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Civil and Environmental Engineering

Selected Works

João F Gomes

Articles 31 - 49 of 49

Full-Text Articles in Nanoscience and Nanotechnology

Reflections On The Use Of The Mccabe And Thiele Method, João F. Gomes Jan 2007

Reflections On The Use Of The Mccabe And Thiele Method, João F. Gomes

João F Gomes

This paper reflects on the continuity of teaching the McCabe and Thiele method on chemical engineering courses for understanding the vapour-liquid equilibrium phenomena involved in distillation. Some exercises comparing the results obtained by this method as well as by other accurate analytical methods are presented and solved, as they are taught in ISEL courses. Because of its accuracy and easiness of use, and also because of the fact as this method allows an easy visualisation of the whole operation itself, the McCabe and Thiele method continues to be widespread used and students show a remarkable adherence to it.

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Forest Fires In Portugal: How They Happen And Why They Happen, João F. Gomes Jan 2006

Forest Fires In Portugal: How They Happen And Why They Happen, João F. Gomes

João F Gomes

Forest fires are recurrent phenomena in Southern European countries, due to the nature of Mediterranean forest and climatic characteristics. However, in Portugal, in the last years, forest fires attained the dimension of public calamity and are now endangering sustainability of forest itself, as well as several derived economic activities. This paper reviews the past and current situation of forest fires in Portugal, analyses its main causes and consequences and derives recommendations to effectively overcome this problem.

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Leaching Of Heavy Metals From Steelmaking Slags, João F. Gomes Jan 2006

Leaching Of Heavy Metals From Steelmaking Slags, João F. Gomes

João F Gomes

Leaching tests with EAF and Ladle slags were performed, using a flow through test and the standard batch test DIN 38414-S4. The previous method was used to simulate the leaching behaviour of steel slags under landfill. The chemical analysis of the leachates during this period shows, in general, for both types of slag, an increase of heavy metal releases with ageing. Standard test method DIN 38414-S4 was used to evaluate leachability of heavy metals by water in unprocessed slags. After more than one year of trials, slag samples submitted to these trials presented very low total leaching levels. The most …

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Estimation Of Uncertainty In The Determination Of Nitrogen Oxides Emissions, João F. Gomes Jan 2006

Estimation Of Uncertainty In The Determination Of Nitrogen Oxides Emissions, João F. Gomes

João F Gomes

This paper presents a methodology for estimation of uncertainty on a reference test method for determination of nitrogen oxides concentration in gaseous emissions from stationary sources. As a first stage for identification of uncertainty sources, the test method is carefully reviewed in detail. Afterwards, these sources are quantified, bearing in mind its partial uncertainty, allowing the determination of the combined uncertainty and, finally, the expanded uncertainty. The calculation procedure was implemented into an excel calculation file. Using this file and considering several numerical applications from real situations, uncertainities around 15 mg/Nm3 over determined concentrations of 350 mg/Nm3 of NOx (expressed …

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Fume Emissions During Metal Arc Welding, João F. Gomes Jan 2006

Fume Emissions During Metal Arc Welding, João F. Gomes

João F Gomes

No abstract provided.

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Avoid Sulfuric Acid Corrosion In Metallic Stacks, João F. Gomes Jan 2005

Avoid Sulfuric Acid Corrosion In Metallic Stacks, João F. Gomes

João F Gomes

Acidic gaseous effluents frequently cause corrosion on metallic stacks. This paper presents a method for prevision of probability of corrosion occurrence caused by gaseous effluents containing sulphur oxides which is based on the sulphur trioxide and moisture content measured in stack

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Emissions Of Dioxin And Dibenzofuran From Electric Arc Furnaces, João F. Gomes Jan 2005

Emissions Of Dioxin And Dibenzofuran From Electric Arc Furnaces, João F. Gomes

João F Gomes

This paper describes work done in order to clarify the formation mechanism of highly toxic micropollutants, such as dioxins and dibenzofurans, from electric arc furnaces used in the production of carbon steel from scrap. The study is allowing to derive relationships between the levels of airborne micropollutants and the operational parameters of the production process so that an abatement of pollution could be achieved. By using the European standard method CEN 1948 for dioxin like compounds sampling and measurement, it was possible to determine the characteristic fingerprint of micropollutants emitted by this particular stationary source.

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Analysis Of Welding Fumes: A Short Notice On The Comaprison Between Two Sampling Techniques, João F. Gomes Dec 2004

Analysis Of Welding Fumes: A Short Notice On The Comaprison Between Two Sampling Techniques, João F. Gomes

João F Gomes

No abstract provided.

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Air Quality Regulation Policy In Portugal, João F. Gomes Jan 2004

Air Quality Regulation Policy In Portugal, João F. Gomes

João F Gomes

Ten years after the publication of first air quality laws in Portugal, and seven years after the publication of the respective emission limits, it seems appropriate to analyse the degree of law enforcement by the Portuguese manufacturing industry. Therefore, based on the emission measurements made regularly by ISQ, as the only officially accredited laboratory, a set of about 400 sources is analysed in terms of the compliance with the emission limits regarding total suspended particulate, sulphur dioxide, nitrogen oxides and VOCs. The compliance is evaluated through a non-dimensional parameter and plotted versus the emission flow rate to derive conclusions: it …

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Emission And Odour Control In Kraft Pulp Mills, João F. Gomes Jan 2003

Emission And Odour Control In Kraft Pulp Mills, João F. Gomes

João F Gomes

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 …

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Diagnostic Of Critical Circuits Of Kraft Pulp Production Process Considering The Environmental Aspects, João F. Gomes Jan 2002

Diagnostic Of Critical Circuits Of Kraft Pulp Production Process Considering The Environmental Aspects, João F. Gomes

João F Gomes

This paper describes systematic work done in the field of atmospheric emissions from Portuguese Kraft pulp mills. This study led to the determination of emission factors from stationary sources that proved to be an important tool to assess the need for investment on air pollution abatement equipment, namely in what concerns mal-odorous gases.

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Characterisation Of Non-Condensable Sulphur Containing Gases From Kraft Pulp Mills (2), João F. Gomes Jan 2001

Characterisation Of Non-Condensable Sulphur Containing Gases From Kraft Pulp Mills (2), João F. Gomes

João F Gomes

This paper describes work performed on the sampling and analysis of non-condensable gases (NCG) emitted from diffuse sources of a Portuguese Kraft pulp mill, which is the background information for a NCG collection, treatment and disposal system. The variability found in the composition of the gaseous compounds showed the existence of gaseous streams other than typical total reduced sulphur (TRS) compounds as usually described. From the measured TRS concentrations and the gas flow rate from each source it was possible to calculate the emission flow rate, E, of each source. These emission flow rates were then divided into 3 categories …

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Practical Determination Of Efficiency Of Electrostatic Precipitators, João F. Gomes Jan 1999

Practical Determination Of Efficiency Of Electrostatic Precipitators, João F. Gomes

João F Gomes

Electrostatic precipitators are one of the most efficient particulate pollution control equipments used mainly for the treatment of gaseous effluents at high flow rates. Consequently electrostatic precipitators are widely used in thermal power plants, cement plants and pulp mills. Apart from a high efficiency other advantages are related with the fact that this type of equipment has a considerable low payback time in industrial plants where the particulate recovered from the gases has commercial value and can be recycled within the industrial process itself or even sold to other industrial companies. Where sulphate (Kraft) pulp mills are concerned an electrostatic …

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Characterisation Of Non-Condensable Sulphur Containing Gases From Kraft Pulp Mills, João F. Gomes Jan 1998

Characterisation Of Non-Condensable Sulphur Containing Gases From Kraft Pulp Mills, João F. Gomes

João F Gomes

This paper describes work performed on the sampling and analysis of non-condensable gases (NCG) emitted from diffuse sources of a Portuguese kraft pulp mill, which is the background information for a NCG collection, treatment and disposal system. The variability found in the composition of the gaseous compounds showed the existence of gaseous streams other than typical total reduced sulphur (TRS) compounds as usually described.

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A Simple Way To Measure Particle Size, João F. Gomes Jan 1998

A Simple Way To Measure Particle Size, João F. Gomes

João F Gomes

The size range of particles is an important parameter for subsequent dispersion estimates and sometimes is quite useful for analysing the performance of combustion equipment as well as dedusting equipment efficiency. So far, no standard method has been developed but several laboratories use laser-beam techniques which are usually quite expensive ones. In this paper a method is presented where the particles are collected isokinetically in a filter from gases circulating in a stack as described in USEPA method 5. Afterwards particles are observed at an optical microscope and measured. In spite of some limitations this appears to be an inexpensive …

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Assessment Of Opacimeter Calibration On Kraft Pulp Mills, João F. Gomes Dec 1997

Assessment Of Opacimeter Calibration On Kraft Pulp Mills, João F. Gomes

João F Gomes

This paper describes the methodology and specific techniques for calibrating automatic on-line industrial emission analysers, specifically equipments that measure total suspended dust installed in pulp mills within the scope of Portuguese Regulation Nº 286/93 on air quality. The calibration of opacimeters is a multi-parameter relationship instead of the bi-dimensional calibration which is used in industrial practice. For a stationary source from a pulp mill such as the recovery boiler stack, which is subjected to significant variations, the effects of parameters such as the humidity and gas temperature, deviations on isokinetism, size range of particles and characteristic transmitance of equipment are …

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Pollutant Atmospheric Emissions From Portuguese Kraft Pulp Mills, João F. Gomes Jan 1997

Pollutant Atmospheric Emissions From Portuguese Kraft Pulp Mills, João F. Gomes

João F Gomes

This paper describes systematic work done in the field of atmospheric emissions from Portuguese Kraft pulp mills. This study led to the determination of emission factors from stationary sources that proved to be an important tool to assess the need for investment on air pollution abatement equipment.

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Notice On A Method For Measuring Size Range Of Particles In Gases From Stationary Sources, João F. Gomes Jan 1990

Notice On A Method For Measuring Size Range Of Particles In Gases From Stationary Sources, João F. Gomes

João F Gomes

No abstract provided.

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Program Calculates Critical Properties, João F. Gomes Jan 1988

Program Calculates Critical Properties, João F. Gomes

João F Gomes

No abstract provided.

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