Tesis sobre el tema "CO₂ separation"
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1
Xie, Xiaofeng. "CO₂-expanded liquids for separation and reaction". Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/10077.
2
Shen, Dawei. "Co-channel digital signal separation : application and practice". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/42408.
Resumen
Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2008.Includes bibliographical references (leaves 84-86).
This thesis studies the theory and application of co-channel digital signal separation techniques. We set up a test-bed with the GNU Software Defined Radio (SDR) platform where we implement and experiment with single-antenna signal separation algorithms. We mainly investigate linearly-modulated digital signals. To do this, we design a multiple RFID card reader capable of decoding multiple commodity ID cards simultaneously. These passive RFID cards transmit DBPSK waveforms once activated. A signal separation function at the receiver delivers great convenience to the users without increasing the complexity and cost of the cards. Second, we derive the optimal criteria for deciding the start of an RFID frame. We show that the commonly utilized correlation rule is suboptimal and that a correction term needs to be considered to achieve the best detection performance. Several rules for frame synchronization are proposed and analyzed numerically using Monte Carlo simulation. These signal separation techniques present an opportunity to improve the capacity of wireless systems and combat interference. This thesis documents design issues in the physical and application layers, thereby demonstrating the great flexibility and strength of the GNU SDR system.
by Dawei Shen.
S.M.
3
Jegede, Oluwatoyin Enitan. "Metastable liquid phase separation in Co-Cu alloys". Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/19808/.
Resumen
Two Co – Cu alloys were studied by drop tube processing technique in a view of investigating the effects of rapid solidification on the phase transformations and microstructural evolution in the metastable alloys. The as – solidified samples had diameters ranging from 53 – 850+ μm and these were analysed using various characterization techniques such as optical (OM) and scanning electron (SEM) microscopy, x- ray diffraction (XRD) and differential thermal analysis (DTA). The Cu – 50 at. % Co alloy was observed to experience liquid phase separation at lower undercooling than the Cu – 68.5 at. % Co alloy. This is found to be in accordance to the asymmetrical metastable miscibility gap determined for the alloy system. Significant number of liquid phase separated structures were observed at cooling rates in excess of 15000 Ks-1, evidenced by a range of microstructural morphologies including stable core shell structures, evolving core shell structures and structures in which the demixed liquid phases were randomly distributed. A large number of these structures experienced multiple liquid phase separation processes. The configuration of the core shell structures were found to be independent of the composition of phases and their relative abundance, with the core always formed by the higher melting point phase. The optimum production of the core shell structures were found to be a function of cooling rate.
4
Woo, Grace R. "Demonstration and evaluation of co-channel DBPSK source separation". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42170.
Resumen
Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2007.Includes bibliographical references (leaves 51-53).
This thesis presents a Differential Binary Phase Shift Key (DBPSK) source separation system implemented with the GNU Software Defined Radio (SDR) platform and interfaced with the existing MIT community Radio Frequency Identification (RFID) system. Source separation, well studied in the theoretical signal processing setting, presents an opportunity to achieve higher throughput in a practical SDR deployment. While much research has centered around the design of complex multi-input-multi-output (MIMO) and code division multiple access (CDMA) systems, single antenna source separation presents a simple alternative that is suitable in settings such as RFID where sources are naturally synchronized. Motivated by the analysis of physical channel properties with GNU SDR, this thesis documents the complete design process from the physical layer to the application layer and presents a realization of a co-channel DBPSK source separating technique. The result is an intelligent RFID source-separating reader that is capable of decoding multiple "dumb" cards.
by Grace R. Woo.
S.M.
5
Kim, Sangil. "Modified ordered mesoporous silica membranes for CO₂ -N₂ separation". Cincinnati, Ohio : University of Cincinnati, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1070484926.
6
Corcoran, Edward W., Ronald R. Chance, Harry W. Deckman, Gregory J. DeMartin, Sebastián C. Reyes, C. J. Yoon y Trevor E. Clark. "Molecular transport in inorganic membranes: CO 2 /CH 4 separation". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194810.
7
Corcoran, Edward W., Ronald R. Chance, Harry W. Deckman, Gregory J. DeMartin, Sebastián C. Reyes, C. J. Yoon y Trevor E. Clark. "Molecular transport in inorganic membranes: CO 2 /CH 4 separation". Diffusion fundamentals 3 (2005) 18, S. 1, 2005. https://ul.qucosa.de/id/qucosa%3A14307.
8
Abbassi, Maria. "Selective CO Adsorption Separation from CO2 via Cu-modified Adsorbents". Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42151.
Resumen
CO2 capture and conversion appears to be a prominent solution to mitigate greenhouse gas
emissions (GHG) and global warming issue. Among different CO2 conversion approaches,
CO2 hydrogenation via reverse water gas shift (RWGS) reaction is one of the most promising
technology to convert CO2 to CO. Subsequently, CO is transformed to value added chemicals
or liquid fuels. To improve the overall CO2 conversion for RWGS reaction, product separation
and recycling is being proposed.
In this research, adsorption separation technology has been explored to selectively separate
CO from CO2 in RWGS using pressure swing adsorption (PSA) process. To investigate the
adsorption capacity and selectivity of CO, different porous materials have been identified for
CO separation. In this research, activated carbons, ordered mesoporous silica, and metal
organic framework materials were studied. Equilibrium isotherms of CO and CO2 were
measured in a gravimetric system at a temperature of 25 °C for pressures up to 20 bar.
Preliminary adsorption isotherm results had shown an insufficient CO uptake and low
selectivity level compared to CO2, thus not justifying their application for CO separation.
Herein, to improve the CO adsorption capacity and selectivity, Cu-based adsorbents were
developed using copper (II) chloride (CuCl2) as a precursor to synthesize six different
adsorbents. The adsorbents were prepared using two different synthesis methods; the modified
polyol method for reduction and nanoparticle deposition of Cu (I) ions, and thermal monolayer
auto-dispersion method. Furthermore, different copper (II) loadings were investigated to
determine the monolayer dispersion capacity of CuCl2 on the support.
The modified adsorbents by copper salt exhibited significantly high CO uptake with large
CO/CO2 selectivity, reversing the results obtained before adsorbent modification. Thus, Cubased adsorbents are promising materials for CO separation and recovery from a gaseous mixture containing CO2.
9
Cowan, Oliver. "Co-occurrence and phenological niche separation in rodent pollinated Proteaceae". Bachelor's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/24855.
Resumen
Despite the numerous studies regarding rodent pollination in the Cape Floristic Region in the last few decades, little or no work has been done on patterns of co-occurrence and flowering phenology. The presence of three potentially rodent-pollinated Protea species at Fernkloof Nature Reserve, two of which were observed to co-occur, facilitated the following questions: i) are P. cordata, P. scabra and P. angustata therophilous? ii) do therophilous species co-exist at a fine scale? iii) do they have the same pollinator? iv) do they exhibit staggered flowering phenology? The floral characteristics of the study species suggest they were rodent pollinated and that the co-occurring species, P. cordata and P. scabra, would have staggered flowering phenologies. All three of the species' pollen was found in the faeces of Acomys subspinosus, the shared pollinator, while the phenological data provided the first empirical evidence of staggered flowering phenologies between fine scale, sympatric therophilous Protea species.
10
Vaughn, Justin. "Development and evaluation of aromatic polyamide-imide membranes for H₂S and CO₂ separations from natural gas". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47576.
Resumen
Over the past decade, membrane based gas separations have gained traction in industry as an attractive alternative to traditional thermally based separations due to their potential to offer lower operational and capital expenditures, greater ease of operation and lower environmental impact. As membrane research evolves, new state-of-the-art membrane materials as well as processes utilizing membranes will likely be developed. Therefore, their incorporation into existing thermally based units as a debottlenecking step or as a stand-alone separation unit is expected to become increasingly more common. Specifically for natural gas, utilization of smaller, more remote natural gas wells will require the use of less equipment intensive and more flexible separation technologies, which precludes the use of traditional, more capital and equipment intensive thermally based units.
The use of membranes is, however, not without challenges. Perhaps the most important hurdle to overcome in membrane development for natural gas purification is the ability to maintain high efficiency in the presence of harsh feed components such as CO₂ and H₂S, both of which can swell and plasticize polymer membranes. Additionally, as this project demonstrates, achievement of similarly high selectivity for both CO₂ and H₂S is challenged by the different governing factors that control their transport through polymeric membranes. However, as others have suggested and shown, as well as what is demonstrated in this project, when CO₂ is the primary contaminant of interest, maintaining high CO₂/CH₄ efficiency appears to be more important in relation to product loss in the downstream. This work focuses on a class of fluorinated, glassy polyamide-imides which show high plasticization resistance without the need for covalent crosslinking. Membranes formed from various polyamide-imide materials show high mixed gas selectivities with adequate productivities when subjected to feed conditions that more closely resemble those that may be encountered in a real natural gas well. The results of this project highlight the polyamide-imide family as a promising platform for future membrane material development for materials aimed at aggressive natural gas purifications due to their ability to maintain high selectivities under aggressive feed conditions without the need for extensive stabilization methods.
11
Nzama, Nosipho Mercy. "Adsorptive separation of Ce Co Ru Sb and Sr ions using inorganic ion exchangers". Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/79295.
Resumen
Ion exchange and adsorption (can both be referred to as ‘sorption’) are widely used as purification
and concentration methods in the nuclear industry. Various mathematic models have been
developed to describe the mechanisms of sorption using the kinetics and equilibrium data. In this
study, the ion exchange and adsorption capability and efficacy of various inorganic sorbent
materials to remove contaminants were investigated with the intent of applying the process in the
purification of post reactor uranium for reuse and cleaning of research reactors pool water. The
contaminants studied are Ce, Co, Ru, Sb and Sr ions. The sorbent materials candidates investigated
are antimony pentoxide, CoTreat®, IONSIV R9120B, activated carbons, alumina, titania,
manganese oxide and SrTreat®.
The sorption of Ce and Sr on antimony pentoxide was determined to be a slow sorption process.
The sorption kinetics data obtained for Sr removal by antimony pentoxide conformed to the
pseudo-second order kinetic model, with the sorption process reaching completion after 78 hours
contact time. The considerably slow kinetics makes the sorbent material a less suitable candidate.
At fixed solid/aqueous ratio, various parameters affecting sorption of Co on CoTreat® were
studied which include initial Co concentration, contact time, solution pH and temperature. The
sorption capacity of CoTreat® for Co ions was identified to increase with increasing contact time
and with increasing initial Co concentration. The Co sorption was halted at pH < 2. The sorption
of Co on CoTreat® reaction can be approximated to first order reversible kinetics at high initial
concentrations of Co while the sorption kinetics followed the pseudo-second order kinetics at low
initial concentrations of Co. The examination of the thermodynamic parameters revealed that the
sorption of Co on CoTreat® is an endothermic process and is spontaneous in the studied
temperature range. The equilibrium isotherm data was analysed using the Langmuir, Freundlich
and Dubinin-Radushkevich equations. The sorption of Co on CoTreat® followed the Langmuir
isotherm model. The Dubinin-Radushkevich parameters revealed that the sorption process is
driven by ion exchange. Slow kinetics were obtained for the Co removal by IONSIV R9120B
sorption process, therefore making the sorbent material not a good candidate for practical
application.
The sorption capacities of manganese oxide for Ru removal from aqueous solutions was
investigated at different initial concentrations of Ru. The fitting of the Langmuir and Freundlich
sorption models to the equilibrium data was investigated. The equilibrium data for the Ru sorption
on manganese oxide followed the Freundlich isotherm. The monolayer sorption capacity was determined to be 0.90 mg/g at 30 °C. The pseudo-first order and the pseudo-second order kinetic
models were used to fit the kinetic experimental data. The sorption of Ru on manganese oxide
follows the pseudo-second order kinetic model. The temperature dependent data revealed that the
sorption process is an endothermic and spontaneous ion exchange process. Poor sorption
capacities were determined for Ru removal by activated carbons.
The maximum sorption of Sb on titania was obtained at 0.1 M nitric acid medium. Kinetics studies
revealed that the sorption process followed pseudo-second order kinetics. The equilibrium data
was evaluated using the Langmuir and Freundlich isotherm models, and well fitted the Freundlich
isotherm. The obtained negative values of ΔG° and positive value of ΔH° advocate that Sb
sorption on titania is a spontaneous and endothermic process.
The effect of the experimental parameters: contact time, initial concentration of metal ion and
solution pH were investigated for Sb removal by alumina. The sorption capacity increased with
increasing contact time and initial Sb concentration. The sorption data could be explained by the
pseudo-first order kinetic model and the Langmuir isotherm.
The sorption data on Sr removal by SrTreat® revealed that the sorption capacity increases with
increasing initial Sr concentration. The sorption of Sr ions on SrTreat® was halted at pH < 2, and
the kinetics data obtained at high initial Sr concentration can be approximated to the pseudosecond
order kinetics.
The dynamic sorption studies revealed that efficacy of the studied sorbent materials to remove the
target contaminants drastically declined in the presence of uranium ions.Dissertation (MSc)--University of Pretoria, 2019.
Chemical Technology
MSc
Unrestricted
12
Zhang, Naiyuan. "Hydrogen Isotope Separation in Metal-Organic Frameworks". Oberlin College Honors Theses / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1532013686771173.
13
Kim, Danny Jinsoo. "Effects of polymerization conditions and imidization methods on performance of crosslinkable polymer membrane for CO₂/CH₄ separation". Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/48938.
Resumen
Natural gas feeds often contain contaminants such as CO₂, H₂S, H₂O, and small hydrocarbons. Carbon dioxide is a major contaminant reducing the heating value of the gas and causing pipeline corrosion, so CO₂ level should be lowered to
below 2% to meet the United States pipeline specifications. Membrane separation technology can be advantageous over cryogenic distillation and amine adsorption in terms of cost and efficiency. The key hurdle to overcome in polymeric membrane separation technology is improvement in selectivity, productivity, and durability without introducing significant additional cost. The ultimate goal of this study is to analyze effects due to polymerization
conditions and imidization methods on properties of 1,3-propanediol monoesterified crosslinkable polyimide (PDMC). Hillock, Omole, Ward, and Ma did work on PDMC synthesis; however, variability of polymer properties remains a challenge that must be overcome for industrial implementation of PDMC material. First, reaction temperature and reaction time of polymerization prior to
imidization were considered as key conditions to affect molecular weight, crosslinkability and transport properties of polymer. Batches with controlled reaction
temperature and time were prepared, and properties of each dense film were measured and optimized in terms of permeability, selectivity, and plasticization suppression. Second, imidization methods for PDMC were also studied. There are mainly two kinds of Imidization: chemical Imidization and thermal Imidization. Surprisingly,
thermally imidized PDMC showed 70% higher permeability than chemically imidized samples with minimal acrifice in selectivity. At high reaction temperature during the thermal imidization, transamidation can occur. It is believed that the transamidation
led to more randomized sequence distribution in the thermally imidized samples. We thus hypothesize that the higher permeability of the thermally imidized PDMC results
from greater uniformity of the sequence distribution, as compared to the chemically
imidized sample that does not experience high temperature during imidization. XRD, DSC, DMA, and permeation instruments checked and supported this hypothesis. FTIR, TGA, and NMR ruled out the possibility of an alternate hypothesis related to side reaction. Finally, effects of aggressive feed conditions on both chemically imidized
PDMC and thermally imidized PDMC dense film were examined. The aggressive feed conditions include high CO₂ partial pressure, operating temperatures, and exposure to high feed pressure. Testing aggressive feed conditions for dense film should be pursued before pursuing hollow fiber applications, to decouple effects on the basic material from those on the more complex asymmetric morphology. This study enables understanding of the disparity between various previous
researchers’ selectivity and permeability values. The work shows clearly that polymerization conditions and imidization methods must be specified and controlled to achieve consistently desirable polymer properties. In addition, for batch scale-up and development to a hollow fiber, this fundamental study should enable production of high molecular weight PDMC with good fiber spinnability and defect-free structure.
14
Wilson, Graeme Barnetson. "Fathers as co-parents : how non-resident fathers construe family situations after divorce or separation". Thesis, University of Glasgow, 2003. http://theses.gla.ac.uk/1131/.
Resumen
A model of the co-parental role based on personal construct theory is described, with inter-parental conflict explained in terms of the constructivist concept of hostility. Four unstructured group interviews, on the theme of the experience of separated parenthood, were conducted with separated fathers (n=14) from throughout Strathclyde. Thematic analysis of the results suggests that while participants recognised the importance of maintaining relations with the other parent, that relationship was seen as adversarial, and fathers frequently feel controlled or powerless; different strategies for coping with this control emerged. From common post-separation parenting experiences recounted by the participants, situational elements were developed for a series of repertory grid interviews, intended to identify and examine the co-parental role construct system. Grids were administered, at three points over a year, to a cohort of separated, non-resident fathers from Strathclyde (n=17) still in contact with their children. The results were analysed using construct content categories developed for this research, inter-element distance measures, and asymmetric coefficients to assess ordinal relationships between constructs. Support was found for the model of a co-parental role covering interactions with children and their mothers. Perceptions of parity in parents' flexibility regarding contact arrangements were associated with recent experience, particularly ongoing disputes over contact allocation, and reflect strategies for dealing with being controlled. Conflict emerges as having distinct and multiple implications for separated non-resident fathers, whose responses to change were also consistent with the constructivist conception of hostility. One strategy for dealing with this may be a gradual distancing from the role of co-parent, in line with recent theories of core construing. These findings are discussed along with strengths and limitations of this research; implications for policy, practice and future research are outlined.
15
Kane, Dellwyn. "Hydrograph separation using end member mixing models in the Oona Water river catchment, Co Tyrone". Thesis, University of Ulster, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529518.
16
KIM, SANGIL. "MODIFIED ORDERED MESOPOROUS SILICA MEMBRANES FOR CO 2 -N 2 SEPARATION". University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1070484926.
17
Popp, Nadine [Verfasser] y Jürgen [Akademischer Betreuer] Senker. "Poröse organische Netzwerke zur selektiven CO₂ Speicherung und Separation von Gasgemischen / Nadine Popp ; Betreuer: Jürgen Senker". Bayreuth : Universität Bayreuth, 2017. http://d-nb.info/1130243249/34.
18
Bubier, Jennifer L. "Co-occurrence of Oppositional Defiant Disorder with Generalized and Separation Anxiety Disorders Among Inner-city Children". Diss., Temple University Libraries, 2010. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/48936.
Resumen
PsychologyPh.D.
There is a paucity of research that has examined co-occurring oppositional defiant disorder and generalized anxiety disorder (ODD+GAD) symptoms and oppositional defiant disorder and separation anxiety disorder (ODD+SAD) symptoms among children. To address this gap, I investigated multiple explanations for the co-occurrence of ODD+GAD and ODD+SAD. Specifically, I investigated whether (a) GAD symptoms prospectively predicted ODD symptoms and SAD symptoms prospectively predicted ODD symptoms (Explanation 1), (b) ODD symptoms prospectively predicted GAD symptoms and ODD symptoms prospectively predicted SAD symptoms (Explanation 2), and (c) shared risk processes accounted for the co-occurrence of ODD+GAD and ODD+SAD (Explanation 3). Participants were an ethnic minority, inner-city sample of first through fourth grade children (N = 88, 51% male) and their primary caregivers. I used data collected at the baseline and 1-year follow-up assessments of the Child Health and Behavior Study, a longitudinal survey of families residing in North Philadelphia. Findings provided support for Explanation 2 and Explanation 3 in the development of co-occurring ODD+GAD symptoms and support for Explanation 3 in the development of co-occurring ODD+SAD symptoms. This study contributes to the extant literature by providing the first empirical examination of these multiple explanations in an ethnic minority, inner city sample of children.
Temple University--Theses
19
Foster, Paul J. "Continuous Co-Separation by Liquid Absorption in Aqueous Cuprous Chloride (CuCl) and Magnesium Chloride (MgCl2) Solution". Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1789.pdf.
20
Sahin, Mustafa. "Baseband receiver algorithms for 4G co-channel femtocells". [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003283.
21
Brunson, Kennard. "POLYURETHANE-BASED POLYMER SURFACE MODIFIERS WITH ALKYL AMMONIUM CO-POLYOXETANE SOFT BLOCKS: REACTION ENGINEERING, SURFACE MORPHOLOGY AND ANTIMICROBIAL BEHAVIOR". VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/2258.
Resumen
Concentrating quaternary (positive) charge at polymer surfaces is important for applications including layer-by-layer polyelectrolyte deposition and antimicrobial coatings. Prior techniques to introduce quaternary charge to the surface involve grafting of quaternary ammonium moieties to a substrate or using polyurethanes with modified hard segments however there are impracticalities involved with these techniques. In the case of the materials discussed, the quaternary charge is introduced via polyurethane based polymer surface modifiers (PSMs) with quaternized soft segments. The particular advantage to this method is that it utilizes the intrinsic phase separation between the hard and soft segments of polyurethanes. This phase separation results in the surface concentration of the soft segments. Another advantage is that unlike grafting, where modification has to take place after device fabrication, these PSMs can be incorporated with the matrix material during device fabrication. The soft segments of these quaternized polyurethanes are produced via ring opening copolymerization of oxetane monomers which possess either a trifluoroethoxy (3FOx) side chains or a quaternary ammonium side chain (C12). These soft segments are subsequently reacted with 4,4’-(methylene bis (p-cyclohexyl isocyanate)), HMDI and butanediol (BD) to form the PSM. It was initially intended to increase the concentration of quaternary ammonium charge by increasing PSM soft segment molecular weight. Unexpectedly, produced blends with surface microscale phase separation. This observation prompted further investigation of the effect of PSM soft segment molecular weight on phase separation in PSM-base polyurethane blends and the subsequent effects of this phase separation on the biocidal activity. Analysis of the surface morphology via tapping mode atomic force microscopy (TMAFM) and scanning electron microscopy (SEM) revealed varying complexities in surface morphology as a function of the PSM soft segment molecular weight and initial annealing temperature. Many of these features include what are described as nanodots (100-300 nm), micropits (0.5-2 um) and micropeaks (1-10 um). It was also observed that surface morphology continued to coarsen with time and that the larger features were typically observed in blends containing PSMs with low molecular weight soft segments. This appearance of surface morphological feature correlates with decreased biocidal activity of the PSM blends, that is, the PSM blends exhibit little to no activity upon development of phase separated features. A model has been developed for phase separation and concomitant reduction of surface quaternary charge. This model points the way to future work that will stabilize surface charge and provide durability of surface modification.
22
Armstrong, Shannon Renee. "Novel Applications of Co-Extruded Multilayer Polymeric Films". Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1370531152.
23
Salim, Witopo. "CO2-selective Membranes for Fuel Cell H2 Purification and Flue Gas CO2 Capture: From Lab Scale to Field Testing". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1514889154359659.
24
Wilson, Sean M. W. "Adsorption Separation of CO2 from CO in Syngas: Improving the Conversion of the Reverse Water Gas Shift Reaction". Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/33169.
Resumen
In this research project, adsorption is considered for the separation of CO2 from CO for applications such as industrial syngas production and in particular to improve the conversion of the Reverse Water Gas Shift (RWGS) process. The use of adsorption technology for these applications requires an adsorbent that can effectively separate out CO2 from a gas mixture containing CO2, CO, and H2. However, adsorption of H2 is insignificant when compared to both CO2 and CO, with only CO2 and CO being the adsorbed species. The adsorption of CO2 and CO was investigated in this work for four major types of industrial adsorbents which include: activated aluminas, activated carbons, silica gels, and zeolites. Zeolites, with their ability to be fine tuned many parameters which may affect adsorption, were investigated in terms of the effect of the cations present, SiO2/Al2O3 ratios, and structure to determine how to optimize adsorption of CO2 while decreasing adsorption of CO. This will help to determine a promising adsorbent for this separation with focus on maximizing the selective adsorption of CO2 over CO.
To investigate this separation three scientific experimental methods were used; gravimetric adsorption isotherm analysis, volumetric adsorption isotherm analysis, and packed bed adsorption desorption breakthrough analysis. Gravimetric and volumetric methods allow for testing the adsorbent with the individual species of CO2 and CO. This investigation will let us determine the pure component adsorption capacity, heats of adsorption, regenerability, and basic selectivity. Packed bed adsorption breakthrough experimentation was then carried out on promising adsorbents for the CO2 separation from a mixture of CO2, CO, and H2. These experiments used a gas mixture that would be comparable to that produced from the RWGS reaction to determine the multicomponent gas mixture behaviour for adsorption. Temperature swing adsorption (TSA) with a purge gas stream of H2 was then used to regenerate the adsorbent.
25
Gupta, Himanshu. "NOx reduction by Carbonaceous Materials and CO₂ separation using regenerative metal oxides from fossil fuel based flue gas /". The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486399160107212.
26
Keller, Laura [Verfasser], Matthias [Akademischer Betreuer] Wessling y Ryan P. [Akademischer Betreuer] Lively. "Microtubes made of carbon nanotube hybrid materials for CO$_2}$ separation / Laura Keller ; Matthias Wessling, Ryan P. Lively". Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1218787910/34.
27
Anand, K. "Methods for Blind Separation of Co-Channel BPSK Signals Arriving at an Antenna Array and Their Performance Analysis". Thesis, Indian Institute of Science, 1995. https://etd.iisc.ac.in/handle/2005/123.
Resumen
Capacity improvement of Wireless Communication Systems is a very important area of current research. The goal is to increase the number of users supported by the system per unit bandwidth allotted. One important way of achieving this improvement is to use multiple antennas backed by intelligent signal processing. In this thesis, we present methods for blind separation of co-channel BPSK signals arriving at an antenna array. These methods consist of two parts, Constellation Estimation and Assignment. We give two methods for constellation estimation, the Smallest Distance Clustering and the Maximum Likelihood Estimation. While the latter is theoretically sound,the former is Computationally simple and intuitively appealing. We show that the Maximum Likelihood Constellation Estimation is well approximated by the Smallest Distance Clustering Algorithm at high SNR. The Assignment Algorithm exploits the structure of the BPSK signals. We observe that both the methods for estimating the constellation vectors perform very well at high SNR and nearly attain Cramer-Rao bounds. Using this fact and noting that the Assignment Algorithm causes negligble error at high SNR, we derive an upper bound on the probability of bit error for the above methods at high SNR. This upper bound falls very rapidly with increasing SNR, showing that our constellation estimation-assignment approach is very efficient. Simulation results are given to demonstrate the usefulness of the bounds.
28
Anand, K. "Methods for Blind Separation of Co-Channel BPSK Signals Arriving at an Antenna Array and Their Performance Analysis". Thesis, Indian Institute of Science, 1995. http://hdl.handle.net/2005/123.
Resumen
Capacity improvement of Wireless Communication Systems is a very important area of current research. The goal is to increase the number of users supported by the system per unit bandwidth allotted. One important way of achieving this improvement is to use multiple antennas backed by intelligent signal processing. In this thesis, we present methods for blind separation of co-channel BPSK signals arriving at an antenna array. These methods consist of two parts, Constellation Estimation and Assignment. We give two methods for constellation estimation, the Smallest Distance Clustering and the Maximum Likelihood Estimation. While the latter is theoretically sound,the former is Computationally simple and intuitively appealing. We show that the Maximum Likelihood Constellation Estimation is well approximated by the Smallest Distance Clustering Algorithm at high SNR. The Assignment Algorithm exploits the structure of the BPSK signals. We observe that both the methods for estimating the constellation vectors perform very well at high SNR and nearly attain Cramer-Rao bounds. Using this fact and noting that the Assignment Algorithm causes negligble error at high SNR, we derive an upper bound on the probability of bit error for the above methods at high SNR. This upper bound falls very rapidly with increasing SNR, showing that our constellation estimation-assignment approach is very efficient. Simulation results are given to demonstrate the usefulness of the bounds.
29
Tarun, Cynthia. "Techno-Economic Study of CO2 Capture from Natural Gas Based Hydrogen Plants". Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2837.
Resumen
As reserves of conventional crude oil are depleted, there is a growing need to develop unconventional oils such as heavy oil and bitumen from oil sands. In terms of recoverable oil, Canadian oil sands are considered to be the second largest oil reserves in the world. However, the upgrading of bitumen from oil sands to synthetic crude oil (SCO) requires nearly ten times more hydrogen (H2) than the conventional crude oils. The current H2 demand for oil sands operations is met mostly by steam reforming of natural gas. With the future expansion of oil sands operations, the demand of H2 for oil sand operations is likely to quadruple in the next decade. As natural gas reforming involves significant carbon dioxide (CO2) emissions, this sector is likely to be one of the largest emitters of CO2 in Canada. In the current H2 plants, CO2 emissions originate from two sources, the combustion flue gases from the steam reformer furnace and the off-gas from the process (steam reforming and water-gas shift) reactions. The objective of this study is to develop a process that captures CO2 at minimum energy penalty in typical H2 plants.
The approach is to look at the best operating conditions when considering the H2 and steam production, CO2 production and external fuel requirements. The simulation in this study incorporates the kinetics of the steam methane reforming (SMR) and the water gas shift (WGS) reactions. It also includes the integration of CO2 capture technologies to typical H2 plants using pressure swing adsorption (PSA) to purify the H2 product. These typical H2 plants are the world standard of producing H2 and are then considered as the base case for this study. The base case is modified to account for the implementation of CO2 capture technologies. Two capture schemes are tested in this study. The first process scheme is the integration of a monoethanolamine (MEA) CO2 scrubbing process. The other scheme is the introduction of a cardo polyimide hollow fibre membrane capture process. Both schemes are designed to capture 80% of the CO2 from the H2 process at a purity of 98%.
The simulation results show that the H2 plant with the integration of CO2 capture has to be operated at the lowest steam to carbon (S/C) ratio, highest inlet temperature of the SMR and lowest inlet temperatures for the WGS converters to attain lowest energy penalty. H2 plant with membrane separation technology requires higher electricity requirement. However, it produces better quality of steam than the H2 plant with MEA-CO2 capture process which is used to supply the electricity requirement of the process. Fuel (highvale coal) is burned to supply the additional electricity requirement. The membrane based H2 plant requires higher additional electricity requirement for most of the operating conditions tested. However, it requires comparable energy penalty than the H2 plant with MEA-CO2 capture process when operated at the lowest energy operating conditions at 80% CO2 recovery.
This thesis also investigates the sensitivity of the energy penalty as function of the percent CO2 recovery. The break-even point is determined at a certain amount of CO2 recovery where the amount of energy produced is equal to the amount of energy required. This point, where no additional energy is required, is approximately 73% CO2 recovery for the MEA based capture plant and 57% CO2 recovery for the membrane based capture plant.
The amount of CO2 emissions at various CO2 recoveries using the best operating conditions is also presented. The results show that MEA plant has comparable CO2 emissions to that of the membrane plant at 80% CO2 recovery. MEA plant is more attractive than membrane plant at lower CO2 recoveries.
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Maurer, Ronald W. "Competitive Adsorption of Poly(1-vinylpyrrolidone-co-styrene) and Kymene onto Wood Fibers: the Improved Effect of Sequential Adsorption". Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14075.
Resumen
Non-ionic copolymers, such as poly(1-vinylpyrrolidone-co-styrene), are used in the production of filtration membranes and fibers because of their ability to provide both hydrophilic and hydrophobic character. However, their non-ionic character and solubility in water prevents inexpensive recovery from waste streams. Wood fibers show potential as recovery agents because they are inexpensive, environmentally friendly, and have a large surface area per unit mass (200 m2/g). However, due to the anionic nature of the fiber surface, their adsorptive behavior is often limited to cationic species. We have shown that low-dosage application of a cationic polyamide epichlorohydrin resin, Kymene 557H®, using a sequential adsorption process can alter the fiber surface charge so as to provide more neutral surface area for the non-ionic polymer to adsorb; furthermore, the adsorbed Kymene 557H® does not block the approach of poly(1-vinylpyrrolidone-co-styrene). Single-component adsorption of poly(1-vinylpyrrolidone-co-styrene) was on the order of 10-3 g/g; with Kymene 557H® adsorbed on the fiber, the adsorption increased one order of magnitude to 10-2 g/g. This significant increase is caused by neutralization of fiber surface charge via Kymene 557H® adsorption, creating a surface more favorable for adsorption and recovery of non-ionic species.
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Landaverde, Alvarado Carlos Jose. "Sorption, Transport and Gas Separation Properties of Zn-Based Metal Organic Frameworks (MOFs) and their Application in CO₂ Capture". Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73214.
Resumen
Adsorption, separation and conversion of CO₂ from industrial processes are among the priorities of the scientific community aimed at mitigating the effects of greenhouse gases on the environment. One of the main focuses is the capture of CO₂ at stationary point sources from fossil fuel emissions using porous crystalline materials. Porous crystalline materials can reduce the energy costs associated with CO₂ capture by offering high adsorption rates, low material regeneration energy penalties and favorable kinetic pathways for CO₂ separation. MOFs consist of polymeric inorganic networks with adjustable chemical functionality and well-defined pores that make them ideal for these applications. The objective of this research was to test the potential for CO₂ capture on Zn-based MOFs by studying their sorption, transport and gas separation properties as adsorbents and continuous membranes.
Three Zn-based MOFs with open Zn-metal sites were initially studied. Zn4(pdc)4(DMF)2•3DMF (1) exhibited the best properties for CO₂ capture and was investigated further under realistic CO₂ capture conditions. The MOF exhibited preferential CO₂ adsorption based on a high enthalpy of adsorption and selectivity of CO₂ over N₂ and CH₄. Sorption dynamics of CO₂ indicated fast adsorption and a low activation energy for sorption. Diffusion inside the pores is the rate-limiting step for diffusion, and changes in the process temperature can enhance CO₂ separation. Desorption kinetics indicated that CO₂ has longer residence times and lower activation energies for desorption than N₂ and CH₄. This suggests that the selective adsorption of CO₂ is favored.
MOF/Polymer membranes were synthesized via a solvothermal method with structural defects sealed by a polymer coating. This method facilitates the permeation measurements of materials that cannot form uniform-defect-free layers. The membrane permeation of CO₂, CH₄, N₂ and H₂ exhibited a linear relation to the inverse square root of the molecular weight of the permanent gases, indicating that diffusion occurs in the Knudsen regime. Permselectivity was well-predicted by the Knudsen model with no temperature dependence, and transport occurs inside the pores of the membrane. MOF (1) exhibits ideal properties for future applications in CO₂ capture as an adsorbent.Ph. D.
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Abdollahi, Farhang. "Gas Separation by Adsorption in Order to Increase CO2 Conversion to CO via Reverse Water Gas Shift (RWGS) Reaction". Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/23993.
Resumen
In this research project, adsorption is considered in conjunction with the reverse water gas shift reaction in order to convert CO2 to CO for synthetic fuel production. If the CO2 for this process can be captured from high emitting industries it can be a very good alternative for reduced fossil fuel consumption and GHG emission mitigation. CO as an active gas could be used in Fischer-Tropsch process to produce conventional fuels. Literature review and process simulation were carried out in order to determine the best operating conditions for reverse water gas shift (RWGS) reaction. Increasing CO2 conversion to CO requires CO2/CO separation downstream of the reactor and recycling unreacted CO2 and H2 back into the reactor. Adsorption as a viable and cost effective process for gas separation was chosen for the CO2/CO separation. This was started by a series of adsorbent screening experiments to select the best adsorbent for the application. Screening study was performed by comparing pure gas isotherms for CO2 and CO at different temperatures and pressures. Then experimental isotherm data were modeled by the Temperature-Dependent Toth isotherm model which provided satisfactory fits for these isotherms. Henry law’s constant, isosteric heat of adsorption and binary mixture prediction were determined as well as selectivity for each adsorbent. Finally, the expected working capacity was calculated in order to find the best candidate in terms of adsorption and desorption. Zeolite NaY was selected as the best candidate for CO2/CO separation in adsorption process for this project. In the last step breakthrough experiments were performed to evaluate operating condition and adsorption capacity for real multi component mixture of CO2, CO, H2 in both cases of saturated with water and dry gas basis. In multi components experiments zeolite NaY has shown very good performance to separate CO2/CO at low adsorption pressure and ambient temperature. Also desorption experiment was carried out in order to evaluate the working capacity of the adsorbent for using in industrial scale and eventually temperature swing adsorption (TSA) process worked very well for the regeneration step. Integrated adsorption system downstream of RWGS reactor can enhance the conversion of CO2 to CO in this process significantly resulting to provide synthetic gas for synthetic fuel production as well as GHG emission mitigation.
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Vinnakota, Keerthi. "Chemical Recycling of Poly (Ethylene Terephthalate) and its Co-polyesters with 2, 5-Furandicarboxylic Acid using Alkaline Hydrolysis". University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1535106967389994.
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Ghafouri-Bakhsh, Shakour. "Morphological studies of polymer blends by scanning tunneling microscopy, phase separation in poly(methyl methacrylate)/poly(styrene- co-methylmethacrylate) systems". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1994. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ51530.pdf.
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Jung, Kyung Sook. "CO2 Separation and Regeneration Study From Power Plant Flue Gases With Reclaimed Mg(OH)2". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1122333773.
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Zago, Gustavo Pereira. "Estudo da co-cristalização em sistema ternário NaCI-CaSO4-H2O para dessalinização de água". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-15012018-132007/.
Resumen
O crescimento acelerado da população mundial e o consequente aumento da produção de bens de consumo tem impulsionado uma crise na disponibilidade de recursos naturais, principalmente os hídricos. Diante da escassez de recursos hídricos, processos de tratamento de efluentes industriais e domésticos que visam o descarte zero de líquido (ZLD - Zero Liquid Discharge) vêm sendo cada vez mais estudados. Atualmente, diversos processos têm sido empregados com este propósito. No entanto, ainda há a geração, juntamente com a água recuperada, de uma corrente composta por uma solução salina concentrada, cuja composição normalmente é constituída por diferentes tipos de sais inorgânicos. Uma das formas de alcançar o descarte zero de líquidos é por meio da implementação de um processo adicional de separação, sendo a cristalização evaporativa considerada viável para essa finalidade. O emprego deste processo é limitado ao controle das características morfológicas das partículas obtidas, visto que estas influenciam diretamente na efetividade de separação dos processos subsequentes à cristalização (filtração, centrifugação). Além disso, efluentes industriais são soluções complexas, e a utilização da cristalização envolve a presença de mais de um sal em solução (co-cristalização). Este processo é pouco investigado na literatura científica, logo, a determinação de condições de processos visando controlar a características destas partículas não é trivial. Neste trabalho, foram estudados o efeito da taxa de evaporação e da presença de sementes na morfologia, composição, tamanho e hábito de partículas de cloreto de sódio e sulfato de cálcio obtidas por co-cristalização evaporativa em bateladas. Os resultados serviram para a determinação de parâmetros de operação para a co-cristalização visando a obtenção de partículas com elevado tamanho médio e baixa dispersão de tamanhos. Taxas de evaporação elevadas favoreceram a obtenção de aglomerados de partículas. A presença de sulfato de cálcio em solução resultou em partículas maiores, menos polidispersas e com menor grau de aglomeração. Tal resultado foi considerado positivo, visto que, estas características são desejáveis para a separação dos cristais da solução mãe. Foi também observado que as sementes de hemihidrato atuam inibindo a aglomeração dos cristais de NaCl. O aumento da quantidade de sementes destes sais culminou na obtenção de partículas menos aglomeradas, porém houve um alargamento das distribuições de tamanho de partículas. Nos experimentos em que foram utilizadas sementes de ambos os sais, o mesmo efeito na aglomeração foi observado. Em todos os experimentos com semeadura de hemihidrato, foi observada a aglomeração deste sal com o NaCl, que foi intensificada com o aumento da taxa de evaporação e com o aumento da concentração de sementes. Foi identificada a possibilidade de recuperação de ambos os sais e obtenção - em determinadas condições - de mais de 90% do NaCl com até 99,50% de pureza.The accelerated growth of the world population and the consequent increase in the production of consumer goods, has driven to a crisis in the availability of natural resources, especially water. Due to the scarcity of water resources, industrial and domestic wastewater treatment processes that aim the Zero Liquid Discharge (ZLD) have been increasingly studied. Nowadays, several processes have been used for this purpose. However, in all of them, there is still the generation of a brine composed of a concentrated salt solution, concomitantly with the recovered water, whose composition is normally constituted by different types of inorganic salts. One way to achieve the ZLD is through the implementation of an additional separation process, for which the evaporative crystallization is considered technically viable for this purpose. The use of this process is limited to the control of the morphological characteristics of the particles obtained, since this influences directly the separation effectiveness of the downstream processes to crystallization (filtration, centrifugation). Besides, industrial effluents are complex solutions and its crystallization involves the presence of more than one salt in solution (cocrystallization). This process is still not well investigated on scientific literature, thus, the determination of process conditions aiming to control the characteristics of these particles is not trivial. In this work, the effect of the evaporation rate and the presence of seeds on the morphology, composition, size and habit of sodium chloride and calcium sulfate particles obtained by batch evaporative co-crystallization were studied. The results were used to determine the operating parameters for the cocrystallization in order to obtain particles with high average size and narrow dispersion of sizes. High evaporation rates favored the obtaining of agglomerated particles. The presence of calcium sulfate in solution resulted in larger particles, less polydisperse and with less degree of agglomeration. Such result was considered positive, since, these characteristics are desirable for the separation of the crystals from the solution. Seeds of hemihydrate inhibited the agglomeration of the NaCl crystals. The increase in seed load of hemihydrate culminated in obtaining less agglomerated particles, but there was an increase in particle size distributions. In the experiments in which seeds of both salts were used, the same effect in the agglomeration was observed. In all experiments with seeds of hemihydrate, agglomeration of this salt with NaCl was observed, which was intensified with increasing evaporation rate and increasing seed amount. It was identified the possibility of recovery of both salts and, for certain conditions, obtaining more than 90% of NaCl with up to 99.50% purity.
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Wang, Di. "Ιnnοvative cοmpοsite pοlymer materials fοr CΟ2 separatiοn". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMIR09.
Resumen
Actuellement, les émissions de CO₂, principal responsable du réchauffement climatique, augmentent à un rythme alarmant. Par conséquent, il existe un besoin mondial croissant de technologies de pointe capables de séparer et de capturer efficacement le CO₂. Dans ce travail, une série de membranes composites PSF/IL et PES/IL pour la séparation du CO₂ ont été étudiées. Six IL ([Meim][TFSO₃], [Vim][TFSO₃], [Meim][Tf₂N], [Vim][Tf₂N], Li(DOBA)[Tf₂N] et Li(HDA)[Tf₂N]) ont été synthétisés avec succès et caractérisés par FT-IR, 1H RMN, TGA et DSC. Des membranes composites avec différentes quantités d'IL ont été fabriquées par évaporation de solvent puis étudiées par FT-IR, TGA, DSC, MEB, cartographie du F, énergie de surface, essais de traction et perméation aux gaz (CO₂, N₂ et O₂). A 25°C et 4 bar, la membrane PES/10[Vim][Tf₂N] présente une perméabilité au CO₂ de 1,92 Barrer avec des sélectivités CO₂/N₂ et CO₂/O₂ améliorées de 20,4 et 6,1, respectivementCurrently, the emission of CO₂, which is the primary contributor to global warming, is increasing at an alarming rate. Consequently, there is a growing global need for cutting-edge technologies that can effectively separate and capture CO₂. In the present work, a series of PSF/IL and PES/IL composite membranes for CO₂ separation were investigated. Six ILs ([Meim][TFSO₃], [Vim][TFSO₃], [Meim][Tf₂N], [Vim][Tf₂N], Li(DOBA)[Tf₂N] and Li(HDA)[Tf₂N]) were synthesized successfully and characterized by FT-IR, 1H NMR, TGA and DSC. Composite membranes with different IL loadings were fabricated by solution casting method and exhaustively studied by FT-IR, TGA, DSC, SEM, F-mapping, surface energy, tensile tests, and gas permeation (CO₂, N₂ and O₂). Under 25°C and 4 bar, PES/10[Vim][Tf₂N] membrane showed a CO₂ permeability of 1.92 Barrer with improved CO₂/N₂ and CO₂/O₂ selectivities of 20.4 and 6.1, respectively
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Vogel, Jörn-Oliver. "Co-deposited films of rod-like conjugated molecules". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2009. http://dx.doi.org/10.18452/15978.
Resumen
In dieser Arbeit wird die Phasenseparation und Mischung zwischen konjugierten Stäb-chenmolekülen in dünnen Filmen untersucht. Hauptaugenmerk liegt darauf zu ergrün-den welche molekularen Eigenschaften zu Mischung und/ oder Phasenseparation füh-ren. Mit den 5 Molekülen Pentacen (PEN), Quaterthiophen (4T), Sexithiophen (6T), p-Sexiphenylen (6P), alpha,omega-Dihexylsexithiophen (DH6T) werden Materialpaare zusammen gestellt, die sich in den Parametern „optische und elektrische Eigenschaf-ten“, „Länge des konjugierten Kerns“ und Alkylkettensubstitution unterscheiden. Alle Schichten werden mittels organischer Molekularstrahlabscheidung auf die Substrate Siliziumoxid und Mylar, einer PET Folie, simultan von zwei Quellen aufgedampft. Das Mischungsverhältnis wird mittels der individuellen Aufdampfraten eingestellt und eine Gesamtrate von 0.5 nm/min eingehalten. Es wird Phasenseparation für Materialpaare mit ungleicher konjugierter Kernlänge, z.B. [4T/6T], beobachtet. Erstaunlicherweise führt die Co-Verdampfung von Molekülpaaren mit ähnlicher konjugierter Kernlänge [4T/PEN] und [6T/6P] zu wohlgeordneten Fil-men, in denen die Moleküle in gemischten Lagen parallel zur Substratoberfläche auf-wachsen und die Längsachse der Moleküle fast senkrecht zur Substratoberfläche orien-tiert ist. Molekülpaare mit ähnlicher konjugierter Kernlänge und Alkylsubstitution [6T/DH6T] und [6P/DH6T] zeigten ebenfalls geordneten Schichten, wobei als Besonderheit eine lineare Abhängigkeit des Lagenabstandes vom DH6T-Gehalt zu beobachten ist. Dies wird mit einer Phasenseparation in eine aromatische und eine alkyl Domäne erklärt. Mit abnehmendem DH6T-Gehalt im Film ist die Alkyldomäne weniger dicht gepackt, was auf Grund der Flexibilität der Alkylketten zu einer Abnahme des gesamten Lagenab-standes führt. Die besonders geringe Oberflächenrauhigkeit und die miteinander verbundenen Inseln der [DH6T/6T] Filme prädestinieren sie zur Verwendung in Feldeffekttransistoren. Es wird gezeigt, dass es möglich ist, die Ladungsträgerdichte im Kanal durch Änderung des Verhältnisses zwischen DH6T und 6T so zu verändern, dass der Transistor im Verar-mungs- oder Anreicherungsregime betrieben werden kann. Dabei bleibt die Ladungsträ-germobilität auf gleich bleibend hohem Niveau. Dies entspricht dem Dotieren eines anorganischen Halbleiters.This thesis is centered on studies of phase separation and mixing in co-deposited thin films of rod-like conjugated molecules. The main focus is to determine which molecular properties lead to phase separation and/or mixing of two materials. To address this question I used five materials, of importance in the context of “organic electronics”: pentacene (PEN), quaterthiophene (4T), sexithiophene (6T), p-sexiphenylene (6P), alpha,omega-dihexylsexithiophene (DH6T). With these it was possible to form material pairs which differ in the parameters: energy levels, length of the conjugated core, and alkyl-end-chain-substitution. All films were deposited by organic molecular beam deposition onto the chemically inert substrates silicon oxide and Mylar, a polyethylene terephthalate (PET) foil. The material pairs were deposited simultaneously from two thermal sublima-tion sources. The mixing ratio was controlled by the individual deposition rates, which were measured online by a microbalance. The total deposition rate was 0.5 nm/min, and the film thicknesses ranged from 4 nm to 40 nm. Phase separation is observed for material pairs with dissimilar conjugated core sizes, i.e. [4T/6T]. Noteworthy, the co-deposition of material pairs with similarly sized conju-gated cores [4T/PEN] and [6T/6P] lead to well ordered layered structures. The mole-cules show mixing within layers on a molecular scale and the long molecular axis is ori-ented almost perpendicular to the substrate surface. Material pairs with similarly sized conjugated core and alkyl-end-chain-substitution [6T/DH6T] and [6P/DH6T] show also growth in mixed layered structures. An especially appealing fact is that the interlayer distance increases proportional to the DH6T content in the film. This can be explained with a phase separation into an aromatic and an alkyl domain vertically to the substrate surface. A decrease of the DH6T content in the film leads to a less dense packing in the alkyl domain. This leads, due to the flexibility of the alkyl chains, to a decrease of the overall interlayer distance. The low surface corrugation and the interconnected islands render the material pair [6T/DH6T] well suitable for the use as active layer in organic field effect transistors. It is shown that it is possible to tune the charge carrier density in the channel by changing the ratio between 6T and DH6T. This effect enables switching the transistor from en-hancement to depletion mode, while maintaining a high charge carrier mobility. This is comparable to p-type doping of inorganic semiconductors.
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Wieczorek, Jens [Verfasser] y Uwe [Akademischer Betreuer] Bovensiepen. "Separation von laserinduzierten- ultraschnellen Transporteffekten und Spin-Flip-Streuung in Co/Cu(001) - Eine schichtdickenabhängige Magnetisierungsprofilanalyse mittels magnetooptischen Methoden / Jens Wieczorek. Betreuer: Uwe Bovensiepen". Duisburg, 2015. http://d-nb.info/1079793526/34.
40
Huang, Jin. "CO2(H2S) membrane separations and WGS membrane reactor modeling for fuel cells". Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1166640509.
41
Tzou, Nicholas. "Low-cost sub-Nyquist sampling hardware and algorithm co-design for wideband and high-speed signal characterization and measurement". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51876.
Resumen
Cost reduction has been and will continue to be a primary driving force in the evolution of hardware design and associated technologies. The objective of this research is to design low-cost signal acquisition systems for characterizing wideband and high-speed signals. As the bandwidth and the speed of such signals increase, the cost of testing also increases significantly; therefore, innovative hardware and algorithm co-design are needed to relieve this problem.
In Chapter 2, a low-cost multi-rate system is proposed for characterizing the spectra of wideband signals. The design is low-cost in the sense of the actual component cost, the system complexity, and the effort required for calibration. The associated algorithms are designed such that the hardware can be implemented with low-complexity yet be robust enough to deal with various hardware variations. A hardware prototype is built not only to verify the proposed hardware scheme and algorithms but to serve as a concrete example that shows that characterizing signals with sub-Nyqusit sampling rate is feasible. Chapter 3 introduces a low-cost time-domain waveform reconstruction technique, which requires no mutual synchronization mechanisms. This brings down cost significantly and enables the implementation of systems capable of capturing tens of Gigahertz (GHz) signals for significantly lower cost than high-end oscilloscopes found in the market today. For the first time, band-interleaving and incoherent undersampling techniques are combined to form a low-cost solution for waveform reconstruction. This is enabled by co-designing the hardware and the back-end signal processing algorithms to compensate for the lack of coherent Nyquist rate sampling hardware. A hardware prototype was built to support this work. Chapter 4 describes a novel test methodology that significantly reduces the required time for crosstalk jitter characterization in parallel channels. This is done by using bit patterns with coprime periods as channel stimuli and using signal processing algorithms to separate multiple crosstalk coupling effects. This proposed test methodology can be applied seamlessly in conjunction with the current test methodology without re-designing the test setup. More importantly, the conclusion derived from the mathematical analysis shows that only such test stimuli give unbiased characterization results, which are critical in all high-precision test setups. Hardware measurement results and analysis are provided to support this methodology. This thesis starts with an overview of the background and a literature review. Three major previously mentioned works are addressed in three separate chapters. Each chapter documents the hardware designs, signal processing algorithms, and associated mathematical analyses. For the purpose of verification, the hardware measurement setups and results are discussed at the end of these three chapters. The last chapter presents conclusions and future directions for work from this thesis.
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Lima, Juliana Aristeia de. "Comportamento de fases de soluções binarias e ternarias de poli(etileno-co-alcool vinilico), poli(metacrilato de metila) e dimetilformamida". [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248789.
Resumen
Orientador: Maria Isabel FelisbertiTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Neste trabalho foram estudadas blendas de poli(etileno-co-álcool vinílico) (EVOH), um copolímero semicristalino que combina segmentos hidrofílicos e hidrofóbicos e poli(metacrilato de metila) (PMMA), um polímero amorfo e hidrofílico. As blendas de EVOH, com teor de etileno variando de 27 a 44 mol %, e PMMA foram preparadas por casting a partir de soluções em DMF, e por mistura mecânica em um mini-misturador, objetivando: i) avaliar o comportamento de fases e a morfologia das blendas, EVOH/PMMA, em função da composição das misturas, do teor de etileno nos copolímeros de EVOH e do método de preparação; ii) obter os diagramas de fases das soluções binárias, EVOH/DMF, e ternárias, EVOH/PMMA/DMF, através do processo de separação de fases induzido termicamente (TIPS). O comportamento de fases das blendas, EVOH/PMMA, foi estudado através de Calorimetria Diferencial de Varredura (DSC) e Análise Dinâmico-Mecânica (DMA). A morfologia das blendas foi investigada por Microscopia Eletrônica de Varredura (SEM). As blendas independentemente do modo de preparação e da composição são imiscíveis. Como conseqüência desta imiscibilidade, as temperaturas de fusão (Tf) e cristalização (Tc) não são afetadas pela presença de PMMA. A morfologia das blendas varia com a composição e método de preparação. As blendas obtidas pelo método mecânico são compactas, apresentando morfologia de fase dispersa em uma matriz, com inversão de fases em aproximadamente 50 % em massa de cada componente. As soluções binárias, EVOH/DMF, e ternárias, EVOH/PMMA/DMF, foram submetidas a ensaios para a determinação das temperaturas de turvamento (Tturv) por microscopia ótica, e de cristalização dinâmica (Tcd), por DSC. As soluções binárias apresentaram comportamento UCST (upper critical solution temperature), sendo que a separação de fases L-L ocorre a temperaturas superiores à separação de fases S-L. O modelo de interações binárias prevê que a curva de separação L-L para as soluções EVOH- 38/DMF esteja situada a temperaturas superiores em relação às soluções EVOH-32/DMF e indica que a separação de fases resulta da baixa afinidade entre segmentos hidrofóbicos do EVOH com os segmentos do polímero contendo hidroxila e com o solvente, DMF, concordando com os dados obtidos experimentalmente. Filmes de EVOH obtidos pela evaporação do solvente mostraram-se densos, sem a presença de poros. As soluções ternárias também apresentaram comportamento UCST, resultando em duas fases macroscópicas, F1 e F2, à temperatura ambiente. A composição destas fases foi determinada por Análise Termogravimétrica (TGA), e os resultados mostraram que uma das fases macroscópicas é rica em EVOH e outra fase é rica em PMMA. As blendas resultantes da secagem dos sistemas ternários apresentaram duas camadas: uma densa e rica em PMMA e outra porosa e rica em EVOH. A presença de PMMA foi decisiva à formação de estruturas porosas
Abstract: In this work blends of poly (ethylene-co-vinyl alcohol) (EVOH), a semicrystalline copolymer which combines hydrophobic and hydrophilic segments and poly (methyl methacrylate) (PMMA), an amorphous and hydrophilic polymer were studied. EVOH blends, with ethylene content ranging from 27 to 44 mol% and PMMA were prepared by casting from solutions in DMF, and by mixing into a mini-mixer, with the objective of: i) evaluate the phase behavior and the morphology of the blends, EVOH/PMMA, depending on the composition of mixtures, the ethylene contents in the copolymers of EVOH and the conditions of mixing; ii) obtain the phase diagrams of the binary and ternary solutions, EVOH/DMF and EVOH/PMMA/DMF, respectively, by the process of thermally induced phase separation (TIPS). The phase behavior of the blends, EVOH / PMMA, was investigated by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The morphology of the blends was investigated by Scanning Electron Microscopy (SEM). The blends independently of the method of preparation and of the composition are immiscible. As a result of immiscibility, the melting temperature (Tm) and the crystallization temperature (Tc) are not affected by the presence of PMMA. The morphology of the blends varies with the composition and with the method of preparation. The blends produced by the mechanical method is compact, showing morphology of dispersed phase in a matrix, with inversion of phases in about 50% by weight of each component. The binary solutions, EVOH-38/DMF and EVOH-32/DMF, were submitted to experiments to determine the cloud temperature (Tcloud) by optical microscopy, and the dynamic crystallization (Tcd), by DSC. The binary solutions show UCST behavior (upper critical solution temperature), and the L-L phase separation occurs at higher temperatures than the S-L phase separation. The binary interaction model provides the L-L line to the EVOH-38/DMF, solutions which was situated at higher temperatures than the EVOH-32/DMF solutions and indicates that the phase separation results from the low affinity between the hydrophobic segments of EVOH with the segments of the polymer containing hydroxyl and the solvent, DMF, which agrees with the data obtained experimentally. Films of EVOH obtained by the solvent evaporating seemed to be dense, without the presence of pores. The ternary solutions also had UCST behavior, resulting in two macroscopic phases, F1 and F2, at room temperature. The phase compositions were determined by Thermogravimetric Analysis (TGA), and the results showed that one of the macroscopic phases is rich in EVOH and the other phase is rich in PMMA. The blends resulting from drying of ternary systems had two layers: a dense and rich in PMMA and another porous and rich in EVOH. The presence of PMMA was crucial to the formation of porous structures
Doutorado
Físico-Química
Doutor em Ciências
43
Elmsjö, Albert. "Selectivity in NMR and LC-MS Metabolomics : The Importance of Sample Preparation and Separation, and how to Measure Selectivity in LC-MS Metabolomics". Doctoral thesis, Uppsala universitet, Avdelningen för analytisk farmaceutisk kemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-318296.
Resumen
Until now, most metabolomics protocols have been optimized towards high sample throughput and high metabolite coverage, parameters considered to be highly important for identifying influenced biological pathways and to generate as many potential biomarkers as possible. From an analytical point of view this can be troubling, as neither sample throughput nor the number of signals relates to actual quality of the detected signals/metabolites. However, a method’s selectivity for a specific signal/metabolite is often closely associated to the quality of that signal, yet this is a parameter often neglected in metabolomics. This thesis demonstrates the importance of considering selectivity when developing NMR and LC-MS metabolomics methods, and introduces a novel approach for measuring chromatographic and signal selectivity in LC-MS metabolomics. Selectivity for various sample preparations and HILIC stationary phases was compared. The choice of sample preparation affected the selectivity in both NMR and LC-MS. For the stationary phases, selectivity differences related primarily to retention differences of unwanted matrix components, e.g. inorganic salts or glycerophospholipids. Metabolites co-eluting with these matrix components often showed an incorrect quantitative signal, due to an influenced ionization efficiency and/or adduct formation. A novel approach for measuring selectivity in LC-MS metabolomics has been introduced. By dividing the intensity of each feature (a unique mass at a specific retention time) with the total intensity of the co-eluting features, a ratio representing the combined chromatographic (amount of co-elution) and signal (e.g. in-source fragmentation) selectivity is acquired. The calculated co-feature ratios have successfully been used to compare the selectivity of sample preparations and HILIC stationary phases. In conclusion, standard approaches in metabolomics research might be unwise, as each metabolomics investigation is often unique. The methods used should be adapted for the research question at hand, primarily based on any key metabolites, as well as the type of sample to be analyzed. Increased selectivity, through proper choice of analytical methods, may reduce the risks of matrix-associated effects and thereby reduce the false positive and false negative discovery rate of any metabolomics investigation.
44
Marchand, Jean-Pierre. "Relaxation magnétique nucléaire dans les solutions ternaires de polyacrylonitrile ou de polyacrylonitrile-co-méthallylsulfonate de sodium : détermination et caractérisation du diagramme de phases". Grenoble 1, 1993. http://www.theses.fr/1993GRE10193.
Resumen
Ce travail concerne l'etude des proprietes des solutions de polyacrylonitrile (pan) et des copolymeres d'acrylonitrile et de methallylsulfonate de sodium observees a l'equilibre ou hors equilibre thermodynamique. Utilisees dans la fabrication de membranes de dialyse renale, ces solutions ont ete explorees par rmn a une echelle d'espace caracteristique des processus physiques (cristallisation, demixtion) responsable des proprietes de permeabilite de ces membranes. Le pan et son copolymere presentent en solution un diagramme de phases typiques d'un polymere semi-cristallin; les conditions d'etablissement de la transition de phase solide-liquide et de la transition liquide-liquide ont ete precisees pour des solutions en solvant binaire dmf-eau equimolaire. La presence de charges ioniques sur la chaine polymere provoque un elargissement du domaine de la demixtion; cet effet a ete modelise dans le cadre de description des solutions proposees par flory. La cinetique de mise en ordre de ces polymeres en solution peut etre decrite comme un processus gouverne par une nucleation heterogene et sporadique, sans etape de croissance; cette cristallisation conduit a la formation de domaines ordonnes dont la taille moyenne a ete evaluee a l'aide de donnees thermodynamiques. Les membranes de dialyse renale realisees a partir de ces solutions peuvent etre decrites comme des gels physiques composes de domaines ordonnes interconnectes par des chaines polymeres a l'etat amorphe. La presence de ces domaines gouverne les proprietes de permeabilite et de selectivite de ces membranes
45
Tilli, Paola. "Production, characterization and modeling of hollow fiber membranes for biogas purification". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Resumen
One type of technology for biogas purification which has experienced substantial growth during past decades is membrane-based technology which presents the advantage of high energy efficiency, simplicity in design and environmental compatibility. The market for CO₂ is dominated by polymeric membranes due to their relatively low manufacturing cost. In this work, the performance of different P84 hollow fibers membranes for CO₂/CH₄ separation is investigated. Different spinning parameters are studied on their effect on gas separation performance of the produced fibers. The attention is focused on air gap length and spinning temperature, since they both affect the formation of the selective layer during the spinning process. Scanning Electron Microscopy (SEM) is used to investigate the morphological characteristics of the developed fibers. Permeation rates of CO₂ and N₂ are measured using the pressure increase method. The achieved ideal selectivity was 30/40 for CO₂/N₂ separation, while permeances are quite low. The permeance of CO₂ through asymmetric hollow fibers increases with pressure because of plasticization. Both gases permeance increases by increasing the air gap and higher spinning temperatures lead to lower permeances. Finally, NE-LF model is used to calculate CO₂ and CH₄ solubility and CO₂/CH₄ solubility selectivity in P84. Large deviation from ideal conditions is predicted underlining a marked competition which affects more CH₄ than CO₂ and results in a real solubility selectivity higher than the ideal one. By considering that real mixed gas perm-selectivity generally presents negative deviation, it follows that diffusivity of CH₄ in P84 is enhanced in presence of CO₂ lowering the diffusivity-selectivity.
46
Marques, Rosalva dos Santos. "Comportamento de fases de soluções de poliolefinas funcionalizadas e implicação na obtenção de membranas pelo processo TIPS". [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248781.
Resumen
Orientador: Maria Isabel FelisbertiTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Neste trabalho, estudou-se o comportamento de fases de soluções binárias e ternárias de poliolefinas funcionalizadas com hidroxilas (EVOH) e ácido carboxílico (PEAA) nos solventes dimetilformamida e álcool benzílico. Utilizou-se EVOH contendo 27 e 44 mol % e PEAA contendo 80 mol % de etileno. As soluções exibem o comportamento de fases do tipo UCST, apresentando separações de fases líquido-líquido (L-L) e sólido-líquido (S-L). As temperaturas de separação de fases L-L e S-L, TL-L e TS-L, respectivamente, foram determinadas para soluções com diferentes composições por inspeção visual e por DSC, respectivamente. Enquanto TS-L para as soluções binárias de EVOH varia fortemente da com a composição das soluções binárias, TS-L para as soluções binárias de PEAA é praticamente constante. Estes resultados foram interpretados sob a ótica de um modelo em que a cristalização do PEAA, que envolve os segmentos de etileno do copolímero, ocorre quase na ausência de solvente. Já a cristalização do EVOH, que envolve os segmentos hidroxilados, ocorre em meio ao solvente, em uma condição em que o potencial químico do polímero varia com a composição da solução. Este modelo pode ser comprovado por estudos de fluorescência empregando-se o pireno e o acetato de uranila como sondas hidrofóbica e hidrofílica, respectivamente. Estes estudos de fluorescência permitiram também acessar transições não detectáveis por DSC. As soluções ternárias homogêneas apresentam mais de uma separação de fases L-L quando submetidas a resfriamento. O diagrama de fases ternário foi construído determinando-se as composições das soluções em equilíbrio, decorrentes da primeira separação de fases L-L, por termogravimetria de alta resolução. Os diagramas de fases das soluções ternárias resultantes das combinações possíveis entre os diferentes polímeros e solventes apresentam regiões de miscibilidade limitadas localizadas em regiões próximas aos vértices, sendo as composições das fases em equilíbrio características de cada combinação nas soluções ternárias. Os materiais resultantes da evaporação do solvente de soluções submetidas ao processo TIPS (Temperature Induced Phase Separation) são compactos ou porosos, dependendo da afinidade polímero-solvente. Entretanto, as morfologias dos materiais resultantes de soluções ternárias submetidas ao processo TIPS são únicas e características do par polímero-polímero, demonstrando que a estratégia de combinação de polímeros para controlar a morfologia é viável
Abstract: The phase behavior of binary and ternary solutions of functionalized poliolefins with hydroxyls (EVOH) and carboxylic acid (PEAA) were studied using dimethylformamide and benzyl alcohol as solvents. PEAA containing 80 mol % and EVOH containing 27 and 44 mol % of ethylene were used. The binary and ternary solutions present a typical UCST behavior associated to liquid-liquid (L-L) and solid-liquid (S-L) phase separation. The temperatures related to L-L and S-L phase separation, TL-L e TS-L, respectively, were determined visually and using DSC, respectively. While TS-L depends on the EVOH solution composition, it is practically constant for PEAA solutions. These results were explained using a model in which the crystallization of PEAA from the solution occurs in absence of solvent, once it involves the polyethylene segments. On the contrary, the crystallization of EVOH from the solution, that involves the hydroxylated segments, occurs in presence of the solvent. This condition leads to the decrease of the chemical potential of EVOH in the solution. The models could be proved by fluorescence experiments using pyrene and uranyl acetate as hydrophobic and hydrophilic probes, respectively. Moreover, the fluorescence experiments allow accessing other transitions not detectable by DSC for ternary solutions. The homogeneous ternary solutions present more than one L-L phase separation by cooling. The ternary diagram was determined by the first L-L phase separation using the composition data accessed by high resolution thermogravimetry. The ternary solutions of all possible combination of polymers and solvents show a restricted miscibility window in the regions near the vertices. The composition of the phases in equilibrium is characteristic of each ternary solution, as well as, the morphology of the materials resulting from the evaporation of the solvent after the solution being subjected to TIPS (Temperature Induced Phase Separation) process. This process applied to binary and ternary solutions resulted in dense or porous materials depending on the polymer-solvent affinity. However, the morphology resulting from ternary solutions subjected to TIPS process and solvent evaporation is unique, showing that the strategy of combining different polymers is a viable route to control the morphology of polymers
Doutorado
Físico-Química
Doutora em Ciências
47
Anselmi, Hélène. "Modélisation et évaluation environnementale d’une unité de captage de CO₂ intégrée à un procédé industriel". Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0080.
Resumen
Limiter les émissions de dioxyde de carbone (CO2) est devenu un enjeu d’envergure internationale, notamment pour les industries des secteurs énergétique, chimique et métallurgique. À cette fin, des technologies de captage de CO2 ont été développées durant ces dernières décennies. Dans cette étude, nous nous intéressons à trois types de technologies de captage de CO2 : par absorption chimique à la MEA, par séparation membranaire et par adsorption sur charbon actif. Le CO2 considéré est émis par une centrale à charbon puis directement valorisé au sein d’un procédé de fabrication sur le même site. L’objectif de cette étude est de quantifier les bénéfices environnementaux de l’installation d’une technologie de captage de CO2, en comparaison à la configuration actuelle, sans captage du CO2. Notre approche associe modélisation systémique des procédés et analyse de cycle de vie (ACV). La méthodologie adoptée consiste à modéliser le système complet (la centrale, le procédé de fabrication et les différentes unités de captage) en utilisant un logiciel de diagrammes de flux (Aspen Plus), puis à déterminer les impacts environnementaux par une ACV. Les résultats montrent que le procédé par adsorption chimique à la MEA est fortement pénalisé par l’utilisation du solvant, tant en ce qui concerne la consommation énergétique que les impacts environnementaux. Le procédé membranaire montre des impacts environnementaux importants, malgré une consommation énergétique bien plus faible, en raison de l’utilisation massive de polymères (matériaux membranaires). Enfin, le procédé par adsorption au charbon actif présente des impacts environnementaux moins élevés que les deux autres procédés dans la grande majorité des catégories d’impactLimiting carbon dioxide (CO2) emissions is a major global issue, particularly for the energy, chemical and metallurgical industries. To this end, CO2 capture technologies have been developed in recent decades. In this study, we focused on three types of CO2 capture technologies: chemical absorption by MEA, membrane separation and activated carbon adsorption. The CO2 considered is emitted by a coal-fired power station and then directly valorized within a manufacturing process on the same site. The objective of this study was to quantify the environmental benefits of installing a CO2 capture technology in comparison to the current configuration, without CO2 capture. Our approach combined process modeling and life cycle assessment. The methodology adopted was to model the complete system (the power plant, the manufacturing process and the various capture units) using a flowsheeting software (Aspen Plus), then to determine the environmental impacts by LCA. The results show that the MEA chemical adsorption process is strongly penalized by the use of the solvent, both regarding the energy consumption and the environmental impacts. The membrane process exhibits significant environmental impacts, despite a much lower energy consumption, due to the massive use of polymers (membrane materials). Finally, the activated carbon adsorption process has lower environmental impacts than the other two processes in the vast majority of impact categories
48
Anselmi, Hélène. "Modélisation et évaluation environnementale d’une unité de captage de CO₂ intégrée à un procédé industriel". Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0080.
Resumen
Limiter les émissions de dioxyde de carbone (CO2) est devenu un enjeu d’envergure internationale, notamment pour les industries des secteurs énergétique, chimique et métallurgique. À cette fin, des technologies de captage de CO2 ont été développées durant ces dernières décennies. Dans cette étude, nous nous intéressons à trois types de technologies de captage de CO2 : par absorption chimique à la MEA, par séparation membranaire et par adsorption sur charbon actif. Le CO2 considéré est émis par une centrale à charbon puis directement valorisé au sein d’un procédé de fabrication sur le même site. L’objectif de cette étude est de quantifier les bénéfices environnementaux de l’installation d’une technologie de captage de CO2, en comparaison à la configuration actuelle, sans captage du CO2. Notre approche associe modélisation systémique des procédés et analyse de cycle de vie (ACV). La méthodologie adoptée consiste à modéliser le système complet (la centrale, le procédé de fabrication et les différentes unités de captage) en utilisant un logiciel de diagrammes de flux (Aspen Plus), puis à déterminer les impacts environnementaux par une ACV. Les résultats montrent que le procédé par adsorption chimique à la MEA est fortement pénalisé par l’utilisation du solvant, tant en ce qui concerne la consommation énergétique que les impacts environnementaux. Le procédé membranaire montre des impacts environnementaux importants, malgré une consommation énergétique bien plus faible, en raison de l’utilisation massive de polymères (matériaux membranaires). Enfin, le procédé par adsorption au charbon actif présente des impacts environnementaux moins élevés que les deux autres procédés dans la grande majorité des catégories d’impactLimiting carbon dioxide (CO2) emissions is a major global issue, particularly for the energy, chemical and metallurgical industries. To this end, CO2 capture technologies have been developed in recent decades. In this study, we focused on three types of CO2 capture technologies: chemical absorption by MEA, membrane separation and activated carbon adsorption. The CO2 considered is emitted by a coal-fired power station and then directly valorized within a manufacturing process on the same site. The objective of this study was to quantify the environmental benefits of installing a CO2 capture technology in comparison to the current configuration, without CO2 capture. Our approach combined process modeling and life cycle assessment. The methodology adopted was to model the complete system (the power plant, the manufacturing process and the various capture units) using a flowsheeting software (Aspen Plus), then to determine the environmental impacts by LCA. The results show that the MEA chemical adsorption process is strongly penalized by the use of the solvent, both regarding the energy consumption and the environmental impacts. The membrane process exhibits significant environmental impacts, despite a much lower energy consumption, due to the massive use of polymers (membrane materials). Finally, the activated carbon adsorption process has lower environmental impacts than the other two processes in the vast majority of impact categories
49
Behloul, Chakib Rafik. "Méthodes de conception de réacteurs multifonctionnels (réacteur-échangeur-séparateur) : application à la synthèse directe de DME à partir de CO₂ et d’H₂". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0249.
Resumen
L'épuisement des ressources et l'accumulation des gaz polluants dans l'atmosphère suscitent aujourd'hui des inquiétudes grandissantes. La transition énergétique en cours nécessite que certains procédés de transformation de la matière et de l'énergie soient partiellement modifiés ou profondément repensés pour s'adapter à des conditions de fonctionnement plus durables. L'électricité et l'hydrogène bas carbone peuvent se substituer aux énergies fossiles conduisant ainsi à un mix énergétique dont l'empreinte Gaz à Effet de Serre (GES) est faible. Outre l'hydrogène, la production de carburants alternatifs et des produits à forte valeur ajoutée est une autre piste pour accompagner la transition énergétique. La recherche de procédés optimaux, durables et économiques est donc un défi majeur auquel les ingénieurs procédés sont confrontés. Le présent travail s'est ainsi focalisé sur l'intensification des procédés de transformation de la matière et de l'énergie, au travers d'unités multifonctionnelles qui exploitent les synergies entre fonctions élémentaires de transformation (réaction, transfert, séparation, etc.) au sein d'un équipement intensif. La notion de réacteurs multifonctionnels, couplant plusieurs fonctions élémentaires, a connu un réel succès d'estime lorsque des démonstrateurs historiques ont vu le jour (procédé Eastman-Kodak, etc.), mais leur implémentation ne s'est pas généralisée par manque de méthodologie de conception pratique. Ce travail porte sur l'application de certaines méthodologies d'intensification pour la compréhension et l'amélioration des performances d'un procédé mettant œuvre des réactions exothermiques équilibrées. La synthèse directe du diméthyl éther (DME) à partir de CO₂ et d'H₂ est retenue comme cas d'étude. Différentes voies exploratoires de développement du procédé de synthèse directe du DME ont été étudiées en s'appuyant sur la modélisation et la simulation. Le réacteur-échangeur de chaleur, le réacteur multifonctionnel (réacteur-échangeur de chaleur-séparateur membranaire), les procédés hybrides de briques élémentaires et un procédé plaçant le réacteur refroidi dans un environnement de procédé classique en présence d'autres opérations unitaires et de recyclages, sont étudiées sous différents angles. Différents cas et stratégies d'optimisation ont été traités qui se distinguent par les variables de décision et la méthode de résolution. Les différentes méthodologies appliquées ont permis de démontrer leur pertinence en termes de solutions obtenues et d'ouverture vers l'innovation des procédés. A l'échelle de l'équipement, l'optimisation des profils représente le cœur de la méthodologie. Les résultats mettent en évidence le potentiel des réacteurs multifonctionnels : une conversion de CO₂ par passe de l'ordre de 98%, un rendement en DME de l'ordre de 95% et une possibilité d'élimination d'une colonne de distillation sont obtenus. Dans le but d'évaluer les caractéristiques du maximum atteignable dans un réacteur multifonctionnel, un procédé hybride de briques élémentaires a été optimisé. A l'échelle du procédé, le comportement du réacteur a été étudié pour comprendre l'impact de l'intégration du réacteur dans une boucle de recyclage et estimer les effets locaux et globaux sur les multiples critères de performances. Sur la base de critères de rendement global en DME, de conversion globale de CO₂, de TRL, etc., la comparaison des différents designs a montré qu'une réduction du nombre d'équipements d'un facteur 11 est possible dans le cas du choix d'un réacteur multifonctionnelThe depletion of resources and the accumulation of pollutant gases in the atmosphere are nowadays of growing concern. The current energy transition requires that certain material and energy transformation processes be partially modified or profoundly reconsidered to fit more sustainable operating conditions. Low-carbon electricity and hydrogen can substitute fossil fuels, leading to an energy mix with a low greenhouse gas (GHG) footprint. In addition to hydrogen, the production of alternative fuels and high value-added products is another way to support the energy transition.Looking for optimal, sustainable and economical processes is therefore a major challenge that process engineers are facing. The present work has thus focused on the intensification of mass and energy transformation processes, through multifunctional units, which take advantage of the synergies between elementary functions of transformation (reaction, transfer, separation, etc.) within an intensive equipment. The concept of multifunctional reactors, coupling several elementary functions, has been a real success when historical demonstrators were created (Eastman-Kodak process, etc.), but their implementation has not been generalized, due to a lack of practical design methodology.This work focuses on the implementation of some intensification methodologies to understand and improve the performance of a process involving balanced exothermic reactions. The dimethyl ether (DME) direct synthesis from CO₂ and H₂ is considered as a case study. Different exploratory ways for the DME direct synthesis process development have been investigated based on modeling and simulation. Reactor- Heat exchanger, multifunctional reactor (reactor-heat exchanger-membrane separator), hybrid elementary block processes and a process involving the cooled reactor in a conventional process environment in the presence of additional unit operations and recycle loop are studied from different angles. Different optimization cases and strategies have been addressed which differ by the decision variables and the solving method. The different methodologies applied have demonstrated the relevance of the solutions obtained and the opening towards process innovation.At the equipment level, the profiles optimization represents the heart of the methodology. The results demonstrate the potential of multifunctional reactors: a CO₂ conversion per pass of 98%, a DME yield of 95% and the possibility to remove a distillation column are obtained. In order to assess the maximum achievable performance in a multifunctional reactor, a hybrid process of elementary blocks has been optimized. At the process scale, the reactor behavior has been studied to further understand the impact of the reactor integration in a recycle loop and to estimate the local and global effects on the multiple performance criteria. Based on various criteria (overall DME yield, overall CO₂ conversion, TRL, etc.), the comparison of the different designs revealed that a reduction of the equipment number by a factor of 11 is possible in the case of a multi-functional reactor choice
50
Norén, Sara y Theresé Thyselius. "Nollseparation mellan förälder och nyfött barn : En begreppsanalys ur barnmorskans perspektiv". Thesis, Högskolan Dalarna, Sexuell, reproduktiv och perinatal hälsa, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:du-36033.
Resumen
Bakgrund: Nollseparation har ingen tydlig definition och tycks vara ett relativt nytt begrepp som används inom förlossnings- och eftervården. Det framgår tydliga riktlinjer om att barnet ska ligga hud mot hud med sin moder efter förlossningen. Men i vissa fall separeras modern och barnet av olika anledningar. Barnmorskan har en central roll i vården av nyförlösta kvinnor och deras nyfödda barn.Syfte: Syftet med studien var att analysera och definiera begreppet nollseparation mellan förälder och nyfött barn ur ett barnmorskeperspektiv.Metod: En begreppsanalys baserad på en hybridmodell. Hybridmodellen är uppdelad i en teoretisk fas med litteratursökning, en fältstudiefas baserad på intervjuer av sex kliniskt verksamma barnmorskor samt en sammanfattande syntetiseringsfas.Resultat: Nollseparation är likställt med; hud mot hud-kontakt, att alltid ha en förälder närvarande, att familjen ska få vara tillsammans samt att samarbete mellan olika vårdinstanser för att bedriva samvård krävs för att upprätthålla nollseparationen. Barnmorskan får en betydelsefull nyckelfunktion i upprätthållandet av nollseparation.Slutsats: Nollseparation är ett paraplybegrepp som involverar hud mot hud-kontakt, förälders närvaro, att familjen ska få vara tillsammans, att det ska finnas en fungerande samvård mellan olika instanser samt att det ingår i barnmorskans arbetsuppgifter att främja nollseparation.Klinisk tillämpbarhet: Resultatet från detta examensarbete kan komma till nytta inom förlossnings- och eftervården, men kompetensen behöver även ökas inom andra instanser i sjukvården som kan komma i kontakt med nyfödda barn och deras föräldrar.Background: Zero-separation has no distinct definition and appears to be a relatively new concept used in delivery- and postpartum care. There are obvious guidelines that the child should be skin-to-skin with the mother after birth. But in some cases the mother and child are separated for different reasons. The midwife has a central part in the care of emergent mothers’ and their newborn children.Aim: The aim in this study was to analyze and define the concept of zero-separation between parent and infant from a midwifes’ perspective.Method: A concept analysis based on a hybridmodel. The hybrilmodel is divided into a theoretical phase with literature search, a field study phase based on interviews with six clinically active midwives and a summary synthesis phase.Results: Zero-separation is equated with; skin-to-skin, always have a parent present, the family being together always and that couplet care is needed to maintain zero-separation. The midwife has a significant keyrole in maintaining zero-separation. Conclusion: Zero-separation is an umbrellaconcept which involves skin-to-skin, parental presence, that the family should be allowed to be together, a functioning couplet care between different instances and that maintaining zero-separation is a part of the midwifes’ assignments.Clinical application: The results from this study can be useful in delivery- and aftercare, but the competence needs to be increased in other instances in healthcare that may come in contact with newborn children and their parents.