Propriedades Termofísicas de alguns Gases, Sólidos e da Água

Trata-se de um trabalho que resultou da compilação de informação com o objectivo de fornecer informação de base aos modelos computacionais que temos em uso para diversas finalidades (docência, investigação e desenvolvimento)

Gas mass-flow meters: Principles and applications

Gas mass-flow meters (GMFM) for original equipment manufacturers (OEM) applications are presently found in a relatively easy and cheap way. GMFM may be applied in a number of different situations but technical formation concerning its principles of measurement and applications are still misleading. In this paper, the principles of GMFM measurement are discussed and the operating parameters are clarified. A concept of gas mass-flow response factor is introduced and further used in a model for gas mass-flow measurement that is suitable to any gas mixture of known composition. In addition, a model for the application of GMFM to dynamic volumetric methods of dilution is presented and generalized

Estudo da pegada de carbono de óleo vegetal alimentar

A produção de óleo vegetal alimentar faz-se a partir de sementes de plantas oleaginosas. Para este efeito, em Portugal uma das principais sementes é o girassol, produzido no Ribatejo e no Alentejo, geralmente sobre a forma de culturas de sequeiro. Neste caso de estudo considerou-se que as sementes são enviadas para Espanha onde sofrem o processo de extracção e refinação. O óleo vegetal refinado volta a Portugal onde é embalado e distribuído ao consumidor. A análise de inventário das emissões de gases com efeito de estufa (pegada de carbono) para disponibilizar 1 litro de óleo vegetal alimentar em garrafa de PET nas prateleiras dos hipermercados nacionais permitiu concluir que a (pegada de carbono) do referido produto é de 2.77 kgCO 2 eq, tendo-se concluído que é a fase de produção agrícola das sementes a que apresenta a maior contribuição (80%), seguida da fase da extracção e refinação com cerca de 12% e depois da fase de empacotamento com cerca de 6%. A distribuição em alta é responsável por 0,5% e a distribuição até aos retalhistas por cerca de 1% do total da pegada de carbono. A análise do processo produtivo das sementes de girassol e da composição dos gases com efeito de estufa emitidos mostra que o maior contributo para a pegada de carbono advém do óxido nitroso, que resulta dos processos de desnitrificação associados ao uso de fertilizantes na agricultura. O transporte por estrada é responsável por apenas cerca de 3% da pegada de carbono total. Tratando-se de um produto obtido a partir de recursos biológicos que, apesar de fixarem CO 2 atmosférico, este não pode ser deduzido da pegada de carbono pois volta a ser novamente mobilizado para a atmosfera uma vez consumido como alimento, o que ocorre num prazo inferior a um ano

Custos de sistema de gestão de resíduos urbanos

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Study of retention-treatment basins in highways: case study of A24 (northern Portugal)

In runoff water from highways are diluted several pollutants, that can affect groundwater resources, that depend on the traffic, as well as, on the automobile wear, type of road, infrastructure installed and waterproofing area. These discharges have impacts on the environment. To mitigate such impacts usually there are used retention/treatment basins. In this paper there was analyzed runoff water quality and the efficiency of five basins located in a highway in northern Portugal, in a sensitive area, where are explored mineral waters. It was verified that the results are according with Portuguese legislation in terms of limits of discharge. The treatment efficiency of theses basins is good. The obtained results from the previous analyses were compared with others case studies with different traffic volume and different precipitation patterns

Formação e redução de NOx na combustão de coque em leito fluidizado

Doutoramento em Ciências Aplicadas ao AmbienteOs estudos da cinética da reacção do NO com partículas de coque, efectuados num reactor laboratorial de leito fluidizado, a temperaturas compreendidas entre 600 e 920°C, envolvendo granulometrias na gama de 0.125 a 2.8mm, e coques preparados a partir de antracite, carvão vegetal, carvão activado e grafite - mostraram que a constante de velocidade de reacção heterogénea de primeira ordem do NO, baseada na unidade de massa de coque (k/cm3.s-1.g-1), dependia inversamente do tamanho das partículas. Foi aplicado um processo de cálculo da área total que participa na reacção química, tendo sido encontrados valores para a participação da área interna das partículas da mesma ordem de grandeza da área externa. Estudos semelhantes e efectuados com alguns dos coques referidos mas na presença de outros agentes de gasificação (N2O e O2), mostraram comportamento semelhante, isto é, para a mesma massa de partículas reactivas, a conversão dependia inversamente do tamanho das partículas. A constante de velocidade de reacção dos vários materiais apontou para energias de activação sensivelmente semelhantes para os vários materiais, e factores pré-exponenciais diferentes e que traduzem a reactividade diferenciada dos vários materiais. Tendo em vista esclarecer o papel desempenhado pelas superfícies internas e externas dos vários coques, prepararam-se amostras de coque não atacadas e atacadas parcialmente com NO, e em alguns casos com N2O e O2, e efectuaram-se análises de densidade, porosimetria de mercúrio, área BET, e análises da superfície por XPS e SEM. Estas análises que também permitiram concluir que as reacções de gasificação das partículas de coque com as dimensões típicas das usadas em combustão em leito fluidizado, ocorrem nos primeiros micron da superfície externa das partículas e que quer a composição quer a estrutura das superfícies atacadas são claramente distintas das superfícies internas, que permanecem idênticas às do coque original, mesmo e apesar das dimensões dos poros apresentados pelo coque. A determinação das constantes de velocidade dos vários gases com o coque foi efectuada a partir de um quadro de modelos de leito fluidizado, baseados na teoria clássica das duas fases de Davidson & Harrison para o escoamento, especialmente desenvolvidos para contemplar simultaneamente reacções heterogéneas, catalíticas e homogéneas. A sua aplicação aos casos mais complexos de reacções muito rápidas (caso do O2 com o coque) apresentou várias dificuldades relacionadas com as técnicas numéricas de cálculo que ainda necessitam de ser resolvidas.The kinetics of NO char reaction in a laboratory scale fluidized bed reactor, at temperatures between 600 to 920°C, with size graded particles from 0.125 to 2.8mm of chars prepared by devolatilization of anthracite, charcoal, activated carbon and graphite particles - has shown that the true first order rate constant based on unit mass of char (k/cm3.s-1.g-1), was dependent inversely of particle size. A mathematical procedure of data treatment was developed, and has shown that the internal area available for reaction was of the same order of magnitude of the external particle area. Similar studies conducted with those chars involving N2O and O2, has shown the same trends, e.g. the rate of reaction was found to be inversely proportional on the particle size. The activation energy of NO-char was found to be independent of the the char origin, but the pre-exponential factor is related with the reactivity of the char that differs widely between them. Meanwhile, a set of analysis of all these chars was performed (both reacted and unreacted), such as: Hg porosimetry, BET area, SEM and XPS of surfaces. The main conclusion of these studies is that the char gasification occurs in the few micron at the external surface of the char particles, and that both the composition and the structure of the attacked surfaces are clearly distinct from the inner ones, that remain identical to the original unreacted char, irrespectively of the presence of (large) pores such as those occurring in the wood derived char. Based on the classical two phase theory from Davidson & Harrison, a set of fluidized bed models was developed in order to include simultaneously homogeneous and heterogeneous (catalytic and/or not) reactions. However their application to the kinetic studies concerning the faster complex reactions have some numerical problems that needs further developments

VENASEAL: A GOOD SOLUTION IN THE TREATMENT OF SEVERE SUPERFICIAL VENOUS INSUFFICIENCY IN VERY ELDERLY PATIENTS

Introduction: Chronic venous disease is a prevalent condition that worsens with age and is associated with poor quality of life. The treatment of varicose veins (VV) has multiple alternatives, and different practices across Europe. The aim of this article is to analyze the treatment of very elderly patients with severe forms of chronic venous disease using the VenaSeal technique. Method, Material and Results: Report of 5 very old patients with severe venous insufficiency treated with Vena- Seal in 2021. Clinical case 1: A 86-year-old woman, with untreated bilateral varicose veins and recurrent ulcers, was observed in consultation, complaining of severe pain in left leg with an doppler ultrasound (DUS) showing bilateral great saphenous vein (GSV) insufficiency. An outpatient basis treatment of the left great saphenous vein with VenaSeal associated with phlebectomies was performed in the left side. After 6 months of follow-up, she is asymptomatic with small areas of repermeabilization of the proximal trunk of GSV. Clinical case 2: A 85-year-old man was observed in consultation describing two episodes of varicorrhagia in his right leg and and DUS with bilateral great saphenous vein insufficiency. An outpatient basis treatment of the right great saphenous vein with VenaSeal associated with varicose veins foam esclerotherapy DUS guided was performed. After a 3-month follow-up, the patient is asymptomatic with the imaging control showing occlusion of the trunk of the great saphenous vein. Clinical case 3: A 97-year-old woman was observed in consultation complaining of severe pain in left leg associated with an ulcer with severe interference with her quality of life and a DUS with bilateral great saphenous vein insufficiency. An outpatient basis treatment of the left great saphenous vein with VenaSeal associated with varicose veins foam esclerotherapy DUS guided was performed. After a 2-month follow-up, the patient is asymptomatic with a healed ulcer, with the DUS control showing occlusion of the great saphenous trunk. Clinical case 4: A 95-year-old woman was observed in consultation describing bilateral severe pain and ulcers in both legs and DUS with bilateral great saphenous vein insufficiency. An outpatient basis treatment of bilateral great saphenous vein with VenaSeal associated with varicose veins foam esclerotherapy DUS guided was performed. After 1-month follow-up, she is asymptomatic with healed ulcers and has occlusion of the right GSV ́s trunk and areas of repermeabilization of left GSV ́s trunk. Clinical case 5: An 84-year-old woman was observed in consultation with severe pain and severe pruritus of the left leg and a DUS with left GSV insufficiency. An outpatient basis treatment of the left GSV with VenaSeal associated with phlebectomies was performed. After 1 month of follow-up, the patient is asymptomatic with occlusion of the proximal left GSV ́s trunk. Discussion/Conclusion: Treatment with Venaseal is not considered in the 2015 Guidelines of the ESVS, however the VeClose Study compared VenaSeal with radiofrequency ablation and reported equivalent improvement in symptoms scores and GSV occlusion. VenaSeal treatment doesn ́t require use of elastic compression after surgery and allows return to routine activity immediately, so it may be a good therapeutic option in this age group of patients with high clinical risk. In our experience, VenaSeal resulted in complete resolution of the symptoms and ulcers in the short term. However, a complete occlusion of GSV was not observed in all cases, so new studies and protocols doses can be necessary

Proposal for the Location of a Municipal Solid Waste Management Facility for a Metropolitan Region

Only 16 of the 246 municipalities of Goiás State, Brazil, dispose their municipal solid waste (MSW) in licensed landfills. Therefore, this study proposes the host municipality (HM) of the future shared MSW management facility (MSWMF), serving the Metropolitana de Goiânia (MGyn) microregion. First, the potential areas to construct MSW final disposal facilities (landfills) were identified. Subsequently, using mass point geometry, the HM of the proposed MSWMF for MGyn was defined. The results show that only 19.4% of the area of the studied municipalities is available or subject to approval for landfill construction. The HM will be Aparecida de Goiânia, which will process most of the MSW and send the rejects of treated MSW to the landfill that will be established in the neighboring municipality of Hidrolândia. Additionally, this MSWMF will serve 19 municipalities and will have nine waste transfer stations that will receive waste from 17 municipalities, to minimize MSW transport costs.Apenas 16 dos 246 municípios do Estado de Goiás, Brasil, dispõem seus resíduos sólidos urbanos (RSU) em aterros licenciados. Assim, este estudo propôs o município sede (MS) do futuro sistema de gestão de RSU (SGRSU) compartilhado para a microrregião Metropolitana de Goiânia (MGyn). Primeiramente identificaram-se potenciais áreas para instalar sistemas de disposição final de RSU (aterros). Posteriormente, utilizando-se a metodologia da geometria das massas, definiu-se o MS do SGRSU proposto para a MGyn. Os resultados mostram que apenas 19,4% da área dos municípios estudados é livre ou sujeita à anuência para instalar aterros. O MS será Aparecida de Goiânia, que tratará a maior parte dos RSU e enviará os rejeitos dos RSU tratados para o município vizinho de Hidrolândia. Além disso, este SGRSU servirá 19 municípios e terá nove estações de transferência que receberão os resíduos de 17 municípios, para minimizar os custos com o transporte dos RSU

Palm oil kernel shell as solid fuel for the commercial and industrial sector in Ecuador: tax incentive impact and performance of a prototype burner

The Ecuadorian industrial and commercial sectors are in general supported in the use of diesel for energy purposes. An alternative to replace diesel could be the use of palm oil residual biomass as solid fuel. It is estimated that 57.7% of the capital costs required to implement a biomass boiler that use untreated palm oil kernel shell (KS) as fuel in replacement of a diesel boiler would be covered by in force tax incentives. Nonetheless, untaxed and subsidized diesel utilization coupled to the important capital and operating costs associated to the biomass boiler results in relatively high payback periods, within the range of 6 to 7.9 years. Analyzing a base case, it is observed that replacement of diesel by KS results in a reduction of 8 times the fuel costs. Implementation of pre-treatment processes (e.g. pelletizing) could increase the KS price, affecting the potential to lower the costs of thermal energy production. Accordingly, utilization of raw KS for thermal energy production was demonstrated using a horizontal burner prototype. The experimental analysis of the KS combustion process shows that combustion efficiency (99.8%) is as high as that observed in other type of biomass burners. During the steady state operation periods, CO concentration in the flue gases (260.1 mg/Nm3) was below the limit established by the European standards for solid fuel boilers (500 mg/Nm3). Ash sintering was observed in the grate during the combustion experiments. The ash discharge process induced periodic fluctuations in the combustion chamber temperature profile as well as fluctuations in the flue gas composition. Despite these localized and periodic temperature and gas composition fluctuations, in the whole, and considering longer periods of operation, the combustion system was under steady state conditions and showed to be suitable for energetic valorization of untreated KS.publishe

Films negros en edifícios históricos de Oporto: caracterización y experiencias de limpieza

Los films negros constituyen el principal motivo de las intervenciones de limpieza de fachadas de edificios históricos en la ciudad de Oporto, Portugal, construidos con el granito de Oporto de dos micas, de grano medio a grueso, compuesto de cuarzo, microclina, plagioclasa, muscovita y biotita. Varios estudios realizados sobre la calidad del aire urbano y la deposición de partículas atmosféricas apuntan a un origen antropogénico de estas capas de alteración. El estudio llevado a cabo sobre muestras de films negros del “Hospital de Santo António” revela la presencia de hidrocarburos aromáticos policíclicos (PAH) en cantidades apreciables, detectada por LC-FD (Cromatografía líquida con detector de fluorescencia). El análisis por SEM-EDX (Microscopía electrónica de barrido con microanálisis de rayos X) de estos films muestra que están constituidos por una gran cantidad de partículas de dimensión reducida (que raramente pasan los 10-20 m), asociadas a una matriz de material homogéneo de naturaleza probablemente amorfa. Estas partículas se caracterizan por una gran complejidad mineralógica y morfológica, destacándose partículas ricas en Fe, partículas ricas en Pb, no cristalinas, cenizas volantes esféricas de superficie lisa de Si y Al. Las consecuencias de la presencia de estos compuestos en la superficie de los materiales pétreos son su oscurecimiento. Estas capas de alteración se diferencian de las costras negras debido a su textura, forma, exposición a la acción del agua de la lluvia y composición mineralógica. En consecuencia, las técnicas aplicables a su limpieza son también distintas de las habitualmente usadas para las costras negras. Finalmente, se describen experiencias en operaciones de limpieza llevadas a cabo en edificios de la ciudad de Porto con métodos abrasivos y químicos y se discuten posibilidades tecnológicas y parámetros de control de calidad de las intervenciones.Tópico 6: Patrimonio Urbano de los siglos XVIII al XX. Técnicas de Limpieza y de Conservación