Carlos Dantas - Academia.edu (original) (raw)

Papers by Carlos Dantas

International Journal of Metrology and Quality Engineering, 2013

The solid flow in air-catalyst in circulating fluidized bed was simulated with CFD model to obtai... more The solid flow in air-catalyst in circulating fluidized bed was simulated with CFD model to obtain axial and radial distribution. Therefore, project parameters were confirmed and steady state operation condition was improved. Solid holds up axial end radial profiles simulation and comparison with gamma transmission measurements are in a good agreement. The transmission signal from an 241 Am radioactive source was evaluated in NaI(Tl) detector coupled to multichannel analyzer. This non intrusive measuring set up is installed at riser of a cold pilot unit to determine parameters of FCC catalyst flow at several concentrations. Mass flow rate calculated by combining solid hold up and solid phase velocity measurements was compared with catalyst inlet measured at down-comer. Evaluation in each measured parameter shows that a relative combined uncertainty of 6% in a 95% interval was estimated. Uncertainty analysis took into account a significant correlation in scan riser transmission measurements. An Eulerian approach of CFD model incorporating the kinetic theory of granular flow was adopted to describe the gas-solid two-phase flows in a multizone circulating reactor. Instantaneous and local gas-particle velocity, void fraction and turbulent parameters were obtained and results are shown in 2 D and 3D graphics.

Proceeding Series of the Brazilian Society of Computational and Applied Mathematics, 2015

Brazilian Journal of Radiation Sciences, 2020

O Craqueamento Catalítico Fluido (FCC) é um processo utilizado na indústria petroquímica para con... more O Craqueamento Catalítico Fluido (FCC) é um processo utilizado na indústria petroquímica para converter algumas frações do petróleo que são mais pesadas em frações mais leves, como a gasolina e o GLP, por exemplo. A conversão ocorre devido à introdução de partículas sólidas denominadas catalisadores no interior de risers industriais de FCC. O catalisador aquecido entra em contato com gasóleo líquido na base do riser, promovendo a vaporização e o craqueamento dos vapores de hidrocarbonetos que compõem o gasóleo. Os parâmetros físicos e de fluxo da partícula, na maioria das vezes, são determinados por meio do uso de técnicas não intrusivas envolvendo a tomografia por transmissão gama, que possuem a vantagem de não pertubar o sistema. Este estudo teve por objetivo caracterizar a morfologia, composição química e densidade aparente do catalisador de FCC em estado ativado, bem como, avaliar o coeficiente de atenuação linear e mássico através de simulações no código MCNPX e irradiação experimental utilizando fontes radioativas de Césio-137 e Amerício-241 e comparar com as informações extraídas do XCOM do NIST. Os dados de saída das simulações e experimentos foram introduzidos na equação de Beer-lambert, aqui adaptada para a equação linear reduzida de uma reta, onde foi aplicado o coeficiente de determinação como fator de ajuste, que atestou o bom funcionamento do modelo proposto.

Analytica Chimica Acta, 1979

A convenient approach is proposed for the quantitation of elemental cofactors in proteins and the... more A convenient approach is proposed for the quantitation of elemental cofactors in proteins and the determination of metal:protein stoichiometry, based on energy dispersive X-ray fluorescence spectroscopy (EDXRF). The analysis of proteins containing the metals Cu, Fe, Zn, Ca and also the non-metallic element P are shown as a demonstration of the generality of the method. In general, the reported method gives a limit of detection (LOD) and limit of quantification (LOQ) values in the low ppm range and requires only a few microliters of protein sample at micromolar concentrations. Moreover, sample preparation does not require any digestion steps before the analysis. The expected metal:protein stoichiometry was observed for each protein analyzed, highlighting the precision and accuracy of the method in all the tested cases. Furthermore, it is shown that the method is compatible with multimeric proteins and those with post-translational modifications such as glycosylation.

Anais do XX Congresso Brasileiro de Engenharia Química

RESUMO-O presente trabalho propõe uma modelagem tridimensional do escoamento ascendente das fases... more RESUMO-O presente trabalho propõe uma modelagem tridimensional do escoamento ascendente das fases fluida e particulada de um riser, em uma unidade piloto à frio (UPF), semelhante à um leito fluidizado circulante (CFB), por meio da aplicação da fluidodinâmica computacional (CFD). Reatores tipo CFB são amplamente utilizados em processo de FCC (craqueamento catalítico fluido) na industria do refino de petróleo, sobretudo em petróleos pesados de cadeia longa. O riser é o local onde ocorrem as reações que dão origem aos produtos de alto valor agregado, e seu desepenho dependente das características hidrodinâmicas do leito. Estudou-se diferentes condições de fluxo mássico de catalisador e velocidade superficial do gás em um riser construído em material transparente, com 5.64 m de altura e 0.092 m de diâmetro. Os resultados das simulações foram comparados com os dados experimentais de velocidade e fração volumétrica de sólidos, obtidos a partir métodos não-invasivos, por meio de transmissão de radiação gama. As medidas experimentais foram realizadas ao longo de diferentes posições axiais na UPF. As frações volumétricas e velocidade do catalisador foram obtidas em seções de teste que possuem fontes de amerício (Am-241) e detector blindados, posicionadas axialmente à 0.650, 1.384 e 3.424 metros. O detector utilizado foi um cintilador de NaI(Tl) de 2" x 2". A modelagem foi capaz de prever e representar as principais características do escoamento em regime de fluidização rápida.

Materials Research

Gamma tomography was used in this work to evaluate the recurrent defects in welding processes in ... more Gamma tomography was used in this work to evaluate the recurrent defects in welding processes in naval steel sheets. It was used a first-generation equipment consisting of a source of Cesium-137, with activity of the order of 200 mCi, coupled to a Thallium-doped Sodium Iodide detector, NaI (Tl). For the study, specimens were produced in ASTM A131-AH36 steel sheets with 13.7 mm thickness; all welded by Metal Active Gas process. One reference sample was fabricated, with no macroscopically measurable defects and another welded under wind conditions producing a weld bead with different types of discontinuities. The microstructural characterization of welded joints made possible a qualitative evaluation between defective joints, in relation to the joint without defects. With the data of the tomography, 3D graphics were drawn that enabled the statistical survey and analysis of clusters of the results that allowed the localization and the dimensioning of the discontinuities that appeared as counting peaks in these graphics. It was revealed that the defective welding showed porosity of up to 39.28% of its volume, and the acceptable size crack must be less than 1 mm based on ASME-B31.3, showing the viability of the tomography for this type of nondestructive analysis.

Weld discontinuity in steel tubes was investigated and dimensioned in a data analysis sequence. T... more Weld discontinuity in steel tubes was investigated and dimensioned in a data analysis sequence. The correlation matrix, cosine distance and hierarchical cluster were applied as multivariate data processing in this analysis. Welded rings of 9236 mm 3 were scanned in gamma ray CT in test tubes and compared with steel base and references. The discontinuity volume detected in the welded rings was assessed based on the pixel volume in data sampling. By modeling gamma ray trajectories and rotation angles in CT scanning, a discontinuity of 0.3 mm was determined and a limit detection of 23 mm 3 was obtained.

International Journal of Metrology and Quality Engineering, 2013

The solid flow in air-catalyst in circulating fluidized bed was simulated with CFD model to obtai... more The solid flow in air-catalyst in circulating fluidized bed was simulated with CFD model to obtain axial and radial distribution. Therefore, project parameters were confirmed and steady state operation condition was improved. Solid holds up axial end radial profiles simulation and comparison with gamma transmission measurements are in a good agreement. The transmission signal from an 241 Am radioactive source was evaluated in NaI(Tl) detector coupled to multichannel analyzer. This non intrusive measuring set up is installed at riser of a cold pilot unit to determine parameters of FCC catalyst flow at several concentrations. Mass flow rate calculated by combining solid hold up and solid phase velocity measurements was compared with catalyst inlet measured at down-comer. Evaluation in each measured parameter shows that a relative combined uncertainty of 6% in a 95% interval was estimated. Uncertainty analysis took into account a significant correlation in scan riser transmission measurements. An Eulerian approach of CFD model incorporating the kinetic theory of granular flow was adopted to describe the gas-solid two-phase flows in a multizone circulating reactor. Instantaneous and local gas-particle velocity, void fraction and turbulent parameters were obtained and results are shown in 2 D and 3D graphics.

Proceeding Series of the Brazilian Society of Computational and Applied Mathematics, 2015

Brazilian Journal of Radiation Sciences, 2020

O Craqueamento Catalítico Fluido (FCC) é um processo utilizado na indústria petroquímica para con... more O Craqueamento Catalítico Fluido (FCC) é um processo utilizado na indústria petroquímica para converter algumas frações do petróleo que são mais pesadas em frações mais leves, como a gasolina e o GLP, por exemplo. A conversão ocorre devido à introdução de partículas sólidas denominadas catalisadores no interior de risers industriais de FCC. O catalisador aquecido entra em contato com gasóleo líquido na base do riser, promovendo a vaporização e o craqueamento dos vapores de hidrocarbonetos que compõem o gasóleo. Os parâmetros físicos e de fluxo da partícula, na maioria das vezes, são determinados por meio do uso de técnicas não intrusivas envolvendo a tomografia por transmissão gama, que possuem a vantagem de não pertubar o sistema. Este estudo teve por objetivo caracterizar a morfologia, composição química e densidade aparente do catalisador de FCC em estado ativado, bem como, avaliar o coeficiente de atenuação linear e mássico através de simulações no código MCNPX e irradiação experimental utilizando fontes radioativas de Césio-137 e Amerício-241 e comparar com as informações extraídas do XCOM do NIST. Os dados de saída das simulações e experimentos foram introduzidos na equação de Beer-lambert, aqui adaptada para a equação linear reduzida de uma reta, onde foi aplicado o coeficiente de determinação como fator de ajuste, que atestou o bom funcionamento do modelo proposto.

Analytica Chimica Acta, 1979

A convenient approach is proposed for the quantitation of elemental cofactors in proteins and the... more A convenient approach is proposed for the quantitation of elemental cofactors in proteins and the determination of metal:protein stoichiometry, based on energy dispersive X-ray fluorescence spectroscopy (EDXRF). The analysis of proteins containing the metals Cu, Fe, Zn, Ca and also the non-metallic element P are shown as a demonstration of the generality of the method. In general, the reported method gives a limit of detection (LOD) and limit of quantification (LOQ) values in the low ppm range and requires only a few microliters of protein sample at micromolar concentrations. Moreover, sample preparation does not require any digestion steps before the analysis. The expected metal:protein stoichiometry was observed for each protein analyzed, highlighting the precision and accuracy of the method in all the tested cases. Furthermore, it is shown that the method is compatible with multimeric proteins and those with post-translational modifications such as glycosylation.

Anais do XX Congresso Brasileiro de Engenharia Química

RESUMO-O presente trabalho propõe uma modelagem tridimensional do escoamento ascendente das fases... more RESUMO-O presente trabalho propõe uma modelagem tridimensional do escoamento ascendente das fases fluida e particulada de um riser, em uma unidade piloto à frio (UPF), semelhante à um leito fluidizado circulante (CFB), por meio da aplicação da fluidodinâmica computacional (CFD). Reatores tipo CFB são amplamente utilizados em processo de FCC (craqueamento catalítico fluido) na industria do refino de petróleo, sobretudo em petróleos pesados de cadeia longa. O riser é o local onde ocorrem as reações que dão origem aos produtos de alto valor agregado, e seu desepenho dependente das características hidrodinâmicas do leito. Estudou-se diferentes condições de fluxo mássico de catalisador e velocidade superficial do gás em um riser construído em material transparente, com 5.64 m de altura e 0.092 m de diâmetro. Os resultados das simulações foram comparados com os dados experimentais de velocidade e fração volumétrica de sólidos, obtidos a partir métodos não-invasivos, por meio de transmissão de radiação gama. As medidas experimentais foram realizadas ao longo de diferentes posições axiais na UPF. As frações volumétricas e velocidade do catalisador foram obtidas em seções de teste que possuem fontes de amerício (Am-241) e detector blindados, posicionadas axialmente à 0.650, 1.384 e 3.424 metros. O detector utilizado foi um cintilador de NaI(Tl) de 2" x 2". A modelagem foi capaz de prever e representar as principais características do escoamento em regime de fluidização rápida.

Materials Research

Gamma tomography was used in this work to evaluate the recurrent defects in welding processes in ... more Gamma tomography was used in this work to evaluate the recurrent defects in welding processes in naval steel sheets. It was used a first-generation equipment consisting of a source of Cesium-137, with activity of the order of 200 mCi, coupled to a Thallium-doped Sodium Iodide detector, NaI (Tl). For the study, specimens were produced in ASTM A131-AH36 steel sheets with 13.7 mm thickness; all welded by Metal Active Gas process. One reference sample was fabricated, with no macroscopically measurable defects and another welded under wind conditions producing a weld bead with different types of discontinuities. The microstructural characterization of welded joints made possible a qualitative evaluation between defective joints, in relation to the joint without defects. With the data of the tomography, 3D graphics were drawn that enabled the statistical survey and analysis of clusters of the results that allowed the localization and the dimensioning of the discontinuities that appeared as counting peaks in these graphics. It was revealed that the defective welding showed porosity of up to 39.28% of its volume, and the acceptable size crack must be less than 1 mm based on ASME-B31.3, showing the viability of the tomography for this type of nondestructive analysis.

Weld discontinuity in steel tubes was investigated and dimensioned in a data analysis sequence. T... more Weld discontinuity in steel tubes was investigated and dimensioned in a data analysis sequence. The correlation matrix, cosine distance and hierarchical cluster were applied as multivariate data processing in this analysis. Welded rings of 9236 mm 3 were scanned in gamma ray CT in test tubes and compared with steel base and references. The discontinuity volume detected in the welded rings was assessed based on the pixel volume in data sampling. By modeling gamma ray trajectories and rotation angles in CT scanning, a discontinuity of 0.3 mm was determined and a limit detection of 23 mm 3 was obtained.