Rozprawy doktorskie na temat „Automobiles Catalytic converters”

In response to the increasingly widespread use of catalytic converters for meeting automotive exhaust emission regulations considerable attention is currently being directed towards improving their performance. Experimental analysis is costly and time consuming. A desirable alternative is computational modelling. This thesis describes the development of a fully integrated computational model for simulating monolith type automotive catalytic converters. Two commercial CFD codes, PHOENICS and STAR-CD, were utilised to implement established techniques for modelling the flow field in catalyst assemblies. To appraise the accuracy of the flow field predictions an isothermal steady flow rig was designed and developed. A selection of axisymmetric inlet diffusers and 180o expansions were tested, with the velocity profile across the monolith, the wall static pressure distribution along the inlet section and the total pressure drop across the assembly being measured. These datum sets were compared with predictions using a variety of turbulence models and solution algorithms. The closest agreement was achieved with a two-layer near wall approach, coupled to the fully turbulent version of the RNG k-ε model, and a nominally second order differencing scheme. Even with these approaches the predicted velocity profiles were too flat, the maximum velocity being as much as 17.5% too low. Agreement on pressure drops was better, the error being consistently less than 10%. These results illustrate that present modelling techniques are insufficiently reliable for accurate predictions. It is suggested that the major reason for the relatively poor performance of these techniques is the neglecting of channel entrance effects in the monolith pressure drop term. Despite these weaknesses it was possible to show that the model reproduces the correct trends, and magnitude of change, in pressure drop and velocity distributions as the catalyst geometry changes. The PHONETICS flow field model was extended to include the heat transfer, mass transfer and chemical reactions associated with catalysts. The methodology is based on an equivalent continuum approach. The result is a reacting model capable of simulating the three-dimensional distribution of solid and gas temperatures, species concentrations and flow field variables throughout the monolith mat and the effects that moisture has on the transient warm-up of the monolith. To assess the reacting model’s accuracy use was made of published light-off data from a catalyst connected to a test bed engine. Comparison with predicted results showed that the model was capable of reproducing the correct type, and time scales, of temperature and conversion efficiency behaviour during the warm-up cycle. From these predictions it was possible to show that the flow distribution across the monolith can significantly change during light-off. Following the identification, and subsequent modelling, of the condensation and evaporation of water during the warm-up process it was possible to show that, under the catalyst conditions tested, these moisture effects do not affect light-off times. Conditions under which moisture might affect light-off have been suggested. Although the general level of model accuracy may be acceptable for studying many catalyst phenomena, known deficiencies in the reaction kinetics used, errors in the flow field predictions, uncertainty over many of the physical constants and necessary model simplifications mean that accurate quantitative predictions are still lacking. Improving the level of accuracy will require a systematic experimental approach followed by model refinements.

Automotive catalytic converters are increasingly used to reduce emissions from internal combustion engines to comply with emission regulations. Maldistributed flow across the catalyst affects its warm up, light off time, ageing, and conversion efficiency. This thesis concerns flow distribution in automotive catalytic converters and methods to improve CFD predictions. Previous studies showed that modelling the monolith flow resistance using the Hagen- Poiseuille’s formulation under predicted flow maldistribution. The predictions were improved by incorporating an additional pressure loss term V2 2 1  , where V is transverse velocity just upstream of a monolith channel, for oblique entry of the flow into the monolith known as the entrance effect. Further improvement was obtained by incorporating the critical angle of attack method. However, there was no experimental evidence to support these oblique entry loss formulations. There also remained the possibility that under prediction of flow maldistribution might be due to the failure to predict flow in the diffuser accurately. A one-dimensional oblique angle flow rig was designed and built to measure the effect of oblique entry flow losses in monoliths. Experiments were performed at different angles of attack (α), using different lengths of substrate and a methodology was developed to obtain the oblique flow entrance losses. The results showed that the pressure loss attributed to the entrance effect increased with the angle of attack. The entrance effect was also found to be dependent on channel Reynolds number and substrate length. The theoretical assumption of V2 2 1  predicts accurately at low Reynolds number but looses its validity at high Reynolds number. From the experimental studies, an improved correlation for the entrance effect has been derived as a function of major controlling variables, i.e., angle of attack, length of the substrates and Reynolds number. A two-dimensional rig was designed to measure the flow field using PIV in a 2-D diffuser placed upstream of two different length substrates. The results showed that the flow in a wide angle diffuser consisted of a central core, free shear layer and recirculation regions. The near-field region was found similar to that of a plane jet. The flow field was found to be independent of Reynolds number. Increasing the substrate length resulted in a flattening of the axial profiles close to the substrate face. A CFD study was undertaken to predict maldistributed flow at the exit of the substrate for an axisymmetric catalyst model by incorporating the measured entrance effect correlation. A fixed critical angle of attack (αc,F) approach was used whereby the entrance effect is assumed constant for α>αc,F. Incorporating the entrance effect with αc,F= 810 improved the prediction of maldistribution in the flow profiles. A 2-D CFD study was undertaken to predict the flow distribution in the diffuser and downstream of the substrate. A comparison of the CFD predictions in the diffuser using different turbulence models showed that all the turbulence models used in this study over predicted the width of the central core region and the V2F turbulence model gave velocity predictions that compared best with PIV. Incorporating the entrance effect improved the predictions close to the diffuser-substrate interface and downstream of the substrate.

The research problem addressed in this study was to determine what the main factors are that contribute to the competitive advantage of the catalytic converter industry cluster in the Eastern Cape. To achieve this objective theoretical models of competitive advantage and literature of industry clustering were identified. For the models on competitive advantage, Porter’s diamond was used for national competitive advantage and Porter’s model on the competitive environment, which affects the competitive advantage of a region. Other theories on competitive advantage of cities and regions were identified, leading up to the theory on the cluster approach. The literature mentioned was broken down and analysed using literature, from knowledgeable people in the automotive industry in the Eastern Cape, identified during the study. A questionnaire was developed to test the degree to which the catalytic converter industry cluster in the Eastern Cape is in agreement with the literature study. The empirical study obtained a strong concurrence with the literature study on national competitive advantage and the theory of clusters. This resulted in a strategy for the catalytic converter industry cluster to sustain competitive advantage and remain globally competitive.

Considerable research is being carried out into the parameters that affect catalyst performance in order to meet the latest emission regulations. The conversion efficiency and the durability of automotive catalytic converters are significantly dependent on catalyst flow performance. Related investigations are commonly conducted using CFD techniques which represent an inexpensive and fast alternative to experimental methods. This thesis focuses on the flow performance of automotive catalytic converters using both experimental and computational techniques. The work describes the effects of inlet flow conditions on catalyst performance, the application of radial vanes to catalyst systems and the refinement of the CFD flow model which increases the accuracy of the predicted catalyst flow performance. the effects of inlet flow conditions on the flow maldistribution across the catalyst face and the total pressure loss through the system were assessed using a steady air flow rig. Tests were conducted over a range of Reynolds numbers typically encountered in automotive catalytic converters using a uniform and a fully-developed inlet flow condition. The results showed that the flow maldistribution significantly increases with Reynolds number notably in wide-angled diffusers. The catalyst flow performance is considerably improved when the inlet flow is uniform rather than fully-developed, the non-dimensional total pressure loss is reduced by 8% at Re=60000 and the flow maldistribution across the catalyst face is decreased by 12.5% and 15% respective Reynolds numbers of 30000 and 60000 when using a 60 degree diffuser. The total pressure loss through the system was found to be mostly associated with the monolith brick resistance. When the flow maldistribution is approximately 2, the pressure loss across the monolith brick represents 80% of the system pressure loss. The flow maldistribution across the catalyst face was improved by locating a system of radial splitters in the diffuser. The optimum flow performance was found to be a complex function of the vane design. A maximum improvement in the flow maldistrution indices M and Mi of 25% and 50% respectively was achieved at the expense of an increase in total pressure loss of 13.5% at Re = 60000. Both CFD and flow visualisation techniques were used as an aid to interpreting the flow field in the diffuser. Although a qualitative agreement was obtained using CFD, the flow maldistribution across the catalyst face was underpredected by up to 20%. The accuracy of the flow predictions was significantly improved by investigating the flow field in the monolith channels. Flow recirculation occurs in the channel entry length when the flow approaches the monolith channels at an angle which induces an additional implemented into four models of the flow through axisymmetric catalyst assemblies using various diffuser geometries and inlet flow conditions. By including the flow entrance effects in the porous media approach, the flow maldistribution was predicted within 8% instead of 15% when these effects are neglected. Further investigation of the flow in the monolith channels will be required to accurately model three-dimentional flows (racetrack catalysts) and to include various channel geometries and system flow rates.

Automotive catalytic converters are used extensively in the automotive industry to reduce toxic pollutants from vehicle exhausts. The flow across automotive exhaust catalysts is distributed by a sudden expansion and has a significant effect on their conversion efficiency. The exhaust gas is pulsating and flow distribution is a function of engine operating condition, namely speed (frequency), load (flow rate) and pressure loss across the monolith. The aims of this study are to provide insight into the development of the pulsating flow field within the diffuser under isothermal conditions and to assess the steady-state computational fluid dynamics (CFD) predictions of flow maldistribution at high Reynolds numbers. Flow measurements were made across an automotive catalyst monolith situated downstream of a planar wide-angled diffuser in the presence of pulsating flow. Cycle-resolved Particle Image Velocimetry (PIV) measurements were made in the diffuser and hot wire anemometry (HWA) downstream of the monoliths. The ratio of pulse period to residence time within the diffuser (J factor) characterises the flow distribution. During acceleration the flow remained attached to the diffuser walls for some distance before separating near the diffuser inlet later in the cycle. Two cases with J ~ 3.5 resulted in very similar flow fields with the flow able to reattach downstream of the separation bubbles. With J = 6.8 separation occurred earlier with the flow field resembling, at the time of deceleration, the steady flow field. Increasing J from 3.5 to 6.8 resulted in greater flow maldistribution within the monoliths; steady flow producing the highest maldistribution in all cases for the same Re. The oblique entry pressure loss of monoliths were measured using a one-dimensional steady flow rig over a range of approach Reynolds number (200 < Rea < 4090) and angles of incidence (0o < α < 70o). Losses increased with α and Re at low mass flow rates but were independent of Re at high flow rates being 20% higher than the transverse dynamic pressure. The flow distribution across axisymmetric ceramic 400 cpsi and perforated 600 cpsi monoliths were modelled using CFD and the porous medium approach. This requires knowledge of the axial and transverse monolith resistances; the latter being only applicable to the radially open structure. The axial resistances were measured by presenting uniform flow to the front face of the monolith. The transverse resistances were deduced by best matching CFD predictions to measurements of the radial flow profiles obtained downstream of the monolith when presented with non-uniform flow at its front face. CFD predictions of the flow maldistibution were performed by adding the oblique entry pressure loss to the axial resistance to simulate the monolith losses. The critical angle approach was used to improve the predictions, i.e. the oblique entry loss was limited such that the losses were assumed constant above a fixed critical angle, αc. The result showed that the perforated 600 cpsi monolith requires the entrance effect to be restricted above αc = 81o, while the losses were assumed constant above αc = 85o for the ceramic 400 cpsi monolith. This might be due to the separation bubble at the monolith entrance being restricted by the smaller hydraulic diameter of the perforated monolith thus limiting the oblique entry loss at the lower incidence angle.

The Eastern Cape Region, once had sufficient job seekers with automotive component manufacturing skills and experience. Indications are that this pool has been desiccated. The draining of skills out of the area is starting to affect growth potential and competitiveness in the industry in the area. In 1998, the Skills Development Act was passed to implement the National Skills Development Plan, and to encourage employers to train personnel. The strategy promotes a three faceted approach to encourage the development of skills; Workplace Skills Development Plans, Learnerships and Sector Specific Initiatives. This study will focus on the implementation of learnerships in the Catalytic Converter Canning Industry. The aim of this research is to verify the skills shortages; identify which skills are required by the Catalytic Converter Canning Industry in the Eastern Cape and propose a strategy of addressing these needs by means of learnerships. By studying the Legislation supporting the National Skills Development Plan, conducting a literature study, and interviewing knowledgeable people in the industry, the skills requirements of the industry were identified. Thereafter, a questionnaire was drawn up and completed together with representatives from Eberspächer South Africa, Faurecia Exhaust Systems South Africa, Precision Exhaust Systems and Tenneco Automotive South Africa, the active manufacturers of catalytic converters, for OEM’s worldwide, who are based in the Eastern Cape Region. The empirical study confirmed the findings of the research and skills deficiencies were identified. In conclusion, a strategy is proposed whereby the Catalytic Converter Canning Industry could address the skills shortage by the implementation and development of learnerships.

Thesis (MBA (Business Management))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: South Africa has historically benefited from its mineral wealth, building one of the leading mining industries in the world. South Africa holds the worlds largest known PGM (or precious group metals) resource base (in a geological formation known as the Bushveld Igneous Complex), with an estimated life of 230 years (at current mining rates). This precious commodity is a precious source of both the direct as well as indirect contributions into the South African economy, as well as a leading source of employment in the South African mining industry. PGMs are predominantly used in auto catalysts, with an estimated 60% of global demand emanating from this application, where the commodity is used in breaking down noxious compounds in exhaust emissions. Given the strong correlation between automotive production and platinum sales, it seems viable to assume that platinum sales will continue to grow as more stringent legislation is introduced globally to reduce automotive emissions. This can currently only be down by increasing the platinum loads in auto catalysts, as alternative technologies are not widely accepted or developed at present. Given the influence (and positive correlation between) demand and prices, it appears that PGM prices will be driven upwards as demand continues to grow. This effect may be exacerbated by the fact that the expansion in demand is likely to outgrow the expansion in supply, given that few significant platinum operations have been started in recent years. Following the strong rally of commodity prices, specifically PGM prices in mid-2008 that saw platinum at a record high of USD2276/oz, major automotive producers have indicated that they are investigating alternatives to the application of precious metals in catalytic converters, in an attempt to curtail production costs. Although no viable substitute could be developed as yet, various alternatives (such as silver alloys) have been mentioned throughout the media. The purpose of this paper is to investigate the impact of such a substitution event on South African PGM producers and its resultant effect on the South African economy. The study will attempt to determine, at a high level, the direct impact of the event, as well as the indirect consequences of the proposed substitution event.
AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse ekonomie is histories op die mynbou- en landbousektore gebaseer, wat gelei het tot Suid-Afrika se wêreldklas mynbou industrie. Suid-Afrika beskik oor die wêreld se grootste PGM reserwes (in 'n geologiese formasie, ook bekend as die Bosveld Stollings Kompleks), met ‘n geskatte lewe van 230 jaar (teen huidige mynbou tempo's). Die komoditeite is verantwoordelik vir ‘n aansienlike hoeveelheid direkte en indirekte waardetoevoeging tot die Suid-Afrikaanse ekonomie. PGM’s word hoofsaaklik in katalisators in voertuie gebruik, met nagenoeg 60% van wêreldwye vraag wat uit die toepassing voortspring. PGMs word gebruik om uitlaatgasse op te breek en te verwerk in motorvoertuie. Gegewe die hoë mate van korrelasie tussen PGM en voertuigverkope, blyk dit voor die handliggend dat platinumverkope sal aanhou styg soos wat omgewingswetgeging in bepaling van toelaatbare uitlaatgasse in motorvoertuie strenger word. Die vermindering van uitlaatgasse is huidiglik slegs moontlik deur die verhoging van PGM ladings in katalisators, gegewe dat alternatiewe tegnologieë nog nie ver genoeg gevorder is om geimplementeer te word nie. Die hoë mate van korrelasie tussen PGM pryse en PGM vraag dui dat dit hoogs waarskynlik is dat die prys van edelmetaal sal aanhou styg soos wat vraag toeneem. Die verskynsel sal moontlik verder bou op die verwagting dat vraag vir die metaalaanbod oor die langtermyn sal oorskadu, siende dat geen wesenlike nuwe PGM myne onlangs oopgemaak is nie. Voertuigvervaardigers het aangedui dat hul alternatiewe tegnologieë opndersoek, nadat die platinumprys tot 'n rekord hoogtepunt van USD2276/ oz gestyg het in mid 2008. Die uitspraak is gelewer met die oog op koste kontrole in die vervaardiging van motorvoertuie. Alhoewel geen werkbare alternatief vir die edelmetale huidiglik bestaan nie, is verskeie moontlike materiale reeds in die media bespreek (byvoorbeeld verskeie silwer allooie). Die doel van die dokument is om die potensiële impak van so ‘n vervangings senario op die Suid-Afrikaanse ekonomie te ondersoek. Die studie sal poog om op ‘n hoë vlak die direkte en indirekte gevolge van die gebeurtenis te bepaal.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
FAPESP:00/02118-9

Commercial decisions are been made with respect to the competitive advantage of manufacturing catalytic converters in South Africa. This thesis identifies those factors relating to the sourcing of stainless steel and the impact it has of securing future business in a competitive environment. The catalytic converter industry requires the support of a stainless steel plant that provides high quality products at a competitive price, while keeping abreast with international developments.

Hydrogen sulphide emission by catalytic converter-fitted automobiles is a problem, because the gas has an extremely unpleasant odour, which is detectable by the human nose at concentrations below 1 ppm. The problematic hydrogen sulphide emissions are produced by the "storage release" mechanism, in which the catalyst absorbs sulphur dioxide during net oxidising conditions and releases it very rapidly as hydrogen sulphide when the stoichiometry of the exhaust gas changes to net reducing. After a prolonged period of oxidative storage the peak emission of hydrogen sulphide by "storage release" can greatly exceed that possible by direct conversion of sulphur dioxide during net reduction conditions (termed the "steady state" mode of emission). Components of the formulation of typical TWCs (Three Way Converters), as well as iron, nickel and barium doped analogues, were prepared. Storage-release sequences were then simulated on the samples at a number of different temperatures on purpose-built 'catalyst test apparatus'. Temperature programmed reductions were performed in the same apparatus by dosing the samples with sulphur dioxide in oxidising conditions at 500°C (the temperature at which the emission of hydrogen sulphide is conventionally said to become a problem). The TPR spectra exhibited sulphur dioxide and hydrogen sulphide peaks, the hydrogen sulphide peak always occurring at the higher temperature. The addition of platinum to various oxides and oxide mixtures was shown to increase the proportion of stored sulphur emitted as hydrogen sulphide and to lower the temperature at which storage-release effects occur. These effects were evident in the lowered temperatures at which the TPR spectra peak maxima occurred and the increased size of hydrogen sulphide peaks relative to hose of sulphur dioxide.

Thesis (M.S.)--University of Cincinnati, 2007.
Title from electronic thesis title page (viewed July 12, 2007). Includes abstract. Keywords: Solvent extraction; Soils; Pentachlorophenol; Automobile catalytic converters; Metal chelating agents Includes bibliographical references.

Conception d'un pot catalytique et etude de l'efficacite de la catalyse. Mise au point d'un support metallique. Preparation du support par passivation de l'alliage fer-chrome-aluminium. Stabilisation de l'alumine par ajout de terres rares. Utilisation de platine et de palladium comme materiaux catalytiques

Dans les véhicules hybrides électrique-essence, les stratégies de gestion de l’énergie déterminent la répartition des flux d'énergies des moteurs thermique et électrique avec pour objectif classique la réduction de la consommation. Par ailleurs, pour respecter les seuils réglementaires d’émissions polluantes, les motorisations essence sont équipées d’un catalyseur 3-voies chauffé par les gaz d’échappement. Une fois amorcé, ce catalyseur convertit presque entièrement les émissions polluantes du moteur. C’est donc au démarrage que la plupart de la pollution est émise, lorsque le catalyseur est froid et que la pollution du moteur n’est pas convertie. La chauffe du catalyseur est donc l’étape clé de la dépollution. Ce mémoire propose une démarche de prise en compte des émissions polluantes par la gestion d’énergie. Le véhicule hybride est assimilé à un système dynamique à deux états, l’état de charge batterie et la température du catalyseur. Un problème d’optimisation dynamique est défini, qui minimise un critère original pondérant judicieusement la consommation et les émissions polluantes. La théorie de la commande optimale, avec les Principes du Minimum de Pontryaguine et de Bellman, permet de résoudre ce problème d’optimisation. Des stratégies optimales sont déduites et simulées avec un modèle de véhicule intégrant un modèle thermique multi-zones de catalyseur, validé expérimentalement, qui simule précisément la chauffe. Le compromis entre la consommation et la pollution est exploré. Une stratégie de chauffe du catalyseur, plus méthodique, analytique et efficace que les stratégies empiriques actuelles, est alors proposée. Cette stratégie est validée expérimentalement dans un environnement HyHIL (Hybrid Hardware In the loop). Une importante réduction de la pollution est obtenue, confortant l’approche d’optimisation dynamique pour la mise au point des stratégies de gestion d’énergie du véhicule hybride
In hybrid gasoline-electric vehicles, the energy management strategies determine the distribution of engine and motor energy flows with fuel consumption reduction as classical objective. Furthermore, to comply with pollutant emissions standards, SI engines are equipped with 3-Way Catalytic Converters (3WCC) heated by exhaust gases. When 3WCC temperature is over the light-off temperature, engine pollutant emissions are almost totally converted. Most of the pollution is produced at the vehicle start, when the 3WCC is cold and the engine pollution is not converted. The 3WCC heating is thus the key aspect of the pollutant emissions. This dissertation proposes an approach to take into account pollutant emissions in energy management. The hybrid electric vehicle is considered as a dynamic system with two states, the battery state of charge and 3WCC temperature. A dynamic optimization problem is defined, minimizing an original criterion weighting judiciously fuel consumption and pollutant emissions. Optimal control theory, with the Pontryaguine Minimum and Bellman principles, allows solving this optimization problem. Optimal strategies are derived and simulated with a vehicle model including a multi-zones 3WCC thermal model, experimentally validated, which simulates precisely the 3WCC heating. The compromise between fuel consumption and pollutant emissions is explored. Then, an innovative 3WCC heating strategy is proposed and validated experimentally in a HyHIL (Hybrid Hardware In the loop) environment. A significant reduction of the pollutant emissions is obtained, strengthening the dynamic optimal approach to set up the energy management strategies for hybrid vehicles

A novel multi-scale model is developed to describe in detail the reaction and diffusion processes taking place in the catalytic layers of three-way automobile converters. This comprehensive model considers the simultaneous oxidation of carbon monoxide, hydrogen and one hydrocarbon species, as well as the reduction of nitrogen oxide. The resulting problem of coupled and nonlinear ordinary differential equations is solved using an adaptive spline collocation technique. Our computations reveal significant diffusional limitations in the catalytic layers and important interactions among the various gaseous reactants. A systematic study is carried out to determine the relative importance of various operating and system parameters, and several possible ways are suggested to improve the operating efficiency of the catalytic converters.

The recovery of platinum-group metals (PGMs) from secondary sources, such as spent devices like automobile catalytic converters (ACC), has been gaining interest in the last decades due to their scarcity in the earth crust and their high demand. Their extended applications among different industries, together with their difficulty to be replaced by other materials, has created the urge to develop new technologies for PGMs recovery that can help with the supply requirements, while being environmentally friendlier than the existing processes. Hydrometallurgical techniques represent a possible strategy to recover PGMs and avoid the high energy consumption of smelting processes in pyrometallurgical plants. In this study, a hydrometallurgical approach was adopted, starting with a leaching step for the solubilization of the metals into an aqueous phase, employing the use of an oxidizing agent for the formation of metal chlorocomplexes, thus facilitating their dissolution; after this, the recovery of PGMs was intended by using a solvent extraction (SX) step with appropriate extractants, to transfer the selected metals into a more purified aqueous phase, from which the PGMs recovery and transformation into forms with commercial interest would be easier. Two spent ACCs were collected (H98 and I95), and their initial metal compositions were evaluated by an X-ray fluorescence (XRF) analysis. Two different elemental compositions were found, leading to a separate treatment of each sample. In the first stage of the work, the leaching process, the most relevant variables such as temperature (°C), acid concentration (M), L/S ratio (L/kg), time (h), stirring (min-1) and particle size (mm) were evaluated experimentally and through a factorial design methodology (FDM), to establish the individual and joint contributions of the relevant parameters to the leaching efficiency. As a result, the optimised conditions for the leaching of both catalyst samples were T= 60 ºC, [HCl]= 11.6M, L/S= 2L/kg, t= 3h, stirring= 250 min-1, and particle sizes Dp=0.397mm and Dp=0.409mm for H98 and I95, respectively. The FDM treatment showed that time represented the most determinant parameter in terms of leaching efficiency for the H98 sample. For the I95, time, temperature, acid concentration, and the pair time-temperature were the main interactions to be considered, according to the FDM, in order to obtain a higher efficiency of the leaching process. For the second step, the SX, four commercial compounds and/or mixtures (tributyl phosphate (TBP), Cyanex® 471X, trioctylphosphine oxide (TOPO) and Adogen® 464), and one ionic liquid (Cyphos® 101), were employed as extractants, using toluene as diluent. The concentrations of each extractant were calculated according to the concentration of the targeted metals in the solutions. The first part of the SX step was the development of a scheme for each sample using model solutions, prepared with the metals expected to be in higher concentrations in the real leaching solutions obtained. The results achieved with the model solutions showed that the appropriate SX scheme, when using traditional extractants, would involve an approximate 6M HCl concentration for the aqueous phases and the use of TBP to remove Fe(III) in the first extraction, followed by an extraction with Cyanex® 471X to remove Pd(II). In the third extraction, TOPO could be used to remove Pt(IV), and the final extraction could be carried out with Adogen® 464 to remove Rh(III). The above loaded organic phases were subjected to a stripping procedure, to transfer the metals to new aqueous phases and to evaluate the reusability of the organic solutions. The stripping agents chosen were: a 0.1M HCl solution to strip Fe(III) from TBP, a stabilized 1M Na2S2O3 solution to strip Pd(II) from Cyanex® 471X, and a 0.4M malonic acid solution to strip Pt(IV) from TOPO. Due to the low content of Rh(III) in the solutions, the decision of not stripping this metal from Adogen® 464 was taken. Regarding the application of the ionic liquid Cyphos® 101 for the SX of the model solutions, it was found that Pd(II), Pt(IV) and Fe(III) were quantitatively extracted from both 3M and 6M HCl solutions. Two stripping agents were tested, e.g., a 0.1M KSCN to remove Pt(IV), and a 0.1M CH4N2S in 5% v/v HCl to strip Pd(II). Finally, the SX schemes previously developed were tested in the real leaching solutions for each catalyst, and a completely different behavior was found. The extraction and stripping efficiencies were very low compared to the results from the model solutions. This unexpected behavior is attributed to the complexity of the real leaching solutions, to the large number of metals involved that were not considered for the composition of the modelsolutions, and to possible interactions of the extractants with those unanalysed metals
A recuperação de metais do grupo da platina (PGMs) de fontes secundárias, particularmente a partir dos dispositivos usados como conversores catalíticos em automóveis (ACC), tem vindo a ganhar expressão nas últimas décadas, devido à escassez destes metais na crosta terrestre e ao facto de serem muito solicitados. Para além dos ACCs, as aplicações dos PGMs estendem-se a diferentes áreas; por exemplo, os PGMs estão presentes na composição de catalisadores para processos petroquímicos e de refinação de petróleo, na indústria farmacêutica, sendo também frequentes em componentes da indústria eletrónica e em biomedicina, particularmente sob a forma de medicamentos para tratamento de cancro. Atendendo à dificuldade de serem substituídos por outros materiais, a utilização crescente dos PGMs potenciou o desenvolvimento de novas tecnologias para a sua recuperação a partir de materiais em fim de vida, e que, simultaneamente, contribuem para aumentar o seu suprimento global e que são usualmente mais amigáveis sob o ponto de vista ambiental do que a generalidade dos processos existentes. As técnicas hidrometalúrgicas representam uma possível estratégia para recuperar PGMs, pois são em geral mais “amigas do ambiente” e a sua utilização evita o alto consumo de energia dos processos de fundição típicos das instalações pirometalúrgicas. Neste estudo adotou-se uma abordagem hidrometalúrgica. A investigação iniciou-se com uma etapa de lixiviação para a solubilização dos PGMs numa fase aquosa, empregandose um agente oxidante para promover a formação de clorocomplexos metálicos, facilitando a sua dissolução; em sequência, a recuperação de PGMs foi planeada recorrendo à etapa de extração por solventes (SX), com extratantes apropriados, para transferir os metais selecionados para uma fase aquosa mais purificada, a partir da qual a recuperação e transformação dos PGMs em formas com interesse comercial seriam facilitadas. Foram recolhidos dois ACCs usados (H98 e I95), e as suas composições metálicas iniciais foram avaliadas por uma análise de fluorescência de raios-X (XRF). Devido ao facto das duas composições elementares serem significativamente diferentes, procedeuse a tratamentos separados para as duas amostras. Na primeira etapa do trabalho, as variáveis mais relevantes para a eficiência do processo de lixiviação, tais como a temperatura (° C), concentração de ácido (M), relação L / S (L / kg), tempo (h), agitação (min-1) e tamanho de partícula (mm) foram avaliadas experimentalmente e por meio de uma metodologia de planeamento fatorial (FDM), para estabelecer as contribuições individuais e conjuntas dos parâmetros relevantes. Teve-se como objetivo maximizar as concentrações de PGMs em solução mas, simultaneamente, minimizar as concentrações dos metais considerados como principais contaminantes no processo, nomeadamente, alumínio e cério. Como resultado, as condições otimizadas para a lixiviação das amostras de catalisador foram semelhantes para os dois casos, a saber: T= 60 ºC, [HCl]= 11,6M, L / S= 2L / kg, t= 3h, agitação= 250 min-1 e tamanhos de partícula Dp= 0,397 mm e Dp= 0,409 mm para H98 e I95, respetivamente. O tratamento com a metodologia FDM mostrou que o tempo representou ser o parâmetro mais determinante em termos de eficiência de lixiviação para a amostra H98. Para a amostra I95, o tempo, temperatura, concentração de ácido e o par tempo-temperatura foram as principais interações encontradas, que mostraram ser as mais influentes para se obter uma maior eficiência do processo de lixiviação, de acordo com o FDM. Para o segundo passo, a etapa de SX, quatro compostos comerciais e / ou misturas (fosfato de tributilo (TBP), Cyanex® 471X, óxido de trioctilfosfina (TOPO) e Adogen® 464), e um líquido iónico (Cyphos® 101), foram testados como extratantes, utilizando-se tolueno como diluente. As concentrações usadas de cada extratante foram calculadas de acordo com a concentração dos metais alvo a recuperar nas respetivas soluções de lixiviação. A primeira parte desta segunda etapa consistiu no desenvolvimento de um esquema de SX para cada amostra recorrendo a soluções modelo, que foram preparadas com os metais que se espera estarem em concentrações mais altas nas soluções de lixiviação reais obtidas, ou seja, os PGMs e também os principais contaminantes: Al(III), Ce(III) e Fe(III). Os resultados obtidos com as soluções modelo mostraram que o esquema SX mais apropriado, ao usar extratantes tradicionais, envolveria uma concentração aproximada de 6M HCl para as fases aquosas e o uso de TBP para remover Fe(III) na primeira extração, seguindo-se uma extração com Cyanex® 471X para remover o Pd(II). Na terceira extração, o TOPO poderia ser usado para remover Pt(IV), e a extração final poderia ser realizada com Adogen® 464 para remover o Rh(III). As fases orgânicas carregadas acima obtidas foram em seguida submetidas a um processo de reextração, para transferir os metais para novas fases aquosas e para avaliar a capacidade de reutilização das soluções orgânicas. Os agentes de reextração escolhidos foram: uma solução 0,1M de HCl para remover o Fe(III) do TBP, uma solução estabilizada de Na2S2O3 1M para remover o Pd(II) do Cyanex® 471X, e uma solução de ácido malónico 0,4M para remover a Pt(IV) do TOPO. Devido ao baixo conteúdo de Rh(III) nas soluções, foi tomada a decisão de não se testar a reextração deste metal do Adogen® 464. Em relação ao teste do líquido iónico Cyphos® 101 para a SX das soluções modelo, verificou-se que o Pd(II), a Pt(IV) e o Fe(III) foram quantitativamente extraídos das soluções de HCl 3M e 6M. Foram testados dois agentes de reextração, nomeadamente, KSCN 0,1 M para remover a Pt(IV) e CH4N2S 0,1 M em HCl a 5% v/v para retirar o Pd(II). Finalmente, os esquemas SX previamente desenvolvidos foram testados nas soluções de lixiviação reais, em separado para cada catalisador, tendo-se verificado comportamentos completamente diferentes relativamente aos anteriormente conseguidos. Com efeito, as eficiências de extração e de reextração dos PGMs foram muito baixas quando comparadas com os resultados obtidos para as soluções modelo. Estes comportamentos inesperados são atribuídos à complexidade das soluções de lixiviação reais, ao grande número de metais envolvidos que não foram considerados para a composição das soluções modelo (por exemplo, neodímio, lantânio, cálcio, magnésio, zinco, zircónio) e às possíveis interações dos extratantes com esses metais não analisados.
Finally, my deepest gratitude to the European Commission, which through the EMMCChIR study grant helped me to accomplish one of my dreams in life.

碩士
國立虎尾科技大學
機械與機電工程研究所
101
In this study, secondary air was injected into the exhaust of automobile to reduce the time needed for heating up the catalyst. By doing this, the catalyst can reach its working temperature faster, which will be beneficial for the purification of exhaust gas. To carry out the experiment, secondary air was injected at two locations, namely the head exhaust manifold and the head 4-in-2 exhaust manifold of the engine. In addition, one-way valve was installed to create vacuum effect inside the exhaust pipe, resulting from the positive/negative pressure formed when the engine is in operation. The mechanical operation (open/close) of the one-way valve was controlled by the positive/negative pressure to allow fresh air to enter into the exhaust manifold. The entered fresh air was then burned with the exhaust gas before entering the catalytic converter, leaving the unburned residual exhaust gas to go into the catalytic converter. Finally, catalytic reactions conducted inside the catalytic converter transformed pollutants into harmless gases which then left the tail pipe of the exhaust system, achieving the goal of exhaust gas purification. Furthermore, thermal insulating material, such as ceramic fibers, was adopted to study the effect of temperature on the catalytic converter performance. The interaction between secondary air injection, three-element catalytic converter and ceramic thermal insulator was also investigated.

碩士
國立成功大學
環境工程學系
86
A Study on the Effects of Engine Speed and theCatalytic Converter on Automobile VOCs Emission Volatile Organic Compounds (VOCs), such as 1,3-butadiene, benzene, toluene and xylenes, are found in automobile exhaust and other sources. They are known to be neurotoxic, mutagenic or carcinogenic, and thus harzadous to human nervous system and skin.ere used for this study. The engine was fueled separately with 92 and 95 Lead-free gasoline, and was operated at 1000, 1500, 2200, and 3000 rpm, with and without a catalytic converter. Three or more test runs were done under each of the preset conditions and operation parameters. For this study US Method 18 was adopted, with some minor modifications, for sampling and analysis of the exhaust. A fixed portion of the vehicle exhaust was pumped from tThe results show that, when engine speed was raised, VOC concentrations, emission per liter of fuel consumed dropped, while the emission rate increased instead. Under the same operating conditions and with and without a catalytic converter, 95 Lead-free gasoline generates more VOCs than 92 Lead-free. Both concentrations of 1,3-butadiene and benzene in the exhaust were highest in 92 and 95 Lead-free runs at low engine speeds without the catalytic converter. The lowest concentration of these VOCs were found in premium runs at high engine speeds with the catalytic conveter. The concentration of BTEX in 92 and 95 Lead-free are 44.6%~74.2% and 54.9~64.0 respectively.The results of this study imply that, in terms of VOC emission alone, 92 Lead-free gasoline as a fuel is cleaner than 95 Lead-free. Also, citizens living or working in urban areas, where most vehicles are driven at low speed, are exposed to higher VOCs and hence facing higher health risks.