Solubility of Ethene in Water and in a Medium for the Cultivation of a Bacterial Strain

The solubility of ethene in water and in the fermentation medium of Xanthobacter Py(2) was determined with a Ben-Naim-Baer type apparatus. The solubility measurements were carried out in the temperature range of (293.15 to 323.15) K and at atmospheric pressure with a precision of about +/- 0.3 %. The Ostwald coefficients, the mole fractions of the dissolved ethene, at the gas partial pressure of 101.325 kPa, and the Henry coefficients, at the water vapor pressure, were calculated using accurate thermodynamic relations. A comparison between the solubility of ethene in water and in the cultivation medium has shown that this gas is about 2.4 % more soluble in pure water. On the other hand, from the solubility temperature dependence, the Gibbs energy, enthalpy, and entropy changes for the process of transferring the solute from the gaseous phase to the liquid solutions were also determined. Moreover, the perturbed-chain statistical associating fluid theory equation of state (PC-SAFT EOS) model was used for the prediction of the solubility of ethene in water. New parameters, k(ij), are proposed for this system, and it was found that using a ky temperature-dependent PC-SAFT EOS describes more accurately the behavior solubilities of ethene in water at 101.325 kPa, improving the deviations to 1 %.

Optimal location of gas supply units in natural gas system network

Natural gas industry has been confronted with big challenges: great growth in demand, investments on new GSUs – gas supply units, and efficient technical system management. The right number of GSUs, their best location on networks and the optimal allocation to loads is a decision problem that can be formulated as a combinatorial programming problem, with the objective of minimizing system expenses. Our emphasis is on the formulation, interpretation and development of a solution algorithm that will analyze the trade-off between infrastructure investment expenditure and operating system costs. The location model was applied to a 12 node natural gas network, and its effectiveness was tested in five different operating scenarios.

Optimization model for medium term natural gas commitment

In this paper we study the optimal natural gas commitment for a known demand scenario. This study implies the best location of GSUs to supply all demands and the optimal allocation from sources to gas loads, through an appropriate transportation mode, in order to minimize total system costs. Our emphasis is on the formulation and use of a suitable optimization model, reflecting real-world operations and the constraints of natural gas systems. The mathematical model is based on a Lagrangean heuristic, using the Lagrangean relaxation, an efficient approach to solve the problem. Computational results are presented for Iberian and American natural gas systems, geographically organized in 65 and 88 load nodes, respectively. The location model results, supported by the computational application GasView, show the optimal location and allocation solution, system total costs and suggest a suitable gas transportation mode, presented in both numerical and graphic supports.

Natural gas system operation: lagrangean optimization techniques

To comply with natural gas demand growth patterns and Europe´s import dependency, the gas industry needs to organize an efficient upstream infrastructure. The best location of Gas Supply Units – GSUs and the alternative transportation mode – by phisical or virtual pipelines, are the key of a successful industry. In this work we study the optimal location of GSUs, as well as determining the most efficient allocation from gas loads to sources, selecting the best transportation mode, observing specific technical restrictions and minimizing system total costs. For the location of GSUs on system we use the P-median problem, for assigning gas demands nodes to source facilities we use the classical transportation problem. The developed model is an optimisation-based approach, based on a Lagrangean heuristic, using Lagrangean relaxation for P-median problems – Simple Lagrangean Heuristic. The solution of this heuristic can be improved by adding a local search procedure - the Lagrangean Reallocation Heuristic. These two heuristics, Simple Lagrangean and Lagrangean Reallocation, were tested on a realistic network - the primary Iberian natural gas network, organized with 65 nodes, connected by physical and virtual pipelines. Computational results are presented for both approaches, showing the location gas sources and allocation loads arrangement, system total costs and gas transportation mode.

Exposure to dust in poultry: the importance of task differences for detailed exposure assessment

Dust is a complex mixture of particles of organic and inorganic origin and different gases absorbed in aerosol droplets. In a poultry unit include dried faecal matter and urine, skin flakes, ammonia, carbon dioxide, pollens, feed and litter particles, feathers, grain mites, fungi spores, bacteria, viruses and their constituents. Dust particles vary in size and differentiation between particle size fractions is important in health studies in order to quantify penetration within the respiratory system. A descriptive study was developed in order to assess exposure to particles in a poultry unit during different operations, namely routine examination and floor turn over. Direct-reading equipment was used (Lighthouse, model 3016 IAQ). Particle measurement was performed in 5 different sizes (PM0.5; PM1.0; PM2.5; PM5.0; PM10). The chemical composition of poultry litter was also determined by neutron activation analysis. Normally, the litter of poultry pavilions is turned over weekly and it was during this operation that the higher exposure of particles was observed. In all the tasks considered PM5.0 and PM10.0 were the sizes with higher concentrations values. PM10 is what turns out to have higher values and PM0.5 the lowest values. The chemical element with the highest concentration was Mg (5.7E6 mg.kg-1), followed by K (1.5E4 mg.kg-1), Ca (4.8E3 mg.kg-1), Na (1.7E3 mg.kg-1), Fe (2.1E2 mg.kg-1) and Zn (4.2E1 mg.kg-1). This high presence of particles in the respirable range (<5–7μm) means that poultry dust particles can penetrate into the gas exchange region of the lung. Larger particles (PM10) present a range of concentrations from 5.3E5 and 3.0E6 mg/m3.

Influência do volume vesical na diminuição da dose recebida na bexiga e no PTV em doentes com tumor de reto tratados com belly-board

Introdução: O cancro retal continua a ser um dos principais problemas de saúde a nível mundial, sendo a toxicidade gastro-intestinal e génito-urinária os efeitos tardios da radioterapia mais reportados. A utilização da Belly-Board para minimizar essa toxicidade, reduzindo o volume de bexiga e intestino delgado irradiados é recomendada. No entanto, o protocolo mais adequado para o volume vesical nestes doentes é ainda tema de controvérsia. Objetivo: Avaliar a influência do volume vesical na dose recebida na bexiga e no PTV, em doentes com tumor de reto, posicionados em decúbito ventral, com belly-board. Materiais e Métodos: 38 doentes com tumor de reto tratados no CHBM, agrupados em dois grupos: o 1º grupo, com 19 doentes que realizaram tratamento com bexiga cheia e o 2º grupo, com 19 doentes que realizaram tratamento com bexiga vazia. Os dados foram obtidos através dos HDV’s e foram comparadas as doses máximas no PTV e a percentagem de volume de bexiga que recebe 50Gy. Foi utilizado o teste estatístico U-Mann Whitney com um nível de significância de 0,05. A hipótese de pesquisa deste estudo propõe que os dois grupos diferem significativamente entre si e a hipótese nula propõe que os dois grupos não diferem significativamente entre si, para ambas as variáveis. Resultados: Não se observaram diferenças estatisticamente significativas entre os grupos no que diz respeito à dose máxima no PTV. No que se refere à percentagem de volume de bexiga que recebe 50Gy verificaram-se diferenças estatisticamente significativas, tendo o grupo de doentes que realizaram tratamento com bexiga cheia apresentado valores mais baixos. Conclusões: Este estudo demonstrou o benefício da utilização do protocolo de bexiga cheia em doentes com tumor de reto tratados com belly-board, na diminuição da percentagem de volume de bexiga que recebe 50Gy.

Estudos de absorção de CO2 com soluções aminadas

A absorção química de dióxido de carbono (CO2) através de soluções aquosas de aminas tem sido estudada nos últimos anos devido à preocupação ambiental face ao aquecimento global. Nestes estudos, foram tidos como principais objectivos a realização de ensaios preliminares de absorção e desabsorção de CO2 em soluções aquosas de aminas bem como a construção de uma instalação piloto para a mesma finalidade. Inicialmente, a nível laboratorial, procedeu-se à absorção de CO2 através de soluções aquosas de aminas. As aminas utilizadas nestes estudos foram a monoetanolamina (MEA), etilenodiamina (EDA), 1,6- hexanodiamina (HDA) e piperazina anidra (PZ). A absorção de CO2 através destas aminas foi realizada experimentalmente às condições normais de pressão e temperatura. A concentração das soluções aquosas foi de 20% em massa de cada amina. Foram também realizados estudos de regeneração das soluções aquosas de aminas saturadas de CO2 em banho de glicerina, para determinar as condições de regeneração. Para além disso, observou-se o estado físico das aminas no estado puro até saturação com CO2 para garantir a não ocorrência de danos a nível de entupimento numa posterior utilização na instalação piloto. Por fim, voltaram-se a repetir todos estes ensaios experimentais utilizando-se, em vez da água destilada, um solvente polar aprótico, dimetilsulfóxido (DMSO). Numa segunda fase destes estudos, a absorção de CO2 através de soluções aquosas de aminas foi investigada experimentalmente numa instalação piloto. O objectivo era utilizar nesta fase do estudo as mesmas aminas utilizadas nos ensaios preliminares mas uma vez que não se dispunha das quantidades necessárias de aminas e para a sua aquisição teria que se despender bastante tempo e dinheiro, utilizaram-se duas soluções aquosas de alcanolaminas. As alcanolaminas utilizadas no presente estudo foram a amina secundária dietanolamina (DEA) e a amina terciária N-metildietanolamina (MDEA), duas aminas amplamente utilizadas nas indústrias químicas e petroquímicas para a purificação dos gases de combustão. A absorção de CO2 através destas duas alcanolaminas foi realizada experimentalmente às condições normais de pressão e temperatura. As concentrações das soluções aquosas foram de (10, 20 e 30) % em massa de MDEA e de DEA. O processo de adição de cloreto de bário (BaCl2.2H2O) às alcanolaminas ajuda à formação de carbonato de bário, quando o CO2 passa através da solução de alcanolamina. A quantidade de carbonato de bário formado foi utilizado para determinar a solubilidade do CO2 (mol CO2/mol alcanolamina). O principal desafio na captura de CO2 dos gases de combustão é o de reduzir o consumo de energia necessária para a regeneração do solvente. Deste modo, foram também realizados estudos de regeneração das soluções de alcanolaminas saturadas, para determinar as condições de regeneração. Os resultados obtidos, a nível laboratorial, revelaram que uma amina secundária (PZ) e uma amina primária de cadeia longa (HDA) são mais favoráveis ao processo de absorção e regeneração de CO2. No entanto, e devido a essa mesma estrutura molecular, necessitam de maiores valores de temperaturas para desabsorver o CO2. Garantiu-se poder trabalhar com as quatro aminas no estado puro em estudos futuros, na instalação piloto, garantindo que não ocorrerão danos a nível de entupimento. Relativamente ao solvente utilizado concluiu-se que um solvente polar aprótico não é um solvente favorável para estes estudos. Os resultados obtidos, na instalação piloto, revelaram que a amina terciária, MDEA, consegue absorver maiores quantidades de CO2 do que a amina secundária, EDA, bem como é a mais fácil de regenerar com menor perda de capacidade de absorção do que a EDA.

Eficiência energética e a queima de combustíveis limpos

Mestrado em Engenharia Química

Analysis of six fungicides and one acaricide in still and fortified wines using solid-phase microextraction-gas chromatography/tandem mass spectrometry

A multiresidue gas chromatographic method for the determination of six fungicides (captan, chlorthalonil, folpet, iprodione, procymidone and vinclozolin) and one acaricide (dicofol) in still and fortified wines was developed. Solid-phase microextraction (SPME) was chosen for the extraction of the compounds from the studied matrices and tandem mass spectrometry (MS/MS) detection was used. The extraction consists in a solvent free and automated procedure and the detection is highly sensitive and selective. Good linearity was obtained with correlation coefficients of regression (R2) > 0.99 for all the compounds. Satisfactory results of repeatability and intermediate precision were obtained for most of the analytes (RSD < 20%). Recoveries from spiked wine ranged from 80.1% to 112.0%. Limits of quantification (LOQs) were considerably below the proposedmaximumresidue limits (MRLs) for these compounds in grapes and below the suggested limits for wine (MRLs/10), with the exception of captan.

The development and optimization of a modified single-drop microextraction method for organochlorine pesticides determination by gas chromatography-tandem mass spectrometry

We have developed a new method for single-drop microextraction (SDME) for the preconcentration of organochlorine pesticides (OCP) from complex matrices. It is based on the use of a silicone ring at the tip of the syringe. A 5 μL drop of n-hexane is applied to an aqueous extract containing the OCP and found to be adequate to preconcentrate the OCPs prior to analysis by GC in combination with tandem mass spectrometry. Fourteen OCP were determined using this technique in combination with programmable temperature vaporization. It is shown to have many advantages over traditional split/splitless injection. The effects of kind of organic solvent, exposure time, agitation and organic drop volume were optimized. Relative recoveries range from 59 to 117 %, with repeatabilities of <15 % (coefficient of variation) were achieved. The limits of detection range from 0.002 to 0.150 μg kg−1. The method was applied to the preconcentration of OCPs in fresh strawberry, strawberry jam, and soil.

Determination of total petroleum hydrocarbons in soil from different locations using infrared spectrophotometry and gas chromatography

Total petroleum hydrocarbons (TPH) are important environmental contaminants which are toxic to human and environmental receptors. Several analytical methods have been used to quantify TPH levels in contaminated soils, specifically through infrared spectrometry (IR) and gas chromatography (GC). Despite being two of the most used techniques, some issues remain that have been inadequately studied: a) applicability of both techniques to soils contaminated with two distinct types of fuel (petrol and diesel), b) influence of the soil natural organic matter content on the results achieved by various analytical methods, and c) evaluation of the performance of both techniques in analyses of soils with different levels of contamination (presumably non-contaminated and potentially contaminated). The main objectives of this work were to answer these questions and to provide more complete information about the potentials and limitations of GC and IR techniques. The results led us to the following conclusions: a) IR analysis of soils contaminated with petrol is not suitable due to volatilisation losses, b) there is a significant influence of organic matter in IR analysis, and c) both techniques demonstrated the capacity to accurately quantify TPH in soils, irrespective of their contamination levels.

Auditoria e optimização energética à secção de impregnação de uma indústria têxtil

Mestrado em Engenharia Química

Optimization and validation of organochlorine compounds in adipose tissue by SPE-gas chromatography

Scientific evidence has shown an association between organochlorine compounds (OCC) exposure and human health hazards. Concerning this, OCC detection in human adipose samples has to be considered a public health priority. This study evaluated the efficacy of various solid-phase extraction (SPE) and cleanup methods for OCC determination in human adipose tissue. Octadecylsilyl endcapped (C18-E), benzenesulfonic acid modified silica cation exchanger (SA), poly (styrene-divinylbenzene (EN) and EN/RP18 SPE sorbents were evaluated. The relative sample cleanup provided by these SPE columns was evaluated using gas chromatography with electron capture detection (GC–ECD). The C18-E columns with strong homogenization were found to provide the most effective cleanup, removing the greatest amount of interfering substance, and simultaneously ensuring good analyte recoveries higher than 70%. Recoveries>70% with standard deviations (SD)<15% were obtained for all compounds under the selected conditions. Method detection limits were in the 0.003–0.009 mg/kg range. The positive samples were confirmed by gas chromatography coupled with tandem mass spectrometry (GC-MS/MS). The highest percentage found of the OCC in real samples corresponded to HCB, o,p′-DDT and methoxychlor, which were detected in 80 and 95% of samples analyzed respectively. Copyright © 2012 John Wiley & Sons, Ltd.

Mass spectrometry parameters optimization for the 46 multiclass pesticides determination in strawberries with gas chromatography ion-trap tandem mass spectrometry

Multiclass analysis method was optimized in order to analyze pesticides traces by gas chromatography with ion-trap and tandem mass spectrometry (GC-MS/MS). The influence of some analytical parameters on pesticide signal response was explored. Five ion trap mass spectrometry (IT-MS) operating parameters, including isolation time (IT), excitation voltage (EV), excitation time (ET),maximum excitation energy or “q” value (q), and isolationmass window (IMW) were numerically tested in order to maximize the instrument analytical signal response. For this, multiple linear regression was used in data analysis to evaluate the influence of the five parameters on the analytical response in the ion trap mass spectrometer and to predict its response. The assessment of the five parameters based on the regression equations substantially increased the sensitivity of IT-MS/MS in the MS/MS mode. The results obtained show that for most of the pesticides, these parameters have a strong influence on both signal response and detection limit.Using the optimized method, a multiclass pesticide analysis was performed for 46 pesticides in a strawberry matrix. Levels higher than the limit established for strawberries by the European Union were found in some samples.

Análise e optimização dos consumos de utilidades (vapor e energia eléctrica) na Petibol – Embalagens de Plásticos, S.A.

Mestrado em Engenharia Química. Ramo optimização energética na indústria química.