Bibliografie tematiche / Phosphoric acid manufacturing process

Letteratura scientifica selezionata sul tema "Phosphoric acid manufacturing process"

Autore: Grafiati

Pubblicato: 8 giugno 2024

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Articoli di riviste sul tema "Phosphoric acid manufacturing process":

Krupa-Żuczek, Kinga, Zygmunt Kowalski e Zbigniew Wzorek. "Manufacturing of phosphoric acid from hydroxyapatite, contained in the ashes of the incinerated meat-bone wastes". Polish Journal of Chemical Technology 10, n. 3 (1 gennaio 2008): 13–20. http://dx.doi.org/10.2478/v10026-008-0030-6.

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Manufacturing of phosphoric acid from hydroxyapatite, contained in the ashes of the incinerated meat-bone wastes The results of the investigations concerning phosphoric acid manufacturing, by the extraction method, from the ashes containing hydroxyapatite, obtained through the thermal treatment of bone sludge have been presented. The incinerated bone sludge with ~ 16% P content and the minimal amount of impurities can be an alternative source for phosphoric acid production. The process consists in two stages. In the 1st stage, reaction of hydroxyapatite with phosphoric acid resulting in monocalcium phosphate formation in the solution obtained is carried out. The tests revealed that overall hydroxyapatite dissolution in phosphoric acid takes place when the concentration is 37% H3PO4. In the 2nd stage monocalcium phosphate is converted into calcium sulphate using concentrated sulphuric acid at the recommended temperature of 95°C. The principles of the technological idea of the process of phosphoric acid manufacturing from HA-containing ashes, obtained by bone wastes incineration, as well as a preliminary economic analysis for the production of 10 000 t/year of food-grade phosphoric acid have been developed.

Chaabouni, Ahmed, Chaker Chtara, Ange Nzihou e Hafed EL Feki. "Study the Nature and the Effects of the Impurities of Phosphate Rock in the Plants of Production of Phosphoric Acid". JOURNAL OF ADVANCES IN CHEMISTRY 7, n. 2 (1 gennaio 2008): 1296–99. http://dx.doi.org/10.24297/jac.v7i2.5560.

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Phosphate rocks from different deposits vary widely in composition, and these variations have important effects in phosphoric acid production. All phosphate rocks contain many impurities. Knowledge of the nature and contents of the various elements in the phosphate is required in the manufacturing process of phosphoric acid. All these chemical characteristics can help the operator to foresee its objectives under the operating conditions and the cost of production in the manufacturing process of phosphoric acid.Two Tunisian natural phosphates coming from two different deposits were selected. We propose in this work studying the effects of the impurities that depending on their concentration can affect decisively the behavior of these ores in the process of production of phosphoric acid. Study the chemical composition of these ores is carried out according to standard analytical methods used for raw phosphates.The results obtained show a slight difference in chemical properties between the two types of sedimentary phosphates and their aptitude to be used in the plants of production of phosphoric acid.

Li, Hongqiang, Wu Ge, Jun Zhang, Richard M. Kasomo, Jiahao Leng, Xiaoqing Weng, Qian Chen et al. "Control foaming performance of phosphate rocks used for wet-process of phosphoric acid production by phosphoric acid". Hydrometallurgy 195 (agosto 2020): 105364. http://dx.doi.org/10.1016/j.hydromet.2020.105364.

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Ma, Hang, Xiao Feng e Chun Deng. "Water–Phosphorus Nexus for Wet-Process Phosphoric Acid Production". Industrial & Engineering Chemistry Research 57, n. 20 (2 maggio 2018): 6968–79. http://dx.doi.org/10.1021/acs.iecr.7b05399.

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Shibata, Junji, Masataka Morikawa, Norio Yoshikawa, Tomoko Yamada, Norihiro Murayama e Hideki Yamamoto. "Separation and Recovery of Acids from Waste Acid Mixture Mainly Containing Phosphoric Acid Discharged in Liquid Crystal Display Manufacturing Process". KAGAKU KOGAKU RONBUNSHU 29, n. 4 (2003): 521–25. http://dx.doi.org/10.1252/kakoronbunshu.29.521.

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Hasan, Nada. "Chemical characterization of phosphogypsum produced from raw phosphate rock from the phosphoric acid manufacturing process". مجلة المعهد العالي للدراسات النوعية 3, n. 16 (1 luglio 2023): 4971–89. http://dx.doi.org/10.21608/hiss.2023.332907.

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Lin, Tseng-Hsian, Hung-Jung Siao, Sue-Huai Gau, Jen-Hwa Kuo, Ming-Guo Li e Chang-Jung Sun. "Life-Cycle Assessment of Municipal Solid Waste Incineration Fly Ash Recycling as a Feedstock for Brick Manufacturing". Sustainability 15, n. 13 (29 giugno 2023): 10284. http://dx.doi.org/10.3390/su151310284.

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The recovery of municipal solid waste incineration (MSWI) fly ash is currently considered to be the most viable solution for its management. However, in developing resource recovery technologies, it is crucial to consider the overall environmental impact. This study employed a life-cycle assessment (LCA) to compare environmentally friendly red bricks partially utilizing MSWI fly ash as a raw material with conventional red bricks. The results demonstrate that the use of phosphoric acid during the resource recovery process imposes the most significant environmental burden, followed by electricity consumption. To address this issue, in this study, we simulated the replacement of phosphoric acid with phosphoric acid monohydrate recovered from discarded fire extinguishers, resulting in the production of second-generation environmentally friendly red bricks. The analysis revealed that the environmentally friendly red bricks exhibited a mere 5.52% increase in total environmental impact compared with traditional red bricks. Moreover, by stabilizing heavy metals using recovered phosphoric acid monohydrate, the second-generation environmentally friendly red bricks achieved an 8.75% reduction in total environmental impact relative to traditional red bricks. These findings highlight the environmental benefits of fly ash reuse in red brick production, and the incorporation of other industrial waste or byproducts could further enhance its efficacy. The application of the LCA facilitated the identification of key areas for improvement and enabled precise evaluation of the environmental benefits associated with waste reuse.

Chen, Hsiao Ming, Haw Jan Chen, Ying Ming Tsai, Te Wei Lee e Gann Ting. "Development of an improved two-cycle process for recovering uranium from wet-process phosphoric acid". Industrial & Engineering Chemistry Research 26, n. 3 (marzo 1987): 621–27. http://dx.doi.org/10.1021/ie00063a034.

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Gurbuz, Hale, e Nusret A. Bulutcu. "Preparation of Reasonably Pure Calcium Orthophosphates from Wet-Process Phosphoric Acid. 1". Industrial & Engineering Chemistry Research 34, n. 5 (maggio 1995): 1914–18. http://dx.doi.org/10.1021/ie00044a044.

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Abdel-Ghafar, H. M., E. A. Abdel-Aal, M. A. M. Ibrahim, H. El-Shall e A. K. Ismail. "Purification of high iron wet-process phosphoric acid via oxalate precipitation method". Hydrometallurgy 184 (marzo 2019): 1–8. http://dx.doi.org/10.1016/j.hydromet.2018.12.011.

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Più fonti

Tesi sul tema "Phosphoric acid manufacturing process":

Arlow, Antoinette. "Crystallisation aspects of the wet-process phosphoric acid industry". Pretoria : [s.n.], 2003. http://upetd.up.ac.za/thesis/available/etd-04152004-095501.

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Booker, Nicholas Anthony. "Removal of cadmium from wet process phosphoric acid by cation exchange". Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47365.

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Bouchkira, Ilias. "Modélisation thermodynamique des solutions d'acides sulfurique et phosphorique en présence du minerai de phosphate : applications à l'encrassement, à la cristallisation et à l'optimisation multicritère d'une unité industrielle de production d'acide phosphorique". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0056.

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Ce travail de thèse traite du développement d’un modèle thermodynamique et de son exploitation dans la modélisation, la simulation et l’optimisation des procédés de fabrication d’acide phosphorique. Il est décrit par des équations de bilans de matière et de charge, des équations d’équilibres chimiques, et l’équation du modèle de Pitzer. Il met en jeu plusieurs paramètres inconnus à identifier à partir de mesures expérimentales issues d’une base de données construite dans ce travail. Elle contient des mesures de spéciation d’acides phosphorique et sulfurique, des mesures de solubilité de dix minéraux, et des mesures de l’activité de l’eau de huit systèmes binaires. Ces mesures sont effectuées dans des conditions de températures allant de 298K à 353K et des concentrations allant de 0 mol/kg d’eau à 20 mol/kg d’eau. Une méthode basée sur l'analyse de sensibilité globale des paramètres est ensuite développée et utilisée pour évaluer l'estimabilité des paramètres inconnus. Ceux qui sont estimables sont alors identifiés, et les valeurs de ceux qui ne le sont pas sont fixées à partir de la littérature ou de précédentes études. Des mesures expérimentales, différentes de celles qui ont servi pour l’identification des paramètres, sont réalisées pour valider le modèle. Le test statistique F de Fisher-Snedecor et le test de Kolmogorov-Smirnov sont notamment utilisés. Les résultats de ces tests confirment les qualités de prédiction du modèle. Ce dernier est d’abord exploité dans l’optimisation multicritère d’une unité industrielle de production d’acide phosphorique, notamment pour la minimisation des pertes chimiques en phosphate et l’amélioration du rendement de l’unité. Il est ensuite utilisé dans l’analyse des problèmes d’encrassement qui se produisent lors de la production d’acide phosphorique et altèrent les performances des différentes unités du procédé de fabrication. Il est enfin exploité dans la modélisation et la simulation de la cristallisation des sulfates de calcium lors de la production de l’acide phosphorique. Le modèle ainsi validé et déjà exploité peut désormais être utilisé comme outil prédictif pour la conception et le fonctionnement optimal des procédés de fabrication d’acide phosphorique existants, voire pour le développement de nouveaux procédés plus intégrés et plus performants
This PhD work deals with the development of a thermodynamic model and its use in the modeling, simulation and optimization of phosphoric acid manufacturing processes. It consists of mass and charge balance equations, chemical equilibrium equations, and Pitzer’s model equation. The model involves several unknown parameters to be identified from experimental measurements available in a database developed in this work. It contains data on speciation of phosphoric and sulfuric acids, on solubility of ten minerals, and on water activity of eight binary systems. The measurements are performed under temperature conditions ranging from 298K to 353K and concentrations ranging from 0 mol/kg water to 20 mol/kg water. A global sensitivity based estimability analysis is then developed and used to evaluate the estimability of the unknown parameters from the available data. The estimable parameters are then identified, and the values of the non-estimable ones are taken from the literature or from previous studies. Additional experimental measurements, different from those used for the identification of parameters, are carried out to validate the model. The Fisher-Snedecor statistical test and the Kolmogorov-Smirnov test are particularly used. The results of the tests confirmed the quality of the model predictions. The validated model is first exploited in the multi-objective optimization of an industrial unit of phosphoric acid production, in particular to minimize the chemical losses of phosphate and to improve of the performance of the unit. It is then used to investigate the fouling problems that occur during the production of phosphoric acid and alter the performance of different units of the manufacturing process. Finally, the model is exploited in the modeling and simulation of the crystallization of calcium sulfates during the production of phosphoric acid. The model thus validated and already exploited can now be used as a predictive tool for the design and optimal operation of existing phosphoric acid manufacturing processes, or even for the development of new processes which are more integrated and more efficient

Calmeyn, Timothy J. "Optimization of the melt-phase polyethylene terephthalate manufacturing process". Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1179336415.

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Zabot, Giovani Leone 1988. "Obtaining bioactive compounds from clove and rosemary using supercritical technology: influence of the bed geometry, process intensification and cost of manufacturing of extracts = Obtenção de compostos bioativos de cravo-da-índia e alecrim utilizando tecnologia supercrítica: influência da geometria do leito, intensificação de processos de extração e custo de manufatura dos extratos". [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/254901.

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Orientador: Maria Angela de Almeida Meireles
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-26T17:00:04Z (GMT). No. of bitstreams: 1 Zabot_GiovaniLeone_D.pdf: 24740321 bytes, checksum: 93e515a410574c1037b0a53340db63d2 (MD5) Previous issue date: 2015
Resumo: Substâncias naturais extraídas de plantas têm propriedades funcionais que as tornam preferíveis em relação às substâncias sintéticas, havendo grande interesse para aplicação farmacológica e na elaboração de bioprodutos. Técnicas de extração, como a que utiliza fluidos supercríticos, vêm se destacando por proporcionarem a obtenção seletiva de compostos bioativos com elevada qualidade. No campo da tecnologia supercrítica, pesquisas são desenvolvidas para aumentar o rendimento de extração através da alteração de condições de processo, como pressão e temperatura. No entanto, há a necessidade de discriminar mais a influência tecno-econômica de outras variáveis, como a geometria do leito de extração. Em vista disso, realizou-se a avaliação técnica da extração com CO2 supercrítico de compostos bioativos de cravo-da-índia e alecrim em uma unidade de extração laboratorial constituída por dois extratores de 1 L com diferentes razões de altura do leito (HB) pelo diâmetro (DB), sendo para o extrator 1 (E-1) a razão de 7,1 e para o extrator 2 (E-2) a razão de 2,7. Dois critérios utilizados para mudança de geometria e aumento de escala foram aplicados, consistindo em: (1) manutenção da velocidade intersticial do solvente igual em ambas as geometrias; e (2) manutenção da razão de massa de solvente por massa de matéria-prima (S/F) igual em ambas as geometrias para um determinado tempo de processo. De acordo com os resultados cinéticos de rendimento de extrato e composição química, o critério (1) não se mostrou indicado para ser aplicado em processos de extração com fluidos supercríticos (SFE) de compostos de cravo-da-índia. O critério (2) mostrou-se apropriado para a obtenção de óleo volátil de cravo-da-índia, pois houve igualdade nos perfis das curvas de extração em E-1 e E-2, avaliados em termos de parâmetros cinéticos como taxa de transferência de massa, duração dos períodos de taxa constante de extração (CER) e taxa decrescente de extração (FER), rendimento de extrato e razão mássica de soluto no solvente. No entanto, o critério (2) não se mostrou adequado para a obtenção de compostos bioativos de alecrim, sendo que o leito de extração E-2 proporcionou rendimentos até 86 % maiores em relação ao E-1, sendo a diferença mais notória no final do período FER. Houve diferença também no custo de manufatura (COM) dos extratos de alecrim simulado pelo SuperPro Designer 8.5®, sendo 23 % menor em E-2 do que em E-1 para uma planta industrial com 2 extratores de 100 L. Com relação ao alecrim, terpenoides majoritários como 1,8-cineol e cânfora foram extraídos com CO2 supercrítico. No entanto, alguns compostos fenólicos foram extraídos em pequena quantidade (ácido carnósico) ou nem foram extraídos via SFE (ácido rosmarínico). Logo, o conceito de intensificação de processos foi utilizado para facilitar a extração das duas frações presentes em alecrim. O processo consistiu em extrair inicialmente a fração rica em terpenoides com CO2 supercrítico (SFE-CO2) e logo após, no mesmo equipamento e sem desempacotar o leito, a fração rica em terpenos fenólicos foi extraída com água líquida pressurizada (PWE). Com isso, aproximadamente 2,5 % (m/m, base seca) de óleo volátil contendo terpenoides e 18,6 % (m/m, base seca) de extrato não-volátil contendo terpenos fenólicos foram obtidos em frações separadas. Um método analítico para quantificação de terpenos fenólicos por cromatografia líquida de alta eficiência foi desenvolvido e validado, com tempo total de análise de apenas 10 min. O custo operacional anual de uma planta produtiva instalada no Brasil com 2 extratores de 100 L foi simulado para os processos SFE-CO2 + PWE para obtenção de compostos de alecrim. O aproveitamento maior da matriz vegetal para a obtenção diversificada de compostos bioativos permitiu a redução em 28 % dos custos anuais de produção em relação ao processo SFE-CO2
Abstract: Natural substances extracted from plants present functional properties which are preferable against the synthetic ones, being useful in formulating bioproducts and in the pharmaceutical area. Novel extraction techniques, as the use of supercritical fluids, are acquiring notoriety by providing the selective extraction of bioactive compounds with high quality. In the supercritical technology field, researches are performed to increase the extraction yield by changing process conditions (i.e., pressure, temperature). However, there is a need for further techno-economic discriminations about the influence of other variables, as the bed geometry. Thus, we performed the evaluation of the supercritical CO2 extraction of clove and rosemary bioactive compounds using a laboratory equipment containing two extractors of 1 L with different height (HB) to bed diameter (DB) ratios. Bed 1 (E-1) and 2 (E-2) present HB/DB ratios of 7.1 and 2.7, respectively. Two criteria used for geometry shift and scale up were applied: (1) maintaining the solvent interstitial velocity equal in both bed geometries; and (2) maintaining the solvent mass to feed mass (S/F) ratio equal in both bed geometries for a fixed processing time. According to the kinetic results of extraction yields and chemical composition, the criterion (1) is not indicated for supercritical fluid extraction (SFE) of rosemary compounds. Criterion (2) is suitable for obtaining clove extract, because the extraction curves profiles were similar in E-1 and E-2. We evaluated the extraction curves in relationship to kinetic parameters as mass transfer rate, duration of constant extraction rate (CER) and falling extraction rate (FER) periods, extraction yield and mass ratio of solute in the fluid phase. However, criterion (2) is inappropriate for obtaining rosemary bioactive compounds. E-2 provided extraction yields up to 86% higher than E-1. The difference was more pronounced in the end of FER period. We observed differences on the cost of manufacturing (COM) of rosemary extracts simulated by SuperPro Designer 8.5®. COM¿s were 23% lower in E-2 than in E-1 for an industrial plant of 2 extractors of 100 L. With respect to rosemary, major terpenoids as 1,8-cineole and camphor were extracted with supercritical CO2, while some phenolic compounds were low (carnosic acid) or no extracted (rosmarinic acid) using SFE. Thus, process intensification concept was used for becoming possible the extraction of two fractions of bioactive compounds found in rosemary. The procedure comprised the initial extraction of the terpenoids-rich fraction with supercritical CO2 (SFE-CO2) and, thereafter, in the same equipment without unloading the bed, performing the extraction of the polyphenols-rich fraction with pressurized water (PWE). Approximately 2.5 wt.% (dry basis) of volatile oil containing terpenoids and 18.6 wt.% (dry basis) of non-volatile extract containing phenolic terpenes were obtained in separated fractions. We developed and validated an analytical method for quantifying phenolic terpenes by high performance liquid chromatography, presenting a total time of analysis of 10 min. Also, we simulated the annual operating cost of a plant installed in Brazil containing 2 vessels of 100 L applying SFE-CO2 + PWE processes for obtaining rosemary compounds. The higher use of the vegetal matrix for diversifying the extraction of bioactive compounds enabled 28% reduction in the annual production costs whether compared to SFE-CO2 process alone
Doutorado
Engenharia de Alimentos
Doutor em Engenharia de Alimentos

Arlow, Antoinette. "Crystallisation aspects of the wet-process phosphoric acid industry". Diss., 2004. http://hdl.handle.net/2263/23966.

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Fedmis Pty (Ltd) situated in Palaborwa, South Africa produces phosphoric acid using the wet process production process. For this study, two main areas of concern in the wet process phosphoric acid production were investigated. The first area is the formation of sludge in the system due to impurities that reduces the grade of the acid produced, thereby lowering the selling price. The second area is the crystallisation of the gypsum that influences filtration and thereby affects plant productivity. These two aspects were investigated separately as they occur in different steps of the production process at different acid concentrations. A major component of the acid sludge is known as x-compound, ((Fe,Al)3KH)14 (PO4)8.4H2O). The purpose of the investigation of x-compound is to determine what effects different ionic impurities have on its precipitation and to determine if these effects could be used to decrease the amount of sludge formation. Due to the complexity of the system and the wide variety of impurities only the major impurities were considered in this study. These impurities included potassium (K+), sodium (Na+), magnesium (Mg2+), aluminium (Al3+) and iron (Fe3+). For all the experiments investigating the effect of impurities, analytical reagents were used on laboratory scale. For the silica experiments, commercially available samples were used. For the experiments investigating the impurity effects on the precipitation of x-compound it was found that:

Agitation increases x-compound precipitation and can be used commercially to increase the precipitation rate to a point where sludge can be removed before transportation.
Adding x-compound seeding crystals or magnesium ions also increases precipitation.
Adding gypsum, sodium, hexafluorosilicates or fluorosilic acid reduces the precipitation, with sodium ions producing the lowest yield. This reduction is however not sufficient to be used commercially.

From the Raman study it became clear why x-compound precipitation is such a slow process. E At low acid concentrations, more H2PO4 - ions are present that form a complex with iron and aluminium. E As the acid concentration increases the concentration of H2PO4- ions decrease as the degree of dissociation of phosphoric acid decreases. The ferric- H2PO4- and aluminium- H2PO4- complexes become less stable and ultimately precipitation of the x-compound is favoured above solvation. E Addition of potassium impurities to the solutions had no visible effect on the Raman spectra and is suspected not to form a complex with the acid. From the silica sources investigated namely Dicalite, Serina Kaolin, Foskor silica and Aerosil 200 it can be concluded that none of the sources will be useful for the removal of potassium through formation of potassium hexafluorosilicates. For the determination of the concentration of impurities present in the production of phosphoric acid, the Fedmis monitoring program was initiated. It included the monitoring of Foskor rock analyses on a daily basis, and the monitoring of the 27%, 39% and 54% P2O5 phosphoric acid and precipitate, from these acid solutions on a weekly basis. From the investigation of the effect of these impurities on the solubility of potassium hexafluorosilicates, it was found that magnesium causes K2SiF6 to be the most soluble and fluoride the least. Unfortunately, the impurities did not help to reduce the potassium concentrations in the acid to below the required amount for sludge formation. For the calcium sulphate dihydrate surfactant experiments, the purpose of the investigation was to determine whether higher crystallisation qualities could be obtained to improve plant productivity. The investigation was limited to using surfactants with sulphate or phosphate functionalities and experiments were done on laboratory scale using analytical reagents. Atphos E3205, Atpol E3202 and Atpol E1231 are polyethoxylated alkyl phenol phosphate esters that had no visible effect on the crystal structure of the precipitated gypsum, but differences in the crystal sizes were observed. Smaller crystal structures with relatively equal masses compared to reference experiments are an indication of a growth inhibitor and a nucleation promoter as seen with Atphos E3205 and Atpol E3202. Increased crystal sizes were obtained using Atpol E1231. The use of Calsoline Oil caused a wider crystal size distribution in the precipitated crystals as thin and broad crystals with approximately the same length are found. The crystal mass obtained is also approximately the same as that of the reference experiment. Thus, it can be concluded that the surfactant affects the growth of the crystals and not the nucleation. Arlatone 1489, calcium gluconate monohydrate, Dowfax Hydrotrope and Tamol NN 8906 had no visible effect on the structure or size of the precipitated gypsum crystals. With the use of Nansa SS30, drastic effects were seen on the crystallisation of the calcium sulphate as small hexagonal rods were found. With an increase in surfactant concentration, there is a clear decrease in the mass of crystals obtained as well as crystal size. An increase in the crystal size distribution and a decrease in crystal size reduced the filtration rate dramatically. Experiments carried out for 24 hours exhibited the same trends where there is a decrease in yield with an increase in surfactant concentration. Higher yields were however obtained proving that mass transfer barriers were overcome. The results from these experiments again indicate that the surfactant affects crystal growth and nucleation. With the use of Dowfax 3B2 there is definite reduction in yield with an increase in surfactant concentration reaching a minimum at approximately 70% yield. Due to the presence of large amounts of smaller crystals and the almost constant yield obtained compared to the reference experiment, it can be concluded that this surfactant is a growth and not a nucleation inhibitor. As with Nansa SS30, experiments where Empicol LZ/D was used show a continuous decrease in the yield obtained with an increase in the surfactant concentration. At higher concentration of Empicol LZ/D, it seems as if this surfactant changed from a growth promoter to a growth inhibitor because although broad longer crystals are present, there are now also much smaller crystals formed. The crystal size distribution also broadens considerably. Overall, very high yields were obtained using Empimin KSN70 and the observed crystal size distributions were very narrow. The only difference was that the crystals appeared to be more porous or fibrous compared to the reference experiment. It is recommended that the experiments showing promise as crystal habit modifiers like Nansa SS30 and Empicol LZ/D be investigated in more detail as well as combinations of surfactants. Both the areas of concern in the process were investigated successfully. For the sludge formation problem, it is now clear what effects the precipitation of x-compound as well as what affect the impurities and operating conditions have. For the crystallisation of gypsum using surfactants, it was proven that surfactants could be used to affect crystal growth, shape and distribution and in this way influence filtration.
Dissertation (MSc(Chemical Engineering))--University of Pretoria, 2005.
Chemical Engineering
unrestricted

Chang, Shu-Wen, e 張舒雯. "Investigation of GaAs-based wet etching process in phosphoric-acid and citric-acid based solutions". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/25167762306349564419.

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碩士
國立清華大學
材料科學工程學系
90
Wet etching has been widely used in mesa etch and gate recess process in GaAs device process. We prefer to use wet etching when low damage is required since dry etching always accompanies with damage. In this thesis, two etchant systems were used for GaAs wet etching in heterojunction structure. H3PO4/H2O2/MX03 mixture was used to etch GaAs layer with thicker layer thickness due to its etch rate of about 200Å/sec. Citric acid (CA)/KCA/H2O2/H2O mixture was optimized to derive stable and low etching rate so that etch rate can be well controlled and lateral etching can be prevented. Besides, InGaP etchant was optimized to improve etch uniformity. In H3PO4-based system, the etch process was optimized in horizontal and vertical directions respectively. The following experiment conducted for the whole wafer showed that the wet etching uniformity for GaAs wafers in the cassette can be improved to be 5.6%, with the setting of the optimum etching condition of 11000ml H2O2 mixed with 1000ml H3PO4 and 12 ml MX03 with 30psi N2 bubble around by 1.5oC. In CA-based system, CA/KCA/H2O2/H2O=371g/120g/351ml/4983ml performed stable etch rate in an observation duration of 400 hours. Etchant composed of Buffer (CA and KCA in water): H2O2 = 5.6:2 in volume demonstrated GaAs/InGaP etch selectivity of 1277 with the average etch rate of 66.4 Å/sec and 0.052 Å/sec for GaAs and InGaP respectively. This is a suitable etchant for mesa etch and gate recess of GaAs/InGaP heterojunction device.

Van, Rooyen Daniel J. R. "On-line process monitoring in electrolytic manufacturing of chromic acid". Thesis, 2009. http://hdl.handle.net/10539/6712.

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dichromate content in concentrated liquors from the electrolytic production of chromic acid were investigated. Experimental results showed that Artificial Neural Network technology applied to highly diluted hexavalent chromium solutions, which are known to have been prepared from chromic acid and sodium dichromate, do not yield useable results for quantification purposes. Combining ion selective electrode measurements and ultra-violet – visible spectrophotometric techniques to highly diluted hexavalent chromium solutions, prepared from chromic acid and sodium dichromate, yields errors of about 2.3 % for hexavalent chromium and about 2.8 % for sodium determinations versus a standard titrimetric method. Tests to prove the suitability of the standard titrimetric acid –base titration technique confirmed an accuracy of 0.6 % for a known chromic acid content and 0.7 % for titrations based on a known sodium dichromate content for liquors highly concentrated in hexavalent chromium. A simple on-line analytical instrument was developed based on the titrimetric acid –base titration technique. The on-line instrument evidenced average errors of about 1.9 % for the chromic acid content and about 2.6 % for the sodium dichromate content.

He, Shih-Wei, e 何世偉. "Modification of waste carbon fiber using phosphoric acid heating process and studying its adsorption of aqueous copper ions". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/40940020652850745536.

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碩士
國立雲林科技大學
環境與安全衛生工程系碩士班
101
Activation of waste carbon fiber by conventional heating method using phosphoric acid and adsorption of aqueous copper ions using said modified waste carbon fiber was investigated. The conventional heating temperature was 500℃ then maintained one hour and the ratio of weight between waste carbon fiber and phosphoric acid were 1:1, 1:5, 1:10 and 1:15 (named CF-1, CF-5, CF-10 and CF-15). In characteristic of original waste carbon fiber and modified waste carbon fibers for CF-1, the specific surface area was from 2 to 26 m2/g. In addition, modified waste carbon fiber of CF-15 reached 90% for preparation and was the highest ratio in all the modified waste carbon fiber. The result indicated that conventional heating method using phosphoric acid maintained high yield for preparation. In the adsorption material environment application aspect, the simulation and experimental results indicated suitable Freundlich model for equilibrium and pseudo-second order model for kinetic. The adsorption experiments at 320 K, CF-5 was the highest capacity of 5.25 mg/g. However, the original waste carbon fiber was only 0.19 mg/g, and the results showed that the capacity of adsorption increased for activation of waste carbon fiber by conventional heating method using phosphoric acid.

GwGung e 龔國文. "The study of anaerobic fluidized bed process treating purified terephthalic acid manufacturing wastewater". Thesis, 1995. http://ndltd.ncl.edu.tw/handle/77919929412107205155.

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碩士
國立成功大學
環境工程研究所
83
Purified terephthalic acid (PTA) is the major material of synthetic fiber in Taiwan, the PTA manufacturing wastewater contributed to a large quantity of pollutants (more than 25,000 CMD) and high strength of aromatic compounds (COD>5000 mg/L) which are refractory to biodegradation. After one-year study on wastewater characterization, the major constituents were identified as terephthalic acid (TA), acetic acid, toluic acid, and benzoic acid, etc. A series of BMP batch tests was conducted to investigate the anaerobic biodegradability, the specific methane production rate, the biogas conversion percentage of the acclimated sludge degrading the real PTA wastewater. An innovative technology of rapid starting-up in an anaerobic GAC fluidized bed was established with four replicated experiments. A large amount of the inoculated sludge was physically attached onto the GAC media within three days of batch recirculation. During the first phase of continuous flow in fluidized bed process, the anaerobic microbes were acclimated to degrade terephthalic acid. This enrichment culture took 218 days. Then, a large amount of the digested swine sludge was inoculated to enhance the microbial diversity and to increase the total biomass. After 70 days of the second phase, the volumetric loading of the fluidized bed increased to 2.47±1.17 kgCOD/m3-d, with an improved removal efficiency of terephthalic acid up to 53.3±32.3%. The thickness of biofilm attached on GAC was measured as 0.55 mm with an electronic microscope. The microbial morphology demonstrated that the filamentous structure of chained long-rod bacteria was grown out of the GAC cavern. The filamentous bacteria and the extracellular polymers expanded and formed a thick biofilm attached on the GAC surface that could tend to the hydraulic shear stress of flow fluidization. Therefore, the anaerobic fluidized bed process achieved more stable performance.

Libri sul tema "Phosphoric acid manufacturing process":

Frazier, A. W. Redistribution of impurities in wet-process phosphoric acid / A.W. Frzier, Y.K. Kim. Muscle Shoals, Ala: National Fertilizer Development Center, Tennessee Valley Authority, 1988.

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Norwood, Verrill M. Characterization of flourine-, aluminum-, silicon-, and phosphorus-containing complexes in wet-process phosphoric acid using nuclear magnetic resonance spectroscopy. Muscle Shoals, Ala: Chemical Research, Tennessee Valley Authority, National Fertilizer Development Center, 1989.

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El-Shall, Hassan E. Decreasing iron content in wet-process phosphoric acid: Final report. Bartow, Fla. (1855 W. Main St., Bartow 33830): Florida Institute of Phosphate Research, 2001.

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Becker, Pierre. Phosphates and phosphoric acid: Raw materials, technology, and economics of the wet process. 2^a ed. New York: M. Dekker, 1989.

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Becker, Pierre, a cura di. Phosphates and phosphoric acid: Raw materials, technology, and economics of the wet process. 6^a ed. New York: M. Dekker, 1989.

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Walsh, A. J. Development of an analytical method for the determination of dibutyl butyl phosphonate in wet process phosphoric acid. Wolverhampton: University of Wolverhampton, 1994.

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Craig, John Munro. Fluoride Removal from Wet-Process Phosphoric Acid Reactor Gases. Franklin Classics Trade Press, 2018.

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Craig, John Munro. Fluoride Removal from Wet-Process Phosphoric Acid Reactor Gases. Creative Media Partners, LLC, 2018.

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Craig, John Munro. Fluoride Removal from Wet-Process Phosphoric Acid Reactor Gases. Creative Media Partners, LLC, 2018.

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Level II audit of terephthalic acid smoke grenade manufacturing process: Pine Bluff Arsenal, AR. [Champaign, IL]: US Army Corps of Engineers, Construction Engineering Research Laboratories, 1997.

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Capitoli di libri sul tema "Phosphoric acid manufacturing process":

Sluis, S., e G. M. Rosmalen. "A Clean Technology Phosphoric Acid Process". In Environmental Technology, 153–54. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3663-8_20.

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Ukeles, S. D., I. Raz, G. Friedman e L. Kogan. "Effluent treatment in IMI Phosphoric Acid Process". In Hydrometallurgy ’94, 1059–71. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1214-7_73.

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Tarpeh, William A., Brandon D. Clark, Kara L. Nelson e Kevin D. Orner. "Reimagining Excreta as a Resource: Recovering Nitrogen from Urine in Nairobi, Kenya". In Introduction to Development Engineering, 429–62. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-86065-3_16.

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AbstractOnly 10–15% of Nairobi’s informal settlements are sewered, and these sewer pipes are often broken or clogged. In addition to posing a threat to human health, human waste contains high concentrations of nitrogen and phosphorus, which can wreak ecological harm when improperly discharged. However, nitrogen and phosphorus are also key ingredients for fertilizers used in agricultural food production. This case study follows the development of ElectroSan, a pre-revenue process engineering spinoff that focuses on novel processes for converting urine into valuable products. The two primary technologies ElectroSan uses to extract nitrogen from urine are ion exchange and electrochemical stripping. The efficacy of these technologies (primarily ion exchange) was investigated through field trials enabled by a partnership with Sanergy in Nairobi, Kenya. Through experimentation and market analyses, Dowex Mac 3 was identified as the most suitable resin for nitrogen recovery. Additionally, this process could produce ammonium sulfate fertilizer at a lower cost to competing products and also had the advantages of providing a steady, local supply of fertilizer that could be applied by fertigation. This approach thus avoided local ecosystem damage from improper disposal, created local economic opportunities, and partially closed the nutrient cycle locally. Life cycle and techno-economic assessments (in the context of San Francisco, CA) found that the sulfuric acid used for regeneration of the resin represented 70% of greenhouse gas emissions and energy input (embedded energy from the manufacturing process). Providing insights into the importance of partnerships, being adaptive with assumptions, and the realities of conducting fieldwork, the ElectroSan research project continues to explore the valorization of urine and has expanded to new contexts, including other parts of Kenya (with Sanivation) and Dakar, Senegal (with Delvic Sanitation Initiatives).

Mochiyama, T. "Industrial-Scale Manufacturing of Phosphoric Acid Using Sewage Sludge Ash". In Phosphorus Recovery and Recycling, 133–42. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-8031-9_7.

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Tjioe, T. T., P. Weij e G. M. Rosmalen. "Removal of Cadmium by Anion Exchange in a Wet Phosphoric Acid Process". In Environmental Technology, 145–47. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3663-8_17.

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Ashar, Navin G., e Kiran R. Golwalkar. "Cold Process of Manufacturing Sulfuric Acid and Sulfonating Agents". In A Practical Guide to the Manufacture of Sulfuric Acid, Oleums, and Sulfonating Agents, 103–6. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-02042-6_11.

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dos Santos Mascarenhas, Jefferson, Igor Santos Araujo, Salvador Ávila Filho, Danillo Ramos Camargo, Leila Maria Aguilera Campos e Luiz Antônio Magalhães Pontes. "Improved Sulfuric Acid Discharge Through Combined Task and Risk Analysis". In Advances in Manufacturing, Production Management and Process Control, 148–58. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-80462-6_19.

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Wilhide, Wendell D., e Doris H. Ash. "Analysis of Wet-Process Phosphoric Acid and By-Product Filter Cake by X-Ray Spectrometry". In Advances in X-Ray Analysis, 221–26. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4613-2471-3_33.

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Abid, Dorra, Marwa Ben Chobba, Fatma Hached e Mongi Feki. "Degradation Resistance of Graphite in Contact with Industrial Phosphoric Acid Mixed with an Oxidizing Agent Through Dynamic and Static Approaches". In Proceedings of the 2nd International Conference on Innovative Materials, Manufacturing, and Advanced Technologies, 98–107. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-42659-9_11.

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Bonger, Zinash Tadesse, Metadel Kassahun Abera, Takele Ayanaw Habitu, Agimassie Agazie Abera, Mesfin Wogayehu Tenagashaw, Deginet Teferi, Abebaw Teshome, Taddele Andarge, Sadik Jemal Awol e Tadesse Fenta Yehuala. "Identification of Dominant Lactic Acid Bacteria and Yeast Species from Teff Injera Dough Fermentation". In Advancement of Science and Technology in Sustainable Manufacturing and Process Engineering, 133–62. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-41173-1_8.

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Atti di convegni sul tema "Phosphoric acid manufacturing process":

Bouchkira, Ilias, Abderrazak M. Latifi, Lhachmi Khamar e Saad Benjelloun. "Multi-Objective Optimization of the Digestion Tank of an Industrial Phosphoric Acid Manufacturing Process". In 2020 6th IEEE Congress on Information Science and Technology (CiSt). IEEE, 2020. http://dx.doi.org/10.1109/cist49399.2021.9357206.

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Warren, Joshua, Sujit Das e Wei Zhang. "Manufacturing Process Modeling of 100-400 kWe Combined Heat and Power Stationary Fuel Cell Systems". In ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology collocated with the ASME 2012 6th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/fuelcell2012-91183.

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Despite significant cost reductions and reliability improvements in recent decades, combined heat and power (CHP) stationary fuel cells are expected to remain relatively limited in their commercial acceptance until additional advancements are realized. In the present study, three stationary CHP fuel cell technologies — phosphoric acid (PAFC), molten carbonate (MCFC), and solid oxide (SOFC) — operating in the 100–400 kWe range were examined with process based cost models to estimate manufacturing costs and to highlight high cost steps where alternative production methods may have the greatest potential for high impact cost reduction. PAFC manufacturing costs, estimated to be $3049/kWe for a baseline manufacturing volume of 20 MWe/yr, may benefit most from reduced catalyst loading, lower cost substrates, reduced fuel processing balance of plant (BOP) costs, and near net shape bipolar plate manufacturing. MCFC manufacturing costs, while not reported in detail due to the proprietary nature of inputs employed in the model, may be reduced through advances in fuel desulfurization and stainless steel stack component manufacturing. SOFC manufacturing costs, estimated to be $1242/kWe, approach a commercially acceptable level, but significant advancements in seal and bipolar plate reliability are likely required before a commercially acceptable stack life of 40,000 hours is realized.

Tyagi, Pawan, Tobias Goulet, Denikka Brent, Kate Klein e Francisco Garcia-Moreno. "Scanning Electron Microscopy and Optical Profilometry of Electropolished Additively Manufactured 316 Steel Components". In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88339.

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Additive manufacturing (AM) can produce highly complex engineering components that are either extremely challenging for the conventional subtractive manufacturing route or not possible otherwise. High surface roughness can make an AM component highly vulnerable to premature failure during fatigue loading. Post-processing aiming to reduce surface roughness is essential to make as produced AM parts functional. We have explored electropolishing route to achieve optimum surface roughness and surface chemistry. We have performed electropolishing treatment on the steel AM parts around 70 °C in an electrolyte comprising the phosphoric acid and sulfuric acid. Profilometry and scanning electron microscopy were performed to study the electropolished and unpolished areas. Optical profilometry study showed that one needs to remove nearly ∼200 μm material from the surface to achieve very smooth surface. Electropolishing was effective in reducing the surface Ra roughness from ∼2 μm rms to ∼0.07 μm rms. Such low rms roughness makes an AM component suitable for almost every engineering application for which a smooth surface is required. Scanning electron microscopy revealed that electropolished area on AM component possessed distinctively different microstructure as compared to the untreated surface of an AM component. We also conducted the compositional analysis of the electropolished area to investigate the possibility of residual contamination from the electropolishing process. Our study revealed that electropolishing is a highly promising route for improving the surface finishing of AM components.

Rasool, Tabinda, Syed Rehan Ahmed, Iqra Ather, Madeeha Sadia, Rashid Khan e Ali Raza Jafri. "Synthesis and Characterization of Hydroxyapatite Using Egg-Shell". In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51933.

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Advancement in materials science and manufacturing processes helps in expanding the application span of materials in biotechnology. The technological development of biocompatible materials aids in improving health conditions, cancerous treatment, organ implants, and as well as provides several techniques to patient treatment. Hydroxyapatite (HAP) is considered as a potential material for orthopedics and dental implants due to its eminent biocompatibility and natural apatite characteristics. It is regarded as viable and cost effective solution of many biomedical applications. Major challenges in expanding the application span of HAP include obtaining optimum mechanical, chemical, and biological properties simultaneously while making its manufacturing processes cost effective. The main purpose of the current work is to synthesize and characterize high strength HAP with high degree of crystallinity and purity, which could be able to fulfill the requirements of modern biological materials. In this work, egg-shell which is considered as garbage is utilized as calcium source to synthesize HAP. Initially, egg-shells are properly cleaned with distilled water and dried. Ball milling operation is used to produce egg-shell particles of nano to micron range. The particles then mixed with controlled amount of phosphoric acid. The mixture is then sintered by heat treating at 900°C for 2 hours. The heat treatment (sintering) process is used to enhance the density as well as strength of egg-shell material. After synthesis of HAP, it is characterized through X-ray diffraction, scanning electron microscopy, and laser particle analyzer. Composition of HAP is investigated through XRD. Furthermore, surface topography of nano-crystalline HAP powder is measured through Scanning Electron Microscope while particle size distribution is found through laser particle analyzer. It is found that the addition of phosphoric acid in milled egg-shell and heat treatment give rise HAP in the sample. In addition, particle size varies from hundreds of nanometers to several micrometers. The results and analysis of the current work may provide insight of different properties which may lead to the development of optimum and cost effective HAP material. The current study could be further extended in increasing application envelop of biocompatible materials.

Bhamidipati, Kanthi Latha, e Tequila A. L. Harris. "Numerical Analysis of the Effects of Processing Conditions on the Casting of High Temperature PEMFC Membrane Solutions". In ASME 2009 7th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2009. http://dx.doi.org/10.1115/fuelcell2009-85064.

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Polymer Electrolyte Membranes have numerous failure modes resulting from chemical, mechanical and thermal influences. The conventional state–of–the–art low temperature Nafion® membrane is susceptible to such failures due to its sensitivity to high temperatures and the presence of carbon monoxide (CO) in the reactant streams, which poisons the platinum catalyst at low temperatures. To circumvent these problems, novel, cost-effective membranes that operate at high temperatures (>120°C) and low humidity levels, such as phosphoric acid doped polybenzimidazole (PBI/PA) membranes, have been developed. However, an optimized manufacturing process for the PBI membranes is required to negate failure mechanisms that are mechanically and thermally induced; e.g., gas cross-over due to pinholes. This paper focuses on understanding defects arising in the fluid state during manufacturing, using Computational Fluid Dynamics (CFD) techniques. Simulations are performed to understand the effects of processing conditions (substrate velocity, inlet velocity and temperature) on the quality of the cast and pressure drop through the system. It is found that processing speeds affected both the cast quality and pressure drop, while temperature only affected the pressure drop.

Share, Dylan, Lakshmi Krishnan, Dan Walczyk, David Lesperence e Raymond Puffer. "Thermal Sealing of Membrane Electrode Assemblies for High-Temperature PEM Fuel Cells". In ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2010. http://dx.doi.org/10.1115/fuelcell2010-33227.

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The main challenges of low temperature (80–120°C) Nafion-based PEM technology are (1) low cathode performance due to slow kinetics of the oxygen reduction reaction (2) high material costs (3) considerable system design and operation for water management (4) low tolerance to impurities in fuel stream and (5) low quality heat resulting in low overall system efficiency. Furthermore, Nafion membranes achieve maximum conductivity only when hydrated, limiting their operation to <100 C. Operating the fuel cell >100 C is desirable to overcome the aforementioned limitations. Though several high temperature membranes for PEMFC have been developed, polybenzimidazole (PBI) membranes with high Phosphoric acid content (>90%) developed by BASF Fuel cell are currently seeing commercial interest. The most vital step in MEA manufacturing is the sealing of the membrane in between the electrode-substrate assembly to form a five-layer architecture. Currently, MEA sealing is done by a thermal seal process. This paper examines the effect of thermal sealing process parameters, namely (1) sealing temperature (2) percent compression (3) sealing time and (4) manufacturer-specified post-processing after sealing on the fuel cell performance. A design of experiments was developed with these input process parameters and the polarization behavior during single cell operation, as well as internal cell resistance, were analyzed as performance parameters. ANOVA analysis revealed the statistically significant input factors for the thermal sealing process, which are essential for the rapid and high-quality manufacturing of membrane electrode assemblies for high temperature fuel cells. Furthermore, a multiphysics model has been developed to allow for further refinement of the MEA sealing process.

Wing, John. "Hemi Process for Energy-Efficient Phosphoric Acid". In Carbon Management Technology Conference. Carbon Management Technology Conference, 2012. http://dx.doi.org/10.7122/150626-ms.

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Messnaoui, B. "A Steady-State Simulation of Phosphoric Acid Concentration Process". In The Proceedings of the Multiconference on "Computational Engineering in Systems Applications". IEEE, 2006. http://dx.doi.org/10.1109/cesa.2006.313514.

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Messnaoui, B. "A Steady-State Simulation of Phosphoric Acid Concentration Process". In Multiconference on "Computational Engineering in Systems Applications. IEEE, 2006. http://dx.doi.org/10.1109/cesa.2006.4281835.

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Chien, Verna Chang, Chi-Ming Yang e Chi-Chang Hu. "The Etching of Silicon Nitride in Phosphoric Acid with Novel Single Wafer Processor". In 2019 30th Annual SEMI Advanced Semiconductor Manufacturing Conference (ASMC). IEEE, 2019. http://dx.doi.org/10.1109/asmc.2019.8791787.

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Rapporti di organizzazioni sul tema "Phosphoric acid manufacturing process":

Allen, Jeffrey, e Guillermo Riveros. Mesoscale multiphysics simulations of the fused deposition additive manufacturing process. Engineer Research and Development Center (U.S.), maggio 2024. http://dx.doi.org/10.21079/11681/48595.

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As part of an ongoing effort to better understand the multiscale effects of fused deposition additive manufacturing, this work centers on a multiphysics, mesoscale approach for the simulation of the extrusion and solidification processes associated with fused deposition modeling. Restricting the work to a single line scan, we focus on the application of polylactic acid. In addition to heat, momentum, and mass transfer, the solid-liquid–vapor interface is simulated using a front-tracking, level-set method. The results focus on the evolving temperature, viscosity, and volume fraction and are cast within a set of parametric studies to include the nozzle and extrusion velocities as well as the extrusion temperature. Among other findings, it was observed that fused deposition modeling can be effectively modeled using a front-tracking method (i.e., the level-set method) in concert with a moving mesh and temperature-dependent porosity function.

Rouseff, Russell L., e Michael Naim. Characterization of Unidentified Potent Flavor Changes during Processing and Storage of Orange and Grapefruit Juices. United States Department of Agriculture, settembre 2002. http://dx.doi.org/10.32747/2002.7585191.bard.

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Citrus juice flavor quality traditionally diminishes after thermal processing and continuously during storage. Our prior studies found that four of the five most potent off-aromas formed during orange juice storage had not been identified. The primary emphasis of this project was to characterize and identify those potent flavor degrading aroma volatiles so that methods to control them could be developed and final flavor quality improved. Our original objectives included: 1 Isolate and characterize the most important unidentified aroma impact compounds formed or lost during pasteurization and storage. 2. Determination of thiamine and carotenoid thermal decomposition and Strecker degradation pathways in model solutions as possible precursors for the unidentified off-flavors. 3. Evaluate the effectiveness of an "electronic nose" to differentiate the headspace aromas of from untreated and heat pasteurized orange and grapefruit juices. 4. Use model systems of citrus juices to investigate the three possible precursor pathways (from 2) for flavor impact compounds formed or lost during pasteurization or storage. RESULTS - The components responsible for citrus storage off flavors and their putative precursors have now been identified. Certain carotenoids (b-carotene) can thermally degrade to produce b-ionone and b-damascenone which are floral and tobacco smelling respectively. Our GC-O and sensory experiments indicated that b-damascenone is a potential storage off-flavor in orange juice. Thiamine (Vitamin B1) degradation produces 2-methyl-3-furan thiol, MFT, and its dimer bis(2- methyl-3-furyl) disulfide which both produce meaty, savory aromas. GC-O and sensory studies indicated that MFT is another storage off-flavor. Methional (potato aroma) is another off flavor produced primarily from the reaction of the native amino acid, methionine, and oxidized ascorbic acid (vitamin C). This is a newly discovered pathway for the production of methional and is more dominant in juices than the classic Maillard reaction. These newly identified off flavors diminish the flavor quality of citrus juices as they distort the flavor balance and introduce non-typical aromas to the juice flavor profile. In addition, we have demonstrated that some of the poor flavor quality citrus juice found in the market place is not only from the production of these and other off flavors but also due to the absence of desirable flavor components including several potent aldehydes and a few esters. The absence of these compounds appears to be due to incomplete flavor volatile restoration after the making of juice concentrates. We are the first to demonstrate that not all flavor volatiles are removed along with water in the production of juice concentrate. In the case of grapefruit juice we have documented which flavor volatiles are completely removed, which are partially removed and which actually increase because of the thermal process. Since more that half of all citrus juices is made into concentrate, this information will allow producers to more accurately restore the original flavor components and produce a juice with a more natural flavor. IMPLICATIONS - We have shown that the aroma of citrus juices is controlled by only 1-2% of the total volatiles. The vast majority of other volatiles have little to no direct aroma activity. The critical volatiles have now been identified. The ability to produce high quality citrus juices requires that manufacturers know which chemical components control aroma and flavor. In addition to identifying the critical flavor components (both positive and negative), we have also identified several precursors. The behavior of these key aroma compounds and their precursors during common manufacturing and storage conditions has been documented so manufacturers in Israel and the US can alter production practices to minimize the negative ones and maximize the positive ones.