Dissertations / Theses on the topic 'Chemical processing industries'

A unique problem in the continuous processing industries (CPI), arising from integration of statistical process control (SPC) with automatic process control (APC), is choosing the correct variable(s) for process monitoring. It was shown that the manipulated variable displayed superior process monitoring potential for first-order processes with moderate amounts of inertia, subject to an ARMA(1,1) disturbance when the autoregressive parameter, $\phi$, is larger than the moving average parameter, $\theta$. It was also shown for large amounts of process inertia that the reconstructed output (disturbance) was the most effective charting variable ($\phi > \theta$). However, when $\theta$ exceeds $\phi$ the residual chart performed the best. In some very severe cases, process observations are so highly correlated that they display a wandering mean. Such nonstationary disturbances are extremely problematic in the CPI. The n$\sp{\rm th}$-difference chart developed in this work, proved to be efficient at identifying the presence of assignable cause in first-order processes under Minimum Variance feedback control when subjected to IMA(1,1) disturbances displaying moderate degrees of nonstationarity ($\theta >$ 0.7). Furthermore, it was shown that the performance of these charts is significantly affected by the presence of the autoregressive parameter (ie., when $\phi >$ 0.2). A case study involving a C$\sb3$ splitter provided the basis for development of a six-step procedure for the integration of SPC with APC. While carrying out integration on the C$\sb3$ splitter it was determined that the cause of disturbance nonstationarity must be sought out and removed if successful integration is to be achieved. For most nonstationary disturbances the amount of natural drift is often greater than or equal to the size of the step shifts that one is trying to detect. Thus, one is not able to differentiate between the common cause and assignable cause disturbances. (Abstract shortened by UMI.)

In an attempt to provide a better understanding of product costing system design, this study utilises the contingency theory approach to investigate the contingent relationships between several contextual factors and the design of product costing system simultaneously. This study also investigates the contingent relationships between several contextual factors with the importance of cost-plus pricing, and the mediating effect of the importance attached to cost-plus pricing on the relationship between contingent factors and product costing system design. In addition, this study investigates the implications of fit, internal consistency or coalignment between the contextual factors and product costing system design on organisational effectiveness. This study also seeks to develop a wider and more comprehensive view of product costing system design than the approach that has generally been used by previous studies (i. e. classifying costing systems by two discrete alternatives, either traditional or ABC systems). In addition, in today's competitive environment comprehensive product cost systems should provide increased accuracy for managerial decisions concerning products, pricing and discontinuing and/ or reengineering existing products. In markets where there is a generally accepted market price, firms have limited power to make pricing adjustments. Undoubtedly firms have to decide which products to sell and to determine the target product mix. Therefore, undertaking periodic profitability analysis is of vital importance. In the more common situation, where the market price is not given a priori, cost-plus pricing may be used whereby an appropriate percentage mark-up is added to the estimated cost to determine the proposed selling price. Therefore where cost information is used for cost-plus pricing decisions accurate cost information is likely to be crucial. While there is a substantial literature on costing systems, far less is known about the use of cost data in pricing decisions and profitability analysis. A distinguishing feature of the research is that it provides a contribution to the research literature on the understanding of the role that cost information plays in determining the selling prices and profitability analysis. A cross-sectional survey employing a questionnaire method of data collection was adopted. A total of 152 usable responses were received representing a response rate of 17%. For purposes of analysis, the research utilises descriptive statistics and structural equation modeling (SEM) multivariate statistical techniques enabled by EQS 5.7 version software (Bentler, 1995). Thus, this study is one of the first studies in product costing systems and cost-plus contingency literature to utilise SEM for validating the research constructs, controlling measurement error and for testing the structural relationships between the constructs simultaneously. Also, this is the first study to investigate and compare product costing practices in a single industry (i. e. the food industry) with the other UK industries, and therefore, examining and controlling to some extent for industry effects for the observed practices. The results of the descriptive analysis show that direct costing measures are extensively used for costplus pricing and profitability analysis purposes. Other absorption costing measures are also used but to a significantly lesser extent. Despite the popularity of the cost-plus pricing approach, only 50% of the companies report using it in their price setting with emphasis being more given to market factors such as competition and demand. The findings also emphasise that analysing the profitability of products and services at periodic intervals is considered to be a vitally important task. The results of structural equation modelling suggest a strong support for the influence in determining selling prices, importance of cost information, aspects relating to the intensity of competition, and the extent of the use of total quality management have a significant influence on the level of cost system sophistication. This research also provided insightful findings relating to the effectiveness of sophisticated costing systems. The results also indicate that market share, customisation, the influence in determining selling prices, aspects of differentiation strategy, intensity of competition, and the importance of cost information influence the importance of cost-plus pricing. Finally, this study contributes to the literature by utilising the structural equation modelling method, which has several advantages over other multivariate data analysis.

Etude de la reactivite des silicoaluminates avec la chaux en presence de sulfates et de chlorures en vue de leur utilisation comme liant. On synthetise preferentiellement la gehlinite hydratee malgre la presence de portlandite, ce qui accroit la resistance et la stabilite des liants. Deux liants ternaires, a base d'argile activee et de chaux ont pu etre obtenus

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico
Os sucos de frutas sÃo importantes fontes de vitaminas, sais minerais, Ãcidos orgÃnicos e fibras, e incluÃdos na dieta da populaÃÃo podem ajudar a manter a saÃde. Durante as etapas de processamento de sucos, podem ocorrer modificaÃÃes nos componentes dos frutos, afetando suas propriedades sensoriais e nutritivas. Estudos sobre os efeitos do processamento nos constituintes nutricionais dos sucos tropicais sÃo escassos. Geralmente, sÃo avaliadas somente as perdas de vitamina C. Este trabalho objetivou determinar as possÃveis alteraÃÃes quÃmicas e fÃsico-quÃmicas em suco tropical de goiaba durante as etapas de processamento (extraÃÃo, formulaÃÃo / homogeneizaÃÃo e pasteurizaÃÃo) e armazenamento (30 dias). Foram efetuadas determinaÃÃes de sÃlidos solÃveis, pH, acidez, aÃÃcares redutores, aÃÃcares totais, atividade de Ãgua, cor, vitamina C, antocianinas, carotenÃides, compostos fenÃlicos e atividade da pectinametilesterase. Ao final do estudo, constatou-se que somente os parÃmetros de pH, carotenÃides e atividade da pectinametilesterase apresentaram variaÃÃes significativas, durante as etapas de processamento do suco. O suco de goiaba se manteve ao final do processamento com elevados teores de vitamina C, compostos fenÃlicos, antocianinas totais, alÃm do aumento da quantidade de carotenÃides totais. No suco de goiaba armazenado por 30 dias observou-se que os parÃmetros analisados nÃo apresentaram diferenÃa significativa entre o tempo zero e o trinta dias. Concluindo que as caracterÃsticas quÃmicas e fÃsico-quÃmicas sÃo pouco afetadas pelo processamento e armazenamento (30 dias), pode-se considerar, portanto o processo de enchimento à quente (hot fill), as embalagens de vidro utilizadas e os conservantes adicionados como sendo bons fatores de preservaÃÃo para o produto em estudo.
Fruit juices are important vitamin sources, mineral salts, organic acids and fibers, and including in the diet of the population, they can help to keep people healthy. During the stages of juice processing, some modifications in the fruit compounds can happen, affecting its sensorial and nutritional properties. Researches on the effects of processing on the nutritional compound tropical juice are scarce. Usually, only vitamin C losses are evaluated. This study determined the possible chemical and physical-chemical changes during the stages of guava tropical juice processing (extration, formulation / homogenization and pausterization) and storage (30 days). Soluble solids, pH, acidity, reducing sugars, total sugars, water activity, colour, vitamin C, anthocyanins, carotenoids, phenolic compounds and pectinametilesterase activity were analysed. We saw that only pH, carotenoids and pectinametilesterase activity parameters showed significant variations during the stages of juice processing. At the end of the processing, vitamin C, phenolic compounds and total anthocyanins contents were high, and it was an increase of total carotenoid amount in the guava juice. For the guava juice stored during 30 days it was observed no significant difference between the times zero and thirty days, for the analysed parameters. We conclude that since the chemical and physicochemical characteristics were affected just a little by processing and stored during 30 days, the hot fill processing, the glass packings used and added conservant were good factors of product preservation in this study.

Phenol and cresols represent a good example of primary chemical building blocks of which 2.8 million tons are currently produced in Europe each year. Currently, these primary phenolic building blocks are produced by refining processes from fossil hydrocarbons: 5% of the world-wide production comes from coal (which contains 0.2% of phenols) through the distillation of the tar residue after the production of coke, while 95% of current world production of phenol is produced by the distillation and cracking of crude oil. In nature phenolic compounds are present in terrestrial higher plants and ferns in several different chemical structures while they are essentially absent in lower organisms and in animals. Biomass (which contain 3-8% of phenols) represents a substantial source of secondary chemical building blocks presently underexploited. These phenolic derivatives are currently used in tens thousand of tons to produce high cost products such as food additives and flavours (i.e. vanillin), fine chemicals (i.e. non-steroidal anti-inflammatory drugs such as ibuprofen or flurbiprofen) and polymers (i.e. poly p-vinylphenol, a photosensitive polymer for electronic and optoelectronic applications). European agrifood waste represents a low cost abundant raw material (250 millions tons per year) which does not subtract land use and processing resources from necessary sustainable food production. The class of phenolic compounds is essentially constituted by simple phenols, phenolic acids, hydroxycinnamic acid derivatives, flavonoids and lignans. As in the case of coke production, the removal of the phenolic contents from biomass upgrades also the residual biomass. Focusing on the phenolic component of agrifood wastes, huge processing and marketing opportunities open since phenols are used as chemical intermediates for a large number of applications, ranging from pharmaceuticals, agricultural chemicals, food ingredients etc. Following this approach we developed a biorefining process to recover the phenolic fraction of wheat bran based on enzymatic commercial biocatalysts in completely water based process, and polymeric resins with the aim of substituting secondary chemical building blocks with the same compounds naturally present in biomass. We characterized several industrial enzymatic product for their ability to hydrolize the different molecular features that are present in wheat bran cell walls structures, focusing on the hydrolysis of polysaccharidic chains and phenolics cross links. This industrial biocatalysts were tested on wheat bran and the optimized process allowed to liquefy up to the 60 % of the treated matter. The enzymatic treatment was also able to solubilise up to the 30 % of the alkali extractable ferulic acid. An extraction process of the phenolic fraction of the hydrolyzed wheat bran based on an adsorbtion/desorption process on styrene-polyvinyl benzene weak cation-exchange resin Amberlite IRA 95 was developed. The efficiency of the resin was tested on different model system containing ferulic acid and the adsorption and desorption working parameters optimized for the crude enzymatic hydrolyzed wheat bran. The extraction process developed had an overall yield of the 82% and allowed to obtain concentrated extracts containing up to 3000 ppm of ferulic acid. The crude enzymatic hydrolyzed wheat bran and the concentrated extract were finally used as substrate in a bioconversion process of ferulic acid into vanillin through resting cells fermentation. The bioconversion process had a yields in vanillin of 60-70% within 5-6 hours of fermentation. Our findings are the first step on the way to demonstrating the economical feasibility for the recovery of biophenols from agrifood wastes through a whole crop approach in a sustainable biorefining process.

Doctor of Philosophy
Biochemistry and Molecular Biophysics Interdepartmental Program
John M. Tomich
David L. Wetzel
The technique of near infrared chemical imaging has been widely used for many industrial applications. It offers selectivity and/or sensitivity for numerous organic functional groups. The advantage of the near infrared spectroscopic region is the linear relationship of absorbance and concentration that enables quantitation. This universally employed technique has been a boon for research studies in the industrial process of wheat milling for the production of flour. The milling process has numerous sequential grinding and sieving steps that enable selective physical segregation of a starch rich endosperm product from wheat. Thousands of spectra of purified endosperm and non-endosperm standards are collected to develop a spectral library. Quantitation of the purity of individual processing streams is accomplished by applying a partial least squares calibration that is based upon the spectral library. The quantitative chemical imaging technique is useful for determination of endosperm purity profiles for mill flour streams. These plots reveal purity changes as less pure streams are added to produce a flour blend. The chemical structural basis furthermore allows comparison of purity even with changes in the wheat blend being milled with representative standardization. Furthermore, whereas a certain section of sieves is responsible, for designating the material defined as flour, application of the spectroscopic method is obvious. Select examples of key processing streams were studied to show the possibility of sieve-by-sieve analysis of the physical separation to provide mill optimization. These novel methods of analysis would not be possible without the sensitive and selective method of quantitative chemical imaging. Application of this technique to a few select unit processes is projected to reasonably affect a 1% increase in the yield of high quality flour. This amounts to a significant financial gain against low profit margins.

The sub-micron surface region of poly(ethylene terephthalate) (PET) films and bottles has been investigated. Uniaxially drawn and annealed PET films were characterised by bulk and grazing incidence X-ray diffraction (GIXD). Surface-specific diffraction patterns collected below the critical angle (ɑc) for total external reflection reveal a radial shift in diffraction peaks, whereas bulk signals collected above this critical angle occur at the predicted locations. It is calculated that this shift can be described by a ~5 % reduction of the a, b and c unit cell imrameters for PET crystals within the sub-micron surface region. This shift is less apparant in the un-oriented specimens. The crystallite orientation is consistently higher within the surface region of the drawn PET films than the bulk. There is a good agreement between the X-ray diffraction and FTIR orientation measurement over the range of films analysed. Polarised FTIR-ATR spectroscopy was used to map the molecular orientation along the inner and outer surfaces of stretch-blown PET bottles. This work reveals complex orientation trends. For 2-litre bottles, the inner surface shows consistently higher orientation levels than the outer surface. There are also two orientation switches at the shoulder and base regions on the outer surface, but only one switch on the inner wall. In all cases, the maximum orientation occurs on the inner surface at 4-6 cm from the base. This analysis was repeated for various bottles, including examples produced from various polyester co-polymers and a series of bottles stretch-blown after different preform heating times. Heating for 5 seconds longer than the recommended time prior to the stretch seriously reduces the orientation in the finished bottle. Lowering the polymer molecular weight has a similar effect. The use of the popular 1340 cm"' PET IR band for crystallinity evaluation was questioned. It is concluded that the use of this band for crystallinity calculation is erroneous if the specimen possesses molecular orientation. It is shown that the 1340 cm"' band height reveals the orientation trends in highly drawn specimens of low crystallinity. Simple measurements reveal that the 1340 cm ' transition moment for this band lies approximately in the chain direction.

On etudie la synthese de poudres fines de ceo::(2), nd::(2)o::(3), gd::(2)o::(3) et y::(2)o::(3) par voie hydroxyde et par voie sol-gel, ainsi que leur frittage. Toutes les etapes de la constitution d'une ceramique sont abordees

The production of gelatine at Gelita N.Z. Ltd. is a time consuming process. The time limiting step in the process is the pre-treatment of the collagen tissue of the raw material in a lime/sodium sulfide solution. The liming solution breaks down the collagen in the tissue to gelatine. This is a necessary step prior to the extraction of gelatine from the hide pieces. The current liming process takes nearly 50 days to complete. Methods were investigated to increase the rate of penetration of the chemicals into the bovine hide raw material. An increase in the penetration of the liming solutions would lead to shorter processing times for this step in the process. The methods that were investigated were temperature controlled mixing, fluidization of the hide pieces and the use of ultrasound. Of all the methods tested, the fluidization of the hide pieces gave the best results. The pretreatment time of the hide pieces was reduced 9 days with this technique. Methods were also investigated to monitor the levels of conditioning in the raw material An accurate technique to measure hide conditioning was important to pilot plant trials. This helped determine how well any of the trail methods increased the penetration of chemicals into the hide pieces. The use of an ultraviolet dye proved an effective method of measuring conditioning for all the pilot plant trials. The level of chemical penetration was monitored by assessing the penetration of the UV dye. The penetration of the UV dye could be quantified by using imaging software. A possible method of monitoring conditioning in full-scale production was tested. It was determined that the glycosaminoglycans and soluble collagen released into the liming solution could be accurately measured, and related to the overall conditioning of the raw material.

Made available in DSpace on 2014-10-09T12:47:30Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T14:10:22Z (GMT). No. of bitstreams: 1 08988.pdf: 8668818 bytes, checksum: e0f5fe180edb5cadb275182177aa753d (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:52:22Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T14:00:47Z (GMT). No. of bitstreams: 0
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Les 3 methodes de synthese exposees permettent d'abaisser les temperatures de formation des materiaux et d'ameliorer leurs qualites microstructurales. Pour les titanates de mg, l'augmentation de la reactivite des poudres a basse temperature a permis de mettre en evidence la formation intermediaire de phases metastables. On a etabli une correlation etroite entre la granularite des poudres et leur bonne densification lors du frittage. Pour le supraconducteur yba::(2)cu::(3)o::(x), la synthese par voie carboxylique permet d'abaisser la temperature de reaction et de conduire a des poudres peu agglomerees, a morphologie controlee et a granulometrie plus faible. On a etudie l'influence de divers parametres sur le frittage et les proprietes physiques de la ceramique

La dispersion d'inclusions de zro::(2) dans une matrice d'al::(2)o::(3) permet d'ameliorer certaines proprietes mecaniques de la ceramique. Des materiaux a base de al::(2)o::(3)-zro::(2)-ceo::(2) ont ete prepares par fusion ou frittage. La fusion en atmosphere reductrice conduit a la disparition d'une partie de al::(2)o::(3) et zro::(2) sous forme d'aluminate et de zirconate de ce, ce qui degrade les proprietes mecaniques. Le frittage a ete realise sur des poudres obtenues par coprecipitation ou par procede sol-gel. La coprecipitation par nh::(4)oh a conduit a des melanges homogenes et densifies a plus de 94% a une temperature de frittage (1250**(o)c) relativement faible. La preparation par voie sol-gel a permis de controler dans certains cas la morphologie et la taille des particules. Les ceramiques elaborees par ce procedelta e ont presente une mauvaise frittabilite meme aux alentours de 1400**(o)c

Batio::(3) est le principal oxyde utilise pour les condensateurs ceramiques multicouches en raison de la valeur elevee de sa constante dielectrique. On expose trois methodes de preparation d'un precurseur: precipitation d'un sel double de titane et de baryum; cohydrolyse d'une solution d'alcoxyde de baryum et de titane (procede sol-gel); polycondensation d'un alcoxyde de titane et d'un carboxylate de baryum (procede carboxy-alcoxy). On etudie les transformations precurseur-cristal, ainsi que les caracteristiques structurales et dielectriques des ceramiques elaborees a partir des poudres de batio::(3) ainsi synthetisees

O tratamento de efluentes industriais é uma prática que vem se disseminando em ritmo acelerado, porque além de contribuir para reforçar a imagem pública, através do combate à poluição, ela traz vantagens econômicas para as empresas que podem reutilizar a água tratada do efluente em seus próprios processos. A técnica de tratamento estudada no presente trabalho é a que utiliza a oxidação/redução química destacando-se a utilização da radiação ionizante por meio de feixes de elétrons. Esta técnica utiliza um processo oxidativo avançado, gerando radicais altamente reativos que provocam a oxidação, redução, dissociação e degradação em compostos orgânicos e exercendo efeito letal nos microorganismos, protozoários e parasitas em geral. Neste trabalho desenvolveu-se um projeto conceituai e básico de uma unidade móvel de tratamento de efluentes utilizando radiação ionizante, fazendo com que a unidade se desloque até o ponto de tratamento, facilitando assim a logística. Em seguida, elaborou-se um estudo de viabilidade técnica e econômica permitindo dados consistentes sobre a capacidade e custo de processamento de efluentes e valores consolidados dos investimentos necessários para serem apresentados a órgãos financiadores para a construção de uma unidade móvel. Os resultados dos estudos demonstram que é viável tecnicamente a construção de uma unidade móvel, pois atende a legislação pertinente do Brasil, nos aspectos de Radioproteção e limite de transporte de carga. O custo unitário do processamento mostrou-se superior ao de uma unidade fixa em razão da diminuição da eficiência da interação da radiação incidente no efluente processado, devido à redução de energia do acelerador de elétrons e da disponibilidade de operação da unidade.
The treatment of industrial effluents is a practice that is disseminating in accelerated rhythm, of contributing to reinforce the public image, through the combat of the pollution, it brings economical advantages allowing the companies the reuse of the treated water in their own processes. The liquid effluent treatment technique studied in the present work is the one that uses the chemical oxidation/reduction standing out the use of the electron beam (e.b.) radiation. This technique uses an advanced oxidation process, generating radicals highly reagents that provoke the oxidation, reduction, dissociation and degradation in composed organic and exercising lethal effect in general in the microorganisms and parasites. In this work a conceptual and basic project of a movable unit of effluents treatment using electron beam radiation process was developed, in order that the unit moves until the treatment point, where the effluent is produced, facilitating the logistics. A technical and economical feasibility study was also elaborated allowing data on the capacity and cost of effluents processing to consolidate the values of the necessary investments to be presented to foundations organs for the construction of a movable unit. The results of the studies demonstrated that it is technically viable attending the pertinent legislation of Brazil, in the aspects of Radiation Protection and transport limit capacity. The unitary cost of the e.b. radiation processing in the movable unit was shown more expensive than in the fixed unit, the reason is the decrease of the efficiency of the interaction of the incident electrons in the effluent, due to the reduction of electron energy operation time of the unit.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-11-11T09:14:09Z No. of bitstreams: 0
Made available in DSpace on 2016-11-11T09:14:09Z (GMT). No. of bitstreams: 0
A quitina é o principal produto obtido do processamento das cascas de crustáceos. Esse biopolímero e o seu derivado, quitosana, têm despertado grande interesse comercial em virtude das possibilidades de aplicações que possuem. O gerenciamento desses resíduos e dos subprodutos gerados nas etapas no processo de obtenção pode ser considerado um modelo de biorrefinaria. A implementação de plantas para extração de quitina e quitosana é um desafio, uma vez que a demanda produtiva deve ser atendida sem causar danos ao meio ambiente. Uma grande variedade de quitosanas com diferentes propriedades físicoquímicas podem ser obtidas variando-se as condições de reação. Essas propriedades dependem da origem da matéria-prima, do seu grau médio de desacetilação, distribuição média dos grupos acetil ao longo da cadeia principal e da sua massa molecular média. Os fornecedores de quitosana comercial geralmente não mencionam a procedência da matéria-prima e pouca ou nenhuma informação é fornecida acerca do seu processamento. Sendo assim, as características e a reatividade do produto final podem variar gerando resultados não reprodutíveis. No presente estudo, foi utilizada a biomassa oriunda de rejeitos da indústria pesqueira de camarão da região de Cananéia SP. As amostras de - quitina foram obtidas por dois procedimentos diferentes: no primeiro, P1, as cascas de camarão após passar pelo pré-tratamento (lavagem, secagem e moagem) foram desproteinizadas para retirada das proteínas em hidróxido de sódio (NaOH) diluído nas concentrações 2%, 5% e 10% e desmineralizadas em ácido clorídrico (HCl) a 20% (v/v) para retirada dos carbonatos; no segundo procedimento, P2, essas etapas foram invertidas. A biomassa resultante foi desacetilada com hidróxido de sódio concentrado a 30%, 40% e 50% em tempos que variaram de 2 a 6 horas. As principais propriedades físico-químicas das amostras de quitosanas obtidas foram determinadas utilizando a espectroscopia na região do infravermelho com transformada de Fourier (FT-IR) para a determinação do grau médio de acetilação, GA, e a técnica de titulação ácido-base mensurada por condutimetria foi utilizada para comparar os resultados; a viscosimetria capilar para a determinação da massa molar média viscosimétrica, Mv , e a difração de raios X (DRX) para avaliar o grau médio de cristalinidade, X. Além disso, foram empregadas as técnicas de microscopia eletrônica de varredura (MEV) para análises morfológicas dos materiais obtidos e a espectrometria de fluorescência de raios X por dispersão de comprimento de onda (WDXRF) para análise química das quitosanas. O GA e o X das amostras diminuíram à medida em que o tratamento se tornou mais vigoroso, enquanto a Mv aumentou. O procedimento 2 foi o mais viável por eliminar a etapa de despigmentação, pois originou amostras com tonalidade mais clara e fáceis de pulverizar.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

On etudie le procede sol-gel applique au niobium v sous divers aspects. On ameliore les synthese et proprietes physiques des gels. On etudie les gels et oxydes amorphes obtenus par analyse chimique et thermique, diffraction rx, spectrocopies ir, raman et exafs. On etudie les proprietes et applications potentielles: fabrication de ceramiques linbo::(3) et pb(nb2/3 mg1/3)o::(3), avec abaissement de la temperature de frittage et obtention de grains homogenes monodisperses, mesure de la conductivite ionique dans les xerogels hydrates, proprietes optiques(photochromie)

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-11-11T09:28:13Z No. of bitstreams: 0
Made available in DSpace on 2016-11-11T09:28:13Z (GMT). No. of bitstreams: 0
O monocloroacetato de sódio (MCAS) e o dicloroacetato de sódio (DCAS) são compostos tóxicos e irritantes ao ser humano e nocivos ao meio ambiente, sendo impurezas indesejáveis na cocoamido propil betaína (CAPB), que é um surfactante anfótero utilizado em produtos de consumo dos segmentos cosmético e domiciliar. Diante dos requisitos de concentração em nível de mg/kg exigidos pelos órgãos reguladores de saúde do governo, tornou-se mandatório o emprego de metodologia com limite de quantificação, precisão e exatidão adequados aos rígidos controles de processo pelos fabricantes da CAPB, bem como, dispor de técnicas convencionais com poder de resolução e proficiência pelo controle de qualidade e neste contexto inseriu-se a cromatografia a gás. Neste estudo foram estabelecidos os procedimentos analíticos que definiram as melhores condições para identificar e quantificar as impurezas MCAS e DCAS na matriz CAPB por meio da cromatografia a gás. A preparação das amostras consistiu da derivação das impurezas MCAS e DCAS a ésteres etílicos e a extração líquido-líquido em hexano para separar dos demais constituintes da matriz. Os modos de detecção acoplados à cromatografia a gás foram a ionização pela chama (GC/FID), a captura de elétrons (GC/ECD) e a espectrometria de massas (GC/MS). A validação comprovou que as metodologias são lineares entre 4 e 50 mg/kg com recuperação de 70 a 120%, apresentam limites de quantificação inferiores a 10 mg/kg e produziram médias e incertezas similares na amostra examinada, constituindo-se alternativas para a determinação de cloroacetatos em betaínas.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

La motivation de cette etude est d'expliquer l'apparition des macrovides aux tous premiers instants de la formation de la membrane. Il s'agit des lors de relier quantitativement les differents parametres d'elaboration des membranes a l'apparition des doigts de gant et a leur repartition sous la surface. La regularite de l'espacement des macropores sous la surface suggere, au moment de leur initiation, la presence d'un phenomene d'instabilite. Une analogie avec l'instabilite gravitationnelle de rayleigh-taylor a permis recemment l'avenement d'un modele quantitatif (cohen-addad, 1996). L'objet de cette recherche est de valider experimentalement ce modele. De nombreuses techniques ont ete mises en oeuvre pour caracteriser le milieu polymere, avant et apres la formation de la membrane. La rmn a ete utilisee pour determiner l'etat thermodynamique de la solution polymere par un acces quantitatif a la dynamique des milieux, mais aussi pour etudier l'evolution du coefficient de diffusion des molecules de solvant dans la solution polymere et dans le bain de coagulation. En outre, la calorimetrie a permis de quantifier la chaleur de formation de melanges polymere / solvant ou encore de melanges solvant / non-solvant et d'evaluer le gradient de potentiel chimique < du solvant existant entre la solution polymere et le bain de coagulation. La video-microscopie a donne acces aux parametres statistiques de la structure de la membrane, comme la distance moyenne entre macropores. La dsc, la rheologie et la tensiometrie ont egalement ete employees, fournissant des donnees essentielles a la comprehension des systemes etudies. Le modele predictif propose par cohen-addad (cohen-addad, 1997) est utilise pour representer l'evolution de l'espacement moyen des macrovides en fonction de la composition de la solution et du bain de coagulation utilises pour l'elaboration de la membrane. Ce modele, elabore a partir d'une analogie avec le modele d'instabilite gravitationnelle de rayleigh-taylor, est base sur une analyse du comportement diffusionnel du solvant vers le non-solvant. On obtient une superposition des points experimentaux avec une variation lineaire de #* en fonction de ds#-#1, dependant du systeme polymere / solvant / non-solvant etudie. Ce comportement lineaire a ete verifie sur six systemes appartenant a deux familles de polymeres, le polyacrylonitrile et le polyetherimide. Le modele d'instabilite diffusionnelle, dont la force motrice est <, autorise l'utilisation de parametres d'acces simples : l'evaluation du gradient de potentiel chimique < du solvant entre la solution et le bain par des mesures de calorimetrie a dilution a montre que l'approche purement entropique du modele est une approximation raisonnable.

Scale formation in pipe work and process equipment is inherent to the operation of many chemical processing industries. It results in reduced equipment availability; lost

production and is costly to remove. In the Bayer process, where alumina is chemically extracted from bauxite ore, the specific process step used to recover the alumina from

supersaturated caustic-aluminate solution, referred to as Precipitation, results in significant scale formation on tank walls, process piping and process equipment in contact with the fluid. Operational experience has shown that the rate at which the scaling occurs is, in part, a function of the fluid velocity.

This thesis presents and discusses the experimental observations of an investigation into scale growth rate and fluid velocity not previously conducted at the Queensland Alumina Limited (QAL) process plant. The experimental results have identified that gibbsite scale growth is a non-linear function of the flow velocity and viscous sub -layer conditions, and that the rate of deposition, with time, is also exponential.

Agglomerated milk powders are produced to give improved properties such as flowability, dispersibility, reduced dustiness and decreased bulk density. A key function of these powders is to dissolve "instantly" upon addition to water and because of this they are also called "instant milk powders". They are produced by agglomerating the undersized fines that are returned to the top of the spray drier with milk concentrate droplet spray. Interaction occurs in a collision zone, often with multiple sprays and fines return lines. Agglomeration can be a difficult process to control and operators find it hard to fine tune the process to produce specific powder properties. This work aimed to understand the effects of key droplet and fines properties on the extent of agglomeration to allow a mechanistic understanding of the process. Three scales of spray drier were investigated in this study with different rates of evaporation; a small scale drier (0.5 - 7 kg water h-1), a pilot scale drier (80 kg water h-1) and a range of commercial production scale driers (4 - 15 000 kg water h-1). A survey of operators of commercial scale driers showed that control of instant milk powder production to influence bulk density is highly intuitive. Fines recycle rates were expected to be important in control of agglomeration processes and were estimated on a specific plant by using the pressure drop measured in the fines return line. A model based on pressure drop along a pneumatic pipeline under-predicted the experimental values for pressure drop due to solids, which means a calibration curve should be generated for each specific drier. Fines recycle rates were predicted to be significantly higher at 95 to 130 % of production rates compared to those expected by operators of 50%. Experimental measurements agreed with existing models for the effect of temperature on the density and viscosity of milk concentrates. Experimental results showed that the surface tensions of concentrated milks were within the same range as literature values for standard milks below 60°C, but were significantly higher for milk above 60°C. This is thought to be linked to the mechanism of skin formation due to disulphide cross linking at high temperatures and concentrations. Powder properties were also established for selected products produced on the commercial scale driers. These powders were then used in experiments on the two smaller driers. Because collision frequency depends on the velocity and droplet size of sprays; these properties were measured for the small scale drier and estimated, where possible, for the pilot and commercial driers. The small scale agglomerating spray drier was configured to alter droplet and particle properties when interacting a vertical fines particle curtain with a horizontal spray sheet. An extensive design and improvement process was carried out to ensure the system consistently delivered these streams in a controllable manner. The processes of collision and adhesion occur very quickly inside the spray drier. In order to assess the extent of agglomeration that has occurred, the feed streams must be compared to the final product stream. An ideal way to do this is to use an agglomeration index which compares the particle size distributions of the feed (fines recycle and spray streams) and the particle size distribution of the product stream (the agglomerated powder). The index described changes between these steams across the particle size distribution and is called an agglomeration efficiency, ξg. However, it was found that the presence of fines in the product of the one-pass design obscured the agglomerates formed. The agglomeration efficiency, ξg, was modified to become ξh which subtracted the fines stream from the agglomerated product distribution. In this way ξh models industrial operation where the fines are recycled, by effectively just comparing the spray and product streams entering and leaving the process. The small scale drier was used for an experimental study on natural and forced agglomeration, where the drier was operated with spray only, then with spray and fines. For natural agglomeration, SEM images of the product powder indicated that little agglomeration occurred between spray droplets. The product yield was unacceptably low (~ 40%) due to adhesion of spray droplets to the drying chamber wall opposing the horizontal spray. When the fines curtain was introduced in the forced agglomeration experiments, product yield increased above 50% because the fines acted as collectors for the spray droplets. However, the agglomeration performance of the modified spray drier was lower than expected. The equipment design was then optimised by considering three key issues; fines dispersion, droplet dispersion and stickiness, and agglomerate breakdown. Final experiments studied agglomeration at low fines to spray mass flux ratios and showed that increasing the fines size had a positive effect on agglomeration efficiency,ξh. The agglomeration study at pilot scale identified the effect of key variables, total solids, concentrate and fines flow rate, and fines size on the agglomeration efficiency. A dimensionless flux approach was used to explain the experimental results. The fines to spray mass flux ratio and the projected area flux ratio (at constant concentrate flow rate) were found to be the most suitable to represent the physical processes during agglomeration. Experimental results showed that a higher dimensionless flux resulted in more agglomeration and as well as small fines size and atomising low solids concentrate. The critical Stokes number highlighted the importance of particle size and collision velocity on the outcome of the collision as well as the importance of stickiness on adherence following the collision. A statistical analysis established a relational model for predicting the agglomeration efficiency based on fines size, total solids and the fines to spray mass flux ratio. This thesis has gained insight into agglomeration processes during spray drying and knowledge about how to define the extent of agglomeration. Practical findings from this research can have a significant impact on successful spray drying operation for instant powders. There are some practical steps to be taken industrially to promote the control of agglomerating spray driers. The first step is to measure and control the flow of fines recycled to the top of the spray drier. The next step is to validate the findings at industrial scale and link the agglomeration index to the bulk powder properties. However, there are many challenges that remain to be tackled in the area of milk powder agglomeration. Milk powder agglomeration at the top of the spray drier is a complex process involving many different variables. A more detailed study of the micro processes that occur during agglomeration will give increased understanding of the relationships between key operating variables and agglomerate properties.

Currently, when dextranase is used in the sugar factory, modifications are required to normal factory operating conditions in order to achieve cost effective dextran 'removal'. The major change involves the decrease in primary heater temperature from 75°C to about 60°C. A number of processing problems result from this temperature change. Therefore, it was proposed to develop a thermostable dextranase which was active and stable at 75°C. The use of a high temperature dextranase would also overcome the problems associated with operating the primary heater at the lower temperature. Existing culture collections, thermal environments and sites within raw sugar factories were used as the sources of microbial isolates screened for thermostable dextranase producers. Based on the amount of enzyme produced at elevated temperatures, five bacterial strains ( SRI 2125, SRI 2128, AB11A, RT364 and DP17) were selected as the most promising sources of thermostable dextranases.These isolates were grown to pure strain using standard microbial techniques. Thereafter, broth culture of these strains was undertaken to produce sufficient crude extracellular dextranase for liquid assay. However, compared to fungal isolates, the amount of dextranase produced by the bacterial isolates was low. Several assays to measure micro-quantities of dextranase activity were developed or modified to assess the thermal stability of the enzymes. Temperature and pH profiles of the crude extracts were determined using the PAHBAH assay to obtain a rapid and sensitive measure of optimal conditions required for enzymic activity. The subsequent development of the micro-haze test allowed the thermal stability and activity to be reliably assessed under simulated factory conditions. Both new and existing enzymic assays were utilised to determine the activity and thermal stability of the most cost-effective commercial dextranase currently available i.e. the C. gracile dextranase. This enzyme was found to exhibit optimum activity at 55-60°C (pH 5.0) under all assay conditions. However, thermal stability at temperatures above 65°C was very low. A comparative assessment of the commercial potential of new thermostable dextranases was possible using the C. gracile dextranase as the 'bench mark'. In addition, detailed studies on the C. gracile dextranase were performed to determine the physico-chemical characteristics of the enzyme(s) in the commercial preparation. The dextranase was separated into five distinct components by electrophoresis of the native enzyme. However, each of these components were found to possess a similar (if not identical) molecular size. Partial separation of these components was achieved using chromatofocusing. Each fraction obtained exhibited endo-dextranase activity..Crude preparations of the five bacterial dextranases were found to exhibit optimal activity between 63 and 75°C (depending on the assay conditions and the method employed for activity measurement). The specific activities of these crude dextranase preparations were very low (0.021 to 0.68 mole min-¹mg-¹) compared to the crude extracts obtained from fungal sources such as C. gracile. The presence of endo-dextranase activity was confirmed by determining the activity against cane dextran under simulated factory conditions. The dextranase produced by the RT364 isolate was selected for purification investigations as it was the most active in the crude form. Several standard techniques for protein purification were utilised and the purity of the resulting preparations established by electrophoretic analysis. The active dextranase in the fraction of highest purity and activity was shown to represent in excess of 50 per cent of the protein in the preparation. Using this estimate, a final specific activity for the purified thermostable dextranase from RT364 was calculated to be about 20 mo1e min-¹mg-¹. At this level, the specific activity of the RT364 enzyme is approximately 150 times less than that of the commercial C..gracile dextranase measured its optimum at temperature of 55°C. On this basis, the commercial potential of the thermostable dextranase from the RT364 isolate appears to be limited. To date, the specific activities of purified forms of the remaining four thermostable dextranases have not been determined. It is possible that one of these isolates may be the source of a thermo-stable dextranase with greater commercial potential. However, further investigations with these enzymes to establish their commercial viability would require high developmental costs in relation to the very small market (the Australian sugar industry) currently available for these enzymes.