João Fernando Pereira Gomes

p-Xylene Oxidation to Terephthalic Acid: A Literature Review Oriented toward Process Optimization and Development

Oriented toward Process Optimization and Development Rogeŕio A. F. Tomaś,† Joaõ C. M. Bordado,‡ and Joaõ F. P. Gomes*,‡,§ †ARTLANT, Zona Industrial e Logística de Sines, Zona 2, Lote 2E1, Monte Feio, 7520-064 Sines, Portugal ‡Instituto de Biotecnologia e Bioengenharia/Instituto Superior Tećnico (IBB), Universidade Tećnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal Instituto Superior de Engenharia de Lisboa (ISEL), Área Departamental de Engenharia Química, R. Conselheiro Emídio Navarro, 1959-007 Lisboa, Portugal

Fume emissions during gas metal arc welding

The control of exposure to welding fumes is of increasing importance in promoting a healthy, safe and productive work environment. This article describes the effects of shielding gas composition on the amount and composition of welding fumes produced during gas metal arc welding (GMAW). The amount of fumes generated during welding was measured for steady current over a range of wire-feed speeds and arc voltages using the standard procedures contained in ANSI/AWS F1.2 [American Welding Society. ANSI/AWS F1.2. Laboratory method for measuring fume generation rates and total fume emission of welding and allied processes. Miami, Florida; 1992]. Results of these measurements show that the fume formation rates (FFRs) increase with CO2 and O2 in the shielding gas mixture. The lowest FFRs were obtained with the mixtures of Ar + 2%CO2 and Ar + 3%CO2 + 1%O2. The highest FFRs were obtained with the mixtures of Ar + 18%CO2 and Ar + 5%CO2 + 4%O2. The welding fumes contains mainly iron, manganese, silicon, titanium and sodium under oxide forms. The fume cluster particles have dimensions between 0.5 and 2 µm. The FFR was found to be governed by the transfer modes of molten metal, i.e. the current intensity and arc voltage, as well as by the shielding gas mixtures composition. Thus these parameters have to be taken into consideration before designing a welding process. Whenever possible, users of GMAW should use the lowest current intensity. However, when this is not possible, due to the constraints of process productivity, welders should use higher currents, but with Ar + 2%CO2 and Ar + 3%CO2 + 1%O2 shielding mixtures, which will lead to smaller fume emissions.

A simulation study on the abatement of CO2 emissions by de‐absorption with monoethanolamine

Because of the adverse effect of CO2 from fossil fuel combustion on the earth’s ecosystems, the most cost‐effective method for CO2 capture is an important area of research. The predominant process for CO2 capture currently employed by industry is chemical absorption in amine solutions. A dynamic model for the de‐absorption process was developed with monoethanolamine (MEA) solution. Henry’s law was used for modelling the vapour phase equilibrium of the CO2, and fugacity ratios calculated by the Peng–Robinson equation of state (EOS) were used for H2O, MEA, N2 and O2. Chemical reactions between CO2 and MEA were included in the model along with the enhancement factor for chemical absorption. Liquid and vapour energy balances were developed to calculate the liquid and vapour temperature, respectively.

Lixiviación de metales pesados a partir de escorias de acero

* Trabajo recibido el día 8 de noviembre de 2005 y aceptado en su forma final el día 27 de junio de 2006. ** Centro de Tecnologias Ambientais, Instituto de Soldadura e Qualidade, Tagus Park, Apartado 0122780-994 Oeiras, Portugal. Fax: 351.21.3850991 Email: ip241783@ip.pt. *** Universidade Lusófona de Humanidades e Tecnologias, Av. Campo Grande, 376, 1749-024 Lisboa, Portugal. Leaching of heavy metals from steelmaking slags*

Determination of airborne nanoparticles from welding operations

The aim of this study is to assess the levels of airborne ultrafine particles emitted in welding processes (tungsten inert gas [TIG], metal active gas [MAG] of carbon steel, and friction stir welding [FSW] of aluminum) in terms of deposited area in pulmonary alveolar tract using a nanoparticle surface area monitor (NSAM) analyzer. The obtained results showed the dependence of process parameters on emitted ultrafine particles and demonstrated the presence of ultrafine particles compared to background levels. Data indicated that the process that resulted in the lowest levels of alveolar deposited surface area (ADSA) was FSW, followed by TIG and MAG. However, all tested processes resulted in significant concentrations of ultrafine particles being deposited in humans lungs of exposed workers.

Estimating local greenhouse gas emissions - A case study on a Portuguese municipality

Abstract This paper describes the study that led to the development of a carbon dioxide emissions matrix for the Oeiras municipality, one of the largest Portuguese municipalities, located in the metropolitan area of Lisbon. This matrix takes into account the greenhouse gases (GHG) emissions, due to an increase of electricity demand in buildings as well as solid and liquid wastes treatment, from the domestic and services sectors. Using emission factors that were calculated from the relationship between the electricity produced and amount of treated wastes, the GHG emissions in the Oeiras municipality, were estimated for a time series of 6 years (1998–2003). The obtained results showed that the electricity sector accounts for about 75% of the municipal emissions in 2003. This study was developed in order to obtain tools to base options and actions to be undertaken by local authorities such as energy planning and also public information.

Emission and odour control in Kraft pulp mills

This paper describes systematic work done in the field of atmospheric emissions from Portuguese Kraft pulp mills, focused mainly on the gaseous emissions responsible for its characteristic odour. These mal-odorous gases, which were identified as hydrogen sulphide, methyl mercaptan, deimethyl mercaptan and dimethyl-disulphide, were experimentally quantified and classified into groups so that alternatives for abatement could be devised. The considered abatement techniques were evaluated economically and it was concluded that the costs to be incurred by pulp mills for an efficient abatement of TRS gases are not dramatic and could be easily covered by this industry, resulting in an evident reduction of an important and noticeable environmental impact.  2002 Elsevier Science Ltd. All rights reserved.

Comparison of deposited surface area of airborne ultrafine particles generated from two welding processes

This article describes work performed on the assessment of the levels of airborne ultrafine particles emitted in two welding processes metal-active gas (MAG) of carbon steel and friction-stir welding (FSW) of aluminium in terms of deposited area in alveolar tract of the lung using a nanoparticle surface area monitor analyser. The obtained results showed the dependence from process parameters on emitted ultrafine particles and clearly demonstrated the presence of ultrafine particles, when compared with background levels. The obtained results showed that the process that results on the lower levels of alveolar-deposited surface area is FSW, unlike MAG. Nevertheless, all the tested processes resulted in important doses of ultrafine particles that are to be deposited in the human lung of exposed workers.

Solar activity as a possible cause of large forest fires — A case study: Analysis of the Portuguese forest fires

Fires of large dimension destroy forests, harvests and housing objects. Apart from that combustion products and burned surfaces become large ecological problems. Very often fires emerge simultaneously on different locations of a region so a question could be asked if they always have been a consequence of negligence, pyromania, high temperatures or maybe there has been some other cause. This paper is an attempt of establishing the possible connection between forest fires that numerous satellites registered and activities happening on the Sun immediately before fires ignite. Fires emerged on relatively large areas from Portugal and Spain on August 2005, as well as on other regions of Europe. The cases that have been analyzed show that, in every concrete situation, an emission of strong electromagnetic and thermal corpuscular energy from highly energetic regions that were in geo-effective position had preceded the fires. Such emissions have, usually, very high energy and high speeds of particles and come from coronary holes that also have been either in the very structure or in the immediate closeness of the geo-effective position. It should also be noted that the solar wind directed towards the Earth becomes weaker with deeper penetration towards the topographic surface. However, the results presented in this paper suggest that, there is a strong causality relationship between solar activity and the ignition of these forest fires taking place in South-western Europe.

Choosing amine-based absorbents for CO2 capture.

CO2 capture from gaseous effluents is one of the great challenges faced by chemical and environmental engineers, as the increase in CO2 levels in the Earth atmosphere might be responsible for dramatic climate changes. From the existing capture technologies, the only proven and mature technology is chemical absorption using aqueous amine solutions. However, bearing in mind that this process is somewhat expensive, it is important to choose the most efficient and, at the same time, the least expensive solvents. For this purpose, a pilot test facility was assembled and includes an absorption column, as well as a stripping column, a heat exchanger between the two columns, a reboiler for the stripping column, pumping systems, surge tanks and all necessary instrumentation and control systems. Some different aquous amine solutions were tested on this facility and it was found that, from a set of six tested amines, diethanol amine is the one that turned out to be the most economical choice, as it showed a higher CO2 loading capacity (0.982 mol of CO2 per mol of amine) and the lowest price per litre (25.70 €/L), even when compared with monoethanolamine, the benchmark solvent, exhibiting a price per litre of 30.50 €/L.