1,721,007 research outputs found
Copper biosorption onto Rhizopus oligosporus: pH-edge tests and related kinetic and equilibrium modelling
No full textFrom risk assessment to resilience assessment. an application to a hazmat storage plant
No full textThe purpose of this work is to outline a framework for assessing the resilience of a petrochemical storage plant, through the construction of a dynamic hierarchical Bayesian network. The BN approach allows keeping memory of the states, in order to manage the actual safety and reliability evidences during the petrol transfer operation from storage tank to trucks in a repository of oil products. The proposed framework aims at assessing risk in process plants by analysing continuous process hazard data from a Bayesian point of view. A sequence of hazard functions derived for the FTAs, is modelled with a hidden Markov chain. The capability of the model implemented by means of Markov Chain Monte Carlo methods are tested at a real scale plant. Keywords: Data driven model, hidden Markov models, resilience, semi-supervised learning,
Domino effect by pool fire radiation on pipelines: An applicative case-study
No full textAn important feature of tank pool fire is that the targets of interest for critical effects may include other plant units, such gas pipelines, storage sites, process sections, with heat transfer modes not limited to radiation. This paper, which takes inspiration from a recent work of the same authors, considers the physical model of a rectangular pool-fire to provide an analytical trend of the surface emissive power depending on the flame height. The capability of the approach is proved by an applicative case-study where the possible escalation from pool fire to a coke oven gas pipeline failure is analysed, within the context of a coal dry distillation plant. The possibility of escalation with pipeline damage is thoroughly discussed, in order to develop a detailed design of the emergency response capability considering the provision of human and logistical resources. Keywords: Accident escalation, coal, coal tar, coke oven gas, explosion, pool-fire
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Hazardous Spray Release from a Pipeline under Maintenance: Causes and Lessons Learned by a Combined Accident Analysis Perspective
No full textAs widely acknowledged, learning from accidents represents one of the main source of knowledge for future loss prevention. An effective investigation may help enhancing the process of continuous improvement of the safety management system. Recently, during a pipeline batching operation between two storage facilities of the same corporation, a LOC from the flange caused a spary release of atomised diesel, impacting on the adjacent national road. Two complementary approaches for accident investigation are here considered, i.e., customized root cause analysis workflow and Causal Analysis using System Theory approach. The best approach lies in the systemic nature of the selected methods applied to the whole socio-technical hierarchy of the concerned process trying to improve on one hand existing hazard analysis and on the other hand accident analysis. The paper outlines the fact-finding process from the technical viewpoint, as well as preconditions and latent failures
Heavy metals removal and recovery from hazardous leather sludge
No full textThe tanning industry is one of the oldest industries in the world and is known for the production of a wide variety of toxic waste (aqueous and solid) containing chromium salts and other heavy metals. Solid waste is produced during the conversion of putrescible collagen fibres into finished non-putrescible leather products. In this process, the use of a variety of chemicals during the fleshing or trimming phases, results in different hazardous waste, such as wet blue leather, crust leather, chrome shaving, finished leather off-cuts, and unusable chrome spilt. In the present study, we deal with the treatment of these hazardous leather sludge and the recovery of heavy metals contained in them. The leather sludge was pyrolyzed in a torch plasma reactor at a temperature of 1,400-1,500 °C producing an inert solid residue. However, the high temperatures involved induce the volatilization of some metals, which condense to form hazardous dusts (21.8% Zn, 0.70% Cr, 4,080 ppm Pb and 123 ppm Cd) that have to be properly dealt with. Numerous leaching tests have been conducted to maximize the amount of the individual components solubilized from the powder. Then, different treatment strategies have been combined for the recovery of the main metals: precipitation for Pb and Zn, and adsorption on chitosan for Cd
Oil Spill Identification and Monitoring from Sentinel-1 SAR satellite earth observations: A machine learning approach
No full textIdentification of an oil spill is essential to evaluate the potential spread and float from the source to coastal terrains, and their continued monitoring is essential for managing the environmental protection actions to confine the pollution and avoid further damage. The SAR sensor is perceived as the most significant remote sensing apparatus for the oil slick examination. One of the main aspects of oil spreading over sea surface is that it dampens the capillary waves and so, the backscatter radio waves are suppressed. As a result, oil spills are represented as black spots, while the brighter regions are usually related with unspoiled polluted sea areas. Additionally, the wide coverage that the sensor can provide is highly significant including long-range fate, as well as contextual information, such as sensitive coastal areas or vessels, which can be enclosed in the acquired image. However, oceanic natural phenomena such as low wind speed regions, weed beds and algae blooms, wave shadows behind land, grease ice, etc. can also be depicted as dark spots. These dark regions are commonly categorized as "look-Alikes and their discrimination is very challenging. Machine Learning techniques are the most appropriate choice to classify oil spills and look-Alikes. In the present work, a comparison between decision trees models and NN is performed to identify and extract the appropriate set of features characterizing an oil spill allowing effective evolution monitoring and setting up proper emergency actions
Removal of polyethylene glycols from wastewater: A comparison of different approaches
No full textPhysicochemical methods such as adsorption on activated carbon, oxidation with either ozone or Fenton reagent, and chemical precipitation (coagulation), were assessed for the removal of polyethylene glycol (PEG) from wastewater. This contaminant is rarely investigated due to its low toxicity, although its presence limits the use of large water resources. The experimental tests showed that adsorption on activated carbon is well approximated by a Langmuir isotherm, and influenced by contact time, PEG molecular weight, pH, temperature, and initial PEG concentration. Ozonation allowed fragmenting the polymeric chains but was unable to remove completely the PEG, while about 85% of the total organic carbon (TOC) was removed by Fenton oxidation reaction by using a ratio between H2O2 and FeII close to 4. Coagulation did not produce results worthy of note, most likely because the uncharged PEG molecule does not interact with the iron hydroxide flocs. However, when performed after the Fenton oxidation (i.e., by simply raising the pH to values > 8), it allowed a further reduction of the residual TOC, up to 96% of the total, in the best case. Based on the resources used by each process studied and in consideration of the effectiveness of each of them, a semi-quantitative comparison on the sustainability of the different approaches is proposed
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