Dissertations / Theses on the topic '66.097.3'
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Векшин, Віталій Олександрович. "Очищення викидних газів абсорбції від оксидів нітрогену у виробництві нітратної кислоти." Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/22711.
Full textThesis for a Candidate of Techical Sciences degree by speciality 05.17.01 – Technology of inorganic substances. – National technical university "Kharkov polytechnical institute", Kharkov, 2016. Thesis is devoted to the development of technology for preparing the catalyst for industrial processes of selective catalytic reduction (SCR) of nitrogen oxides with ammonia. Optimal technological parameters of preparation of carrier based of titanium oxide for following impregnation with catalytically active substance have been experimentally determined. Optimal parameters of application of the active substance – platinum – from solution of hexachloroplatinic acid on the surface of carrier have been found: the number of impregnations is 1, the impregnation time is 5 min, the concentration of the impregnation solution is 10%. The positive influence of modifiers – monobasic organic acids – on the catalyst preparation by impregnation has been proved. Application of formic acid in impregnation as a competing adsorbate and as a reducing agent has been substantiated by means of physico-chemical investigations. Experimental researches of the influence of industrial parameters (temperature, gas hourly space velocity) on the activity of obtained catalysts have been carried out. Correlation between the size of platinum crystallites and the time of catalyst operation has been determined. It obeys the exponential dependence and shows decrease in running time of the catalyst with increase in size of crystallites during sintering. Mathematical model of the SCR process has been developed. Kinetic investigations of the process of NOx reduction on obtained catalysts have been carried out. They allowed to determine the optimal conditions of purification, which are as follows: the maximum degree of reduction can be achieved at T = 473 – 523 K and the bulk gas flow 50 000 – 60 000 m³/h on a catalyst modified with formic acid. The designs of the block catalyst having cellular structure and industrial reactor for it have been suggested. It is shown that the gas flow resistance of the developed catalyst is 12 times lower than that of the ABK-10. Ecological-economic calculations and economic benefit estimation show that decrease of gas flow resistance and 2.5-fold ecological costs reduction will result in savings of 16,038,720 UAH during 8 years, i.e. during full period of catalyst operation.
Векшин, Віталій Олександрович. "Очищення викидних газів абсорбції від оксидів нітрогену у виробництві нітратної кислоти." Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/22710.
Full textThesis for a Candidate of Techical Sciences degree by speciality 05.17.01 – Technology of inorganic substances. – National technical university "Kharkov polytechnical institute", Kharkov, 2016. Thesis is devoted to the development of technology for preparing the catalyst for industrial processes of selective catalytic reduction (SCR) of nitrogen oxides with ammonia. Optimal technological parameters of preparation of carrier based of titanium oxide for following impregnation with catalytically active substance have been experimentally determined. Optimal parameters of application of the active substance – platinum – from solution of hexachloroplatinic acid on the surface of carrier have been found: the number of impregnations is 1, the impregnation time is 5 min, the concentration of the impregnation solution is 10%. The positive influence of modifiers – monobasic organic acids – on the catalyst preparation by impregnation has been proved. Application of formic acid in impregnation as a competing adsorbate and as a reducing agent has been substantiated by means of physico-chemical investigations. Experimental researches of the influence of industrial parameters (temperature, gas hourly space velocity) on the activity of obtained catalysts have been carried out. Correlation between the size of platinum crystallites and the time of catalyst operation has been determined. It obeys the exponential dependence and shows decrease in running time of the catalyst with increase in size of crystallites during sintering. Mathematical model of the SCR process has been developed. Kinetic investigations of the process of NOx reduction on obtained catalysts have been carried out. They allowed to determine the optimal conditions of purification, which are as follows: the maximum degree of reduction can be achieved at T = 473 – 523 K and the bulk gas flow 50 000 – 60 000 m³/h on a catalyst modified with formic acid. The designs of the block catalyst having cellular structure and industrial reactor for it have been suggested. It is shown that the gas flow resistance of the developed catalyst is 12 times lower than that of the ABK-10. Ecological-economic calculations and economic benefit estimation show that decrease of gas flow resistance and 2.5-fold ecological costs reduction will result in savings of 16,038,720 UAH during 8 years, i.e. during full period of catalyst operation.
Ситнік, Наталія Сергіївна. "Удосконалення технології переетерифікування жирів з використанням гліцератів лужних металів." Thesis, Український науково-дослідний інститут олій та жирів НААН, 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/23535.
Full textThesis for a candidate degree of technical sciences by specialty 05.18.06 – fats, essential oils and perfume-cosmetic products technology. – National Technical University "Kharkov Polytechnic Institute" Ministry of Education and Science of Ukraine, Kharkov, 2016. The thesis is dedicated to specific scientific and practical task to develop the scientific foundations of fat interesterification technology using new catalysts that constitute alkali metals glycerates. Triacylglycerol composition of initial and interesterified samples of individual oils was defined. The influence of interesterification with traditional catalyst to the melting point of oils was installed. The choice of test fat for studies of fat interesterification was grounded. The efficiency of potassium glycerate and sodium glycerate as catalysts for interesterification of fats was proved. The character of triacylglycerol composition changes of test fat in the process of interesterification in the presence of potassium glycerate compared with industrial catalyst sodium methylate was installed. Shelf life of potassium glycerate was defined and the possibility of recovery after the loss of catalytic activity was revealed. The dependence of the catalytic activity of potassium glycerate on basic physical and chemical properties of the original material was installed. The mathematical model of the interesterification of test fat in the presence of potassium glycerate depending on the basic technological parameters was developed. Recommendations on the choice of modes were formulated and rational conditions of the interesterification were defined. The possibility of potassium glycerate use in the production of qualitive interesretified fats with mixtures of oils and fats was proved. Economic analysis of the cost potassium glycerate was conducted. The advanced chemical fat interesrerification technology using alkali metals glycerates was developed. The project of technical regulations for production of interesretified fats using alkali metals glycerates was developed.
Ситнік, Наталія Сергіївна. "Удосконалення технології переетерифікування жирів з використанням гліцератів лужних металів." Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/23534.
Full textThesis for a candidate degree of technical sciences by specialty 05.18.06 – fats, essential oils and perfume-cosmetic products technology. – National Technical University "Kharkov Polytechnic Institute" Ministry of Education and Science of Ukraine, Kharkov, 2016. The thesis is dedicated to specific scientific and practical task to develop the scientific foundations of fat interesterification technology using new catalysts that constitute alkali metals glycerates. Triacylglycerol composition of initial and interesterified samples of individual oils was defined. The influence of interesterification with traditional catalyst to the melting point of oils was installed. The choice of test fat for studies of fat interesterification was grounded. The efficiency of potassium glycerate and sodium glycerate as catalysts for interesterification of fats was proved. The character of triacylglycerol composition changes of test fat in the process of interesterification in the presence of potassium glycerate compared with industrial catalyst sodium methylate was installed. Shelf life of potassium glycerate was defined and the possibility of recovery after the loss of catalytic activity was revealed. The dependence of the catalytic activity of potassium glycerate on basic physical and chemical properties of the original material was installed. The mathematical model of the interesterification of test fat in the presence of potassium glycerate depending on the basic technological parameters was developed. Recommendations on the choice of modes were formulated and rational conditions of the interesterification were defined. The possibility of potassium glycerate use in the production of qualitive interesretified fats with mixtures of oils and fats was proved. Economic analysis of the cost potassium glycerate was conducted. The advanced chemical fat interesrerification technology using alkali metals glycerates was developed. The project of technical regulations for production of interesretified fats using alkali metals glycerates was developed.
Биканова, Вікторія Валеріївна. "Фотокаталітичні покриви змішаними оксидами на основі титан (IV) оксиду для екотехнологій." Thesis, НТУ "ХПІ", 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/17089.
Full textThesis for granting the Degree of Candidate of Technical sciences in specialty 05.17.01 – Technology of Inorganic Substances. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2015. Dissertation is devoted to the improvement of the technology of photocatalytic coatings on the basis of mixed oxides of titanium (IV) oxide to produce materials with synergistic effect for wastewater treatment of organic toxicants. Based on the analysis of the relationship of the synthesis conditions, titanium (IV) oxide to metal and ceramic media with structural parameters of the coatings obtained optimum parameters of the process of synthesis of titanium (IV) oxide fireclay carrier, allowing to obtain a uniform composition and distribution over the surface of coatings with high porosity (46-66%) and the total pore volume resistivity (0,88-2,14 cm³/g); it is determined that the process flow of anodic oxidation at a current density of 1,5 A/dm² and a voltage of 60 V allows to obtain oxide covers the composition of Ti/TiO₂ and mixed oxide coatings doped ZnO, ZrO₂ and zinc content of 0,5-2,6 wt. % and zirconium 0,5-2,1 wt. %. and a pore size of 100 nm. Experimental studies have shown that the materials exhibit enhanced photocatalytic activity compared to the individual oxides in 2-4 times due to the existence of a synergistic effect on the level of 1,9-2,3 during the photocatalytic oxidation of aqueous solutions of methyl orange azo dye and phenol. which is higher than for industrial powder photocatalyst Degussa P25 in similar reactions. Based on the determination of kinetic parameters and process concepts are developed mass production of contact in a variety of nature and technology fenolvmisnih disposal of wastewater by photocatalytic oxidation by atmospheric oxygen under the influence of UV radiation.
Биканова, Вікторія Валеріївна. "Фотокаталітичні покриви змішаними оксидами на основі титан (IV) оксиду для екотехнологій." Thesis, НТУ "ХПІ", 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/17088.
Full textThesis for granting the Degree of Candidate of Technical sciences in specialty 05.17.01 – Technology of Inorganic Substances. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2015. Dissertation is devoted to the improvement of the technology of photocatalytic coatings on the basis of mixed oxides of titanium (IV) oxide to produce materials with synergistic effect for wastewater treatment of organic toxicants. Based on the analysis of the relationship of the synthesis conditions, titanium (IV) oxide to metal and ceramic media with structural parameters of the coatings obtained optimum parameters of the process of synthesis of titanium (IV) oxide fireclay carrier, allowing to obtain a uniform composition and distribution over the surface of coatings with high porosity (46-66%) and the total pore volume resistivity (0,88-2,14 cm³/g); it is determined that the process flow of anodic oxidation at a current density of 1,5 A/dm² and a voltage of 60 V allows to obtain oxide covers the composition of Ti/TiO₂ and mixed oxide coatings doped ZnO, ZrO₂ and zinc content of 0,5-2,6 wt. % and zirconium 0,5-2,1 wt. %. and a pore size of 100 nm. Experimental studies have shown that the materials exhibit enhanced photocatalytic activity compared to the individual oxides in 2-4 times due to the existence of a synergistic effect on the level of 1,9-2,3 during the photocatalytic oxidation of aqueous solutions of methyl orange azo dye and phenol. which is higher than for industrial powder photocatalyst Degussa P25 in similar reactions. Based on the determination of kinetic parameters and process concepts are developed mass production of contact in a variety of nature and technology fenolvmisnih disposal of wastewater by photocatalytic oxidation by atmospheric oxygen under the influence of UV radiation.
Маціпура, Павло Анатолійович. "Інтенсифікація процесу модифікації бітумів епоксидними сполуками." Diss., Національний університет "Львівська політехніка", 2021. https://ena.lpnu.ua/handle/ntb/56683.
Full textБерезка, Тетяна Олександрівна. "Удосконалення технології високостійкого пива з використанням антиоксидантів з рослинної сировини." Thesis, Національний університет харчових технологій, 2014. http://repository.kpi.kharkov.ua/handle/KhPI-Press/25005.
Full textThe thesis for a scientific degree of candidate of technical sciences on specialty 05.18.05 – technology of sugary substances and fermentation products. – National University of Food Technologies, Ministry of Education and Science of Ukraine, Kуiv, 2014. The dissertation paper is devoted to the improvement of beer technology with the use of plant-extracted antioxidants. Iso-alpha acids oxidation by free-radical-chain mechanism during wort boiling with hop or hop products is discussed. The ways to inhibit the oxidation due to the addition of plant-extracted antioxidants are determined. Based on the analysis of kinetics of ozonized air oxidation of hop resins components in methanol CO₂ hop extract solution, the conditions are found that provide accelerated oxidation of hop resins components. The efficiency of application of plant-extracted antioxidants for anti-oxygenation of hop resins components is proved. The most effective antioxidants and their dosing rate have been determined. It is revealed that adding antioxidants extracted from peppermint leaves and oak bark into boiling wort with hop is most effective for wort proteins coagulation and beer clarification, this provides up to 10 % savings in hop or its extracts and increases the physiological value of the beer. It is found that antioxidants extracted from Hypericum and oak bark influence the contents of volatile metabolites of the oxidizing exchange; specifically they reduce the diacetyl and acetic aldehyde content in young and finished beer. The technology of plant-extracted antioxidants application at the stages of wort boiling and cooling is proposed. The conditions of plant-extracted antioxidants and hop products dozing are determined. Industrial tests of production technology for different beer types with the use of plant-extracted antioxidants were performed at the Kharkov branch of the PJSC «SUN InBev Ukraine». An experimental industrial batch of 10,000 dal was produced.
Івасів, Володимир Васильович. "Теоретичні основи технологій гетерогенно-каталітичного одержання акрилатних мономерів." Diss., Національний університет "Львівська політехніка", 2021. https://ena.lpnu.ua/handle/ntb/56689.
Full textДенисенко, Владислав Русланович. "Гідродинаміка неоднорідного псевдозрідження." Master's thesis, Київ, 2019. https://ela.kpi.ua/handle/123456789/27646.
Full textThe object of the research: the hydrodynamics during the pulsation fluidization. The subject of the research: quality characteristics of hydrodynamics of nonuniform fluidization during the granulation process. The aim of the work is establishment of the regularities of the process of non-uniform fluidization in the application of pulsation in self-oscillating mode at elevated height of a layer of granular material and development of methods of calculation of industrial machines. Formulated the principle of interaction of a gas continuous medium with a granular material for the realization of jet pulsation mode of fluidization in Zf/H₀≤0,21. Experimentally determined voids in the areas of camera granulator in self-oscillating mode of fluidization when a fivefold excess of the height of the fixed bed height H₀ of the breakdown of the gas jet Zf. Experimentally investigated the influence of the height of granular material at the dynamics of void and the index of mixing in the core zones of the apparatus. The study proves that the granulation process in the application of a nonuniform jet-pulsed fluidization at elevated heights of a layer of granular material leads to intensification of heat and mass transfer processes in 1,6 times in comparison with barbotine.
Объект исследования: гидродинамика при пульсационном псевдоожижении. Предмет исследования: качественные характеристики гидродинамики неоднородного псевдоожижения при грануляции. Целью работы является установление закономерностей процесса неоднородного струйно-пульсационного псевдоожижения в автоколебательном режиме при повышенных высотах слоя зернистого материала и разработка методики расчета промышленных аппаратов для грануляции. Сформулирован принцип взаимодействия газовой сплошной среды с зернистым материалом для реализации струйно-пульсационного режима псевдоожижения при Zf/H₀≤0,21. Экспериментально определено порозности в зонах камеры гранулятора при неоднородном псевдоожижении в автоколебательном режиме при пятикратном превышению высоты неподвижного слоя H₀ высоты пробоя газового факела Zf. Экспериментально исследовано влияние высоты зернистого материала на динамику изменения порозности и индекс перемешивания в базовых зонах аппарата. Подтверждено исследованиями, что процесс грануляции при применении неоднородного струйно-пульсационного псевдоожижения при повышенных высотах слоя зернистого материала приводит к интенсификации тепломассообменных процессов в 1,6 раза в сравнении с барботажним.
Манастирний, Максим Миколайович. "Процес гранулоутворення у псевдозрідженому шарі при застосуванні механічного диспергатора." Master's thesis, Київ, 2018. https://ela.kpi.ua/handle/123456789/23171.
Full textMaster's thesis on the topic: «The process of granulation in a fluidized bed with the use of mechanical disperator» / National Technical University of Ukraine Igor Sikorsky “Kyiv Polytechnic Institute”;Scientific advisorY. Korniyenko.– K., 2018. – . p. The performer – M. Manastyrnyi. The object of the research: the process of formatting an organic-mineral-humic fertilizers with a layered structure with dehydration of heterogeneous liquid systems with the use of mechanical disperator. The subject of the research: kinetics of the granulation process, dispergation of heterogeneous liquid systems by a mechanical disperser of various constructions. The aim of the work is to establish the regularities of an organic-mineral-humic fertilizers formation process with the given properties and development of efficient equipment. The physical model of fluid motion in mechanical cone-type disperator with taking into account the surface tension forces in process of heterogeneous systems dehydration is developed. The regularity of disperator's design influence on distribution of an irrigation density in the working volume of the dispergation is established. The dependence of the droplets size from the mechanical disperator's design and technological parameters is experimentally determined. The temperature field configuration in the dispergation zone with the use of mechanical conical-type disperator is experimentally determined. The basic principles of the granulator's chamber design with the use of liquid phase injection system through mechanical dispersants are formulated. The design of a conical two-chamber mechanical dispersant is developed.
Магистерская диссертация на тему: «Процесс гранулообразования в псевдоожиженном слое при применении механического диспергатора» / НТУУ «КПИ им. Игоря Сикорского»; Руководитель Я.Н. Корниенко. – К., 2018. – с.Исполнитель – М.Н. Манастырный. Объект исследования: процесс образования органо-минерально-гуминовых удобрений с послойной структурой, при обезвоженные гетерогенных жидких систем с применением механического диспергатора. Предмет исследования: кинетика процесса гранулообразования, диспергирования гетерогенных жидких систем механическими диспергаторами различных конструкций. Целью работы является установление закономерностей процесса образования органо-минерально-гуминовых удобрений с заданными свойствами и разработка эффективного оборудования. Развито физическую модель движения жидкости в механическом диспергаторе конического типа с учетом сил поверхностного натяжения при обезвоживании гетерогенных систем. Установлена закономерность влияния конструкции диспергатора на распределения плотности орошения в рабочем объеме диспергирования. Экспериментально определена зависимость размера капель от конструкции и технологических параметров механического диспергатора. Экспериментально определено конфигурацию температурного поля в зоне диспергирования при применении механического диспергатора конического типа. Сформулированы базовые принципы конструкции камеры гранулятора с применением системы ввода жидкой фазы через механические диспергаторы. Разработана конструкция конического двухкамерного механического диспергатора.
Сімейко, Костянтин Віталійович. "Науково-технологічні основи високотемпературних процесів у електротермічному псевдозрідженому шарі." Diss., Інститут газу Національної Академії Наук України, 2021. https://ena.lpnu.ua/handle/ntb/56157.
Full textAreias, F. "Novos compostos heterocíclicos de azoto com unidades fenólicas : síntese e actividade biológica." Doctoral thesis, 2006. http://hdl.handle.net/1822/5941.
Full textThis work reports the synthesis and characterization of new compounds combining phenolic units with linear or cyclic organic molecules, incorporating mainly nitrogen atoms. The reaction between diaminomaleonitrile and phenolic aldehydes led to the corresponding imines that, in presence of manganese dioxide cyclized to generate 4,5-dicyano-2-hydroxyphenylimidazoles. Three different (Z)-N1-(2-amino-1,2-dicyanovinyl)-N2-hydroxyphenyl formamidines were prepared and used as starting materials in the synthesis of the corresponding 5-amino-4-cyano-1-hydroxyphenylimidazoles and 5-amino-4-cyanoformimidoyl-1-hydroxyphenylimidazoles, in the presence of base. This last family of compounds was used in the synthesis of: a) 5-amino-4-(1´-amino-2´,2´-dicyanovinyl)-1-hydroxyphenylimidazole, 5,7-diamino-6-cyano-3-hydroxyphenyl-3H-imidazo[4,5-b]pyridine and 5-amino-6,7-dicyano-3-hydroxyphenyl-3H-imidazo[4,5-b]pyridine, by reaction with malononitrile, in the absence or in the presence of base; b) 6-carbamoyl-2,2-dimethyl-9-hydroxyphenyl-1,2-dihydropurine, by reaction with acetone; c) 6-carbamoyl-2,9-dihydroxyphenylpurine and 1-carbamoyl-6,7-dihydro-3,6-dihydroxyphenyl-7-imino-imidazo[1,5-e]imidazole, by reaction with phenolic aldehydes, under different experimental conditions. Several (Z)-N-[1,2-dicyano-2-(hydroxylphenylidenamino)vinyl]-O-alkylformamidoximes were synthesized and, in presence of base, cyclized intramolecularly to generate 6-cyano-8-hydroxyphenylpurines. Heating the same O-alkylformamidoximes in the presence manganese dioxide, led to the corresponding 4,5-dicyano-N-(N´-alcoxyformimidoyl)-2-hydroxyphenylimidazoles. The reaction of malononitrile with phenolic aldehydes generated hydroxybenzylidenemalononitrile, 2-amino-3,5-dicyano-6-methoxy-4-hydroxyphenyl-pyridine and the triethylammonium salt of 2-amino-3,5-dicyano-6-dicyanomethyl-4-hydroxyphenyl-1,4-dihydropyridine, depending on the solvent that was used. The reaction of malononitrile with salicylaldehyde led to an unknown dimeric structure, possibly a substituted chromene. The compounds were tested for their antioxidant activity by cyclic voltammetry, by the DPPH discoloration method and by the deoxyribose degradation assay. The antimicrobial activity of all compounds was evaluated against two yeasts Saccharomyces cerevisiae and Candida albicans and against bacteria Bacillus subtilis (Gram+) e Escherichia coli (Gram-). From 93 compounds synthetised, 74 are new, 21 presented relevant antioxidant activity, 11 presented antifungal activity and 5 presented antibacterial activity. The imidazole and purine-based compounds or their linear precursors incorporating 3,4-dihydrophenyl and 3,4,5-trihydroxyphenyl units present the highest antifungal activities, low values for the oxidation potencial and high antioxidant activities. Additionally, the cyclization increased the antifungal activity of the compounds and a synergistic effect between the phenolic and nitrogen units was observed.
Fundação para a Ciência e a Tecnologia (FCT) - SFRH / BD / 3185 /2000.
Araya-Kroff, P. "Quantitative image analysis as a diagnostic tool for identifying structural changes of anaerobic granular sludge." Doctoral thesis, 2007. http://hdl.handle.net/1822/8576.
Full textIn this thesis quantitative image analysis techniques were applied to monitor structural changes of anaerobic sludge under different operating conditions. In a first experiment that lasted 177 days, the phenomenon of aggregation of dispersed sludge was quantitatively monitored through the recognition and quantification of aggregates and free filaments. Free filaments were defined as filaments completely buoyant in the medium possessing both extremities free and those with only one free extremity being the other attached to an aggregate. A parameter defined as the ratio between the total free filament length and the total aggregate area (LfA) proved to be sensitive to structural changes in the aggregation status of the anaerobic sludge. LfA allowed the recognition of the aggregation time and revealed to be a good indicator of granular sludge fragmentation and erosion which usually leads to washout in high rate reactors. In a second operation period, image analysis was applied to monitor morphological changes in the previously formed granules, induced by increases in the upflow velocity and in the organic loading rate. In a further work, the initial stages of granules formation in EGSB reactors was assessed, with glucose and also gelatine as primary substrates. Granule development was monitored by image analysis techniques and FISH combined with confocal laser scanning microscopy. Strength, density and settling velocity were the bulk properties analyzed. Supported by the results, it is proposed that instead of nucleating and growing as a dense conglomerate, anaerobic granules initially grow in a sparse conglomerate to a large size, and then increase in density to maturity. In a later work, four EGSB reactors were operated at different influent nitrate concentrations (0, 20, 60 and 100 mgN-NO3-/L). After about 20 days of operation, the granular sludge was characterized morphologically by quantitative image analysis. Also specific methanogenic activities and settling velocities were measured. LfA parameter, was sensitive to quantify the different surface morphology, induced by nitrate in the anaerobic granular sludge. In a final experiment and in order to study the recovery of the SAA in granular sludge, an EGSB reactor was operated with ethanol was fed as the sole carbon source, during a trial period of 106 days. Quantitative image analysis allowed for information to be obtained on granular fragmentation/erosion and filaments release. Granular fragmentation and increase of filaments in the bulk simultaneous with the increase in the acetoclastic activity are described for the first time and might represent a structural response of granular sludge to promote the optimal substrate uptake at minimal diffusion limitations.
Nesta tese são aplicadas técnicas de análise quantitativa de imagem para monitorizar alterações estruturais de biomassa anaeróbia em diferentes condições operatórias. Numa primeira experiência de 177 dias monitorizou-se o fenómeno de agregação de biomassa anaeróbia dispersa, através do reconhecimento e quantificação de agregados e filamentos livres. Filamentos livres foram definidos como filamentos que estão completamente livres no meio e que portanto possuem as duas extremidades livres, e também os filamentos que têm apenas uma extremidade livre e a outra ligada a um agregado. Definiu-se uma parâmetro que representa a razão entre o comprimento total de filamentos livres e a área total dos agregados (LfA). LfA provou ser sensível a alterações do estado de agregação da biomassa, e permitiu identificar o tempo de granulação. Mostrou ainda ser um bom indicador de fenómenos de erosão e fragmentação granulares que estão normalmente associados ao “washout” em reactores de alta carga. Numa segunda experiência, as técnicas de análise de imagem descritas foram aplicadas na monitorização dos grânulos previamente formados e nas alterações estruturais induzidas por variações na velocidade superficial e na carga orgânica aplicada. Numa outra experiência foram monitorados os estágios iniciais da formação de grânulos, usando glucose e gelatina como substratos. O desenvolvimento dos grânulos foi monitorizado por técnicas de análise de imagem e por técnicas de hibridização “in-situ” de fluorescência, combinadas com microscopia confocal laser. Foram medidas características físicas dos grânulos tais como resistência mecânica, densidade e velocidade de sedimentação. Com base nos resultados obtidos é proposto um novo modelo de granulação, segundo o qual, em vez de haver uma nucleação inicial e o crescimento de um agregado denso, se formam inicialmente agregados pouco densos que crescem até um tamanho razoável e que então se tornam mais densos, numa fase de maturação. Numa outra experiência foi utilizada a técnica de análise de imagem para avaliar as alterações morfológicas induzidas pela presença de nitrato em quatro reactores EGSB, alimentados com 0, 20, 60 e 100 mgN-NO3-/L, respectivamente. Após 20 dias de operação a biomassa granular foi caracterizada em termos de actividade metanogénica, morfologia e velocidade d sedimentação. O parâmetro LfA foi sensível às alterações morfológicas dos agregados microbianos, induzidas pelo nitrato. Numa experiência final foi estudada a recuperação da actividade metanogénica acetoclastica em biomassa anaeróbia granular durante 106 dias, num reactor EGSB alimentado com etanol. Através da análise quantitativa de imagem foi possível quantificar fenómenos de fragmentação erosão e libertação de filamentos durante o processo e relacioná-los com o aumento de actividade metanogénica acetoclastica observada durante o período experimental. Sugeriu-se que as alterações estruturais dos grânulos observadas, nomeadamente a libertação de filamentos e a fragmentação poderão ser um mecanismo de resposta dos agregados no sentido de promover a máxima assimilação de substrato minimizando problemas de limitações difusionais.
Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/3187/2000.
GRICES/Danish Rector's Conference.
Neves, L. "Anaerobic co-digestion of organic wastes." Doctoral thesis, 2009. http://hdl.handle.net/1822/9875.
Full textAnaerobic digestion is an already established process but the increasing need of bio‐waste recovery has determined the emergence of new substrates, revamping the research in this field. Contrary to some other European countries, in Portugal this technology is still scarcely in use. Nonetheless, the current legislation endorses this application as a waste management and as an energy recovery process. The rapid growth of the world population, in the past decades, and the economical development of several countries resulted in the production of large amounts of related to food waste and animal manure. These wastes are good substrates for biogas production. This dissertation reports several studies that were performed in order to evaluate and optimize the methane production of organic wastes anaerobic co‐digestion. Emphasis was placed on the role of fatty wastes in the co‐digestion process. Within this scope, a method is described in order to extract, indentify and quantify Long Chain Fatty Acids (LCFA), in both the solid and liquid phase. Moreover, the feasibility of anaerobic digestion of several bio‐wastes that currently are landfilled is also reported. The substrates used during these research studies were as follows: (1) simulated food waste which was made by blending melted pork lard, white cabbage, chicken breast, and potato flakes to simulate lipids, cellulose, protein, and carbohydrates, respectively; (2) food waste, collected in restaurant of the University of Minho; (3) cow manure; (4) oily waste collected in a canned fish processing industry; (5)five wastes from a coffee substitutes production facility and (6) activated sludge. It was observed that food waste composition altered the single biomethanation potential, which implies that anaerobic digestion facilities with large variations in lipids input can have significant changes in process performance. However, whilst imposing transient fluctuations in the fat content of food waste co‐digestion with cow manure, the results proved that cow manure/food waste co‐digestion presents a sufficient buffer capacity to endorse lipids fluctuations, up to concentrations of 7.7 gCODoil/LReactor (55% OilCOD/TotalCOD), maintaining an efficient overall reactor performance and stability, when the total chemical oxygen demand (COD) fed was constant. Codigestion process of cow manure/food waste was improved by addition of oily wastes pulses. The threshold input of oily waste that enhanced the methane production in this co‐digestion process was 12 gCODoil/Lreactor, considering the mixture of lipids present in the oily waste added. This corresponds to a continuous feeding of 10% (Vfood waste/Vmanure) with intermittent oil pulses of 5% (Voil/Vmanure). A pulse feeding of 18 gCODoil/Lreactor induced a persistent process inhibition, detected by the decrease in pH to a minimum of 6.5 and by an increase in the effluent soluble COD and volatile fatty acids. Negative linear correlations between the achieved biomethanation % and the solid‐associated LCFA or palmitic acid (C16:0), allowed to establish threshold values of 180‐220 gCOD‐LCFA/kg TS and 120‐150 gCOD‐C16:0/kg TS, respectively, that should not be surpassed in order to prevent reactor failure. Four of the five assayed wastes from coffee substitutes, are feasible to be co‐digested with activated sludge, instead of landfilled. The coffee substitute solid waste composed of 100% barley is preferable to be co‐digested with the organic fraction of municipal solid waste. Although an alkaline pre‐treatment before co‐digestion with activated sludge is also beneficial to improve methane production, but the cost of this approach should be evaluated.
A digestão anaeróbia é um processo já bem estabelecido, mas a necessidade crescente de valorizar bio‐resíduos em alternativa à sua deposição em aterro, tem determinado um crescente interesse pela investigação neste domínio, nomeadamente ao nível do estudo de biodegradabilidade de substratos potenciais. Ao contrário de alguns países europeus, em Portugal esta tecnologia ainda é muito pouco usada. No entanto, a legislação actual prevê a sua implementação tanto como uma aplicação na gestão integrada de resíduos sólidos, como para a produção de energia. O elevado volume de resíduos biodegradáveis agroindústriais, agropecuários e alimentares produzidos, torna‐os interessantes substratos ou co‐substratos para a produção de biogás. Esta dissertação reúne uma série de estudos que foram realizados com o objectivo de avaliar e optimizar a produção de metano na co‐digestão de resíduos orgânicos. Foi dada ênfase ao estudo do efeito que resíduos lipídicos têm no processo de co‐digestão. Neste contexto, é apresentado um método que foi desenvolvido para extrair, identificar e quantificar ácidos gordos de cadeia longa (AGCL) tanto na fase sólida como liquida. Conjuntamente são apresentados estudos de aplicabilidade da digestão anaeróbia a vários bio‐resíduos que são actualmente enviados para aterro. Os substratos utilizados nos ensaios realizados foram: (1) resíduo alimentar simulado constituído por uma mistura de banha de porco, couve branca, peito de galinha e puré de batata, para simular os lípidos, celulose, proteína e os hidratos de carbono, respectivamente; (2) resíduo alimentar, recolhido no restaurante da Universidade do Minho; (3) chorume de vacas; (4) óleo residual de uma indústria conserveira de peixe; (5) cinco resíduos da indústria de processamento dos substitutos de café e (6) lamas activadas. Os resultados mostraram que a composição do resíduo alimentar, quando utilizado como monosubstrato, alterou o potencial da produção de metano, sugerindo que digestores anaeróbios que sofram uma grande variação no conteúdo lipídico na corrente de alimentação de um resíduo facilmente biodegradável como o estudado, possam apresentar alterações na sua performance. No entanto, quando se provocaram flutuações ocasionais de gordura na co‐digestão de chorume de vacaria com resíduos alimentares, os resultados demonstraram que este sistema apresenta uma boa capacidade tampão para suportar flutuações de lípidos, até concentrações de 7.7 gCQOóleo/Lreactor (55% ÓleoCQO/TotalCQO), mantendo a performance e estabilidade dos reactores, quando a carência química de oxigénio (CQO) da alimentação era constante. A produção de metano do processo de co‐digestão de chorume de vacaria/resíduos alimentares foi favorecida pela adição de pulsos de óleo até 12 gCODóleo/Lreactor. Este valor corresponde a uma alimentação contínua de 10% (Vresíduos alimentares/Vchorume) com pulsos intermitentes de 5% (Vóleo/Vchorume). Foi no entanto detectada uma inibição persistente da produção de metano para um pulso de 18 gCODóleo/Lreactor. A diminuição de metano foi acompanhada de uma diminuição do pH para valores mínimos de 6.5 e um aumento da CQO solúvel e ácidos gordos voláteis no efluente. Obtiveram‐se correlações lineares negativas entre a percentagem de bio‐metanização e os AGCL e ácido palmítico (C16:0) associados aos sólidos, que permitiram estabelecer valores limite de 180‐220 gCQO‐AGCL/kg ST e 120‐150 gCQO‐C16:0/kg ST, respectivamente, que não devem ser ultrapassados de forma a prevenir a falha do processo de co‐digestão. Quatro dos cinco resíduos de sucedâneos de café que foram testados mostraram ser passíveis de ser co‐digeridos com lamas activadas. O resíduo composto só por cevada mostrou melhor eficiência quando co‐digerido com resíduos de alimentos. Outra opção para este resíduo, é submetê‐lo a uma pré‐hidrólise alcalina antes do processo de co‐digestão, mas esta opção acarreta custos que devem ser avaliados.
Fundação para a Ciência e Tecnologia (FCT) - SFRH/BD/18174/2004
Fundo Social Europeu (FSE)
Cerqueira, M. A. "Development and characterization of edible coatings to the preservation of cheese quality." Doctoral thesis, 2010. http://hdl.handle.net/1822/12378.
Full textConventional synthetic packaging films have led to serious ecological problems due to their nonbiodegradability. New natural polymeric materials have been studied in order to replace the conventional packaging materials. Being so, the future generation of packaging materials will be derived from renewable and biodegradable sources. Edible coatings and films, in particular, can provide additional protection for food, being a fully biodegradable and environmental friendly packaging system; and can be combined with antimicrobial, antifungal and antioxidant substances found in many natural sources. They have been extensively applied in fruits and vegetables, however hardly explored in dairy products. Based in these ideas, the main purpose of this thesis was the development and characterization of new edible coatings for cheese preservation. The research was based in a sequence of tasks, which started by the study of a method for the extraction of galactomannans from non-traditional sources (Gleditsia triacanthos, Caesalpinia pulcherrima and Adenanthera pavonina) and determination of their physicochemical properties. Phenolic and antioxidant compounds were recovered during extractions and their utilization as possible functional compounds to be introduced in edible films was evaluated. The ability of those galactomannans to act as main material for edible coatings and films was studied simultaneously with a commercial polysaccharide (chitosan). Finally, different formulations of polysaccharide, plasticizer and corn oil were tested as coatings for cheese based on their wettability and physical properties. The influence of the coatings and storage temperature on gas transfer rates, chemical and microbiological properties of cheese was evaluated. The work performed has shown that the extraction and purification methodology used could be applied successfully to three galactomannans giving a clear indication that it may be used for other galactomannan sources as well. The results have also shown that the extracted galactomannans present adequate physicochemical characteristics to be used in the food industry. During galactomannans extraction procedures it was possible to obtain phenolic and antioxidant compounds from ethanolic and aqueous extracts. These extracts have shown ability to be incorporated in galactomannan films, imparting them functional properties. The incorporation of glycerol and corn oil in galactomannan and chitosan films has shown that the water affinity of the components of the coatings/films is one of the most influencing factors over their physicochemical properties. Furthermore, chitosan and galactomannan coatings/films showed to have different properties associated with their different structures, affecting principally the glass transition temperature, water vapour permeability and elongation-at-break values of the edible films. The methodology used for coating selection has shown to be useful to obtain the best formulation to be applied on cheese. The application of chitosan and galactomannan coatings and storage temperature influences the cheese gas exchange rate, being galactomannan coatings the ones allowing a lower gas transfer rate. The use of a galactomannan coating together with a storage temperature of 4 °C showed to improve shelf-life parameters of cheese. The evaluation of the application method of the coating, despite presenting similar performances, when referring to weight and moisture loss and colour changes of the cheese, presents different efficiencies, being the brushing application the one where less coating forming solution is wasted. In conclusion, galactomannans can be used as edible coatings for application on cheese and their properties can be tailored (within limits) by the addition of plasticizer and oil, turning these coatings into promising replacements for synthetic packaging materials.
Os revestimentos e embalagens sintéticas têm gerado problemas ecológicos devido ao facto de não serem biodegradáveis. Novos polímeros de origem natural têm sido estudados com o objectivo de substituir os materiais sintéticos e, espera-se que a nova geração de materiais para embalagens provenha de fontes renováveis e biodegradáveis. Neste sentido, nos últimos anos os revestimentos e filmes edíveis surgiram como possíveis substitutos das embalagens sintéticas, através da utilização de fontes renováveis e biodegradáveis. Os revestimentos e filmes edíveis podem ser usados para aumentar o tempo de prateleira dos alimentos, onde pode também haver a adição de agentes antimicrobianos, antifugicos e antioxidantes possibilitando uma protecção mais eficaz. No entanto, e apesar de serem muito utilizados em frutos e vegetais, têm sido pouco estudados em produtos lácteos. Neste seguimento, o principal objectivo da presente tese foi o desenvolvimento e caracterização de novos revestimentos edíveis para a conservação do queijo. Para a sua concretização começou por estudar-se um método de extracção de novas fontes de galactomananos (Gleditsia triacanthos, Caesalpinia pulcherrima e Adenhantera pavonina) e a sua caracterização. No decorrer das extracções, os compostos antioxidantes e fenólicos foram recuperados e testados como possíveis compostos funcionais para adicionar a filmes edíveis. Posteriormente, a possibilidade de utilizar esses galactomananos como revestimentos e filmes edíveis foi testada juntamente com um polissacarídeo commercial (quitosano). Diferentes formulações, com a variação das concentrações de polissacarídeo, plasticizante e óleo foram testados como revestimentos e filmes. Em seguida, foi avaliada a influência dos revestimentos edíveis na transferência de gases, e nas propriedades químicas e microbiológicas do queijo durante o armazenamento. O trabalho realizado demonstrou que a metodologia de extracção e purificação utilizada pode ser aplicada com sucesso em três tipos de galactomananos, permitindo antever a sua aplicação a outras fontes de galactomananos. Os galactomananos obtidos apresentaram características físico-químicas adequadas para serem aplicados na indústria alimentar. Durante as extracções foi possível obter compostos fenólicos e antioxidantes dos extractos aquosos e etanólicos, que mostraram poder ser incorporados em filmes edíveis de galactomananos, conferindo-lhes propriedades funcionais. A adição de glicerol e óleo de milho aos revestimentos e filmes edíveis de galactomanano e quitosano mostrou que afinidade à água dos revestimentos e filmes edíveis é um dos factores que mais influencia as suas propriedades físico-químicas. Além disso, o revestimentos e filmes de quitosano e galactomanano mostraram diferentes propriedades associadas às suas distintas estruturas, afectando a temperatura de transição vitrea, a permeabilidade de vapor de àgua e os valores elongação à quebra dos filmes. A metodologia utilizada na selecção do revestimento a ser aplicado no queijo mostrou ser útil para a obtenção da melhor formulação. A aplicação dos revestimentos de galactomanano e quitosano, assim como a temperatura, mostraram influenciar a transferência de gases do queijo, sendo o revestimento de galactomanano o que garantiu uma menor transferência de gases. O revestimento de galactomanano juntamente com uma temperatura de armazenamento de 4 °C mostrou ser a melhor opção para melhorar os parâmetros de tempo de prateleira do queijo. A avaliação do método de aplicação do revestimento no queijo mostrou, que apesar dos queijos apresentarem resultados de perda de água e diferenças de cor semelhantes, apresentam diferentes eficiências de aplicação, verificando-se que o método por pincelamento é o método onde menos revestimento é desperdiçado. Em suma, os galactomananos podem ser utilizados como revestimentos para aplicação em queijo, as suas propriedades podem ser modificadas (dentro dos limites) recorrendo à adição de plasticizante e óleo de milho, apresentando-se como um substituinte promissor dos materiais sintéticos usados em embalagens.
Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/23897/2005).