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- 3-D scale model study of wave run-up, overtopping and damage in a rubble-mound breakwater subject to oblique extreme wave conditionsPublication . Santos, João Alfredo; Pedro, Francisco; Coimbra, Mário; Figuero, Andrés; Fortes, Conceição Juana; Sande, José; Körner, Moritz; Lemos, Rute; Bornschein, Antje; Weimper, Julius; van den Bos, Jeroen; Dost, Bastian; Hofland, Bas; Carvalho, Rita F.; Alvarellos, Alberto; Peña, Enrique; Pohl, Reinhard; Kerpen, Nils B.; Reis, Maria TeresaA set of scale-model tests carried out to enlarge the range of wave steepness values analysed in run-up, overtopping and armour layer stability studies, focusing on oblique extreme wave conditions and on their effects on a gentler slope breakwater’s trunk armour and roundhead, is presented in this paper. A stretch of a rubble mound breakwater (head and part of the adjoining trunk, with a slope of 1(V):2(H)) was built in a wave basin at the Leibniz University Hannover to assess, under extreme wave conditions (wave steepness of 0.055) with different incident wave angles (from 40º to 90º), the structure behaviour in what concerns wave run-up, wave overtopping and damage progression of the armour layer. Two types of armour elements (rock and Antifer cubes) were tested. Non-intrusive methodologies including a new application of laser scanning technique for the assessment of both armour layer damage and wave run-up and overtopping were used. It is expected that such work will contribute also with data to improve empirical formulas as well as to validate complex numerical model for wave-structure interaction.
- Accurate ocean bottom seismometer positioning method inspired by multilateration techniquePublication . Benazzouz, Omar; Pinheiro, Luis; Matias, Luis; Afilhado, Alexandra; Herold, Daniel; Haines, Seth S.The positioning of ocean bottom seismometers (OBS) is a key step in the processing flow of OBS data, especially in the case of self popup types of OBS instruments. The use of first arrivals from airgun shots, rather than relying on the acoustic transponders mounted in the OBS, is becoming a trend and generally leads to more accurate positioning due to the statistics from a large number of shots. In this paper, a linearization of the OBS positioning problem via the multilateration technique is discussed. The discussed linear solution solves jointly for the average water layer velocity and the OBS position using only shot locations and first arrival times as input data.
- Activity–acidity relationship in zeolite Y: Part 1. Transformation of light olefinsPublication . Costa, Carla; Lopes, Jose M.; Lemos, Francisco; Ribeiro, F. RamôaReactions of ethene, propene, 1-butene and iso-butene over two series of catalysts, HNaY (prepared from NaY zeolite) and HNaUSY (prepared from NH4USY zeolite), were studied. The catalytic activity for the transformation of these olefins follows the expected order according to the ease of formation of the respective carbocations: ethene
- Activity–acidity relationship in zeolite Y: Part 2. Determination of the acid strength distribution by temperature programmed desorption of ammoniaPublication . Costa, Carla; Lopes, Jose M.; Lemos, Francisco; Ribeiro, F. RamôaIn this paper we will have a detailed look at a numerical procedure that allows the estimation of the acid site strength distribution using a single temperature programmed desorption (TPD) experiment. The possibility of estimating these parameters is of paramount importance in the determination of quantitative relationships between activity and acidity. The application of the procedure to a set of simulated thermograms gives a clear view of the applicability of this method. The procedure was tested both in single and multi energy distributions, as well as quasi-continuum distributions. Then the method has been applied on TPD thermograms obtained from catalysts based on two different forms of zeolite Y. In part 3 of this series, the acid site distributions obtained here will be used in an activity–acidity relationship, using a Brönsted type equation, similar to the one used in homogeneous acid catalysis.
- Activity–acidity relationship in zeolite Y: Part 3. Application of Brönsted type equationsPublication . Costa, Carla; Lopes, Jose M.; Lemos, Francisco; Ribeiro, F. RamôaThe relation between activity and acidity in a variety of Y zeolite catalysts for the transformation of small olefins: ethene, propene, 1-butene and iso-butene, is presented. The acid site distribution of these samples was estimated by temperature-programmed desorption of ammonia, by using a numerical deconvolution technique. This information was then correlated with catalytic activity measurements using Brönsted type equations. Despite the complexity of calculations it is clear that this gas phase solid acid catalysed reactions follow simple rules, similar to the one observed in homogeneous processes.
- Activity–acidity relationship in zeolite ZSM-5. Application of Brönsted-type equationsPublication . Costa, Carla; Dzikh, I. P.; Lopes, Jose M.; Lemos, Francisco; Ribeiro, Fernando RamôaIn this paper the relation between activity and acidity in a variety of ZSM-5 zeolite catalysts, with different Si/Al ratios and different protonic content, is analysed and a quantitative correlation is obtained. The acid site strength distribution was estimated using temperature-programmed desorption (TPD) of ammonia by applying a digital deconvolution method to the curves. These data were then correlated with experimental catalytic activity data for the same catalysts towards n-heptane cracking reaction, by means of a Brönsted-type equation similar to the ones used for homogeneous acid catalysis and already used for other zeolites. It can be noticed that the same types of equation that are used for homogeneous acid catalysis also hold for heterogeneous acid catalysis and that the activation energy for ammonia desorption can be used as acid-strength scale for the purpose of correlation with catalytic activity.
- Alkali-activated binders produced from petrochemical fluid catalytic cracking catalyst wastePublication . Costa, Carla; Ferreira, Cátia; Ribeiro, Maria Filipa; Fernandes, AugusteThis paper describes research on the viability of producing alkali activated binders using the aluminosilicate catalyst waste-generated by the fluid catalytic cracking (wFCC) unit in the Portuguese oil refinery company-as precursor. For this purpose, alkali-activated wFCC catalyst based mortars and cement pastes were produced. Tests were carried out to evaluate the effect of initial solids composition (wFCC catalyst/Ca(OH) 2 ratio) on mortars workability or mechanical strength. The mineralogy and microstructure of the hardened alkali activated wFCC catalyst pastes were studied by means of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results obtained at macroscale showed that the content of Ca(OH) 2 incorporated in the binder has a significant effect on compressive strength of hardened mortars. At microscale, FTIR and XRD results confirmed the occurrence of alkali-activation of the wFCC catalyst which leads to the formation of distinctive amorphous and crystalline products. Moreover, the obtained results also suggest that initial solids composition influences the alkali-activation reaction kinetics and mechanism.
- An SEM investigation of the pozzolanic activity of a waste catalyst oil refineryPublication . Costa, Carla; Marques, Paulo; Carvalho, P. A.The most active phase of the fluid catalytic cracking (FCC) catalyst, used in oil refinery, is zeolite-Y which is an aluminosilicate with a high internal and external surface area responsible for its high reactivity. Waste FCC catalyst is potentially able to be reused in cement-based materials - as an additive - undergoing a pozzolanic reaction with calcium hydroxide (Ca(OH)2) formed during cement hydration [1-3]. This reaction produces additional strength-providing reaction products i.e., calcium silicate hydrate (C-S-H) and hydrous calcium aluminates (C-A-H) which exact chemical formula and structure are still unknown. Partial replacement of cement by waste FCC catalyst has two key advantages: (1) lowering of cement production with the associated pollution reduction as this industry represents one of the largest sources of man-made CO2 emissions, and (2) improving the mechanical properties and durability of cement-based materials. Despite these advantages, there is a lack of fundamental knowledge on pozzolanic reaction mechanisms as well as spatial distribution of porosity and solid phases interactions at the microstructural level and consequently their relationship with macroscopical engineering properties of catalyst/cement blends. Within this scope, backscattered electron (BSE) images acquired in a scanning electron microscope (SEM) equipped with Energy-Dispersive Spectroscopy (EDS) and by X-ray diffraction were used to investigate chemical composition of hydration products and to analyse spatial information of the microstructure of waste FCC catalyst blended cement mortars. For this purpose mortars with different levels of cement substitution by waste catalyst as well as with different hydration ages, were prepared. The waste FCC catalyst used is produced by the Portuguese refinery company Petrogal S.A.
- Analysis of constructed wetland performance for irrigation reusePublication . Monte, Helena Marecos; Albuquerque, AntonioMost of the wastewater treatment systems in small rural communities of the Cova da Beira region (Portugal) consist of constructed wetlands (CW) with horizontal subsurface flow (HSSF). It is believed that those systems allow the compliance of discharge standards as well as the production of final effluents with suitability for reuse. Results obtained in a nine-month campaign in an HSSF bed pointed out that COD and TSS removal were lower than expected. A discrete sampling also showed that removal of TC, FC and HE was not enough to fulfill international irrigation goals. However, the bed had a very good response to variation of incoming nitrogen loads presenting high removal of nitrogen forms. A good correlation between mass load and mass removal rate was observed for BOD5, COD, TN, NH4-N, TP and TSS, which shows a satisfactory response of the bed to the variable incoming loads. The entrance of excessive loads of organic matter and solids contributed for the decrease of the effective volume for pollutant uptake and therefore, may have negatively influenced the treatment capability. Primary treatment should be improved in order to decrease the variation of incoming organic and solid loads and to improve the removal of COD, solids and pathogenic. The final effluent presented good physical-chemical quality to be reused for irrigation, which is the most likely application in the area.
- Application of GIS-based multi-criteria analysis for site selection of aquifer recharge with reclaimed waterPublication . Pedrero Salcedo, Francisco; Albuquerque, Antonio; Monte, Helena Marecos; Cavaleiro, Victor; ALARCON, JUAN JOSEReclaimed water from small wastewater treatment facilities in the rural areas of the Beira Interior region (Portugal) may constitute an alternative water source for aquifer recharge. A 21-month monitoring period in a constructed wetland treatment system has shown that 21,500 m(3) year(-1) of treated wastewater (reclaimed water) could be used for aquifer recharge. A GIS-based multi-criteria analysis was performed, combining ten thematic maps and economic, environmental and technical criteria, in order to produce a suitability map for the location of sites for reclaimed water infiltration. The areas chosen for aquifer recharge with infiltration basins are mainly composed of anthrosol with more than 1 m deep and fine sand texture, which allows an average infiltration velocity of up to 1 m d(-1). These characteristics will provide a final polishing treatment of the reclaimed water after infiltration (soil aquifer treatment (SAT)), suitable for the removal of the residual load (trace organics, nutrients, heavy metals and pathogens). The risk of groundwater contamination is low since the water table in the anthrosol areas ranges from 10 m to 50 m. Oil the other hand, these depths allow a guaranteed unsaturated area suitable for SAT. An area of 13,944 ha was selected for study, but only 1607 ha are suitable for reclaimed water infiltration. Approximately 1280 m(2) were considered enough to set up 4 infiltration basins to work in flooding and drying cycles.