto serra, attraverso l’adozione di sistemi agricoli conservativi.
Sustainable intensification of agricultural practices represents a paradigm shift from traditional farming systems to the application of modern technologies and techniques to crop production. At global level it has been widespread interest towards Sustainable Agriculture (SA) model, in view of some issues that will may threaten the world food security: growing world population, changes in agricultural product’s demand, high prevalence of undernourishment, climate changes, decreasing of natural resources. The project “Production of proper food: sufficient, safe, sustainable" is still working to achieve some purposes: (1) to detect the availability quantity and quality of food for human consumption, (2) to propose new agro-livestock production systems, (3) to develop appropriate techniques for processing and storage of foodstuffs, in order to achieve food security, environmental and economic sustainability. The objective of this work is to show what are the possible alternatives ways at traditional agricultural systems, both in Developed and Developing Countries, in order to increase the efficiency and to decrease the impacts on the environment, raising a global condition of food security. For Developing Countries the attention is focused on integrated rural development practices in order to implement food production and the state of food security, while preserving the environment. For Developed Countries, in which yields are already potentially higher, the attention is focused on enhance soil productivity while reducing external farming input and greenhouse gases emission by the adoption of conservation agricultural systems.

La investigació plasmada en aquesta tesi doctoral tracta l’aplicació dels principis d’enginyeria de reacció i immobilització enzimàtica per a la millora de reaccions d’oxidoreducció biocatalitzades. En una primera part de la tesi, es va estudiar la co-immobilització de la monooxigenasa P450 BM3 juntament amb un enzim regenerador del cofactor NADPH, la glucosa deshidrogenasa (GDH-Tac). Els millors derivats es van obtenir utilitzant dos suports d’agarosa, un funcionalitzat amb grups epoxy (83% i 20% activitats retingudes respectivament) i l’altre amb grups amino (28% i 25% activitats retingudes respectivament). Posteriorment es va provar de re-utilitzar aquests enzims immobilitzats en diferents cicles de reacció utilitzant un dels substrats naturals de la P450 BM3, el laurat de sodi. Un cop demostrat que ambdós enzims immobilitzats podien ser reciclats, es va estudiar l’aplicació d’aquests en dues reaccions d’interès industrial, la hidroxilació de la α-isoforona i la hidroxilació del diclofenac. En el primer cas, va fer falta optimitzar certs paràmetres de la reacció abans d’aplicar els derivats. Un cop es van tenir unes condicions acceptables, es va comprovar que els resultats obtinguts anteriorment amb el laurat de sodi, no podien ser extrapolats. La reutilització no va ser possible. En quant al diclofenac, es van obtenir resultats similars. En ambdós casos però, l’aplicació dels enzims en la seva forma soluble, va permetre obtenir conversions altes: 86.2% per a la α-isoforona (50 mM inicial) i 100% per al diclofenac (3.5 mM inicial). El producte hidroxilat de l’α-isoforona, la 4-hidroxi-isoforona, ha de ser oxidat en un segon pas per arribar a l’intermediari desitjat, la keto-isoforona. Aquesta segona reacció es duu a terme amb una alcohol deshidrogenasa, la qual també necessita un regenerador de cofactor, la NADPH oxidasa. Al aplicar els dos enzims en la seva forma soluble, al cap de 24h, es va aconseguir un 95.7% de rendiment i una productivitat de 6.52 g L-1 dia-1. A part, l’enzim diana, l’alcohol deshidrogenasa, es va poder immobilitzar en epoxy-agarosa obtenint una activitat retinguda del 58.2%. Al intentar re-utilitzar-lo, es va poder operar durant 96h (4 cicles) millorant el rendiment del biocatalitzador fins a 2.5 vegades comparat amb la reacció en soluble. La reacció d’hidrogenació de la α-isoforona, per altre banda, resulta en la 3,3,5- trimetilciclohexanona, un substrat amb interès industrial per a l’obtenció de polímers. En aquest cas, es va utilitzar la Baeyer-Villiger ciclohexanona monooxigenasa juntament amb una glucosa deshidrogenasa comercial (GDH-01) per a realitzar la reacció d’inserció d’un àtom d’oxigen en l’anell de carbonis. Es van optimitzar diferents paràmetres de la reacció com la formulació del biocatalitzador, la velocitat d’adició de substrat i la quantitat d’enzim afegida. Un cop optimitzada la reacció es va escalar primer a 1 litre i finalment a 100 litres. En aquesta última reacció a escala pre-industrial, es va obtenir una conversió del 85%, una productivitat de 2.7 g L- 1 h-1 i un rendiment del biocatalitzador de 0.83 g g-1 cww. Finalment aquesta mateixa reacció es va realitzar utilitzant els enzims immobilitzats i reciclantos. Tant la ciclohexanona monooxigenasa com la glucosa deshidrogenasa (GDH-01) es van poder immobilitzar en agarosa funcionalitzada amb grups amino. En el primer cas es va obtenir una activitat retinguda del 62.4% (mètode obtingut de la bibliografia) i en el segon cas del 62.6%. En reacció, els dos enzims immobilitzats van ser utilitzats tant per separat com conjuntament. Al cap de sis cicles de reacció (132.5 mM de substrat inicial), es va assolir un rendiment de biocatalitzador 3.6 vegades superior per a la monooxigenasa i 1.9 vegades superior per a la GDH- 01 comparat amb la reacció en soluble.
The research performed and disclosed in this thesis deals with the reaction engineering and the enzyme immobilization principles as tools to improve biocatalyzed oxidoreductive reactions. On a first stage, the co-immobilization of the P450 BM3 monooxygenase together with a NADPH cofactor regeneration enzyme, the glucose dehydrogenase (GDH-Tac), was studied. The best derivates were obtained when using two agarose supports, an epoxy functionalized (83% and 20% retained activity respectively) and an amino functionalized (28% and 25% retained activity respectively). Later on, the re-cycling of the immobilized enzymes was tested in reaction cycles using one of the natural substrates of the P450 BM3, the sodium laurate. Once it could be demonstrated that re-cycling of both P450 BM3 and GDH-Tac was possible, both enzymes were studied in two of the project’s target reactions, the hydroxylation of α- isophorone and the hydroxylation of diclofenac. In the first case, the optimization of the reaction conditions had to be performed prior to the reaction cycles. The reactor configuration, the oxygen income or the glucose concentration were adjusted. However, when the reaction was performed using the co-immobilized enzymes, the P450 BM3 was deactivated and it could not be re-used. The same happened with the hydroxylation of diclofenac. On the other hand, the reaction using soluble enzymes, resulted in 86.2% conversion for the α-isophorone (50 mM initial concentration) and 100% for the diclofenac (3.5 mM initial concentration). The product resulting from the hydroxylation of α-isophorone, the 4-hydroxy-isophorone, can be further oxidized to keto-isophorone, an intermediary for the synthesis of carotenoids and vitamin E. In order to enzymatically perform this step, an alcohol dehydrogenase and a NADPH oxidase, as a cofactor regenerator, were employed. When used in their soluble form, after 24 hours, 95.7% yield and a space time yield of 6.52 g L-1 day-1 were achieved. Moreover, the alcohol dehydrogenase was immobilized on epoxy-agarose and 58.2% retained activity was obtained. When re-used, the derivate could operate for 96h (4 cycles) improving the biocatalyst yield 2.5- fold compared with the reaction with soluble enzymes. The hydrogenation of α-isophorone results in 3,3,5-trimethylcyclohexanone, an industrial interesting substrate due to the polymers that can be obtained from its oxidized product, the trimethyl-ε-caprolactone. This compound is obtained by the Baeyer-Villiger insertion of an oxygen atom into the carbon ring. For this purpose, a cyclohexanone monooxygenase together with a commercial glucose dehydrogenase (GDH-01) were used. Different parameters of the reaction were optimized such as the biocatalyst formulation, the substrate addition rate or the biocatalyst loading. Afterwards, the reaction was scaled up to 1 liter first and then up to 100 liters. In this last pre-industrial reaction, 85% conversion, a space time yield of 2.7 g L-1 h-1 and a biocatalyst yield of 0.83 g g-1 cww could be obtained. Finally, this same reaction was performed using both enzymes immobilized and re-cycling was intended. The cyclohexanone monooxygenase could be immobilized following a previously described method and 62.4% retained activity was achieved. In the GDH-01 case, different supports were screened albeit at the end, it was also the amino functionalized agarose that resulted successful. A retained activity of 62.6% was obtained. In the reaction cycles, the immobilized enzymes were used either separately or both together. In the best case scenario, after six cycles of reaction (132.5 mM initial substrate) 3.6-fold and 1.9-fold higher biocatalysts yields were obtained for the monooxygenase and the GDH-01, respectively.

This study used "Streptomyces coelicolor" A3(2) as a model organism to study the potential for process intensification in antibiotic production using solid phase growth. This organism produces three chromosomally encoded antibiotics, actinorhodin, prodigiosin, and calcium dependent antibiotic (CDA), and one plasmid encoded antibiotic methylamycin. In this study the production of prodigiosin was the focus for this process intensification. A novel technique was developed in the preparation of the bacterial support (PHP) , which ensures a well-controlled internal architecture. Solid phase growth on this matrix was shown to support the production of prodigiosin and actinorhodin. The growth of "Streptomyces coelicolor" A3(2) on this nano-structured, macro-porous, polymeric support with hierarchic connectivity, generically known as PolyHIPE polymer. Variations of PHP were investigated and compared with conventional flask growth; the production of prodigiosin in PHP was demonstrated to exceed that in flask growth, offering the potential for an order of magnitude improvement in volumetric productivity. A micro-bioreactor was designed to improve spore penetration, the distribution of cells, viability and nutrient supply. Growth was observed by electron microscopy, SEM and TEM. It was operated as a forced inoculation of pre-germinated spore suspension in modified R5 media, this micro-bioreactor enhanced productivity by an order of magnitude. This study shows that bacterial growth rate and secondary metabolism are influenced by the pore size and surface chemistry of the support material. To understand these surfaces and scale dependent phenomena a series of microporous structures with different functionalised surfaces were generated. An initial proteomic study was performed to determine whether solid phase culture had lead to a fundamentally different pattern of growth. One dimensional SDS gel electrophoresis revealed some variations in the pattern of protein bands between samples from growth in flasks and on the different PHP supports. Mass spectrometric analysis by peptide mass fingerprinting, of differentially observed bands, revealed the predominance of elongation factor EF-tu in liquid culture and increases in S-adenosylmethionine synthetase and hypothetical protein SC07276 in solid phase culture.

This thesis is about agricultural intensification and the role of smallholder farmers in the future of agriculture in Rwanda. Intensification of agriculture has been the central objective of policy in Rwanda since independence in 1962. Over five decades, one of the dominant approaches to achieving this goal has been through mixed farming, i.e. the integration of crop and livestock production. However, despite continued efforts to transform agricultural and rural livelihood through mixed farming, many farmers have not achieved intensification. Thus, there seems to be a critical disjuncture between the government's vision of modern agriculture based on increasing levels of intensification and commercialisation, and the ability of many smallholders to engage with this intensification and commercialisation agenda. In this thesis, I argue that the disjuncture between the long-standing policy objective and Rwanda's rural realities poses serious repercussions to the rural development and the livelihoods of millions of smallholder farmers. I substantiate the argument by addressing the following question: “how does the integration of crop and livestock production contribute to agricultural intensification for smallholder farmers in Rwanda?” Firstly, I situate the research context within the historical development of agricultural policies promoting the mixed farming agenda. Secondly, I study two villages in Rwamagana district as rural and peri-urban cases. Various patterns of interactions between crop and livestock production systems are identified, characterised and analysed within the broader household livelihood strategies. Thirdly, I incorporate the life history accounts of farmers with diverse background and capabilities to engage in mixed farming to better understand the wide-ranging issue of livestock-based asset accumulation which is crucial for the crop-livestock integration. Finally, I discuss the implications for the government's continued efforts to transform agriculture and rural livelihoods through mixed farming and possible ways to assist many farmers who lack the resources required for intensification through integrated crop-livestock production.

Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, Dec. 2001.
Thesis advisor, Roger T. Williams. "December 2001." Includes bibliographical references (p. 74-79). Also available in print.

This dissertation explores the theoretical and methodological implications involved in the policy framework needed to intensify urban residential areas in a developing country. Metropolitan Khartoum, Sudan, has been chosen as a case study. The aim of the study is to further our understanding of the implications of transforming a sprawling city form to an intensified form. The objectives are: to identify the factors that have shaped Sudanese urban form in general and Metropolitan Khartoum in specific; to identify the policies that can intensify the urban residential neighborhoods in Metropolitan Khartoum; and, to influence both the demand and requisite housing needs for this intensified form. This research is qualitative in its nature: the complexity of the study problematic required the adoption of a constructivist paradigm as the fundamental set of beliefs. Inductive arguments are used in conjunction with a wide range of methods, including detailed descriptions of Sudan and metropolitan Khartoum, with special emphasis on how local environment, urban challenges, policy, legislation and practices affect the study problematic. The theoretical premises of intensification are reviewed along with development issues, urban infrastructure challenges and opportunities in developing countries and local acceptability of intensification. The different forces that can shape urban forms have been described and the suitability of metropolitan Khartoum, with different general urban intensification policies and practices and of urban management tools in large African cities has been investigated. The outcome of the study provides detail for a discussion of results that work to explain some of the cause and effect of urban sprawl in Metropolitan Khartoum. It also suggests possible change in both policy and regulation to induce successful city reform towards intensification.